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  • 1.
    Abbas, Wasim
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Asghar, Imran
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    The Role of Leadership In Organizatinal Change: Relating the successful Organizational Change with Visionary and Innovative Leadership2010Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The globalization has converted the world into a small global village; a village in which there is an ever high stream of contentions and competitions between organizations. In this scenario the most effective and beneficial maneuver for any organization is to create innovative ways in conducting business. This thesis deals with the role of leadership in the phenomena of organizational change and innovation. The leader as a person in charge or as a change agent can manage an organization or the process of organizational change more effectively and successfully if h/she is capable and competent. Rapid technological advancements, high expectations of customers, and ever changing market situations have compelled organizations to incessantly reassess and reevaluate how they work and to understand, adopt and implement changes in their business model in response of changing trends. Organizational change is a demand of the day, and needed for organizations to survive. Organizations now a days, well understand the importance of the matter, and are serious to prepare themselves not only the current, but also for the future trends to get the level of sustainable success, but Along with all of its implications and importance the process of organizational change is also a very complex and challenging.  Research shows that 70 percent of organizational changes fail to get their goals. As leadership has a central role in evolution and cultivating an organization, the process of organizational change demands a very effective and highly competent leadership that is well capable to perceive the most desirable shape of an organization and address the issue of organizational change in most appropriate way. The analysis of literature reviewed and the results of real life cases of organizations which are studied for this thesis shows, that a leadership with the competencies of “Vision” and “Innovative Approach” along with other characteristics can prove more effective to conclude the complex phenomena of organizational change with success. Further the successful organizational change can leads to innovation for organization, which is the key of long term success and sustainability. This thesis as a result proposed a model which is derived from the leadership competencies, organizational change, and sustainable success and innovation literature. This model expresses relationship between successful organizational change and leadership on the basis of h/her characteristics, which are ‘Vision” and “Innovative Approach”. With the help of proposed model this relationship can be viewed graphically.

  • 2.
    Abbasi, Saeed
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Airborne wear particles from train traffic2010Conference paper (Refereed)
  • 3.
    Abbasi, Saeed
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Olander, Lars
    A field investigation of the size and morphology and chemical composition of airborne particles in rail transport2010Conference paper (Refereed)
  • 4.
    Abdallah, Lana
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Industrial Economics.
    Persson, Mattias
    Blekinge Institute of Technology, Faculty of Engineering, Department of Industrial Economics.
    The effects of environmental uncertainty conditions on organisational innovativeness and performance of SMEs.2014Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Innovativeness is considered to be an important factor for firm’s survival and their ability to compete in today’s market. Therefore, researchers have become more interested in studying innovativeness and its drivers. Studies have also showed that there’s a positive relationship between environmental uncertainty and innovativeness. Organisations are responsive to turbulent environments through innovativeness in order to stay competitive and improve performance. The purpose of this thesis is to rank critical environmental factor’s effect on organisational innovativeness of small and medium enterprises in Sweden, through investigating the impact of market/demand turbulence and technological turbulence on innovativeness. Additionally, we want to examine the relationship between innovativeness and business performance, as well as the indirect relationship between environmental uncertainty and performance. Based on previous literature, we have developed hypotheses and proposed a research model to study the formulated problems. Data for the study were collected from 50 SMEs in Sweden, through a survey with well-known scales and were analysed using regression analysis. The results of the study, reveal that environmental uncertainty has a positive effect on the innovativeness of SMEs. In addition, technological turbulence showed to have a positive significant effect on an SME’s innovativeness; however, contrary to general belief, market/demand turbulence did not have any prominent effect. Our findings also proved that innovativeness have a strong positive impact on business performance, and that only technological turbulence have an indirect influence on performance through innovativeness. This study aimed to contribute to the management a better understanding, of which conditions of environmental turbulences SMEs should adapt to, in order to increase their level of innovativeness. Keywords: environmental uncertainty, organizational innovativeness, performance, market/demand turbulence, technological turbulence, SMEs.

  • 5.
    Abid, Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.). Högskolan i Gävle, Sweden.
    Relationship between competitive priorities and global supply chain design: A conceptual frameworkManuscript (preprint) (Other academic)
  • 6.
    Abid, Muhammad
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation.
    Relationship between competitive priorities and global supply chain design: A conceptual frameworkManuscript (preprint) (Other academic)
  • 7.
    Abid, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.). Högskolan i Gävle, Sweden.
    Bengtsson, Lars
    Hellberg, Roland
    Dabhilkar, Mandar
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Factors affecting global supply chain design2012Conference paper (Refereed)
    Abstract [en]

    Due to the limited existing knowledge pertaining to the factors which govern localization of operations and capabilities in a global supply chain, the purpose of the paper is to find out which factors and how they jointly affect the design of global supply chains. The relevant literature is reviewed and a concept matrix is developed. Five companies were selected in order to illustrate the issues of global supply chain design. Among them, three companies are considered to have efficient supply chain and less complex products, while the two others are considered to have responsive supply chain and more complex products. The issues discussed with the selected companies cover global sourcing, challenges, technological advancement and issues related to management control. The study identifies about fifty factors that affect global supply chain design, and specifically how theses relate to design decisions on location of factories and production, supplier selection and development, distribution of products and organisation of interfaces along the supply chain. The discrepancies between theory and practice as well as the implications for further research are discussed.

  • 8.
    Abrahamsson, Mats
    et al.
    Linköping University, Department of Management and Engineering, Logistics Management. Linköping University, The Institute of Technology.
    Rehme, Jakob
    Linköping University, Department of Management and Engineering, Industrial Marketing and Industrial Economics. Linköping University, The Institute of Technology.
    The Role of Logistics in Retailers' Corporate Strategy: A Driver for Growth and Customer Value2010In: Supply Chain Forum: an International Journal, ISSN 1625-8312, Vol. 11, no 4, 14-23 p.Article in journal (Refereed)
    Abstract [en]

    This article explores the role of logistics and supply chain management (SCM) in retailers’ corporate strategy and is based on reviewing multiple qualitative case studies of companies in the Swedish food retail sector. The article proposes that the role of logistics for what is referred to in this paper as modern retailers is twofold: to create profitability and to support growth and market expansion. International modern retailers are empirically compared with similar companies in the Swedish market. The dominating Swedish food retailers have taken command in the food supply chain but are primarily concerned with traditional logistics roles in cost cutting. This role is perfectly fine as long as the strategic intent of the companies is focused on market retention and not on geographical expansion and/or new marketing or store concepts. We argue that the success of modern retailers in terms of growth rate, profitability, and market expansion is explained to a large extent by the role of logistics in corporate strategy—when the role for supporting growth and increasing customer value from high-performance supply capabilities is a driver for market expansion. However, in many of our cases the traditional logistics roles of cutting costs and lead-times is still the dominating pattern that limits the possibility of expanding into new markets. Better knowledge of logistics’ role in retail corporate strategy can help companies develop and improve their strategic intent as well as redefine the role of logistics.

