基于ARC的闪存数据库缓冲区算法

闪存是一种纯电子设备,具备体积小、数据读取速度快、能耗低、抗震性强等优点,被用来部分替代机械硬盘从而提升存储系统的性能.但是,现有的缓冲区置换算法都是针对机械硬盘的物理特性进行设计和优化,因此有必要针对闪存的物理特性重新设计缓冲区置换算法.提出一种新的面向闪存数据库的缓冲区替换算法CF-ARC.算法设计了一种新的页替换机制,即在替换干净页或者脏页的时候考虑其访问频度的大小,优先将访问频度少的干净页替换出缓冲区,使得热页继续留在缓冲区提高命中率,从而获得更好的性能,通过对实验结果的对比分析发现CF-ARC在多数情况下具有比其它置换算法更高的性能.     

含改性氯酸钾烟火药剂的安全性研究

为了研究含改性氯酸钾的烟火药剂的安全性,采用绝热加速量热仪、撞击和摩擦感度仪等,对由改性前后氯酸钾组成的烟火药剂的热安全性和摩擦感度、撞击感度进行了对比测试.结果表明,含改性氯酸钾的烟火药剂初始放热温度提高了36.08℃;达到最大放热速率的时间延长了6倍多;单位质量最大压力减小了0.63MPa·g-1;绝热温升降低了95.99℃;摩擦感度降低了64%,撞击感度降低了72%.含改性氯酸钾组成的烟火药剂安全性明显提高.     

Comparing three coordination models: Reo, ARC, and PBRD

Three models of coordination-Reo, Actors-Roles-Coordinators (ARC), and Policy-based Russian Dolls (PBRD)-are compared and contrasted according to a set of coordination features. Mappings between their semantic models are defined. Use of the models is illustrated by a small case study.     

Inverse design of anti-reflection coatings using the nonlinear approximate inverse

We consider a multi-frequency inverse scattering problem arising in the design of anti-reflection coatings. These thin films are deposited onto photovoltaic solar cells to enhance their performance. The objective is to determine the space-dependent refractive index in an inhomogeneous optical layer from the reflection coefficients at the surface. The relevant model yields a boundary value problem for the one-dimensional (1D) Helmholtz equation, which we formulate as an equivalent integral equation. The resulting inverse problem is nonlinear and ill-posed. We consider a series expansion of the field depending on the order of nonlinearity of the model. The first-order solution is obtained by using the Born approximation which is valid for weak scattering. Stronger scatterers are sought by considering a nonlinearity of higher order. The mathematical and numerical framework is provided by the (noniterative) method of the approximate inverse (AI) for nonlinear inverse problems. Numerical results are presented to attest the efficiency and stability of the method.     

逆变弧焊电源主电路器件及整机可靠性

本文主要论述逆变弧焊电源主电路各部分器件的选取及其对整机可靠性的影响，同时介绍了国外名牌逆变弧焊电源主电路所采用的关键器件及目前可使用的先进而实用的器件。     

Structure-property changes during hardening and tempering of new ultra high strength medium carbon low alloy steel

Abstract

A medium carbon low alloy steel, electroslag refined, modified AFNOR 15CDV6, has been developed for satellite launch vehicle and related applications. Conventionally processed (without electroslag refining) mostly bainitic AFNOR 15CDV6 (with 0·15 wt-% carbon and ~ 3·5 wt-% other alloying elements) has a yield strength of ~ 800 MPa. Electroslag refining, coupled with increased carbon (0·29 wt-% carbon, but no change in percentage of other alloying elements), increased the yield strength to about 1300-1400 MPa, without sacrificing ductility. The microstructure of the modified grade was martensitic. Martensite in the as hardened state was mostly in the form of laths, although ~20% plate martensite was also observed. Until 150°C tempering, no noticeable loss of tetragonality was observed, while the unit cell parameter c/a ratio dropped to almost 1 after 300°C tempering. The interesting observation at 150°C tempering was the predominant presence of fine rodlike ? carbide, which may also explain the increased yield strength. Tempering above 150°C converted the ? carbide to cementite, relatively thicker precipitates of similar morphology. At higher tempering temperatures, no evidence of spheroidisation of cementites was noted. The highest tempering temperatures of 500 and 600°C resulted in two marked changes in the microstructure: the appearance of M₂₃C₆ type (Cr, Fe and Mo bearing) carbides, and the appearance of, in some regions of the microstructure at least, a relatively 'recovered' lath structure. Misorientation among adjacent laths, nearly constant at 8-9° until 450°C tempering, increased noticeably, to 13 and 16°, after the respective tempering temperatures of 500 and 600°C.     

