半轴套管热挤压成形工艺数值模拟

通过对半轴套管的工艺分析,基于体积不变原则,采用逆向法计算零件毛坯,确定了热挤压成形工艺方案;结合刚粘塑性有限元法基本原理,运用有限元软件对半轴套管的反挤压过程进行3-D热力耦合模拟。影响半轴套管热挤压成形的主要工艺参数有挤压温度、挤压速度、模具预热温度等。在其他条件相同情况下,分别设置不同的挤压温度、挤压速度、模具预热温度,通过对不同参数模拟结果的分析比较,得出工艺参数对半轴套管成形的影响状况,揭示热挤压成形过程中的金属流动规律。优化的成形参数,提高了半轴套管的成形性能和经济性能。     

钢质渔船的腐蚀研究

本文根据对实船测厚数据的统计分析,阐述了钢质渔船船体外板的腐蚀特点,分析了造成腐蚀的原因,并对渔船易腐部位的防护提出了建议。     

力作甜味剂产品的引导者——专访苏卡斯(瑞士)调味技术有限公司全球技术研发总监罗伯·爱比先生

<正>苏卡斯(瑞士)调味技术有限公司为全球首家专业、专注于饲料甜味剂的研发、生产和销售的企业。紧紧围绕动物味觉生理研究进展,以甜     

Response to dietary phosphorus deficiency is affected by genetic background in growing pigs

Concern over the environmental effect of P excretion from pig production has led to reduced dietary P supplementation. To examine how genetics influence P utilization, 94 gilts sired by 2 genetic lines (PIC337 and PIC280) were housed individually and fed either a P-adequate diet (PA) or a 20% P-deficient diet (PD) for 14 wk. Initially and monthly, blood samples were collected and BW recorded after an overnight fast. Growth performance and plasma indicators of P status were determined monthly. At the end of the trial, carcass traits, meat quality, bone strength, and ash percentage were determined. Pigs fed the PD diet had decreased (P < 0.05) plasma P concentrations and poorer G:F (P < 0.05) over the length of the trial. After 4 wk on trial, pigs fed the PD diet had increased (P < 0.05) plasma 1,25(OH)(2)D(3) and decreased (P < 0.05) plasma parathyroid hormone compared with those fed the PA diet. At the end of the trial, pigs fed the PD diet had decreased (P < 0.05) BW, HCW, and percentage fat-free lean and tended to have decreased LM area (P = 0.06) and marbling (P = 0.09) and greater (P = 0.12) 10th-rib backfat than pigs fed the PA diet. Additionally, animals fed the PD diet had weaker bones and also decreased (P < 0.05) ash percentage and increased (P < 0.05) concentrations of 1alpha-hydroxylase and parathyroid hormone receptor mRNA in kidney tissue. Regardless of dietary treatment, PIC337-sired pigs consumed more feed and gained more BW than their PIC280-sired counterparts (P < 0.05) during the study. The PIC337-sired pigs also had greater (P < 0.05) HCW, larger (P < 0.01) LM area, and tended to have (P = 0.07) greater dressing percentage. Meat from the PIC337-sired pigs also tended to have greater (P = 0.12) concentrations of lactate but decreased (P = 0.07) concentrations of total glucose units 24 h postslaughter. Although plasma 1,25(OH)(2)D(3) concentrations were elevated (P < 0.05) in all the animals fed the PD diet, this elevation due to P deficiency tended (P = 0.09) to be greater in the PIC337-sired pigs after 12 wk on the treatment. The PIC337-sired pigs had stronger (P < 0.01) bones with greater ash percentage than the PIC280-sired pigs. The difference in the strength of the radii between the PIC337-sired pigs fed the PA and PD diets was greater than their PIC280-sired counterparts, which resulted in sire line x treatment interactions (P < 0.05). These data indicate differing mechanisms of P utilization between these genetic lines. Elucidating these mechanisms may lead to strategies to increase efficiency of growth in a more environmentally friendly manner.     

西藏“一江两河”流域中部草地沙漠化与防治

据１：３．５×１０＾４假彩色红外航空像片室内判读与野外调查，本区沙漠化草地可分为中度及轻度两种，面积１２．８２３万ｈｍ＾２，导致草地沙漠化的人为因素主要是超载过牧，樵柴，放牧制度不合理等，草地沙漠化防治可采取生物，管理及工程等措施。     

基于超星学习通的混合式教学模式应用研究—— 以发酵工程课程为例

为了提高发酵工程课程的教学质量和教学效果,针对发酵工程课程的内容和特点,将互联网+技术与教学相结合,进行了基于超星学习通平台的混合式线上线下教学方式的改革,结果表明:在增强了学生自主学习能力的同时,也促进了教师的自我提升.     

畜牧生产对环境的污染及对策

随着畜牧业生产规模的不断扩大和集约化程度的不断提高。畜牧生产中产生的氨气、硫化氢、粪臭素等恶臭气体以及粪尿中的氮磷元素、重金属、病原微生物。不仅对空气、土壤和水体造成了严重的污染．而且也成为人畜共患病的重要传播途径．极大地影响了人类的生存质量和身体健康。因此。减少畜牧生产对环境的污染。促进畜牧业可持续发展具有十分重要的现实意义。下面就畜牧生产对环境的污染及对策两个方面的问题作一阐述。     

氨基脲人工抗原的合成及其多克隆抗体的制备

目的合成氨基脲人工抗原并制备其多克隆抗体。方法以氨基脲(SEM)和对醛基苯甲酸(CP)为原料合成半抗原(CP-SEM),并采用碳化二亚胺法和混合酸酐法将其分别与牛血清白蛋白(BSA)和鸡卵清蛋白(OVA)偶联,合成氨基脲人工抗原。以氨基脲人工抗原(CPSEM-BSA)为免疫原免疫Balb/c小鼠,利用间接ELISA法测定其抗体效价。结果经薄层层析、红外光谱和元素分析等方法鉴定合成半抗原即为CP-SEM。紫外扫描、聚丙烯酰胺凝胶电泳结果表明人工抗原合成成功。免疫获得抗氨基脲的多克隆抗体,其抗体效价为1:64000。结论氨基脲人工抗原合成成功,并获得抗氨基脲的多克隆抗体。     

病死畜禽处理的现状及其无害化处理技术

近年来出现的"黄浦江漂猪事件"和"江西高安病死猪事件",引发了人们对病死畜禽无害化处理问题的担忧。病死畜禽的无害化处理还存在养殖者不受重视、政府部门监管不到位、补贴政策落实不到位和处理技术落后等问题。本文分析了当前病死畜禽处理的现状,阐述了五种病死畜禽的无害化处理技术,并提出了4点对策建议。