  • 9.
    Abu Baker Karim, Aria
    et al.
    Örebro University, School of Science and Technology, Örebro University, Sweden.
    Schnelzer, Anna
    Örebro University, School of Science and Technology, Örebro University, Sweden.
    Optimering av glidlager och utveckling av dess konstruktion2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We have in this project become engrossed in a plain bearing design that is located in a screw press. The screw press compact an unknown mass that is confidential. Robustus have a suggestion to over dimensioning the present plain bearing. The aim of this project was to analyze and to do an optimization on some plain bearings and compare them to the present bearing and to take the choice of material and the environment where the bearing is located into account. The analysis and the optimizations showed that the current plain bearing had the best geometry but not the optimal material selection. The project is in an early state and it needs some geometrical changes. The most important of everything is that the problem has been identified with the help of the wrecked plain bearing and with an excel model.

  • 10.
    Achten, Peter A J
    et al.
    Innas BV, Netherlands.
    Vael, Georges E M
    Innas BV, Netherlands.
    Heybroek, Kim
    Volvo Constrúction Equipment, Sweden.
    Efficient hydraulic pumps , motors and transformers for hydraulic hybrid systems in mobile machinery2011In: Wissensforum VDI: VDI-Fachkonferenz Getriebe in Mobilen Arbeitsmaschinen, 2011Conference paper (Refereed)
    Abstract [en]

    A detailed simulation of a large 33 metric ton wheel loader, carrying out the short loading cycle, has been performed. Two systems have been compared and examined side by side: • The conventional system, having a mechanical transmission for driving the wheels and a conventional load sensing hydraulic circuit for the work and steering cylinders. • A new hydraulic hybrid system for the wheel drive and the implements, applying new and efficient hydrau- lic pumps and motors. The core of the new system is the hydraulic transformers which convert and control all the hydraulic power flows inside the loader. The new system results in a reduction of the fuel consumption of about 50% in the analyzed cycle. The new transmission and hydraulic system also results in a strong reduction of the cooler demands.

  • 11.
    Adamson, Göran
    et al.
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Wang, Lihui
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre. Department of Production Engineering, Royal Institute of Technology, Stockholm, Sweden.
    Moore, Philip
    University of Skövde, School of Engineering Science. University of Skövde, The Virtual Systems Research Centre.
    Feature-based control and information framework for adaptive and distributed manufacturing in cyber physical systems2017In: Journal of manufacturing systems, ISSN 0278-6125, E-ISSN 1878-6642, Vol. 43, 305-315 p.Article in journal (Refereed)
    Abstract [en]

    Modern distributed manufacturing within Industry 4.0, supported by Cyber Physical Systems (CPSs), offers many promising capabilities regarding effective and flexible manufacturing, but there remain many challenges which may hinder its exploitation fully. One major issue is how to automatically control manufacturing equipment, e.g. industrial robots and CNC-machines, in an adaptive and effective manner. For collaborative sharing and use of distributed and networked manufacturing resources, a coherent, standardised approach for systemised planning and control at different manufacturing system levels and locations is a paramount prerequisite.

    In this paper, the concept of feature-based manufacturing for adaptive equipment control and resource-task matching in distributed and collaborative CPS manufacturing environments is presented. The concept has a product perspective and builds on the combination of product manufacturing features and event-driven Function Blocks (FB) of the IEC 61499 standard. Distributed control is realised through the use of networked and smart FB decision modules, enabling the performance of collaborative run-time manufacturing activities according to actual manufacturing conditions. A feature-based information framework supporting the matching of manufacturing resources and tasks, as well as the feature-FB control concept, and a demonstration with a cyber-physical robot application, are presented.

  • 12.
    Adebring, Carl Jonas
    et al.
    Linköping University, Department of Management and Engineering.
    Zachrisson, Fredrik
    Linköping University, Department of Management and Engineering.
    Leverantörsrelationer på Volvo Aero Corporation: En modell för val av lämplig strategi för leverantörshantering2007Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    Volvo Aero Corporation is one of the major subcontractors for the three big aero-engine manufacturers today, Rolls-Royce, General Electric and Pratt & Whitney. The company produces parts that are in over 80 % of commercial jet engines today. New engine programs where Volvo Aero tries to have a more active part in the design and development of the engine as well as consolidation among its suppliers has resulted in new challenges for the company. To fulfill these new demands there is an interest in improving the company’s relationships and collaboration with its suppliers to improve efficiency, costs and lead-times for these projects.

    To achieve this, Volvo Aero gave us the task to study and analyze theories on the subject of supplier relationships to determine if there was anything substantial that could be applied to the new situations that the company faces.

    We based our studies on a wide range of theories with the objective of finding parameters that were applicable to Volvo Aero as well as having a definite impact on the supplier relationship. A lot of the theory that we found was based on the automotive industry and lean production, and from this we tried to narrow the theories we studied down to their most basic parameters. The parameters we searched for were those that reflected the specifics that make up a relation between two companies, for example the power balance in the relationship or the amount of adaptation and investment in the relation.

    From there we built a model where we applied and adapted our parameters to the specifics of Volvo Aero. The model we created is used to deduce what kind of relationship is appropriate given the reality that our parameters should have captured should have captured the basis for a relationship.

    We then applied this model to analyze three specific cases as well as a general analysis of the supplier relations of the company. The cases were supplier relations that Volvo Aero wanted us to study more in depth and on these we applied the model as usual. With the general analysis we were forced to do a more abstract reasoning where we based our analysis on the parameters and theories that made up the model.

    What we found from this analysis was that the model was working the way we intended and that it was possible to apply these theories to this company with good results. We also think that this model, with possibly small adjustments, should be applicable to a wide range of corporate relations as well as to other companies.

  • 13. Adlerborn, J
    et al.
    Björk, L
    Westman, Anna-Karin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Larker, H
    Particulate-reinforced ceramics densified by glass encapsulated HIP1991In: Hot isostatic pressing: Theory and applications / [ed] R J Schaefer; Melvin Linzer, Materials Park, Ohio: ASM International, 1991, 211-216 p.Conference paper (Refereed)
  • 14. Adrovic, Dzemil
    Utveckling av metoder att mäta centrering av skruvhål i skär2013Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There have been, in some rare cases, difficulties with clamping of inserts with U-holes

    in their tool holder. According to the complaints, the inserts could not be properly

    clamped or could fracture when clamped. A study has shown that variations in

    clamping behaviour are mainly depending by the position of the screw hole in the tool

    holder and the centering of the screw hole in the insert.

    The focus of this project has been the centering of screw hole in insert. It has been

    shown that the screw holes are not always enough centered in the insert. The

    problem may occur after a certain step in the production, i.e. peripheral grinding.

    Today, the centering can be measured by a certain measurement jig. The

    measurement jig has a very good Gauge R and R value but is not easy to use,

    especially if it is to be reinstated into the production. The aim of this thesis has been

    to use SmartScope for developing a new method for measuring the centering of

    screw hole in insert. The goal with the new method was to be able to measure faster

    and to be easier to use than the existing one.

