Consecutive combined response spectrum

Appropriate estimates of earthquake response spectrum are essential for design of new structures, or seismic safety evaluation of existing structures. This paper presents an alternative procedure to construct design spectrum from a combined normalized response spectrum （NRSc） which is obtained from pseudo-velocity spectrum with the ordinate scaled by different peak ground amplitudes （PGA, PGV, PGD） in different period regions. And a consecutive function./（/） used to normalize the ordinates is defined. Based on a comprehensive study of 220 strong ground motions recorded during recent eleven large worldwide earthquakes, the features of the NRSc are discussed and compared with the traditional normalized acceleration, velocity and displacement response spectra （NRSA, NRSv, NRSD）. And the relationships between ground amplitudes are evaluated by using a weighted mean method instead of the arithmetic mean. Then the NRSc is used to define the design spectrum with given peak ground amplitudes. At last, the smooth spectrum is compared with those derived by the former approaches, and the accuracy of the proposed spectrum is tested through an analysis of the dispersion of ground motion response spectra.

Weighted Hard Combination for Cooperative Spectrum Sensing in Cognitive Radio Networks

Weighted one bit hard combination for cooperative spectrum sensing is proposed in this paper. Two thresholds are adopted to divide the possible energy value into three weighted regions. If the energy value falls into the corresponding region,it will be judged as "1",no information or "0". When the probability of false alarm is constrained to be constant,the objective is to maximize the probability of detection. The optimization problem is simplified by separating the weight of the middle region into several intervals. Simulation results show that the sensing performance of the proposed scheme is much better than that of the traditional one bit hard combination scheme and almost the same as that of the equal gain combination(EGC) scheme. Moreover,compared with the traditional one bit hard combination,fewer average sensing bits are required to transmit to the data fusion center with the proposed method.

A new spatial coherence model and analytical coeffi cients for multi-support response spectrum combination

In this paper, a new spatial coherence model of seismic ground motions is proposed by a fitting procedure. The analytical expressions of modal combination （correlation） coefficients of structural response are developed for multi-support seismic excitations. The coefficients from both the numerical integration and analytical solutions are compared to verify the accuracy of the solutions. It is shown that the analytical expressions of numerical modal combination coefficients are of high accuracy. The results of random responses of an example bridge show that the analytical modal combination coefficients developed in this paper are accurate enough to meet the requirements needed in practice. In addition, the computational efficiency of the analytical solutions of the modal combination coefficients is demonstrated by the response computation of the example bridge. It is found that the time required for the structural response analysis by using the analytical modal combination coefficients is less than 1/20 of that using numerical integral methods.

Collaborative Spectrum Sensing for Cognitive Radio: Diversity Combining Approach

In this paper it is shown that cyclostationary spectrum sensing for Cognitive Radio networks, applying multiple cyclic frequencies for single user detection can be interpreted (with some assumptions) in terms of optimal incoherent diversity addition for “virtual diversity branches” or SIMO radar. This approach allows proposing, by analogy to diversity combining, suboptimal algorithms which can provide near optimal characteristics for the Neyman-Pearson Test (NPT) for single user detection. The analysis is based on the Generalized Gaussian (Klovsky-Middleton) Channel Model, which allows obtaining the NPT noise immunity characteristics: probability of misdetection error (PM) and probability of false alarm (Pfa) or Receiver Operational Characteristics (ROC) in the most general way. Some quasi-optimum algorithms such as energetic receiver and selection addition algorithm are analyzed and their comparison with the noise immunity properties (ROC) of the optimum approach is provided as well. Finally, the diversity combining approach is applied for the collaborative spectrum sensing and censoring. It is shown how the diversity addition principles are applied for distributed detection algorithms, called hereafter as SIMO radar or distributed SIMO radar, implementing Majority Addition (MA) approach and Weighted Majority Addition (WMA) principle.

An adaptive over/under data combination method

The traditional ＂dephase and sum＂ algorithms for over/under data combination estimate the ghost operator by assuming a calm sea surface. However, the real sea surface is typically rough, which invalidates the calm sea surface assumption. Hence, the traditional ＂dephase and sum＂ algorithms might produce poor-quality results in rough sea conditions. We propose an adaptive over/under data combination method, which adaptively estimates the amplitude spectrum of the ghost operator from the over/under data, and then over/under data combinations are implemented using the estimated ghost operators. A synthetic single shot gather is used to verify the performance of the proposed method in rough sea surface conditions and a real triple over/under dataset demonstrates the method performance.

