Gaussian beamed millimetre wave propagation characteristics due to reflecting behaviour in circle tunnel

Propagation characterization is one of the main building blocks for millimetre wave （MMW） communication. The Gaussian beam has attractive features to become a prospective wave form for millimetre radio communication, especially for the utility inside tunnels. A ray tracing method embedded with spectral features of Gaussian beam is employed to analyze mil- limetre wave propagation in a circle tunnel in this paper. In consideration of geometrical figure of the tunnel, the superposition behaviour of direct and reflective beams is analyzed via simplified approximation of Gaussian beam spectral feature. Then the propagation models are established to derive amplitude, phase, and delay spread of received wave. A typical straight tunnel model is used to simulate the propagation behaviour, where strong multi-path effect with deeply fading of signal intensity and dramatically enhancing of delay spread emerges. For investigation of the spectral feature of the multi-path effect, a reflection loss of 14 dB is taken into consideration at a designated point. To analyze the influences of frequency and transmission distance, the propagation characteristics at three different frequencies of 45 GHz, 65 GHz and 85 GHz are compared with the beam travelling down the tunnel. In addition, three different reflection losses of 14 dB, 20 dB, and 26 dB at the frequency of 65 GHz are also investigated to research the influence of the reflecting coefficient.

Formation and instability of spiral wave induced by Gaussian coloured noise

In this paper, we studied the effect of Gaussian coloured noise on the formation and instability of spiral waves described by one class of modified FitzHugh Nagumo equation. It was found that Gaussian coloured noise plays a constructive role in the formation, transition and instability of spiral wave. Too weak or too strong noise may act against the formation of spiral waves. At a certain noise level, spiral wave is maintained in a medium, in which spiral wave cannot be observed in the absence of the noise. It is difficult to make a stable spiral wave into unstable state by Gaussian coloured noise, unless the noise level is very high. The parameter regions of Gaussian coloured noise for spiral forming and spiral instability were given and discussed with numerical simulations.

Electromagnetic Resonance of Astigmatic Gaussian Beam to the High Frequency Gravitational Waves

The high frequency gravitational waves （around lOS-lO12 Hz） could interact with a specially designed electro- magnetic resonance system. It is found that the power of transverse perturbative photon flux （PPF） of an electromagnetic resonance system can be improved significantly by virtue of an astigmatic Caussian beam. Cor- respondingly the signal-to-noise ratio （SNR） would also be improved. When the eccentric ratio of waist satisfying w0x ： w0y 〉 1, the peak value of signal photon flux could be raised by 2-4 times with typical systematic parameters, while the background photon flux would be depressed. Therefore, the ratio of transverse PPF to background photon flux （i.e., SNR） can be further improved 3-8 times with dimensionless amplitude of relic gravitational wave ht = 10-36.

The Study of Optoacoustic First and Second Sound Waves in Superfluid Helium under the Effect of Gaussian Laser Light Considering Electrostriction Mechanism

The present paper is aimed to study the effect of Gaussian laser light on first and second sound waves in superfluid helium theoretically using optoacoustic method. The mechanism applied in this study is electrostriction mechanism. This study considers crystal parts of superfluid helium with a zero absorption coefficient applying electrostriction mechanism. Affecting Gaussian laser light on these crystal parts, a spectrum of cylindrical first and second sound waves and cylindrical slow and rapid waves is obtained. Meanwhile, frequency of waves amplitudes proportionate to time period of laser light is calculated.

The retrieval of the nonlinear random waves from the non-Gaussian characteristics of the sea surface elevation distribution

In this paper, without recourse to the nonlinear dynamical equations of the waves, the nonlinear random waves are retrieved from the non-Gaussian characteristic of the sea surface elevation distribution. The question of coincidence of the nonlinear wave profile, spectrum and its distributions of maximum (or minimum) values of the sea surface elevation with results derived from some existing nonlinear theories is expounded under the narrow-band spectrum condition. Taking the shoaling sea wave as an example, the nonlinear random wave process and its spectrum in shallow water are retrieved from both the non-Gaussian characteristics of the sea surface elevation distribution in shallow water and the normal sea waves in deep water and compared with the values actually measured. Results show that they can coincide with the actually measured values quite well, thus, this can confirm that the method proposed in this paper is feasible.

Theoretical Study of Electromagnetic Wave Propagation: Gaussian Bean Method

In this work, we present the study of electromagnetic wave propagation through a medium with a variable dielectric function using the concept of Gaussian Beam. First of all, we start with wave equation with which we obtain the solution in terms of the electric field and intensity distributions approximate to Gaussian Function, . With this, we analyze the dependency of r on Gaussian beam distribution spread, the distant from the axis at which the intensity of the beam distribution begins to fall at a given estimate of its peak value. The influence of the optimum beam waist wo and the beam spread on the intensity distribution will also be analyzed.

