基于FPGA有限域构造的QC-LDPC分层译码器设计

针对QC-LDPC码的Tanner图中存在的短环,尤其是4环,对迭代译码性能产生不利影响的问题,寻找到一种有限域乘群构造法,该方法构造的QC-LDPC码的Tanner图中不存在任何4环。基于此方法构造的码长为3 060,码率为的(3,12)规则QC-LDPC码,选用Altera公司StratixII系列的EP2S60F484C4器件,对其实现了分层译码器硬件结构的设计。实现结果表明,在最大迭代次数为5时,时钟频率最高可达35.38 MHz,吞吐量达到92.27 Mbit·s-1。     

显微结构对BaTiO3陶瓷电热性能的影响

该文研究了显微结构对BaTiO3陶瓷电热特性与击穿电场的影响.采用固相反应法制备BaTiO3粉体,经干压结合冷等静压工艺成型后,在不同温度下烧结成陶瓷样品.随烧结温度提高,陶瓷晶粒长大、结构更致密,由此导致极化强度与电热效应绝热变温明显提高,但击穿电场下降.等静压工艺可进一步提升瓷体致密度并促进晶粒长大,使电热效应提升.     

High-performance simple-encoding generator-based systematic irregular LDPC codes and resulted product codes

Low-Density Parity-Check (LDPC) code is one of the most exciting topics among the coding theory community.It is of great importance in both theory and practical communications over noisy channels.The most advantage of LDPC codes is their relatively lower decoding complexity compared with turbo codes,while the disadvantage is its higher encoding complexity.In this paper,a new ap- proach is first proposed to construct high performance irregular systematic LDPC codes based on sparse generator matrix,which can significantly reduce the encoding complexity under the same de- coding complexity as that of regular or irregular LDPC codes defined by traditional sparse parity-check matrix.Then,the proposed generator-based systematic irregular LDPC codes are adopted as con- stituent block codes in rows and columns to design a new kind of product codes family,which also can be interpreted as irregular LDPC codes characterized by graph and thus decoded iteratively.Finally, the performance of the generator-based LDPC codes and the resultant product codes is investigated over an Additive White Gaussian Noise (AWGN) and also compared with the conventional LDPC codes under the same conditions of decoding complexity and channel noise.     

驱油用Janus 片状纳米材料研究现状

纳米流体驱作为一种新型的低渗透油藏驱油技术,具有注入性好、储层伤害小、驱油能力强、智能响应等优势,越来越受到广泛关注。相比于球形纳米颗粒,Janus片状纳米材料界面自由能低、转动更加受限、可进一步阻止内外相分子扩散并形成界面强度更高的固体颗粒膜,展现出优异的驱油性能。目前,已开发出多种Janus片状纳米材料的制备方法,其在驱油方面的应用主要集中于纳米乳液技术和纳米稳泡技术,此外,智能响应特性同样赋予其更多潜能。当片状纳米材料两面呈现不同的亲油-亲水性时,则同时具有两亲特性和“Pickering”乳液效应,大大提高其作为高效纳米流体驱的能力。随着未来低成本、大规模、绿色环保的可控制备,以及耐温耐盐等性能的进一步提高,应用Janus片状纳米材料有望大幅提高原油采收率,为油田稳产增产带来创新性解决方案。     

The performance of uplink LDPC‐coded multirelay cooperation based on virtual V‐BLAST processing

This paper proposes an efficient uplink low‐density parity‐check (LDPC)‐coded multirelay cooperation architecture based on virtual Vertical‐Bell Labs Layered Space–Time (V‐BLAST) processing over a Rayleigh fading channel, where minimum mean square error in combination with a successive interference canceller and belief propagation‐based joint iterative decoder based on the introduced multilayer Tanner graph are effectively designed to detect and decode the corrupted received sequence at the destination. By introducing V‐BLAST transmission to coded multirelay cooperation, relays send their symbol streams simultaneously, which significantly reduce the transmission delay and provide higher transmission efficiency. The theoretical analysis and numerical results show that the proposed LDPC‐coded cooperation scheme outperforms the coded noncooperation under the same code rate and achieves a better compromise, with respect to the performance, signal delay, and encoding complexity associated to the number of relays, than the conventional LDPC‐coded cooperations without V‐BLAST transmission. This performance gain can be credited to the proposed V‐BLAST processing architecture and belief propagation‐based joint iterative decoding by the introduced multilayer Tanner graph at a receiver side. Copyright © 2013 John Wiley & Sons, Ltd.     

Joint iterative decoding for simple-encoding systematic irregular-LDPC-based coded cooperation in non-ideal relay channel

In this paper, a new kind of simple-encoding irregular systematic LDPC codes suitable for one-relay coded cooperation is designed, where the proposed joint iterative decoding is effectively performed in the destination which is in accordance with the corresponding joint Tanner graph characterizing two different component LDPC codes used by the source and relay in ideal and non-ideal relay cooperations. The theoretical analysis and simulations show that the coded cooperation scheme obviously outperforms the coded non-cooperation one under the same code rate and decoding complex. The significant performance improvement can be virtually credited to the additional mutual exchange of the extrinsic information resulted by the LDPC code employed by the source and its counterpart used by the relay in both ideal and non-ideal cooperations.     

汽车用铅酸蓄电池控制因素的探讨

分析了正极、负极和电解液为控制因素对容量的影响，降低控制因素的影响能提高电池的性能。     

国产PEEK为基体的复合材料成型工艺研究

本文论述了用热压法成型热塑性树脂PEEK和碳织物或玻璃织物复合材料的工艺研究,表明复合材料的质量与温度、压力和时间等条件有关。通过流变性能试验,计算表观流动活化能和在同样剪速下熔体相差40℃的粘度,考察了PEEK对温度的依存性。用超声C-扫描的结果表征工艺参数的变化,表明该方法有很好的选择性,较其他方法敏感。     

Joint iterative decoding for pragmatic irregular LDPC-coded multi-relay cooperations

In this article, a new kind of pragmatic simple-encoding irregular systematic low-density parity-check (LDPC) code for multi-relay coded cooperation is designed, where the introduced joint iterative decoding is performed in the destination based on a proposed joint Tanner graph for all the constituent LDPC codes used by the source and relays in multi-relay cooperation. The theoretical analysis and numerical results show that the coded cooperations outperform the coded non-cooperation under the same code rate, and also achieve a good trade-off between the performance and the decoding complexity associated with the number of relays. This performance gain can be credited to the additional exchange of extrinsic information from the LDPC codes used by the source and the relays in both ideal and non-ideal cooperations.     

Decode and forward polar coding for Half-duplex two-relay channels based on multilevel construction

Polar codes represent an emerging class of error-correcting codes with power to approach the capacity of the physically degraded relay channel and relevant coding schemes have been proposed in the literature. This paper aims to design new cooperative decode-and-forward (DF) polar coding schemes for half-duplex two-relay channel based on the Plotkin’s construction illustrating their performances gain. In these schemes, we consider the use of time-division process in transmission. The source node transmits its polar-coded information to both relays and the destination nodes during the first time slot. Each relay node receives the data from the source and processes it using the DF protocol. For the second transmission period, each relay first decodes the source signal then after reconstruction of the information reduction matrix based on the multilevel characteristics of polar codes, the extracted data at each relay are recoded using another polar code and transmitted to the destination. At destination node, the signals received from each relay and source nodes are processed by using multi-joint successive cancellation decoding for retrieving the original information bits. We demonstrate via simulation results that by carefully constructed polarisation matrix at each relay node, we can achieve the theoretical capacity in the half-duplex relay channel.