• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.220-220
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• 2009

In case of favourable irradiation conditions, the ratio of irradiation to the total irradiation went up and then the irradiation increased in the area with high angle of inclination. The study showed that on a clear day with the irradiation of more than $800[W/m^2]$, the pattern of alternating current power change in the fixed system was similar with that in the single-axis tracker. On the contrary, in case of unfavourable irradiation conditions, the ratio of diffuse irradiation to the total irradiation went up and then the horizontal irradiation increased. In the demo system, the fixed system, the single-axis tracker and the dual-axis tracker all had low generation power and similar generation pattern with each other. The study showed the generation power varied with the irradiation in the fixed system, while in the single-axis tracker and the dual-axis tracker, the amount of the generation power variation was much more than the irradiation variation. The demo system was operated from 11:00 AM to 2:00 PM for generating power, during which time, 46[%] to 56[%] of the total generation power was produced. In this study. the generation power was increased by 147[%] in the fixed system, by 136[%] in the single-axis tracker, and by 164[%] in the dual-axis tracker, and the pattern of generation power was similar with the generation power variation in the situation where the irradiation increased by 140[%] in the spring with plenty of insolation. The alternating current power was more sensitive to variation of the irradiation than to that of the surface temperature of a module. The variation of the irradiation had a more positive effect on the generation power than the type of array.

• The korean journal of orthodontics
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• v.19 no.1 s.27
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• pp.45-59
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• 1989

This study was undertaken to analyze the displacement and stress distribution in the mandible according to the pulling directions during mandibular first molar cervical traction after mandibular second molar extraction. The 3-dimensional finite element method(FEM) was used for a mathematical model composed of 594 elements and 1019 nodes. An orthodontic force, 450 gm, was applied to the each mandibular first molar in parallel, and below the occlusal plane by $7^{\circ}\;and\;25^{\circ}$ and meet the midsagittal plane by $40^{\circ}$ toward posterior direction. The results were as follows: 1. Mandibular teeth were displaced in more downward, posterior and lateral direction. Especially high stress was noted in case of parallel pull than in case of below the occlusal plane by $7^{\circ}\;and\;25^{\circ}$. 2. Mandibular first molar was moved bodily. 3. Generally, alveolar bone, mandibular body, ascending ramus and mandibular angle portion were displaced in downward, posterior and lateral direction. But coronoid process was displaced in downward, forward and lateral direction, and anterior and inner middle portion of condyle head and neck were displaced in downward, forward and medial direction, and posterior and outer middle portion of condyle head and neck were displaced in upward, forward and medial direction. 4. Maximum stress was observed at the condyle head and neck portion. With steeper direction of force, condyle head and neck showed more stress than parallel relation to the occlusal plane.

• Membrane and Water Treatment
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• v.7 no.2
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• pp.101-113
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• 2016

In this study, to improve the water flux of porous hydrophobic membranes, various water-soluble polymers including neutral, cationic and anionic polymers were adsorbed using 'salting-out' method. The adsorbed hydrophobic membrane surfaces were characterized mainly via the measurements of contact angles and scanning electron microscopy (SEM) images. To enhance the durability of the modified membranes, the water-soluble polymers such poly(vinyl alcohol) (PVA) were crosslinked with glutaraldehyde (GA) and found to be resistant for more than 2 months in vigorously stirred water. The water flux was much more increased when the ionic polymers used as the coating materials rather than the neutral polymer and in this case, about 70% of $0.31L/m^2{\cdot}h$ (LMH) to 0.50 LMH was increased when 300 mg/L of polyacrylamide (PAAm) was used as the coating agents. Among the cationic coating polymers such as poly(styrene sulfonic acid-co-maleic acid) (PSSA_MA), poly(acrylic acid-comaleic acid) (PAM) and poly(acrylic acid) (PAA), PSSA_MA was found to be the best in terms of contact angle and water flux. In the case of PSSA_MA, the water flux was enhanced about 80%. The low concentration of the coating solution was better to hydrophilize while the high concentration inclined to block the pores on the membrane surfaces. The best coating condition was found: (1) coating concentration 150 to 300 mg/L, (2) ionic strength 0.15, (3) coating time 20 min.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.43-45
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• 2009