    The project was started with exercises and exploration of some of the functions of

    SmartScope and its software Measuremind 3D. Parallel with this, a study was made of

    the existing documentation for a better understanding of the problem.

    A method which measures how well the screw holes are centered in their inserts has

    been developed. The method consists of a number of measuring tools which are

    joined into a measurement sequence. Measurements of single inserts are fully

    automated. Provided that a system which picks and puts the inserts in specific

    locations can be implemented, a series of inserts can be measured fully automated.

    This method is faster and especially more automated than the current measurement

    jig. Measurements have shown that the accuracy of the method is well within the

    tolerance and that it has a good repeatability.

  • 15.
    Aftab, Ahmad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Khan, Suleman
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    A stiffness modeling methodology for simulation-driven design of haptic devices2014In: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 30, no 1, 125-141 p.Article in journal (Refereed)
    Abstract [en]

    Efficient development and engineering of high performing interactive devices, such as haptic robots for surgical training benefits from model-based and simulation-driven design. The complexity of the design space and the multi-domain and multi-physics character of the behavior of such a product ask for a systematic methodology for creating and validating compact and computationally efficient simulation models to be used in the design process. Modeling the quasi-static stiffness is an important first step before optimizing the mechanical structure, engineering the control system, and performing hardware in the loop tests. The stiffness depends not only on the stiffness of the links, but also on the contact stiffness in each joint. A fine-granular Finite element method (FEM) model, which is the most straightforward approach, cannot, due to the model size and simulation complexity, efficiently be used to address such tasks. In this work, a new methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device is proposed, which considers the stiffness of actuation systems, flexible links and passive joints. For the modeling of passive joints, a hertzian contact model is introduced for both spherical and universal joints, and a simply supported beam model for universal joints. The validation process is presented as a systematic guideline to evaluate the stiffness parameters both using parametric FEM modeling and physical experiments. Preloading has been used to consider the clearances and possible assembling errors during manufacturing. A modified JP Merlet kinematic structure is used to exemplify the modeling and validation methodology.

  • 16.
    Aftab, Ahmad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Khan, Suleman
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kinematics and Dynamics of a novel 6-DoF TAU Haptic Device2011In: Proceedings of the 2011 IEEE International Conference on MechatronicsInternational Conference on Mechatronics, April 13-15, 2011, Istanbul, Turkey, IEEE conference proceedings, 2011, 719-724 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents the kinematics and dynamics modeling of a novel hybrid kinematic concept, i.e. the TAU haptic device. This new concept was obtained from the modification of TAU-2 structure proposed by Khan et al. First a kinematic model for inverse and forward kinematics was developed and analyzed. Then an algorithm to solve the close form inverse dynamics is presented using Lagrangian formulation. Numerical simulation was carried out to examine the validity of the approach and accuracy of the technique employed. A trigonometric helical trajectory of 5th order spline was developed in Cartesian space for each degree of freedom of the moving platform in order to verify and simulate the inverse dynamics; the motion of the platform is such that the tool centre point remains on this trajectory while its orientation is changing constantly in roll, pitch and yaw.

  • 17.
    Agenyi, Benjamin
    Blekinge Institute of Technology, Faculty of Engineering, Department of Industrial Economics.
    Mobile Banking and Entrepreneurship in Developing Countries:A case study of Nigeria2013Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    The purpose of this study was to identify ways by which entrepreneurial mobile banking growth could be accelerated in developing countries. An exploratory research method was adopted to identify the facilitators and obstacles to entrepreneurial mobile banking. The finding reveals some facilitators which include government policies and efforts of donor agencies, stiffer competition among banks, need for efficiency and lower cost, telecoms focus on customers retention. While some obstacles include conservative and vague regulation, security issues, underdeveloped infrastructures, lack of interoperability and lack of basic need for financial services. The main contribution of this study is the concise identification of the facilitators and obstacles to entrepreneurial mobile banking especially in developing countries. Suggestion for further study was made. The findings could be useful to policy-makers, donor agencies and other development partners in designing and directing their policies intervention

  • 18.
    Aggerstam, Elina
    et al.
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Lehman, Karolina
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Materialvalets miljöpåverkan på transporten: En jämförelsestudie mellan transporter till flerfamiljshus i trä och betong.2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Under året 2015 bedömde 240 av Sveriges 290 kommuner att det existerade ett underslott på bostäder. För att kunna möta behovet krävs det att många bostäder ska byggas på en kort tid. Med de klimathot som världen står inför krävs det att produktionen är uthållig och hållbar i längden. För att nå klimatmålen måste användandet av tunga fordon minskas, logistiken måste effektiviseras och alternativa transportmedel bör undersökas.

    Syftet med studien var att identifiera eventuella skillnader mellan byggnadsmaterialen trä och betong i transportledet. Med den insamalade datan togs olika relations- och nyckeltal fram som sedan utgjorde basen för de två formlerna som presenteras i studien.

    Resultatet av de olika relationstalen indikerar på att den lastade vikten inte har stor betydelse på hur mycket CO2 som släpps ut, utan att det är antalet transporter med tung lastbil som är grundproblemet till utsläppen och miljöpåverkan. Med formlerna som presenteras i studien kan antalet transporter som krävs till ett flerfamiljshus räknas ut, men även mängden CO2 som släpps ut vid fraktandet av planelementen.

  • 19.
    Agostini, Lara
    et al.
    University of Padova.
    Bengtsson, Lars
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Industrial economics. University of Gävle, Center for Logistics and Innovative Production.
    Lazzarotti, Valentina
    Carlo Cattaneo University LIUC.
    Manzini, Raffaella
    Carlo Cattaneo University LIUC.
    Nosella, Anna
    University of Padova.
    Pellegrini, Luisa
    Stefan, Ioana
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Industrial economics. University of Gävle, Center for Logistics and Innovative Production.
    Open innovation with scientific partners andpatenting: the moderating role of the internal context for innovation2017Conference paper (Refereed)
  • 20.
    Ah Shenga, Pedro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Luleå University of Technology.
    SAWING STRATEGIES FOR TROPICAL HARDWOOD SPECIES: Simulation studies based on industrial conditions of Mozambique2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The harvesting of Mozambique tropical hardwood species is considerable higher than the natural regrowth in the forest and the stock is decreasing drastically. Therefore, it is important to improve the material recovery when the wood is refined (i.e., in sawing and further refinement to products such as joineries, furniture etc.) to reduce the waste and to re-utilize efficiently the by-products to increase the added value. The wood processing industry is an important means to boost the industries in the rural areas and also to generate incomes for the local communities by creating jobs and business opportunities.

