• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.914-918
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• 2008

연안지역의 갑작스런 개발은 예상치 못한 여러 가지 문제들을 발생시키고 있다. 이와 같은 문제들 중에서 가장 심각한 문제는 해안침식이다. 해안침식은 어떤 원인에 의해 토사의 평형이 손상되어 퇴적되는 양보다 더 많은 양이 유실되면서 해안선이 점점 후퇴하는 현상이다. 해안에 쌓여 있는 모래는 태풍과 폭풍해일로부터 육지를 보호하는 완충지대의 역할을 하고, 또한 관광자원으로도 그 활용가치가 증가하고 있기 때문에 침식현상을 분석하고 침식의 발생 및 진행을 억제하기 위한 연구가 반드시 필요하다고 하겠다. 본 연구에서는 해안침식을 제어하기 위한 기초적인 연구의 일환으로 연안류에 따른 연안표사의 분포특성에 대하여 살펴보았다. 연안류는 표사 이동이 가장 활발한 쇄파대로부터 해안선 사이에서 발생하는 흐름으로 파랑에 의해 발생한다. 일정경사를 갖는 해빈에 대해 연안류를 계산하고 계산된 연안류를 Komar(1977)가 Bagnold(1963) 모형을 이용하여 파의 응력과 흐름속도의 곱의 함수로 연안표사의 분포를 나타나낸 식에 대입하여 연안류에 따른 연안표사의 분포를 계산하였다.

• Journal of Biosystems Engineering
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• v.24 no.1
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• pp.31-40
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• 1999

The objective of this study were to develop a cooling simulation model for fixed-bed of rough rice and to analyze the factors affecting cooling time of rough rice. A computer simulation model based on equilibrium conditions between grain and air was developed to predict temperature and moisture content changes during cooling of rough rice. the result of t-test showed that there were no significant differences between predicted and measured temperature changes on significance model agreed well with measured values. This cooling simulation model was applied to analyze the effect of some factors, such as air flow rate, cooling air temperature and humidity, initial grain temperature and moisture content, and bed depth, on cooling time of rough rice. Cooling rate increased with increase of air flow rate and bed depth whereas it decreased with increase of cooling air temperature and humidity and initial grain temperature. Among these factors, the most important factor was air flow rate. Specific air flow rate of 0.35㎥/min㎥ was required for cooling rough rice in 24 hours.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1181-1192
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• 2008

A laboratory investigation was carried out into effects of strain rate on undrained shear behavior of Holocene clay underneath Kobe Airport with an objective to evaluate the factor of safety of the retaining structure built on it. It was examined in a series of triaxial compression and extension tests performed using different rate of axial straining. A comparative compression test in which the strain rate was changed in steps was also carried out. Similar tests were performed in constant-volume direct shear box (DSB) test. And, the deformation characteristics of the clay were also examined in order to evaluate the variation of stiffness during undrained shearing. It was found that the undrained strength increased with not only the shear rate but also the consolidation period. ISOTACH properties seemed a key to govern the undrained shear behavior.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.65-70
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• 2018

본 연구에서는 2차원 수치모형을 통해 보의 설치 각도 변화에 대한 보 상하류에서 흐름특성 변화와 하도 변화를 정량적으로 분석하였다. 수치모의 결과, 흐름은 경사형보를 월류하면서 경사진 방향으로 굴절되었으며, 보의 설치 각도가 증가할수록 흐름의 굴절 각도가 증가하는 경향을 보였다. 또한 보의 설치 각도가 증가할수록 무차원유속은 감소하였다. 보의 보 상류에서는 보의 의해 형성된 배수의 영향이 끝나는 지점에서 유사가 퇴적되어 델타가 발달하였다. 델타는 흐름방향을 따라 하류로 이동하였다. 이동속도는 보에 가까워질수록 감소하며, 크기는 증가하였다. 보 하류에서는 무차원 보의 길이가 증가함에 따라, 무차원 사주의 파장이 감소하고, 무차원 사주의 파고는 증가하였다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.125-137
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• 1997

To study the vertical variation of heavy metal and Rare Earth Element (REE) contents in deep-sea sediments, eighteen cores were sampled from the Korea Deep-sea Environmental Study (KODES)-96 area in the C-C zone (Clarion-Clipperton fracture zone), northeast equatorial Pacific. Sediment columns can be divided into three units based on sediment colors and geochemical characters; uppermost Unit I with brown color, middle Unit II with pale brown color and smaller Ni/Cu ratio than the ratio in Unit I, and lowermost Unit III with dark (brown) colors and higher contents of Mn, Ni, Cu, and REEs than those in Unit I and II. Unit II can be divided more into two layers of upper Unit IIa and lower Unit IIb. Unit IIb is characterized by high contents of Cu, 3+REEs (REEs except Ce), smectite, and severely deteriorated fossil tests. Unit III can also be divided into two units; upper Unit IIIa with dark brown color, and lower Unit IIIb with black color and enriched Mn and Fe. The KODES area was located near from the East Pacific Rise (EPR) When Unit III Sediments were deposited, considering the hiatus between Unit II and III (Quaternary-Tertiary boundary) and the spreading rate (10 cm/yr) and direction (north southern west) of the Pacific plate from the EPR. High contents of Mn and Fe in Unit IIIb may be related with hydrothermal influence from the EPR. Meanwhile, Unit IIb (about 2~3 Ma) and Unit III (11~30 Ma) layers were probably formed near (or under) the equatorial high productivity zone, and accordingly received a lot of organic materials. As a result, Cu and 3+REEs, closely associated with organic materials, are enriched in smectite and/or Ca-P composites (fish bone debrise, biogenic apatite) after decomposition and reprecipitation on the sea floor. Higher contents of Cu and 3+REEs in Unit IIb and III are suggested to be the result of abundant supply of organic substances in the equatorial high productivity zone.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.341-352
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• 2013

