Shape of crossover between mean-field and asymptotic critical behavior in a three-dimensional Ising lattice

Recent numerical studies of the susceptibility of the three-dimensional Ising model with various interaction ranges have been analyzed with a crossover model based on renormalization-group matching theory. It is shown that the model yields an accurate description of the crossover function for the susceptibility.Comment: 4 pages RevTeX + 3 PostScript figures. Uses epsf.sty and rotate.sty. Final version; accepted for publication in Physics Letters

Frozen capillary waves on glass surfaces: an AFM study

Using atomic force microscopy on silica and float glass surfaces, we give evidence that the roughness of melted glass surfaces can be quantitatively accounted for by frozen capillary waves. In this framework the height spatial correlations are shown to obey a logarithmic scaling law; the identification of this behaviour allows to estimate the ratio $kT\_F/\pi\gamma$ where $k$ is the Boltzmann constant, $\gamma$ the interface tension and $T\_F$ the temperature corresponding to the ``freezing'' of the capillary waves. Variations of interface tension and (to a lesser extent) temperatures of annealing treatments are shown to be directly measurable from a statistical analysis of the roughness spectrum of the glass surfaces

Static and Dynamic Critical Behavior of a Symmetrical Binary Fluid: A Computer Simulation

A symmetrical binary, A+B Lennard-Jones mixture is studied by a combination of semi-grandcanonical Monte Carlo (SGMC) and Molecular Dynamics (MD) methods near a liquid-liquid critical temperature $T_c$. Choosing equal chemical potentials for the two species, the SGMC switches identities (${\rm A} \to {\rm B} \to {\rm A}$) to generate well-equilibrated configurations of the system on the coexistence curve for $T<T_c$ and at the critical concentration, $x_c=1/2$, for $T>T_c$. A finite-size scaling analysis of the concentration susceptibility above $T_c$ and of the order parameter below $T_c$ is performed, varying the number of particles from N=400 to 12800. The data are fully compatible with the expected critical exponents of the three-dimensional Ising universality class. The equilibrium configurations from the SGMC runs are used as initial states for microcanonical MD runs, from which transport coefficients are extracted. Self-diffusion coefficients are obtained from the Einstein relation, while the interdiffusion coefficient and the shear viscosity are estimated from Green-Kubo expressions. As expected, the self-diffusion constant does not display a detectable critical anomaly. With appropriate finite-size scaling analysis, we show that the simulation data for the shear viscosity and the mutual diffusion constant are quite consistent both with the theoretically predicted behavior, including the critical exponents and amplitudes, and with the most accurate experimental evidence.Comment: 35 pages, 13 figure

Critical Dynamics in a Binary Fluid: Simulations and Finite-size Scaling

We report comprehensive simulations of the critical dynamics of a symmetric binary Lennard-Jones mixture near its consolute point. The self-diffusion coefficient exhibits no detectable anomaly. The data for the shear viscosity and the mutual-diffusion coefficient are fully consistent with the asymptotic power laws and amplitudes predicted by renormalization-group and mode-coupling theories {\it provided} finite-size effects and the background contribution to the relevant Onsager coefficient are suitably accounted for. This resolves a controversy raised by recent molecular simulations.Comment: 4 pages, 4 figure

Histogram Reweighting Method for Dynamic Properties

The histogram reweighting technique, widely used to analyze Monte Carlo data, is shown to be applicable to dynamic properties obtained from Molecular Dynamics simulations. The theory presented here is based on the fact that the correlation functions in systems in thermodynamic equilibrium are averages over initial conditions of functions of the trajectory of the system in phase-space, the latter depending on the volume, the total number of particles and the classical Hamiltonian. Thus, the well-known histogram reweighting method can almost straightforwardly be applied to reconstruct the probability distribution of initial states at different thermodynamic conditions, without extra computational effort. Correlation functions and transport coefficients are obtained with this method from few simulation data sets.Comment: 4 pages, 3 figure

Cultural Influences on Academic Performance in Fiji: A Case Study in the Nadroga/Navosa Province

At an upper level of education, especially Forms 5, 6 and 7 of secondary school and in tertiary institutions, Indo-Fijian students often perform better than their ethnic Fijian counterparts. This pattern of ethnic difference in academic performance is a long standing one, lasting over 70 years. However, both ethnic groups have been participants in the same educational system in Fiji. Educational policies have been implemented to reduce this difference. This present case study argues that there are cultural differences of values, beliefs and practices with respect to educational achievement among Indo-Fijians and ethnic Fijians. The achievement ethic of the two ethnic groups differs. Indo-Fijian culture respects and values education highly. Generally speaking, educating children has been always the top priority of Indo-Fijian culture. They believe that education changes people for the better, and the only way to “success” is through education. Thus, Indo- Fijian parents believe that helping children to strive for academic excellence is one of the most important tasks for them. The priority attached by such parents to educational success is one of the strongest forces behind academic success. By contrast, ethnic Fijian culture encourages children to have a strong sense of loyalty to their community and of becoming good members of their koro (i.e., village). Indeed, one’s total commitment to communal activities and cultural requirements is of vital importance. Although ethnic Fijian parents generally understand the importance of their children’s education and wish to support their education, ethnic Fijian communal demands are enormous in terms of time and labour. The pressure to maintain their moral and social obligations within the community tends to make ethnic Fijians spend a large amount of time, energy and money on functions such as ceremonial events and church activities, at the possible expense of providing for the formal education of their children. These demands mean that parents are often absent from home, and unable to supervise children’s homework. Ethnic Fijian children, upper secondary schoolers, feel strong pressure from their peers within their koro to conform to social activities, such as attending church, playing sports such as rugby and volleyball, and hanging around in the koro and town. Besides, the layout of the typical ethnic Fijian home is a more difficult environment than Indo-Fijian households for children’s study, largely due to the limited space to study independently. The socio-cultural background of ethnic Fijians, especially their home environment including family values and priorities, is one of the major barriers to their children’s educational progress. In addition, school leadership, teachers’ expectations, colonial policies and legacies, e.g., land tenure issues, play important roles in affecting differences in the academic performance of these two ethnic groups. Consequently, the educational achievement differences between ethnic Fijians and Indo-Fijians are revealed substantially during the secondary and tertiary educational institutions

Влияние размера частиц горной породы на параметры пневмотранспортирования

Приведені результати досліджень впливу розміру часток гірської породи, що транспортується, на параметри пневмотранспортування. Отримані залежності для визначення швидкості пневмотранспортування та витрат стислого повітря від розміру часток матеріалу, що транспортується, з урахуванням параметрів пневмотранспортної системи.The brought results over of researches of influence of size of parts of mountain breed that is transported, on the parameters of pneumatic portage. The got dependences are for determination of speed of pneumatic portage and charges of the compressed air from the size of parts of material that is transported, taking into account the parameters of the pneumatic portage system