The Planck Constant and Its Relation to the Compton Frequency

The Planck constant is considered one of the most important universal constants of physics, and despite all we know much about it, the physical nature of it has not been fully understood. Further investigation and new perspectives on the Planck constant should therefore be of interest. We demonstrate that the Planck constant also can be directly linked to the Compton frequency of one, which again is divided by the Compton frequency in one kg. If this is right, it means also the Planck constant is linked to quantization of matter, not only energy. However, as we will show the frequency of one when expressed in relation to kg will be observational time dependent. This means the missing mass gap surprisingly both is equal to the Planck mass, which is larger than any known particle and also it is linked to a very small mass that again is equal to what has been suggested as the photon mass in the existing literature. This new view could be an important step forward in understanding the physical nature of the Planck constant as well as the mass gap and even the rest mass of a photon.

The Control System Simulation of Variable-Speed Constant-Frequency Wind Turbine

In general,Variable-Speed Constant Frequency (VSCF)Wind generation system is controlled by stator voltage orientation method which based on the mathematic model of VSCF Wind generation system and discussed the control strategy.Present the whole dynamic control model of variable-speed wind generator system in MATLAB/ Simulink,and the simulation results confirm the validity and effectiveness of the proposed control strategy.

Enriched Constant Elements in the Boundary Element Method for Solving 2D Acoustic Problems at Higher Frequencies

The boundary element method(BEM)is a popular method for solving acoustic wave propagation problems,especially those in exterior domains,owing to its ease in handling radiation conditions at infinity.However,BEM models must meet the requirement of 6–10 elements per wavelength,using the conventional constant,linear,or quadratic elements.Therefore,a large storage size of memory and long solution time are often needed in solving higher-frequency problems.In this work,we propose two new types of enriched elements based on conventional constant boundary elements to improve the computational efficiency of the 2D acoustic BEM.The first one uses a plane wave expansion,which can be used to model scattering problems.The second one uses a special plane wave expansion,which can be used tomodel radiation problems.Five examples are investigated to showthe advantages of the enriched elements.Compared with the conventional constant elements,the new enriched elements can deliver results with the same accuracy and in less computational time.This improvement in the computational efficiency is more evident at higher frequencies(with the nondimensional wave numbers exceeding 100).The paper concludes with the potential of our proposed enriched elements and plans for their further improvement.

Joint Estimation of Carrier Frequency and Phase Offset Based on Pilot Symbols in Quasi-Constant Envelope OFDM Satellite Systems

Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high spectral efficiency and low peak-to-average power ratio(PAPR). Therefore, the QCE-OFDM technique is considered as a promising candidate multi-carrier technique for satellite systems. However, the Doppler effect will cause the carrier frequency offset(CFO), and the non-ideal oscillator will cause the carrier phase offset(CPO) in satellite systems. The CFO and CPO will further result in the bit-error-rate(BER) performance degradation. Hence, it is important to estimate and compensate the CFO and CPO. This paper analyzes the effects of both CFO and CPO in QCE-OFDM satellite systems. Furthermore, we propose a joint CFO and CPO estimation method based on the pilot symbols in the frequency domain. In addition, the optimal pilot symbol structure with different pilot overheads is designed according to the minimum Cramer-Rao bound(CRB) criterion. Simulation results show that the estimation accuracy of the proposed method is close to the CRB.

On maximum power point tracking control strategy for variable speed constant frequency wind power generation

Based on the characteristic of AC-excited variable speed constant frequency(VSCF)wind power generation,the vector control technique was applied in a doubly fed induction generator(DFIG).Maximum wind energy or maximum output power point can be tracked by decoupling control of active power and reactive power.The research result shows that the net power of generation system delivered to grid in maximum wind energy tracking mode is not the most.We presented a novel maximum power point tracking(MPPT)control strategy by analyzing the DFIG mathematic model and power relations which delivered the maximum power to the grid.The maximum power point could be tracked automatically without measuring wind speed in the control strategy and the control was independent of optimal turbine power curve,which had excellent dynamic and static performances and robustness.Simulation and experimental results testify the accuracy and validity of the control strategy.

