EPTR: expected path throughput based routing protocol for wireless mesh network

For effective routing in wireless mesh networks, we proposed a routing metric, expected path throughput (EPT), and a routing protocol, expected path throughput routing protocol (EPTR), to maximize the network throughput. The routing metric EPT is based on the estimated available bandwidth of the routing path, considering the link quality, the inter- and intra-flow interference and the path length. To calculate the EPT of a routing path, we first calculate the expected bandwidth of the link and the clique, and then consider the decay caused by the path length. Based on EPT, a distributed routing protocol EPTR is proposed, aiming to balance the network load and maximize the network throughput. Extensive simulations are conducted to evaluate the performance of the proposed solution. The results show that the proposed EPTR can effectively balance the network load, achieve high network throughput, and out-perform the existing routing protocols with the routing metrics previously proposed for wireless mesh networks.     

偏振模色散及其对光纤通信系统影响的判断

本介绍了偏振模色散（PMD）的产生及其属性，介绍了工程测量仪表方法，结合工程实例，介绍了PMD对光通信系统的影响及其判断。     

用非均匀时频变换提高音频编码器性能

预回声对音频压缩编码器的性能影响很大。人们一般采用窗切换技术来降低其不利影响。窗切换中短窗提高了对暂态信号的时间分辨率,同时降低了对低频稳态信号的频率分辨率。设计了一种非均匀时频变换方法,它在保留了对信号低频平稳分量的频率分辨率的同时提高了对高频暂态分量的时间分辨率。最后用实验验证了方法的可行性和有效性。     

软交换网络中媒体网关控制器的研究与设计

300万像素对于专业摄影来说可能不值一提，但是对于家庭用户而言却已经十分完美了。下面三款数码相机是300万家庭中令人兴奋的新品，它们的价格都在3000元到4000元人民币之间，想想一年前3000万像素的相机要花多少钱？而在测试中它们的表现也的确让人觉得物有所值。     

300脚MSA 10 Gbit/s Transponder模块

分析了开发10Gbit/sTransponder模块的必然性，介绍了10Gbit/sTransponder模块的原理、特点和参数指标。并且用开发出的两只40km300脚10Gbit/sTransponder模块成功地进行了43km的无误码传输试验和测试。     

激光熔覆钴基合金涂层的组织结构

利用5kWCO2连续激光器在16Mn钢表面进行激光熔覆钴基合金涂层，研究了激光覆合金涂层的显微组织形貌，相结构以及显微硬度。激光熔覆涂层可分为三个区域：熔化区（合金层）结合区及基材热影响区。合金涂层由γ-Co枝晶及其间的共晶组织组成，合金涂层的主要组成相为γ-Co和（Cr,Fe)7^C3。     

Diphenylamine‐Substituted Cruciform Oligo(phenylene vinylene): Enhanced One‐ and Two‐Photon Excited Fluorescence in the Solid State

1,4‐di(4′‐N,N‐diphenylaminostyryl)benzene (DPA‐DSB) is a well known compound with a large two‐photon absorption (TPA) section and strong fluorescence in solution. However, the ease with which it crystallizes results in the formation of discontinuous crystalline phases during vacuum deposition processes, thereby greatly limiting its applicability in solid‐state devices. A cruciform dimer of DPA‐DSB, 2,5,2′,5′‐tetra(4′‐N,N‐diphenylaminostyryl)biphenyl (DPA‐TSB) is reported, wherein two DPA‐DSB molecules are linked through a central biphenyl bond. The DPA‐TSB molecules take on a cruciform configuration because of the steric crowding around the central biphenyl core, which has the effect of efficiently suppressing crystalline and intermolecular interactions. The neat DPA‐TSB solid shows strong green–blue fluorescence because of both steady‐state absorption as well as TPA. The DPA‐TSB solid exhibits a photoluminescence (PL) efficiency (η_solid) of 29 % and a solid‐state two‐photon action cross section (δη_solid) of 954 GM (1 GM = 1 × 10^–50 cm⁴ s photon^–1 molecule^–1), which is much greater than for the model compound DPA‐DSB (η_solid = 16 % and δη_solid = 150 GM, where δ is the TPA cross section and η is the fluorescence quantum yield). Based on its high PL efficiency, good film‐forming ability, and strong TPA, DPA‐TSB seems to be a good candidate for applications in solid‐state optical devices.     

Performance Enhancement of Multiwavelength Conversion of RZ-DPSK Based on Four-Wave Mixing in Semiconductor Optical Amplifier

In this letter, we propose two methods to enhance the performance of multichannel wavelength conversion of return-to-zero differential phase-shift-keying signal in a semiconductor optical amplifier (SOA) based on four-wave-mixing effect. The first one is optimizing the relative time delay of the multichannel signal to reduce the crosstalk-induced penalty in SOA. The second one is using the synchronous clock pumping to raise the power of converted signal. The experiment on wavelength conversion of two channels at 10-Gb/s signal showed the power penalty was improved more than 1 dB in the first method and about 1.5 dB in the second method.     

Rapid Generation of Biologically Relevant Hydrogels Containing Long‐Range Chemical Gradients

Many biological processes are regulated by gradients of bioactive chemicals. Thus, the generation of materials with embedded chemical gradients may be beneficial for understanding biological phenomena and generating tissue‐mimetic constructs. Here a simple and versatile method to rapidly generate materials containing centimeter‐long gradients of chemical properties in a microfluidic channel is described. The formation of a chemical gradient is initiated by a passive‐pump‐induced forward flow and further developed during an evaporation‐induced backward flow. The gradient is spatially controlled by the backward flow time and the hydrogel material containing the gradient is synthesized via photopolymerization. Gradients of a cell‐adhesion ligand, Arg‐Gly‐Asp‐Ser (RGDS), are incorporated in poly(ethylene glycol)‐diacrylate (PEG‐DA) hydrogels to test the response of endothelial cells. The cells attach and spread along the hydrogel material in a manner consistent with the RGDS‐gradient profile. A hydrogel containing a PEG‐DA concentration gradient and constant RGDS concentration is also shown. The morphology of cells cultured on such hydrogel changes from round in the lower PEG‐DA concentration regions to well‐spread in the higher PEG‐DA concentration regions. This approach is expected to be a valuable tool to investigate the cell–material interactions in a simple and high‐throughput manner and to design graded biomimetic materials for tissue engineering applications.