철도화물수송의 환적효과분석 연구

정성봉 ( Sung Bong Chung ) 한국로지스틱스학회 2011 로지스틱스연구 Vol.19 No.1

본 연구에서는 SP설문조사를 통해 수단별 효용함수를 도출하여 통행시간 및 환적시간 가치를 산출함으로써, 화물 운송 시 발생되는``환적``이 수단선택에 미치는 영향을 살펴보았다. 이를 위해 철도수송의 대부분을 차지하는 양회품목을 대상으로 트럭, 철도, 해운 등 3가지 수단에 대한 효용함수를 구축하고, 한계대체율을 이용하여 시간가치 및 환적영향을 분석하였다. 모형을 통해 분석된 양회의 통행시간 및 환적시간가치는 각각 284원/ton?시, 1,394원/ton?시로 도출되었으며, 통행시간가치의 경우 기존 연구와도 유사한 결과를 가지는 것으로 나타났다. 또한 통행시간(비용)에 대한 한계대체율을 비교하여 환적에 대한 영향 및 변수간 상쇄관계를 파악하였다. 분석결과 통행시간(비용) 대비 환적시간(비용)의 한계대체율이 6.6876(1.3636)으로 환적과 관련된 비용의 영향이 다른 비용에 비해 상대적으로 큰 영향을 주는 것으로 나타났다. 본 연구에서 도출된 결과는 향후 효율적인 물류수송체계를 구축하는 과정에서 환적으로 인한 효과를 정량적으로 평가?반영함으로써 물류수송의 효율성 제고에 큰 도움을 줄 것으로 기대된다. In this study, based on the SP (Stated Preference) survey, the values of time of freight transportation and of transshipment were calculated from utility function. Also the effect of transshipment on mode choice was analyzed by calculating the ratio of the parameter of time in transportation over the time in transshipment of the utility function. To see the effect of transshipment in more detail, the case study of cement transportation was carried out. Usually, the cement is transported by truck, railway, and shipping so that each utility function was estimated using LIMDEP software. From these utility functions the value of time and the effect of transshipment in freight transportation were calculated from the method of Marginal Rate of Substitution(MRS). According to the results, the values of transportation and transshipment time are respectively 284 won/ton hour and 1,394 won/ton?hour. Comparing these values to existing results, they seem to be similar to each other so that the results in this study are proper. To see the effect of transshipment and the trade-off relationship between variables, the ratio of parameters in the utility function was calculated by considering marginal rate of substitution of transportation and transshipment time(cost). The MRS of transshipment time(cost) over transportation time(cost) are 6.6876(1.3636) so that the effect of transshipment on mode choice is higher than that of transportation. This research will help to raise the efficiency in logistics system by giving the proper value of transshipment and by considering the effect of transshipment the logistics system can be established properly in the future.

Time Utility and Channel State based Wireless Downlink Packet Scheduling Algorithm for OFDMA System

류승완,서현화,정수정,임순용,박세권,Ryu, Seung-Wan,Seo, Hyun-Hwa,Chung, Soo-Jung,Lim, Soon-Yong,Park, Sei-Kwon 대한산업공학회 2004 산업공학 Vol.17 No.S

In this paper, we propose an urgency and efficiency based wireless packet scheduling (UEPS) algorithm that is able to schedule real time (RT) and non-real time (NRT) traffics at the same time. The proposed UEPS algorithm is designed to support wireless downlink packet scheduling in the OFDMA system which is a strong candidate wireless system for the next generation mobile communications. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average one as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics with satisfying QoS requirements of RT traffics. The simulation study shows that the proposed UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modified-largest weighted delay first (M-LWDF) while satisfying QoS requirements of RT traffics such as the average delay and the packet loss rate under various traffic loads.

