动态载荷下基于声发射技术的杨木破坏过程检测

利用声发射检测和力学试验相结合的方法,研究山杨木材在动态载荷下的声发射演变过程;结合木材粘弹性特点,通过声发射参数分析研究在不同受力阶段木材的声发射特点.结果表明:1)声发射信号幅值不连续,是跃迁的;材料断裂前声发射信号的幅值和能量比断裂后小,在断裂点对应声发射信号幅值和能量的局部极大值.2)随时间和载荷的变化,声发射累计撞击数和累计能量增加快慢可以体现杨木在受力条件下的完全弹性、弹性为主的弹塑性共存、塑性为主的弹塑性共存3种状态.3)声发射率和幅值参数可以预测材料纤维开始断裂进入危险期的第一"临界点"和材料大量纤维断裂进入严重危险期的第二"临界点",如果继续加载材料将会破坏断裂.     

野生动物在人兽共患病发生、传播中的作用

近年来,人兽共患病已经成为影响全球的重大公共卫生问题,野生动物作为许多人兽共患病原体的"储存宿主",其作用正为越来越多的人所重视.介绍几种古老的和近年来新出现的重大人兽共患病的流行和危害情况,阐述野生动物在其发生和流行中的作用,探讨人兽共患病的预防、控制措施.     

国内外粮食水分快速检测方法的研究

综述了国内外粮食水分快速检测的方法,分析了各类方法及仪器设备的特点和局限性.     

一起饲料药物交叉污染事件引发的反思

通过对一起典型的因交叉污染造成的饲料药物残留事件的调查,笔者分析了产生药物残留污染的原因,并提出建设性的纠正措施及几点反思。     

A reovirus disease in cultured mud crab, Scylla serrata, in southern China

A reovirus, designated mud crab reovirus (MCRV), associated with large economic losses was recently isolated from marine cultured mud crab, Scylla serrata, in southern China. The complete viral particle is 70 nm in diameter, icosahedral and non-enveloped. The virus infects connective tissue cells of the hepatopancreas, gills and intestine in mud crab and develops in the cytoplasm. Hundred per cent mortality was observed in mud crab experimentally infected by intramuscular injection, bath inoculation and oral inoculation, while cohabitation infection caused 80% mortality. The viral genome consists of 13 linear dsRNA segments, with an electrophoretic pattern 1/5/7. The results of this study suggest that the virus is highly pathogenic and can be transmitted enterically as well as via the body surface of mud crab. Although the genomic organization of this virus is different from that of the other crab reoviruses, CcRV-W2 and DpPV, all three of these reoviruses have similar electrophoresis patterns. Therefore, MCRV may be a new member of the DpPV and CcRV-W2 group.     

轴流式脱粒-清选装置试验台的设计

针对全喂入联合收获机田间试验费时、费工,诸多参数无法调整,数据获取困难、精度不高,可重复性较差等问题,设计了轴流式脱粒-清选室内试验台。机械系统采用可组合的模块化结构,工作部件更换和运动参数调整方便,设计了分析脱出物、清选后籽粒的空间分布的接粮箱。以PLC作为硬件控制系统的核心,采用虚拟仪器技术构建的测控软件系统,可方便实现对工作部件的转速、振幅、频率、扭矩、功率等参数进行实时采集、显示、处理与分析,为轴流式脱粒-清选装置的设计提供试验依据。     

基于知识工程的车内布置可视化系统

根据中国人体尺寸和人机工程学知识,建立了通用的三维参数化中国人体模型。综合汽车设计标准、设计知识和专家经验,采用面向对象的知识表达方法及基于规则的推理技术,开发了基于知识工程的汽车车身内部布置系统。实现了视野校核、脚踏板与手操纵件的设计、操纵空间与操纵力校核、安全带固定点位置范围确定等功能。     

轴-轴承系统动力学摩擦学弹性力学耦合分析

采用动力学仿真软件ADAMS和有限元分析软件ANSYS,结合手工编程的方法,研究了变载荷作用下轴-轴承系统动力学、摩擦学、弹性力学(轴的刚度和强度)耦合分析问题,重点讨论正弦载荷作用下轴-轴承系统的共振响应和考虑动态油膜压力分布时的轴颈表面动应力计算。计算结果表明,动应力在轴颈表面沿轴向和周向的分布与油膜压力沿轴向和周向的分布密切相关;动应力随时间的变化与轴-轴承系统的动力学响应密切相关。     

Effects of dietary vitamin E and fat supplementation in growing-finishing swine fed to a heavy slaughter weight of 150 kg: II. Tissue fatty acid profile,vitamin E concentrations,and antioxidant capacity of plasma and tissue

The study aimed to assess the effects of vitamin E (VE) supplementation and fat source on fatty acid (FA) composition, VE concentrations, and antioxidant capacity in plasma and tissues of pigs fed to a heavy slaughter weight (150 kg). A total of 64 pigs (32 barrows, 32 gilts; 28.41 ± 0.83 kg) were blocked by sex and weight, and randomly assigned to one of eight dietary treatments (n = 8 per treatment) in a 4 × 2 factorial arrangement. Fat sources included corn starch (CS), 5% tallow (TW), 5% distiller’s corn oil (DCO), and 5% coconut oil (CN); VE supplementation levels were 11 and 200 ppm. Five-phase diets were formulated to meet requirement estimates of NRC (2012) and fed to pigs for each period of 25 kg from 25 to 150 kg. Increasing VE supplementation level increased C16:1 (P < 0.05) content but decreased C20:0 (P < 0.05) content in backfat and belly fat, while in liver, it increased C17:0 (P < 0.05) but decreased C18:0 (P < 0.05). Compared to the pigs fed the CS diet, the pigs fed the CN diet had greater (P < 0.05) content of total saturated FA, the pigs fed the DCO diet had greater (P < 0.05) content of total polyunsaturated FA content and iodine value, and the pigs fed the TW diet had greater (P < 0.05) content of total monounsaturated FA in backfat, belly fat, and liver. Plasma VE concentrations increased linearly (P < 0.05) with increasing length of feeding but faster (P < 0.05) in the pigs fed the CN and TW diets compared with the CS and DCO diets within the 200 ppm VE level; the pigs fed the DCO diet had the highest plasma VE concentrations (P < 0.05) from Phase 2 to Phase 5 within the 11 ppm VE level. The VE concentrations in liver and loin muscle (P < 0.05) increased with increasing dietary VE level from 11 to 200 ppm, but it was not affected by dietary fat source. There was no effect of VE supplementation and fat source on antioxidant capacity in plasma and liver except that pigs fed the DCO diet had greater liver SOD activity (P < 0.05) than the pigs fed the CN diet. In conclusion, dietary VE supplementation did not affect FA profile in backfat, belly fat, and liver consistently, while dietary FA composition with different fat sources affected much of the FA profile in backfat, belly fat, and liver. The higher level of VE supplementation increased liver and muscle VE concentrations and dietary fat sources affected plasma VE concentrations differently (P < 0.05), wherein the TW and CN diets increased the VE absorption greater than the DCO diet.     

Integration of meta-QTL discovery with omics:Towards a molecular breeding platform for improving wheat resistance to Fusarium head blight

Fusarium head blight (FHB) is a global wheat disease that devastates wheat production. Resistance to FHB spread within a wheat spike (type II resistance) and to...