• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.131-136
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• 2016

Currently, an EDM tapping procedure has comprised some parts of the engraving discharge process for the press die. Usually, tapping has been used in cases where we are unable to mechanically machine using steelwork processes due to an increase in the hardness of a material after heat treatment in relation to a design change or missing process. Here, we analyze the influence of discharge tap shape on discharge time, discharge current, and the number of repetition conditions when a cold-work tool steel (STD11) has been treated with a discharge tapped by a screw-shaped cu electrode. The most important influence on processing condition has been determined to be the number of discharge repetitions. As this number increases, the angle reduction of a thread closes to an angle of the electrode via a power generation reduction. The optimal combination of conditions has been determined to be three discharge repetitions, $180{\mu}s$ of discharge time (same as existing regulations), and 25.4A of peak current. A 0.2749db advantage has emerged after comparing between this combination of optimal conditions and the SN rate of existing regulations.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.58-67
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• 1996

This paper describes some computational results of various energy and environmental systems using Patankar's SIMPLE method. The specific topics handled in this study are jet bubbling reactor for flue gas desulfurization, cyclone-type afterburner for incineration, 200m tall stack for 500 MW electric power generation, double skin and heat storage systems of building energy saving for the utilization of solar heating, finally turbulent combustion systems with liquid droplet or pulverized coal particle. A control-volume based finite-difference method with the power-law scheme is employed for discretization. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, that is, SIMPLEC. Reynolds stresses are closed using the standard $k-{\varepsilon}$ and RNG $k-{\varepsilon}$ models. Two-phase turbulent combustion of liquid drop or pulverized coal particle is modeled using locally-homogeneous, gas-phase, eddy breakup model. However simple approximate models are incorporated for the modeling of the second phase slip and retardation of ignition without consideration of any detailed particle behavior. Some important results are presented and discussed in a brief note. Especially, in order to make uniform exit flow for the jet bubbling reactor, a well-designed structure of distributor is needed. Further, the aspect ratio in the double skin system appears to be one of important factors to give rise to the visible change of the induced air flow rate. The computational tool employed in this study, in general, appears as a viable method for the design of various engineering system of interest.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.114.2-114.2
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• 2017

Transparent film heaters (TFHs) based on Joule heating are currently an active research area. However, TFHs based on an indium tin oxide (ITO) monolayer have a number of problems. For example, heating is concentrated in part of the device. Also, heating efficiency is low because it has high sheet resistance ($R_S$). Resistance of indium zinc oxide (IZO) is similar to ITO and it can be used to flexible applications due to its amorphous structure. To solve these problems, our study introduced hybrid layers of IZO/Ag/IZO deposited by magnetron sputtering, and the electrical, optical, and thermal properties were estimated for various thickness of the metal interlayer. It was found that the sheet resistance of the multilayer was mainly dependent on the thickness of the Ag layers. The $R_S$ of IZO(40)/Ag/IZO(40nm) multilayer was 5.33, 3.29, $2.15{\Omega}/{\Box}$ for Ag thickness of 10, 15, and 20nm, respectively, while the $R_S$ of an IZO monolayer(95nm) was $59.58{\Omega}/{\Box}$. The optical transmittance at 550nm for the IZO(95nm) monolayer is 81.6%, and for the IZO(40)/Ag/IZO(40nm) multilayers with Ag thickness 10, 15 and 20nm, is for 72.8, 78.6, and 63.9%, respectively. The defrost test showed that the film with the lowest RS had the highest heat generation rate (HGR) for the same applied voltage. The results indicated that IZO(40)/Ag(15)/IZO(40nm) multilayer has the best suitable property, which is a promising thin film heater for the application in vehicle windshield.

• Journal of Korean Society on Water Environment
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• v.36 no.1
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• pp.55-68
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• 2020