    The majority of the logging that can be used for sawmilling in Mozambique is exported as roundwood due to the inability of companies to meet the product standards set for export and to generate profit. The lack of capabilities of the local sawmills to generate profit, also foments the illegal logging because of the higher price of roundwood for export which contributes to increase the number of unlicensed individuals in harvesting. This threatens the law enforcement and thus the degradation of the local wood industry. An alternative to increase the profit and empower the local community could be to export more refined wood products such as sawn timber, parquet, and veneer instead of the roundwood.

    The objective of the work was to investigate alternative sawing strategies of tropical hardwood species that could increase the profitability of the Mozambique wood industry in general and at sawmill in particular. The subject was approached using a database of virtual logs and together with a sawing simulator. The thesis has two main focus areas: (1) creating the log database with the corresponding algorithms for sawing simulation, and (2) investigations of alternative sawing strategies.

    The first focus was to build the database of surface-scanned logs and develop the algorithm for the saw simulation. The results are a database of 15 logs models describing the logs outer shape in which 10 jambirre (Millettia stuhlmannii Taub.) and 5 umbila (Pterocarpus angolensis DC.), and the algorithm for the sawing simulation. The algorithm use “brute force” i.e., determines all volume yields of sawn timber from the combination of all settings of log-positioning parameters (offset, skew and rotation) and selects the maximum value of volume yield. From simulation, using three sawing patterns (cant-sawing, through-and-through sawing and square-sawing) combined with two positioning parameters (offset and rotation) it was found that the sawing pattern has great impact on volume yield and that the square-sawing gave higher yield followed by through-and-through sawing pattern.

    The second focus was on alternative sawing strategies; having in mind that the optimal volume yield is achieved by aid of computerized production systems and that these resources are not yet in use in Mozambique. Hence, the objective was to find the positioning parameters that can be set manually and improve the volume yield. The result have shown that the rotation is the most affecting parameter followed by offset and skew, and that the volume yield can decrease by between 7.7% and 12.5% from the optimal positioning when the logs are manually positioned with the knowledge about the optimal log position. In another study, using crook-up or horns-down positioning as alternative to the optimal positioning, the volume yield decreases by between 10% and 13% from the optimal positioning. By using bucked logs , the optimal volume yield increased by between 8% and 13% in relation to full lengths logs, and the volume yield of bucked logs when using crook up positioning decreases 2% in relation to optimal positioning of full length logs.

    It is concluded that there is an unexploited value potential in the wood chain which can be reached using alternative positioning and modern measurement techniques and that the grading of wood will facilitate and improve the sawing process.

  • 21.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    External Log Scanning for Optimizing Primary Breakdown of Tropical Hardwood Species2015Conference paper (Other academic)
    Abstract [en]

    The sawing of tropical hardwood species is a big challenge for sawmills in developing countries. In order to investigate sawing strategies and volume recovery of tropical hardwood species, a log shape database was created using a portable 3D laser scanner. The data were collected in Mozambique, where twelve Jambirre (Millettia stuhlmannii Taub.) and five Umbila (Pterocarpus angolensis DC) logs were scanned. The logs were selected among the most commercialized species and the crook was the main selection parameter. In addition, straight logs were incorporated as reference. A saw simulation Matlab algorithm that combines skew and rotation was developed. The results show that point cloud data from the 3D scanner provide detailed models of the external log geometry and accurately describe the log shapes and volumes. Preliminary results from breakdown simulation revealed that the through-and-through sawing pattern yields more than the cant saw pattern and that the increase in yield was almost the same for both species.

  • 22.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulated Breakdown of Two Tropical Hardwood Species2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, 450-456 p.Article in journal (Refereed)
    Abstract [en]

    A simulation study has been performed on a small log database of tropical hardwoods consisting of 10 Jambirre (Millettia stuhlmannii Taub.) and 5 Umbila (Pterocarpus angolensis D.C.) logs. The outer log shape was acquired by a 3D laser scanner before sawing and the heartwood content was estimated by measurement on images of the centre slabs after through-and-through sawing. Yield and value recovery using different sawing techniques and different sawing patterns, together with rotational and skew positioning errors, are presented. The results show that through-and-through sawing in the best rotation and skew positions tested improves the yield of Umbila logs by an average of 4.5 percentage points and Jambirre logs by 3.6 percentage points compared to cant sawing. It can be concluded that positioning and sawing patterns have a great influence on the yield and value recovery of these species and that log grade and species have an impact on the sawing pattern that should be used.

  • 23.
    Ah Shenga, Pedro António
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Simulation of Tropical Hardwood Processing: Sawing Methods, Log Positioning, and Outer Shape2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 4, 7640-7652 p.Article in journal (Refereed)
    Abstract [en]

    To increase understanding of breakdown strategies for Mozambican timber, simulations were carried out using different sawing patterns that can be alternatives to the low degree of refinement performed for export today. For the simulations, 3D models of 10 Jambirre and 5 Umbila logs were used. The log shape was described as a point cloud and was acquired by 3D-laser scanning of real logs. Three sawing patterns (cant-sawing, through-and-through sawing, and square-sawing) were studied in combination with the log positioning variables skew and rotation. The results showed that both positioning and choice of sawing pattern had a great influence on the volume yield. The results also showed that the log grade had an impact on the sawing pattern that should be used for a high volume yield. The volume yield could be increased by 3 percentage points by choosing alternative sawing patterns for fairly straight logs and by 6 percentage points for crooked logs, compared to the worst choice of sawing pattern.

  • 24.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    3D Phase-shift Laser Scanning of Log Shape2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, 7593-7605 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, a portable scanner to determine the 3D shape of logs was evaluated and compared with the measurement result of a computer tomography scanner. Focus was on the accuracy of the shape geometry representation. The objective is to find a feasible method to use for future data collection in Mozambique in order to build up a database of logs of tropical species for sawing simulations. The method chosen here was a 3D phase-shift laser scanner. Two logs, a birch log with bark and a Scots pine log without bark, were scanned, resulting in 450 cross sectional “images” of the pine log and 300 of the birch log. The areas of each point cloud cross section were calculated and compared to that of the corresponding computer tomography cross section. The average area difference between the two methods was 2.23% and 3.73%, with standard deviations of 1.54 and 0.91, for the Scots pine and birch logs, respectively. The differences in results between the two logs are discussed and had mainly to do with presence of bark and mantle surface evenness. Results show that the shape measurements derived from these methods were well correlated, which indicates the applicability of a 3D phase-shift laser scanning technology for gathering log data.

  • 25.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 4, 257-262 p.Article in journal (Refereed)
    Abstract [en]

    The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber.

  • 26.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bomark, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, 9560-9571 p.Article in journal (Refereed)
    Abstract [en]

    This study investigated the effect of the positioning of the log before sawing on the volume yield of sawn timber from tropical hardwood species. Three positioning parameters were studied, the offset, skew, and rotation, combined with two sawing patterns of cant-sawing and through-and-through sawing. A database consisting of two tropical hardwood species with very different outer shapes, jambirre (Millettia stuhllmannii Taub.) and umbila (Pterocarpus angolensis DC.), was used to simulate the sawing process. The result of the simulation revealed that, according to the combined effect of offset, skew, and rotation positioning, the positioning of the log before sawing is extremely important to achieve a high volume yield of sawn timber. The positioning parameter that has the highest effect on the volume yield is the rotation, and the variation in the volume yield associated with a deviation in the positioning can reduce the volume yield of sawn timber by between 7.7% and 12.5%.

