Low-complexity signal detection for massive MIMO systems via trace iterative method

Linear minimum mean square error(MMSE)detection has been shown to achieve near-optimal performance for massive multiple-input multiple-output(MIMO)systems but inevitably involves complicated matrix inversion,which entails high complexity.To avoid the exact matrix inversion,a considerable number of implicit and explicit approximate matrix inversion based detection methods is proposed.By combining the advantages of both the explicit and the implicit matrix inversion,this paper introduces a new low-complexity signal detection algorithm.Firstly,the relationship between implicit and explicit techniques is analyzed.Then,an enhanced Newton iteration method is introduced to realize an approximate MMSE detection for massive MIMO uplink systems.The proposed improved Newton iteration significantly reduces the complexity of conventional Newton iteration.However,its complexity is still high for higher iterations.Thus,it is applied only for first two iterations.For subsequent iterations,we propose a novel trace iterative method(TIM)based low-complexity algorithm,which has significantly lower complexity than higher Newton iterations.Convergence guarantees of the proposed detector are also provided.Numerical simulations verify that the proposed detector exhibits significant performance enhancement over recently reported iterative detectors and achieves close-to-MMSE performance while retaining the low-complexity advantage for systems with hundreds of antennas.

Research on Design Method of the Full Form Ship with Minimum Thrust Deduction Factor

In the preliminary design stage of the full form ships, in order to obtain a hull form with low resistance and maximum propulsion efficiency, an optimization design program for a full form ship with the minimum thrust deduction factor has been developed, which combined the potential flow theory and boundary layer theory with the optimization technique. In the optimization process, the Sequential Unconstrained Minimization Technique（SUMT） interior point method of Nonlinear Programming（NLP） was proposed with the minimum thrust deduction factor as the objective function. An appropriate displacement is a basic constraint condition, and the boundary layer separation is an additional one. The parameters of the hull form modification function are used as design variables. At last, the numerical optimization example for lines of after-body of 50000 DWT product oil tanker was provided, which indicated that the propulsion efficiency was improved distinctly by this optimal design method.

A New Regularized Minimum Error Thresholding Method

To overcome the shortcoming that the traditional minimum error threshold method can obtain satisfactory image segmentation results only when the object and background of the image strictly obey a certain type of probability distribution,one proposes the regularized minimum error threshold method and treats the traditional minimum error threshold method as its special case.Then one constructs the discrete probability distribution by using the separation between segmentation threshold and the average gray-scale values of the object and background of the image so as to compute the information energy of the probability distribution.The impact of the regularized parameter selection on the optimal segmentation threshold of the regularized minimum error threshold method is investigated.To verify the effectiveness of the proposed regularized minimum error threshold method,one selects typical grey-scale images and performs segmentation tests.The segmentation results obtained by the regularized minimum error threshold method are compared with those obtained with the traditional minimum error threshold method.The segmentation results and their analysis show that the regularized minimum error threshold method is feasible and produces more satisfactory segmentation results than the minimum error threshold method.It does not exert much impact on object acquisition in case of the addition of a certain noise to an image.Therefore,the method can meet the requirements for extracting a real object in the noisy environment.

Determination of the Minimum Testing Time for Wireline Formation Testing with the Finite Element Method

The wireline formation tester （WFT） is an important tool for formation evaluation, such as calculating the formation pressure and permeability, identifying the fluid type, and determining the interface between oil and water. However, in a low porosity and low permeability formation, the supercharge pressure effect exists, since the mudcake has a poor sealing ability. The mudcake cannot isolate the hydrostatic pressure of the formation around the borehole and the mud seeps into the formations, leading to inaccurate formation pressure measurement. At the same time, the tool can be easily stuck in the low porosity/low permeability formation due to the long waiting and testing time. We present a method for determining the minimum testing time for the wireline formation tester. The pressure distribution of the mudcake and the formation were respectively calculated with the finite element method （FEM）. The radius of the influence of mud pressure was also computed, and the minimum testing time in low porosity/low permeability formations was determined within a range of values for different formation permeabilities. The determination of the minimum testing time ensures an accurate formation pressure measurement and minimizes possible accidents due to long waiting and testing time.

Generalized Minimum Perpendicular Distance Square Method of Estimation

In case of heteroscedasticity, a Generalized Minimum Perpendicular Distance Square (GMPDS) method has been suggested instead of traditionally used Generalized Least Square (GLS) method to fit a regression line, with an aim to get a better fitted regression line, so that the estimated line will be closest one to the observed points. Mathematical form of the estimator for the parameters has been presented. A logical argument behind the relationship between the slopes of the lines and has been placed.

