• Nuclear Engineering and Technology
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• v.25 no.3
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• pp.437-446
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• 1993

More realistic calculation models for evaluating man's annual intakes of radionuclides released from operating nuclear facilities were established. For the application of these models, the harvest years of food and feed crops consumed in the year of dose assessment and every year's average concentrations of a radionuclide in air and in water for the whole period of real operation had to be taken into account. KFOOD, an existing equilibrium food chain computer code for the Korean dose assessment, was modified according to the models. Sample runs of the modified code on the assumption of a constant release during 10 years' operation were made with three kinds of the input data files enabling the dose assessment in the improved method, the KFOOD method and another existing method, respectively, and the results were compared. Annual committed effective doses to Korean adult by intakes of Mn-54, Co-60, Sr-90, I-131 and Cs-137 calculated in the improved method were about 11, 2, 5, 60 and 3%, respectively, lower than the corresponding KFOOD dose. To the intakes of the radionuclides except Sr-90 evaluated in the improved method, foliar uptake contributed much more than root uptake did but, in the case of Sr-90, the result was opposite.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.803-810
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• 2007

An analytical method capable of predicting various stress-strain responses in axially loaded concrete confined with FRP (fiber reinforced polymers) composites in a rational manner is presented. Its underlying idea is that the volumetric expansion due to progressive microcracking in mechanically loaded concrete is an important measure of the extent of damage in the material microstructure, and can be utilized to estimate the load-carrying capacity of concrete by considering the corresponding accumulated damage. Following from this, an elastic modulus expressed as a function of area strain and concrete porosity, the energy-balance equation relating the dilating concrete to the confining device interactively, the varying confining pressure, and an incremental calculation algorithm are included in the solution procedure. The proposed method enables the evaluation of lateral strains consecutively according to the related mechanical model and the energy-balance equation, rather than using an empirically derived equation for Poisson's ratio or dilation rate as in other analytical methods. Several existing analytical methods that can predict the overall response were also examined and discussed, particularly focusing on the way of considering the volumetric expansion. The results predicted by the proposed and Samaan's bilinear equation models correlated with observed results with a reasonable degree, however it can be judged that the latter is not capable of predicting the response of lateral strains correctly due to incorporating the initial Poisson's ratio and the final converged dilation rate only. Further, the proposed method seems to have greater benefits in other applications by the use of the fundamental principles of mechanics.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.5-5
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• 2000

액체 추진 로켓 엔진의 고주파 연소 불안정 관련 이론은 대체로 연소기 내부의 음향 공명 모드와 분무 연소 과정의 상호 작용을 구동 메커니즘으로 전제하며 Rayleigh Criterion의 재해석에 기초하여 불안정성 평가를 위한 매개변수를 도입하고 연소 불안정성을 예측한다. 여기에는 음향장 분석 이론, 음향 불안정 이론, 연소응답 및 기화반응 이론 등이 포함된다. 본 연구에서는 LOX/RPl 추진제 조합의 액체 추진 로켓 엔진 연소기를 대상으로 다차원 순수 음향장 해석과 연소-음향장 분석을 통해 대상 엔진의 고주파 연소 불안정 특성을 예측하였다. 수동 제어 기기인 음향공 설치에 따른 연소기의 음향장 및 연소-음향장의 특성 변화를 고찰하고 위 결과를 종합하여 음향공의 연소 불안정 억제 성능 및 대상 엔진의 연소 불안정성을 평가하였다. 연소기 형상 및 음향공 설치에 따른 다차원 순수 음향장 해석은 상용코드인 ANSYS를 사용하여 수행하였다. 내부 유체는 압축성, 비점성 유체로 유체의 평균 유동은 무시하며 위치에 관계없이 균일한 물성치를 부여하였다. 정상상태 연소과정을 가정하고 평형 화학을 이용한 분석 결과로부터 연소 기체의 관련 물성치를 결정하였다. 연소기 길이 방향, 반경 방향, 원주 방향 격자점들의 음향 특성을 주파수 영역에 대해 해석하고 3차원 음향 모드 형상을 토대로 음향장을 분석하였다. 연소-음향장 해석은 음향 불안정 이론 중 n- $\tau$ 2 매개변수 기법을 사용하였다. 연료 액적의 분무 연소 과정을 1차원적으로 가정하고 정상상태의 평형 화학 계산 결과를 이용하여 엔진의 연소면을 1차원적으로 설정하였다. 상류 연소응답과 중립 안정 곡선을 토대로 대상 엔진의 연소 불안정 특성을 분석하였다.구 분석 결과 기술적 문제점으로는 배기 가스온도가 낮은데 따른 출구 부분의 Bearing, Sealing이 문제가 될 수 있다고 판단되며 배기 가스 자체에 대기 공기중에 함유되어 있던 습기가 얼어붙는(Icing화) 문제가 발생하기 때문에 배기가스의 Icing을 방지하기 위하여 압축기 끝단에서 공기를 추출하여 배기부분에 송출할 필요성이 있는 것으로 판단되었다. 출구가스의 기체 유동속도가 매우 빠르므로 (100-l10m.sec) 이를 완화하기 위한 디퓨저의 설계가 요구된다고 판단된다. 또 연소기 후방에 물을 주입하는 경우 열교환기 및 기타 부분품에 발생할 수 있는 부식 및 열교환 효율 저하도 간과할 수 없는 문제로 파악되었다. 이러한 기술적 문제가 적절히 해결되는 경우 비활성 가스 제너레이터는 민수용으로는 대형 빌딩, 산림, 유조선 등의 화재에 매우 적절히 사용되어 질 수 있을 뿐 아니라 군사적으로도 군사작전 중 및 공군 기지의 화재 그리고 지하벙커에 설치되어 있는 고급 첨단 군사 장비 등의 화재 뿐 아니라 대간첩작전 등에 효과적으로 활용될 수 있을 것으로 판단된다.가 작으며, 본 연소관에 충전된 RDX/AP계 추진제의 경우 추진제의 습기투과에 의한 추진제 물성 변화는 미미한 것으로 나타났다.의 향상으로, 음성개선에 효과적이라고 사료되었으며, 이 방법이 편측 성대마비 환자의 효과적인 음성개선의 치료방법의 하나로 응용될 수 있으리라 생각된다..7%), 혈액투석, 식도부분절제술 및 위루술·위회장문합술을 시행한 경우가 각 1례(2.9%)씩이었다. 13) 심각한 합병증은 9례(26.5%)에서 보였는데 그중 식도협착증이 6례(17.6%), 급성신부전증 1례(2.9%), 종격동기흉과 폐염이 병발한 경우와 폐염이 각 1례(2.9%)였다. 14)

