Scattering Center Modeling Using Adaptive Segmental Compressive Sampling

In order to deal with aliasing distortions of Doppler frequencies shown in time-frequency representation (TFR) with aspect undersampling,an approach using adaptive segmental compressive sampling according to the aspect dependencies of the scattering centers is proposed.The random noise problem induced by compressive sampling is solved by employing a series of signal processing techniques of filtering,image transformation and Hough Transform.Three examples are presented to verify the effectiveness of this approach.The comparisons between the built models and the precise scattered fields computed by a well-validated full-wave numerical method are investigated,and the results show good agreements between each other.     

The mechanism study on annealing embrittlement of Al_(88)Ce_2Ni_9Fe_1 metallic glass

The mechanism of annealing embrittlement of Al88Ce2Ni9Fe1 metallic glass is studied by using SAXS. For this alloy the activation energy for embrittlement, Eb=(160±10) kJ·mol-1 is obtained It approaches the value of the activation energy for crystallization, Ec= (170± 10} kJ·mol-1 . The significant change in SAXS intensity is observed as the sample transformed from the ductile to the brittle state. About 0. 1 volume fraction of Al crystalline particle and 60 m2/cm3 of specific inner surface between crystalline and amorphous phase appear as the sam ple transformed from the ductile to the brittle state. The annealing embrittlement is caused by crystallization of this alloy.     

Calculation of Apparent Activation Energy of Coal Oxidation at Low Temperatures by Measuring CO Yield

By analyzing previous studies on activation energy of coal oxidation at low temperatures, a theoretical calculation model of apparent activation energy is established. Yield of CO is measured by using the characteristic detector of coal oxidation at 30-90 ℃. The impact of parameters, such as airflow and particle size, on activation energies is analyzed. Finally, agreement was obtained between activation energies and the dynamic oxygen absorbed in order to test the accuracy of the model. The results show that： 1） a positive exponential relation between concentration of CO and temperature in the process of the experiment is obtained： increases are almost identical and the initial CO is low; 2） the apparent activation energies increase gradually with the sizes of particle at the same airflow, but the gradients increase at a decreasing rate; 3） the apparent activation energies increase linearly with airflow. For the five coal particles, the differences among the energies are relatively high when the airflow was low, but the differences were low when the airflow was high; 4） the optimum sizes of particle, 0.125-0.25 ram, and the optimum volume of airflow, 100 mL/min, are determined from the model; 5） the apparent activation energies decrease with an increase in oxygen absorbed. A negative exponential relation between the two is obtained,     

An area method for visualizing heat-transfer imperfection of a heat exchanger network in terms of temperature–heat-flow-rate diagrams

The identification of the imperfection originating from finite-temperature-difference heat transfer is an indispensable step for both the performance analysis and the better design of a heat exchanger network(HEN) with the aim of energy saving. This study develops a convenient area method for visualizing the heat-transfer imperfection of a HEN in terms of temperature–heat flow diagrams( T-Q diagrams) by combining the composite curves that have already been used in pinch analysis and the recently developed entransy analysis. It is shown that the area between the hot and cold composite curves and the hot and cold utility lines on a T-Q diagram is just equal to the total entransy dissipation rate during the multi-stream heat transfer process occurred in a HEN, and this area can be used to graphically represent the total heat-transfer imperfection of the HEN. The increase in heat recovery or decrease in energy requirements with decreasing the minimum temperature difference, ΔT_(min), of a HEN can then be attributed to a lower entransy dissipation rate, quantitatively represented by the decrease of the area between the composite curves and the utility lines. In addition, the differences between the T-Q diagram and the pre-existing energy level–enthalpy flow diagram(Ω-H diagram) in the roles of visualizing process imperfection and designing HENs are discussed.     

Simulating frictional contact in smoothed particle hydrodynamics

Smoothed Particle Hydrodynamics (SPH) is a powerful tool for large deformation computation of soil flow. However, the method to simulate frictional contact in the framework of SPH is still absent and needs to be developed. This paper presents an algorithm to simulate frictional contact between soil and rigid or deformable structure in the framework of SPH. In this algo-rithm, the computational domain is divided into several sub-domains according to the existing contact boundaries, and contact forces are used as bridges of these sub-domains to fulfill problem solving. In the process of the SPH discretization for govern-ing equation of each sub-domain, the inherent problem of boundary deficiency of SPH is handled properly. Therefore, the par-ticles located at contact boundary can have precise acceleration, which is critical for contact detection. Then, based on the as-sumption that the SPH particle of soil can slightly penetrate into the structure, the contact forces along normal and tangential directions of the contact surface are computed by momentum principle, and the frictional force is modified if sliding occurs.Compared with previous methods, in which only particle-to-particle contact is considered or frictional sliding is just ignored,the method proposed in this study is more efficient and accurate, and is suitable for simulating interaction between soft materi-als and rigid or deformable structures, which are very common in geotechnical engineering. A number of numerical tests have been carried out to verify the accuracy and stability of the proposed algorithm, and the results have been compared with ana-lytical solutions or FEM results. The consistency obtained from these comparisons indicates that the algorithm is robust and can enhance the computing capability of SPH.     

RESEARCH ON CHEMICAL AND PHYSICAL ACTIVATION OF γ-C_2S

This paper reports the experiments of chemi-cal and physical activation of γ-C_2S and their results.Chemi-cal activation is that the addition of active substances to γ-C_2Scan promote its 3 days hydrated ratio to 20% and 7 days to26-31%.Physical activation,on the other hand,by irradiat-ing γ-C_2S with energetic ray,can promote its 3 dsays hydrat-ed ratio to 29%.Our experiments illustrate the mechanisms ofγ-C_2S chemical activation and physical activation.The for-mer is the formation of the insoluble by combination of theadded active substances with Ca(OH)_2,which is dissolvedfrom γ-C_2S,breaks the γ-C_2S dissolving-precipitating equilib-rium and promotes its hydration process.As a result,CSHhydrate is formed more rapidly.The latter is that the elasticcollision between the enegetic particles,which eater the γ-C_2S,and cause some atoms in lattice to deviate from their normalpositions and become interstitial atoms,and forms vacancy de-fects simultaneously.As crystal defect density increases,freeenerg     

A comprehensive method for joint wear prediction in planar mechanical systems with clearances considering complex contact conditions

A comprehensive method to predict wear in planar mechanical systems with clearance joints is presented and discussed in this paper.This method consists of a system dynamic analysis and a joint wear prediction.As the size and shape of the clearance are dictated by wear and evolve with the dynamic response of the system,the contact between the journal and bearing could be conformal or non-conformal,which makes the contact conditions in clearance joints quite complicated.Therefore a modified contact force model is employed to evaluate the joint reaction force in this study.As the nonlinear stiffness coefficient is related to the physical and geometrical properties of contact bodies and varies with the deformation,this contact force model is applicable to different contact conditions between the journal and bearing.Furthermore,based on the Archard’s wear model,the amount of wear can be quantified in the joint.And the geometry is updated to reflect the evolving contact boundary.Then,the wear process and the contact force model are integrated into the motion equations of the system to perform coupled iterative analyses between system dynamic response and joint wear prediction.In addition,a slider-crank mechanism is simulated as an example to demonstrate efficiency of the proposed method and to carry out a parametric study on mechanical systems considering joint wear.The influence of clearance size and driving power are discussed and compared respectively.The index of concordance is introduced to quantify contributions of contact pressure and sliding distance to wear rate under different types of journal motion.This study could help to predict joint wear in mechanical systems with clearances and optimize mechanisms in design.     

Automatic Satisfaction Analysis in Call Centers Considering Global Features of Emotion and Duration

Analysis of customers' satisfaction provides a guarantee to improve the service quality in call centers.In this paper,a novel satisfaction recognition framework is introduced to analyze the customers' satisfaction.In natural conversations,the interaction between a customer and its agent take place more than once.One of the difficulties insatisfaction analysis at call centers is that not all conversation turns exhibit customer satisfaction or dissatisfaction.To solve this problem,an intelligent system is proposed that utilizes acoustic features to recognize customers' emotion and utilizes the global features of emotion and duration to analyze the satisfaction.Experiments on real-call data show that the proposed system offers a significantly higher accuracy in analyzing the satisfaction than the baseline system.The average F value is improved to 0.701 from 0.664.     

