• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.13-18
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• 2011

Experimental studies were carried out to investigate the characteristics of explosion mitigations by varying concentrations of agar gel barriers in an explosion chamber, 1400 mm in length, with a square cross-section of $100{\times}100mm^2$. Another extension chamber, $100{\times}100{\times}300mm^3$, was made to hold a gel barrier. Four different gel concentrations were used in the measurements: 2, 3, 4, 5 %(by weight of gel). Displacement of the gel barrier was measured using a high speed camera, and pressure development was measured using pressure transducers and a data acquisition system. It was found that as the concentrations of the gel barriers increased, the gel rupture time and the time taken to reach the maximum pressure increased. It was also found that the increment of gel concentrations increased the reduction percentage in the maximum pressure between before and after gel barrier.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.40-44
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• 2019

Experimental studies have been carried out to investigate characteristics of gas explosion using a multi layered water gel barrier in a vented explosion chamber. The chamber is consisted of 1600 mm in length, with a square cross-section of $100{\times}100mm^2$. The gel concentration of inner layer of MLWGB ranged from 10% to 90% with intervals of 10% by weight of gel. Displacement of the MLWGB was photographed with a measured using a high-speed video camera, and pressure development was measured using a data acquisition system. It was found that MLWGBs with 10 ~ 20% inner layer concentrations were ruptured during the explosions. As the concentrations of inner layer increased from 30% to 90%, the barriers were not ruptured. As the gel concentrations of the inner layer increased, the displacement increased toward the chamber exit and the pressure decreased for the ruptured barriers. It was found that the pressure attenuation obtained from the MLWGB was higher than that of the single water gel barrier. For the cases of non-ruptured barriers, the pressure inside the chamber less increased with increasing gel concentrations of the inner layer. It was also found that the displacement moved back into the chamber for non-ruptured MLWGBs, and it was sensitive to the gel concentrations.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.160-165
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• 1999

Agarose gels can be used as reference standards for the measurement of fluid properties in porous media because the relaxation properties of the gel reference standard and those of the fluid in porous media can be closely matched. The use of reference standard to determine porosity and saturation is discussed and the requirements for gel NMR properties given. The relaxtion times of agarose gels measured at 2.0 Tesla are illustrated as a function of agarose and paramagnetic impurity ($CuSO_4$) concentrations. This work shows an empirical result between agarose gel composition and gel relaxtion times. The average value for the porosity distribution is 17.7%, which compares well with the value calculated with the gravimetric analysis. Finally, two phase immiscible displacement using agarose gels as a reference standard was performed. The saturation profiles appear to be consistent with what one might calculate for a one-dimensional displacement in a uniform porous media.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.2
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• pp.200-211
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• 1999

For many years permanent soft denture liners has been widely used in dental practice directly or indirectly because of its function in absorbing and distributing the impact force. However, it reveals problems such as lack of permanency and decreased bond strength in long term use. The purpose of this study is to measure the bond strength and failure between denture base resin and several permanent liners. Lucitone 199 was used as denture base resin with soft acrylic liners (Triad, Tokuso Rebase) and silicone elastomers (Tokuyama, Ufi Gel C) bonded to measure the tensile strength before and after thermocycling. The thermocycling was done in 2000 cycles at $5^{\circ}C,\;26^{\circ}C\;and\;55^{\circ}C$ and the measured tensile strength values before and after thermocycling were compared. The mode of failure was investigated in the separated specimens. The results are as follows. 1. As to tensile strength, the strongest material is Tokuso Rebase followed by Triad, Tokuyama, Ufi Gel C in before thermocycling and the order of Triad, Tokuso Rebase, Tokuyama, Ufi Gel C in after thermocycling state. There was significant difference between the values of Triad, Tokuso Rebase and Tokuyama, Ufi Gel C(p<0.05). 2. As to degree of displacement, Ufi Gel C showed most displacement with or without thermo-cycling treatment and also the difference was significant with the other materials(p<0.05). 3. As to comparisons before and after thermocycling, Tokuso Rebase and Tokuyama showed significant difference in bond strength, whereas Triad and Tokuso Rebase showed significant difference in the degree of displacement(p<0.05). 4. In debonded specimens, Triad and Ufi Gel C showed adhesion failure and Tokuyama showed cohesion failure. Both failures were observed in Tokuso Rebase with adhesion failure up to 70%. The results of this study showed that degree of bond strength between permanent soft denture liner and denture base resin were variable. There was a significant difference between soft acrylics and silicone elastomers with regard to bond strength. Further research in improving bond strength of widely used silicone elastomers and in developing the method of measuring bond strength between denture base resin and the lining materials is needed.

