刀具螺旋角对高速铣削系统稳定性的影响

考虑铣刀螺旋角的影响，将刀齿的切削过程划分为连续，切入和切出3个过程，建立了高速铣削系统的动力学模型。运用半离散估计技术，将无限维特征值稳定性判定问题转化为有限维Floquet变换矩阵特征乘子稳定性判定问题，判定了系统的稳定性，获得了系统的稳定性极限图。结果显示，在考虑刀具螺旋角影响的情况下，铣削系统稳定性极限较传统情况有所增大，出现了类似“岛”的结构，其位置由轴向切削深度和螺旋齿距的关系决定，且由于切削刀齿切入、切出过程的影响，“岛”不是孤立的，而是有稳定性“桥”连接。理论结果通过铣削实验进行了验证。     

民国时期农村改进的实践与经验教训——走马乡农村实验研究

走马乡实验区采取“经济为中心,文化为手段,政治为枢纽“的实验方法,以农民的自治、自卫、自给、自强为目的,从管、教、养、卫四个方面开展农村实验工作,在农村社会改造方面为我们留下了宝贵的经验教训.     

应激因素对东北虎生殖的影响

通过观察动物园里的东北虎在环境、食物、社群交往中产生的应激因素来探讨其对东北虎妊娠的影响，为东北虎在催情，配种，妊娠等方面提供参考。     

鸡痘病毒282E_4株基因组2.9kbBamHI片段的序列测定与分析

对我国鸡痘病毒 ( FPV) 2 82 E4株基因组 2 .9kb Bam HI片段进行了序列测定与分析。结果表明 ,该片段全长 2 92 3 bp,A T含量为 72 .0 8%,含 6个完整的开放读码框架 ( ORF)和 2个不完整的 ORF,最大的ORF所编码多肽的相对分子质量为 2 4 60 0。在 2个 ORF的上游存在痘苗病毒晚期启动子的保守序列TAAAT,在 6个 ORF的下游和 2个 ORF的编码区内存在痘苗病毒早期转录终止信号 T5NT。把该片段的核苷酸序列和每个 ORF所编码的氨基酸序列分别对 EMBL核酸序列库和 SWISS-PROT蛋白质序列库进行了同源性搜索 ,未发现同源性片段     

重塑国有森工企业政企关系的对策研究

深入研究了一直困扰国有林区林业企业发展的“政企关系”问题.分析了政府对国有森工企业的“越权”与“缺失”背景及效应;国有森工企业的社会性、政府性职能的无奈与责任.从较为理性的角度研究了政企分离中来自于政府、企业主管部门以及企业自身的压力与障碍;在此基础上,从各利益集团可接受的角度,提出了渐进式过渡性的国有林区政企分离对策.指出政府相关制度的有效供给是政企分离能成为现实的最关键对策.     

Scale-dependent seasonal habitat selection by jaguars (Panthera onca) and pumas (Puma concolor) in Panama

Landscape Ecology - Few habitat modeling studies consider multiple spatial or temporal scales; less identify the operative scale of an organism's response to predictor variables. Optimizing...     

The Influence Analysis of Failure Affected by Reducing the Consequences

With the social progress, some modern method has been used in the industry. It can reduce the failure of pressure vessel. The method includes supervision, emergency cut-off and emergency relief etc. Each method is refined and quantized in the article. And it helps exact forecast for the failure.     

Dynamic QTL analysis for activity of antioxidant enzymes and malondialdehyde content in wheat seed during germination

Antioxidant enzymes played an important role in seed germination. In this study, Quantitative trait locus (QTLs) for activity of antioxidant enzymes (AEAs) and malondialdehyde (MDA) content in different time of seed germination were first identified, and antioxidant enzymes investigated included superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). QTL analysis was conducted both in unconditional and conditional methods., which demonstrated the “static” and “dynamic” expression of QTLs controlling AEAs and MDA content during wheat germination, respectively. Twenty-two unconditional QTLs were detected on 1A, 1B, 1D, 2B, 2D, 3A, 4A, 6B, 7A, 7B, and the contributions ranged from 8 % of CAT3 to 28.46 % of MDA3. Fifteen conditional QTLs were detected on 1A, 1B, 1D, 2B, 2D, 4A, 5B, 6B, 7A, 7D, and the contributions ranged from 8.59 % of CAT5|3 to 30.18 % of MDA3|1.     

Properties of stick-slip stage of yarn pull-out in para-aramid woven fabric

The aim of this study was to understand stick-slip properties of para-aramid woven fabrics. For this reason, pullout test was conducted on para-aramid Kevlar®29 and Kevlar®129 woven fabrics. The stick-slip and accumulative retraction force regions were defined based on the force-displacement curve. It was found that the stick-slip force and accumulative retraction force depended on fabric density and the number of pulled ends in the fabric. Stick-slip force in the multiple yarn pull-out test was higher than those of the single yarn pull-out test. Stick-slip force in single and multiple yarn pull-out tests in the dense K29 fabric were higher than those of the loose K129 fabric. In addition, long fabric samples showed high stick-slip force compared to that of the short fabric samples. On the other hand, the amount of stick-slip force was related to the number of interlacement points in the fabric whereas the amount of accumulative retraction force was related to fabric structural response.