• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1571-1577
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• 2013

Electrical tree structure is one of the most important influencing factors for electrical treeing characteristics in polymers. In this paper, we focused on the structure characteristics of electrical treeing in epoxy resins (original) insulation under different high-frequency voltages (60, 500, 1000Hz). Effects of voltage frequency on the ac electrical treeing phenomena in an epoxy resins were carried out in needle-plate electrode arrangement. To measure the treeing initiation and propagation, and the breakdown rate, constant AC of 10 kV with three different voltage frequencies (60, 500 and 1,000 Hz) was applied to the specimen in needle-plate electrode specimen at $30^{\circ}C$ of insulating oil bath. At 60 Hz, the treeing initiation time was 360 min and the propagation rate was $6.85{\times}10^{-4}mm/min$, and the morphology was dense branch type. As the voltage frequency increased, the treeing initiation time decreased and the propagation rate increased. At 1,000 Hz, the treeing initiation time was 0 min and the propagation rate was $7.81{\times}10^{-2}mm/min$, and the morphology was dense bush type.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1132-1137
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• 2011

MRE(magneto-rheological elastomers) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb vibration of broader frequency range. These characteristic phenomena result from the orientation of magnetic particles named carbonyl iron powder(CIP) in rubber matrix. In this paper, simulation on variation rate of shear modulus for anisotropic MRE due to volume fraction of CIP and an effective permeability model was applied to predict the field-induced shear modulus of MREs. Also, the variation rate of shear modulus for anisotropic MRE was derived using magneto-mechanical theory. Based on Maxwell-Garnett mixing rule, the increment of shear modulus was calculated to evaluate the shear modulus of MREs with column structure of CIP due to induced current. The simulation results on variation rate of shear modulus can be applied to the variable mechanical system of MRE such as tunable vibration absorber, stiffness variable bush and mount.

• Korean Journal of Agricultural Science
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• v.38 no.2
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• pp.235-241
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• 2011

Recently, as people have become more interested in health issues, their demand on forest trails for bush walking exercise has increased. The purpose of the study is to select barrier factors into forest trail for disabled using wheelchairs. As a result this, it has selected 31 barrier factors through the Delphi method. Of all the these factors, the information board of forest trails, showing the location of the trails, has indicated the highest score of importance at 4.50. Next, securing hiker' walking safety space has indicated an importance level of 4.44; both the slope of forest trails and the height of obstacles have indicated an importance level of 4.38; and the effective width of forest trails has indicated the highest score of importance level of 4.33. From these indicated levels of importance, the respondents of the Delphi method consider the safety of users of forest trail' as the most important factor while the physically disables are hiking. That is why these factors have resulted in acquiring relatively higher values.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.631-653
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• 2020

Sign language is a natural, visually oriented and non-verbal communication channel between people that facilitates communication through facial/bodily expressions, postures and a set of gestures. It is basically used for communication with people who are deaf or hard of hearing. In order to understand such communication quickly and accurately, the design of a successful sign language translation system is considered in this paper. The proposed system includes object detection and classification stages. Firstly, Single Shot Multi Box Detection (SSD) architecture is utilized for hand detection, then a deep learning structure based on the Inception v3 plus Support Vector Machine (SVM) that combines feature extraction and classification stages is proposed to constructively translate the detected hand gestures. A sign language fingerspelling dataset is used for the design of the proposed model. The obtained results and comparative analysis demonstrate the efficiency of using the proposed hybrid structure in sign language translation.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.3
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• pp.211-215
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• 2017

This research analyzes bucket elevator roller chain pins by finite element (FE) analysis and static structural analysis for a lightweight pin design. The stress distribution of light weight roller chain pins under static load is analyzed for safety factors and damping effect. The results show that the stress distribution is higher on the plate than on the bush pin. In order to compare experimental and FE analysis results, a light weight design approach was used to produce a prototype base pin. Because the inner diameter of the pin was different, the impact damping effect was most appropriate when the inner diameter was 34.05 mm, and it is used as basic research data on the impact of the roller chain and sprocket.

