随机回退的TCP拥塞控制算法

 面对目前大量使用弃尾队列管理的网络中间节点,提出了一种随机回退的TCP拥塞控制算法TCP Njust,拥塞时在一定范围内随机减少拥塞窗口,拥塞避免时其拥塞窗口在一定范围内随机增加,以减缓TCP全局同步.该算法在Newreno基础上增加了一个随机函数,仿真表明该算法的性能优于Newreno,在网络突发数据流较多时,其性能优于Vegas,适合在Internet上使用.     

高速高精度连杆精镗机床的设计

摩托车连杆大端孔的精加工是连杆加工中的重要工序,通过对连杆加工前状况的分析和本序加工后要达到的各项精度进行分析,设计卧式双轴精镗床,保证了节拍28s/两件,圆度0.01 μm,孔的粗糙度达到Ra0.8,重点对机床的总体结构、机床的刀具、机床的镗头、工件在夹具上的定位、夹具上的让刀机构、机床的工作循环等进行分析,这对研制同类型的高精度的镗床具有一定的参考价值.     

Upgrading Computational Design

Shajay Bhooshan heads up the computation and design ZHACODE group at Zaha Hadid Architects (ZHA) and is a course master at the Architectural Association Design Research Laboratory (AADRL). Here he argues that Parametricism 2.0 has a vital role to play in the progressing of computational design. Assimilating the exploratory developments of the last 15 years, he asserts how the next phase of Parametricism will enable a further consolidation and evolution of digital practices.     

磨溪气田水平井射孔枪卡钻解卡工艺技术

磨005-H10井和磨017-H3井为磨溪气田雷一^1气藏和嘉陵江气藏的两口水平井，均采用127mm尾管射孔完成，油管传输射孔后即发生卡钻。由于射孔枪与套管间隙小，打捞工具选择困难，再加上水平井的特殊性，解卡工艺难度大，工程风险大。该两口井采用震击器震击解卡工艺和倒扣解卡工艺处理卡钻事故，获得成功，对水平井井下作业和水平井修井具有一定指导意义。     

大斜度井管柱割捞一体化作业技术应用

在大斜度井井下作业过程中,通常使用的技术主要是切割、倒扣、打捞、套磨铣等。但由于存在储层认识不足,井眼或井身结构复杂,修井工具选择不匹配或操作不合适等因素,井下故障时有发生。而传统的将切割和打捞工艺分开进行的修井作业,不仅施工周期长、劳动强度大、原材料消耗多,而且作业成本很高。本文综合考虑了大斜度井修井中在地面进行加压、上提或驱动倒扣时,加不上钻压、扭矩不能被充分传递到井下,以及同一井段长时间重复作业,可能导致的损伤套管等问题,提出运用割捞一体化管柱组合和液压倒扣器井下倒扣,在大斜度井中进行井下故障处理的技术,将切割与打捞工艺结合起来,将切割工具和打捞工具连接起来,组合成为一趟管柱,完成切割和打捞的一体化作业。应用结果表明,割捞一体化技术能顺利完成作业,极大地缩短了施工周期,降低了作业成本,并由于工期缩短等,减少了对油气层的伤害。     

QY-10气液崩扣器

针对液压崩扣器液压传动机构在钻井现场使用存在的缺陷，为满足钻井工程的需要研制了QY－10气液崩扣器。崩扣器由气动液压源、控制机构和执行机构组成，气动液压源中的气液泵是整套设备的核心部件，以井场压缩空气作气液泵动力，气液泵推动执行液缸带动大钳，实现崩扣操作。经两口井现场使用，崩扣350次，次次成功，实践证明这种崩扣器结构简单，操作方便，经久耐用，安全可靠。     

插内齿让刀干涉的分析及多截面仿真软件开发

内斜齿的插削让刀干涉一直是困扰内齿圈设计和加工的技术瓶颈。要解决让刀干涉问题,在设计时应考虑插齿退刀干涉的工艺性,加工时通过调整刀具和切削参数来消除退刀干涉。本文研究了插齿刀回程间隙的算法和切削仿真的思路,编写了让刀干涉曲线图和任意截面的内齿插削仿真软件。干涉曲线图可用来判断产品参数是否有好的工艺性及读取合理的主轴偏置和首刀切深,仿真软件可在选定偏置参数下模拟切削过程并验证是否存在干涉。     

Fixed collision rate back-off scheme for collision resolution in wireless networks

This investigation proposes a fixed collision rate (FCR) back-off algorithm for wireless networks. The proposed scheme takes advantage of the central unit (CU) in a wireless network to broadcast a common back-off window size to all the users, significantly alleviating the unfairness of bandwidth utilization in conventional binary exponential back-off (BEB) algorithms. It is shown that, when maximum throughput is achieved, collision rate is almost a constant for any traffic load. In the operation of the FCR, the CU dynamically adjusts the back-off window size to keep the collision rate at a constant level for maximum throughput. Simulation results demonstrate that the unfairness of bandwidth utilization in the BEB is significantly lessened and the throughput can be maintained at e^-1≈0.368 when the number of users approaches infinity. The capture effect even further improves system performance.     

Phyllis A. Katz: Award for Distinguished Senior Career Contributions to the Public Interest.

Announces that Phyllis A. Katz has won the Award for Distinguished Senior Career Contributions to the Public Interest. The award is presented for the honoree's research on the origins and development of both racial and gender attitudes and her contributions to psychology in the public interest within the American Psychological Association. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

一种VDSL上行链路自适应功率回馈方案

上行链路功率回馈技术(UPBO：upstream power back-off)是VDSL(very high-speed digital subscriber lines)系统中的关键技术，它用于抵消同一电缆中短线对长线引起的严重的远端串扰(FEXT:far-end crosstalk)。文中从功率控制的角度分析了基于迭代注水的自适应UPBO方案，并进行了性能仿真分析。