植树挖坑机钻头主轴扭转振动数学建模与求解

介绍国内外机械化植树造林机械发展状况,指出国内植树用挖坑机研究重点,利用空间运动学和机械振动理论以及弹性动力学原理着重分析建立钻头主轴扭转振动模型并用数值方法进行求解,同时系统地分析钻头主轴下端部件与土壤的相互作用力、钻头主轴重力及惯性力等因素的影响,给出动态的准随机边界条件和初始条件.为下一步的钻头动力学特性仿真及整机动态特性研究,合理预测和控制钻头的运动规律,改善钻头的动力学特性,提高钻头工作效率及改进设计方法提供新的理论依据.     

奶牛难产激发应激性急性肾上腺皮质功能不全——心衰、水电解质严重失调辩析

应激性急性肾上腺皮质功能不全症的病理机制十分复杂,目前人医的各类文献中大都以“垂体—肾上腺轴”功能不全、功能衰竭、或发生广泛性出血坏死性病演作解释。本病在奶牛分娩难产过程中并不少见,病牛的症状表现以心衰和失钠性低血症为主征。但在兽医临床上由于认识不足,曾有不少中外学者将奶牛产后卧地不起的各类疾病,含糊地统称为“母牛睡倒爬不起来综合征”;更由于救治不当,病牛常以淘汰或死亡告终。本文通过对一具体典型病例辨析,着重讨论了本病的基本病理反应和确立诊断依据,强调对本病救护施治时应遵循的基本原则,供同道们在分析和解决这一实际问题时参考。     

Effect of rifaximin on gut-lung axis in mice infected with influenza A virus

Gut-lung axis injury is a common finding in patients with respiratory diseases as well as in animal model of influenza virus infection. Influenza virus damages the intestinal microecology while affecting the lungs. Rifaximin, a non-absorbable derivative of rifamycin, is an effective antibiotic that acts by inhibiting bacterial RNA synthesis. This study aimed to determine whether rifaximin-perturbation of the intestinal microbiome leads to protective effects against influenza infection, via the gut-lung axis. Our results showed that influenza virus infection caused inflammation of and damage to the lungs. The expression of tight junction proteins in the lung and colon of H1N1 infected mice decreased significantly, attesting that the barrier structure of the lung and colon was damaged. Due to this perturbation in the gut-lung axis, the intestinal microbiota became imbalanced as Escherichia coli bacteria replicated opportunistically, causing intestinal injury. When influenza infection was treated with rifamixin, qPCR results from the gut showed significant increases in Lactobacillus and Bifidobacterium populations, while Escherichia coli populations markedly decreased. Furthermore, pathology sections and western blotting results illustrated that rifaximin treatment strengthened the physical barriers of the lung-gut axis through increased expression of tight junction protein in the colon and lungs. These results indicated that rifaximin ameliorated lung and intestine injury induced by influenza virus infection. The mechanisms identified were the regulation of gut flora balance and intestinal and lung permeability, which might be related to the regulation of the gut-lung axis. Rifaximin might be useful as a co-treatment drug for the prevention of influenza virus infection.     

Insulin-like growth factor I in growing thoroughbreds

The objective of this longitudinal study was to characterize growth and plasma insulin-like growth factor I (IGF-I) concentrations in pasture-raised thoroughbreds fed two sources of dietary energy. Mares and foals were randomly assigned to either a sugar and starch (SS) or fat and fibre (FF)-rich feed, and plasma IGF-I and growth were measured once a month from 1 to 16 months of age. These dependent variables were also compared with day length and ambient temperature. There was an association between plasma IGF-I concentration and average daily gain (ADG) (r = 0.32, p < 0.001). There were also clear seasonal patterns in both ADG and plasma IGF-I, with high values in June and May, and a low value in March. Plasma IGF-I and ADG were positively associated with day length and temperature. Plasma IGF-I was never higher (p > 0.10) in the FF group when compared with the SS group, and was higher in the SS group during a rapid growth phase in the spring of year 2 (p < 0.10). The results establish an association between ADG and IGF-I in the horse and indicate that environment and age may influence this relationship. In addition, plasma IGF-I is influenced by dietary energy source at particular times of year. This link has important implications in designing feeding management strategies that are aimed at addressing skeletal development.     

固定轮系的旋轮线及在车削多面体中的应用

根据坐标变换公式推导了一对定轴齿轮旋轮线的公式,由内、外啮合的公式得出一系列旋轮线图,分析了影响旋轮线性质和形状的有关参数及变化规律。根据定轴轮系的传动性质,可推导出多齿轮固定轮系旋轮线的轨迹。在误差允许的范围内,可以利用定轴轮系的旋轮线在其中心部分形成近似的正多边形的性质来车削正多边形。以正四边形为例,进行了误差分析和试验验证。     

大型双向X型流道泵站机组减振技术研究

安徽省凤凰颈排灌站是一座大型双向X型流道泵站，文中简述了凤凰颈泵站机组运行中出现的故障，即机组振动问题；分析了故障产生的主要原因，是由出水流道水流脉动压强差引发了泵轴振摆，导致机组振动；本研究采用隔开振动源的措施消除了故障，通过运行实践证明，隔开振动源的方法简单、合理、可行，达到了使机组运行平稳的预期效果，并取得了显著的经济和社会效益。     

柴油发动机烧瓦抱轴的原因及预防措施

主要介绍了柴油机烧瓦时的现象及其烧损机理,分析了引发烧瓦抱轴的原因,主要是由于轴颈与轴瓦的装配间隙调整不当;发动机在使用中机油变质或短缺;没有合理正常形成油膜间隙;使得曲轴与轴瓦之间因缺少机油润滑而咬死,并就此问题提出了预防措施,可供借鉴.     

短肢剪力墙设计在新高规中的变化

根据实际设计经验,简单阐述2010年版高规的短肢剪力墙在高层建筑结构设计中的注意事项以及相对2002年版高规的不同。2010年版高规规定不论是否短肢剪力墙多少,所有短肢剪力墙都要按短肢剪力墙设计。对普通剪力墙结构而言,2010年版高规更明确、适用,安全。     

浅谈额济纳旗狼心山水利枢纽工程的利弊

由于全球气候变化而导致的气候干旱正严重影响着我国的西部地区,黑河流域上游过度的农业开发和城市用水的快速增加,导致下游的额济纳绿洲干旱缺水严重,为了解决这个问题,修建了狼心山水利枢纽工程。此工程虽然部分的解决了干旱缺水的问题、但也存在着弊端。如何解决这一工程缺陷,是今后研究的问题,文章提出了解决的方法供参考。