• 한국안전학회지
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• 제31권5호
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• pp.22-27
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• 2016

The Electrostatic Charge Prevention Technology is a core factor that highly influences the yield of Ultra High Resolution Flat Panel Display and high-integrated semiconductor manufacturing processes. The corona or x-ray ionizations are commonly used in order to eliminate static charges during manufacturing processes. To develop such a revolutionary x-ray ionizer that is free of x-ray radiation and has function to control the volume of ion formation simultaneously is a goal of this research and it absolutely overcomes the current risks of x-ray ionization. Under the International Commission on Radiological Protection, it must have a leakage radiation level that should be lower than a recommended level that is $1{\mu}Sv/hour$. In this research, the new generation of x-ray ionizer can easily control both the volume of ion formation and the leakage radiation level at the same time. In the research, the test constraints were set and the descriptions are as below; First, In order not to leak x-ray radiation while testing, the shielding box was fully installed around the test equipment area. Second, Implement the metallic Ring Electrode along a tube window and applied zero to ${\pm}8kV$ with respect to manage the positive and negative ions formation. Lastly, the ion duty ratio was able to be controlled in different test set-ups along with a free x-ray leakage through the metallic Ring Electrode. In the result of experiment, the maximum x-ray radiation leakage was $0.2{\mu}Sv/h$. These outcome is lower than the ICRP 103 recommended value, which is $1{\mu}Sv/h$. When applying voltage to the metallic ring electrode, the positive decay time was 2.18s at the distance of 300 mm and its slope was 0.272. In addition, the negative decay time was 2.1s at the distance of 300 mm and its slope was 0.262. At the distance of 200 mm, the positive decay time was 2.29s and its slope was 0.286. The negative decay time was 2.35s and its slope was 0.293. At the distance of 100 mm, the positive decay time was 2.71s and its slope was 0.338. The negative decay time was 3.07s and its slope was 0.383. According to these research, the observation was shown that these new concept of ionizer is able to minimize the leakage radiation level and to control the positive and negative ion duty ratio while ionization.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권2호
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• pp.172-181
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• 2012

One of the most critical issues in naval architecture these days is the operational safety. Among many factors to be considered for higher safety level requirements, the hull stability in intact and damaged conditions is the first to ensure for both commercial and military vessels. Unlike the intact stability cases, the assessment of the damaged ship stability is very complicated physical phenomena. Therefore it is widely acknowledged that computational fluid dynamics (CFD) methods are one of most feasible approaches. In order to develop better CFD methods for damaged ship stability assessment, it is essential to perform well-designed model tests and to build a database for CFD validation. In the present study, free roll decay tests in calm water with both intact and damaged ships were performed and six degree-of-freedom (6DOF) motion responses of intact ship in regular waves were measured. Through the free roll decay tests, the effects of the flooding water on the roll decay motion of a ship were investigated. Through the model tests in regular waves, the database that provides 6DOF motion responses of intact ship was established.

• Bulletin of the Korean Chemical Society
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• 제16권10호
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• pp.938-945
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• 1995

Hydrolysis of p-nitrophenyl acetate (PNPA) and p-nitrophenyldiphenyl phosphate (PNPDPP) by N-chloro compounds in micellar solution were studied. N,N'-dichloroisocyanuric acid sodium salt (DCI) in cetyltrimethylammonium chloride (CTACl) micellar solution gave pseudo first-order kinetics. But, DCI in cetyltrimethylammonium bromide (CTABr) micellar solution showed typical series first-order kinetics - fast hydrolysis of the esters and concomitant slow decay of the hydrolyzed product, p-nitrophenolate. The hydrolysis rate was decreased as the hydrophobicity of N-chloro compounds was increased, which is the opposite trend to the usual bimolecular micellar reaction. This curious behavior of the N-chloro compounds in the catalytic hydrolysis of PNPA and PNPDPP in a cationic micellar system can be best explained by participation of counter ions of the surfactants during hydrolysis.

