• Nuclear Engineering and Technology
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• v.45 no.6
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• pp.759-766
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• 2013

As passive safety features for nuclear power plants receive increasing attention, various studies have been conducted to develop safety systems for 3rd-generation (GEN-III) nuclear power plants that are driven by passive systems. The Passive Auxiliary Feedwater System (PAFS) is one of several passive safety systems being designed for the Advanced Power Reactor Plus (APR+), and extensive studies are being conducted to complete its design and to verify its feasibility. Because the PAFS removes decay heat from the reactor core under transient and accident conditions, it is necessary to evaluate the heat removal capability of the PAFS under hypothetical accident conditions. The heat removal capability of the PAFS is strongly dependent on the heat transfer at the condensate tube in Passive Condensation Heat Exchanger (PCHX). To evaluate the model of heat transfer coefficient for condensation, the Multi-dimensional Analysis of Reactor Safety (MARS) code is used to simulate the experimental results from PAFS Condensing Heat Removal Assessment Loop (PASCAL). The Shah model, a default model for condensation heat transfer coefficient in the MARS code, under-predicts the experimental data from the PASCAL. To improve the calculation result, The Thome model and the new version of the Shah model are implemented and compared with the experimental data.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.3
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• pp.254-260
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• 2007

Trichloroethylene(TCE) is widely used as a degreasing solvent in workplaces. TCE is primarily toxic to the nervous system, however, systemic disorder like Stevens-Johnson syndrome has been recently reported in small-scale factories, where the government has had limited information of chemical use. A survey was performed to investigate the actual condition of using TCE and to provide practical information to occupational health service agencies and professionals. This survey was carried out on 103 factories out of 430 factories which were conducted periodic work environment measurement for TCE. Degreasing was the most popular reason for using TCE in Korea, which reached to 94%. TCE was also used as a solvent for rubber in the coating or molding process, and adhesives in the bonding process. Metal fabrication was the most common as 23%, followed by assembling automobile parts (17%), and machinery (12%). Workers exposed to TCE during full-shift were 52% while 48% were exposed during short period of the shift or intermittently. Manual or semi-automatic work occupied 87% while automatic work was just 13%. Though automatic work by a closed system was generally lower exposed to TCE, compared to manual work, it can cause a high exposure when the maintenance system is improper. Semi-automatic work especially like open-top degreasing process can cause a high exposure when local exhaust system with condensing and refrigerating coils in the degreaser does not work well. In conclusion, the survey showed nationwide status of TCE exposure in various aspects. It can be used to monitor workplaces and workers exposed to TCE to prevent occupational diseases.

• Journal of computational fluids engineering
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• v.10 no.2
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• pp.38-47
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• 2005

Substructuring methods are often used in finite element structural analyses. In this study a multi-level substructuring(MLSS) algorithm is developed and proposed as a possible candidate for finite element fluid solvers. The present algorithm consists of four stages such as a gathering, a condensing, a solving and a scattering stage. At each level, a predetermined number of elements are gathered and condensed to form an element of higher level. At the highest level, each sub-domain consists of only one super-element. Thus, the inversion process of a stiffness matrix associated with internal degrees of freedom of each sub-domain has been replaced by a sequential static condensation of gathered element matrices. The global algebraic system arising from the assembly of each sub-domain matrices is solved using a well-known iterative solver such as the conjugare gradient(CG) or the conjugate gradient squared(CGS) method. A time comparison with CG has been performed on a 2-D Poisson problem. With one domain the computing time by MLSS is comparable with that by CG up to about 260,000 d.o.f. For 263,169 d.o.f using 8 x 8 sub-domains, the time by MLSS is reduced to a value less than $30\%$ of that by CG. The lid-driven cavity problem has been solved for Re = 3200 using the element interpolation degree(Deg.) up to cubic. in this case, preconditioning techniques usually accompanied by iterative solvers are not needed. Finite element formulation for the incompressible flow has been stabilized by a modified residual procedure proposed by Ilinca et al.[9].

