• 대한안전경영과학회:학술대회논문집
• /
• 대한안전경영과학회 1999년도 추계학술대회
• /
• pp.147-155
• /
• 1999

This paper discusses an optimal burn-in procedure to minimize total costs based on the assumption that the failure rate pattern follows a bimodal mixed Weibull distribution. The procedure will consider warranty period as a factor of the total expected burn-in cost. A cost model is formulated to find the optimal burn-in time that minimizes the expected burn-in cost. Conditional reliability for warranty period will be discussed. An illustrative example is included to show how to use the cost model in practice.

• 대한교통학회지
• /
• 제26권1호
• /
• pp.103-112
• /
• 2008

경제성 분석과정에서 브레이스 파라독스는 교통시설의 확충에도 불구하고 음(-)의 사회적 편익을 창출하는 형태로 나타난다. 이런 경우 사업시행 효과를 정확하게 추정할 수 없어 사업의 필요성을 판단하는데 많은 어려움을 겪게 된다. 본 연구에서는 경제성 분석 과정에서 나타나는 브레이스 파라독스 현상을 살펴보고 이에 대한 해결방안을 모색하는 것을 목적으로 하였다. 간단한 네트워크에 대한 분석결과, 경제성 분석 상에서 파라독스가 발생하는 경우는 교통량 수준이 특정 조건을 만족하는 경우에만 나타난다는 것을 확인할 수 있었다. 통행배정 기법에서는 사용자 평형보다는 체계 최적 상태의 경우가 파라독스의 발생을 줄일 수 있었다. 하지만, 통행배정 기법에 상관없이 운행비용 절감편익에 있어서는 모든 조건에 대해 파라독스가 발생하였으며, 이로 인해 전체 총 편익측면에서도 지속적으로 파라독스가 발생한다는 것을 확인할 수 있었다. 이와 같은 경제성 분석의 파라독스 해결을 위해, 본 연구에서는 운행비용을 포함하는 새로운 링크비용 함수를 제시하였다. 새로운 링크비용 함수는 운행비용 절감편익 측면의 파라독스를 완화시켜 사용자 평형 상태에서는 파라독스를 완화시켰으며, 체계 최적 상태에서는 파라독스를 완전히 제거하는 것으로 분석되었다.

• 한국경영과학회지
• /
• 제6권1호
• /
• pp.57-64
• /
• 1981

The continuous increase of crude oil consumption has struck great impact into the world economy, When we consider disadvantageous articles in contract for oil import, it would be desirable to import in batch the total quantity of crude oil contracted, but which is not available under the present situation which has many constraints This paper treats of the ways to deliver the crude oil in a given period so as to maximize the profit derived from the sales of oil products, To do this we should consider the prices of crude oil and oil products, inventory cost, transportation cost, oil refinement cost, and fluctuations of these parameters in a given period. The case of Korea Oil Corporation is treated in this paper to generalize the problem of crude oil transportation from Middle East and formulated in a mathematical programming. This programming is transformed into Dynamic Programming through specifing states, stages, payoffs, and recursive function. To clarify these procedure and methods, the case of Korea Oil Corporation is dealt with again and demonstrated in detail.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 2001년도 추계학술대회 논문집
• /
• pp.191-194
• /
• 2001

We consider a postal transportation planning in the transportation network of the form of hub and spoke. Given mail sorting centers and an exchange center, available vehicles and amount of mails to be transported between mail sorting centers, postal transportation planning is to make a transportation plan without violating various restrictions. The objective is to minimize the total transportation cost. To solve the problem, a tabu search algorithm is Proposed. The algorithm is composed of a route construction procedure and a route improvement procedure to improve a solution obtained by the route construction procedure using a tabu search. Computational results show that the proposed algorithm can solve practically sized problems within a reasonable time and the quality of the solution is acceptable.

• Journal of Biosystems Engineering
• /
• 제5권2호
• /
• pp.58-66
• /
• 1980

A survey was conducted to investigate the power tiller accidents. Eight provinces were covered for this study, and 278 power tiller owners were selected randomly by computer random generator. The results are summarized as follows : A. Frequency of accident. (1) Each power tiller had an accident 0.98 times a year and once every 361 hours of use. Higher frequency of accident was found during the miscellaneous operations including the preparation for farming operation, and there was one accident for every 92 hours of use. (2) The power tiller, which are more than six years old, met an accident 1.19 times a year , or one every 311 hours of use. This value was the highest one compared with any other group. (3) Kerosene engine power tillers met an accident 0.97 times a year, or one every 389 hours of use. It was one tie a year, or once every 329 hours of use for diesel engine power tillers. (4) Among diesel-engine power tillers, 10 horse-power group showed a higher frequency tillers. B. Cause of accident (1) The accidents of power tiller were mainly of sefety , which occurred due to the lack of attention during the operation and 47.4% of the total accidents. The next was of accidental, which represented 26.3% of the total accidents. (2) High percentage of safety accidents occurred during the preparation for farming operation including adjustment. Most of the accidental accidents occurred during the transportation. (3) Lower frequency of accident was found in the power tiller group which were operated by the 21-40 years old operator in comparison with that of the power tiller which was operated by other age group. Power tillers which were operated by high school graduates experienced less accidents compared to other education levels. C. Damage by accident (1) Eighty seven pescents of the total accidents caused damage to the power tiller operator , and 13 % of the total accidents caused property damage only. (2) With regard to the damage to the power tiller operator, 73.8% of the total accidents caused light injury but 26.3% caused heavy injury. (3) Accidents which occurred during machine preparation , and farming operations caused minor injury to the operator, but the accidents during transportation caused heavy injury which cost more than 15 days for recovery. (4) Among the 39 accidents , which caused property damage 18 accidents were from the transportation . Among the total property damage accidents 53.8% were light one which cost only less than 1,000 won. (5) The property damage from each accident cost 1,017 won, on the average, with regard to the kinds of operation, the highest property damage occurred during transportation work, with the value of 2, 965won.

