查询词典 radio frequency

The working load of engin e in plowing can be taken for stable and normal random load whose power spectrum peak value is below 2 Hz. The working load of engine in rototilling contains bo th periodic element whose fundamental frequency is rotating speed of the blade s haft and normal random load of which the parts of energy centers in fundamental frequency and others are distributed over wider frequency band.

证实了犁耕作业发动机的载荷可以认为是平稳的正态分布的随机载荷，其功率谱曲线的谱峰在低于2 Hz处；旋耕作业发动机的载荷是兼有随机成分和周期成分的动态载荷，其中周期谐波的基频为刀轴转速，随机成分一部分能量集中于基频以内，部分分布于较宽频率范围。

The correlation detection using the periodicity of the direct sequence autocorrelation function can estimate the symbol period at intermediate frequency or at baseband. Simulation results indicate that the former is superior to the latter when the demodulated frequency is unequal to the carrier frequency.

时域相关检测方法利用扩频信号的周期自相关特性，能在中频和基带对扩频码周期进行估计，仿真结果表明中频检测时性能较好。

Takes several energy saving measures for air conditioning system, such as large capacity centrifugal chillers working with variable frequency small capacity chillers, variable frequency and variable flow control on secondary pump water systems, cooling tower for four-pipe water system in winter, fan-coil unit for commercial peripheral zones and all-air systems for interior zones, variable frequency control on supply and exhaust air fans,...

采用了多项空调节能措施：大冷量离心冷水机组搭配变频小冷量机组，二次泵变频变流量空调水系统，四管制风机盘管冬季用冷却塔换冷供冷设计，商业外区风机盘管、内区全空气空调系统，送风机、排风机变频控制，过渡季、冬季利用室外新风通风降温的焓值控制设计。

The vibrating wire sensors is excited by single-coil structure and the vibration signal will be feedback through the phototube and MCU.This structure not only simplify the hardware circuit,but also solve the problem of electromagnetic interference which generated by the course of frequency's excitation and pick-up,improve the measurement accuracy and stability of frequency.The application of sweeping frequency makes the vibration wire start-up more stable and reliable.

振弦传感器采用单线圈电磁激振方式，应用光电管结合MCU进行振动信号反馈，不但简化了硬件电路，而且解除了激振和拾振中电磁干扰问题，提高了测量的精度和稳定性；激振中采用的扫频技术也使振弦的起振更加稳定可靠。

In this chapter, three kinds of target recognition methods are performed, which are:①Target recognition method based on the description of polarization parameter plane. The echo polarization states of target are projected onto the polarization state plane described by the ellipticity ε and the tilt angle τ of the polarization ellipse, the change of parameter following ferquency becomes the chart. According to the changing trait of the chart, the multidimensional polarization feature space of target has been contructed. Furthermore, a series of polarization feature parameters used in designing the structure of target recognition device are extracted, and they are insensible to the posture of target.②Target recognition method based on the description of Poincare polarization sphere. The echo polarization states of target expressed by Stokes vector are projected onto the Poincare polarization sphere. The conception of polarization ferquency stability, which is used in describing the dynamic distribution characteristics of the target echo polarization states on Poincare polarization sphere, has been defined. A group of polarization feature parameters used in designing the structure of target recognition device are extracted, and they are insensible to the posture of target.③Target recognition method based on the description of frequency sensitivity. In accordance with the conception of the polarization state distance defined on Poincare polarization sphere, the frequency sensibility of the physical structure property of target has been investigated, the frequency distribution feature curves in PSD domain are obtained, and targets'features are extracted by means of the curve-fitting method with Least Square Criterion.