시뮬레이션 기반 철도 선로용량의 최적 활용범위 설정

노학래(Hag Lae Rho) 한국도시철도학회 2020 한국도시철도학회논문집 Vol.8 No.2

철도운영에서는 철도 인프라의 활용도를 최대화하면서 동시에 열차 간 간섭에 의한 운영품질 저하를 최소화할 수 있는 용량 활용의 적정 범위를 결정하여야 한다. 이를 위해서는 해당 인프라의 최대용량과 열차 교통량에 따른 대기시간 함수가 필요하다. 본 논문에서는 열차시각표 시뮬레이션을 통하여 얻은 열차당 평균 대기시간과 최대용량 자료를 이용하여 대기시간 함수의 파라미터를 추정하였다. 이 대기시간 함수식을 기반으로 대기시간의 상대적 최소 민감도와 평균 정규화 트래픽의 최대 성능을 나타내는 철도 선로용량 이용률의 상‧하한을 도출하였다. 따라서 철도 인프라의 적정이용률은 이와 같은 상‧하한 사이에서 결정되어야 할 것이다. 본 논문에서 제시하는 시뮬레이션 실험기반의 최적 용량 활용범위 설정 방법은 복잡한 역 구내 선로 또는 네트워크 구조의 철도 노선용량분석에 활용 가능할 것으로 기대되며, 이는 철도 인프라의 추가 투자수요를 파악하는 데에도 도움이 될 것이다. Railway operation deals with determining optimal degree of capacity utilization for given infrastructure. This is to fully use railway infrastructure and to minimize the decreasing operation quality which is caused by conflicts between trains. For this, we need a maximum capacity for given infrastructure and a waiting time function on train traffic. In this paper, the parameters of waiting time function are estimated using average waiting time per train and maximum capacity obtained from timetable simulation. Based on this waiting time function, the lower and upper bounds of capacity utilization rate are derived, which show minimum relative sensitivity of waiting time and maximum average normalized traffic performance, respectively. Therefore, the reasonable capacity utilization rate of railway infrastructure should be decided between these lower and upper limits. Simulation-based estimation for optimal capacity utilization range in this paper could be used to determine the utilization of existing infrastructure including large stations with complicated track-layout and railway lines with network structure, which will help us to identify additional investment needs for rail infrastructure.

