• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.39-48
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• 2005

As the industrial development is accelerated, a new machining process and system are keenly required to achieve super precision surface finish. Especially to get ground surface finish fer complicated and narrow inner shape of molds, it is impossible with the existing methods so that a new method is being required to be developed. A new material, called Magic(MAGnetic Intelligent Compounds), is finally made and it is called Magic machining that uses this material. There is a way to make a material as follows, the mixture of magnetic particles, bonding material and particles of abrasive grain should be melt down by proper heat, and then this mixture put in a mold and cool down in magnetic field which has a uniform direction. This new polishing method is spotlighted as an excellent solution to the existing problems. However it hasn't reported any study about the influence of the machining conditions of polishing velocity, amplitude and polishing pressure to the surface roughness yet. This study would examine closely the influence of polishing conditions of the Magic polishing tool to the surface finish to decide the optimum polishing condition and to standardize the Magic polishing work.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.2
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• pp.9-16
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• 2015

High loading of base paper is regarded as one of reasons to aggravate fold cracking of coated paper. But the relationship between the ash content of base paper and fold cracking of coated paper has not been shown yet. We investigated the effect of ash content in base paper on the fold cracking of coated paper. Handsheets with three different ash contents (19.5-23.5%) were prepared, and double layered coating were applied on the top side of the handsheets. A gravimetric water retention meter (AA-GWR) was employed to fold the paper with a uniform pressure after solid printing on the coated surface. The fold cracking was digitized by calculating the cracked area by means of an image analysis technique. Results suggested that high ash content in the base paper increased the fold cracking of the outer surface of coated papers. In the case of inner surface greater fold crack areas were obtained, and the number of cracks decreased because long and wide cracks were formed. Reduction in tensile strength and thickness appeared to give greater fold cracking for highly loaded papers.

• Journal of Biosystems Engineering
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• v.28 no.6
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• pp.497-504
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• 2003

The objectives of this study were to develop a harvesting gripper for perilla leaves and test its performance, which was a partial work of the automated perilla leaves harvesting system development. The results of this study could be summarized as the followings: The shear forces for harvesting the perilla were measured. The measured results showed that the average shear force required was 12.13N for cutting the petioles attached to the perilla stalks, and the maximum of 17.42N. The inner diameter of air cylinder used was 6mm and the air pressure was maintained as 0.7㎫ during the tests. The time required for cutting perilla leaves could be adjusted by the control program and cutting operation could be done within 1- 10 seconds. The performance tests were conducted to harvest the perilla leaves by the gripper developed. The average success rates of cutting were 72.2％ for the first test, 78.5％ for the second, and 74.2％ for the last. The perilla leaves were not damaged by the gripper The whole system operation could be finished within three seconds except the delay time for dropping harvested leaves.

• Korean Journal of Animal Reproduction
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• v.8 no.1
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• pp.29-35
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• 1984

These experiments were carried out to obtain basic information necessary for in vitro culture of aggregated mouse embryos. Inbred ICR mice were used to obtain embryos. The zona pellucida was removed by placing the embryos in Whittingham's medium containing 0.5% protease for about 5-10minutes at 37$^{\circ}C$. Total 263 pairs of 2-, 4- and 8-cell zona free mouse embryos were subjected to aggregation by physical pressure and cultured in Whittingham's medium under the gas phase of 5% CO2 in air at 37$^{\circ}C$ for 24 to 60 hours. The results obtained in these experiments were summarized as follows: 1. Time needed for fusion of 2-, 4- and 8-cell embryos were 0-3, 0-3 and 0-3 hours, respectively and average time needed for in vitro development of 2-, 4- and 8-cell embryos after aggregation to morula and blastocyst were 42, 30 and 13.5 hours, and 51, 39 and 27 hours, respectively. 2. Of total 263 pairs of naked embryos, 227 were firmly aggregated together and the rats of aggregation in 2-, 4- and 8-cell embryos were 71.8, 88.3 and 97.0%, respectively. 3. The rates of aggregated pairs which obtained from 2-, 4- and 8-cell embryos developed to morula were 96.7, 95.6 and 96.9%, respectively, and embryos developed to blastocysts were 88.5, 89.7 and 90.8%, respectively. 4. Conspicuous differences in size of volume and inner cell masses between single and double blastocysts were observed. Although a single blastocolic cavity was formed in most double blastocysts, several formed two distinct cavities from the very beginning.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.165-169
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• 2004