Investigation into micro-tungsten inert gas arc behaviour and weld formation

Abstract

Current pulsing patterns are defined for the micro-tungsten inert gas welding apparatus developed and are described as: no pulsation (NP), high frequency pulsation (HFP), slightly hybrid pulsation (SHP), and heavily hybrid pulsation (HHP). The characteristics of the microarc behaviour and weld formation are then investigated in detail for these patterns. The parameters and pattern of the pulsating current dominate arcing power and arc stiffness at a given average current, thus affecting arc state and bead formation. The arc image analysis shows that the HFP and HHP arcs can burn more steadily even at an average current of 2 A because of the arc stabilising effect from the superimposed high frequency components. During the on time of the pulse, the state of the hybrid pulsating (HP) arc varies successively from an apple like shape to a cone with an increased taper. Furthermore, this HP arc shrinks owing to the decreases in the peak current and arcing power with increasing frequency of the base pulse, but is still much greater in size than the NP and HFP arcs. Finally, welding experimental results demonstrate that the HP welds are the widest and become narrow with an increase in the pulse frequency, and the NP and HHP beads are somewhat wider than the HFP and SHP beads respectively.     

Arc power and efficiency in gas tungsten arc welding of aluminium

Abstract

A calorimetric study of gas tungsten arc welding of aluminium is described. The present study comprised experiments in which autogenous welding runs were each made on a block of electrical conductor grade aluminium. The blocks were all approximately cubic in shape which, when combined with the high thermal conductivity of aluminium, ensured that their temperature equalised soon after the completion of a run. Each sample was immersed in insulating material before welding so that heat losses to the surroundings were minimised. Thermocouples were attached to the block in each experiment and the bulk temperature rise was related to the energy input associated with the welding run. The effects of arc polarity, alternating current balance, shielding gas composition, arc length and welding current on the arc power and arc efficiency were investigated. The results obtained with alternating current are compared to those for direct current, and the differences are explained.     

用加速量热仪研究PBX-HKF的热稳定性

采用加速量热仪(ARC)研究了一种由HMX、苦味酸钾、增塑剂、粘结剂组成的新型PBX HKF炸药的热稳定性,得到了塑性炸药样品在绝热条件下热分解温度和压力随时间的变化曲线以及自热速率、分解气体产物压力随温度的变化曲线,分析了在绝热条件下热分解反应动力学,计算了表观活化能Ea为337. 32kJ·mol-1,指前因子A为9. 32E34s-1。结果表明所测试的PBX HKF具有良好的热稳定性。     

A general kinetic model framework for the interpretation of adiabatic calorimeter rate data

Notwithstanding the variety and complexity of the reactions studied by adiabatic calorimeters like ARC, the data interpretation techniques are not general enough. Traditional thermokinetic analysis primarily lumps a complex multi-step reaction into a single overall reaction and ignores possible thermal effects in some of the possible side reactions. With detailed chromatographic/mass spectrometric analysis of the headspace gases and the condensed phase residues, the pressure profile becomes an additional source of identification of the mechanism and the kinetics of the overall reaction. Finally, in the context of new multiphase catalytic processes of greater efficiency and environment friendliness and with reference to the storage of potentially incompatible fluid mixtures in metallic containers, ARC studies of heterogeneous reaction systems are becoming part of the mandatory safety evaluations. With a few additional measurements a proper kinetic interpretation of the ARC data on such systems seems possible. The paper presents a general model that was shown to be easily adaptable to a number of published reactions of various complexities referred to above. Standard thermal hazard characteristics like the onset temperature, adiabatic temperature rise, self-heat rate, time-to-maximum rate, pressure–temperature profile, etc. could be accurately calculated by the model and these compared closely with the experimental data. It is hoped that the model would be useful as a general-purpose tool for the interpretation of adiabatic calorimetric data for the purpose of process hazard assessment.