处理桥头跳车的几点认识

本文通过采用常规和采用新材料、新工艺(土工格栅)两种方法对处理桥头跳车现象进行了论述。重点介绍了采用土工格栅处理桥头跳车的具体做法。     

我国防沙治沙科研的突破口初探-以河西走廊沙区为例

河西走廊的防沙治沙科研在我国广大沙区具有代表性。河西走廊防沙治沙科研存在的主要问题是 :⑴宏观战略研究薄弱 ,研究缺乏系统性。主要表现在 :治沙措施散件得不到优化组合 ,其功能得不到充分发挥 ;研究客体之间互相割裂 ,缺乏从总体上控制沙漠化的研究 ;农业开发与生态资源保护的结合点问题没有解决 ;研究课题重复。⑵散件成果多属定性结论 ,缺乏操作性。运用系统科学的思想方法是治沙科技发展的突破口 :只有运用系统科学的思想方法才能科学处理生态资源保护、生态环境建设和资源开发利用三方面的关系 ,才能实现各种防沙治沙措施的优化配置 ,才能实现治理结果的持续稳定。运用现代数学方法建立沙区生态环境综合治理数学模型才能科学处理多系统的复杂关系。现代数学方法是系统科学的主要方法。运用系统科学的思想方法和现代数学方法是治沙科技发展必须达到的 ,是治沙科技发展的突破口。     

Predicting the spatial distribution of ground flora on large domains using a hierarchical Bayesian model

Accomodation of important sources of uncertainty in ecological models is essential to realistically predicting ecological processes. The purpose of this project is to develop a robust methodology for modeling natural processes on a landscape while accounting for the variability in a process by utilizing environmental and spatial random effects. A hierarchical Bayesian framework has allowed the simultaneous integration of these effects. This framework naturally assumes variables to be random and the posterior distribution of the model provides probabilistic information about the process. Two species in the genus Desmodium were used as examples to illustrate the utility of the model in Southeast Missouri, USA. In addition, two validation techniques were applied to evaluate the qualitative and quantitative characteristics of the predictions.This revised version was published online in May 2005 with corrections to the Cover Date.     

猪胚胎死亡的影响因素及其预防措施

猪胚胎死亡直接影响着母猪的产仔数，并进而影响着养猪生产的经济效益。因此，在深入研究猪胚胎死亡规律及其影响因素的基础上，通过有效的措施降低胚胎死亡率，对提高母猪窝产仔数和经济效益具有十分重要的意义。本文综述了影响猪胚胎死亡的遗传、环境、营养和疾病等因素，并对生产实践中如何通过综合预防措施降低猪胚胎死亡率进行了初步探讨。     

基于MCMC模拟的MGPD模型及其在地质灾害风险度量中的应用

基于马尔科夫链蒙特卡洛(简记为MCMC)模拟的参数贝叶斯估计,对改进的广义帕累托分布(简记为MGPD)模型进行了优化,并利用该模型得到了地质灾害损失的在险损失值(简记为VaR)和条件损失值(简记为CVaR).以湖南娄底市地质灾害损失数据进行实证分析及模型适应性检验,结果表明:优化后的模型不仅具有很好的极值数据描述能力,而且具有较强的适用性.     

浅析网络时代大学生自我管理能力的培养

良好的自我管理是大学生文明成人,健康成才,和谐成功的基础。自我管理能力是当代大学生必备的素质,也是我国高教体制改革的必然要求。在互联网时代,受到各种信息的冲击,加强大学生自我管理能力的培养是大学生适应社会发展、有效开发自身潜能、提高自身综合素质的根本需要。本文就网络时代下大学生做好自我管理的重要性,现实状况以及网络时代下如何培养大学生的自我管理能力进行简要分析,为网络时代下提高自我管理能力提供现实参考。     

基于信号博弈的阳澄湖大闸蟹绿色标签市场应用分析

水产品绿色标签对消费者来说是高质量的信号,对卖家来说则是卖出高价的资本.但是欺诈行为的存在损害了消费者和其他卖家的利益,扰乱了市场秩序.以阳澄湖大闸蟹为例,通过信号博彝理论,对螃蟹市场中关卖双方的消费行为进行博彝分析,得到了精炼贝叶斯Nash均衡.     

