随机删失下半参数回归模型中估计的渐近性质

考虑半参数回归模型Yi=xiβ g(ti) iσiε,i=1,2,…,n,其中2iσ=f(ui).当Yi因受某种随机干扰而被随机右删失时,就删失分布未知的情形,利用所获得的删失数据定义了β与g(t)的估计^βn和^gn(t),在适当的条件下,证明了^nβ的渐近正态性,同时得到了^gn(t)的最优收敛速度.     

随机右删失部分线性模型中小波估计的强相合性

研究随机右删失部分线性模型中回归参数β和回归函数g（t）的估计问题.分别在删失分布函数已知和未知的情形下,基于变换后的观测数据构造了β和g（t）的小波估计,在适当的条件下,证明了它们均具有强相合性.     

Uni- and bimodal Weibull distribution for analyzing the tensile strength of Diss fibers

The present work considered several statistical distribution functions with the aim to critically analyze the strength data of natural Diss fibers. Besides the Weibull two-parameter distributions, three-parameter and bimodal Weibull were used. Kolmogorov–Smirnov, Anderson–Darling and chi-square goodness-of-fit test were used to judge how accurate the theoretical Weibull probability density function (PDF) fits with tensile strength data.

Tensile test results indicated that the fibers have good tensile strength and Young’s modulus. However, their fracture strength exhibits high scatters due to the presence of defects within the fiber and/or on the fiber surface. Microscopic observation revealed that the rupture of the fibers is governed by two types of defects, the rough surface of the fiber formed by several spines and the internal defects such as the defects of connection between fibrils.

The statistical analysis of variability in strength showed that the results of the shape and scale parameters calculated using bimodal Weibull distribution give larger values compared to those using the single Weibull distribution. Also, the strength data points fit well to the bimodal Weibull PDF curve. All three goodness-of-fit tests indicated also that the bimodal Weibull model gives a more accurate prediction of data strength compared to the unimodal Weibull model.     

自适应逐步混合截尾MOEE分布的统计分析

在自适应逐步混合截尾恒加试验模型下,研究Marshall-Olkin扩展指数分布的可靠性指标。基于失效数据,建立似然函数,获得了参数的极大似然估计,并利用自助模拟的百分位Bootstrap方法构建了参数的置信区间。利用蒙特卡洛模拟方法对自适应逐步混合截尾恒加试验模型进行仿真。数值模拟结果表明:随着样本容量的增大,参数极大似然估计值越接近真值,Bootstrap区间的效果更优。     

混合Weibull分布在棉纤维长度分布表征上的应用

利用含参数的概率密度函数来表征棉纤维的长度分布,不仅有利于纤维长度指标的计算,而且能够全面度量纤维的长度分布状态。本文基于USTER 的AFIS单纤维测试仪测得的纤维长度分布直方图,依据现有的混合Weibull分布模型,选用两组分与三组分的混合分布对其进行了拟合,并计算了相应的长度指标。结果表明：利用Weibull分布构建的混合分布模型能很好地拟合棉纤维的重量及根数加权长度分布。此外,通过指标计算值与实测值的对比,一般情况下二组分混合模型优于三组分模型。     

Improvement in mechanical properties of sponge-gourd fibers through different chemical treatment as demonstrated by utilization of the Weibull distribution model

ABSTRACT

Sponge-gourd natural fibers obtained from Luffa cylindrica plant were chemically treated separately using 5?15 wt% NaOH, acetic anhydride and benzoyl chloride solutions. Surface morphological, mechanical and thermal characteristics of untreated and chemically treated fibers were studied. Untreated and modified surfaces of the fibers were characterized by field emission scanning electron microscopy. Tensile tests were carried out by equal length of single fibers to obtain their mechanical properties. The two-parameter Weibull distribution model was applied to find the variation in mechanical properties. Tensile strength, elastic modulus and thermal stability of the fibers were found to significantly increase after chemical treatment.     

大豆水溶性蛋白质含量在设定条件下变化的研究

以豆奶制作中磨浆与前处理工艺为设定条件,在不同温度、时间、pH值以及盐浓度下对豆浆进行处理,以测定大豆水溶性蛋白质含量.初步对大豆水溶性蛋白含量在豆奶加工工艺条件下的变化进行了探索,进而根据试验总结出能提高大豆水溶性蛋白质含量和质量的豆奶加工新工艺.试验确定的豆浆前处理的最佳处理工艺为:温度40℃,时间30min,pH10.00,盐浓度0.01 mol/L.     

