• Journal of Radiation Protection and Research
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• v.34 no.1
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• pp.31-36
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• 2009

The purpose of this study is to measure the tube voltage, the tube current/volume, exposure time and exposure dose of diagnostic X-ray unit in each doctor offices, hospitals and general hospitals for evaluating the performance of such device, to learn the method and technology of its measurement and to suggest its importance. Research subjects were total 30 X-ray units and divided into groups of 10 X-ray units each. The tube voltage, the tube current/volume, exposure time and exposure dose were measured using percentage average error, and then reproducibility of exposure dose was measured through calculating coefficient of variation. The results are like followings; The tube voltage correctness examination showed that incongruent devices among total 30 X-ray units were 5 devices (16.7%). The tube current correctness examination showed that incongruent X-ray units were 3 devices (10.0%). The tube current volume correctness examination showed that incongruent X-ray units were 4 devices (13.3%). Finally, according to exposure time correctness examination, incongruent X-ray units were 5 devices (16.7%) and according to reproducibility examination of exposure dose, incongruent X-ray units were 7 devices (23.3%). Above results showed serious problem in performance management based on management regulation of diagnostic X-ray unit; it means that regular checkout and safety management are required, and as doing so, patients will be able to receive good quality of medical service by the reduction of radiation exposure time, image quality administration, unnecessary retake and etc. Therefore, this study suggests that the performance of diagnostic X-ray units should be checked regularly.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.12a
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• pp.87-94
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• 2005

Results from previous studies revealed that metal level in the body is related to certain types of diseases. For example. serum copper level with chronic heart failure, iron and transferrin in the blood serum with acute cerebral vascular diseases, Zn in the CNS, lead with neurotoxicity, hypertension, genetic damage, arsenic with cancer skin lesion, Al with neurobehavioral function (cognitive impairment and memory disorder), and etc. The rate of stroke has increased in recent years and several metals were found to be responsible for causing stroke. This study compared several blood metal concentrations between stroke and non-stroke patients. Patients with stroke (116 samples) and non-stroke (111 samples including lowback pain and others) participated in this study. Total of 227 blood samples were collected and participants completed questionnaires regarding age, gender, occupation, residence, alcohol, smoking, and etc. To be qualified into the stroke group, patients have never experienced stroke previously. Subjects only included ischemic stroke and intracerebral hemorrhage patients diagnosed by brain CT and brain MRI. Patients with high risk of metal exposure such as herbal intake and job related exposure were excluded. 10ml of blood samples were analyzed by ICP-MS method at the Center of Nature and Science at Sangji University. Metal geometric mean (SD) concentrations in blood of study subjects showed higher values, 2.64-36.12%, than WHO reference values in Mn, Ni, Hg, Se, and As. Metal concentration in blood of stroke patients non-adjusted for potential confounders was higher except for Hg and also higher except for Ni in adjusted for potential confounders. Co was significantly higher in stroke patients (p=0.002) than non-stroke patients adjusted for potential confounders. Regression coefficient values of stroke patients was 0.17-8.25 in each metals. Odd ratio of stroke patients had 0.96 (Ni)-2.68 (Co) compared to non-stroke cases. This result means that Co increase of 1 raises the risk ratio of stroke by 2.86 times. Based on the results, metal concentration in blood seems to affect incidence of stroke.

• Journal of Korean Society of Forest Science
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• v.77 no.1
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• pp.23-31
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• 1988

A total of 320 Larix leptocepzs Trees growing in Kyonggi and Kangwon Province were examined to estimate tree volume and height with DBH and age. The criteria of selecting the "best" regression equation were based on coefficient of determination, $R^2$, adjusted standard error, I, and the ease of application. From the results obtained in this study, the method of estimating tree volume and height with DBH and age showed the following advantages ; 1. Since no measurement of tree height is needed, it saves time and labor in forest survey. 2. It has the ease of application because age is determined directly in artificial forests. 3. Volume and height can be estimated more easily and accurately with DBH and age than other methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.863-874
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• 2015

