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Multibody approach for tolerance analysis andoptimization of mechanical systems
Hyungho Chun,권상직,Taeoh Tak 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.2
A multibody approach is suitable for tolerance analysis of mechanical systems since multibody formulation can directly consider part-level tolerance variables. In this study, procedures for performing tolerance analysis and corresponding sensitivity analysis for spatial multibody systems are proposed. First, statistical formulation for performing multibody system tolerance analysis is developed to obtain system level tolerance for given part-level tolerances. One very useful aspect of the proposed formulation is that in the process of computing system tolerance, the sensitivity of system tolerance with respect to part-level tolerances can be additionally obtained. The kinematics of spatial multibody systems has been redefined in terms of both generalized coordinates and part-level tolerance variables. Tolerances in geometry of a body are specified in terms of the variations in relative locations of joint definition points and relative distance between them. Tolerances in the joint kinematics are defined through variations in vector closure equations and orthogonality equations that are two fundamental constraint equations for most kinematic joints. To demonstrate the validity and effectiveness of the proposed tolerance analysis procedure, tolerance analysis of a spatial 4-bar mechanism and tolerance optimization are performed.
Monte-Carlo 시뮬레이션을 이용한 확률적 차량동역학 해석
전형호(Hyungho Chun),탁태오(Taeoh Tak) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Monte-Carlo simulation technique has advantages over deterministic simulation in various engineering analysis, since Monte-Carlo simulation can take into consideration of scattering of various design variables, which is inherent characteristics of physical world. In this work, Monte-Carlo simulations for steady-state cornering and J-turn behavior of a truck with design variables like hard points and busing stiffnesses have performed to achieve better dynamic performance. The main purpose is to improve understeer gradient at steady-state cornering and minimize peak lateral acceleration and peak yaw rate at J-turn. through correlation analysis, design variables that have high impacts on the cornering behavior were selected, and significant performance improvement has been achieved by appropriately changing the high impact design variables
Jin-Won Seo,Hyungho Kim,Jung-Hwa Chun,Irdika Mansur,Chang-Bae Lee 경상대학교 농업생명과학연구원 2015 농업생명과학연구 Vol.49 No.4
Jabon tree(Anthocephalus cadamba Miq.) is a native and fast growing species in Indonesia that is preferred by the local community because of its good adaptability and economic profitability. However, information on this tree and its appropriate silvicultural practices are still lacking. Therefore, the aims of this study were to (1) document the existing silvicultural practices used by local communities, (2) investigate tree growth performance among different sites, and (3) examine the linkage between silvicultural practices and soil fertility and their effects on stand quality in West Java. The results obtained from interviews indicated that most of the jabon plantations are owned by outsiders from Jakarta or other cities. In addition, there are three types of management: partnership, hiring employees and direct management. There are only a few practitioners with silvicultural training; however, all practitioners have implemented basic silvicultural practices. Jabon plantations in West Java were inventoried and 53 plots were established across 19 sites. This species was introduced into Java in 2008; therefore, tree age ranges from 0.5 to 3.5years. The mean diameter ranges from 2.45 to 14.57cm with a maximum of 29.3cm, and the mean height ranges from 1.29 to 12.62m with a maximum of 18.68m in Situgede. Regression modeling was performed using dominant height, and the Chapman model was selected to generate a site index curve: Hd=10.6982(1-exp(-0.8915t))1.3078, with an R2 value of 0.6513. This model divided the 19sites into three categories, i.e., good, medium and poor. Based on these results, there are 2 good, 11 medium and 6 poor sites. Three DBH-age equations were generated based on site classification. A comparison between good and poor sites suggests that site conditions and soil fertility have more significant effects on the growth of jabon than silvicultural practices such as fertilization and site maintenance.
Analysis of Human Arm Movement During Vehicle Steering Maneuver
Taeoh Tak,Kunyoung Kim,Hyungho Chun 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.1S
The analysis of human arm motion during steering maneuver is earned out for Investigation of man-machine Interface of driver and steering system Each arm is modeled as interconnection of upper arm, lower arm, and hand by rotational Joints that can properly represents permissible Joint motion, and both arms are connected to a steering wheel through spring and damper at the contact points The Joint motion law during steering motion is determined through the measurement of each arm movement, and subsequent inverse kinematic analysis Combining the Joint motion law and inverse dynamic analysis, Joint stiffness of arm is estimated Arm dynamic analysis model for steering maneuver is setup, and is validated through the comparison with experimentally measured data, which shows relatively good agreement To demonstrate the usefulness of the arm model, It is applied to study the effect of steering column angle on the steering motion<br/>
대류난방시 가습연동에 의한 실내환경변화 및 쾌적성 검증
박동률(Dongryul Park),권서현(Suhhyun Kwon),박형호(Hyungho Park),이윤희(Yoonhee Lee),한지은(Jieun Han),전정윤(Chungyoon Chun) 대한설비공학회 2019 대한설비공학회 학술발표대회논문집 Vol.2019 No.-
Convective heating can lead to high temperature and low humidity conditions, which can cause to discomfort. The heat pump air conditioner equipped with a heating type humidifier was used to evaluate the change of the room temperature and humidity condition according to the presence or absence of the humidification operation during heating. The subjective evaluation and the skin wetness were measured through the experiment of the subjects and the improvement effect of the dry feeling and the discomfort. The tendency of the room temperature was similar, and the relative humidity was increased by about 10% in the heating and humidifying condition compared to the single heating condition. By comparing of behavior on psychrometric chart with comfort zone, the effect of the humidification operation can be verified. The subjective evaluation and skin moisture were measured physiologically. The results of the subjective response evaluation under the advanced experimental conditions did not distinguish between the two conditions. The skin measurement showed higher stratum corneum hydration(SCH) and lower transepidermal water loss(TEWL) in humidification heating mode.