as a first approximation 中文意思是什麼

as a first approximation 解釋
作為一級近似值
  • as : adv （同…）一樣…；同樣〈在此是指 as… as… 結構中的第一個 as 它在主句中為指示副詞，第二個 as （在子...
  • a : an 用在以母音音素開始的詞前〉 indefinite art 1 〈普通可數名詞第一次提到時，冠以不定冠詞主要表示類...
  • first : adj 1 最初的，最早的。2 最上等的，第一流的。3 基本的，概要的。4 高音（調）的。n 1 最初，第一；第...
  • approximation : n. 1. 接近；近似。2. 【數學】近似值。3. 概算，略計。
  1. This paper starts with interrogatory with capm ; analyzes the most basic risk concept, the risk expression method ; clarify the concept of systematic risk with idiosyncratic risk ; questions about marketing portfolio, diversification investment. then, we accept the capm as a reasonable first order approximation

    本文的思路是先破后立，將研究的起點放在對capm的質疑上，從分析最基本的風險概念、風險的表示方法入手，層層抽絲撥繭，對系統性風險與非系統性風險的劃分、市場組合、組合投資等概念提出疑問。
  2. The equation including the nonlinear dispersion, i. e. the modified nonlinear schrodinger ( mnls ) equation, is a better model. in this thesis, we take mnls solitons as a model for femtosecond soltions. then based on the recently developed direct perturbation theory for perturbed mnls equation, we study the raman self - frequency shift of femtosecond solitons and its suppression by the means of frequency filters. for this purpose, first, we define the physical parameters of mnls solitons ; next, through the direct perturbation theory for perturbed mnls equation, under adiabatic approximation, we obtain the evolving parameters of mnls soliton on our questions and then choose the parameters of frequency filters based on it ; at last, we directly numerically simulated our questions by split - step fourier ( ssf ) method after improving the arithmetic of the differentiation of the nonlinear item for satisfying mnls equation

    本論文以mnls孤子作為光纖飛秒孤子的模型，通過新近建立的mnls孤子直接微擾理論，研究光纖中由拉曼效應引起的飛秒孤子在傳輸中的自頻移，以及通過頻率濾波對自頻移的抑制。為此，首先給出描述mnls孤子的各物理量，然後用mnls孤子直接微擾理論，解析地得到這些問題絕熱近似下的孤子參數演化，並由此選擇頻率濾波的參數，最後用分步傅里葉方法，在對非線性項微商的演算法做出了適合於mnls孤子的改善後，對拉曼效應及頻率濾波進行了直接數值模擬，其中頻率濾波參數用微擾理論確定。
  3. Secondly, the effectiveness and limitation of the classical perturbation, such as the method of multiple scales and the poincare - lindstedt method, are discussed in detail through a duffing oscillator with delayed velocity feedback. it is shown that the two perturbation methods are effective only in solving the approximate solution of the first two orders. an ambiguity or paradox will be encountered when they are used to seeking for the third or higher order approximation of solution

    其次，以一具有時滯速度反饋的duffing系統為例，研究了經典攝動法如多尺度法， poincar - lindstedt法等在求解時滯微分方程級數解時的適用性和局限性問題，指出利用這些方法只能有效求得系統的前兩階近似解，而在求系統的三次以上近似解時會出現矛盾或二義性。
  4. The results of numerical experiments, using the four - dimensional variational data assimilation system of the nonhydrostatic mesoscale model mm5, show that : the tangent linear model and adjoint model conducted by keeping the " on - off " switches the same as the basic state, can provide a good approximation of the first - order information to the nlm perturbation and a good descent direction for the minimization procedure ; switching on and off at every other time step in the kuo cumulus parameterization scheme do n ' t impact the convergence rate of cost function ; the existence of the switches do n ' t impact improvement to the mm5 model rainfall prediction because that not only specific humidity, but also wind, temperature and pressure are assimilated into the model

    非靜力中尺度數值模式mm5的四維變分資料同化系統進行的數值試驗結果表明： 「開關」變量保持與基態一致，所構造的切向線性模式能夠提供關于非線性模式擾動的一階近似，伴隨模式所計算的梯度值能夠為最小化過程提供較好的下降方向；郭氏降水參數化方案中對流每隔一個積分步的交替發生並不影響目標函數最小化的收斂速度； 「開關」變量的存在也不影響將風、溫度、氣壓和比濕結合起來同化對mm5降水預報準確性的提高。
  5. So as to deal with this problem, local b - spline surface designing method with complicated trimmed boundary constraints is advanced. for two neighboring surfaces, we first trim a belt along the common boundary and then bridge a b - spline surface between these two trimmed surfaces with a smooth blending. with respect to the comer area comprised of several adjoining surfaces, a rectangular region covering the comer area is obtained by trimming operations at first, and later a local b - spline for filling the rectangular region is completed through interpolation or approximation

    在兩張相鄰的曲面之間，先在其公共邊界處裁剪出一個帶狀區域，然後再採用曲面搭接的方式實現曲面之間的光滑過渡；而在鄰接曲面的公共角點處，先在該角點附近區域裁剪出一個矩形拓撲域，然後運用插值或逼近的方法，設計出一張既滿足於該區域的邊界條件同時又插值或逼近內部采樣點的b樣條曲面。
  6. Simulations results demonstrate the optimized model has a higher approximation to the objective system than does the previous one. next, fuzzy controller for the supply system is designed as follows : first, the structural decoupling is performed to formally decompose the 2 - input 3 - output controller as three 2 - input single - output ones, which greatly simplifies the design of the fuzzy controller. second, rudimentary control rules are identified and then improved by trial - and - error adjustment

    進而，本論文又研究設計了供水系統的模糊控制器：首先採用結構解耦的方法，把兩輸入三輸出模糊控制器形式化地分解為三個兩輸入單輸入的模糊控制器，這樣就大大簡化了模糊控制器的設計，接著採用模糊辨識方法得到初步的模糊控制規則，並通過進一步的調試使控制規則得以完善。
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