基于背包模型的认知OFDM系统中的资源分配

本文针对多用户的OFDM认知无线电系统,提出了基于背包模型的资源分配新算法。该算法以最大化系统容量为目标,同时考虑各认知用户的QoS需求,将资源分配问题建模为多维0-1背包模型,并通过贪婪算法对其进行求解。仿真对比结果表明,该算法在性能上不仅逼近优化算法,而且具有较低的复杂度。     

Advanced Development of Supercritical Fluid Chromatography in Herbal Medicine Analysis

The greatest challenge in the analysis of herbal components lies in their variety and complexity. Therefore, efficient analytical tools for the separation and qualitative and quantitative analysis of multi-components are essential. In recent years, various emerging analytical techniques have offered significant support for complicated component analysis, with breakthroughs in selectivity, sensitivity, and rapid analysis. Among these techniques, supercritical fluid chromatography (SFC) has attracted much attention because of its high column efficiency and environmental protection. SFC can be used to analyze a wide range of compounds, including non-polar and polar compounds, making it a prominent analytical platform. The applicability of SFC for the separation and determination of natural products in herbal medicines is overviewed in this article. The range of applications was expanded through the selection and optimization of stationary phases and mobile phases. We also focus on the two-dimensional SFC analysis. This paper provides new insight into SFC method development for herbal medicine analysis.     

你也需要蒙特卡罗方法——一个得心应手的工具

本文通过几个例子和通俗的语言简要介绍蒙特卡罗(MC)方法的应用.文中例子显示,即使是一些尚无其它办法计算的复杂问题,应用MC方法也可以获得可用的结果,并且使用中档的个人电脑也可以在极短的时间内完成.文中还提供了一个品质优良的随机数发生器,据此读者不难把MC方法立刻用于自己的研究工作中。     

Comprehensive ultra-high pressure capillary liquid chromatography/ion mobility spectrometry

Summary An ultra-high pressure liquid chromatograph was interfaced to a moderately high-resolution nanoelectrospray ionization ion mobility spectrometer operating at ambient temperature and pressure to achieve fast multidimensional separations. The potential of using ion mobility spectrometry as the second dimension in a comprehensive arrangement with liquid chromatography to offer improved qualitative information for compounds under specific operating conditions, is discussed. Separation and detection of selected benzodiazepines and triazine herbicides are demonstrated. Composite peak capacities of 39 and 33 for benzodiazepine and triazine herbicide mixtures, respectively, were achieved in less than 75 s using a 16.5 cm×50 μm internal diameter fused silica capillary liquid chromatographic column packed with 1.5 μm diameter ODS-bonded silica particles.     

Current status and future trends on automated multidimensional separation techniques employing sorbent‐based extraction columns

Determination of target analytes present in complex matrices requires a suitable sample preparation approach to efficiently remove the analytes of interest from a medium containing several interferers while at the same time preconcentrating them aiming to improve the output signal detection. Online multidimensional solid‐phase separation techniques have been widely used for the analysis of different contaminants in complex matrices such as food, environmental, and biological samples, among others. These online techniques usually consist of two steps performed in two different columns (extraction and analytical column), the first being employed to extract the analytes of interest from the original medium and the latter to separate them from the interferers. The extraction column in multidimensional techniques presents a relevant role since their variations as building material (usually a tube), sorbent material, modes of application, and so on can significantly influence the extraction success. The main features of such columns are subject of constant research aiming improvements directly related to the performance of the separation techniques that utilize multidimensional analysis. The present review highlights the main features of extraction columns online coupled to chromatographic techniques, inclusive for in‐tube solid‐phase microextraction, online solid phase and turbulent flow, aiming the determination of analytes present at very low concentrations in complex matrices. It will critically describe and discuss some of the most common instrumental set up as well as comments on recent applications of these multidimensional techniques. Besides that, the authors have described some properties and enhancements of the extraction columns that are used as first dimension on these systems, such as type of column material (poly (ether ether ketone), fused silica, stainless steel, and other materials) and the way that the extractive phase is accommodated inside the tubing (filled and open tubular). Practical applications of this approach in fields such as environment, food, and bioanalysis are also presented and discussed.     

基于时间序列的飞机运动扰动建模

飞机的运动常常受到各种扰动因素的影响,这使得对其运动状态的刻画较为困难.由于确定飞机状态的三个量航速、航向、高度三者具有强相关性,采用了时间序列中的多维自回归方法对飞机扰动进行统计建模,以实例验证了所提方法是可行和有效的.     

Transfer Function Computation for Multidimensional Systems

A theoretically interesting technique is proposed for the determination of the coefficients of the determinantal polynomial and the coefficients of the adjoint polynomial matrix of a given n-D system, described by the Fornasini-Marchesini state space model. The proposed algorithms are based on the discrete Fourier transform (DFT), and easily can be implemented. An example is included to illustrate the application of the algorithm.     

二维NMR技术在有机结构分析中的应用

联合应用二维远程碳 -氢相关 (coloc)技术和二维碳 -氢相关(hxdept)技术 ,对三个含季碳较多的化合物进行了谱峰归属与结构指定。从而显示出多维NMR技术在有机结构分析中的重要作用。     

Isoenergy Spectral Problem for Multidimensional Difference Operators

In this paper, the direct and inverse isoenergy spectral problems are solved for a class of multidimensional periodic difference operators. It is proved that the inverse spectral problem is solvable in terms of theta functions of curves added to the spectral variety under compactification, and multidimensional analogs of the Veselov–Novikov relations are found.     

一种改进的分布式多维定标算法的研究

无线传感器网络中节点间通信容易受到环境因素和传输衰减因素等的影响,从而造成节点的定位不准确.为减小节点定位误差,在分布式多维定标算法基础上提出了改进的WMDS-MAP(P)算法.采用加权算法求出每个锚节点的环境影响参数和传输衰减参数对,并在构建局部空间的节点矩阵时考虑这两个因素;采用最小二乘算法选出锚节点中最优的环境影响参数和传输衰减参数对,从而使节点间的一跳距离估计值更逼近真实值.仿真结果显示改进的算法相对于经典的MDS-MAP(P)算法节点平均定位误差减少了17％左右,可以有效提高节点的定位精度.