• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.67-74
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• 2010

Most of domestic low-voltage consumers are supplied from the TN-C system of KEPCO, but their load installations have established according to the national statutory standard for electrical installations based on the TT system. In this work, to propose the proper system earthing arrangements of ensuring the protection of information-technology equipment against lightning surges, the protection performance of TT and TN systems against lightning surges was investigated. As a result, when lightning surge was injected to the neutral line of distribution system, the potential difference between the equipment earth terminal and neutral point of low-voltage mains in a TT system was significantly raised. The TT system is not advised due to the risk of damage to the sensitive computer equipment. Main equipotential bonding is an important requirement for protection of low-voltage installations against lightning surges. The TN system provides the best means to reduce the incoming lightning surges through the neutral line of low-voltage service systems. In addition, It is highly recommended to install the additional earthing at the service position of low-voltage consumers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.599-609
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• 2021

A novel grounding system, which is presented in IEC 60364, has been adopted since 2021. A safety evaluation for the human body on the grounding system is required due to the various characteristics of the touch voltage and current passing when the human body experiences an electric shock. The Korea Electrical Safety Corporation (KESCO) and Korea Electric Association (KEA) have been conducting a safety technical education on the grounding system. On the other hand, it is difficult to instruct the electrical safety manager because of a lack of safety evaluations for the test equipment on the grounding system. Therefore, this paper modeled and implemented a test device for a safety evaluation depending on the grounding system of IEC 60364. Namely, this paper presents the modeling of the test device for a safety evaluation using PSCAD/EMTDC S/W, which is composed of an AC grid section, s test device section on the grounding system, and a sub-device section. This paper implemented a test device for safety evaluation, which consisted of an AC grid section, TT grounding system section, TN-S grounding system section, and monitoring section. From the simulation and test results with the safety characteristics of the human body in the TT and TN-S grounding system, when the fault impedances are 0[Ω], 10[Ω], and 100[Ω], the currents passing through the human body in the TT grounding system are 104[mA], 87.4[mA], and 35.5[mA], respectively. The corresponding currents in the TN-S grounding system are 54.9[mA], 4.1[mA], and 0.4[mA], respectively. Based on the results, the protection performance for an electric shock to the human body in the TN-S system is better than the TT system. This can be improved when the existing grounding system is changed from the TT system to the TN-S system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.650-658
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• 2017

A grounding system in a large-scale apartment complex consists of a TT grounding system when viewed in each building unit, but the characteristics of TN grounding system appears when viewed in the total ground system function. Therefore, this study examined the characteristics of a grounding system in a large-scale apartment complex using design draft, field measurements and PSCAD/EMTDC modeling. This paper proposes an algorithm for fault analysis depending on the grounding system structure in large-scale apartment complexes considering the connection of the underground culvert as well as a design algorithm for each grounding system considering the contact voltage and step voltage. The simulation results based on the proposed modeling and algorithm confirmed that it is useful for analyzing the characteristics of a grounding system in a large-scale apartment complex.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.140-143
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• 2001

As global trade system transferred GATT into WTO, the harmonization of technological standards, certification, construction, testing is the trend of world. This drift is based on WTO / TBT agreement coming. In effect after 12th, April, 1979. For Korea, the distribution system has a strong resemblance to American system so that engineers are confused in adopting standards. IEC60364 and NEC are in part similar but unconvertible because IEC 60364 originated from Europe while NEC originated from USA. This thesis deals with the fundamental elements of electrical safety system with comparing IEC 60364 with NEC. It serves as a guide how to apply standards when engineers select electrical installations.

• Journal of radiological science and technology
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• v.39 no.4
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• pp.615-622
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• 2016

The 18~20G needle is used to computer tomography (CT) contrast examination. Therefore, a patient has to apply a self-administering hemostasis (conventional method: CM) and often experience bleeding in the course. Thus, we developed the new disposable transparent tourniquet (TT) for reducing. This study was to compare the usefulness between the proposed transparent tourniquet and the existing hemostatic methods. A Satisfaction survey was conducted by 50 patients and 25nurses. The survey contained the satisfaction of the convenience, safety, sanitation, and wearing sensation of transparent tourniquet. We employed face-to-face interview on 5 points likert scales. And Chi-square, paired T-test were used for the statistics verification. As for the patients, the satisfaction levels were measured for each category with the gender, age. Patients evaluation, overall satisfaction high average sore used TT and there were statistical significance by paired T-test(p<0.05). The following is the average satisfaction level for each category: $4.4{\pm}0.53$ in; $4.28{\pm}0.57$ in safety; $4.52{\pm}0.54$ in sanitation; $4.16{\pm}0.54$ in wearing sensation. So the overall satisfaction level is measured at $4.34{\pm}0.51$. As for the nurses, CT work experience and the current satisfaction with tourniquet were counted as variables. The satisfaction level for each category is: $3.8{\pm}0.7$ in; $3.6{\pm}0.68$ in safety; $3.4{\pm}0.5$ in sanitation; $3.9{\pm}0.49$ in hemostasis. The overall satisfaction level is $3.8{\pm}0.3$. Patients' satisfaction levels were very high with little difference among variables. Nurses' satisfaction levels were different with the TT depending on their work experience but their overall satisfaction was high. This TT will be a starting point to minimizing patient's inconvenience and more studies are necessary to enhance their satisfaction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.609-614
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• 2009

