• 대한산업공학회지
• /
• 제27권3호
• /
• pp.315-327
• /
• 2001

This paper considers the problem of operation sequencing in nonlinear process planning, which is the problem of selecting and sequencing operations required to produce a part with the objective of minimizing the sum of operation processing costs and machine, setup and tool change costs. Main constraints are the precedence relations among operations. The problem can be decomposed into two subproblems: operation selection and operation sequencing. We suggest four simulated annealing algorithms, which solve the two subproblems iteratively until a good solution is obtained. Here, the operation selection problem can be solved using a shortest path algorithm. Application of the algorithms is illustrated using an example. Also, to show the performances of the suggested algorithms, computational experiments were done on randomly generated test problems and the results are reported. In particular, one of the suggested algorithms outperforms an existing simulated annealing algorithm.

• 대한산업공학회지
• /
• 제21권3호
• /
• pp.329-343
• /
• 1995

Traditionally, machining process sequence was influenced and constrained by the design information obtained from CAD data base, i.e., class of operations, geometric shape, tooling, geometric tolerance, etc. However, even though all the constraints from design information are considered, there may exist more than one way to feasibly machine parts. This research is focused on the integrated problem of operations sequencing and machine tools selection in the presence of the product mix and their production volumes. With the transitional costs among machining operations, the operation sequencing problem can be formulated as a well-known Traveling Salesman Problem (TSP). The transitional cost between two operations is expressed as the sum of total machining time of the parts on a machine for the first operation and transportation time of the parts from the first machine to a machine for the second operation. Therefore, the operation sequencing problem formulated as TSP cannot be solved without transitional costs for all operation pairs. When solved separately or serially, their mutual optima cannot be guaranteed. Machining operations sequencing and machine tool selection problems are two core problems in process planning for discretely machined parts. In this paper, the interrelated two problems are integrated and analyzed, zero-one integer programming model for the integrated problem is formulated, and the solution methods are developed using a Tabu Search technique.

• Management Science and Financial Engineering
• /
• 제15권2호
• /
• pp.23-52
• /
• 2009

This study compares the cycle times of handling operations of yard cranes under different sequencing rules. An operation cycle was divided into several elementary movements and formulas for the expectation and the variance of each elementary movement were analytically derived. The expected waiting time of trucks was estimated based on the given arrival rate of trucks. The previous studies focused on developing a method to make an efficient schedule of operations for yard cranes. This paper introduces several sequencing rules, such as first-come-first-served, unidirectional travel, and Z pick travel rules. In addition, a formula for estimating the cycle times of yard cranes under each sequencing rule is derived, and the performance under the different sequencing rules are compared with each other.

• 산업경영시스템학회지
• /
• 제35권2호
• /
• pp.37-44
• /
• 2012

This paper focuses on scheduling problems arising in the military. In planned artillery attack operations, a large number of threatening enemy targets should be destroyed to minimize fatal loss to the friendly forces. We consider a situation in which the number of available weapons is smaller than the number of targets. Therefore it is required to develop a new sequencing algorithm for the unplanned artillery attack operation. The objective is to minimize the total loss to the friendly forces from the targets, which is expressed as a function of the fire power potential, after artillery attack operations are finished. We develop an algorithm considering the fire power potential and the time required to destroy the targets. The algorithms suggested in this paper can be used in real artillery attack operations if they are modified slightly to cope with the practical situations.

• Industrial Engineering and Management Systems
• /
• 제15권1호
• /
• pp.11-18
• /
• 2016

This paper considers a scheduling problem in a flexible job shop with a reconfigurable manufacturing cell. The flexible job shop has both operation and routing flexibilities, which can be represented in the form of a multiple process plan, i.e. each part can be processed through alternative operations, each of which can be processed on alternative machines. The scheduling problem has three decision variables: (a) selecting operation/machine pairs for each part; (b) sequencing of parts to be fed into the reconfigurable manufacturing cell; and (c) sequencing of the parts assigned to each machine. Due to the reconfigurable manufacturing cell's ability of adjusting the capacity, functionality and flexibility to the desired levels, the priority scheduling approach is proposed in which the three decisions are made at the same time by combining operation/machine selection rules, input sequencing rules and part sequencing rules. To show the performances of various rule combinations, simulation experiments were done on various instances generated randomly using the experiences of the manufacturing experts, and the results are reported for the objectives of minimizing makespan, mean flow time and mean tardiness, respectively.

• 한국지반환경공학회 논문집
• /
• 제4권3호
• /
• pp.61-67
• /
• 2003

축산폐수를 처리 시 우선 탈수 후 고상은 퇴비화, 액상을 연속회분식반응기(Sequencing batch reactor, SBR)로 이용하여 처리하는 시스템을 구상하였다. 영양염류 제거를 위한 SBR 공정의 안정적인 운전을 위한 운전모드 결정 실험을 수행하였다. K시 공공축산폐수처리장의 원심분리기에서 나온 유출수를 사용한 실험에서 질소를 제거하기 위한 적정 fill ratio는 1/12, SRT는 15일, 폭기/비폭기 주기는 2시간/1시간이었다. 탈질을 위하여 주입한 외부탄소원으로는 메탄올을 사용하였고 single feeding 방법과 step feeding 방법을 사용하였다. 이 결과 step feeding 방법을 사용시 더 효과적으로 유기물을 사용 탈질효율을 증가시킬 수 있었다.

