• 한국자동차공학회논문집
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• 제13권4호
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• pp.121-128
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• 2005

In most researches on the ride comfort analysis of passenger vehicles, the flexibility of the vehicle body has been not considered as an important factor, because the resonance frequencies of the vehicle body related to pitching, yawing and rolling motions are below 10Hz while the resonance frequencies of the vehicle body related to the flexibility are above 20Hz approximately. Nevertheless, the paper shows that the consideration of the local flexibility (or local stiffness) of the 4 corners on which shock absorbers are mounted influences the ride comfort. A simple beam model is devised to qualitatively examine the effect of the change of the local stiffness of the vehicle body on the ride comfort. Based on the results obtained from the analysis of the one-dimensional model, multi-body dynamic analysis considering the flexibility of the vehicle body is performed using ADAMS and MSC/NASTRAN. Natural frequencies and mode shapes computed by MSC/NASTRAN are used as input data for multi-body dynamic analysis in ADAMS. Through simulations using ADAMS, it has been found that the ride comfort can be improved by changing the local stiffness of the vehicle body and that the simulation results agree with experiment results.

• 한국의류산업학회지
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• 제22권6호
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• pp.853-861
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• 2020

Various types of clothing are being developed to boost thermal comfort during cold winters along with research on change of body temperature when heating is applied. There is a noticeable behavioral difference by gender when using heating panels in a cold environment; however, research on women has been insufficient. This study find a temperature range that provides sustainable thermal comfort in a low temperature environment by observing temperature and change of temperature when subjects are classified according to physical activities or cold sensitivities. For the study results, 8 women in their 20s were subjected to experiment in a low temperature environment for 75 minutes (sitting position: 30 min., running: 15 min., and sitting position: 30 min.). Subjects were asked to turn on/off the heating panel freely to analyze the range of comfortable temperature and clothing microclimate; in addition, skin temperature and heating panel temperature were measured and analyzed at 9 points. As a result, temperature at which subjects turn on and off the heating panel indicated a statistically meaningful difference between the cold sensitivity group depending on exercise or non-exercise. The range of comfortable abdomen temperature was wider than the lower back and was significantly reduced when the subject was running. The range of comfortable temperature was also largest for the heating panel temperature, microclimate, and skin temperature in suggesting that adequate adjustment will be required depending on the surrounding environment or movement of the wearer.

• 한국소음진동공학회논문집
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• 제13권5호
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• pp.341-347
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• 2003

This paper presents an improved escalator dynamic model so as to reflect the experimental observation on the pseudo-resonance affected by load applied. The experimental evidence reveals that backlash on gearbox as well as sag of driving Chain are most critical factors to the pseudo-resonance in escalators. The dynamic model effectively reflects vibration characteristics measured in real escalators with respect to different conditions of driving chain and the number of passengers. For validation of the dynamic model developed. numerical results from the model are compared with experimental results. The developed model and its simulation results are used rigorously for the design of escalator systems in enhancing the ride comfort.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.238-243
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• 2002

This paper presents an improved escalator dynamic model so as to reflect the experimental observation on the pseudo-resonance affected by load applied. The experimental evidence reveals that backlash of gearbox as well as sag of driving chain are most critical factors to the pseudo-resonance in escalators. The dynamic model effectively reflects vibration characteristics measured in real escalators with respect to different conditions of driving chain and the number of passengers. For validation of the dynamic model developed, numerical results from the model are compared with experimental results. The developed model and its simulation results are used rigorously for the design of escalator systems in enhancing the ride comfort.

• 한국소음진동공학회논문집
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• 제27권2호
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• pp.162-167
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• 2017

The chevron rubber spring is used for subway vehicle as a primary suspension. Generally, the primary suspension has an influence to the running performance and not so much effect on the ride comfort in railway vehicle. But the stiffness of chevron spring is harder and harder as time goes on because of rubber characteristics. Therefore the dynamic characteristics such as ride comfort and derailment coefficient should be reviewed according to the stiffness variation of chevron rubber spring. In this paper the effect of chevron rubber spring on dynamic characteristics was studied by considering multi-body dynamics of railway vehicle on one straight line and seven curved lines.

• 감성과학
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• 제5권3호
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• pp.67-74
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• 2002

Testing device was newly designed and built to measure the dynamic contact angle. The measurement was made using microscope interfaced with computerized image analysis system while the dynamic condition being controled using Instron. As specimens for the experiment, two different types of fibers, i.e., hydrophilic and hydrophobic, were prepared. In case of hydrophilic fiber, the increase of twist level gave the increase of contact angle. However, in hydrophobic yarn the increase of twist level gave the decrease of contact angle. When saline was used as a telling liquid, the increase of the concentration gave the increase of contact angle. The results rationalized clearly on the basis of known concepts could be used in designing fabric structure for the improvement of comport performance.

