• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.985-992
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• 2011

The 3D computational fluid dynamics (CFD) was performed in relation to the internal fluid characteristics and flow distribution for the development of the most optimal model in the complex post-disposal device. As it is expected that a channeling (drift) would be made by the semi-dry reactor due to the large difference in the flow distribution by the compartment in the bag filter, a structural improvement should be urgently made for more uniformed flow distribution in the bag filter. Three types of modifications such as i) changing the plenum shape, ii) orifice install in the exit part of cleaned gas, iii) increasing the plenum number were established. From the results of computational fluid dynamics, it was revealed that the changing of plenum shape and orifice install in the exit part of cleaned gas was more reasonable than the increasing the plenum number because of the difficulties of retrofit. The complex post-disposal device, modified and supplemented with this analysis, integrated the semi-dry reactor and the bag filter in a single body, so it follows that the improvement can make the device compact, save the installation area, save the operation fee, and management more convenient.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.362-368
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• 1998

The magnetic properties, thermal stability and anti-corrosion properties of $Cr_86Al_14$ spin valves multilayers were studied. It was found that the magnetic properties of $Cr_86Al_14$ spin valves depend on the thickness of antiferromagnetic, ferromagnetic and non-ferromagnetic layers. Exchange coupled field ($H_{ex}$) and magnetoresistance ratio (%) showed the largest value of 20 Oe, 2 % in $glass/Cr_{86}Al_{14}(600 $\AA$)/Ni_{81}Fe_{19}(50$\AA$)/Cu(40 $\AA$)/Ni_{81}Fe_{19}(40 $\AA$)$ spin valves. The $H_{ex}$ MR ratios (%) of CrAl and FeMn spin valves were decreased with increasing annealing temperatures and were lost at 150 $^{\circ}C$, 250 $^{\circ}C$ respectively. Based on these result, it was elucidated that CrAl is more thermally stable than FeMn. It was also shown that there was no change of $H_{ex}$ MR ratios in CrAl, while FeMn was changed and lost 15 days later in corrosion resistance test under 35 $^{\circ}C$, 90 % humidity condition. FeMn was found to be pitted and peeled off 15 days later by SEM micrographic analysis.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.23-29
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• 2011

The oxidation slag has been widely used in civil engineering project, whereas the reduced slag from electric furnace has yet to be applied. Consequently in order to find out the recycling method in civil engineering field, the mineral compositions of the reduced slag were analyzed and some tests on water quality were performed to estimate the potential release of toxic compounds. Slag-soil mixtures of 0, 10, 20 and 30%(dry weight) soil were prepared in lysimeter columns and the effluents were collected with the period of one, two and four week options in closed system, respectively. The result from qualitative and quantitative analysis using X-ray Diffraction(XRD) and X-ray Fluorescence(XRF) indicates that the main mineral of the reduced slag is $Ca_2(SiO_4)$, a kind of calcium silicate. Also, the leaching medium analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy(ICP-OES) showed that main heavy metals such as Al, Fe and Mn are included in the reduced slag due to the effect of steel production process. It can be seen that the leachate does not violate the regulation guide line of waste material of heavy metal. Also the pH levels were increased from pH 6.9 for 0% soil to pH 10 for 30% soil. However the influence on leachate circulation period of one through four weeks was negligible.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.382-393
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• 2020

The engineered barrier system of high-level radioactive waste disposal must maintain its performance in the long term, because it must play a role in slowing the rate of leakage to the surrounding rock mass even if a radionuclide leak occurs from the canister. In particular, it is very important to clarify gas dilation flow phenomenon clearly, that occurs only in a medium containing a large amount of clay material such as a bentonite buffer, which can affect the long-term performance of the bentonite buffer. Accordingly, DECOVALEX-2019 Task A was conducted to identify the hydraulic-mechanical mechanism for the dilation flow, and to develop and verify a new numerical analysis technique for quantitative evaluation of gas migration phenomena. In this study, based on the conventional two-phase flow and mechanical behavior with effective stresses in the porous medium, the hydraulic-mechanical model was developed considering the concept of damage to simulate the formation of micro-cracks and expansion of the medium and the corresponding change in the hydraulic properties. Model verification and validation were conducted through comparison with the results of 1D and 3D gas injection tests. As a result of the numerical analysis, it was possible to model the sudden increase in pore water pressure, stress, gas inflow and outflow rate due to the dilation flow induced by gas pressure, however, the influence of the hydraulic-mechanical interaction was underestimated. Nevertheless, this study can provide a preliminary model for the dilation flow and a basis for developing an advanced model. It is believed that it can be used not only for analyzing data from laboratory and field tests, but also for long-term performance evaluation of the high-level radioactive waste disposal system.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.05a
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• pp.35-81
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• 1998

