• Environmental Engineering Research
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• v.15 no.3
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• pp.135-140
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• 2010

With the various urban characteristics of each city, the existing water demand prediction, which uses average liter per capita day, cannot be used to achieve an accurate prediction as it fails to consider several variables. Thus, this study considered social and industrial factors of 164 local cities, in addition to population and other directly influential factors, and used main substance and cluster analyses to develop a more efficient water demand prediction model that considers unique localities of each city. After clustering, a multiple regression model was developed that proved that the $R^2$ value of the inclusive multiple regression model was 0.59; whereas, those of Clusters A and B were 0.62 and 0.74, respectively. Thus, the multiple regression model was considered more reasonable and valid than the inclusive multiple regression model. In summary, the water demand prediction model using principal component and cluster analyses as the standards to classify localities has a better modification coefficient than that of the inclusive multiple regression model, which does not consider localities.

• Transactions of Materials Processing
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• v.5 no.3
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• pp.232-238
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• 1996

A dynamic mill set-up technique was developed to achieva a more precise roll gap set-up of the finishing mill stands for steel strip rolling. In the conventional mill set-up model the set-up values such as roll gap and roll speed are determined before the sheet bar reached the entry side of the finishing mill train and maintained constant until the strip top end passes through the last stand. In the way however a dynamic set-up logic that gives a way to adjust the roll gap value of the final mill stand for the strip ingoing from the ahead of the front stand was developed and attached to the existing set-up model. The roll gap modification is based on the analysis of the observation in the third stand of the finishing mill train. The dynamic set-up model was proved very effective for the more precise mill set-up and for operational stability in the hot strip finishing mill train.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.99-106
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• 2011

This paper deals with engine room layout design optimization of fuel cell electric vehicle (FCEV), which has been proposed as a potential alternative to fossil fuel depletion. Investing the great R&D efforts, the global vehicle manufacturers, especially Honda motor corporate, have shown not prototype vehicle but commercial vehicle using fuel cell in the market recently. In this paper, we analyze cooling performance and flow characteristic in the engine room of newly FCEV, in addition we suggest the optimization process for engine room layout design optimization. The two radiators in the vehicle for fuel cell stack and electronic components cooling have been analyzed and their performance are obtained in terms of cooling performance ratio (CPR). The value of CPR should always be less than one and based on criteria, we have achieved the optimum cooling performance of radiators for stack and electronic components. Aerodynamic performance is evaluated in terms of drag coefficient, improved through underbody modification using air devices.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.383-390
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• 2005

This study proposes an innovative design guideline to assist the evaluation and improvement of the dynamic comfort of vehicle seating. The existing evaluation method for the comfort of vehicle seating was investigated to broach problems in evaluation. It was found that the currently existing evaluation method employs the resonance frequency of the vibration system composed of the seat and the human body and the maximum vibration transmissibility. This study proposes a design guideline aimed at the enhancement of vibration transmission characteristics above the resonance range, particularly within the range of 10-18 Hz. In order to meet this guideline, a seat was constructed out of foam having a low damping coefficient. It was then installed in a vehicle for a driving test. The driving test confirmed the improvement of the dynamic comfort of the seat. The result of evaluation of the improved seat using the SEAT index, an industry standard widely used to evaluate the dynamic comfort of a seat considering the perceptivity characteristics of the human body, showed that the perceptive vibration transmission had reduced by more than $11\%$. The effect of the modification of seat foam was also verified through a subjective assessment of dynamic comfort of the seats.

• Tribology and Lubricants
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• v.24 no.3
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• pp.122-128
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• 2008

To reduce the friction losses and the wear amounts in the piston assembly two methods were proposed. One is the modification of surface profile of the skirt part. The surface coating is another method to protect the sliding surfaces. To modify the profile of the skirt surfaces the surfaces were ground to have three different shapes of profiles. Also, several coatings, such as graphite, TiN, and $MoS_2$, and DLC, were used to protect the surfaces of the piston skirts. The specimens of the skirt and the cylinder bores were tested with the reciprocating wear tester. SAE 5W40 engine oil was used in boundary lubrication regime. Among several coatings the graphite and DLC coatings were very effective to reduce the friction forces. Especially, DLC film represented much better tribological performances than the others. The friction coefficient of the graphite coating was the lowest, but the graphite coating was not effective to protect the surfaces.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.2
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• pp.57-62
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• 2007

