广义螺旋曲面工件轮廓度统一测量方法

对国标规定的标准螺旋曲面的测量方法进行分析,得出普通螺纹和丝杠形位误差测量方法中的共性问题。利用微分几何的曲面包络理论,结合坐标投影变换法和相对运动法对工件的曲面方程进行研究,得到了在母线曲面已知的情况下广义螺旋曲面的统一方程。通过广义螺旋曲面测量要素分析,得出异型螺旋面的测量方法。结合曲面统一方程,提出了广义螺旋面的统一测量方法。实例表明,该方法能够快速、准确地测量出对应工件的型面尺寸,避免了测量的复杂性和低效性。     

New Method of Founding Profile Equations and Pressure Angle Formula to the Cylindrical Cam Mechanism with Slide Roller-Follower

According to existent problems on design and application of the cylindrical cam mechanism with the slide roller-follower, the one correct concept about profile design and pressure angle is presented. Based on this concept, the theoretical profile,practical profile,meshing surface equations and pressure angle formula of the cam mechanism are built up by using opp.rotation analysis and offset surface principle. This method is very simple and clear, and avoids the abstract analysing process in meshing principle. The mathematic models built by this paper can be used to design,manufacture and check this type of cam mechanism correctly, and also create conditions to make deeply meshing property analysis of this mechanism.     

高速柴油机配气机构凸轮型线设计

概述了配气机构凸轮型线的设计方法。根据配气机构振动特征数ε确定了两种型线函数(组合式和高次方式),对4108型高速柴油机凸轮型线进行了设计计算,并对配气机构进行了动力特性计算。在相同的初始条件下,比较了两种型线的各种性能参数的差别,对两种凸轮型线的优劣作出了评判。     

静电凝并中荷电粒子的运动方程及近似解

本文分析静电除尘器预凝并粒子的运动情况,研究了荷电气固两相流中粒子运动与气流运动的关系,通过对荷电粒子的受力分析,在粒子运动过程中考虑了库仑力、压差力、附加质量力、Stokes阻力以及Basset力对荷电粒子的作用,而忽略其它力的影响,建立了湍流中描述粒子运动的基本方程—BBO(Basset-Boussinesq-Oseen)方程,用谱分解方法进行求解,并得到荷电粒子凝并运动方程的两组近似解,从而确定了粒子运动与气流运动的关系,αr为近似解的重要参数,随着αr的变化,粒子运动的复杂性随之变化。     

低温对2种紫草科植物△6 脂肪酸脱氢酶基因表达的影响

以紫草科植物新疆软紫草(Arnebia euchroma)和假狼紫草(Nonea capsica(willd.)G.Don)为材料,翻译延伸因子EF1a为内参基因,利用半定量逆转录聚合酶链式反应(semi-RT-PCR)技术,对2种紫草植物中γ-亚麻酸合成关键酶基因△6-脂肪酸脱氢酶基因的表达进行研究。结果表明,△6-脂肪酸脱氢酶基因在紫草植物的叶、茎、根中均表达,在低温诱导不同时间后紫草植物叶片中△6-脂肪酸脱氢酶基因的表达有所增强。气相色谱分析显示,其产物γ-亚麻酸在低温下积累,推测紫草科植物叶片中△6-脂肪酸脱氢酶基因表达量增加可能与适应低温胁迫的逆境有关。     

三江源地区饮用水源中隐孢子虫和贾地鞭毛虫的检测

通过膜过滤、絮凝沉淀法浓缩收集了三江源地区水源中隐孢子虫和贾第鞭毛虫,并用蔗糖漂浮法纯化了上述"两虫"。及抗酸染色后镜检,结果显示:在三江源地区10条河流中的6条(60%)检出隐孢子虫,32个采样点11个点(34%)的样品检出隐孢子虫;在10条河流中有2条(20%)检出贾地鞭毛虫,32个采样点的4个点(12.5%)的样品中检出贾地鞭毛虫。     

Thromboelastography: a tool for measuring hypercoagulability, hypocoagulability, and fibrinolysis

Objective: To describe the technique of thromboelastography (TEG) and review the applications of this coagulation test in humans and small animals. Data sources: Data sources included scientific reviews and original research publications. Human data synthesis: TEG in humans has been used for documentation of hypercoagulable and hypocoagulable states and has been shown to be beneficial in patient management. Veterinary data synthesis: Clinical evaluation of TEG in veterinary medicine is limited; however, recent reports have documented evidence of hypercoagulability in dogs with parvovirus and protein‐losing nephropathy. Additionally, many of the research models may be relevant to veterinary patients. Conclusions: TEG provides information about coagulation that is not available through routine coagulation tests. The application of TEG monitoring to veterinary patients shows promise; however, prospective clinical studies are needed.     

Effects of oxypolygelatin and dextran 70 on hemostatic variables in dogs

Objective To evaluate and compare coagulation variables following the administration of oxypolygelatin and dextran 70 to clinically healthy dogs. Study design Randomized cross‐over experimental study. Animals A total of eight healthy adult female Beagles aged 2–4 years old and weighing 11.8 ± 2.7 kg. Methods The dogs received a 15‐minute intravenous (IV) infusion of 5 mL kg^?1 oxypolygelatin or 10 mL kg^?1 6% dextran 70. Before (PRE) and at 2, 5, and 24 hours after administration, packed cell volume (PCV), total solids concentration (TS), prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen concentration (FIB), platelet numbers (Plat), factor VIII coagulant activity (VIII:C), von Willebrand factor antigen concentration (vWf:Ag) and platelet function and buccal mucosal bleeding time (BMBT) were measured. Platelet function was assessed using aggregation and by measuring ATP release from aggregating platelets over 6 minutes, with 20, 10, and 5 µm ADP and 5 and 10 µg of collagen mL^?1 as platelet activation agonists. Results All baseline values were within our normal ranges, except for one dog that had low vWf:Ag PRE values prior to both dextran and oxypolygelatin administration. Following dextran and oxypolygelatin administration, the PCV and TP were significantly (p < 0.05) decreased. Plat, FIB, and vWf:Ag decreased, while BMBT and VIII:C increased following dextran administration. Dextran also caused a significant decrease in platelet aggregation in response to ADP. Oxypolygelatin caused a significant decrease in vWf:Ag, Plat, and FIB compared to PRE values. The total amount of ATP released, standardized to platelet number, did not vary significantly for either group at any sampling time from PRE values. No significant changes from PRE values were noted at any time in either group for PT or APTT. Conclusion At the doses administered, both dextran and oxypolygelatin can interfere with hemostatic variables in healthy dogs, but dextran's effect is more profound and prolonged when compared to oxypolygelatin. Clinical relevance Oxypolygelatin causes fewer hemostatic abnormalities when compared to dextran, making it a superior colloid for administration at the doses tested.