城市道路交通噪声频谱及其对隔声评价中频谱修正量的影响

现行隔声评价标准中交通噪声频谱修正量参考的是20世纪80年代北欧测量得到的交通噪声数据。为了研究C_(tr)修正量是否适用于评价建筑外窗对新时代城市道路交通噪声的隔声性能,对多种城市交通道路进行噪声监测,根据测量结果提出一组新的交通噪声频谱修正曲线C_(A),计算11种常见外窗构造在不同频率范围内的计权隔声量,并对比分析不同频谱修正量声压级频谱的差异性。结果表明:不同城市道路交通噪声频谱都具有低频声压级高、中频平稳、高频下降的相似特点;当今的城市道路交通噪声低频能量远低于C_(tr)所参考的频谱,其能量频谱分布更接近于C_(100~3150);对比分析11组外窗的交通噪声频谱修正量C_(A)与现行标准的频谱修正量的差异,C_(A)均落于C和C_(tr)参考频谱之间的范围内;C_(A)与C、C_(tr)参考频谱的相关系数R2的值均>0.9且高于C与C_(tr)的相关性,因此C_(A)对城市道路交通噪声频谱修正具有更好的适用性与代表性,研究结果可为临街住宅的隔声降噪工程提供数据参考。

道路交通噪声频谱修正量

对广州市和北京市的普通公路、快速路和高速路道路交通噪声进行实测,经计算得到城市道路交通噪声的平均归一化频谱,并与《建筑隔声评价标准》(GB/T 50121—2005)中用于计算C和Ctr的频谱修正曲线相比较,发现差异较大,进而定义了用于计算频谱修正量Cdl的平均归一化声压级谱,以评价建筑构件对城市道路交通噪声的实际隔声效果。计算25种常用建筑外墙、门和窗的空气声隔声频谱修正量,结果表明采用频谱修正量Cdl对计权隔声量修正可更准确地反映建筑构件对城市道路交通噪声的实际隔声性能。与Ctr相比,Cdl与C更接近。

基于频谱累积量的线性分组码检测识别方法

针对非合作信号处理中的线性分组码盲识别问题,提出了一种基于有限域傅里叶变换(Galois field Fourier transform,GFFT)的检测识别方法。该方法对接收码序列按不同长度进行分段,对分段码字进行有限域上的傅里叶变换并计算其频谱的累积量。通过频谱累积量的不同分布情况,可以估计出正确的分组码长度。同时从频谱累积量中找出码字生成多项式的根,进而得到码字的生成多项式。仿真实验验证了算法的有效性,并对算法的误码适应能力和计算复杂度进行了仿真分析,最后给出了在不同误码环境下最优的频谱累积次数。

地脉动及特殊波形的频谱特性在地震预报中的应用

利用功率谱和Sompi港分析方法，对大震前地脉动及展前特殊波形等记录进行了比较深入的研究，结果表明；①较大地震前短周期地脉动及展前特殊波形频谱的峰值频率几，拐角频率人，相对频带宽度f，相对峰值人Sm／So，高频段的斜率绝对值问及Sompi港的卓越频率入等特征量均可能呈现出较明显的下降（少数为上升）异常变化；②各频谱特征量呈现异常的时间基本上同步，并与波速异常发展趋势基本相符；③以上异常变化可能反映震前孕震区地下微破裂的形成与发展过程；④地脉动特征量可能为地震中长期及短临预报的研究提供一些有用的信息，有广泛的应用前景。

永登5.8级地震前后地震波频谱变化特征研究

研究了１９９５年７月２２日甘肃永登５．８级地震前后发生在该区的３２个小地震的地震波频谱变化特征，结果表明Ｐ、Ｓ波频谱的峰值频率、拐角频率、频谱峰值、零频谱值、高频段的谱线斜率绝对值等频谱特征量大多数在主震前后出现了明显的上升或下降异常变化，因而可作为地震预报指标。

