• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.928-938
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• 2008

Though services requiring Quality-of-Service (QoS) guarantees such as Voice over Internet Protocol (VoIP) have been widely deployed on the internet, most of internet backbone networks, unfortunately, do not distinguish them from the best-effort services. Thus estimating the effective capacity meaning the traffic volume that the backbone networks maximally accommodate with keeping QoS guarantees for the services is very important for Internet Service Providers. This paper proposes a test-bed based on ns-2 to evaluate the effective capacity of backbone networks and then estimates the effective capacity of an experimental backbone network using the test-bed in terms of the service standard of the VoIP service. The result showed that the effective capacity of the network is estimated as between 12% and 55% of its physical capacity, which is depending on the maximum delay guarantee probability, and strongly affected by not only the type of offered workload but also the quality standard. Especially, it demonstrated that in order to improve the effective capacity the maximum end-to-end delay requirement of the VoIP service needs to be loosened in terms of the probability to guarantee.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.216-218
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• 2001

The transformer role is very important in power system operation and control; also its price is very expensive. Therefore many kinds of the efforts for transformer protection have been executed. So for as, current differential relay(87) has been mainly used for transformer protection. But current differential relaying method has several troubles as followings. Differential current can be occurred by transformers inrush current between winding1 and winding2 of transformer when transformer is initially energized. Also harmonic restrained element used in current differential relaying method is one of the causes of relays mal-operation because recently harmonics in power system gradually increase by power switching devices(SVC, FACTS, DSC, etc). Therefore many kinds of effort have been executed to solve the trouble of current differential relay and one of them is method using ratio of increment of flux linkages(RIFL) of the primary and secondary windings. This paper introduces a novel protective relay for power transformers using RIFL of the primary and secondary windings. Novel protective relay successfully discriminates between transformer internal faults and normal operation conditions including inrush and this paper includes real time test results using RTDS(Real Time Digital Simulator) for novel protective relay. A novel protective relay was designed using the TMS320C32 digital signal processor and consisted of DSP module. A/D converter module, DI/DO module, MMI interface module and LCD display module and developed by Xelpower co., Ltd.

• Journal of ILASS-Korea
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• v.14 no.4
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• pp.147-152
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• 2009

Since a liquid-phase LPG injection system allows accurate control of fuel injection and increase in volumetric efficiency, it has advantages in achieving higher engine power and lower emissions compared to the mixer type LPG supplying system. However, this system also leads to an unexpected event called icing phenomenon which occurs when moisture in the air near the injector freezes and becomes frost around the nozzle hole due to extraction of heat from surrounding caused by instant fuel vaporization. As a result, it becomes difficult to control air/fuel ratio in engine operation, inducing exacerbation of engine performance and HC emission. One effort to mitigate icing phenomenon is to attach anti-icing injection tip in the end of nozzle. Therefore, in this study, the effect of engine operation parameters as well as surrounding conditions on icing phenomenon was investigated in a bench test rig with commercially-used anti-icing injection tips. The test results show that considerable ice was deposited on the surface near the nozzle hole of the anti-icing tip in low rpm and low load operating conditions in ambient air condition. This is because acceleration of detachment of deposited ice from the tip surface was induced in high load, high rpm conditions, resulting in decrease in frost accumulation. The results of the bench testing also demonstrate that little or no ice was formed at surrounding temperature below a freezing point since the absolute amount of moisture contained in the intake air is too small in such a low temperature.

• Journal of Digital Convergence
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• v.15 no.12
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• pp.615-623
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• 2017

The purpose of this study was to investigate the factors affecting quality of sleep among middle-aged male workers. The participants of this study were 127 middle-aged male workers working in Jeonnam region, and the data were collected through self-reported structured questionnaire. Descriptive statics, t-test, one-way ANOVA, Pearson correlation coefficient and step wise multiple regression with SPSS/WIN 18.0 were used to analyze the data. According to the results, among the variables related to sleep quality, job stress showed a positive correlation, and job satisfaction showed a negative correlation. In addition, the factors such as job demands, occupational climate, job itself explained the quality of sleep at 24.5%. Based on the findings from the study, in order to improve the quality of sleep program for middle-aged male workers should be combined both strategies to increase job satisfaction and to decrease job stress. It is believed that the effort to reduce the amount of work needed to improve the quality of sleep will be necessary and the efforts among members of the organization will be necessary to establish a healthy workplace.

• Journal of Digital Convergence
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• v.14 no.12
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• pp.257-265
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• 2016

This study is the descriptive survey to understand the knowledge, attitude, and education needs of the university students on the dementia and to examine their relationships. Collected data were analyzed using t-test, ANOVA, and Pearson's correlation coefficients with the SPSS 20.0 for Windows Program. The rate of corrective answers on dementia was shown as 79.6%, mean attitude with 3.74 points, and mean education needs with 4.02 points. Significant positive correlations were detected between the knowledge and the attitude (r=.23, p=.005), and between the attitude and education needs (r=.61, p<.001). Based on the results of this study, it is required to make an effort to enhance the correct knowledge of the university students on dementia and to establish their positive attitude. The objective education needs proven by this study are expected to be used as the fundamental data for the development of customized education program for the university students.

