课程文献中心 更多>>

关键词： APPROXIMATION  

摘要： The exact values of constants are obtained in the space L (2)(a"e) for the Jackson-type inequalities for special moduli of continuity of the k th order defined by the Steklov operator S (h) () instead of the translation operator T (h) () in the case of approximation by entire functions of exponential type sigma a (0,a) . The exact values of the mean nu -widths (linear, Bernstein, and Kolmogorov) are also obtained for the classes of functions defined by the indicated characteristic of smoothness.

关键词： POWER plants   ELECTRIC power production  

摘要： The article focuses on high demand for electricty in North Dakota. Power company Basin Electric Power Cooperative (BEPC) signed a 25-year power purchase agreement with Infinity Wind Power LLC. BEPC has also made a balanced plan that involve two new peaking plants, synchronous condensing for voltage support, wind farms, and new transmission lines

关键词： Ring Gear   Crankshaft   Pinion Starter   Starter Motor   Engine Stop  

摘要： Being the future standard in all vehicle categories, start/stop systems shall allow a further reduction in fuel consumption. However, there is little acceptance of conventional solutions by the end customers up to now due to their operational behaviour. To improve the system behaviour and in particular the starting performance of a combustion engine, BorgWarner is developing a compact dry running permanently engaged starter system that can be easily integrated into existing powertrains.

关键词： 离合器   打滑   维修  

摘要： 离合器安装在发动机与变速器之间,是发动机与传动系之间切断和传递动力的部件。手动挡汽车在行驶中因路况不同为了适应道路行驶,需要频繁地变换挡位,同时离合器使用频繁,会出现许多故障。本文就离合器打滑故障进行分析。

关键词： cell motility   retrograde flow   C. elegans sperm cell   cytoskeleton   SPERM PROTEIN MSP   MAJOR SPERM   CAENORHABDITIS-ELEGANS   RETROGRADE FLOW   NEMATODE SPERM   AMEBOID MOVEMENT   ASCARIS SPERM   LEADING-EDGE   GROWTH CONE   MIGRATION  

摘要： Many cell movements occur via polymerization of the actin cytoskeleton beneath the plasma membrane at the front of the cell, forming a protrusion called a lamellipodium, while myosin contraction squeezes forward the back of the cell. In what is known as the 'molecular clutch' description of cell motility, forward movement results from the engagement of the acto-myosin motor with cell-matrix adhesions, thus transmitting force to the substrate and producing movement. However during cell translocation, clutch engagement is not perfect, and as a result, the cytoskeleton slips with respect to the substrate, undergoing backward (retrograde) flow in the direction of the cell body. Retrograde flow is therefore inversely proportional to cell speed and depends on adhesion and acto-myosin dynamics. Here we asked whether the molecular clutch was a general mechanism by measuring motility and retrograde flow for the Caenorhabditis elegans sperm cell in different adhesive conditions. These cells move by adhering to the substrate and emitting a dynamic lamellipodium, but the sperm cell does not contain an acto-myosin cytoskeleton. Instead the lamellipodium is formed by the assembly of major sperm protein, which has no biochemical or structural similarity to actin. We find that these cells display the same molecular clutch characteristics as acto-myosin containing cells. We further show that retrograde flow is produced both by cytoskeletal assembly and contractility in these cells. Overall this study shows that the molecular clutch hypothesis of how polymerization is transduced into motility via adhesions is a general description of cell movement regardless of the composition of the cytoskeleton.

关键词： BEND PROPAGATION   DOUBLET PAIR   FLAGELLAR   MODEL   SIMULATION   AXONEMES   FORCES   SPERM  

摘要： It is 20 years since the publication of the geometric clutch (GC) hypothesis as a mechanistic explanation of ciliary and flagellar beating (1). It was an idea that resulted from constructing wooden models of the flagellar axoneme and observing the way they distorted during bending. The key insight was that a structure composed of linear elements that experience curvature while under tension or compression experience transverse forces (t-forces) that can push the linear elements closer together or pry them apart.

关键词： 东方红-75型拖拉机   离合器分离   解析   轴向移动   离合器盖   整体旋转   压紧装置   操纵机构  

摘要： 东方红－75型拖拉机离合器主要由主动部分、从动部分、压紧装置、操纵机构、小制动器等组成。 1．主动部分 发动机的动力经过飞轮与压盘的摩擦面传给从动盘。飞轮上有甩油孔，以便在离心力的作用下将漏入离合器中的油甩到离合器室内，从放油孔放出。压盘用灰铸铁制成，有足够的刚度，可防止变形；同时，为了有效地吸收滑磨过程中产生的热量，压盘有足够的厚度和体积。压盘与飞轮一起旋转，并在离合器分离或接合过程中作轴向移动。在压盘圆周上均布着三个方形切口，在离合器盖的外圆表面上铆有三个销座，座孔内压装着方头驱动销。三个方头驱动销分别插入压盘的三个切口内。离合器盖用螺钉固定在飞轮上，因此压盘通过驱动销与飞轮构成一个整体旋转，同时又可轴向移动。

关键词： 离合器分离   故障排除   牵引车   发动机转速   离合器踏板   300型   故障现象   行驶无力  

摘要： 故障现象：一辆陕汽SX2300型汽车，在行驶途中出现了换高速挡后行驶无力的现象。踩下油门踏板，发动机转速迅速升高．但车速提升很慢。减挡后车辆动力传输失效，车速逐渐下降，直至停车。再次挂挡起步。车辆根本无法前进。整个过程离合器烧焦气味明显，松开离合器踏板后助力器排气声音不明显。