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排序方式: 共有888条查询结果,搜索用时 31 毫秒
1.
Scientometrics - Examining the relationships among scientific disciplines is important today, but existing methods are limited by the contents and structure of their bibliographic databases. We... 相似文献
2.
Water Resources Management - Public awareness of water quality concerns has increased since the Flint, MI crisis, but knowledge about water resources management remains low. Consequently,... 相似文献
3.
van de Kamp M.M.J.L. Tervonen J.K. Salonen E.T. Baptista J.P.V. 《Electronics letters》1996,32(12):1074-1075
The prediction models for scintillation variance of ITU-R and Karasawa et al. (1988) are compared to measurements on a time base which is much shorter than originally considered for these models. It is shown that even after averaging over just three days, a good correlation with the measured variance is found. Both models predict higher scintillation variance than is measured at 19.8 GHz on a 12.7° elevation path in Kirkkonummi, Finland 相似文献
4.
Investigated the ways in which patient and therapist gender influence the nature of patients' internalized representations of their therapist and the therapeutic relationship. A sample of 66 patients (29 males) completed the Therapist Representation Inventory (J. D. Geller et al, 1982), a self-report instrument designed to assess discrete properties of evoked representations. Results indicated widespread similarities between male and female patients in terms of the forms with which representations are evoked and the themes embodied in these representations. The differences that emerged suggest that women are more likely to keep their therapists in mind (and for longer periods of time) when working on their problems outside of therapy and that women with male therapists are especially likely to daydream about therapy and acknowledge missing their therapist in between sessions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Many school systems, in both the developed and developing world, are implementing educational technology to assist in student learning. However, there is no clear consensus on how to evaluate these new technologies. This paper proposes a comprehensive methodology for estimating the value of a new educational technology in three steps: benefit analysis, through the administration of a well-designed experiment; cost analysis, which incorporates costs to weigh against the benefits; and feasibility analysis, which introduces real-world concerns that may affect the ability to actually implement the technology. To illustrate the methodology, a case study from Chile is used where portable educational video games were introduced into first and second grade classrooms with the aim of improving learning in mathematics and language. This paper demonstrates the importance of all three steps in the evaluation process and provides a framework for future analyses. 相似文献
6.
Jesse Taub 《Circuits, Systems, and Signal Processing》1985,4(1-2):351-363
Current magnetostatic wave technology applicable to EW systems is assessed. Some of the developments currently underway with dispersive and non-dispersive delay lines, tunable oscillators and bandpass filters are examined and projected performance three years from now is given. Various EW applications are then described based on these projections. This includes compressive receivers, fast call receivers, phased arrays, scanning receivers, and channelizers. In many instances MSW technology can replace SAW provided further improvements materialize. 相似文献
7.
Hubert A. M. G. Vaessen Antonie van Ooik Cor G. van de Kamp 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1991,193(4):351-355
Summary Sodium, potassium, arsenic, selenium and tin have been determined in 38 different types of domestic and imported fresh fruits. All samples (n=242) were analysed for Na und K whereas a limited number of samples (n=85) of each fruit type was selected for the determination of As, Se and Sn. The median contents, in mass fractions of the edible portion, found for fresh fruits are: Na<0.001%; K 0.17%; As 4 g/kg; Se 2 g/kg and Sn< 0.05 mg/kg. The corresponding 90th percentile values are: Na 0,002%, K 0.34%; As 12 g/kg; Se 10 g/kg and Sn 0.10 mg/kg. Results for selenium reported here differ substantially from those given for a number of fresh fruits in the German Food Composition Tables 1986/1987. The average consumption of 129 g fresh fruit by Dutch citizens in the age category of 22–75 years contributes, in general, marginally to the total daily dietary intake of sodium, arsenic, selenium and tin. Fresh fruit can contribute substantially, up to 23%, to the average oral daily intake of potassium.
