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  • 1.
    Baek, Seung Ki
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Cluster Monte Carlo study of magnetic dipoles2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 3, s. 2381-2386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We implement a cluster-update Monte Carlo algorithm to simulate magnetic dipoles of the XY-spin type, confined in the two-dimensional plane. The long-range character and anisotropy in the dipole interaction are handled by the Luijten-Bl\"ote algorithm and the Dotsenko-Selke-Talapov algorithm, respectively. We have checked performance of this algorithm in comparison to the Metropolis algorithm and found that it equilibrates the system faster in terms of the number of flipped spins, although the overall computational complexity of the problem remains the same.

  • 2. Benyattou, T.
    et al.
    Martin, M.
    Orobtchouk, R.
    Talneau, A.
    Berrier, Audrey
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Mulot, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Anand, Srinivasan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Optical Bloch waves studied by near optical field microscopy2005Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 47, s. S72-S75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Photonic bandgap structures are very promising for the integration of optical function at the nanoscale level and particularly 2D structures perforated on a slab waveguide. In this context, photonic crystal waveguides obtained by removing rows of holes in the periodic structure are very interesting. We will present here, results of near field optical microscopy conducted on PCW. With a Fourier transform analysis of the image, we can image the Bloch waves propagating in the waveguide. The results are compared to FDTD simulations and we will show that the images obtained correspond to the electric field. Such result allows us to study the interaction of the optical tip with the electromagnetic field. 2D FDTD simulations of 1D photonic crystal interaction with a SNOM tip is presented. The results obtained confirm that the SNOM signal is mainly related to the electric field.

  • 3. Bevilacqua, R.
    et al.
    Pomp, S.
    Simutkin, V. D.
    Tippawan, U.
    Hayashi, M.
    Hirayama, S.
    Naitou, Y.
    Watanabe, Y.
    Prokofiev, A. V.
    Hjalmarsson, A.
    Andersson, P.
    Blomgren, J.
    Osterlund, M.
    Tesinsky, Milan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Lecolley, F. -R
    Marie, N.
    Kolozhvari, A.
    Light-Ion Production in the Interaction of 175 MeV Neutrons with Iron and Bismuth2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1701-1704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have measured double-differential (angle and energy) cross sections for light-ion (p, d, t, (3)He, and a) production in the interaction of quasi-monoenergetic 175 MeV neutrons with iron and bismuth. Measurements have been performed at the The Svedberg Laboratory, Uppsala (Sweden), using the Medley setup which allows low-energy thresholds and wide energy and angular ranges. Medley is a spectrometer system consisting of eight three-element telescopes placed at angles from 20 degrees to 160 degrees, in steps of 20 degrees. Each telescope is composed of two silicon surface barrier detectors and a CsI(Tl) scintillator, to perform particle identification, fully stop the produced light-ions and measure their kinetic energy. The time-of-flight was used to reduce the contribution from the low energy tail in the accepted incident neutron spectrum. We report double-differential production cross sections for protons, deuterons, tritons, (3)He and alpha particles and compare them with model calculations with TALYS-1.2.

  • 4.
    Bevilacqua, Riccardo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Simutkin, Vasily D.
    Tippawan, U.
    Hayashi, M.
    Hirayama, S.
    Naitou, Y.
    Watanabe, Y.
    Prokofiev, Alexander V.
    Uppsala universitet, The Svedberg-laboratoriet.
    Hjalmarsson, Anders
    Uppsala universitet, The Svedberg-laboratoriet.
    Andersson, P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Blomgren, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Tesinsky, M.
    Lecolley, F. -R
    Marie, N.
    Kolozhvari, A.
    Light-Ion Production in the Interaction of 175 MeV Neutrons with Iron and Bismuth2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1701-1704Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have measured double-differential (angle and energy) cross sections for light-ion (p, d, t, (3)He, and a) production in the interaction of quasi-monoenergetic 175 MeV neutrons with iron and bismuth. Measurements have been performed at the The Svedberg Laboratory, Uppsala (Sweden), using the Medley setup which allows low-energy thresholds and wide energy and angular ranges. Medley is a spectrometer system consisting of eight three-element telescopes placed at angles from 20 degrees to 160 degrees, in steps of 20 degrees. Each telescope is composed of two silicon surface barrier detectors and a CsI(Tl) scintillator, to perform particle identification, fully stop the produced light-ions and measure their kinetic energy. The time-of-flight was used to reduce the contribution from the low energy tail in the accepted incident neutron spectrum. We report double-differential production cross sections for protons, deuterons, tritons, (3)He and alpha particles and compare them with model calculations with TALYS-1.2.

  • 5. Choi, Y. W.
    et al.
    Koo, Y. M.
    Kwon, S. K.
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Department of Physics and Astronomy, Division of Materials Theory Uppsala University Uppsala Sweden; Wigner Research Center for Physics Institute for Solid State Physics and Optics Budapest Hungary.
    Ordered Phases in Fe-Si Alloys: A First-Principles Study2018Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 72, nr 6, s. 737-740Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is known that the formation of ordered phases causes the brittleness of electrical steels. We employed first-principles method in order to examine the possibility of the ordered-phases formation in Fe-Si alloys. It is found that the D03-like ordered configuration is most stable among other atomic configurations in the ferromagnetic state. In the paramagnetic state, for low Si concentration, the stability of the ordered configurations is comparable to that of disordered ones. However, as Si content increases, the B2 ordered phase as well as the D03 phase becomes more stable than the disordered ones. 

