周期图

By using the algebraic method, we obtain a new formula for the expected hitting time of random walks on strong-connected and aperiodic digrahs (irreducible and aperiodic Markov chain). From this formula, we obtain the explicit expressions for the expected hitting times of random walks on directed de Bruijn graph, directed Kautz graph and some graphs constructed from strong regular graph, etc.

利用代数方法给出了强连通非周期有向图上随机游动（即不可约非周期马尔可夫链）平均首达时间一个新的表达式，并利用这个表达式得到了有向de Bruijn图，有向Kautz图以及和强正则图相关的几类图上随机游动任意两点之间的平均首达时间。

For example, if a graph has exactly one cycle, then all graphs in its isomorphism class also have exactly one cycle.

"这一概念图同构"使我们能够区分图形性能固有的结构图自己从性能与图申述：图图，数据结构的图形，图表标号等例如，如果一个图，正是一个周期，然后在其所有图形类也有同构的一个周期。

The spectrum resource of WiMAX system is very scarce. How to improve the spectrum utilization and reduce interference with other systems to achieve co-existence needs to be resolved. The performance and spectrum utilization improvement of WiMAX system is studied by using periodogram detection and spectrum pool technology.

为提高WiMAX系统频谱利用率，减小与其他系统之间的干扰，实现共存，利用感知无线电的周期图频谱检测和频谱池技术，对WiMAX性能加以改进。

Chemical rocket propulsion is essentially a controlled explosion of some of the most volatile elements on the periodic chart.

化学火箭推进，基本上是控制爆破的一些最不稳定的元素对周期图。

In determining the power spectrum of the wind, Lomb-Scargle periodogram was used.The planetary waves with periods 120 hours,60hours and 35 hours, diurnal, semidiurnal and terdiurnal tides were found at height 86.4km in the zonal wind.

首先利用Lomb-Scargle周期图方法计算了大气纬向风场的功率谱，除了行星波和潮汐外，在行星波、潮汐的频率和与频率差处有明显的谱峰，双谱分析表明这些谱峰是行星波和潮汐相互作用形成的。

By using integral periodogram to estimate the spectral functions of a stationary time series, the invariance principle for the error process has been demonstrated either for Gaussian or non-Gaussian series.

用积分周期图估计平稳时间序列的谱函数，不论是高斯序列还是非高斯序列，其误差过程的不变原理都已被证明￣（［1］，［3］），许重光￣［5］采用自迥归谱估计的积分估计谱函数也证明了误差过程的不变原理成立。

According to by the time series estimate power spectral density\'s periodogram law principle,the research adopts five level of orbital power spectra which US Federal railway Administrative bureau FRA proposed;then,through the Fourier inverse transformation,the orbital not smooth time domain samples are obtained, which determine the track irregularity peak-to-peak value and the corresponding wave length; on the basis of the research,the influence of the wheel track dynamic contact force are considered.Based on the orbital roadbed coefficient\'s definition,computation model is established to solve the roadbed equispaced spring constant,and the roadbed uniform spring stiffness is obtained by using the numerical simulation method.Finally,based on the Matlab procedure platform,the computational procedure is established,and the load time interval caused by the moving train acts on the roadbed is obtained.

根据由时间序列估计功率谱密度的周期图法原理，采用美国联邦铁路管理局FRA提出的五级轨道功率谱，通过Fourier逆变换得到轨道不平顺的时域样本，确定了轨道不平顺的幅值及对应的波长，以此为基础考虑轮轨动态接触力的影响；基于轨道路基系数的定义建立了求解路基均布弹簧刚度的计算模型，采用数值模拟得到了路基均布弹簧刚度；最后，基于Matlab程序平台编制了计算程序，得到了运行列车作用到路基上的荷载时程。

By virtue of bifurcation diagrams, Poincaré maps, orbits, time histories and frequency spectrum diagrams, the nonlinear dynamic responses of the generator rotor and hydraulic turbine rotor with coupling faults were analyzed. The results confirmed rich nonlinear motions such as periodic motion and quasi-periods with different values of parallel misalignment and declination. Moreover, the process of rub-impact is so complex that many low frequencies with large amplitude are in the range of

通过分岔图、Poincaré截面图、轴心轨迹图、时域波形图和幅值谱图系统地分析了发电机转子与水轮机转子在耦合故障下非线性动力学响应，发现机组转子系统随不对中平行量和偏角变化存在周期运动和复杂的拟周期，其碰摩过程非常复杂，机组故障特征频率除主要在1倍频外，还在0.3~0.4倍频处存在幅值较大的谐波分量。

On the basis of studying EH-4 data processing, we ase a menthod to read time-sires file correctly, adopt periodogram means to recalculate auto-power spectrum, cross-power spectrum and tensor impedance component, and recalculate resistivity depend on tensor impedance component. We compile proprietary softwareEH-4 Data Processing Program.

本文在剖析EH-4系统数据处理流程的基础上，正确地读取了EH-4系统原始时间序列文件，采用周期图方法重新计算了自功率谱、互功率谱和张量阻抗分量，以及由阻抗定义的视电阻率，编制了专用软件EH4 Data Processing Program。

The space between frequency bins is 8 sub-carrier spaces. Before the transmission of each data frame, secondary user use periodogram detection technology to detect spectrum hole, then transmit data on the spectrum hole by spectrum pool technology.

每帧数据传输开始时，二级用户利用周期图频谱检测技术对信道频段进行检测，获得频谱空洞，然后采用频谱池技术在频谱空洞上传输数据。

As she looked at Warrington's manly face, and dark, melancholy eyes, she had settled in her mind that he must have been the victim of an unhappy attachment.

每逢看到沃林顿那刚毅的脸，那乌黑、忧郁的眼睛，她便会相信，他一定作过不幸的爱情的受害者。

Maybe they'll disappear into a pothole.

也许他们将在壶穴里消失