本研究利用有限差分時域(finite difference time domain)法配合實驗計畫法(design of experiment)以數值實驗方式，分析因子對輻射性質變化並找出顯著的因子。首先為了減少有限差分時域法程式運算時間以便後續之討論，利用訊息傳遞介面(message passing interface)程式庫建立平行運算程式加速運算時間，結果顯示平行運算對比串行運算程式可減少四成以上之運算時間。數值實驗探討的波長分別為1 m、54.545 mm及632 nm，針對三個波長以2水準的實驗，分析因子效應並篩選顯著因子，所針對的輻射性質分別為1 m實驗的自行建立之評估背向散射增強(backscattering enhancement)的函數，54.545 mm與632 nm實驗的反射率，並於波長632 nm以中央合成設計(central composite design)找尋最低之反射率與其參數組合。在篩選實驗上皆針對各自反應變數所配適之模型以F檢定找出顯著之因子。中央合成設計在初始的參數設計上發生極值之參數水準並未在實驗範圍內，故以最陡下降法逼近，實驗後發現反射率仍為一單調遞減的趨勢。

This work uses finite different time domain method with design of experiments to explore factors which impact wide-band radiative property of rough surface by numerical experiments. First, in order to reduce computing time of finite different time domain method for the following discussion, use the message passing interface library to build a parallel computing program. In contrast to the serial computing program, the parallel computing program reduces over 40% computing time. Wavelengths of numerical experiments are 1 m, 54.545 mm and 632 nm. For this three wavelengths, explore factor treatments and screen significant factors. The radiative property of wavelength 1 m experiment is the function estimates backscattering enhancement which is builded by ourselves. However, we aim at reflectivity at wavelength 54.545 mm and 632 nm experiments, and then try to find the local minimum reflectivity and combinations of factor at wavelength 632 nm by central composite design. In factor screening experiments, use F test to screen significant factors in the regression model of response variables. In central composite design, the location of stationary point isn’t at range of experiment. So, use the method of steepest scape to approach the vicinity of optimum. After experiments, find the trend of reflectivity is still monotonically decreasing.

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