• 한국물환경학회지
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• 제20권5호
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• pp.397-408
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• 2004

Due to the growing impact of non-point source pollution and limitation of water treatment technology, a new policy of water quality management, called a source protection, is now becoming more important in drinking water supply. The source protection means that the public agency purchases the pollution sensitive area, such as riparian zone, and prohibit locations of point and non-point sources. Many studies have reported that this new policy is more economical in drinking water supply than the conventional one. However, it is very difficult to determine location and size of the pollution sensitive zone in the watershed. In this paper, we presented the scientific criteria for the priority of the pollution sensitive zone, along with a case study of the upstream watershed of the Paldang Reservoir, Han River. This study includes applications of the analytical hierarchy process(AHP) and a watershed-based land prioritization(WLP) model. After major criteria affecting water quality were selected, the AHP and geographic analysis were performed. The WLP model allowed us to include both quantity and quality criteria, using AHP as the multi-criteria method in making decision and reflecting local characteristics and various needs. By adding a travel-time function, which represents the prototype effectively, the results secured adaptability and scientific objectivity as well. As such, the WLP model appeared to provide reasonable criteria in determining the prioritization of land acquisition. If the tested data are used with a validated travel-time and AHP method is applied after further discussion among experts in such field, highly reliable results can be obtained.

• 한국물환경학회지
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• 제35권6호
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• pp.470-480
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• 2019

The Doam lake watershed was designated as a non-point pollution management area in 2007 to improve water quality based on watershed management implementation. There have been studies of non-point source reduction with respect to the watershed management impacting the pollutant transport of the reservoir. However, a little attention has been focused on the impact of water quality improvement by the management of the dam operation or the guidelines on the dam operation. In this study, the impact of in-lake management practices combined with watershed management is analyzed, and the appropriate guidelines on the operation of the dam are suggested. The integrated modeling system by coupling with the watershed model (HSPF) and reservoir water quality model (CE-QUAL-W2) was applied for analyzing the impact of water quality management practices. A scenario implemented with sedimentation basin and suspended matter barrier showed decrease in SS concentration up to 4.6%. The SS concentration increased in the scenarios adjusting withdrawal location from EL.673 m to the upper direction(EL.683 m and EL.688 m). The water quality was comparably high when the scenario implemented all in-lake practices with water intake at EL.673 m. However, there was improvement in water quality when the height of the water intake was moved to EL.688 m during the summer by preventing sediments inflow after the rainfall. Therefore, to manage water quality of the Doam lake, it is essential to control the water quality by modulating the height of water intake through consistent turbidity monitoring during rainfall.

• Asian-Australasian Journal of Animal Sciences
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• 제25권11호
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• pp.1634-1640
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• 2012

The objective of this study was to compare pork characteristics and to determine consumer acceptability of pork chops from antibiotic free Yorkshire crossbreds sired by Berkshire (BY), Large Black (LBY), Tamworth (TY) or Yorkshire (YY) boars and reared in hoop houses. The experiments were conducted at the North Carolina Agricultural and Technical State University (NCA&TSU) Farm in Greensboro, NC and the Cherry Research Station Center for Environmental Farming Systems (CEFS) Alternative Swine Unit in Goldsboro, NC (source of antibiotic free Yorkshire sows used at both places). Twenty-four sows were artificially inseminated at each location in each of three trials. Litters were weaned at 4 wks old, and reared within deep-bedded outdoor hoop houses. To compare pork characteristics, 104 randomly selected animals were harvested at a USDA-inspected abattoir at approximately 200 d of age. Variables measured included pH, color score, $L^*$, $a^*$, $b^*$, marbling score, drip loss, hot carcass weight, backfat thickness (BF), loin muscle area (LMA), and slice shear force. Sensory panel tests were also conducted at two time periods. The data was analyzed with GLM in SAS 9.01 including location, trial, and sire breed as fixed effects. Backfat thickness, LMA, color score and $a^*$ were different among breeding groups (p<0.05). The LBY pigs had thicker backfat and smaller LMA than the other breed types. The TY and YY had less backfat than all other breed groups. Color score was lower for YY than BY and LBY but intermediate for TY. The $a^*$ was lower for TY than other breeds except LBY which was intermediate. For one sensory panel test, YY pork was more preferred overall as well as for juiciness and texture compared to BY and LBY (p<0.05), but no impact of breed type was noted for the other test, with values similar for BY, LBY, TY and YY pork. This information may help small farmers make decisions about breed types to use for outdoor production.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.17-22
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• 2006

