| 摘要: | 摘要 近年來國際航空快遞業成長迅速且競爭激烈。由於其營運相當重視「時效」的掌握，因此在貨物處理作業上，如何有效率進行貨物收集、分類及組裝等作業程序顯得相當重要。其中，貨物裝櫃作業對於總處理時間與成本影響甚鉅，故如何妥善規劃快遞貨物裝櫃方式，以達到整體成本最小，實為一重要課題。由於快遞貨物系統裝櫃方式與各機場城市及空運中心處理成本相關，而處理成本與貨物指派整櫃或混櫃之決策、處理量及可允許處理時間等因素密切相關，且呈現非線性關係，因此使得此等快遞貨櫃裝櫃問題變得相當複雜。然而，目前業界多以經驗法則及人工判斷來決策，此做法在面臨目前大型空運中心及複雜的營運網路環境下，甚不具效率及效果。其次，在學術上，至今尚未發現有類似課題之研究或探討。因此，本研究以一國際航空快遞公司立場，以總成本最小為目標，考量相關營運限制，構建一國際航空快遞貨物裝櫃決策模式。本研究能提供一有效的決策輔助工具，以幫助快遞業者決定整櫃與混櫃的貨物指派與裝載，降低營運成本，進而提升其獲利及市場競爭力。此模式為一非線性混合整數規劃問題，屬於NP-hard性質，求解上遠較一般線性整數規劃問題為難，尤其針對實際大型問題，在有限時間內難以求得最佳解。由於目標式中的部份函數含有非線性(nonlinear)且呈階梯式的函數型態，本研究使用線性分段技巧將含此特性之目標函數轉換成線性函數，並進一步透過C程式語言並配合數學規劃軟體CPLEX，發展有效的演算法以求解模式。最後，為了驗證本研究之實用性，本研究以一國際快遞公司的營運為例，並在個人電腦上執行求解，測試效果甚佳。 Abstract In recent years, international air express services have grown rapidly. The markets become very competitive for the carriers. Since air express services rather emphasize on time-definite deliveries, it is important for carriers to efficiently to collect, classify and assembly cargos at every service station. In which, the cargo container loading operation, in general, significantly affects the total operating time and cost. As a result, how to determine a suitable cargo container loading plan in order to minimize the operating cost is an important issue for air express carriers. Since the cargo container loading plan is related to the operating cost of each airport and the hub, which is further nonlinearly correlated with the assignment of cargos to pure/mixed containers, the cargo quantity and their allowable operating times, the cargo container loading plan problem is very complicated. However, the current cargo container loading plan in practice is solved manually with staff’s experience, which is neither effective nor efficient, especially for the environment of large hubs and complicated network operations today. As to academics, there has not yet research found on the cargo container loading plan problem of international air express cargos. Therefore, on the basis of the international air express carriers’ perspective, this research develops a cargo container loading plan model, with the objective of minimizing total cost, subject to related operating constraints. The model is a useful planning tool for International air express carriers to decide on their cargo loading plans in order to lower their operating costs, so that their profits and market competitiveness can be enhanced. The model is formulated as a nonlinear mixed integer program that is characterized as NP-hard and is more difficult to solve than integer linear programs, especially for realistically large-scale problems that cannot be optimally solved in a reasonably short time. Since the model’s objective contains nonlinear ladder-functions, we convert them into piece-wise linear functions. Furthermore, we employ C computer language, coupled with a mathematical programming solver, CPLEX, to develop an efficient algorithm to solve the problem. To evaluate the model and the solution algorithm, we perform a case study using real operating data from an international air express carrier. The results are good. |
