Comparison of coded orthogonal frequency division multiplexing and multicarrier code division multiple access systems for power line communications

Orthogonal frequency division multiplexing (OFDM) and multicarrier code division multiple access (MC‐CDMA) systems are comparatively evaluated for power line communications (PLC) in a frequency‐selective fading environment with additive coloured Gaussian noise which is used to model the actual in‐home power line channel. OFDM serves as a benchmark in order to measure the performance of various MC‐CDMA systems, since multicarrier modulation systems are considered the best candidate for this kind of channel. Both single‐user and multi‐user cases are taken into account, making use of the appropriate combiner schemes to take full advantage of each case. System efficiency is enhanced by the application of different coding techniques, a fact which shows that powerful coding can make the difference under such a hostile medium. The impact of block interleaving is investigated, while the simulation examines how different modulation schemes fair under the imposed channel conditions as well. The performance of the system is assessed by the commonly used bit error rate vs signal‐to‐noise ratio diagrams and there is also a comparison regarding throughput efficiency among all the tested systems. As stated in Section 4, a promising PLC application is attained. Copyright © 2004 John Wiley & Sons, Ltd.     

用漫反射光谱校正组织自体荧光光谱的研究

利用漫反射光谱所含信息来消除组织对自体荧光散射和吸收的影响，从而提取出组织的固有荧光光谱。利用蒙特卡罗（MC）方法分析组织的荧光失真因数曲线和漫反射光谱之间的关系，发现两者的曲线形状基本相同，并以胃肠正常和癌变组织的漫反射光谱来校正实验获得的自体荧光（LIAF）光谱。最终得到的固有荧光光谱体出了组织的生化信息变化。     

MC33370系列单片开关集成电路及其应用

MC33370系列IC产品是美国摩托罗拉（Motorola）公司新近推出的五端单片开关电源集成电路。该系列产品具有较完善的工作状态控制能力。本文阐述了它们的性能特点、内部结构和工作原理，并对其状态控制方式进行了较为详细的分析，最后给出了构成开关电源的典型实例。     

正交频分复用技术及其在CDMA中的应用

主要介绍正交频分复用技术的基本原理和多载波ＣＤＭＡ技术的实现方法，并简要讨论了正交频分复用技术相对于多载波ＣＤＭＡ技术的优缺点。     

基于MC FQRD RLS算法的功放建模方法

在地面广播电视传输系统中,为了提高效率,功率放大器通常工作在非线性区.由此引入的非线性,必须进行校正.如果能够得到功率放大器的非线性模型,校正工作就能取得很好的效果.提出了一种基于多通道快速QR分解RLS算法的建模方法.传统的QRD RLS算法具有收敛速度快和数值稳定的优点.但其缺点是算法的计算量很大,对硬件资源的需求...     

On the performance of joint space‐frequency pre‐filtering and equalization for downlink multi‐carrier code division multiple access

We analyze the performance of joint space‐frequency pre‐filtering and equalization techniques for downlink multi‐carrier code division multiple access in terms of average bit error rate performance. Several linear power allocation strategies combined with single‐user equalization schemes are compared with a joint pre‐filtering with an equal power constraint at the base station and maximal ratio combining at the mobile terminals. Our bit error rate analysis obtained in this paper facilitates predicting the performance of various space‐frequency pre‐filtering schemes without massive simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

用蒙特卡罗“测量”离散程序中的参数

为了快速、精确地计算高能X射线照相中的散射光子分布,提出了将该过程中的粒子输运问题近似为一个有效的纯光子输运问题。针对该纯光子输运方程提出了一种适合于计算机计算的逐级迭代求解公式,并将该公式进行了离散化,然后编写成了计算机离散程序。用蒙特卡罗程序MCNP模拟得到了该程序所需要的参数和分布函数。最后用MCNP对该程序进行了检验。对于薄客体离散程序的计算结果与MCNP符合较好,但对于厚客体二者有较大偏离。目前可以把该程序应用于一些定性的计算分析。     

A k-mean-directions Algorithm for Fast Clustering of Data on the Sphere

A k-means-type algorithm is proposed for efficiently clustering data constrained to lie on the surface of a p-dimensional unit sphere, or data that are mean-zero-unit-variance standardized observations such as those that occur when using Euclidean distance to cluster time series gene expression data using a correlation metric. We also provide methodology to initialize the algorithm and to estimate the number of clusters in the dataset. Results from a detailed series of experiments show excellent performance, even with very large datasets. The methodology is applied to the analysis of the mitotic cell division cycle of budding yeast dataset of Cho et al. [Molecular Cell (1998), 2, 65–73]. The entire dataset has not been analyzed previously, so our analysis provides an understanding for the complete set of genes acting in concert and differentially. We also use our methodology on the submitted abstracts of oral presentations made at the 2008 Joint Statistical Meetings (JSM) to identify similar topics. Our identified groups are both interpretable and distinct and the methodology provides a possible automated tool for efficient parallel scheduling of presentations at professional meetings.

The supplemental materials described in the article are available in the online supplements.     

光纤激光器功率控制系统的设计

以单片机MC9S12XDP512为控制核心,结合相关外围电路完成了光纤激光器功率控制系统的设计。通过单片机控制数字电位器DS1867的阻值,来改变开关电源控制端的电压,实现了对光纤激光器电源电流的控制。采用压控开关电流源PCO-6131,进而改变光纤激光器的输出功率。系统还可以检测光纤激光器所在环境温度,实现高温报警、定时控制等功能。试验结果表明,光纤激光器应用在打标工作过程中,获得稳定的功率输出,实现温度检测功能,整机系统稳定可靠。     

The Physical,Chemical and Biological Effects by Room Temperature Ceramic Far‐infrared Ray Emitting Material Irradiated Water: A Pilot Study

Far infrared ray (FIR) is non‐ionizing electromagnetic radiation with wavelengths of 4‐16 μm. Ceramic far infrared ray emitting materials (cFIR) are sources of FIR that exhibit only non‐thermal effects at room temperature. Certain physical, chemical and biological effects of cFIR irradiation were investigated in this study that heretofore has not been well characterized. We demonstrated that cFIR irradiation reduced the size of water clusters, and significantly increased the freezing temperature of water. We also observed an increase in the volatility of a complex mixture of alcohol, water and solutes and recorded elevated total phenol in green tea infusions prepared using cFIR irradiated water. The effects of cFIR irradiated water on living cells were also investigated. The MC3T3‐E1 murine osteoblast cells grown in the presence of cFIR irradiated water exhibited anti‐oxidative effects on H₂O₂‐mediated toxicity, as evidenced by late stage increase in intracellular alkaline phosphatase. The presence of cFIR irradiated water also resulted in significant decrease in COX‐2 production in the chondrosarcoma cell line, SW1353, in response to lipopolysaccharide induction. Based on our findings, the possible anti‐inflammatory effects of cFIR irradiated water and implications of our study with regard to bone and joint health were discussed.