• Korean Journal of Social Welfare
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• v.47
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• pp.272-309
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• 2001

It is a recent trend to emphasize community services for the rehabilitation of the mentally ill. However, it is also necessary to provide social work services for those living in the institutions, who is the most underprivileged in our society. To deal with interpersonal skill deficits which is one of the main characteristics of the mentally ill, social skills programs are being utilized, usually in the communities, but not in the institutions. Therefore, the objective of this study is to develop and evaluate institution-relevant program for the improvement of assertiveness, which is the basic ability among the interpersonal skills, and self-esteem, which is the emotional basis of assertiveness. Because there has been little literature on such a program, a preliminary program had been implemented in order to include the peculiarities of the life in the institutions on the main program. The evaluation of the program effect was done by pretest-post test control group design, and its results are as follows. Firstly, in regard to program effectiveness, the pre and post test showed that self-esteem improved in a statistically meaningful way, but that assertiveness did not so. However, the staff verified the improvement of the group members' assertiveness to some degree in their actual lives. Secondly, in regard to the group process, the group interaction improved in a statistically meaningful way between 2nd and 5th session, and the improvement maintained till the program termination. Also the group members evaluated the program as helpful in their everyday lives. Therefore it can be said that the result of this program is encouraging. In light of this, several suggestions were made: utilizing more dynamic techniques in the program; developing the advanced level of the program; making an effort to change environmental structures as well as individuals; applying this kind of program to another living facilities such as those for the homeless or handicapped.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.322-326
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• 2003

Dae-gu subway accident raise whole points in connection with safety facilities and operating of national urban transit system like rolling stocks, facilities, management of human. Rolling stock is made every effort for improvement of performance, guarantee of comfortableness, insurance of economical efficiency. But Security like safety of fire is not thoroughgoing enough. Especially, interior material has used although it is not prove its degree of safety. it is a main cause of Dae-gu subway accident. Safety regulation of urban transit vehicle that legislate for security in March 2000 does not applied manufacturing vehicles before in 2000. It has be prescribed in the regulations that incombustibles must be used. But detailed test standard related with incombustibles is not prescribe. Thus that regulation be required reinforcement of detailed test standard. Main cause of Dae-Gu subway accident is a fire in vehicle. However, many defects are found in infrastructure and operating vehicle of urban transit, such as inexperienced disposal of driver and CCC in early stage of the fire accident, unskilled opening and closing doors, insufficient escape facilities and safety facilities of a station house and tunnel, and incomplete communication system between vehicle and CTC, extraordinary step. Thus the aims of this study are prevention of urban transit accident, improvement plan of safety driving, and proposal of quick action plan through analysis of total faculty of vehicle.

• Food Science and Preservation
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• v.16 no.5
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• pp.782-788
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• 2009

The genotoxicological safety of gamma-irradiated egg white and yolk was examined to ensure that required safety parameters were met, and in an effort to further apply gamma-irradiation for improvement of the hygienic qualities of eggs. Egg white and yolk were irradiated at 20 kGy, much higher than the legally approved dose (less than 5 kGy), and possible genotoxicity was evaluated using in vitro and in vivo tests. The SOS chromotest employing Escherichia coli PQ37, and a chromosomal aberration test in cultured Chinese hamster lung (CHL) cells, were performed in vitro with or without metabolic activation (S9). An in vivo micronucleus development test was conducted using mouse bone marrow cells. Negative results were obtained in the SOS chromotest. The incidence of chromosomal aberration in CHL cells and the frequency of micronuclear developmentin mouse bone marrow cells treated with irradiated samples were not significantly different from those of non-irradiated controls. Thus, it may be concluded that up to 20 kGy of gamma irradiation applied to egg white and yolk did not show any genotoxic effects under our experimental conditions.

• Progress in Superconductivity and Cryogenics
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• v.16 no.2
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• pp.29-32
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• 2014

The critical current, $I_c$ of HTS superconducting tapes can be measured by transport or contactless method. Practically, the transport method using the four-probe method is the most common. In this study, a simple test procedure by clipping the voltage lead taps have been introduced instead of soldering which reduces time and effort and thereby achieving a much faster measurement of $I_c$. When using a pair of iron clips, $I_c$ value decreased as compared with the measured one by standard method using soldered voltage taps and varies with the width of the clipped specimen part. However, when using a pure Cu clip, both by clipping and by soldering voltage taps give a comparable result and $I_c$ measured are equal and close to the samples specification. As a result, material to be used as voltage clip should be considered and should not influence the potential voltage between the leads during $I_c$ measurement. Furthermore, the simulation result of magnetic flux during $I_c$ measurement test showed that the decrease of $I_c$ observed in the experiment is due to the magnetic flux density, $B_y$ produced at the clipped part of the sample by the operating current with iron clips attached to the sample.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.368-372
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• 2007

Recently, construction companies prefer to use large scale system forms to prepare for lacking of skilled workers, aging and the chances of application of pre-build&post-sale policy. In result of the effort and interest, the duration for framework of domestic high rise buildings has been accomplished to 3-4days per floor but for the apartment housing which form over 90% of the domestic construction industry, and especially the middle story RC apartments which is the main part, the duration for framework is only about 6-8days per level. This is only about 50% of the duration per level of RC residential buildings in North America. In previous researches elementary technology, which has potential of duration reduction, was proposed and this research suggest the applicability in construction sites and ways to improve it using elementary technology applied Mock-up Test. Furthermore, we analyze the productivity and T/C usage rate of the 6day-Cycle and suggest an improved model.