SiCxOy相分解方式对SiCO(Al)纤维烧结致密化的影响

研究了SiCO(Al)纤维向SiC(Al)纤维的高温转化过程, 并研究了纤维中SiC_xO_y相的分解特征及不同高温处理方式对纤维结构和烧结致密化的影响。结果表明: 纤维中SiC_xO_y相分解的温度范围为1430~1850℃, 当采用连续处理方式处理, 即使在1800℃下, 纤维芯部SiC_xO_y相未能彻底分解, 且快速分解速率导致纤维中形成粗大结晶颗粒和气孔, 无法得到致密的高结晶结构。而在静态条件下处理, 可以提高SiC_xO_y相分解程度。1650℃下保温处理1 h后可以完全脱除SiC_xO_y相, 同时保持晶粒均匀。再经过1900℃烧结, 即可制得呈致密高结晶结构SiC(Al)纤维。     

The new pyrochlores Pb2(M0 · 5Sb1 · 5)O6 · 5 (M = Al,Sc, Cr,Fe, Ga,Rh)

From mixtures of PbO, M₂O₃ (M = Al, Sc, Cr, Fe, Ga, Rh), and Sb₂O₃, the new oxides Pb₂(M_{0 · 5}Sb_{1 · 5})O_{6 · 5} have been obtained as coloured powders giving X-ray diffraction patterns typical of cubic pyrochlores, S.G. Fd3?m (No. 227), and $\text{a}\text{A}\text{?}$ values from 10.3964(1) (M = Al) to 10.5558(1) (M = Sc). The best R factors were obtained for Pb in 16(c) positions, M and Sb (1:3) randomly distributed in 16(d), oxygen in 48(f) and one half of the 8(a) sites, and $\text{x}$ values for the oxygen positional parameter (origin at center, 3?m) from 0.430 (M = Sc) to 0.436 (M = Al). Apparent interatomic distances compare with those calculated. The angles of the coordination polyhedra around the metals are reported for the compounds of Al and Sc. Seven-coordination of Pb(II) is accounted for by the non-bonded electron pair effect.     

ZnO-MgO-TiO_2-SnO_2系高频介电陶瓷的制备与介电性能

在ZnO-TiO2-SnO2陶瓷基础上,掺杂MgO得到(1-x)ZnO-xMgO-0.88TiO2-0.12SnO2系新型介电陶瓷。对其相转变、微观组织结构和高频介电性能进行了研究,结果表明,在不加入任何烧结助剂情况下,试样可于1 080℃达到烧结,其相对密度为94.4%;当x=0.05时,陶瓷为纯相尖晶石结构(Zn0.95,Mg0.05)2(Ti0.88,Sn0.12)O4,其介电性能优良,1 MHz时ε=18.88,tanδ=5×10-4,τε=2.89×10-6/℃,可用作高频电容器材料的优秀候选材料。     

胆酸钴凝胶超分子自模板法制备一维纳米α-Co(OH)2及其电化学电容行为

以Co(NO₃)₂•6H₂O和胆酸钠溶液混合制备了超分子自组装凝胶纳米纤维, 以此凝胶纳米纤维为自模板, NH₃•H₂O为沉淀剂, 在温和条件下制备了纳米α-Co(OH)₂。X射线衍射(XRD)、红外光谱(FT-IR)、扫描电子显微镜(SEM)及透射电子显微镜(TEM)测试表征了其组成和微观结构。实验结果表明所得材料为纯相一维纳米纤维交错形成疏松网状结构的α-Co(OH)₂, 其直径在100~200 nm之间。用循环伏安和恒电流充放电等测试方法对α-Co(OH)₂电化学电容行为进行了研究, 结果表明: 所得α-Co(OH)₂在6 mol/L KOH溶液中, 0~0.5 V(vs Hg/HgO)电位范围内, 电流密度为1 A/g时, 其单电极比容量达到1200 F/g, 经过800周循环, 比容量稳定保持在初始容量的75%。其独特的纳米结构使其易于浸入电解液, 具有快速的电化学响应特性, 提高了电极材料的有效利用率, 这种自模板法为制备纳米电容器电极材料提供了简易的途径。     

Study of (Zr,Ti)CN, (Zr,Hf)CN and (Zr,Nb)CN films prepared by reactive magnetron sputtering

(Zr,Ti)CN, (Zr,Hf)CN and (Zr,Nb)CN coatings, in which Ti, Hf and Nb were added to ZrCN base compound, have been prepared by reactive magnetron sputtering. The coatings, with two different non-metal/metal ratios, were comparatively investigated in terms of elemental and phase composition, texture, surface morphology, hardness and friction performance. It has been shown that the films exhibit nanocomposite structures, consisting of a mixture of crystalline metal carbonitride and amorphous carbon. As compared with ternary ZrCN coatings, the quaternary coatings were found to exhibit superior mechanical and friction characteristics. In general, the films with higher non-metal content revealed finer morphologies, higher hardness and lower friction coefficient. Depending on the coating type and non-metal/metal ratio, the hardness values ranged from about 21 to 29 GPa, being higher than those of ZrCN reference films. The coefficients of friction varied from 0.2 to 0.5, the lowest values being obtained for the coatings with the highest non-metal content.     

Tackling the storage problem through genetic algorithms

The capability of a company to implement an automated warehouse in an optimized way might be nowadays a crucial leverage in order to gain competitive advantage to satisfy the demand.The order picking is a warehouse function that needs to deal with the retrieval of articles from their storage locations.Merging several single customer orders into one,a picking order can increase efficiency of warehouse operations.The aim of this paper is to define throughout the use of ad-hoc genetic algorithm(GA) how better a warehouse can be set up.The paper deals with order batching,which has a major effect on efficiency of warehouse operations to avoid wastes of resources in terms of processes and to control possibility of unexpected costs in advance.     

