• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1004-1009
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• 2002

There are four servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is conventional and the other is newly developed. Focus error signal between lens and disk is detected using LDV 2 beam method. The system is observable and all states are estimated. Full states feedback controller and minimum order observed are designed using those states. Impulse responses are simulated. And experiment is performed to compare with responses of conventional model.

• Journal of Biomedical Engineering Research
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• v.20 no.1
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• pp.21-27
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• 1999

In order to increase our understanding of the injury mechanism in the child occupant, three year old child model was developed using commercial dynamic package DADS. Total 14 segments and 12 joints were used to compose a model in three points belted condition with booster seat. HYGE sled test case was simulated to validate the developed model. Based on the comparison of the model and published test results, the developed model appears to be a resonable representation of the three year old dummy.

• Journal of Auto-vehicle Safety Association
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• v.4 no.2
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• pp.37-43
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• 2012

The purpose of this research is to obtain and analyze dynamic responses from human volunteers for the development of the human-like mechanical or mathematical model for Korean males in automotive rear collisions. This paper focused on the introduction to a low-speed rear impact sled test involving Korean male subjects, and the accumulation of the motion of head and neck. A total of 50 dynamic rear impact sled tests were performed with 50 human volunteers, who are 30-50 year-old males. Each subject can be involved in only one case to prevent any injury in which he was exposed to the impulse that was equivalent to a low-speed rear-end collision of cars at 5-8 km/h for change of velocity, so called, ${\Delta}V$. All subjects were examined by an orthopedist to qualify for the test through the medical check-up of their necks and low backs prior to the test. The impact device is the pendulum type, tuned to simulate the crash pulse of a real vehicle. All motions and impulses were captured and measured by motion capture systems and pressure sensors on the seat. Dynamic responses of head and T1 were analyzed in two cases(5 km/h, 8 km/h) to compare with the results in the previous studies. After the experiments, human subjects were examined to check up any change in the post medical analysis. As a result, there was no change in MRI and no injury reported. Six subjects experienced a minor stiffness on their back for no more than 2 days and got back to normal without any medical treatment.

• Composites Research
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• v.36 no.4
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• pp.253-258
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• 2023

Although the development of transportation means has realized the right to mobility for the disabled who have difficulty in moving, it can be said that the improvement of the safety of passengers with disabilities that can occur in a car accident is lower than that of ordinary passenger seats. In particular, in the case of a rear-end collision that can occur suddenly, it is a reality that disabled passengers are vulnerable to head and neck injuries. Therefore, in this study, a multi-layer headrest foam that divides the headrest into three parts in the coronal plane was proposed to improve the head and neck injury index of disabled passengers in the vehicle in the event of a rear-end collision of a wheelchair transport vehicle. A range of stress scale factors was selected to give various compressive characteristics of the foam through low-speed rear-end collision analysis through a simple model, and GA optimization was performed by specifying the range as a parameter. Through the optimization result, the phase relationship between HIC and NIC was analyzed according to the compression characteristics of the layers. HIC responded most sensitively to the compression characteristics of the front layer and NIC responded to the compression characteristics of the mid layer, and the compression characteristics of the rear layer showed the lowest. A normal headrest and an optimized multi-layer headrest were placed in the validation model to analyze the low-speed rear-end collision sled test, and HIC and NIC were derived lower in the multi-layer headrest than in the general headrest. The compression behavior of the multi-layer headrest was also clearly shown, and it was verified that the multi-layer headrest was effective in improving the injury index of the head and neck compared to the general headrest.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.580-584
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• 1997

As the optical disk drive is getting applied to wider ranges, higher density of media and higher velocity of spindle motor are demanded and therefore its design criterion is becoming more strict. Especially, the vibration problem is one of the most important factors to be considered for reliable performance. In this study, the possibility of the application of the vibration absorber using rubber mount was investigated by 3 dimensional modeling and analysis by Recurdyn program. The model chosen was a vibration absorber using rubber mount installed on the sled base of the optical disk drive.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.397.2-397
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• 2002

There are 4 servo systems in a DVD drive such as a focus servo system, a tracking servo system, a sled servo system and a spindle servo system. Focus servo system maintains relative distance between lens and disk. In this paper, two plant models for the focus servo system will be presented. One of them is newly developed and the other is conventional. Focus error signal between lens and disk is detected using LDV 2 beam method. (omitted)

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.1
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• pp.172-182
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• 2000

A hybrid type automotive drivers seat was invented with new concepts for the reduction of weight and manufacturing costs. Fundamental studies were performed to determine the basic geometry of reinforcing support. A prototypical design was provided by the manufacturer considering compatibility with other parts. Several structural analyses simulating various crash situations were performed and modifications were continued until a final design was reached. A sample product was manufactured and sled crash tests were performed to verify the safety of the seat. Comparisons of test results with the previous model and a seat from another company proved safety performances to be superior.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.60-65
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• 2002

The computer simulation techniques were adopted to evaluate effects of seating positions of passenger under the various accident scenarios. The baseline of computer simulation model was tunned by the sled impact tests which conducted under the upright and standard seating positions. This study shows the effect of relative velocity between occupant and struck vehicle while occupant is impacted to a front seat's seatback. Although, base on the current accident scenarios, KHST is performed well enough to protect average adult male occupants. However, Results from the tests indicate small size occupant or higher impact speed may cause sever neck and femur injuries.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1009-1014
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• 2007

To improve passenger safety, seatbelt systems with pre-tensioner that tightens seatbelt webbing using explosives just before collision are widely adopted. Even though seatbelt must not be unlatched without passenger's operation, release of a buckle due to explosion of pre-tensioner takes place in some situations resulting in serious injury to passengers. To prevent the unintended unlocking, a pendulum like part called anti-g mass is attached to the buckle to block displacement of release button. In this study, the unlocking conditions of anti-g buckle when pre-tensioner explodes has been theoretically investigated. Through multibody model of the seatbelt system incorporating every detailed part of the buckle, dynamic analysis of the seatbelt system with pre-tensioner has been performed including the driver's body model that interacts with seatbelt system. The simulations results has been validated through actual sled test with driver dummy and the seatbelt system.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3085-3099
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• 2021

Investigations of large commercial aircraft impact effect on nuclear power plant (NPP) buildings have been drawing extensive attentions, particularly after the 9/11 event, and this paper aims to numerically assess the damage and vibrations of NPP buildings subjected to aircrafts crash. In Part I of present paper, two shots of reduce-scaled model test of aircraft impact on NPP were conducted based on the large rocket sled loading test platform. In the present part, the numerical simulations of both scaled and prototype aircraft impact on NPP buildings are further performed by adopting the commercial program LS-DYNA. Firstly, the refined finite element (FE) models of both scaled aircraft and NPP models in Part I are established, and the model impact test is numerically simulated. The validities of the adopted numerical algorithm, constitutive model and the corresponding parameters are verified based on the experimental NPP model damages and accelerations. Then, the refined simulations of prototype A380 aircraft impact on a hypothetical NPP building are further carried out. It indicates that the NPP building can totally withstand the impact of A380 at a velocity of 150 m/s, while the accompanied intensive vibrations may still lead to different levels of damage on the nuclear related equipment. Referring to the guideline NEI07-13, a maximum acceleration contour is plotted and the shock damage propagation distances under aircraft impact are assessed, which indicates that the nuclear equipment located within 11.5 m from the impact point may endure malfunction. Finally, by respectively considering the rigid and deformable impacts mainly induced by aircraft engine and fuselage, an improved Riera function is proposed to predict the impact force of aircraft A380.