A Few Remarks About the Gurney Energy of Condensed Explosives

After reconsidering the definition and characteristics of the Gurney energy, we explain some points related to the evaluation and practical use of this quantity. We correct a recently published relationship between the detonation velocity of an explosive and its Gurney energy at infinite expansion. Then, in the framework of cylinder tests, we indicate that the Gurney energy gives only a rough evaluation of experimental results; it can, however, be reasonably used to compare the ability of explosives to accelerate metals. Besides, the value γ=3 classically evoked for the polytropic gamma of the detonation products generally leads to significant errors in the evaluation of the Gurney energy at infinite expansion.     

Sensitivity Analysis for a Planar SOFC: Size Effects of the Porous Gas Diffusion Layer Underneath the Channel Rib

This paper investigates the size effects of the gas diffusion layer underneath the channel rib on the performance of a planar solid oxide fuel cell (SOFC). Based on 3‐dimensional numerical simulations, the sensitivities of the electrical performance parameters (Nernst potential and current density) and the thermal performance parameters (heat generation and temperature) are examined as a function of variations in the channel rib width and anode thickness. The sensitivity values of the Nernst potential and current density are calculated to guide the design of a cell in a planar SOFC. In particular, the changes in ohmic losses for the interconnectors and anode are analyzed as a function of the variations of the channel rib width and anode thickness. The variations of the mole fractions of hydrogen, oxygen, and water in the active areas of the channel rib and the channel are presented, which provide sensitivity profiles for gas diffusion with respect to changes in the anode thickness.     

A Constant-Density Gurney Approach to the Cylinder Test

The previous analysis of the Cylinder test required the treatment of different wall thicknesses and wall materials separately. To fix this, the Gurney analysis is used, but this results in low values for full-wall standard, ideal explosives relative to CHEETAH analyses. A new constant metal-density model is suggested, which takes account of the thinning metal wall as the cylinder expands. With this model, the inner radius of the metal cylinder moves faster than the measured outer radius. Additional small corrections occur in all cylinders because of energy trapped in the copper walls. Also, the half-wall cylinders have a small correction because the relative volumes of the gas products are smaller at a given outside wall displacement. The Fabry-Perot and streak camera measurements are compared. The Fabry method is shown to equate to the constant density model.     

A methodology for predicting and comparing the full‐scale fire performance of similar materials based on small‐scale testing

Reconstructive fire testing is an important tool used by fire investigators to determine the cause, origin, and progression of a particular fire. Accurate reconstruction of the fire requires the laboratory structure to be outfitted with materials that, in terms of contribution to fire growth, perform similarly to the original materials found at the fire scene. Therefore, a procedure was developed to enable fire investigators to select these replacement materials on the basis of a quantitative assessment of their relative fire performance. This procedure consists of gram‐scale and/or milligram‐scale standard testing accompanied by inverse numerical modeling of these tests, which is used to obtain relevant material properties. A numerical model composed of a detailed pyrolysis submodel and empirical flame heat feedback submodels, which were developed in this study, is subsequently employed to simulate the early stages of the Room Corner Test, which was selected to represent full‐scale material performance. The results of these simulations demonstrate that this procedure can successfully differentiate between fire growth propensities of several commercially available medium density fiberboards.     

A New Approach to the Application of Molecular Surface Electrostatic Potential in the Study of Detonation

In a sample of 22 nitramines, the simplest features of surface electrostatic potentials (SEPs), their positive (V_S,max) and negative (V_S,min) extremes, are related to their detonation velocities, D, at maximal theoretical densities. The relationships between the V_S,min and D values logically show the nitramino group as responsible for detonation initiation for these compounds. On the other hand, the V_S,max values gave complicated relationships. As a criterion of the imbalance between the V_S,max and V_S,min extremes their sum was derived and used as a new simple characteristic of SEPs, V_S,Σ. The V_S,Σ values have close relationships with the D values and the corresponding relationships uniquely determine the nitramino grouping as a reactivity center for detonation of nitramines. This new criterion is shown to be the best SEP characteristic for the study of detonation initiation. In all the relationships mentioned in this study of nitramines, the increase in potentials and/or their sum correspond with an increase in the D values (energy content of molecules).     