Wind turbine fault detection based on SCADA data analysis using ANN

Wind energy is one of the fast growing sources of power production currently, and there is a great demand to reduce the cost of operation and maintenance. Most wind farms have installed supervisory control and data acquisition(SCADA) systems for system control and logging data. However, the collected data are not used effectively. This paper proposes a fault detection method for main bearing wind turbine based on existing SCADA data using an artificial neural network(ANN). The ANN model for the normal behavior is established, and the difference between theoretical and actual values of the parameters is then calculated. Thus the early stage of main bearing fault can be identified to let the operator have sufficient time to make more informed decisions for maintenance.     

Optimum calibration of a parallel kinematic manipulator using digital indicators

This paper presents a calibration method for parallel manipulators using a measurement system specially installed on an external fixed frame.The external fixed frame is important as an error reference for calibration in certain operations,such as in the configuration of a parallel manipulator functioning as a machine tool where the workpiece is fixed to a worktable.The pose of the end-effector is measured using three digital indicators installed on the external fixed frame.To enable measurement,the end-effector is assumed to be a plane large enough that all digital indicators could touch.The error is defined as the difference between the theoretical and actual readings of the digital indicators.The geometric parameters of the parallel manipulator are optimized to minimize this error.This calibration method is low cost and feasible for compensating geometric parameter errors for a parallel manipulator.Optimal pose selection for the calibration is achieved using a swarm intelligence search algorithm.The method is implemented on a prototype of a six degrees-of-freedom(DOFs) Gough-Stewart platform constructed to function as a machine tool.     

Magnetization Study of (Hg,Cr)Sr2CuO4 + δ Superconductor

(Hg,Cr)-Sr-1201 type superconductor of nominal composition Hg_0.7Cr_0.3Sr₂CuO_{4 +} was synthesized by the sealed quartz-tube method. X-ray diffraction analysis of the sample showed it has tetragonal symmetry with lattice parameters a = 3.841(1) Å, and c = 8.664(3) Å. The as-prepared sample is superconducting at 60 K as shown by dc-magnetization and dc-resistivity measurements. The irreversibility line (IL) obtained from the merging point of the zero-field-cooled and the field-cooled magnetization measurements at several applied fields was found to obey the equation H = A(1 – T/T _c) ⁿ and gave a value of 2.55 for the exponent n. Using magnetic hysteresis loops the critical current density of superconducting (Hg,Cr)-Sr-1201 was estimated. The irreversibility line and magnetic hysteresis showed reduced pinning properties of (Hg,Cr)-Sr-1201 as compared to HgBa₂CuO_{4 +} .     

A review on high power SOFC electrolyte layer manufacturing using thermal spray and physical vapour deposition technologies

Manufacturing of solid oxide fuel cell(SOFC)components remains nowadays a key point for the industrial development of this technology.Especially,the deposition of the dense electrolyte layer which is sandwiched between the porous anode and the porous cathode is of paramount importance and thus focuses a lot of attention.Therefore,this paper considers and reviews recent developments concerning solid electrolyte layers manufacturing using thermal spray(TS) and physical vapour deposition(PVD) technologies.     

Tandem rapid manufacturing of Inconel-625 using laser assisted and plasma transferred arc depositions

This paper presents an investigation on deposition of Inconel-625 using laser rapid manufacturing (LRM) and plasma transferred arc (PTA) deposition in
individual and tandem mode. LRM has advantages in terms of dimensional accuracy, improved mechanical properties,finer process control, reduced heat input and lower thermal distortion, while PTA scores more in terms of lower initial investment, lower running cost and higher deposition rate.To quantify the clubbed advantages and limitations of both processes, these were studied individually and in tandem. A number of samples were deposited at different process parameters like power, scan speed, powder feed rate. They were subjected to tensile test, adhesion-cohesion test,impact test and micro hardness measurement. The results of individual tests showed the comparable mechanical properties with ±20% variation. The mixed dendritic-cellular and dendritic-columnar microstructures were respectively observed for LRM and PTA deposits with a distinct interface for the case of tandem deposition. The interface
strength of tandem deposits was evaluated employing adhesion-cohesion test, and it was found to be (325 ±35) MPa. The study confirmed the viability of LRM and PTA deposition in tandem for hybrid manufacturing.     

A framework for ICT-enabled real-time production planning and control

This paper aims to develop a conceptual framework for real-time production planning and control(PPC).Firstly,we discuss the most prominently applied contemporary information and communication technologies for PPC.Enterprise resource planning(ERP) systems that integrate the value chain in an enterprise,manufacturing execution systems that manage and control the production on shopfloor,and advanced planning and scheduling(APS)systems that develop solutions for complex planning problems are the planning and control systems that have been analyzed.We emphasize the application of radio frequency identification as the most advanced and promising emerging real-time data capture technology that is currently available to manufacturers.Having analyzed the features and shortcomings of the individual systems perse,and by considering the advantages that may be realized through effective integration of these otherwise discrete systems,we propose a framework for real-time PPC.     

Electric Field Effect on the Magnetic Properties of III–V Ferromagnetic Semiconductor (In,Mn)As and ((Al),Ga,Mn)As

We have investigated the magnetotransport properties of field-effect transistors (FET) having a III–V ferromagnetic semiconductor channel layer. One can control not only the ferromagnetic transition temperature T _C but also the magnetization and the coercive force of (In,Mn)As channel layers isothermally and reversibly by gate electric fields. A small change of the magnetization upon application of gate electric fields is also observed in FETs with a (Ga,Mn)As channel. Results on a (Al,Ga,Mn)As channel FET are also presented.