快速凝固技术制备颗粒增强铝基复合材料的研究进展

颗粒增强铝基复合材料的快速凝固技术是新近发展起来的一种新型材料复合技术，旨在将复合材料和快速凝固的优势相结合。目前其工艺和材料研究在国际上尚处于初期阶段，已出现的制备方法主要有三类，即快速凝固熔铸、粉末冶金和雾化沉积。着重分析、对比和评价了这些方法的工艺过程和材料制备特点。     

快速凝固耐磨高硅铝合金研究现状

采用快速凝固／粉末冶金技术可制备出高硅含量的铝合金，这种合金具有高耐磨性和低热膨胀性，经合金化后还具有较高的常温和高温力学性能及热稳定性，现已发展成为一系列合金。简述了国内外快速凝固高硅铝合金的研究进展。     

快速凝固粉末铝锂合金的研究及发展(一)

本文综述了快速凝固粉末铝锂合金在成分选定、粉末的制取和成型、合金组织与性能等几方面的主要研究成果。分析了粉末冶金铝锂合金的发展前景和趋势。简要介绍了铝锂合金粉末冶金的两种新技术的基本原理。     

大块非晶合金制备新技术--非晶粉末固结成形法

大块非晶材料是一种高性能的结构材料，并具有优异的软磁性能，综述了大块非晶材料的发展过程及应用现状，对快速凝固粉末冶金技术（RS/RM）在大块非晶材料制备方面的重要作用进行了评述。     

快速凝固粉末铝锂合金的研究及发展(二)

本文综述了快速凝固粉末铝锂合金在成分选定、粉末的制取和成型、合金组织与性能等几方面的主要研究成果。分析了粉末冶金铝锂合金的发展前景和趋势。简要介绍了铝锂粉末冶金的两种新技术的基本原理。这是文章的后面部分,续完。     

喷射沉积快速凝固材料的研究及应用概况

喷射沉积是一种新型的快速凝固技术，近年来广泛应用于研究和开发多种高性能愉速凝固材料。简要介绍了喷射沉积技术的基本原理和特点，对其在快速凝固材料中的应用进行了综述。     

超细组织结构材料的发展

出现了许多新的粉末冶金技术、快速固结技术,大大提高了超细组织结构材料的发展;而通过对实验、中试、生产的技术装备与研制的投入,加快了超细组织结构材料的应用步伐和范围。超细组织的概念在此得以明确,提出了统一的界定标准,出现了快速凝固和快速固结等粉末冶金新技术。超细组织结构材料的产业化,将按照由大到小的晶粒尺寸、由贵重制品到常规块状材料的顺序得到实现。     

快速凝固Al—Li合金塑韧性的改进研究

本文从合金化，粉末颗粒界面强化和断裂行为三个方面探讨了快速凝固粉末冶金（ＲＳＰ）Ａｌ－Ｌｉ合金塑韧性改进的途径，并取得了新的进展。     

快速凝固技术在材料科学中的应用(上)

本文综述了快速凝固技术近年来研究和应用的进展,介绍了快速凝固的方法,快速凝固材料的成型工艺及快速凝固技术在材料科学中的应用。     

快速凝固Al－Li合金塑韧性的改进研究

本文从合金化、粉末颗粒界面强化和断裂行为三个方面探讨了快速凝固粉末冶金（ＲＳＰ）Ａｌ－Ｌｉ合金塑韧性改进的途径，并取得了新的进展。     

Microstructure and Tensile Properties of ZK60 Alloy Fabricated by Simplified Rapid Solidification Powder Metallurgy (S-RS P/M) Process

This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy (RS P/M) processing system (S-RS P/M), which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of～1 μm in width. TEM (transmission electron microscopy) observations illustrated nano-size magnesia particles (10-30 nm) constituted oxide stringer in deta...     