中国民族乐器声的空气声隔声频谱修正曲线研究

对两类中国民族乐器声频谱修正曲线在建筑构件空气声隔声测量评价中的适用性作进一步分析。首先对民族乐器声压级频谱和标准中给出的两类噪声声压级频谱进行比较,以一种加气混凝土砌块轻质隔墙为对象进行空气声隔声实验室测量。通过对比测量得到的声级和计算得到的频谱修正量,说明民族乐器声频谱修正曲线适用于两类民族乐器声源的建筑构件空气声隔声频谱修正量的计算。

高铁噪声声源的空气声隔声评价频谱修正研究

将华南理工大学戴然捷等人在厦深铁路和武广高铁测得的高速铁路交通噪声的频谱经A计权和归一化,计算出多种常用隔墙构造对其的空气声隔声频谱修正量。通过计算验证,得到了针对高铁交通噪声的频谱修正曲线,以期完善相关隔墙隔声性能评价体系。

空气声隔声单值评价量的不确定度评定及分析

在建筑隔声评价标准(GB/T 50121—2005)中,建筑构件隔声性能等级的划分并没有体现空气声隔声单值评价量的测量不确定度,这对建筑构件隔声性能的分级造成影响,给实验室对构件隔声性能的符合性判定带来困扰。对此,依据GUM法和ISO 12999-1:2020标准,确定建筑构件空气声隔声实验室测量结果不确定度的来源,建立不确定度数学分析模型,为建筑构件的各1/3倍频带的空气声隔声量以及空气声隔声单值评价量的不确定度分析提供依据,通过实例证明了不确定理论应用于空气声隔声测量的可操作性。通过计算17个构件的单值评价量不确定度,结果表明在100~5 000 Hz频率范围内,3种不同频谱修正的正全相关不确定度随计权隔声量的增加而增加,但前提是不同构件的各频带隔声量的标准不确定度相差较小。

基于凯塞窗插值快速傅里叶变换的电压互感器校验仪全自动检定方法

为使电压谐波在正弦波、余弦波、正切波输出条件下的相位幅值能够较好地贴合给定的谐波幅值结果,从而使电压互感器元件的电量输出行为得到准确检验,本文提出基于凯塞窗插值快速傅里叶变换(FFT)的电压互感器校验仪全自动检定方法。首先,根据Kaiser窗函数存在形式,确定凯塞窗插值的修正计算结果,根据频谱泄露量指标的具体数值,完成基于凯塞窗插值FFT的电压谐波分析;其次,在此基础上,按照互感器校验仪测量原理,定义电压信号之间的配比关系;最后,联合已知电压参量指标,确定FFT导数算法的实施流程,完成基于凯塞窗插值FFT的电压互感器校验仪全自动检定方法的设计。实验结果表明:与RTDS仿真验证方法相比,全自动检定方法在正弦波、余弦波、正切波输出条件下的相位幅值均与给定的谐波幅值结果完全相同,能够较好满足精准检验电压互感器元件电量输出行为的实际应用需求。

Passive-source multitaper-spectral method based low-frequency data reconstruction for active seismic sources

Passive seismic data contain large amounts of low-frequency information. To effectively extract and compensate active seismic data that lack low frequencies, we propose a multitaper spectral reconstruction method based on multiple sinusoidal tapers and derive equations for multisource and multitrace conditions. Compared to conventional cross correlation and deconvolution reconstruction methods, the proposed method can more accurately reconstruct the relative amplitude of recordings. Multidomain iterative denoising improves the SNR of retrieved data. By analyzing the spectral characteristics of passive data before and after reconstruction, we found that the data are expressed more clearly after reconstruction and denoising. To compensate for the low-frequency information in active data using passive seismic data, we match the power spectrum, supplement it, and then smooth it in the frequency domain. Finally, we use numerical simulation to verify the proposed method and conduct prestack depth migration using data after low-frequency compensation. The proposed power-matching method adds the losing low frequency information in the active seismic data using the low-frequency information of passive- source seismic data. The imaging of compensated data gives a more detailed information of deep structures.