Distinct Element Method(DEM) has a great advantage to model the discontinuous behaviour of jointed rock masses such as rotation, sliding, and separation of rock blocks. Geometrical data of joints by a field monitoring is not enough to model the jointed rock mass though the results of DE analysis for the jointed rock mass is most sensitive to the distributional properties of joints. Also, it is important to use a properly joint law in evaluating the stability of a jointed rock mass because the joint is considered as the contact between blocks in DEM. In this study, a stochastic modelling technique is developed and the dilatant rock joint is numerically modelled in order to consider th geometrical and mechanical properties of joints in DE analysis. The stochastic modelling technique provides a assemblage of rock blocks by reproducing the joint distribution from insufficient joint data. Numerical Modelling of joint dilatancy in a edge-edge contact of DEM enable to consider not only mechanical properties but also various boundary conditions of joint. Preprocess Procedure for a stochastic DE model is composed of a statistical process of raw data of joints, a joint generation, and a block boundary generation. This stochastic DE model is used to analyze the effect of deviations of geometrical joint parameters on .the behaviour of jointed rock masses. This modelling method may be one tool for the consistency of DE analysis because it keeps the objectivity of the numerical model. In the joint constitutive law with a dilatancy, the normal and shear behaviour of a joint are fully coupled due to dilatation. It is easy to quantify the input Parameters used in the joint law from laboratory tests. The boundary effect on the behaviour of a joint is verified from shear tests under CNL and CNS using the numerical model of a single joint. The numerical model developed is applied to jointed rock masses to evaluate the effect of joint dilation on tunnel stability.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.120-132
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• 2021

Although the development of high-Nickel is being actively carried out to solve the capacity limitation and the high price of raw cobalt due to the limitation of high voltage use of the existing LiCoO₂, the deterioration of the battery characteristics due to the decrease in structural stability and increase of the Ni content. It is an important cause of delaying commercialization. Therefore, in order to increase the high stability of the Ni-rich ternary cathod material LiNi_0.6Co_0.2Mn_0.2O₂, precursor Ni_0.6Co_0.2Mn_0.2-x(OH)₂/xTiO₂ was prepared using a nanosized TiO₂ suspension type source for uniform Ti substitution in the precursor. It was mixed with Li₂CO₃, and after heating, the cathode active material LiNi_0.6Co_0.2Mn_0.2-xTi_xO₂ was synthesized, and the physical properties according to the Ti content were compared. Through FE-SEM and EDS mapping analysis, it was confirmed that a positive electrode active material having a uniform particle size was prepared through Ti-substituted spherical precursor and Particle Size Analyzer and internal density and strength were increased, XRD structure analysis and ICP-MS quantitative analysis confirmed that the capacity was effectively maintained even when the Ti-substituted positive electrode active material was manufactured and charging and discharging were continued at high temperature and high voltage.

• Journal of Mushroom
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• v.16 no.2
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• pp.111-117
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• 2018

This study was conducted to compare the composition and antioxidant activity of 1- and 2-year-old Poria cocos Wolf cultivated at a mortuary and cemetery. An elemental analyzer test showed oxygen, carbon, hydrogen, nitrogen, and sulfur to be present at concentrations of 45~46%, 39~41%, 6.06~6.1%, 0.21~0.22%, and 0%, respectively. No differences in composition were observed among samples. Eleven minerals (S, Ca, Mg, P, As, Se, Cu, Fe, Pb, Zn, and Cd) found in P. cocos cultivated at the mortuary and cemetery were analyzed by inductively coupled plasma mass spectrometry (ICP). The levels of S, Fe, Mg, and Zn in P. cocos were higher in cemetery-cultivated samples than in mortuary-cultivated samples. A 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay for antioxidant activity revealed half-maximal inhibitory concentration ($IC_{50}$)values of P. cocos to be 8.601 mg/mL (mortuary, 1 year old), 12.85 mg/mL (cemetery, 1 year old), 1.23 mg/mL (mortuary, 2 years old), and 1.18 mg/mL (landfill, 1 year old). A 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assay revealed $IC_{50}$ values of 15.85 mg/mL (mortuary, 1 year old),14.59 mg/mL(cemetery, 1 year old), 3.9 mg/mL (mortuary, 2 years old), and 14.92 mg/mL (cemetery, 1 year old). The results showed a concentration-dependent effect. Two-year-old mortuary-cultivated P. cocos had the highest antioxidant activity among samples. Ultrastructure analysis with a field emission scanning electron microscope (FE-SEM) showed no obvious differences among samples.