  • 6.
    Choi, Young Won
    et al.
    Pohang Univ Sci & Technol, Grad Inst Ferrous Technol, Pohang 37673, South Korea.
    Koo, Yang Mo
    Pohang Univ Sci & Technol, Grad Inst Ferrous Technol, Pohang 37673, South Korea.
    Kwon, Se Kyun
    Pohang Univ Sci & Technol, Grad Inst Ferrous Technol, Pohang 37673, South Korea.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden;Inst Solid State Phys & Opt, Wigner Res Ctr Phys, H-1525 Budapest, Hungary.
    Ordered Phases in Fe-Si Alloys: A First-Principles Study2018Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 72, nr 6, s. 737-740Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is known that the formation of ordered phases causes the brittleness of electrical steels. We employed first-principles method in order to examine the possibility of the ordered-phases formation in Fe-Si alloys. It is found that the D0(3)-like ordered configuration is most stable among other atomic configurations in the ferromagnetic state. In the paramagnetic state, for low Si concentration, the stability of the ordered configurations is comparable to that of disordered ones. However, as Si content increases, the B2 ordered phase as well as the D0(3) phase becomes more stable than the disordered ones.

  • 7. Furuta, T.
    et al.
    Hyomi, K.
    Souma, I.
    Oka, Y.
    Murayama, A.
    Dagnelund, Daniel
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Buyanova, Irina
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Chen, Weimin
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Spin-injection dynamics and effects of spin relaxation in self-assembled quantum dots of CdSe2008Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 53, s. 163-166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the spin injection dynamics and the effects of spin relaxation in self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor (DMS) layer of ZnMnSe, where spin-polarized excitons can be injected from the DMS into the QDs because of the potential difference. The degree of circular polarization, $P$, of excitonic photoluminescence (PL) at 5 T in the coupled QDs shows a rapid increase with increasing delay time after a linearly polarized pulse excitation, indicating the spin-injection dynamics. The $P$ value tends to decay gradually because of the exciton-spin relaxation in the QDs after the spin injection. The spin-polarized excitons in the QD ensemble migrate simultaneously from QDs with higher exciton energies to those with lower exciton energies. This inter-dot transfer of excitons also affects the $P$ value in the lower energy region of the QD-emission band because the excitons lose their spin polarizations due to the spin relaxation in the dots during the migration. The detailed analysis for the exciton-spin transfer is presented in a coupled QD system after spin injection.

  • 8. Hakim, M. A.
    et al.
    Hoque, S. Maqjura
    Sikder, S. S.
    Mahmud, Md. Sultan
    Nordblad, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Dilution of the magnetic moment of Fe by Cr for Fe73.5-xCrxCu1Nb3Si13.5B9 and the field-cooled and zero-field-cooled behavior for higher Cr content2008Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 53, nr 2, s. 766-771Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The temperature and the field dependences of the magnetization have been measured for Fe73.5-xCrxCu1Nb3Si13.5B9 (0 < ;= x < ;= 17.5) prepared by using a melt spin technique. The temperature dependence of the magnetization in the range of 5 to 300 K with an applied field of I Tesla for all the compositions follows the relaxation M(T) = M-0(1 - BT3/2 - CT5/2), which is indicative of the presence of a spin wave excitation. The saturation magnetizations at 5 and 300 K decrease linearly with Cr concentration for the entire composition range, which indicates that a simple dilution of the Fe moment takes place due to Cr substitution. The field-cooled (FC) and the zero-field-cooled (ZFC) magnetizations measured with an applied field of 1 Oe show divergences for x = 10, 12.5, 15 and 17.5, which may be attributed to the magnetic hardening at low temperatures.

  • 9. Hambsch, F. -J
    et al.
    Oberstedt, S.
    Al-Adil, A.
    Borcea, R.
    Oberstedt, Andreas
    Örebro universitet, Akademin för naturvetenskap och teknik.
    Tudora, A.
    Zeynalov, Sh.
    Investigation of the Fission Process at IRMM2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1654-1659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The investigation of the fission process is and has been a major undertaking at IRMM. The most recent investigations concerned the reaction (234)U(n,f) and (238)U(n,f) around vibrational resonances at the barrier of the fission cross-section. Furthermore prompt neutron emission of (252)Cf(SF) has been investigated understanding for the first time the prompt neutron multiplicity as a function of total kinetic energy (TKE). Theoretical modelling of reaction cross sections as well as prompt neutron multiplicity and spectra has been performed using the experimental data as input parameters. Also instrument developments for correlation measurements of fission fragment properties has been pursued in recent years with the time-of-flight spectrometer VERDI and detectors for prompt fission gamma-ray.

  • 10.
    Han, K.-H.
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Esquinazi, Pablo
    Diaconu, M.
    Schmidt, H.
    Spmann, D.
    Butz, T.
    Aging and annealing effects on the magnetic ordering induced by proton irradiation in graphite2006Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 48, nr 6, s. 1427-1431Artikkel i tidsskrift (Fagfellevurdert)
  • 11. Hirayama, S.
    et al.
    Watanabe, Y.
    Naitou, Y.
    Andersson, P.
    Bevilacqua, R.
    Gustavsson, C.
    Osterlund, M.
    Pomp, S.
    Simutkin, V.
    Sjostrand, H.
    Hjalmarsson, A.
    Prokofiev, A.
    Tesinsky, Milan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Tippawan, U.
    Light-ion Production from a Thin Silicon Target Bombarded by 175 MeV Quasi Mono-energetic Neutrons2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1447-1450Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Double-differential production yields of light ions (p, d, t, (3)He, and alpha) from a thin silicon target induced by 175 MeV quasi mono-energetic neutrons were measured using the MEDLEY setup at the The Svedberg Laboratory (TSL) in Uppsala in order to benchmark evaluated nuclear data and nuclear reaction models. The MEDLEY is a conventional spectrometer system which consists of eight counter telescopes. Each telescope is composed of two silicon surface barrier detectors as the Delta E detectors and a CsI(Tl) scintillator as the E detector for particle identification. The telescopes are placed at angles from 20 degrees to 160 degrees in steps of 20 degrees. The measured double-differential yields of light ions are compared with PHITS calculations using the following nuclear reaction options: the high-energy nuclear data library (JENDL/HE-2007), the quantum molecular dynamics (QMD) model, and the intra-nuclear cascade (INC) model.