A Review of Demand Theory on Choice Behavior

Lee,Won Jae 서울大學校保健大學院 1994 國民保健硏究所硏究論叢 Vol.4 No.2

도시 농촌간 의료자원의 불균형적 분포는 농촌지역에서의 의료접근성을 제한해 왔다. 농촌지역에서의 낮은 접근성을 제고하기 위하여 정부는 농촌지역에 보건의료원, 보건소, 보건지소, 보건진료소를 설립해왔다. 이들 공공의료 시설 중 일부는 농촌지역의 의료수요의 양적, 질적 팽창과 상반되게 활발히 이용되지 못하고 있다. 따라서, 이들 공공의료 시설에 대한 평가가 필요하다. 환자의 의료서비스 선택행태의 관점에서 고찰하였다. 의료수요 이론은 환자들이 일정한 수입하에서 자신들의 효율을 극대화하려 노력한다는 가정을 근거로 한다. Becker의 이론에 의하면, 물품 구매시의 시간비용이 증가하면 소비자들은 시간비용이 높은 저가의 상품을 구매하는 대신에 시간비용이 낮은 고가의 물품을 선택하게 된다. 따라서 농촌지역에서의 의료기관의 설립은 의료시설에 대한 시간비용을 낮추게 되어 이들 시설의 이용을 높일 것으로 기대된다. 소득 중의 가득소득(earned income)의 증가는 소득의 증가를 통한 의료수요를 증가시킬 수 있다. 반면에, 이는 기회비용을 놓이게 되고, 따라서 환자의 시간비용을 높이게 되어 시간비용이 낮은 의료서비스를 선택하도록 영향을 미치게 된다. Grossman의 소비모형(consumption model)에 따르면, 의료서비스의 이용과 연령은 현재와 미래의 건강 사이의 한계대체율에 따라 결정된다. 그의 투자모형(investment model)에서는 연령에 따른 의료이용은 기회비용의 탄력성에 달려있다. 또한 임금의 증가는 의료수요를 증대시킨다. 교육수준은 의료수요에 반대 방향으로 영향을 미친다. 침상일수와 통증을 느끼며 일한 일수로 측정된 상병의 중증도가 심할수록 의료수요는 증가되고, 질이 낮은 서비스 대신에 질이 높은 서비스를 선택하도록 영향을 미친다. 환자들은 또한 의료서비스와 생산성에 대한 인식에 따라 의료서비스를 선택하게 된다. 국민건강조사 자료는 의료수요 이론이 설명하는 주요 변수들 중 임금과 소득에 관한 변수를 포함시키지 않고 있다. 국민건강조사 자료의 활용도에 비추어 보아 이들 변수들을 포함시키는 것이 이 자료의 의료기관 선택형태 분석과 의료수요 분석을 통한 공공의료기관의 평가에 더욱 기여하리라고 사료된다. 또한 환자의 의료기관 선택행태에 관한 연구가 더욱 활발히 이루어짐으로써 공공의료기관에 대한 정책에 도움이 되는 기초 자료가 많이 생산될 수 있을 것이다. 의료수요 이론에 따르면, 공공의료기관은 다양한 서비스를 제공함으로써 환자의 의료기관 선택에 따르는 시간비용을 감소시켜주고 충분한 의사인력과 약품, 장비등의 확보를 통해 서비스의 질을 향상시키도록 하여야 할 것이다. Korean government established various of health care facilities in rural Korea. The provision of the public facilities was expected to improve access to care in rural areas. However, some of the public facilities are utilized very low. This paper discussed some economic theories on demand for health care. In considering the low utilization of public facilities, it is required to study on public facilities. For public facilities, patient choice behavior is to studied. Economic theories say monetary price of care, time cost of care, age and education level of patients, severity of illness, patient's perception on quality of care, family size, and sex are related to the demand for health care. This paper reviewed about the variables. The relationships of those variables to the demand for health services can be summarized as follows. According to Becker(1965), time cost works as a rationing factor in choosing type of care. When time cost to purchase a good increases, individuals would substitute the more expensive good with lower time cost for the cheaper good with higher time cost. His theory says that a rise in earned income would increase not only the quantity but the quality of goods purchased by a substitution of quality goods for time intensive goods as well as by the effect of income on quality. However, a rise in property income would not affect the substitution of goods. Based on Becker theory, Grossman(1972) developed a human capital model. Grossman hypothesized two models, the consumption model and the investment model. In the consumption model, which assumed only psychic bendrits, he hypothesized that medical purchases and age depends on the marginal rate of substitution between present and future health. Under the investment model, he assumed only pecuniary return to health. In the investment model, if age is a good proxy for the deprediation rate of health capital, the demand for health capital is negatively related to age. However, if the demand for health investments is inelastic to the opportunity cost, the demand for medical services is positively related. In the investment model, wage rate is positively related to demand for health services. Whereas, the consumption model hypothesized negative relationship between wage reate and demand for medical services. Education is considered to have positive effect on the demand for health capital. However, education may reduce purchase of medical care as it contributes to the efficiency of home production of health. Severity of illness is considered to affect demand for health care in quantity and quality. As bed-days and work-days-with-pain increase, and individual would substitute quality services for lower quality services.

