• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.64-68
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• 2005

In this study, the smoke flows of the inner subway station were visualized through a numerical analysis and visualization experiment in the subway fire. A transparent acrylic model was designed and installed as 1:25th scale-down as the actual subway station by using geometrical similarity The properties of subway fire were reconstructed according to Densimetric Froude Similarity. The 47 to 53 ratio of the mixed air and Helium was inputted in the inner acrylic model to describe 1MW fire intensity with reference to the experiment paper. For the same time, the fire smoke from a smoke generator was inputted in the inner acrylic model with the mixture. At this time, the buoyancy effect of Helium gas went up the smoke to the acrylic model. When the sheet beam of Ar-lon laser was given out to the top and stair of subway model, the digital camcorder took the images of the scattered cluster of smoke particles when applying the smoke management system and PSD.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.847-849
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• 1992

Fluorine-doped ($SnO_2$:F) thin films obtained by pyrosol deposition method have been exposed to R.F. excited pure hydrogen plasma under the following conditions; substrate temperature of 200$^{\circ}C$, $H_2$ pressure of 1 Torr, R.F. input power of 50 mW/$\textrm{cm}^{2}$, $H_2$ flow rate of 30cc/min and exposure time of 15-600 seconds. It is found that the sheet resistance of the films remains unchanged or rather slightly reduces for initial exposure time of 30-60 seconds, but increases sharply with further increasing the exposure time. The optical transmittance of $SnO_2$:F films slows a rapid fall with increasing exposure time except for a film obtained with a solution having $CH_3OH/H_2O$ mol ratio of 2.65, its degradations at the exposure time of 30-60 seconds are about 7-15%. In addition, the exposure of the films to hydrogen plasma atmosphere leads to remarkable changes in the microstructure and chemical composition, which should be attributed to the reduction of $SnO_2$ to SnO and to elemental Sn.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.97-100
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• 2007

Fuel Cell Stack performance, which is influenced by the maintenance of a constant internal environment, requires high levels of air tightness. Used for analysis, gasket for fuel cell is made of elastic rubber materials and placed over separator, and shape of deformation of a gasket affects the transformation separator and airtightness while fastening structure. Separator as made of steel sheet isn't broken under pressure but can affect gas and cool water flow by the plastic deformation process. Therefore， it is understood that assembly process is well developed in case distribution of stress and shape of deformation is shown uniformly. This study is conducted on the assumption that a fuel cell maintenance is advantageous in that conditions. In this paper, analyses of unit cell and partial model were performed and distribution of stress and shape of deformation of Gasket and separator were analyzed to evaluate the airtightness while fastening structure.

• Journal of the Korean Society for Marine Environment & Energy
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• v.1 no.2
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• pp.40-51
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• 1998

The interaction of contained oil slicks with current was investigated with a two-dimensional experimental setup in the circulating water channel facility. A vertical plate was used to contain the oils against the currents and the evolution of the oil slick, mainly focusing on the water/oil interface, was examined with an aid of a laser sheet. Two different oils - soy bean oil and diesel oil - were studied with varying the current speed (10 cm/sec to 35 cm/sec), the barrier depth (4 cm and 8 cm) and the volume of oil (2 liter to 12 liter). Different types of the interface behavior were observed according to the conditions and their mechanism was discussed based basically on the dimensional analysis. The critical speeds of two types of oil loss mechanism (entrainment failure and drainage failure) were also examined.

• Journal of Nutrition and Health
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• v.34 no.6
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• pp.701-714
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• 2001

The purpose of this study was to apply a PERT-type system, a combination of the project evaluation and review technique(PERT) and critical path method(CPM) on the employees' work time management of flood preparation, assembly, transportation and cleaning in home-delivered meals program for elderly The resources allotment heuristic program was developed by considering the number of employees and cooking utilities, being limited resources of home- delivered meals program. This program could assign the employees to perform the works included in flood preparation, assembly, transportation ind cleaning. Critical path and activities ware identified by PERT-type system on the basic of work time investigation in five senior centers. Work sheets were invented to perform the work by the shortest path with flexible employees'maximum flow As a result of the work time investigation, the most prevalent activities were ones of preparation in center C and E. Besides, the preparation(over fifty percent) was the most proportion among flood preparation, assembly, transportation and cleaning in center C and E. Critical path and activities of 'C'center were cucumber in sauce preparation path and assembly, wrapping in assembly path and case delivery in transportation path. Critical path and activities of 'E'center were Pan-fried Potato Preparation Path and assembly, case covering, wrapping in assembly Path. The work sheet invented by the heuristic program and PERT-type system reduced the work completion time and man hours in both centers.

