查询词典 frequency analysis

Nowadays the researches of frequency distribution of data are almost limited to normal distribution, while other distributions are seldom studied. Many frequency distributions of data are not normal. This kinds of frequency distribution of data widely exist. Unimodal frequency distribution of data often occurs.

现在绝大多数关于频数资料分布的研究都是基于正态分布的，而对其他类型的分布研究得比较少，实际上频数分布在许多情况下并非呈现正态分布，分布的形态丰富多彩，很多资料都是呈现单峰分布，本研究就是利用数学上常见的八种连续型变量的分布类型去拟合单峰频数资料。

The curve obviously declined from the low frequency to the middle frequency section, and was reduced to zero in the high frequency section, which objectively showed the change in imaging characteristics of the eyes from the low to high frequency areas.

PSF分析系统可直接采用屈光系统MTF曲线表达人眼的成像特征，该曲线MTF值从低频至中频迅速下降，高频趋向缓和至零，定量并客观地表达了人眼成像质量从低频至高频的改变。

The study on the electrical property shows that its dielectric property decreases with the slowly increase of frequency in dry state; in hygrometric state (52.9%), the dielectric property grows obviously and declines swiftly with the increase of frequency; and it tends to be stable when the frequency is over 10^4Hz. The specific resistance decreases linearly with the increase of the frequency. The results indicate that the electric properties of the hot press moulded wheat gluten are subject to the compaction rate of the material structure.

对小麦麸质模压板的电性能研究表明，干态下其介电性能随电场频率增加而下降，但变化小；湿态下其介电性能明显提高，且随频率增加迅速下降，超过10^4Hz后区域变化趋于稳定；热压小麦麸质材料的电阻率随频率的增加呈直线下降；小麦麸质热压材料的电性能主要决定于材料结构的密实程度。

The digital frequency source this paper researched uses high integrated DDS chip AD9851 as frequency sources and signal mirac processors AT89C51 as system control center, it can output 10Hz-20MHz signal with high-precision and high stability frequency. The evenness of signal within the range of 10MHz is low to 0.1dB degree, and the smallest step is low to 10Hz frequency.

本课题研究的数字频率源采用高集成度DDS芯片AD9851作为频率源；以单片机AT89C51作为系统的控制中心，实现了10Hz～20MHz的高精度、高稳定度的频率输出。10MHz内信号幅度的平坦度为0.1dB、频率最小步进为10Hz。

The effect of endoscopic plasma radio-frequency therapy for gastrointestinal polyps is obvious and very safe, and bequite with high-frequency eletrosetion, plasma radio-frequency electrosetion could be used on special locations and excelled to the comparisonal group in therapic time,be good for clinical using as the preferred method to therapy for gastrointestinal polyps.Key words: polypus recti; endoscope; radio–frequency therapy; cutting

等离子射频技术应用于消化内镜下息肉切除，具有安全、疗效可靠，其疗效与高频电切相当，且能够在内镜反转状态针对胃底、直肠下段等特殊部位息肉实施有效切除，在术后愈合时间上明显优于对照组，可尝试作为内镜下切除消化道息肉的首选方法，对具有消化内镜诊疗条件的医疗机构，值得临床推广应用。

The findings: with the apparent dominant frequency of the Ricker wavelet rising, the detection SNR will get worse gradually, it is obvious that the variety of the SNR is slower during the portion of high frequency than during the portion of low frequency; in the usual range of seismic prospecting frequency, the SNR of the chaotic oscillator detection system could partially make up the amplitude attenuation aroused by the transmit of the seismic wave; the results could provide help for detecting the event constituted by aberrant wavelets.

本文以Ricker子波模拟地震子波，研究Ricker子波视主频变化的相应检测效果。研究结果：随着Ricker子波视主频的升高，检测SNR逐渐变差，在高频部分SNR的变化明显比低频部分缓慢；在通常地震勘探频率范围内，混沌振子系统检测SNR有可能部分补偿由于地震波传播引起的幅度降低；为检测由畸变子波构成的同相轴提供一定的可能。

According to the field variation with frequency in the test volume, the work frequency of GTEM cell can be divided into three frequency areas, namely, quasi-static area, high frequency area and out of the vertical polarization area.

根据测试区场分布随频率的变化情况，可将GTEM传输室的工作频率分为三个特征频段，即：准静态区、高频区和非垂直极化区。

Based on the requisition of wireless system debugging, this paper develops a novel radio-frequency beaconing. Design method and system constitution of a novel beaconing based on PLL IC PE3336 are given, and the accomplish method of the system's hardware and software arc expounded. The test results show that the beaconing adopted in this method has a reliable and stable frequency conversion features. The more applications in the wireless system find that the users can set necessary frequency conveniently. Especial1, the friendly man-machine interface makes the operation is more flexible. It is as excellent performance-price-ratio beaconing, and as a signal source, it can be used in the research and the debug procession of variable radio-frequency components.

根据无线电数据链系统及部件的调试需要，研制开发了一种新型的以锁相环为核心、由单片机控制的射频信标机；文中给出了基于锁相环芯片PE3336的新型信标机的设计方法与系统组成，阐述了系统硬件及软件的具体实现为法；测试结果表明，利用该方法设计的信标机具有稳定、可靠的变频特性，且各项指标均达到了要求；进一步在某无线电系统中的应用发现，用户可方便地设置所需频点；特别是友好的人机界面，使用户操作更为灵活方便，是一种性能价格比优良的信标机；并可作为信源用于不同的射频部件研制与调试过程中。

Taking the development platform of HVDC power transmission for example, the calculation result of impedance-frequency characteristic of traditional line commutated converter and that of FCC are compared. Simulation results show that the impact of impedance-frequency characteristic of converter on the resonance frequency of AC system is not negligible, and FCC can enhance the strength of AC system in a certain extent, improve system stability and effectively reduce AC equivalent impedance under resonance frequency, thus the harmonic instability of HVDC power transmission system can be avoided.

以直流输电开发平台为例，对传统电网换相换流器(line commutated converter，LCC)与FCC的阻抗频率特性计算结果进行对比，仿真结果表明换流器的阻抗频率特性对交流系统的谐振频率有着不可忽略的作用，FCC在一定程度上提高了交流系统强度，改善了系统稳定性，有效降低了系统谐振频率下的交流等值阻抗，从而更好避免直流输电系统谐波不稳定现象的发生。

According to the method, model dimension is contracted to five by the way of selecting the unit in which amount of I/K is m inimal. Then sensitivity of frequency to stiffness is calculated. After the diff erence between measured frequency and calculated frequency have been got, the ad justed amount of stiffness is calculated by the using of the sensitivity and the frequency difference.

该方法按照I/K最小优先合并原则，将轴系模型自由度数缩聚为5，分析该模型4个刚度对前4阶频率的敏感度，算出实测的前4阶频率和模型计算频率之间的差值，利用敏感度和频率差值计算出刚度的调整量。

I hope that this success is just the first in a long series.

我希望这只是成功的开始。

Three dimensional stresses on the interface of tire and soil, tire deflection and soil sinkage are measured.

测试轮胎——沙土界面上的三向应力、轮胎变形和沙土沉陷；建立考虑剪切应力对沙土承载特性产生影响的车轮牵引性能预测模型；分析车轮作用下土壤的纵向稳定性。