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981.
Kurt Binder Benjamin Block Subir K. Das Peter Virnau David Winter 《Journal of statistical physics》2011,144(3):690-729
Excess contributions to the free energy due to interfaces occur for many problems encountered in the statistical physics of
condensed matter when coexistence between different phases is possible (e.g. wetting phenomena, nucleation, crystal growth,
etc.). This article reviews two methods to estimate both interfacial free energies and line tensions by Monte Carlo simulations
of simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid exhibiting a miscibility gap, and a simple
Lennard-Jones fluid). One method is based on thermodynamic integration. This method is useful to study flat and inclined interfaces
for Ising lattices, allowing also the estimation of line tensions of three-phase contact lines, when the interfaces meet walls
(where “surface fields” may act). A generalization to off-lattice systems is described as well. The second method is based
on the sampling of the order parameter distribution of the system throughout the two-phase coexistence region of the model.
Both the interface free energies of flat interfaces and of (spherical or cylindrical) droplets (or bubbles) can be estimated,
including also systems with walls, where sphere-cap shaped wall-attached droplets occur. The curvature-dependence of the interfacial
free energy is discussed, and estimates for the line tensions are compared to results from the thermodynamic integration method.
Basic limitations of all these methods are critically discussed, and an outlook on other approaches is given. 相似文献
982.
Badr Benmansour Ludovic Stephan Jean-Yves Cabon Laure Deschamps Philippe Giamarchi 《Journal of fluorescence》2011,21(3):843-850
This work presents spectroscopic properties of some Endocrine Disrupting Compounds (EDCs), frequently found in food and in
natural water. Studied molecules belong to the groups of phenolic and phthalate EDCs. In a first part, we have examined their
absorption and fluorescence properties. Fluorescence emission wavelengths are about 300 nm for phenolic compounds and 360 nm
for phtalate compounds; main excitation wavelengths being comprised between 210 nm and 230 nm. Fluorescence lifetimes measured
are short (about 4 ns) and the fluorescence quantum yield has been determined. In a second part, to avoid the time consuming
solvent extraction step, an analytical application to evaluate the performance of a direct analysis by laser induced fluorescence
spectroscopy of ECDs traces in tap water and in raw water is presented. Good detection limits have been obtained, i.e.: 0.35 μg.L−1 of chlorophenol in tap water, which are always lower than the reported Predictive Non Efficient Concentration (PNEC). 相似文献
983.
984.
纳磁逻辑电路具有低功耗、非易失和可常温下制备等优点, 实现低功耗片上时钟是其集成化的必备条件. 本文提出了一种基于交换作用的纳磁逻辑电路片上时钟结构, 用载流铜导线产生的奥斯特场将铁磁体薄膜覆层进行磁化, 然后依靠铁磁体层与纳磁体界面存在的交换作用场使后者磁化方向发生翻转. 与轭式铁磁体时钟用外磁场控制纳磁体磁化方向相比, 该方案在功耗方面降低了5/6, 时钟边界杂散场强度降低了2/3, 达到降低功耗、减轻串扰的目的. 此外, 采用微磁仿真进一步验证了该时钟结构上的纳磁体逻辑阵列可以实现逻辑功能.
关键词:
纳磁逻辑
片上时钟
交换作用 相似文献
985.
研制了基于4阵列传感器的光声内窥镜探头,并基于此搭建了光声内窥镜成像系统,开展了仿体实验成像研究,通过内窥镜探头4个阵元位置激光吸收强度的变化情况来分析仿体中吸收体的位置,论证了其定位能力,利用光声内窥镜系统对人体离体的正常组织、直肠癌早期组织进行成像研究;通过对不同阵元位置的光吸收强度分布进行统计分析,证明了光声内窥镜对早期直肠癌组织和正常组织的辨别能力,此项技术有望提高直肠癌早期诊断的准确率,具有潜在的临床应用前景。 相似文献
986.
