• 전기학회논문지
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• 제67권4호
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• pp.498-504
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• 2018

The conventional photovoltaic(PV) systems are designed the installation angle for maximizing power output by considering a geographical characteristics, weather and climate conditions such as the solar radiation and atmosphere temperature. However, the PV generators must be designed to deal with the extreme situations like typhoons, earthquakes because PV systems are exposed to the ambient conditions and external shock due to condition of PV location. Especially, the wind has relatively higher influence on the design of PV systems, in this paper we proposed the method of determining the optimal nominal dimension of the facilities, which can withstand the maximum wind pressure. By using the proposed method, we determined the optimal installation angle for the aspect stability of PV facilities and amount of power output. Moreover, we analyzed the monthly amount of power for each installation angle of PV systems, and proposed the changing strategy of installation angle by determining the optimal angle to produce maximum power for each period.

• 한국항공우주학회지
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• 제31권4호
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• pp.76-81
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• 2003

Kerosene/LOX를 추진제로 사용하는 액체로켓의 추력실에서 발생하는 열유속을 측정하기 위하여 calorimetric combustion chamber를 제작하여 연소실험을 수행하였다. 본 실험에 사용된 calorimetric combustion chamber는 연소실 및 노즐 부분이 각각 하나의 구역으로 제작되었으며, 각각의 구역에서 발생하는 열유속을 측정하기 위하여 냉각제의 출구에 열전대를 설치하였다. 실험은 O/F ratio 2.0에서 연소압 100psi에서 300psi까지 수행하였다. 본 실험에서 연소실에서 복사 열전달은 고려하지 않았다. 측정된 열유속은 연소압에 다라 거의 선형적인 변화를 보였다.

• 한국소음진동공학회논문집
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• 제24권9호
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• pp.695-705
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• 2014

In this paper, two types of techniques for the prediction of radiated sound pressure due to vibration of a structure are investigated. The prediction performance using wave-number sensing technique is compared to that of conventional prediction method, such as Rayleigh's integral method, for the prediction of far-field radiated sound pressure. For a coupled plate, wave-number components are predicted by the vibration response of plate and the prediction performance of far-field sound is verified. In addition, the applicability of distributed sensors that are not allowable to Rayleigh's integral method is considered and these can replace point sensors. Experimental implementation verified the prediction accuracy of far-field sound radiation by the wave-number sensing technique. Prediction results from the technique are as good as those of Rayleigh's integral method and with distributed sensors, more reduced computation time is expected. To predict the radiated sound by the efficient configuration of structural sensors, composed(synthesized) mode considering sound power contribution is determined and from this size and location of sensors are chosen. Four types of sensor configuration are suggested, simulated and compared.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.37-43
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• 2014

Nuclear power plants(NPPs) are consisted of power production functions and safety functions preventing leakage of radiation. Operators working in NPPs shall maintain these functions during an operation period through various activities such as improvement & modification, corrective maintenance, preventive maintenance and surveillance test. According to the performance of these work activities, there are configuration changes in NPPs systems. Its changes cause the increase of safety risks(CDF) and plant trip risks. Recently, the importance of risk management is increasing gradually in the operation process of NPPs. Therefore, this paper presents the work management methods using the various risk monitoring systems during power operation and overhaul period. Also this paper suggests the optimum application ways of risk systems for work management.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.537-553
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• 2016

This paper addresses the safety of two-row tank design by performing the extensive sloshing model tests. Owing to the uncertainties entangled with the scale law transforming the measured impact pressure up to the full scale one, so called comparative approach was taken to derive the design sloshing load. The target design vessel was chosen as 230 K LNG-FPSO with tow-row tank arrangement and the reference vessel as 138 K conventional LNG carrier, which has past track record without any significant failure due to sloshing loads. Starting with the site-specific metocean data, ship motion analysis was carried out with 3D diffraction-radiation program, then the obtained ship motion data was used as 6DOF tank excitation for subsequent sloshing model test and analysis. The statistical analysis was carried out with obtained peak data and the long-term sloshing load was determined out of it. It was concluded that the normalized sloshing impact pressure on 230 K LNG-FPSO with two-row tank arrangement is higher than that of convectional LNG carrier, hence requires the use of reinforced cargo containment system for the sake of failure-free operation without filling limitation.

