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이원태(Wontae Lee),김영현(Younghyun Kim) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
The steering system of forklifts should have enough rigidity in order to minimize deformation caused by the wheel operation and to block the vibrations from engine, hydraulic systems and the road surface. Especially, the steering system of the small-class forklift has disadvantage in vibration transmission path since it is difficult to obtain proper structural stiffness. In this paper design optimization technique of the steering system for small-class forklifts considering idle vibration reduction is presented. Two types of engines are mounted with small-class forklift; 2-ton class forklift with 3-cylinder and 3-ton class forklift with 4-cylinder diesel engine. Considering the excitation frequency of the engines, the vehicle body and steering system of the forklift were designed to minimize the idle vibration.
소셜미디어 유력자의 네트워크 특성 : 한국의 트위터 공동체를 중심으로
이원태(Wontae Lee),차미영(Meeyoung Cha),양해륜(Haeryun Yang) 서울대학교 언론정보연구소 2011 언론정보연구 Vol.48 No.2
본 연구는 최근 트위터와 같은 소셜미디어에서 의제설정, 여론형성 등에 큰 영향력을 발휘하고 있는 새로운 유형의 오피니언 리더, 즉 소셜미디어 유력자들(social media influentials)의 네트워크 특성과 역할을 규명하는 것을 목적으로 한다. 연구결과 한국의 트위터 유력자들은 글로벌 네트워크와는 달리 이용자 상호작용(user interaction)의 측면에서 매우 강력한 네트워크 호혜성을 특징적으로 보여주고 있으며, 이들 트위터 유력자의 영향력도 그들이 보유한 팔로어 규모에 의존하기보다는 적극적인 리트윗(RT)을 매개로 하는 수많은 팔로어들과의 개방적 소통방식에 의해 적극 추동된다는 점을 보여주었다. 특히 ‘매개적 유력자(intermediary influentials)’의 역할에서 보듯이, 강력한 유력자 네트워크의 이면에는 네트워크 구성원들의 추천과 평판에 기반한 쌍방향적인 의사소통이 놓여 있음을 알 수 있다 This study aims to shed light on the network property and roles of social media influentials who are emerging as a new type of opinion leaders in setting the agenda and forming public opinions on online social networking sites such as Twitter. The result shows that the Korean Twitter influentials exhibit very strong reciprocity in terms of topology and user interaction. Their impact on other users relies more on open communication with followers via retweeting (RT) than on how many followers they have. In particular, beneath the surface of the powerful influentials network, intermediary influentials engage in interactive communications with the network members based on peer recommendation and reputation.
화학침전을 이용한 발효액의 젖산 회수 및 유기물 특성분석
이원태(Wontae Lee) 유기성자원학회 2018 유기물자원화 Vol.26 No.1
유기성 폐기물 소화공정의 발효액에서 젖산(lactic acid)을 회수하기 위해 화학침전법을 평가하였다. 젖산(lactic acid)의 회수율을 높이기 위하여 화학침전제 종류와 교반속도 및 침전시간 등 반응조건이 회수율 향상에 미치는 영향을 살펴보았다. 화학침전제의 종류에 관계없이 주입양이 증가할수록 젖산(lactic acid) 회수율 이 증가하는 경향을 보였으며, CaO가 Ca(OH)2와 CaCO3에 비하여 높은 회수율을 나타냈다. CaO를 사용한 반응조건 최적화 실험결과, 교반속도 180 rpm, 침전시간 24 h, ethanol 주입량 25%(v/v)에서 회수율이 48%로 가장 높게 나타났다. 본 연구에서는 발효액 내 젖산(lactic acid)의 농도만 고려하여 주입할 침전제의 양을 계산하였기 때문에 실제 적용을 위해서는 발효액의 유기산 종류 및 농도를 고려하여 침전제의 투입량을 결정해야할 것이다. 유기물의 정성적 분석(FEEM, SEC) 결과로 볼 때 침전공정은 유기산의 특성에 큰 영향을 미치지 않았다. Recovery of lactic acid from fermentation broth using chemical precipitation was investigated with various chemicals. Effects of chemical types, mixing speeds, settling duration, and solvent addition were evaluated to improve the recovery rates of lactic acid. Overall, recovery efficiencies increased as the dosage of chemicals increased. Recovery rate of lactic acid by CaO was higher than those of Ca(OH)2 and CaCO3. Recovery of lactic acid increased by 48% under the optimized reaction conditions which included a mixing speed at 180 rpm, a settling duration of 24 h, and addition of ethanol at 25%(v/v). Practical application needs to consider types and concentrations of other organic acids as well as lactic acid. Based upon the results of fluorescence excitation emission matrix (FEEM), size exclusion chromatography (SEC), characteristics of recovered lactic acid were same as that in the fermentation broth.
물류수송의 환적저항에 따른 수단선택 행태 변화 : 양회 중심으로
이원태(Lee Wontae),김성은(Kim Sungeun),김시곤(kim Sigon),정성봉(Chung Sungbong) 한국철도학회 2010 한국철도학회 학술발표대회논문집 Vol.2010 No.7
Recently, there has been an increase in interest from the aspects of transshipment and connection between the means of transportation. Not only for passengers but also for freight transportation as the need for transportation efficiency is growing while the importance of logistic railway transportation is emerging. The domestic freight transportation is carried out by roads, railroads, ships, and port. However, as other means of transportation, except road, is impossible for Door to Door Service, multimodal transportation accompanied by road transportation is carried out. Here, even though 'transshipment' occurs, because of the lack of basic data regarding this, it is difficult to reflect it in the demand forecasting. With respect to the Korean freight O-D, it was very difficult to have equivalent comparison on the competitiveness and availability of transportation services between the point of departure and the final destination. Taking into account the study of implementation of logit model considering the time and cost of transshipment of multimodal transportation and the transshipment resistance value upon selecting means of freight transportation on multimodal transportation was comparatively insufficient. This study consisted of questionnaire targeting shippers, and based on this, transshipment resistance value was calculated by deriving utility function. By doing so, I intend to examine the effect 'transshipment' has on selecting the means of transportation occurring from freight transportation.
소형 지게차의 Idle 진동 저감을 위한 차체 구조 최적 설계
이원태(Wontae Lee),김영현(Younghyun Kim) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.10
A diesel forklift truck under 3-ton class has disadvantages in the vibration transmission path. Because the weight ratio of body structure to powertrain which is source of excitation force is lower th an a midclass forklift. In addition, the torsional and bending vibration mode frequencies of body structure are within the engine excitation frequency range, then high idle vibration generated by resonance. In this paper vehicle body structure design and optimization technique considering idle vibration reduction are presented. Design sensitivity analysis is applied to search the sensitive of design parameters in body structure. The design parameters such as thickness and pillar cross section were optimized to increase the torsional and bending vibration mode frequencies.