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.182-188
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• 2011

In this paper, analysis on the performance characteristics of R744-R404A cascade refrigeration system is presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in R404A high- and R744 low-temperature cycle, respectively. The main results were summarized as follows : It was observed that the highest COP of the system is achieved by higher superheating degree in R744 cycle than that in R404A cycle. The COP of the system increased by giving the subcooling degree in both cycles. The COP of the cascade system is the highest value when the system is operated at an optimum evaporation temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.189-195
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• 2011

In this paper, prediction and comparison on COP(coefficient of performance) of R744-R404A cascade refrigeration system are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooling and superheating degree, compressor efficiency, and condensing and evaporating temperature in the R404A high- and R744 low-temperature cycle, respectively. The main results were summarized as follows : The prediction for performance of R744-R404A cascade refrigeration system have been proposed through multiple regression analysis and compared with other researcher's correlations. As a result, prediction proposed in the study shows disagreement with existing equations. Therefore, it is necessary to propose the more accurate correlation predicting the COP of R744-R404A cascade refrigeration system through an addition experiments.

• Journal of the Korea Computer Industry Society
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• v.8 no.2
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• pp.103-106
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• 2007

In order to construct a Video Database, shot change detection should be made first. But, because these processes are not automated perfectly, we need a lot of time and efforts now. And, there are many shot change detection algorithms, which can't always insure the perfect result because of the editing effects such as cut, wipe, and dissolves used in film production. Therefore, in order to receive the exact shot change, It needs the verification and correction by manual processing at any cost. Spatiotemporal slice is a simple image condensing method for the content changes of video. The editing effects are expressed on the Spatiotemporal slice in the visually noticed form of vertical line, diagonal line, curved line and gradual color changes, etc. Accordingly the parts doubted as a shot change can be easily detected by the change of the Spatiotemporal slice without replaying the video. The system proposed in this study makes it possible to delete the false detected key frames, and create the undetected key frames on the Spatiotemporal slice.

• Korean Journal of Pharmacognosy
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• v.11 no.3_4 s.43
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• pp.133-140
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• 1980

In order to develop the radio-immunoassay procedure for the ginsenoside $Rg_1$ we prepared the $Rg_1-BSA$ conjugate and $Rg_1-tyramine$ conjugate by condensing the $Rg_1-azide$, which was prepared by a series of six step chemical modification of the $Rg_1-side$ chain, with bovine serum albumin(BSA) or with tyramine. Rabbits were immunized by repeated injection of $Rg_1-BSA$ conjugate with Freund's Complete Adjuvant for 5 month long to obtain very potent $anti-Rg_1$ serum. The radio-labelled haptene was prepared by direct radio-iodination $(125_J)$ of $Rg_1-tyramine$ according to the chloramine-T method. The radio-immunoassay procedure was successfully furnished by using DCC method (dextran coated charcoal) and the anti-body titer of the anti-serum was found as being $1600{\sim}3200$ by using 15000cpm tracer per test. Calibration test using non-labelled $Rg_1$ showed linear competetive binding response in the $(8-300){\times}34pg$. range of non-labelled $Rg_1$. The cross reaction test using 19 ginsenoside analogues enabled us a full structure-activity analysis on the antigen-antibody reaction that the anti-body in the serum would recognize the full structure of ginsenoside $Rg_1$ except the side chain moiety.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1245-1252
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• 2001

