随机激励下载荷谱识别

采用逆虚拟激励法进行载荷识别，识别结构所受平稳随机激励的功率谱密度，在钢悬臂梁和有机玻璃框架上进行了多次试验，识别的载荷与实际值符合得较好，同时研究了相干和不相干随机激励两种情况下载荷识别结果的异同，通过实测数据讨论了不同噪音对识别结果的影响。此方法的优点在于识别未知载荷的准确性、计算的高效性和对频响函数病态的克服能力。     

遗传算法求解粘弹性反问题

建立粘弹性本构参数与准静态位移的显式关系 ,并由此给出了有限元形式的数值计算模型 .在遗传算法的实现过程中采取了一些新的措施 ,利用改进后遗传算法 ,提出粘弹性本构参数辨识的一般方法 ,进行了数值验证 ,并初步考虑了信息误差的影响 .     

结构损伤识别中部分相关噪声模型

详细地讨论了噪声的来源和产生的物理机制,分析了经典不相关噪声模型的物理意义和适用范围,将测试噪声分为与信号大小无关的测试系统基础噪声和与测试信号幅值和相位有关的环境噪声两部分,提出与结构试验实际环境符合的部分相关噪声模型.计算比较了部分相关噪声模型和传统噪声模型下仿真测试信号的信噪比和方差比,并比较了其对结构振型的识别精度和损伤识别定位的影响.结果表明,所提出的部分相关噪声模型较为符合工程测试实际,而传统噪声模型未能有效模拟系统和环境噪声.     

Sequence and analysis of chromosome 3 of the plant Arabidopsis thaliana

Arabidopsis thaliana is an important model system for plant biologists. In 1996 an international collaboration (the Arabidopsis Genome Initiative) was formed to sequence the whole genome of Arabidopsis and in 1999 the sequence of the first two chromosomes was reported. The sequence of the last three chromosomes and an analysis of the whole genome are reported in this issue. Here we present the sequence of chromosome 3, organized into four sequence segments (contigs). The two largest (13.5 and 9.2 Mb) correspond to the top (long) and the bottom (short) arms of chromosome 3, and the two small contigs are located in the genetically defined centromere. This chromosome encodes 5,220 of the roughly 25,500 predicted protein-coding genes in the genome. About 20% of the predicted proteins have significant homology to proteins in eukaryotic genomes for which the complete sequence is available, pointing to important conserved cellular functions among eukaryotes.     

基于权函数法的含裂纹叶片的应力强度因子研究

基于两个已知的参考应力强度因子和权函数的基本特性,分别计算了含单边裂纹、双边裂纹和中心裂纹的有限宽板的权函数。然后,将所计算的权函数分别用于确定含单边、双边及中心裂纹的旋转平板叶片的裂尖应力强度因子K。最后,在线弹性断裂力学范围内由断裂准则KKIC分别对含单边、双边和中心裂纹的平板叶片的临界转速进行了估算。研究结果表明:旋转平板叶片所含的裂纹深度越深、裂纹位置距旋转轴越近,所引起的裂尖应力强度因子就越大,所允许的临界转速就越低。     

一种改进的耗散型接触力模型及实验验证

为了研究含间隙运动副对连杆机构动态性能的影响,基于能够描述碰撞过程中能量损失的连续接触模型,建立了一个新的耗散型接触力模型.在这个新模型下对含间隙连杆机构进行动力学仿真,并进行了实验研究.主要考察了间隙尺寸和加载强度对连杆受力的影响.结果表明:间隙的存在会影响传递力曲线,使机构产生明显的振动冲击,间隙大小和加载速度是影响机构动态响应的主要因素.该仿真结果得到了实验的验证.     

电流变体单链的轴向应变对导电性质的影响

研究了由平均直径为２１０μｍ的玻璃球在硅油中加直流电场后形成的单链的导电行为，主要研究了链的轴向应变对其导电性质的影响。     

Mapping copy number variation by population-scale genome sequencing

Genomic structural variants (SVs) are abundant in humans, differing from other forms of variation in extent, origin and functional impact. Despite progress in SV characterization, the nucleotide resolution architecture of most SVs remains unknown. We constructed a map of unbalanced SVs (that is, copy number variants) based on whole genome DNA sequencing data from 185 human genomes, integrating evidence from complementary SV discovery approaches with extensive experimental validations. Our map encompassed 22,025 deletions and 6,000 additional SVs, including insertions and tandem duplications. Most SVs (53%) were mapped to nucleotide resolution, which facilitated analysing their origin and functional impact. We examined numerous whole and partial gene deletions with a genotyping approach and observed a depletion of gene disruptions amongst high frequency deletions. Furthermore, we observed differences in the size spectra of SVs originating from distinct formation mechanisms, and constructed a map of SV hotspots formed by common mechanisms. Our analytical framework and SV map serves as a resource for sequencing-based association studies.