高压辊磨机柱钉辊面的受力分析与应用

介绍了高压辊磨机柱钉辊面自生成料衬原理及辊面失效形式,从柱钉的受力情况分析了辊面断钉失效的原因,阐述了大柔性液压系统降低传动系统冲击负荷、延长辊面寿命的作用机理,总结了提高高压辊磨机作业率应采取的措施。

农民的儿子、洛克菲勒的女婿与世行副总裁

在美国一个农村,住着一个老头,他有三个儿子。大儿子、二儿子都在城里工作,小儿子和他在一起,父子相依为命。 突然有一天,一个人找到老头,对他说:“尊敬的老人家,我想把你的小儿子带到城里去工作?” 老头气愤地说:“不行,绝对不行。

Corrugate Fiber Reinforced Plastic Sheet in Repairing Tunnel Linings

This paper represented the numerical analysis of the FRP （fiber reinforced plastics） tunnel lining which was used for maintaining the old tunnel. An old tunnel covered with a concrete is prone to deteriorate due to an aging effect and a v^ater penetration. In the rehabilitation of lining concrete, a steel plate and FRP or carbon sheet have been applied. However, these sheets show small flexural rigidity and do not flow out the penetrating water. In this paper, FRP corrugate sheet was proposed. The tunnel lining was made by FRP corrugate sheet that supported the lining concrete in the tunnel and flowed the water and the moisture swept on the tunnel surface. The FRP corrugate sheet was supported by the anchor bolts. In numerical analyses, the finite element degenerate shell was adopted to represent the FRP sheet behavior. Assuming that the concrete liner at the top was fallen down, the peeled concrete was applied as the load. From the numerical analysis, the effectiveness of the FRO corrugate sheet was confirmed.

Blast and tensile properties of tantalum/niobium lined SiC/SiC composite tubes for nuclear cladding

The mechanical performances such as tensile strength and blast property of metal lined SiC/SiC composite cladding tubes were investigated. Nb or Ta was selected as liner material, and the SiC/SiC composite layer was fabricated by winding and different precursor impregnation and pyrolysis(PIP) processes. The tensile strengths of different tube samples were measured at room temperature(RT) and 1200 °C, respectively. The blast property was investigated through the maximum water pressure of tubes. And the fracture microstructures were observed by SEM.The highest tensile strength at RT was 150.7 MPa. The blast strength was enhanced with the PIP process increasing from 1 to 4 cycles and the tube of 4 PIP cycles had the highest water pressure of 34.7 MPa. Compared with the metal tubes, the multi-layer structure improved tensile and blast properties significantly. The different processes such as PIP cycles and pyrolytic carbon(PyC) coating were important factors to enhance the mechanical performances of SiC/SiC-based tubes. However, the retention rate of tensile strength was only 18.5% at 1200 °C.

Development of a Test Program for Assessing the SCC, Pitting and Crevice Corrosion Behaviour of Selected Corrosion Resistant Alloy Liner Materials for Clad Pipe for Offshore Applications

The development of an offshore gas field involves production of oil and gas from subsea wells. Design considerations for a particular subsea system have identified the maximum temperature for operations which is greater than 130 ~C. Consequently, for large diameter flowlines, this precludes the use of duplex stainless steels as CRA＇s （corrosion resistant alloys） for service under the expected operating conditions. Attention has therefore focused on alternative CRA＇s such as austenitic stainless steels and Ni based alloys as mechanically clad or lined clad pipe for carbon steel subsea gas flowlines. One design concern is the recognized temperature limit for CRA materials, such as 316L stainless steel and similar alloys in production fluids is taken to be 120 ~C. This then raises concerns surrounding their suitability for providing sufficient corrosion resistance/stress corrosion cracking resistance in gas environments containing COz and H2S at temperatures higher than 130 ~C. It was recommended that specific testing should be completed at temperatures greater than 133 ~C to establish that candidate materials are still corrosion resistant. The focus of this study was to develop, implement and assess a testing program that would predict the suitability of a series of CPA＇s alloys for use in mechanical clad/lined subsea gas flowlines, with respect to pitting corrosion, crevice corrosion and stress corrosion cracking. This paper will present the rationale adopted for this testing program to simulate the stringent operating conditions, the results from these findings and the overall assessment/integrity of the candidate alloys selected.

