Relationship between Sea Surface Single Carrier Waves and Decreasing Pressures of Atmosphere Lower Boundary

Descriptions of unusually high waves appearing on the sea surface for a short time (freak, rogue or killer waves) have been considered as a part of marine folklore for a long time. A number of instrumental registrations have appeared recently making the community to pay more attention to this problem and to reconsider known observations of freak waves. To allow a better understanding of the behavior of rogue waves associated with tornadoes in terms of their origin, the nonlinear theory of off-balance systems is developed in the specific case of strong agitations constantly seen on the surface of extensive and deep rivers, when they are crossed by an atmosphere’s low pressure system (tornadoes, cyclones, hurricanes, etc.). A mathematical model based on the Navier-Stokes and Euler Lagrange equations coupled with assumptions derived from instrumental registrations on the training locations (or birth places) of freak waves is developed to enhance the physics of processes responsible for the formation (or origin) of the waves associated with atmosphere’s low pressure systems. Freak waves births’ constraints are mainly the need for both consistent water (i.e., extensive-deep rivers) and potential velocity flow availabilities. Numerical simulations, based on the use of the NLSE (Nonlinear Schrodinger Equation) are performed to validate our mathematical model on the births of single carrier waves associated with atmosphere’s low pressure systems.

Effect of Hot Carrier on Amplitude Modulation and Demodulation of Gaussian High Power Helicon Wave in Homogeneous Longitudinally Magnetized Strain Dependent Dielectric Material

In the present communication, the hydrodynamic model is used to investigate the amplitude modulation as well as demodulation of an electromagnetic wave of high power helicon pump wave into another helicon wave in strain dependent dielectric material incorporating carrier heating (CH) effects. The consideration of CH in modulation and demodulation is prime importance for the adding of new dimension in analysis of amplification of acoustic helicon wave. By using the dispersion relation, threshold pump electric filed and growth rate of unstable mode from the modulation and demodulation of the high power helicon wave well above from the threshold value will be discussed in the present analysis. The numerical analysis is applied to a strain dependent dielectric material, BaTiO3 at room temperature and irradiated with high power helicon wave of frequency 1.78 × 1014 Hz. This material is very sensitive to the pump intensities, therefore during studies, Gaussian shape of the helicon pump wave is considered during the propagation in stain dependent dielectric material and opto-acoustic wave in the form of Gaussian profile (ω0,κ0) is induced longitudinally along the crystallographic plane of BaTiO3. Its variation is caused by the available magnetic field (ωc), interaction length (z) and pulsed duration of interaction (τ). From the analysis of numerical results, the incorporation of CH effect can effectively modify the magnitude of modulation or demodulation of the amplitude of high power helicon laser wave through diffusion process. Not only the amplitude modulation and demodulation of the wave, the diffusion of the CH effectively modifies the growth rate of unstable mode of frequency in BaTiO3. The propagation of the threshold electric field shows the sinusoidal or complete Gaussian profile, whereas this profile is found to be completely lost in growth of unstable mode. It has also been seen that the growth rate is observed to be of the order of 108 - 1010 s-1 but from diffusion of carrier heating, and that its order is enhanced from 1010 - 1012 s-1 with the variation of the magnetized frequency from 1 to 2.5 × 1014 Hz.

THEORETICAL ANALYSIS AND EXPERIMENTAL VERIFICATION ON TERNARY-WAVES METHOD TO COMPILE ACCELERATED SPECTRA

The equivalent damage calculation formulae of fatigue crack formation andgrowth are established. In order to compile the fatigue crack formation and growth accelerated loadspectra, the main wave shapes and load sequence of the actual load spectrum are kept constant, andthe carrier waves are cut off. And secondary waves are put together into new secondary waves toshorten the test time according to the equivalent damage calculation formulae respectively. Then bythe fatigue cumulative damage calculation of the fatigue crack formation and growth accelerated loadspectra, the one corresponding to the bigger damage is determined as the fatigue accelerated testload spectrum. Therefore in the test process, the fatigue accelerated test spectrum may be appliedtill fatigue failure, the engineering fatigue crack length of full-scale structure need not beinspected, and the fatigue crack formation accelerated load spectrum need not be transferred intothe fatigue crack growth accelerated load spectrum. Finally, it is verified by tests of two kinds ofspecimens that the damages of the specimens caused by the accelerated load spectra are near tothose by the actual load spectra; namely, the tested life of actual load spectra is similar to thatof accelerated load spectra. But the test time of accelerated load spectra is shortened by aboutthree-quarters that of actual load spectra. From these tests, it is also found that the fatigueaccelerated test spectrum has an advantage over FALSTAFF spectra.

