Multiscale Analysis of Fracture of Carbon Nanotubes Embedded in Composites

Due to the enormous difference in the scales involved in correlating the macroscopic properties with the micro- and nano-physical mechanisms of carbon nanotube-reinforced composites, multiscale mechanics analysis is of considerable interest. A hybrid atomistic/continuum mechanics method is established in the present paper to study the deformation and fracture behaviors of carbon nanotubes (CNTs) in composites. The unit cell containing a CNT embedded in a matrix is divided in three regions, which are simulated by the atomic-potential method, the continuum method based on the modified Cauchy–Born rule, and the classical continuum mechanics, respectively. The effect of CNT interaction is taken into account via the Mori–Tanaka effective field method of micromechanics. This method not only can predict the formation of Stone–Wales (5-7-7-5) defects, but also simulate the subsequent deformation and fracture process of CNTs. It is found that the critical strain of defect nucleation in a CNT is sensitive to its chiral angle but not to its diameter. The critical strain of Stone–Wales defect formation of zigzag CNTs is nearly twice that of armchair CNTs. Due to the constraint effect of matrix, the CNTs embedded in a composite are easier to fracture in comparison with those not embedded. With the increase in the Young’s modulus of the matrix, the critical breaking strain of CNTs decreases.     

Modeling and simulation of hard-particle interaction in head/disk interfaces

A hard particle interacting with a slider and a disk in the head/disk interface of hard-disk drives can produce a scratch on the disk and result in data loss. Our work emphasizes modeling and simulation of slider, particle, and disk interactions, scratch generating mechanisms, and linking of scratch to interface design parameters. Two models are presented. The Monte Carlo method was used to calculate scratch probabilities and parametric studies were performed to determine the effect on scratch probability of various parameters, such as friction coefficients, particle mean size, slider wall angles, the ion-milling (IM) etch depth from the air-bearing surface (ABS) of the slider, and the efficacy of additional ABS structures acting as particle shields. Simulation results show that the friction coefficient is a dominant parameter. If the disk friction coefficient is smaller than the slider friction coefficient, scratches are not produced. Using shallow IM depths is an effective and practical way to reduce the scratch probability. Experimental results are very close to the simulation predictions.     

品牌和包装的提升与超越

赖永初酒是以茅台酒创始人赖永初先生的名字命名的酱香型白酒，被中国白酒界专家誉为“酱香经典，酒中极品”，优良的品质受到国内外消费者的一致好评。赖茅酒在历史上曾被奉为上品，声名显赫，但多年以来由于种种原因没有达到它应有的所期望的高知名度和应得到的丰厚的销售收入。我们以为其中一个重要的原因是新的赖永初品牌与产品形象缺乏高水平的“再包装”，因此许多消费者只知道茅台酒而不知道赖永初酒，更不知道它们的历史渊源了。赖永初酒虽在贵州省内外的范围有一定的知名度与销售成效，但总体上处于一般水平。     

Electronic and junction properties of poly(2,5-dimethoxyaniline)-polyethylene oxide blend/metal Schottky diodes

Schottky barrier diode devices were fabricated in a sandwich configuration with a blend film consisting of a conducting polymer, poly(2,5-dimethoxyaniline), PDMA in an insulating matrix, polyethylene oxide (PEO). The influence of two different dopants, sulphate anion (SA) or methane sulfonate anion (MSA), in the electronic properties of the device was followed using the devices: ITO/PDMA (SA)-PEO/Al and ITO/PDMA (MSA)-PEO/Al. Current (I)-Voltage (V) characteristics were recorded for making a comparative evaluation of the electronic and junction properties of the devices. The junction and electronic parameters were analyzed and compared in the light of differences in the electronic state, morphology and transport of carriers. The device turn on voltage was found to be higher for Al/ PEO-PDMA (MSA)/ITO (∼3.0 V) in comparison to Al/ PEO-PDMA (SA)/ITO (∼2.85 V). The electronic states of PDMA doped with SA or MSA dopant were ascertained by optical UV-Visible spectroscopy. AC-impedance measurements were made for the devices and the values of bulk resistance (R_c), depletion resistance (R_d) and depletion layer width (W) were deduced through a proposed equivalent circuit. W for the device with PEO-PDMA (MSA) is more (∼24 nm) than the device with PEO-PDMA (SA) (∼8.5 nm). The observed higher Φ_B for PDMA-PEO (MSA) is consistent with this observation.     

电镀厂化验废液中银的再生利用

针对电镀厂化验室产生的含银废液的再生利用方法进行了研究，建立了从电镀厂化验废液中回收银，并直接制成分析纯硝酸银的工艺。该方法简单可行，对减少化验室废水对环境的污染，提高银二次资源的利用率，降低化验成本具有现实意义。该工艺可推广到硝酸银消耗量较大的其他化验室。     

IC平台专用标准产品的快速定制化

当前数量飞速增长的嵌入式软件及最近的电子掩膜可编程嵌入式门阵列定制了专用标准产品(ASSP)。文中所提出的方案致力于解决两方面的问题一是对较高灵活性的高度要求;二是对缩短产品生产周期的需求。这可以从使用单个通道可编程逻辑和相应的软硬件协同设计流程来解决。采用0.3μm的CMOS工艺,系统所需的硅片面积为23mm2。嵌入式通道可编程逻辑大约占系统总面积的30%。     

一种基于PC打印口设计的A/D转换器

描述了基于PC打印口设计的A／D转换器工作原理，着重介绍了实现A／D转换器的硬件电路以及软件编程．     

防雷在新机场的应用

本文介绍广州新白云国际机场航站楼的建筑物防雷，建筑物防雷是建筑中比较常见的保护措施，而广州新白云国际机场建筑物的防雷，也有它的优点和特色。     

A novel numerical approach to heterojunction bipolar transistors circuit simulation

In this paper we present a novel computational method for calculating the heterojunction bipolar transistor (HBT) physical characteristics in the time domain. To calculate the HBT high frequency properties, the Gummel-Poon equivalent circuit model is applied to replace the HBT in the circuit and a set of governing ordinary differential equations (ODEs) is formulated. We directly decouple the system ODEs and solve each decoupled ODE with the monotone iterative method in the time domain. This solution methodology proposed here has been applied to semiconductor device simulation by us earlier, and we find this method for the HBT simulation has good accuracy and converges globally. Compared with the HSPICE circuit simulator results, our results present the accuracy, efficiency, and robustness of the method.     

使用Authorware与网页制作技术相结合的方法开发多媒体软件

本文介绍一种使用Authorware与网页制作技术相结合的开发多媒体软件的新方法，借助于Authorware中可以使用控件的特性，将Web浏览器控件嵌入在Authorware开发的多媒体软件之中，使用这种方法，可以充分利用较成熟的网页制作技术，简化开发工作，缩短软件开发周期，并且便于维护。