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Access type: Open accessSubject: search.filters.subject.optimization

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    A study on the optimization methods for optomechanical alignment
    (2006-01-01)
    Yu, Ming-Ta
    ;
    Lin, Tsung-Yin
    ;
    Lia, Yi-You
    ;
    Shu, Pei-Feng
    ;
    機械工程學系
    The alignment for optomechanical components is important in designing and manufacturing optical systems. This study uses optical fibers for example to find suitable optimization strategies for optomechanical alignment. The core diameter of the single-mode fiber is about 6 mu m to 9 mu m. Any slight misalignment or deformation of the optical mechanism will cause signification optical losses during connections. The alignment methods can be divided into passive and active ones. In the passive alignment, optical connectors, ferrules, and sleeves are used to align two optical fibers. In the active alignment, the best connection position with minimum connection losses must be found, and users usually take a lot of effort to do this. This study uses different optimum methodologies: non-gradient-based, gradient-based, and Hessian-based methods, to find the optimum position. The non-gradient-based method has low accuracy and the efficiency cannot be increased. The gradient-based methods seem to have better efficiency to find the optimum position because it uses gradient information to calculate the search direction in every iteration. Finally for the Hessian-based methods, it is found that the advantage of using Hessian matrix is not obvious because the light intensity distribution is similar to the Gaussian distribution.
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    Application of global optimization to design of an aspheric pickup head for multiple wavelengths
    (2006-01-01)
    Tsao, Chao-Hsi
    ;
    Chern, Jyh-Long
    ;
    光電工程學系
    ;
    Department of Photonics
    An optimization process combining of global optimization algorithm and further optimization treatment is proposed and demonstrated with application to the objective lenses of multiple-wavelength configurations. Based on the optimal variable set of aspheric coefficients obtained by the proposed global optimization strategy, singlet objective lens for different operational configurations, i.e., for CD and DVD, and for DVD and HDDVD, can be deduced.
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    Novel optomechanical alignment method using a numerical optimization methodology
    (2007-06-01)
    Lin, Tsung Y.
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    Yu, M. T.
    ;
    Liu, W. T.
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    Alignment of optomechanical components is important when designing and manufacturing optical systems. This study used an optical fiber as a case study to develop an alignment method. The core diameter of a single-mode fiber is about 9 mu m, and any slight misalignment or deformation of the optical mechanism will cause significant optical losses in connections. Previous studies have shown that the currently used alignment methods are not efficient, and the precise position for the connection is not easy to locate. This study proposes a two-stage method to overcome these problems. In the first stage, the Nelder-Mead simplex method is used to move quickly to the optimum solution. In the second stage, a numerical optimization method is used to improve the accuracy. This study compares different numerical optimization method that can be used to find the ideal connection position. It can be concluded that the most stable method for the search direction is the steepest-descent method, because the light intensity distribution is similar to a Gaussian one, and the most efficient method for the step-size determination is polynomial interpolation. Therefore, the second stage uses the steepest-descent method with polynomial interpolation. (c) 2007 Society of Photo-Optical Instrumentation Engineers.
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    Macro-cell placement fos custom-chip design using self-organizing fuzzy technique
    (1998-01-01)
    Chang, RI
    ;
    Hsiao, PY
    ;
    資訊工程學系
    ;
    Department of Computer Science
    In this paper, a new optimization technique called SOFT (self-organizing fuzzy technique) is proposed to solve the macro-cell placement problem. In SOFT, different criteria are simultaneously accounted by a novel fuzzy gain function which models expert knowledge to control the optimization process. The presented procedure is an adaptation of Kohonen's self-organization algorithm which is well suited for implementation on massively parallel architecture for fast computing. The MCNC benchmark examples are presented to verify the performance and feasibility of SOFT. Comparisons are made with the Hopfield network, SOAP and TimberWolf MC5.6. Experiments show that the proposed method yields an average of 17% improvement in total wire length compared with previous methods. Large size problems with 225 and 1024 arbitrarily-sized macrocells are also presented.