Craniofacial dysostosis is considered to be one of rarely observed syndromes characterized by premature closing of all cranial sutures. The first patient was a 4-year-old male infant who had been complaining of empyema. Clinical findings showed exophthalmos, hypertelorism and facial asymmetry. Conventional radiographs demonstrated abscence of cranial sutures and underdeveloped maxilla. CT scan demonstrated the digital impressions of the inner surface of the cranial vault, enlarged and depressed sella turcica. The second patient was a 2-year-old female infant who had been complaining of facial deformity. Clinical findings showed hypertelorism and underdeveloped maxilla. Radiographs showed premature synostosis of all cranial sutures, depressed and enlarged sella turcica, and hypoplastic maxilla. 3 years after operation, her look improved. However, resurgery may be considered to decreasing intracranial pressure and for correction of facial deformity. Two interesting cases showing ‘cloverleaf’ skulls were presented.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.172-179
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• 2004

Average Bi-directional flow tube was suggested to measure single and two phase flow rate. Its working principle is similar with Pilot tube, however, it makes it possible to eliminate the cooling system which is normally needed to prevent from flashing in the pressure impulse line of Pilot tube when it is used in the depressurization condition. The suggested instrumentation was tested in the air-water vertical test section which has 80mm inner diameter and 10m length. The flow tube was installed at 120 of L/D from inlet of test section. From the test, single air and water flow rate was measured successfully. For the emasurement of two phase flow rate, Chexal drift-flux correlation was used. In the test a new correlation of momentum exchange factor was suggested. The test result shows that the suggested instrumentation using the measured void fraction and Chexal drift-flux correlation can predict the mass flow rates within $10\%$ error of measured data.

• Bulletin of the Society of Naval Architects of Korea
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• v.19 no.1
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• pp.23-32
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• 1982

Herein the motion of a freely-floating sphere in a water of finite depth is analysed within the framework of a linear potential theory. A velocity potential describing fluid motion is generated by distributing pulsating sources and dipoles on the immersed surface of the sphere, without introducing an inner flow model. The potential becomes the solution of an integral equation of Fredholm's second type. In the light of the vertical axisymmetry of the flow, surface integrals reduce to line integrals, which are approximated by summation of the products of the integrand and the length of segments along the contour. Following this computational scheme the diffraction potential and the radiation potential are determined from the same algorithm of solving a set of simultaneous linear equations. Upon knowing values of the potentials hydrodynamic forces such as added mass, hydrodynamic damping and wave exciting forces are evaluated by the integrating pressure over the immersed surface of the sphere. It is found in the case of finite water depth that the hydrodynamic forces are much different from the corresponding ones in deep water. Accordingly motion response of the sphere in a water of finite depth displays a particular behavior both in a amplitude and phase.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.1022-1035
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• 2016

A double-tube once-through steam generator (DOTSG) consisting of an outer straight tube and an inner helical tube is studied in this work. First, the structure of the DOTSG is optimized by considering two different objective functions. The tube length and the total pressure drop are considered as the first and second objective functions, respectively. Because the DOTSG is divided into the subcooled, boiling, and superheated sections according to the different secondary fluid states, the pitches in the three sections are defined as the optimization variables. A multi-objective optimization model is established and solved by particle swarm optimization. The optimization pitch is small in the subcooled region and superheated region, and large in the boiling region. Considering the availability of the optimum structure at power levels below 100% full power, we propose a new operating scheme that can fix the boundaries between the three heat-transfer sections. The operation scheme is proposed on the basis of data for full power, and the operation parameters are calculated at low power level. The primary inlet and outlet temperatures, as well as flow rate and secondary outlet temperature are changed according to the operation procedure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.340-348
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• 2005

Repeated ribs are used on heat exchange surfaces to promote turbulence and enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concern detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue is tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall have a $45{\circ}C$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increase with increasing the number of rough walls.

• Microbiology and Biotechnology Letters
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• v.20 no.3
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• pp.243-248
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• 1992

In order to examine the viability depending on rehydration process and membrane injury of Nocardia mediterranei upon lyophilization, We labeled $3^H$-thymidine in deoxyribonucleic acid of N. mediterrranei to obtain information on the mechanisms of injury caused by lyophilization. Suspensions of rehydrated cells were incubated with added DNase in a buffer solution. Extracellular radioactivity levels appeared to be high in the rehydrated solutions after lyophilization than freezing-thawing. Thus, the membrane systems were injured by lyophilization, but not ovenvhelmed. These considerations were confirmed by electron microscopy. In effects of rehydration, the cell membrane was seriously damaged by strong atmospheric pressure as soon as the inner ampule was opened, but this was not the case without admitting air under vacuum. N. rnediterranei cells, with no additives, were lyophilized and reconstituted without admitting air, virtually about 84% of the cells were viable.