• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.1062-1073
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• 2007

Acoustic Target Strength (TS) is a major parameter of the active sonar equation, which indicates the ratio of the radiated intensity from the source to the re-radiated intensity by a target. In developing a TS equation, it is assumed that the radiated pressure is known and the re-radiated intensity is unknown. This research provides a TS equation for polygonal plates, which is applicable to near field acoustics. In this research, Helmholtz-Kirchhoff formula is used as the primary equation for solving the re-radiated pressure field; the primary equation contains a surface (double) integral representation. The double integral representation can be reduced to a closed form, which involves only a line (single) integral representation of the boundary of the surface area by applying Stoke's theorem. Use of such line integral representations can reduce the cost of numerical calculation. Also Kirchhoff approximation is used to solve the surface values such as pressure and particle velocity. Finally, a generalized definition of Sonar Cross Section (SCS) that is applicable to near field is suggested. The TS equation for polygonal plates in near field is developed using the three prescribed statements; the redection to line integral representation, Kirchhoff approximation and a generalized definition of SCS. The equation developed in this research is applicable to near field, and therefore, no approximations are allowed except the Kirchhoff approximation. However, examinations with various types of models for reliability show that the equation has good performance in its applications. To analyze a general shape of model, a submarine type model was selected and successfully analyzed.

• The Journal of Internal Korean Medicine
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• v.38 no.6
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• pp.877-890
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• 2017

Objectives: Lonicerae flos (LF), a dried flower part of Lonicera japonica Thunb., has been widely used in Korean medicine as anti-inflammatory and antioxidative agent. The purpose of this study was to determine the cardioprotective effects of LF, through potential antioxidant effects, on the pressure overload (PO)-induced heart failure (HF) in C57BL/6 mice after transverse aortic constriction (TAC) surgery. Methods: Resveratrol (10 mg/kg body weight) or LF (125, 250 or 500 mg/kg body weight) was orally administered, once daily for 14 days, starting 14 days after TAC surgery. Changes in the mortality, body weights, heart weights, histopathology of the heart, and antioxidant defense systems of the heart were analyzed. Results: Marked and noticeable increases of heart weights, mortalities, and hypertrophic, focal, and lytic fibrotic histological changes in the LVs were observed, with destruction of heart antioxidant defense systems after surgery. However, HF signs, induced by TAC surgery through PO, and destruction of heart antioxidant defense systems were significantly and dose-dependently inhibited by 14 days of maintained oral treatment with LF 500, 250 or 125 mg/kg. Treatment with 250 mg/kg LF was comparable to treatment with 10 mg/kg resveratrol. Conclusions: The results in this study suggest that oral administration of LF favorably relieves PO-induced HF following TAC, through increase of heart antioxidant defense systems. The overall effects of 250 mg/kg LF were similar to those of 10 mg/kg resveratrol. More detailed mechanistic studies should be conducted in the future, with screening of the biologically active compounds in LF.

• Journal of Biomedical Engineering Research
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• v.35 no.6
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• pp.203-210
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• 2014

Wearable medical device has been a resurgence of interest thanks to the development of technology and propagation of smart phone in recent years. Various types of wearable devices have been introduced and available in market. Capacitive coupled electrode which measures electrocardiogram over cloth is able to be applied wearable device. In previous approaches of capacitive electrode, they need proper pressure for stable contact of the electrode to body surface. However, wearable device that gives pressure on body surface is not suitable for long-term monitoring. In this study, we proposed adhesive polyurethane-based capacitive electrode for patch-type wearable electrocardiogram (ECG) monitoring device. Self-adhesive polyurethane make the electrode and whole system be adhered to the surface of skin without any pressure. The patch-type system is consisted of analog filter, analog-to-digital converter and wireless transmission module and designed to be attached on the body as a patch. To validate the feasibility of the developed system, we measured ECG signal in stable and active state and extracted heart rate. Therefore, we observed skin response after long-term attachment for biocompatibility of the adhesive polyurethane and adhesive strength of it. The result shows the possibility of applying the developed system for ECG monitoring in real-life.