Research of the Unity Theory Between Three-level Space Vector and Carrier-based PWM Modulation Strategy

两电平空间矢量脉宽调制（space vector pulse widthmodulation,SVPWM）与正弦脉宽调制（sinusoidal pulse widthmodulation,SPWM）存有一定的本质关系,对于三电平,在常见的8段式SVPWM序列中可以证明,SVPWM与SPWM本质上也存在某种统一。实际的SVPWM调制中,由于要考虑中点电压平衡、减少谐波等其它性能问题,一般会利用开关冗余状态得到8段以上的开关调制序列。目前的文献中还未曾有对这些情况进行统一性地验证,因此三电平SVPWM与SPWM的统一理论存在一定的不足。研究发现,可通过严格地理论推导将传统意义上的调制波分解为2个子调制波,再进行SPWM调制,可以得到与SVPWM完全吻合的序列。该文在此方法基础上深入研究了8段以上（10、12、14段）的SVPWM调制序列与SPWM的统一。经过严格地理论推导,成功实现了含任意段数的SVPWM序列与SPWM的统一。仿真结果证明了该理论的正确性。

Anomalous behaviours of terahertz reflected waves transmitted from GaAs induced by optical pumping

Femtosecond pump-terahertz probe studies of carrier dynamics in semi-insulating CaAs have been investigated in detail for various pump powers. It is observed that, at high pump powers, the reflection peaks flip to the opposite polarity and dramatically enhance as the pump arrival time approaches the reflected wave of the terahertz pulse. The abnormal polarity-flip and enhancement can be interpreted by the pump-induced enhancement in the photoconductivity of GaAs and half-wave loss. Moreover, the carrier relaxation processes and surface states filling in GaAs are also studied in these measurements.

Analysis on Existence of Magnetostatic Solitons in Ferromagnetic Film under the Influence of Carriers

This article studies the characteristics of magnetostatic surface waves (MSSW) in a ferromagnetic film attached to a semiconductor cladding with carriers and shows the existence of magnetostatic solitons in the film. The results indicate that under the influence of drifting carriers, and within some frequency ranges, MSSW can develop into magnetostatic solitons, with the group velocity and phase velocity opposite under some conditions, and the velocity magnitude is related to the carrier density.

Estimation of Springing Response for 550 000 DWT Ore Carrier

The desire to benefit from economy of scale is one of the major driving forces behind the continuous growth in ship sizes. However, models of new large ships need to be thoroughly investigated to determine the carrier's response in waves. In this work, experimental and numerical assessments of the motion and load response of a 550,000 DWT ore carrier are performed using prototype ships with softer stiffness, and towing tank tests are conducted using a segmented model with two schemes of softer stiffness. Numerical analyses are performed employing both rigid body and linear hydroelasticity theories using an in-house program and a comparison is then made between experimental and numerical results to establish the influence of stiffness on the ore carrier's springing response. Results show that softer stiffness models can be used when studying the springing response of ships in waves.

