Review on development of metal/ceramic interpenetrating phase composites and critical analysis of their properties

Metal/ceramic composites are in high demand in several industries because of their superior thermo-mechanical properties. Among various composite types, the interpenetrating phase composites (IPCs) with percolating metallic and ceramic phases offer manifold benefits, such as a good combination of strength, toughness, and stiffness, very good thermal properties, excellent wear resistance, as well as the flexibility of microstructure and processing route selection, etc. The fabrication of metal/ceramic IPCs typically involves two steps - i) processing of an open porous ceramic body, and ii) infiltration of metallic melt in the pores to fabricate the IPC. Although significant progress has been made in recent years for developing both porous ceramics and melt infiltration methods, to the best of the knowledge of the authors, no review article summarizing all the aspects of processing and properties of IPCs has been published till date. This review article is aimed at filling this gap. Starting with a brief introduction about the current status and applications of IPCs, the various processing routes for fabricating open porous ceramic preforms and melt infiltration techniques have been discussed. Subsequently, the data available for various important physical, mechanical, and thermal properties for IPCs have been critically analyzed to thoroughly understand their dependence on various structural and processing parameters. To compare the properties of IPCs with other relevant materials, seven different Ashby material property maps have been used, and the domains for IPCs have been created in them. For each map, the concept of material indices has been employed to critically discuss how IPCs perform in relation to other material classes for various optimum design conditions. Finally, a detailed future outlook for further research on IPCs has been provided.     

Investigation on the Interactions between Self-Assembled β-Sheet Peptide Nanofibers and Model Cell Membranes

Self-assembled peptide nanofibers (NFs) obtained from β-sheet peptides conjugated with drugs, including antigenic peptides, have recently attracted significant attention. However, extensive studies on the interactions of β-sheet peptide NFs with model cell membranes have not been reported. In this study, we investigated the interactions between three types of NFs, composed of PEG-peptide conjugates with different ethylene glycol (EG) lengths (6-, 12- and 24-mer), and dipalmitoylphosphatidylcholine (DPPC) Langmuir membranes. When increasing the EG chain length, those interactions significantly decreased considering measurements in the presence of the NFs of: (i) changes in surface pressure of the DPPC Langmuir monolayers and (ii) surface pressure–area (π–A) compression isotherms of DPPC. Because the observed trend was similar to the EG length dependency with regard to cellular association and cytotoxicity of the NFs that was reported previously, the interaction of NFs with phospholipid membranes represented a crucial factor to determine the cellular association and toxicity of the NFs. In contrast to NFs, no changes were observed with varying EG chain length on the interaction of the building block peptide with the DPPC membrane. The results obtained herein can provide a design guideline on the formulation of β-sheet peptide NFs, which may broaden its potential.     

A review on China's wind power accommodation in the background of “Internet+” strategy

The consumption of fossil fuel has resulted in global warming, environmental pollution, and many other crucial problems. Replacing fossil fuel with renewable energy has become an important issue over the recent decades. As a renewable clean energy, wind power is a relatively well‐developed and promising energy method for current technology development in China. Under the background of growing demand for electricity and enhancing awareness for environmental, the “Internet+ wind power” concept has emerged based on both the wind power's characteristics that renewable and non‐polluting, and the rapid development of the Internet in China. Through querying an amount of literature and information, this paper reveals the resource endowment and policy environment about wind power and energy Internet at first. Then, the PEST‐SWOT strategy analysis model is used to analyze the internalities (strengths and weaknesses) and the externalities (opportunities and threats) of “Internet+ wind power”. According to these results, the paper puts forward some measures (development and utilization, business mode) for wind power accommodation. Then some policy recommendations have been proposed. The government should provide favorable conditions for wind power grid with the “Internet+” technology innovation.     

