• 제어로봇시스템학회논문지
• /
• 제18권9호
• /
• pp.854-862
• /
• 2012

The optimal design of batch-storage network by using periodic square wave model provides analytical lot sizing equations for a complex supply chain network characterized as multi-supplier, multi-product, multi-stage, non-serial, multi-customer, cyclic system including recycling and/or remanufacturing. The network structure includes multiple currency flows as well as material flows. The processes are represented by multiple feedstock/product materials with fixed composition which are very suitable for production processes. In this study, transportation processes that carry multiple materials with unknown composition are added and the time frame is changed from single period into multiple periods in order to represent nonperiodic parameter variations. The objective function of the optimization involves minimizing the opportunity costs of annualized capital investments and currency/material inventories minus the benefit to stockholders in the numeraire currency. The expressions for the Kuhn-Tucker conditions of the optimization problem are reduced to a multiperiod subproblem for average flow rates and analytical lot-sizing equations. The multiperiod lot sizing equations are different from single period ones. The effects of corporate income taxes, interest rates and exchange rates are incorporated.

• 제어로봇시스템학회논문지
• /
• 제11권11호
• /
• pp.956-962
• /
• 2005

This paper presents an integrated analysis of production and financing decisions. We assume that a cash storage unit is installed to manage the cash flows related with production activities such as raw material procurement, process operating setup, Inventory holding cost and finished product sales. Temporarily financial investments are allowed for more profit. The production plant is modeled by the Batch-Storage Network with Recycle Streams in Yi and Reklaitis (2003). The objective function of the optimization is minimizing the opportunity costs of annualized capital investment and cash/material inventory while maximizing stockholder's benefit. No depletion of all the material and cash storage units is major constraints of the optimization. A novel production and inventory analysis formulation, the PSW(Periodic Square Wave) model, provides useful expressions for the upper/lower bounds and average level of the cash and material inventory holdups. The expressions for the Kuhn-Tucker conditions of the optimization problem can be reduced to two subproblems and analytical lot sizing equations under a mild assumption about the cash flow pattern of stockholder's dividend. The first subproblem is a separable concave minimization network flow problem whose solution yields the average material flow rates through the networks. The second subproblem determines the decisions about financial Investment. Finally, production and financial transaction lot sizes and startup times can be determined by analytical expressions as far as the average flow rates are calculated. The optimal production lot and storage sizes considering financial factors are smaller than those without such consideration. An illustrative example is presented to demonstrate the results obtainable using this approach.

• Korean Chemical Engineering Research
• /
• 제45권3호
• /
• pp.249-257
• /
• 2007

사각파 모형은 회분식 공정-저장조 망구조의 최적설계에 성공적으로 적용되었다. 설계된 망구조는 재순환 흐름을 포함하는 회분식의 모든 생산 재고 및 분배 체계를 내포한다. 본 연구에는 사각파 모형의 적용범위를 연속 또는 회분식 공정 뿐 만 아니라 반연속 공정에 까지 확대하려 한다. 이전의 연구에서는 원료조성이나 제품수율은 알려진 상수로 취급되었다. 본 연구에서는 이러한 제약이 완화되어 원료조성이나 제품 수율이 최적화 되어져야 하는 독립변수로 취급된다. 이러한 수정은 정유공장에서 흔히 접하는 최적제품 배합문제를 취급할 수 있게 한다. 원료조성과 제품수율이 독립변수일 때 발생하는 많은 문제의 복잡성에도 불구하고 사각파 모형은 여전히 해석적인 최적용량 공식을 제공한다. 최적공장설계에 적용되는 본 연구의 유용성은 고밀도 폴리에틸렌 공장설계의 예를 통해 나타내었다. 연구결과를 토대로 모든 공정의 최적성을 비교할 수 있는 척도를 제시하였다. 이 척도는 다수의 공정의 성능을 직접 비교할 수 있게 하므로 공정의 상태를 진단하는 유용한 도구가 될 것이다. 공정의 비용이 유속의 제곱근에 비례한다는 결과는 공장설계에서 늘리 알려진 6/10 경험법칙과 유사하다.