Because of the intensified environmental problems such as climate change and resource depletion, sewage treatment technology focused on energy management has recently attracted attention. The conversion of primary sludge from the primary sedimentation tank and excessive sludge from the secondary sedimentation tank into biogas is the key to energy-positive sewage treatment. In particular, the primary sedimentation tanks recover enriched biodegradable organic matter and anaerobic digestion process produces methane from the organic wastes for energy production. Such technologies for minimizing oxygen demand are leading the innovation regarding sewage treatment plants. However, sewage treatment facilities in Korea lack core technology and operational know-how. Actually, the energy potential of sewage is higher than sewage treatment energy consumption in the sewage treatment, but current processes are not adequately efficient in energy recovery. To improve this, it is possible to apply chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), and anaerobic membrane bioreactor (AnMBR) to the primary sedimentation tank. To maximize the methane production of sewage treatment plants, organic wastes such as food waste and livestock manure can be digested. Additionally, mechanical pretreatment, thermal hydrolysis, and chemical pretreatment would enhance the methane conversion of organic waste. Power generation systems based on internal combustion engines are susceptible to heat source losses, requiring breakthrough energy conversion systems such as fuel cells. To realize the energy positive sewage treatment plant, primary organic matter recovery from sewage, biogas pretreatment, and co-digestion should be optimized in the energy management system based on the knowledge-based operation.

• Nuclear Engineering and Technology
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• v.47 no.1
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• pp.47-58
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• 2015

Four recycling scenarios involving pyroprocessing of spent fuel (SF) have been investigated for a 600-MWe transmutation sodium-cooled fast reactor (SFR), KALIMER. Performance evaluation was done with code system REBUS connected with TRANSX and TWODANT. Scenario Number 1 is the pyroprocessing of Canada deuterium uranium (CANDU) SF. Because the recycling of CANDU SF does not have any safety problems, the CANDU-Pyro-SFR system will be possible if the pyroprocessing capacity is large enough. Scenario Number 2 is a feasibility test of feed SF from a pressurized water reactor PWR. Thefsensitivity of cooling time before prior to pyro-processing was studied. As the cooling time sensitivity of cooling time before prior to pyro-processing was studied. As the cooling time increases, excess reactivity at the beginning of the equilibrium cycle (BOEC) decreases, thereby creating advantageous reactivity control and improving the transmutation performance of minor actinides. Scenario Number 3 is a case study for various levels of recovery factors of transuranic isotopes (TRUs). If long-lived fission products can be separated during pyroprocessing, the waste that is not recovered is classified as low- and intermediate-level waste, and it is sufficient to be disposed of in an underground site due to very low-heat-generation rate when the waste cooling time becomes >300 years at a TRU recovery factor of 99.9%. Scenario Number 4 is a case study for the recovery factor of rare earth (RE) isotopes. The RE isotope recovery factor should be lowered to ${\leq}20%$ in order to make sodium void reactivity less than <7$, which is the design limit of a metal fuel.

• Journal of the Korea Institute of Building Construction
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• v.10 no.1
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• pp.39-47
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• 2010

Fly ash has the advantages, among others, of improving the characteristics of concrete, reducing the price of concrete products, improving the durability, and reducing hydration heat. However, when added in mass, it leads to problems such as insufficient concrete intensity, increase of AE use, and others, resulting in a limitation of the use volume. Therefore, this study is undertaken to solve the problems associated with themass use of fly ash through the high concentration powder ($4000{\sim}8000cm^2/g$) of fly ash, curing method, the addition of an alkali stimulation agent and others for the purpose of increasing the added value of the fly ash. The research showed that the intensity manifestation has an outstanding status, with the hydrates reaching a very stable condition if the rate of addition of a stimulation agent is appropriately used with the heightening of the fineness of the fly ash in the temperature range of $40^{\circ}C$, and if the applicable study is continued, it is likely to result ineffective value generation on the massive replacement of fly ash.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.457-469
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• 2016

During the late phase of severe accidents of light water reactors, a porous debris bed is expected to develop on the bottom of the flooded reactor cavity after breakup of the melt in water. The geometrical configuration, i.e., internal and external characteristics, of the debris bed is significant for the adequate assessment of the coolability of the relocated corium. The internal structure of a debris bed was investigated experimentally using the DAVINCI (Debris bed research Apparatus for Validation of the bubble-Induced Natural Convection effect Issue) test facility. Particle sedimentation under the influence of a two-phase natural convection flow due to the decay heat in the debris bed was simulated by dropping various sizes of particles into a water vessel with air bubble injection from the bottom. Settled particles were collected and sieved to obtain the particle mass, size distribution in the radial and axial positions, and the bed porosity and permeability. The experimental results showed that the center part of the particle bed tended to have larger particles than the peripheral area. For the axial distribution, the lower layer had a higher fraction of larger particles. As the sedimentation progressed, the size distribution in the upper layers can shift to larger sizes because of the higher vapor generation rate and stronger flow intensity.

