• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1184-1194
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• 2007

Recently, framed structure is increasingly being used as apartment structure due to the advantages during remodeling. Therefore, the use of lightweight panel as separating wall is increasing. To construct lightweight panel structures with sound insulation performance appropriate to the conditions of each field, measurement of sound reduction index(SRI) through panel structures should be performed. In this study, measurement of SRI through 46 kinds of panel structures was performed in the condition of various factors such as surface density, air space and absorber. The result showed that SRI of panel structures was generally higher by increasing of surface density. In the case of double panel with no absorber, SRI at below critical frequency was gradually increased according to rise of air space. Double panel with absorber make remarkable improvement in SRI at low frequency, but there is a little difference compared with SRI of double panel with no absorber over critical frequency.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.35-38
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• 2021

Conventional direct current (DC) rotating machines are usually used for crane and press machine using high torque in metal and steel industries, because of a constant output power along variable rotating speed. A general DC motor with permanent field magnets could not increase a magnetic flux density at a gap between armature coils and field magnets. However, a superconducting DC motor has field magnets composed with high temperature superconducting (HTS) coils and it could increase the magnetic flux density at the gap to over 10 times than those of a general DC motor by control the excitation current into HTS coils. The superconducting DC motor could be operated with extremely high torque and constant output power at a low rotational speed. In this paper, a 500 W superconducting DC rotating machine was conceptually designed with a LN₂ (Liquid Nitrogen) cooling method and the operation characteristics results of HTS field magnets were presented. The two no-insulation HTS magnets for a 500 W superconducting DC rotating machine were fabricated. The excitation current for the HTS magnets could be controlled from 0 to 40 A. This test results will be available to design large-sized HTS magnets for a number of hundred kW class superconducting DC rotating machine under LN₂ cooling system.

• Journal of Chest Surgery
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• v.20 no.3
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• pp.483-488
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• 1987

Phrenic nerve injury has been reported with the use of iced slush for topical cardiac hypothermia. A review of the preoperative and the postoperative chest roentgenograms was performed to detect phrenic nerve injury in patients undergoing cardiac operation with the use of iced slush for topical hypothermia from January, 1985 to June, 1987. The reviewed series included 45 patients who had undergone valve replacement. In this review, the injured site of phrenic nerve was left in 13 cases, right in 1 case and the overall incidence of phrenic nerve paralysis following open heart surgery was 31%. Compared to the incidence of phrenic nerve paralysis in the control group [without pericardial insulation] [406, 12 cases/30 cases], that in the group of patients receiving pericardial insulation [13.3%, 2 cases/15 cases] was lower, but there was no statistical significance. The initial time that diaphragmatic paralysis developed was mean 3.5 days [range 1-8 days] postoperatively and the recovery time of the paralysis was mean 4.7 months [range 0.5-10.5 months] postoperatively.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.913-918
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• 2001

This paper investigates insulating effects and strength properties of concrete under cold climate carrying out the experiment with insulating forms on the slab member. According to test results, under $-10^{\circ}C$ of outer temperature, the surface of concrete exposed to outer temperature goes below zero after 10hours since exposed. And, the surface of concrete covered with vinyl and blanket goes below zero after 42hours. However, the surface of concrete covered with insulating materials such as polystyrene foam does not drop below zero until 55hours. And, according to coring sample strength test, compressive strength cured with insulation shows much higher strength than no insulation curing condition and vinyl and blanket curing condition.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1396_1397
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• 2009

Recently, there has been considerable interest in electromagnetic pulse (EMP) source for no lethal directed energy weaponry applications. The compactness of the Marx generator, coupled with its ability to be powered by battery technology, makes it a viable handled impulse source. The marx generator has 2 stages. Each stage was constructed one charging capacitor, two electrodes and one charging resistor. A inductance structure is used in order to improve the switching performances fo the whole generator. The experiments of rise time in pure gas and mixtures of gases were described. The experimental results show that the rise time characteristics of the marx generator can be controlled through varying insulation gas.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2010.05a
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• pp.71-72
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• 2010

The study is compared temperature history and strength of concrete followed by covering method of insulation curing of cold weather concrete with double bubble sheet. The results were as follows. First of all, in temperature history of concrete, the internal temperature of concrete fell down to $0^{\circ}C$ before/after 60 hours, having nothing to do with covering method. The study could see that, when sheet was isolated, it fell down to low temperature quickly in early curing. When the study measured compressive strength of core specimen, there were no large differences among placing methods. However, compressive strength fell down in all ages when sheet was isolated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.255-256
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• 2011

This study investigates the effect of a curing condition on the temperature history and strength development of concrete under -10℃. Combination of various curing methods was applied, i.e. a conventional form was combined with compressed insulation, heat panel and heat cable. Results showed that the concrete cured by a single use of a conventional form resulted in serious deterioration of early strength development. However, other concretes cured by the proposed curing methods maintained the temperature of the concretes between 5 and 20℃, and thus resulted in no frost damage.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.54-61
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• 2004

The purpose of this study is to improve of energy performance in school buildings. Many building renovations have mainly focused on commercial buildings and houses, but school buildings have no attention in this field although there are many buildings that show degraded energy performance and there are many old fashioned buildings which need renovation. This study was carried out through the survey, field study, energy simulation and life cycle cost analysis. The results of this study can be summarized as follows: In model building, large amount of heat were lost at the building envelope, such as non-insulated skins, window-sills and window-frame joints. According to the simulation result, about 15％ of heating energy is saved by the insulating works compared to pre-renovation condition. Also, LCC analysis revealed to be more effective to select a exteria wall insulation such as a dryvit system.

• Proceedings of the KIEE Conference
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• 2004.11d
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• pp.83-88
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• 2004

As the electric system is getting larger to meet the increasing demand for electric power, the rating of power apparatus is becoming inevitably higher in its working voltage and larger in its capacity. According to KEPCO reports, power transformers in the KEPCO system have undergone troubles such as winding short insulation breakdowns every year since 1981. the cause of this troubles were high one line grounding fault currents in KEPCO systems that had direct grounding systems. KEPCO has installed the NGR(neutral grounding reactor) to lower this fault current and reduced winding short insulation breakdowns in power transformers. But when a circuit breaker opened a no load bus, some trips of circuit breakers for protecting transformer have occurred by mal-operation of 59GT(overvoltage ground relay) that detect disconnection of NGR. Therefore, in this paper, we analyzed the cause and examined the effect of time delav circuit to prevent wrong operation of 59GT.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.18-19
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• 2014

NORWAY 해역에서 시추 및 생산 작업을 위한 시추선 및 생산 설비의 경우, 엄격한 기준인 NORSOK 기준을 만족해야 한다. NORSOK 기준은 선원들의 안전과 안락성을 위한 Working Environment 만족을 요구하고 있다. 특히 선원들의 거주구역에 안락성은 더욱 중요시되고 소음의 기준을 제시하고 만족을 요구한다. Cabin Unit 이 적용되는 선박의 경우 실선과 동일 조건의 Mock Up 을 제작하여 차음성능 계측 및 평가를 실시한다. 본 논문에서는 NORSOK 이 적용되는 선박의 Cabin Unit 의 Mock Up 차음성능 만족 사례를 소개하고자 한다.