• Advances in environmental research
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• 제3권3호
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• pp.231-251
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• 2014

The present study examines the phosphate adsorption potential and behavior of mixture of Ground Burnt Patties (GBP), a solid waste generated from cooking fuel used in earthen stoves and Red Soil (RS), a natural substance in fixed bed column mode operation. The characterization of adsorbent was done by Proton Induced X-ray Emission (PIXE), and Proton Induced ${\gamma}$-ray Emission (PIGE) methods. The FTIR spectroscopy of spent adsorbent reveals the presence of absorbance peak at $1127cm^{-1}$ which appears due to P = O stretching, thus confirming phosphate adsorption. The effects of bed height (10, 15 and 20 cm), flow rate (2.5, 5 and 7.5 mL/min) and initial phosphate concentration (5 and 15 mg/L) on breakthrough curves were explored. Both the breakthrough and exhaustion time increased with increase in bed depth, decrease in flow rate and influent concentration. Thomas model, Yoon-Nelson model and Modified Dose Response model were used to fit the column adsorption data using nonlinear regression analysis while Bed Depth Service Time model followed linear regression analysis under different experimental condition to evaluate model parameters that are useful in scale up of the process. The values of correlation coefficient ($R^2$) and the Sum of Square Error (SSE) revealed the Modified Dose Response model as the best fitted model to the experimental data. The adsorbent mixture responded effectively to the desorption and reusability experiment. The results of this finding advocated that mixture of GBP and RS can be used as a low cost, highly efficient adsorbent for phosphate removal from aqueous solution.

• 기술사
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• 제44권1호
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• pp.44-47
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• 2011

Huge amount of energy produced by an underground nuclear test is released into the surrounding rock. Depending on the properties of the bed rock surrounding the detonation and overlaying it a variety of effects can occur. At some particular depth the increasing amount of material thrown upward is exactly balanced by the decreasing fraction escaping the crater, the crater volume reaches to a maximum. This depth is called the optimum depth of burial and varies somewhat with the geology of the site, being greater for less dense and structurally weaker material.

• Water Engineering Research
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• 제4권2호
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• pp.99-109
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• 2003

Since bed elevation changes are mainly dependent on the flow velocity and corresponding shear stress, it is possible to predict bed elevation numerically using velocity components. For the scour analysis due to channel contraction, a bed load transport model is developed and applied to estimate scour depth around coffer dam in the Mississippi River. During Phase I of the Lock & Dam No. 26 replacement project, a coffer dam was constructed to reduce the flow area approximately by 50%. Flow velocity increases due to the flow area reduction yields significant lowering (erosion) of the channel bed elevation. The proposed numerical model solves the sediment continuity equation using the finite element method to evaluate scour process in the vicinity of the coffer dam

• 물과 미래
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• 제26권4호
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• pp.107-115
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• 1993

본 연구는 3가지 교각형상에 대하여 국부적 정지상세굴에 대한 수리실험결과를 분석한 것이다. 실험결과에 의하면 국부적 상대세굴심은 교각형사, 하상입경의 기하표준편차, 유속비, 교각 푸르드수와 관계가 있는 것으로 나타났다. 교각의 상대세굴심은 반원사각형교각에서 가장 작고 하상재료가 균일할 때 보다 불균일할 때 현저하게 작게 나타났다. 입도의 불균일성으로 인한 세굴감소효과는 Raudkivi와 Ettema의 연구결과와 비교 검토하였다.

• Ocean and Polar Research
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• 제30권4호
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• pp.537-543
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• 2008

The sediment resuspension and diffusion model is an integral part of a sediment transport and morphologic change model. We examined a vertical one-dimensional sediment resuspension and diffusion model using field data collected at about 10-m depth off the Saemangeun $4^{th}$ dike. The field data include waves, currents and suspended sediment concentration near the bed for about a day in May, 2007. The suspended sediment concentration obtained from the 1D model overestimated the observation about two orders of magnitude with single grain size and multiple grain sizes. The incorporation of the bed armoring effect, which adjusts the amount of suspended sediment with the available bed sediment, improved the agreement between the model and observation within a factor of two.

