• 한국경영과학회지
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• 제35권4호
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• pp.33-53
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• 2010

When purchase prices of a raw material fluctuate over time, the total purchasing cost is mainly affected by reordering time. Existing researches focus on deciding the right time when the demand for each period is replenished at the lowest cost. However, the decision is based on expected future prices which usually turn out to include some error. This discrepancy between expected prices and actual prices deteriorates the performance of inventory models dealing with fluctuating purchase prices. In this paper, we propose a new inventory model which incorporates not only cost but also risk into making up a replenishment schedule to meet each period's demand. For each replenishment schedule, the risk is defined to be the variance of its total cost. By introducing the risk into the objective function, the variability of the total cost can be mitigated, and eventually more stable replenishment schedule will be obtained. According to experimental results from crude oil inventory management, the proposed model showed better performance over other models in respect of variability and cost.

• 한국철도학회논문집
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• 제12권1호
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• pp.135-143
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• 2009

대부분의 개발 프로젝트는 목표 비용과 일정을 $40{\sim}200%$ 초과한다. 이러한 초과 현상은 계획시 업무를 과소 평가하거나 재작업을 고려하지 않음으로써 발생한다. 현재 국내에서 사용되는 대표적인 일정 계획/관리 기법(Gantt Chart, PERT/CPM 등)들은 재작업을 반영할 수 없다. 이 논문은 일정 계획시 보다 현실적인 일정 계획 값을 예측하기 위해서 재작업을 고려하는 방법을 고안하구 또한 과업의 과소평가를 방지하기 위해 수행시간의 불확실성을 확률변수로 나타내어 다루기 위해서 시뮬레이션을 수행하여 최종 완료 날짜의 예상치와 분산도를 계산하는 방법을 제안한다.

• 경영과학
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• 제21권1호
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• pp.39-55
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• 2004

Efficient crew scheduling for cockpit crew is important in airline industry due to operational safety and cost associated with the flight duty time. Because of complexity of regulations imposed to the cockpit crew. it is complicated to generate an efficient schedule. Schedule of cockpit crew can be generated through two steps; selecting of flight patterns. and scheduling of them to the specific time horizon. Heuristic method is developed and applied with massive data in a limited time of computation. A set of flight patterns is selected from all possible flight patterns. which are generated by composing the flight leg based on regulations. by using the set partitioning problem with objective function of oversea stay cost. The selected set of flight patterns found at the first step is allocated to 4 week crew schedule to minimize the variance of total fight time assigned to each crew. The crew schedules obtained are evaluated and compared with the ones currently used in one of major airline company.

• 한국건설관리학회논문집
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• 제10권1호
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• pp.26-35
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• 2009

건설공사 공정 공사비 통합관리시스템(EVMS, Earned Value Management System)에서 대부분의 정보들은 공사정보 분류체계(WBS, Work Breakdown Structure)를 중심으로 활용된다. 즉, 공정편차와 비용편차 등의 EVM 성과정보 역시 WBS에서 선택된 공종을 중심으로 결과물이 분석되므로, EVMS에서 WBS는 정보중심 역할을 하게 된다. 본 연구에서는 WBS 정보가 4상한의 좌표방식으로 표현되어 프로젝트의 대 중 소 공종이 용이하게 표현될 수 있는 좌표식 공사정보분류체계(WBS Map) 표현기법을 구축하였다. 또한 연구에서는 WBS Map에 근거한 EVMS를 개발하였으며, 개발된 EVMS에서는 각종 속성 지표값들을 색상기호 등으로 시각화하는 방법론을 구축하여 EVMS 정보의 실무 활용성을 높일 수 있도록 하였다.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.403-411
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• 2013

Horizontal construction projects such as oil and gas pipeline projects typically involve repetitive-work activities with the same crew and equipment from one end of the project to the other. Repetitive scheduling also known as linear scheduling is known to have superior schedule management capabilities specifically for such horizontal construction projects. This study discusses on expanding the capabilities of repetitive scheduling to account for the variance in production rates and visual representation by developing an automated alignment based linear scheduling program for applying temporal and spatial changes in production rates. The study outlines a framework to apply changes in productions rates when and where they will occur along the horizontal alignment of the project and illustrates the complexity of construction through the time-location chart through a new linear scheduling model, Linear Scheduling Model with Varying Production Rates (LSM_VPR). The program uses empirically derived production rate equations with appropriate variables as an input at the appropriate time and location based on actual 750 mile natural gas liquids pipeline project starting in Wyoming and terminating in the center of Kansas. The study showed that the changes in production rates due to time and location resulted in a close approximation of the actual progress of work as compared to the planned progress and can be modeled for use in predicting future linear construction projects. LSM_VPR allows the scheduler to develop schedule durations based on minimal project information. The model also allows the scheduler to analyze the impact of various routes or start dates for construction and the corresponding impact on the schedule. In addition, the graphical format lets the construction team to visualize the obstacles in the project when and where they occur due to a new feature called the Activity Performance Index (API). This index is used to shade the linear scheduling chart by time and location with the variation in color indicating the variance in predicted production rate from the desired production rate.

