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Spin-dependent localization of electrons in quadruple quantum dots

Physical Review B 2010年第24期82卷 245306-245306页

作者： A. Kwaśniowski J. Adamowski Faculty of Physics and Applied Computer Science AGH University of Science and Technology Kraków Poland

An all electrical manipulation with singlet and triplet states of an electron pair in a quadruple quantum dot (QD) has been studied by a configuration interaction method. We have investigated two nanodevices that consist of four weakly coupled lateral QDs, in which the electron localization can be changed by tuning the external voltages: the gate voltage in the first nanodevice and the source-drain voltage in the second. The electrons that—in the initial state—singly occupy the two identical input QDs are transferred to the two asymmetric output QDs by the sufficiently high electric field. We have shown that—for the QDs with suitably chosen parameters—the localization of the electrons in the output QDs depends on the spin states of the electron pair and the final spin state can be uniquely determined by a single-shot measurement of the electric charge gathered in only one of the output QDs. This leads to a possibility of performing the controlled operations on the electron-spin qubits in the quadruple QDs. We have found that the classical exclusive OR (XOR) logic gate can be performed with the electric field-induced transitions and the output read out by the spin-to-charge conversion.

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Experimental determination of the electron screening potential energy for the d(d, n)3He Reaction in ZrD2 and D2O in the ultralow energy region

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Bulletin of the Russian Academy of sciences: physics 2010年第11期74卷 1570-1574页

作者： Bystritsky, V.M. Gerasimov, V.V. Il'guzin, D.A. Krylov, A.R. Parzhitskii, S.S. Anan, P.S. Dudkin, G.N. Kaminskii, V.L. Nechaev, B.A. Padalko, V.N. Petrov, A.V. Filipowicz, M. Wozniak, J. Bystritskii, Vit.M. Tuleushev, Yu.Zh. Joint Institute for Nuclear Research Dubna 141980 Russia Nuclear Physics Institute Tomsk Polytechnic University Tomsk 634050 Russia Faculty of Energy and Fuels University of Science and Technology PL-30059 Krakow Poland Faculty of Physics and Applied Computer Sciences University of Science and Technology PL-30059 Krakow Poland Department of Physics and Astronomy University of California Irvine CA 92697 United States National Nuclear Center Institute of Nuclear Physics Almaty 050032 Kazakhstan

This work is devoted to measuring of the values of the astrophysical S-factors and electron screening potential energy for a d(d,n)3He reaction occurring at ultralow energies in zirconium deuteride ZrD2 (3.5-7.0 keV) and heavy water D2O (2.2-6.0 keV). The experiment was performed on the Hall pulsed plasma accelerator at the TPU Nuclear physics Institute (Tomsk) with ZrD2 and D2O targets produced by the magnetron sputtering of zirconium in a deuterium environment and heavy water freezing-out on a copper support, respectively. A Χ analysis of the dependence of the neutron yields and astrophysical S-factors for the dd reaction on the deuteron collision energy E revealed that the upper bounds of the electron screening potential energy for interacting deuterons in ZrD2 and D2O and of the astrophysical S-factors at the deuteron collision energy E = 0 were Ue(ZrD2) e(D2O) 2), S(0) = (58.6 ± 3.6) keV • b (D2O) at the 90% confidence level. © Allerton Press, Inc., 2010.

关键词： Heavy water

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Estimating effective DNA database size via compression

Estimating effective DNA database size via compression

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10th Conference on Theory and Practice of Information Technologies - Applications and Theory 2010, ITAT 2010

作者： Višňovská, Martina Nánási, Michal Vinař, Tomáš Brejová, Broňa Department of Applied Informatics Faculty of Mathematics Physics and Informatics Comenius University Mlynská Dolina 842 48 Bratislava Slovakia Department of Computer Science Faculty of Mathematics Physics and Informatics Comenius University Mlynská Dolina 842 48 Bratislava Slovakia

Search for sequence similarity in large-scale databases of DNA and protein sequences is one of the essential problems in bioinformatics. To distinguish random matches from biologically relevant similarities, it is customary to compute statistical P-value of each discovered match. In this context, P-value is the probability that a similarity with a given score or higher would appear by chance in a comparison of a random query and a random database. Note that P-value is a function of the database size, since a high-scoring similarity is more likely to exist by chance in a larger database. Biological databases often contain redundant, identical, or very similar sequences. This fact is not taken into account in P-value estimation, resulting in pessimistic estimates. One way to address this problem is to use a lower effective database size instead of its real size. In this work, we propose to estimate the effective size of a database by its compressed size. An appropriate compression algorithm will effectively store only a single copy of each repeated string, resulting in a file whose size roughly corresponds to the amount of unique sequence in the database. We evaluate our approach on real and simulated databases.

关键词： Database systems

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Do we understand the structure of the metal-rich (001) surfaces of Ⅲ-Ⅴ compounds?

Do we understand the structure of the metal-rich (001) surfa...

