瞬時近似 的英文怎麼說
中文拼音 [shùnshíjìnsì]
瞬時近似
英文
sudden approximation-
Due to the short distance among the planes which fly in a group, the conventional low resolution radar can not distinguish them in both distance and azimuth ? if we use the technology of isar to resolve the difference among doppler frequency of the targets and obtain a fine resolution cross - cross image, we may separate them, but a long time of coherent processing is needed <, for the formation targets, it can be approximately divided to rigid body and nonrigid body, so for the formation targets, that can be regarded as rigid which has a relative position and an identical movement, can be approximately considered as a large target, and be compensated by translational phase with the rule of minimum entropy, but for the most those cannot accord with the approximation of rigid, being the doppler - frequency of the aim is linear changed, by the relax method with short data, increases the resolving performance of multiple target to the aim in the frequency domain, since cross - range resolution is based on the accumulative time, so it is greatly improve the resolution to formation targets by the instant cross - range image which produced by radon - wigner transformation
低分辨isan成像及干涉技術應用研究一因此直接無法分辨編隊目標的架數，我們借鑒isar的技術，通過較長時間的相干積累，在多普勒頻域上對目標進行分辨。而對于編隊目標，可分為近似剛性的多目標和非剛性的多目標，所以對于可以近似為剛體的編隊目標相對位置固定，運動方式一致，可以近似看作一個大目標，採用最小墑準則對平動相位的進行補償，但是大多數並不滿足剛體近似的編隊目標，由於目標在相干積累時間的多普勒頻率近似呈線性變化，通過對較短數據利用relax的時頻分析方法，提高了頻率域上目標分辨的性能。由於橫向解析度取塊于橫向積累時間，所以利用radnwigner變換得到瞬時的一維橫向距離像大大提高了對編隊目標的分辨，對模擬和實測數據的大量分析結果表明此方法的有效性和可行。Stationary phase method shows that by using information along the ridge defined by the phase on transformed domain, original signal could be represented and reconstructed
利用穩定位相法的近似公式分析可知，脊上分佈參數包含的信息與信號瞬時頻率變化規律密切相關，並且可以用來對信號進行重建。An on - line minimum - variance estimator was developed for thrust acceleration applied to orbit transfer using discrete - time radar measurements. the mass - flow - rate of propellant was selected as a state variant, which was estimated by employing an integral state model and ekf filter. the variation equations for measurement vector to mass - flow - rate have been established to linearize the discrete - time measurement equations. the algorithm has applied successfully to maneuver process in commanding satellite into geo - stationary orbit. the results show that the algorithm developed here can monitor and determine whether engine works well or failure precisely and quickly during orbit transfer process
飛行器軌道機動過程中，為跟蹤、定位機動目標和干預機動控制過程，需要統計處理離散的雷達觀測量實時估計推進發動機的推力，進而確定飛行器的瞬時軌道參數.本文所述演算法是該工程問題的探討和解決方案.文章建立了軌道機動過程中連續變質量運動模型和離散雷達量測模型，推進發動機的質量秒耗量作為表徵推力加速度的一個近似常量，應用擴展卡爾曼濾波對離散的雷達測量數據進行順序統計處理給出秒耗量的最小方差估計;文章詳細地推導了線性化量測模型的變分方程和觀測矩陣;模擬結果表明該演算法能快速、準確地估計推進發動機的質量秒耗量和向機動目標施加的實際推力Solving the rate equation numerically, the influence of the factor a and the reflectivity r on the transient characteristics of the ecld has been analyzed when the shape of the hysteresis loop looks like a parallelogram approximately
通過對速率方程組進行數值求解，分析了當ecld雙穩環呈現近似的平行四邊形時，譜線展寬因子和ld鍍膜端面反射率r對雙穩跳變瞬間動態特性的影響。This feature reflects the physical phenomenon of breaking of waves and development of shock waves. in the fields of fulid dynamics, ( 0. 2. 1 ) is an approximation of small visvosity phenomenon. if viscosity ( or the diffusion term, two derivatives ) are added to ( 0. 2. 1 ), it can be researched in the classical way which say that the solutions become very smooth immediately even for coarse inital data because of the diffusion of viscosity. a natural idea ( method of regularity ) is obtained as follows : solutions of the viscous convection - diffusion pr oblem approachs to the solutions of ( 0. 2. 1 ) when the viscosity goes to zeros. another method is numerical method such as difference methods, finite element method, spectrum method or finite volume method etc. numerical solutions which is constructed from the numerical scheme approximate to the solutions of the hyperbolic con - ervation laws ( 0. 2. 1 ) as the discretation parameter goes to zero. the aim of these two methods is to construct approximate solutions and then to conside the stability of approximate so - lutions ( i, e. the upper bound of approximate solutions in the suitable norms, especally for that independent of the approximate parameters ). using the compactness framework ( such as bv compactness, l1 compactness and compensated compactness etc ) and the fact that the truncation is small, the approximate function consquence approch to a function which is exactly the solutions of ( 0. 2. 1 ) in some sense of definiton
當考慮粘性后，即在數學上反映為（ 0 . 1 . 1 ）中多了擴散項（二階導數項） ，即使很粗糙的初始數據，解在瞬間內變的很光滑，這由於流體的粘性擴散引起，這種對流-擴散問題可用古典的微分方程來研究。自然的想法就是當粘性趨于零時，帶粘性的對流-擴散問題的解在某意義下趨于無粘性問題（ 0 . 1 . 1 ）的解，這就是正則化方法。另一辦法從離散（數值）角度上研究僅有對流項的守恆律（ 0 . 1 . 1 ） ，如構造它的差分格式，甚至更一般的有限體積格式，有限元及譜方法等，從這些格式構造近似解（常表現為分片多項式）來逼近原守恆律的解。Compared to heat transfer in the external region of borehole, mass and heat capacity of materials inside the borehole are insignificant and negligible. thus, heat transfer inside the borehole is approximated as steady - state heat transfer except for analyses of short times ( a few hours )
與鉆孔周圍區域傳熱過程相比，由於鉆孔內材料的熱容量較小，因此除了討論短時間（數小時）的瞬變傳熱問題以外，可以忽略鉆孔內材料的熱容量，把該部分的傳熱近似作為穩態傳熱處理。分享友人