• Membrane and Water Treatment
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• v.5 no.2
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• pp.73-86
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• 2014

Membrane fouling is a major challenge limiting the use of membrane applications. In this study high induced shear rates were utilized at the membrane surface in order to reduce the organic and inorganic scaling by using the torsional vibration of flat sheet membranes. The performances of a vibratory shear-enhanced processing (VSEP) system for the ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membrane filtration of industrial dairy wastewater were investigated. The vibration and non-vibration methods were compared with the same membrane and operational parameters during the purification of real dairy industrial process wastewater. In the initial experiments, short-term tests were carried out in which the effects of vibration amplitude, recirculation flow rate and transmembrane pressure were measured and compared. The permeate flux, turbidity, conductivity and chemical oxygen demand (COD) reduction of dairy wastewater were investigated by using UF, NF and RO membranes with vibration and non-vibration methods. In the subsequent experiments, concentration tests were also carried out. Finally, scanning electron microscopy (SEM) revealed that the vibration method gave a better performance, which can be attributed to the higher membrane shear rate, which reduces the concentration of solids at the membrane, and the transmission.

• Journal of Computational Design and Engineering
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• v.3 no.1
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• pp.63-70
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• 2016

Deep drawing is a forming process in which a blank of sheet metal is radially drawn into a forming die by the mechanical action of a punch and converted to required shape. Deep drawing involves complex material flow conditions and force distributions. Radial drawing stresses and tangential compressive stresses are induced in flange region due to the material retention property. These compressive stresses result in wrinkling phenomenon in flange region. Normally blank holder is applied for restricting wrinkles. Tensile stresses in radial direction initiate thinning in the wall region of cup. The thinning results into cracking or fracture. The finite element method is widely applied worldwide to simulate the deep drawing process. For real-life simulations of deep drawing process an accurate numerical model, as well as an accurate description of material behavior and contact conditions, is necessary. The finite element method is a powerful tool to predict material thinning deformations before prototypes are made. The proposed innovative methodology combines two techniques for prediction and optimization of thinning in automotive sealing cover. Taguchi design of experiments and analysis of variance has been applied to analyze the influencing process parameters on Thinning. Mathematical relations have been developed to correlate input process parameters and Thinning. Optimization problem has been formulated for thinning and Genetic Algorithm has been applied for optimization. Experimental validation of results proves the applicability of newly proposed approach. The optimized component when manufactured is observed to be safe, no thinning or fracture is observed.

• Journal of ILASS-Korea
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• v.6 no.4
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• pp.14-21
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• 2001

Rotary atomizer is widely used in practical application ranging from combustion, cooling, spray drying, agriculture, chemical system. Rotary cup atomizer has some advantages such as extreme versatility and liquid atomization successfully varying widely in viscosity. In rotary atomization, the feed liquid is centrifugally accelerated to high velocity and the liquid extends over the rotating surface as a thin film before being discharged into an atmosphere. The degree of rotary atomization depends upon peripheral speed, feed rate, liquid properties and atomizer design. An important asset is that thickness and uniformity of the liquid sheet can readily be controlled by regulating the liquid flow rate and the rotational speed. LDPA(Laser Diffraction Particle Analyser) and image aquisition system are used to measure drop size distribution and spray pattern. The atomization characteristics of the rotary cup atomizer is investigated experimentally by varing the liquid feed rate, rotary cup speed and air velocity for atomization. As a results, the effect of air velocity on the atomization characteristics such as drop size and spray uniformity is considerably greater than variation of those with liquid feed rate.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.605-608
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• 2008

The preparation and characteristics of flexible indium tin oxide electrodes grown on polyethylene terephthalate (PET) substrates using a specially designed roll-to-roll sputtering system for use in flexible optoelectronics In spite of low a PET substrate temperature, we can obtain the flexible electrode with a sheet resistance of 47.4 ohm/square and an average optical transmittance of 83.46 % in the green region of 500~550 nm wavelength. Both x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analysis results showed that all flexible ITO electrodes grown on the PET substrate were an amorphous structure with a very smooth and featureless surface, regardless of the Ar/$O_2$ flow ratio due to the low substrate temperature, which is maintained by a cooling drum. In addition, the flexible ITO electrode grown on the Ar ion beam treated PET substrates showed more stable mechanical properties than the flexible ITO electrode grown on the wet cleaned PET substrate, due to an increased adhesion between the flexible ITO and the PET substrates.

• Journal of the Korean Ceramic Society
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• v.44 no.8
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• pp.407-411
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• 2007

A 3-cell stacked anode-supported solid oxide fuel cell was designed and fabricated to achieve a complete gas seal and the facile stacking of components. The stack was assembled with a unit cell with $10{\times}10cm^2$ area, and each cell was interconnected by a stainless steel 430 separator using a proprietary sealant sheet. The stack performance was examined at various gas flow rates of $H_2+3.5vol%\;H_2O$, and air at a fixed temperature of $800^{\circ}C$. No gas leakage was found from the sealing between cells and inter-connects within a measurement system in this research during a prolonged time of 500 h in operation. The test resulted in an open circuit voltage of 3.12 V, a peak power of 149 W, and a power density of $0.61W/cm^2$, while the long term durability of the power showed 19.1% degradation during the prolonged time of 500 h when tested at $800^{\circ}C$.