  • 12. Hirayama, S.
    et al.
    Watanabe, Y.
    Naitou, Y.
    Andersson, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Bevilacqua, Riccardo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Gustavsson, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Simutkin, Vasily
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Sjöstrand, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Hjalmarsson, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik. Uppsala universitet, The Svedberg-laboratoriet.
    Prokofiev, Alexander V.
    Uppsala universitet, The Svedberg-laboratoriet.
    Tesinsky, M.
    Tippawan, U.
    Light-ion Production from a Thin Silicon Target Bombarded by 175 MeV Quasi Mono-energetic Neutrons2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1447-1450Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Double-differential production yields of light ions (p, d, t, (3)He, and alpha) from a thin silicon target induced by 175 MeV quasi mono-energetic neutrons were measured using the MEDLEY setup at the The Svedberg Laboratory (TSL) in Uppsala in order to benchmark evaluated nuclear data and nuclear reaction models. The MEDLEY is a conventional spectrometer system which consists of eight counter telescopes. Each telescope is composed of two silicon surface barrier detectors as the Delta E detectors and a CsI(Tl) scintillator as the E detector for particle identification. The telescopes are placed at angles from 20 degrees to 160 degrees in steps of 20 degrees. The measured double-differential yields of light ions are compared with PHITS calculations using the following nuclear reaction options: the high-energy nuclear data library (JENDL/HE-2007), the quantum molecular dynamics (QMD) model, and the intra-nuclear cascade (INC) model.

  • 13. Holme, Petter
    Local symmetries in complex networks2007Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 50, nr 1, s. 300-303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Symmetry-invariance to certain operators-is a fundamental concept in many branches of physics. We propose ways to measure symmetric properties of vertices, and their surroundings, in networks. To be stable to the randomness inherent in many complex networks, we consider measures that are continuous rather than dichotomous. The main operator we suggest is permutations of paths of a certain length leading out from a vertex. If these paths are more similar (in some sense) than expected, the vertex is a local center of symmetry in the network. We discuss different precise definitions based on this idea and give examples how different symmetry coefficients can be applied to protein interaction networks.

  • 14.
    Hussain, Laiq
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS).
    Pettersson, Håkan
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Wang, Q.
    Acreo Swedish ICT AB, Kista, 16425, Sweden.
    Karim, A.
    Acreo Swedish ICT AB, Kista, 16425, Sweden.
    Anderson, J.
    Acreo Swedish ICT AB, Kista, 16425, Sweden.
    Jafari, Mehrdad
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Song, J.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    Choi, W. J.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    Han, I. K.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    Lim, J. Y.
    Center for Opto-Electronic Convergence Systems, Korea Institute of Science and Technology, Seoul, 02792, South Korea.
    SWIR-LWIR Photoluminescence from Sb-based Epilayers Grown on GaAs Substrates by using MBE2018Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 73, nr 11, s. 1604-1611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Utilizing Sb-based bulk epilayers on large-scale low-cost substrates such as GaAs for fabricating infrared (IR) photodetectors is presently attracting significant attention worldwide. For this study, three sample series of GaAsxSb1−x, In1−xGaxSb, and InAsxSb1−x with different compositions were grown on semi-insulating GaAs substrates by using molecular beam epitaxy (MBE) and appropriate InAs quantum dots (QDs) as a defect-reduction buffer layer. Photoluminescence (PL) signals from these samples were observed over a wide IR wavelength range from 2 ÎŒm to 12 ÎŒm in agreement with the expected bandgap, including bowing effects. In particular, interband PL signals from InAsxSb1−x and In1−xGaxSb samples even at room temperature show promising potential for IR photodetector applications. © 2018, The Author(s).

  • 15.
    Hussain, Laiq
    et al.
    Halmstad University, Sweden.
    Pettersson, Håkan
    Halmstad University, Sweden.
    Wang, Qin
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Karim, Amir
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Anderson, Jan
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Jafari, Mehrdad
    Halmstad University, Sweden.
    Song, Jindong
    Korea Institute of Science and Technology, Korea.
    Choi, Won Jun
    Korea Institute of Science and Technology, Korea.
    Han, Il Ki
    Korea Institute of Science and Technology, Korea.
    Lim, Ju Young
    Korea Institute of Science and Technology, Korea.
    SWIR-LWIR Photoluminescence from Sb-based Epilayers Grown on GaAs Substrates by using MBE2018Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 73, nr 11, s. 1604-1611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Utilizing Sb-based bulk epilayers on large-scale low-cost substrates such as GaAs for fabricating infrared (IR) photodetectors is presently attracting significant attention worldwide. For this study, three sample series of GaAsxSb1−x, In1−xGaxSb, and InAsxSb1−x with different compositions were grown on semi-insulating GaAs substrates by using molecular beam epitaxy (MBE) and appropriate InAs quantum dots (QDs) as a defect-reduction buffer layer. Photoluminescence (PL) signals from these samples were observed over a wide IR wavelength range from 2 μm to 12 μm in agreement with the expected bandgap, including bowing effects. In particular, interband PL signals from InAsxSb1−x and In1−xGaxSb samples even at room temperature show promising potential for IR photodetector applications.