  • 27.
    Ah Shenga, Pedro
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    A review of Mozambican wood exploitation: map of the processing chain2013In: Proceedings of the 21th International Wood Machining Semina: August 4th – 7th, Tsukuba International Congress Center, Japan, 2013, 293-301 p.Conference paper (Other academic)
  • 28.
    Ahlm, Andreas
    et al.
    Jönköping University, School of Engineering, JTH, Industrial Engineering and Management.
    Salo, Erik
    Jönköping University, School of Engineering, JTH, Industrial Engineering and Management.
    Beslutsprocess för sourcingbeslut2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    It seems like outsourcing often does not live up to the expected results. Furthermore, sourcing decisions are often unplanned and improvised based upon insufficient short term foundation. Poor basis for sourcing decisions can lead to that some important factors, which can result in long term consequences, could get overlooked in the decision foundation.

    The purpose of the master thesis is to create a structured decision process that could lead to a well balanced sourcing decision and apply this at Husqvarna AB.

    The method used is a case study which includes a theoretical and an empirical study.

    The decision process is based upon the theoretical framework and is structured as a number of activities. Each activity includes a number of questions that should be answered if a well balanced sourcing decision is to be made. The questions are developed so that they include all the factors that could be affected by outsourcing.

    The case at Husqvarna AB was analyzed and evaluated by using the theoretical decision process. This showed how the decision process can be used by Husqvarna AB.

    The conclusion of the thesis is that the purpose was fulfilled since a decision process was developed that could be applied at Husqvarna AB.

  • 29.
    Ahlqvist, Nicolin
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Rydh, Mathilda
    Mälardalen University, School of Innovation, Design and Engineering.
    Valideringssystem för diskmaskin inom vården2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete har tagit upp frågan om hur ett valideringssystem inom vården skulle kunna fungera på bästa sätt samt dess design

  • 30.
    Ahlsén, David
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    Fartygsprojektering och Flytande havsbaserad vindkraft2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Den här rapporten behandlar tre områden anknutna till den gemensamma sektorn marina system. Inledningsvis beskrivs sjöfartsnäringens olika delar däribland olika typer av gods och fartygstyper samt sjöfartens aktörer och reglerande organ. Sjöfarten diskuteras med hänsyn till miljö och visar att godstransport till havs är relativt energieffektivt, men att alla typer av gods inte kan motiveras ur ett hållbart perspektiv.

    En inledande fartygsprojektering genomförs för ett transportscenario där 5500 ton kiwifrukt ska transporteras från Nya Zeeland till länder kring Östersjön inom en tidsrymd som garanterar att frukten håller god kvalitet. Fartygstypen är ett kylfartyg dimensionerat att rymma lasten, minimera motstånd och uppfylla stabilitetskriterier från IMO. För att uppfylla transportscenariot är fartyget designat för en marschfart på 20 knop, med ett deplacement på 12500 ton, en längd på 138 m, 21 m i bredd och ett djupgående på 7.7 m.

    Avslutningsvis identifieras kriterier och förutsättningar för flytande havsbaserad vindkraft. Detta med syfte genomföra en inledande projektering av en vindkraftpark stor nog att Gotland kan täcka sin elkonsumtion med endast förnybara energikällor. Parken anläggs längs en ny kabelanslutning mellan Gotland och fastlandet utom synhåll från såväl Gotland, Öland och fastlandet. Området uppfyller krav på vindförhållanden och utgörs av 24 vindkraftverk med kapacitet på 5 MW vardera.

  • 31.
    Ahmad, Aftab
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Effective development of haptic devices using a model-based and simulation-driven design approach2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Virtual reality (VR)-based surgical simulators using haptic devices can increase the effectiveness of surgical training for surgeons when performing surgical procedures in hard tissues such as bones or teeth milling. The realism of virtual surgery through a surgical simulator depends largely on the precision and reliability of the haptic device, which reflects the interaction with the virtual model. The quality of perceptiveness (sensation, force/torque) depends on the design of the haptic device, which presents a complex design space due to its multi-criteria and conflicting character of functional and performance requirements. These requirements include high stiffness, large workspace, high manipulability, small inertia, low friction, high transparency, and cost constraints.

    This thesis proposes a design methodology to improve the realism of force/torque feedback from the VR-based surgical simulator while fulfilling end-user requirements.

    The main contributions of this thesis are:

    1. The development of a model-based and simulation-driven design methodology, where one starts from an abstract, top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized.

    2. A methodology for creating an analytical and compact model of the quasi-static stiffness of a haptic device, which considers the stiffness of actuation systems, flexible links and passive joints.

    3. A robust design optimization approach to find the optimal numerical values for a set of design parameters to maximize the kinematic, dynamic and kinetostatic performances of a 6-degrees of freedom (DOF) haptic device, while minimizing its sensitivity to variations in manufacturing tolerances and cost, and also satisfying the allowed variations in the performance indices.

    4. A cost-effective approach for force/torque feedback control using force/torque estimated through a recursive least squares estimation.

    5. A model-based control strategy to increase transparency and fidelity of force/torque feedback from the device by compensating for the natural dynamics of the device, friction in joints, gravity of platform, and elastic deformations.

     

  • 32.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A deterministic and probabilistic approach for robust optimal design of a 6-DOF haptic device2014In: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference--2013: Volume 3 B, 2013, ASME Press, 2014, V03BT03A032- p.Conference paper (Refereed)
    Abstract [en]

    This work suggests a two-stage approach for robust optimal design of 6-DOF haptic devices based on a sequence of deterministic and probabilistic analyses with a multi-objective genetic algorithm and the Monte-Carlo method. The presented model-based design robust optimization approach consider simultaneously the kinematic, dynamic, and kinetostatic characteristics of the device in both a constant and a dexterous workspace in order to find a set of optimal design parameter values for structural configuration and dimensioning. Design evaluation is carried out based on local and global indices, like workspace volume, quasi-static torque requirements for the actuators, kinematic isotropy, dynamic isotropy, stiffness isotropy, and natural frequencies of the device. These indices were defined based on focused kinematic, dynamic, and stiffness models. A novel procedure to evaluate local indices at a singularity-free point in the dexterous workspace is presented. The deterministic optimization approach neglects the effects from variations of design variables, e.g. due to tolerances. A Monte-Carlo simulation was carried out to obtain the response variation of the design indices when independent design parameters are simultaneously regarded as uncertain variables. It has been observed that numerical evaluation of performance indices depends of the type of workspace used during optimization. To verify the effectiveness of the proposed procedure, the performance indices were evaluated and compared in constant orientation and in dexterous workspace.