An Improved Frequency Domain Technique for Determining Soil Water Content

For many years a soil water content sensor with low cost, reliability and sufficient accuracy has been desirable. Thus, an improved measurement method based on the frequency domain (FD) principle for determining soil water content was considered. Unlike other measurement principles, a new measurable index, η, which was independent of the output impedance and the amplitude of the oscillator while relying on the electrical impedance of a multi-pin probe, was pro- posed. Moreover, a model for processing the impedance of the multi-pin soil probe was developed, and several important electrical parameters for establishing their operating ranges applicable to this probe were evaluated. In order to confirm the theoretical analysis, an experiment was conducted with a 4-pin probe. Using the developed model, the relationship between the proposed index η and soil volumetric water content was shown to be linear (R2 = 0.9921). Thus, as the measurable index, η seemed satisfactory.

Influence of Temperature and Frequency on Microwave Dielectric Properties of Lunar Regolith Simulant

The dielectric constant of the lunar regolith can directly influence the reflection coefficient and the trans-mission coefficient of the Moon′s surface, and plays an important role in the Moon research. In order to study the di-electric properties of the lunar regolith, the lunar regolith simulant was made according to the making procedure of the CAS-1 simulant made by Chinese Academy of Sciences. Then the dielectric constants of the lunar regolith simulant were measured with 85070E Aiglent Microwave Network Analyzer in the frequency ranging from 0.2 GHz to 20.0 GHz and at temperature of 25.1℃, 17.7℃, 13.1℃, 11.5℃, 9.6℃, 8.0℃, 4.1℃, -0.3℃, -4.7℃, -9.5℃, -18.7℃, -27.7℃, and -32.6℃, respectively. The Odelevsky model was employed to remove the influence of water in the air on the final effective dielectric constants. The results indicate that frequency and temperature have apparent influences on the dielectric constants of the lunar regolith simulant. The real parts of the dielectric constants increase fast over the range of 0.2 GHz to 3.0 GHz, but decrease slowly over the range of 4.0 GHz to 20.0 GHz. The opposite phenomenon occurs in the imaginary parts. The influences of the frequency and temperature on the brightness temperature were also estimated based on the radiative transfer equation. The result shows that the variation of the frequency and temperature results in great changes of the microwave brightness temperature emitting from the lunar regolith.

Geometrical structures, vibrational frequencies, force constants and dissociation energies of isotopic water molecules (H_2O, HDO, D_2O, HTO, DTO, and T_2O) under dipole electric field

The dissociation limits of isotopic water molecules are derived for the ground state. The equilibrium geometries, the vibrational frequencies, the force constants and the dissociation energies for the ground states of all isotopic water molecules under the dipole electric fields from -0.05 a.u. to 0.05 a.u. are calculated using B3P86/6-311＋＋G（3df,3pf）. The results show that when the dipole electric fields change from -0.05 a.u. to 0.05 a.u., the bond length of H-O increases whereas the bond angle of H-O H decreases because of the charge transfer induced by the applied dipole electric field. The vibrational frequencies and the force constants of isotopic water molecules change under the influence of the strong external torque. The dissociation energies increase when the dipole electric fields change from -0.05 a.u. to 0.05 a.u. and the increased dissociation energies are in the order of H2O, HDO, HTO, D2O, DTO, and T2O under the same external electric fields.

REGULARITY OF VIBRATION RESPONSE OF MECHANICAL SYSTEM UNDER AFFECT OF VARI-FREQUENCY EXCITING FORCE

The vibration response formulas of the mechanical system under the affect of thevari-frequency exciting force are deduced. It is proved by the theoretical analysis and experimentalresults that the vibration response amplitude of the mechanical system under the affect of thevari-frequency exciting force is far smaller than that under the affect of the constant frequency exciting force on condition that the exciting force amplitudes are just the same;while the vari-fre-quency rate a increases to 5 Hz per second the vibration amplitude will decrease to 10% only as lowas that under the affect of the constant frequency exciting force. All these conclusions will be of significance for revealing the mechanism of suppressing chatter in van-speed cutting and analyzing theexperimental results of sine-wave scanning exciting test.

Frequency Synchronization in OFDM System

An accurate frequency synchronization method using the zadoff-chu (ZC) constant envelop preamble is analyzed, and a new preamble weighted by pseudo-noise sequence is used for orthogonal frequency division multiplexing (OFDM) systems. Using this method, frequency offset estimator range is greatly enlarged with no loss in accuracy. The range of the frequency estimation is ±30 of subcarrier spacing using ZC sequence as preamble. Simulations in the MATLAB for an AWGN channel show that the proposed method achieves superior performance to existing techniques in terms of frequency accuracy and range.