An Improved Minimum Distance Method Based on Artificial Neural Networks

MDM (minimum distance method) is a very popular algorithm in staterecognition. But it has a presupposition, that is, the distance within one class must be shorterenough than the distance between classes. When this presupposition is not satisfied, the method isno longer valid. In order to overcome the shortcomings of MDM, an improved minimum distance method(IMDM) based on ANN (artificial neural networks) is presented. The simulation results demonstratethat IMDM has two advantages, that is, the rate of recognition is faster and the accuracy ofrecognition is higher compared with MDM.

On the Computing of the Minimum Distance of Linear Block Codes by Heuristic Methods

The evaluation of the minimum distance of linear block codes remains an open problem in coding theory, and it is not easy to determine its true value by classical methods, for this reason the problem has been solved in the literature with heuristic techniques such as genetic algorithms and local search algorithms. In this paper we propose two approaches to attack the hardness of this problem. The first approach is based on genetic algorithms and it yield to good results comparing to another work based also on genetic algorithms. The second approach is based on a new randomized algorithm which we call 'Multiple Impulse Method (MIM)', where the principle is to search codewords locally around the all-zero codeword perturbed by a minimum level of noise, anticipating that the resultant nearest nonzero codewords will most likely contain the minimum Hamming-weight codeword whose Hamming weight is equal to the minimum distance of the linear code.

可倾瓦推力轴承惰转过程的最小膜厚预测方法

为建立可倾瓦推力轴承惰转过程中最小油膜厚度的预测方法,依据核主泵推力轴承的实际工作情况,基于雷诺方程的自编程序,分别进行热态和冷态下主、副轴瓦润滑性能参数的计算与数值模拟分析,提出可倾瓦推力轴承的最小油膜厚度的理论拟合公式,并对最小膜厚的计算值和拟合值进行对比和分析。结果表明:随着转速降低,主轴瓦的最小膜厚单调减小,副轴瓦的最小膜厚先增加后减小;主、副轴瓦最小膜厚的计算值可以和拟合值较好地对应,验证了理论拟合公式的可靠性。提出的理论拟合公式可以通过额定转速下的最小膜厚计算结果预测多种工作条件下的最小油膜厚度,为主泵惰转的安全性提供重要参考。

基于fminimax优化函数的圆度误差评定

依据圆度误差标注代号和附加符号的含义,基于最小外接法、最大内切法和最小区域法分别建立了参考圆的圆心坐标优化目标函数和圆度误差评定模型,采用MATLAB软件编写了参考圆的圆心坐标优化目标函数子程序和圆度误差评定子程序,给出了圆度误差评定中fminimax优化函数调用方法。用Talyrond 585LT圆柱度测量仪对三个试样的圆周轮廓进行了提取,基于最小二乘法、最小外接法、最大内切法和最小区域法对提取的圆周轮廓分别进行了圆度误差评定。研究了优化搜索范围对圆度误差评定结果的影响,并将fminimax优化函数圆度误差评定的优化符合度与其他优化方法圆度误差评定的优化符合度进行了比较。fminimax优化函数的应用结果表明,评定结果精度高于或等于其他优化方法评定结果的精度,可满足圆度误差评定的需要。

中医体质分型对全麻诱导时七氟醚MAC值的影响

目的:探讨气管插管全麻诱导时,在常见的四种中医体质分型患者中,吸入七氟醚使意识消失的最低肺泡有效浓度的半数有效浓度(EC_(50))的差异。方法:研究纳入80例拟择期行气管插管全麻手术患者,根据《中医体质分类与判定》标准分为平和质(A组)、血瘀质(B组)、阴虚质(C组)、阳虚质(D组)共四组,每组20例。以吸入麻醉药七氟醚诱导麻醉,使患者意识消失,设定起始七氟醚的呼气末浓度为1.72%,并计算出5个阶梯的七氟醚呼吸末浓度值,分别为0.84%、1.21%、1.72%、2.45%和3.50%,最终用序贯法测定患者意识消失时七氟醚最低肺泡浓度的EC_(50)。结果:四组病人意识消失时七氟醚EC_(50)及对应的95%可信区间(CI)分别是:A组EC_(50)为2.37%(95%CI:1.97%~2.85%);B组EC_(50)为2.21%(95%CI:1.88%~2.58%):C组EC_(50)为2.83%(95%CI:2.63%~3.03%);D组EC_(50)为1.85%(95%CI:1.57%~2.18%)。结论:七氟醚最低肺泡有效浓度在不同中医体质患者中的存在一定差异性,阳虚患者七氟醚EC_(50)比阴虚患者明显降低。