• Geotechnical Engineering
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• v.12 no.4
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• pp.75-86
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• 1996

Current methods to estimate the earth pressure for retaining wall analysis are based on Rankine or Coulomb approaches, in which the soil mass behind wall is assumed to reach to failure state with sufficient lateral movements. Some of recent research works carried out by field measurements reveal that the active earth. pressures by Ranking or Coulomb method are underestimated. It means that the lateral movements of wall and soil would not be mobilized enough to reach the failure state. In this study, the finite element method with Drucker -Prager model for soil is employed to investigate the behavior of concrete cantile,tier retaining wall, together with the influence of inclined backfill. The results indicate that the earth pressures on the retaining wall are strongly related to the mobilized lateral movements of wall and soil and that Ranking and Coulomb methods underestimate the resultant earth pressures and the increasing effect on earth pressure by inclined backfill. Based on this study, a simplified method to determine to earth pressures on cantilever retaining wall with horizontal backfill is proposed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.510-519
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• 2001

The tensile and fracture toughness tests have been conducted to investigate the degradations of mechanical properties induced mainly by neutron irradiations in Zr-2.5Nb CANDU pressure tube materials operated in Wolsung Unit-1. the tests were performed at room, 150, 200, 250, 300 $\^{C}$ for the irradiated and unirradiated specimens in hot cell. The specimens were directly machined from the tube retaining original curvature using specially designed electric discharge machine(EDM). From the tensile tests of the irradiated specimens, it was found that tensile strength was increased and total elongation was decreased compared to those of the unirradiated ones. The active voltages in the fracture toughness tests for the irradiated showed the discontinuous abrupt increases caused by crack jumping in lower temperature. In the crack resistance curves we found the stable crack growth in the unirradiated, whereas the unstable and three crack growth stages in the irradiated specimens due to the accumulated irradiation defects. The various fracture characteristic values in the irradiated are remarkably lower than those of the unirradiated. Through the fractography, we found in the irradiated that smaller dimple and shorter fissures than the unirradiated, and that the fractured surface had three regions that were flat, transition and slant/shear area. These can explain the difference in the crack growth characteristic values of the irradiated and the unirradiated ones.

• The Journal of Korean Physical Therapy
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• v.25 no.2
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• pp.76-80
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• 2013

Purpose: The objective of this study was to offer primary clinical data examining whether change of imaging structure and quantitative evaluation of muscle activity on myofascial trigger points can lead to implementation of an analytical technique for evaluation of myofascial pain diagnoses. In addition, we examined the effect of a variety of mediation techniques, in order to examine neuromuscular physiological characteristics of myofascial trigger points muscle by comparing differences in pressure pain threshold and ultrasound imaging. Methods: Participants in the study included 30 adults in their twenties. The subjects were divided into the normal and myofascial trigger points groups. Clinical outcomes were evaluated by pressure pain threshold for pain and ultrasound imaging was performed for evaluation of the structural characteristics of muscle. Independent t-test was used for statistical analysis. Results: The two groups showed statistical significance in the change in pressure pain threshold (p<0.05). Findings of ultrasound imaging analysis showed no significant differences, increased muscle thickness was observed (p>0.05). Findings of ultrasound imaging analysis showed significant differences, increased muscle echodensity was observed (p<0.05). Findings on ultrasound imaging analysis showed significant differences, increased muscle white area index was observed (p<0.05). Conclusion: From these results, active myofascial trigger points muscle showed quality deterioration on ultrasound imaging. Thorough evaluation of imaging structure and physiological characteristics can be useful quantitative analytical techniques for diagnosis of myofascial pain syndrome and a primary factor reflected in physical therapy intervention.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.69-74
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• 2017

The validity of friction factor theory, based upon conventional-sized passages for microchannel flows, is an active area of research. The high surface to volume ratio of a microchannel offers many advantages over macroscale devices and processes. This study focused on the laminar flow (16$161{\mu}m$ to $664{\mu}m$ for single-phase liquid flow. A controllable syringe pump was used to provide flow while a differential pressure transducer was used to record the pressure drop. These results demonstrated that a 3D printer can drastically simplify custom microchannel fabrication and still support complex features, which are typically only accessible with advanced fabrication techniques.