蒙脱石含量测定方法改进研究

用吸蓝量(MB)换算法测定蒙脱石含量,换算系数0.442不能用来准确计算其实际含量。由于吸蓝量和阳离子交换容量(CEC)与蒙脱石含量正相关,通过测定原矿、原矿提纯样以及提纯后杂质矿物的吸蓝量或CEC,进行加权或对比计算,即可得到原矿中蒙脱石的含量,这样可消除膨润土属性、属型等对测定结果的影响。改进的结果表明,不论加权法还是比值法,CEC也可用于测定蒙脱石含量;但加权法计算更为合理。蒙脱石、杂质矿物的纯度,以及它们的吸蓝量、CEC的精密度和准确度,是加权法测定准确与否的关键;比值法适用于细粒级或提纯后纯度较高情况下的测定。     

基于87c196mc单片机控制的蓄电池电机车脉宽调速系统

目前，我国煤矿使用蓄电池机车的调速控制基奉上是采用直流串励电机串电阻调速和可控硅脉冲调速。电阻调速的缺点是机车运行时耗能大，触头易损坏。经济效益差，调速不平稳；可控硅调速工作频率低。缓冲回路复杂，维修精度高。随着电力电子技术的发展。以大功率半导体器件IPM（智能功率模块）为主开关元件、以87c196mc为控制核心的直流斩波调速可以很好的解决以上问题，而且可以简化电路，提高调速的可靠性和调速性能。     

利用超声波测量沥青贮罐的液位

介绍了一种利用超声波原理开发的由单片机控制的非接触式测量装置，通过该装置可较方便地测量沥青贮罐的液位。     

Structural models of critical regions in old-type r.c. frames with smooth rebars

Structural assessment of existing reinforced concrete constructions under gravity loads and seismic actions has a high social and economical impact; actually in many European countries, most of the buildings dates back to 1960s and 1970s and cannot ensure satisfactory seismic response, since many areas have been later classified as seismic or since design has been carried out according to obsolete codes. These structures are generally reinforced with smooth bars that exhibit poor bond and need specific anchoring end details. In the present paper, some key aspects of structural models of smooth reinforcement for old-type r.c. frame analysis are reported. Results of experimental tests on smooth reinforcement and circular hook anchoring devices are also used to discuss some aspects of behavioural models of beam to column critical regions.     

商品混凝土开盘技术资料计算机管理系统的开发及应用

本文介绍了商品混凝土开盘技术资料自动化管理系统的开发思路和使用方法。该系统是根据商品混凝土搅拌站的实际应用情况研制开发出来的,是商品混凝土技术资料管理的有效的辅助工具。     

Consistent boundary conditions for flows within the atmospheric boundary layer

In computational wind engineering the neutrally stable atmospheric boundary layer (ABL) is often simulated using the standard k-ε model. The application of boundary conditions that are inconsistent with the profiles used at the inflow boundary causes streamwise gradients in the solution and prevents the simulation of a horizontally homogeneous boundary layer. In the present work these problems are overcome by applying a simple extension of the shear stress boundary condition at the top of the domain and by using one-dimensional models to generate inflow profiles in equilibrium with the ground boundary condition. This procedure allows the impact of the inconsistent boundary conditions to be quantitatively assessed. It is shown that inconsistent boundary conditions at the top of the domain result in erroneous streamwise gradients throughout the domain. These errors are reduced by enlarging the domain in the vertical direction but are not removed. The errors are also found in simulations with idealised and real topography included in the domain. A brief discussion of the impact of the errors on simulations of wind energy projects is given.     

Numerical studies on air flow around a cube

In this paper, air approach flow moving towards a cube will be studied using computational fluid dynamics (CFD). The Reynolds Averaging of Navier-Stokes (RANS) equation types of k-ε turbulence model are used. Some RANS predicted results are compared with different upstream air speeds. Flow separation at the corner above the top of the cube, level of separation and reattachment are investigated. Reference is made to the experimental data on wind tunnels reported in the literature.A method similar to ‘recirculation bubble promoter’ is used for different approach flow speed distributions. Problems encountered in numerical simulations due to the sharp corner are discussed with a view to obtaining better prediction on recirculation flow in regions above the top of the cube. Correlations between the turbulent kinetic energy above the cube and the recirculation bubble size are derived for different distributions of approach flow speed.By limiting the longitudinal velocities in the first cell adjacent to the sharp edge of the cube or rib, and making good use of the wall functions at the intersection cells of the velocity components, positions of maximum turbulent kinetic energy and the flow separation and reattachment can be predicted by a standard k-ε model. The results agree with those obtained in the experiments.