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  • 151.
    Allström, Andreas
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ekström, Joakim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ringdahl, Rasmus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Rydergren, Clas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Bayen, Alexandre M.
    Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
    Patire, Anthony D.
    Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
    Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways2016Ingår i: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2554, s. 60-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Traffic management and traffic information are essential in urban areas and require reliable knowledge about the current and future traffic state. Parametric and nonparametric traffic state prediction techniques have previously been developed with different advantages and shortcomings. While nonparametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during nonrecurring traffic conditions, such as incidents and events. Hybrid approaches have previously been proposed; these approaches combine the two prediction paradigms by using nonparametric methods for predicting boundary conditions used in a parametric method. In this paper, parametric and nonparametric traffic state prediction techniques are instead combined through assimilation in an ensemble Kalman filter. For nonparametric prediction, a neural network method is adopted; the parametric prediction is carried out with a cell transmission model with velocity as state. The results show that the hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 min into the future, with a prediction horizon of up to 50 min ahead in time to allow the journey to be completed

  • 152.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Developments in Topology Optimization in the ADDMAN Project2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This document gives an account of some of the work done so far on topology optimization (TO) in the ADDMAN project. As well as the mathematical formulations and implementations details, short discussions are presented on some of the nuances of the different formulations and how they should be used efficiently

  • 153.
    Alm, Therese
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska fakulteten.
    Design av en användarvänlig Androidapplikation för trådlös kommunikation med Electronic Control Unit för bil eller testmiljö2015Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det här examensarbetet har utförts inom programmet högskoleingenjör datateknik vid Linköpings Universitet under våren 2015 och utförts på begäran av ArcCore i Linköping. Syftet med det här examensarbetet är att skapa och designa en användarvänlig Androidapplikation som trådlöst kan kommunicera med electronic control units i bil eller testmiljö.

    Androidapplikationen består av fem huvudskärmar, fyra vars uppgift är att skriva ut informationen som åker över CAN bussen. De fem skärmarna är start, felkoder, sensorer, ECU extract och overview. Start tar dig vidare till de andra skärmarna, felkoder skriver ut alla felkoder, sensorer skriver ut alla sensorvärden, ECU extract skriver ut all information och overview visar en virtuell instrumentbräda. Användarutvärderingar har utförts för att ta fram både designen och layouten på applikationen. Utvecklingsprocessen för att få fram applikationen har genomförts med hjälp av utvecklingsmetoden extreme programming och utvärderingar har utförts med traditional usability tests och binary success. Utvärderingarnas feedback har använts för att utveckla både designen och användarvänligheten på applikationen.

    Androidapplikationen har utvecklats i Android Studio och kommunicerar med ECU:erna med hjälp av en PEAK PCAN wireless gateway som kopplats upp mot Hercules Development Kit TMS570 MCU.

    Resultatet är att vi tydligt kan se att användarvänligheten har ökat under utvecklingsprocessen och att vi nu med hjälp av utvärderingar har en snygg och lättanvändarvänlig Android applikation som kommer kunna användas av alla som vill ta del av informationen som finns på CAN bussen.

  • 154.
    Almgren, Richard
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling. Linköpings universitet, Tekniska fakulteten. Green Business AB.
    Näringslivets insatser på miljöområdet: För Naturvårdsverket2015Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Uppdraget för denna rapport har varit att beskriva näringslivets insatser på miljöområdet med avseende på vilka miljöfrågor som näringslivet prioriterar, hur företagen organiserar sina insatser och vilka verktyg de använder för att förbättra sin miljöprestanda, hur de ser på några vanliga statliga styrmedel, vilka som är de viktigaste drivkrafterna och hindren till förbättrad miljöprestanda samt att även blicka utanför Sveriges gränser.

    Generationsperspektivet, ungefär 3-års cykler, på miljöfrågorna innebär att det ofta tar lång tid innan ett miljöproblem uppenbarar sig som ett problem. Likaså tar det ofta lång tid att åtgärda upptäckta problem med hänsyn till att de ofta kräver omställningar med nya tekniska lösningar, som inte alltid finns till hands, och som också behöver inför as brett i näringslivet.

    När det gäller den första frågan om vilka de viktigaste miljöfrågorna är för näringslivets del visar denna studie att det främst gäller klimatfrågan och produkternas miljöaspekter i ett värdekedjeperspektiv. Båda frågorna är globala till sin karaktär. De studerade företagen har hög beredskap och har redan påbörjat arbetet att för svensk del bidra till att minska klimatpåverkan. Innebörden av de antagna målen hos de 50 studerade företagen är att företag som verkar i Sverige enligt denna studie ska kunna medverka till att nå den nivå på insatser som IPCC indikerat för år 2050. Det är den tidpunkt som IPCC siktar på i sina senaste utvärderingar. Flera företag har vardera skisserat en trovärdig färdplan för att göra verksamheten koldioxidsnål eller koldioxidneutral till nämnda tidpunkt. Det är känt från andra liknande studier att det f rån näringslivets perspektiv dock också behövs ett politiskt mål av flera skäl, bl a för att regeringar och näringsliv i alla länder ska dra åt samma håll. Det som emellertid är intressant nu är att näringslivet i Sverige enligt denna studie har påbörjat arbetet med att finna lösningar för att nå ett ev kommande politiskt globalt mål. De studerade företagen i Sverige har även i stor utsträckning upprättat egna mål och genomför åtgärder på de områden som de nationella miljökvalitetsmålen täcker, bl a med inriktning på att begränsa förorening av luft- och vattenområden men även på att värna den biologiska mångfalden i jord- och skogsbruk samt att värna och utveckla naturvärden i den bebyggda miljön. Resultaten i form av utsläppsminskningar på de föroreningsanknutna områdena är goda även om det på flera områden återstår insatser att göra. Miljökvaliteten i Sverige på dessa områden påverkas dock främst av verksamhet i länder utanför Sveriges gränser. Den miljöpåverkan som uppstår som följd av den ökade handeln mellan länder är idag svår av kvantifiera på grund brister i lämplig statistik och mätetal. Inriktningen av handeln pekar emellertid på att Sverige exporterar mer varor med goda miljöprestanda, räknat i hela värdekedjan, än importerar varor med dåliga. Utöver nämnda områden har företagen ofta mål för användning av resurser och utveckling av förnybara energikällor.

    När det gäller den andra frågan om företagens egna insatser visar studien att det i rapporten studerade delen av näringslivet i Sverige i betydande omfattning på frivillig väg har infört egna verktyg för att effektivt kunna hantera sina miljöfrågor. Den viktigaste förändringen är att begreppet hållbar utveckling nu har slagit rot. Det medför att miljöfrågorna nu fått en tydligare plats i företagens ledningar i samverkan med andra frågor inom begreppet hållbarhet. De viktiga förebilderna för innebörden av hållbar utveckling är UN Global Compact, OECDs vägledning för multinationella företag och den internationella standarden ISO 26000 om socialt ansvarstagande. Rapporteringen av studerade företagens insatser på hållbarhetsområdet sker i stor utsträckning enligt den modell som utarbetats av GRI (Global Reporting Initiative). Den egna målstyrda verksamheten baseras väsentligen på miljöledningssystem som upprättats med stöd av den internationella miljöledningsstandarden ISO 14001, inom vilken även lagstyrda insatser hanteras internt . Syftet med sådana miljöledningssystem är att bidra med en effektiv metod att hantera miljöfrågorna i ett företag. Den logik som denna standard har byggt upp, m ed målstyrning som viktigaste komponent, lyser igenom i alla företagens hållbarhetsredovisningar. Det är alltså tydligt att ISO 14001 har fått stort genomslag i den praktiska hanteringen av miljöfrågorna. Vidare är det tydligt att företagen idag fäster sto r vikt vid att värna och utveckla den biologiska mångfalden i skogen. Mer än 70 procent av den produktiva skogsmarken i Sverige är certifierad enligt något av de stora förekommande certifieringssystemen (FSC/PEFC). Det innebär omfattande åtaganden för skog sägarna att värna om den biologiska mångfalden och att sätta av marker för naturvårdsändamål.

    När det gäller den tredje frågan om näringslivets förhållningssätt till statliga styrmedel har näringslivet i Sverige generellt sett en positiv syn på det regel verk som reglerar deras verksamhet. Efterlevnaden synes vara god av gällande regler. Den statliga individuella, integrerade tillståndsprövningen anses av berörda företag vara ett bra styrmedel. Det gäller även den europeiska kemikalielagstiftningen REACH. Däremot framgår det tydligt av studien att den nuvarande utformningen av tillståndsprövningen enligt berörda företag efter hand har blivit alldeles för omständlig och tidsmässigt utdragen. Idag tar tillståndsprocessen över tre år i genomsnitt. Det bör tydliggöras att inget företag har yrkat på att sänka miljökraven i sig utan framförallt att få tillståndsprocessen att gå fortare. Studien visar att det finns flera sådana möjligheter utan att varken göra avkall på kraven i direktiv från EU eller hänsyn till miljön. Avgiften på kväveoxider har mer eller mindre förlorat sin roll som styrmedel och fungerar numera mest som subvention av energisektorn på bekostnad av skogsindustrin. Det är framförallt skogsindustrin som framför kritik på denna punkt. Vidare ans er berörda företag att handeln med utsläppsrätter enligt EU ETS bör utvidgas till ett globalt system för att kunna bli verkningsfullt.