对我国LULUCF碳计量监测方法的探讨

围绕我国林业编制温室气体清单这一重要工作,介绍了IPCC关于LULUCF温室气体清单编制系列技术指南的技术要点和要求,阐明了我国林业温室气体清单编制工作的进展,提出了林业开展LULUCF碳监测工作未来面临的需求。同时,在分析美国、欧盟、加拿大等发达国家LULUCF温室气体清单编制做法和经验的基础上,提出了"在森林资源清查样地系统上构建"、"新布设LULUCF大样地系统"等2种开展LULUCF碳监测的思路,目的是为推动我国林业LULUCF碳监测达到国际先进水平提供建议。     

Identification of potential genomic regions for egg weight by a haplotype-based genome-wide association study using Bayesian methods

ABSTRACT

1. Theoretically, haplotype blocks might be a more suitable alternative to SNP genotypes as they are usually better at capturing multi-allelic QTL effects, compared to individual SNP genotypes in genome-wide association studies. The objectives of this study were to identify genomic regions related to egg weight traits by Bayesian methods (BayesA, BayesB, and BayesN) that fit fixed-length haplotypes using GenSel software.

2. Genotypes at 294,705 SNPs, that were common on a 600K Affymetrix chip, were phased for an egg-laying hen population of 1,063 birds. Recorded traits included first egg weight (FEW) and average egg weight at 28, 36, 56, 66, 72 and 80 weeks of age.

2. Fitting 1Mb haplotypes from BayesB resulted in the highest proportion of genetic variance explained for the egg weight traits. Based on the trait, the genetic variance explained by each marker ranged from 27% to 76%.

3. Different haplotype windows associated with egg weight traits only explained a small percentage of the genetic variance.

4. The top one 1-Mb window on GGA1 explained approximately 4.05% of total genetic variance for the FEW. Candidate genes, including PRKAR2B, HMGA2, LEMD3, GRIP1, EHBP1, MAP3K7, and MYH were identified for egg weight traits.

5. Several genomic regions, potentially associated with egg weight traits, were identified, some of which overlapped with known genes and previously reported QTL regions for egg production traits.     

Bayesian estimation of diagnostic accuracy of a new bead-based antibody detection test to reveal Toxoplasma gondii infections in pig populations

The success of a Toxoplasma gondii surveillance program in European pig production systems depends partly on the quality of the test to detect infection in the population. The test accuracy of a recently developed serological bead-based assay (BBA) was investigated earlier using sera from experimentally infected animals. In this study, the accuracy of the BBA was determined by the use of sera from animals from two field subpopulations. As no T. gondii infection information of these animals was available, test accuracy was determined through a Bayesian approach allowing for conditional dependency between BBA and an ELISA test. The priors for prevalence were based on available information from literature, whereas for specificity vague non-informative priors were used. Priors for sensitivity were based either on available information or specified as non-informative. Posterior estimates for BBA sensitivity and specificity were (mode) 0.855 (Bayesian 95% credibility interval (bCI) 0.702–0.960) and 0.913 (bCI 0.893–0.931), respectively. Comparing the results of BBA and ELISA, sensitivity was higher for the BBA while specificity was higher for ELISA. Alternative priors for the sensitivity affected posterior estimates for sensitivity of both BBA and ELISA, but not for specificity. Because the difference in prevalence between the two subpopulations is small, and the number of infected animals is small as well, the precision of the posterior estimates for sensitivity may be less accurate in comparison to the estimates for specificity. The estimated value for specificity of BBA is at least optimally defined for testing pigs from conventional and organic Dutch farms.