A Robust Lane Recognition Technique for Vision-Based Navigation with a Multiple Clue-Based Filtration Algorithm

서승범,강연식 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.2

This paper proposes a novel multiple clue-based filtration algorithm (MCFA), which is developed to detect lane markings on roads using camera vision images for autonomous mobile robot navigation. The main goal of the algorithm is the robust estimation of the relative position and angle of the lane in the image by using multiple clues based on different characteristics of the lane. In particular, robustness against environmental changes is enhanced greatly since a dynamic model of the lane, be-sides static features of the lane such as color, intensity, etc., is incorporated for reliable estimation. The efficiency of the algorithm is verified through mobile robot experiments under various extreme illumi-nation conditions in outdoor environments. The increased robustness performance enables reliable closed-loop control of a mobile robot that operates in a variety of navigation-related missions.

수자원의 합리적 배분 방안 마련 기초연구 : 합리적 물 수급 분석 방안 연구

서승범 한국환경정책평가연구원 2019 한국환경정책평가연구원 기초연구보고서 Vol.2019 No.-

■ 연구의 주요 내용 ○ 국가 수자원계획의 물 수급 전망 현황을 파악하고 미흡한 점과 개선방향을 제시 ○ 국내 수자원계획의 물 수급 전망기법의 현황 분석 ○ 물 수급 전망기법 개선 연구 사례분석 ○ 물 수급 전망기법 개선 방향에 대한 시사점 도출 ■ 정책 제안 ○ 목표 이수안전도 도입을 위한 정책 연구가 필요 ○ 광범위한 물 수급 자료의 DB화 추진 필요 ○ 기후변화에 대응하기 위한 중장기적 수자원계획 수립 필요

Asymptotically Optimal Solution for TSF-Constrained Staffing Problem

서승범 대한경영학회 2019 大韓經營學會誌 Vol.32 No.9

Finding the right balance between the customer service and personnel expenditure has been an important task both in practice and academia and in academia this problem was usually approached using a total cost problem. However, it is difficult to directly apply this formulation in practice and hence recent works in queueing systems have investigated this problem with staffing minimization with constraints on quality-of-service constraints. Our work contributes on this stream of works by studying TSF measure, which shows the percentage of customers who waited beyond the prespecified threshold. TSF measures the proportion of customers whose waiting time exceed a certain threshold. It is one the most prevalent kind of quality of service measure, along with ASA, which measures the average of waiting time. TSF measure is intuitive to understand and hence widely been used but has not received sufficient attention in academia. Part of the reason comes from the unnatural property of TSF measure. Once a customer waits more than the threshold, the incentive to serve that customer starkly diminishes since decreasing the eventual waiting time of him does not enhance the performance of the system. Hence a policy that is far from FIFO turns out to be more efficient. Especially we are interested in context where service level differentiation among various classes of customers. Hence, we work on V-model where multiple classes of customer and homogeneous pool of servers exist. Our task is to come up with the minimum possible number of servers while maintaining TSF measure on the pre-defined level. The decision variables are two-kind: number of servers and prioritization policy. The prioritization policy defines which class of customer to server first when a server becomes available. The nature of TSF measure, which tends to give lower priority to the customers who had already waited beyond the threshold, makes the problem more difficult to solve and hence it was usually treated in literature more added conditions or constraints added. We devise an optimal solution of TSF constrained problem without adding more structures. Since the problem is difficult to solve in exact analysis, we apply the heavy traffic technique to solve the problem. First, we show that our suggested staffing level is the lower bound for all the feasible solutions. Second, it is proved that the proposed prioritization policy combined with our staffing level actually is feasible and hence asymptotically optimal.

이차원 소재 및 응용 소자 기술 동향

서승범,장병철,최성율,Seo, Seung-Beom,Jang, Byeong-Cheol,Choe, Seong-Yul 한국정보디스플레이학회 2016 인포메이션 디스플레이 Vol.17 No.3

Minimization of Concave Holding Costs in Queueing System

서승범 연세대학교 경영연구소 2020 연세경영연구 Vol.57 No.2

Since the advent of basic  rule, minimization of holding costs has been one of the most fundamental problems in queueing theory. The first results on holding cost minimization was under the linear cost assumption and the more general case of convex costs has been solved with help of queueing approximation method named heavy traffic. Even with many sophisticated solutions on general settings, there is scarce literature that goes beyond convex or linear cost structure. Especially, a holding cost minimization problem with concave cost structure has not been discuessed yet. As far as we know, our work is the first to study concave cost structure in queueing theory. We study how the customers from multiple classes should be prioritizized. We figure out that so-called bang-bang policy is always included in the set of optimal prioritization policies when the costs are concave and that all the optimal solutions to strict concave costs are bang-bang. With this property, we construct a simple and general solution for the concoave cost minimization problem. We also provide a condition that produces a solution that assigns the whole workload to a single class.