ASYMPTOTICS OF THE SOLUTIONS TO STOCHASTIC WAVE EQUATIONS DRIVEN BY A NON-GAUSSIAN LéVY PROCESS

In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Lévy process. We shall prove that under some appropriate conditions, the exponential stability of the solutions holds. Finally, we give two examples to illustrate our results.

Wave Period Distributions in Non-Gaussian Mixed Sea States

The wave period probability densities in non-Gaussian mixed sea states are calculated by utilizing a transformed Gaussian process method. The transformation relating the non-Gaussian process and the original Gaussian process is obtained based on the equivalence of the level up-crossing rates of the two processes. A saddle point approximation procedure is applied for calculating the level up-crossing rates in this study. The accuracy and efficiency of the transformed Gaussian process method are validated by comparing the results predicted by using the method with those predicted by the Monte Carlo simulation method.

机器学习的高精度毫米波雷达测距信号误差补偿方法

毫米波雷达是一种常用的非接触式测距技术,受环境因素以及测量过程中存在的各种误差影响,测距结果可能存在一定的误差。研究误差补偿方法可以有效提高毫米波雷达的测距精度,从而更准确地获取目标物体的距离信息。为此,提出了机器学习的高精度毫米波雷达测距信号误差补偿方法。通过高斯滤波器去除雷达测距信号中的噪声,完成信号的去噪处理。利用模拟插入脉冲计数法和四象限光斑定位法,测量目标物体的距离和角度信息,通过自适应惯性权重与收敛因子优化粒子群算法,并利用优化后的粒子群算法改进BP神经网络,将测量的距离和角度信息输入到改进的BP神经网络中展开训练,即可得到补偿后的雷达测距信号。实验结果表明,该方法的信号处理效果好,补偿后的毫米波雷达测距信号方位角和俯仰角误差接近于0,且信号平滑度较高。

激波与轻质气柱作用过程的磁场抑制特性

本文采用CTU(corner transport upwind)+CT(constrained transport)算法求解理想可压缩磁流体动力学(magneto-hydro-dynamic,MHD)方程,仿真研究了不同方向磁场控制下高斯分布轻质气柱界面受平面冲击波扰动后的演化过程,揭示了磁场方向对界面不稳定性的影响机理.仿真结果探讨了有/无磁场作用下流场特性与波系结构的发展,对比分析了磁场方向对气柱的长度、高度、射流宽度和体积压缩率的影响,并结合流场上半区环量、能量分量、速度和磁场力分布,多角度分析了磁场方向对界面不稳定性的影响机理.结果表明,磁压力推动涡量远离界面,降低了涡量在密度界面上的沉积而附着在分裂后的涡层上,从而有效抑制Richtmyer-Meshkov不稳定性对界面的影响;由于磁张力附着在被分离的涡层上,且其作用方向与界面因速度剪切而卷起涡的方向相反,因此抑制了界面因Kelvin-Helmholtz不稳定性而形成涡串.另外,纵向磁场控制下的磁张力反作用于中轴射流方向,同样抑制了Rayleigh-Taylor不稳定性的发展.

非高斯波浪作用下深水高墩的非线性随机振动

首先,建立非高斯波浪作用下深水高墩的随机动力学模型,采用泊松白噪声激励模拟非高斯随机波浪过程,利用达朗贝尔原理和伽辽金方法推导深水高墩的运动方程。然后,通过径向基神经网络法求解广义FPK方程,获得系统的瞬态响应概率密度函数。最后,考察不同结构参数对系统响应的影响,并采用蒙特卡罗模拟(MCS)验证理论解。结果表明:理论解与模拟结果吻合良好;浸入比和质量比增加均会放大高墩的响应;采用高斯模型会使结构设计偏于保守。

一种基于多波地震的多尺度属性融合

相比于多波地震数据采集和处理方法,多波地震数据解释方法进展较慢,难以体现多波地震技术的优越性。常规地震属性提取与分析多基于纵波地震资料,并未综合利用储层纵、横波信息。为此,提出了一种多尺度属性融合技术,以增强多波复合属性的油气敏感性。对于实际二维地震剖面,首先,构造一个高斯金字塔,以生成不同分辨率的各种复合属性;其次,融合不同尺度的所有属性形成有效的多尺度增强属性;再次,借鉴图像叠加理论,将不同的多尺度增强属性混合叠加,可有效突出储层发育区域,且保留了各种属性间的差异,能更好地描述砂体的含油气性。模型试算表明,对于含油气砂岩与围岩差异较小的复杂二维模型,依据RGB的多波地震融合属性能够检测储层,并可识别反射界面位置。实际数据试算表明,所提方法能分辨靶区河道砂体的储层分布。