• Journal of Physiology & Pathology in Korean Medicine
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• v.20 no.6
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• pp.1485-1496
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• 2006

Various kinds of related parameters on hypertension such as anti-oxygen effect, ACE, weight of body, hwart and kidney, blood pressure, heartbeat rates, contents of aldosterone, catecholamine, change rates, of plasma constituents, uric acid, BUN, creatinine were determined to verify the effects on hypertension by Kamisamul-tang (KSMT). And the results are concluded as follows. KSMT did not show any cytotoxicity at the range of concentration (1-250 ${\mu}g/m{\ell}$) on the human fibroblast cell (hFCs). KSMT decreased the production of reactive oxygen species (ROS) and DPPH generation depending on the concentration. KSMT significantly inhibited angiotensin converting enzyme(ACE) activity depending on the concentration compared with control. KSMT maintained body weight of body, heat and kidney nearly normal group in hypertensive rat induced by DOCA-salt. KSMT significantly blood pressure and heart beat rate compared with control in hypertensive rat induced by DOCA-salt. KSMT significantly decreased aldosterone, dopamine, norepineph- rine, epinephrine compared with control in hypertensive rat induced by DOCA-salt. KSMT significantly decreased the level of potassium and cloride compared with control wheareas increased that of calcium significantly in hypertensive rat induced by DOCA-salt. KSMT significantly decreased the level of uric acid and BUN compared with control in hypertensive rat induced by DOCA-salt. It is verified experimentally tat Kamisamultang(KMST) which has been used broadly as a clinical therapeutics in oriental medicine is effective for anti-hypertension mechanism. And it could be applied to develope the reliable prescriptions for anti-hypertension in the future.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.534-540
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• 2014

The analysis of the change in the herbal tea composition according to the difference in processing conditions result. Was slightly reduced crude is treated ash puffing process was relatively increased, moisture, crude protein, the solid elution rate than the roasting process. Benzopyrene content was significantly reduced to 0.18 ppb from 0.35 ppb. Generation of food $B({\alpha})P$ is mainly include the thermal decomposition of food cooking, when the processing which is a main component of food carbohydrate, protein, fat reason despite severe heat treatment as a whole is to be detected even though the $B({\alpha})P$ in this way is considered to be. Generally the taste, aroma and color did not show a big difference but tasted quite stuffy and the strong sour taste reduced its preference.

• The Journal of the Petrological Society of Korea
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• v.1 no.2
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• pp.91-103
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• 1992

Eruptive mechanisms and processes at Udo tuff cone can be inferred from indicative characters of products, bedforms and lithofacies, and ring faults. In terms of bedforms and lithofa-cies in particular, massive lapilli tuff beds and chaotic lapilli tuff beds are derived from subaerial falls of aggregated tephra of wet tephra finger jets, occurring dominantly at the lower sequences of proximal part at the tuff cone. Crudely stratified lapilli tuff are derived from subaerial falls of slightly aggregated tephra of less wet tephra finger jets, whereas reversely graded lapilli tuff beds are from slightly disaggregated subaerial falls of continuous uprush. Both beds frequently occur in the middle sequences at proximal and near medial part of the tuff cone. Block and lapilli tephra lenses, ash-coated lapilli tephra beds(lenses) and thin-bedded tuff beds are derived from extremely disaggregated subaerial falls of dry tephra in the continuous uprush, frequently occurring at the upper sequences of medial part at the tuff cone. Udo tuff cone is a basaltic volcano emergent through the sea water surface while water could flood across or into the vent area. Emergence of the tuff cone was from the type-Surtseyan eruption characterized by earlier tephra finger jets and later continuous uprush columns of tephra with copious volumes of steam. Explosions began when boiling of wter produced a bubble column reducing the hydrostatic pres-sure, allowing exsolution of gases from the magma. This expansion of magma into a vesiculating froth fragmented the magma and permitted mixing of magma and water so that a more vigorous generation of steam could proceed. Tephra finger jetting explosions continued to build the crater rims, then remove water from the vent that their deposits flowed like slsurries until the continuous uprush explosion ensued. Continuous uprush explosions were associated with most rapid accumula-tion of tephra. The increasing volume rate led to partial removal of water from the vent area by the newly tephra ring so that more vigorous activity could be attended by a reducing water supply. This might restrain surplus of cold water entering the vent and thus enhance the vigour of the eruption by allowing optimal heat exchange. Eventually the crater became so deep and unsuported that piecemeal sliding, or massive subsidence on indipping ring faults, filled and closed the vent, and the cycle of explosions and collapse began anew.