• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5689-5695
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• 2012

In this study, vibration properties of seat and human body are analyzed through test and numerical analysis methods by taking into account the viscoelastic characteristics of polyurethane foam as seat material which is applied for vehicle. These viscoelastic characteristics which show nonlinear and quasi-static behavior are obtained by compression test. In addition, the viscous elastic property of polyurethane foam is modelled mathematically by using convolution integral and nonlinear stiffness model. In order to analyze the performance on ride comfort of seat, vertical vibration model is established by using dynamic model of seat and vertical vibration model of human body at ISO5982, and so the related motion equations are derived. A numerical analysis simulation is applied by using the nonlinear motion equation with Runge-Kutta integral method. The dynamic responses of seat and human body on the input of vibration acceleration measured at the floor of the railway vehicle are examined. The variation of the index value at ride comfort on seat design parameters is analyzed and the methodology on seat design is suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.34-40
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• 2016

In ventilated seats for cars, air flow is generated by a fan and passed through a foam pad, foam filter, and seat cover. There is a significant loss of air flow in this process, and it is not easy to analyze the amount delivered to the driver. Another difficulty is the geometric complexity of the air flow passage inside the seats. In this paper, the air flow through a foam pad was analyzed. Proper modeling of the bumps in the ventilation mat was found to be important in the analysis. Air flow is lost when it passes through the porous pad foam, which was measured and used to correct the analysis results. The corrected analysis results were in a good agreement with the experimental results. The amount of air flow delivered to a driver was measured using an airflow cone. Only 35.7% of the air flow from the fan was delivered.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3435-3441
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• 2014

A dynamic modeling and prediction of polyurethane foam material, which is used as the seat in vehicles is very important for improving the ride quality of vehicle occupants. In this study, parameters to define the nonlinear stiffness and time-variant characteristics of the viscoelasticity of polyurethane foam were obtained using a static compression test. Polynomial functions and convolution integral were used to model the nonlinear and viscoelastic characteristics of polyurethane foam mathematically. The dynamic behaviors excited by the seat floor displacement were analyzed using a numerical integration method for the nonlinear vibration model. As a result, the viscoelastic characteristics of polyurethane foam was found to be an important parameter for improving the ride quality.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.138-145
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• 2005

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.3
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• pp.205-211
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• 2014

The purpose of this document is to provide basic data helpful in selecting seating device material by examining the affects of polyurethane foam material on seating pressure. In order to achieve this study objective, four seats, 6cm in height, were produced in hardness of: 13, 28, 25, and $45kg/cm^2$. To measure the sitting pressure distribution (depending on the characteristics of the produced seats), 10 healthy subjects participated in the experiment. XSENSOR was used a measuring device, and each seat was mounted on a wheelchair simulation. By analyzing the obtained data with Average Pressure(AP), Peak Pressure(PP,), and Contact Area(CA), the sitting pressure was measured for five minutes on each seat. This experiment showed the following results: There were significant differences between the AP, PP, and CA in the seat material (p<0.5). While the hardness of $18kg/cm^2$ showed low pressure, the hardness of $45kg/cm^2$ showed high pressure. This study also showed that seat material made of polyurethane should be considered when selecting seats. If polyurethane foam is used in seat recommendations, it will be recommended to use $18kg/cm^2$ for the proper hardness of the seat material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.85-86
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• 2013

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.110-120
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• 1997

One of the most important factor for the comfort of the passenger vehicles is the minimization of the compressible transmissibility during the running vehicles. Seat foam materials of I2 series(index 95 and the contents of isocyanate TDI was changed in percentages 75, 70, 65, 60, 50, 40) and DI series(density 50kg/$\textrm{m}^3$, index was changed 100, 95, 90) showed the significant differences in their transmissibility depended upon their chemical constitution such as index and contents of isocyanate TDI. The minimum trasmissibility of seat foam materials of I2 series was found from the materials with the contents of 65% isocyanate TDI and the index 95 at the frequency 4.79~5.31Hz. Also the minimum transmissibility of seat foam materials of DI series was found from the materials with the index 90 and the density of 50kg/$\textrm{m}^3$ at the frequency of 4.79~5.31Hz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.444-449
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• 2001

The purpose of the work is to improve comfort of a car seat, especially dynamic comfort which affects driver's discomfort during the long time driving. Definition of dynamic comfort was made before the investigation of which parameter affects seat comfort. In order to optimize design parameters so as to maximize seat comfort as well as to know the cause of discomfort, benchmarking on a target vehicle and competitive vehicles was performed, which showed both the vibration transmission characteristics and the compression set due to dynamic loading should be reduced. As a solution ball rebounds was increased by about 10％ of the original foam, which showed reduction of S.E.A.T. value by 10％ and of compression set by 60％.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.675-682
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• 2013

In this study, to enhance the quality of concrete surface by removing the surplus water, permeable liner attached the euroform was applied for manufacturing concrete specimens. Various kinds of concrete mixtures with different water to binder ratios were applied and the strength properties of the hardened concrete surfaces were evaluated at different heights. Experimental results showed that the rebound values by schmidt hammer test and the compressive strengths on the surfaces of concrete specimens were increased as proportion to the amount of mixture water which is dependent on the water to binder ratio of each concrete mixture, and more enhancements were observed on the middle and lower specimen surfaces than the upper region. SEM analysis also showed that much denser hydrate structures were observed on the specimen surfaces by the application of the permeable liner while similar hydrate formations were occurred regardless of surface treatment conditions. From the MIP test results of the concrete surfaces, it was observed that, by the application of permeable liner, the pore volume below $0.01{\mu}m$ was decreased with a maximum of 50% resulting in the densification of pore structures.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.36-42
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• 2021

With recent developments in the Fourth Industrial Revolution, the manufacturing industry has changed rapidly. Through key aspects of Fourth Industrial Revolution super-connections and super-intelligence, machine learning will be able to make fault predictions during the foam-making process. Polyol and isocyanate are components in polyurethane foam. There has been a lot of research that could affect the characteristics of the products, depending on the specific mixture ratio and temperature. Based on these characteristics, this study collects data from each factor during the foam-making process and applies them to machine learning in order to predict faults. The algorithms used in machine learning are the decision tree, kNN, and an ensemble algorithm, and these algorithms learn from 5,147 cases. Based on 1,000 pieces of data for validation, the learning results show up to 98.5% accuracy using the ensemble algorithm. Therefore, the results confirm the faults of currently produced parts by collecting real-time data from each factor during the foam-making process. Furthermore, control of each of the factors may improve the fault rate.