铁道车辆轴箱振动非高斯特征与分布研究

以对铁道车辆轴箱振动非高斯特征与分布为对象开展研究。基于列车线路轴箱实测加速度信号,提取由轨道冲击引起的轴箱振动特征非高斯信号。使用多个概率密度函数(Probability Density Function,PDF)模型对实测信号进行拟合,并与实测特征信号的经验分布进行对比,评估各模型对轴箱特征非高斯信号的拟合精度。基于W-H非线性变换模型,建立一种非高斯信号模拟方法。利用模拟信号分析非高斯特征对各模型拟合精度的影响。结果表明:列车在行驶过程中具有非高斯特征,当列车经过轨道焊接接头、道岔与波磨路段时,由于轮轨冲击,非高斯特征明显增大,车轮多边形对信号非高斯特征几乎没有影响;基于W-H模型的非线性变换法,可以在保证模拟信号功率谱与指定功率谱基本一致的情况下,进行不同非高斯特征的信号模拟;高斯混合模型能够对铁道车辆非高斯信号较为准确地拟合;随着模拟非高斯信号峭度与偏度的增大,各模型与经验分布的相对误差也会增大,其中高斯混合模型拟合精度相对较高。

适应波达时刻不确定性及较低采样率的新能源送出线路就地暂态量主保护判据

不对称接地故障占所有线路故障的90%以上,接地距离保护在应对此类故障方面发挥了不可替代的作用。随着新能源高比例渗透,各种传统单端工频量保护性能显著下降已成为共识。基于故障分量线模和零模波速差的保护判据理论上仅需利用到故障初始行波到达时刻信息,是一种原理简单可靠的单端量快速保护判据,已经在直流电网中成功实践。但在尝试将这类保护应用于交流电网时发现,受波头前陡较缓而难以精确定位波到时刻、依赖高采样率等诸多不利因素影响,存在过大的模糊判别区,除了特长线路外,对绝大部分线路几乎没有应用可行性。波到时刻的精准辨识是一个复杂的非线性问题,利用人工智能的方法进行辨识是一条可行的解决思路,对此,该文提出一种新的单端暂态量主保护判据。首先,分析波达时刻与波形关系,并指出这种关系能够采用机器学习来映射;其次,引入高斯过程回归(Gaussian process regression,GPR),在对初始行波数据进行预处理得到样本集后,输入GPR预测模型进行训练;然后,依据模型评估指标得到最优训练模型以输出高可信性的线-零模波达时差,据此实现了基于行波模量传输时间差的保护判据;最后,在利用PSCAD仿真验证所提保护判据有效性和普适性的基础上,进一步利用现场实测数据对判据进行测试,验证其实用性。该文工作为新能源交流系统下单端暂态量保护的性能提升提供新的解决思路。

海底四分量各向异性介质高斯束偏移方法

基于弹性波动方程的多波多分量高斯束偏移方法计算高效且成像精确,适用于复杂地质构造,目前多应用于陆地三分量数据,对于海底地震数据存在明显的适应性问题:①不完整的海底边界条件导致P波和S波无法彻底分离,上、下行波会在海底的记录方式下发生混叠,造成虚假成像;②地下介质中普遍存在的各向异性带来运动学信息误差,导致最终成像出现反射波归位不准确、绕射波收敛效果差、能量不聚焦等问题。为此,提出一种兼顾各向异性特性、直接使用包含水压分量的海底四分量地震数据进行弹性高斯束偏移成像的方法。首先,假设海底接收界面为各向同性,以弹性波波动方程和海底完整边界为基础进行波场延拓,得到四分量数据的波型分离矩阵;然后,结合各向异性射线追踪和动力学参数近似,实现了VTI介质的弹性波高斯束偏移。2D层状模型和北海Gullfaks区域模型的数值试算结果表明,所采用的海底四分量各向异性介质高斯束偏移方法抑制了不完整边界条件造成的成像假象,能够自动分离海底各向异性介质中的PP波和PS波,实现转换波的准确成像,更精确地恢复和归位地震波,提高了地震资料成像分辨率,尤其适用于复杂海底的大炮检距、宽方位地震勘探。

