降低了的频率

Based on the high frequency power amplifier,a class E resonant high frequency DC/DC and a phase-shifted control strategy are proposed in this paper,the converter based on the idea can heighten switching frequency,reduce the loss of the system,widen the range of output.

以高频功率放大器为基础，提出了一种超高频E类谐振DC/DC变换器的移相控制策略，基于这种思想的变换器可以提高开关频率，降低系统损耗，拓宽输出范围。

to reduce the impact of carrier frequency offset in ofdm system,this thesis designs a new carrier frequency offset estimation scheme for ofdm system.the carrier frequency offset estimation includes acquisition and tracking.we adopt variable step size adaptive algorithm.the acquisition range of the proposed algorithm is as large as one half of the overall signal bandwidth.through this method we can not only avoid the feedback by using forward error correction,but also reduce the times of complex multiplication in order to reduce the power consumption of the system.this algorithm not only has low complexity and fast convergence nut also can improve the demodulation performance of ofdm system.computer simulation illustrates the superior performance of the proposed algorithm with regard to estimation accuracy in both awgn channel and multi—path channel.

摘 要：为了减小正交频分复用系统受频率偏差的影响，在ofdm系统中设计了一种新的载波频偏估计算法。频偏估计包括跟踪和捕获两个阶段，文中采用变步长自适应算法来进行跟踪，这个跟踪算法的捕捉范围是整个信号带宽的一半。通过此方法，不但可以利用前向纠错的方式来避免反馈，而且可以缩减复数乘法的次数以降低计算复杂度和系统功耗。该方法运算复杂度低，并具有较好的收敛性，能改善odfm的解调性能。从计算机的仿真效果可以看出无论是在awgn信道上还是在多径信道上都表现出了卓越的性能。

When the flexible drawgear is used, the peak values both of the dynamics longitudinal force and of its instantaneous PSD have decreased largely, and the distribution status of the instantaneous PSD along both the time axles and the frequency axles have been improved. So the working stability of the tractor-trailer combinations braking process would been improved when the optimized flexible drawgear was used.

仿真分析和试验结果均表明，使用柔性牵引装置后，牵引架动态纵向力峰值及其瞬时功率谱的峰值有了大幅度的降低，动态纵向力瞬时功率谱密度沿时间轴和频率轴的能量分布得到了改善，这说明使用柔性牵引装置后有利于提高挂接车辆制动工况的工作稳定性。

The results indicate that its dynamic stress-strain curve is hyperbolic type. The dynamic strain of LCES decreases with increasing confining pressure, cement content, curing ages and cyclic loading frequency when it is subjected to the same dynamic stress. At the same dynamic strain, the dynamic secant elastic modulus E_(sec of LCES increases and the damping ratio decreases with increasing confining pressure, cement content, curing ages and cyclic loading frequency. The curves ofσ_d～ε_d,E_～ε_d and D～ε_d with different EPS content intersect respectively, the trend of LCES deformation characteristic is inversely proportional to EPS content near the intersection. The value of dynamic strain at the intersection is about 0.5%~3.0%, the magnitude of which is related to the mixing proportions and confining pressure.

试验结果表明，LCES的动应力应变骨干曲线形态符合双曲线；在相同的动应力作用下，LCES产生的动应变随着固结压力、水泥掺量、试样养护龄期和振动频率的增大而减小；在动应变相同的情况下，随着固结压力、水泥掺量、试样养护龄期和振动频率的增大，LCES的动模量增大而阻尼比减小；随着加载次数的增大，LCES的动模量在开始阶段显著降低，然后趋于稳定，但当加载次数达到几百次时，动模量又有增大的趋势；不同EPS掺入比的LCES的动应力应变骨干曲线、动模量随应变变化曲线和阻尼比随应变变化曲线都发生了相交，交点前后EPS掺入比的大小对LCES动力变形特性的影响趋势是截然相反的，交点处的动应变值一般在0.5％～3.0％范围内变化，其大小与LCES的配比以及固结压力有关。

This simple definition ignores the fact that amplifier output impedance usually varies considerably across the audio band, increasing with frequency as the negative feedback factor falls; this indicates that the output resistance is actually more like an inductive reactance.

这个简单的定义忽略了功放输出阻抗通常是随着音频带而变化，负反馈因素降低的时候频率也增加这一事实。这就意味着输出电阻实际上更像是一个电感电抗。

Based on the Lagrangian equation with dissipation function, the motion equation of a microbubble with shell is obtained, and the dynamic characteristics of microbubble with shell in free space are studied. It shows that the inner and outer maximum radii of the microbubble increase when the acoustic pressure and its initial radius increase, as well as when the ultrasonic frequency decreases.