Based on Biot's dynamic poroelastic theory, a foundation–soil interaction model is established to investigate the vertical vibrations of a rigid circular foundation on poroelastic soil excited by incident plane waves, including the fast P waves and SV waves. Scattering waves caused by the foundation and fluid–solid coupling due to the pore water in the soil are also considered in the model. The solution of the vertical vibrations of the foundation subjected to seismic waves are obtained by solving two sets of dual integral equations derived from the mixed boundary-value conditions. The different vertical vibrations of foundation rest on elastic and saturated half-space are compared. The influences of incident angle, permeability of soil and foundation mass on the vertical vibrations of the foundation are then discussed. The results show that resonant phenomenon of the foundation is observed at certain excitation frequencies; the effects of the pore water on the foundation vertical vibrations are significant. In addition, significant differences are found when the foundation is excited by P waves and SV waves, respectively. 相似文献
987.
Jin Mu Zhenfang Gu Lei Wang Zhiqing Zhang Hua Sun Shi-Zhao Kang 《Journal of nanoparticle research》2008,10(1):197-201
MnS nanocrystals with different phases and shapes were prepared through solvothermal synthesis. The products were characterized
by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–vis absorption and photoluminescence (PL) spectra.
The solvent and reaction time played an important role in controlling the phase and shape of MnS nanocrystals. The possible
mechanism of the shape evolution was investigated, which revealed that the crystal growth along the unique c axis of γ-MnS resulted in the rod-like MnS at the primary period, and the tetrahedral crystal seed of β-MnS with zincblende structure resulted in the interlinking of MnS rods, so the zigzag and three-branched and palm-like MnS
appeared; with increasing reactive time the thermodynamically stable spherical α-MnS was favored through the Ostwald ripening process. The PL results showed that the intensity of γ-MnS was much weaker than that of α-MnS, and the trap state emissions of γ-MnS at 470 and 482 nm, respectively, disappeared, which might be ascribed to the difference of the shapes between the sphere
and the rod or branch. 相似文献
988.
The effect of environmental temperature on neuronal spiking behaviors is investigated by numerically simulating the temperature
dependence of spiking threshold of the Hodgkin-Huxley neuron subject to synaptic stimulus. We find that the spiking threshold
exhibits a global minimum in a specific temperature range where spike initiation needs weakest synaptic strength, which form
the engineering perspective indicates the occurrence of optimal use of synaptic transmission in the nervous system. We further
explore the biophysical origin of this phenomenon associated with ion channel gating kinetics and also discuss its possible
biological relevance in information processing in neuronal systems.
相似文献
989.
Tom Kennedy 《Journal of statistical physics》2008,131(5):803-819
We simulate several models of random curves in the half plane and numerically compute the stochastic driving processes that
produce the curves through the Loewner equation. Our models include models whose scaling limit is the Schramm-Loewner evolution
(SLE) and models for which it is not. We study several tests of whether the driving process is Brownian motion, as it is for
SLE. We find that testing only the normality of the process at a fixed time is not effective at determining if the random
curves are an SLE. Tests that involve the independence of the increments of Brownian motion are much more effective. We also
study the zipper algorithm for numerically computing the driving function of a simple curve. We give an implementation of
this algorithm which runs in a time O(N
1.35) rather than the usual O(N
2), where N is the number of points on the curve. 相似文献
990.
We present the number of dimer coverings N
d
(n) on the Sierpinski gasket SG
d
(n) at stage n with dimension d equal to two, three, four or five. When the number of vertices, denoted as v(n), of the Sierpinski gasket is an even number, N
d
(n) is the number of close-packed dimers. When the number of vertices is an odd number, no close-packed configurations are possible
and we allow one of the outmost vertices uncovered. The entropy of absorption of diatomic molecules per site, defined as
, is calculated to be ln (2)/3 exactly for SG
2. The numbers of dimers on the generalized Sierpinski gasket SG
d,b
(n) with d=2 and b=3,4,5 are also obtained exactly with entropies equal to ln (6)/7, ln (28)/12, ln (200)/18, respectively. The number of dimer
coverings for SG
3 is given by an exact product expression, such that its entropy is given by an exact summation expression. The upper and lower
bounds for the entropy are derived in terms of the results at a certain stage for SG
d
(n) with d=3,4,5. As the difference between these bounds converges quickly to zero as the calculated stage increases, the numerical
value of
with d=3,4,5 can be evaluated with more than a hundred significant figures accurate.
This paper is written during the Lung-Chi Chen visit to PIMS, University of British Columbia. The author thanks the institute
for the hospitality. 相似文献