The TT&C communication subsystem of STSAT-3 is consisted of communication link to send telemetry data of spacecraft to the ground station and receive command data from ground station. The S-band receiver is used to receive command data from ground station, Engineering Qualification Model of S-band receiver has been designed and manufactured. The Designed S-band Receiver uses a single conversion for a simple frequency conversion, including a DC-DC Converter and EMI Filter. Also, Digital demodulation part designed using FPGA and RS-422 data interface. The performance of S-band Receiver in functional and space environments test satisfies the requirements of STSAT-3.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.187-191
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• 2008

Transgranular stress corrosion cracking of nickel base alloys was reported by Copson and Dean in 1965. Study to establish this cracking mechanism needs to be carried out. Laboratory stress corrosion tests were performed for mill annealed(MA) or thermally treated(TT) steam generator tubing materials in a high temperature water containing lead. An electrochemical interaction of lead with the alloying elements of SG tubings was also investigated. Alloy 690 TT showed a transgranular stress corrosion cracking in a 40% NaOH solution with 5000 ppm of lead, while intergranular stress corrosion racking was observed in a 10% NaOH solution with 100 ppm lead. Lead seems to enhance the disruption of passive film and anodic dissolution of alloy 600 and alloy 690. Crack tip blunting at grain boundary carbides plays a role for the transgranular stress corrosion cracking.

• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.334-342
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• 2016

In order to evaluate the modified installation methods of roof ventilation devices, derived from the previous experiment ('investigation into the optimum capacity of roof ventilation devices and their deployment'), the conventional and modified (improved) roof ventilation systems were installed in the single-span plastic greenhouse for growing oriental melons. The roof vents ($60{\varphi}$) and roof fans (maximum air capacity of $38m^3/min$) were installed in the spacing of 15m (FT, modified 'side vent+roof fan' ventilation) and 6m (TT, modified 'side vent+roof vent' ventilation) respectively on the roof of greenhouses for the modified roof ventilation treatments, and 20m (FC, conventional 'side vent+roof fan' ventilation) and 8m (TC, conventional 'side vent+roof vent' ventilation) for the conventional ones. The stem diameter, leaf blade lengh, petiole length, and leaf width were lower in the FT and TT treatments than those in the conventional treatments, FC and TC. Although the fruit weight and total yields were slightly lower in the FT and TT treatments, the marketable fruit ratio (%) were higher, as a result of increased fruiting ratio (%) in these treatments, than those of FC and TC. The marketable yields (kg/10a) in the FT and TT treatments were 8,391 kg/10a and 7,283 kg/10a, which were respectively 661 kg/10a and 487 kg/10a higher than those in the treatments of FC and TC. The modified installation methods of roof fan resulted in production of more female flowers and lower fruit drop ratio (%) compared to conventional meathods. In the treatment of the conventional ventilation with roof vent, the fruit weight, fruit length & width, and flesh thickness were higher than in other treatments, but there were no significant differences in the fruit width and flesh thickness among the treatments.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.363-365
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• 2014

기존의 알람 어플리케이션은 음향 효과를 통한 자극이라는 단순한 방식으로 과거와 같거나 알람 해제 방식이 유사한 알람 어플리케이션들이다. 이러한 기존의 방식을 벗어나, 알람을 해제하려는 사용자에게 질문을 하고 그에 대한 답변을 Google TTS로 입력받아 알람을 끌 수 있도록 하였다. 또한 알람 종료 시 블루투스 통신을 이용하여 사용자가 입력한 값에 따라 아두이노를 통하여 실내의 조명과 커튼을 제어하여 더 효과적인 알람 효과를 낼 수 있도록 구현하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.668-671
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• 1995

In this study, the fatigue charateristics of weld specimen was studied experimentally by using the various specimen types. The specimen type were tensile shesr(TS) specimen, cross tension(CT) specimen, and T typr (TT) specimen. Tensile test and fatigue test were carried out and microstucture was investigated. Finite element method was used to investigate stress distribution near nugget edge. Finally fracture mechanics approach was tried to the various specimen types.