这章具体研究了基于三种极化散射特性描述的相应的目标识别方法：①基于极化参数平面描述的目标识别方法，将目标回波极化状态投影到以极化椭圆参数，即椭圆率角ε和倾角τ表征的极化状态平面上，参数随观测频率的变化就形成了图，根据图的变化特点构造了目标的多维极化特征空间，并提取了不敏感目标姿态变化的极化特征参数组来设计目标的识别器结构；②基于Poincare极化球面描述的目标识别方法，采用Stokes矢量表征目标回波的极化状态，并将其投影到描述极化状态的Poincare极化球面上，定义了极化频率稳定度的概念用以刻画目标回波极化状态在Poincare极化球面上的动态分布信息，提取了准方位不变性的目标极化特征，最后设计了目标的识别器结构；③基于频率敏感性描述的目标识别方法，通过在Poincare极化球面上所定义的极化状态距离的概念，研究的是复杂目标物理结构特性对探测信号频率的敏感程度问题，获得了在极化状态距离下的频率分布特性曲线，采用最小二乘估计曲线拟合方法，它既用于极化特征的降维，同时又直接将拟合参数作为目标的分类特征。

The results showed that food ingestion and frequency of the polecat in constant food patches were higher than that in the variable food patches and time of the polecat was the same between two patches during the training period. Only the frequency of the polecat in constant food patches was higher than that in variable food patches when the polecat was starved for 1 day. Its foraging pattern between the two patches was the same as that during the training period when the polecat was starved for 2 days. Meanwhile, the food ingest ion amount in the two patches was not affected by starvation, but the time and frequency of the polecat using the two patches significantly decreased when starvation increased.

研究结果表明，训练期实验中，艾虎对固定食物量斑块中的取食量和利用频次明显高于变化食物量斑块，而对两个斑块的利用时间基本相同；艾虎饥饿一天后对固定食物量斑块中的利用频次明显高于变化食物叠斑块，而对两个斑块的利用时间和取食量基本相同；艾虎饥饿两天后对两个斑块利用程度与训练期的结果相同：同时，艾虎在两个斑块中的取食量均与饥饿程度无关，而对两个斑块的利用时间和利用频次均随饥饿程度明显降低。

This dissertation studies several kinds of instantaneous frequency estimation methods, pay much attention to the performance of instantaneous frequency estimation algorithm based on the peak of time-frequency distribution. It gives the theory and algorithm of polynomial Wigner-Ville distribution, analyzes its performance to the noise of the moving target in the air.

对常用的几种瞬时频率估计算法进行了研究，重点研究了基于时频分布峰值的瞬时频率估计算法的性能，给出了多项式Wigner-Ville分布的原理与算法，分析了在直升机定位这种特定情况下的有效性。

It gives performance comparison of instantaneous frequency estimation algorithms based on the peak of Wigner-Ville distribution and fourth-order polynomial Wiger-Ville distribution, analyzes the influence of window width to the estimation performance of instantaneous frequency estimation algorithms based on time-frequency distribution.

在不同飞行状态下，给出了基于Wigner-Ville分布、四阶多项式Wigner-Ville分布峰值的瞬时频率估计算法的性能对比，并分析了窗长对瞬时频率估计性能的影响。

The change of frequency, draws the conclusion through observing fish's respiratory rate and coughing: Luo is not the respiratory rate of fish and bright cloud porgy, drop with increase of Cu2+ density, cough frequency increases with increase of Cu2+density; Respiratory rate and frequency of coughing of black carp, appear downward trend after rising with Cu2+ increase of density first.

通过观察鱼呼吸频率和咳嗽频率的变化，得出结论：罗非鱼和彩云鲷的呼吸频率，随着Cu2+浓度的增加而下降，咳嗽频率随着Cu2+浓度的增加而增加；鲫鱼的呼吸频率和咳嗽频率，随着Cu2+浓度的增加都呈现先上升后下降的趋势。

The first adjustment was to replace logarithm function by S function for modeling the inner hair cells in cochlea,and the other was distributing frequency bins on frequency axis with the width of frequency bin proportionably increasing.

利用S函数取代对数函数对耳蜗内毛细胞进行模拟，将频率箱按照频率范围等比递增的方式在频率轴上进行分布；同时，利用Gammatone滤波器组进行耳蜗基底膜的建模。

Listen,point and check your answers.

听，指出并且检查你的答案。

Warming needle is one of effective treatment methods for knee arthralgia aggravated by cold,and it is simple,safety,so it should be developed in clinical acupuncture and moxibustion extensively.

但以本院科针灸门诊在2005年1月—2006年6月期间共收治膝痛患者100余例，经过临床的诊断后，其中施以温针治疗的48例，疗效显著，报道如下。1临床资料本组病例48