diffusion approximation 中文意思是什麼

diffusion approximation 解釋
擴散近似法
  • diffusion : n. 1. 散布，發散。2. 傳播，普及。3. 冗長。4. 【化學】滲濾。5. 【物理學】擴散，漫射。
  • approximation : n. 1. 接近；近似。2. 【數學】近似值。3. 概算，略計。
  1. In the section 2, firstly based on the diffusion approximation theory, the temporal characteristics of the reflectance and the transmittance were theoretically analyzed in turbid tissues ; secondly, the curves were simulated that the intensity and the pulse shape of the time resolved reflectance and transmittance versus the absorption a, the scattering s and the anisotropy coefficient g in two different boundary conditions : semi - infinite turbid media and homogeneous slab ; at last, the optical properties can be derived from the curves ; in the section 3, the conditions of ultra short laser pulses of different pulse - width and shapes has been theoretical analyzed and calculated, besides, the simulated the curves of the intensity and pulse shapes of the reflectance and transmittance in a homogeneous slab are obtained for use and future studying

    第二章中首先根據漫射近似理論對超短脈沖在以生物組織為典型的混濁介質中傳輸進行了理論分析，然後對兩種邊界條件下產生的漫反射、漫透射光脈沖強度和形狀隨各光學特性參數的變化情況進行了數值模擬，最後得到了混濁介質的光學特性參數與漫反射、透射脈沖強度與形狀的關系曲線。第三章對不同形狀和脈寬的脈沖光源入射到混濁介質中產生的漫反射、漫透射脈沖的強度和形狀進行了理論分析和數值模擬，並將高斯脈沖與方波脈沖情況進行了對比，得到了各種情況的漫反射、漫透射脈沖強度、形狀與各光學特性參數的關系曲線，這對從分析脈沖形狀中提取介質的光學特性參數的信息有重要的意義。
  2. The various medium parameters have different influence on the reflection of the laser pulse. based on the diffusion approximation theory, the boundary condition of semi - infinite homogeneous media, the influence of the absorption a, the scattering s and the anisotropy coefficient g on the ultra short laser pulse of different pulse - width and shapes has been researched

    論文對超短脈沖在混濁介質中的傳輸進行了理論分析和數值模擬，並在不同脈寬的高斯脈沖和方波脈沖入射到混濁介質的漫反射、漫透射脈沖強度和形狀進行了理論分析和數值模擬，得到了它們與各光學特性參數的關系曲線。
  3. ( 5 ) discuss some mathematical models of the pollutant transport problems in some local river flow fields. by integral transform method, the paper establishes the usual finite difference approximation scheme to solve the numerical solutions and gives examples for the computation of the approximating solutions, moreover, discusses one - dimensional characteristic finite difference method for a convection - diffusion equation under usual conditions

    （ 5 ）針對水域中污染物輸移問題的數學模型，通過積分變換法，得到了簡化模型在理想化條件下的近似精確解，同時給出數值算例，並且對非理想化條件下模型的特徵差分方法進行了討論。
  4. The characteristic approximation is used to handle the convection part along the direc - tion of fluid namely characteristic direction to ensure the high stability of the method in approximating the sharp fronts and reduce the numerical diffusion ; the mixed finite element spatial approximation is employed to deal with diffusion part and approximate the scalar unknown and the adjoint vector function optimally and simultaneously ; in order to preserve the integral conservation of the method, we introduce the modified characteristic method

    該方法對方程的對流部分沿流體流動的方向即特徵方向離散以保證格式在流動的鋒線前沿逼近的高穩定性，消除數值彌散現象；對方程的擴散部分採用最低次混合有限元方法離散、同時以高精度逼近未知函數及未知函數的梯度；為保證方法的整體守恆性，在格式中引入修正項
  5. The new method is a combination of characteristic approximation to handle the convection part, to ensure the high stability of the method in approximating the sharp fronts and reduce the numerical diffusion, a smaller time truncation is gained at the same time, and a mixed finite element spatial approximation to deal with the diffusion part, the sealer unknown and the adjoint vector function are approximated optimally and simultaneously

    此方法即為對方程的對流項沿流體流動的方向即特徵方向進行離散，從而保證格式在流動鋒線前沿逼近的高穩定性，消除了數值彌散現象，並得到了較小的時間截斷誤差；另一方面，對方程的擴散項採用混合元離散，可同時高精度逼近未知函數及其伴隨向量函數，理論分析表明，此方法是穩定的，具有最優的l ~ 2逼近精度。
  6. 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。
  7. Diffusion approximation for a re - entrant network under the priority service discipline

    一類重入型網路在優先服務原則下的擴散近似
  8. Using the method of stochastic analysis, we demonstrate c - tightness of the scaled queue length processes and derive a sufficient condition for the existence of the diffusion approximation under a general priority service discipline

    在優先服務原則下，給出了這類網路的標準化隊長過程擴散近似存在的充分條件。
  9. Validity of the diffusion approximation in determining the optical properties of biological

    漫射近似在測量生物組織光學性質中的適用范圍
  10. Then the model is simplified, the theory of martingale, simulation, and diffusion approximations are discussed firstly. these methods are applied in the model. then get some useful results, so we can estimate the upper bound for the ruin probability and the approximation of the finite time ruin probability

    並詳細的討論了模型有限時間內破產概率和最終破產概率的估計，應用隨機過程序列弱收斂，鞅以及隨機模擬等理論，得出一些有意義的結果? ?在有限時間內破產概率的逼近表達式；最終破產概率的上界和有限時間內破產概率上界；有限時間內破產概率的隨機模擬演算法；並得到最終破產概率滿足的泛函方程。
  11. For light particles, 1 when observed within the whole water depth. the relationship between theoretical and measured values of the suspension falls to the second approximation to the solution of the diffusion theory

    輕質顆粒在整個水深內有pzi ，懸浮指標實測值和理論值之間的關系符合擴散理論的第二近似解。
  12. The bilinear finite element approximation for semi - singularly perturbed reaction - diffusion problems is considered

    摘要考慮半奇異攝動反應擴散問題的雙線性有限元逼近。
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