基于三状态PWM的电动汽车电机驱动系统多模式调制策略研究

在电动汽车电驱动系统中,逆变器中的高频开关动作是产生开关损耗影响逆变器效率的主要因素,特别是为适应驱动电机高速化的趋势,不得不采用较高的开关频率,从而在低速时产生不必要的开关损耗,使逆变器效率偏低。因此,该文提出一种基于三状态脉冲宽度调制(TSPWM)的多模式调制策略来减少逆变器的开关损耗,提高全工况范围的逆变器效率。根据工况动态改变调制模式:在不同转速下采取变载频分段异步TSPWM;根据电机的相电流幅值动态地改变TSPWM不连续调制的钳位模式,使电流幅值较大的相保持在钳位状态以减小损耗。为了解决不同模式切换时相位突变导致电流或转矩冲击的问题,提出一种基于载波周期角度计算的电压矢量相位补偿算法,通过精确分析调制模式改变时刻对电压矢量角的影响,计算出切换后的补偿角度对空间电压矢量角进行补偿,从而实现不同模式的平滑切换。最后,通过算法仿真和电机实验验证了所提策略的有效性。结果表明,采用基于TSPWM的多模式调制策略的电机驱动系统,其逆变器效率得到了显著提升,且具有较小的共模电压。

悬浮电容H桥级联七电平逆变器的混合载波频率调制策略

多电平逆变器具有输出电压谐波含量少、开关器件电压应力低、等效开关频率高等优点,广泛应用于新能源发电场合。悬浮电容H桥级联七电平逆变器,因开关频率低、器件数量少、输出电平数量多得到广泛的关注。为了降低损耗,使H桥逆变单元开关管以低开关频率动作,悬浮电容逆变单元开关管以高开关频率动作,但是会引起过调制和悬浮电容电压失控的问题。为解决过调制问题,该文提出基于调制波分解的混合载波频率调制策略,增加过调制区间的调制过程,分解悬浮电容逆变单元超出载波部分的调制波,使H桥逆变单元开关管以低开关频率运行;同时提出基于工作模式切换的有功功率分解控制,详细分析两种工作模式下的稳压控制原理,根据电容电压的状态改变悬浮电容逆变单元有功功率大小,实现不同工况下悬浮电容电压均衡。最后通过仿真和实验验证了所提调制策略的正确性。

固体介质中的冲击极化效应研究进展

冲击波在固体介质内传播时,内部电荷随冲击波作用向两极迁移形成电势差并对外输出电压/电流的极化效应称作冲击极化效应。针对晶体、金属、陶瓷以及聚合物等典型固体介质的冲击极化效应进行了系统梳理;总结了现阶段发展的冲击极化测试方法,分析了落锤/摆锤、SHPB、轻气炮以及炸药爆轰等加载方式诱发固体介质极化响应的差异;概述了有限元方法、分子动力学、近场动力学方法以及相场分析方法在固体介质冲击极化数值模拟领域的应用;围绕Allison理论、张裕恒理论、冲击挠曲电理论以及冲击波相关理论,总结了固体介质冲击极化的宏观唯象理论,并从固体介质微观结构、载流子输运模式、输运模型、迁移率以及态密度等方面说明了冲击极化的微观机理;分析了冲击极化效应在传感器、俘能器以及致动器等领域的应用前景,对固体介质冲击极化效应的发展趋势和需求进行了展望。

强信号全覆盖环境高精密传感器微弱信号调制设计

在强信号的存在下,传感器微弱信号会被干扰、淹没或认为噪声,导致信号无法准确读取影响传感器的性能。为了解决这个问题,提出了一种强信号全覆盖环境高精密传感器微弱信号调制设计方法。该方法利用压缩感知技术重构完整的高精密传感器微弱信号集,通过自适应滤波器进行滤波以降低噪声,提高微弱信号的信噪比。利用基于正弦载波的扩频调制技术对微弱信号展开调制,将微弱信号扩展到宽频带中,以提高微弱信号的抗干扰能力和传输效率。实验结果表明,所提方法的信号重构精度高,能够有效滤除信号中的噪声,提高信号的抗噪声能力。并且信号调制性能好、抗干扰能力强。

A new optimization algorithm based on chaos

In this article, some methods are proposed for enhancing the converging velocity of the COA (chaos optimization algorithm) based on using carrier wave two times, which can greatly increase the speed and efficiency of the first carrier wave’s search for the optimal point in implementing the sophisticated searching during the second carrier wave is faster and more accurate. In addition, the concept of using the carrier wave three times is proposed and put into practice to tackle the multi-variables opti- mization problems, where the searching for the optimal point of the last several variables is frequently worse than the first several ones.