    När det gäller den fjärde frågan om drivkrafter och hinder för förbättrad miljöprestanda var lagstiftningen den stora drivkraften under 1970- och 1980-talen. Olika marknadsbaserade krav har numera fått en betydligt större roll än tidigare. Kraften i dessa krav skiftar från bransch till bransch och från miljöfråga till miljöfråga. En notering som stödjer tesen om att marknad en tagit över är det faktum att även de i denna undersökning utvalda företag, som inte i någon påtaglig utsträckning styrs av lagstiftning, också har ambitiösa program och planer. En annan bild av samma utveckling är relationen till kunder och andra intressenter. Det framkommer av företagen i studien att de knappast idag kan verka på marknaden samtidigt som förtroendet för företaget sviktar hos kunder och andra intressenter. En viss reservation kan dock vara befogad. Bakom olika marknadsrelaterade krav står ofta myndighetskrav eller lagstiftning. Det motsatta gäller naturligtvis också, dvs bakom lagstiftningskrav finns ofta ytterst ett krav på marknaden. Vidare är det tydligt från studien att d en värdegrund som idag omfattar de flesta svenskar, att värna om miljön, gäller också för företag. Sverige är ett relativt homogent land med en i stora delar gemensam värdegrund. En betydande del av alla insatser för miljön görs därför på helt frivillig väg av ren omtanke om miljön. Också detta bekräftas av det faktum att även de företag som inte omfattas av statliga krav på tillstånd, anmälan eller andra ”skarpa krav” också vidtar åtgärder för att skydda miljön med liknande inriktning och omfattning som de med sådana krav.

    Genomgången av olika verktyg och styrmedel får konsekvenser för de statliga och kommunala myndigheterna. Olika statliga regelverk är inte längre är det enda svaret på förbättrad miljöprestanda hos näringslivet. Det innebär att miljöpolitiken för regering och myndigheter snarare bör vara att skaffa sig ett rimligt förhållningssätt till de olika initiativen på marknaden med innebörd att staten underlättar för och stödjer företag, snarare än reglerar. Efter genomgången i denna rapport är svaret entydigt nej på frågan om det behövs kompletterande styrmedel. Det saknas i varje fall miljömotiv för det.

    Informationen för att besvara frågorna i denna undersökning har främst hämtats från en grupp av 50 stora företag med verksamhet i Sverige. Därutöver har information inhämtat s från intervjuer (11 företag, varav 6 från gruppen av 50), andra tillgängliga undersökningar och litteratur. De 55 företagen utgör inte ett representativt urval av näringslivet idag. Däremot vet vi från tidigare undersökningar att den värdegrund och de insatser som de stora företagen gör efter hand verkar som inspiration för de mindre företagen. Många av de mindre företagen är också leverantörer till de stora och har krav fr ån kunden att förhålla sig till. Det de stora företagen gör idag förmodas vara giltiga för en större del av näringslivet om några år.

  • 155.
    Almquist, Mathias
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Almquist, Viktor
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Vergara Alonso, Ekhiotz Jon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Communication Energy Overhead of Mobiles Games2015Ingår i: MobiGames '15: Proceedings of the 2nd Workshop on Mobile Gaming, Association for Computing Machinery (ACM), 2015, s. 1-6Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Although a significant proportion of the mobile apps are games there has been little attention paid to their specific characteristics with respect to communication energy. In this paper we select 20 mobile games among the top 100 free Android games, and study their data patterns and communication energy use over a total of 25 hours of playing. The analysis of the energy for communication over 3G networks indicates that there is a wide variation among the games, the largest footprint being 8 times higher than the lowest one. The results also indicates both app-specific and category-specific relations between data pattern and energy use, as well as variations in CPU utilisation.

  • 156.
    Almqvist, Roland M.
    et al.
    Företagsekonomiska institutionen, Stockholms universitet.
    Graaf, Johan
    Företagsekonomiska institutionen, Stockholms universitet.
    Jannesson, Erik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell ekonomi. Linköpings universitet, Tekniska fakulteten.
    Parment, Anders
    Företagsekonomiska institutionen, Stockholms universitet.
    Skoog, Matti
    Företagsekonomi, Åbo akademi / Företagsekonomiska institutionen, Stockholms universitet.
    Boken om ekonomistyrning2016 (uppl. 1)Bok (Övrigt vetenskapligt)
    Abstract [sv]

    Denna bok ger en bred introduktion till ämnet ekonomistyrning. Boken speglar ekonomistyrningens relevans för dagens organisationer inom näringsliv, offentlig sektor och civilsamhälle. Författarna går igenom de grundläggande modeller, verktyg och processer som traditionell ekonomistyrning erbjuder. Här märks ekonomiska ansvarsenheter, resultat- och balansräkning, kassaflödesanalys, nyckeltal, belöningssystem, budgetering, kalkylering på kort och lång sikt, internpriser samt avvikelseanalys.

    Boken om ekonomistyrning utgår från att ekonomistyrningen har en central roll i att skapa mer hållbara organisationer och lägger betydande vikt vid aspekter som sociala och miljömässiga kostnader, projektstyrning, miljöinvesteringar och humankapital. Boken har därmed ett tydligt hållbarhets- och samhällsperspektiv.

    Författarna betonar även vikten av att ekonomistyrningen utgör en välavvägd helhet genom den så kallade styrmixen. En genomtänkt styrmix ger verktyg för att motivera medarbetare att arbeta mot gemensamma mål och skapa konkurrenskraftiga organisationer. Till boken finns ett rikt övningsmaterial i form av en övningsbok.

  • 157.
    Alnoor, Hatim
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Toward the Optimization of Low-temperature Solution-based Synthesis of ZnO Nanostructures for Device Applications2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    One-dimensional (1D) nanostructures (NSs) of Zinc Oxide (ZnO) such as nanorods (NRs) have recently attracted considerable research attention due to their potential for the development of optoelectronic devices such as ultraviolet (UV) photodetectors and light-emitting diodes (LEDs). The potential of ZnO NRs in all these applications, however, would require synthesis of high crystal quality ZnO NRs with precise control over the optical and electronic properties. It is known that the optical and electronic properties of ZnO NRs are mostly influenced by the presence of native (intrinsic) and impurities (extrinsic) defects. Therefore, understanding the nature of these intrinsic and extrinsic defects and their spatial distribution is critical for optimizing the optical and electronic properties of ZnO NRs. However, identifying the origin of such defects is a complicated matter, especially for NSs, where the information on anisotropy is usually lost due to the lack of coherent orientation.

    Thus, the aim of this thesis is towards the optimization of the lowtemperature solution-based synthesis of ZnO NRs for device applications. In this connection, we first started with investigating the effect of the precursor solution stirring durations on the deep level defects concentration and their spatial distribution along the ZnO NRs. Then, by choosing the optimal stirring time, we studied the influence of ZnO seeding layer precursor’s types, and its molar ratios on the density of interface defects. The findings of these investigations were used to demonstrate ZnO NRs-based heterojunction LEDs. The ability to tune the point defects along the NRs enabled us further to incorporate cobalt (Co) ions into the ZnO NRs crystal lattice, where these ions could occupy the vacancies or interstitial defects through substitutional or interstitial doping. Following this, high crystal quality vertically welloriented ZnO NRs have been demonstrated by incorporating a small amount of Co into the ZnO crystal lattice. Finally, the influence of Co ions incorporation on the reduction of core-defects (CDs) in ZnO NRs was systematically examined using electron paramagnetic resonance (EPR).

  • 158.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Chey, Chan Oeurn
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nour, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Effect of precursor solutions stirring on deep level defects concentration and spatial distribution in low temperature aqueous chemical synthesis of zinc oxide nanorods2015Ingår i: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, nr 8, artikel-id 087180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hexagonal c-axis oriented zinc oxide (ZnO) nanorods (NRs) with 120-300 nm diameters are synthesized via the low temperature aqueous chemical route at 80 degrees C on silver-coated glass substrates. The influence of varying the precursor solutions stirring durations on the concentration and spatial distributions of deep level defects in ZnO NRs is investigated. Room temperature micro-photoluminesnce (mu-PL) spectra were collected for all samples. Cathodoluminescence (CL) spectra of the as-synthesized NRs reveal a significant change in the intensity ratio of the near band edge emission (NBE) to the deep-level emission (DLE) peaks with increasing stirring durations. This is attributed to the variation in the concentration of the oxygen-deficiency with increasing stirring durations as suggested from the X-ray photoelectron spectroscopy analysis. Spatially resolved CL spectra taken along individual NRs revealed that stirring the precursor solutions for relatively short duration (1-3 h), which likely induced high super saturation under thermodynamic equilibrium during the synthesis process, is observed to favor the formation of point defects moving towards the tip of the NRs. In contrary, stirring for longer duration (5-15 h) will induce low super saturation favoring the formation of point defects located at the bottom of the NRs. These findings demonstrate that it is possible to control the concentration and spatial distribution of deep level defects in ZnO NRs by varying the stirring durations of the precursor solutions.