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第18届国际真空大会

作者： J. J. Kolodziej G. Goryl Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University

The metal rich (001) surfaces of indium antimonide, indium arsenide and gallium arsenide have been studied a few times in the pas but no conclusion about their structure have been reached yet. Based on electron diffraction experiments and scannig probe microscopy images recorded at room temperature the reconstruction of the surfaces is assigned as c(8x2) or c(8x2)/(4x2). However, scanning tunnelling microscopy patterns of the surface recorded at cryogenic temperatures indicate different symmetry, domains, disorder and fluctuations. In this presentation, using scanning probe microscopy and electron diffraction techniques we will analyse structure of these surfaces and we will show that, at elevated temperatures, there exist chaotically fluctuating vacancies confined to certain atomic rows on the surface. Averaging effects cause that microscopic studies done at room and elevated temperatures evidence highly symmetric c(8x2) or c(8x2)/(4x2) structures while, at low temperatures, when the vacancy gas is condensed on the surface lattice, due to uncomplete filling of certain surface sites lowering of the surface symmetry, domains and disorder are observed. It will be also shown that there are other fascinating and not yet understood phenomena on these complex surfaces.

关键词： III-V surfaces, scanning tunelling microscopy, surface reconstruction

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Structural and magnetic transformations in HoMn2Hx hydrides

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Journal of physics: Conference Series 2011年第1期303卷

作者： A Budziak M Bałanda H Figiel L Kolwicz-Chodak Z Tarnawski The H. Niewodniczański Institute of Nuclear Physics PAN ul. Radzikowskiego 152 31-342 Kraków Poland Faculty of Physics and Applied Computer Science AGH University of Science and Technology Al. Mickiewicza 30 30-059 Kraków Poland

The HoMn2 compound crystallizes in the C15 or C14 Laves phases depending on preparation. The effect of hydrogen absorption on structural, magnetic and thermodynamic properties of HoMn2Hx hydrides for both phases has been investigated by XRD, AC/DC magnetometry, and calorimetry in the temperature range of 80–300 K. In addition to general features revealed by RMn2Hx compounds (R = rare earth or Yttrium), unusual behavior of these hydrides was found. In particular, a transformation from the cubic to the monoclinic structure was detected, which so far has not been reported for other cubic RMn2Hx (R – rare earth or Yttrium) compounds. The structural transformations are reflected in the magnetic behavior. The change in ordering temperatures indicates a strong correlation between the magnetic interactions and the Mn-Mn distance modified by hydrogen absorption. Tentative magnetic and structural phase diagrams are proposed. The presented results are compared with the properties of other cubic and hexagonal RMn2Hx hydrides.

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Low power, high dynamic range, sample&hold circuit and analogue multiplexer for multi-channel recording of neuronal signals

Low power, high dynamic range, sample&hold circuit and analo...

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International Conference on Mixed Design of Integrated Circuits and Systems (MIXDES)

作者： Przemysław Rydygier Władysław Dąbrowski Tomasz Fiutowski Piotr Wiącek Faculty of Physics and Applied Computer Science AGH University of Science and Technology Krakow Poland

In the paper we present the design and test results of an integrated circuit combining the sample&hold and the analogue multiplexer, which is foreseen to be implemented in a multi-channel Application Specific Integrated Circuit (ASIC) for recording signal from alive neuronal tissue. The design is optimised with respect to critical requirements for such circuits, i.e. short sampling time, low power dissipation, good linearity and high dynamic range. Presented design comprises sample&hold circuits with class AB operational amplifier, novel shift register, which allows minimising cross-coupling of the clock signal and control logic. The circuit has been designed in a 0.35 μm CMOS process and has been successfully implemented in a prototype multi-channel ASIC.

关键词： Multiplexing Shift registers Clocks Operational amplifiers Capacitance Capacitors Dynamic range

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Using a hall accelerator to investigate d(d, n)3He and d(p, γ)3He reactions in the astrophysical energy region

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Bulletin of the Russian Academy of sciences: physics 2010年第4期74卷 531-534页

作者： Bystritsky, V.M. Gerasimov, V.V. Krylov, A.R. Parzhitsktii, S.S. Il'guzin, D.A. Ananin, P.S. Dudkin, G.N. Kaminskii, V.L. Nechaev, B.A. Padalko, V.N. Petrov, A.V. Mesyats, G.A. Filipowicz, M. Wozniak, J. Bystritskii, Vit. M. Joint Institute for Nuclear Research Dubna Moscow oblast 141980 Russia Nuclear Physics Institute Tomsk Polytechnic University Tomsk 634050 Russia Lebedev Physical Institute Russian Academy of Sciences Moscow 119991 Russia Faculty of Energy and Fuels AGH University of Science and Technology Krakow PL-30-059 Poland Faculty of Physics and Applied Computer Sciences AGH University of Science and Technology Krakow PL-30-059 Poland Department of Physics and Astronomy University of California Irvine CA 92697 United States

We present new results on astrophysical S-factors and cross sections for reactions dd → 3He + n(2.5MeV) and pd → 3He + γ (5.5MeV) in ultra-low energy ranges 2.3-6.2 keV and 8.3-10.1 keV, respectively. Experiments were performed with proton and neutron beams produced by a pulsed Hall accelerator (Nuclear physics Institute, Tomsk) and deuterated polyethylene (CD2) and frozen heavy water (D2O) targets. Within measurement errors, our results are consistent with the literature's experimental results on pd and dd reactions for the given energy ranges, where D2O or gaseous deuterium targets were used. © Allerton Press, Inc., 2010.

