PSO算法下GP-周期随机共振的微弱OFDM信号检测

为了解决传统随机共振系统在微弱正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)信号解调应用中存在的人工选择参数困难、解调效果差的问题,提出一种基于粒子群优化(Particle Swarm Optimization,PWO)算法的GP(Gaussian Potential)-周期随机共振系统的微弱OFDM信号检测方法。该方法利用GP-周期随机系统对OFDM信号经正交变换后的两路高频信号分别进行随机共振,同时运用阻尼参数与信号频率之间的关系对两路信号进行降频处理,使得上下两路信号都能够发生随机共振;然后使用PWO算法对随机共振的系统参数进行优化处理,以使得上下两路信号达到最优的共振效果;最后,将上下两路共振之后的信号合成完成OFDM信号解调,得到最终的数字序列。本文探讨了优化前后GP-周期随机共振系统的共振效果,研究了优化前后GP-周期随机共振诱导下的OFDM系统星座图的聚集程度以及误码率情况,对比分析了经典双稳随机共振、经典三稳随机共振和所提模型对OFDM信号检测的影响。仿真结果表明:相比常用的传统随机共振模型,该方法用于OFDM信号检测的星座图中信号点的聚集程度更高,同时OFDM系统误码率在同样的信噪比下降低50%左右。

Time-Domain Analysis of the Periodically Discontinuously Forced Fractional Oscillators

A new method for the solution of non-sinusoidal periodic states in linear fractionally damped oscillators is presented. The oscillator is forced by a periodic discontinuous waveform and a viscous element is taken into account. The presented method avoids completely the Fourier series calculations of the input and output oscillator waveforms. In the proposed method, the steady-state response of fractionally damped oscillator is formulated directly in the time domain as a superposition of the zero-input and forced responses for each continuous piecewise segments of the forcing waveform, separately. The whole periodic response is reached by taking into account the continuity and periodicity conditions at instants of discontinuities of the excitation and then using the concatenation procedure for all segments. The method can be applied efficiently to discontinuous and continuous non-harmonic excitations equally well. Solutions are exact and there is no need to apply any of the widely up-to-date used frequency approaches. The Fourier series is completely cut out of the oscillator analysis.

Experimental Investigation on the Effect of Seal Presence on the Behavior of Double-Deck Floating Roofs in Cylindrical Steel Storage Tanks

Liquid storage,particularly oil and petrochemical products which are considered hazardous liquid,are an important part of the oil industry.Thin-walled vertical cylindrical steel storage tanks are widely used in recent years.Due to high sensitivity of these structures in an earthquake and other external excitations may lead to catastrophic consequences.For instance,huge economic losses,environmental damages,and casualities,many studies have been done about these structures.past studies showed that liquid storage tanks,equipped with a floating roof,are potentially vulnerable while subjected to seismic loads and earthquake has been considered as one of the most destructive natural hazards.The reason is that such tanks are made of two separated parts(shell and roof)which each may have its own responses;sometimes causing resonance phenomenon and so that,roof movements,rooffluid interaction,roof-shell interaction,and also the way they are attached should still be investigated.Experimental tests of floating roof’s vertical fluctuation was performed in a full-scale reservoir tank and assessing of the results demonstrated that presence of a seal between floating roof and shell plate can significantly increase damping ratio in liquid sloshing and also suppress the roof`s vertical displacements.In other words,seal can control a floating roof and make it stop moving vertically over few cycles.

弹性SDOF体系地震动输入能量的影响因素分析

按美国抗震设计规范ATC 3-06的分类标准将4种场地类别上的420条地震波记录分为12组,进行了大量的单自由度(SDOF)体系的弹性时程分析;重点研究了场地类别、地震设计分组及阻尼比对地震动输入能量的影响;通过回归分析建立了考虑不同阻尼比影响的地震峰值等效速度与地震特征周期的相关公式。结果表明:随着阻尼比的增大,地震动输入能量呈降低趋势;地震设计分组及场地类别对地震动输入能量有显著影响。

Seismic response of bridge pier on rigid caisson foundation in soil stratum

An analytical method to study the seismic response of a bridge pier supported on a rigid caisson foundation embedded in a deep soil stratum underlain by a homogeneous half space is developed. The method reproduces the kinematic and inertial responses, using translational and rotational distributed Winkler springs and dashpots to simulate the soil-caisson interaction. Closed-form solutions are given in the frequency domain for vertical harmonic S-wave excitation. Comparison with results from finite element （FE） analysis and other available solutions demonstrates the reliability of the model. Results from parametric studies are given for the kinematic and inertial responses. The modification of the fundamental period and damping ratio of the bridge due to soil-structure interaction is graphically illustrated.

