作物品种区域试验中品种均值的Bayes估计

本研究根据Bayes统计原理，提出了作物品种区域试验中品种均值的Bayes估计方法，并利用一套包含4年，7个试点和10个棉花品种的多年多点试验对Bayes估值和算术平均值的预测精度进行比较，结果表明，Bayes估值和算术平均值的平均预测差分别为6．88％和12．77％，而且Bayes估值与验证值之间夺数值和品种排序上都有着更高的相关，相关系数分别达0．963和0．976，高于算术平均值的0．876和0．830，Bayes估值显示出比值算术平均值更高的预测精度。     

Genetic association between leg conformation in young pigs and sow longevity

Longevity is important in pig production with respect to both economic and ethical aspects. Direct selection for longevity might be ineffective because ‘true’ longevity can only be recorded when a sow has been culled or died. Thus, indirect selection for longevity using information from other traits that can be recorded early in life and are genetically correlated with longevity might be an alternative. Leg conformation has been included in many breeding schemes for a number of years. However, proving that leg conformation traits are good early indicators for longevity still remains. Our aim was to study genetic associations between leg conformation traits of young (5 months; 100 kg) Swedish Yorkshire pigs in nucleus herds and longevity traits of sows in nucleus and multiplier herds. Data included 97 533 animals with information on conformation (Movement and Overall score) recorded at performance testing and 26 962 sows with information on longevity. The longevity traits were as follows: stayability from 1st to 2nd parity, lifetime number of litters and lifetime number of born alive piglets. Genetic analyses were performed with both linear models using REML and linear‐threshold models using Bayesian methods. Heritabilities estimated using the Bayesian method were higher than those estimated using REML, ranging from 0.10 to 0.24 and 0.07 to 0.20, respectively. All estimated genetic correlations between conformation and longevity traits were significant and favourable. Heritabilities and genetic correlations between conformation and longevity indicate that selection on leg conformation should improve sow longevity.     

使用惩罚距离进行说话人改变检测

在说话人改变判决中，为了避免使用贝叶斯信息准则（Bayesian information criterion，BIC）需要不断调节惩罚因子的问题，作者从BIC中推导出惩罚距离公式并将其应用于说话人改变检测中．试验结果表明，提出的算法和BIC相比不需要调节参数，与BIC距离相比，F1提高了2％．     

荷耦合作用下沥青混凝土疲劳寿命

针对我国通货膨胀水平与不确定性的时变性特征，分别建立了随机波动均值模型和非对称随机波动均值模型，在MCMC稳态模拟的框架下研究了我国通货膨胀水平与不确定性的动态关系。研究结果表明：我国通货膨胀不确定性中具有明显的持续性特征，并且通胀水平中虽然不存在与金融资产价格运动类似的杠杆效应，但是正向冲击增加了经济行为主体对未来不确定性的预期，由此将导致明显的“示范效应”和“追涨效应”；特别是风险溢出系数的贝叶斯估计为正，反映了通胀不确定性对通胀水平的正向影响作用，说明我国目前的货币政策框架中含有相机抉择的成分因素。     

Parameter estimation in selected populations with missing data

This study proposes a procedure to estimate genetic parameters in populations where a selection process results in the loss of an unknown number of observations. The method was developed under the Bayesian inference scope following the missing data theory approach. Its implementation requires slight modifications to the Gibbs sampler algorithm. In order to show the efficiency of this option, a simulation study was conducted.     

The role of spatial factors in the success of an Aujeszky's disease eradication programme in a high pig density area (Northeast Spain, 2003–2007)

We tested the role of several spatial variables on the risk of a sow herd being Aujeszky's disease virus (ADV) seropositive in certain areas of North Eastern Spain and during different periods of the eradication programme. Distance to the nearest slaughterhouse, distance to the nearest conventional road and number of ADV serologically positive sows and ADV serologically positive fattening pigs within different distances (1000, 1500 and 2000 m) of each sow herd, were included in a hierarchical Bayesian binomial model. A variable without spatial characteristics, type of herd (farrow to weaning and farrow to finish), was also included. Presence of positive fattening pigs or positive sows up to a distance of 1500 m of a sow herd increased its risk of being seropositive, although this variable had no effect on the risk when located at distances up to 1000 or 2000 m. The number of seropositive sows increased the risk of a sow herd being ADV seropositive only in the first period of study, when the proportion of serologically positive sow herds was nearly 60%. The spatial pattern of the residuals of the hierarchical Bayesian binomial model (observed versus predicted) was very similar to the observed infection in sow herds in all of the eradication periods, showing that spatial factors might not be the main factors related to the eradication of Aujeszky's disease from sow herds. Other herd-specific risk factors might be much more strongly related to the risk of a sow herd being ADV seropositive.     

基于贝叶斯网络及时序模拟的配电系统可靠性评估

针对适合配电系统可靠性评估的贝叶斯网络模型还不够完善,研究了贝叶斯网络模型的组成,建立了“联合”关系模型和“因果”关系模型;针对贝叶斯网络精确推理难以计算大规模配电系统的可靠性指标,将贝叶斯网络和时序模拟技术相结合,提出了一种时序模拟推理算法。该算法能产生元件的状态与随机时间段,实时进行系统状态的推理与时间、停电用户次数和停电量的累计,利用这些累计量不但可以计算系统的可靠性指标,还可进行诊断推理和因果推理,从而既能实现对系统的总体评价,又能找出钳制系统的薄弱环节。通过与配电系统可靠性测试系统数据及贝叶斯网络精确推理数据相比较,验证了该算法的合理性和有效性。     

Genetic associations of visual scores with subsequent rebreeding and days to first calving in Nellore cattle

Records of Nellore animals born from 1990 to 2006 were used to estimate genetic correlations of visual scores at yearling (conformation, C; finishing precocity, P; and muscling, M) with primiparous subsequent rebreeding (SR) and days to first calving (DC), because the magnitude of these associations is still unknown. Genetic parameters were estimated by multiple‐traits Bayesian analysis, using a nonlinear (threshold) animal models for visual scores and SR and a linear animal models for weaning weight (WW) and DC. WW was included in the analysis to account for the effects of sequential selection. The posterior means of heritabilities estimated for C, P, M, SR and DC were 0.24 ± 0.01, 0.31 ± 0.01, 0.30 ± 0.01, 0.18 ± 0.02 and 0.06 ± 0.02, respectively. The posterior means of genetic correlations estimated between SR and visual scores were low and positive, with values of 0.09 ± 0.02 (C), 0.19 ± 0.03 (P) and 0.18 ± 0.05 (M). On the other hand, negative genetic correlations were found between DC and C (?0.11 ± 0.09), P (?0.19 ± 0.09) and M (?0.16 ± 0.09). The primiparous rebreeding trait has genetic variability in Nellore cattle. The genetic correlations between visual scores, and SR and DC were low and favourable. The genetic changes in C, P and M were 0.02, 0.03 and 0.03/year, respectively. For SR and DC, genetic trends were 0.01/year and ?0.01 days/year, respectively, indicating that the increase in genetic merit for reproductive traits was small over time. Direct selection for visual scores together with female reproductive traits is recommended to increase the fertility of beef cows.