On-machine interlocking of 3D laminate structures for composites

By using an adjacent-layer interlocking method on a weaving machine, multi-layer preform structures are developed. The on-loom interlocking method eliminates the yarn breakage resulting from needle penetration which is the case for off-loom interlocking of fabric layers. The concept of this three-dimensional (3D) fabric design is to bind each pair of adjacent layers at one connecting point in every other plain-weave repeat within each layer. The mechanical properties of the resulting composites are investigated by means of impact, short-beam shear and the long-beam flexural testing. The failure mechanisms found in 3D on-loom interlocked composites include fiber breakage, fiber debonding and fiber pull-out.     

An effective method for classification with missing values

Classification is one of the most important tasks in machine learning with a huge number of real-life applications. In many practical classification problems, the available information for making object classification is partial or incomplete because some attribute values can be missing due to various reasons. These missing values can significantly affect the efficacy of the classification model. So it is crucial to develop effective techniques to impute these missing values. A number of methods have been introduced for solving classification problem with missing values. However they have various problems. So, we introduce an effective method for imputing missing values using the correlation among the attributes. Other methods which consider correlation for imputing missing values works better either for categorical or numeric data, or designed for a particular application only. Moreover they will not work if all the records have at least one missing attribute. Our method, Model based Missing value Imputation using Correlation (MMIC), can effectively impute both categorical and numeric data. It uses an effective model based technique for filling the missing values attribute wise and reusing then effectively using the model. Extensive performance analyzes show that our proposed approach achieves high performance in imputing missing values and thus increases the efficacy of the classifier. The experimental results also show that our method outperforms various existing methods for handling missing data in classification.     

新疆湿地资源时空变化特征及其保护

基于GIS平台,以新疆维吾尔自治区国土资源厅统计出的湿地资源数据为基础,结合统计分析,对新疆1996~2005年湿地资源数量、类型及其变化进行了分析。分析得出,在10年尺度上湿地资源总的动态特征是:河流湿地、湖泊湿地、滩涂湿地、永久积雪及冰川湿地和库塘湿地面积增加,增加面积共46 417 hm2,沼泽湿地、稻田湿地和芦苇湿地面积减少,减少面积共12 966 hm2。最后引入湿地资源类型相对变化率反映出新疆各地州市湿地资源变化存在明显的区域差异,克拉玛依市、哈密地区和巴音郭楞蒙古自治州湿地资源类型的变化幅度均大于全疆相应的湿地资源类型变化幅度。政策变动、水利工程建设和人口增长是新疆湿地资源变化的主要原因。     

TIME-DOMAIN BEM ANALYSIS FOR THE 2D SCALAR WAVE EQUATION: INITIAL CONDITIONS CONTRIBUTIONS TO SPACE AND TIME DERIVATIVES

The complete expressions corresponding to space and time derivatives of Volterra's integral representation of the time-dependent scalar wave equation are presented in this paper. The concept of finite part of an integral is used in order to compute boundary kernels contributions. Time integration of boundary kernels is performed analytically for linear and constant time approximations for the potential and its normal derivative, respectively. The new integral representations presented in this text are quite general, as contributions due to the initial conditions have also been included. Two examples are presented in order to assess the accuracy of the formulation.     

Photocatalytic degradation of methylene blue with Co alloyed CdZnS nanoparticles

In our present study, firstly; cadmium zinc sulfide (CdZnS) nanoparticles (NPs) with 1, 2, 5, 10% of Zn concentration were synthesized in aqueous solution by simple chemical co-precipitation method and their photocatalytic activity was investigated using the degradation of methylene blue under visible light in air at room temperature. It was found that CdZnS NPs with 2% of Zn concentration indicates the highest degradation efficiency compare to other Zn concentrations. CdZnS NPs with 2% of Zn concentration was symbolized as CdZnS_1. Later; 0.1, 0.2, 0.5, 1, 5, 10% of cobalt (Co) concentration was separately alloyed on the CdZnS_1 NPs. It was oberved that Co(5%):CdZnS NPs has the highest degradation efficiency. Structure, surface morphology, elemental analysis and optical properties of CdZnS_1 and Co (5%): CdZnS NPs 0were analyzed using X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray and UV–Vis absorption measurements, respectively. The results showed that Co doped CdZnS NPs can be employed as capable materials to ehance the photocatalytic activity.     

Performance of Cognitive Radios in Dynamic Fading Channels Under Primary Outage Constraint

This article investigates the performance of a cognitive user in a dynamic fading environment. The cognitive user communicates, using a spectrum-sharing technology, over a channel reserved to a primary user (PU). The transmit power of the cognitive user satisfies the outage probability constraint of the PU. The channels of the primary and cognitive users experience independent and non-identically distributed fading models. Nakagami- $m$ and hyper-Nakagami- $m$ channel fading models are specifically considered. The cognitive user’s mean transmit power, channel capacity, and bit error rate are derived for this setup. In addition, numerical results are presented to verify the theoretical analysis and investigate the effects of the parameters of the communication environment on the performance measures of the cognitive user.     

Performance Analysis of Cognitive Radio Multiple-Access Channels Over Dynamic Fading Environments

In dynamically changing environments, the spectrum-sharing method is a promising method to address the spectrum underutilization problem for cognitive radio (CR) systems. This paper investigates the capacity of cognitive radio multiple-access channel (CR-MAC) over a dynamic fading environment. Multiple secondary users (SUs) transmit to the secondary base station under the transmit power (TP) and interference temperature (IT) at the primary base station constraints. In order to perform a general analysis, a theoretical dynamic fading model termed hyper-fading model, which is suitable to the dynamic nature of cognitive radio channel, is considered. The optimal power allocation method is employed to maximize the capacity of CR-MAC for hyper-fading channel with TP and IT constraints and full channel side information. Through the numerical simulations, the capacity of the hyper-fading channels are compared with that of other channel fading models such as Rayleigh, Nakagami-2, and with an additive white Gaussian noise channel. Additionally, the impacts of the number of SUs on capacity is investigated.     

微混合技术研究进展

在微尺度混合下,传递和反应性能得到明显改善;微混合器易与微反应系统集成,使化学反应更为可控,效率更高。综述了微混合技术的发展和研究现状,探讨了微混合技术的特点和优势及其在反应过程中的应用前景。     

Synthesis of Fe alloyed PbS thin films and investigation of their photovoltaic properties

Lead sulfide (PbS) and iron (Fe)-alloyed PbS thin films with different Fe concentrations were synthesized by chemical bath deposition (CBD) technique, which is suitable for cost on glass substrates at room temperature. The structural, elemental and optical properties of the synthesized thin films were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX) and optical absorption measurements, respectively. It was observed that Fe dopant alters crystal size and energy band gap of PbS although it does not change the structure of PbS. PbS and Fe-alloyed PbS thin films with different Fe concentrations were grown on zinc tin oxide (Zn₂SnO₄) substrates coated on fluorine-alloyed tin oxide conductive glasses to investigate their photovoltaic properties. Incident photon-to-current efficiency (IPCE) and current density (J)–voltage (V) measurements were carried out to determine IPCE (%) and power conversion efficiency (η%) values of thin films. As a result, it was observed that as the concentration of Fe dopant is increased in Fe-alloyed PbS thin films, there is an increase in η%.