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group velocity

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group velocity 【物理學】波群速度。

【物理學】波群速度。 “group“ 中文翻譯：   n. 1.群；批，簇。 2.集團，團體，小組。 3.【化 ...“velocity“ 中文翻譯：   n. 1.迅速；快速。 2.速度，速率。 3.周轉率。 ...“phase velocity and group velocity“ 中文翻譯：   相速和群速“anomalous group velocity“ 中文翻譯：   異常群速度“global average group velocity“ 中文翻譯：   全球平均瑞利波群速“rayleigh group velocity“ 中文翻譯：   瑞利波群速度“velocity of wave group“ 中文翻譯：   波群速度“wave group velocity“ 中文翻譯：   波群速度“velocity“ 中文翻譯：   n. 1.迅速；快速。 2.速度，速率。 3.周轉率。 at a velocity of 100 miles per hour 用每小時一百英里的速度。 dart off with the velocity of a bird 像鳥一樣迅速飛跑過去。 drag-free velocity無阻力飛速，真空飛速。 escape velocity(克服地球引力的)第二宇宙速度，逃逸速度。 final velocity (發射物的)終速。 initial [muzzle] velocity(發射物的)初速[腔口速度]。 uniform [variable] velocity勻[變]速。 “a group of“ 中文翻譯：   一群“group“ 中文翻譯：   n. 1.群；批，簇。 2.集團，團體，小組。 3.【化學】基，團，組；(周期表的)屬，族。 4.(雕塑等的)群像。 5.【地質學；地理學】界。 6.(英、美的)空軍大隊。 7.〔G-〕 【宗教】牛津團契。 a group of people 一群人。 the grain group谷類。 blood group血型。 a ginger group 要求政府采取堅決行動的議員，起推動作用的政黨骨干小組。 a pressure group 〔美國〕(對國會等施加影響的)壓力集團。 group by group 分批地。 in a group ＝ in groups 成群地。 vt. 1.集合，使成一團 (with)。 2.組合，配合 (together)。 3.把…分類。 vi. 成群；聚集，類集。 “group a“ 中文翻譯：   a組賽車“group of t“ 中文翻譯：   非洲加勒比和太平洋地區國家集團“group-t“ 中文翻譯：   汶理工“in a group“ 中文翻譯：   成群接隊地“in group“ 中文翻譯：   內群體“in group to“ 中文翻譯：   以便，為了“in-group“ 中文翻譯：   n. 內部集團，自己人集團。 “t group“ 中文翻譯：   訓練小組; 訓練組“t-group“ 中文翻譯：   n. 訓練小組〔現代美國的一種所謂精神治療法，受治療者在專門訓練員的指導下，在小組內不受約束地用言語表達內心感情〕。 “the group“ 中文翻譯：   全職大盜“they group“ 中文翻譯：   他人團體“to group“ 中文翻譯：   到組, 到程序組“group by group“ 中文翻譯：   分批地“average velocity, mean velocity“ 中文翻譯：   平均速度

group work

The dispersive characteristic of sws is a very important parameter of the rbwo and rtwt , other parameters such as the phase velocity , group velocity , coupling impedance can be derived from the linear dispersion relation . recently , the photonic crystal have attracted many attentions of the scientists , which has become a hot point of the research , it is also a ps 周期慢波結構色散特性是研究高功率微波器件的一個重要參量,其他重要特性如相速、群速、耦合阻抗等參量都可以從色散關系衍生出來,準確,快速獲得周期電磁結構的色散特性就顯得尤為重要。

The followings were discovered in the simulations of undersized waveguide : when the pulse width of input signal , a gaussian packet , is rather wide , the output signal distorted little . a superluminal group velocity 3 . 21c was revealed when the wave packet crossing 50mm forbidden region 對凹陷波導（ undersizedwaveguide ）的模擬發現：輸入脈沖寬度較大的高斯波包，模擬結果顯示輸出波形失真較小，經過計算得到電磁波包穿過長50mm的截止區時，電場的幅度衰減了- 41 . 5db ，群速度為3 . 21c 。

On the following , on the basis of formulas given above , three kinds of effects due to ionosphere are presented : image shift due to group delay which was caused by the difference between the group velocity and the velocity of light in the ionosphere ; image distortion due to ionospheric dispersion which can create second phase error of lfm signals ; the last , the phase perturbation caused by the irregularities of the ionosphere can reduce the coherent length and affect azimuthal resolution 文中主要研究了電離層的三種影響：信號經過電離層傳播的群延遲引起的成像偏移；電離層的色散效應給線性調頻信號帶來二次相位誤差，導致圖像退化、失真；以及電離層的閃爍、湍流等不規則性引起的信號相位起伏。在此基礎上，比較分析了不同波段、帶寬條件下電離層的影響。

