镁质波形瓦机械化设备的研制

讲述了镁质波形瓦机械化设备的构造,并对生产过程中碰到的难题作了剖析,也指出了其中的不足之处。     

Sharpening polycrystalline phase boundary for potassium sodium niobate ceramics with MnF2 modification

The influence of anion on structure and performance is unclear in potassium sodium niobate ((K,Na)NbO₃; KNN)-based ceramics, while cation doping has been widely researched. Here, the phase structure and electrical properties are explored in MnF₂-doped KNN ceramics. Significantly, sharp rhombohedral–orthorhombic (R–O) and orthorhombic–tetragonal (O–T) phase boundary as well as reduced diffusion degree is exhibited in the ceramics along with little changed phase transition temperatures due to the optimized F⁻ content at O site, which is different from that of cation replacement for A and B sites. Notably, the domain wall motion is facilitated due to the increased A vacancy and decreased O vacancy along with strengthened polarity, originating from the higher valence state and electronegativity of F⁻ with respect to O²⁻. And then, enhanced ferroelectricity is realized via MnF₂ modification, the piezoelectricity is elevated in turn. This work presents a new idea of anion doping for controlling structure and properties in perovskite materials.     

定向破片拦截下RPG-7类反坦克火箭弹(静态)毁伤模式的试验研究

为优化主动防护系统的性能,文中以静态放置的RPG-7类反坦克火箭弹战斗部为例,对其在密集破片作用下的毁伤模式进行了理论分析,并在典型条件下进行了试验验证。试验结果表明,战斗部结构解体、引信失效、装药被击爆、装药和药型罩被损坏以及装药燃烧等毁伤模式都存在,验证了理论分析的结果。文中的研究结果可为主动防护系统拦截交会参数的选择、拦截弹战斗部破片场参数的优化设计提供有益的参考。     

Preparation and characterization of porous PDMS beads for oil and organic solvent sorption

In this article, poly (dimethyl siloxane) (PDMS) porous beads were prepared by suspension polymerization method using n‐octane and carbon tetrachloride (CCl₄) as diluents and pore formation agents. The apparent density, porosity and other characteristics were characterized. The absorption experiments showed that the porous PDMS beads exhibited more absorption capacity and faster absorption rate toward oils than the nonporous or oligoporous PDMS beads did, moreover they are of remarkable stability and recyclability, which could provide a path to absorb the oils floating on water. POLYM. ENG. SCI., 54:2965–2969, 2014. © 2014 Society of Plastics Engineers     

A Moisture Transfer Model for Isothermal Drying of Plant Cellular Materials Based on the Pore Network Approach

Plant materials with cellular structure, like fruits and vegetables, are often viewed as porous media in terms of model building of the drying process, on the basis of a hypothesis that all of the moisture of a plant tissue is trapped in a continuous and connected pore network system. However, most of the moisture in the plant tissue is contained naturally in enclosed cells. In the course of drying, the trapped moisture has to cross the cell membranes and then migrates in the extracellular space. Based on this concept, a pore network model for isothermal drying of plant materials was developed in which two stages of moisture movement—transmembrane transfer and extracellular transfer in the pore network—were considered. Finally, the isothermal convective air-drying processes of a potato slice were simulated. The calculated results were validated by the experiments conducted under the simulation conditions.     

锅炉点火系统故障分析与处理

我厂有两台循环流化床锅炉,各有一套独立的自动点火系统。两套点火系统均使用天然气作为燃料,自投用以来经历了无数次的点火,其过程中也出现了许多问题,本文将对其中的典型故障进行分析和探讨。     

Quality dependence study on dimensions for plano-concave molded glass lenses

A comprehensive study was conducted to analyze the quality dependence of a plano-concave molded glass lens on its own dimensions, i.e. the effective diameter, sag ratio, and center thickness ratio. To achieve this goal, a thermal-displacement coupled finite element analysis was carried out on the whole molding process, in order to get the results of curve deviation, temperature gradient, and residual stress with sets of variations in these dimensions. Then Taguchi method, one approach for design of experiments, was incorporated to conduct sensitivity analysis on the simulation results to figure out the dominating sequence of these dimensions. The results show that the effective diameter is the most influential factor among these three dimensions. In addition, curve deviation is sensitively proportional to diameter and sag ratio, but decreases insignificantly with greater center thickness ratio. However, residual stress is distinctly proportional to diameter and center thickness ratio, but increases very slightly with greater sag ratio. Results also confirmed the consequential relationship between temperature gradient and residual stress. These discoveries are fundamentally meaningful in getting an overall understanding of the dimensions’ influence on the molded lens quality, thus will help make decision in choosing proper dimensions for optical design.     

Enantioselective One‐Pot Reaction: Organocatalyzed Synthesis of Fully Functionalized Oxabicyclo[2.2.2]octanes with Seven Contiguous Stereocenters

An enantioselective one‐pot Michael/Michael/Henry/hemiacetalization reaction between α,β‐unsaturated aldehydes, α‐ketoamides, and nitroalkenes under mild conditions catalyzed by a diarylprolinol silyl ether has been developed. The sequential methodology provides a direct approach to a wide range of fully substituted chiral oxabicyclo[2.2.2]octanes with seven contiguous stereocenters in moderate to excellent yields (up to 99%), high to excellent diastereoselectivities (up to >25:1 dr), and high to excellent enantioselectivities (up to 99% ee).

     

Production of glass-ceramics using Municipal solid waste incineration fly ash

Municipal solid waste incineration(MSWI) fly ash is a by-product from municipal waste incineration.According to incomplete statistics, each year more than one million tons MSWI fly ash was produced in China. Owing to high heavy elements content, widely used disposal methods of landfill are not suitable for MSWI fly ash treatment. In this study, by using MSWI fly ash as raw materials, glassceramics was synthesized for the solidification of heavy metals and waste recycle. Process parameters, including composition, heat treatment temperature and time, were studied and optimized. Under optimizing conditions, the product has good properties of density of 3.42 g·cm~(-3) and Vickers hardness of 6.91 GPa. Moreover, the leaching concentration of heavy metal elements meets allowable values of toxicity characteristic leaching procedure(TCLP).This study offers an alternative for MSWI fly ash recycle.