基于组合赋权与灰云模型的综合能源系统需求响应效益评价

考虑到当前综合能源系统研究缺乏完善的需求响应量化评估方案,难以在优化运行层面综合评估需求响应效益这一问题,提出了一种基于改进AHP群决策—CRITIC组合赋权与灰云模型的综合能源系统需求响应效益评价方法。首先,从综合能效性、社会经济性和需求侧互动性三个维度构建了需求响应效益评价指标体系。其次,采用一致性和权重拟合性更优的指数标度法构造判断矩阵,降低赋值误差,并通过AHP群决策法确定主观权重,从而削弱主观极值偏差对权重的影响;在由CRITIC法确定客观权重后,基于最小欧氏距离建立组合权重模型,并通过非线性规划求取最优组合权重;针对评价等级信息的模糊性与隶属等级的随机性,采用正态灰云白化权模型确定指标分类等级与场景评分。最后,以北方某综合能源系统为例,根据用户参与需求响应方式设置了4种运行场景,分析了不同需求响应对系统运行的影响与作用,算例结果表明所提指标体系与评价方法科学有效。

基于能量原理不同含水率下煤岩体变形破坏能量损伤演化机制

为探究不同含水率下煤岩体在变形破坏过程中的能量演化规律与损伤演化特征,对双马一矿煤岩体开展了在不同含水率条件下单轴压缩试验,基于能量计算及最小耗能原理,分析不同含水率下煤岩体能量耗散特征及损伤演化机制,结果表明:不同含水率下煤岩体力学性质不同,峰值应变与含水率呈正相关,抗压强度、弹性模量与含水率呈负相关;煤岩体含水率越高,其在峰值处弹性应变能及破坏吸收总应变能越小,耗散能占总应变能比例越高;基于最小耗能原理建立的损伤本构模型表明:随着煤岩体含水率增加,损伤门槛值逐渐降低;干燥状态下,煤岩体在应力峰值处损伤变量分别为0.36、0.28,当含水率增至自然状态时,煤岩体在应力峰值处损伤变量值分别下降0.09、0.18,但当含水率增至饱水状态时,煤岩体在应力峰值处损伤变量值反而分别大幅度上升0.102、0.49,总体呈先减后增的发展趋势;进一步建立了不同含水率煤岩损伤应变能释放率演化模型,低含水率煤岩较干燥煤岩的最大损伤应变能释放率大幅度下降,降幅分别为45.61%、31.29%,而随着含水率增加至饱水状态,其最大损伤应变能释放率增大幅度较平缓,分别为3.08%、8.80%,表明煤岩破坏剧烈程度并未大幅度增加。研究成果对煤岩矿柱水害预测评价与岩石损伤评估具有一定参考意义。

配电网的最小供电能力:定义、模型、求解和应用

最小供电能力是最大供电能力的对偶指标,它们分别位于供电能力曲线的最低点和最高点。提出最小供电能力的定义、数学模型、求解方法和应用方法。建立最小供电能力的数学模型,它是严格安全边界上以总负荷最小为目标函数的线性规划模型;提出基于最大冗余方程的求解方法,以得到达到最小供电能力时的工作点,针对每个取得最小供电能力的边界,该方法将冗余量等于最大冗余的约束添加到边界约束中,形成最大冗余方程,通过求解该方程得到边界上最小供电能力点的表达式;对所有的最小供电能力点表达式取并集得到最终结果。算例结果验证了所提模型和方法的正确性。

中药混合液对耐甲氧西林金黄色葡萄球菌的体外抗菌作用的研究

目的探究中药混合液对耐甲氧西林金黄色葡萄球菌(Methicillin-resistant Staphylococcus Sureus,MRSA)的体外抗菌作用。方法选取2022年1月—2023年6月江苏省启东市中医院检验科临床分离的40株MRSA。万古霉素、中药混合液对MRSA的体外最低抑菌浓度(Minimum Inhibitory Concentration,MIC)值采用微量肉汤稀释法测定;用K-B纸片扩散法测定万古霉素和中药混合液对MRSA的抑菌效果,探究不同药物浓度对MRSA抑菌活性的影响。结果万古霉素MIC值为(1.56±0.55)mg/L,低于中药混合液的(1.63±0.62)mg/mL,差异有统计学意义(P<0.05)。万古霉素抑菌圈直径为(20.56±0.87)mm,优于中药混合液的(19.89±0.73)mm,差异有统计学意义(P<0.05)。抑菌圈直径大小随浓度增加而增大且中药混合液各浓度抑菌圈直径均大于万古霉素,差异有统计学意义(P均<0.05)。结论中药混合液对MRSA的体外最低抑菌浓度极低,可以有效抑制耐甲氧西林金黄色葡萄球菌的生长。

基于视觉传感器的钢管塔焊缝特征提取方法

为了快速、准确地提取输电钢管塔纵向焊缝的特征点,提出一种基于视觉传感器的钢管塔焊缝特征提取方法。通过激光视觉传感器采集焊缝图像,利用中值滤波、顶帽变换去除焊缝图像中因坡口表面弧光反射所产生的干扰信息,采用基于灰度值累加法和最小距离划分感兴趣区域,采用灰度重心法提取中心线,采用坐标法和Hough变换相结合提取特征点。试验表明,该方法能够稳定、准确地提取钢管塔焊缝的特征点,提取的焊缝特征点与实际焊点的误差均不大于0.23 mm,为基于视觉传感器的焊缝跟踪系统研究奠定了基础。