• 한국해양공학회지
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• 제11권1호
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• pp.106-112
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• 1997

This paper describes the development of a test-bed vehicle named TAUV which can be a tool to evaluate the performance of a new control algorithm, operating software and the characteristics of sensors for an AUV. The test-bed AUV is designed to operate at depth of ten meters. It is 19.5kg in air and neural buoyancy in water and the dimension is $535{\times}400{\times}102mm$. TAUV is equipped with a magnetic compass, a biazial inclinometer, a rate gyro, a pressure sensor and an altitude sonae for measuring the motion of the vehicle. Two horizoltal thursters and two elevators are installed in order to propel and control the AUV. This paper persents the control system of TAUV which is based on a 16 bit single-chip microprocessor, 80c196kc, and the software architecture for the operating system. Experimental results are included to verify the performance of the TAUV.

• Carbon letters
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• 제11권1호
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• pp.13-21
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• 2010

Coconut shell activated carbon (CSAC) was investigated for its ability in the removal of two neutral chlorinated organic compounds, namely trichloroethylene (TCE) and dichloromethane (DCM) from aqueous solution using a packed bed column. The efficiency of the prepared activated carbon was also compared with a commercial activated carbon (CAC). The important design parameters such as flow rate and bed height were studied. In all the cases the lowest flow rate (5 mL/min) and the highest bed height (25 cm) resulted in maximum uptake and per cent removal. The experimental data were analysed using bed depth service time model (BDST) and Thomas model. The regeneration experiments including about five adsorption-desorption cycles were conducted. The suitable elutant selected from batch regeneration experiments (25% isopropyl alcohol) was used to desorb the loaded activated carbon in each cycle.

• Geomechanics and Engineering
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• 제4권2호
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• pp.79-90
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• 2012

Air pluviation method is widely adopted for preparation of large, uniform and repeatable sand beds of desired densities for laboratory studies to simulate in-situ conditions and obtain test results which are highly reliable. This paper presents details of a portable traveling pluviator recently developed for model sand bed preparation. The pluviator essentially consisted of a hopper, orifice plates for varying deposition intensity, combination of flexible and rigid tubes for smooth travel of material, and a set of diffuser sieves to obtain uniformity of pluviated sand bed. It was observed that sand beds of lower relative density can be achieved by controlling height of fall, whereas, denser sand beds could be obtained by controlling deposition intensity. Uniformity of pluviated sand beds was evaluated using cone penetration test and at lower relative densities minor variation in density was observed with depth. With increase in relative density of sand bed higher repeatability of uniform pluviation was achieved.

• 한국터널지하공간학회 논문집
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• 제22권2호
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• pp.171-183
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• 2020

이 연구의 목적은 대심도 복층터널 Test Bed 구조물에 대한 슬래브의 사전 구조안전성 평가를 통해 슬래브의 가설시와 공용하중 작용시에 발생 가능한 문제점과 개선점을 미리 분석하는 것이다. 대심도 복층터널의 설계 및 시공기술개발의 성과물을 Test Bed 구축을 과정을 통해 검증하고 확인할 수 있으며, 엔지니어 및 일반인들의 학습현장으로도 활용할 수 있어 지하공간 개발의 시기를 더욱 앞당길 수 있는 계기가 마련될 것이다. 특히, 원형의 대심도 복층터널 단면 내부에 구축되는 슬래브는 시공방법과 사용하는 시공장비에 따라 설계하중이 달라지며, 이번 Test Bed 구조체는 그 내부에 상부 슬래브 및 풍도슬래브를 전용 가설장비를 이용하여 설치하는 동안 가설장비하중과 상·하부 슬래브에 공용하중으로 가정된 KL-510의 3등급 트럭하중을 하중조합별 작용위치를 달리하며 상·하부 슬래브에 각각 재하하여 그 영향을 분석하였다.

• 물과 미래
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• 제28권4호
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• pp.147-154
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• 1995

본 연구에서는 특별한 에너지 감세를 위한 수공구조물이 설치되지 않은 중 소규모 단락부 하류부에서 자유낙하하는 수맥으로 인하여 발생되는 비점착성 하상재료의 세굴특성을 수리모형실험을 통하여 분석하였다. 단락수맥 하류부에서의 세굴특성을 분석하기 위하여 먼저 직사각형 단락수맥의 흐름특성을 조사하였으며, 하상재료, 유량, 하류수심을 변화시키면서 세굴공의 직하류부에 생성되는 둔덕(mound)의 유무로 인한 세굴특성을 비교 분석하였다. 평형세굴심 뿐만 아니라 둔덕의 높이도 밀도 후르드수의 함수로 표시되며, 밀도 후르드수는 다른 무차원량 보다 평형세굴심과 비교적 깊은 관계가 있는 것을 확인하였다. 단락부 하류부 하상 보호공의 설계시 둔덕의 영향을 고려해야 한다는 결론을 얻었다.