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Numerical investigation of bus stop structures in Seoul for the reduction of fine dust entry
노승윤,Duck-ShinPark,육세진 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.1
Fences and air curtains can effectively reduce fine dust entry into roadside bus structures, thus decreasing the exposure of passengers to particulate matter. In this study, bus stop structures that reduce the entry of fine dust formed or dispersed by vehicles was derived through simulation models. These bus stop structures consist of a fence that blocks particle entry from a relatively low position in front of the bus stop and an air blast structure that blocks particle entry from a relatively high position. Three bus stop styles were considered: a bus stop without a fence, that with a vertical flat fence, and that with a vertical curved fence toward the road. Among these styles, the curved fence model was superior to other models, and particle entry into the bus stop was estimated to be reduced by 15.5 % for the curved fence model compared with the model without a fence. After the selection of the fence model, three air blast structures were considered: canopy, wall, and fence types, which blast air from the ceiling of the bus stop, toward the direction of the road from the rear wall of the bus stop, and upward from the top of the curved fence, respectively. The canopy-type air blast structure was found to be the most effective in decreasing particle entry into bus stops, with a reduction rate of 88 % compared with the reference model without a fence and air blast system.
Measurement of re-suspended road dust emission factor using mobile laboratory and flux tower
노승윤,Jun Ho Ji,Hyung-Seok Kim,Se-Jin Yook 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5
Re-suspended road dust is one of the main urban atmospheric pollutants. Thus, systematic management of polluted roads is essential, which requires precise measurement of re-suspended road dust emission factors. A mobile laboratory (ML) and a flux tower (FT) were used to measure re-suspended road dust. Re-suspended road dust concentration was measured while driving the ML at speeds of 40, 50, and 60 km/h along straight sections of five different roads in Incheon City, Korea. The correlation between measurements using the ML and the FT was anlyzed according to the ML speed. The results revealed a linear relationship between the mass concentration measured by the ML and the emission factor obtained from the FT. At faster ML speeds, the same emission factor was associated with higher concentrations measured by the ML. Thus, if the ML measurements are adjusted for the ML speed by employing the methods of this study, re-suspended road dust emission factors can be measured more accurately. Based on these findings, it is expected that the use of the MLs will contribute to reducing re-suspended road dust by enabling more effective management of road pollution levels.
Required flux tower height for measurement of re-suspended road dust
노승윤,지준호,Hyung-Seok Kim,육세진 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4
Concentration of road dust re-suspended by passing vehicles can be measured using fine-dust measuring devices installed at various heights of a flux tower. In this study, simulations were performed to analyze the distribution of dust plumes along the height of a flux tower according to its distance from the center of the road, the vehicle speed, wind direction, and wind speed. Simulation results were compared with field measurements of re-suspended road dust collected by a flux tower during the passage of a van-type mobile laboratory vehicle to confirm the accuracy of the simulation. A parametric study was then conducted using the simulation of the mobile lab vehicle to evaluate the effects of vehicle speed, wind direction, and wind speed. To accurately capture re-suspended road dust concentrations, the flux tower must be at least 4.5, 5.1, 5.8, and 6.2 m high when located 2, 4, 6, and 8 m, respectively, from the road center. The results of this study are expected to serve as guidelines in determining the location and height of flux towers when measuring re-suspended road dust.
Study on the Tooth Micro-Geometry Optimization of Planetary Gear for Drive Reducer
노승윤(Seung Yoon Noh),김래성(Lae Sung Kim),조성현(Sung Hyun Cho),류성기(Sung Ki Lyu) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.6
A popular approach to optimize the performance of a gear transmission system is the modification of the gear tooth microgeometry, which includes the intentional removal of material from the gear teeth flanks, so that the shape is no longer a perfect involute. Such modifications compensate teeth deflections under load, and the resulting transmission error is minimized under a specific torque. Therefore, micro-geometry modifications can be applied on the involute (or profile) and lead of the gear teeth. In order to study the tooth micro-geometry optimization, this research selected a mass produced planetary gear type drive reducer as a prototype. The original design was modeled by a commercial software named Romax Designer, which analyzes and optimizes different types of gear power transmission systems. The series analysis results obtained reveal some anomalies that require modification. Based on the result, optimization and gear tooth modification were done to deal with the load distributions on gear tooth, gear durability problem, safety factor and bearing life problem. This thesis presents the outstanding performance improvement obtained after such optimization.