  • 16. Kim, H.
    et al.
    Lee, H.
    Chung, S. J.
    Department of Physics, Korea University.
    Lee, S.
    Cho, Y. J.
    Liu, X.
    Furdyna, J. K.
    Magneto-transport properties of GaMnAs:Si ferromagnetic semiconductors2009Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 55, nr 1, s. 304-308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic properties of a series of GaMnAs:Si ferromagnetic semiconductor films, in which the Mn concentration ranges from 7% to 10%, were investigated by using magneto-transport measurements. The temperature dependence of the resistivity revealed a systematic increase in the Curie temperature (T c) with increasing Mn concentration in the series. Since the T0 of the undoped GaMnAs ferromagnetic semiconductor decreases with increasing Mn concentration above 6%, the observation of a systematic increase of T c with increasing Mn concentration in our GaMnAs:Si series indicates the effectiveness of our counter doping for the incorporation of a a large amount of 7% Mn in the system. The field scan of the planar Hall effect (PHE) showed a typical two-step switching behavior at low temperatures, indicating the presence of a strong cubic anisotropy. The switching fields, however, systematically decreased with increasing Mn concentration in the series. The angular dependences of the switching fields were fitted by using the magnetic free energy and Cowburn's model to obtained the domain pinning energy, which showed systematically smaller values as the Mn concentration of the sample was increased. The temperature dependences of the pinning energies indicated a change in the uniaxial anisotropy from the [110] to the [110] direction with increasing Mn concentration in the series.

  • 17. Kim, J J
    et al.
    Olin, Håkan
    CHALMERS UNIV TECHNOL, DEPT PHYS.
    Electron localization probed by temperature-dependent tunneling spectroscopy in 1T-TaS21997Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 31, nr 1, s. 131-134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to present a clear picture of the density of states at both sides of the Fermi level (E-F) in 1T-TaS2 near the nearly commensurate to commensurate transition (similar to 187 K) and at low temperatures, we have done a temperature-dependent tunneling spectroscopy study using a scanning tunneling microscope. We observed an abrupt transition from a charge-density-wave induced depletion to an opening of a deep pseudo gap near the E-F of the nearly commensurate to commensurate transition within similar to 1 K. The measured pseudo gap turned out to be deep enough to form localized states at E-F. In contrast to an inverse photoelectron spectroscopy study, our tunneling results indicate the gap structures of two Hubbard subbands resulting from band splitting of the Ta 5d band due to the electron correlation effect.

  • 18. Kim, J J
    et al.
    Olin, Håkan
    Low temperature scanning tunneling microscopy spectroscopy study of two different layers in poly-type 4Hb-TaS2 at 4.2 K1997Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 31, s. 127-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using scanning tunneling microscope (STM), we have fabricated steps of 4Hb-TaS2 with the height similar to 6 Angstrom and investigated the electronic and atomic structures on the two different layers near the step region at 4.2 K. The measured STM images and tunneling spectra revealed completely different atomic and electronic structures of the 1T and 1H type layers. The 1T type layers showed the typical root 13 x root 13 charge-density-wave (CDW) structures showing insulating behaviors, whereas the 1H type layers showed metallic behaviors and had the triangular atomic structure with a very weak 3x3 CDW superlattice at a low bias voltage and with a superposed root 13 x root 13 CDW superlattice at a high positive bias voltage. The bias dependent STM image on the surface of 1H layer can be explained by the energy dependent tunneling process between STM tip and a stack of metallic 1H layer and insulating 1T layer.

  • 19. Kim, T.
    et al.
    Chung, S. J.
    Shin, D. Y.
    Choi, I. S.
    Lee, S.
    Liu, X.
    Furdyna, J. K.
    Strain-engineered magnetic anisotropy of GaMnAs ferromagnetic semiconductors2007Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 50, nr 3, s. 829-833Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of GaMnAs epilayers grown on GaInAs buffer layers have been investigated. The concentrations of Mn in the GaMnAs layer and In in the GaInAs layer were varied in the series, for which the tensile strain condition for the GaMnAs layer are systematically changed. The X-ray measurement provided the lattice constants of the layers, from which the stain of the GaMnAs layer was determined. The magneto-transport data revealed in-plane anisotropy in the GaMnAs sample grown on a GaInAs buffer with a low concentration of In. Such in-plan magnetic anisotropy of the GaMnAs layer continuously changed to a vertical magnetic anisotropy when the tensile strain was increased in the sample grown on the GaInAs buffer with a higher In concentration. This experiment clearly demonstrated that the magnetic anisotropy of GaMnAs could be continuously engineered by using the strain introduced by the GaInAs buffer layers.

  • 20.
    Lee, Eun
    et al.
    Sungkyunkwan University.
    Holme, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Network characteristics of individual pigments in cyanobacterial photosystem II core complexes2013Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 63, nr 11, s. 2255-2261Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Part of the excitation energy transfer (EET) characteristics of the photosystem II (PSII) comes from the interconnection between pigments. To understand the correlation between the EET and the pigments’ interaction structure, we construct a network from the EET rates which are related to both the distance between the pigments (chlorophylls and pheophytins) and their spatial orientations. Especially, we investigate how well the PS II core complex’s EET functionality can be explained by using only the network topology in Thermosynechococcus vulcanus 1.9 °A. Starting from the Förster theory, we construct a network of EET pathways. For an analysis of the network structure, we calculate common network-structural measures like betweenness centrality, eigenvector centrality and weighted clustering. These measures can reflect the role of individual pigments in the EET network. In our work, we found that some well-known properties were reproduced by the network analysis of the simplified network, which means that the topology of the network encodes functionally relevant information. For example, from the network structural analysis, we can infer that most of the chlorophyll molecules (clorophylls) in the pigment-protein complex CP47 have heightened probability to transfer energy compared with other chlorophylls. We also see that the active branch chlorophylls in the reaction center are characterized by a high eigenvector centrality, a high betweenness centrality and a low weighted clustering coefficient. This is indicative of functionally important vertices.

