流控制

The converter combines the advantages of the PWM technique and soft-switching technique, the PWM is effected all over the whole loads range, and soft-switching is effeted only in the switching transition period, the ZVS of leading-leg is achieved by using the energy stored in leakage inductor of the transformer and the output inductor, the ZCS of lagging-leg is achieved by using a blocking DC capacitor, the ZVS and ZCS are achieved for the whole load ranges (5A~250A).

控制电路采用相移控制方式，综合了PWM控制和软开关技术的优点，在大范围内实现PWM控制，而在功率器件换流期间实现软开关换流，其中超前桥臂利用变压器的漏感，实现了零电压开关，滞后桥臂利用隔直电容，实现了零电流开关，并且整个变换电路能在（5A~250A）的范围内实现软开关工作条件，满足弧焊电源负载变化大的特点。

According to the present situation of Guangzhou subway line 4, a control system based on programmable logic controller is presented, which can be used to alternate the working mode of subway locomotives between contacting collector and pantograph for collecting current.

介绍受电弓和受流靴这两种受流器各自的优缺点及工作原理，并针对广州地铁4号线运行中的实际情况，提出了受流方式转换过程的技术要点，设计了一种由可编程序控制器为控制核心的系统，该系统可控制地铁列车在两种受流方式之间的转换。

In this system, we introduces cluster architecture to provide global and scalable streaming caching proxy service mechanism; We implement streaming media transfer protocol on caching proxy end; We implement layered caching mechanism (global disk caching and memory caching) using dynamic sharing running memory buffer algorithm to support more stable and real-time parallel streams; We implement client request aggregation by means of streaming session sharing to reduce disk I/O and serve more user; We propose single streaming image to support the unify of pre-fetching streaming and caching streaming, which guarantees the proxy streaming of transparency for client; We design and implement streaming pre-fetching mechanism based on packet feedback information to reduce the number of "rebuffering" on client end; We bring forward streaming caching admission control policy fit for streaming caching proxy server to guarantee the QoS of streaming service.

该系统引入集群架构以提供全局的、可扩展的缓存代理服务机制；实现了缓存代理端的流媒体传输协议；采用动态共享运行缓冲区算法实现了分层缓存机制(全局磁盘缓存和内存缓存)以支持更多稳定、实时的并发流；利用流会话共享机制实现了客户请求聚集，从而减少磁盘I/O同时能服务更多的客户；提出了单一流映像，以支持预取流和缓存流的统一，从而保证代理端服务流对客户的完全透明；设计并实现了基于包反馈信息的流数据预取机制，从而减少了客户端的"rebuffering"次数；提出了适合于缓存代理服务器的流缓存准入控制策略，保证了流服务的QoS。

The effect of switching modes on the entrancement,combustion and billet heating process in furnace were analyzed numerically,and the computational results were compared with production records and onsite measurement,which verified the practicability of this CFD system.

结果表明：采用分段同侧换向控制的HTAC加热炉能获得很好的流场和温度场分布，基本满足高质量的钢坯加热需要，但该炉在生产条件下的温度制度存在不合理之处，在今后设计和操作中应进一步优化和改进；全同侧换向控制的火焰布置方式不利于钢坯的均匀、快速加热；而采用交叉换向控制的火焰布置方式可以改善加热炉内的流场和温度分布，更有利于满足钢坯的加热工艺要求。

An instance was given by means of the numerical solution for the first boundary value inverse problem of Laplace's equation.

将直匀流绕物面作二维无旋不可压缩定常流动时的流函数表达为曲面后，利用流函数曲面控制边界与流曲线的对应关系，采用拉普拉斯方程第一边值逆问题的数值解法，提出了来流为直匀流的流曲线造型方法并给出了实例。

The high speed advantage of FPGA's operation is made hard to demonstrate for the inconsequence in structural arrangement. The pipeline technology had well solved this problem. We presents a new pipeline optimization technology of inventer's control system based on FPGA,and completed the optimization design of the inventer controller. Analyzed the design process in detail and offered a kind of thought for the people who devoted to FPGA's application in power electronic field.

分析了"流水线操作"等设计优化问题，并针对逆变器控制系统中，控制系统算法呈多层结构，且层与层之间还有数据流联系，其执行顺序和数据流的走向较为复杂，不利于直接采用流水线技术进行设计的特点，提出一种全新的"分层多级流水线"设计技术，有效地解决了复杂控制系统的流水线优化设计问题。

To reduce conflicts of branch line traffic flow and trunk road traffic flow in urban traffic networks, a region coordination fuzzy control algorithm is proposed in this paper.It is based on the control theory of classification and coordination of the system engineering.

为了缓解城市区域交通网络中支线交通流与主线交通流之间的矛盾，根据系统工程中大系统分解协调的控制思想，提出了一种区域协调模糊控制算法，重点介绍了协调控制的设计思想及控制结构。

Based on an analysis of distribution pattern of hydrocyclone"s axial velocity, by changing the inlet flow rate Qi and split ratio Fand making an investigation in the effect of Qi and F on axial velocity field, the factors causing the forming of short-cut circuit and circulating flow are found. It is considered that the short-cut circuit and circulating flow are produced by the structure of the hydrocyclone, and can"t be eliminated completely, though they interfere the flow field inside a hydrocyclone and affect the separation accuracy. Test results show that, by increasing Qi and F and controlling them in a certain range, the separation efficiency of the hydrocyclone can be improved.

在研究旋流器轴向速度分布规律的基础上，分析了短路流与循环流的形成原因，试验研究了改变操作参数，即改变入口流量Qi与分流比F对轴向速度场的影响认为短路流与循环流是由旋流器结构决定的，很难完全消除，它们干扰了旋流腔和大锥段的流场，在一定程度上也影响了分离精度试验结果表明，加大入口流量Qi与分流比F，并将其控制在一定范围内，便可提高分离效率这项研究对水力旋流器分离机理的认识与实际应用均有重要意义

The regurgitant volume was calculated by temporally integrating the instantaneous flow volume rate of each frame during systole.

建立了基于经食道旋转扫描二维和经胸实时三维超声多普勒血流图像获取方法和图像插值、配准算法获得体数据，经多维重建描述二尖瓣反流速度的空间分布，立体观察返流的时相、方向、反流束长度、面积、体积、空间传播和严重程度等；通过重建反流后的速度场，从血流动力学角度分析了二尖瓣反流的性质，计算偏心反流束的湍流强度，利用反流束角度和湍流强度对计算结果进行修正；基于实时三维彩色多普勒成像技术，利用控制体原理对二尖瓣反流束在反流瓣口横断面的速度分布进行空间与时间积分获得二尖瓣偏心性反流的每搏反流量。

The supersonic interacting flowfield induced by gaseous secondary flow injected into supersonic flow is typical and encountered in many fields, such as thrust vector control, gas-turbine cooling, and fuel-air premixing in scramjet engines, et al.

二次射流与超音速来流的干扰流场主要应用在推力矢量控制、飞行器气动控制、超音速燃烧和气膜冷却等方面。因为其复杂性和应用的广泛性，二次射流干扰流场多年以来一直是流体力学界的重要研究课题。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。