• Wind and Structures
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• 제31권5호
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• pp.393-402
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• 2020

Long-span bridges with high flexibility and low structural damping are very susceptible to the vortex-induced vibration (VIV), which causes extremely negative impacts on the ride comfort of vehicles running on the bridges. To assess the ride comfort of vehicles running on the long-span bridges subjected to VIV, a coupled wind-vehicle-bridge system applicable to the VIV case is firstly developed in this paper. In this system, the equations of motion of the vehicles and the bridge subjected to VIV are established and coupled through the vehicle-bridge interaction. Based on the dynamic responses of the vehicles obtained by solving the coupled system, the ride comfort of the vehicles can be evaluated using the method given in ISO 2631-1. At last, the proposed framework is applied to several case studies, where a long-span suspension bridge and two types of vehicles are taken into account. The effects of vehicle speed, vehicle type, road roughness and vehicle number on the ride comfort are investigated.

• Wind and Structures
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• 제23권1호
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• pp.19-43
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• 2016

In the present study, a new methodology is presented to study the ride comfort and bridge responses of a long-span bridge-traffic-wind coupled vibration system considering stochastic characteristics of traffic flow and bridge surface progressive deterioration. A three-dimensional vehicle model with 24 degrees-of-freedoms (DOFs) including a three-dimensional non-linear suspension seat model and the longitudinal vibration of the vehicle is firstly presented to study the ride comfort. An improved cellular automaton (CA) model considering the influence of the next-nearest neighbor vehicles and a progressive deterioration model for bridge surface roughness are firstly introduced. Based on the equivalent dynamic vehicle model approach, the bridge-traffic-wind coupled equations are established by combining the equations of motion of both the bridge and vehicles in traffic using the displacement relationship and interaction force relationship at the patch contact. The numerical simulations show that the proposed method can simulate rationally the ride comfort and bridge responses of the bridge-traffic-wind coupled system; and the vertical, lateral, and longitudinal vibrations of the driver seat model can affect significantly the driver's comfort, as expected.

• Smart Structures and Systems
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• 제18권1호
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• pp.53-74
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• 2016

This paper presents an experimental study on constructing a tunable secondary suspension for high-speed trains using magneto-rheological fluid dampers (referred to as MR dampers hereafter), in the interest of improving lateral ride comfort. Two types of MR dampers (type-A and type-B) with different control ranges are designed and fabricated. The developed dampers are incorporated into a secondary suspension of a full-scale high-speed train carriage for rolling-vibration tests. The integrated rail vehicle runs at a series of speeds from 40 to 380 km/h and with different current inputs to the MR dampers. The dynamic performance of the two suspension systems and the ride comfort rating of the rail vehicle are evaluated using the accelerations measured during the tests. In this way, the effectiveness of the developed MR dampers for attenuating vibration is assessed. The type-A MR dampers function like a stiffness component, rather than an energy dissipative device, during the tests with different running speeds. While, the type-B MR dampers exhibit significant damping and high current input to the dampers may adversely affect the ride comfort. As part of an ongoing investigation on devising an effective MR secondary suspension for lateral vibration suppression, this preliminary study provides an insight into dynamic behavior of high-speed train secondary suspensions and unique full-scale experimental data for optimal design of MR dampers suitable for high-speed rail applications.

• 한국철도학회논문집
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• 제19권5호
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• pp.565-575
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• 2016

철도차량 영업 운행 중 빈번히 발생하는 차륜 마모, 손상 등의 결함을 제거하기 위하여 실시되는 차륜 전삭 공정과 관련하여 전삭 전후의 차량 동적성능을 분석하였다. 전동차를 대상으로 차륜 전삭 전후의 차륜답면형상을 계측, 분석하였으며 진동 및 승차감 특성을 분석하고자 차량 주행시험을 실시하였다. 시험결과, 차륜 전삭 후 차량 진동 RMS값은 전삭 전에 비하여 저감되었으며 철도차량 기술기준에 의거 분석한 차체 진동성능은 전삭 전에 비하여 개선되었다. 승차감레벨은 전삭 전에 비하여 전삭 후 좌우, 상하방향 모두 최대 약 3dB의 개선 효과를 보였으며 주행안전성 또한 개선됨을 확인하였다.