  • 159.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Iandolo, Donata
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, nr 16, s. 165702-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5M exhibit stronger yellow emission (similar to 575 nm) compared to those based on 1:1 and 1:3M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination. Published by AIP Publishing.

  • 160.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Seed layer synthesis effect on the concentration of interface defects and emission spectra of ZnO nanorods/p-GaN light-emitting diode2017Ingår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 214, nr 1, artikel-id 1600333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As the low-temperature aqueous chemical synthesis (LT-ACS), holds great promises for the synthesis of one-dimensional (1D) ZnO nanostructure-based light-emitting diodes (LEDs) and hence require parameter tuning for optimal performance. N-ZnO nanorods (NRs)/p-GaN heterojunction LEDs have been synthesized by the LT-ACS using ZnO nanoparticle (NPs) seed layers prepared with different precursor solutions. The effect of these seed layers on the interface defect properties and emission intensity of the as-synthesized n-Zn/p-GaN heterojunction LEDs has been demonstrated by spatially resolved cathodoluminescence (CL) and electroluminescence (EL) measurements, respectively. A significant reduction of the interface defects in the n-ZnO NRs/p-GaN heterostructure synthesized from a seed layer prepared from zinc acetate (ZnAc) with a mixture of potassium hydroxide (KOH) and hexamethylenetetramine (HMTA) (donated as ZKH seed) compared with those prepared from ZnAc and KOH (donated as ZK seed) is observed as revealed by spatially resolved CL. Consequently, the LEDs based on n-ZnO NRs/p-GaN prepared from ZKH seed show an improvement in the yellow emission (approximate to 578nm) compared to that based on the ZK seed as deduced from the electroluminescence measurements. The improvement in the yellow EL emission on the ZKH LED probably attributed to the low presence of the non-radiative defect as deduced by light-output current (L-I) characteristics analysis.

  • 161.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Savoyant, Adrien
    Aix Marseille University, France.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    An effective low-temperature solution synthesis of Co-doped [0001]-oriented ZnO nanorods2017Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, nr 21, artikel-id 215102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate an efficient possibility to synthesize vertically aligned pure zinc oxide (ZnO) and Co-doped ZnO nanorods (NRs) using the low-temperature aqueous chemical synthesis (90 degrees C). Two different mixing methods of the synthesis solutions were investigated for the Co-doped samples. The synthesized samples were compared to pure ZnO NRs regarding the Co incorporation and crystal quality. Electron paramagnetic resonance (EPR) measurements confirmed the substitution of Co2+ inside the ZnO NRs, giving a highly anisotropic magnetic Co2+ signal. The substitution of Zn2+ by Co2+ was observed to be combined with a drastic reduction in the core-defect (CD) signal (g similar to 1.956) which is seen in pure ZnO NRs. As revealed by the cathodoluminescence (CL), the incorporation of Co causes a slight red-shift of the UV peak position combined with an enhancement in the intensity of the defect-related yellow-orange emission compared to pure ZnO NRs. Furthermore, the EPR and the CL measurements allow a possible model of the defect configuration in the samples. It is proposed that the as-synthesized pure ZnO NRs likely contain Zn interstitial (Zn-i(+)) as CDs and oxygen vacancy (V-O) or oxygen interstitial (O-i) as surface defects. As a result, Co was found to likely occupy the Zn-i(+), leading to the observed CDs reduction and hence enhancing the crystal quality. These results open the possibility of synthesis of highly crystalline quality ZnO NRs-based diluted magnetic semiconductors using the low-temperature aqueous chemical method. Published by AIP Publishing.

  • 162.
    Al-Omaishe, Allaa
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten. 860418-9061.
    The impacts of adopting large touch screens and tablets with access  to electronic healthcare records2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the last decade modern information technology systems have been introduced to healthcare in order to improve it. The aim of this study is to present the impact of such information system’s adoption on patient safety and efficiency within healthcare.

    Interviews, observations along with literature study were conducted in order to study the impact of the adoption on patient safety and efficiency at hospital’s wards where a new information system is implemented.

    The conclusion of this study is that such information technology systems can improve patient safety. However it is believed that the information technology system can improve efficiency in some aspects such as the communication among medical care personnel while other aspects within efficiency can be achieved if some improvements are made. Moreover the ability to access Electronic Healthcare Records is considered to be important to improve the medical care, which can increase patient safety. 

  • 163.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Hemm-Ode, Simone
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska högskolan. University of Applied Sciences and Arts Northwestern Switzerland.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Influence on Deep Brain Stimulation from Lead Design, Operating Mode and Tissue Impedance Changes – A Simulation Study2015Ingår i: Brain Disorders and Therapy, ISSN 2168-975X, Vol. 4, nr 3, artikel-id 1000169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Deep brain stimulation (DBS) systems in current mode and new lead designs are recently available. To switch between DBS-systems remains complicated as clinicians may lose their reference for programming. Simulations can help increase the understanding.

    Objective: To quantitatively investigate the electric field (EF) around two lead designs simulated to operate in voltage and current mode under two time points following implantation.

    Methods: The finite element method was used to model Lead 3389 (Medtronic) and 6148 (St Jude) with homogenous surrounding grey matter and a peri-electrode space (PES) of 250 μm. The PES-impedance mimicked the acute (extracellular fluid) and chronic (fibrous tissue) time-point. Simulations at different amplitudes of voltage and current (n=236) were performed using two different contacts. Equivalent current amplitudes were extracted by matching the shape and maximum EF of the 0.2 V/mm isolevel.

    Results: The maximum EF extension at 0.2 V/mm varied between 2-5 mm with a small difference between the leads. In voltage mode EF increased about 1 mm at acute compared to the chronic PES. Current mode presented the opposite relationship. Equivalent EFs for lead 3389 at 3 V were found for 7 mA (acute) and 2.2 mA (chronic).

    Conclusions: Simulations showed a major impact on the electric field extension between postoperative time points. This may explain the clinical decisions to reprogram the amplitude weeks after implantation. Neither the EF extension nor intensity is considerably influenced by the lead design.

  • 164.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Göransson, Nathanael
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US.
    Zsigmond, Peter
    Region Östergötland, Sinnescentrum, Neurokirurgiska kliniken US. Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för neuro- och inflammationsvetenskap. Linköpings universitet, Medicinska fakulteten.
    Wårdell, karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Investigation into Deep Brain Stimulation Lead Designs: A Patient-Specific Simulation Study2016Ingår i: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 6, nr 3, s. 1-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New deep brain stimulation (DBS) electrode designs offer operation in voltage and current mode and capability to steer the electric field (EF). The aim of the study was to compare the EF distributions of four DBS leads at equivalent amplitudes (3 V and 3.4 mA). Finite element method (FEM) simulations (n = 38) around cylindrical contacts (leads 3389, 6148) or equivalent contact configurations (leads 6180, SureStim1) were performed using homogeneous and patient-specific (heterogeneous) brain tissue models. Steering effects of 6180 and SureStim1 were compared with symmetric stimulation fields. To make relative comparisons between simulations, an EF isolevel of 0.2 V/mm was chosen based on neuron model simulations (n = 832) applied before EF visualization and comparisons. The simulations show that the EF distribution is largely influenced by the heterogeneity of the tissue, and the operating mode. Equivalent contact configurations result in similar EF distributions. In steering configurations, larger EF volumes were achieved in current mode using equivalent amplitudes. The methodology was demonstrated in a patient-specific simulation around the zona incerta and a “virtual” ventral intermediate nucleus target. In conclusion, lead design differences are enhanced when using patient-specific tissue models and current stimulation mode.

  • 165.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Vogel, Dorian
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. University of Applied Sciences and Arts Northwestern Switzerland FHNW, 4132 Muttenz, Switzerland.
    Johansson, Johannes
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Hemm, Simone
    Linköpings universitet, Institutionen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. rthwestern Switzerland FHNW, 4132 Muttenz, Switzerland.
    Electric Field Comparison between Microelectrode Recording and Deep Brain Stimulation Systems: A Simulation Study2018Ingår i: Brain Sciences, ISSN 2076-3425, E-ISSN 2076-3425, Vol. 8, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The success of deep brain stimulation (DBS) relies primarily on the localization of the implanted electrode. Its final position can be chosen based on the results of intraoperative microelectrode recording (MER) and stimulation tests. The optimal position often differs from the final one selected for chronic stimulation with the DBS electrode. The aim of the study was to investigate, using finite element method (FEM) modeling and simulations, whether lead design, electrical setup, and operating modes induce differences in electric field (EF) distribution and in consequence, the clinical outcome. Finite element models of a MER system and a chronic DBS lead were developed. Simulations of the EF were performed for homogenous and patient-specific brain models to evaluate the influence of grounding (guide tube vs. stimulator case), parallel MER leads, and non-active DBS contacts. Results showed that the EF is deformed depending on the distance between the guide tube and stimulating contact. Several parallel MER leads and the presence of the non-active DBS contacts influence the EF distribution. The DBS EF volume can cover the intraoperatively produced EF, but can also extend to other anatomical areas. In conclusion, EF deformations between stimulation tests and DBS should be taken into consideration as they can alter the clinical outcome

  • 166.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Vogel, Dorian
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten.
    Hemm-Ode, Simone
    Linköpings universitet, Institutionen för medicinsk teknik, Avdelningen för medicinsk teknik. Linköpings universitet, Tekniska fakulteten. Institute for Medical and Analytical Technologies and Department of Biomedical Engineering, University of Applied Sciences and Art Northwestern Switzerland.
    Comparison between intraoperative and chronic and deep brain stimulation2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    INTRODUCTION

    The success of the deep brain stimulation (DBS) therapy relies primarily in the localization of the implanted electrode, implying the need of utmost accuracy in the targeting process. Intraoperative microelectrode recording and stimulation tests are a common procedure before implanting the permanent DBS lead to determine the optimal position with a large therapeutic window where side effects are avoided and the best improvement of the symptoms is achieved. Differences in dimensions and operating modes exist between the exploration and the permanent DBS electrode which might lead to different stimulation fields, even when ideal placement is achieved. The aim of this investigation is to compare the electric field (EF) distribution around the intraoperative and the chronic electrode, assuming that both have exactly the same position.