• 한국건축시공학회지
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• 제10권1호
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• pp.199-212
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• 2010

국내 건설산업에 있어서 기술과 정보의 기반구조를 확립하기 위하여 몇몇 건설정보관련 법규가 제도화되었다. 그러나 국내 건설정보 분류체계, 공정 공사비 통합관리(EVM), 프로젝트관리 정보시스템(PMIS)은 주요한 문제점을 내포하고 있다. 특히 현행 PMIS의 기능은 시공자 위주의 시스템으로 되어 있고, EVM이 적용되지 않아 발주자를 위한 보고, 분석, 예측기능이 매우 취약하다. 더욱이 EVM과 PMIS가 서로 분리된 체계로 운영되고 있어 발주자가 실시간으로 공정 및 공사비 정보를 확인할 수 없다. 본 연구의 목적은 PMIS가 EVM기능을 제공하고 사업참여자들이 제반정보를 공유할 수 있도록 WBS 구축방안과 EVM - PMIS 통합모델을 제안하여, E-비즈니스 업무환경하에서 PMIS를 효율적으로 운용할 수 있는 틀(framework)을 제공하는 것이다. EVM - PMIS 통합의 핵심은 EVM과 PMIS가 액티비티 기반의 동일한 운영체계를 갖는 것이다. 통합의 원리는 액티비티의 정보항목(field)을 PMIS의 공정 및 공사비관리 기능을 위한 하위모듈을 구성하는 관계형 데이터베이스 테이블(table)의 항목과 연계시키는 것이다. 따라서 액티비티의 계획공사비(PA), 달성공사비(EV), 실투입비(AC), 공정편차(SV), 공정수행지수(SPI), 공사비편차(CV), 공사비지출지수(CPI)는 PMIS의 공정 및 공사비 하위모듈을 위한 데이터베이스 테이블의 항목으로 연계된다.

• Journal of Construction Engineering and Project Management
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• 제3권4호
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• pp.5-11
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• 2013

Construction industry is overwhelmed by delay and often has suffered cost and time overrun. In this context, Last Planner System (LPS) has been considered as a very useful tool for the management of the construction process. Many previous studies have reported its effectiveness in construction performance. This study aims to evaluate the level of importance of the Last Planner processes in the Vietnam construction industry (VCI), and analyze the existing barriers when implementing these processes in construction management. These barriers were collected based on previous studies from International Group for Lean Construction (IGLC). A survey was carried out through questionnaire. The respondents are been experienced people in construction project management. There are four processes of LPS that were investigated including master schedule, phase schedule, lookahead plan, and weekly work plan. The results showed that master schedule is the most important item when performing a construction project in the VCI. The highest degree of agreement belongs to 'owner - contractor' pair with 77.1% importance indices; whereas the lowest belongs to 'consultants - contractors' pair with 63.8% importance indices. Eventually, three barrier factors were extracted from factor analysis technique with 62.2% of variance explained.

• International Journal of Contents
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• 제6권2호
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• pp.10-13
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• 2010

For applications that are grid enabled, the grid can offer a resource balancing effect by scheduling grid jobs on machines with low utilization. When jobs communicate with each other, the internet, or with storage resources, an advanced scheduler could schedule them to minimize communications traffic or minimize the distance of the communications. We propose an intelligent load distribution algorithm to minimize communications traffic and distance of the communications using genetic algorithm. The experiments show the proposed load redistribution algorithm performs efficiently in the variance of load in grid environments.

• 한국직업건강간호학회지
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• 제29권4호
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• pp.306-315
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• 2020

Purpose: This study was conducted to identify the effects of caffeine intake by shift workers on sleep, considering various variable related to the sleep health of shift workers. Methods: A descriptive survey study was conducted with 128 employees who worked shifts. Respondents were surveyed on their of caffeine intake behavior, schedule type, quality of sleep, health promotion behavior, and occupational stress. Differences in their quality of sleep were assessed using the t-test and analysis of variance, while factors influencing the effect of caffeine intake on the quality of sleep were analyzed using hierarchical logistic regression. Results: The average Pittsburgh Sleep Index, Korean Version score of those surveyed was 7.3±3.25, indicating that their quality of sleep was low. On the other hand, their aveage daily intake of caffeine was 1.6±0.99 cups (1 cup =150 mL) and 116.4±77.58 mg/dL of caffeine. When the various variables that could have affected the quality of sleep were corrected, an increase in the amount of caffeine consumed was found to lead to a decrease in the quality of sleep (p=.015). Conclusion: Caffeine intake by shift workers has a significant bearing on their quality of sleep; therefore, such intake should be adjusted to improve their sleep health.

• 사상체질의학회지
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• 제24권2호
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• pp.39-46
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• 2012

1. Objectives : The purpose of this study was to validate the Sasang Personality Questionnaire (SPQ) with Positive And Negative Affection Schedule(PANAS) for emotionality and Body Mass Index (BMI) for body constituents. 2. Methods : The SPQ along with Questionnaire for Sasang Constitution Classification (QSCC) II, PANAS, BMI was measured with 232 College students. The correlation coefficient was measured with Pearson correlation between SPQ and PANAS, BMI. The SPQ, PANAS, and BMI score of each Sasang constitution groups based on QSCCII were compared using analysis of variance and profile analysis. 3. Results : The SPQ score of each Sasang constitution groups was significantly (p<0.01) different. The SPQ showed significant correlation with PANAS Positive Affect (r=0.201, p=0.002), but not with the BMI (r=0.097, p=0.146). The SPQ-Emotionality scale, unlike other SPQ subscales, showed positive correlation with PANAS Negative Affection. 4. Conclusions : We performed the constructive validity of SPQ using PANAS and BMI. The SPQ would be useful for the study on psychophysiological mechanism of the Sasang constitutions.