• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.87-95
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• 2016

This study examined the characteristics of the hourly demand of city gas in Korea and proposed multiple regression models to obtain precise estimates of the hourly demand of city gas. Forecasting the hourly demand of city gas with accuracy is essential in terms of safety and cost. If underestimated, the pipeline pressure needs to be increased sharply to meet the demand, when safety matters. In the opposite case, unnecessary inventory and operation costs are incurred. Data analysis showed that the hourly demand of city gas has a very high autocorrelation and that the 24-hour demand pattern of a day follows the previous 24-hour demand pattern of the same day. That is, there is a weekly cycle pattern. In addition, some conditions that temperature affects the hourly demand level were found. That is, the absolute value of the correlation coefficient between the hourly demand and temperature is about 0.853 on average, while the absolute value of the correlation coefficient on a specific day improves to 0.861 at worst and 0.965 at best. Based on this analysis, this paper proposes a multiple regression model incorporating the hourly demand ahead of 24 hours and the hourly demand ahead of 168 hours, and another multiple regression model with temperature as an additional independent variable. To show the performance of the proposed models, computational experiments were carried out using real data of the domestic city gas demand from 2009 to 2013. The test results showed that the first regression model exhibits a forecasting accuracy of MAPE (Mean Absolute Percentage Error) around 4.5% over the past five years from 2009 to 2013, while the second regression model exhibits 5.13% of MAPE for the same period.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.345-350
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• 2003

현대의 많은 제조산업에서 제품 모델의 다양성은 점점 증가하고 있다. 제품 모델을 관리하기 위한 이론적 모델이 존재하지만, 현실의 변수들을 이론적으로 다루기 쉽지 않으며, 수리적인 접근도 한계가 있다. 본 논문은 생산재고 정책을 적용하기 위하여 다수의 제품 모델을 군집화 하기 위한 실증연구를 목표로 한다. 수요 분포, 생산 특성, 재고 수준의 세 가지 측면에서 각 모델의 공급에 영향을 미칠 수 있는 몇 가지 변수들을 정의하였다. 먼저 변수들의 상호 연관관계를 파악하기 위해서 요인 분석을 수행하여 변수들의 주요 유형을 파악하고, 이를 실제 생산 데이터에 적용함으로써 실증적 분석을 하였다. 본 논문에서 는 자동차 속기 모델에 위의 변수들을 적용하여 모델의 군집화를 수행하였다. 이러한 제품 모델 관리에 관한 연구는 다단계 공급망의 형성과 민첩한 생산정책 수립의 요구와 함께 중요한 의미를 가질 것이다.

• The Journal of the Korea Contents Association
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• v.15 no.12
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• pp.483-492
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• 2015

This study involved elementary schoolchildren in Busan Metropolitan city and assumed the foundation of social cooperative associations that provide education services for meteorological fields, then we analyzed expected profits in a year for successful operation of first year. Twelve variables relating to profits and expenses were derived, and we used the decision tree for analyzing optimal expected profits. Profit-related variables were lecture's fee per hour and price of textbooks. Expense-related variables were production costs for the textbooks, annual salary for a teacher, education costs for a teacher, developing costs for the textbooks, traveling expenses, rental fees, and operating costs. Besides, by adding education demands, the number of grades, and the number of teachers, we analyzed changes in expected profits, considering variability of profits and expenses. As a result, despite of expected lower demands, to increase price of textbooks and education costs per hour was of advantage to enhance expected profits. The reason is that the more demand, the more increased production costs for textbooks, which is because not to make enough profits to offset the increased expenses due to lowered price of textbooks and education costs. Considering the value of public interest for social cooperative associations, price determination only concerning increase in demands will be avoided.

• Journal of Korean Society of Transportation
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• v.31 no.2
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• pp.33-44
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• 2013

The land use-transportation models typically have complicated model structure that is good for empirical execution but bad for theoretical probe. This complexity makes it very difficult to derive the first-order conditions for system optimization in tractable forms. Yu and Rhee (2011) and Rhee (2012) show how to simplify the derivative of the model's objective function with respect to policy variables in the computable general equilibrium model of land use and transportation. However, the travel demand in their model was fixed. This drawback fundamentally limits the applicability of their methodology in the planning field. We relax this restriction. Once this is done, we can employ the methodology developed in analyzing the impacts of various types of policy instruments in the models where land market is treated endogenously and transportation network is embedded.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.557_558
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• 2009

본 논문은 제 4차 전력수급계획의 발전설비 건설 계획을 기준으로 2022년까지 SMP를 P-Pool 전산모형을 이용하여 전망하였다. 미래 SMP 전망에 가장 영향을 크게 미치는 변수인 전력수요, 연료가격, 공급설비용량을 각각 3개의 시나리오로 가정하고 시나리오별 SMP를 예측및 각 변수별 민감도를 분석하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.4
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• pp.1-11
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• 2016

