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991.
J.R. Tolchard 《Journal of Physics and Chemistry of Solids》2008,69(10):2433-2439
High-resolution neutron powder diffraction studies of the oxide ion conductor La9.67Si6O26.5 are reported for temperatures ranging between 25 and 900 °C. The best fit to the data was obtained for space group P63 and there was no evidence for any change in symmetry over the temperature range studied. Interstitial oxide ions are identified lying in sites similar to those predicted by previous computer modelling studies, and in agreement with structural studies on related materials. Furthermore, occupancy of these sites is enhanced by Frenkel-type disorder from neighbouring positions. The results thus add further weight to the interpretation that, in these apatite-type systems, the silicate substructure is important for the accommodation of interstitial oxide ions and their migration. 相似文献
992.
Cavin III Ralph K. Herr Daniel J.C. Zhirnov Victor V. 《Journal of nanoparticle research》2000,2(3):213-235
The purpose of this paper is to identify areas in the basic physical sciences where additional research is needed to sustain the extraordinary progress in electronics that has now extended for several decades. Also, it is argued that basic research will provide the foundation for the discovery of new generations of nanoelectronic devices that will continue the experimental rate of reduction in cost per function. Some of the fundamental areas requiring further research are the chemistry and physics of material interfaces, conductivity at small dimensions, deterministic doping effects, and nanomagnetics. Discovery research also is needed in the functional synergy of nanoelectronic materials and non-traditional fabrication methods. 相似文献
993.
Numerical simulation results derived from a Schrödinger–Poisson tool applied to scaled double-gate (DG) MOSFETs, supplemented by analytical characterizations of the pertinent physics, are presented to give insight concerning the near-ideal features of DG devices and to explain how the low-voltage drive current of the asymmetrical DG MOSFET, having only one predominant channel, can be comparable to, and even higher than, that of the symmetrical-gate counterpart designed to have the same off-state current. 相似文献
994.
995.
Wenjie Xie Siu-Chung Tam Hongru Yang Jianhui Gu Gang Zhao Yee-Loy Lam Chan-Hin Kam 《Optics & Laser Technology》1999,31(5):387
It is important for laser designers to study the characteristics of heat transfer from the laser crystal slab to the coolant in high-power DPSS laser operations. We have simulated and obtained the optimum heat transfer coefficient and coolant flow rate for our cavity design, in which the circulating coolant is maintained at a constant temperature. It has been determined that the coolant temperature and the convective heat transfer coefficient (h) are important parameters in the thermal analysis. The coefficient h is affected by the coolant flow rate, the physical properties of the laser slab and the coolant and the pumping cavity geometry. Using analytical heat transfer equation, for cooling water temperature of 300 K, the optimum flow rate for our cavity geometry is found to be 390 cm3/s, corresponding to h=5 W/cm2 K. 相似文献
996.
A. Andreone A. Di Chiara G. Peluso U. Scotti di Uccio F. Tafuri A. Barone G. Pepe F. Fontana 《Il Nuovo Cimento D》1990,12(6):863-868
Summary Some of the main anomalies in conductance characteristics of high-T
C tunnel junctions are considered. Mainly, the extreme, depression of gap structures, the presence of conductance peaks in
corrispondence to the counterelectrode gap, and ?zero-bias anomalies? will be examined. The possibility of application of
the proximity McMillan model to describe the behaviour in conductance of high-T
C junctions is considered. Discussion and preliminary comparison with experimental data on YBCO junctions are also reported. 相似文献
997.
Summary The magnetic circular dichroism has been in the past an excellent tool to clarify the optical cycle of theF centres in alkali halides and the nature of the relaxed excited state. We have used such technique to study the weak doubleF emission found recently in NaI and the luminescence ofF andF
A
centres (of both type I and II) in KCl. We have found that the long-wavelengthF emission in NaI and theF
A
(I) emission in KCl∶Na+ behave like the well-known emission of theF centres, confirming the attribution of the above luminescence in NaI to the normal relaxed excited state. A completely different
behaviour is displayed by the short-wavelengthF emission in NaI and by theF
A
(II) emission in KCl∶Li+. The experimental data have been compared with the Ham and Grevsmuhl vibronic theory of the relaxed excited state.
Riassunto Gli effetti di dicroismo magnetico circolare hanno costituito in passato un ottimo mezzo per chiarire il ciclo ottico dei centriF in alogenuri alcalini e la natura dello stato eccitato rilassato. Abbiamo usato tale tecnica per studiare la debole doppia emissioneF trovata recentemente in NaI e la luminescenza dei centriF edF A (di tipo I e II) in KCl. Si è trovato che l'emissioneF a minore energia in NaI e l'emissioneF A (I) in KCl∶Na+ si comportano come la ben nota emissione dei centriF, il che conferma l'attribuzione di tale luminescenza in NaI allo stato eccitato rilassato normale. L'emissioneF a energia maggiore in NaI e l'emissioneF A (II) in KCl∶Li+ mostrano un comportamento completamente diverso. I dati sperimentali sono stati confrontati con la teoria vibronica di Ham e Grevsmuhl dello stato eccitato rilassato.
Резюме Магнитный круговой дихроизм ранее применялся как инструмент для выяснения оптического циклаF центров в щелочных галогенидах и природы релаксирующего возбужденного состояния. В этой работе мы используем эту технику для исследования слабого двойного F излучения, обнаруженного недавно в NaI и при люминесценцииF иF A центров (типа I и типа II) в KCl. Мы обнаружили, что длинноволновоеF излучения в NaI иF A (I) излучение в KCl∶Na+ ведет себя как хорошо известное излучениеF центров, что подтверждает приписывание вышеуказанной люминесценции в NaI нормальному релаксирующему возбужденному состоянию. Полностью отличное поведение обнаруживает коротковолновоеF излучение в NaI иF A (II) излучение в KCl∶Li+. Полученные экспериментальные данные сравниваются с вибрационной теорией Гама и Гревсмула для релаксирующего возбужденного состояния.相似文献
998.
新疆雪莲(Saussurea involucrata Kar. et Kin)为我国西北地区名贵中草药,可用于治疗风湿性关节炎和妇科疾病,从中分离得到一种新的倍半萜内酯的β葡萄糖苷,命名为大苞雪莲内酯(右图),其结晶为无色透明针状,m.p.219~221℃。 相似文献
999.
Summary Brief pressure changes take often place within a liquid chromatography column, e.g., during sample injection. It is shown
that pressure jumps may cause local changes in the composition of a mixed effluent and the rise of system peaks in the chromatogram.
This is a consequence of the dependence of sorption equilibrium on pressure. 相似文献
1000.