基于简化LSCMA算法的STBC MC－CDMA系统盲多用户检测

在空时分组编码（STBC）的MC－CDMA系统中,根据STBC正交编码的特点,提出了一种简单可行 的基于常模（CM）准则的盲多用户检测算法。该算法基于最小二乘常模算法（LSCMA）的盲多用户检测算法, 算法大为简化,抽头系数减少了一半,性能略有下降。     

基于线性非冗余预编码的MIMO-OFDM系统信道估计算法

文章针对MIMO-OFDM系统中的信道估计关键技术提出了一种信道估算方法—基于线性非冗余预编码和二阶统计量的信道盲估计算法,该算法利用预编码信号的二阶统计特性消除了调制信号的信息,然后又利用STBC（Space-Time Block Coding空时分组编码）特殊的复正交特性对参考子载波信道矩阵进行变换,将求逆过程转换成简单的线性处理过程,从而实现了低复杂度的信道估计。另外,该算法通过选取合适长度的统计数据,能够较快收敛。     

适用于水声信道的新的盲均衡算法

由于时变水声信道的随机相位失真，常模算法（CMA）的误码性能将严重下降。在文献[1]中双模式盲均衡算法的基础上，提出了一种适用于水声信道的新的盲均衡算法（NCMA）。计算机仿真结果表明在时变水声信道中，该算法性能优于双模式算法，能够达到信号相位失真的恢复．并且收敛性能优于双模式算法。     

智能天线MC-CDMA系统中空频联合盲多用户检测算法

提出了智能天线多载波CDMA系统中一种空域和频域联合的盲多用户自适应检测算法,它是将空域波束形成和频域合并检测合二为一,使得检测器在空域和频域两维上同时优化,从而提高了系统的检测性能.对这种空频联合检测算法的误码性能进行了分析,并与先自适应波束形成然后再进行频域合并的分步算法进行了仿真比较,仿真结果表明,提出的空频联合盲多用户自适应检测算法的检测性能优于分步检测算法.     

CDMA移动通信系统中基于子空间的信号检测

讨论了线性空间中的子空间投影理论及其在CDMA（码分多址）移动通信系统中的应用,提出了已知各用户特征序列条件下基于子空间斜投影的多用户检测技术以及仅知目标用户特征序列条件下基于伪特征分解和子空间正交投影的盲检测技术,并通过计算机仿真进行了比较研究。     

基于ZF-DPC机制的多天线下行系统的自适应调制

以系统总速率最大化为目标,基于迫零污纸编码（ZF-DPC）机制提出了MIMO多用户下行系统的一种保障用户QoS的自适应调制方案。根据这一方案,基站应用空分多址接入（SDMA）同时支持多个用户;针对污纸编码（DPC）的极高复杂度,利用次优的ZF-DPC消除用户间的干扰;在理想信道信息情形下实现可变速率可变功率自适应调制。考虑到最优算法的高复杂度,提出了两种可应用到实际系统的低复杂度次优算法。仿真结果表明,次优算法在极大降低系统复杂度的同时,总速率比较接近最优算法的性能。     

嵌入式小波图像编码算法的研究

分析了嵌入式零树小波编码（EZW）算法原理和特点。讨论了两个基于EZW算法的改进算法，即多级树集合分裂算法（SPIHT），集合分裂嵌入块编码（SPECK）。最后，对这些算法原理进行了比较和讨论，说明了嵌入式图像编码的研究方向。     

时间分辨力约束下目标检测的波形优化设计

以最大化检测概率为优化准则，采用基于凸优化和随机化方法的具有相似性约束的相位编码算法（Phase Coding Algorithm with Similarity Constrain，PCA-SC）来设计发射波形，解决了主动声呐系统增大探测目标发射功率却不能提高检测概率的问题。同时，为有效降低PCA-SC算法所设计编码自相关函数的整体旁瓣级，提高其检测微弱目标的能力，在PCA-SC算法的基础上，结合新循环算法（Cyclic Algorithm-New，CAN）多相编码技术，提出了基于CAN的PCA-SC波形优化方法（Cyclic algorithm-new Phase Coding Algorithm with Similarity Constrain，CAN-PCA-SC）。仿真实验结果表明，PCA-SC和CAN-PCA-SC两种波形优化方法获得的发射信号均能够在满足系统所需时域分辨能力的要求下，实现检测概率的最大化，提高了目标检测性能，将时域分辨能力和检测性能有效地统一起来。相比PCA-SC波形设计方法，CAN-PCA-SC波形设计方法在保证获得的发射信号的检测概率优化效果一致的情况下，具有更低的积累旁瓣水平和更好的检测微弱目标的能力。     

无损图像压缩技术

本文介绍了图像数据的无损压缩技术。无损压缩编码算法可分为两大类：基于统计概率的方法和基于字典的技术，前者主要包括霍夫曼（Huffman）编码方法和算术编码，后者主要包括游程编码（Running Length Coding)RLC和LZW编码。     

多用户检测技术分析

本文主要分析了多址干扰对WCDMA网络的影响情况，从而引入了WCDMA网络采用多用户检测技术的重要性。其次对WCDMA网络采用多用户检测的效果进行验证，并对多用户检测算法进行了分析比较，指出了今后在算法研究上较可能的发展方向。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.