• 해양환경안전학회지
• /
• 제29권3호
• /
• pp.288-295
• /
• 2023

The purpose of this study is to evaluate the feasibility of the new marine leisure ships. In order to achieve the research purpose, the cost and income were calculated based on the operating of other marine leisure ships, and the feasibility of the project was empirically analyzed. This study established a research model that applies the values derived by empirically analyzing ships with similar specifications, to the new marine leisure ships. We then calculated the cost-benefit analysis, net present value, and internal return, and evaluated the feasibility of the project based on this. As a result of the business feasibility analysis of investing in marine leisure ship, it was found that economic feasibility exists with a B/C of 1.042 and 1.049 for new and secondhand ships, respectively; however, considering the stability of the ship and the publicity and continuity of the business operation, it is recommended to invest in new ships compared to secondhand ships. The total benefit over the 10-year operating period using a social discount rate of 4.5% was evaluated to be about KRW 292.0 billion, which is higher than the total cost of KRW 256.6 billion. In conclusion, the profitability analysis showed that the B/C was 1.042, the NPV was KRW 193 billion, and the IRR was 2.1%, which indicates that profitability is weakly secured.

• 국제학술발표논문집
• /
• The 5th International Conference on Construction Engineering and Project Management
• /
• pp.219-225
• /
• 2013

State transportation agencies utilize fleets of heavy equipment to construct and maintain roadways. Equipment cost models can be developed to forecast economic life, which is the point at which the average unit cost to date reaches a minimum. A calculated economic life and cost models can be used to quantify the impacts of management strategies applied to a fleet. The purpose of this research was to develop an accurate method of quantifying the results of management strategies applied to a fleet of heavy construction equipment. The strategies evaluated are related to the annual usage of the fleet and the size of the fleet. More specifically the methodology is used to adjust the economic model to consider a limit to the annual decline in machine usage and a reduction in the number of machines in the fleet. When limiting annual machine usage, a specified rate is applied to the usage of the fleet, while total usage is held constant. This causes aging at a modified rate. A reduction in fleet size also causes a change to the usage of a fleet as the fleet must use fewer machines to produce the same total usage.

• 대한교통학회지
• /
• 제26권3호
• /
• pp.211-221
• /
• 2008

본 논문에서는 교통사고로 인해 사고 피해자 및 그 가족이나 친지, 주변사람들이 느끼는 정신적 고통을 사회적비용으로 환산한 심리적비용에 대해 고찰하여 보았다. 선택실험방법, 직접질문법, 양분선택형방법 등 3가지 방법을 사용하여 설문설계를 하였으며 이들 설문 설계방법별로 각각의 모형을 구축하였다. 모형 구축 시에는 확률선택모형에서 가장 일반적으로 사용되는 로짓모형을 이용하였으며 직접질문법은 토빗모형을 이용하였다. 이들 모형을 검증한 결과 모형에 따라 차이는 있었으나 대부분 모형의 적합도 및 각 계수의 신뢰도가 95% 신뢰수준에서 유의한 것으로 나타났다. 심리적비용 산정모형으로 산출된 국내 도로교통사고의 심리적비용은 사상자 1인당 1,563만원으로 총 5조 1천억 원이며, 전체 교통사고비용의 37.1%를 점유하는 것으로 분석되었다.

• 대한산업공학회지
• /
• 제33권3호
• /
• pp.322-328
• /
• 2007

Highly standardized products are suitable for automated purchasing using electronic commerce technology, where the price becomes the most important factor. Suppliers can change the prices dynamically based on the inventory level and market situation in order to maximize the sales and profit. In the virtual marketplace where multiple customers purchase multiple standardized products from multiple suppliers repetitively, customers can purchase the required amount of each item as a dynamic bidding by allocating purchase orders to the suppliers based on the current price. Customers need a method to quickly determine the optimal allocation of orders to the suppliers using the dynamically changing data to minimize the total cost. We present a LP model which minimizes the sum of the total price plus transportation cost for this problem. Simulation results using random data show meaningful reduction of the total cost.

• 산업경영시스템학회지
• /
• 제38권3호
• /
• pp.136-148
• /
• 2015

We analyzed the effect of three different types of inventory systems for saving the total cost using simulation on the system where multiple depots and many retailers disperse on the limited area. Three types of inventory systems are single echelon system with inventory exchange and two-echelon system and the variant two-echelon system. Variant two echelon system is the two-echelon system where the inventory transshipmentsare allowed on every two stage inventory echelons. Inventories kept on every retailer are commonly used for all retailers when certain retailer has stock-out. And when all retailers are stock-out, inventories kept on every depot are commonly used for the retailers whose assigned depots are stock-out. These all three systems are simulated with the constraint of service level on wide range of parameter settings. Simulation results show that cost saving effect appear clear for single echelon system and two-echelon system when shortage cost portion and transportation cost portion becomes large respectively irrespective of depot number. Variant two echelon system seems to be superior to two other systems when transportationcost portion becomes very small. But this superiority is not proved in terms of statistics. So we may conclude that the variant two echelon system may be useless with the higher administrative efforts due to frequent inventory exchange. Also we note that the traditional two echelon system becomes inferior to two other systems in terms of statistics when service level becomes high or when demand variance becomes very large. And inventory integration effect that cost becomes saved when depot number decrease, diminishes when transportation cost or stock-out cost increases irrespective of inventory systems.