기후변화에 따른 물수급 분석 기술 최신 연구동향

서승범,이재경,김영오 한국수자원학회 2010 한국수자원학회논문집 Vol.43 No.9

기후변화에 따른 물수급 분석 기술 최신 연구동향

서승범,이재경,김영오,Seo, Seung-Beom,Lee, Jae-Gyeong,Kim, Yeong-O 한국수자원학회 2010 물과 미래(한국수자원학회지) Vol.43 No.9

지속 가능한 수자원 관리를 위한 지표수-지하수 연계이용 최적화

서승범,김영오,Seo, Seung-Beom,Kim, Yeong-O 한국수자원학회 2018 물과 미래(한국수자원학회지) Vol.51 No.12

한국 기업의 채찍효과에 대한 고찰: 코스피 상장 기업을 중심으로

서승범,박승재,Soh, Seung-Bum,Park, Seung-Jae 강원대학교 경영경제연구소 2022 Asia-Pacific Journal of Business Vol.13 No.3

Purpose - We study whether the bullwhip effect is prevalent among Korean firms and how the characteristics of it differ from the ones in other countries. Design/methodology/approach - We obtained quarterly financial and operational information on KOSPI-listed firms in manufacturing, wholesale, and retail industries from 2013 to 2019. We explore the variation of the bullwhip effect across firms and validate hypotheses. Findings - First, we find that for the KOSPI-listed firms, the bullwhip effect is more prevalent compared with the production smoothing. We provide additional findings by using sub-samples of manufacturing firms, wholesaling and retailing firms, big-sized firms, small- and medium-sized firms, domestic-sales intensive firms, and export intensive firms. Second, we show that in general, the bullwhip effect of Korean firms increases with the days in inventory or the demand seasonality ratio. However, the persistence of demand shock does not affect the bullwhip effect of Korean firms. Research implications or Originality - We compare our results with those in other studies that use information on the U.S. and Chinese firms. Our findings show that factors explaining the bullwhip effect across Korean firms have similarities and differences compared with firms in the U.S. and Chinese firms.

전완부 후골간 동맥 유리피판술을 이용한 안면부 조직 결손 재건 치험례

서승범,이상원,안태황,정성균,김창현,Seo, Seung Bum,Lee, Sang Won,An, Tae Whang,Jung, Sung Gyun,Kim, Chang Hyun 대한미세수술학회 2000 Archives of reconstructive microsurgery Vol.9 No.2

With esthetic concern in the reconstruction of skin and soft tissue defects of face, the use of local flap has been the method of choice. However, when there is extensive tissue loss in the face, local flaps do not provide satisfactory results. The amazing development of microsurgical technique has decreased the percentage of free flap failure, thus making free flap use in reconstruction of facial soft tissue defects. Many free flaps has been applied for reconstruction of face defects. Especially, the radial forearm flap has numerous advantages with which facial reconstruction is made possible. But, its disadvantages are ; the sacrifice of one major artery supplying the hand and donor site complications. In order to circumvent these disadvantages, we employed posterior interosseous artery(PIA) forearm free flap for the reconstruction of the face defects. The posterior interosseous forearm island flap was first described by Zancolli and Angrigiani(1985). Currently, the PIA island flap and free flap have been used for hand reconstructions. The disadvantages of the PIA flap are ; the small caliber of the pedicle, different locations of the perforating branches, and the proximity of the motor branch of the radial nerve. But, its advantages lies in preserving the major artery of the hand, minimal donor site morbidity, and fairly well matched skin texture and color, and that the flap volume is sufficient, not too bulky with convenient handling. By using this flap, we performed 1 case of tumor resection and 1 case of traumatic defect. From our experiences we conclude that it is one of many useful methods in the reconstruction of the skin and soft tissue defects of the face. We also have discussed advantages and some limitations of various free flaps for reconstruction of the face.