Freak wave simulation based on nonlinear model and the research on the time-frequency energy spectrum of simulation results

VOF （volume of fluid） method has been used to make the numerical simulation of freak wave come true. The comparisons between the numerical results and linear theoretical results corresponding to Eq.（5） have been carried out to show that the numerical results have a better exhibition of nonlinear characteristics. Wavelet analysis method has been adopted to investigate the time-frequency energy spectrum of simulation freak waves and the results reveal strong nonlinear interaction enables energy to be transferred to high harmonics during the progress of its formation. Varying water depth can enhance the nonlinear interaction, making much more energy be transferred to high harmonics and freak waves with higher asymmetry be generated.

面向多买家系统的频谱共享策略

动态频谱共享带来同频干扰和安全问题,静态频谱共享又面临着频谱利用率低的问题。为了引入一种无干扰、安全、有效的频谱共享技术,提出了一种应用于多买家系统的基于报童模型的静态频谱共享策略。报童模型将业务需求看作一个动态变化的过程,因此租售策略需要周期性地进行调整。通过理论分析得到了报童策略在一个租售周期中的使用方法,通过仿真结果得出了仿真场景下的最佳租售周期、最佳申请频谱量和最佳用户服务定价系数。与传统的静态频谱共享策略相比,报童策略在不引入额外问题的前提下,能使系统利润更高、频谱利用率更高。

Optimal decision threshold for soft decision cooperative spectrum sensing

In order to achieve higher spectrum efficiency in cognitive radio （CR） systems, a closed-form expression of the optimal decision threshold for soft decision cooperative spectrum sensing based on the minimum total error probability criterion is derived. With the analytical expression of the optimal decision threshold, the impact of different sensing parameters on the threshold value is studied. Theoretical analyses show that the optimal threshold achieves an efficient trade-off between the missed detection probability and the false alarm probability. Simulation results illustrate that the average signal-to-noise ratio （SNR） and the soft combination schemes have a great influence on the optimal threshold value, whereas the number of samples has a weak impact on the optimal threshold value. Furthermore, for the maximal ratio combing （MRC） and the modified deflection coefficient （MDC） schemes, the optimal decision threshold value increases and approaches a corresponding individual limit value while the number of CR users increases. But the number of CR users has a weak influence on the optimal decision threshold for the equal gain combining （EGC） scheme.

A Novel System Model based on Cost-prediction for Spectrum Leasing in Cognitive Radio

In current researches on spectrum leasing, Common model and Property-right model are two main approaches to dynamic spectrum sharing. However, Common model does not consider the obligation of Primary System (PS) and is unfair to Secondary System (SS), while the cooperation based on Property-rights model has problems on its feasibility. This paper proposes a novel system model, in which a Cost-Prediction scheme for Spectrum Leasing (CPSL scheme) is designed to forecast the cost that PS would pay for leasing spectrum. Cost Function is introduced as a criterion to evaluate the potential cost of spectrum leasing for PS. The simulation results show that compared with Common model based scheme, CPSL scheme substantially improves the QoS of the delay-sensitive traffic in SS at the cost of a small degradation of PS performance.

IEEE 802.11aj(45GHz):A New Very High Throughput Millimeter-Wave WLAN System

This paper presents an overview of a new very high throughput millimeterwave WLAN system operating at 45 GHz band. We begin by reviewing standards process of IEEE 802.11aj(45GHz). Then the frequency spectrum allocation at 45 GHz band is introduced. Next, the channel measurement and mod-eling is given. Specifically, the millimeter-wave MIMO for physical layer enhancement is given in detail.