• Safety and Health at Work
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• v.7 no.4
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• pp.284-292
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• 2016

Background: In Ghana, fire incidents have become a regular occurrence, with thousands of lives and millions of dollars lost every year. Hardly a day passes without news of a fire outbreak in some part of Ghana, causing fear and panic among the people. This generates much discussion centering on rumors relating to politics, sabotage, misfortune, religious differences, etc. This article seeks to discuss the trend of fire incidents occurring in Ghana from 2000 to 2013 and the different ways to prevent these incidents. Methods: The pattern of fire incidence in Ghana as a whole as well as in each region is discussed. The study took into consideration the causes, mechanisms, as well as preventive measures against the fire menace. Data were obtained from the head office of Ghana's national fire service. Results: It was noticed that in general the rate of fire incidence increased each year. This increase was attributed to several factors: rate of population growth and industrialization, unstable electricity, urbanization, negligence, illegal electrical connection, etc. The cause of fire was categorized into domestic, industrial, vehicular, institutional, electrical, commercial, bush, and others. Among these causes, domestic fire accounted for 41% of the total number of fire incidents in the country. Conclusion: Finally, this study presents several recommendations to help prevent and mitigate fire incidents in Ghana.

• Tribology and Lubricants
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• v.25 no.5
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• pp.318-323
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• 2009

The oil characteristics and wear particles of Diesel engines with a DPF have been investigated as a function of a driving distance. The engine oil of SAE 5W30 with ACEA C3 is used for an oil film lubrication of the engine, which is equipped with Diesel particulate filter. Depending on the oil test results, the kinematic viscosity of used engine oils at 40 is degraded up to 5.1% compared with that of unused engine oils, SAE 5W30. And the kinematic viscosity of used engine oils at 100 is more degraded up to 8.1% compared with that of unused engine oils. The oil characteristic as a function of a mileage is not changed depending on the driving distance because of high quality of engine oils. But the aluminum and copper compounds, which are used as base materials of the engine bearing and a pin bush, are much worn and contaminated for the increased mileage of the car. The oil properties of used engine oils are relatively good except phosphorus and calcium additives, which are heavily engaged in the performance of the oils.

• Convergence Security Journal
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• v.11 no.4
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• pp.19-29
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• 2011

After a change of government and the inauguration of President Barack Obama in 2009, there are various effort to set up a cybersecurity policy which is better than its predecessor. The legislative trend of cybersecurity is the one aspect of that. So we compare the legislative trend of cybersecurity in the Obama era to one in the Bush era and analyze that and find items which is helpful to Korea. It seems that the point of cybersecurity legislation of U.S.A. changes from tougheners of penalties to improvements to implementation system. We can find the implications for Korea From that. Cybersecurity is covered as a problem all over the nation and a security problem. It is necessary for Korea to get ready for new Pax Americana in cybersecurity in advance and to guarantee fundamental human rights.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.177-182
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• 1997

The purpose of this study is to analyze how tools, guide bush type and the change of cutting speed have effects on the diameter of cutting hole, surface roughness of workpiece and roundness during the deep hole machining of SM55C with solid BTA drill by using BTA drilling system through experiment. Conclusion reached is as follows. (1) The diameter was expanded for 25${\mu}{\textrm}{m}$ at the first section and then was reduced 0${\mu}{\textrm}{m}$ and 15${\mu}{\textrm}{m}$ respectively at the 10m and 20m section comparing to the diameter of tool with respect to the variation of cutting length. (2) It was proved that roughness was below 12S for the whole section of cutting length. (3) The roundness has been below 12${\mu}{\textrm}{m}$. Regarding the polygon phenomenon, it has bee proved that not only uneven number of angle but also even number (quadrilateral, elliptical) of angle were made. (4) Variation of diameter, surface roughness of workpiece and roundness turned out to ve the best at 70m/min of cutting speed, 0.15mm/rev of feed.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.197-204
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• 2003

This paper develops a computer model for estimating the handling of a cabover type large-sized truck. The truck is composed of front and rear suspension systems, a frame, a cab, and ten tires. The computer model is developed using ADAMS. A shock absorber, a rubber bush, and a leaf spring aunt a lot on the dynamic characteristic of the vehicle. Their stiffness and damping coefficient are measured and used as input data of the computer model. Leaf springs in the front and rear suspension systems are modeled by dividing them three links and joining them with joints. To improve the reliability of the developed computer model, the frame is considered as a flexible body. Thus, the frame is modeled by finite elements using MSC/PATRAN. A mode analysis is performed with the frame model using MSC/NASTRAN in order to link the frame model to the computer model. To verify the reliability of the developed computer model, a double lane change test is performed with an actual vehicle. In the double lane change, lateral acceleration, yaw rate, and roll angle are measured. Those test results are compared with the simulation results.