Thermal expansion of CaAl4O7-based refractory compositions containing MgO and CaO additions

Various compositions of recently developed CaAl₄O₇-based ceramics are mentioned with special reference to those called “nonexpansive refractories” (=NER). The observed effect of deep depression of their thermal expansion is mainly ascribed to the creation of a specific microstructure resulting from high temperature reactions of CaAl₄O₇ with MgO or CaO additives yielding a CaAl₂O₄-based liquid. Some details characterizing the phase composition of the reaction zone are given. The effect of the calculated approximate content of CaAl₂O₄ in the specimens is interpreted graphically. Basing on the results of changes in the CaAl₄O₇ single crystal dimensions presented in comparison with some other expansion data, the presumable nature of the specific behavior of NER bodies on heating up to 500 °C is discussed. The NER products fired at 1620 °C are characterized by high strength and low open porosity.     

3D Printing Conductive Composites with Poly(ionic liquid) as a Noncovalent Intermedia to Fabricate Carbon Circuits

In this study, a kind of imidazole type poly(ionic liquid) ([PEP-MIM]Cl) is synthesized, which can disperse carbon effectively. [PEP-MIM]Cl is used as an intermediate to coat carbon on the poly(acrylic acid)(PAA-co-MBA) via ion exchange to obtain conductive polymer composite (CPC). A series of characterizations are performed. Experiments show that carbon can be coated on the PAA-co-MBA uniformly, and compared with using carbon as filler, this method requires less carbon to achieve good conductive performance. The carbon layer on the polymer's surface is enriched via the swelling-shrinking properties of PAA-co-MBA according to the SEM images. Furthermore, in combination with 3D printing technology, PAA-co-MBA can be designed into different shapes to achieve various functions such as pressure-sensing element. Finally, a new type of CPC named carbon clad polymeric laminate (CCPL) is prepared by using the carbon coating method and 3D printing technology. It has the potential to replace copper clad laminate (CCL) and printed circuit board (PCB), to a certain extent. This technology expands the preparation method and application of the CPC such as flexible and wearable conductive fabrics.     

水土保持措施对汾河水库泥沙淤积的影响

对山西省汾河水库1962～2008年淤积情况的分析结果表明:水库淤积量总体呈减小趋势。汛期降水量和来水量是造成水库淤积的主要原因,实施水土保持措施可减少水库淤积。     

Support principles of NPR bolt/cable and control techniques of large-deformation disasters

Deep mining has been paid much more attention because of the depletion of shallow mining resources.Traditional bolts could be invalid to accommodate large displacement and deformation in geomaterials.Consequently, alternative support and reinforcement bolts need to be studied and their constitutive models also need to be developed to help understanding for the complex stress-strain responses of rock masses under loadings. The effect of Negative Poisson's Ratio(NPR) that is attributed to the swelling phenomenon along the lateral direction may appear in metal materials under tensional loadings. Thence NPR materials often have an advantage over NPR ones in mechanical behavior such as impact resistance, antishearing, and energy absorbed. From the characteristics of NPR materials, a series of bolt and cable supports with the effect of NPR and constant-resistance have been recently developed. We here firstly introduce the structural features of NPR support. Then the constitutive model of NPR support is presented and its corresponding equation of energy equilibrium. Its basic principle interacted on rock masses is further discussed. Finally, NPR cables are employed to support the slope of an open-pit mine. The applications show that NPR cables can ease failure within the slope and play an important role in predicting and providing early warning of slope failure, together with a monitoring system of slope stability.     

Controlled interconversion of semiconducting and metallic forms of polyaniline nanofibers

Self-assembled polyaniline nanofibers doped with 2-acrylamido-2-methyl-1-propanesulfonic acid were prepared by oxidative polymerization of aniline in the presence of a nonionic surfactant. These nanofibers were dedoped to the semiconducting emeraldine base and then redoped to the metallic emeraldine hydrochloride. It was possible to introduce a different dopant anion from that used in the initial synthesis with no significant changes in fiber morphology or diameter, as observed by scanning electron microscopy (SEM). The method of sample preparation for SEM significantly affected the observed morphology. Deposition from aqueous dispersions resulted primarily in nanofibers that ranged in diameter from 28 to 82 nm (average: 56 nm), whereas drying to solid powder resulted in a less fibrous material. UV–vis–NIR absorbance spectroscopy indicated that the electronic structure of the emeraldine base nanofibers was identical to bulk emeraldine base obtained by conventional synthesis. Estimates from X-ray diffraction data suggested that the fractional crystallinity of emeraldine hydrochloride nanofibers did not differ significantly from the bulk powder.     

黄河下游引黄涵闸清淤设备的设计方案研究

本文解决了快速清除引黄涵闸淤积泥沙设备的设计方案问题。该设备的工作原理是将高压水喷射到闸门前淤积的泥沙层,靠高压水的冲击力清除闸门前的淤积泥沙。它主要由高压供水喷水系统和喷水装置牵引支撑系统两部分构成,被固定地安放在闸门上方,其构造简单、安装维护方便,具有良好的实用价值,有利于推广应用。     

基于TSpaces的并行计算环境

讨论TSpaces技术的通讯和同步机制,提出一种基于TSpaces的并行计算模型,设计基本并行函数。实验结果表明该并行计算环境的可行性、实用性。     

Deterministic convergence of conjugate gradient method for feedforward neural networks

Conjugate gradient methods have many advantages in real numerical experiments, such as fast convergence and low memory requirements. This paper considers a class of conjugate gradient learning methods for backpropagation neural networks with three layers. We propose a new learning algorithm for almost cyclic learning of neural networks based on PRP conjugate gradient method. We then establish the deterministic convergence properties for three different learning modes, i.e., batch mode, cyclic and almost cyclic learning. The two deterministic convergence properties are weak and strong convergence that indicate that the gradient of the error function goes to zero and the weight sequence goes to a fixed point, respectively. It is shown that the deterministic convergence results are based on different learning modes and dependent on different selection strategies of learning rate. Illustrative numerical examples are given to support the theoretical analysis.     

引黄灌区跨地区水权转让补偿 标准的研究

针对黄河流域引黄灌区的跨地区水权转让补偿标准的定量问题,探讨了转让费用构成中的农业风险补偿、生态补偿、水管单位补偿的含义和计算方法,并以内蒙古自治区鄂尔多斯市引黄灌区的水权转让一期项目为实例,通过计算得出3项补偿费用为889.92万元/年,在25年水权转让期内应付出的补偿费用为22 248万元,水的转让价格平均增加补偿费用为3.45元/m3。对黄河流域水权转让费用构成中的补偿费用进行准确的定量计算,将会进一步推动水权转让更加科学合理的实施,并为引黄灌区的健康持续发展奠定基础。     

基于DSP56F805的直流无刷电机控制系统设计

介绍了基于Freescale公司DSP56F805的直流无刷电机控制系统的设计.DSP56F805数据处理能力强且具有丰富的专用电机控制模块,设计的控制器硬件电路简洁,控制可靠,已应用于机器人机械手控制中.对系统硬件实现和控制原理进行了详细论述.