关键词： 混合动力   工程机械   轴系   振动   机电耦合  

摘要： 摘要：本文根据并联式混合动力工程机械的结构特点,探讨了混合动力系统轴系在发动机的机电耦合振动问题,分析了其振动产生的原因和特点,对于轴系的设计和振动控制都具有理论意义。 首先,选取发动机曲轴单曲柄模型,分析了曲轴产生机械振动耦合的原因并推导了其振动耦合的方程；针对混合动力系统多动力源的特点,将发动机和电机构成的轴系进行了简化,采用两自由度系统推导出混合动力轴系机电耦合振动的方程。 其次,根据混合动力工程机械的特点,建立了驱动系统、负载系统、动态协调控制器以及并联式混合动力系统的模型,通过仿真得到了轴系的激励作用力数据,为轴系振动的多体动力学研究提供基础。 再次,利用多体动力学理论,联合ANSYS、MATLAB和ADAMS建立了混合动力工程机械轴系机电耦合振动多体动力学仿真模型,进行了轴系在不同工况下的仿真研究,结果表明：助推模式下轴系的扭转振动、弯曲振动和纵向振动幅值均有增加,且谐次增多；发电模式下的扭振和弯曲振动均有所减小,纵向振动幅值有所增大。 最后,进行了混合动力轴系机电耦合振动的试验研究,结果表明：不同油门开度下的扭转振动以2谐次的幅值最大,这与理论仿真在趋势上是吻合的；不同工作模式下,轴系的扭转振动和弯曲振动都有所不同,助推模式相对于发动机模式对于轴系的振动幅值有所加剧；电机不同接入断开周期下,其接入混合动力系统的周期越短,轴系的振动越厉害。图50幅,表15个,参考文献72篇。

关键词： 碾米机   故障原因   盘式磨粉机   常见故障   农用   动力机械   油路  

关键词： 发动机   热动力   机械制造   机械工程   行走速度   牵引速度   燃油消耗率   稳定电压   农机   专家   涉农  

摘要： 重庆鑫源农机股份有限公司之所以被称为"小型热动力涉农机械制造专家",是因为其研发并生产了多样的相关产品,且品种齐全,质量可靠。如汽/柴油机动力、汽/柴油发电机组、汽/柴油水泵机组等通用机械,以及微耕机、微型收割机、茶/果园管理机、田园管理机、插秧机等农业机械。前文中已经详细介绍了微型收割机产品,让我们再来了解一下鑫源农机生产的部分其他产品吧。

关键词： Thiol   Sweetening   Cobalt phthalocyanine sulfonamide catalyst   Line weaver plot   Michaelis-Menten kinetics  

摘要： In the present study the kinetics of liquid phase oxidation of light thiols using novel cobalt phthalocyanine sulphonamide catalyst developed indigenously was investigated in a semi batch reactor. 1-Butanethiol was chosen to represent thiols in lighter range of petroleum fractions like liquefied petroleum gas and light straight run naphtha. Rate data was collected under experimental conditions representing industrial conditions. Effects of process parameters like catalyst concentration and initial feed mercaptan concentration on reaction rates were investigated. A mechanism based rate expression was deduced to explain the observed behavior. Its parameters estimated using Line weaver plots and further fine tuned by using optimization technique. The effective rate law represented a first order kinetics which explained the observed experimental phenomenon reasonably well for commonly encountered industrial conditions. (C) 2012 Elsevier B.V. All rights reserved.

关键词： BLOCK copolymers   MOLECULAR structure   SUBSTRATES (Materials science)   MOLECULAR dynamics   COMPUTER simulation   MICROEMULSIONS   VISCOELASTICITY  

摘要： Using computer simulations of a soft, coarse-grained model and a Lennard-Jones bead-spring model, we investigate the behavior of random block copolymer (RBCP) blends in the bulk and in the vicinity of a solid substrate. The RBCP is comprised of six random sequences of A and B blocks and adopts a microemulsion-like morphology as we increase the incompatibility between A and B segment species. The soft, coarse-grained model is used to efficiently equilibrate the morphology and molecular conformations in the melt, and its explicit molecular conformations are used to generate equilibrated starting configurations for the bead spring model. Since the pure A and B melts are structurally asymmetric, A-rich and B-rich domains differ in their density and viscosity in the melt or mechanical properties in the glassy state, respectively. We demonstrate that the self-assembled morphology in the melt gives rise to a viscoelastic transient plateau in the stress autocorrelation function. While an analysis of the entanglement density reveals a slight increase of the number of entanglements in response to microphase separation, the viscoelasticity of the RBCP blend chiefly stems from the slow morphological relaxation and the transient trapping of blocks inside domains. Upon quenching the microphase-separated structure below the glass transition temperature, the shear modulus increases about an order of magnitude compared to the viscoelastic plateau. The structural asymmetry of the segment species gives rise to spatially heterogeneous, local bulk and shear moduli that correlate with local composition fluctuations. The vicinity of a solid substrate that prefers one segment species gives rise to variations of the composition that propagate about three molecular extensions into the bulk. In this extended interphase, we observe an oscillatory decay of the composition and the local mechanical properties.

