基于RS485总线的存储器网络化技术研究

传统网络化测试技术存在网络化测试精准度低、不能对全部数据进行测试、数据属性测试不明确等问题,为此,基于RS485串行连接框图和存储器结构对网络化测试技术展开研究。采用信息融合技术中的信息融合算法得出测试估计误差方阵,完善传统技术中精准度低的问题。利用定义模型和动态模型有限内存的处理技术,对整个存储内存进行访问,从而对全部数据进行测试。采用分布式计算技术,利用二元制算法测试存储器中数据的质量,从而确定数据的属性。通过实验得出结论,本文测试技术不但能够确定数据属性,还能提高网络化测试精准度,并对全部数据进行测试,为我国未来网络化测试技术奠定了坚实的基础。     

一种新型的FPGA实现RS422串口通信方法

在FPGA实现RS422串口通信的常用方法中经常遇到诸多问题,如FIFO深度读取不正确、FIFO写数据端口与读数据端口时序竞争、多个模块间信号延时导致FPGA亚稳态等问题,因此设计了一种新型的RS422串口通信实现方法;该方法通过利用寄存器数组作为循环缓存代替FIFO,利用计数器代替传统的波特率产生模块,把常用方法中的多个模块整合成一个模块,只采用一个主时钟,所有寄存器的时钟输入端共享一个时钟,对FPGA逻辑与时序进行了有效约束,避免了FPGA中亚稳态产生;试验结果表明该方法实现的RS422串口通信高速、可靠、稳定,并且利用FPGA实现RS422串口通信,可使整个系统更为灵活、紧凑,减小整个电路的体积,提高系统的可靠性和稳定性。     

基于钟控神经MOS管的多值双边沿D触发器设计

通过对钟控神经MOS管特性和冗余抑制技术的研究,提出了一种新型多值双边沿D触发器的设计方案．该方案利用钟控神经MOS管多输入栅加权信号控制、浮栅上的电容耦合效应及具有对浮栅进行初始化并将数据保存在浮栅上等特性,实现D触发器的多值输出．与传统触发器相比较,此多值触发器不但减少时钟冗余信号,降低电路功耗,提高电路效率,而且无需改变电路的结构就可实现不同基的多值D触发器．最后,采用0．25μm CMOS工艺,利用PSPICE模拟验证了所设计的电路具有正确的逻辑功能,并与相同功能多值D触发器比较,多值双边沿D触发器具有明显的低功耗特性．     

一种集成接口调试单元的设计和实现

基于综合化航电平台需求,设计了一种集成接口调试单元,其硬件组成包含以太网交换、协议转换、复位及供电控制等电路。其以太网交换和协议转换分别采用商用BCM53242和Nechip芯片实现,同时实现了快速复位,调试模式离散量控制上下电等功能。集成接口调试单元集成了以太网及RS232接口,体积小、重量轻,接线简单,无额外功率消耗,能很方便地应用于综合化航电平台等复杂系统,不影响用户调试习惯,值得推广应用。     

Controversial Variable Node Selection-Based Adaptive Belief Propagation Decoding Algorithm Using Bit Flipping Check for JSCC Systems

An end-to-end joint source–channel (JSC) encoding matrix and a JSC decoding scheme using the proposed bit flipping check (BFC) algorithm and controversial variable node selection-based adaptive belief propagation (CVNS-ABP) decoding algorithm are presented to improve the efficiency and reliability of the joint source–channel coding (JSCC) scheme based on double Reed–Solomon (RS) codes. The constructed coding matrix can realize source compression and channel coding of multiple sets of information data simultaneously, which significantly improves the coding efficiency. The proposed BFC algorithm uses channel soft information to select and flip the unreliable bits and then uses the redundancy of the source block to realize the error verification and error correction. The proposed CVNS-ABP algorithm reduces the influence of error bits on decoding by selecting error variable nodes (VNs) from controversial VNs and adding them to the sparsity of the parity-check matrix. In addition, the proposed JSC decoding scheme based on the BFC algorithm and CVNS-ABP algorithm can realize the connection of source and channel to improve the performance of JSC decoding. Simulation results show that the proposed BFC-based hard-decision decoding (BFC-HDD) algorithm (ζ = 1) and BFC-based low-complexity chase (BFC-LCC) algorithm (ζ = 1, η = 3) can achieve about 0.23 dB and 0.46 dB of signal-to-noise ratio (SNR) defined gain over the prior-art decoding algorithm at a frame error rate (FER) = 10−1. Compared with the ABP algorithm, the proposed CVNS-ABP algorithm and BFC-CVNS-ABP algorithm achieve performance gains of 0.18 dB and 0.23 dB, respectively, at FER = 10−3.     

