非均匀采样信号的数字频谱分析

本文介绍了一种近年来发展起来的非均匀采样信号的基本理论,以及由此推出的非均匀采样信号的数字谱表达式。分析了非均匀采样正弦信号的数字谱及其信噪比。文中还对几种典型的非均匀采样实例进行了分析,推导出其各自的信噪比。     

数据挖掘中聚类分析技术的应用

介绍了数据挖掘中的聚类分析技术和方法,并根据数据挖掘实施的步骤,结合其在实际工作中的应用,对区域经济指标体系进行了分析和综合,得出的分析结果同所采用数据当时的经济状况基本吻合,结论较为合理,对制定决策具有积极的指导意义.通过这个实例的应用分析,说明这个方法在解决实际问题时具有全面性和客观性等优点,为数据挖掘技术在实际工作中的应用做了一些有益的探讨.     

Rates of inbreeding and genetic diversity in Canadian Holstein and Jersey cattle

The accumulation of inbreeding and the loss of genetic diversity is a potential problem in the modern dairy cattle breeds. Therefore, the purpose of this study was to analyze the pedigrees of Canadian Holstein and Jersey cattle to estimate the past and current rates of inbreeding and genetic diversity, and to identify the main causes of diversity loss. Completeness and depth of the pedigrees were good for both breeds. For Holsteins, the average rates of inbreeding per generation showed a decreasing trend in recent years when compared with the 1990s. The estimated current effective population size was about 115 for Holsteins and is not expected to significantly change in the near future if generation intervals stay at current value, as rates of increase in inbreeding and coancestry showed decreasing trends. For Jerseys, the estimated effective population size was about 55 and it is expected to decrease in the near future due to the observed increasing rates of coancestry and inbreeding. Ancestors with the highest marginal genetic contributions to the gene pool in current years and with the highest contributions to inbreeding were identified. The 2 most heavily used and represented ancestors in the Holstein pedigree (i.e., Round Oak Rag Apple Elevation and his son Hanoverhill Starbuck), accounted for 30% of inbreeding. Analyses revealed that the most important cause of genetic diversity loss in both breeds was genetic drift accumulated over nonfounder generations, which occurred due to small effective population size. Therefore, a need exists in both breeds, particularly in Jerseys, for managing selection and mating decisions to control future coancestry and inbreeding, which would lead to better handling of the effective population size.     

Pedigree analysis and inbreeding effects on calving traits in large dairy herds in Germany

A pedigree analysis was carried out for a subset of the German Holstein population with respect to the effective number of founders and the ancestors with the highest effect on 2 defined reference populations. Reference population 1 contained animals born between 1998 and 2002 (n = 19,537), and reference population 2 included animals born between 2003 and 2007 (n = 19,060). The pedigree file included 73,946 animals in total. The effective number of founders was 111.3 and 92.8 in reference populations 1 and 2, respectively. In reference population 1, 52.22% of the gene pool could be explained by 10 ancestors. In reference population 2, the 10 ancestors with the greatest effect contributed 57.22% of the gene pool. The effect of inbreeding on birth weight, calving ease, and stillbirth was also analyzed in this study. Two models were used to estimate the effect of inbreeding. One model fitted inbreeding as a regression on the inbreeding coefficient of the dam, whereas the other model fitted inbreeding as a regression on the inbreeding coefficient of the calf. Phenotypic data for this study were collected on 3 large commercial milk farms. Data recording took place from February 1998 to December 2008 and 36,623 calving events were recorded; 8.19% of the calves died at or within 48 h after calving. All calves were weighed after birth and the average birth weight was 43 kg for calves born alive and 42 kg for stillborn calves. Calving ease was recorded on a scale between 1 and 4. The distribution of scores was 69.81, 21.02, 8.96, and 0.22%, ranked 1 (without assistance or assistance by 1 person), 2 (assistance by 2 or more persons or mechanical assistance), 3 (veterinary assistance), and 4 (operation), respectively, on the calving-ease scale. Twins were excluded from all analyses. Dam inbreeding had no significant effect on the traits of this study. The inbreeding coefficient of the calf had no significant effect on birth weight and calving ease but showed a significant effect on stillbirth: the risk of stillbirth was found to increase by 0.22% per 1% increase of the inbreeding coefficient of the calf.     

文化基因视域下文旅特色小镇品牌塑造实践研究

目的 针对当下特色小镇品牌塑造泛化、内涵空洞以及产业关联性差等痛点,提出围绕地域文化探索当下特色小镇品牌塑造理论及设计的实践途径。方法 以浙江省温岭市石塘镇金沙湾特色小镇品牌塑造为例,在文化基因视域下通过地域文化基因梳理归类,构建基因谱系图,提出基因提取及转承路径,提炼小镇品牌文化基因核心点,构建小镇品牌理念及文化内生系统。结果 通过核心文化基因构建金沙湾地域文化产业发展框架,完成特色小镇品牌塑造,最终实现该地域文化的可持续发展。结论 特色小镇品牌塑造的核心是地域文化的提炼,文化核心基因的提取。只有在文化基因视域下探索地域文化核心基因的提取及转承方式,完成文化资源到文化价值符号的转变,才能赋予小镇品牌核心竞争力并实现地域文化的永续发展。     

如何研究一个宗族遗传网络

社会人群都离不开姓氏符号,它记载着人与人之间亲疏关系的演化与博弈。该文以史姓为例,阐述姓氏、血缘、族谱之间的区别,探寻如何构建具有科学意义的宗族遗传网络,以及其中涉及的某些科学问题。     

基于空间基因的村镇聚落空间谱系构建 研究

村镇聚落空间形态具有显著的地域分异性,表现出 明显的群系特征。综合多学科视角构建基于空间基因的村镇聚 落空间谱系,一是精准刻画村镇聚落空间形态的地域特征类 型,二是准确判读村镇聚落类型的内在关联,进而从群体关联 的视角科学认知村镇聚落空间形态类型的差异性和相似性规 律。以重庆永川地区为例,对村镇聚落的多尺度空间形态特征 进行数字化解析,在此基础之上,采用聚类方法,对村镇聚落 空间形态进行类型划分,将永川村镇聚落分为5种类型;运用 形态类型学等方法识别提取村镇聚落空间基因,并采用信息编 码的方式,以空间基因序列信息为索引,构建村镇聚落空间谱 系,为全面解析村镇聚落形态类型特征的共性和差异性规律提 供一种新的思路,从而为村镇聚落的特色保护和风貌管控提供 借鉴。