• Economic and Environmental Geology
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• v.40 no.5
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• pp.551-561
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• 2007

This case study is about the sampling and interpretation of soil pore water in order to understand and to predict the diffusion and behavior of soil pollution. For the measurement of polycyclic aromatic hydrocarbons(PAHs) in two representative hydrocarbon-contaminated sites, the extraction system of the soil pore water was set up with respect to soil depths and the behavior of contaminants was interpreted. The soil solution extraction system consisted of peristaltic pump, and extraction and sampling compartment, and can measure simultaneously the soil water pressure. The concentration of PAHs with respect to extraction pressure and time decreased due to dilution through soil pore water. Particularly, the concentration of PAHs was more reduced under the unsaturated oxic condition than saturated anoxic condition. Therefore, the soil solution extraction with respect to soil water pressure can interpret the extent of equilibrium between porewater and soil surface.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.2
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• pp.247-258
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• 2003

In this paper, we present a pen-shaped input device equipped with accelerometers and gyroscopes that measure inertial movements when a user writes on 2 or 3 dimensional space with the pen. The measurements from gyroscope are integrated once to find the attitude of the system and are used to compensate gravitational effect in the accelerations. Further, the compensated accelerations are integrated twice to yield the position of the system, whose basic concept stems from the field of inertial navigation. However, the accuracy of the position measurement significantly deteriorates with time due to the integrations involved in recovering the handwriting trajectory This problem is common in the inertial navigation system and is usually solved by the periodic or aperiodic calibration of the system with external reference sources or other information in the filed of inertial navigation. In the presented paper, the calibration of the position or velocity is performed on-line and off-line. In the on-line calibration stage, the complementary filter technique is used, where a Kalman filter plays an important role. In the off-line calibration stage, the constant component of the resultant navigational error of the system is removed using the velocity information and motion detection algorithm. The effectiveness and feasibility of the presented system is shown through the experimental results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.279-285
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• 2011

We perform a numerical study to determine the time of onset of natural convection in a transient hot wire (THW) device for measuring the thermal conductivity of nanofluids. The samples used in this simulation are water-based $Al_2O_3$ nanofluids with volume fractions of 1%, 4%, and 10%, and the properties are calculated by theoretical models and experimental correlations. The THW apparatus using coated wire is modeled by the control-volume-based finite difference method, and the start of natural convection is determined by observing the temperature rise of the wire under a gravity field. The onset time is 11.5 s for water and 41.6 s for water-based $Al_2O_3$ nanofluids predicted by Maxwell thermal conductivity model with a 10% volume fraction. We confirm that the onset time of natural convection of nanofluids in the cylinder increases with the nanoparticle volume fraction. We suggest a correlation for predicting the onset time on the basis of the numerical results. Finally, it is shown that the measurement error due to natural convection is negligible if the measurement using the transient hot wire method is completed before the onset of natural convection in the base fluid.

• The Journal of Korean Society for Radiation Therapy
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• v.29 no.2
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• pp.83-91
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• 2017

Objectives: The purpose of this study was to evaluate the error of the leaf position accuracy of the MLC due to the gravity effect according to the gantry angle by using picket fence test using EPID and GafChromic EBT3 film. Materials and Methods: A 5 cm solid phantom was placed on the table and the SAD was set to 100 cm. The EBT3 film was placed exactly over the solid phantom and covered a 1.5 cm solid phantom and the picket fence test was performed. The EPID was measured under the same conditions as the EBT3 film at SID 100 cm. The gantry angles were measured at $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$ in order to evaluate the position of the MLC according to the gantry angle. For the geometric evaluation of the MLC, the leaf position accuracy of the MLC was analyzed using the analysis program. Results: In case of EPID, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.18 mm, 0.31 mm, 0.20 mm, 0.26 mm on the average and the maximum values of the errors were respectively 0.44 mm, 0.54 mm, 0.34 mm, 0.44 mm. In case of EBT3 film, when the gantry angle was changed to $0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$, the difference of the position errors of the leaves was 0.19 mm, 0.21 mm, 0.19 mm, 0.31 mm on the average and the maximum values of the errors were respectively 0.35 mm, 0.45 mm, 0.36 mm, 0.48 mm. Conclusion: In this study, we analyzed the position error of the leaf of the MLC according to the gantry angle, and confirmed the position error of the leaf by gravity effect. As a result of comparing the leaf position accuracy using EPID and EBT3 film according to the variation of gantry angle, a larger error occurred in the error analysis method using EPID than that of EBT3 film. Therefore, in the case of IMRT based on MLC, as well as verification of accurate dosimetry should be conducted, it is considered that the quality control and verification for the precise operation of the MLC will be needed. and it is necessary to compare and verify the method of analysis.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.82-88
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• 2007

The objective of this study is to examine the effect of the waste oyster shell powder as the addition agent in bulking sludge thickening of paper manufacturing plant using DAF(Dissolved Air Flotation) and gravitational sedimentation. The effect of parameters such as dosage and size distribution of oyster shell were examined. The results showed that the optimum dosage of mixed oyster shell(size range : $\sim250{\mu}m$) was 0.8 g/L. The oyster shell addition of 5.0 g/L in sedimentation process was increased thickening concentration of 3.25 times. When 5.0 g/L of oyster shell was added in DAF process, water content of sludge was decreased from 95.5% to 82.7% in dewatering process using Buchner funnel test device. When size of oyster shell was divided four ranges($\sim53{\mu}m$, $53\sim106{\mu}m$, $106\sim150{\mu}m$, $150\sim250{\mu}m$), optimum size range for the flotation and dewatering was $53\sim106{\mu}m$.

