标准模型下多个PKG的基于身份广义签密

广义签密是指除了能实现签密功能,还可单独实现加密和认证功能的密码机制。该文定义了不同PKG环境下基于身份的广义签密方案较为全面的安全模型,并提出一个具体方案,进而在标准模型下证明了方案的安全性。和已有的不同PKG环境下基于身份签密方案相比,文中方案的效率较高,且应用范围更为广泛。     

可证安全的传统公钥密码-无证书公钥密码异构聚合签密方案

异构签密可以保证异构密码系统之间数据的机密性和不可伪造性。分析现有的异构签密方案,发现它们只针对单个消息,无法实现批验证。聚合签密能够把不同用户对多个消息产生的签密密文同时发送给接收者,而且可以提供批量验证,降低验证开销。该文提出一个传统公钥密码-无证书公钥密码异构聚合签密方案,该方案不仅能够保证传统公钥密码(TPKI)和无证书公钥密码(CLPKC)系统间通信的机密性和认证性,而且聚合验证时不需要双线性对。在随机预言模型下,基于间隙双线性Diffie-Hellman困难问题、计算Diffie-Hellman困难问题和离散对数问题,证明该方案满足自适应性选择密文攻击下的不可区分性和自适应选择消息下的不可伪造性。     

非均匀环境中的参量多通道目标检测

该文研究了非均匀环境中的参量多通道目标检测,其中,干扰信号用向量自回归(VAR)模型表示,且模型的空域协方差矩阵服从自由度为,均值为Q的复逆Wishart分布。当Q未知时,文章根据纽曼皮尔逊(NP)准则提出了NP参量自适应匹配滤波器(NP-PAMF),贝叶斯PAMF(B-PAMF)和归一化形式B-NPAMF;当Q已知时,文章根据最大后验概率(MAP)准则提出了MAP-PAMF和归一化形式MAP-NPAMF。结果表明：NP-PAMF和B-PAMF均和有关,当时,B-PAMF趋于经典的PAMF;B-NPAMF与无关,和经典的NPAMF一致。在MAP-PAMF中,空域协方差矩阵的MAP估计由经典估计和先验知识构成,控制后者的权重。最后,文中分析了检测器的复杂度和检测性能。实验表明：贝叶斯的参量检测器具有很好的检测性能,且比归一化检测器的性能优越。     

A two-stage affine projection algorithm with mean-square-error-matching step-sizes

This paper proposes a two-stage affine projection algorithm (APA) with different projection orders and step-sizes. The proposed algorithm has a high projection order and a fixed step-size to achieve fast convergence rate at the first stage and a low projection order and a variable step-size to achieve small steady-state estimation errors at the second stage. The stage transition moment from the first to the second stage is determined by examining, from a stochastic point of view, whether the current error reaches the steady-state value. Moreover, in order to prevent the sudden drop of convergence rate on switching from a high projection order to a low projection order, a matching step-size method has been introduced to determine the initial step-size of the second stage by matching the mean-square errors (MSEs) before and after the transition moment. In order to continuously reduce steady-state estimation errors, the proposed algorithm adjusts the step-size of the second stage by employing a simple algorithm. Because of the reduced projection orders and variable step-size in the steady-state, the algorithm achieves improved performance as well as extremely low computational complexity as compared to the existing APAs with selective input vectors and APAs with variable step-size.     

Signal-to-noise enhancement in TSSI–GC–IMS: Development of two dimensional sensor for detection of chemicals

Over the years, Ion Mobility Spectrometry (IMS) which refers to the techniques and cutting-edge instruments for characterizing of analytes by their gas phase mobility has been gaining popularity and validity among scientific researchers for detecting chemicals. This novel gas sensor with its high analytical speed, low detection limits, ease of use and ruggedness during transport has also become the dominant commercial technology in different industries. In spite of these paramount advantages, this detector has difficulty identifying matrix compounds. To overcome this problem a Gas Chromatograph (GC) can be used to introduce individual components of mixture into an IMS. The output signal of the hyphenated GC–IMS method is an extraordinary small, time-dependent current produced by mobile ions in atmospheric pressure. To exploit the qualitative and quantitative information hidden in this sensitive noisy signal, various signal processing methods have been nominated for spectrum filtration and improving signal-to-noise ratio (SNR). In the present paper an attempt is made to design and construct a GC–IMS instrument coupled with a Thermal Solid Sample Introduction (TSSI) module for injection of solid samples to capillary GC column. Moreover, various spectrum filtration methods for removing noise from GC–IMS signal would be investigated. The GC–IMS instrument used in this research was designed and constructed in Institute of Materials and Energy, Isfahan, Detector group and can be used as a chemical sensor for rapid detection of a broad range of chemical mixtures in many operational environments including on-board Volatile Organic Analyzer Sensor (VOAS) in space missions. The capability of constructed sensor for detection of complex mixtures has been proved by analyzing a mixture of three pesticides as test materials. Our proposed method for removing noise from the real-time TSSI–GC–IMS signal will be presented and its efficacy will be proved by offering real experiments.     

