• 한국물환경학회지
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• 제33권1호
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• pp.1-7
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• 2017

식생체류지는 도시 강우유출수 관리를 위한 저영향개발 및 그린인프라 기술이며, 개발이전의 상태를 최대한 유지하는 강우유출수 관리기술로 자연을 모방하면서 생태계의 다양성을 향상시키는 기술이다. 본 연구는 식생체류지의 물순환 능력과 비점오염물질의 저감효율에 영향을 끼치는 인자를 도출하기 위하여 4개의 식생체류지 시스템에 대하여 연구를 수행하였다. 2개의 식생체류지, 즉 Type A-C와 Type A-FC에는 국화와 매발톱꽃이 식재되었으며, Type B-A와 Type B-JM식생체류지에는 진달래 및 조팝나무와 같은 관목식물이 식재되었다. 연구결과 식생체류지의 유출저감, 저류량 및 오염물질 저감에 영향을 끼치는 인자로는 TV, 침투기작, 여과재의 두께와 식생 종류로 나타났다. Type B-A와 Type B-JM식생체류지 설계시에는 유출저감, 지하수 충진, 긴 체류시간과 첨두유출량 저감과 비점오염물질 저감을 고려하여 설계가 필요한 것으로 나타났다. 반면에 Type A-C와 Type A-FC 식생체류지 설계시에는 지하수 오염 저감을 중요하게 고려하여야 하는 것으로 나타났다.

• 한국산학기술학회논문지
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• 제20권1호
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• pp.217-223
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• 2019

국내외에서 점토층이나 준설토 등이 있는 연약지반을 개량하고, 그 지반위에 구조물을 건설하는 수요는 점차적으로 늘어나고 있다. 그리고 이러한 개발과 더불어 태풍, 산사태, 지진 등과 같은 자연재해의 빈도와 규모도 증가하고 있다. 이러한 자연재해로 인한 피해를 예방하기 위한 방법 중 하나가 지반개량공법이다. 본 연구에서는 쇄석을 띠기초 형식으로 설치하였을 때의 주변지반의 가속도 변화를 1-G 진동대 실험을 이용하여 분석하였다. 점토를 이용하여 지반을 조성하고 기초는 쇄석을 띠형식으로 설치하였다. 주기가 다른 입력지진파에 대해 응답가속도와 응답스펙트럼을 분석하였다. 쇄석 띠기초와의 인접거리에 따른 가속도 변화를 분석하여 지진시 쇄석 띠기초가 주변지반의 가속도 변화에 미치는 영향을 평가하였다. Hachinohe 지진파 결과에서는 쇄석띠기초와의 거리에 비해 가속도가 큰 감소는 없지만, 두가지 지진파에 대한 최대응답가속도가 쇄석띠기초와의 거리에 반비례하였다. 응답스펙트럼 분석결과, 장주기와 단주기 입력파에서의 감쇠되는 주기가 달랐으며, 이와 같은 응답스펙트럼 변화가 가속도의 최대가속도값에 영향을 준 것으로 판단된다. Hachinohe 지진파에서는 쇄석띠기초와 멀어질수록 0.08~0.5초 사이의 주기에서 감쇠가 컸으며, Northridge 입력파에서는 쇄석띠기초와 멀어질수록 0.2초 이내의 주기에서 감쇠가 컸다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.769-770
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• 2005

This study aims to demonstrate the practical value of radioscopic differentiation of materials. The dual energy method is proposed for identifying materials according to atomic numbers. The differentiation of materials is achieved by comparing the attenuation ratio of low and high energy photons. We used gamma-rays of 0.662 MeV and 1.25 MeV and NaI(Tl) scintillation detector with a Multi-channel Analyzer (MCA). We also carried out the Monte Carlo simulation for the case of bremsstrahlung radiation from dual electron beams of 4 MeV and 9 MeV.

