连续玻纤增强聚丙烯预浸带熔融浸渍过程纤维断裂研究

为提高连续玻纤增强聚丙烯预浸带（PP/GF）性能,采用熔融浸渍法制备连续玻璃纤维增强聚丙烯预浸带,研究了PP熔体浸渍连续GF束过程。基于Weibull分布函数建立了纤维断裂数学模型,预测预浸带生产过程中纤维断裂率并描述实验结果。结果表明,模型与实验数据吻合较好,能够为工业化生产提供指导;纤维束在浸渍模具中受到树脂熔体的作用,及纤维与设备之间的摩擦是影响纤维断裂的主要因素,适当提高浸渍模具温度,降低纤维束牵引速度,增大浸渍模具间隙能有效降低纤维断裂率,提高工艺稳定性。     

基于改进人工蜂群算法的机车车辆关键零部件可靠性研究

针对我国机车车辆现行检修制度中可能存在的过修、欠修问题,提出了一种综合图解法和改进人工蜂群(ABC)算法的机车车辆关键零部件可靠性模型拟合方法,对三参数威布尔分布进行参数估计并确立三参数威布尔可靠性模型。首先利用图解法求得三参数威布尔分布参数的初始估计值以及ABC算法的搜索空间,随后运用改进ABC算法进行迭代计算以获得较优的参数估计值,最后将可靠性模型拟合方法与最小二乘法以及概率加权矩法进行分析比较。研究结果表明,提出的可靠性模型拟合方法能够较为准确地确定三参数威布尔可靠性模型。以该模型为基础对机车车辆关键零部件进行可靠性指标计算,为决策人员确定机车车辆最佳维修周期和改进检修规程提供了科学依据。     

Multi-Censored Sampling in the Three Parameter Weibull Distribution

In life and fatique testing, multi-censored samples arise when at various stages of a test, some of the survivors are withdrawn from further observation. Sample specimens which remain after each stage of censoring continue to be observed until failure or until a subsequent stage of censoring. In this paper, maximum likelihood estimators and estimators which utilize the first order statistic are derived for the three parameter Weibull distribution. Estimators are also derived for the special case in which the shape parameter is known, a special case which includes the two parameter exponential distribution. An illustrative example is included.     

Preparation and characterization of ceramic interconnect La0.8Ca0.2Cr0.9M0.1O3−δ (M = Al, Co, Cu, Fe) for IT-SOFCs

The lattice parameters, electrical conductivity, activation energy, mechanical properties, and microstructure of (La_0.8Ca_0.2)CrO_3−δ-based specimens were investigated systematically in this paper. The tolerance factors for (La_0.8Ca_0.2)CrO_3−δ-based specimens were all greater than 0.9, indicating the perovskite was not distorted with different cations (Al³⁺, Co³⁺, Cu²⁺, Fe³⁺) substitution for B site of (La_0.8Ca_0.2)CrO_3−δ. (La_0.8Ca_0.2)Cr_0.9Co_0.1O_3−δ specimen revealed the maximum electrical conductivity, σ_850 °C = 59.59 S/cm with minimum activation energy, E_a = 11.2 kJ/mol among (La_0.8Ca_0.2)CrO_3−δ-based specimens. The grain size seemed dependent on doping species and the grain sizes were distributed in the range of 2.4-5.6 μm for (La_0.8Ca_0.2)CrO_3−δ-based specimens. The rate of grain growth was proportional to the boundary mobility M_b, which was related to the diffusion coefficient of doping cation. (La_0.8Ca_0.2)CrO_3−δ-based specimens revealed variety in microhardness, in the range of 4.33-9.85 GPa and the fracture toughness were distributed in the range of 3.52-4.33 MPa m^1/2. Based on the results in terms of grain size and mechanical properties, we concluded that the microhardness and fracture toughness were dependent on the dopant ions. The (La_0.8Ca_0.2)Cr_0.9Co_0.1O_3−δ specimen shows high electrical conductivity and mechanical properties Consequently, it is a promising candidate as an interconnect material for intermediate temperature solid oxide fuel cell (IT-SOFC) applications.     