The thesis mainly deals with the third part of across : “ sompi “ cepstrum methods . the principle and system structure of across a re first introduced . the propagation of wave in media is simply studied and its transfer function in frequency domain is modeled as superimposed damped exponential sinusoids , each damped exponential sinusoid is called as a wave element and its exponential index part consists of two factors : group velocity travel time and decayed factor 為此，首先介紹了across的原理與組成和通過簡單地討論地震波在介質中的傳播情況建立起介質的傳遞函數模型，指出：在一個狹窄的頻率窗口里，介質的傳遞函數可以用有限個阻尼正弦項的疊加的形式表示，每個阻尼正弦項代表一個波成分，其指數部分包括兩個因子：波成分在介質中的傳播時間和衰減因子。

When the pulse width of input gaussian wave packet was reduced and the length of forbidden region retained , the result displayed the output signal distorted seriously and its spectrum changed very hard . a frequency above the cut - off frequency became the main frequency and the group velocity was below than c 在保持截止區長度不變，而減小輸入高斯波包的脈沖寬度時，模擬顯示輸出波形嚴重失真，而且，頻譜也發生很大的變化，主頻已變為一高于截止頻率的頻率，群速度小于光速c 。

In the picosecond and femtosecond time field , the durations of the pump and signal pulses are so short that special propagating characteristics of ultrashort pulse laser should be taken into account , especially the pulse broadening induced by the group velocity mismatch and the group velocity dispersion 在皮秒和飛秒時域，由于泵浦光與產生的信號光的持續時間特別短，故在討論超短脈沖與物質相互作用時必須計及超短脈沖在介質中傳輸的特殊性質，尤其是群速失配與群速色散引起的脈沖展寬。

The accurately controlled signal source generates sinusoidal elastic wave accurately controlled in frequency and stable in phase to “ illustrate “ underground media . time signal stacker receive signal by stacking and doing fft to measure the transfer function of media . “ sompi “ cepstrum method retrieve group velocity travel times and decayed factors of wave element from observational data of transfer function in a limited frequency window 精密可控震源用于產生頻率精確相位穩定的正弦彈性波以照射地層內部，信號疊加器通過對接收信號進行疊加和進行傅立葉變換的方式實現對介質傳遞函數的精密測量， “存否”倒譜方法能夠根據一段窄帶頻域傳遞函數數據獲得時域上各個波成分的群速度傳播時間和介質衰減因子。

There has been a revolutionary advance in ultrashort pulse technology since the discovery of self - mode locking of ti : sapphire lasers . few - femtosecond pulses have already been generated from ti : sapphire lasers , by means of combining self - phase modulation with negative group velocity dispersion , which is similar to the way of soliton generation 鈦寶石激光自鎖模的發現使得超短脈沖技術發生了革命性的變化，利用自相位調制和負群速度色散結合的類孤子產生方式，人們已經在鈦寶石鎖模激光器上得到了脈寬只有幾個飛秒的光脈沖。

Based on these foundations , we give a perfect scheme of the bbo opos : single pass amplification coefficient of the opg under different pump intensity is calculated ; collinear type - i and type - ii phase matching tuning curve pumped by the q switch nd : yag various harmonics as well as noncollinear type - i tuning curve are calculated in details ; the effect of the walkoff for the nonlinear effect coefficient and the group velocity matching are analyzed ; the acceptance angle in parametric process is calculated ; the numerical threshold of the bbo opo is calculated ; the process of the saturation and depletion of the pump beam are analyzed ; the relationship of the conversion efficiency and reflectance of output mirror are discussed ; various linewidth controlling methods are discussed ; the improvement of the beam quality applying the unstable cavity is discussed ; and the crystal bbo design is considered 在此基礎上，給出了一整套bbo - opo激光參數設計方案：計算了不同泵浦強度下的參量放大倍數；詳細計算了在nd : yag調q激光器各次諧波泵浦條件下的共線類和類相位匹配的調諧曲線，以及非共線類相位匹配調諧曲線；分析了走離角對非線性系數和群速匹配的影響；計算了參量過程的允許角；計算了bbo - opo的理論閾值條件；分析了飽和與泵浦光束的消耗過程；給出了轉換效率與超過泵浦閾值的倍數的關系；討論了轉換效率與輸出鏡反射率的關系；討論了線寬控制的各種方法；研究了利用非穩腔改善光束質量的方法；考慮了bbo晶體的設計。

In this paper , first , the study of the distribution of electromagnetic field , energy , power , reflection coefficient and transmission coefficient in waveguide with piecewise different dielectric constants are studied . then , the behavior of propagation of am signal and gauss pulse signal through the waveguide are simulated by magic code ， and the plots of electromagnetic field , energy , ponyting vector and their spectrums at different time and different position are obtained . and , the group velocity and energy velocity of wave packet through barrier are calculated 從90年代開始， emig和martin 、 landauer等人研究了分段填充不同介質的波導中的電磁脈沖的傳播。在本論文中，作者首先推導出分段填充不同介質的波導中的電磁場分布、能量、傳輸功率以及反射系數和傳輸系數的表達式,然后，采用magic程序模擬了這種波導結構中電磁波的傳播情況，得到了在不同時刻和不同位置處的電磁場分布圖、能量圖、坡印廷矢量圖以及它們的頻譜圖,并由模擬結果計算了波包穿越勢壘的群速和能量速度。