Physical Mechanism and Performance Factors of Metal Oxide Based Resistive Switching Memory:A Review

This review summarizes the mechanism and performance of metal oxide based resistive switching memory The origin of resistive switching(RS) behavior can be roughly classified into the conducting filament type and the interface type. Here,we adopt the filament type to study the metal oxide based resistive switching memory,which considers the migration of metallic cations and oxygen vacancies,as well as discuss two main mechanisms including the electrochemical metallization effect(ECM) and valence change memory effect(VCM). At the light of the influence of the electrode materials and switching layers on the RS characteristics,an overview has also been given on the performance parameters including the uniformity endurance,the retention,and the multi-layer storage. Especially,we mentioned ITO(indium tin oxide electrode and discussed the novel RS characteristics related with ITO. Finally,the challenges resistive random access memory(RRAM) device is facing,as well as the future development trend,are expressed.     

The Effect of Polymer Coating Systems on the Preparation, Tableting, and Dissolution Properties of Sustained-Release Drug Pellets

The preparation of sustained-release (SR) drug pellets and their tablets was evaluated. Pellets containing indomethacin, pseudoephedrine hydrochloride (P-HCl), or pseudoephedrine (P) base were prepared by spraying a mixture of drug, Eudragit S-100 resins, dibutyl sebacate, and alcohol onto nonpareil seeds via the Wurster-column process. The oven-dried drug/Eudragit S-100 (DS) pellets were coated with different levels of Eudragit RS and Eudragit S-100 acrylic resins. Tablets containing P-HCl or P-base SR pellets, microcrystalline cellulose, and Methocel K4M were compressed. The solubility of the drug entity in the polymer solution was found to be the most critical factor affecting the yield and the physical properties of the resultant DS pellets. Dissolution studies of Eudragit RS coated drug pellets demonstrated that the release profiles depended not only on the physicochemical properties of the drug, particularly aqueous solubility, but also on the coating levels. The release rate profiles of the matrix tablets can be modified by varying the types of P-HCl or P-base SR pellets in the formulation. The release of drug from the matrix tablets is primarily matrix controlled.     

Deadlock control of autonomous vehicle storage and retrieval systems via coloured timed Petri nets and digraph tools

This paper addresses the deadlock control problem for the autonomous vehicle storage and retrieval system (AVS/RS). For an AVS/RS with several autonomous vehicles running in bi-direction, deadlock control is one of the key issues in the implementation of AVS/RS. The cycle-deadlock is the main type of deadlock in AVS/RS. In the paper, the dynamic model of AVS/RS is investigated by using coloured timed Petri nets (CTPN). Based on the CTPN model, a route digraph is built to detect cycle-deadlock in AVS/RS with digraph tools; the necessary and sufficient conditions of deadlock-free are established. Moreover deadlock-free control policies are proposed, the critical state in deadlock free is also identified and FCFS policy is applied to solve it. Finally, a case study is given to validate the policies.     

自动存取系统及其仿真分析

自动存取系统是一种新的存取系统,其效率取决于库位地址的分配方式、存取方式以及堆垛机的运行方式等特性。自动存取系统相对于传统存取方式有优点也有缺点。其效率主要采用通过率来评价。对此,提出了用数学模型的方法来仿真分析,给出了模型的一些相应参数、重要假设和理论结果。最后,对一个实例运用Ａｗｅｓｉｍ软件仿真,给出仿真结果。     

Closed form models for determining the optimal dwell point location in automated storage and retrieval systems

This paper examines the problem of where a storage/retrieval machine should reside, or dwell, when an automated storage and retrieval system (AS/RS) becomes idle to minimize the expected value of the next transaction time. After a review of the relevant literature on AS/RS dwell point strategies, this paper proposes several analytical models of these expected response times of the AS/RS based on the relative locations of the input and output ports of the AS/RS. It uses a continuous rack approximation to provide analytical models of the dwell point location problem. These models provide closed form solutions for the dwell point location in an AS/RS. Extensions are made to consider AS/RS with a variety of configurations including multiple input and output ports. These models not only provide solutions to the dwell point location problem, but they provide considerable insight into the nature of this problem, which is particularly valuable when the requirements facing the AS/RS are uncertain.     

