• 소음진동
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• 제8권6호
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• pp.1043-1052
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• 1998

The noise sources in the outdoor unit of RAC are identified by the sound intensity method. The main noise sources are compressor noise and fluid noise which is caused by the fan. heat exchanger and shroud. First. the fluid noise is reduced through the design of new fan and shroud. reduction of the system resistance by rearrangement of heat exchanger. and optimization of the complex parameter between the fan and shroud. Next, in order to reduce the compressor noise, the new shape of compressor mount and sound-proof material was applied. As a result, the overall noise was reduced by 4∼5dB (A).

• Smart Structures and Systems
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• 제10권2호
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• pp.155-179
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• 2012

This paper aims at assessing the seismic performance of Tuned Mass Dampers (TMDs) based on sets of recorded ground motions. For the simplest configuration of a structure-TMD assembly, in a comprehensive study characteristic response quantities are derived and statistically evaluated. Optimal tuning of TMD parameters is discussed and evaluated. The response reduction by application of a TMD is quantified depending on the structural period, inherent damping of the stand-alone structure, and ratio of TMD mass to structural mass. The effect of detuning on the stroke of the TMD and on the structural response is assessed and quantified. It is verified that a TMD damping coefficient larger than the optimal one reduces the peak deflection of the TMD spring significantly, whereas the response reduction of the main structure remains almost unaffected. Analytical relations for quantifying the effect of a TMD are derived and subsequently evaluated. These relations allow the engineer in practice a fast and yet accurate assessment of the TMD performance.

• 한국환경과학회지
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• 제28권11호
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• pp.1027-1032
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• 2019

This study aimed to analyze the prioritized area for the functional change of agricultural reservoir according to the rapid urbanization and social changes through the mapping method. Changwon-si, Gimhae-si, and Jinju-si in Gyeongnam province were selected as the study area, considering the results of land-use and cluster analysis. As the planning unit of management area, watershed was used and land coverage map from 1975 to 2015 were analyzed for changes of land use. The reduction ratio (%) of farmland was calculated for identifying the changes in 2013 compared to 1975. As a result, the reduction ratio was 11.9% for Changwon-si, 12.2% for Gimhae-si and 9.3% for Jinju-si, and the number of watershed having functionally reduced potential-area was relatively high in the proportion to the city size.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.121-129
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• 2005

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate of amount proportional to the failure intensity, which increases since the last PM and slows down the wear-out speed to that of new one. And the proportion of reduction in hazard rate decreases with the number of PMs. Our model is similar to $ARI_1$ proposed by Doyen and Gaudoin(2004) in the sense of reduction of hazard rate. Our model has totally different wear-out pattern of hazard rate after PM's, however, and the proportion of reduction depends on the number of PM's. Assuming that the system undergoes only minimal repairs at failures between PM's, the expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• 한국건축시공학회지
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• 제13권6호
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• pp.609-618
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• 2013

The unit modular construction system is a building technique in which unit modules are manufactured at a factory and then assembled at the construction site. It has many benefits, including reduction of the construction period and improvement in quality. For this reason, it is utilized for various purposes in Japan and England. While it has been introduced in Korea, there have been few Korean studies conducted on the unit modular system. In particular, little research has been done on the method of safely fixating the unit modules to a truck. Therefore, this study reviewed the fixation methods of unit modules for transport, analyzed the problems, and designed a fixation device for unit modules. In addition, a device for the fixation of unit modules to a truck was developed, and a structural simulation was implemented for a safety test by considering the maximum stress generated during the transport of the unit modules fixed on a truck. When the device for the fixation of unit modules is manufactured based on the results of the structural simulation done in this study, it is expected to aid the development of a more practical fixation device for unit modules.

• Architectural research
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• 제19권4호
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• pp.101-108
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• 2017

The use of the air conditioner is increasing due to the rise of the outdoor temperature during summer, and the problems of the fire and the cooling performance deterioration are caused due to lack of maintenance of the outdoor unit. In particular, overall performance of cooling system and efficiency in outdoor units have been degraded due to an intake of high-temperature outdoor air thereby increasing cooling energy and operating cost. Thus, this study aimed to increase efficiency of outdoor units by evaporating and cooling intake air through mist spray at the intake port surface in the outdoor unit. The measurements results showed that total power consumption of misting outdoor unit compared to that of conventional outdoor units was reduced by 21% approximately, and total power consumption of the entire system including pump was reduced by 16.7%. In addition, the operating cost including water use was reduced by 13.5% approximately. In summary, if a mist-spray nozzle kit is installed in air-cooled outdoor units, the reduction in the usage of cooling energy and operating cost will be achieved without replacement of existing cooling systems or a large scale of repairs.