粉煤灰用于中川高速公路路面基层的研究

本文研究二灰类路面基层材料在不同配合比、不同石灰剂量、不同压实度时在不同龄期的强度增长规律。进而用该材料铺筑试验路段,以验证其强度、稳定性和施工方法     

An Approach to the Analysis of Mixing in Reactive Systems

A simple mixing approach for use in reactive systems is considered. This mixing approach has so far been applied to reburning and selective non‐catalytic reduction (SNCR) processes, two well‐known techniques to reduce NO_x emissions. Detailed kinetic models together with the mixing approaches, based on the work of Zwietering, are used to simulate both the chemistry and mixing of the reactants. Two different configurations for the mixing approach have been considered: the so‐called direct and reverse approach. The study includes a comparison between different experimental results obtained in pilot installations and theoretical results calculated with the present approach.     

Mechanical Response of a Large Fuel Cell Stack to Impact: A Numerical Analysis

Large fuel cell stacks usually undergo dynamic load (vibration and impact) during packing, transportation, and serving time, in particular for those used in the automobiles. This may cause the decay in the performance, and even structure damage of the stack. We numerically analyze the mechanical response of a large fuel cell stack clamped by steel belts to a violent impact in the present paper. It is found that the location of the clamping belts has a great effect on the anti‐impact performance of the stack. The results also indicate that the cells near the endplates have a worse anti‐impact performance than those far from the endplates. When subjected to a large impact in the direction parallel with the cells, the stack may give rise to interface slippage between cells, showing a downward bowing phenomenon. The relative slippage between cells is affected by the clamping force, impact acceleration and the friction coefficient between cells. A large interface friction coefficient and a reasonable high clamping force are expected in order to increase the anti‐impact performance.     

Reply to the Comment by K. Jorgensen et al. to “Analysis of constant rate period of spray drying of slurry”

Previously developed model for spray drying of slurry droplets with high solid content (Liang, 2001) was revised to describe correctly a boundary condition on the outer surface of droplet on basis of the rate of liquid evaporation.     

On the simulation of the flaking paint due to internal stresses: A simple model

We present a simple theoretical and experimental model to explain the flaking off of paints, from a pre-existing defect, due to the influence of internal stresses provoked by the variation of ambient temperature and a long or strong illumination. The experimental model is made of two superimposed rubber strips, one of them being submitted to an instantaneous elongation or to a constant speed of strain. The detachment of the other strip, that represents the peeling and the flaking off of the paint layer, is measured and analyzed using concepts of the fracture mechanics, such as the strain energy release rate, in order to determine the conditions of stability and propagation of a crack at the interface, and to draw a master curve representing the dissipation function as a function of the crack propagation speed.     

我国研究生资助体系存在的主要问题及对策分析

本文主要分析了当前我国研究生资助体系中存在的一些主要问题,并在此基础上提出了改革我国研究生资助体系的几点建议,以期为新形势下进一步完善我国新型研究生资助体系以及更好地发挥其作用提供决策参考。     

A Contribution to the Investigation of Enzyme‐Catalysed Hydrolysis of Poly(ethylene terephthalate) Oligomers

Summary: One strategy to solve the problem of unwanted PET oligomer deposits in textile production is their enzymatic cleavage. In this work a selection of different enzymes (esterases, lipases) were tested for this purpose. The capacity to hydrolyse PET oligomers of some of the tested enzymes has been previously described in the literature. In order to imitate practical conditions both dry and precipitated PET oligomers were used. The decrease in the amount of cyclic trimer, the main component of the PET oligomers, was monitored by HPLC. After treatment with the lipase from Triticum aestivum a decrease of 80 wt.‐% was found. However, the effect of this lipase seems to have less to do with catalysing hydrolytic cleavages of ester groups than with the absorption of the oligomer on the enzyme protein.

Cyclic PET trimer (cyclo‐tris[ethyleneglycolterephthalate]).     

Contribution of Colloidal Forces in Non-contact Area to the Adhesion Between a Micro-probe and a Substrate Surface: Theoretical Analysis

Colloidal forces outside the microscopic probe (particle)–substrate adhesion contact area were analyzed theoretically. Equations describing the van der Waals, electrical double layer, and hydrophobic forces were derived for the non-contact area of a probe–substrate system assuming a simple sphere–flat geometry. Two cases were considered: particles freely resting on the substrate surface and particles pulling off the substrate. The results of modeling presented in this communication suggest that the adhesion of fine particles (microscopic and sub-microscopic particles) to flat surfaces can be affected by the forces acting outside the contact area. However, due to increased distance between the particle and substrate during separation, both the van der Waals and electrostatic forces acting outside the contact area are negligibly small compared to the short-range adhesion forces and they do not contribute to the measured pull-off force to any great extent for most systems. On the contrary, our calculations suggest that the long-range hydrophobic forces can contribute to the strength of adhesion between hydrophobic fine particles and hydrophobic substrates.     

