• The KIPS Transactions:PartC
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• v.17C no.2
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• pp.159-164
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• 2010

The data wiping is a technique which perfectly deletes data in a storage to prevent data recovery. Currently, management of stored data is important because of increasing an accident of personal information leakage. Especially, if you need to discard data contained personal information, using a wiping tool which permanently deletes data to prevent unnecessary personal information leakage. The data wiping is also used for data security and privacy protection. However the data wiping can be used intentionally destruction of evidence. This intentionally destruction of evidence is important clues of forensic investigation. This paper demonstrates the methods for detecting the usage of wiping tools in digital forensic investigation.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.46.2-46.2
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• 2019

We propose a deep learning model that can generate a waveform of coalescing binary black holes in merging and ring-down phases in less than one second with a graphics processing unit (GPU) as an approximant of gravitational waveforms. Up to date, numerical relativity has been accepted as the most adequate tool for the accurate prediction of merger phase of waveform, but it is known that it typically requires huge amount of computational costs. We present our method can generate the waveform with ~98% matching to that of the status-of-the-art waveform approximant, effective-one-body model calibrated to numerical relativity simulation and the time for the generation of ~1500 waveforms takes O(1) seconds. The validity of our model is also tested through the recovery of signal-to-noise ratio and the recovery of waveform parameters by injecting the generated waveforms into a public open noise data produced by LIGO. Our model is readily extendable to incorporate additional physics such as higher harmonics modes of the ring-down phase and eccentric encounters, since it only requires sufficient number of training data from numerical relativity simulations.

• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.360-368
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• 2020

Wear resistance of cutting tools is one of the most important requirements in terms of the durability of cutting tool itself as well as the machining accuracy of the workpiece. Generally, tungsten carbide ball end mills have been processed with hard coatings for high durability and wear resistance such as diamond coating and tetrahedral amorphous carbon(ta-C) coating. In this study, we developed multilayer ta-C coatings whose wear resistance is comparable to that of diamond coating. First, we prepared single layer ta-C coatings according to the substrate bias voltage and Ar gas flow, and the surface microstructure, raman characteristics, hardness and wear characteristics were evaluated. Then, considering the hardness and wear resistance of the single layer ta-C, we fabricated multilayer coatings consisting of hard and soft layers. As a result, it was confirmed that the wear resistance of the multilayer ta-C coating with hardness of 51 GPa, and elastic recovery rate of 85% improved to 97% compared to that of the diamond coated ball end mill.

• Natural Product Sciences
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• v.5 no.2
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• pp.88-92
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• 1999

Inhibition of gap junction-mediated intercellular communication (GJIC) has been considered as an important factor in the tumor promotion phase of carcinogenesis. Recovery effects of natural products on gap junctional intercellular communication are measured by scrape-loading and dye transfer method using Lucifer yellow after administration of phorbol-12-myristate-13-acetate (PMA) on WBF344 cells. Among tested natural products, the hexane fraction and subfractions (F-01 and F-04) of Setaria italica were relatively effective for recovery of GJIC. The hexane fraction of Setaria italica $(EC_{25},\;12.14\;{\mu}g/ml)$ and subfractions $(F-01:EC_{50},\;10.74\;{\mu}g/ml;EC_{25},\;1.58\;{\mu}g/ml,\;F-04:EC_{50},\;11.03\;{\mu}g/ml;\;EC_{25},\;3.12\;{\mu}g/ml)$ revealed dose-dependent recovery effects on GJIC. Our data show GJIC activity measurement by Lucifer yellow spread on cells can be an effective tool for the screening of natural products with possible cancer chemopreventive effects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.6
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• pp.403-410
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• 2009

This paper proposes a new approach to find the optimum ratios between sizes of the heat exchangers of the heat recovery steam generator (HRSG) system with limited size to maximize the efficiency of the steam turbine (bottom) cycle of combined cycle power plants (CCPP), but without performing the bottom cycle analysis. This could be achieved by minimizing the unavailable exergy (the sum of the destroyed and the lost exergies) resulted from the heat transfer process of the HRSG system. The present approach is relatively simple and straightforward because the process of the trial-and-error method, typical in performing the bottom cycle analysis for the system optimization, could be avoided. To demonstrate the usefulness of the present method, a single-stage HRSG system was chosen and the optimum evaporation temperature was obtained corresponding to the condition of the maximum useful work. The results show that the optimum evaporation temperature based on the present exergy analysis appears similar to that based on the bottom cycle analysis. Also shown is the dependency of size (NTU) ratios between the heat exchangers on the inlet gas temperature, which is another important factor in determining the optimum condition once overall size of the heat recovery steam generator is given. The present approach turned out to be a useful tool for optimization of the singlestage HRSG systems and can easily be extended to multi-stage systems.