In case of favourable irradiation conditions, the ratio of irradiation to the total irradiation went up and then the irradiation increased in the area with high angle of inclination. The study showed that on a clear day with the irradiation of more than 80$[W/m^2]$, the pattern of alternating current power change in the fixed system was similar with that in the single-axis tracker. On the contrary, in case of unfavourable irradiation conditions, the ratio of diffuse irradiation to the total irradiation went up and then the horizontal irradiation increased. In the demo system, the fixed system, the single-axis tracker and the dual-axis tracker all had low generation power and similar generation pattern with each other. The study showed the generation power varied with the irradiation in the fixed system, while in the single-axis tracker and the dual-axis tracker, the amount of the generation Power variation was much more than the irradiation variation. The demo system was operated from 11:00 AM to 2:00 PM for generating power, during which time, 46[%] to 56[%] of the total generation power was produced. In this study, the generation power was increased by 147[%] in the fixed system, by 136[%] in the single-axis tracker, and by 164[%] in the dual-axis tracker, and the pattern of generation power was similar with the generation power variation in the situation where the irradiation increased by 140[%] in the spring with plenty of insolation. The alternating current power was more sensitive to variation of the irradiation than to that of the surface temperature of a module. The variation of the irradiation had a more positive effect on the generation power than the type of array.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.109-117
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• 2020

A structured grid system can be efficiently constructed by applying the patched-grid algorithm that alleviates many constraints of the conventional structured grid system. Three approaches were applied to case 4 of the EFD-CFD workshop: delta wing-cylindrical body shape to solve the existing grid generation problems and verify the results by comparing them with experimental data. Surface pressure distributions slightly differed from the experimental data at high angles of attack. The slope variation of the pitching moment with Mach number is analyzed and the variation can be explained with the tuck under phenomenon. In the supersonic region, the bow shock waves in front of the shape expand the region generating lift up to the rear of the configuration. Also, the tendency of the pitching moment with both Mach number and angle of attack was analyzed by comparing the positions of the center of pressure and the center of gravity.

• Fire Science and Engineering
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• v.24 no.5
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• pp.79-86
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• 2010

In this study, we confirmed the fact that air egress velocity of pressure differential system which is installed in vestibule of smokeproof stairway in domestic high-rise building becomes back-flow into the vestibule not into the livingroom when the doors open to escape in case of fire by actual measurement. It concerned that fire smoke inflow into the vestibule of smokeproof stairway. so, reflux symptoms were developing the condition does not occur by creating an area of $2m^2$ and a model. if it‘s area is less, airflow in upper area was severely reflux. in the case upward 45 gradient of supply damper’s angle of blade, The results that reflux symptoms include upper door but bottom has some reflux. also vestibule of smokeproof stairway‘s area of $4m^2$ in the living room door in the direction of the flow distributon was normal. if a vestibule of smokeproof stairway is smaller, it designed to be performance-based design should be.

• Fibers and Polymers
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• v.7 no.3
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• pp.317-322
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• 2006

