• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.132-137
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• 2005

This paper addresses what amount of whole-body vibration is exposed to pilots of UH60 helicopters during flight. To measure the whole-body exposed from the feet and seat, the 12-axis vibration measurement system was used. It enables simultaneous measurement of vibration exposure from the body contact area of the feet, hip and back. The measured 12-axis vibration signals are exploited to the comfort level of UH60 helicopters during flight. It is shown that the evaluated ride value is close to $0.74{\sim}0.79m/s^2$ and that it is equivalent to the semantic scale of 'fairly uncomfortable'. To assess the health effects of whole-body vibration exposed to pilots of UH60 helicopters during their flight, the rms-based and VDV(vibration dose value)-based evaluation results of measured four-axis vibration signals are shown in this work. The fatigue-decreased proficiency limit, whose level is half of the exposure limit, is expected to come after the two-hour flight. The exposure limit is shown to reach after the 10-hour flight.

• Korean Institute of Interior Design Journal
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• v.16 no.2 s.61
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• pp.13-23
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• 2007

This paper has focused on comprehending the interior designs and characteristics of modern department stores in Korea by looking into the birth and changes of those built under the Japanese Forced Occupation Period. The first modem department stores including Mitsukoshi, Georgia and Hwashin Department Stores began to appear in Korea under the Japanese Colonial Rule. They considered a variety of architectural elements like construction planning, shop arrangement, path of customer movement and interior design. The interior of modem department stores aimed to pursue the so-called modernization movement, but failed to fully contain the unique characteristics of the times in that particular period. Modem department stores took on new western styles prevailed in Korea and were characterized by the eclecticism in which various architectural forms exist together. In other words, their interiors implied a sign of the times in the confusing and corrupt world then. Especially those modern department stores were designed, repaired and extended by foreign designers who were ignorant of the history of Korean architecture. What is worse, their further remodelling practices made big mistakes by considering only functional and economical aspects and giving a back seat to the architectural and historical value of existing modern department stores. Therefore, we should make more efforts to study and conserve the fundamentals of modem architectures like modem department stores in order to have better understanding of the aesthetic value of indoor space and facilitating smooth communication between past and present.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.68-75
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• 2002

Stellite 12 alloy-powders were overlaid on 410 stainless steel valve seat by plasma transferred arc(PTA)process. Variation of microstructure and hardness of overlaid deposit with aging time at $750^{\circ}C$ was investigated. The deposit showed hypoeutectic microstructure, which was consisting of primary cobalt dendrite and networked $M_{7}C_{3}$type eutectic carbides. After aging new M_{23}C_{6}$ carbide was formed by the partial decomposition of $M_7C_3$ type eutectic carbides and finely dispersed $M_{23}C_6$ type carbides were also precipitated in the matrix. Hardness of the deposit was increased with increase of aging time at $750^{\circ}C$ and showed maximum value at 35hours. After showing maximum value, it was fallen down again at 70hours because of overaging. The increase of hardness in aging is ascribed to the formation of new stable $M_{23}C_6$ type carbide by the partial decomposition of $M_7C_3$ type eutectic carbides and also precipitation of finely dispersed $M_{23}C_6$ carbides in matrix.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.2
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• pp.16-29
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• 1995

In this study a tracked vehicle is idealized as a 2-dimensional 9-degrees-of-freedom model which takes into account the effects of HSU units, torsion bars, and track. For the model equations of motion are derived using Kane's method. By using the equations of motion, a numerical example is solved and results are compared to those obtained by using a general purpose multi body dynamic analysis program. The comparison study shows the reasonable coherence between the two results. which confirms the effectiveness of the model. With the model, dynamic response optimization is carried out. The objective function is the peak value of the vertical acceleration of the vehicle at the driver's seat, and the constraints are the wheel travel limits, the ground clearance. and the limits of other design variables. Three different sets of design variables are chosen and used for the optimization. The results show the attenuation of the acceleration peak value. Thus the procedure presented in this study can be utilized for the design improvement of the real system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.234-240
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• 2003