  • 21.
    Lee, S.
    et al.
    Department of Physics, Korea University.
    Chung, S. J.
    Department of Physics, Korea University.
    Liu, X.
    Furdyna, J. K.
    Doping effect on the properties of III-V ferromagnetic semiconductor GaMnAs epilayers and their superlattices2005Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 47, nr 3, s. 444-447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a systematic study on the properties of the ferromagnetic (FM) III-V-based semiconductor GaMnAs, including extrinsically doped GaMnAs: Be and its heterostructures in the form of superlattices. In an attempt to further improve the Curie temperature T c of GaMnAs, we have undertaken a systematic program of extrinsic p-doping of this material. In GaMnAs with low x (x = 0.03), T c is, indeed, seen to increase monotonically with increasing Be doping. We also studied the effect of p-doping of non-magnetic spacer layers on the magnetic properties of GaMnAs/GaAs superlattices (SLs). While Be-doped SLs exhibited relatively robust remanent magnetization and a larger coercivity over a broad temperature range, undoped SLs showed a fast decrease in the remanent magnetization with temperature, and a rather small coercivity. We propose that the observed hardness of the magnetization in SLs with Be-doped GaAs layers is related to the interlayer coupling introduced by the doping of the non-magnetic layers.

  • 22. Lee, S. K.
    et al.
    Zetterling, Carl-Mikael
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Östling, Mikael
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Moon, B. M.
    Electrical characterization of titanium-based ohmic contacts to 4H-Silicon carbide for high-power and high-temperature operation2002Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 40, nr 4, s. 572-576Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on titanium-based ohmic contacts (titanium carbide. titanium tungsten, and titanium) on both highly doped epilayers (n(+) and p(+)) and Al-ion-implanted layers. The TiC contact layer was epitaxially grown on epilayers as well as an Al-ion-implanted layers of 4H-SiC by co-evaporation Ti and C-60 under an ultra-high vacuum condition at low temperature (<500 degreesC). For comparison and long-term stability test, we also deposited TiW (weight ratio 30 : 710) ohmic contacts to p and n-type epilayers of 4H-SiC. The specific contact resistances (p(c)) were found to be as low as p- 5X10(-6), 2x10(-5), 2x10(-5), 3x10(-4), 4x10(-5), and 1X10(-4) Omegacm(2) for TiC contacts to n(+) epilayers, p(+) epilayers, and Al-ion-implanted layers, Ti contacts to p(+) epilayers, and TiW contacts to p(+) and to n(+) epilayers, respectively, by using linear transmission line method (TLM) measurements. During the long-term reliability tests in a vacuum chamber, we found that evaporated Au capping layers helped to keep the contacts from degrading.

  • 23. Naitou, Y.
    et al.
    Watanabe, Y.
    Hirayama, S.
    Hayashi, M.
    Prokofiev, A.
    Hjalmarsson, A.
    Pomp, S.
    Andersson, P.
    Bevilacqua, R.
    Gustavsson, C.
    Österlund, M.
    Simutkin, V.
    Sjöstrand, H.
    Tesinsky, Milan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Tippawan, U.
    Characterization of ANITA and QMN Neutron Beams at TSL Using Proton Recoil Techniques2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1439-1442Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neutron beam characterization measurements have been carried out in both the AN:ITA and QMN modes using the incident proton beam of 180 MeV at the The Svedverg Laboratory (TSL) in Uppsala. The spectral neutron flux data have been obtained by measuring elastic np-scattering with the Medley setup. The experimental results in the ANITA and QMN modes are compared with an MCNPX simulation and with the systematics of QMN spectra, respectively.

  • 24. Naitou, Y.
    et al.
    Watanabe, Y.
    Hirayama, S.
    Hayashi, M.
    Prokofiev, Alexander V.
    Uppsala universitet, The Svedberg-laboratoriet.
    Hjalmarsson, Anders
    Uppsala universitet, The Svedberg-laboratoriet. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Andersson, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Bevilacqua, Riccardo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Gustavsson, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Osterlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Simutkin, Vasily
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Sjostrand, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Tesinsky, M.
    Tippawan, U.
    Characterization of ANITA and QMN Neutron Beams at TSL Using Proton Recoil Techniques2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1439-1442Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neutron beam characterization measurements have been carried out in both the AN:ITA and QMN modes using the incident proton beam of 180 MeV at the The Svedverg Laboratory (TSL) in Uppsala. The spectral neutron flux data have been obtained by measuring elastic np-scattering with the Medley setup. The experimental results in the ANITA and QMN modes are compared with an MCNPX simulation and with the systematics of QMN spectra, respectively.