The condensation pressure drop for pure refrigerants R-22, R-134a, and a binary refrigerant mixture R-410A flowing in a small diameter tube was investigated. The test section is a counterflow heat exchanger with refrigerant flowing in the inner tube and coolant flowing in the annulus. The test section consists of 1220 [mm] length with horizontal copper tube of 3.38 [mm] outer diameter and 1.77 [mm] inner diameter. The refrigerant mass fluxes ranged from 450 to 1050 [kg/(㎡$.$s)] and the average inlet and outlet qualities were 0.05 and 0.95, respectively. The main experimental results were summarized as follows : In the case of single-phase flow, the pressure drop of R-134a is much higher than that of R-22 and R-410A for the same Reynolds number. The friction factors for small diameter tubes are higher than those predicted by Blasius equation. In the case of two-phase flow, the pressure drop increases with increasing mass flux and decreasing quality. The pressure drop of R-134a is much higher than that of R-22 and R-410A for the same mass flux. Most of correlations proposed in the large diameter tube showed enormous deviations with experimental data. However, the correlation predicted by Honda et al showed relatively good agreement with experimental data for R-134.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.21-29
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• 2012

A dual loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency of gasoline vehicles has been investigated. A high temperature loop (HT loop) only recovers the heat of the exhaust gas. A low temperature loop (LT loop) recovers the residual heat from the HT loop, the coolant heat and the remaining exhaust gas heat. The two separate loops are coupled with a heat exchanger. This paper has dealt with a layout of the dual loop system, the review of the working fluids, and the design of the cycle. The design point and the target heat recovery of the HT boiler, a core part of a HT loop, have been presented. The prototype of the HT boiler was evaluated by experiment. For the performance evaluation of the HT boiler, inlet temperature of the HT boiler working fluid was set equal to the temperature degree of sub-cool of $5^{\circ}C$ at the condensing pressure. The exit condition was the degree of super-heat set at $5^{\circ}C$. The characteristics of the HT boiler such as heat recovery and pressure drops of fluids were evaluated with varying flow rates and inlet temperatures of exhaust gas under various evaporating pressure conditions.

• Economic and Environmental Geology
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• v.25 no.3
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• pp.283-296
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• 1992

The Keumryeong deposits is a low grade copper deposits in which copper minerals form disseminated grains and thin veinlets in felsic volcanics seem to be dacite. Alteration of the volcanics consists mainly pervasive propylitization and silicification. Potassic alteration characterized by biotite developed locally adjacent to southwestern contact of granodiorite body. Principal sulfide minerals in altered zone are mainly pyrite and lesser chalcopyrite. Chalcopyrite content in potassic zone is relatively higher than that of surrounding propylitized zone. Pyrite and chalcopyrite accompanies magnetite, molybdenite, sphalerite, pyrrhotite, arsenopyrite, pentlandite, marcasite, hematite, ilmenite, rutile, bismuthinite and native Bi as disseminations, veinlets and knots. Granodiorite body is propylitized and contains veinlets of pyrite, chalcopyrite and molybdenite. Fluid inclusions in sulfide-bearing quartz veinlets and quartz grains of felsic volcanics and granodiorite in altered zone consist of liquid-rich, vapor-rich, $CO_2-bearing$ and halite-bearing inclusions. These four types of inclusion intimately associated on a microscopic scale and indicate condensing or boiling of ore fluid during mineralization. Homogenization temperature of coexisting fluid inclusions are mostly in the range of 350 to $450^{\circ}C$. High salinity fluid contains 28.6 to 48.4 weight percent NaCI equivalent and moderate salinity fluid cotains 0.5 to 12.5 weight percent NaCl equivalent. Pressure estimated from $CO_2$ mole fraction of $CO_2-bearing$ inclusion range 160 to 375 bars. The Kigu copper deposits is a fissure filling copper vein developed 500 m south from the Keumryong deposits. Mineralogy and fluid inclusion data of the Kigu deposits are similar to that of the Keumryeong deposits. Homogenization temperature of fluid inclusions from the Kigu deposits are reasonable agreement with temperature estimated from sulfidation curve of cubanite-chalcopyrite-pyrite-pyrrhotite and pyrite-pyrrhotite mineral assemblages. Not only mineral occurrence and wall rock alteration in the Keumryeong deposits but also fluid inclusion data such as temperature, salinity, pressure and boiling evidences are similar to those of porphyry copper deposits.