Hilbert spectrum and intrinsic oscillation mode of dynamic response of a bilinear SDOF system: influence of harmonic excitation amplitude

Under harmonic wave excitation, the dynamic response of a bilinear SDOF system can be expressed by the Hilbert spectrum. The Hilbert spectrum can be formulated by (1) the inter-wave combination mechanism between the steady response and the transient response when the system behaves linearly, or (2) the intra-wave modulation mechanism embedded in one intrinsic mode function (IMF) component when the system behaves nonlinearly. The temporal variation of the instantaneous frequency of the IMF component is consistent with the system nonlinear behavior of yielding and unloading. As a thorough study of this fundamental structural dynamics problem, this article investigates the influence of the amplitude of the harmonic wave excitation on the Hilbert spectrum and the intrinsic oscillatory mode of the dynamic response of a bilinear SDOF system.

Research on Strong Pulsed Electromagnetic Field Test Method by Time-frequency Combination

Many conventional methods of testing strong and pulsed electromagnetic fields,the ones used in radars for example,had deficiencies due to the difficulty in obtaining simultaneous information about the electromagnetic field's peak both in the time domain and in the frequency domain.With regard to this problem,after analyzing the time-domain and the frequency-domain characteristics of radar pulsed signals,we propose a new time-frequency combination test method based on the correction of the test parameters,as well as its correction method at different bandwidths.The test method is applied in a quick test of a high-power pulsed radar signal,and the corrected results have error less than 1 dB in both the time domain and the frequency domain,which indicates that the proposed time-frequency combined method is effective in testing strong and pulsed electromagnetic fields.

Complex complete quadratic combination method for damped system with repeated eigenvalues

A new response-spectrum mode superposition method, entirely in real value form, is developed to analyze the maximum structural response under earthquake ground motion for generally damped linear systems with repeated eigenvalues and defective eigenvectors. This algorithm has clear physical concepts and is similar to the complex complete quadratic combination （CCQC） method previously established. Since it can consider the effect of repeated eigenvalues, it is called the CCQC-R method, in which the correlation coefficients of high-order modal responses are enclosed in addition to the correlation coefficients in the normal CCQC method. As a result, the formulas for calculating the correlation coefficients of high-order modal responses are deduced in this study, including displacement, velocity and velocity-displacement correlation coefficients. Furthermore, the relationship between high-order displacement and velocity covariance is derived to make the CCQC-R algorithm only relevant to the high-order displacement response spectrum. Finally, a practical step-by-step integration procedure for calculating high-order displacement response spectrum is obtained by changing the earthquake ground motion input, which is evaluated by comparing it to the theory solution under the sine-wave input. The method derived here is suitable for generally linear systems with classical or non-classical damping.

Estimation of dynamic stress spectrum distribution in structural fatigue test

The determination of structural dynamic stress spectrum distribution is of great signifi- cance in the structural fatigue strength evaluation as well as reliability design. In previous empirical data processing methods, the data grouping and distribution fitting were excessively coarse and contained distinctive defects. This paper proposed an effective approach to statistically group actual measured dynamic stress data and validly extrapolate the combined distribution to fit the dynamic stress spectrum distribution. This approach has been verified its effectiveness through chi-square test, stress spectrum extrapolation and damage calculation in dynamic stress study.

Cooperative Self Encoded Spread Spectrum in Fading Channels

Self-encoded spread spectrum (SESS) is a unique realization of random spread spectrum. SESS eliminates the need for the traditional transmitting and receiving PN code generators. Instead, the time varying, random spreading sequence is obtained from the data source. Cooperative diversity (CD) has been attracting increas-ing attention as a novel and promising diversity technique. This paper analyzes the cooperative SESS for Amplify and Forward CD links in Rayleigh channels. The results show that our cooperative SESS improves the system performance significantly over MRC-based cooperative systems.