一种适用于大型阵列的递推干扰抑制算法

天线阵列在雷达与卫星通信中有着广泛的应用,它可以通过波束形成来抑制干扰.对于具有较多阵元数的大型阵列,普通的波束形成算法计算量很高.本文给出一种适用于大型阵列的递推干扰抑制算法,它是在波束空间分解最大信干噪比准则下基于干扰矢量进行变维递推处理,所需递推步数为干扰数,且每步递推中数据矩阵的维数很小,因而所需的总计算量较低.阵元数越多该递推算法的计算效率越高.仿真结果表明,该递推算法可以有效实现干扰抑制.     

A comparison of two meshing schemes for CFD analysis of the impulse turbine for wave energy applications

This paper presents the comparison of a three-dimensional Computational Fluid Dynamics (CFD) analysis with empirical performance data of a 0.6 m Impulse Turbine with Fixed Guide Vanes used for wave energy power conversion. Pro-Engineer, Gambit and Fluent 6 were used to create a 3-D model of the turbine. A hybrid meshing scheme was used with hexahedral cells in the near blade region and tetrahedral and pyramid cells in the rest of the domain. The turbine has a hub-to-tip ratio of 0.6 and results were obtained over a wide range of flow coefficients. Satisfactory agreement was obtained with experimental results. The model yielded a maximum efficiency of approximately 54% as compared to a maximum efficiency of around 49% from experiment. A degree of insight into flow behaviour, not possible with experiment, was obtained. Sizeable areas of separation on the pressure side of the rotor blade were identified toward the tip. The aim of the work is to benchmark the CFD results with experimental data and to investigate the performance of the turbine using CFD and to with a view to integrating CFD into the design process.     

蓝莓花色苷体外及模拟人体胃肠环境的抗氧化活性研究

以野生蓝莓为原料提取花色苷,对其进行纯化、121℃高温加热6 min和模拟人体胃肠环境处理,测定处理后的样液的抗氧化活性,对结果进行综合分析比较,得出不同条件对花色苷抗氧化活性的影响。结果表明:同一处理环境下,水溶液中的花色苷的抗氧化活性随纯度的增大而明显增强,二次纯化物的活性是粗提物的4倍左右,但在模拟胃肠环境中活性受纯度的变化影响较小;在同一纯度下,花色苷经过模拟胃肠和高温加热处理后抗氧化活性大大的降低,水溶液中的花色苷活性是模拟胃肠环境中的2倍以上;花色苷经121℃高温加热后活性大大降低,同一条件下活性损失了一半左右,但这种损失在模拟人体胃肠环境中较小,粗提物水溶液中的花色苷的活性是121℃加热后的花色苷的2.7倍。     

Simulating the structure and air permeability of needle-punched nonwoven layer

The aim of this article is to study and simulate the structure of needle-punched nonwoven fabrics in order to predict air permeability of nonwoven filters. For this purpose, the Poisson’s random number process has been used to model the random position of fibers in a web. A simple and easy-to-use expression was developed to predict the number of webs in a layer, considering the thickness and areal density of nonwoven fabrics. A 3D model was generated by assembling simulated webs. The GAMBIT meshing software was used to generate the mesh for the Computational Fluid Dynamic (CFD) solver. The outlet pressure of generated model was determined by means of CFD tool. Different types of needle-punched nonwoven fabrics were produced using Polyester fibers with different cross section and counts. The air permeability test was carried out on the samples, and the outlet pressure of each sample were measured and compared with theoretical values. The results showed that the simulated structure is capable to predict the air permeability of nonwoven filters adequately. The main novelty of the model is the ability of simulating the structure and air permeability of multi constituent nonwoven layers.