The use of pile reinforcement is considered as one of the most promising techniques for improving load carrying capacity of piles in offshore area. In this study, to consider the horizontal and uplift bearing capacity of submerged breakwater bearing pile, exclusive analysis on load-transfer behaviour of pile was conducted. First of all, check the reinforcing effect from the three-dimensional finite element method, and estimate load transfer curve (ground reaction force). Based on these results, the reinforcing effect was quantified by estimating the coefficients of horizontal and uplift reinforcement of reinforced piles. Load transfer function with consideration of the reinforcing effect was proposed from estimated coefficients. A comparison of the analysis using the proposed load transfer function with three-dimensional finite element analysis has resulted that the proposed load transfer function is displaying good accuracy of predicting behavior of the load transfer between the pile and soil reinforcement. Interpretation of the submerged structure by applying a load transfer function considering the reinforcing effect, has shown that the reinforced pile's shear, bending moment and displacement are less than that of non-reinforced piles, while the subgrade reaction modulus arises greater. Thus, it is expected to be relatively cost effective in terms of design.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.224-232
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• 1999

Latent heat storage system using micro-encapsuled phase change material is effective method for floor heating of house and building. The temperature profile in capsule block and flow rate of hot water are important parameters for the development of heat storage system. In the present study, a mathematical model based on 3-D, non-steady state, Navier-Stokes equations, scalar conservation equations and turbulence model ($\kappa$-$\varepsilon$), is used to predict the temperature profiles in capsule and the velocity vectors in hot water pipe. The multi-block grids and fine grids embedding are used to join the circle in hot water pipe and square in capsule block. The phase change process of the capsule is quite complex not only because the size of phase change material is very small, but also because phase change material is mixed with the cement to form thermal storage block. In calculation, it's assumed that the phenomena of phase change is limited only the thermal properties of phase change material and the change of boundary is not happened in capsule. The purpose of this study is to calculate the temperature profiles in capsule block and velocity vectors in hot water pipe using the numerical calculation. Two kinds of thermal boundary condition were considered, the first (case 1) is the adiabatic condition for the both outside surfaces of the wall, the second (case 2) is the case in which one surface is natural convection with atmosphere and another surface is adaibatic. Calculation results are shown that the temperature profile in capsule block for case 1 is higher than that for case 2 due to less heat loss in adaibatic surface. Specially, in the domain of near Y=0, the difference of temperature is greater in case 1 than in case 2. The detailed experimental data of capsule block on the temperature profile and the thermal properties such as specific heat and coefficient of heat transfer with the various temperature are required to predict more exact phenomena of heat transfer.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.61-68
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• 2019

Recently, climate indices represented by quantifying atmospheric-ocean circulation patterns have been widely used to predict hydrologic variables for considering long-term climate variability. Hydrologic forecasting models based on artificial neural networks have been developed to provide accurate and stable forecasting performance. Forecasts of hydrologic variables considering climate variability can be effectively used for long-term management of water resources and environmental preservation. Therefore, identifying significant indicators for hydrologic variables and applying forecasting models still remains as a challenge. In this study, we selected representative climate indices that have significant relationships with dam inflow time series in the Han-River basin, South Korea for applying the dam inflow forecasting model. For this purpose, the ensemble empirical mode decomposition(EEMD) method was used to identify a significance between dam inflow and climate indices and an artificial neural network(ANN) ensemble model was applied to overcome the limitation of a single ANN model. As a result, the forecasting performances showed that the mean correlation coefficient of the five dams in the training period is 0.88, and the test period is 0.68. It can be expected to come out various applications using the relationship between hydrologic variables and climate variability in South Korea.