Research of Climatic Zoning Index System of Red Cartridge Kiwifruit in Guizhou

The climate data of 84 meteorological stations in Guizhou from 1981 to 2010 was used,including the statistical data of daily precipitation,temperature,sunshine hours,evaporation,frost free period and so on. Using the equations of light and heat coefficient,light and heat index,latitude and temperature index,active accumulated temperature,effective accumulated temperature,aridity index,and arid-wet index,the red cartridge kiwifruit zoning index of Guizhou was analyzed and studied. The results showed that the zoning index system for the climatic characteristics of Guizhou mountainous area must be established in order to realize the variety regionalization of red cartridge kiwifruit in Guizhou mountainous area,and ten climatic factors were taken as climatic zoning indexes of red cartridge kiwifruit planting,including active accumulated temperature,effective accumulated temperature,annual average temperature,average temperature of July,light and heat coefficient,light and heat index,latitude and temperature index,frost free period,aridity index and arid-wet index. These indicators were giving a comprehensive evaluation for climate suitability conditions of red cartridge kiwifruit planting,and providing the scientific and reasonable basis for the promotion planting of red cartridge kiwifruit in mountain area of Guizhou.

Effect of long period stacking ordered phase on damping capacities of as-cast Mg-Zn-Y alloys

The microstructure and damping capacities of MgZnxYi.33x(x=l-4at.%)alloys were discussed and researched.The main phase composition of the alloys consists of a_Mg and long-period stacking ordered(LPSO)phase.Due to increasedLPSO phase,grain size was refined.LPSO phase was advantageous to the damping properties of the Mg-Zn-Y alloys.Mg-7%Zn-12.8%Y has the highest damping capacity up to0.04.Due to stacking fault probability,the LPSO phase in the Mg-Zn-Yalloys could be new damping source to dissipate energy so as to contribute to the improvement of damping capacities.

Fundamental Characteristics of Reduction System for Seismic Response using Friction Force

A new device of reduction for seismic response using friction force was developed. In this paper, fundamental characteristics of reduction system for seismic response using this device were investigated by excitation experiment using artificial seismic waves. The peak acceleration amplitude on this system has decreased to about 50-90% over the input waves. Although a spectral peak around the frequency of 0.5Hz that is the natural period of this system was identified, the value of a spectral peak was decreased using bearings with the high friction force. This device is useful for reduction of seismic response.

Dynamic Analysis of a Single-Column Platform (II)

This paper describes the study of a single-column structure used as well-head platform. In order to check the reliability of computation theory and programme, model tests have been carried out. The paper introduces the conclusion of tests and the dynamic properties of single-column platform are obtained.

Dynamic Analysis of a Single-Column Platform

In this paper, a single-column structure used as well-head platform is studied. The loads of wave and current exerted on the single-column will be greatly reduced, therefore the cost of the structure will be decreased. The advantages of the single-column structure compared with ordinary jacket structure are explained. A dynamic analysis of this type of structure is made and some problems related to dynamic analysis are solved. In order to check the reliability of computation theory and programme, model tests have been carried out. However, as space is limited, the conclusion of tests will be introduced in another paper. Therefore, this type of structure is applicable for proctical engineering.

CFRP层合周期结构的阻尼性能

碳纤维复合材料(CFRP)层合周期结构由于具有优异的阻尼性能,适用于多种减振装置,但是,其刚度、阻尼等振动特性会受到铺层方式的周期变化、纤维的非连续性等因素的影响。针对CFRP层合周期结构的特点,设计了一种沿长度方向单周期包含两个元胞的CFRP层合周期结构板,制备了相应试验件并进行了自由模态试验,研究该结构阻尼性能变化规律。实验结果表明,随着周期个数与元胞单元厚度占比的增加,一阶和二阶阻尼损耗因子逐渐变大,一阶和二阶弯曲固有频率逐渐下降;保持CFRP层合周期结构中一个元胞的铺层角度不变,随着另一个元胞铺层角度的增加,一阶、二阶阻尼损耗因子都呈现先增大后减小的趋势,一阶和二阶弯曲固有频率在铺层角度为15°时达到最大值,之后随着铺层角度的增加呈现出轻微上下波动的变化,并未出现较大波动。当CFRP层合周期结构板元胞单元厚度占比为50%、周期个数为4时,相比于传统的CFRP层合板,前两阶弯曲模态下的阻尼损耗因子分别提高19.59%和15.63%,通过三点弯曲试验测试结果得知,该结构弯曲刚度相比传统CFRP层合板降低18.21%。