• Archives of Reconstructive Microsurgery
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• v.25 no.2
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• pp.29-36
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• 2016

Purpose: Skin grafting is used for the transfer of cutaneous tissue from one site of the body to another. To improve graft survival, close contact between the graft and the wound bed is essential for vessels to grow across the gap. Here, we introduce an easy and efficient dressing method to improve graft survival. Materials and Methods: A retrospective chart review was performed to identify patients who underwent split thickness skin graft and negative pressure wound therapy (NPWT) or conventional treatment between January 2007 and April 2015. Overall, 25 consecutive patients were included in the NPWT group and 49 were included in the conventional dressing group to compare the outcome of the procedure. The data were obtained from medical records, including age, sex, cause of the skin defect, size of graft, time for healing, wound preparation time, and complications. Results: Of the NPWT group, the average wound size was $147.04{\pm}146.74cm^2$ (range, $9{\sim}900cm^2$). With the exception of one patient, all wounds healed without the need for further procedure. The average duration of time required for the NPWT group, which was defined as removal of stitches (or staples) and no need for additional active dressing, was $6.4{\pm}1.97days$ (range, 5~15 days). The average time for the conventional dressing group was $10.78{\pm}2.38days$ (range, 5~15 days). Conclusion: NPWT can be used to cover regions in which wound healing does not occur fully or when neither tie-over nor compressive dressings are applicable. This treatment also reduced wound healing time and allowed earlier patient mobilization and hospital discharge.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.905-912
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• 2011

In this study, the novel concept catalytic reactor was designed for water-gas shift reaction (WGS) under high pressure. The novel concept catalytic reactor was composed of an autoclave, the catalyst, and liquid water. Cu-ZnO/$Al_2O_3$ as the low temperature shift catalyst was used for WGS reaction. WGS in the novel concept catalytic reactor was carried out at the ranges of 150~$250^{\circ}C$ and 30~50 atm. The liquid water was filled at the bottom of the autoclave catalytic reactor and the catalyst of pellet type was located at the gas-liquid water interface. It was concluded that WGS reaction occurred over the surface of catalysts partially wetted with liquid water. The conversion of CO for WGS was also controlled with changing content of Cu and ZnO used as the catalytic active components. Meanwhile, the catalyst of honey comb type coated with Cu-ZnO/$Al_2O_3$ was used in order to increase the contact area between wet-surface of catalyst and the reactants of gas phase. It was confirmed from these experiments that $H_2$/CO ratio of the simulated coal gas increased from 0.5 to 0.8 by WGS at gas-liquid water interface over the wet surface of honey comb type catalyst at $250^{\circ}C$ and 50 atm.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.24 no.3
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• pp.113-120
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• 2018

The one-way gas valve developed in this study was designed to prevent the breakage of packages from increased internal pressure, which is a problem in packaged Kimchi, and simultaneously reduce the outflow of the offodor release. The effect of the one-way gas valve on the headspace atmospheric compositions was investigated in the packaging system. The changes of atmospheric compositions and quality factors of Kimchi, such as $CO_2$ accumulation, pH, titratable acidity, and salinity, were measured during a 4-week storage period at $4^{\circ}C$. The Kimchi package with the one-way gas valve dramatically reduced pressure build-up in the pouch by allowing the controlled flow of gas to the atmosphere. In addition, the package design allows the possibility of controlling the gas generated from Kimchi by adjusting the viscosity of the open pressure control oil. The one-way gas valve did not affect the sensory characteristics of Kimchi products during the storage period. Furthermore, the deodorizing capability of the activated carbon contained in the one-way gas valve effectively reduced the off-odor of Kimchi products released along with carbon dioxide. The novel one-way gas valve is considered to be an active packaging system that can solve major problems of expansion and off-odor leakage in the packaging of Kimchi.