High-temperature mechanical properties of a glass sealant for solid oxide fuel cell

The high-temperature mechanical properties of a newly developed silicate-based glass sealant, designated as GC-9, have been studied for use in planar solid oxide fuel cell (pSOFC). Four-point bending tests were conducted at room temperature, 550 °C, 600 °C, 650 °C, 700 °C and 750 °C to investigate the variation of flexural strength, elastic modulus, and stress relaxation with temperature for the given glass sealant. Weibull statistic analysis was applied to describe the fracture strength data. The results indicated that the flexural strength was increased with temperature when the testing temperature was below the glass transition temperature (T_g, 668 °C). This was presumably caused by a crack healing effect taking place at high temperatures for glasses. However, with a further increase of temperature to a level higher than T_g, significant stress relaxation was observed to cause extremely large deformation without breaking the specimen. When the controlled displacement rate was increased by an order of magnitude, the stress relaxation effect at 750 °C became less effective. However, the mechanical stiffness of the given glass was significantly reduced at a temperature higher than T_g.     

Impact fracture of a ferritic steel in the lower shelf regime

This paper reports the results of a systematic investigation on the fracture of Charpy-V notch A508 steel specimens, tested in the lower shelf regime. The fracture energy has been determined for quasi-static, standard Charpy and one-point-bend impact. The results show a general trend for the fracture energy to increase with the loading rate, at the lower temperature (–160 °C). At this temperature, the roughness of the fracture surface increases markedly with the loading rate. The fractographic analysis shows the presence of 3–4 cleavage initiation sites situated at 100–800 m from the crack front, irrespective of the loading rate. Numerous cleavage microcracks are observed underneath the main fracture plane. The statistical analysis shows that the length distribution of the microcracks is adequately described by Weibull statistics. It is also found that the number of microcracks increases with the loading rate. It is suggested that the larger number of microcracks is responsible for the observed increased roughness and energy dissipation.     

Determination of Damage Accumulated in Structural Materials by the Parameters of Scatter of Their Hardness Characteristics

The authors propose a method for estimating degradation of the structural state of materials due to damage accumulation during their operation. The scatter of hardness characteristics determined from the results of mass tests is taken as a damage parameter. The paper presents the findings of experimental studies of the scatter of hardness characteristics of materials after some operation time under cyclic, short- and long-term static loading conditions.     

求解旅行商问题的循环局部搜索算法的运行时间和性能分布分析

旅行商问题（Traveling Salesman Problem，TSP）是组合优化中最典型的NP难问题之一，长期以来人们都在寻求快速高效的近似算法以在合理的计算时间内准确地解决大规模问题，并设计出许多高效实用的启发式和宏启发式算法，其中循环LK算法是性能最好和最具代表性的算法之一．作者研究了该算法的运行时间分布：通过对TSPLIB中大量不同规模的TSP实例的运行时间分布的统计分析和拟合，发现求解TSP问题的循环LK算法的运行时间分布很好地服从Weibull分布，并进一步给出了该分布对求解TSP问题的物理意义．作者同时首次给出了循环LK算法求解TSP问题得到的解的性能分布以及由此得到的一些有实际指导意义的结论．     

三星新型手机指令应用

*#8999*8378#(显示测试模式，有1版本、2硬件测试、3锁状态、4SIM卡信息和5产品，共5项内容。以前有玩家说这个指令行货不能用，其实是可以的，有行货的朋友可以试试)     

带损伤的脆性材料的断裂概率研究

脆性材料压缩破坏过程是一个较为复杂的过程,在应力达到最大值时并不发生断裂,而在经历一个较长的非线性过程后伴随着应力下降以及较大的塑性变形而发生突然的断裂.这种过程对某些大尺度物理现象的机理的认识,特别是对地震爆发过程的认识,有一定的启发.从统计的角度认识这一过程,做了大量的实验,初步的统计结果验证了带扭转损伤的铸铁材料的压缩断裂强度服从三参数的Weibull分布,并对参数作了估计.