频率

Gabor-ring is often used in texture feature extraction, but it is based on the assumption that texture is narrowband signal and can not applied to most actual textured images that have more than one center frequency in power spectrum. To overcome the limitation of existing method, an improved method is proposed. According to this method, Gabor filters are constructed in accordance with the spectrum feature vector of texture, and a relaxation parameter is used to determine the effect of difference filters so as to integrate the frequencies and phases into the process of extraction.

Gabor环（即在频率域成环形分布的Gabor滤波器组）常被用于提取图像纹理特征，但它是以"纹理是窄带信号"为基础的，实际的纹理图像并不能很好地满足"窄带信号"的假设，用一个中心频率来描述一种纹理对能量集中在多个频率点的纹理图像往往不能取得理想的效果，而根据频谱特征值向量构造Gabor环的改进方法，通过松弛因子的加入改变不同滤波器的作用强度，综合考虑了多频率多相位对纹理特征提取的影响。

The frequency step-by-steps in the above frequency range is 250Hz; The phase noise is low; The output profile degree of distortion is small, and outputs the frequency after ring circuit locking the temperature stability and the time stability and the datum frequency is same.

在上述频率范围内频率步进是250Hz；相位噪声低；输出的波形的失真度小，并且在环路锁定后输出频率的温度稳定度和时间稳定度与基准频率相同。

This paper analyzes the principle of chief anti jamming technologies of frequency agile radar FAR frequency diversity radar FDR and self adapt frequency agile radar SAFAR in frequency domain studies the effectiveness measurement methods of these technologies brings forward the self adapt improvement factor which measuring the anti jamming effectiveness of self adapted frequency agile radar .

分析了频率捷变，频率分集，自适应频率捷变等雷达在频域的主要抗干扰技术原理，研究了这些技术的效果度量方法，提出了度量自适应频率捷变雷达抗干扰效果的自适应改善因子。

ABSTRACT:The half-power bandwidth method is the commonly used method at home and abroad, the authors discover that factors, such as the sampling frequency, the frequency resolution, the ratio of the sampling frequency to the signal frequency, the analyzed width and the damping ratio, make the estimated damping ratio fluctuate vastly. Mostly the result is incredible except for some conditions, the error is sometime amazing, which is not acceptable.

半功率带宽法是国内外常用的测试阻尼的方法，笔者发现半功率带宽法由于受到信号处理中的①采样频率SF②频率分辨率△f③采样频率与信号频率之比K ④采样分析的长度T和⑤阻尼比D的大小等因素的影响使得测得的阻尼比值波动很大，除少数状态是可信的外，多数状态是不稳定的，有时误差惊人，得到的测试数据不能使用，易导致错误的结论。

By Using CPB to analyze the sound insulation character, it show that when the cavity depth is 30mm, the sympathetic vibration exist around the centre frequency of 200Hz of the system, the frequency character contours of sound insulation represent a lowest value. While the cavity depth is 40mm

使用CPB分析材料组合系统的隔声特性，当空腔深度为30mm，系统在中心频率200Hz附近产生共振，隔声频率特性曲线在该位置形成一个低谷；当空腔深度为40mm，隔声频率特性曲线在中心频率为160Hz位置形成一个低谷。

On the other hand, with the purpose of fuzzy feature extraction and fuzzy classification device design, the undulatory property of maximum and minimum scattering power corresponding respectively to the maximum and minimum eigen-polarization has been investigated in frequency domain. Furthermore, the anisotropy polarization degree of target, which is determined by both maximum and minimum scattering power of target, has been studied; meanwhile, the dynamic changing characteristic of eigen-polarization on Poincare polarization sphere has been investigated by means of the conception of polarization frequency stability, the research result shows that PSD value has a big jump near π, forming a sharp pulse, and different target has their individual distribution property of PSD pulse.

另外，围绕目标模糊特征提取及模糊分类器的设计，研究了目标最大、最小本征极化所对应的目标最大、最小散射能量随观测频率的起伏特性，考察了由目标最大、最小散射能量共同决定的目标的各向异性极化程度；同时，采用极化频率稳定度的概念，研究了本征极化在Poincare极化球面上的动态变化特性，在最大、最小散射能量相等的频率点上，PSD曲线呈现为幅度接近π值的尖锐脉冲，反映了目标极化散射结构对这一频率跳变极为敏感，但不同目标的这种PSD曲线特征又有很大的不同。

It tells particularly the debris flow"s the encironment and the development characteristic by numbers . And according to its character , selecting the latest research results at present , the anthor calculates the debris flow"s the moving , dynamical characteristics and the scale , such as , the velocity of flow , the wallop , the peak value flux , and the total flux . And the anthor calculates density in different design frequency by the empirical formula method . In the text, the author uses the modle of evaluating a single gully to evaluate the risk of the debris flow . First , the author calculates the hazard degree in different design frequency , and forecasts the risk range of debris flow in Shenjia gully based on the maximum pile thickness and the total solid amount of a denbris flow . Then , on the basis of the risk range in different design frequency , the author carries out the damageability and risk assessment . The basic purpose of risk management is reducing risk or transferring risk , reducing the loss of life and property . The text constructs the system of risk management of debris flow in Shenjia gully , basis on the condition of Shenjia gully .

本文从地形地貌、地层岩性、地质构造、气象水文等方面系统地阐述了深家沟泥石流的发育环境及发育特征；分别从形成区、流通区、堆积区对深家沟流域特征进行描述；依据泥石流沟自身特点，选用现阶段最新的研究成果，推算了不同设计频率下的深家沟泥石流流速、峰值流量、总流量、冲击力等动力特征和规模数据；并且根据经验公式法来确定深家沟不同设计频率下的泥石流容重；本文采用单沟泥石流风险评价模型对深家沟泥石流进行风险评价，首先对不同的设计频率下的深家沟泥石流进行危险度评价，根据最大堆积厚度与一次泥石流冲出量来预测不同频率下的泥石流危险范围，然后，根据预测的评估范围，评价对应范围内的易损度，最后作出风险评价；城镇泥石流风险管理的根本目的是降低风险或转移风险，减少生命财产的损失，本论文根据泸定深家沟泥石流的具体情况，构建了深家沟泥石流风险管理体系。

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。

In patient group, 40.74%(11/27) had DQB1 * 0503. The gene frequencies were 0.2302. In control group only 3. 75%(6/160) had DQB1 * 0503. The gene frequency was 0.0189. The differ- ence between the two groups was significant. After P value cor- rection, the difference was still significant.

在病人组中检出频率为40.74%（11/27），基因频率为0.2302，而对照组中DQB1*0503出现的频率只为3.75%（6/160），基因频率为0.0189，二组差别具有显著意义，校正P值后仍有显著意义。

This paper bases on frequency-hopped and frequency synthesis theories, and through demonstrating three schemes of frequency synthesis, the paper selects one of these schemes that uses DDS spiriting up PLL and improves on the method according to the practical target and synchronously, the paper analysis the capability of the output signal and the conversion time of the frequency.

本文在对跳频理论及频率合成理论分析的基础上，在讨论三种频率合成方案后，设计完成了一种适于本课题的DDS激励PLL的混合方案，并对频率合成器主要性能中的输出信号的噪声特性和频率转换性能做了研究分析。

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。