  • 25. Nam, D. N. H.
    et al.
    Dai, N. V.
    Hong, L. V.
    Phuc, N. X.
    Bau, L. V.
    Nordblad, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Newrock, R. S.
    Effects of selective dilution on the magnetic properties of La0.7Sr0.3Mn1-xM ' O-x(3) (M ' = Al, Ti)2008Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 52, nr 5, s. 1460-1464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic lattice of mixed-valence Mn ions in La0.7Sr0.3MnO3 is selectively diluted by partial substitution of Al or Ti for Mn. The ferromagnetic transition temperature T-c and the saturation magnetization M-s both decrease with substitution. By presenting the data in terms of selective dilution, T-c in the low-doping region is found to follow the relation T-c = T-c0 (1 - n(p)), where T-c0 refers to the undiluted system and np is the dilution concentration defined as n(p) = x/0.7 or n(p) = x/0.3 for M' = Al or Ti, respectively. The scaling behavior of T-c(n(p)) can be analyzed in the framework of the molecular-field theory and the still valid when Mn is replaced by both Al and Ti. The results are discussed with respect to the contributions from ferromagnetic double exchange and other possible antiferromagnetic superexchange interactions coexisting in the material.

  • 26. Park, J. H.
    et al.
    Souma, I.
    Oka, Y.
    Murayama, A.
    Dagnelund, Daniel
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Buyanova, Irina
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Chen, Weimin
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material.
    Transfer dynamics of spin-polarized excitons in ZnCdMnSe/ZnCdSe double quantum wells2008Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 53, s. 167-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the transfer dynamics of spin-polarized excitons in diluted magnetic semiconductor (DMS) double quantum wells (QWs) of ZnCdMnSe/ZnCdSe, where the spin-polarized excitons tunnel from the non-magnetic ZnCdSe to DMS-ZnCdMnSe wells and subsequently relax to the ground state in the DMS well with phonon emissions. The exciton-transfer time decreases when the exciton-energy difference between both the wells is equal to the one-LO-phonon energy, indicating the LO-phonon-assisted acceleration of the spin transfer. Moreover, the exciton transfer alters into the separate transfer of the electron and the heavy hole when the electron potential difference becomes larger than the LO-phonon energy. This observation demonstrates the importance of energy-relaxation dynamics in the spatial transport of spins in semiconductor quantum structures.

  • 27.
    Rosquist, Kjell
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Some Consequences of Gravitationally Induced Electromagnetic Fields in Microphysics2010Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 56, nr 5 (Pt. I), s. 1612-1618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We discuss the relation between the gravitational and electromagnetic fields as governed by the Einstein-Maxwell field equations. It is emphasized that the tendency of the gravitational field to induce electromagnetic effects increases as the size of the system decreases. This is because the charge-to-mass ratio $Q/M$ is typically larger in smaller systems. For most astrophysical systems, $Q/M$ is $\ll 1$ while for a Millikan oil drop, $Q/M \sim 10^6$. Going all the way down to elementary particles, the value for the electron is $Q/M \sim 10^{21}$. For subatomic systems there is an additional phenomenon which comes into play. In fact, according to general relativity, the gravitational field tends to become dominated by the spin at distances of the order of the Compton wavelength.The relevant quantity which governs this behavior is the ratio $S/M^2$ where $S$ is the (spin) angular momentum. For an electron, $S/M^2 \sim 10^{44}$.As a consequence, the gravitational field becomes dominated by gravitomagnetic effects in the subatomic domain.This fact has important consequences for the electromagnetic fields of spinning charged particles.To analyze this situation we use the asymptotic structure in the form of the multipole fields.%Such an approach avoids the pitfalls should one try to use a near-field approach using some kind of semi-classical formulation of the Einstein-Maxwell equations for example. To obtain more exact results however, one must take quantum effects into account including radiative contributions. Although such effects are not considered in this work, the order of magnitude of the considered effects are not expected to change drastically when going to a quantum mechanical treatment. The most relevant solution of the Einstein-Maxwell equations in this context is the Kerr-Newman metric. It is the preferred solution which is in accord with all the four known multipole moments of the electron to an accuracy of one part in a thousand. Our main result is that general relativity predicts corrections to the Coulomb field for charged spinning sources. Experimentally verifiable consequences include a predicted electric quadrupole moment for the electron, possible quasi-bound states in positron-heavy ion scattering with sizes corresponding to observed anomalous peaks, as well as small corrections to energy levels in microscopic bound systems such as the hydrogen atom

  • 28.
    Rosquist, Kjell
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. International Center for Relativistic Astrophysics Network (ICRANet), Italy.
    Samuelsson, Lars
    Generating Spatial Curvature in an Inhomogeneous Universe: A Bottom-up Approach to Cosmology2010Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 57, nr 3, s. 586-590Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We take the first steps towards a new bottom-up approach to cosmology. The dynamics is described in terms of the world lines of the cosmic grains (galaxies or clusters of galaxies). The description is microscopic in the sense that there is no fluid assumption. The motion of each grain is geodesic ensuring the presence of gravitational interactions only. The scheme is fully general in that there is no restriction to homogeneous or isotropic models. Our approach is mathematically similar to Buchert's averaging method, but there are important differences. In particular, we use statistical averages, when needed, not volume averages. For example, a crucial ingredient in any cosmological framework is the spatial curvature. Here we give an estimate of the scalar curvature based on statistical averages of the actual mass distribution in the universe.

  • 29. Rosquist, Kjell
    et al.
    Samuelsson, Lars
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Nordita, Stockholm.
    Generating Spatial Curvature in an Inhomogeneous Universe: A Bottom-up Approach to Cosmology2010Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 57, nr 3, s. 586-590Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We take the first steps towards a new bottom-up approach to cosmology. The dynamics is described in terms of the world lines of the cosmic grains (galaxies or clusters of galaxies). The description is microscopic in the sense that there is no fluid assumption. The motion of each grain is geodesic ensuring the presence of gravitational interactions only. The scheme is fully general in that there is no restriction to homogeneous or isotropic models. Our approach is mathematically similar to Buchert's averaging method, but there are important differences. In particular, we use statistical averages, when needed, not volume averages. For example, a crucial ingredient in any cosmological framework is the spatial curvature. Here we give an estimate of the scalar curvature based on statistical averages of the actual mass distribution in the universe.

