A parametric bootstrap approach for ANOVA with unequal variances: Fixed and random models

This article is about testing the equality of several normal means when the variances are unknown and arbitrary, i.e., the set up of the one-way ANOVA. Even though several tests are available in the literature, none of them perform well in terms of Type I error probability under various sample size and parameter combinations. In fact, Type I errors can be highly inflated for some of the commonly used tests; a serious issue that appears to have been overlooked. We propose a parametric bootstrap (PB) approach and compare it with three existing location-scale invariant tests—the Welch test, the James test and the generalized F (GF) test. The Type I error rates and powers of the tests are evaluated using Monte Carlo simulation. Our studies show that the PB test is the best among the four tests with respect to Type I error rates. The PB test performs very satisfactorily even for small samples while the Welch test and the GF test exhibit poor Type I error properties when the sample sizes are small and/or the number of means to be compared is moderate to large. The James test performs better than the Welch test and the GF test. It is also noted that the same tests can be used to test the significance of the random effect variance component in a one-way random model under unequal error variances. Such models are widely used to analyze data from inter-laboratory studies. The methods are illustrated using some examples.     

一个二阶非线性中立时滞微分方程的正解

研究了一个二阶非线性中立时滞微分方程,给出了关于此方程正解存在的一些充分条件,其优点在于省略了对任意的a〉0,aQ1（t）-Q2（t）都是最终非负的限制条件。最后通过数值例子说明研究结果的优越性。     

基于不动点理论的改进遗传算法及其应用

针对遗传算法的遗传效率问题,引入不动点理论的“剖分—标号—剖分”思想,通过寻找全标单纯形来对最优解进行定位,对全标单纯形再次剖分,寻找其内部的全标单纯形,使最优解得范围进一步缩小。遗传算法按相对适应度大小随机选取全标单纯形内的点作为初始化群体,极大地提高了遗传算法的效率。将遗传变异区间化,锁定在全标单纯形内或附近单纯形,使得最优解的精确度也得到极大地提高。     

小波包滤波在齿轮故障诊断中的应用

为快速准确地判断齿轮故障的类型,提出了小波包滤波和神经网络相结合进行齿轮故障分类的方法。介绍了小波包去噪的原理和神经网络的设计方法,对阈值算法和神经网络优化算法作了改进,得到了不含噪声的信号和准确的故障分类方法。仿真结果表明,基于小波包滤波的神经网络方法具有更高的准确性和稳定性,可以满足工业故障诊断的要求。     

Effect of fungal damage on seed composition and quality of soybeans

Fungal damage caused by pathogens such asFusarium, Cercospora, andPhomopsis can have a devastating impact on physical quality and farm price of soybeans. In some price-discount schedules, soybeans may be rejected with as low as 5% fungal damage. Although the severity of this problem varies throughout the United States, millions of bushels of fungus-damaged soybeans may be destroyed annually due to a lack of markets. The effect of fungal damage on seed composition was evaluated to assess potential utility of highly damaged soybeans. Graded samples of the cv. Centennial soybean were dried to 10% moisture and blended on a proportional weight basis to derive a series of treatments from 0 to 80% fungal damage. A positive correlation was found between fungal damage and both protein and oil concentrations. This condition was attributed to loss of residual seed mass. As a result, the protein concentration of defatted meal increased from ca. 54 to 66% over the range of 0 to 80% fungal damage. Mycotoxin contamination appeared to be insignificant in these high-protein meals. Fixed colors in bleached, alkali refined oils were intensified by heat treatment prior to extraction. No significant differences, however, were noted in total polar lipid content, phospholipid, or tocopherol composition among treatments of up to 20% fungal damage. Oils from treatments of more than 40% fungal damage were more severely oxidized and could not be degummed effectively. These data suggest that fungus-damaged soybeans may be blended with high-quality soybeans to alleviate the chemical symptoms associated with unacceptable product quality. Thus, through various blend ratios, processors may consider using fungus-damaged soybeans to gain economic advantage, especially when high-quality soybeans have lower protein concentration.     

Nonlinear inertia weight variation for dynamic adaptation in particle swarm optimization

The particle swarm optimization (PSO) is a relatively new generation of combinatorial metaheuristic algorithms which is based on a metaphor of social interaction, namely bird flocking or fish schooling. Although the algorithm has shown some important advances by providing high speed of convergence in specific problems it has also been reported that the algorithm has a tendency to get stuck in a near optimal solution and may find it difficult to improve solution accuracy by fine tuning. The present paper proposes a new variation of PSO model where we propose a new method of introducing nonlinear variation of inertia weight along with a particle's old velocity to improve the speed of convergence as well as fine tune the search in the multidimensional space. The paper also presents a new method of determining and setting a complete set of free parameters for any given problem, saving the user from a tedious trial and error based approach to determine them for each specific problem. The performance of the proposed PSO model, along with the fixed set of free parameters, is amply demonstrated by applying it for several benchmark problems and comparing it with several competing popular PSO and non-PSO combinatorial metaheuristic algorithms.     

W6Mo5Cr4V3SiCo5钢的超微粒强化与力学性能研究

超微粒强化是金属强化途径之一，讨论了含钴高速钢W6Mo5Cr4V3SiCo5的超微粒强化工艺对组织与性能的影响。通过透射电镜观察，超微粒强化处理后的高速钢淬火的基体中有弥散分布直径在1nm左右的微细碳化物。研究结果表明，超微粒强化处理可显著地提高W6Mo5Cr4V3SiCo5钢的硬度、抗弯强度和冲击韧性，使刀具使用寿命提高2～3倍，耐用度提高150％～300%。     

莱钢150 mm×150 mm连铸坯生产20CrMnTiH齿轮钢的工艺实践

莱钢特殊钢厂采用20 t电弧炉-LF(喂丝)-3流150 mm×150 mm方坯连铸-热轧工艺生产Φ40 mm 20CrMnTiH齿轮钢材.冶炼成分控制为(%)0.19～0.21C, 0.17～0.30Si, 0.92～1.02Mn, 1.10～1.23Cr, 0.05～0.07Ti,0.015～0.035Al,连铸钢水过热度20～30 ℃,连铸速度1.4～1.6 m/min,二冷比水量0.5～0.6 L/kg.根据111炉检验结果统计分析可得,Φ40 mm钢材疏松≤1.5级,偏析0.5级,J9(HRC)30～40,J15(HRC)22～35,满足标准要求.     

浅析固定资产评估增减值的会计处理

在固定资产评估过程中 ,按照现行会计制度来处理固定资产增、减值既复杂也不尽合理 ,本文对此进行了对比分析 ,提出了新的会计处理方法。