This study aims to investigate dynamic properties of express buses in the very low frequencies which affect motion sickness incidence. Since passengers often use express buses for long distance traveling, it is a critical point whether a give rise to motion sickness or not. In the study accelerations at the three points on the floor of the six test vehicles were measured during the driving at constant speeds. By applying frequency weighting curves suggested in ISO 2631-1 and ISO 2631-3, physical amount of accelerations were changed into perceptual amount which determines incidence of motion sickness. Motion sickness dose values were calculated from the frequency weighted time history of accelerations, and compared between the vehicles, driving conditions, and the seat positions in the bus. During the driving on public road and high ways for 50 minutes vomiting incidence ratios ranged 0.4 to 0.8%, which were equivalent to 2.4 to 4.8% for 5 hours' driving. The value of 4.8 % means two among 45 passengers may vomit after the traveling, which is very serious situation. Considering the very smooth driving condition at which the data were collected, motion sickness dose values will increase in real situations

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.6 s.111
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• pp.658-664
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• 2006

Shock vibrations are usually experienced in vehicles excited by impulsive input, such as bumps. The frequency weighting functions of the current standards in ISO 2631 and BS 6841 are to help objectively predict the amount of discomfort of stationary vibration. This experimental study was designed to develop frequency weighting shape for shock vibration having various fundamental frequencies from 0.5 to 16Hz. The specks were produced from the response of single. degree-of-freedom model to a half-sine force input. Fifteen subjects used the magnitude estimation method to judge the discomfort of vertical shock vibration generated on the rigid seat mounted on the simulator. The magnitudes of the shocks, expressed in terms of both peak-to-peak value and un-weighted vibration dose values (VDVs) , were correlated with magnitude estimates of the discomfort. The frequency weighting shapes from the correlation were developed and investigated having nonlinearity due to the magnitude of the shock.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.142-151
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• 1997

In order to reduce passenger injuries in side collisions, car makers are developing a side impact airbag system while Volvo has already adopted. This study examines dummy injury reduction effect of a side airbag system using full car side impact simulation according to FMVSS 214 test procedure. The simulation result without side airbag shows a good correlation with test data. The folded airbag simulation is carried out to check main design factors. Through the simulation with side airbag module integrated in the seat frame, it is found that the side airbag system provides a substantially enhanced protection for car occupants in side collisions.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.646-653
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• 2001

LQG/LTR Control Methology is recently used for the analysis of multi-variable control in frequency domain. Target filter loop is designed by the demanding requirements such as cross-over frequency, disturbance rejection in low frequency domain, zero steady-state error, identification of maximum and minimum singular values and sensor noise rejection in high frequency domain. Loop transfer recovery is accomplished by solving the cheap control and then simulation close to the target filter loop. In this study, LQG/LTR Control Methodology is applied to the seat suspension system. It is found that this technique is very effective to control the system and improve the ride quality of human body.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1527-1532
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• 2007

We have evaluated the toxicity of interior materials for the railway passenger car by checking the release of $CO_2$, CO, NOx, SO2, HCl, HF, HBr, HCN. The NOx is one of the most effective for the determination of Toxic Index R value. It is generally known that the mechanism of thermal NOx generation without the Interior Material nitrogen source. This study started from the idea to check the NOx difference according to the furnace temperature. But from the results, it was revealed that NOx is not so sensitive for the furnace temperature in case of solid burning. Other gases such as HCN, CO were more changeable to the furnace Temp. We reported the test result as for toxicity index r(x).

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.109-121
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• 2000

A simplified modeling approach of free vibration for occupied car seats was demonstrated to be feasible. The model consisting of interconnected masses springs and dampers was initially broken down into subsystems and experiments conducted to determine approximate values for model parameters. Which were each stiffness and damping value. Nonlinear equations of motion were derived and model parameters obtained in experiments were applied to these equations. A mathematical model of free vibration for car seat and mannequin system was built with 7 degrees of freedom. in order to calculate natural frequencies and the corresponding mode shapes. linear equations of motion were obtained through linearization. In order to explore the effects of each model parameter free vibration analysis were preformed.