  • 30. Ryzhov, I. V.
    et al.
    Tutin, G. A.
    Simutkin, Vasily D.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Blomgren, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Andersson, P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Bevilacqua, Riccardo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Onegin, M. S.
    Vaishnene, L. A.
    Meulders, J. P.
    Prieels, R.
    Measurement of Fragment Mass Yields in Neutron-induced Fission of (232)Th and (238)U at 33, 45 and 60 MeV2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1864-1867Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Incineration of spent nuclear fuel in Accelerator Driven Systems requires nuclear data on neutron-induced fission of actinides at energies above 20 MeV - the upper limit of conventional evaluated nuclear data files. Over the past years, a significant effort has been devoted to measurements of neutron-induced fission cross-sections at intermediate energies but there is a lack of experimental data on fission yields. Here we describe recent measurements of pre-neutron emission fragment mass distributions from intermediate energy neutron-induced fission of (232)Th and (238)U. The measurements have been carried out at the neutron beam of the Louvain-la-Neuve cyclotron facility CYCLONE. Quasi-monoenergetic neutrons with peak energies at 32.8, 45.3 and 59.9 MeV were produced by protons impinging on a thin lithium target. A multi-section Frisch-gridded ionization chamber was used as a fission fragment detector. The measurement results are compared with available experimental data as well as with predictions of the multi-modal random neck-rupture model implemented into the TALYS code.

  • 31. Tesinsky, M.
    et al.
    Andersson, P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Gustavsson, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Blomgren, J.
    Simutkin, Vasily
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Bevilacqua, Riccardo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Hjalmarsson, Anders
    Uppsala universitet, The Svedberg-laboratoriet.
    Pokofiev, Alexander
    Uppsala universitet, The Svedberg-laboratoriet.
    Tippawan, U.
    Lecolley, F. -R
    Marie, N.
    Kolozhvari, A.
    Neutron Elastic Scattering Cross-Section Measurements at 175 MeV2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1797-1800Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An off-line data analysis of an experimental campaign on elastic neutron cross-section measurements at 175 MeV for iron and bismuth performed by the SCANDAL set-up has started. Energy calibration has shown expected values of energy resolution and MCNPX simulations have provided suggestions for further analysis.

  • 32.
    Tesinsky, Milan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Andersson, P.
    Gustavsson, C.
    Pomp, S.
    Osterlund, M.
    Blomgren, J.
    Simutkin, V.
    Bevilacqua, R.
    Hjalmarsson, A.
    Pokofiev, A.
    Tippawan, U.
    Lecolley, F. -R
    Marie, N.
    Kolozhvari, A.
    Neutron Elastic Scattering Cross-Section Measurements at 175 MeV2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1797-1800Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An off-line data analysis of an experimental campaign on elastic neutron cross-section measurements at 175 MeV for iron and bismuth performed by the SCANDAL set-up has started. Energy calibration has shown expected values of energy resolution and MCNPX simulations have provided suggestions for further analysis.

  • 33. Tippawan, U.
    et al.
    Vilaithong, T.
    Pomp, S.
    Andersson, P.
    Bevilacqua, R.
    Blomgren, J.
    Gustavsson, C.
    Nilsson, L.
    Osterlund, M.
    Simutkin, V.
    Sjostrand, H.
    Hayashi, M.
    Hirayama, S.
    Naitou, Y.
    Watanabe, Y.
    Hjalmarsson, A.
    Prokofiev, A.
    Tesinsky, Milan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Light-ion Production in 175 MeV Neutron-induced Reactions on Oxygen2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1979-1982Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, special consideration on carbon and oxygen is needed since they are, by weight, the most abundant elements in human tissue. The MEDLEY setup at The Svedberg Laboratory (TSL), Uppsala, Sweden has been used to measure such data with double-differential cross sections (DDX) for the (n, xp), (n, xd), xt), (n,(3)He), and (n,alpha) reactions from C, 0, Si, Ca, Fe, Pb, and U around 96 MeV. At the new Uppsala neutron beam facility the available energy range of quasi mono-energetic neutron beams is extended up to 175 MeV. The detector setup used in MEDLEY consists of eight so-called telescopes mounted at different angles inside all evacuated reaction chamber. Each of the telescopes consists of two fully depleted Delta E silicon surface barrier detectors (SSBD) and a CsI(Tl) crystal. In order to make measurements at this higher neutron energy possible some changes in the detector setup compared to the campaign at 96 MeV were applied Accordingly, the second Delta E detectors have been replaced by 1000 mu m thick SSBDs as well as the size of the crystals used as E detectors was increased to a total length of 100 mm and a diameter of 50 mm. The Delta E - E technique is used to identify the light ions, and cutoff energies as low as 2.5 MeV for protons and 4.0 MeV for alpha particles are achieved. The data are normalised relative to elastic up scattering measured in one of the telescopes at 20 degrees. Preliminary DDXs for oxygen are presented and compared with theoretical calculations.