Modeling and Analysis of Variable Frequency Inverted Sine PWM Technique for a Hybrid Cascaded Multilevel Inverter

In cascaded H-bridge multilevel inverter, a variable frequency inverted sine PWM technique is modeled for hybrid electric vehicles. It has a particular advantage of increasing power which is achieved using series connection of H-bridge and also this topology is capable to produce superior spectral quality with considerable improvement of fundamental voltage. The variable frequency inverted sine PWM technique produces lesser torque ripple and enhances the fundamental output voltage mainly at lower modulation index ranges. The topologies of multilevel inverter are flying capacitor, diode clamped and cascaded inverter. In the paper, we will discuss about the cascaded multilevel inverter based on inverted sine PWM technique. The two switching strategies widely used to control multilevel inverters are constant frequency inverted sine PWM (CF-ISPWM) and variable frequency inverted sine PWM (VF-ISPWM). This implies that switch utilization substantially reduces 32.35% of the constant frequency inverted sine PWM switching technique. The performance of the technique is validated in terms of Total Harmonic Distortion (THD) and Torque ripple which significantly reduces when compared to constant frequency ISPWM. The analysis of conventional triangular PWM inverter and inverted sine PWM inverter using constant and variable switching scheme is done in MATLAB Simulink and verified experimentally by FPGA Spartan 3E processor.

基于频率切换实现恒流/恒压输出的电场耦合无线电能传输系统

电场耦合无线电能传输(electric-field coupled wireless power transfer,EC-WPT)技术的实际应用中,有些用电设备需要系统具有不同的恒定输出特性(恒流/恒压),即系统输出电压或输出电流与负载解耦,此外,系统还需具备在恒流、恒压模式间按需切换的功能。针对该需求,基于LC-CLC谐振网络提出1种具有恒流/恒压输出特性的EC-WPT系统,分析LC-CLC谐振网络特性,推导恒流/恒压输出特性的实现条件以及恒流频率和恒压频率的计算方法,并给出系统参数设计方法,分析系统对工作频率的敏感性。最后通过仿真和实验验证所提出的EC-WPT系统恒流/恒压输出特性及其参数设计方法的正确性和有效性。实验结果表明所提出的系统在输入电压恒定的不同负载工况下分别实现2 A的恒流输出以及96 V的恒压输出,其最大传输效率分别为87.83%及88.17%。

抽油机井恒功率变频控制系统研究

抽油机作为陆上油田最重要的机械采油装备之一,近年来已发展出一系列的变频节能技术,但其研究主要集中在硬件方面,缺乏相关基础理论,导致现场应用普适性差,应用效果参差不齐。为此,研究有杆泵变频测控机理,优选了主要部件,对测试数据提出了要求,形成了有杆泵抽油变频控制系统。构建BP神经网络系统对正常井和漏失、柱塞碰泵、气体影响等异常井进行识别,分类提出变频计算模型:考虑负扭矩和抽油机冲次界限等建立了正常井恒功率变频计算模型,实例对比分析了变频后抽油机速度、加速度变化规律,产液量一定时,负功功率和有功功率分别下降了65%和44%。建立了上行程漏失的异常井变频计算模型,针对性地提高上行程冲次,形成“上快下慢”运行模式。实例计算表明:该系统缩短上行程时间2.6 s,较好地解决有杆泵上行程漏失和变频节能的问题。研究成果可为抽油机变频技术提供理论支持,对油田节能和提产具有指导意义。

基于PLC与变频器的恒压供水系统设计

采用PLC和变频器相结合设计恒压供水系统,采集管网的水压力,经A/D转换后送入PLC,经PLC的PID运算后输出信号来控制变频器的输出电压和频率,改变电动机的转速来改变供水量,最终使管网水压力值稳定在恒定值。实践证明,该系统稳定可靠,同时还具有良好的节能效果。

基于驯服钟控技术的时间频率源设计

标准时间频率信号是系统高效工作的基石,越来越高的时间频率测量精度对时频信号的产生提出了高稳定高准确度的要求。介绍了时间频率源的基本概念,阐述了一种基于驯服钟控技术的高稳定度高准确度时间频率源的基本工作原理及其设计,其输出的频率信号短期稳定度可达1.46×10-13/s。该设计方案已经成功应用于多个车载测控通信系统。