Human skin equivalents are an excellent tool to study the effect of moisturizers on the water distribution in the stratum corneum

In this study, the mode of action of moisturizers on the level of water in the stratum corneum was studied using cryo‐scanning electron microscopy. As model for dry skin, we used human skin equivalents (HSEs) generated at 93% or 60% relative humidity (RH). During the generation of the HSEs, the moisturizers were applied during a period of maximal 2 weeks. In HSEs generated under normal culture conditions (93% RH), application of 10% glycerol or 5% urea formulations resulted in increased water levels. Whereas the 5% urea formulations resulted mainly in the formation of intercellular water domains, after 10% glycerol both swelling of corneocytes and formation of intercellular water domains were noticed. A reduction in RH to 60% during treatment reduced the stratum corneum water levels drastically. Treatment with the non‐occlusive lipophilic moisturizer isopropyl isostearate resulted in increased water level in the central part of the stratum corneum compared with the untreated control. Our results show that HSEs can be used as a model to study the water distribution.     

Short communication: estimates of genetic parameters of body condition score in the first 3 lactations using a random regression animal model

The objective of this research was to estimate the genetic parameters of body condition score (BCS) in the first 3 lactations in Canadian Holstein dairy cattle using a multiple-lactation random regression animal model. Field staff from Valacta milk recording agency (Sainte-Anne-de-Bellevue, QC, Canada) collected BCS from Québec herds several times throughout each lactation. Approximately 32,000, 20,000, and 11,000 first-, second-, and third-parity BCS were analyzed, respectively, from a total of 75 herds. Body condition score was a moderately heritable trait over the lactation for parity 1, 2, and 3, with average daily heritabilities of 0.22, 0.26, and 0.30, respectively. Daily heritability ranged between 0.14 and 0.26, 0.19 and 0.28, and 0.24 and 0.33 for parity 1, 2, and 3, respectively. Genetic variance of BCS increased with days in milk within lactations. The low genetic variance in early lactation suggests that the evolution of the ability to mobilize tissue reserves in early lactation provided cattle with a major advantage, and is, therefore, somewhat conserved. The increasing genetic variance suggests that more genetic differences were related to how well cows recovered from the negative energy balance state. More specifically, increasing genetic variation as lactation progressed could be a reflection of genetic differences in the ability of cows to efficiently control the rate of mobilization of tissue reserves, which would not be crucial in early lactation. The shape of BCS curves was similar across parities. From first to third parity, differences included the progressively deeper nadir and faster rate of recovery of condition. Daily genetic correlations between parities were calculated from 5 to 305 DIM, and were summed and divided by 301 to obtain average daily genetic correlations. The average daily genetic correlations were 0.84 between parity 1 and 2, 0.83 between parity 1 and 3, and 0.86 between parity 2 and 3. Although not 1, these genetic correlations are still strong, so much of the variation observed in BCS was controlled by the same genes for each of the first 3 lactations. If a genetic evaluation for BCS is developed, regular collection of first-lactation BCS records should be sufficient for genetic evaluation.     

Suitability of the Weibull four‐parameters model to predict the induction phase of α‐amylase production during red sorghum malting when a steep in dilute NaOH is used prior to a re‐steep in a Bacillus subtilis‐S499 based treatment

In previous studies, Bacillus subtilis has been used to control mould growth during red sorghum malting. The use of this biocontrol in steeping liquor has been optimized with some success and the combined use of a 0.2% NaOH steep, followed by a re‐steep in a B. subtilis‐based biocontrol, has been proposed. The sharpness and variability of the β‐amylase peak and the higher levels of β‐glucanase, obtained in the presence of B. subtilis cells, were highlighted. In this work, the suitability of the Weibull four‐parameters model to predict sorghum malt α‐amylase activity during the enzyme induction stage of red sorghum germination has been compared with that of a second order polynomial model and a general linear model. Results obtained showed that the Weibull four‐parameters model could be used to predict α‐amylase activity, with significant goodness of fit when compared with the second order polynomial model and the general linear model. The effects of steeping treatment (combined use of 0.2% NaOH and B. subtilis‐S499 starters) and the germination temperature are presented. When the B. subtilis culture used as a starter was diluted, the treatment efficacy to develop α‐amylase activity was lost. This study also showed that the germination temperature affected the α‐amylase activity rate increase during the induction phase. Copyright © 2013 The Institute of Brewing & Distilling