Joint coding-precoding with low-complexity turbo-decoding

We combine error-control coding with linear precoding (LP) for flat-fading channels, as well as for wireless orthogonal frequency-division multiplexing transmissions through frequency-selective fading channels. The performance is analyzed and compared with the corresponding error-control-coded system without precoding. By wedding LP with conventional error-control coding, the diversity order becomes equal to the error-control code's minimum Hamming distance times the precoder size. We also derive a low-complexity turbo-decoding algorithm for joint coded-precoded transmissions. We analyze the decoding complexity and compare it with an error-control-coded system without LP. Extensive simulations with convolutional and turbo codes for HiperLan/2 channels support the analysis and demonstrate superior performance of the proposed system.     

Hybrid switching and p-routing for optical burst switching networks

One promising switching technology for wavelength-division multiplexing optical networks is optical burst switching (OBS). However, there are major deficiencies of OBS. (1) The delay offset between a control message and its corresponding data burst is based on the diameter of a network. This affects network efficiency, quality-of-service, and network scalability.( 2) OBS adopts one-way resource reservation scheme, which causes frequent burst collision and, thus, burst loss. We address the above two important issues in OBS. In particular, we study how to improve the performance of delay and loss in OBS. To reduce the end-to-end delay, we propose a hybrid switching scheme. The hybrid switching is a combination of lightpath switching and OBS switching. A virtual topology design algorithm based on simulated annealing to minimize the longest shortest path through the virtual topology is presented. To minimize burst collision and loss, we propose a new routing algorithm, namely, p-routing, for OBS network. The p-routing is based on the wavelength available probability. A path that has higher available probability is less likely to drop bursts due to collision. The probability-based p-routing can reduce the volatility, randomness, and uncertainty of one-way resource reservation. Our studies show that hybrid switching and p-routing are complementary and both can dramatically improve the performance of OBS networks.     

一个面积和功耗优化且适用于10/100 Base-T以太网的CMOS时钟恢复电路

提出了一个新的用于10 / 10 0 Base- T以太网中面积和功耗优化的时钟恢复电路.它采用双环路的结构,加快了锁相环路的捕获和跟踪速度;采用复用的方式,通过选择信号控制电路可分别在10 Mbps或10 0 Mbps模式下独立工作且能方便地实现模式间的互换,与采用两个独立的CDR电路相比节省了一半的面积;同时,电路中采用一般的延迟单元来取代DL L,并能保证环路性能不随工艺温度等条件引起的延迟单元、延迟时间的变化而变化,从而节省了功耗.Hspice模拟结果显示,在Vdd=2 .5 V时,10 0 Mbps模式下电路的功耗约为75 m W,稳态相差为0 .3 ns;10 Mbps模式时电路功耗为5 8m W     

考虑加筋切向阻力的土坡稳定分析

目前在加筋边坡的极限平衡稳定分析中,认为加筋中产生的预应力能约束土体的运动或者能使抵抗土体运动的阻力增加,而对于加筋的切向阻力作用却没有考虑。主要讨论了在加筋土坡稳定分析时,加筋的切向阻力在加筋工程中起到的作用。认为在加筋边坡的极限平衡稳定分析中,也应考虑加筋的切向阻力作用;提出了计算公式,编制了相应的程序,给出了算例。     

液动旋冲接头冲击功测试方法研究

液动旋冲接头性能参数是旋冲接头设计的主要依据之一，如何对液动旋冲接头的参数进行检测是非常重要的工作。在分析和比较了测试液动旋冲接头性能参数各种方法的基础上，选择了冲击力法来进行破岩液动旋冲接头的性能参数测试，以YD系列测力传感器为检测元件，建立了一套比较完善的自动检测系统。分析了影响单次冲击功测试的因素，得出了测试旋冲接头的性能参数的影响规律。     

Reliability of Au bump––Cu direct interconnections fabricated by means of surface activated bonding method

As a room temperature bonding method, surface activated bonding (SAB) method has been introduced to be one of the most appropriate interconnection methods for the next generation of electronic packaging. Thus it is important to study the reliability of SAB interconnection in long term life test.In this paper, interconnections of Au bump and Cu film bonded by SAB method were performed in high temperature thermal aging test. Degradation of properties such as electrical resistance, shear strength of bump and interface microstructure during aging process were studied to investigate the failure mechanism of the interconnection. Intermetallic compound Cu₃Au was found formed at the interface during thermal aging, and it causes evolvement of the properties and failure mode of the interconnection changing in shear test. Results reveal that SAB is suitable for the interconnection between Au bump and Cu film and it is reliable in thermal reliability test.     

A highly efficient polarized superfluorescent fiber source for fiber-optic gyroscope applications

We demonstrate a novel polarized superfluorescent fiber source (SFS) that increases the output power in the desired polarization by a factor of 1.96 over that of an unpolarized SFS at the same pump. This is achieved by inserting a polarizer at the optimal point in the bidirectionally pumped erbium-doped fiber of an unpolarized SFS. Stable pump-power-dependent mean wavelength operation and less sensitivity to the insertion loss, important for fiber-optic gyroscope applications, are obtained in this configuration.     

水力脉冲式钻井工具的研制与应用

水力脉冲式钻井是利用特定的工具使钻井管柱中的连续流转变为脉冲射流,从而改变井底流场的压力状况,进而提高机械钻速的一种钻井新工艺。在分析水力脉冲产生机理的基础上,探讨了基于瞬变流理论的机械阻断式水力脉冲破岩机理,介绍了SLPMC机械阻断式水力脉冲工具的工作原理及结构特点,简单叙述了该工具在胜利油田进行的2口井的现场试验情况。该钻井工具对于提高机械钻速和降低钻井成本具有一定的积极意义。     

Contractor-Performed Quality Control: Is the Fox Guarding the Henhouse?

At the same time that state departments of transportation are allowing contractor-performed quality control, they are also concerned about using the contractor-reported data for acceptance and payment purposes. The question is, are we putting the fox in charge of guarding the chickens? To address this concern, a large number of asphalt and concrete projects in Kentucky were examined. The statistical analyses showed that for the most part there is no significant difference between the contractor-performed acceptance data and concomitant highway agency-performed verification data. This is obviously a very encouraging finding that is expected to enhance the level of trust between the contractors and highway agencies.