    METHODS

    3D models of the intraoperative exploration electrode and the chronically implanted DBS lead 3389 (Medtronic Inc., USA) were developed using COMSOL 5.2 (COMSOL AB, Sweden). Patient-specific MR images were used to determine the conductive medium around the electrode. The exploration electrode and the first DBS contact were set to current and voltage respectively (0.2mA(V) - 3 mA(V) in 0.1 mA(V) steps). The intraoperative model included the grounded guide tube used to introduce the exploration electrode; for the chronic DBS model, the outer boundaries were grounded and the inactive contacts were set to floating potential considering a monopolar configuration. The localization of the exploration and the chronic electrode was set according to the planned trajectory. The EF was visualized and compared in terms of volume and extension using a fixed isocontour of 0.2 V/mm.

    RESULTS

    The EF distribution simulated for the exploration electrode showed the influence of the parallel trajectory and the grounded guide tube. For an amplitude of e.g. 2 mA/2 V, the EF extension of the intraoperative was 0.6 mm larger than the chronic electrode at the target level; the corresponding difference in volume was 76.1 mm3.

    CONCLUSION

    Differences in the EF shape between the exploration and the chronic DBS electrode have been observed using patient-specific models. The larger EF extension obtained for the exploration electrode responds to its higher impedance and the use of current controlled stimulation. The presence of EF around the guide tube and the influence of the parallel trajectory require further experimental and clinical evaluation.

  • 167.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Electric Field Comparison of Deep Brain Stimulation Lead Designs - a Stimulation Study2016Konferensbidrag (Refereegranskat)
  • 168.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Comparison of Three Deep Brain Stimulation Lead Designs under Voltage and Current Modes2015Ingår i: WORLD CONGRESS ON MEDICAL PHYSICS AND BIOMEDICAL ENGINEERING, 2015, VOLS 1 AND 2 / [ed] David A. Jaffray, Springer, 2015, Vol. 51, s. 1196-1199Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since the introduction of deep brain stimulation (DBS) the technique has been dominated by Medtronic sys-tems. In recent years, new DBS systems have become available for patients, and some are in clinical trials. The present study aims to evaluate three DBS leads operated in either voltage or current mode. 3D finite element method (FEM) models were built in combination with a neuron model for this purpose. The axon diameter was set to D = 5 μm and simulations performed in both voltage (0.5-5 V) and current (0.5-5 mA) mode. The evaluation was achieved based on the distance from the lead for neural activation and the electric field (EF) extension at 0.1 V/mm. The results showed that the neural activation distance agrees well between the leads with an activation distance dif-ference less than 0.5 mm. The shape of the field at the 0.1 V/mm isopotential surface in 3D is mostly spherical in shape around the activated section of the steering lead.

  • 169.
    Alonso, Fabiola
    et al.
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Wårdell, Karin
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Latorre, Malcolm
    Linköpings universitet, Institutionen för medicinsk teknik, Biomedicinsk instrumentteknik. Linköpings universitet, Tekniska fakulteten.
    Neural Activation Compared to Electric Field Extension of Three DBS Lead Designs2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    SINCE the introduction of deep brain stimulation (DBS) about 20 years ago, the stimulation technique has been dominated by Medtronic DBS-system setup. In recent years, new DBS systems have become available, of which some are in clinical trials or available to patients [1]. In the present study three different lead designs are investigated via computer simulation:

    Medtronic 3389, St. Jude 6148 and Sapiens SureStim. The aim was to compare the neural activation distance and the electric field (EF) maximum spatial extension for each lead.

    A 3D finite element method model was built using COMSOL Multiphysics 4.4a (COMSOL AB, Stockholm, Sweden) to simulate the electric potential around the DBS lead. Brain tissue was modelled as a homogeneous volume of grey matter (electric conductivity of 0.09 S/m). The electrode-tissue interface was modelled with a 250μm thick peri-electrode space mimicking the fibrous tissue which covers the lead at the chronic stimulation stage (σ = 0.06S/m, equivalent to white matter electric conductivity). The stimulation amplitude was set to 1V in monopolar configuration using C1 electrode or equivalent in all cases. Each simulated electric potential distribution was exported to MatLab (The MathWorks, USA) and used as input to a cable neuron simulation.

    An axon cable model with 21 nodes based on the concept by Åström et al., [2] was set up in MatLab and combined with the exported field distributions. The model considered a 5 μm thick neuron, a pulse width of 60 μs and a drive potential ranging from 0.5 V to 5 V in 0.5 V steps.

    The SureStim lead results showed a shorter neural activation distance and EF extension. The distance to the isolevel of 0.2 V/mm is close to the neural activation distance at each stimulation amplitude, and we conclude that the electric field is a suitable predictor to visualize the stimulated regions.

  • 170.
    Alonso-Magdalena, Paloma
    et al.
    Departamento de Biología Aplicada, Universidad Miguel Hernández.
    Rivera, Fransisco J.
    Laboratory of Stem Cells and Neurogeneration, Institute of Anatomy, Histology and Pathology, Facultu of Medicine and Center for INterdiciplinary Studies on the Nervous System (CISNe), Universitad Austral de Chile; Institute for Molecular Regenerative MEdicine and Spinal Cord Injury and Tissue Regeneration Center Salzburg (SCI-TReCS), Paracelsus University, Salzburg, Austira.
    Guerrero Bosagna, Carlos
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi. Linköpings universitet, Tekniska fakulteten.
    Bisphenol-A and metabolic diseases: epigenetic developmental and transgenerational basis2016Ingår i: Environmental Epigenetics, ISSN 2058-5888, Vol. 2, nr 3, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Exposure to environmental toxicants is now accepted as a factor contributing to the increasing incidence of obesity and metabolic diseases around the world. Such environmental compounds are known as ‘obesogens’. Among them, bisphenol-A (BPA) is the most widespread and ubiquitous compound affecting humans and animals. Laboratory animal work has provided conclusive evidence that early-life exposure to BPA is particularly effective in predisposing individuals to weight gain. Embryonic exposure to BPA is reported to generate metabolic disturbances later in life, such as obesity and diabetes. When BPA administration is combined with a high-fat diet, there is an exacerbation in the development of metabolic disorders. Remarkably, upon BPA exposure of gestating females, metabolic disturbances have been found both in the offspring and later in life in the mothers themselves. When considering the metabolic effects generated by an early developmental exposure to BPA, one of the questions that arises is the role of precursor cells in the etiology of metabolic disorders. Current evidence shows that BPA and other endocrine disruptors have the ability to alter fat tissue development and growth by affecting the capacity to generate functional adipocytes, as well as their rate of differentiation to specific cell types. Epigenetic mechanisms seem to be involved in the BPA-induced effects related to obesity, as they have been described in both in vitro and in vivo models. Moreover, recent reports also show that developmental exposure to BPA generates abnormalities that can be transmitted to future generations, in a process called as transgenerational epigenetic inheritance.

  • 171.
    AlSalhi, M S.
    et al.
    King Saud University, Saudi Arabia .
    Atif, M
    King Saud University, Saudi Arabia; National Institute of Laser and Optronics, Nilore, Islamabad, Pakistan.
    Ansari, A A.
    King Saud University, Saudi Arabia .
    Khun, Kimleang
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Hussain Ibupoto, Zafar
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan. King Saud University, Riyadh, Saudi Arabia.
    Growth and characterization of ZnO nanowires for optical applications2013Ingår i: Laser physics, ISSN 1054-660X, E-ISSN 1555-6611, Vol. 23, nr 6, artikel-id 065602Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, cerium oxide CeO2 nanoparticles were synthesized by the sol-gel method and used for the growth of ZnO nanorods. The synthesized nanoparticles were studied by x-ray diffraction (XRD) and Raman spectroscopic techniques. Furthermore, these nanoparticles were used as the seed layer for the growth of ZnO nanorods by following the hydrothermal growth method. The structural study of ZnO nanorods was carried out by means of field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM) and XRD techniques. This study demonstrated that the grown ZnO nanorods are well aligned, uniform, of good crystal quality and have diameters of less than 200 nm. Energy dispersive x-ray (EDX) analysis revealed that the ZnO nanorods are composed only of zinc, cerium as the seed atom, and oxygen atoms, with no other impurities in the grown nanorods. Moreover, a photoluminescence (PL) approach was applied for the optical characterization, and it was observed that the near-band-edge (NBE) emission was the same as that of the zinc acetate seed layer, however the green and orange/red emission peaks were slightly raised due to possibly higher levels of defects in the cerium oxide seeded ZnO nanorods. This study provides an alternative approach for the controlled synthesis of ZnO nanorods using cerium oxide nanoparticles as the seed nucleation layer, improving both the morphology of the nanorods and the performance of devices based upon them.