구매시점을 중심으로 소셜커머스 구매환경이 미치는 소비자 선호 별 효용 분석

최소영(Soyeong Choi),임형수(Hyung Soo Lim),전덕빈(Duk Bin Jun),강성열(Sungyeol Kang) 한국경영과학회 2017 韓國經營科學會誌 Vol.42 No.2

Based on increased popularity and use of social network services as a marketing tool, social commerce became an emerging trend in e-commerce platforms. Social commerce involves sellers offering potential consumers the products and services at a lower price in a limited time period. Through comparison of the performances of domestic social commerce websites, we found that the buying environment such as price, number of available products, and the remaining time period for sale has a significant difference influencing on the purchase decisions of consumers. This study aims to analyze the interaction effects and preference levels of four characteristics (price, discount rate, number of purchases and purchase time) by conducting choice-based conjoint analysis. Survey experiment was performed using a sample of 146 undergraduate and graduate students. The results showed that consumers importantly consider purchase time, discount rate, price, number of purchases in the order of their preference. Also, discount effect is more significant on purchase decisions than price effect and consumers distinguish less the differences among the buying environment characteristics in the closing days of purchase period. Customer segmentation using the preference levels of characteristics indicates that the preference levels have different effects in the purchase utility of each segment. The proposed customer segmentation and differences in feature utilities are expected to be valuable in forming future sales promotion strategies in social commerce.

Sequential estimation for covariate-adjusted response-adaptive desi

Yuan-chin Ivan Chang,박은식 한국통계학회 2013 Journal of the Korean Statistical Society Vol.42 No.1

In clinical trials, a covariate-adjusted response-adaptive (CARA) design allows a subject newly entering a trial a better chance of being allocated to a superior treatment regimen based on cumulative information from previous subjects, and adjusts the allocation according to individual covariate information. Since this design allocates subjects sequentially, it is natural to apply a sequential method for estimating the treatment effect in order to make the data analysis more efficient. In this paper, we study the sequential estimation of treatment effect for a general CARA design. A stopping criterion is proposed such that the estimates satisfy a prescribed precision when the sampling is stopped. The properties of estimates and stopping time are obtained under the proposed stopping rule. In addition, we show that the asymptotic properties of the allocation function, under the proposed stopping rule, are the same as those obtained in the non-sequential/fixed sample size counterpart. We then illustrate the performance of the proposed procedure with some simulation results using logistic models. The properties, such as the coverage probability of treatment effect, correct allocation proportion and average sample size, for diverse combinations of initial sample sizes and tuning parameters in the utility function are discussed.

Sequential estimation for covariate-adjusted response-adaptive designs

Chang, Yuan-Chin Ivan,Park, Eunsik 한국통계학회 2013 Journal of the Korean Statistical Society Vol.42 No.1

In clinical trials, a covariate-adjusted response-adaptive (CARA) design allows a subject newly entering a trial a better chance of being allocated to a superior treatment regimen based on cumulative information from previous subjects, and adjusts the allocation according to individual covariate information. Since this design allocates subjects sequentially, it is natural to apply a sequential method for estimating the treatment effect in order to make the data analysis more efficient. In this paper, we study the sequential estimation of treatment effect for a general CARA design. A stopping criterion is proposed such that the estimates satisfy a prescribed precision when the sampling is stopped. The properties of estimates and stopping time are obtained under the proposed stopping rule. In addition, we show that the asymptotic properties of the allocation function, under the proposed stopping rule, are the same as those obtained in the non-sequential/fixed sample size counterpart. We then illustrate the performance of the proposed procedure with some simulation results using logistic models. The properties, such as the coverage probability of treatment effect, correct allocation proportion and average sample size, for diverse combinations of initial sample sizes and tuning parameters in the utility function are discussed.

한국시장에서의 주식프리미엄과 무위험이자율 의문현상 : 외환위기 이후의 자료를 이용한 재검토

김민직,조재호 한국재무학회 2020 財務硏究 Vol.33 No.1

Time Utility and Channel State based Wireless Downlink Packet Scheduling Algorithm for OFDMA System

Seungwan Ryu,Hyun Hwa Seo,Soo Jung Chung,Soon Yong Lim,Seikwon Park 대한산업공학회 2004 산업공학 Vol.17 No.S