关键词： buckling   chirality   compressibility   compressive strength   elasticity   molecular dynamics method   molybdenum compounds   nanotubes   tensile strength   torsion  

摘要： The mechanical behavior of different types of single-walled and double-walled MoS2 nanotubes when subjected to external compressive, tensile, and torsional loading is investigated using classical molecular dynamics simulations. The forces on the atoms are determined using a reactive empirical bond-order potential parameterized for Mo-S systems. The simulations report on the elastic properties of the different MoS2 nanotube systems as well as the interrelationships between the buckling behavior and the structural parameters of the nanotubes, such as length, diameter, chirality, and number of walls. The simulations predict that the most important factor influencing mechanical response is the number of walls present and, to a lesser extent, the diameters of the nanotubes, with the other structural parameters predicted to have little effect on the results over the range investigated. These findings are consistent with reported density functional theory calculations and experimental data for WS2 and MoS2 nanotubes. (C) 2012 American Institute of Physics. [http://***/10.1063/1.4769739]

关键词： MOLECULAR dynamics   MOLECULAR structure   ENZYME regulation   ENZYME activation   DNA helicases   DEPHOSPHORYLATION  

摘要： RIG-I is a cytosolic sensor of viral RNA, comprised of two N-terminal CARDs followed by helicase and C-terminal regulatory domains (helicase-CTD). Viral RNA binds to the helicase-CTD and "exposes" the CARDs for downstream signaling. The role of the second CARD (CARD2) is essential as RIG-I activation requires dephosphorylation of Thr170 followed by ubiquitination at Lys172. Here, we present the solution structure and dynamics of human RIG-I CARD2. Surprisingly, we find that Thr170 is mostly buried. Parallel studies on the phosphomimetic T170E mutant suggest that the loss of function upon Thr170 phosphorylation is likely associated with changes in the CARD1-CARD2 interface that may prevent Lys172 ubiquitination and/or binding to free K63-linked polyubiquitin. We also demonstrate a strong interaction between CARD2 and the helicase-CTD, and show that mutations at the interface result in constitutive activation of RIG-I. Collectively, our data suggests a close interplay between phosphorylation, ubiquitination, and activation of human RIG-I, all mediated by CARD2.

关键词： 电动轮驱动   永磁同步电机   弱磁   电子差速  

摘要： 根据工程机械行走系统运行特点,建立其轮边电力驱动方式,满足永磁同步电机工作在低速大转矩和高速恒功率状态,确定永磁同步电机的弱磁控制算法。研究基于弱磁控制的速度和转差率相结合的电子差速控制策略,协调驱动电机牵引时的差速。最后建立前轮轮边电力驱动装载机试验台架,永磁同步电机提供的最大牵引力为29KN,实际测得最大牵引力为26 KN,电动轮效率达到89.7%,且转向平稳转向。

关键词： 故障诊断   起动系统   农用动力机械   起动装置   启动操作   启动困难   排气管   冒烟  

摘要： 起动装置作用正常,按正确步骤和方法多次进行启动操作,发动机启动困难或不能启动;排气管根本不冒烟,或小股冒烟;排气管冒白烟,或只在开始时冒烟,后来不冒烟。出现这些故障时,应从以下几个系统去诊断及排除。

关键词： Collagen fibril   Molecular dynamics simulations   Point mutations   Osteogenesis Imperfecta   Mechanical properties  

摘要： Understanding sequence dependent mechanical and structural properties of collagen fibrils is important for the development of artificial biomaterials for medical and nanotechnological applications. Moreover, point mutations are behind many collagen associated diseases, including Osteogenesis Imperfecta (OI). We conducted a combination of classical and steered atomistic molecular dynamics simulations to examine the effect of point mutations on structure and mechanical properties of short collagen fibrils which include mutations of glycine to alanine, aspartic acid, cysteine, and serine or mutations of hydroxyproline to arginine, asparagine, glutamine, and lysine. We found that all mutations disrupt structure and reduce strength of the collagen fibrils, which may affect the hierarchical packing of the fibrils. The glycine mutations were more detrimental to mechanical strength of the fibrils (WT>Ala>Ser>Cys>Asp) than that of hydroxyproline (WT>Arg>Gln>Asn>Lys). The clinical outcome for glycine mutations agrees well with the trend in reduction of fibril's tensile strength predicted by our simulations. Overall, our results suggest that the reduction in mechanical properties of collagen fibrils may be used to predict the clinical outcome of mutations. (C) 2012 Elsevier B.V. All rights reserved.