  • 33.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Andersson, Kjell
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Elements.
    An approach to stiffness analysis methodology for haptic devices2011In: 2011 3rd International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT), IEEE conference proceedings, 2011, , 8 p.1-8 p.Conference paper (Refereed)
    Abstract [en]

    In this work a new methodology is proposed to model the static stiffness of a haptic device. This methodology can be used for other parallel, serial and hybrid manipulators. The stiffness model considers the stiffness of; actuation system; flexible links and passive joints. For the modeling of the passive joints a Hertzian contact model is introduced for both spherical and universal joints and a simply supported beam model for universal joints. For validation of the stiffness model a modified JP Merlet kinematic structure has been used as a test case. A parametric Ansys FEM model was developed for this test case and used to validate the resulting stiffness model. The findings in this paper can provide an additional index to use for multi-objective structural optimization to find an optimum compromise between a lightweight design and the stiffness performance for high precision motion within a larger workspace.

  • 34.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A model-based and simulation-driven methodology for design of haptic devices2014In: Mechatronics (Oxford), ISSN 0957-4158, Vol. 24, no 7, 805-818 p.Article in journal (Refereed)
    Abstract [en]

    High precision and reliable haptic devices are highly complex products. The complexity that has to be carefully treated in the design process is largely due to the multi-criteria and conflicting character of the functional and performance requirements. These requirements include high stiffness, large work-space, high manipulability, small inertia, low friction, high transparency, as well as cost constraints. The requirements are a basis for creating and assessing design concepts. Concept evaluation relies to a large extent on a systematic usage of kinematic, dynamic, stiffness, friction, and control models. The design process can benefit from a model-based and simulation-driven approach, where one starts from an abstract top-level model that is extended via stepwise refinements and design space exploration into a detailed and integrated systems model that can be physically realized. Such an approach is presented, put in context of the V-model, and evaluated through a test case where a haptic device, based on a Stewart platform, is designed and realized. It can be concluded, based on simulation and experimental results that the performance of this deterministically optimized haptic device satisfies the stated user requirements. Experiences from this case indicate that the methodology is capable of supporting effective and efficient development of high performing haptic devices. However, more test cases are needed to further validate the presented methodology.

  • 35.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    An optimization approach towards a robust design of 6-DOF haptic devicesManuscript (preprint) (Other academic)
  • 36.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Model-based control strategy for 6-DOF haptic devicesManuscript (preprint) (Other academic)
  • 37.
    Ahmad, Aftab
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Kjell, Andersson
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Boegli, Max
    Evaluation of friction models for haptic devices2013Conference paper (Refereed)
    Abstract [en]

    In this work different friction models are evaluated to determine how well these models are suited for performance simulation and control of a 6-DOF haptic device. The studied models include, Dahl model, LuGre model, Generalized Maxwell slip model (GMS), smooth Generalized Maxwell slip model (S-GMS) and Differential Algebraic Multistate (DAM) friction model. These models are evaluated both numerically and experimentally with an existing 6-DOF haptic device that is based on a Stewart platform. In order to evaluate how well these models compensate friction, a model-based feedback friction compensation strategy along with a PID controller were used for position fracking accuracy The accuracies of the friction compensation models are examined separately for both low-velocity and high-velocity motions of the system. To evaluate these models, we use criteria based on fidelity to predict realistic friction phenomena, easiness to implement, computational efficiency and easiness to estimate the model parameters. Experimental results show that friction compensated with GMS, S-GMS and DAA4 models give better accuracy in terms of standard deviation, Root Mean Squared Error, and maximum error between a reference and measured trajectory. Based on the criteria of fidelity, ease of implementation and ease to estimate model parameters, the S-GMS model, which represents a smooth transition between sliding and pre-sliding regime through an analytical set of differential equations, is suggested.

  • 38.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cloutier, Alain
    Wood Research Center (CRB), Department of Wood and Forest Sciences, Faculty of Forestry, Geography and Geomatics, Laval University, Quebec.
    Fang, Chang-Hua
    Wood Research Center (CRB), Department of Wood and Forest Sciences, Faculty of Forestry, Geography and Geomatics, Laval University, Quebec.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 24, 8571-8579 p.Article in journal (Refereed)
    Abstract [en]

    Approximately, 13.5 % of the standing volume of productive forest land in Sweden is covered by birch and aspen, which provides the vast potential to produce value-added products such as densified wood. This study shows whether it is possible to densify those species with a thermo-hygro-mechanical (THM) process using heat, steam, and pressure. In this process, transverse compression on thin European aspen (Populus tremula) and downy birch (Betula pubescens) boards was performed at 200 ºC with a maximum steam pressure of 550 kPa. To obtain a theoretical 50 % compression set, the press’s maximum hydraulic pressure ranged from 1.5 to 7.3 MPa. Preliminary tests showed that ~75 % of the birch boards produced defects (blisters/blows) while only 25 % of the aspen boards did. Mainly, radial delamination associated with internal checks in intrawall and transwall fractures caused small cracks (termed blisters) while blows are characterized by relatively larger areas of delamination visible as a bumpy surface on the panel. Anatomical investigations revealed that birch was more prone to those defects than aspen. However, those defects could be minimized by increasing the pre-treatment time during the THM processing.

  • 39.
    Ahmed, Sheikh Ali
    et al.
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Blom, Åsa
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University.
    Effect of oil impregnation on water repellency, dimensional stability and mold susceptibility of thermally-modified European aspen and downy birch wood2017In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 63, no 1, 74-82 p.Article in journal (Refereed)
    Abstract [en]

    Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study is to investigate if these properties enhanced in thermally-modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC, showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth. Whereas, a significant anti-mold effect was observed on Beckers oil treated samples.

  • 40.
    Ahrén, Mats
    et al.
    Linköping University, Department of Management and Engineering.
    Dahllöf, Martin
    Linköping University, Department of Management and Engineering.
    Utformning av planerings- och styrningssystem för tillverkning av luckor till Boeing 787: en studie vid Saab Aerostructures2008Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Saab Aerostructures är en del av Saab-koncernen och företaget utvecklar och tillverkar strukturer för flygindustrin. Tillverkningen av stridsflygplan är den dominerande verksamheten, men antalet civila projekt ökar stadigt. I många av de civila projekten verkar Saab Aerostructures som underleverantör till antingen Boeing eller Airbus. Det finns flera skillnader mellan de militära och de civila projekten, exempelvis är leveranstakten betydligt högre i de civila projekten. I och med de förändrade förutsättningarna görs försök med att tillämpa lean production. Detta har påbörjats i två pilotprojekt varav ett är tillverkningen av luckor till Boeing 787.

    Syftet med denna rapport är att komma med rekommendationer för hur produktionen av luckor till Boeing 787 skall planeras och styras. Då företaget började använda ett nytt ERP-system under hösten 2006, är det även av intresse att se hur detta system skall användas utefter de rekommendationer som uppkommer. För att utreda dessa frågor undersöks både produktionsstrategiska och operativa aspekter i de två produktionsavsnitten Sammanbyggnad och Kompositverkstad.

