具有非参数AR(1)误差的回归模型的局部线性估计

考虑随机设计下具有一阶非参数自回归误差的线性回归模型,构造了参数和非参数函数的局部线性估计。在适当的条件下,证明了参数估计量的渐近正态性,并给出了非参数函数估计的收敛速度。模拟算例表明局部线性方法优于核方法。     

非参数自回归函数的有限元估计及其收敛速度

针对局部方法不能给出所拟合模型的简单的显式表达式,而且拟合和预报的计算量较大,本文考虑一种估计非参数自回归函数的全局有限元方法。该方法不但能克服上述局部方法之不足,而且在一定情形下优于多项式样条方法。在α-混合条件下得出了非参数自回归函数有限元估计的收敛速度,同时给出了利用AIC准则自动选择结点个数的数据追赶法,模拟算例说明了有限元估计方法的可行性。     

关于单元能量投影法的两点注记

最近,袁驷等基于力学原理提出了一种一维有限元超收敛后处理计算格式,称为单元能量投影(EEP)法。大量数值例子显示:若真解充分光滑,对m次有限元解,EEP法后处理节点恢复导数具有h2m阶精度。首先利用限元超收敛理论中的一个基本估计式证明了线性元(m=1)节点恢复导数具有h2阶精度。另外,对EEP法高次元的内点计算公式提出了一点简化。     

求解非定常N-S方程的稳定化分数步长法研究

本文研究了求解非定常Navier-Stokes方程的稳定化分数步长法.首先,通过一阶精度的算子分裂,将非线性项和不可压缩条件分裂到两个不同的子问题中,并对非线性项采用Oseen迭代.格式分为两步:第一步求解一个线性椭圆问题;第二步求解一个广义的Stokes问题.这两个子问题关于速度都满足齐次Dilichlet边界条件.同时,在格式的第二步添加了局部稳定化项,使用等阶序对来加强数值解的稳定性.通过能量估计方法,对速度与压力做了收敛性分析和误差估计.最后,数值实验验证了方法的有效性.     

基于Gabor重构的发动机振声信号阶次分量瞬时幅值的提取

从数值试验中总结了高斯窗STFT幅值谱对阶次分量的分隔能力与连续时间域内高斯窗的时间宽度之间的定量关系,并指出STFT幅值谱的阶次切片做为瞬时幅值估计所存在的问题。论述了Gabor阶次波形重构技术有效的前提条件,并基于确立的高斯窗宽与STFT幅值谱对阶次分量的分隔能力之间的关系,提出了一种改进的Gabor阶次波形重构流程,该流程摒弃了试凑分析参数的模式。仿真表明重构的阶次波形经Hilbert变换得到的包络可以做为瞬时幅值的有效估计。     

一种同时求多项式所有零点及其重数的混合并行策略（英文）

本文提出一种计算多项式所有重零点及其重数的混合并行迭代策略.新算法包括两个部分:粗略计算部分和加速计算部分.在第一部分中,我们利用一种局部2阶收敛的方法求出所有低精度重根和重数;在第二部分中我们提出一种新的Gargantini型迭代法并证明新方法是局部4阶收敛.利用这种新方法对已求出的低精度重根进行加速.最后用数值算例验证新策略的有效性和优越性.     

一种基于贝叶斯正交匹配追踪的水下多径稀疏信道估计方法

使用训练序列构成的测量矩阵并采用稀疏恢复算法是近年来常用的多径稀疏信道估计思路。提出一种贝叶斯匹配追踪算法的正交化改进方法,有效地改善了原方法的收敛速度,并将其应用于水下多径稀疏信道估计。进行了新方法的理论推导和两种水下稀疏信道模型中的仿真试验,进而与传统贪婪迭代和贝叶斯估计方法的估计效果进行了对比。仿真结果证明,所提出的新方法比原方法的收敛速度更快,能更高效地进行多径稀疏信道估计。新方法在低信噪比和呈簇状集中分布的水下多径稀疏信道中也有更好的估计效果。     

部分线性模型中参数分量与非参数分量估计的收敛速度

对于部分线性回归模型,基于未知函数 ｆ （·） 与 ｇ （·） 分别取一类核估计和最近邻估计,文中构造了参数β的最小二乘估计β和加权最小二乘估计β,获得了参数β估计量的渐近正态性与函数ｇ （·） 估计量的最优弱收敛速度。     

半变系数模型的M估计

本文讨论半变系数模型的稳健M估计.先用局部线性方法给出未知可测函数的一步估计,并讨论其弱一致性和渐近正态性;通过Back-fitting技巧,给出未知参数向量的一般M估计,然后再通过局部M方法给出未知函数的两步估计,并讨论它们的渐近正态性.     

具有随机回归子的不完全信息和随机截尾的广义线性模型的重对数律

在可靠性研究中,带有不完全信息随机截尾的线性模型经常受到关注.本文将带有不完全信息随机截尾的线性模型推广到带有随机回归子的不完全信息的随机截尾广义线性模型,并运用概率极限理论对后者的极大似然估计的收敛速度进行了研究,得到了两个重对数律.从渐近的意义看,第一个重对数律给出了未知参数的最小100％置信区间,而第二个重对数律给出了估计量能够达到的精确下界.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.     

Mechanism Study on the Wear of CrAlTiN Coated High-Speed Steel Twist Drills Under Dry Cutting Conditions

As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion.     

Study on Bond Ability of Arc-Spraying Coatings with Different Surface Pretreatment on Cast-Iron

Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting.     

Structural Characteristics of TiO2 Ceramic Coating by Micro-Plasma Oxidation

TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure.     

Evaluation of fatigue life of steel using steel grain size

The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase.