认知无线网络频谱协作感知能耗与吞吐量的凸优化研究

针对认知无线电(cognitive radio,CR)双门限频谱协作感知能量效率与吞吐量优化的问题,提出了利用凸优化理论使能量效率与网络吞吐量达到最优平衡.在能耗一定条件下推导吞吐量关于虚警率与检测率等参数的目标方程;然后,对虚警率和检测率作合理约束,利用凸优化理论对吞吐量方程分析,推导出最优化目标函数的服从条件在一定范围内,关于感知时间与较大门限值满足联合凸或分别凸,吞吐量目标函数的变形在一定范围内,关于感知时间与较大门限值满足联合凸或分别凸;最后,利用凸优化工具获得感知时间与感知门限的最优值.理论分析和仿真结果表明,在能耗一定条件下,对于较为广泛的信噪比区间,该优化方案均可明显提高网络吞吐量及双门限认知无线电频谱协作感知的能量效率.     

基于正交试验设计的粒子群优化算法

针对粒子群优化(particle swarmopti mization,PSO)算法在进化初期收敛速度快但容易陷入局部最优、在进化后期收敛速度变慢且精度低的缺陷,为了提高粒子群算法的收敛速度和全局寻优能力,提出了基于正交试验设计的粒子群优化(orthogonal-experi mental-design-based PSO)算法.在基本粒子群算法的基础上,算法OE-PSO对当前搜索到的解进行局部寻优,利用正交试验设计对搜索空间的分布均匀性在可行解的领域选择有代表性的解进行测试.算法OE-PSO用搜索到的更好的解在下一次迭代中引导粒子进行搜索,从而获得更快的收敛速度和更精确的解,同时避免局部最优.实验结果表明,算法OE-PSO不但具有较快的收敛速度,而且能够有效提高解的精确性,增强算法的鲁棒性.     

基于数值分析理论的低复杂度MED算法

经典的最大特征值检测（MED）算法在检测相关信号时具有优异的性能.然而,随着信号维度的不断增大,MED算法面临着严重的感知判决量和判决门限计算的效率和实现问题,从而极大地限制了该算法在现代认知通信系统中的进一步应用.为此,提出了一种基于数值分析理论框架的低复杂度MED频谱感知算法.所提算法利用Rayleigh商加速幂法迭代地计算感知判决量,与经典的幂法相比,在检测高维信号时具有更快的收敛速度;此外,不同于经典的查表法,新算法基于三次样条插值法快速、准确地确定任意给定目标虚警概率所对应的感知判决门限.所提MED算法在保持原有算法检测性能的同时,有效提升了计算效率,降低了算法实现复杂度;其对于高维条件下的频谱感知问题尤其具有吸引力.最后,仿真结果证明了所提算法的有效性.     

基于改进粒子群优化的快速协作式频谱感知算法

为了改进算法的计算效率和感知性能,提出了一种新的线性协作式频谱感知算法.在新算法中,通过动态地改变粒子群优化（PSO）方法在每次迭代过程中的迭代系数,以获取最优的权重向量,从而最大化算法的检测概率.采用时变迭代系数后,基于PSO的协作式频谱感知算法在粒子飞行的初期具有很好的全局探索能力,而随着迭代次数的增加,算法具有很好的局部搜索能力.仿真结果表明,新算法相比基于传统PSO的频谱感知算法具有更快的收敛速度,相比传统的基于修正系数和基于传统PSO的协作式感知算法具有更好的性能.不同场景下的仿真结果验证了新算法的有效性.     

基于不完全频谱感知的认知中继网络能量效率研究

针对认知中继网络中基于能量效率的资源分配问题,提出一种基于次用户能量效率最大化的功率分配优化算法,通过建立多重约束条件下的频谱感知和传输联合优化模型,在考虑单位发射速率消耗功率和干扰限制的情况下,利用分数规划将问题中的混合整数非线性规划问题转化为等价的凸优化问题,分析了不同参数对能量效率的影响。仿真结果表明,提出的功率分配优化算法在达到能量效率最优的同时降低了算法复杂度低。     

无人机无线能量传输网络多波束阵列设计与位置部署

针对无人机(unmanned aerial vehicle, UAV)辅助的无线能量传输(wireless power transfer, WPT)系统，构建了一种能量波束设计以及无人机悬停位置部署的联合优化方案，以最大化所有用户接收的总能量。针对优化问题是非凸、难以直接求解的情况，提出一种联合优化多波束设计和无人机三维位置的迭代算法，利用巴特勒矩阵设计高增益、宽覆盖范围的能量多波束，利用穷举算法寻找无人机最优二维位置，通过单调性理论得到无人机的最佳悬停高度。仿真结果表明，所提出的算法能显著提升无线能量传输效率。     

基于混合鲸鱼优化算法的鲁棒多用户检测

针对冲击噪声环境下多用户检测误码率高的问题,提出一种基于混合鲸鱼优化的鲁棒多用户检测算法。该算法首先利用基于非线性控制策略的改进鲸鱼优化算法,加速寻优算法迭代过程的收敛;再利用自适应差分进化算法丰富算法种群个体信息,增强优化算法的全局收敛性;同时将适应度较好的个体信息保存到集合中,以保证下一次迭代寻优方向的可靠性,最终实现对最优解位置的快速解算。仿真结果表明,基于本文算法设计的多用户检测器相比采用遗传算法、差分进化算法,以及鲸鱼优化算法的多用户检测器寻优迭代次数更少,且误码率低。     

基于MDFT滤波器组的两步检测算法

认知无线电(Cognitive Radio, CR)在解决频谱资源匮乏问题和提高频谱资源利用率方面被寄予厚望。频谱感知的循环特征检测算法复杂度较高,而能量检测算法在信噪比比较低的情况下检测性能不理想,针对这种情况,在改进离散傅里叶变换(MDFT)滤波器组结构的多载波调制系统中,提出一种基于MDFT滤波器组调制的两步检测算法。该算法结合了循环特征检测较强的抗噪声干扰特性以及能量检测算法复杂度低的优势。仿真结果表明：所给出的两步检测算法在较低信噪比时相对于MDFT能量检测、OFDM循环特征检测等其他算法,其检测性能有明显改善,同时较MDFT循环特征检测算法可有效降低算法复杂度。     

嵌入不动点迭代法的粒子群算法

针对利用粒子群优化算法寻找最优极值的问题,本文提出了一种对粒子群优化算法的改进方式.在粒子群优化算法中,加入不动点迭代法,即在进行粒子群迭代寻优之后,再利用不动点迭代策略再次进行迭代寻优计算.通过两次迭代寻优计算,让算法更加快速的收敛到最优值,并且能够找到更小的极值,且不易陷入局部极值.让粒子群算法更加稳定,寻优更加优化.     

基于改进离散傅里叶变换滤波器组的两步检测算法

认知无线电(cognitive radio,CR)在解决频谱资源匮乏问题和提高频谱资源利用率方面被寄予厚望。频谱感知的循环特征检测算法复杂度较高,而能量检测算法在信噪比比较低的情况下检测性能不理想;针对这种情况,在改进离散傅里叶变换(MDFT)滤波器组结构的多载波调制系统中,提出一种基于MDFT滤波器组调制的两步检测算法。该算法结合了循环特征检测较强的抗噪声干扰特性,以及能量检测算法复杂度低的优势。仿真结果表明:所给出的两步检测算法在较低信噪比时相对于MDFT能量检测、OFDM循环特征检测等其他算法,其检测性能有明显改善;同时MDFT循环特征检测算法可有效降低算法复杂度。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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