Shear modulus is directly linked to material's stiffness and is one of the most critical engineering parameters. Seismically, shear-wave velocity (Vs) is its best indicator. Although methods like refraction, down-hole, and cross-hole shear-wave surveys can be used, they are generally known to be tougher than any other seismic methods in field operation, data analysis, and overall cost. On the other hand, surface waves, commonly known as ground roll, are always generated in all seismic surveys with the strongest energy, and their propagation velocities are mainly determined by Vs of the medium. Furthermore, sampling depth of a particular frequency component of surface waves is in direct proportion to its wavelength and this property makes the surface wave velocity frequency dependent, i.e., dispersive. The multichannel analysis of surface waves (MASW) method tries to utilize this dispersion property of surface waves for the purpose of Vs profiling in 1-D (depth) or 2-D (depth and surface location) format. The active MASW method generates surface waves actively by using an impact source like sledgehammer, whereas the passive method utilizes those generated passively by cultural (e.g., traffic) or natural (e.g., thunder and tidal motion) activities. Investigation depth is usually shallower than 30 m with the active method, whereas it can reach a few hundred meters with the passive method. Overall procedures with both methods are briefly described.

• 천문학회지
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• 제50권2호
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• pp.29-39
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• 2017

We investigate two abnormal CME-Storm pairs that occurred on 2014 September 10 - 12 and 2015 March 15 - 17, respectively. The first one was a moderate geomagnetic storm ($Dst_{min}{\sim}-75nT$) driven by the X1.6 high speed flare-associated CME ($1267km\;s^{-1}$) in AR 12158 (N14E02) near solar disk center. The other was a very intense geomagnetic storm ($Dst_{min}{\sim}-223nT$) caused by a CME with moderate speed ($719km\;s^{-1}$) and associated with a filament eruption accompanied by a weak flare (C9.1) in AR 12297 (S17W38). Both CMEs have large direction parameters facing the Earth and southward magnetic field orientation in their solar source region. In this study, we inspect the structure of Interplanetary Flux Ropes (IFRs) at the Earth estimated by using the torus fitting technique assuming self-similar expansion. As results, we find that the moderate storm on 2014 September 12 was caused by small-scale southward magnetic fields in the sheath region ahead of the IFR. The Earth traversed the portion of the IFR where only the northward fields are observed. Meanwhile, in case of the 2015 March 17 storm, our IFR analysis revealed that the Earth passed the very portion where only the southward magnetic fields are observed throughout the passage. The resultant southward magnetic field with long-duration is the main cause of the intense storm. We suggest that 3D magnetic field geometry of an IFR at the IFR-Earth encounter is important and the strength of a geomagnetic storm is strongly affected by the relative location of the Earth with respect to the IFR structure.

• 환경영향평가
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• 제9권3호
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• pp.163-176
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• 2000

The purpose of this study is to analyze the pollutant loads and its distribution, and to suggest the management of nonpoint sources in Daechong Reservoir. The loads from point and nonpoint sources such as population, industry, livestock and land use were calculated per stream or river with topography(1:25,000) of the watershed of Daechong Reservoir. The generating pollutant loads were obtained through multiplication of pollutant sources by generating pollutant quantity per unit pollutant source. The effluent point sources loads is defined as loads from wastewater treatment facilities such as domestic, industrial and livestock wastewater treatment facilities, which were calculated through multiplication of effluent flowrates by water quality constituents concentration. Untreated point sources loads were estimated to be 35 % of total point sources loads. The effluent nonpoint sources pollutant loads were obtained through the multiplication of generating nonpoint sources loads by effluent ratios based on previous studies. The effluent nonpoint sources loads have the ratio of 26.2% of total BOD effluent loadings, 20.1% of total T-N effluent loadings, and 10.5% of total T-P effluent loadings. For the reduction of nonpoint sources loads in Daechong Reservoir, silviculture, artificial wet land, and grassed waterways could be applied. And untreated livestock waste scattered can result in nonpoint loadings, so required the livestock wastes treatment facilities and purifying facilities together with the management of shed, pasture, livestock waste storage site and composting site. Finally, remote sensing and GIS should be applied to the identification of distribution of water quality, watershed, the location and scale of nonpoint sources, effluent process during rainfall, for more detailed analysis of nonpoint sources.

• 터널과지하공간
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• 제25권6호
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• pp.568-576
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• 2015