    Sammanlagt tillverkas sju olika luckor, varav de två största produceras i en lina som håller en jämn produktionstakt. Projektet är försenat, bland annat på grund av svårigheter att tillverka de 20 kompositartiklar som ingår i de tre största luckorna. Komposittillverkningen sker i en funktionell verkstad, med många transporter mellan byggnader för att knyta ihop flödet. Undersökningen visar att Saab Aerostructures har en mismatch mellan planeringsstrategin och den kapacitetsstrategi som tillämpas i Kompositverkstaden. Företaget försöker följa den efterfrågan de olika projekten har, men har samtidigt ont om kapacitet. Det leder till överbeläggning och leveranssvårigheter. På grund av kapacitetsbristen bör en cyklisk planering användas i Kompositverkstaden, där flaskhalsen styr takten. På detta sätt kan kötiderna i verkstaden minskas. Kompositverkstaden bör bli mer flödesinriktad för att minska ledtider och få till en enklare styrning. På detta sätt blir det möjligt att hålla en jämn leveranstakt även för dessa artiklar.

    Tillverkningstider, kötider och transporttider i ERP-systemet bör anpassas efter den cykliska planeringen som tas fram. Att uppdatera dessa tider blir extra viktigt i inkörningsförloppet, då tiderna är betydligt längre och varierar kraftigt. På grund av den hantverksmässiga produktionen i Kompositverkstaden och den stora kassationsrisken som föreligger är det viktigt att införa säkerhetsmekanismer. När den cykliska planeringen tas fram bör en säkerhetsledtid användas för de operationer som har stor variation i operationstid. För att inte linan skall stå stilla vid störningar är det även viktigt att skapa buffertar, dels innan linan men även framför den flaskhals som identifieras i flödet.

    Produktionstakten för kompositartiklarna är högre än takten i Sammanbyggnad, vilket inte stöds av ERP-systemet. För att systemet ändå skall föreslå rätt antal tillverkningsorder bör en kassationsfaktor användas. På detta sätt ges stöd för den långsiktiga planeringen. Slutligen visar undersökningen att styrning via ett kanbansystem ej bör genomföras, främst på grund av de höga kassationstalen och produktionsupplägget som en funktionell verkstad.

  • 41.
    Ahvenlampi Svensson, Amanda
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Exploring challenges in a verification process - when adapting production processes to new environmental requirements2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The requirements on the products and production processes within the manufacturing industry are continuously increasing according to environmental standards. The new requirements are coming from a growing awareness of what our planet can provide for example by the global challenge of climate change. The industry needs to reduce energy consumption and waste to meet the upcoming requirements.

    One of the processes with high environmental impact in a discrete manufacturing industry is the paint shop. Surface treatment is also of great importance to maintain a high quality product. In scientific literature, technological risk is one of the barriers in implementing environmental conscious manufacturing. Therefore the area of sustainable operations management needs building bridges with other functions and disciplines such as economics, strategies and behavioral sciences in order to manage the transitions. The supply of competence around paint shops today is usually provided by suppliers and other sources within the industry and to make the collaboration to work is essential. In this process of collaboration with external sources, substantial measurements are required to maintain the desirable quality. In order to ensure the competence of testing the quality eventuate when switching technology at a pre-treatment line, this report sets out to explore what the challenges to be taken into consideration are when to assure the product- and- process quality. To respond to this question, a multiple case study is conducted during spring 2016 where the phenomenon to study is the change process and the unit of analysis is the challenges that can be faced during the verification process. The case studied is automotive companies located in Sweden which are producing components for heavy duty vehicles. Data collection is performed by studying documents, participatory observations and semi-structured interviews. The results will give insights to academia on what challenges that are occurring during the verification process of implementing new and cleaner technologies. The conclusions are drawn upon the literature and the empirical results. The managerial implications are to increase the awareness of any potential barriers in the verification process in order to be prepared for managing the technological change process.

  • 42.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Dynamics of some vibro-impacting systems with amplitude constraints1995Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the dynamics of some vibro-impacting systems with fixed or moving amplitude constraints. It is based on and includes five papers, marked A to E. Simple models of three different vibro-impacting systems with applications in the fields of impact hammers, granular flow and disk brakes in vehicles are analysed. A 2-DOF (two-degree-of-freedom) model of a threshold-limited impact hammer is studied (Paper A). The stability of a class of periodic motions is analysed. For some parameter values these periodic motions are found to be qualitatively similar to the ones observed for a corresponding 1-DOF system. At other parameter combinations, however, new kinds of periodic or chaotic motions can be observed. For low damping, phenomena resembling antiresonance for linear systems can also be observed. Granular shear flows show a transitional behaviour in the rapid flow regime as the shear speed or the concentration of the grains is varied. The motion can, for example, change from smooth and orderly to erratic and turbulent. Some aspects of this transitional behaviour in granular shear flow are studied numerically, analytically and experimentally (Papers B, C and D). Simple vibro-impacting models are suggested to get some analytical insight into the dynamics of shear layers. Results from a 1-DOF model show that for high forcing frequencies, which correspond to high shear speeds, periodic as well as chaotic motions can exist, whereas, for low forcing frequencies the vibrations are completely damped out to a stationary state (Paper B). Stability of this stationary state is studied analytically (Paper C), and experimentally (Paper D), where the motions of granular particles in a transparent shear cell are followed by using video techniques. For low shear speeds a single shear layer adjacent to the bottom boundary of the shear cell is observed. As the shear speed is increased, a transition to a random like state involving many layers is found to occur. In order to understand the phenomenon of squeal in disk brakes, a 3-DOF model is suggested to simulate the dynamics of a brake pad. The region of contact between the brake pad and the disk is described by using a coefficient of friction and distributed stiffness. The brake pad is allowed to have adjustable support locations and possibilities of impacts with its surroundings. The equilibrium state of the pad is determined by using a static analysis. The assumption is that the instability of this stationary state is a possible explanation of squeal, therefore, the stability is analysed in detail. Examples of different kinds of pad motions are presented. A rich variety of motions are found to exist including periodic, seemingly chaotic, stationary behaviour in slip, vibrations with full contact with the disk, stick-slip and impacts.