计及静态电压稳定约束的最少发电机优化调度方法

电压稳定控制中的控制数量多,且紧急状态时要求控制措施快速响应。构建一种以最少发电机调整数量为目标的优化调度数学模型,该模型为包含离散变量和连续变量的非线性混合整数规划问题,为快速获得高质量的可行解,提出一种由快速筛选和模型转化组成的阶段式求解方法。利用负荷裕度对发电机有功出力的灵敏度快速筛选出可提高负荷裕度的发电机集合,缩小离散变量的搜索范围;将原问题转化为混合整数线性规划子问题以及非线性规划子问题进行交替求解,得到需要调整的发电机数量及其出力。通过IEEE 118和IEEE 300节点系统进行测试,结果表明所提控制模型和求解方法可有效提高电力系统负荷裕度,减少可行解中包含的发电机调整数量,与分支定界法的对比验证了所提求解方法的快速性和有效性。

桌面级协作机械臂设计与仿真分析

由于桌面级协作机器人具有低成本、小型化、模块化等特点,被广泛的应用在医疗、食品、科研、3C等行业。针对模块化关节,设计了满足强度刚度要求、额定负载为1kg的桌面级协作机器人,建立了基于CoppeliaSim与Matlab的实验仿真平台。首先利用旋量法建立了机器人正、逆运动学模型,提出了基于最小变化角为准则的位置控制算法,成功的实现了机器人的运动控制,验证了正、逆运动学求解模型的准确性。实验平台的仿真结果表明,该算法能够有效的控制机器人的运动,具有实用性。

考虑建模误差的某型火箭末级制导方法研究

运载火箭末级发动机点火后,在制导系统的导引下,火箭最终抵达入轨位置、取得入轨速度,卫星进入运行轨道。火箭末级飞行动力学模型为非线性微分方程形式,难以利用解析方法得到火箭姿态变化特性,进而控制火箭飞行过程中的状态变量。将火箭入轨约束条件转化为最优控制的性能指标函数,利用庞德里亚金极小值原理与牛顿梯度法相结合的方式来解决动力学方程求解问题,得到末级飞行标准轨道;火箭动力学建模过程中,由于参数难以精确计量等的影响,存在建模误差,导致火箭实际飞行轨道会偏离标准轨道。对模型进行线性化处理,引入状态反馈,可以使实际飞行轨道接近于标准轨道,提高卫星荷载入轨要求精度。仿真结果表明:该制导算法可较好地减小火箭载荷入轨误差。

计及制冷系统和过热保护的含高温超导电缆配电网可靠性评估方法

为适应高温超导电缆商业化运行需求,提出一种考虑不同应用模式下制冷系统和过热保护影响的含高温超导电缆的配电网可靠性评估方法。依据高温超导电缆制冷系统的工作原理、故障特性及过热保护装置的动作逻辑和自动重合规则,对高温超导电缆系统可靠性进行建模分析。考虑了低压联络和配电线路增效2种典型应用模式下高温超导电缆接入对配电网的可靠性影响,采用融入了计及高温超导电缆的新增故障模式的最小割集法求解配电网可靠性指标,实现含高温超导电缆的配电网可靠性评估。以某实际配电网为算例,通过仿真分析了制冷系统故障和过热保护对配电网不同可靠性指标的影响,并与传统的配电网改造方案进行对比,验证了所提方法的有效性。

中国南方冬季最低温延伸期预报方法尝试

未来10~30天的延伸期预报一直是当前的难点问题.本文针对对极端低温事件异常敏感的中国南方地区,构建了预报时效为25天的冬季最低温的有效延伸期预报模型.利用1979/1980—2019/2020年冬季日平均再分析资料,本文研究发现,在季节内尺度,相比于原始变量,利用当候值减去其5候前值的增量方法可以放大和延长预测信号.中国南方地区的土壤温度和平流层50 hPa位势高度作为影响南方冬季最低温的关键因子,它们通过影响西伯利亚地区环流异常、北大西洋涛动以及欧亚遥相关型,对中国南方冬季最低温进行调制.由于两个增量形式的关键因子具有50天的准周期性,存在超前5候的显著自相关,超前5候增量形式的土壤温度和平流层极涡异常可以有效预报我国南方最低温增量.将预报的最低温增量,加上5候前的观测,得到的独立试报时段(2009/2010—2019/2020年冬季)的最低温与观测的时间相关系数为0.45,极端低温日命中率为57%.本研究使用的增量方法可以为当前极端天气事件的延伸期预报提供新思路.