본 연구에서는 압축공기에너지저장 설비를 운영함에 있어 위험성이 크다고 분석된 '내조시스템 파손에 따른 압축공기 유출'과 '접근갱도 내 화재 발생' 리스크를 대상으로 시나리오를 작성하여 분석을 실시하였다. Bernoulli 방정식과 운동량 방정식을 결합하여 압축공기 분출에 따른 충격력을 계산하기 위한 식을 유도하였다. 이 식을 바탕으로 시나리오를 작성하여 충격력을 계산한 결과 충격력은 균열 직경의 제곱 및 압축공기의 압력에 비례하는 것으로 나타났다. 계절의 변화 및 화원의 위치에 따른 연기 확산 거동을 분석하기 위하여 4가지의 화재 시나리오를 작성하였다. 저장 공동 벽면 근처에서 화재가 발생한 경우는 10 m 떨어진 지점에서 화재가 발생한 경우보다 연기가 호흡한계선까지 하강하는 데 소요되는 시간이 더 짧은 것으로 나타났는데 이는 연기 파선단 전파로 인해 발생한 것으로 예측된다. 갱내로의 공기 유동 방향에 따라 연기의 확산 거동이 달라지기 때문에 겨울에 화재가 발생한 경우는 여름에 발생한 경우보다 연기의 확산속도가 빠르고 더 멀리까지 연기가 퍼지는 것으로 나타났다. 피난 시뮬레이션 해석 결과 여름과 겨울 화재에서의 피난요구시간(RSET)은 각기 262, 670 s로 분석되었다.

• 동력기계공학회지
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• 제3권3호
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• pp.60-69
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• 1999

The noise and vibration sources of rotary compressor for room air-conditioner are pressure pulsation of compression process, cavity resonance of inner space, structural radiation noise of shell and impact noise of discharge valve. Among them, pressure pulsation is very important noise and vibration source. Because it transferred various kinds of noise and vibration like as mentioned above. In this reason, muffler and resonator are used in order to absorb and remove these noises. But an analytical prediction using acoustic analysis does not coincident with the experimental result. The difference between analysis and actual state is due to the assumption of analysis. This paper covered with new concept of muffler design based on the turbulence kinetic energy of flow by using CFD. From this analysis, it is possible to decide the best position of discharge port of muffler. Therefore $2{\sim}3dB$ noise reduction effect is acquired in rotary compressor of 5000 BTU grade. Also new approach of resonator design is suggested. From this study, the characteristics of resonator and surge hole (a kind of resonator without pipe length) are identified. The former is useful for pure tone noise (narrow frequency band), and the latter is effective for broad frequency band. This paper shows that it is very available to use 3 dimensional analysis of resonator in order to predict more exact tuning frequency. The result is proved by a lot of experiments. From combination of fluid analysis and acoustic analysis, up stream position is effective location of resonator concerning turbulence motion of fluid.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.90-94
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• 2021

주거지에서의 정숙함에 대한 관심이 높아짐에 따라 구조물에서 발생하는 소음을 최소화할 필요가 있다. 중요한 소음원 중 하나는 엘리베이터 작동 소음이다. 엘리베이터는 층 사이에서 작동하며 인근 생활 공간에 상당히 성가신 소리를 생성한다. 입주민들에게 성가심을 유발하는 주요 소음원으로 인식되고 있다. 엘리베이터는 층간 이동을 위해 여러 위치에서 건물 구조에 지지되어 있다. 본 연구에서는 지지 위치에 폴리머 콘크리트를 사용하여 진동을 감소시키는 것을 실증하였다. 시멘트 콘크리트와 폴리머 콘크리트에 지지했을 때의 진동 발생량을 측정 및 비교하여 소음 저감 성능을 평가하였다. 폴리머 콘크리트는 승강로를 모방한 벽에 삽입되는 형태로 제작되었다. 브라켓에 충격진동을 인가하고 진동전달크기를 측정하였다. 감쇠비는 과도응답의 정규화 및 곡선맞춤을 통해 평가하였고, 각 레진 혼합 질량비에 대하여 비교하였다. 폴리머 콘크리트를 사용하여 구조적 강성에 대한 손실 없이 효과적인 방식으로 진동 발생을 감소시킬 수 있다.

• 한국지반신소재학회논문집
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• 제21권3호
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• pp.21-27
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• 2022

최근 탄소중립을 위하여 친환경 에너지원인 수소 에너지에 대한 연구 개발 및 인프라 구축에 대한 관심이 증가되고 있다. 특히, 도심지에 설치되는 수소충전소의 경우에는 수소저장탱크 폭발에 따른 인접 구조물의 안정성을 확보하기 위하여 폭발 위험이 있는 수소저장탱크를 지하(지중)에 배치하여 충분한 안전거리를 확보하는 방안이 고려되고 있다. 적절한 지하 수소인프라의 위치 및 심도를 선정하기 위하여 지하 수소인프라 폭발에 따른 인접 구조물의 영향 평가가 필요하다. 본 논문에서는 지하 수소인프라 폭발에 따른 인접 구조물의 영향을 분석하기 위한 수치모델을 구축하였으며, 등가 TNT (Trinitrotoluene) 모델을 활용하여 수소저장탱크의 폭발압을 산정하였다. 또한, 매개변수해석을 수행하여 지하 수소인프라의 시공조건에 따른 인접 구조물의 안정성을 평가하였다.