理论上利用有耗散函数的Lagrange方程，建立了有壳微泡的R运动方程，开展了自由空间中有壳微泡动力学特性的研究，表明微泡内外半径增量随声压的增大、超声频率的降低、初始内径的增大及壳厚的减薄而迅速增大。

A sample numerical design method for constant beamwidth beamformer is given. This method is easy to implement and has no restriction on array geometry and sensor patterns; Three methods for the design of broadband frequency invariant beamformer are proposed, which are the method of resampling signals received by the array, the DFT interpolation method and adaptive synthesis method, respectively. Examples and performance analyses are given for each method; A simplified linear constrained minimum variance broadband adaptive algorithm that based on DFT interpolation method is presented. Compared with conventional broadband adaptive algorithms, the presented method can reduce computation work greatly.

提出了一种简单、易于实现的恒定束宽波束形成器设计方法，该方法对阵形和阵元指向性没有任何限制；分别提出了基于阵列接收数据重采样、基于DFT插值和自适应综合的三种具有频率不变波束图的宽带波束形成器设计方法，对于每一种设计方法都给出了一个设计实例并做了性能分析；提出一种基于DFT插值的简化线性约束最小方差宽带自适应阵列算法，该方法可以大大降低自适应阵列的运算量。

Reactive oxygen species causing DNA oxidative damage comes from two kinds of ways:one is from cellular normal physiological metabolism;the other is from outer environment.Redox-sensitive green fluorescent protein was expressed in Saccharomyces cerevisiae.Recombinant cells were evaluated in monitoring the changes in the redox state of living cells when challenged with toxicologically relevant metal ions NaAsO_2 or Pb(NO_3)_2 by measuring emission intensity at 510 nm with a Hitachi F6500 fluorescence spectrophotometer,roGFP expressed in yeast responded not only to typical membrane-permeant oxidants H_2O_2 and reductants DTT,but also to toxicological metal ion-induced intracellular redox changes in a dose-dependent manner.Moreover,exposure of yeast cells to NaAsO_2 or Pb(NO_3)_2 at concentrations that induced redox changes reported by roGFP caused up to 2～3 fold increases in DNA mutation frequency.This mutagenic effect was largely caused by oxidative stress since blocking the production of hydryl radicals with thiourea significantly reduced the mutation rate as well as delayed the cell death.

本文将对氧化还原状态变化敏感的绿色荧光蛋白roGFP1-R12，在酵母细胞中实现了多拷贝强表达；荧光扫描经强氧化剂H_2O_2和还原剂DTT以及环境中重金属NaAsO_2或Pb(NO_3)_2处理后的酵母细胞悬液，测定510 nm处的荧光发射强度结果显示，表达的绿色荧光蛋白对氧化还原水平敏感，且在510 nm处的荧光强度与一定的重金属浓度呈正相关，即roGFP1-R12在510nm处的荧光发射值随重金属浓度的增高而增强，从而说明重金属对细胞的毒性在一定程度上很可能是通过破坏细胞内的氧化还原平衡发生作用；同时通过该绿色荧光蛋白对胞内氧化还原状态变化的响应情况可以来实时检测环境中的重金属；遗传学的点突变频率及致死率实验数据表明，重金属能导致菌体的点突变频率和致死率升高，且活性氧的清除剂巯基脲能明显降低这种点突变和致死率，说明由重金属引发的这种点突变和致死效应在很大程度上是依赖于重金属对细胞诱导产生的氧化胁迫。

An antenna device and a portable wireless communication apparatus are disclosed to securely lower a local average SAR in correspondence to at least two or more kinds of radio communication systems using different radio communication frequencies even when any radio communication frequency is used.

公开了一种天线装置和便携式无线通信装置，即使在使用任何无线通信频率的时候，也能安全降低对应于至少两种或多种无线通信系统的局部平均SAR。

The whole process of text representation were discussed — word segmentation, building stop words list, feature selection, weight computation and generating vector space. Aim at the influence of stop words, a list, which is fit for text categorization, is set up and makes the vector dimension reduce.

针对停用词对分类的影响，建立了适合文本分类的停用词表，使向量维数得到初步降低；对现有特征选择方法进行了介绍和对比，构造了一种适合支持向量机的特征选择函数——基于类内频率的特征选择函数。

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。