• Journal of Home Health Care Nursing
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• v.4
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• pp.5-22
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• 1997

The purpose of the study was to development an information delivery system for the home nursing service, to demonstrate and to evaluate the efficiency of it. The period of research conduct was from September 1996 to August 31, 1997. At the 1st stage to achieve the purpose, Firstly Assessment tool for the patients with cerebral vascular disease who have the first priority of HNS among the patients with various health problems at home was developed through literature review. Secondly, after identification of patient nursing problem by the home care nurse with the assessment tool, the patient's classification system developed by Park (1988) that was 128 nursing activities under 6 categories was used to identify the home care nurse's activities of the patient with CAV at home. The research team had several workshops with 5 clinical nurse experts to refine it. At last 110 nursing activities under 11 categories for the patients with CVA were derived. At the second stage, algorithms were developed to connect 110 nursing activities with the patient nursing problems identified by assessment tool. The computerizing process of the algorithms is as follows: These algorithms are realized with the computer program by use of the software engineering technique. The development is made by the prototyping method, which is the requirement analysis of the software specifications. The basic features of the usability, compatibility, adaptability and maintainability are taken into consideration. Particular emphasis is given to the efficient construction of the database. To enhance the database efficiency and to establish the structural cohesion, the data field is categorized with the weight of relevance to the particular disease. This approach permits the easy adaptability when numerous diseases are applied in the future. In paralleled with this, the expandability and maintainability is stressed through out the program development, which leads to the modular concept. However since the disease to be applied is increased in number as the project progress and since they are interrelated and coupled each other, the expand ability as well as maintainability should be considered with a big priority. Furthermore, since the system is to be synthesized with other medical systems in the future, these properties are very important. The prototype developed in this project is to be evaluated through the stage of system testing. There are various evaluation metrics such as cohesion, coupling and adaptability so on. But unfortunately, direct measurement of these metrics are very difficult, and accordingly, analytical and quantitative evaluations are almost impossible. Therefore, instead of the analytical evaluation, the experimental evaluation is to be applied through the test run by various users. This system testing will provide the viewpoint analysis of the user's level, and the detail and additional requirement specifications arising from user's real situation will be feedback into the system modeling. Also. the degree of freedom of the input and output will be improved, and the hardware limitation will be investigated. Upon the refining, the prototype system will be used as a design template. and will be used to develop the more extensive system. In detail. the relevant modules will be developed for the various diseases, and the module will be integrated by the macroscopic design process focusing on the inter modularity, generality of the database. and compatibility with other systems. The Home care Evaluation System is comprised of three main modules of : (1) General information on a patient, (2) General health status of a patient, and (3) Cerebrovascular disease patient. The general health status module has five sub modules of physical measurement, vitality, nursing, pharmaceutical description and emotional/cognition ability. The CVA patient module is divided into ten sub modules such as subjective sense, consciousness, memory and language pattern so on. The typical sub modules are described in appendix 3.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.528-537
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• 2008

60 nm and 20 nm thick hydrogenated amorphous silicon(a-Si:H) layers were deposited on 200 nm $SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by an e-beam evaporator. Finally, 30 nm-Ni/(60 nm and 20 nm) a-Si:H/200 nm-$SiO_2$/single-Si structures were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 40 sec. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide from the 60 nm a-Si:H substrate showed low sheet resistance from $400^{\circ}C$ which is compatible for low temperature processing. The nickel silicide from 20 nm a-Si:H substrate showed low resistance from $300^{\circ}C$. Through HRXRD analysis, the phase transformation occurred with silicidation temperature without a-Si:H layer thickness dependence. With the result of FE-SEM and TEM, the nickel silicides from 60 nm a-Si:H substrate showed the microstructure of 60 nm-thick silicide layers with the residual silicon regime, while the ones from 20 nm a-Si:H formed 20 nm-thick uniform silicide layers. In case of SPM, the RMS value of nickel silicide layers increased as the silicidation temperature increased. Especially, the nickel silicide from 20 nm a-Si:H substrate showed the lowest RMS value of 0.75 at $300^{\circ}C$.