• 예술인문사회 융합 멀티미디어 논문지
• /
• 제9권3호
• /
• pp.261-270
• /
• 2019

4차 산업혁명의 도래와 함께 제조 환경의 다품종화가 더욱 급격히 진행되고 있다. 다품종화된 생산 환경은 전반적인 생산계획 및 관리를 더욱 어렵게 하고 있으며, 효과적인 작업순서 결정을 통한 생산 효율 제고의 필요성을 더욱 높이고 있다. 기본적으로 효과적인 작업순서는 설비의 셋업을 감소시키고 설비의 효율적 활용과 함께 셋업 시간 단축을 도모하여 궁극적으로는 생산성 향상에 기여할 수 있다. 본 연구는 단일 기계가 다중 작업을 수행하는 상황에서의 효율적인 작업순서 결정 문제를 다룬다. 이는 대부분의 기존 연구에서 다루고 있는 한 대의 기계에서 하나의 작업만을 수행하는 경우와 비교할 때 문제의 복잡성이 매우 높다. 본 연구에서는 특히 셋업 횟수를 최소화하기 위한 정수계획 모형을 제안한다. 이는 자동차 전장 구성품의 하나인 와이어링 하네스 제조 공정을 대상으로 주어진 생산주문을 처리하는 과정에 금형 교체횟수를 최소화하는 문제를 대상으로 한다. 또한 제안된 수리 모형의 유효성을 검증하기 위해 간단한 사례연구 결과를 함께 제시한다.

• 한국정보시스템학회지:정보시스템연구
• /
• 제25권1호
• /
• pp.159-182
• /
• 2016

Purpose This paper aims to develop a novel tabu search algorithm for solving the sequencing problems with precedence constraints. Due to constraints, the traditional meta heuristic methods can generate infeasible solutions during search procedure, which must be carefully dealt with. On the contrary, the candidate order based tabu search (COTS) is based on a novel neighborhood structure that guarantees the feasibility of solutions, and can dealt with a wide range of sequencing problems in flexible manner. Design/methodology/approach Candidate order scheme is a strategy for constructing a feasible sequence by iteratively appending an item at a time, and it has been successfully applied to genetic algorithm. The primary benefit of the candidate order scheme is that it can effectively deal with the additional constraints of sequencing problems and always generates the feasible solutions. In this paper, the candidate order scheme is used to design the neighborhood structure, tabu list and diversification operation of tabu search. Findings The COTS has been applied to the single machine job sequencing problems, and we can see that COTS can find the good solutions whether additional constraints exist or not. Especially, the experiment results reveal that the COTS is a promising approach for solving the sequencing problems with precedence constraints. In addition, the operations of COTS are intuitive and easy to understand, and it is expected that this paper will provide useful insights into the sequencing problems to the practitioners.

• 환경위생공학
• /
• 제11권2호
• /
• pp.1-7
• /
• 1996

The behavior of total organic carbon (TOC) and phosphate were observed for 15 days with immobilized activated sludge using polyacrylamide (PAA) by sequencing batch reactor (SBR). In the preparation of immobilized sludge by PAA, it was found that suitable acrylamide concentration for actual wastewater treatment was to be 15% through the batch test. When SBR system was operated in the repeated aerobic and anaerobic conditions, TOC removal efficiency was 92%. The uptake rate of phosphate was increased from 1.78 mg-P/g cell/hr on the 5th day of acclimation to 2.5 mg-P/g cell/hr on the 15th day of acclimation. And the total phosphorus content in PAA bead was increased from 40 mg-P/g cell on the 1st day of operation to 55 mg-P/g cell on the 15th day of operation. From this study, lowering the volume of aeration tank was possible when PAA bead was used in wastewater treatment and long operation was also possible without the settler.

• 대한환경공학회지
• /
• 제35권1호
• /
• pp.1-9
• /
• 2013

혐기성 연속 회분식 반응조(Anaerobic sequencing batch reactor; ASBR)를 이용하여 혼합배양을 통한 장기간의 수소생산특성을 조사하였다. 실험에 사용된 기질은 글루코오스(8,250 mg/L)였고, pH 5.5, 온도 $37^{\circ}C$, 교반속도 150 rpm으로 설정하여 160일 동안 반응조를 운전하였다. 운전초기에 F/M비 2로 유지되어 수소생산 수율은 0.8 mol $H_2/mol$ glucose의 수소가 생산되었고, 운전 80일째 수소생산수율은 2.68 mol $H_2/mol$ glucose까지 증가하였다. 그러나 그 이후로 수소 생산량이 지속적으로 감소하여 운전 130일경 이후 수소의 생산은 없는 것으로 나타났다. PCR-DGGE분석을 통해 반응조내 미생물은 일반적인 수소생성 균으로 알려지고 있는 Clostridium sp.가 검출되었으나 반응조 운전 조건의 변화가 수소생산 저감의 주된 원인으로 밝혀졌다. 즉 반응조의 MLSS 농도가 증가함에 따라 F/M비가 감소하고 생산된 수소는 propionic acid의 생성으로 소모되는 것으로 추정할 수 있고 이는 반응조의 F/M비 0.5와 propionic acid 농도는 2,130 mg/L로 높게 유지된 것으로 확인하였다.