We have calculated and plotted the curves of the refractive index , group velocity index , lowest - order and second - order dispersion indexes as a function of wavelength . the lowest - order and higher - order dispersion - induced broadening and deforming of light pulses is analyzed for various pulse shapes , such as gaussian , super - gaussian and hyperbolic secant pulses 給出了折射率、群速指數、低階和二階色散系數隨波長變化的關系曲線，研究了高斯脈沖、超高斯脈沖和雙曲正割脈沖等超短脈沖在clbo晶體中傳播時，由于低階色散和高階色散引起的脈沖展寬和形變。

X4 ? gridding attenuation and 2 ? x2 ? gridding group velocity are calculated respectively , based on the attenuation and velocity , the distribuation of rayleigh wave quality factor qr are yielded finally . ( 3 ) building the s - wave quality factor og3d structure of the continental crust and upper mantle of china area 為此把中國大陸區域劃分成4 4網格和2 2網格，利用lsqr方法分別進行衰減系數和群速度網格化反演，得到4 4單元格的衰減系數分布和2 2單元網格的群速度分布。

The features of phase and group velocity were advanced by means of preparing samples with different shaping . the phenomenon of “ cusp “ in group surface of quasi - shear wave ( qsv ) was observed . the inversed velocity surface according to calculated elastic constants in real orthotropic media is consistent with practical measured velocity surface 用加工不同樣品形態的方法給出了正交各向異性介質的相速度和群速度特征，觀測到各向異性介質群速度面上的尖點現象，并用測試得到的正交介質的彈性常數進行了數學模擬，其波場特征與測試的速度面特征相符。

The phase matching and group velocity matching conditions of type - i and type - ii second harmonic generation ( shg ) are obtained according to the momentum and energy conservation laws . the group velocity delay of ultrashort pulse shg on clbo and the crystal length decided by the group velocity delay are analyzed and compared with bbo ' s 從動量守恒、能量守恒出發推導得出了超短脈沖倍頻的類、類相位匹配和群速匹配條件，對clbo晶體用于超短脈沖倍頻時的群速延遲以及由群速延遲決定的晶體長度進行了分析和數值模擬，并與bbo晶體進行了比較。

We derive an analytic expression of the group velocity dispersion ( gvd ) induced chirp and the self - phase modulation ( spm ) induced chirp in the normal dispersionregion of non - kerr - like optical fibers with saturable nonlinarity . the evolution of chirp is simulated by numerical methods . the studied results show that the more powerful saturable effects , the smaller is chirp and the gently is chirp . the net chirp is zero in the central region of the pulse 從理論上推導出具有飽和非線性的非克爾光纖正常色散區內，群速度色散效應導致的啁啾和自相位調制效應導致的啁啾解析表達式.利用數值解法模擬了非克爾光纖正常色散區啁啾演變過程.研究結果表明：當非克爾光纖的飽和非線性增強時，凈啁啾不斷減小，而且，越來越平緩，脈沖中心附近區域凈啁啾接近零

Generally speaking , the high group velocity and low attenuation factor and high qr in the same area , but relatively low group velocity and high attenuation factor and low qr in the same area in china is the general distribution 在不同周期，面波衰減系數或品質因子在整個中國大陸區域分布是不均勻的；總體表現為高群速度分布的區域呈現高叢和低衰減系數、低群速度分布的區域呈現低叢和高衰減系數分布的特點。

By using transducers with different central frequency and diameter , the approximate demands for the length of those samples and the transducers “ frequency and diameter were presented in order to attain the phase or group velocities in the experiment 通過多種頻率和不同直徑的換能器，給出了實驗室測試各向異性介質相速度和群速度時換能器頻率和直徑與樣品長度之間的相對關系。

Under certain conditions , in spite of their different modal indices the two polarized components of the pulse can trap one anther and move at a common group velocity due to xpm , the phenomenon referred as self - trapping occur 在一定條件下，盡管脈沖的兩個偏振分量的模式折射率不同，但由于交叉相位調制效應，它們能相互俘獲并以共同的群速度傳輸，產生自捕獲現象。

( 2 ) calculating the gridded rayleigh wave attenuation factor y and group velocity . the lsqr algorithm is used to inverse the attenuation factor and group velocity under 4 ? x4 ? gridding and 2 ( 2 )進行rayleigh波衰減系數、群速度網格化純路徑衰減反演計算，得到網格單元純路徑衰減系數和群速度分布結構。