内孤立波速度-高斯函数模型构建与评估

内孤立波一维理论模型已广泛应用在内孤立波的预警预报中,但一方面由于理论模型在计算波函数时高度依赖温、盐数据,需要搭载全水深温、盐观测仪器,经济成本较高;另一方面,理论模型对复杂流场环境的预警预报误差较大,如计算的内孤立波的非线性相速度以及波函数的准确度偏低。本文提出一种速度-高斯函数模型,它根据南海某单个潜标的上层海水实测流速反向推演得到内孤立波的振幅和波函数,再进一步结合一维理论模型计算波致流和非线性相速度等关键参数。对比实测数据与速度-高斯函数模型结果,发现该模型可仅通过海洋上层150 m实测流速实现对全水深波致流的模拟,并且模拟的非线性相速度与实测值相比,误差控制在10%以内。应用速度-高斯函数模型可在复杂的南海实现对内孤立波的准确预警预报,同时无需潜标搭载温、盐观测仪器,大大降低了内孤立波观测成本。

非微扰的极早期宇宙现象学:共振的原初扰动与非高斯尾巴

在精确宇宙学的时代,多信使、高精度、小尺度的宇宙学观测在帮助人们从更加深刻的层面理解宇宙极早期的同时,也给基于线性近似和微扰展开宇宙学扰动理论带来了新的挑战.近年来,对原初引力波和原初黑洞的搜寻使得研究人员们对早期宇宙在小尺度上的非线性非微扰过程产生了浓厚的研究兴趣.综述了在宇宙学小尺度上关于原初黑洞产生以及引力波研究取得的诸多进展,重点关注了使用Mathieu方程的共振效应来研究小尺度功率谱放大以及诱导产生可观测的原初引力波的方法.此外,还尝试探讨了非高斯尾巴对原初黑洞形成的影响.发现Mathieu方程所具备的共振效应可以提供一种有效的方法来刻画原初宇宙中小尺度的非微扰动力学过程,从而能够更好地理解原初黑洞的形成以及相关的引力波产生机制.同时,非微扰的非高斯性在原初黑洞形成中可能会产生不可忽视的影响.

基于ACBO-GM联合方法的高维变量结构模型修正

工程结构模型修正常面临变量维度高、非线性程度强等现实问题,其模型修正的精度和效率受到严重影响,为改善这一不足,提出基于改进物体碰撞算法(Advanced Colliding Bodies Optimization,ACBO)和高斯白噪声扰动(Gaussian-white-noise Mutation,GM)的联合修正方法。在联合方法中,ACBO实现从传统的“一对一”到“优对多”的碰撞模式的转变,GM则用于保证碰撞过程中种群的多样性,可有效提升结构模型修正效率。基于一系列测试函数,对比分析标准物体碰撞算法(Colliding Bodies Optimization,CBO)和联合优化方法的优化性能;给出基于ACBO-GM联合方法的修正流程,并将其应用于钢框架修正算例和悬臂梁修正实例,对比研究基于联合修正方法与基于遗传算法(Genetic Algorithm,GA)的修正精度和效率。研究表明,ACBO-GM联合优化方法在精度和效率方面都明显优于传统的CBO方法,该优化方法的可行性得到验证;基于ACBO-GM联合方法在钢框架和悬臂梁两个工程结构修正案例中的应用,其修正精度均与基于GA方法的精度一致,但修正效率显著优于基于GA的修正方法。

船行波对H-ADCP影响分析研究

作为当今世界上最先进的测流仪器,水平式声学多普勒流速剖面仪(Horizontal Acoustic Doppler Current Profiler,H-ADCP)因其精度高、速度快等突出优势在河流中的应用越来越广泛,但在航运业发达地区,由于受船行波的影响,很难得到稳定可靠的流速数据,阻碍了HADCP在平原河网地区的应用和推广。目前技术上很难做到完全消除船行波的影响,本文将HADCP应用在平原河网地区对流速进行测量,并分析了船行波对测量精度的影响。从H-ADCP设备选型、测量和安装方式、测量预处理、数据后处理等多方面入手,可以有效消减船行波对H-ADCP的影响,从而提高测流精度。同时,通过实验测量断面一天内平均流速变化情况,得到受船行波影响后的流速波形,然后采用数据处理手段,验证了所提方法的可行性。

基于小样本机器学习的海上低渗储层横波速度预测

横波速度信息对于海上古近系扇三角洲低渗储层精细预测极为重要,但由于成本和采集技术的局限性,有效获取横波速度信息成为低渗储层精细刻画中亟需解决的问题之一。实际低渗有效储层的多样性和沉积环境的复杂性导致基于数据驱动的经验公式法和物理规律驱动的岩石物理模型法进行海上小样本横波速度预测都存在不足。为此,开展基于高斯过程回归机器学习算法研究,其算法具有训练数据需求小、预测精度高和可实现对结果进行不确定性评价等优点。以渤海M油田古近系低渗区的测井数据曲线为应用对象,结果表明基于高斯过程回归机器学习算法可快速实现弹性波速度预测,并可实现对预测结果不确定性的量化分析。