卧式旋耕机弯形刀侧切刃曲线滑切作用的动态分析

卧式旋耕机弯形刀侧切刃曲线滑切作用的理论分析,尚停留在以前进速度Vm=0为前提下滑切角变化的静态分析,与实际工作中的滑切作用相差甚远。木文提出的旋耕机组在向前运动时旋耕机弯形刀侧切刃曲线滑切作用的动态分析,与实际情况更为接近。     

驱动轴最大静扭强度与表面淬硬层状态关系浅析

拖拉机驱动轴的最大静扭强度和表面淬硬层状态具有直接关系,并进而直接影响驱动轴的疲劳强度。表面淬硬层不连续会使驱动轴的疲劳强度大幅降低而造成驱动轴早期断裂、失效;驱动轴表面淬硬层不连续会使其最大静扭强度降低30%以上;表面淬硬层过浅也会降低最大静扭强度。     

Transmission of methicillin resistant Staphylococcus aureus among pigs during transportation from farm to abattoir

The prevalence of methicillin resistant Staphylococcus aureus (MRSA) in pigs at abattoirs is higher than in pigs sampled on farms. This study investigated whether MRSA negative pigs can become MRSA positive during transportation from the farm to the abattoir after exposure to other pigs and environmental sources of MRSA. Nasal swabs were collected from four batches of pigs during loading at the farm, on arrival at the abattoir and after stunning. Environmental wipes were taken from lorries after transporting pigs and from lairages after holding pigs. All pigs (n = 117) tested MRSA negative before transportation. On arrival at the abattoir, 12/117 (10.3%) pigs in two batches tested MRSA positive. In lorries that tested positive after transportation, the prevalence of MRSA positive pigs was 21.1%, whereas no MRSA was detected in pigs that had been transported in lorries that tested negative after transportation. At stunning, all batches and 70/117 (59.8%) pigs tested MRSA positive. Pigs can become MRSA positive in the short period of time during transportation from the farm to stunning at the abattoir.     

农业拖拉机发动机变速器控制系统的计算机模拟

对手动换档、自动负载换档、自动无级变速等各类传动系,以固定作业速度运行模式进行模拟比较表明,负载换档变速器自动运行模式有较好节能效果。该文对负载换档变速器全油门变速作业的运行模式进行模拟结果表明,这种操用模式在节油及提高生产率方面有更明显的效果。     

太行山干旱低山丘陵区林草复合系统能量环境特征研究

研究了太行山干旱低山丘陵区林草复合系统能量环境特征,结果表明复合系统年太阳总辐射量为49868.65GJ.hm-2.a-1,光合有效辐射为24244.67GJ.hm-2.a-1,复合系统的平均反射率为22.5%,高于单作苹果系统,平均透射率为18.0%,低于单作苹果系统,说明林草复合系统可以截获和利用更多的光能。     

汽缸与曲轴修理对发动机压缩比的影响

发动机汽缸和曲轴修理中,往往影响发动机压缩比的变化。由于燃烧室结构形状复杂,给计算压缩比变化带来不便。本文通过分析,提出了计算压缩比变化的简便方法。     

BBP112型枝丫材剥皮机主要参数的确定与计算

本文对BBP112型枝丫材剥皮机的合理装填量、枝丫材长度和合理转速的确定进行了介绍。并对该机所需功率及刀轴的强度和刚度等主要参数进行了设计计算。为使用和设计该机提供了理论依据。     

A preliminary study of the role of ducks in the transmission of Newcastle disease virus to in-contact rural free-range chickens

The role of ducks in the transmission of Newcastle disease virus (NDV) to free-range village chicken was investigated experimentally. Newcastle disease (ND) seronegative ducklings reared in a pen were infected oronasally with velogenic NDV of intracerebral pathogenicity index (ICPI) 1.8 isolated from outbreaks in village chickens in Uganda. A first group of 3-week-old ND seronegative chicks was mixed with the ducks and they were kept together for 7 days. Both ducks and chicks were observed for ND clinical signs and any mortality, and they were bled and their sera were tested for ND antibodies by haemagglutination inhibition (HI) test. The chicks were removed, euthanized and examined for any ND lesions, while the ducks were transferred to a fresh pen and a second group of chicks was introduced and observed and treated as above. The ducks and the chicks tested positive for ND antibodies 7 days post infection and contact, respectively, but showed no clinical signs, post-mortem lesions or mortality. The mean ND antibody titre of the second group of chicks was lower than for the first group. This study has shown that although ducks can be infected with velogenic NDV, they do not show clinical signs but are able to transmit NDV to in-contact chicks. Further investigations are needed of the lack of clinical signs in the in-contact chicks and how long the ducks remain infective.     

输气站场自控系统夜间无人值守功能的实现

基于西气东输管道系统的实际运行情况,给出了实现夜间无人值守功能所需的功能逻辑。根据西气东输站场自动化控制系统的构架,对现有系统程序进行编辑与修改,加入了流量计算机的故障报警逻辑、压力调节自动分输逻辑和流量调节自动分输逻辑,提出了实现夜间无人值守功能的自动化控制系统改造方法,包括:PLC逻辑设置、RCI文件修改、增加站控画面及数据库建点。西气东输分输站夜间无人值守功能的实现,在保证管道安全生产的同时,提高了自动控制水平和管理水平。     

Potentiation of triclabendazole action in vivo against a triclabendazole-resistant isolate of Fasciola hepatica following its co-administration with the metabolic inhibitor, ketoconazole

An in vivo study in the laboratory rat model has been carried out to monitor morphological changes in adult Fasciola hepatica over a 4-day period resulting from co-treatment with triclabendazole (TCBZ) and ketoconazole (KTZ), a cytochrome P450 inhibitor. Rats were infected with the triclabendazole-resistant Oberon isolate of F. hepatica, dosed orally with triclabendazole at a dosage of 10 mg/kg live weight and ketoconazole at a dosage of 10 mg/kg live weight. Flukes were recovered at 24, 48, 72 and 96 h post-treatment (p.t.) and changes to fluke ultrastructure were assessed using transmission electron microscopy (TEM). Results showed an increase in the severity of changes to the fluke ultrastructure with time p.t. Swelling of the basal infolds and the associated mucopolysaccharide masses became more severe with time. Golgi complexes, if present, were greatly reduced in size and number by 96 h p.t., and sub-tegumental flooding was seen from the 72 h time-period onwards. Some sloughing of the tegumental covering over the spines was observed at 96 h p.t. The results demonstrated that the Oberon isolate is more sensitive to TCBZ action in the presence of KTZ than to TCBZ alone, reinforcing the idea that altered drug metabolism is involved in the resistance mechanism. Moreover, they support the concept that TCBZ + inhibitor combinations (aimed at altering drug pharmacokinetics and potentiating the action of TCBZ) could be used in the treatment of TCBZ-R populations of F. hepatica.