• 한국물환경학회지
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• 제20권4호
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• pp.327-332
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• 2004

This study was carried out to examine the effect of gamma irradiation on the physico-chemical characteristics and ultimate anaerobic biodegradability of sewage sludge. The results found that the solubilization rates of SCOD in wasted activated sludge(WAS) and thickened sludge(T-S) with gamma irradiation of 3kGy were 8 times and 7 times greater than these of the raw WAS and T-S without the irradiation, respectively; each soluble concentration protein were 4 times and 3 times greater than these of the raw WAS and T-S; each soluble carbohydrate concentration was 8 times and 6 times greater than these of the raw WAS and T-S. The ultimate anaerobic biodegradabilities of WAS and T-S with gamma irradiation were 51 % and 50%, which corresponds to each 8% and 10% greater than these of the raw sludges. Approximately 83% and 81% of the each biodegradable substrates in the irradiated WAS and the T-S were degraded within 11 days with the first order decay rate coefficients, $k_1$ that ranged $0.143{\sim}0.164day^{-1}$ for WAS and $0.134{\sim}0.152day^{-1}$ for T-S. Based on the results, it can be concluded that when irradiated with gamma the solubilization of sewage sludge greatly increases resulting in substrates suitable for the subsequent biological treatment processes.

• 한국환경보건학회지
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• 제32권1호
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• pp.53-59
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• 2006

This study was carried out to investigate the physicochemical characteristics with the elapsed time of $1\~10$ minutes after adding green tea leaves in the tap water. The results are summarized as follows: 1. $UV_{254}$ measurement increased sharply in direct opposition to increasing conductivity slowly. It is expected that the water soluble organic matters were better extracted than minerals. 2. Residual chlorine decay coefficients evaluated by assuming first-order reaction was increased in proportion to adding weights of green tea leaves. 3. In DBP formation experiments, residual chlorine decreased when reaction time was elapsed. whereas DBPs such as HAAs and THMs increased with the passing of time. From these results, it was showed that residual chlorine decay was related with the formation of DBPs. Therefore, use of boiled tap water in preparation of green tea is suggested if the residual chlorine in the tap water is high.

• 보존과학회지
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• 제2권2호
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• pp.15-24
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• 1993

To understand the morphological change of ancient woods, samples classified by cell type, burial environment and species were collected and observed using microscopy. Decay of wood by cell type could classified into two types. First, degraded secondary wall was formed granular residues in $S_2$ layer and was remained $S_3$ layer and compound middle lamella. Second, the cell wall was slightly degraded and cracked in secondary wall. A gradual thinning of cell wall was occured. The compound middle lamella was separated from secondary wall. The resistance of degradation is increased at vessels, parenchyma, and tracheid and wood fiber in the order named. The type of degradation by species could be classified into four types. Overall degradation type; the degradation of cell wall is usually heavy and the extent of degradation Varies by part of the same sample. Partial degradation type ; this type shows severely different decay type by part of the sample. Nondegraded cells were mixed with degraded cells on the same sample. Erose degradation type ; thinning of the cell wall was occoured and the degradation type was different by part. Slight degradation types ; secondary wall was slightly degraded, cracked and separated from compound middle lamella. Considering different type of burial environment, dry wood was similiar to sound wood and slightly decayed. Waterlogged and peat burial wood was heavilydecayed. Between species of under the same environment, decay type and extent were diferentiated from each other.

• 한국수자원학회논문집
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• 제34권4호
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• pp.289-301
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• 2001

비보존성 오염물질의 종확산에 관한 단계분리 유한차분 모형을 낙동강에 적용하여, 1991년에 발생한 페놀누출 사고에 따른 종확산 모의계산을 수행하였다. Preissmann의 4점 음해법에 근거한 부정류 계산모형으로부터 산정된 계산결과를 종확산 모형의 입력자료로 사용하였다. 종확산계수의 산정을 위한 경험식 및 1차 반응의 감쇠계수에 따른 종확산 계산결과의 민감도를 분석하였다. 하류 지점에서의 첨두농도 발생 시각은 사용된 종확산계수 식에 따라 상당히 달라짐을 알 수 있었다. 또한 농도 분포형은 감쇠계수에 따라 변하지 않는 반면, 농도값은 감쇠계수에 상당히 좌우되는 것으로 나타났다. 최적화 기법을 사용하여 흐름 모형 및 종확산 모형을 보정하였으며, 낙동강에 위치한 주요 취수지점들에 대한 첨두농도 발생시각을 모의하여 제시하였다.