• Parasites, Hosts and Diseases
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• v.21 no.2
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• pp.135-141
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• 1983

The epidemiological relationship between the current prevalence and monthly reinfection rate of Ascaris lumbricoides was observed in rural communities in Korea by means of blanket mass chemotherapy and worm collection for measurement of the prevalence and reinfection rates. During the period from 1975 to 1980, a total of 4,466 inhabitants in 10 different localities were treated with 10 mg/kg of pyrantel pamoate and 2 days' whole stools were collected from 2,547 inhabitants. The stools were examined for the presence of expelled adult and/or young worms, which represent the prevalence and reinfection rates for past 2 months respectively. After then, the obtained rates were correlated each other applying the timeprevalence curve proposed by Hayashi. It was observed that the prevalence (overall worm positive rate) and worm burden per individual ranged by areas from 13. 6 to 72. 3% and 1.4~10. 2 respectively. The calculated monthly reinfection rates (X) (from young worm positive rates) according to areas were in the range, 2.6~16.2%, and clearly correlated with the current prevalence (Y) under the equation, $Y=1-(l-X)^{7.2}$ where 7.2 is time in month. The equation means that after one time mass chemotherapy the period needed to attain equilibrium of prevalence again would be about 7~8 months. And it is inferred that the majority of reinfected worms in human host turn over every 7~8 months.

• The Journal of Engineering Geology
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• v.14 no.3 s.40
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• pp.259-272
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• 2004

The purpose of this study is to investigate the effect of hydrochemical variation of groundwater on the gas tigtness in an unlined oil storage cavern. The groundwater chemistry is greatly influenced by the seawater mixing, the water curtain and the dissolution of grounting cements. The chemical composition of groundwater greatly varies ac-cording to both the location of monitoring wells and the sampling period. Most of groundwater shows alkaline pH and high electrical conductivity. The chemical types of groundwater show the dominant order as follows : Na-Cl type > Ca-Cl type > $Ca-HCO_3(CO_3)$ type. Thermodynamic equilibrium state between chemical composition of groundwater and major minerals indicates that carbonate minerals except clay minerals can be precipitated as a secondary mineral. It means that the secondary precipitates can not greatly exerts the clogging effect into fracture aperture in rock mass around oil storage cavern. The content of total organic carbon (TOC) shows a slightly increasing trend from initial stage to late stage. The $EpCO_2$ was computed so as to assess the gas contribution on the $CO_2$ in groundwater. The $EpCO_2$ of 0$\~$41.3 indicates that the contribution of oil gas on $CO_2$ pressure in groundwater system can be neglected.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.6159-6166
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• 2012

A discharge measurement is difficult in flood season which is especially important in the water resources field and the continuous discharge measurement for all rivers is impossible on the present system. So, the stage-discharge curve has been used for a long time to produce discharge data of rivers. However, there has been problems from a reliability angle due to the fact that this method uses only stage-discharge relationship, although the stage-discharge curve has the convenience. Therefore, a new mean velocity equation was derived by using Chiu's 2D velocity formula of the entropy concept in this paper. The derived equation reflected hydraulic characteristics such as the depth, gravity acceleration, hydraulic radius, energy slope, kinematic coefficient of viscosity, etc. and estimated also a maximum velocity. In addition, this method verified the relationship between a mean and maximum velocity and estimates an equilibrium state ${\phi}(M)$ well presenting properties of a river cross section as the results. The mean velocity was estimated by using the equilibrium state ${\phi}(M)$, and then the discharge was estimated. To prove this equation to be accurate, the comparison between the measured and estimated discharge is conducted by using the measured laboratory data in the unsteady condition flow showing loop state and the results are consistent. If this study is constantly carried out by using various laboratory and river data, this method will be widely utilized in water resources field.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.2
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• pp.85-97
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• 2001