Automatic Satisfaction Analysis in Call Centers Considering Global Features of Emotion and Duration

Analysis of customers' satisfaction provides a guarantee to improve the service quality in call centers.In this paper,a novel satisfaction recognition framework is introduced to analyze the customers' satisfaction.In natural conversations,the interaction between a customer and its agent take place more than once.One of the difficulties insatisfaction analysis at call centers is that not all conversation turns exhibit customer satisfaction or dissatisfaction.To solve this problem,an intelligent system is proposed that utilizes acoustic features to recognize customers' emotion and utilizes the global features of emotion and duration to analyze the satisfaction.Experiments on real-call data show that the proposed system offers a significantly higher accuracy in analyzing the satisfaction than the baseline system.The average F value is improved to 0.701 from 0.664.     

Rock burst proneness prediction by acoustic emission test during rock deformation简

Rock burst is a severe disaster in mining and underground engineering, and it is important to predict the rock burst risk for minimizing the loss during the constructing process. The rock burst proneness was connected with the acoustic emission （AE） parameter in this work, which contributes to predicting the rock burst risk using AE technique. Primarily, a rock burst proneness index is proposed, and it just depends on the heterogeneous degree of rock material. Then, the quantificational formula between the value of rock burst proneness index and the accumulative AE counts in rock sample under uniaxial compression with axial strain increases is developed. Finally, three kinds of rock samples, i.e., granite, limestone and sandstone are tested about variation of the accumulative AE counts under uniaxial compression, and the test data are fitted well with the theoretic formula.     

瑞利衰落信道下NNC-DFH接收机抗PBNJ性能分析

提出了一种噪声归一化合并(NNC)差分跳频(DFH)接收机模型,以提高差分跳频系统抗部分频带干扰能力。分析了瑞利衰落信道下NNC-DFH接收机在部分频带干扰下的误符号性能,比较了线性合并、乘积合并和噪声归一化合并DFH接收机的抗部分频带干扰性能,分析了背景热噪声的影响。研究结果表明:在瑞利衰落信道下,针对NNC-DFH接收机的最坏部分频带干扰为全频带干扰,该接收机的抗部分频带干扰性能优于传统的线性合并和乘积合并接收机,当信噪比为21.4 dB,符号错误概率为10-4时,其干扰容限改善量达8 dB。     

以栎精为电化学探针伏安法测定DNA

栎精与DNA之间可以通过静电作用和嵌入作用而发生相互作用。本研究以栎精为电化学探针 ,用电化学方法建立了测定DNA的新方法。栎精本身有良好的电化学行为 ,DNA的加入可以导致栎精氧化还原峰电流降低 ,优化了最佳结合反应条件和电化学测定条件。在最佳条件下 ,检测DNA的线性范围为 7 2× 1 0 - 6～ 8 6× 1 0 - 5 mol·L- 1 。     

关于结构致癌活性关系的研究

本文综述了结构致癌活性关系的研究,讨论了Schmidt,Pullman等人开创了这一研究领域以来的研究状况,评价了“湾区理论”和我国近年来提出的“双区理论”,作者根据DNA股间横向交联是致癌关键步骤的概念,提出了抗氧化剂抑癌作用机理的新观点。     

基于背景类别分层分离的不透水面间接提取——以兰州城关区EO-1 ALI图像为例

以兰州市城关区EO-1 ALI图像作为基础数据源,对比LOOC与最邻近分类（NNC）方法提取不透水面的精度差异. LOOC方法对融合后EO-1 ALI图像进行LBV变换,将变换结果作为解译底图;设置4个尺度层次,分别对应水体、农用地、灌木林地、城市绿地和草地这5种主要背景类别,对解译底图执行4尺度面向对象分割;将上述类别对象的光谱特征和形态特征差异作为判别规则,利用决策树分类,将这5种背景类别依次从解译底图上提取、分离,生成不透水面初级提取图层;通过光谱反射率差异分析,选定EO-1 ALI图像的近红外波段8和中红外波段10作为分类特征,利用基于模糊C-均值（FCM）算法的非监督分类,从初级图层中分离出砂土、阴影这两种与高、低反照度不透水面光谱特征相近的类别,采用数学形态学开闭运算整饬图像,生成不透水面二级提取图层. 结合目视评判和总体精度、Kappa系数,定量分析LOOC方法与NNC方法的提取精度差异. 结果表明：LOOC方法提取不透水面的总体精度、Kappa系数分别为87.13%、0.830 3,较NNC方法分别提高5.91%、7.19%. LOOC方法依据各背景类别的遥感多特征知识,分两级将其分离出解译底图,从而间接、逐步逼近不透水面精准空间分布信息,辨识不透水面的效率优于NNC方法.     