浮动载波技术在中波数字调幅发射机上的应用

随着通信技术的飞速发展,浮动载波技术因其灵活的频率调整能力,逐渐在中波数字调幅发射机领域受到广泛关注。这种技术不仅为广播行业带来了更高的信号适应性,而且在应急通信和节目切换等领域展现出独特的价值。通过深入分析浮动载波技术在中波数字调幅发射机上的应用及其相关注意事项,揭示其在广播电视、应急通信等领域的应用价值。

载波移相SPWM开关频率的选取

载波移相正弦脉冲宽度调制(SPWM)应用于高压大容量链式多电平逆变器场合时,若载波频率太低,各载波初相位对输出电压相位影响较大,可能造成链式逆变器各单相桥输出电压基波初相位存在明显差异,引起电容电压不平衡。推导了载波移相SPWM输出电压的数学表达式,分析了低开关频率下输出电压的谐波特性及其对逆变器运行的影响,提出应选择较高的载波频率。数字仿真和物理实验结果表明,在一相串联桥数大于4时,选择高于300Hz的载波频率,可保证各桥输出电压初相位差异小于0.5°,对电容电压的影响可忽略。

载波PWM方法三电平逆变器中点电位控制研究

分析了三电平中点箝位(Neutral Point Clamping,简称NPC)逆变器的中点电位平衡问题,讨论了通过注入零序电压实现中点电位控制的载波PWM方法,并在此基础上对一种实时控制中点电位平衡的方法进行了改进,提出一种基于零序电压注入的载波交叠PWM方法。仿真及实验结果验证了该方法良好的中点电位控制能力及输出电压谐波特性。

非均匀传输特性的低压电力线载波传输模型

在传统电力线均匀传输电路模型的基础上,结合电力线的非均匀传输特性,提出一种新的电力线载波通信的通信传输模型,该模型充分考虑了低压电力线阻抗特性、噪声干扰、衰减特性等因素对低压电力线载波通信的影响,从而为信号信道模型的建立提供了较好的理论依据。

低压电力载波技术及其在抄表系统中的应用

对几种比较典型的低压电力载波技术做了介绍,并对载波抄表系统载波调制方式、信号传输特性、实际应用效果等方面做了技术分析。通过比较和分析,总结了电力载波集中抄表的技术发展趋势。

基于apFFT的罗兰-C信号相位编码识别

针对现有罗兰-C接收机普遍采用锁相环硬件电路跟踪相位的情况,提出了利用全相位谱分析(apFFT)的罗兰-C信号相位编码软件识别方法,分析了罗兰-C载波信号初相位的apFFT识别原理,基于apFFT方法用Matlab对罗兰-C接收信号在噪声和载波干扰等情况下的初相位识别进行了仿真.结果表明,apFFT方法既能像FFT一样分析出干扰频率成分,又能识别出各频率成分的初相位,尤其信干比在-20 dB情况下仍可准确地识别出罗兰-C载波信号初相位,为增强型罗兰接收机的设计提供了一种新的相位编码识别方法.

一种改进的载波电子散斑干涉处理方法

提出了一种新的载波电子散斑干涉的处理方法,该方法将载波所形成的直条纹和包含物体变形信息的弯曲条纹在频域直接比较,避免了传统载波干涉方法中的载波频率计算和由此带来的误差 因此在准确程度和方便性方面都有明显改进 本文在给出理论分析的同时进行了实验验证.

一二次配合的配电线路自适应重合闸

针对配电线路常规重合闸因重合前不能区分永久性和瞬时性故障可能造成多次短路冲击的问题,系统论述了基于一二次配合的配电线路自适应重合闸技术。介绍了基于一二次配合的配电线路自适应重合闸4种实现途径,即:限流试探法、电容放电试探法、脉冲试探法和载波试探法。分别论述了限流试探法串联型和并联型两种结构的工作原理以及技术特点,并给出限流阻抗典型参数。理论分析了电容试探法的回路放电特性及阻容参数的选取原则并给出了典型取值。指出脉冲试探法的关键在于分相快速开关的分闸速度和动作离散度,并建议了脉冲试探法下的阻抗参数识别方法实现原理。给出了载波试探法的信号频率及试探电压的选取原则以及典型值。