垂直上升管内密度波不稳定性的研究

在低压自然循环水回路上，对垂直上升管内两相流动密度波不稳定性进行了实验研究，实半记录了不同工况下的脉动曲线，用多元线性回归这实验数据进行拟合，得出一个低压两相自然循环密度波的稳定性判据准则式，实验参数范围为，系统压力Ｐ＝０．２１～１．７５ＭＰａ，质量流速Ｇ＝３４５～１９４７ｋｇ／ｍ＾２．ｓ，进口对冷度△Ｔｓｕｂ＝６～６０℃，加热功率Ｑ＝２．３～２４ｋＷ。     

Defect chemistry of the high-Tc superconductors

In the high temperature superconductors the critical temperature is intimately connected to the electronic charge-carrier concentration. The absolute values of this quantity and its dependencies on the controlling parameters temperature, oxygen partial pressure and doping content, is phenomenologically determined by the thermodynamics and kinetics of reactions involving point defects. Due to the low mobility of the ionic constituents the behavior at elevated temperatures is particularly important. Here, the kinetics are controlled by the mass transport parameters, essentially by the ionic conductivity. The scientific discipline whose objective is precisely described in the above terms is called defect chemistry. It quantitatively deals with the nature of excess and lacking native ionic or electronic particles as well as with foreign species. It describes the thermodynamics and kinetics of their formation, annihilation, interaction and motion in the phase under consideration and thus determines the chemistry within this phase.     

椭球体放矿理论的几个主要问题：类椭球体放矿理论建立的必要性

本文根据实验和散体力学等理论，分析了椭球体放矿理论在放出体形状、密度场、速度场和移动边界等几个方面存在的缺陷和不足，说明了建立类椭球体放矿理论的必要性。     

Thermodynamic analysis of liquid desiccants

Liquid desiccants are widely used in many solar applications. In order to analyze the performance of the system using desiccant technology, the thermophysical properties of desiccants are essential. In particular, the vapor pressure of the liquid desiccant is one of the important properties in air dehumidification. In this paper, an attempt is made to predict this property based on a classical thermodynamics approach and it is found that the predicted values for lithium chloride agree very well with the experimental results. The desired sorption properties can also be obtained by mixing the desiccants, which is another method of developing a new cost-effective liquid desiccant. In this paper, simple mixing rules are used to predict the vapor pressure, density, and viscosity of the desiccant mixture, namely calcium chloride and lithium chloride. It is found that the interaction parameter need not be included in calculating the density and vapor pressure of the above mixture but must be included in predicting the viscosity.     

泡沫水泥的研究与应用

泡沫水泥是一种超低密度水泥。对泡沫水泥的性能、实验研究方法、泡沫水泥固井施工工艺及设备和泡沫水泥的应用评价作了系统的评述。泡沫水泥的主要优点是水泥浆密度低、强度高及渗透性较低,对减少气窜、防止套管腐蚀及漏失层固井、长封固段固井及注气井固井作业十分有利。泡沫水泥固井的评价应将变密度测井、伽玛测井和声幅测井等资料联系起来,则其评价鉴定效果会更好。     

On the density profile within random and oriented wood-based composite panels: horizontal distribution

Wood composites are produced from the processing of discontinuous wood elements such as flakes and strands, with resin and other additives. Consolidation of the loose mat structure into a panel is achieved under heat and pressure, and the final product structure and properties are therefore governed not only by the properties of the wood elements but also by the forming and pressing processes. This paper deals with the density variation within the horizontal plane of flakeboards, in an approach that combines a structural model, based on the layout of the flakes, together with the consolidation model and mass transfer, both resulting from the hot-pressing process. The density distribution within the panels manufactured according to several possible combinations of random orientation and placement of flakes is analyzed, and the significant influence of the random character of the orientation of flakes during the forming process is highlighted.     

Spectroscopic studies of Nd-doped alkali fluoroborophosphate glasses

A new family of three optical glasses of the following chemical composition with 1 mol% of Nd³⁺ were prepared to examine the effects of alkali fluorides in unmixed form:

Full-size image

, where RF=LiF, NaF and KF. On the basis of the measured values of densities and refractive indices, the dielectric constant, reflection losses, molar refraction, Nd³⁺ ion concentration in glasses and several other physical properties were determined. Absorption spectra of these glasses were recorded and Judd–Ofelt intensity parameters (Ω_λ) have been calculated. Radiative lifetimes (τ_R) and branching ratios (β_R) for the fluorescent levels have been determined. To understand the laser efficiency of these materials, the values of the spectroscopic quality factor (Ω₄/Ω₆) has been evaluated and it is found that glass C could be suggested as a suitable lasing material.     

Analytical Model for Calculating Trapped Charge in a－Si：H and Its Relative Error Analysis

ＡｎａｌｙｔｉｃａｌＭｏｄｅｌｆｏｒＣａｌｃｕｌａｔｉｎｇＴｒａｐｐｅｄＣｈａｒｇｅｉｎａ－Ｓｉ：ＨａｎｄＩｔｓＲｅｌａｔｉｖｅＥｒｒｏｒＡｎａｌｙｓｉｓＷＡＮＸｉｎｈｅｎｇ；ＸＵＺｈｏｎｇｙａｎｇ；ＺＯＵＸｕｅｃｈｅｎｇ（ＨｕａｎｚｈｏｎｇＵｎｉｖ...     

Investigating Density Distributions for Tablets of Different Geometry During the Compaction of Pharmaceuticals

The axial and radial powder movements during the compaction process were investigated using flat- and curved-face punches for the case of single-ended axial strain applications. The density distributions in microcrystalline cellulose tablets were determined experimentally using a colored layer technique and digital image analysis. Nondestructive topography measurements were taken to assess the variation in surface roughness of the tablets and relate this to the forming pressure and density distribution. Results showed that the tablets produced were highly nonhomogeneous with high density regions in the "top corners" (adjacent to the moving punch surface) and "middle bottom half" for the flat-face tablets. For instance, at 92.7 MPa, density values were recorded at greater than 1.2 g/cc in the high density regions and greater than 0.6 g/cc in low density regions with regards to experimental results. High density regions were noted in the corners where the powder was in contact with the die wall for the curved-face tablets; both axial and radial powder movement was seen to be taking place. Surface topography and surface form results also showed that the geometric location of the corresponding surfaces of the tablets were relocated after the compaction process due to elastic recoil and stress relief.     

Computational materials science: The emergence of predictive capabilities of material behaviour

The availability of high performance computers and development of efficient algorithms has led to the emergence of computational materials science as the third branch of materials research complementing the traditional theoretical and experimental approaches. It has created new virtual realities in materials design that are either experimentally not realizable easily or are prohibitively expensive. The possibilities of doing calculations from first principles have led to predictive capabilities that open up new avenues of discovering novel materials with desired properties, understanding material behaviour on the nano- to the macroscopic scale and helping research in new frontiers that could interface between nano-materials and drug design, as well as in understanding biological systems. Here, we describe some significant recent developments related to alloy and steel design as well as the study of matter on the nano-scale — an area that has gained much prominence in current materials research.