Reduction of yam hairiness by nozzles in ring spinning and winding is a new approach. Simulation of the airflow pattern inside the nozzles provides useful information about actual mechanism of hairiness reduction. The swirling air current inside the nozzles is capable of wrapping the protruding hairs around the yam body, thereby reducing yam hairiness. Since production rate of winding is very high and the process itself increases yarn hairiness any method to reduce the hairiness of yarns at this stage is a novel approach. A CFD (computational fluid dynamics) model has been developed to simulate the airflow pattern inside the nozzles using Fluent 6.1 software. In this study, both S- and Z-type nozzles having an axial angle of 500 and diameter of 2.2 mm were used for simulation studies. To create a swirling effect, four air holes of 0.4 mm diameter are made tangential to the inner walls of the nozzles. S- and Z-twisted yams of 30 tex were spun with and without nozzles and were tested for hairiness, tensile and evenness properties. The total number of hairs equal to or exceeding 3 mm (i.e. the S3 values) for yam spun with nozzle is nearly 49-51 % less than that of ring yams in case of nozzle-ring spinning, and 15 % less in case of nozzle-winding, while both the yarn types show little difference in evenness and tensile properties. Upward airflow gives best results in terms of hairiness reduction for nozzle-ring and nozzle wound yams compared to ring yarns. Yarn passing through the centre of the nozzle shows maximum reduction in S3 values.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.307-314
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• 2004

A circumferential guided wave method was developed to detect the axial crack on the bent feeder pipe. Dispersion curves of circumferential guided waves were calculated as a function of curvature of the pipe. In the case of thin plate, i.e. infinite curvature, as the frequency increases, the $S_0$ and $A_0$ mode coincide and eventually become Rayleigh wave mode. In the case of pipe, however, as the curvature increases, the lowest modes do not coincide even in the high frequencies. Based on the analysis, a rocking technique using angle beam transducer was applied to detect an axial defect in the bent region of PHWR feeder pipe. Based on the analysis of experimenal data for artificial notches, the vibration modes of each signal were identified. It was found that the notches with the depth of )0% of wall thickness can be detected with the method.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.1
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• pp.31-36
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• 2019

As the number of elderly population increases, the proportion of edentulous patients is increasing, and the demand for traditional dentures will also increase. Arranging the artificial teeth according to the relationship and shape of the upper and lower alveolar ridge is an important factor increasing the stability of the denture. This case is a 79 year old female patient who wishes to make denture covered by national health insurance for psychological and economical reasons. With the alveolar bone severely atrophic, the dental CAD software was used for accurate diagnosis and the posterior teeth were arranged in a cross bite according to the interalveolar crest line angle by the program. After completion, the denture showed adequate stability and maintenance in periodic examinations and treatment, and the patient also expressed high satisfaction.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.156-157
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• 1998

It is a diffcult and challenging pproblem to control the growth of eppitaxial films. Heteroeppitaxy is esppecially idfficult because of the lattice mismatch between sub-strate and depposited layers. This mismatch leads usually to a three dimensional(3D) island growth. But the use of surfactants such as As, Sb, and Bi can be beneficial in obtaining high quality heteroeppitaxial films. In this study medium energy ion scattering sppectroscoppy(MEIS) was used in order to reveal the growth mode of Ge on Si(001) and the strain of depposited film without and with dynamically supplied atomic hydrogen at the growth thempperature of 35$0^{\circ}C$. It was ppossible to control the growth mode from layer-by-layer followed by 3D island to layer-by-layer by controlling the hydrogen flux. In the absent of hydro-gen the film grows in the layer-by-layer mode within the critical thickness(about 3ML) and the 3D island formation is followed(Fig1). The 3D island formation is suppressed by introducing hydrogen resulting in layer-by-layer growth beyond the critical thickness(Fig2) We measured angular shift of blocking dipp in order to obtain the structural information on the thin films. In the ppressence of atomic hydrogen the blocking 야 is shifted toward higher scattering angle about 1。. That means the film is distorted tetragonally and strained therefore(Fig4) In other case the shift of blocking dipp at 3ML is almost same as pprevious case. But above the critical thickness the pposition of blocking dipp is similar to that of Si bulk(Fig3). It means the films is relaxed from the first layer. There is 4.2% lattice mismatch between Ge and Si. That mismatch results in about 2。 shift of blocking dipp. We measured about 1。 shift. This fact could be due to the intermixing of Ge and Si. This expperimental results are consistent with Vegard's law which says that the lattice constant of alloys is linear combination of the lattic constants of the ppure materials.