• Journal of applied mathematics & informatics
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• 제9권2호
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• pp.869-877
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• 2002

In the presence of unit nonresponse we perform the calibration estimation procedure for the population total corresponding to the levels of auxiliary information and derive the Taylor and the Jackknife variance estimators of it. We study the nonresponse bias reduction and the variance stabilization, and then show the efficiency of the Taylor and the Jackknife variance estimators by simulation study.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제42권
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• pp.35.1-35.6
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• 2020

Background: Miescher's cheilitis granulomatosa (MCG) is a rare chronic inflammatory disease and is known as the monosymptomatic clinical form of Melkersson-Rosenthal syndrome (MRS). It is characterised by swelling of one or both lips and more frequently affects the upper lip. Histopathological findings show the presence of numerous inflammatory infiltrates and granuloma formations. Pharmacological treatments and surgery have provided results that are positive yet insufficiently stable in the long term. The clinical case described is of a 68-year-old female patient with a diagnosis of MCG of the upper lip. Case presentation: The patient was diagnosed and treated at the Oral Medicine and Oral Pathology outpatient clinic of Maxillofacial and Odontostomatology Unit, Fondazione Cà Granda IRCCS Ospedale Maggiore Policlinico. The patient was recommended localised treatments of photobiomodulation (PBM) using a diode laser with a 635 nm and 980 nm dual-wavelength (λ) approach, a 600-micron fibre, and a handpiece with a 1-cm-diameter lens at 300 mW. Three treatments a week were administered for four weeks for a total of 12 treatment sessions (T₁-T₁₂). After that, the patient had a long follow-up period of about 2 years. The therapeutic results were clear from the initial stages of treatment. There was an immediate, gradual, and consistent reduction in labial swelling. A reduction in the size of the lip by about 35% at T₁₀-T₁₂ was observed, returning the size and volume of the upper lip within the normal clinical range. The painful symptoms subsided after the seventh treatment (T₇). The histopathological check at 3 months and the follow-up in particular confirmed the disease was in remission with satisfactorily stable treatment results. Moreover, the patient did not use any other treatments on the area from the early laser treatments through to the end of the follow-up period. Conclusions: Our experience describes a clinical case of MCG treated with PBM and effectively resolved with a reduction of the lip swelling. The real success of the treatment emerged over time, showing that the tissue healing was stable. In absence of any collateral phenomena, this confirms the effective and documented therapeutic potential of PBM for chronic inflammatory infiltrates.

• 청정기술
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• 제21권2호
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• pp.96-101
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• 2015

수소를 환원제로 사용한 산화철의 유동 환원에서, 환원율에 대한 다양한 공정 변수를 통해 산화철의 하나인 적철광의 환원 거동을 면밀히 관찰하였다. 본 연구를 위해 특별히 설계된 실험실 규모의 유동층 장치에서 목적으로 하는 환원 특성에 대한 가스 속도, 환원 시간 및 온도의 최적 값을 평가 하였다. 최적의 환원율을 나타낸 온도는 750 ℃, 환원 시간은 30분이며 이들을 다음의 시험을 위한 시작점으로 매개 변수 값을 설정 하였다. 가장 높은 관심을 갖는 변수들 중 하나는 가스의 소비 원단 위로, 이는 최적의 조건에서 산화철 1톤을 기준하여 90% 이상의 환원율을 달성하기 위해 요구되는 가스의 양을 말한다. 이 매개 변수는 실험실 수준 장치의 스케일 엎에 있어서 중요한 인자이며, 본 연구를 통해 1,500 Nm³/ton-ore가 산화철이 가장 높은 환원율을 갖기 위한 최적의 가스 소비 원단위 임을 확인하였다.

• 대한토목학회논문집
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• 제32권5B호
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• pp.273-285
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• 2012

현행 수질오염총량관리제는 원인자부담원칙를 기본으로 설정된 단위유역별 지자체별 할당부하량을 해당 지자체가 개별적으로 대처하도록 하고 있다. 그러나 하천으로 유입되는 수질오염물은 공기오염물과 달리 상류에서 하류로 일방적으로 흐르고, 하나의 하천에 다수의 지자체가 연관이 되어 있으며, 일반적인 하수처리시설은 '규모의 경제'를 따르는 시설물임을 감안한다면 지자체간 협조를 통해 수질관리비용을 절감할 수 있다. 본 연구는 유역 전체의 관점에서 비용효과를 가질 수 있도록 삭감량을 재배분함으로써 수질관리비용을 절감하는 방법을 제시하였다. 이를 위해 영산강 유역을 대상으로 현재 단위유역별 지자체별로 할당된 계획삭감량을 총량의 증감없이 오염원이 집중된 지역으로 재배분하여 발생하는 수질개선 효과와 비용절감 효과를 분석하였다. 분석결과, 기존 계획에 의한 영산강 유역 전체의 비용은 787,575.0 백만원이며, 시나리오-1과 2는 각각 123,671.8 백만원, 171,433.5 백만원의 비용이 절감되었다. 본 연구는 오염총량관리제를 준수하기 위한 지자체의 수질관리 비용을 절감하는 방안으로서 사례가 될 것으로 기대된다.