• 상하수도학회지
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• 제29권1호
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• pp.77-88
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• 2015

Soil column experiments were evaluated effects of silver nanoparticles (i.e., 0, 2.5, 5, and 10 mg/L) on the microbial viability which is strongly associated with the degradation of organic matter, pharmaceutically active compounds(PhACs) and biological oxidation of nitrogenous compounds during river bank filtration. The addition of silver nanoparticles resulted in almost no change in the aqueous matrix. However, the intact cell concentration decreased with addition of silver nanoparticles from 2.5 to 10 mg/L, which accounted for 76% to 82% reduction compared to that of control (silver nanoparticles free surface water). The decrease in adenosine triphosphate was more pronounced; thus, the number and active cells in aqueous phase were concurrently decreased with added silver nanoparticles. Based on the florescence excitation-emission matrix and liquid chromatograph - organic carbon detection analyses, it shows that the removal of protein-like substances was relatively higher than that of humic-like substances, and polysaccharide was substantially reduced. But the extent of those substances removed during soil passage was decreased with the increasing concentration of silver nanoparticles. The attenuation of ionic PhACs ranged from 55% to 80%, depending on the concentration of silver nanoparticles. The attenuation of neutral PhACs ranged between 72% and 77%, which was relatively lower than that observed for the ionic PhACs. The microbial viability was affected by silver nanoparticles, which also resulted in inhibition of nitrifiers.

• Computers and Concrete
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• 제33권5호
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• pp.621-630
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• 2024

This study presents novel electromagnetic wave-based methods for evaluating the integrity of cement-based structures using time domain reflectometry (TDR). Two cement-based plates with embedded rebars are prepared under sound and defective conditions. TDR tests are carried out using transmission lines with various numbers of artificial joints, and electromagnetic waves are measured to assess the integrity of the plates. The experimental results show that the travel time of electromagnetic waves is consistently longer in sound plates than in defective ones, and an increase in the reflection coefficients is observed in the defect zone of the defective plates. Electromagnetic wave velocities are higher in the defective plates, especially when connectors are present in the transmission line. A novel approach based on the area of the reflection coefficient provides larger areas in the defective plates, and the attenuation effect of the electromagnetic waves induces a difference in the areas of the reflection coefficient between the two defect conditions. An alternative method using the centroid of the defect zone slightly overestimates the location of the defect zone. The length of the defect zone is estimated using the defect ratio and wave velocities of cement, air, and plate. The length of the defect zone can also be calculated using the travel times within the plate, total measured length of the plate, and wave velocities in the cement and air. Therefore, the electromagnetic wave-based methods proposed in this study may be useful for estimating the location and length of defect zones by considering attenuation effects.

• 한국산림과학회지
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• 제90권1호
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• pp.113-123
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• 2001

본 연구는 소나무림과 참나무림을 대상으로 수림대별 소음감쇄효과에 대한 기준을 제시하고자 수행되었다. 수림대별로 소음감쇄에 영향을 미치는 주요인자로 흉고직경, 수고, 지하고, 입목밀도, 수관면적, 경사, 거리 등을 상관과 회귀식에 의하여 분석하였으며 이로부터 얻어진 결과는 다음과 같다. 1. 참나무림과 소나무림의 소음감쇄효과를 비교한 결과 큰 차이를 발견할 수 없었다. 2. 임목형상조건과 거리는 소음감쇄와 높은 상관관계를 나타내었으나, 경사도와는 상관관계가 적은 것으로 나타났다. 소음에 대하여 가장 높은 상관관계를 갖는 인자는 소나무림의 경우 흉고직경(r=0.9133)과 거리(r=0.9630)이며, 참나무의 경우도 흉고직경(r=0.9296)과 거리(r=0.9565)로 나타났다. 3. 소나무림과 참나무림 모두 소음에 대하여 흉고직경과 거리의 2변수로 구성된 최적 회귀식을 도출하였으며, 회귀식을 통하여 소음감쇄표를 작성하였다. 소나무림의 경우 수림대의 폭이 5m에서 29%, 10m에서 31.6~32.6%, 20m에서 38.3~39.8%, 30m에서 45.2~46.6%의 감쇄율을 보였고, 참나무림의 경우 폭이 5m에서 29%, 10m에서 31.6~34.2%, 20m에서 38.6~41.4%, 30m에서 45~47.2%의 감쇄율을 보였다. 4. 주거지역 및 녹지의 경우에 맞는 소음의 환경기준은 55dB인 바, 이 기준에 맞추어 감쇄표에 의하면, 소나무림의 경우 거리가 20m일 때, 흉고직경의 합계가 400~450cm이고 본수가 30~35본이거나, 거리가 25m일 때, 흉고직경의 합계가 250~300cm이고, 본수가 20~25본 일 경우로 나타났으며, 참나무림의 경우에는 거리가 20m일 때, 흉고직경합계가 400cm이고 본수가 30~35본이거나, 거리가 25m일 때 흉고직경의 합계가 250~300cm이며 본수가 20~25본인 경우로 나타났다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 총회 및 춘계학술발표회
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• pp.503-508
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• 2004