Low-Complexity Chase Decoding of Reed–Solomon Codes Using Channel Evaluation

A novel time-varying channel adaptive low-complexity chase (LCC) algorithm with low redundancy is proposed, where only the necessary number of test vectors (TVs) are generated and key equations are calculated according to the channel evaluation to reduce the decoding complexity. The algorithm evaluates the error symbol numbers by counting the number of unreliable bits of the received code sequence and dynamically adjusts the decoding parameters, which can reduce a large number of redundant calculations in the decoding process. We provide a simplified multiplicity assignment (MA) scheme and its architecture. Moreover, a multi-functional block that can implement polynomial selection, Chien search and the Forney algorithm (PCF) is provided. On this basis, a high-efficiency LCC decoder with adaptive error-correcting capability is proposed. Compared with the state-of-the-art LCC (TV = 16) decoding, the number of TVs of our decoder was reduced by 50.4% without loss of the frame error rate (FER) performance. The hardware implementation results show that the proposed decoder achieved 81.6% reduced average latency and 150% increased throughput compared to the state-of-the-art LCC decoder.     

LiNbO3交叉型波导光触发器

利用在集成光路中串联的两个LiNbO_3交叉型光波导调制器,代替KDP晶体普克尔效应调制器,构成两个混合双稳态器件,制成光学T触发器(flip-flop),并给出实验结果.     

时钟信号竞争型边沿触发器

本文通过对触发器存贮函数的形式变换,导出各种钟控锁存器的结构设计;并根据对一次操作型(边沿操作型)触发器时钟的要求,设计与解释了二类时钟信号竞争型边沿触发器.     

Water absorption and enzymatic degradation of poly(lactic acid)/rice starch composites

Poly(lactic acid) (PLA) composites consisting of PLA, rice starch (RS) (0–50 wt%) and epoxidised natural rubber (ENR50) were compounded by a twin-screw extruder and compression moulded into dumbbell specimens. Tensile tests were performed to characterize the mechanical properties of the PLA/RS composites. Morphological studies were done on the tensile fractured surface of the specimens by using scanning electron microscopy (SEM). Twenty weight percent of RS achieved a good balance of strength and stiffness. Beyond 20 wt% loading of RS, the tensile strength and elongation at break of PLA decreased drastically. This may be attributed to the agglomeration of RS, which could then act as stress concentrator. The incorporation of ENR50 increased the tensile strength and elongation at break of the PLA/RS composites remarkably, owing to the elastomeric behaviour and compatibilisation effects of ENR50. Interestingly, the morphology of PLA/RS composites transformed to a more ductile one with the addition of ENR. The kinetics of water absorption of the PLA/RS composites conforms to Fick's law. The M_m and D values are dependent on the RS and ENR concentrations. The tensile properties of the PLA/RS composites deteriorated after water absorption. The retention-ability and recoverability of the PLA/RS composites are relatively low, attributed to the hydrolysis of PLA, degradation of the PLA–RS interface and leaching of the RS particles. In addition, the tensile properties of PLA/RS composites decreased drastically upon exposure to enzymatic degradation. Extensive pinhole and surface erosion on the PLA/RS composites indicate high degree of hydrolysis. Whilst the addition of ENR leads to some improvements in tensile properties, nevertheless, it enhanced the biodegradability of the PLA/RS composites when exposed to water and -amylase enzymatic treatments.     

(RS)‐Propranolol: enantioseparation by HPLC using newly synthesized (S)‐levofloxacin‐based reagent,absolute configuration of diastereomers and recovery of native enantiomers by detagging

Diastereomers of (RS)‐propranolol were synthesized using (S)‐levofloxacin‐based new chiral derivatizing reagents (CDRs). Levofloxacin was chosen as the pure (S)‐enantiomer for its high molar absorptivity (ε_o ～ 24000) and availability at a low price. Its ‐COOH group had N‐hydroxysuccinimide and N‐hydroxybenzotriazole, which acted as good leaving groups during nucleophilic substitution by the amino group of the racemic (RS)‐propranolol; the CDRs were characterized by UV, IR, ¹H‐NMR, high resolution mass spectrometry (HRMS) and carbon, hydrogen, nitrogen, and sulphur fundamental elemental components analyser (CHNS). Diastereomers were separated quantitatively using open column chromatography; absolute configuration of the diastereomers was established and the reagent moiety was detagged under microwave‐assisted acidic conditions. (S)‐ and (R)‐propranolol as pure enantiomers and (S)‐levofloxacin were separated, isolated and characterized. Optimized lowest‐energy structures of the diastereomers were developed using Gaussian 09 Rev. A.02 program and hybrid density functional B3LYP with 6‐31G* basis set (based on density functional theory) for explanation of elution order and configuration. In addition, RP HPLC conditions for separation of diastereomers were optimized with respect to pH, concentration of buffer, flow rate of mobile phase and nature of organic modifier. HPLC separation method was validated as per International Conference on Harmonization guidelines. With the systematic application of various analytical techniques, absolute configuration of the diastereomers (and the native enantiomers) of (RS)‐propranolol was established. Copyright © 2016 John Wiley & Sons, Ltd.