高压油泵阻尼孔对燃油系统压力特性的影响研究

为实现更高的热效率和更优的排放,柴油机的喷射压力不断提高。阻尼孔作为高压油泵等压出油阀的关键结构,对燃油系统的压力特性有重要影响。本文研究了阻尼孔大小对喷油器的喷射特性以及高压油管压力波动特性的影响,结果表明:随着阻尼孔由0.1 mm增大至2.0 mm,喷油器喷油持续期相对缩短,循环喷油量减小,这是不同阻尼孔对应的高压油管残余压力大小不同,以及不同阻尼孔大小对系统压力调节的速度不同的结果;此外,阻尼孔较小(0.1 mm)时,燃油系统存在二次喷射现象,而阻尼孔过大(3 mm)时,系统内还会存在零压区,即存在穴蚀的风险;对高压油管残余压力的频谱分析发现,阻尼孔较小时,高压油管内压力脉动与出油阀的运动存在较强的相关性,而阻尼孔较大时,压力脉动与回油阀的运动相关,即供油系统中多种阀件的运动是高压油管压力脉动的主要原因。

用于材料毫米波介电特性测试的光子晶体谐振器研究

在微波能应用研究中,材料的介电特性是其重要特性,决定了材料被微波的处理能力。为开展毫米波频域的微波能应用研究,本文研究了一种用于材料毫米波介电特性测试的光子晶体谐振器。该谐振器基于三角晶格分布的光子晶体结构,所设计介质光子晶体的带隙为87~107 GHz。在其基础上,通过增加线缺陷和两个锥形结构形成直接与WR-10波导相连接的介质光子晶体波导,通带范围为88~99 GHz。在此介质光子晶体波导的中心增加直径为d=0.51 mm的通孔,构成光子晶体谐振器。向谐振器中心通孔放入待测量的介质材料,待测材料的介电常数将对谐振腔的谐振频率产生影响,通过测量谐振频率的变化,则可得到待测材料在88~99 GHz频段的介电常数。通过CST仿真研究,所设计的结构可以对高介电常数材料的介电特性进行测试,可测量材料的介电常数测量范围在67~94.5 GHz之间。

孤岛微电网电流同步U-I下垂控制方法

采用电压-电流(U-I)下垂控制的孤岛微电网系统始终运行于工频频率,避免了传统下垂控制存在的频率偏差及频率越限问题,但电源间易产生环流,功率分配精度差。为此,提出电流同步U-I下垂控制方法,该方法由电流同步控制及U-I幅值下垂控制两部分构成。前者通过调节输出电压相角使各电源输出电流相角一致,以抑制电源间环流;后者依据输出电流的幅值调节输出电压的幅值,使各电源出力依据自身容量分配。在此基础上,建立双端系统的小信号模型,分析电流同步控制环路中控制参数对系统稳定性的影响,为参数设计提供依据。仿真及实验结果表明,相比U-I下垂控制,所提方法的系统环流减小50%以上,电压畸变率改善近10%,电源间功率分配精度及系统电能质量均得到明显提升。

杭州国家版本馆恒温恒湿空调系统调适

恒温恒湿空调作为一种工艺性专用空调系统,对受控的室内环境温度和湿度有严格要求,而且维护系统运行需要相当高的能耗。在此以杭州国家版本馆项目为例,介绍了恒温恒湿空调系统的调适过程,分析水系统静态水力平衡、水系统最不利压差调整、风系统合理组织气流、水泵和风机变频调节、系统异常情况处理、气温反常变化应对等技术,并给出了有效的解决方案,为系统稳定节能运行提供良好保证。

LCL型三电平并网逆变器定频滞环控制研究

为增强并网逆变器控制性能,降低入网电流谐波含量,提出一种基于LCL型三电平逆变器的定频滞环控制。推导桥侧电流与网侧电流关系,通过对桥侧电流的直接控制进而间接控制网侧电流。将参考电压六边形区域分为12个小平行四边形区域,实现对相间误差电流的解耦控制。根据上一周期的开关时间和环宽,实时调整下一周期环宽以实现定频控制。此外,借助扩张状态观测器进行微分跟踪,完成参考电压矢量扇区判断和桥侧参考电流估计。最后通过仿真和半实物仿真对定频滞环控制策略进行验证。