• Journal of Korea Foundry Society
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• v.37 no.1
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• pp.1-13
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• 2017

The purpose of this study is to increase the part recovery rate (to more than 70%) during the casting of a ductile cast iron turbo charger housing using a heater around the riser. Before creating a casting mold, various runner and riser systems were designed and analyzed with a casting simulation analysis tool. The design variables were the heater temperature, top insulation, riser location, riser diameter and the riser shape. During the feeding from the riser to the part, the reverse model was better than the forward model. When heating the riser (above $600^{\circ}C$), solidification of the riser was delayed and the feeding effect was suitable compared to that without heating. At a higher heating temperature, less solidification shrinkage and porosity were noted inside the part. On the basis of a casting simulation, eight molds were fabricated and casting experiments were conducted. According to the experimental conditions, external and internal defects were analyzed and mechanical properties were tested. The ultimate tensile strength and elongation outcome were correspondingly more than 540MPa and 5% after a heat treatment. In addition, a maximum part recovery rate of 86% was achieved in this study.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.458-465
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• 2017

The purpose of the present study was to examine the method of physically processing oyster shells for use as raw material(aggregate) through experimentation. The results of the experiment found that the adequate particle size of the pulverized oyster shells should be smaller than 10mm due to their shape. Also, after considering various particle size distributions and residual rates by particle size, the study found the cutter mill to be the most suitable tool for pulverizing oyster shells. The use of a cutter mill resulted in recovery rates of 97.3%, 98.2%, and 98.9% for inner screens of 8mm, 12mm, and 20mm respectively, revealing how the increase of screen size results in slightly higher recovery rates. The experiment involving the difference between the inner screen of the cutter mill and the speed of the inverter shows that a smaller screen size and a faster inverter speed result in a lower fineness modulus, while a rise in inverter speed for an identical screen made possible the material recovery of a much lower range of particle sizes.

• Clinical and Experimental Reproductive Medicine
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• v.21 no.3
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• pp.261-266
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• 1994

Semen preparation for Assisted Reproductive Technology(ART) involves the separation of the motile sperm from non-motile, dead sperm, cellular debris and seminal fluid. The aim of this study is to compare the motile sperm recovery rate and motility index of different sperm preparation method(swim-up method, 80% isotonic continuous percoll method, two-layer discontinuous percoll method, mini-percoll method). In Mini-Percoll method, pellets from patients were suspended in 0.3ml of medium and layerd on a discontinuous percoll gradient consisting of 0.3ml each of 50, 70, 95% isotonic percoll. All semen samples are divided into normal and subnormal sperm group(oligo-, astheno-, oligoasthenozoospermia). Especially, we evaluated the effect of mini-percoll method in subnormal sperm group. In normal sperm group, mini-percoll method and two layer discontinuous percoll method (40%/80%) allowed increasing of motile sperm recovery rate. But motility index was higher in swimup method than the other methods. In subnormal sperm group, mini-percoll method has advantages as compare with the other methods in motile sperm recovery rate and motility index. These results suggest that modified mini-percoll method could be certainly a valuable tool in some cases of severe male factor sperm.

• Women's Health Nursing
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• v.4 no.1
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• pp.67-83
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• 1998

A quasi-experiment, repeated measures design with non-equivalent control group was used to test the influence of cold therapy on the perineal discomfort and the healing state of the postpartum women undergoing vaginal delivery with episiotomy. Experiment was carried out from July 28, through October 2, 1996 with 40 postpartum women conveniently sampled from one university hospital located in Seoul. The 40 postpartum women undergoing vaginal delivery with episiotomy were as signed to experimental and control groups evenly(20 each). The instrument of measurement of perineal discomfort was 0-10 rating scale that was made by researcher and that of perineal healing state was Davidson's REEDA tool. The perineal discomfort and the healing state level were measured before and after each treatment. The treatment using ice glove that was given for the only experimental group was carried out at three points ; as soon as returning to the recovery room, 3 hours after returning to the recovery room and 6 hours after returning to the recovery room. The data was analysed by using t-test, chi-square test to determine the similarity between experimental and control groups. The hypotheses were tested using repeated measures ANOVA. The results of this study are summarized as follows; 1. The first hypothesis that the perineal discomfort level of the experimental group will be significantly lower than that of the control group(df(1,38), F=24.12, p=.0001) was supported. 2. The second hypothesis that the perineal healing state of the experimental group wil be better than that of the control group(df(1,38), F=0.48, p=.49) was not supported. Based on the results of this study, could therapy was turned out to have significant effect on the perineal discomfort of the postpartum women undergoing vaginal delivery with episiotomy.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.448-451
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• 2008

Three methods of nozzle flow analysis, frozen-equilibrium, shifting-equilibrium and non-equilibrium approaches, were used to rocket nozzle flow, those were coupled with the methods of computational fluid dynamics code. For a design of high temperature rocket nozzle, chemical equilibrium analysis which shares the same numerical characteristics with frozen flow analysis can be an efficient design tool for predicting maximum thermodynamic performance of the nozzle. Frozen fluid analysis presents the minimum performance of the nozzle because of no consideration for the energy recovery. On the other hand, the case of chemical-equilibrium analysis is able to forecast the maximum performance of the nozzle due to consideration for the energy recovery that is produced for the fast reaction velocity compared with velocity of moving fluid. In this study, using the chemical equilibrium flow analysis code that is combined the modified frozen-equilibrium and the chemical-equilibrium. In order to understand the thermochemical characteristic components and the accompanying energy recovery, shifting-equilibrium flow analysis was carried out for the 30 $ton_f$-class KARI liquid rocket engine nozzle together with frozen flow. The performance evaluation based on the 30 $ton_f$-class KARI LRE nozzle flow analyses will provide an understanding of the thermochemical process in the nozzle and performances of nozzle.