高温合金熔炼工艺讨论

分析了高温合金所采用的各种冶炼方法,调研了几种主要冶炼方法的设备情况,讨论了其应用及发展动态,对比了国内外高温合金的熔炼数据,讨论了国内外粉末高温合金熔炼方法的差别,研究了我国粉末高温合金VIM+VAR双联工艺对锻件性能的影响。研究结果表明,为提高我国粉末高温合金纯净度,在着力改进高温合金熔炼工艺的基础上,应积极发展并提高双联及三联熔炼等新工艺。     

Influence of surface residual stresses on gigacycle fatigue response of high chromium cold work tool steel

The effect of surface compressive residual stresses (RS) induced by surface grinding and polishing on the gigacycle fatigue behavior of medium‐carbon high‐chromium alloy cold work tool steel was evaluated. Two test series were performed: Specimens of series I revealed high compressive RS of about ‐800 MPa at the surface, resulting from grinding with fine emery paper, which treatment had definitely a beneficial influence on the fatigue endurance strength. The existence of surface RS was also revealed to be responsible for the location of the fatigue crack initiation. High compressive RS favored internal crack origins. In this case crack nucleation sites were primary carbide clusters in the interior of the specimen, forming so‐called fish‐eyes at the fracture surface. In contrast, specimens of test series II had only very low RS, which enabled crack initiation near/at the surface at primary carbides/clusters. Furthermore, it has been shown that the high initial RS are prone to partial relaxation through cyclic loading for which the mechanisms are currently unknown. In this case near‐surface induced failure was obtained. It was possible to confirm the experimentally obtained data by the use of the concept of local fatigue strength as function of effective RS. The relaxation of high initial RS was experimentally confirmed through RS measurements at runout specimens (10¹⁰ cycles without failure).     

Travel time model for double-deep shuttle-based storage and retrieval systems

Technological developments in the global supply chain have changed processes in warehousing. This reflects in short response time in handling the orders, which has a consequence on high automation degree in warehousing. An important part of automated warehouses is presented by shuttle-based storage and retrieval systems (SBS/RS), which are used in practice when demand for the throughput capacity is high. In this paper, analytical travel time model for the computation of cycle times for double-deep SBS/RS is presented. The advantage of the double-deep SBS/RS is that fewer aisles are needed, which results in a more efficient use of floor space. The proposed model considers the real operating characteristics of the elevators lifting table and the shuttle carrier with the condition of rearranging blocking totes to the nearest free storage location during the retrieval process of the shuttle carrier. Assuming uniform distributed storage locations and the probability theory, the expressions for the single and dual-command cycle of the elevators lifting table and the shuttle carrier have been determined. The proposed model enables the calculation of the expected cycle time for single- and dual-command cycles, from which the performance of the double-deep SBS/RS can be evaluated. The analysis show that regarding examined type of the double-deep SBS/RS, the results of the proposed analytical travel time model demonstrate good performances for evaluating double-deep SBS/RS.     

Travel time models for double-deep automated storage and retrieval systems

In this paper new analytical travel time models for the computation of cycle times for unit-load double-deep automated storage and retrieval systems (in continuation double-deep AS/RS) are presented. The proposed models consider the real operating characteristics of the storage and retrieval machine and the condition of rearranging blocking loads to the nearest free storage location during the retrieval process. With the assumption of the uniform distributed storage rack positions and the probability theory, the expressions of the single and modified dual command cycle have been determined. The proposed models enable the calculation of the mean cycle time for single and dual command cycles, from which the performance of the double-deep AS/RS can be evaluated. A simulation model of the selected double-deep AS/RS has been developed to compare the performances of the proposed analytical travel time models. The numerical analyses show that with regard to the examined type of double-deep AS/RS with a different fill-grade factor, the results of the proposed analytical travel time models correlate with the results of simulation models of double-deep AS/RS.