  • 34.
    Tippawan, Udomrat
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Vilaithong, T.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Andersson, P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Bevilacqua, Riccardo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Blomgren, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Gustavsson, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Nilsson, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Simutkin, Vasily
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Sjöstrand, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Hayashi, M.
    Hirayama, S.
    Naitou, Y.
    Watanabe, Y.
    Hjalmarsson, Anders
    Uppsala universitet, The Svedberg-laboratoriet.
    Prokofiev, Alexander
    Uppsala universitet, The Svedberg-laboratoriet.
    Tesinsky, M.
    Light-ion Production in 175 MeV Neutron-induced Reactions on Oxygen2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1979-1982Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Data on light-ion production in light nuclei such as carbon, nitrogen and oxygen are particularly important in calculations of dose distributions in human tissue for radiation therapy at neutron beams, and for dosimetry of high energy neutrons produced by high-energy cosmic radiation interacting with nuclei (nitrogen and oxygen) in the atmosphere. When studying neutron dose effects, special consideration on carbon and oxygen is needed since they are, by weight, the most abundant elements in human tissue. The MEDLEY setup at The Svedberg Laboratory (TSL), Uppsala, Sweden has been used to measure such data with double-differential cross sections (DDX) for the (n, xp), (n, xd), xt), (n,(3)He), and (n,alpha) reactions from C, 0, Si, Ca, Fe, Pb, and U around 96 MeV. At the new Uppsala neutron beam facility the available energy range of quasi mono-energetic neutron beams is extended up to 175 MeV. The detector setup used in MEDLEY consists of eight so-called telescopes mounted at different angles inside all evacuated reaction chamber. Each of the telescopes consists of two fully depleted Delta E silicon surface barrier detectors (SSBD) and a CsI(Tl) crystal. In order to make measurements at this higher neutron energy possible some changes in the detector setup compared to the campaign at 96 MeV were applied Accordingly, the second Delta E detectors have been replaced by 1000 mu m thick SSBDs as well as the size of the crystals used as E detectors was increased to a total length of 100 mm and a diameter of 50 mm. The Delta E - E technique is used to identify the light ions, and cutoff energies as low as 2.5 MeV for protons and 4.0 MeV for alpha particles are achieved. The data are normalised relative to elastic up scattering measured in one of the telescopes at 20 degrees. Preliminary DDXs for oxygen are presented and compared with theoretical calculations.

  • 35. Yoon, Y. J.
    et al.
    Chung, S. J.
    Lee, H. J.
    Lee, S.
    An, S. Y.
    Liu, X.
    Furdyna, J. K.
    Effect of p-type buffer layer on the properties of GaMnAs ferromagnetic semiconductors2004Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 45, nr SUPPL., s. S720-S723Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have studied the magnetic and transport properties of Ga 1-xMn xAs epilayers grown either on undoped or on p-type doped GaAs buffer layer. The temperature dependence of the resistivity at zero magnetic field reveals that the Curie temperature (T C) in the Ga 1-xMn xAs layer grown on p-type doped GaAs buffer is slightly higher than that observed in the layer grown on undoped GaAs buffer. The magnetic and transport properties of the two samples show significant differences when they are placed in a magnetic field. In SQUID measurements, the Ga 1-xMn xAs layer grown on p-type buffer shows a larger coercive field and much slower decay of remanent magnetization than the layer grown on undoped buffer. This robust magnetic behavior observed in the doped sample is discussed in terms of the increase of free carrier concentration in the system arising from p-type doping in the buffer layer.

  • 36. Yu, Chung-Jong
    et al.
    Han, Kyoohyun
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kim, Euikwoun
    Suh, Suil
    Lee, Yoon Man
    Kim, Jae Yong
    Physical and magnetic characteristics of carbon nanotubes radiated by proton beams2007Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 50, nr 5, s. 1524-1527Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single-walled carbon nanotubes were radiated by proton beams with energy of 35.7 MeV at the Bragg peaks, and magnetic force gradient images and topography were simultaneously measured by using a Nanoscope IV scanning probe microscope while changing the tip distance from the sample. The results show that the magnetic force gradient images become unclear as the scan height increases from 10 nm from the surface of the specimen and completely disappear at 50 nm. When the CNTs were radiated by proton beams, however, clear magnetic force gradient images were observed even at higher scan heights (100 nm) while very little change was noticed in the physical properties, including the tube shapes. It is interesting to note that magnetic force gradient images were not changed by reversing the magnetization of the tip, which reflects an induction of magnetism on the carbon nanotubes.

  • 37. Öhrn, A.
    et al.
    Gustavsson, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Blann, M.
    Blideanu, V.
    Blomgren, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Chiba, S.
    Duarte, H.
    Haddad, F.
    Kalbach, C.
    Klug, J.
    Koning, A.
    Le Brun, C.
    Lebrun, C.
    Lecolley, F. R.
    Ledoux, X.
    Marie-Noury, N.
    Mermod, P.
    Nilsson, L.
    Österlund, Michael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Pomp, Stephan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Prokofiev, Alexander V.
    Uppsala universitet, The Svedberg-laboratoriet.
    Tippawan, U.
    Watanabe, Y.
    Measurements of Inelastic Neutron Scattering at 96 MeV from Carbon, Iron, Yttrium and Lead2011Inngår i: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 59, nr 2, s. 1817-1820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Inelastic neutron scattering for (12)C, (58)Fe, (89)Y and (208)Pb have been measured at 96 MeV at the The Svedberg Laboratory in Uppsala and double-differential cross sections are reported. Data cover an excitation energy range of 0-45 MeV and the angular intervals are 28 - 58 degrees for (12)C, 26 - 65 degrees for (58)Fe and 26 - 52 degrees for (89)Y and (208)Pb. In this experiment, neutron detection is based on conversion to protons in an active scintillator converter. An analysis technique in which the neutron spectra have been obtained through a folding procedure using the response of the detector system has been used. The results are compared to and are in reasonable agreement with several model predictions and with inelastic neutron scattering data at 65 MeV from University of California, Davis, USA.

1 - 37 of 37
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