Relay Selection and Power Allocation in Amplify-and-Forward Cognitive Radio Systems Based on Spectrum Sharing

In this paper, we consider a spectrum sharing scheme that is a joint optimization of relay selection and power allocation at the secondary transmitter, which aims to achieve the maximum possible throughput for the secondary user. This paper considers the scenario where the primary user is incapable of supporting its target signal-to-noise ratio (SNR). More especially, the secondary transmitter tries to assist the primary user with achieving its target SNR by cooperative amplify-and-forward (AF) relaying with two-phase. By exhaustive search for all candidate secondary transmitters, an optimal secondary transmitter can be selected, which not only can satisfy the primary user’s target SNR, but also maximize the secondary user’s throughput. The optimal secondary transmitter acts as a relay for the primary user by allocating a part of its power to amplify-and-forward the primary signal over the primary user’s licensed spectrum bands. At the same time, as a reward, the optimal secondary transmitter uses the remaining power to transmit its own signal over the remaining licensed spectrum bands. Thus, the secondary user obtains the spectrum access opportunities. Besides, there is no interference between the primary user and the secondary user. We study the joint optimization of relay selection and power allocation such that the secondary user’s throughput is maximized on the condition that it satisfies the primary user’s target SNR. From the simulation, it is shown that the joint optimization of relay selection and power allocation provides a significant throughput gain compared with random relay selection with optimal power allocation (OPA) and random relay selection with water-filling power allocation (WPA). Moreover, the simulation results also shown that our spectrum sharing scheme obtains the win-win solution for the primary system and the secondary system.

基于红外光谱与多种预处理组合的柴油纯度检测方法

利用红外光谱技术采集51种不同体积分数的柴油光谱数据,采用主成分马氏距离法剔除异常样本,通过71种预处理组合及偏最小二乘法建立了柴油纯度性质模型。结果表明:合理预处理后的建模效果明显优于未经预处理的效果,预测均方根误差(RMSEP)降到了0.0400以下,相关系数(R_(p))达到了0.9900以上,且预处理组合方法的顺序不同,其建模效果即模型评价指标RMSEP、R_(p)也不同;1stderivative+SNV、1^(st) derivative+SNV+center、1^(st) derivative+center+SNV、center+1stderivative+SNV这4种预处理组合方法的模型预测效果最好,RMSEP可达0.0187,R_(p)可达0.9978,可适用于柴油纯度光谱数据的处理,实现柴油纯度的检测。

基于奇异谱分解和LSTM-ARIMA组合模型的生猪价格预测

针对生猪价格波动过于剧烈难以预测的问题,提出基于奇异谱分解的LSTM-ARIMA组合模型对生猪价格进行预测。以2000年1月-2021年12月的月度价格数据作为样本,利用奇异谱分析对生猪价格数据进行分解,得到趋势项和波动项,选用累计贡献率达前70%的构建趋势项,剩下的30%构造波动项。趋势项非平稳且具有长记忆性,对其建立LSTM模型;波动项平稳,对其建立ARIMA模型,最后将两部分预测结果重组作为生猪价格的预测值,构建LSTM-ARIMA组合预测模型。将预测值和生猪真实价格进行对比,结果表明:预测值与真实值之间的均方根误差RMSE为2.75,平均绝对百分比误差MAPE为10.81%,平均绝对误差MAE为2.27,方向对称性DS为81.81;此组合模型能很好地预测生猪价格走势,对我国生猪价格预测具有更高地适用性与参考。

Investigation on experimental load spectrum for high and low cycle combined fatigue test

As the outfield load spectrum is so complicated that it cannot be used directly for test study in laboratory.This paper presents a method to determine load spectrum for high and low cycle combined fatigue of turbine mortise at elevated temperature through experimental and numerical method.First of all,the low cycle load spectrum with duration time is determined through cumulative damage rule.The rain flow counting method is applied to obtain main cycles and sub cycles,and then the stress cycle is converted into pulsation cycle(stress ratio=0)based on the S-N curve and the Goodman curve;Secondly,three groups of different amplitudes tests are established to determine the high cycle amplitude.Finally,another three groups of the high-low combined cycle fatigue(HLCCF)tests for turbine mortise of a certain type engine are carried out.The results show that the macro and micro failure modes are identical with outfield's,which verifies the accuracy of the conversion method.

基于加权联合提升包络谱的轴箱轴承故障诊断

为解决列车轴箱轴承微弱故障特征在宽频带上难以提取的问题,基于轴承故障信号的二阶循环平稳特性,提出了一种利用加权联合提升包络谱进行故障诊断的方法.首先,利用谱相干算法将振动信号分解到由频谱频率和循环频率构成的双频域,实现振动信号在全频带内的精细化解调,并基于谱相干的局部特征识别轴承候选故障频率;接着,利用1/3二叉树滤波器将频谱频率分割为不同中心频率和带宽的窄带,在窄带内沿着频谱频率对谱相干的模进行积分,得到窄带提升包络谱;然后,以候选故障频率在窄带提升包络谱中的能量占比为诊断性指标,在每一分解层上构造联合提升包络谱;最后,对不同分解层的联合提升包络谱进行加权平均,得到轴承振动信号的加权联合提升包络谱.轨道车辆轴箱轴承台架试验信号的研究结果表明:所提方法的优势在于能充分整合分布于不同窄带内的轴承故障信息,且不依赖于名义故障周期信息;和现有方法相比,能更有效地揭示轴承故障特征频率及其谐波特征,在提取和识别轴箱轴承微弱故障方面具有一定优势.