• Analytical Science and Technology
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• v.33 no.6
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• pp.274-284
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• 2020

This study described the analytical method for simultaneous determination of 89Sr and 90Sr in liquid sample using automated separation system. Radiostrontium in 0.5 kg of liquid sample was concentrated as SrCO3 to reduce the volume of sample, and purified from the sample using Sr-resin 2 mL (BV, Bed volume). The behavior of Sr and interferences such as Ba, Ca and Y were estimated with various flow rate ranging from 1 to 4 mL min-1. The detailed procedure for the purification of Sr on Sr-resin was presented. The purified radiostronitum was measured in Cerenkov mode and then measured in Scintillation mode by mixing scintillation cocktail. The measured value in both modes were used to calculate the activity of 89Sr and 90Sr. The performance tests were carried out the lab-control-sample having various activity ratio of between 89Sr and 90Sr. The recovery of Sr was ranged from 68 to 94 %. The relative bias of 89Sr activity was ranged from -5 to 20 %, and it was ranged from -10 to 10 % for 90Sr.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.283-290
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• 2020

In this study, a floater was developed for a frame-type solar power plant. The floater supports the frame and the solar panels. A finite element analysis was performed to design its shape and thickness, and the floater was manufactured by a rotational molding method using linear low-density polyethylene. It was found that the floater did not cause collapse and it maintained its stiffness even at 4 times the maximum load of 322.7 kgf. To perform a long-term compression test, a weight-type load application device that uses gravity was designed and manufactured. The amount of compressive deformation was measured for 7 days, and a long-term deformation equation was obtained. Even under small loads, continuous deformation was observed. However, the 10-year deformation amount for a constant load of 100 kgf was predicted to be small at about 4.64 mm. As a result, it was found that the developed floater could be used in a solar power plant on a body of water.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.2
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• pp.101-108
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• 2009

A fretting wear test rig for dry ambient condition, which employs a piezoelectric actuator, has been developed. It is driven and loaded in a very simple manner with acceptable experimental accuracy. By using the rig, Inconel 690 tube has been tested under the normal load of 10 and 15N with sliding amplitude of less than $100{\mu}m$ during $10^6$cycles. The wear resistance of the material has been characterized in terms of the wear coefficient based on the work rate model. SEM micrographs show the complex structures of the scars, which consist of risen peaks, plate-type thin layers and locally exposed bare surfaces. The cracks spread over the layers give clue to the fretting wear mechanism of the material.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.122-122
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• 2014

수중방전을 환경분야에 적용하기 위한 플라즈마 부상법이 개발되었다. 플라즈마 부상법은 물 속에서 발생시킨 플라즈마가 가지고 있는 주요특성 중 물리적 특징인 쇼크웨이브, UV조사, 버블생성 등과 화학적 특징인 OH라디칼 및 염소산화물 생성 등을 이용하여 물 속에 존재하는 용존성 및 입자성 물질을 부상분리 기법으로 제거하는 공법이다. 유기물을 제거하는 기작으로는 침전, 여과, 분해 등이 있고, 이를 구현하기 위한 공정으로 중력침강법, 부상분리법, 멤브레인법, 미생물법 등이 있다. 이 중에서 가압공기부상법은 침강법에 비해 부지면적을 적게 소모하고 처리시간이 50% 이상 감소되는 특징이 있다. 가압공기부상법은 물 속에 공기를 과포화시킨 후 노즐을 통해 재분사할 때 발생하는 압력차에 의해 미세기포가 발생함을 이용하여 유기물을 분리하는 공법이다. 그러나, 가압용 장비 및 반송수가 필요하고, 미생물분리는 불가능한 단점이 있다. 이에 본 연구에서는 미생물살균과 유기물 분리가 동시에 일어나는 플라즈마를 이용한 부상분리기법을 개발하였다. 본 연구에서는 난분해성 용존유기물인 휴믹산 100 mg/L의 플라즈마 공기부상법에 의한 제거능을 확인하였다. 용존성 휴믹산을 입자성 물질로 전환하여 플록을 형성시키고자 알루미늄설페이트(Al2(SO4) $3{\cdot}18H2O$)를 100 mg/L 주입하였고, 침출수와 같이 염도가 높은 물을 모사하고자 35 g/L의 염화나트륨을 첨가한 상태에서 방전을 실시하였다. 방전에 사용된 전원은 EESYS사에서 제작한 펄스형 고전압 전원장치를 사용하였고 최대 15 kW의 출력 중 6 kW의 전력을 인가하였다. 전극 한 개는 2 mm 텅스텐봉을 세라믹튜브로 감싼 구조로 총 사용전극은 28개이다. 전극 한 개당 대략 200 Watt의 전력이 소모되며 이 때 최대의 버블이 생성됨을 확인하였다. 전극 1개에서 생성되는 버블의 부피는 14 mL/min 로 측정되었다. 버블의 크기는 평균 70 um이고 가압공기부상법에서 최적공기크기로 제시하고 있는 40~80 um 의 버블은 약 80% 가량 생성된다. 본 연구에서 사용된 반응시스템에서의 물의 높이는 약 500 mm 이고 전체 40 L의 수조가 3개의 벽으로 분리되어 4개의 수조로 분리되었다. 각 수조는 하부에 7개의 전극을 포함하고 있다. 플라즈마 발생시 생성되는 기포는 약 1분 방전 후에 포화농도에 도달하며 방전종료 후 약 4분간 수체 내에 남아있게 된다. 이를 공정에 적용하여 1분 방전 및 4분 휴지의 순서로 플라즈마를 인가하였다. 휴믹산 용액의 유량을 2 lpm 으로 운전하였을 때 최종 처리율은 94% 이고 이때의 대장균 살균능은 99%이다.