Evaluating coking resources. 2. State standard GOST 25543-88 as a coding system for coal and coal mixtures in evaluating their technological properties

The codification of coal in State Standard 25543-88 is compared with the international codification of coal of medium and high rank. The ranking of coking coal on the basis of State Standard GOST 25543-88 is evaluated.     

Tellurium clusters in channels of the porous silica ZSM-11

The distribution and structure of tellurium nanoclusters synthesized in crystal channels of the porous silica ZSM-11 are investigated using the maximum-entropy method and the Rietveld analysis. It is shown that the intercalated tellurium atoms are arranged in channels of the ZSM-11 zeolite not randomly but in the form of scraps of infinite chains similar to those observed in massive tellurium. The distances between the nearest neighbor tellurium atoms vary in the range 2.53(4)–2.70(3) ?. The clusters Te₄ are formed at the intersections of channels in the structure. These clusters have the form of distorted tetrahedra in which the tellurium atoms are separated by distances of 2.53(4) and 2.90(4) ?. Original Russian Text ? A.E. Lapshin, Yu.F. Shepelev, Yu.I. Smolin, E.A. Vasil’eva, 2008, published in Fizika i Khimiya Stekla.     

Noise–Power Optimization of Incremental Data Converters

Incremental data converters (IDCs) are useful in instrumentation and measurement applications, where low-frequency analog signals need to be converted into digital form with high accuracy and low power dissipation. They are particularly well suited for applications where a single analog-digital converter is multiplexed between many channels. This paper proposes an exact design methodology for IDCs, which optimizes the signal-to-noise ratio of the converter under practical design constraints. The process also allows the designer to apportion the noise budget in an arbitrary manner between thermal and quantization noise. The design process is illustrated by an example which describes the optimization of a third-order multiplexed IDC.     

ADI-FDTD Method With Fourth Order Accuracy in Time

This letter presents an unconditionally stable alternating direction implicit finite-difference time-domain (ADI-FDTD) method with fourth order accuracy in time. Analytical proof of unconditional stability and detailed analysis of numerical dispersion are presented. Compared to second order ADI-FDTD and six-steps SS-FDTD, the fourth order ADI-FDTD generally achieves lower phase velocity error for sufficiently fine mesh. Using finer mesh gridding also reduces the phase velocity error floor, which dictates the accuracy limit due to spatial discretization errors when the time step size is reduced further.     

Structural study of cubic pyrochlores based on quantum mechanical simulation

In the ideal A₂B₂O₆O′ pyrochlore structure, the x-value of O atom position is a variable parameter. In Bi_1.5ZnNb_1.5−xTa_xO₇ (BZNT) cubic pyrochlores, the x-values alter with the different compositions of Nb/Ta. In this work, a series of initial models for BZNT were established by analyzing X-ray diffraction data. Then three structure modifying methods, including Rietveld refinement, Rietveld refinement with energy and geometry optimization based on quantum mechanics, were employed to obtain the precise models using Materials Studio. Moreover, the reflectivities of BZNT were computed by quantum mechanical simulation based on the refined models. Comparing the simulation results from different modifying models with the experimental results, it is found that Rietveld refinement with energy optimization is the most accurate method for BZNT pyrochlores. According to the simulation results, the different reflectivities correspond well with various x-values of O atom positions in BZNT pyrochlores.     

情境故事法在产品设计开发中的应用

从产品设计中"以使用者为中心"的设计要求出发,引入情境故事法的相关内容.详细论述了情境故事法的概念、流程、操作方法,并以商务笔记本为研究载体,对商务笔记本的典型用户的使用特性,以及使用过程中的最初情境和遇到的问题进行综合分析.站在用户的角度建立情境故事以寻求商务笔记本设计的创新点,从而得到新的故事方案.最后对情境故事法使用的局限性作了些简要评述.     

Comparative Study of Rubidium and Cesium as Promoters in Carbon-supported Ruthenium Catalysts for Ammonia Synthesis

Sibunit-supported Ru-catalysts promoted with cesium or rubidium compounds have been comparatively studied with XPS. The cesium promoter interacts both with support and with active component. The absence of the promoter–support interaction in the case of rubidium provides a stronger interaction between promoter and active component compared to the cesium-based catalysts. These differences in the promoter–support and promoter–metal interactions are exhibited when a sequence of ruthenium and alkali introduction are changed.