影响轨道车辆门系统空气声隔声性能分析

轨道车辆门系统空气声隔声性能直接影响到乘客乘坐舒适性。本文从空气声隔声测试原理出发,分析比较了门系统面密度、密封性能等对门系统隔声性能的影响。为轨道车辆门系统前期指标响应、测试样品设计和检测提供一定的参考。

IMPROVING THE FREQUENCY RESOLUTION OF DIGITALLY SYNTHESIZED PERIODIC SIGNALS BY A SEQUENTIAL ADDRESSING SCHEME

In the digital synthesis of wideband periodic signals using an Arbitrary Waveform Gen-erator(AWG),the frequency resolution and spectral complexity of the synthesized signals are com-monly limited by the memory capacity and clock frequency of the AWG.This paper proposes a novel sequential addressing scheme and then presents several sequences to improve the frequency resolution of the synthesized periodic signals without changing their spectral envelopes and basic time-domain characteristics under the condition of a fixed memory capacity and a fixed clock fre-quency.The main idea of the scheme is using the address generator in an AWG to program and produce addresses to read fixed waveform data in variable order,and thus to generate waveforms of various periods and profiles.The scheme is applied in simulating signal scenarios for military com-munication countermeasure experiments,and achieves high performance.

Performance Analysis of Uplink Distributed Massive MIMO System with Cross-Layer Design over Rayleigh Fading Channel

The performance of uplink distributed massive multiple-input multiple-output(MIMO)systems with crosslayer design(CLD) is investigated over Rayleigh fading channel, which combines the discrete rate adaptive modulation with truncated automatic repeat request. By means of the performance analysis, the closed-form expressions of average packet error rate(APER)and overall average spectral efficiency(ASE)of distributed massive MIMO systems with CLD are derived based on the conditional probability density function of each user’s approximate effective signal-to-noise ratio(SNR)and the switching thresholds under the target packet loss rate(PLR)constraint.With these results,using the approximation of complementary error functions,the approximate APER and overall ASE are also deduced. Simulation results illustrate that the obtained theoretical ASE and APER can match the corresponding simulations well. Besides,the target PLR requirement is satisfied,and the distributed massive MIMO systems offer an obvious performance gain over the co-located massive MIMO systems.

Observed typhoon wave spectrum in northern South China Sea

To describe both the way in which a wave spectrum grows and the growth processes of realistic wave conditions,the dependence relationship between the spectrum parameters and wind parameters must be obtained. Based on data measured in 2010 by a Wave Rider buoy,which was deployed in the South China Sea at coordinates 21.89°N,115.13°E,we evaluated the wave spectrum in the sea area when affected by three typhoons:Conson,Chanthu,and Megi. The Joint North Sea Wave Project spectrum was parameterized based on the observed wave spectrum. We proposed a spectrum with three parameters:the dimensionless lowest moment of the spectrum,dimensionless peak frequency,and spectrum width. The relationships between these spectral parameters and the dimensionless fetch were also discussed.

INTERFERENCE COORDINATION METHOD BASED ON GRAPH THEORY IN TWO-TIER CELLULAR NETWORKS

This paper studies an interference coordination method by means of spectrum allocation in Long-Term Evolution (LTE) multi-cell scenario that comprises of macrocells and femtocells. The purpose is to maximize the total throughput of femtocells while ensuring the Signal-to-Interference plus Noise Ratio (SINR) of the edge macro mobile stations (mMSs) and the edge femtocell Mobile Stations (fMSs). A new spectrum allocation algorithm based on graph theory is proposed to reduce the interference. Firstly, the ratio of Resource Blocks (RBs) that mMSs occupy is obtained by genetic algorithm. Then, after considering the impact of the macro Base Stations (mBSs) and small scale fading to the fMS on different RBs, multi-interference graphs are established and the spectrum is allocated dynamically. The simulation results show that the proposed algorithm can meet the Quality of Service (QoS) requirements of the mMSs. It can strike a balance between the edge fMSs' throughput and the whole fMSs' throughput.