The lubricational characteristics about friction wear has an effect on the material quality of surface. In this paper, we studied the lubricational characteristics through the surface modification experiment by spray coating the surface with $MoS_{2}$ and PTFE solid lubricants. In the case of $MoS_{2}$ and PTFE coating, the friction coefficient of Journal is lower than that for noncoating so the friction characteristics is excellent. In particular, the beginning characteristics of $MoS_{2}$ coating is excellent, and in the case of PTFE coating, seizure dose not appear seizure. $MoS_{2}$ and PTFE coating are excellent in the extreme pressure at high load. The wear characteristics is excellent in the following order; PTFE < $MoS_{2}$ < Non Coating. For Non coating, seizure appears at the beginning due to the heat, but in the case of $MoS_{2}$ and PTFE coating, it will have the excellent heat stability even at high temperature.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.625-633
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• 2015

The effect of altitude on thermal conduction, surface temperature, and thermal radiation of partial arc was investigated on the basis of molecular gas dynamics to facilitate a deep understanding of the pollution surface discharge mechanism. The DC flashover model was consequently modified at high altitude. The validity of the modified DC flashover model proposed in this paper was proven through a comparison with the results of high-altitude simulation experiments and earlier models. Moreover, the modified model was found to be better than the earlier modified models in terms of forecasting the flashover voltage. Findings indicated that both the thermal conduction coefficient and the surface thermodynamics temperature of partial arc had a linear decrease tendency with the altitude increasing from 0 m to 3000 m, both of which dropped by approximately 30% and 3.6%, respectively. Meanwhile, the heat conduction and the heat radiation of partial arc both had a similar linear decrease of approximately 15%. The maximum error of DC pollution flashover voltage between the calculation value according to the modified model and the experimental value was within 6.6%, and the pollution flashover voltage exhibited a parabola downtrend with increasing of pollution.

• Tribology and Lubricants
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• v.24 no.4
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• pp.163-169
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• 2008

Tribological properties of ceramic brake discs were investigated using a commercial friction material. The discs were manufactured by liquid silicon infiltration (LSI) into a C-C preform. The disc surface was modified by two different methods, producing sliding surfaces with chopped carbon fibers and carbon felt. In addition, the composition of the surface was also changed. Friction characteristics of the discs were examined using a 1/5 scale dynamometer. Results showed that the type and composition of the disc surface significantly affected the level of braking effectiveness and high temperature brake performance. The discs with felt surfaces showed higher friction levels than those with chopped fiber surfaces and SiC tended to increase the friction level while C lowered the friction coefficient. The ceramic disc was more sensitive to the deceleration rate than gray iron, showing high speed sensitivity.

• Earthquakes and Structures
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• v.12 no.2
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• pp.251-262
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• 2017

The present research intends to study the effects of the seismic soil-foundation-structure interaction (SFSI) on the dynamic response of various buildings. Two methods including direct and Cone model were studied through 3D finite element method using ABAQUS software. Cone model as an approximate method to consider the SFSI phenomenon was developed and evaluated for both high and low rise buildings. Effect of soil nonlinearity, foundation rigidity and embedment as well as friction coefficient between soil-foundation interfaces during seismic excitation are investigated. Validity and performance of both approaches are evaluated as reference graphs for Cone model and infinite boundary condition, soil nonlinearity and amplification factor for direct method. A series of calculations by DeepSoil for inverse earthquake record modification was conducted. A comparison of the two methods was carried out by root-mean-square-deviation (RMSD) tool for maximum lateral displacement and story shear forces which verifies that Cone model results have good agreement with direct method. It was concluded that Cone method is a convenient, fast and rather accurate method as an approximate way to count for soil media.

• Water for future
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• v.14 no.1
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• pp.51-58
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• 1981

This study attempts to examine and estabilish a simulation model from the stochastic analysis of daily streamflow. Daily streamflow records obstained at the main gauging stations along the Han, Nakdong and Geum River were used in the analysis. The following results were abtained. From the analysis of time series of streamflow by the correlogram and spectraal density, The serial component of one-year periodicity, serial correlation and irregular or random component were found. The coefficient of determination R2 of multilag model remaine a plateau at log-two, so that second order mu.ltilag model was Known to fit in the simulation of daily streamflow, Consequently, multilag and recised Markov model of the sewnd order give the best results in simulatin of daily streamflow. But the former generally gives better results than the latter. And theoretical markev model is unfit in the simulation of daily series without modification.