• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.2
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• pp.117-124
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• 2011

Valve springs with non-circular cross-section are widely used in automotive engines. Because of the reduced height, the oval cross-section provides some merits in its install height and stress distribution. This paper introduces a new method to generate optimal shape of the non-circular cross-section. For given width and height, arbitrary shape of the cross-section are described using the Hermite spline curves. Cross-section area and maximum stress level are chosen as performance indices, and nonlinear optimization problems are formulated with inequality constraints. Compared to a production spring wire, cross-section area can be reduced about 2.4 [%] without increasing maximum stress level. In addition, the other approach gives an optimum cross-section which reduces maximum stress level of 2.0 [%] without increasing cross-section area.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.1
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• pp.135-147
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• 2000

Section design of vehicle structure has been developed by two methods. One is the section property method which uses section property as a design variable. This method shows the tendency of an optimum section approximately. The other method is the section shape method which utilizes geometric parameter of section as a design variable. Practical solutions are obtained by this method. However, it is very expensive for large-scale problems due to the large number of geometric parameters. These two methods are compared through several sample problems. The finite element method is used for the structural and sensitivity analyses. The results are analyzed based on the number of function evaluations, the quality of cost function, the complexity of programing, and etc. The applications of both methods are also discussed.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.1
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• pp.16-22
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• 2003

While passing through the AC/DC section insulators installed at electric railroad catenary, some electric trains undergo mis-operation of main circuit breaker after AC/DC change-over operation. This paper provides insulation resistance measurements of AC/DC section insulators, which confirm the insulation levels of section insulators are below the standard of insulators. The insulation deterioration and pantograph arrangement on the electric train can produce voltage impression on section insulator which induces mis-operation of main circuit breaker To mitigate the insulation deterioration of the section insulator installed at underground railroads, the section insulators have been cleaned periodically, but section insulator structure should be modified to make the section insulator performance perfect. Based on the above analysis, effective modification method of AC/DC section insulator is provided.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.212-219
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• 2002

In the frontal collision of cars, front parts of cars such as engine rail and side members that are composed of hatted section tubes should absorb most of the collision energy far the passenger compartment not to be deformed. For these reasons the study on the collapse characteristics, maximum crushing load and energy absorption capacity of hatted section tubes are needed. In this study, top hatted section tubes and double hatted section tubes are investigated. The maximum crushing load of hatted section tubes is induced from plastic buckling stress of plates by considering that the hatted section tubes are composed of plates with each different boundary conditions and that its material has a strain hardening effect. On this concept maximum crushing load equations of hatted section tubes are derived and verified by experiments. from the results of experiment, the differences of collapse characteristics between top hatted section tube and double hatted section tube are analysed. And mean crushing loads of hatted section tubes from experiments are compared with other theory.

• Research in Community and Public Health Nursing
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• v.11 no.2
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• pp.499-512
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• 2000

The number of deliveries by cesarean section has increased internationally. However, The cesarean section rate is different by country to country. It is because each country has different social and cultural background and. practices its unique delivery policies. Hence, it is very important to understand the uniqueness that one country faces related with the cesarean section. In Korea, there have been many researches on the clinical. maternal. hospital and community factors and so on. However, few studies have attempted to reveal the physician factors in Korea because it is difficult to approach hospital records. So, in this study, the physician factors that influence the increase of cesarean section rate in Korea was investigated, and preliminary research agenda for policy establishment to keep the cesarean section rate from excessive increase was provided. In this study, all 2744 cesarean section deliveries performed by 36 physicians at the hospital was considered. and detailed delivery records of 12 months selected randomly from January 1996 to August 1998 was reviewed retrospectively. Chi-square analysis is used to examine the homogeneity of distribution of maternal, fetal, and clinical factors. In addition, multiple regression analysis is used to examine the effect of physician characteristics on the cesarean section rate. Physician characteristics as independent variable and the cesarean section rate as dependent variable was put in this analysis. Follows are the results of this study. 1) Total cesarean section rate is 34.8%. primary cesarean section rate is 12.5 % and repeated cesarean section rate is 22.3 %. Among the indications for the primary cesarean section, 15.6 % is for breech presentation. 40.2 % is for dystocia. 7.6 % is for fetal distress. and 36.6 % is for others. 2) There is positive correlation between physician's age and the cesarean section rate (p<0.001). And statistically significant correlation is found between the physician's educational attainment and the cesarean section rate (p<0.001). A physician with Ph.D degree has lower cesarean section rate than a physician with B.A only and M.A. degree (p<0.001). However. physician's gender, location of graduated university. position at the hospital, and the religious belief were not shown statistically significant relations with the cesarean section rate. 3) Among all cesarean sections in this study, only 15.4 % is performed during weekend. While 18.2 % is performed on monday only. This suggests that physicians may not prefer weekend operation of cesarean section. In addition, 86.1 % among all cesarean section operations is performed from 6 a.m. to 6 p.m. So the cesarean section rate could be related with a day of the week and a time of the day. From this results. there is a possibility that the physicians' personal comfort may influence the cesarean section rate.

• Honam Mathematical Journal
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• v.39 no.4
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• pp.515-525
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• 2017

In this paper, we study planar normal section curves. We have interpreted curvatures of normal section curves. On the other hand we have investigated sufficient and necessary conditions for a normal section curve to be biharmonic.

• Proceedings of the KTCVS Conference
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• 1993.06a
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• pp.13-13
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• 1993

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1470-1474
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• 2013

In this paper, proper length of neutral section and neutral section system configuration is proposed to minimize accidents if ATO urban railway vehicle stops maintaining the leading vehicles in air section at regular intervals. When considering the minimum voltage sensing of power conversion unit in the urban railway vehicle, the effective length of 14,280[mm] with neutral section can be minimized damage due to high current because the urban railway vehicle is very little present chance compare neutral section with pantograph interval installed on a unit vehicle. In addition, uplift of catenary line and contact wire consider to minimize damage. The result of theoretical review, as the proposed neutral section shorter, isolated neutral section is effective than the integrated neutral section.

• Journal of Information Processing Systems
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• v.7 no.4
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• pp.561-580
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• 2011

This paper describes different aspects of a typical RFID implementation. Section 1 provides a brief overview of the concept of Automatic Identification and compares the use of different technologies while Section 2 describes the basic components of a typical RFID system. Section 3 and Section 4 deal with the detailed specifications of RFID transponders and RFID interrogators respectively. Section 5 highlights different RFID standards and protocols and Section 6 enumerates the wide variety of applications where RFID systems are known to have made a positive improvement. Section 7 deals with privacy issues concerning the use of RFIDs and Section 8 describes common RFID system vulnerabilities. Section 9 covers a variety of RFID security issues, followed by a detailed listing of countermeasures and precautions in Section 10.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.149.2-149
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• 1998