  • 172.
    Al-Salihi, Hayder
    et al.
    The Department of Informatics, King’s College London, UK.
    Van Chien, Trinh
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Le, Tuan Anh
    The Department of Design Engineering and Mathematics, Middlesex University, London, UK.
    Nakhai, Mohammad Reza
    The Department of Informatics, King’s College London, London, UK.
    A Successive Optimization Approach to Pilot Design for Multi-Cell Massive MIMO Systems2018Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 22, nr 5, s. 1086-1089Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this letter, we introduce a novel pilot designapproach that minimizes the total mean square errors of theminimum mean square error estimators of all base stations (BSs)subject to the transmit power constraints of individual users inthe network, while tackling the pilot contamination in multicellmassive MIMO systems. First, we decompose the originalnon-convex problem into distributed optimization sub-problemsat individual BSs, where each BS can optimize its own pilotsignals given the knowledge of pilot signals from the remainingBSs. We then introduce a successive optimization approach totransform each optimization sub-problem into a linear matrixinequality form, which is convex and can be solved by availableoptimization packages. Simulation results confirm the fast convergenceof the proposed approach and prevails a benchmarkscheme in terms of providing higher accuracy.

  • 173.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    A continuous-time dynamical system that can sort agents through distributed protocols2014Ingår i: 2014 IEEEMulti-conference on Systems and Control, Antibes, France: Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 2153-2158Konferensbidrag (Refereegranskat)
    Abstract [en]

    A class of continuous-time dynamical systems able to sort a list of real numbers is introduced in this paper. The dynamical sorting is achieved in a completely distributed manner, by modifying a consensus problem, namely right multiplying a Laplacian matrix by a diagonal matrix of weights that represents the desired order. The sorting obtained is relative, i.e., a conservation law is imposed on the dynamics. It is shown that sorting can be achieved in finite-time even in a globally smooth way.

  • 174.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Involutive flows and discretization errors for nonlinear driftless control systems2017Ingår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 110, s. 29-37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a continuous-time nonlinear driftless control system, an involutive flow is a composition of input profiles that does not excite any Lie bracket. Such flow composition is trivial, as it corresponds to a "forth and back" cyclic motion obtained rewinding the system along the same path. The aim of this paper is to show that, on the contrary, when a (nonexact) discretization of the nonlinear driftless control system is steered along the same trivial input path, it produces a net motion, which is related to the gap between the discretization used and the exact discretization given by a Taylor expansion. These violations of involutivity can be used to provide an estimate of the local truncation error of numerical integration schemes. In the special case in which the state of the driftless control system admits a splitting into shape and phase variables, our result corresponds to saying that the geometric phases of the discretization need not obey an area rule, i.e., even zero-area cycles in shape space can lead to nontrivial geometric phases. (C) 2017 Elsevier B.V. All rights reserved.

    Publikationen är tillgänglig i fulltext från 2019-11-04 12:15
  • 175.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Minimal eventually positive realizations of externally positive systems2016Ingår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 68, s. 140-147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is a well-known fact that externally positive linear systems may fail to have a minimal positive realization. In order to investigate these cases, we introduce the notion of minimal eventually positive realization, for which the state update matrix becomes positive after a certain power. Eventually positive realizations capture the idea that in the impulse response of an externally positive system the state of a minimal realization may fail to be positive, but only transiently. As a consequence, we show that in discrete-time it is possible to use downsampling to obtain minimal positive realizations matching decimated sequences of Markov coefficients of the impulse response. In continuous-time, instead, if the sampling time is chosen sufficiently long, a minimal eventually positive realization leads always to a sampled realization which is minimal and positive.

  • 176.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Nonintegrable discrete-time driftless control systems: geometric phases beyond the area rule2016Ingår i: 2016 IEEE 55th Conference on Decision and Control (CDC), IEEE Press, 2016, s. 4692-4697Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a continuous-time nonlinear driftless control system, a geometric phase is a consequence of nonintegrability of the vector fields, and it describes how cyclic trajectories in shape space induce non-periodic motion in phase space, according to an area rule. The aim of this paper is to shown that geometric phases exist also for discrete-time driftless nonlinear control systems, but that unlike their continuous-time counterpart, they need not obey any area rule, i.e., even zero-area cycles in shape space can lead to nontrivial geometric phases. When the discrete-time system is obtained through Euler discretization of a continuous-time system, it is shown that the zero-area geometric phase corresponds to the gap between the Euler discretization and an exact discretization of the continuous-time system.

  • 177.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Representing externally positive systems through minimal eventually positive realizations2015Ingår i: Proceedings of the IEEE 54th Annual Conference on Decision and Control (CDC),, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 6385-6390Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to investigate the cases in which an externally positive discrete-time system fails to have a minimal positive realization, in this paper we introduce the notion of minimal eventually positive realization, fr which the state update matrix becomes positive after a certain power. This property captures the idea that in the impulse response of an externally positive system the state of a minimal realization may fail to be positive, but only transiently. It is shown in the paper that whenever a minimal eventually positive realization exists, then the sequence of Markov parameters of the impulse response admits decimated subsequences for which minimal positive realizations exist and can be obtained by downsampling the eventually positive realization.

  • 178.
    Altafini, Claudio
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    The Geometric Phase of Stock Trading2016Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, nr 8, s. e0161538-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Geometric phases describe how in a continuous-time dynamical system the displacement of a variable (called phase variable) can be related to other variables (shape variables) undergoing a cyclic motion, according to an area rule. The aim of this paper is to show that geometric phases can exist also for discrete-time systems, and even when the cycles in shape space have zero area. A context in which this principle can be applied is stock trading. A zero-area cycle in shape space represents the type of trading operations normally carried out by high-frequency traders (entering and exiting a position on a fast time-scale), while the phase variable represents the cash balance of a trader. Under the assumption that trading impacts stock prices, even zero-area cyclic trading operations can induce geometric phases, i.e., profits or losses, without affecting the stock quote.

  • 179.
    Altafini, Claudio
    et al.
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska fakulteten.
    Facchetti, Giuseppe
    John Innes Centre, England.
    Metabolic Adaptation Processes That Converge to Optimal Biomass Flux Distributions2015Ingår i: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 11, nr 9, artikel-id e1004434Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In simple organisms like E. coli, the metabolic response to an external perturbation passes through a transient phase in which the activation of a number of latent pathways can guarantee survival at the expenses of growth. Growth is gradually recovered as the organism adapts to the new condition. This adaptation can be modeled as a process of repeated metabolic adjustments obtained through the resilencings of the non-essential metabolic reactions, using growth rate as selection probability for the phenotypes obtained. The resulting metabolic adaptation process tends naturally to steer the metabolic fluxes towards high growth phenotypes. Quite remarkably, when applied to the central carbon metabolism of E. coli, it follows that nearly all flux distributions converge to the flux vector representing optimal growth, i.e., the solution of the biomass optimization problem turns out to be the dominant attractor of the metabolic adaptation process.

  • 180.
    Altimiras, Jordi
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi. Linköpings universitet, Tekniska fakulteten.
    Anderson, W. Gary
    University of Manitoba, Canada.
    Ecophysiology methods: Refining the old, validating the new and developing for the future2016Ingår i: Comparative Biochemistry and Physiology A, ISSN 1095-6433, E-ISSN 1531-4332, Vol. 202Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    n/a

  • 181.
    Altimiras, Jordi
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi. Linköpings universitet, Tekniska fakulteten.
    Lindgren, Isa
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biologi. Linköpings universitet, Tekniska fakulteten.
    Giraldo-Deck, Lina Maria
    University of Mayor San Andres, Bolivia.
    Matthei, Alberto
    Tinamou Chile SL, Chile.
    Garitano-Zavala, Alvaro
    University of Mayor San Andres, Bolivia.
    Aerobic performance in tinamous is limited by their small heart. A novel hypothesis in the evolution of avian flight2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikel-id 15964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Some biomechanical studies from fossil specimens suggest that sustained flapping flight of birds could have appeared in their Mesozoic ancestors. We challenge this idea because a suitable musculoskeletal anatomy is not the only requirement for sustained flapping flight. We propose the "heart to fly" hypothesis that states that sustained flapping flight in modern birds required an enlargement of the heart for the aerobic performance of the flight muscles and test it experimentally by studying tinamous, the living birds with the smallest hearts. The small ventricular size of tinamous reduces cardiac output without limiting perfusion pressures, but when challenged to fly, the heart is unable to support aerobic metabolism (quick exhaustion, larger lactates and post-exercise oxygen consumption and compromised thermoregulation). At the same time, cardiac growth shows a crocodilian-like pattern and is correlated with differential gene expression in MAPK kinases. We integrate this physiological evidence in a new evolutionary scenario in which the ground-up, short and not sustained flapping flight displayed by tinamous represents an intermediate step in the evolution of the aerobic sustained flapping flight of modern birds.