The physical and mechanical properties of red shale and black shale exposed in the Daegu area were investigated in tests conducted to determine unit weight, absorption ratio, porosity, ultrasonic velocity, unconfined compressive strength, point load strength, slake durability index, and deterioration characteristics. XRD, XRF, and SEM analyses were also performed on the shale specimens. While the unit weights of the two shales were similar, the absorption ratio and porosity were higher in the red shale than in the black shale. Despite the higher porosity of the red shale, the ultrasonic velocity, compressive strength, and point load strength were higher in the red shale, which is an unexpected result that may be due to the presence of fine laminations in the black shale. The deterioration rate, as determined from the point load strength and the slake durability index, increased with increasing immersion time and with the acidity of the immersion liquid. The deterioration rate was higher for the red shale than for the black shale because of the higher porosity of the former.

• Journal of Animal Environmental Science
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• v.9 no.2
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• pp.79-84
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• 2003

1.퇴비 온도의 상승에 비례하여 폐사계 체내의 온도도 상승하여 퇴적식 퇴비단의 경우 $55^{\circ}C$내외의 고온지속기간이 약 30일정도 유지되었다. 반면에 토양 중에 매립된 폐사계의 체내 온도는 발효 전 기간 동안 $30^{\circ}C$ 이상으로 상승하지 못한 채 주변토양 온도와 거의 비슷한 수준을 유지하였다. 토양온도는 외기온의 변화에 즉각적인 반응을 보이지 않았다. 2. 시험용 발효조 내에서의 송풍여부에 따른 퇴비의 발효온도 변화추이는 송풍 처리구에서는 퇴비화 3일째에 최고온도 $68^{\circ}C$를 기록한 반면에 무송풍구에서는 퇴비화 5일째에 최고온도 $72^{\circ}C$를 기록하였다. 3. 퇴비단 표층에서 채취된 시료에서 검출된 $H_2S$와 $CH_3$SH 농도는 송풍 처리구에 있어서는 퇴비화 개시 후 20일 경과 후 각 각 28.5, 16.0 ppb 수준을 나타냈고 35일 경과 시에는 각각 57.7, 11.7 ppb, $CH_3SH$의 경우에는 23.7, 9.9 ppb 수준의 발생량을 기록하는 등 전반적으로 송풍처리구가 무송풍 처리구에 비해 악취가스의 발생량이 상대적으로 낮았다. 4. 폐사계를 밀폐용기 내에서 발표 시 수거된 침출수 중의 미생물 수가 토양매립 상태 하에서 수거된 침출수 중의 미생물 수보다 더 적은 경향을 보이고 있다. 5. 퇴비단 내에서 발효에 따른 폐사계 중량은 최초 3일간에 급격히 감소하고 시간의 경과에 따라 그 감소속도는 줄어든다. 발효온도가 높을수록 조직의 분해속도가 빨라지고 폐사계의 중량감소 속도도 빨라졌다. 6. 일반 퇴비와 폐사계를 발효시킨 퇴비 사이에 비료성분과 중금속 함량의 유의적인 차이는 발견되지 않았다.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.4
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• pp.302-309
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• 2000

These experiments have been conducted to study the effect by microbial inoculums currently on the market of enhancing the decomposition of organic matters. As a result of studying the effect of enhancing the decomposition of rice straw and chicken manure mixed with saw dust treated with commercial inoculums, it was found that the use of inoculums have speeded up the rate of decomposing straws at the early stage. The decomposition rate of rice straws that have speeded up with the use of comcrial inoculums in at early incubation periods has slow down in the later stage while the decomposition rate of chicken manure that has slowed down in the early stage has speeded up at the later incubation. As a result, it is found that there have been no differences between the use of microbial inoculums and control. In the experiment, filamentous fungus is found to have played an important role in decomposing the rice straws and bacteria is considered to have played a greater role in the decomposition of chicken manure mixed with saw dust.

• Membrane Journal
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• v.13 no.2
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• pp.88-100
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• 2003

A change of filtrate flux in Taylor vortex flow filtration was investigated experimentally by rotating speed of inner cellulose ester membrane cylinder (average pore size: 1.2 ${\mu}m$), slurry concentration, and particle size. The filtrate flux was a direct proportion relation with TMP, but an inverse relation with resistances. A change of cake resistance with time was examined by rotating speed, slurry concentration, and particle size. Initial resistance increased dramatically as raising slurry concentration, and the pseudo-steady state was maintained at high resistance value. However, times to reach the pseudo-steady state did not depend on slurry concentration. The resistance was larger as smaller particle size, because possibility of pore blocking inside membrane could be higher and shear effect should be lower as smaller particle size. A model equation suggested in this study was composed of particle deposition and removal terms, and could confirm well experimental data using average values of experimental coefficients.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.34-40
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• 2005

We have used the microtremor method, with arrays of up to 96 m diameter, to carry out non-invasive estimation of shear-wave velocity profiles to a depth of 30 to 50 m in unconsolidated Quaternary Yarra Delta sediments. Two silt units (Coode Island Silt, and Fishermans Bend Silt) dominate our interpretation; the method yields shear velocities for these units with precision of $5\%$, and differentiates between the former, softer unit ($V_s$=130 m/sec) and the latter, firmer unit ($V_s$=235 m/sec). Below these silts, the method resolves a firm unit correlating with known gravels ($V_s$ 500 to 650 m/sec). Using surface traverses with the single-station H/V spectral ratio method, we show that the variation in thickness of the softer silt can be mapped rapidly but only qualitatively. The complexity of the geological section requires that array methods be used when quantitative shear-wave velocity profiles are desired.