关键词： Heavy water

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Decision Support System for Skin Cancer Diagnosis

Decision Support System for Skin Cancer Diagnosis

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第九届运筹学及其应用国际研讨会

作者： Karol Przystalski Leszek Nowak Maciej Ogorzalek Grzegorz Surówka Department of Information Technologies Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University

computer aided medical diagnosis is mostly based on very advanced analysis of huge amounts of measured data. Application of computational intelligence methods helps medical doctors to process data faster, and give better, more reliable diagnoses. In dermatology computer analysis is getting more important every year. Differentiation of malignant melanoma images requires very fast image processing and feature extraction/classification algorithms. Applying artificial intelligence algorithms to explore and search large database of dermatoscopic images allows doctors to semantically filter out images with specified characteristics. This paper describes a decision-support system which is based on semantic analysis of melanoma images and further classification of characteristic objects commonly found in pigmented skin lesions. For classification Artificial Neural Networks and Support Vector Machines are used and their performance is evaluated and compared.

关键词： Semantic analysis melanoma artificial neural networks radial basis function image analysis image processing support vector machines

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Electronic structure of the σ phase of paramagnetic Fe-V alloys

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Physical Review B 2010年第17期81卷 174203-174203页

作者： J. Cieslak J. Tobola S. M. Dubiel Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Krakow Poland

The electronic structure of complex σ-phase Fe100−xVx compounds with 33.3≤x≤60.0 was calculated with the charge self-consistent Korringa-Kohn-Rostoker method. The chemical disorder effects appearing in real samples were accounted for by considering the most representative ordered approximants. Bearing in mind neutron-diffraction data on atom occupancy over nonequivalent lattice sites, hyperfine parameters were finally obtained by averaging the first-principles results using the deduced probability distribution. In particular, charge densities ρA(0) and electric field gradients (EFG) were determined at Fe nuclei that occupy five nonequivalent lattice sites in this structure. Furthermore, using the computed ρA(0) and EFG, isomer shifts, and quadrupole splittings values were found for each site in the σ-phase Fe-V and compared with the previously studied σ-phase Fe-Cr alloy. The calculated aforementioned quantities combined with experimentally determined site occupancies were applied to analyze F57e Mössbauer spectra recorded on a series of several samples in a paramagnetic state and a very good agreement between the theoretical and experimental results was found.

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Magnetic properties of σ-FeCr alloys as calculated with the charge- and spin-self-consistent KKR(CPA) method

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Physical Review B 2010年第22期82卷 224407-224407页

作者： J. Cieslak J. Tobola S. M. Dubiel W. Sikora Faculty of Physics and Applied Computer Science AGH University of Science and Technology al. Mickiewicza 30 30-059 Krakow Poland

Magnetic properties of a σ-Fe16Cr14 alloy calculated with the charge- and spin-self-consistent Korringa-Kohn-Rostoker (KKR) and combined with coherent potential approximation (KKR-CPA) methods are reported. Nonmagnetic state as well as various magnetic orderings were considered, i.e., ferromagnetic (FM) and more complex antiparallel (called APM) arrangements for selected sublattices, as follows from the symmetry analysis. It has been shown that the Stoner criterion applied to nonmagnetic density of states at the Fermi energy, EF is satisfied for Fe atoms situated on all five lattice sites, while it is not fulfilled for all Cr atoms. In FM and APM states, the values of magnetic moments on Fe atoms occupying various sites are dispersed between 0 and 2.5 μB, and they are proportional to the number of Fe atoms in the nearest-neighbor shell. Magnetic moments of Cr atoms having much smaller values were found to be coupled antiparallel to those of Fe atoms. The average value of the magnetic moment per atom was found to be ⟨μ⟩=0.55μB that is by a factor of 4 larger than the experimental value found for a σ-Fe0.538Cr0.462 sample. Conversely, admitting an antiparallel ordering (APM model) on atoms situated on C and D sites, according to the group theory and symmetry analysis results, yielded a substantial reduction of ⟨μ⟩ to 0.20 μB. Further diminution of ⟨μ⟩ to 0.15 μB, which is very close to the experimental value of 0.14 μB, has been achieved with the KKR-CPA calculations by considering a chemical disorder on sites B, C, and D.

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