  • 182.
    Alvbrant, Joakim
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    A study on emerging electronics for systems accepting soft errors2016Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Moore’s law has until today mostly relied on shrinkage of the size of the devices inintegrated circuits. However, soon the granularity of the atoms will set a limit together with increased error probability of the devices. How can Moore’s law continue in thefuture? To overcome the increased error rate, we need to introduce redundancy. Applyingmethods from biology may be a way forward, using some of the strategies that transformsan egg into a fetus, but with electronic cells.

    A redundant system is less sensitive to failing components. We define electronic clayas a massive redundancy system of interchangeable and unified subsystems. We show how a mean voter, which is simpler than a majority voter, impact a redundant systemand how optimization can be formalized to minimize the impact of failing subsystems.The performance at given yield can be estimated with a first order model, without the need for Monte-Carlo simulations. The methods are applied and verified on a redundant finite-impulse response filter.

    The elementary circuit behavior of the memristor, ”the missing circuit element”, is investigated for fundamental understanding and how it can be used in applications. Different available simulation models are presented and the linear drift model is simulated with Joglekar-Wolf and Biolek window functions. Driven by a sinusoidal current, the memristor is a frequency dependent component with a cut-off frequency. The memristor can be densely packed and used in structures that both stores and compute in the same circuit, as neurons do. Surrounding circuit has to affect (write) and react (read) to the memristor with the same two terminals.

    We looked at artificial neural network for pattern recognition, but also for self organization in electronic cell array. Finally we look at wireless sensor network and how such system can adopt to the environment. This is also a massive redundant clay-like system.

    Future electronic systems will be massively redundant and adaptive. Moore’s law will continue, not based on shrinking device sizes, but on cheaper, numerous, unified and interchangeable subsystems.

  • 183.
    Alvbrant, Joakim
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska fakulteten.
    Keshmiri, Vahid
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten.
    Wikner, Jacob
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Transfer Characteristics and Bandwidth Limitation in a Linear-Drift Memristor Model2015Ingår i: 2015 EUROPEAN CONFERENCE ON CIRCUIT THEORY AND DESIGN (ECCTD), IEEE , 2015, s. 332-335Konferensbidrag (Refereegranskat)
    Abstract [en]

    The linear-drift memristor model, suggested by HP Labs a few years ago, is used in this work together with two window functions. From the equations describing the memristor model, the transfer characteristics of a memristor is formulated and analyzed. A first-order estimation of the cut-off frequency is shown, that illustrates the bandwidth limitation of the memristor and how it varies with some of its physical parameters. The design space is elaborated upon and it is shown that the state speed, the variation of the doped and undoped regions of the memristor, is inversely proportional to the physical length, and depth of the device. The transfer characteristics is simulated for Joglekar-Wolf, and Biolek window functions and the results are analyzed. The Joglekar-Wolf window function causes a distinct behavior in the tranfer characteristics at cut-off frequency. The Biolek window function on the other hand gives a smooth state transfer function, at the cost of loosing the one-to-one mapping between charge and state. We also elaborate on the design constraints derived from the transfer characteristics.

  • 184.
    Amarasuriya, Gayan
    et al.
    Princeton University, NJ 08544 USA.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Vincent Poor, H.
    Princeton University, NJ 08544 USA.
    Wireless Information and Power Transfer in Multiway Massive MIMO Relay Networks2016Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 15, nr 6, s. 3837-3855Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Simultaneous wireless information and power transfer techniques for multiway massive multiple-input multiple-output (MIMO) relay networks are investigated. By using two practically viable relay receiver designs, namely 1) the power splitting receiver and 2) the time switching receiver, asymptotic signal-to-interference-plus-noise ratio (SINR) expressions are derived for an unlimited number of antennas at the relay. These asymptotic SINRs are then used to derive asymptotic symmetric sum rate expressions in closed form. Notably, these asymptotic SINRs and sum rates become independent of radio frequency-to-direct current (RF-to-DC) conversion efficiency in the limit of infinitely many relay antennas. Moreover, tight average sum rate approximations are derived in closed form for finitely many relay antennas. The fundamental tradeoff between the harvested energy and the sum rate is quantified for both relay receiver structures. Notably, the detrimental impact of imperfect channel state information (CSI) on the MIMO detector/precoder is investigated, and thereby, the performance degradation caused by pilot contamination, which is the residual interference due to nonorthogonal pilot sequence usage in adjacent/cochannel systems, is quantified. The presence of cochannel interference (CCI) can be exploited to be beneficial for energy harvesting at the relay, and consequently, the asymptotic harvested energy is an increasing function of the number of cochannel interferers. Notably, in the genie-aided perfect CSI case, the detrimental impact of CCI for signal decoding can be cancelled completely whenever the number of relay antennas grows without bound. Nevertheless, the pilot contamination severely degrades the sum rate performance even for infinitely many relay antennas.

  • 185.
    Ambuluri, Sreehari
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska fakulteten.
    Garrido, Mario
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Caffarena, Gabriel
    Boadilla del Monte, Madrid, Spain.
    Ogniewski, Jens
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten.
    Ragnemalm, Ingemar
    Linköpings universitet, Institutionen för systemteknik, Informationskodning. Linköpings universitet, Tekniska fakulteten.
    New Radix-2 and Radix-22 Constant Geometry Fast Fourier Transform Algorithms For GPUs2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents new radix-2 and radix-22 constant geometry fast Fourier transform (FFT) algorithms for graphics processing units (GPUs). The algorithms combine the use of constant geometry with special scheduling of operations and distribution among the cores. Performance tests on current GPUs show a significant improvements compared to the most recent version of NVIDIA’s well-known CUFFT, achieving speedups of up to 5.6x.

  • 186.
    Aminifar, Amir
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Analysis, Design, and Optimization of Embedded Control Systems2016Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Today, many embedded or cyber-physical systems, e.g., in the automotive domain, comprise several control applications, sharing the same platform. It is well known that such resource sharing leads to complex temporal behaviors that degrades the quality of control, and more importantly, may even jeopardize stability in the worst case, if not properly taken into account.

    In this thesis, we consider embedded control or cyber-physical systems, where several control applications share the same processing unit. The focus is on the control-scheduling co-design problem, where the controller and scheduling parameters are jointly optimized. The fundamental difference between control applications and traditional embedded applications motivates the need for novel methodologies for the design and optimization of embedded control systems. This thesis is one more step towards correct design and optimization of embedded control systems.

    Offline and online methodologies for embedded control systems are covered in this thesis. The importance of considering both the expected control performance and stability is discussed and a control-scheduling co-design methodology is proposed to optimize control performance while guaranteeing stability. Orthogonal to this, bandwidth-efficient stabilizing control servers are proposed, which support compositionality, isolation, and resource-efficiency in design and co-design. Finally, we extend the scope of the proposed approach to non-periodic control schemes and address the challenges in sharing the platform with self-triggered controllers. In addition to offline methodologies, a novel online scheduling policy to stabilize control applications is proposed.

  • 187.
    Aminifar, Amir
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Self-Triggered Controllers, Resource Sharing, and Hard Guarantees2016Ingår i: 2016 2ND INTERNATIONAL CONFERENCE ON EVENT-BASED CONTROL, COMMUNICATION, AND SIGNAL PROCESSING (EBCCSP), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today, many control applications in embedded and cyber-physical systems are implemented on shared platforms, alongside other hard real-time or safety-critical applications. Having the resource shared among several applications, to provide hard guarantees, it is required to identify the amount of resource needed for each application. This is rather straightforward when the platform is shared among periodic control and periodic real-time applications. In the case of event-triggered and self-triggered controllers, however, the execution patterns and, in turn, the resource usage are not clear. Therefore, a major implementation challenge, when the platform is shared with self-triggered controllers, is to provide hard and efficient stability and schedulability guarantees for other applications. In this paper, we identify certain execution patterns for self-triggered controllers, using which we are able to provide hard and efficient stability guarantees for periodic control applications.

  • 188.
    Aminifar, Amir
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Bini, Enrico
    Scuola Super Sant Anna, Italy.
    Eles, Petru lon
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Analysis and Design of Real-Time Servers for Control Applications2016Ingår i: I.E.E.E. transactions on computers (Print), ISSN 0018-9340, E-ISSN 1557-9956, Vol. 65, nr 3, s. 834-846Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today, a considerable portion of embedded systems, e.g., automotive and avionic, comprise several control applications. Guaranteeing the stability of these control applications in embedded systems, or cyber-physical systems, is perhaps the most fundamental requirement while implementing such applications. This is different from the classical hard real-time systems where often the acceptance criterion is meeting the deadline. In other words, in the case of control applications, guaranteeing stability is considered to be a main design goal, which is linked to the amount of delay and jitter a control application can tolerate before instability. This advocates the need for new design and analysis techniques for embedded real-time systems running control applications. In this paper, the analysis and design of such systems considering a server-based resource reservation mechanism are addressed. The benefits of employing servers are manifold: providing a compositional and scalable framework, protection against other tasks misbehaviors, and systematic bandwidth assignment and co-design. We propose a methodology for designing bandwidth-optimal servers to stabilize control tasks. The pessimism involved in the proposed methodology is both discussed theoretically and evaluated experimentally.