• 한국재료학회지
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• 제30권4호
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• pp.155-159
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• 2020

Nanoporous silica aerogel insulation material is both lightweight and efficient; it has important value in the fields of aerospace, petrochemicals, electric metallurgy, shipbuilding, precision instruments, and so on. A theoretical calculation model and experimental measurement of equivalent thermal conductivity for nanoporous silica aerogel insulation material are introduced in this paper. The heat transfer characteristics and thermal insulation principle of aerogel nano are analyzed. The methods of SiO₂ aerogel production are compared. The pressure range of SiO₂ aerogel is 1Pa-atmospheric pressure; the temperature range is room temperature-900K. The pore diameter range of particle SiO₂ aerogel is about 5 to 100 nm, and the average pore diameter range of about 20 ~ 40 nm. These results show that experimental measurements are in good agreement with theoretical calculation values. For nanoporous silica aerogel insulation material, the heat transfer calculation method suitable for nanotechnology can precisely calculate the equivalent thermal conductivity of aerogel nano insulation materials. The network structure is the reason why the thermal conductivity of the aerogel is very low. Heat transfer of materials is mainly realized by convection, radiation, and heat transfer. Therefore, the thermal conductivity of the heat transfer path in aerogel can be reduced by nanotechnology.

• 한국소음진동공학회논문집
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• 제12권1호
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• pp.42-47
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• 2002

Sirocco fans are widely used in HVAC and air conditioning systems, and the noise generated by these machines causes one of the most serious problems. In general, the sirocco fan noise is often dominated by tones at BPF(blade passage frequency) and broadband noise. However, only a few researches have been carried out on predicting the aeroacoustic noise because of the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a sirocco fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson\`s method is used to predict the acoustic source. Reasonable results are obtained not only fur the tonal noise but also far the amplitudes of the broadband noise. Acoustic pressure is proportional to (Ω)2.3, which is the similar value with the measured data.

• 상하수도학회지
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• 제20권5호
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• pp.755-761
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• 2006

Recently, there is growing interest in ultraviolet (UV) irradiation as a disinfection technic in drinking water production due to its effectiveness to inactivate microorganisms such as Crytosporidium parvum without forming disinfection byproducts. However, UV disinfection is known for its drawback such as photoreactivation. Despite many works concerning the photoreactivation, most of works were focused on indicator or non pathogenic microorganisms. The objective of this study is to examine the photoreactivation of Pseudomonas aeruginosa which is an opportunistic pathogen as UV radiation by LP and MP UV lamp was applied. The result showed that P. aeruginosa had high photo repair efficiency regardless of the type of UV irradiation. Both of the effective log repair values of LP and MP UV irradiation were found approximately 2.6 log. In addition, photo repaired P. aeruginosa was not significantly different in forming biofilm in comparison with non treated P. aeruginosa.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1174-1180
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• 2015

We investigate in this paper the radiated electromagnetic waves together with the discharge characteristics of Trichel pulse of negative DC corona discharge in air in pin-to-plate and wire-to-plate configurations. The feature of the current pulse and the frequency spectrum of the electromagnetic radiations were measured under various pressures and gas gaps. The results show that the repetition frequency and the amplitude of Trichel pulse current depend on the discharge conditions, but the rising time of the pulse relates only to the radius of needle or wire and keeps constant even if the other conditions (including the discharge current, the gas gap and the gas pressure) change. There exists the characterized spectrum of electromagnetic waves from negative corona discharge in Trichel pulse regime. These characterized radiations do not change their frequency at a given cathode geometry even if the averaged current, the gas gap or the air pressure changes, but the amplitude of radiations changes accordingly. The characterized electromagnetic radiations from Trichel pulse corona relate to the formation or the rising edge of current pulse. It confirms that the characterized radiations from Trichel pulse supply information of discharge system and provide a potential method for detecting charged targets.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.286-291
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• 2000

The reactor pressure vessel is usually cladded with stainless steel to prevent corrosion and radiation embrittlement, and number of subclad cracks have been found during an in-service-inspection. Therefore assessment for subclad cracks should be made for normal operating conditions and faulted conditions such as PTS. Thus, in order to find the optimum fracture assessment procedures for subclad cracks under a pressurized thermal shock condition, in this paper, three different analyses were performed, ASME Sec. XI code analysis, an LEFM(Liner elastic fracture mechanics) analysis and an EPFM(Elastic plastic fracture mechanics) analysis. The stress intensity factor and the Maximum $RT_{NDT}$ were used for characterizing. Analysis based on ASME Sec. XI code does not completely consider the actual stress distribution of the crack surface, so the resulting Maximum allowable $RT_{NDTS}$ can be non-conservative, especially for deep cracks. LEFM analysis, which does not consider elastic-plastic behavior of the clad material, is much more non-conservative than EPFM analysis. Therefore, It is necessary to perform EPFM analysis for the assessment of subclad cracks under PTS.