Optimal remediation design using the pump and treat(P&T) method and natural attenuation was accomplished in consideration for degradation processes, such as sorption and first-order decay rate. Variation of both sorption and first-order decay rate has influence on design of optimal remediation application. When sorption effect increases, the more pumping rate and pumping wells are required. The location of operated wells is on the centerline of contaminant plume and wells near hot spot are mainly operated when sorption effect increases. The higher of first-order decay rate, the less pumping rate is required. These results show that the degradation processes have to be considered as one of the essential factors for optimal remediation design.

• 방사선산업학회지
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• 제4권4호
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• pp.391-395
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• 2010

The characteristics for pollutant transport in tidal influenced area was investigated using tidal wave hydraulic scale model. Hydraulic scale model was composed of the tidal generator, attenuation area and channel. Also, wave height, current meter and conductivity meter were used with the measured instruments in hydraulic scale model. NaCl with a tracer was used to evaluate the advection phenomena under the different velocity profiles. The arrival time of the maximum concentration in the condition of the relatively fast velocity was measured about 30 seconds faster than ones in the conditions of low velocity. The measured concentrations of the tracer were shown in the detection points of the flow direction consecutively.

• Wind and Structures
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• 제29권6호
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• pp.431-440
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• 2019

The aim of this study was to explore the influence of structure coupling effect on structural damping of blade based on the blade vibration characteristic. For this purpose, the scaled blade model of NREL 5 MW offshore wind turbine was processed and employed in the wind tunnel test to validate the reliability of theoretical and numerical models. The attenuation curves of maximum displacement and the varying curves of equivalent damping coefficient of the blade under the rated condition were respectively compared and analyzed by constructing single blade model and whole machine model. The attenuation law of blade dynamic response was obtained and the structure coupling effect was proved to exert a significant influence on the equivalent damping coefficient. The results indicate that the attenuation trend of the maximum displacement response curve of the single blade varies more obviously with the increase of elastic modulus as compared to that under the structure coupling effect. In contrast to the single blade model, the varying curve of equivalent damping coefficient with the period is relatively steep for the whole machine model. The findings are of great significance to guide the structure design and material selection for wind turbine blades.

• 한국지진공학회논문집
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• 제17권2호
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• pp.71-77
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• 2013

The uniform hazard spectra for seven major cities in Korea, Seoul, Daejeon, Daegu, Busan, Gwangju, Ulsan, and Inchon are suggested. Probabilistic seismic hazard analyses were performed using the attenuation equations derived from seismology research in Korea since 2000 and the seismotectonic models selected by expert assessment. For the estimation of the uniform hazard spectra, the seismic hazard curves for several frequencies and PGAs were calculated by using the spectral attenuation equations. The seismic hazards (annual exceedance probability) calculated for the 7 metropolises ranged from about $1.4305{\times}0^{-4}/yr$ to $1.7523{\times}10^{-4}/yr$ and averaged out at about $1.5902{\times}10^{-4}/yr$ with a log standard deviation of about 0.085 at 0.2 g. The uniform hazard spectra with recurrence intervals of 500, 1000, and 2500 years estimated by using the calculated mean seismic hazard on the frequencies presented peak values at 10.0 Hz, and the log standard deviations of the difference between metropolises ranged from about 0.013 to 0.209. In view of the insignificant difference between the estimated uniform hazard spectra obtained for the considered metropolises, the mean uniform hazard spectrum was estimated. This mean uniform hazard spectrum is expected to be used as input seismic response spectrum for rock sites in Korea.