  • 189.
    Aminifar, Amir
    et al.
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, ESLAB - Laboratoriet för inbyggda system. Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska högskolan.
    Jfair: A Scheduling Algorithm to Stabilize Control Applications2015Ingår i: 21st IEEE Real-Time and Embedded Technology and Applications Symposium, Cyber-Physical Systems Week, Seattle, WA, April 2015, IEEE Computer Society, 2015, s. 63-72Konferensbidrag (Refereegranskat)
    Abstract [en]

    Control applications are considered to be among the core applications in cyber-physical and embedded realtime systems, for which jitter is typically an important factor. This paper investigates whether it is possible to guarantee certain amount of jitter for a given set of applications on a shared platform. The effect of jitter on the stability of control applications and its relation with the latency will be discussed. The importance arises from the fact that it is considerably easier to manage the constant part of the delay (known as latency), while the process of coping with the varying part of the delay (known as jitter) is more involved. The proposed solution guarantees certain jitter limits, and at the same time does not lead to overly pessimistic latency values. The results are later used in a design optimization problem to minimize the resource utilized.

  • 190.
    Aminifar, Amir
    et al.
    Embedded Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Optimization of Message Encryption for Real-Time Applications in Embedded Systems2018Ingår i: IEEE Transactions on Computers, ISSN 0018-9340, Vol. 67, nr 5, s. 748-754Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today, security can no longer be treated as a secondary issue in embedded and cyber-physical systems. Therefore, one of the main challenges in these domains is the design of secure embedded systems under stringent resource constraints and real-time requirements. However, there exists an inherent trade-off between the security protection provided and the amount of resources allocated for this purpose. That is, the more the amount of resources used for security, the higher the security, but the fewer the number of applications which can be run on the platform and meet their timing requirements. This trade-off is of high importance since embedded systems are often highly resource constrained. In this paper, we propose an efficient solution to maximize confidentiality, while also guaranteeing the timing requirements of real-time applications on shared platforms.

  • 191.
    Aminifar, Amir
    et al.
    Embedded Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland..
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Cervin, Anton
    Department of Automatic Control, Lund University, Sweden.
    Årzén, Karl-Erik
    Department of Automatic Control, Lund University, Sweden.
    Control-Quality Driven Design of Embedded Control Systems with Stability Guarantees2017Ingår i: IEEE design & test, ISSN 2168-2356, E-ISSN 2168-2364Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today, the majority of control applications in embedded systems, e.g., in the automotive domain, are implemented as software tasks on shared platforms. Ignoring implementation impacts during the design of embedded control systems results in complex timing behaviors that may lead to poor performance and, in the worst case, instability of control applications. This article presents a methodology for implementation-aware design of high-quality and stable embedded control systems on shared platforms with complex timing behaviors.

  • 192.
    Aminifar, Amir
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Tabuada, Paulo
    University of California at Los Angeles, USA.
    Eles, Petru
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Peng, Zebo
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Self-Triggered Controllers and Hard Real-Time Guarantees2016Ingår i: PROCEEDINGS OF THE 2016 DESIGN, AUTOMATION & TEST IN EUROPE CONFERENCE & EXHIBITION (DATE), Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 636-641Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is well known that event-triggered and self-triggered controllers implemented on dedicated platforms can provide the same performance as the traditional periodic controllers, while consuming considerably less bandwidth. However, since the majority of controllers are implemented by software tasks on shared platforms, on one hand, it might no longer be possible to grant access to the event-triggered controller upon request. On the other hand, due to the seemingly irregular requests from self-triggered controllers, other applications, while in reality schedulable, may be declared unschedulable, if not carefully analyzed. The schedulability and response-time analysis in the presence of self-triggered controllers is still an open problem and the topic of this paper.

  • 193.
    Amiri, Shahnaz
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Energisystem. Linköpings universitet, Tekniska fakulteten. University of Gavle, Sweden.
    Weinberger, Gottfried
    University of Gävle, Sweden.
    Increased cogeneration of renewable electricity through energy cooperation in a Swedish district heating system - A case study2018Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 116, s. 866-877Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present study of the district heating (DH) system in the city of Kisa, Sweden, shows how, through energy cooperation with a nearby sawmill and paper mill, a local energy company contributes to energy efficient DH and cost-effective utilization of a new biofuel combined heat and power (CHP) plant. Cases of stand-alone and integrated energy systems are optimized with the linear program MODEST. The European power market is assumed to be fully deregulated. The results show clear advantages for the energy company to cooperate with these industries to produce heat for DH and process steam for industry. The cooperating industries gain advantages from heat and/or biofuel by-product supply as well. The opening to use a biofuel CHP plant for combined heat supply results in cogenerated electricity of almost 29 GWh/a with an increased biofuel use of 13 GWhia, zero fuel oil use and CO2 emission reductions of 25,800 tons CO2/a with coal-condensing power plant on the margin and biofuel as limited resource. The total system cost decreases by -2.18 MEUR/a through extended cooperation and renewable electricity sales. The sensitivity analysis shows that the profitability of investing in a biofuel CHP plant increases with higher electricity and electricity certificate prices. (C) 2017 Elsevier Ltd. All rights reserved.

  • 194.
    Amlinger, Anton
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    An Evaluation of Clustering and Classification Algorithms in Life-Logging Devices2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Using life-logging devices and wearables is a growing trend in today’s society. These yield vast amounts of information, data that is not directly overseeable or graspable at a glance due to its size. Gathering a qualitative, comprehensible overview over this quantitative information is essential for life-logging services to serve its purpose.

    This thesis provides an overview comparison of CLARANS, DBSCAN and SLINK, representing different branches of clustering algorithm types, as tools for activity detection in geo-spatial data sets. These activities are then classified using a simple model with model parameters learned via Bayesian inference, as a demonstration of a different branch of clustering.

    Results are provided using Silhouettes as evaluation for geo-spatial clustering and a user study for the end classification. The results are promising as an outline for a framework of classification and activity detection, and shed lights on various pitfalls that might be encountered during implementation of such service.

  • 195.
    Amloy, Supaluck
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan. Department of Physics, Faculty of Science, Thaksin University, 93110 Phattalung, Thailand .
    Yu, K. H.
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Karlsson, K Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Farivar, R.
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S‐41296 Göteborg, Sweden.
    Andersson, T. G.
    Applied Semiconductor Physics, Department of Microtechnology and Nanoscience, Chalmers University of Technology, S‐41296 Göteborg, Sweden.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Polarized Emission from Single GaN Quantum Dots Grown by Molecular Beam Epitaxy2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Polarization resolved microphotoluminescence measurements of single MBE‐grown GaN/Al(Ga)N quantum dots (QDs) have been performed. The exciton and biexciton peaks with full width at half maximum as narrow as <500 μeV  were observed. Interestingly, there exist both positive and negative binding energies of the biexciton, explained in term of different sizes of the measured dots, resulting in different built‐in electric field. Moreover, a strongly linearly polarized emission is observed for the investigated dots with a degree of linear polarization of about 0.9, interpreted as the valence‐band mixing induced by in‐plane anisotropy due to strain and/or QD shape.

  • 196.
    Ammenberg, Jonas
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Biogas Research Center. Linköpings universitet, Tekniska fakulteten. Linköping University, Biogas Research Center (BRC).
    Anderberg, Stefan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Biogas Research Center. Linköpings universitet, Tekniska fakulteten.
    Lönnqvist, Tomas
    Division of Energy Processes, Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.
    Grönkvist, Stefan
    Division of Energy Processes, Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.
    Sandberg, Thomas
    Department of Industrial Economics and Management, Royal Institute of Technology, Stockholm, Sweden.
    Biogas in the transport sector: Actor and policy analysis focusing on the demand side in the Stockholm region2018Ingår i: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 129, s. 70-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sweden has ambitions to phase out fossil fuels and significantly increase the share of biofuels it uses. This articlefocuses on Stockholm County and biogas, with the aim to increase the knowledge about regional preconditions.Biogas-related actors have been interviewed, focusing on the demand side. Biogas solutions play an essentialrole, especially regarding bus transports and taxis. Long-term development has created well-functioning sociotechnicalsystems involving collaboration. However, uncertainties about demand and policy cause hesitation andsigns of stagnating development.Public organizations are key actors regarding renewables. For example, Stockholm Public Transport procuresbiogas matching the production at municipal wastewater treatment plants, the state-owned company Swedaviasteers via a queuing system for taxis, and the municipalities have shifted to “environmental cars”.There is a large interest in electric vehicles, which is expected to increase significantly, partially due tosuggested national policy support. The future role of biogas will be affected by how such an expansion comesabout. There might be a risk of electricity replacing biogas, making it more challenging to reach a fossil-freevehicle fleet. Policy issues strongly influence the development. The environmental car definition is of importance,but its limited focus fails to account for several different types of relevant effects. The dynamic policylandscape with uncertainties about decision makers’ views on biogas seems to be one important reason behindthe decreased pace of development. A national, long-term strategy is missing. Both the European Union andSweden have high ambitions regarding a bio-based and circular economy, which should favor biogas solutions.

