利用增量矩阵辨识确定型ARMA模型的新算法

本文提出了一种无偏辨识确定型ARMA模型参数及阶次的新方法。和其他辨识算法不同的是在这里我们构造了关于系统开环阶跃响应的增量矩阵,并且通过分析该增量矩阵子矩阵的代数性质而得到了辨识系统阶次的一种简单方法。仿真的结果说明了本文理论的正确性。     

MECHANISM OF NON-EQUILIBRIUM SEGREGATION OF SOLUTE TO GRAIN BOUNDARIES

本文以空位-溶质原子拖曳机制为基础,并考虑了空位、溶质原子和复合体三者的反应平衡及晶界平衡偏聚的作用,得到了溶质原子的非平衡晶界偏聚动力学方程。对硼在奥氏体中等温及连续冷却时所产生的非平衡晶界偏聚现象进行了理论计算,得到了与实验较为一致的结果。     

乳化沥青冷再生混合料疲劳性能及影响因素

为研究乳化沥青冷再生混合料抗疲劳性能关键影响因素,采用应力控制模式下的间接拉伸疲劳试验,分析应力水平、水泥用量、旧料( relaimed asphalt pavement, RAP)掺量、乳化沥青类型及乳化沥青用量等因素对冷再生混合料疲劳性能的影响规律,最后,基于灰关联熵分析,对各影响因素进行了量化与比较。结果表明：乳化沥青针入度指标、RAP掺量对乳化沥青冷再生混合料疲劳寿命影响最为显著,乳化沥青用量、乳化沥青延度指标影响次之,应力水平、水泥用量影响最小。     

THE HARDENABILITY OF BORON STEEL AND THE SEGREGATION OF BORON

用改进的径迹显微照相技术研究了50B钢800—1150℃顶端淬火试样中硼分布状态的变化规律及其与硼钢淬透性的关系。试验表明,硼钢淬透性的变化与冷却时硼向奥氏体晶界偏聚的发展速度密切相关。由硼的成分剖面图可定量测定出这种偏聚的发展速度。 晶界硼偏聚发展过快或过慢均不利于硼提高淬透性的效应。只有当晶界硼偏聚的发展速度与基体成分相变孕育期相配合时,硼才能发挥最大效应。利用这种观点可以说明硼钢淬透性的变化特征,分析影响硼钢淬透性的各种因素。     

BEHAVIOUR OF BORON IN CARBONIZED AND CARBONITRIDED CASE AND CASE-HARDENABILITY OF BORON STEEL

含硼钢渗碳和碳氮共渗时,由于硼与氮及碳之间的相互作用,硼在整个渗层范围内发生明显的再分布。在渗碳层中主要表现为硼在表层富集和次表层内贫化,在碳氮共渗层中主要表现为,在距表面很深的范围内有大量BN形成以及固溶硼量很低的地区发展得很深。 硼的这种再分布对渗层淬透性带来显著影响,渗碳层的淬透性,除了要考虑碳含量的变化以及碳对硼效应的影响外,还要考虑次表层硼贫化的影响。在碳氮共渗层中,大量BN的形成对淬透性有显著的不良影响,固溶硼贫化的作用也表现得更为突出。     

Over-relaxation effect of deformed austenite on ageing behavior of an Nb-bearing microalloyed steel

The ageing behavior of an Nb-bearing microalloyed steel at 525℃was investigated by thermo-simulation test, hardness measurements and transmission electron microscopy (TEM). Prior to ageing, the steel was deformed in austenite zone followed by a long relaxation. Experimental results indicate that the hardness decreases gradually in the initial stage until ageing for 120 min, and then increases continuously until 1200 min. The coarsened precipitates (>10 nm) formed in deformed austenite remain nearly unchanged in size, even after ageing for long time, while the further precipitates, which nucleate in a phase, contribute to the increasing of hardness. By comparison, the undeformed samples in austenite subjected to the same ageing process display a very similar hardness change trend to that of over-relaxation ones and have higher hardness values at each corresponding period.     

Microstructure evolution during reheating of a Nb-bearing steel I. Metallographic examination

Cooled in water after the isothermal relaxation of deformed austenite for different timea, a Nb-bearing microalloyed steel always exhibits synthetic microstructures of bainitic ferrite, granular bainite and acicular ferrite. When these samples were reheated to and held at 650 or 700℃, the non-equilibrious microstructures tend to evolve into equilibrious ones. The sample relaxed for 60 s displays the highest thermostability, while the microstructure evolution is the quickest in the sample relaxed for 1000 s even though it is the softest before reheating. Softening is not a single process occurring during reheating, in which the hardness fluctuates with time. There are two peaks in the hardness-time curve of each sample having undergone relaxation, while a single peak occurs in the curve of the sample having not been relaxed. Pre-strain accelerates the evolution process. These results indicate that the thermostability of microstructures is determined by their history of formation to a considerable degree.     

Refinement of packet size in low carbon bainitic steel by special thermo-mechanical control process

The packet size of bainitic steel can be refined by a special relaxation-precipitation-control phase transformation (RPC) technology, When processed by RPC process, the low carbon bainitic steel composes of two kinds of main intermediate transformation phases. One is ultra-fine lath-like bainitic ferrite and the lath is less than 1 tam in width and about 6 tam in length; the alignment of laths forms a refined packet, and the size of packets is about 5-7 ~am in length and about 3-4 tam in width, The other is acicular structure. The morphology and distribution of these acicular structures are influenced by relaxation process, the thin and short acicular structures cut the prior austenite grain and refine the bainitic packet size, For the optimum relaxation time, the packet size can be refined to the finest. The mechanical properties are influenced by relaxation time and the 800 MPa grade low carbon bainitic steel with excellent toughness can be obtained by RPC process,     

浅埋暗挖法在首钢搬迁工程竖井支护中的应用

首钢搬迁工程旋流井直径大、埋深大,其基坑的开挖和支护不仅要确保边坡稳定,而且要满足变形控制要求.通过旋流井支护方案比选,考虑基坑特点、工程地质条件,采用拱形自撑技术,即浅埋暗挖钢格栅工艺、局部加土钉锚杆喷射混凝土支护方案.采用荷载结构法,经ANSYS有限元计算,降水后,不计水压力作用,结构满足受力要求.给出该支护工艺的关键施工措施,体现土方施工的经济性和施工实践的安全性.     

基于TMS320F2812和TMS320VC5409的多处理器系统及其Bootload设计

本文主要介绍了某水声阵列信号处理机的高速数据采集处理模块的设计.该模块为基于TMS320F2812和TMS320VC5409的多DSP系统,采用双端口RAM构成多处理器互连网络,实现处理器间的大数据量通信.TMS320F2812负责多通道数据采集和系统控制,TMS320VC5409对数据进行实时处理.系统的引导加载设计利用了双端口RAM和DSP各自的结构特点,解决了包含不同系列DSP的多处理器系统程序整体加载问题.