基于软决策融合的CSS性能分析及优化

针对基于数据融合的软合并协作频谱感知占用通信资源较大问题,提出了一种基于软决策融合的协作频谱感知方案,推导了检测性能表达式,并基于NP准则给出了使检测率最大化的优化的协作频谱感知算法。分析和仿真结果表明:基于软决策融合的协作感知相比基于数据融合的协作感知可以有效节约系统资源;所提优化算法可以有效提高检测性能。

基于CCSO-VMD的声发射脱粘信号特征提取

声发射检测方法目前被广泛应用在设备的缺陷检测方面,针对大部分设备产生的声发射信号幅度小,噪声大且特征难以提取的问题,本文提出了一种信号处理方法:基于皮尔逊相关系数-包络熵最小原则的CCSO算法优化VMD中参数的处理方法。该方法在经典的鸡群优化算法之上融入了交叉算法,并通过改进的CCSO算法来精确优化VMD中的关键参数,即模态数K和惩罚因子α。通过采用基于新适应度函数的CCSO-VMD方法,对模拟信号进行分析,信噪比达到了25.8141 dB。这一结果证明,基于新目标函数的CCSO-VMD算法能够显著降低噪声水平,同时最大程度地保留信号中的有效信息。此外,本文提出了一种综合频谱差异指标,CSDI值能有效区分不同状态下的声发射信号。

学龄前孤独症谱系障碍儿童医教结合饮食行为干预的疗效观察

目的观察在医教结合模式干预下,运用作业治疗、早期介入丹佛模式、应用行为分析法等康复技术,对学龄前孤独症谱系障碍(autism spectrum disorder,ASD)儿童饮食行为改善的疗效。方法对宁波市康复医院儿童康复中心康复的80例学龄前ASD儿童进行为期20周的饮食能力干预训练,干预前后采用Peabody运动发育量表(第2版)抓握量表、孤独症婴幼儿早期介入丹佛模式个人独立进餐等级Ⅰ-Ⅳ评定量表、孤独症儿童心理教育评核(第3版)自理能力评定量表对儿童进行评估。结果干预后,观察组与对照组儿童的饮食能力均有所提高,其中运用医教结合策略干预的观察组儿童在抓握能力、饮食能力、自理能力方面提升明显,在行为控制、情绪管理能力方面也得到提高。结论医教结合策略可有效改善学龄前ASD儿童饮食行为,对于改善儿童的行为问题有干预效果。

基于改进广义线性组合的稳健波束形成算法

针对传统波束形成算法在导向矢量失配和协方差矩阵估计存在误差情况下,出现波束形成性能下降的问题,提出一种基于改进广义线性组合的自适应稳健波束形成算法。该算法首先对接收信号作奇异谱分解进行降噪,然后构造与接收信号快拍数相关的对角加载系数函数,结合降噪处理后的数据构造广义对角加载协方差矩阵,最后基于空域积分和子空间投影思想,估计期望信号的实际导向矢量,并结合新生成协方差矩阵进行波束形成。仿真分析结果表明,在存在期望信号角度估计失准导致导向矢量失配,以及样本数较少造成协方差矩阵估计存在误差时,所提算法能保持较好的输出信干噪比,验证了该算法的稳健性。

ICF-CY框架下孤独症儿童青少年教康结合的应用

《国际功能、残疾和健康分类(儿童与青少年版)》(ICF-CY)是一种国际认可并通用的结构体系,在残疾人康复领域有着广泛的应用。教康结合是孤独症个体干预的重要理念。ICF-CY在孤独症儿童青少年教育康复中的应用价值体现在理念价值、编码价值和合作价值三个方面。ICF-CY在孤独症儿童青少年教康结合中的应用思路可从课程开发、评估工具开发以及背景因素的支持三个方面入手。同时讨论应用中的不足并提出建议,以期为孤独症儿童青少年的教育和康复提供参考和借鉴。