  • 43.
    Aidanpää, Jan-Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Multiple solutions in a rub-impact Jeffcott rotor2004In: Extended abstracts, proceedings: 10th international symposium on transport phenomena and dynamics of rotating machinery / [ed] Dieter Bohn, Aachen: Inst. of steam and gas turbines, RWTH , 2004Conference paper (Refereed)
  • 44.
    Aidanpää, Jan-Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Gustavsson, Rolf K.
    Vattenfall, VRD.
    Lundström, Niklas L. P.
    Umeå university.
    Karlsson, Martin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Calleecharan, Yogeshwarsing
    Nässelqvist, Mattias
    Karlberg, Magnus
    Lundin, Urban
    Uppsala University.
    Developments in rotor dynamical modeling of hydropower units2009In: Proceedings of the IUTAM Symposium on Emerging Trends in Rotor Dynamics: held in New Delhi, India, March 23 - March 26, 2009 / [ed] Kshitij Gupta, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2009Conference paper (Refereed)
  • 45.
    Aidanpää, Jan-Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Shen, Hayley
    Clarkson University, Potsdam, NY.
    Onset of transition for cohesive and viscous granular flows1998In: Journal of engineering mechanics, ISSN 0733-9399, E-ISSN 1943-7889, Vol. 124, no 10, 1073-1079 p.Article in journal (Refereed)
    Abstract [en]

    A theory for determining the onset of rapid flow or termination of quasi-static flow in a cohesive granular material mixed in a viscous interstitial fluid is presented. This theory is based on a one-dimensional model introduced in an earlier paper. Linear stability analysis is used to find the combination of material properties and flow rate for which a quasi-static flow becomes unstable, indicating the onset of rapid flow. This theory yields a quantitative criterion to select appropriate constitutive laws for viscous and cohesive granular material. This criterion is a linear approximation of the theoretical result. While it provides the critical condition for quasi-static flow to terminate, it does not give the transitional constitutive law before a rapid flow is fully developed, for which a second power law dependence on the strain rate applies. Nonetheless, the analysis and modeling effort presented in this work are necessary first steps toward a general quantification of how granular materials, with identical physical composition, can behave in drastically different ways.

  • 46.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    A portable roller ski rolling resistance measurement system2013In: The Impact of Technology on Sport V: Procedia Engineering / [ed] Subic A, Fuss FK, Clifton P, Chan KM., Elsevier, 2013, 79-83 p.Conference paper (Refereed)
    Abstract [en]

    Roller skis are used by cross-country skiers, biathletes and ski-orienteers for their snow-free training and in roller ski competitions. Additionally, much of the current sports research into the physiology and biomechanics of crosscountry skiing is conducted indoors on treadmills using roller skis. For elite athletes, the differences in performance are quite small, thus emphasising the importance of knowing the roller skis' rolling resistance coefficient, especially in connection to research and roller ski competitions. The purpose of this study was to develop a roller ski rolling resistance measurement system (P-RRMS) that is portable and therefore useful in different contexts and locations. The P-RRMS was designed as a small treadmill, equipped with roller ski stabilizing lateral supports and a screwed bar for applying different vertical loads on the roller ski. The design uses only one force sensor, with possible measurements of three directions of force and torque around three axes. The weight of the P-RRMS is 100 kg and it is equipped with wheels to facilitate transportation.

  • 47.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Classical style constructed roller skis and grip functionality2011In: Procedia Engineering: The Impact of Technology on Sports IV / [ed] Subic A., Fuss F.K., Alam F., Clifton P., Elsevier, 2011, 4-9 p.Conference paper (Refereed)
    Abstract [en]

    Roller skis are used by cross-country skiers for snow-free training, with the aim of imitating skiing on snow. The roller skis on the market that are constructed for use in the classical style are equipped with a front and a back wheel, one of which has a ratchet to enable it to grip the surface when diagonal striding and kick double poling.

    A new type of roller ski was constructed with a function which makes it necessary to use the same kick technique as that used on snow, i.e. the ski has a camber that must be pushed down to obtain grip. Its stiffness can be adjusted based on factors that influence grip, i.e. the skier’s bodyweight and technical skiing skills.

    Thus, our aim was to make comparative measurements as regards grip between ratcheted roller skis and the roller ski with a camber and compare with previous published results for grip waxed skis during cross-country skiing on snow.  The measurements were carried out using specially developed equipment, with a bottom plate and an overlying rubber mat of the same type as used on many treadmills and a function for applying different loads and generating traction on the back of the roller ski.

  • 48.
    Ainegren, Mats
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering and Sustainable Development.
    The multi functional roller ski2012Conference paper (Refereed)
  • 49.
    Akkerman, Vyacheslav
    et al.
    West Virginia University, Morgantown, WV, United States.
    Bilgili, Serdar
    West Virginia University, Morgantown, WV, United States.
    Bychkov, Vitaly
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Demir, Sinan
    West Virginia University, Morgantown, WV, United States.
    Morella, Haley
    West Virginia University, Morgantown, WV, United States.
    Impacts of the Lewis and Markstein numbers effects on the flame acceleration in channels2016In: 2016 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2016, Eastern States Section of the Combustion Institute , 2016Conference paper (Refereed)
    Abstract [en]

    The effects of flame stretch and thermal/molecular diffusion on the flame acceleration in channels are quantified by means of the analytical and computational endeavours. The internal transport flame properties are accounted in the theory by means of the Markstein number, Mk. Being a positive or negative function of the thermal-chemical combustion parameters, such as the thermal expansion ratio and the Lewis and Zeldovich numbers, the Markstein number either moderates or promotes the flame acceleration. While Mk may provide a substantial impact on the flame acceleration rate in narrow channels, this effects diminishes with the increase of the channel width. The analysis is accompanied by extensive computational simulations of the Navier-Stokes combustion equations, which clarify the impact of the Lewis number on the flame acceleration. It is obtained that, for Le below a certain critical value, at the initial stage of flame acceleration, a globally-convex flame front is splits into two or more "fingers", accompanied by a drastic increase in the flame surface area and associated enhancement of the flame acceleration. Overall, the thermal-diffusive effects substantially facilitate the flame acceleration scenario, thereby advancing a potential deflagration-to-detonation transition. 

  • 50.
    Akkerman, Vyacheslav
    et al.
    Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV, United States .
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Effect of gas compression on flame acceleration in obstructed cylindrical tubes2016In: 2016 Spring Technical Meeting of the Eastern States Section of the Combustion Institute, ESSCI 2016, Eastern States Section of the Combustion Institute , 2016Conference paper (Refereed)
    Abstract [en]

    The role of gas compression on the process of extremely fast flame acceleration in obstructed cylindrical tubes is studied analytically and validated by computational simulations. The acceleration leading to a deflagration-to-detonation transition is associated with a powerful jet-flow produced by delayed combustion in spaces between the obstacles. This acceleration mechanism is Reynolds-independent and conceptually laminar, with turbulence playing only a supplementary role. In this particular work, the incompressible formulation [Combust. Flame 157 (2010) 1012], Ref. 15 is extended to account for small but finite initial Mach number up to the first-order terms. While flames accelerate exponentially during the initial stage of propagation, when the compressibility is negligible, with continuous increase in the flame velocity with respect to the tube wall, the flame-generated compression waves subsequently moderate the acceleration process by affecting the flame shape and velocity, as well as the flow driven by the flame. It is demonstrated that the moderation effect is substantial, and as soon as gas compression is relatively small, the present theory is in good quantitative agreement with the computational simulations. The limitations of the incompressible theory are thereby underlined, and a critical blockage ratio for with this acceleration mechanism can be evaluated.

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