μC／OS—Ⅲ在Cortex—M3处理器上的移植

为了将μC／OS-Ⅲ移植到Cortex—M3处理器上,选用RealView MDK作为软件开发平台,针对Cortex—M3处理器特性编写了移植所需的C语言和汇编语言源代码,并验证了移植的正确性。移植后的μC／OS-Ⅲ能够稳定运行于Cortex～M3处理器上。该移植对大部分Cortex—M3处理器具有通用性,对其他架构处理器的μC／OS-Ⅲ移植具有参考作用。     

Magnetic and mössbauer studies on ductile Fe-Cr-Co permanent magnet alloys

Iron-chromium-cobalt alloys possess attractive magnetic properties combined with good formability and hence are identified as technologically important magnetic materials. Alloys with compositions Fe-28·9 Cr-15·6 Co and Fe-28·4 Cr-20·1Co (weight percent) have been studied. Heat-treatment parameters during thermomagnetic treatment viz temperature, time and external magnetic field were optimized with reference to magnetic properties. The fully treated anisotropic alloys develop remanence=11·5–12·0 kilo Gauss, coercivity=600–650 Oersted and energy product=4–4·5 million Gauss Oersted. Electron microscopic and Mössbauer spectroscopic techniques were used to identify the original and transformed phases. During the various stages of the development of the alloy, the changes in mechanical hardness were correlated with magnetic hardness.     

Ti-22Nb-6Zr(at%)合金的超弹性和形状记忆效应

用弯曲法和拉伸法测定Ti-22Nb-6Zr（at％）合金的超弹性和形状记忆效应，研究固溶处理温度对Ti-22Nb-6Zr合金组织结构及性能的影响。结果表明：固溶处理后Ti-22Nb-6Zr合金的室温组织为单一的β相，晶粒尺寸随固溶处理温度升高而增大；合金的静态弹性模量小于30GPa；Ti-22Nb-6Zr合金具有良好的超弹性和一定的形状记忆效应。室温下变形，合金的超弹性和形状记忆效应随固溶处理温度升高而提高。900℃固溶处理后的合金在室温下拉伸变形，应变为5％时，总的最大回复应变达4．12％，其中超弹性回复应变为3．91％，记忆回复应变为0.21％。     

Crack initiation and propagation induced by inclusions in a nickel-base P/M superalloy under fatigue load

1 IntroductionRecently the key components in advanced aircraftengines are widely made of nickel-base P/M super-alloy. However, non-metallic inclusions are intro-duced into this material during powder metallurgyprocessing. In industry, although many method…     

新型镍基粉末高温合金动态再结晶的数学模型

采用Gleeble 15 0 0热模拟试验机对新型镍基粉末高温合金在 10 70℃～ 1170℃ ,应变速率为 5× 10 - 4s- 1～2× 10 - 1s- 1的条件下进行了轴向压缩试验。通过加工硬化率和应变的关系曲线确定稳态应变εs,并绘制了该合金的动态再结晶图。结果表明 ,Zener Hollomon参数变化对动态再结晶的临界应变量影响较小 ,对稳态应变量影响较大 ,并建立了该合金的动态再结晶动力学模型和晶粒尺寸模型     

药芯焊丝气体保护焊在高压Cr-Mo钢管上的应用

采用钨极惰性气体保护焊(GTAW)打底与药芯焊丝气体保护焊(FCAW)填充、盖面的焊接方法对ASME SA-335 P22和ASME SA-335 P11钢管做了焊接工艺评定。分别对其焊缝进行了拉伸、弯曲、冲击和硬度检测等力学性能试验，并通过金相照片对焊缝的微观组织进行了分析，结果证明工艺评定焊缝的各项力学性能指标都达到了ASME Ⅸ的要求，该焊接方法在实际生产中是可行的。     

300M钢腐蚀疲劳裂纹萌生的超载特性

本文对３００Ｍ钢在空气与３．５％ＮａＣｌ溶液中疲劳裂纹萌生的周期超载和单次超载特性进行了试验研究与理论分析。试验结果表明，３．５％ＮａＣｌ溶液中，单次超载所致腐蚀疲劳裂纹迟滞萌生的迟滞强度远小于周期超载的对应值。３．５％ＮａＣｌ溶液与空气中，超载迟滞强度均随超载比增大或等效应力幅水平的提高而增大，在腐蚀疲劳裂纹萌生寿命估算中，只考虑单次超载的迟滞规律，会得出大大保守的寿命估计，只有将单次超载和周期     

Power of a Unit‐Root Test and the Initial Condition

Abstract. It is now well known that how the initial observation is generated can have a significant effect on the power of a unit‐root test. In this article, we show that by taking a simple data‐dependent weighted average of the initial condition‐robust test of Elliott and Müller [Journal of Econometrics (2006), forthcoming] and the standard augmented Dickey–Fuller test, we are able to produce a new unit‐root test that can improve power, both asymptotically and in finite samples, over a wide range of possibilities governing the generation of the initial observation.     

Estimation in Random Coefficient Autoregressive Models

Abstract. We propose the quasi‐maximum likelihood method to estimate the parameters of an RCA(1) process, i.e. a random coefficient autoregressive time series of order 1. The strong consistency and the asymptotic normality of the estimators are derived under optimal conditions.     

Consistent estimation of the memory parameter for nonlinear time series

Abstract. For linear processes, semiparametric estimation of the memory parameter, based on the log‐periodogram and local Whittle estimators, has been exhaustively examined and their properties well established. However, except for some specific cases, little is known about the estimation of the memory parameter for nonlinear processes. The purpose of this paper is to provide the general conditions under which the local Whittle estimator of the memory parameter of a stationary process is consistent and to examine its rate of convergence. We show that these conditions are satisfied for linear processes and a wide class of nonlinear models, among others, signal plus noise processes, nonlinear transforms of a Gaussian process ξ_t and exponential generalized autoregressive, conditionally heteroscedastic (EGARCH) models. Special cases where the estimator satisfies the central limit theorem are discussed. The finite‐sample performance of the estimator is investigated in a small Monte Carlo study.