A mathematical model was proposed to analyze the damped motion of contact lens which is initially displaced from the equilibrium position. The model incorporates the differential equations and their numerical solution program, based on the formulations of restoring force arising from the capillary action in the tear-film layer between the lens and cornea. The model predicts the capillary action induced surface tension, time dependence of displacement of lens when it is released from the equilibrium position. It seems that the motion of lens is similar to the typical over-damped oscillation caused by the large viscous friction in the liquid layer between the cornea and lens. The effect of variables such as base curves, lens diameters and thickness of tear film layer were illustrated by the computer simulation of the derived program. The time required for the lens to return to the original position increases as the liquid layer thickness increases and it decreases as the diameter of lens increases. With the certain value of base curve the time interval is found to be minimum. The free vibrations of lenses were also simulated varying the parameters such as base curve, diameter, layer thickness. The resonant frequencies are inversely proportional to the liquid layer thickness and it increases as the lens diameter increases. The resonant frequency of lens has a maximum when the diameter is of certain value. If the external impulse or force of the same frequency as the natural frequency of contact lens acted on the cornea in vivo it may cause an excessive movement and thus it might cause the distortion 10 the lens or be pulled off the eye.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.949-956
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• 1994

The objective of this study is to experimentally investigate the ion exchange characteristics of five types of Zeolite(Zeolite-A, 13X, Y, Mordenite, Chabazite) for effective removal of Cs, Sr and Co ions in water solution at low concentration(0.01 N and 0.005 N). Total ion exchange capacity and equilibrium isotherm are measured, and free-energy change(${\Delta}G^0$) and enthalpy change(${\Delta}H^0$) in ion exchange reaction are calculated from experimental results. In addition the ion exchange equilibrium in the three-component system for three types of zeolite showing better efficiency is measured and plotted in triangle coordinates. It is shown from experimental results that the magnitude of free-energy change increases with the increasing ion selectivity, and the difference of free energy change between ions correlates closely with that of ion selectivity. The results also shows that Chabazite is effective for the adsorption of Cs ion, and Zeolite-A and Zeolite-13X for that of Sr and Co ions.

• Economic and Environmental Geology
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• v.40 no.1 s.182
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• pp.29-45
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• 2007

Biogeochemical characteristics involving redox processes in groundwater from a riverine alluvial aquifer was investigated using multi-level monitoring wells (up to 30m in depth). Anaerobic conditions were predominant and high Fe ($14{\sim}37mg/L$) and Mn ($1{\sim}4mg/L$) concentrations were observed at 10 to 20 m in depth. Below 20 m depth, dissolved sulfide was detected. Presumably, these high Fe and Mn concentrations were derived from the reduction of Fe- and Mn-oxides because dissolved oxygen and nitrate were nearly absent and Fe and Mn contents were considerable in the sediments. The depth range of high Mn concentration is wider than that of high Fe concentration. Dissolved organics may be derived from the upper layers. Sulfate reduction is more active than Fe and Mn reduction below 20 m in depth. Disparity of calculated redox potential from the various redox couples indicates that redox states are in disequilibrium condition in groundwater. Carbonate minerals such as siderite and rhodochrosite may control the dissolved concentrations of Fe(II) and Mn(II), and iron sulfide minerals control for Fe(II) where sulfide is detected because these minerals are near saturation from the calculation of solubility equilibria.

• Journal of the Mineralogical Society of Korea
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• v.15 no.2
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• pp.114-121
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• 2002

Buffer capacities for two Bo horizon soils or Andisols developed from different parent materials have been investigated. The titration curves from column leaching experiment show that buffering occurred at pH 4.0 and 6.0. The buffer intensity or soil developed from pyroclastic materials (P-soil) is higher than that from basalts (B-soil). From batch test we have found that proto-imogolite and/or imogolite may control Al solubility as well as $Al(OH) _3$in the moderate acid condition. The buffer intensities ($\beta$) of P-soils were plotted on the theoretical buffering curve of $Al(OH)_3$, while $\beta$ of B-soils approached to that of proto-imogolite, which shows the solubility of short-range-order materials in P-soil control the buffer capacity. Buffering at pH 6.0 is thought to be the result of dissolution of some silicate clays and exchange reactions between $H^{+ }$and base-forming cations. Considering the amount of annual acid precipitation, aluminum solubility of Andisols, and the low BS (Base Saturation percentage), it can be predicted that prolonged acid precipitation will reduce the buffer capacity of soils and lead to soil acidification.