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    奈米材料披覆層之特性識別研究
    (2009)
    金大仁
    ;
    KAM TAI-YAN
    ;
    國立交通大學機械工程學系(所)
    本計畫研究建立一套評估奈米鍍層品質的非破壞檢測方法，此法利用量測鍍膜板的自然頻率來識別奈米鍍層的材料常數及厚度分布，從而判斷奈米鍍層的品質。本研究將建立一分析奈米材料鍍膜平板自然振動頻率的方法，其中將平板分成若干區域，每一區域的鍍膜具有不同的材料常數及厚度，然後利用Rayleigh-Ritz方法建立鍍膜板的振動控制方程式，藉求解特徵值問題來得到鍍膜板的自然振頻。若量測的自然振頻與分析得到的自然振頻有異，則鍍膜的參數(材料常數及厚度)顯然與假設值不同。本研究利用最佳化方法來找尋鍍膜的真實參數，藉使理論與實驗自然振頻間的誤差最小化而找到正確的鍍膜參數。本研究將探討如何選取最佳化中合適的係數，使尋找的過程更快速及有效。本研究將進行奈米材料試片的系列實驗，先決定奈米材料在不同混合比例下的材料常數。然後進行奈米材料的鍍膜製作，預先設計不同鍍膜厚度及材料常數，然後製作鍍膜板供驗證本非破壞檢測方法之正確性。鍍膜板的自然振頻可藉敲擊法的振動試驗或用掃頻振動方法來求得，這些方法都非常方便及有效。量測到的自然頻率以取最低的5-7個頻率來進行鍍膜參數的識別，本研究將探討本方法在不同鍍膜材料及分布狀況的識別能力，結果可供產業界及學術界參考。
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    海岸地區地陷潛能與危險評估技術(II)
    (2002)
    楊錦釧
    ;
    J.C. Yang
    ;
    國立交通大學工學院防災工程研究中心
    台灣地區發生地層下陷之區域大多分布於西南沿海地區，其造成主要原因乃肇於不當之土地利用及水資源無法有效管制使用所致。由於地下水超抽導致台灣海岸地區相繼發生地層下陷現象，並因地勢沉陷衍生暴潮溢淹與水土資源永久性傷害等問題，使社會付出巨大成本。為有效防患地層下陷之潛在危機，除了持續進行長期性的系統性監測工作以掌握地層下陷動態外，對於嚴重地層下陷區與下陷潛勢區，亟需進一步建立地陷潛能與危險評估技術，以提供執行地層下陷區防護管理措施之參考。 貴局為推動「水資源科技發展方案–水資源防災新科技計畫」，爰辦理「海岸地區地陷潛能與危險評估技術」計畫，除有效掌握地層下陷總量/速率與其影響因子之相關性外，並將發展適合本土性之地層下陷預測模式，建立地層下陷潛勢之判別方法及潛能下陷量之預測技術，提供下陷潛勢區防範措施之參考。 本計畫之最終目標係建立區域地下水文平衡最佳推估模式及大區域分區分層下陷模式，經本計畫所建立之地層下陷及地下水優化管理模式之測試，以發展最佳下陷趨勢預測模式，並藉地理資訊決策支援系統之建立，提供地層下陷潛勢區之判別方法及下陷量預測、海岸地區地層下陷區域排水及堤防危險程度評估、水資源利用與管理等技術。
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    海岸地區地陷潛能與危險評估技術(III)
    (2003)
    楊錦釧
    ;
    Yang, Jinn-Chuang
    ;
    國立交通大學工學院防災工程研究中心
    台灣地區發生地層下陷之區域大多分布於西南沿海地區，其造成主要原因乃肇於不當之土地利用及水資源無法有效管制使用所致。由於地下水超抽導致台灣海岸地區相繼發生地層下陷現象，並因地勢沉陷衍生暴潮溢淹與水土資源永久性傷害等問題，使社會付出巨大成本。為有效防患地層下陷之潛在危機，除了持續進行長期性的系統性監測工作以掌握地層下陷動態外，對於嚴重地層下陷區與下陷潛勢區，亟需進一步建立地陷潛能與危險評估技術，以提供執行地層下陷區防護管理措施之參考。「海岸地區地陷潛能與危險評估技術」研究計畫包括區域性地下水文平衡最佳推估模式、大區域分區分層地層下陷計算、地層下陷資料之地理資訊決策支援系統、以及地層下陷及地下水優化模式等四個研究子題。其最終目標係藉由地理資訊決策支援系統，整合其他三個模式，發展一套最佳地層下陷趨勢預測模式，以提供地層下陷潛勢區之判別方法及下陷量預測、水資源利用與管理等技術。本研究分三年逐步實施，各年度之預期成果如下：1.第一年：模式之發展、建立與測試及單機版地下水平衡模式與地 層下陷模式整合系統之開發與測試。2.第二年：應用第一年發展、建立及測試完成之模式，加強模式之功能，並以第一年蒐集較完整之資料予以驗證。另外將地理資訊決策支援系統由單機版轉換至網際網路。3.第三年：建立完整之地層下陷潛能與危險評估技術。
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    An approximately global optimization method for assortment problems
    (1998-03-16)
    Li, HL
    ;
    Chang, CT
    ;
    資訊管理與財務金融系 註：原資管所+財金所
    ;
    Department of Information Management and Finance
    Assortment problems occur when we want to cut a number of small rectangular pieces from a large rectangle to get the minimum area within the rectangle. Recently, Chen et al. proposed a useful model for assortment problems. Although Chen et al.'s model is quite promising to find solutions, there are two inadequacies in their model: firstly, the objective function in their model is a polynomial term, which may not lead to a globally optimal solution; secondly, too many 0-1 variables are used to formulate the non-overlapping constraints. We propose a new method to reformulate an assortment model. Our model is not only able to find the approximately global optimal solution, but involves less 0-1 variables for formulating non-overlapping constraints. (C) 1998 Elsvier Science B.V.
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    Stiffness identification of laminated composite shafts
    (1998-09-01)
    Kam, TY
    ;
    Liu, CK
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    Distributions of bending stiffness along the spans of laminated composite shafts are determined via a non-destructive evaluation approach. The finite element method formulated on the assumption of uniform bending stiffness within each element is used in the deflection analysis of the shafts. Differences between measured and theoretically predicted deflections at any two points on a shaft are used to construct an error function for deflection. The identification of bending stiffness is formulated as a minimization problem in which the elemental bending stiffnesses are determined to make the error function a global minimum. A global minimization technique and a bounding method for establishing side constraints are presented to solve the above minimization problem. Experiments are performed to study the feasibility and applications of the proposed method. (C) 1998 Elsevier Science Ltd. All rights reserved.
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    Finite element analysis and optimization on springback reduction
    (1999-03-01)
    Chou, IN
    ;
    Hung, CH
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    Several springback reduction techniques used in the U-channel bending processes were analyzed with the finite element method, which included are bottoming, pinching die, spanking and movement techniques. The relationship between the amount of springback and the forming parameters in each technique was first established through finite element simulations, and then the optimization analysis was coupled with the finite element analysis to find the optimum forming parameters for each springback reduction technique. (C) 1998 Elsevier Science Ltd. All rights reserved.