QC-LDPC码的截短技术研究

可变码率编码是现代移动通信系统的一项关键技术。在分组码中,截短(short-ening)技术是实现这一目的主要方法之一。截短是一种通过将一些信息比特用预先约定好的值置换,从而将这些比特的置信度设为无限大的技术。通过该技术,可以缩短码长并降低码率,同时提高码字的性能。针对非规则QC-LDPC码,结合PEXIT分析方法,给出了一种优化地选取截短比特的方法。仿真结果和分析表明,本文的方法使得截短后的码字取得良好的译码性能。     

成品支架安装技术

在公用系统安装工程中,支吊架承担着不可替代的作用.不同的支吊浆制作方法决定了安装工程不同的承载能力和施工质量,其不同的安装方法也使安装工程呈现了多样性和灵活性.大多数支吊架都是用角铁、槽钢或方钢等材料制作而成,其不同型号的材料也具有不同的承载力.随着科技的进步和发展,涌现出不少新型的安装材料,多种成品支吊架也随之应运而...     

Strain Dependence of the Uniaxial Compression Response of Vegetable Shortening

Many soft food materials, including vegetable shortening, exhibit complex rheological behavior. For shortening, a precise determination of rheological behavior is necessary to understand its functionality as a food ingredient. Commercial vegetable shortening was subjected to monotonic and cyclic uniaxial compression tests at a wide range of loading rates. The elastic modulus determined from unloading was a function of strain, varying between 740 kPa in the shortening’s strain hardening region to 220 kPa at large strain where perfect plasticity had developed. Visual analysis of shortening specimens during the compression process showed that a rate-dependent stress overshoot was attributable to the development of a shear band following strain hardening. An elastoviscoplastic constitutive model was developed to define the complex rate-dependent compression response of vegetable shortening. Using the fundamental parameters obtained from the different types of compression tests, the proposed model accurately predicted the uniaxial compression response of vegetable shortening over a wide range (three decades) of compression rates. A model with predictive capabilities of large strain properties is desirable because shortening is subject to large strain in essentially all applications.     

基于IFDMA-SIMO系统的信道压缩

高速数据传输IFDMA(interleaved frequency-division multiple-access)系统中,信道扩展将导致严重的符号间干扰,为此,根据IFDMA-SIMO(single-input multiple-output)系统特性,提出了一种新的基于IFDMA-SIMO系统的信道压缩算法。仿真和比较表明,该算法在保持多用户信号正交的基础上,能有效地抑制多径干扰。     

Axial strength of circular concrete-filled steel tube columns — DOE approach

This paper presents the effect of changes in diameter of the steel tube (D), wall thickness of the steel tube (t), strength of in-fill concrete (f_cu), and length of the tube (L) on ultimate axial load (P_ue) and axial shortening at the ultimate point (δ_ue) of circular Concrete Filled steel Tubes (CFT). Taguchi’s approach with an L9 orthogonal array is used to reduce the number of experiments. With the help of initial experiments, linear regression models are developed to predict the axial load and the axial shortening at the ultimate point. A total of 243 circular CFT samples are tested to verify the accuracy of these models at three factors with three levels. The experimental results are analyzed using Analysis Of Variance to investigate the most influencing factor on strength and axial shortening of CFT samples. Comparisons are made with predicted column strengths using the existing design codes, AISC-LRFD-2005 and EC4-1994.     

基于零点消除的无线OFDM系统 信道缩短均衡器

针对无线信道的有限冲激响应及其全零点特性,本文设计了一种基于零点消除的无线正交频分复用(OFDM)系统信道缩短均衡器,该均衡器利用零点消除的方式有效地缩短信道时延扩展长度,并采用反馈滤波器的形式来实现无限冲激响应滤波器,该方案不仅降低了信道缩短均衡器算法的复杂度,而且也大大简化了无线OFDM系统的设计与实现.仿真结果验证了上述方案和算法的有效性.     

Development of Muscle Thermal Rigorometer and Characterization of Heat-induced Muscle Shortening of Tilapia

A muscle thermal rigorometer was constructed, allowing muscle shortenings induced by dynamic heating or isothermal aging to be monitored. Operating isothermally like a traditional rigorometer at 10 °C, postmortem dorsal muscle shortening (S_10°C) developing from 0% to 10% of its initial length in corresponding to RI_fiber along fiber‐direction developing from 0% to 100% within 16 h was monitored for freshwater tilapia. Monitoring meat cooking in the dynamic heating mode, heat‐induced shortenings could be observed for all muscle samples possessing different degrees of rigor induced by 10°C aging. The heat‐induced shortening (S_dynamic) plus its 10°C aging shortening (S_10°C) for each sample was the same, S_overall= S_10°C+ S_dynamic= 10%. Their heat‐induced shortening peak temperatures (Ts) from 30°C to 48°C were inversely correlated with the sample RI_fiber from 0% to near 100%. These findings together with an additional calcium/adenosine triphosphate (ATP) model studies showed that the ATPase related myofibrillar contractile system was responsible for these low‐temperature cooking shortenings, which along with Ts values could thus be adopted as new rigor indices.     

Fast Implementation of MSSNR TEQ for DMT Systems

1　IntroductionInDiscreteMulTitone (DMT)systems,eachsymboliscomprisedofNdatasamplesandvCyclicPrefixes (CP) ,andthelatterissimplythelastvsamplesoftheformer.TheCPlengthisdeterminedbythelengthofthechannelimpulseresponse,andischosentominimizeInterSymbolInterference(ISI) .Ifthechannelimpulseresponseisoflengthv + 1orshorter,thenaCPoflengthvissufficienttoeliminateISI[1～4] .SincetheefficiencyofthetransceiverisreducedbyafactorofN/(N +v) ,itiseitherdesirabletomakevassmallaspossibleorutilizea…     

Numerical Simulation of Pulse Shortening in RBWOs

Pulse shortening hinders improvement of microwave output energy for high power microwave tubes. So far, it is also an unresolved problem in the field of high power microwave devices.In this paper, relativistic backward wave tube (RBWO) is treated as an example to study the pulse shortening phenomena. The influences of gas existing in the tube and explosive emission in inner surface of RBWO are all investigated by means of the particle-in-cell method. Through the simulation results, it can be predicted that the background gas in the tube is one but not the most important factor resulting in pulse shortening, in order to broaden the pulse width of gas-filled RBWO, the pressure of the filled gas must be controlled in a proper value. The explosive emission in the surface of slow wave structure due to intense electric field is one of the most important factors causing pulse shortening in high power microwave tube.Some methods to overcome this kind of explosive emission are also given.