• Ocean Systems Engineering
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• 제5권3호
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• pp.139-160
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• 2015

The global performance of the 5MW OC4 semisubmersible floating wind turbine in random waves was numerically simulated by using the turbine-floater-mooring fully coupled and time-domain dynamic analysis program FAST-CHARM3D. There have been many papers regarding floating offshore wind turbines but the effects of second-order wave-body interactions on their global performance have rarely been studied. The second-order wave forces are actually small compared to the first-order wave forces, but its effect cannot be ignored when the natural frequencies of a floating system are outside the wave-frequency range. In the case of semi-submersible platform, second-order difference-frequency wave-diffraction forces and moments become important since surge/sway and pitch/roll natural frequencies are lower than those of typical incident waves. The computational effort related to the full second-order diffraction calculation is typically very heavy, so in many cases, the simplified approach called Newman's approximation or first-order-wave-force-only are used. However, it needs to be justified against more complete solutions with full QTF (quadratic transfer function), which is a main subject of the present study. The numerically simulated results for the 5MW OC4 semisubmersible floating wind turbine by FAST-CHARM3D are also extensively compared with the DeepCWind model test results by Technip/NREL/UMaine. The predicted motions and mooring tensions for two white-noise input-wave spectra agree well against the measure values. In this paper, the numerical static-offset and free-decay tests are also conducted to verify the system stiffness, damping, and natural frequencies against the experimental results. They also agree well to verify that the dynamic system modeling is correct to the details. The performance of the simplified approaches instead of using the full QTF are also tested.

• Journal of Pharmaceutical Investigation
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• 제35권5호
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• pp.333-336
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• 2005

The objective of this study was to investigate the stability of tetracycline HCl on encapsulation into and inside reverse micelles. To do so, tetracycline HCl was first mixed with cetyltrimethylammonium bromide, water and ethyl formate to make reverse micelles. The degradation kinetics of tetracycline HCl inside the reverse micelles was then assessed by scrutinizing its stability data. Under our experimental conditions, the reverse micelles formed spontaneously in absence of any mixing devices. During the preparation of the reverse micelles, however, considerable portions of tetracycline HCl underwent a chemical reaction (e.g., epimerization). For instance, $51.4{\pm}0.6%$ of an initial concentration of tetracycline HCl was transformed into a degradation product. Once dissolved inside the reverse micelles, the degradation of tetracycline HCl followed an exponential decay pattern. The plot of log{the degradation rate of tetracycline HCl} versus log{tetracycline HCl concentration} made it possible to determine the order of degradation reaction and rate constant. It was proven that the degradation of tetracycline HCl inside the reverse micelles followed a first order kinetics with a rate constant of 0.0027 $hour^{-1}$. Meriting further investigation might be formulation studies to stabilize tetracycline HCl on encapsulation into and inside the reverse micelles.

• 한국물환경학회지
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• 제26권1호
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• pp.156-159
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• 2010

Peroxide is used frequently to provide electron acceptors to aerobes for the purpose of in situ bioremediation of contaminated soil/sediment. In this study, oxygen release rate of peroxides and factors affecting on dissolution and diffusion of oxygen into pore water were evaluated. Peroxides studied in this study were magnesium peroxide ($MgO_2$), calcium peroxide ($CaO_2$), and sodium percarbonate ($Na_2CO_3{\cdot}1.5H_2O_2$). $Na_2CO_3{\cdot}1.5H_2O_2$ showed the highest oxygen release rate per unit mass and the shortest release duration time among three peroxides. A simple first-order decay model for predicting the release rate of oxygen from peroxide into pore water was presented and used to fit the experimental data. The first order oxygen release rate constants k for $MgO_2$, $CaO_2$ and $Na_2CO_3{\cdot}1.5H_2O_2$ were 0.45 /hr, 3.22 /hr and 134 /hr, respectively. If $MgO_2$ was mixed with clay, oxygen release rate was lowered significantly mainly due to limitation of contact area and diffusion, implying that oxygen can be provided to the indigenous aerobes for the extended period of time.