Natural Abundance Carbon Isotopic Analysis Indicates the Equal Contribution of Local Synthesis and Plasma Uptake to Palmitate Levels in the Mouse Brain

Saturated fatty acids are the most abundant fatty acids in the brain, however, there has been some debate regarding the ability of intact dietary saturated fatty acids to be incorporated into the brain. In the present study, we use compound specific isotope analysis to measure the natural abundance carbon isotopic signature of brain, liver, and blood palmitic acid (PAM) and compare it to the dietary PAM and sugar isotopic signatures to calculate the relative contribution of both the incorporation of intact and endogenously synthesized PAM to these pools. Mice were equilibrated to the study diet, and extracted fatty acids were analyzed with gas chromatography isotope ratio mass spectrometry to determine the carbon isotopic signature of PAM (δ¹³C_PAM). Liver, serum total, and serum unesterified fatty acid δ¹³C_PAM ranged between ?20.6 and ?21.1 mUr and were approximately 8.5 mUr more enriched in ¹³C when compared to the dietary PAM signature. Brain δ¹³C_PAM was found to be more enriched than liver or blood pools (?16.7 ± 0.2 mUr, mean ± SD). Two end‐member‐mixed modeling using the carbon isotopic signature of dietary PAM and dietary sugars determined the contribution of synthesis to the total tissue PAM pool to range between 44% and 48%. This suggests that endogenous synthesis and dietary PAM are near equal contributors to brain, liver, and blood PAM pools. In conclusion, our data provide evidence that brain PAM levels are maintained by both local endogenous synthesis and through the uptake of intact PAM from the blood.     

A New Group Contribution Method based on Equation of State Parameters to Evaluate the Critical Properties of Simple and Complex Molecules

A new group contribution method to evaluate the critical properties (temperature, pressure and volume) is presented and applied to estimate the critical properties of biomolecules. Similar to other group contribution methods, the one proposed here divides the molecule into conveniently defined groups and evaluates the properties as the sum of the different contributions according to a specified model equation for each of the properties. The proposed method consists of a one‐step calculation that uses simple model equations and does not require additional data besides the knowledge of the structure of the molecule, except for isomers. For these substances the normal boiling temperature, the molecular mass and the number of atoms in the molecule are used to distinguish among isomers. The method is applicable to high molecular weight compounds, as most biomolecules and large molecules present in natural products.     

利用AutoCAD将三维模型生成布置图的常见操作问题解析

AutoCAD是工程设计行业在绘图方面使用最广泛的软件之一。笔者参与了加拿大某大型油砂项目,该项目主要利用AutoCAD将三维模型生成布置图。在担任EDS(Engineering Design Systems)和AutoCAD Coordinator时,笔者项目组遇到了一些AutoCAD常见操作问题,并且找到了相应的解决方法,谨作此文供大家在类似工作中参考学习。     

浅谈关于水中油类监测分析应注意的几个问题

在从事水中油类监测分析几年间,笔者发现监测结果的准确度受到水样保存方法与时间、四氯化碳批次、分析室内温度、比色皿的正确操作、仪器洗涤方法等因素影响较大。为了确保测定结果准确可靠,针对上述诸多影响,笔者总结了水中油类监测分析应注意的几个问题,仅供同行们参考。     

分散染料染色物若干色牢度问题分析和改进技术

近年涤纶染色物的变褪色和落色等色牢度问题以及色点、色斑等是分散染料存在的主要问题之一,本文分析了产生这些问题的原因与改进技术.     

基于环保标准发生炉冷煤气作为玻璃熔窑燃料相关问题分析

从国家(地方)颁布的玻璃行业污染物排放标准出发,结合玻璃熔窑烟气主要污染物排放特征,通过对发生炉冷脱硫和脱氨工艺技术的系统分析,指出煤气经过有效的脱硫和脱氨处理后,可以有效减少玻璃熔窑SO2和NOx排放,其SO2、 NOx排放水平可以达到甚至优于天然气水平。同时对发生炉冷煤气作为玻璃熔窑燃料其他优势和存在的问题进行了简要分析,并提出了相应的解决办法。