• Journal of Korea Water Resources Association
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• v.51 no.2
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• pp.151-163
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• 2018

The objective of this study was to estimate LOADEST (LOAD Estimator) coefficients for simulating pollutant loads in ungauged watersheds. Regression models of LOADEST were used to simulate pollutant loads, and the multiple linear regression (MLR) was used for coefficients estimation on watershed characteristics. The fifth and third model of LOADEST were selected to simulate T-N (Total-Nitrogen) and T-P (Total-Phosphorous) loads, respectively. The results and statistics indicated that regression models based on LOADEST simulated pollutant loads reasonably and model coefficients were reliable. However, the results also indicated that LOADEST underestimated pollutant loads and had a bias. For this reason, simulated loads were corrected the bias by a quantile mapping method in this study. Corrected loads indicated that the bias correction was effective. Using multiple regression analysis, a coefficient estimation methods according to the watershed characteristic were developed. Coefficients which calculated by MLR were used in models. The simulated result and statistics indicated that MLR estimated the model coefficients reasonably. Regression models developed in this study would help simulate pollutant loads for ungauged watersheds and be a screen model for policy decision.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.28-35
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• 2020

This study is to compare irrigation efficiency between sap flow sensor automated system (SF) and conventional irrigation system based on integrated solar radiation automated system (ISR) in tomato rockwool hydroponics. Total irrigated volumes was higher in the ISR system by 5.0L per plant, a lower drainage rate was found in the SF system, compared to the ISR system. There was no difference in shoot and fruit fresh weights, water use efficiency (WUE) and water amount consumed for producing 200g of tomato fruit. The daily average sap flow density (SFD) was closer to the change of solar irradiance (SI) in the plant grown under the SF system, compared to the ISR system. The correlation coefficient (r²) between the fruit diameter and the volumetric water content during the 56 and 82 days after transplant showed the SF treatment was higher than the ISR at night and daytime, and the correlation was higher at night time. The sap flow density and humidity deficit (HD) of SF treatment was related as closely as the solar irradiance. Further studies should demonstrate that SF irrigation system is a convenient method for hydroponic farmers with advantages, such as growth, higher yield, WUE, and accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.672-679
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• 2018

This paper describes a methodology for shape design using an optimal design system, whereas generally a three dimensional analysis is required for such designs. An automatic finite element mesh generation technique, which is based on fuzzy knowledge processing and computational geometry techniques, is incorporated into the system, together with a commercial FE analysis code and a commercial solid modeler. Also, with the aid of multilayer neural networks, the present system allows us to automatically obtain a design window, in which a number of satisfactory design solutions exist in a multi-dimensional design parameter space. The developed optimal design system is successfully applied to evaluate the structures that are used. This study used a stress gauge to measure the maximum stress affecting the parts of the side housing bracket which are most vulnerable to cracking. Thereafter, we used a tool to interpret the maximum stress value, while maintaining the same stress as that exerted on the spot. Furthermore, a stress analysis was performed with the typical shape maintained intact, SM490 used for the material and the minimizing weight safety coefficient set to 3, while keeping the maximum stress the same as or smaller than the allowable stress. In this paper, a side housing bracket with a comparably simple structure for 36 tons was optimized, however if the method developed in this study were applied to side housing brackets of different classes (tons), their quality would be greatly improved.

• Journal of Conservation Science
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• v.31 no.4
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• pp.477-488
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• 2015

At this, in this study, some tests were conducted to come up with a method to minimize intervention, to reduce the secondary damage to original materials, and to produce remarkable reinforcing effects. The followings show objective standards. The proportion of original material to steel reinforcement bar (the ratio of steel reinforcement bar) needs to be calculated in light of weathering intensity. Second, in the case of partial damage, prosthetic treatment is applied to add new stone materials to original materials. In that case, the ratio of steel reinforcement bar should be calculated based on material that is highly resistant to weathering. With the results of this study, it is possible to suggest conditions that can structurally stabilize stone cultural heritage, according to the weathering area. As a result, the ratio of steel reinforcement bars can be 0.13 to 0.23 in the case of $800kgf/cm^2$ or less, 0.24 to 0.28 in $800kgf/cm^2$ or higher, and 0.29 to 0.5 in $1200kgf/cm^2$ or higher. In particular, there is the need to take the coefficient of rupture of stone material and the properties of the steel reinforcement bar into account in cases of calculating the ratio of steel reinforcement bars according to weathering intensity.