    Publikationen är tillgänglig i fulltext från 2019-10-20 10:58
  • 197.
    Ammenberg, Jonas
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Biogas Research Center.
    Bohn, Irene
    Den Kgl. Veterinær- og Landbohøjskole, Denmark.
    Feiz, Roozbeh
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Biogas Research Center.
    Systematic assessment of feedstock for an expanded biogas production: A multi-criteria approach2017Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Biogas solutions can contribute to more renewable and local energy systems, and also involve other essential aspects such as nutrient recycling. From a theoretical feedstock perspective there is a great biogas potential in Sweden, but the development has been relatively slow as many biogas producers face challenges of different types. Among the many influencing factors, the choice of feedstocks (biomass) is of strategic importance. Within the Biogas Research Center (BRC), hosted by Linköping University in Sweden, a research project focused on feedstock has been ongoing for several years. It has involved researchers, biogas and biofertilizer producers, agricultural organizations and others. The main aim has been to develop a method to assess the suitability of feedstock for biogas and biofertilizer production, and to apply this method on a few selected feedstocks. A multi-criteria method has been developed that covers potential, feasibility and resource efficiency, operationalized via 17 indicators directed towards cost efficiency, technological feasibility, energy and environmental performance, accessibility, competition, policy and other issues. Thus the method it is relatively comprehensive, yet hopefully simple enough to be used by practitioners.

    The main ambition, applying the method, has been to collect and structure relevant information to facilitate strategic overviews, communication and informed decision making. This is relevant for development within the biogas and biofertilizer industry, for policymakers, to define and prioritize among essential research projects, etc. This report presents some essential parts of this project, focusing on the multi-criteria method and results regarding ley crops, straw, farmed blue mussels and food waste (and stickleback to some extent). It clarifies how the method can be applied and highlights barriers, drivers and opportunities for each feedstock. Comparisons are also made. The results indicate that biogas production from food waste and ley crops is the most straightforward, and for straw and farmed blue mussels there are more obstacles to overcome. For all of them, the dynamic and very uncertain policy landscape is a barrier. In the final chapter, some conclusions about the method and its application are drawn.

  • 198.
    Ammenberg, Jonas
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Tekniska fakulteten.
    Feiz, Roozbeh
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Tekniska fakulteten.
    Assessment of Feedstocks for Biogas Production, Part II: Results for Strategic Decision Making2017Ingår i: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 122, s. 388-404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biogas production is essentially based on organic materials and biological processes; hence it can contribute to the transition toward a biobased economy. Biogas is a biofuel that can contribute to a more renewable and local energy system. In comparison with other biofuels, biogas is more flexible and can be produced from many different types of feedstock, including biomass containing various shares of carbohydrates, lipids and, both from primary and secondary raw materials. However, a significantly expanded biogas production is dependent on good business conditions, in turn related to societal acceptance and support. There are many factors that can make a biogas solution more or less suitable for both producers and the broader society. Among the many influencing factors, the choice of feedstocks (biomass) for producing biogas and biofertilizer is of strategic importance. But, to assess the suitability is complicated, because it is linked to many different challenges such as cost, energy balance, environmental impacts, institutional conditions, available technologies, geographical conditions, alternative and competing interest, and so on. Suitability includes aspects related to feasibility for implementation, potential for renewable energy and nutrient recycling, and resource efficiency. In this article, a multi-criteria framework, which is proposed in a companion article (Part II), is used to assess the suitability of four types of feedstocks for producing biogas (considering Swedish conditions). The assessed feedstocks are ley crops, straw, farmed blue mussels, and source-sorted food waste. The results have synthesized and structured a lot of information, which facilitates considerably for those that want an overview and to be able to review several different areas simultaneously. Among the assessed feedstocks, biogas production from household food waste and ley is the most straightforward. For straw and farmed blue mussels, there are more obstacles to overcome including some significant barriers. For all feedstock there are challenges related to the institutional conditions. The assessment contributes to the knowledge about sustainable use of these feedstocks, and the limitations and opportunities for biogas development. It supports more informed decision making, both in industry and policy. Existing, or forthcoming, biogas and biofertilizer producers who are considering altering or expanding their production systems can benefit from a better understanding of different choices of feedstock that are or can be (potentially) at their disposal; thus, identify hotspots, weak points, and possible candidates for implementation in future. This research is performed within the Biogas Research Center (BRC), which is a transdisciplinary center of excellence with the overall goal of promoting resource-efficient biogas solutions in Sweden. The BRC is funded by the Energy Agency of Sweden, Linköping University, and more than 20 partners from academia, industry, municipalities and other several public and private organizations.

  • 199.
    Amsallem, David
    et al.
    Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305-4035, USA.
    Nordström, Jan
    Linköpings universitet, Matematiska institutionen, Beräkningsmatematik. Linköpings universitet, Tekniska fakulteten.
    Energy Stable Model Reduction of Neurons by Non-negative Discrete Empirical Interpolation2016Ingår i: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 38, nr 2, s. B297-B326Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The accurate and fast prediction of potential propagation in neuronal networks is of prime importance in neurosciences. This work develops a novel structure-preserving model reduction technique to address this problem based on Galerkin projection and nonnegative operator approximation. It is first shown that the corresponding reduced-order model is guaranteed to be energy stable, thanks to both the structure-preserving approach that constructs a distinct reduced-order basis for each cable in the network and the preservation of nonnegativity. Furthermore, a posteriori error estimates are provided, showing that the model reduction error can be bounded and controlled. Finally, the application to the model reduction of a large-scale neuronal network underlines the capability of the proposed approach to accurately predict the potential propagation in such networks while leading to important speedups.

  • 200.
    Anandapadamanaban, Madhanagopal
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemi. Linköpings universitet, Tekniska fakulteten.
    Structural insights into protein-protein interactions governing regulation in transcription initiation and ubiquitination2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Virtually every aspect of the cellular processes in eukaryotes requires that the interactions between protein molecules are well coordinated in different regulatory pathways. Any protein dysfunction involved in these regulatory pathways might lead to various pathological conditions. Understanding the structural and functional peculiarities of these proteins molecular machineries will help in formulating structure-based drug design.

    The first regulatory process studied here is the RNA polymerase-II mediated transcription of the eukaryotic protein-coding genes to produce mRNAs. This process requires the formation of the ‘transcription initiation’ by the assembly of Pre-Initiation Complex (PIC) formation at a core promoter region. Regulation at this initiation level is a key mechanism for the control of gene expression that governs cellular growth and differentiation. The transcription Factor IID (TFIID) is a conserved multiprotein general transcription factor with an essential role in  nucleating the PIC formation, composed of TATA Binding Protein (TBP) and about 14 TBP Associated Factors (TAFs). The here presented crystal structure (1.97Å) of TBP bound to TAND1 and TAND2 domains from TAF1 reveals a detailed molecular pattern of interactions involving both transcriptionally activating and repressing regions in TBP, thereby uncovering central principles for anchoring of TBP-binding motifs. Together with NMR and cellular analysis, this work provides the structural basis of competitive binding with TFIIA to modulate TBP in promoter recognition.

    In eukaryotes, another fundamental mechanism in the regulation of cellular physiology is the posttranslational modification of substrate proteins by ubiquitin, termed ‘ubiquitination’. Important actors in this mechanism are the ubiquitin-ligases (E3s) that culminate the transfer of ubiquitin to the substrate and govern the specificity of this system. One E3 ligase in particular, TRIM21, defines a subgroup of the Tripartite Motif (TRIM) family, which belongs to the major RING-type of E3 ubiquitin ligases, and plays an important role in pathogenesis of autoimmunity by mediating ubiquitination of transcription factors. The crystal structure (2.86Å) of the RING domain from TRIM21 in complex with UBE2E1, an E2 conjugating enzyme, together with the NMR and SAXS analysis as well as biochemical functional analysis, reveals the molecular basis for the dynamic binding interfaces. The TRIM21 mode of ubiquitin recognition and activation for catalytic transfer of ubiquitin can be modeled onto the entire TRIM family.

    Finally, we explored the concepts of conformational selection in proteins as a possible key component for protein-mediated transcriptional regulation. In this framework, MexR, a bacterial repressor of the MexAB-OprM efflux pump, and its mutant Arg21Trp were studied as an example for proteins presenting different conformations. The residue Arg21Trp mutation is clinically identified to cause of Multi-Drug Resistant (MDR) by attenuated DNA binding, and leads to the overexpression of the MexAB-OprM efflux pump. With the crystal structure (2.19Å) of MexR mutant Arg21Trp, in combination with MD-simulations and SAXS for both wild-type and mutant, we could unravel the atomic details of the wild-type conformations consisting in subsets of populations of DNA bound and unbound forms. Remarkably, the mutant Arg21Trp stabilize the DNA unbound state and shifts MexR in a pre-existing equilibrium, from a repressed to a derepressed state.

    Taken together, these studies substantially broaden our knowledge at a molecular level in protein interactions that are involved in transcriptional regulation and ubiquitination, studied by a carefully selected combination of complementary structural methods spanning different resolutions and time scales.

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