The purpose of this study is to analyze the effect of public transit accessibility on the Carsharing use demand. By utilizing the rental historical DB of Greencar which is operated in Suwon city and public transit GIS DB, the use demand models for Carsharing by rental offices are built and analyzed in accordance with public transit accessibility. The result indicates 73% of walking as a majority, 3% cycling, and 20% using buses and urban railways to access Carsharing rental offices. The goodness of fit of Carsharing use models reflecting accessibility to buses and railways is verified as 0.818 which proves that public transit accessibility is a significant variable. Therefore, it is verified that installing Carsharing rental offices where public transit transfer is convenient can possibly increase the use demand. Especially, while accessibility to buses is verified as a significant variable out of other public transit means, the accessibility to urban railways is verified as not significant. This suggests that a variety of complementary policies such as transfer discount policy and one-way transfer return policy are necessary in between urban railways and Carsharing in order to promote mutual use demand in accordance with the other public transit means. This study result is yet the basic research on Carsharing, however it is expected to contribute to improvement of transfer demand in between different public transit means.

• Journal of Korean Society of Transportation
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• v.24 no.4 s.90
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• pp.7-17
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• 2006

The purpose or this paper is to investigate the relationship between highway improvement and Induced Travel Demand(ITD) focusing on the Seoul metropolitan area data. In addition, authors tried to estimate basic unit of demand elasticity focusing on zone and trip purpose which can be applied for the ITD forecasting. The results are based on the 2002 Metropolitan Household Transportation Survey Data, where the demand elasticity (DE) is -0.582 in Seoul, -0.597 in Incheon and -0.559 in Gyounggi province, respectively. This study revealed part of the relationship between highway improvement and ITD for metropolitan region and provided the framework for yielding real estimated values by applying the concept of demand elasticity in terms of the relationship by using regional and long-term data. We expect that the basic unit of demand elasticity focusing on zone and trip purpose can be applied for the ITD forecasting to analyze the whole demand exactly The estimated DE's for age group and day of week can also be used for Proper transportation management and transport Policy making. Some limitations have also been discussed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.210-212
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• 2007

본 논문은 내륙 운송 체계 하에서 공 컨테이너의 효율적인 재고관리 문제에 대하여 다루고자 한다. 그리고 실제 컨테이너 선사가 공 컨테이너 운영 관리에 있어서 예측하기 힘든 고객의 수요 및 공급 등의 불확실한 요소들을 고려하기 위하여 공 컨테이너의 수요와 공급을 확률변수로 가정하였다. 이러한 가정을 바탕으로 시뮬레이션을 통하여 재고유지비용, 임대비용 및 총 기대 비용을 추정하고 (R, s, S) 재고 정책을 기본 재고정책으로 한 가정 하에 GA (Genetic Algorithm)를 사용하여 총 기대 비용을 최소화 하는 주문, 발주 정책을 도출하고자 한다.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.256-258
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• 2001

전력 계통의 운용 계획을 최적화 하기 위해서 수요예측에 관한 연구가 활발히 진행되고 있다. 기존의 수요예측 기법의 최대 오차는 특수일이 토요일과 월요일인 경우와 연휴인 경우에 발생한다. 이 중 특수일이 토요일과 월요일인 경우는 퍼지 선형회귀분석법과 상대계수법을 이용하여 우수한 결과를 도출한 바 있다. 구정과 추석은 특수일 중 평일과의 부하 차이가 가장 큰 특수일이며 약 $45{\sim}50%$ 정도가 감소된다. 이러한 부하의 감소 폭은 서서히 줄어서 연휴 당일 4일 후에는 완전히 복구가 되며 연휴 전 부하가 낮아지는 시점은 연휴 당일 3일 전이다. 연휴 예측의 불확실성은 연휴 기간의 길이 변동 및 기타 다양한 변수들에 의한 유동성에 기인한다. 특히 추석의 경우 과거 데이터 이용에 더욱 신중해야 하며 타 특수일에 비해 부하 값의 예측이 힘들다. 또한 직전 평일 대비 추석 연휴의 부하는 변화가 심하게 나타나며 본 논문에서는 퍼지 선형회귀분석법을 기본으로 변형된 알고리즘으로 향상된 예측도를 제시한다.

• Environmental and Resource Economics Review
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• v.10 no.2
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• pp.161-172
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• 2001

누진요금에서의 수요행위는 그 복잡성으로 인해 많은 논의를 불러 왔다. 그러한 논의 중 주요한 하나는 과연 소비자들이 한계가격에 반응하는가 아니면 평균가격에 반응하는가이다. 본 연구에서 우리는 서울시 가정용 상수도 수요 자료를 사용하여 체증 누진요금에서의 가격인식 행동을 분석하였다. Shin (1985)의 방법론이 분석을 위하여 사용되었으며, 내생성 문제를 해결하기 위해 도구변수 추정법이 사용되었다. 분석 결과 서울의 경우에는 소비자들이 한계가격보다는 평균가격에 반응함을 알 수 있었다.