周期阻尼结构在驾驶室降噪铝钢板隔声特性上的应用

针对驾驶室降噪用大块阻尼铺设的缺陷,提出了二周阻尼铝-钢板敷设方式,通过建立周期阻尼结构振动数学模型,仿真计算研究了周期阻尼结构模态分析,并分析了铝-钢板密度、阻尼块密度和形状三个主要参数对隔声量的影响,最后对比周期阻尼和大块阻尼隔声效果。结果表明:模态振幅减小的变化趋势随着频率的增大越来越明显,说明具有周期阻尼的更有利于降低铝-钢板结构的振动;隔声效果随着铝-钢板密度和阻尼块密度的增加而增大,在250~1000 Hz的中高频段,隔声量增加得更为明显。

考虑时间效应的钢渣填料动力特性与微观结构研究

钢渣是冶金行业的第二大废弃物,充分利用废弃钢渣代替部分砂石料作为新型的土工填料,符合“绿色经济”与“可持续发展”战略。因钢渣材料有别于砂石料,化学成分复杂,而力学特征具有时效特性,采用共振柱试验研究考虑水化期影响的钢渣动力特性,分析动剪切模量和阻尼比等动力特性变化规律;基于Hardin-Drnevich双曲线模型描述考虑时间效应的钢渣动力特性,采用Boltzman函数描述最大动剪切模量随水化期变化的关系,给出最大阻尼比范围;并与传统砂土的动力特性对比,得出水化前钢渣动剪切模量略高于传统细砂,水化90 d后可达到标准砂的最大动剪切模量,工程中可以用钢渣作为一种填料代替砂土。最后,通过微观电子显微镜方法分析不同水化期下的钢渣微观结构,发现水化产物Aft相较于其他水化产物生成时间较晚,Aft和C-S-H所组成的胶凝结构是影响钢渣动力特性时效特征的主要因素。

Runoff Variation Law and Its Response to Climate Change in the Headstream Area of the Keriya River Basin,Xinjiang

Based on the runoff and meteorological data of Langan（兰干） Hydrological Station from 1957 to 2009 in Keriya（克里雅） River,the periodicities,abrupt changes,and trends of climate factors and runoff were investigated by wavelet analysis and nonparametric test;then,the future change of the annual runoff was predicted by a periodic trend superposition model.In succession,the influencing volumes of climate change on the annual runoff were separated from the observation values of the an-nual runoff in Keriya River.The results show that（1） temperature series increased significantly,while the annual runoff and precipitation of Keriya River increased insignificantly at the significant level of α=0.05;（2） the common periods of 9 and 15 years existed in the annual runoff evolution process,and the primary periods of temperature and precipitation were 9 and 22 years and 9 and 13 years,respec-tively;（3） the annual runoff did not vary simultaneously with the abrupt change of climate factors in the headstream;the abrupt points of annual runoff and temperature are at 1998 and 1980 year,and that of precipitation is not so significant;and（4） the annual runoff will experience a decrease trend in the future period;the total increasing volume owing to climate change is 23.154×108 m3 in the head-stream during the period of 1999-2009;however,the stream flow has been nearly utilized completely due to the human activities in the mainstream area of Keriya River.

西北干旱区气候变化对灌溉春玉米生产的影响

基于河西走廊中部1984-2022年灌溉春玉米定位观测试验,结合同期气象资料,采用线性回归、相关分析和M-K突变检验等方法,分析气候变化对西北干旱区灌溉春玉米生育期和产量的影响。结果表明:春玉米全生育期平均气温以0.76℃·10a^(-1)的速率呈极显著上升趋势(P<0.01)。≥10℃活动积温呈显著增加趋势,平均每10a增加135.80℃·d。全生育期降水量增加趋势不显著,但乳熟-成熟期以4.50mm·10a^(-1)的速率显著增加(P<0.05)。1984-2004年日照时数以126.88h·10a^(-1)的速率显著增多,近19a以109.38h·10a^(-1)的速率显著减少。1984-2004年春玉米生长期长度以9.86d·10a^(-1)的速率显著延长,近19a以7.39d·10a^(-1)的速率显著缩短。播种-出苗期和七叶-拔节期长度与气温呈显著负相关;播种-出苗期、三叶-七叶期和吐丝-乳熟期长度与降水量呈显著正相关;各生育期长度均与日照时数呈显著正相关。研究期内春玉米产量呈波动变化,气候产量与全生育期内降水量呈显著负相关。综上所述,西北干旱区气候变化对当前灌溉方式下的春玉米生产不利。