Einige Mineralstoffe im einheimischen und importierten Frischobst vom niederländischen Markt
Zusammenfassung Natrium, Kalium, Arsen, Selen und Zinn wurden in 38 verschiedenen Sorten von in- und ausländischem Frischobst bestimmt. Alle Proben (n=242) wurden auf Na und K untersucht; während nur eine beschränkte Zahl von Proben (n=85) für die Bestimmung von As, Se und Sn ausgewählt wurde. Die Medianwerte, in Massenanteilen der eßbaren Portionen, betrugen für frisches Obst: Na<0,001%; K 0,17% As 4 g/kg; Se 2 g/kg und Sn<0,05 mg/kg. Die dazugehörigen Werte für den 90 Perzentil sind: Na 0,002%; K 0,34%; As 12 g/kg; Se 10 g/kg und Sn 0,10 mg/kg. Für einige Obstsorten wurden Selenwerte erhalten, die erheblich von denen der Deutschen Nährwert-Tabellen 1986/1987 abweichen. Frischobst, dessen Verzehr für Einwohner der Niederlande in der Altersklasse von 22–75 Jahre im Schnitt 129 g/Tag beträgt, liefert einen vernachlässigbaren Beitrag zur täglichen Einnahme von Natrium, Arsen, Selen und Zinn; für Kalium hingegen kann dieser Beitrag, mit bis zu 23%, erheblich sein.相似文献
8.
Heyninck Jesse Kern-Isberner Gabriele Thimm Matthias Skiba Kenneth 《Annals of Mathematics and Artificial Intelligence》2021,89(10-11):1075-1099
Annals of Mathematics and Artificial Intelligence - The exact relationship between formal argumentation and nonmonotonic logics is a research topic that keeps on eluding researchers despite recent... 相似文献
9.
Enhanced Structural Stability and Photo Responsiveness of CH3NH3SnI3 Perovskite via Pressure‐Induced Amorphization and Recrystallization
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10.
Jesse Noffsinger Feliciano Giustino Brad D. Malone Cheol-Hwan Park Steven G. Louie Marvin L. Cohen 《Computer Physics Communications》2010,181(12):2140-2148
EPW (Electron–Phonon coupling using Wannier functions) is a program written in Fortran90 for calculating the electron–phonon coupling in periodic systems using density-functional perturbation theory and maximally localized Wannier functions. EPW can calculate electron–phonon interaction self-energies, electron–phonon spectral functions, and total as well as mode-resolved electron–phonon coupling strengths. The calculation of the electron–phonon coupling requires a very accurate sampling of electron–phonon scattering processes throughout the Brillouin zone, hence reliable calculations can be prohibitively time-consuming. EPW combines the Kohn–Sham electronic eigenstates and the vibrational eigenmodes provided by the Quantum ESPRESSO package (see Giannozzi et al., 2009 [1]) with the maximally localized Wannier functions provided by the wannier90 package (see Mostofi et al., 2008 [2]) in order to generate electron–phonon matrix elements on arbitrarily dense Brillouin zone grids using a generalized Fourier interpolation. This feature of EPW leads to fast and accurate calculations of the electron–phonon coupling, and enables the study of the electron–phonon coupling in large and complex systems.
Program summary
Program title: EPWCatalogue identifier: AEHA_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHA_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: GNU Public LicenseNo. of lines in distributed program, including test data, etc.: 304 443No. of bytes in distributed program, including test data, etc.: 1 487 466Distribution format: tar.gzProgramming language: Fortran 90Computer: Any architecture with a Fortran 90 compilerOperating system: Any environment with a Fortran 90 compilerHas the code been vectorized or parallelized?: Yes, optimized for 1 to 64 processorsRAM: Heavily system dependent, as small as a few MBSupplementary material: A copy of the “EPW/examples” directory containing the phonon binary files can be downloadedClassification: 7External routines: MPI, Quantum-ESPRESSO package [1], BLAS, LAPACK, FFTW. (The necessary Blas, Lapack and FFTW routines are included in the Quantum-ESPRESSO package [1].)Nature of problem: The calculation of the electron–phonon coupling from first-principles requires a very accurate sampling of electron–phonon scattering processes throughout the Brillouin zone; hence reliable calculations can be prohibitively timeconsuming.Solution method: EPW makes use of a real-space formulation and combines the Kohn–Sham electronic eigenstates and the vibrational eigenmodes provided by the Quantum-ESPRESSO package with the maximally localized Wannier functions provided by the wannier90 package in order to generate electron–phonon matrix elements on arbitrarily dense Brillouin zone grids using a generalized Fourier interpolation.Running time: Single processor examples typically take 5–10 minutes.References:[1]
P. Giannozzi, et al., J. Phys. Condens. Matter 21 (2009), 395502, http://www.quantum-espresso.org/.