Defect Detection in Raw Si Substrates Using Transmission Polarimetry

Inline characterization for fabrication of silicon wafer PV （photovoltaic） devices may be used to optimize device efficiencies, reduce their performance variance, and their cost of production. In this article, the frozen in strain from a variety of extended defects in silicon is shown to effect the polarization of light transmitted through a silicon substrate due to the photo-elastic effect. Transmission polarimetry on pre-fabricated silicon substrates may be used for identification of extended defects in the materials using a polarization analysis instrument. Instrumentation is proposed for detection of defects in raw silicon wafers for applications like raw silicon wafer sorting, scanning silicon bricks, and inline inspection prior to solar cell metallization. Such analysis may assist with gettering of silicon solar cells, may be implemented in the sorting and rejection procedures in PV device fabrication, and in general shows advantages for detection of defects in silicon wafer solar cell materials and devices.

水泥粉磨系统中应用的辊压机柱钉辊面

本文介绍了目前水泥行业中辊压机采用的几种辊面形式,简要比较各种耐磨辊面的优缺点,经过对不同辊面的应用对比分析,柱钉辊面是目前耐磨性能最好、免维护使用寿命最长的辊面形式,着重介绍了柱钉辊面的原理及其在水泥粉磨系统的应用情况,对于柱钉辊面应用中存在的问题提出了建议.

Exfoliation of 2D van der Waals crystals in ultrahigh vacuum for interface engineering

Two-dimensional(2D)materials and their heterostructures have been intensively studied in recent years due to their potential applications in electronic,optoelectronic,and spintronic devices.Nonetheless,the realization of 2D heterostructures with atomically flat and clean interfaces remains challenging,especially for air-sensitive materials,which hinders the in-depth investigation of interface-induced phenomena and the fabrication of high-quality devices.Here,we circumvented this challenge by exfoliating 2D materials in an ultrahigh vacuum.Remarkably,ultraflat and clean substrate surfaces can assist the exfoliation of 2D materials,regardless of the substrate and 2D material,thus providing a universal method for the preparation of heterostructures with ideal interfaces.In addition,we studied the properties of two prototypical systems that cannot be achieved previously,including the electronic structure of monolayer phospherene and optical responses of transition metal dichalcogenides on different metal substrates.Our work paves the way to engineer rich interface-induced phenomena,such as proximity effects and moirésuperlattices.

Selective Growth of ZnO Nanorods on SiO2/Si Substrates Using a Graphene Buffer Layer

A promising strategy for the selective growth of ZnO nanorods on SiO2/Si substrates using a graphene buffer layer in a low temperature solution process is described. High densities of ZnO nanorods were grown over a large area and most ZnO nanorods were vertically well-aligned on graphene. Furthermore, selective growth of ZnO nanorods on graphene was realized by applying a simple mechanical treatment, since ZnO nanorods formed on graphene are mechanically stable on an atomic level. These results were confirmed by first principles calculations which showed that the ZnO-graphene binding has a low destabilization energy. In addition, it was found that ZnO nanorods grown on SiO2/Si with a graphene buffer layer have better optical properties than ZnO nanorods grown on bare SiO2/Si. The nanostructured ZnO-graphene materials have promising applications in future flexible electronic and optical devices.

Effects of substrate type and material-substrate bonding on high-temperature behavior of monolayer WS2

This study reveals that the interaction between a 2D material and its substrate can significantly modify its electronic and optical properties, and thus can be used as a means to optimize these properties. High-temperature （25-500℃） optical spectroscopy, which combines Raman and photoluminescence spectroscopies, is highly effective for investigating the interaction and material properties that are not accessible at the commonly used cryogenic temperature （e.g., a thermal activation process with an activation of a major fraction of the bandgap）. This study investigates a set of monolayer WS2 films, either directly grown on sapphire and SiO2 substrates by CVD or transferred onto SiO2 substrate. The coupling with the substrate is shown to depend on the substrate type, the material- substrate bonding （even for the same substrate）, and the excitation wavelength. The inherent difference in the states of strain between the as-grown and the transferred films has a significant impact on the material properties.