周期约束阻尼设计板结构减振降噪特性分析

为了探究更加高效的阻尼减振降噪结构设计,结合人工周期结构特性与约束阻尼减振降噪技术,通过对基体板和不同约束阻尼板结构的振动与声辐射进行有限元仿真计算和实验测试,分析周期约束阻尼设计板结构的减振降噪特性。研究结果表明,相比于传统约束阻尼设计,周期约束阻尼设计可以在附加阻尼质量相同的情况下,更加有效抑制基体板宽频振动与声辐射,尤其对350Hz以下的低频振动与噪声状况具有一定改善作用,并有助于实现阻尼结构的轻量化。同时,周期约束阻尼设计也可能会增大约束层的振动与噪声以及改变结构的声辐射效率。总体而言,周期性设计对于改善约束阻尼减振降噪性能具有积极意义。

地铁弹性整体道床钢轨波磨产生机理及影响因素研究

为实现弹性轨道系统响应的准确求解,揭示地铁曲线钢轨波磨产生机理,应用动力学理论和有限元方法建立车辆-弹性轨道系统动力学模型,研究地铁减振轨道振动特性下钢轨波磨产生原因及影响。结果表明,轨道垂/横向振动以及具有周期性变化特征的轮轨蠕滑力(横向)和磨耗指数(垂向)等多种因素的共同作用促进了钢轨波磨的产生,即轨道系统共振和钢轨周期性磨耗特征导致钢轨波磨的产生;车辆满载、摩擦因数大、曲线半径小以及轨道失效时,钢轨波磨更易产生;内侧钢轨比外侧更快出现波磨现象。研究成果可为地铁线路的减振降噪提供理论依据。

化瘀软肝解毒方联合中频脉冲电治疗肝郁脾虚并湿热留恋型乙型肝炎肝硬化代偿期患者的疗效评估

目的:评估化瘀软肝解毒方联合中频脉冲电治疗肝郁脾虚合并湿热留恋型乙型肝炎肝硬化代偿期患者的治疗效果。方法:选取2021年4月至2022年6月诊治的乙型肝炎肝硬化代偿期患者160例,用随机数字表法将其分为对照组和试验组,每组80例。两组患者均给予抗乙型肝炎病毒治疗,对照组患者给予中频脉冲电治疗,试验组患者在对照组治疗基础上给予化瘀软肝解毒方治疗。分析两组患者中医证候疗效,肝功能指标变化,上消化道出血、腹腔积液及肝细胞癌的发生率,生活质量调查简表(SF-36)评分的改善情况。结果:治疗后,试验组患者的总有效率高于对照组(P<0.05);治疗第26、52周以及治疗结束后第26周、52周,两组患者血清总胆红素(TBil)、丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)水平降低,白蛋白(Alb)、胆碱酯酶(CHE)水平升高,且试验组患者血清TBil、ALT、AST水平低于对照组,Alb、CHE水平高于对照组(P<0.05);试验组患者上消化道出血、腹腔积液及肝细胞癌的总发生率低于对照组(P<0.05);治疗后两组患者的SF-36评分均高于治疗前,且试验组高于对照组(P<0.05)。结论:化瘀软肝解毒方联合中频脉冲电治疗效果理想,安全性高,可明显保护肝功能,降低肝硬化重要并发症的发生率,提高患者生活质量。

利用手机CMOS图像传感器测弹簧弹性系数

测量弹簧劲度系数一般有两种方法:拉伸法和简谐振动法.在传统拉伸法测量中,大多通过增减砝码来间接测量,在传统简谐振动法测量实验中,大多采用光电门对弹簧振子周期进行计时.本文主要利用智能手机CMOS图像传感器来测量简谐振动的振子位置随时间变化图像,从图像中提取周期和阻尼信息,进而得出弹簧的弹性系数.改进后,实验数据测量的标准偏差和相对误差较小,分别为0.003 7 N/m和0.26%.本实验能够详细地观察到弱阻尼简谐振动的物理图像,测量出空气和水中的弱阻尼系数.

基于多场融合的开关柜缺陷分析

高压开关柜作为承担电力运输开断功能的重要设备,具有数量多、故障发生频繁、缺陷难以及时发现等特点。因此开关柜内部部件受潮、老化的发展过程及状态监测也成为了电力行业的研究热点。从一起35kV开关柜的受潮故障出发,研究了开关柜在受潮发展过程中相关参数的变化,提出了基于热场——力场——电场的多场融合缺陷分析方法,并验证了该方法的有效性,为开关柜设备的全生命周期管理提供了理论支撑。