查询词典 difference frequency

This thesis contributed to the comprehensive study of the Finite-Difference Time-Domain method and its application to the numerical computation of radiated electromagnetic fields in switched mode power supplies. The work includes mainly three parts: the study on the performance of PML absorbing boundary condition applied to pseudo low frequency electromagnetic problems; the validation of the FDTD method with PML absorbing boundary conditions and the corresponding computer software based on the numerical study of the electromagnetic field of an electric dipole antenna, and its application to the numerical computation of radiated electromagnetic fields in switched mode power supplies; the development of an improved alternating direction implicit finite-difference time-domain method.

在综合前人工作基础上，本文对时域有限差分法及其在开关电源辐射电磁场数值计算中的应用进行了系统的分析和研究，其核心内容包括：伪低频电磁场数值计算中PML吸收边界条件性能的研究；基于基准问题—电偶极子天线三维辐射电磁场，验证了本文构造的基于PML吸收边界条件的三维FDTD法及其计算软件，并应用于高频开关电源辐射电磁场的数值分析；提出了一种改进的交替方向隐格式时域有限差分法。

By means of analyzing the difference between HVDC transmission line and traditional HVAC transmission lines, it is proved that it is not suitable to apply superposition principle to the power grid containing HVDC transmission lines, thus following conclusions are obtained: in the place near to HVDC transmission line the fundamental frequency fault component element should be not adopted; and there is definite relation between the maloperation of directional comparison pilot protection applied in practical project and the adoption of fundamental frequency fault component element.

通过分析HVDC的特性与传统交流系统的不同，证明叠加原理不能应用在含有HVDC的系统中，从而得出结论：在HVDC附近不应该采用工频故障分量元件，实际工程中的纵联方向保护误动作与使用工频故障分量元件有一定关系。

The system comprises low frequency-difference two-frequency laser interferometer measuration module,micro-detection device and two dimension platform.

系统由低频差双频激光干涉度量模块和微探头及二维工作台两部分组成。

The phase and group velocities of Lamb waves in the aluminum plate related to the frequency and the thickness of the plate because of the material characters. However, for the carbon fiber composite lamina, the situation was of difference, in which the velocities were with regarded to the frequency and thickness as well as the propagational direction and the fiber orientation.

输入铝板和碳纤维板的材料参数，即可得出铝板和碳纤维材料单层板中Lamb波的频散曲线，铝板为各向同性材料，其中的Lamb波相群速度只与频率板厚的乘积相关，碳纤维板为各向异性材料，其中的Lamb波相群速度不仅与频厚积有关，还与Lamb波传播方向、碳纤维的铺层方向相关。

Based on the laser longitudinal mode splitting theory, a novel scheme of dual-frequency laser with large frequency-difference is presented using electrically controlled birefringence of liquid crystal, and the transmitted resonant mode splitting by birefringent of Fabry-Perot etalon has been analyzed theoretically. A new element of liquid crystal Fabry-Perot etalon is designed and fabricated, which serves as aselector and splitter of both laser longitudinal modes and Fabry-Perot etalons transmitted resonant modes. Two different experimental systems of laser-diode end-pumped Nd:YAG laser have been set up using two different LDs, and the transmission of liquid-crystal cell have been measured. When the empty LCFP is inserted in the cavity of high-power LD pumped Nd:YAG laser, the oscillation of a single laser longitudinal mode have been observed, such a result shows that the designed and fabricated LCFP element is capable of selecting single axial mode. While an anti-reflected liquid crystal cell is inserted in the cavity of Nd:YAG laser end-pumped by the high-power LD, it is difficult to confirm weather the laser longitudinal modes have been spitted or not. The subject is summarized in this thesis and the improvement of the project has been presented.

论文以激光纵模的分裂理论为基础，提出了可望获得几十GHz甚至上百GHz的液晶电控双折射双频Nd：YAG激光器的总体方案，并对用双折射效应分裂F-P标准具透射谐振模进行了理论分析；设计并加工了一种集激光纵模选择、激光纵模分裂和F-P标准具谐振透射模分裂于一体的多功能元件——液晶电控双折射F-P标准具；建立了两种不同功率激光二极管端面泵浦的Nd：YAG激光实验系统，并对液晶盒的透射性质进行了测试；将未灌注液晶的空液晶F-P摘要标准具插入大功率LD泵浦Nd：、叭G激光谐振腔内，观察到了单纵模激光输出，说明所设计和加工的液晶F一P标准具具有纵模选择能力；将镀有增透膜的液晶盒插入大功率LD泵浦Nd八7AG激光谐振腔内，是否产生了激光纵模分裂现象还难以确定。

In this paper,The necessity of frequency tracking in ultrasonic cleaning equipmens is discussed.Based on a introduction on the principle of the mian circuit of the ultrasonic power supply for cleaning equipmens and the principle of PLL ,the output frequency of 74HC4046 is changed by a singlechip measuring the phase difference between volage and current.

本文讨论了超声波清洗机中自动频率跟踪的必要性，在介绍超声波清洗机的主电路原理、PLL锁相环原理的基础上，利用单片机检测超声电源负载的电流、电压的相位差，来改变74HC4046 的输出频率，完成了变步长频率跟踪软件设计。

modulation is the transmission of information to be loaded onto a high-frequency signal in the process.amplitude modulation using signal to control the rate of carrier,with its linear modulation signal changes,and maintain the same carrier frequency.in the amplitude modulation,in accordance with the strength of signals in the spectrum of different components,it is divided into ordinary am (amplitude modulation standard am),with inhibition of bilateral carrier am,the carrier single sideband suppression am.the main difference is the different methods and structure of the spectrum.

摘 要：调制是将要传送的信息装载到某一高频信号上去的过程。振幅调制是用调制信号去控制载波的幅度，使其随调制信号线性变化，而保持载波的频率不变。在幅度调制中，根据已调信号的频谱分量不同，分为普通调幅、抑制载波的双边带调幅、抑制载波的单边带调幅。它们的主要区别是产生的方法和频谱结构不同。

Paired t-test analysis was performed on the thresholds of SVR and PTA at each frequency (0.5, 1, 2 and 4kHz), and analysis of variance was performed on the difference between the pure tone audiometry threshold and the evoked potential threshold among different frequency.

对听力正常的46名志愿者，分别对双耳进行0.125~8kHz频率范围内的PTA阈值及0.5~4kHz频率范围内的SVR反应阈测试，通过配对t检验比较0.5、1，2、4kHz频率范围的SVR反应阈与PTA阈值的差异，并运用方差分析比较不同频率间的SVR反应阈与PTA阈值差值的差异。

As FSB is the system bus frequency; and refers to the CPU multiplier and FSB frequency in multiples of the difference.

至于外频就是系统总线的工作频率；而倍频则是指CPU外频与主频相差的倍数。

Analysis the effects of the frequency response difference between the sensor channels on the performance of the radar with linear frequency-modulated and pulse compression system.

分析了线性调频脉压体制下通道频率特性差异对雷达性能的影响。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。