灿烂甲酚蓝电化学探针测定脱氧核糖核酸

运用电化学方法研究了灿烂甲酚蓝(BCB)与DNA的相互作用,并提出了以其为电化学探针测定DNA的方法。在pH 6 5的B- R缓冲溶液中,BCB在玻碳电极上有一对氧化还原峰,加DNA到BCB溶液中并在 27℃恒温反应 70min后,溶液中没有新的氧化还原峰出现,而原有的BCB氧化还原峰电流降低,峰电位稍有负移,表明两者在该条件下生成一种非电化学活性的超分子化合物,导致溶液中游离BCB浓度降低,相应的峰电流降低。对结合反应的条件和电化学测定条件进行了优化,在最佳条件下,峰电流减小的程度与DNA浓度呈分段线性关系,由此建立了一种测定DNA的电化学分析方法,该方法的线性范围为 8 00×10-7 ~ 6 00×10-5 mol·L-1,应用于微量核酸试样的分析,结果令人满意。     

二维零相关区周期互补序列偶及其理论界的研究

为了给通信系统提供更多的最佳离散信号,提出了一种新的最佳离散信号,即二维零相关区周期互补序列偶,研究了二维零相关区周期互补序列偶的变换性质,利用矩阵秩的不等式推导出了二维零相关区周期互补序列偶的理论界。基于循环左移算子,以缩小零相关区为代价,给出了一种扩展二维零相关区周期互补序列偶集的方法,该方法可以为通信系统提供大规模的信号集。     

以咪唑并邻菲咯啉铁(Ⅲ)配合物为杂交指示剂的DNA荧光光纤传感器研究

在0.2 mol.L-1的B-R(pH5.0)缓冲溶液中,运用荧光光谱法研究了咪唑并邻菲咯啉铁配合物([Fe(phen)2IP].3Cl O4.2 H2O,phen=邻菲咯啉,IP=咪唑并邻菲咯啉)与鲑鱼精DNA的相互作用。实验结果表明,[Fe(phen)2IP]3+与DNA的作用方式为嵌插结合。以[Fe(phen)2IP]3+为杂交指示剂制成了DNA荧光光纤传感器,检测了与固定在光纤上的探针DNA互补的靶DNA。实验表明,检测的线性范围为1.25×10-8～1.50×10-7mol.L-1,检测限为1.35×10-9mol.L-1。     

基于双区理论的新抗癌铂络合物合成

<正>一切抗癌的烷化剂同时也都是致癌的，铂络合物抗癌药也井不例外‘”。双区理论发现，致癌剂引发细胞癌变的关键步骤是互补碱对间的横向交联。抗癌剂研究的长期实践证朋，癌细胞的修复能力虽然弱于正常哺乳动物细胞，却强于原核细胞，所以抗癌要求双官能或多官能烷化剂，或在体内形成的双官能烷化剂的作用。即对于杀伤癌细胞，引起其股内和股间的各种形式的横向交联是必要的。氮芥等多数抗癌烷化剂，其亲电中心的距离远超过 2.80一3.00人，共引起的股间横向交联必然主要是非互补碱对性质的，因此抗癌并不一定要求互补碱对之间的横向交联。因此，为了加强抗癌烷化剂对正常细胞和癌细胞作用的选择性，双区理论在抗癌剂合成中的必然可以引伸的指导思想，是应力图促使抗癌药在体内引起DNA股内或股间非互补碱对的交联，而避免互补碱对的交联。     

基于神经网络的一种PID控制技术

提出了一种基于神经网络的ＰＩＤ控制方案。用神经网络辨识器与神经网络控制器构成间接自校正控制系统,其中,神经网络辨识器采用单稳层结构,其辨识算法采用预报误差（ＲＰＥ算法）：神经网络控制器为２层的线性结构,具输入为系统偏差及其一阶和于阶微分,控制器具有增量型ＰＩＤ控制结构。将该控制方案应用于电阻炉的炉温控制中,获得了满意结果。     

基于RBF神经网络的非线性模型预测控制

提出了一种基于径向基函数(RBF)神经网络的非线性模型预测控制系统,利用RBF神经网络的非线性拟合性,构建一个神经网络预测器(NNP)来预测模型未来时刻的输出值.然后利用神经网络控制器(NNC)实现基于模型的预测控制.仿真结果表明此方法具有较好的控制效果,并且在有扰动和模型失配的情况下,表现了良好的鲁棒性.