• Korea-Australia Rheology Journal
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• v.20 no.3
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• pp.165-173
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• 2008

Multiple particle tracking microrheology is used to characterize the viscoelastic properties of biomaterial and synthetic polymer gels near the liquid-solid transition. Probe particles are dispersed in the gel precursors, and their dynamics are measured as a function of the extent of reaction during gel formation. We interpret the dynamics using the generalized Stokes-Einstein relationship (GSER), using a form of the GSER that emphasizes the relationship between the probe particle mean-squared displacement and the material creep compliance. We show that long-standing concepts in gel bulk rheology are applicable to microrheological data, including time-cure superposition to identify the gel point and critical scaling exponents, and the power-law behavior of incipient network's viscoelastic response. These experiments provide valuable insight into the rheology, structure, and kinetics of gelling materials, and are especially powerful for studying the weak incipient networks of dilute gelators, as well as scarce materials, due to the small sample size requirements and rapid data acquisition.

• Korean Journal of Materials Research
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• v.31 no.11
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• pp.649-656
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• 2021

K_0.5Bi_0.5TiO₃ (KBT) thin films were prepared by sol-gel processing for future use in piezoelectric generators. It is believed that the annealing temperature of films plays an important role in the output performance of piezoelectric generators. KBT films prepared on Ni substrates were annealed at 500 ~ 700 ℃. Tetragonal KBT films were formed after annealing process. As the annealing temperature increased, the grain size of KBT films increased. KBT thin films show piezoelectric constant (d₃₃) from 23 to 41 pC/N. The increase of grain size in KBT films brought about output voltage and current in the KBT generators. Also, the increase in the displacement of specimens during bending test resulted in increases in output voltage and current. Although KBT generators showed lower output power than those of generators prepared using NBT films, as reported previously, the KBT films prepared by sol-gel method show applicability as piezoelectric thin films for lead-free nano-generators, along with NBT films.

• Smart Structures and Systems
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• v.11 no.2
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• pp.199-215
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• 2013

During the service life of a structure, design complications and unexpected events may induce unforeseen vibrations. These vibrations can be generated by malfunctioning machinery or machines that are modified or placed without considering the original structural design because of a change in the intended use of the structure. Significant vibrations occurred at a natural gas plant cooling structure during its operation due to cavitation effect within the hydraulic system. This study presents findings obtained from the in-situ vibration measurements and following finite-element analyses of the cooling structure. Comments are made on the updated performance level and damage state of the structure using the results of these measurements and corresponding numerical analyses. An attempt was also made to assess the applicability of traditional displacement-based vulnerability estimation methods in the health monitoring of structures under vibrations with a character different from those due to seismic excitations.

• Archives of Plastic Surgery
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• v.38 no.3
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• pp.323-325
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• 2011

Purpose: Breast implant ruptures and displacement are problematic complications after augmentation mammoplasty. The authors report a patient whose cohesive silicone gel implant ruptured and migrated into the pleural cavity after augmentation mammoplasty. Methods: A 23-year-old female had received augmentation mammoplasty at a local clinic a week before visiting our hospital. When the patient's doctor performed a breast massage on the sixth postoperative day, the left breast became flattened. The doctor suspected a breast implant rupture and performed revision surgery. The implant, however, was not found in the submuscular pocket and no definite chest wall defect was found in the operative field. The doctor suspected implant migration into the pleural cavity, and after inserting a new breast implant, the doctor referred the patient to our hospital for further evaluation. The patient's vital signs were stable and she showed no specific symptoms except mild, intermittent pain in the left chest. A CT scan revealed the ruptured implant in the left pleural cavity and passive atelectasis. Results: The intrapleurally migrated ruptured implant was removed by video-assisted thoracic surgery (VATS). There were no adhesions but there was mild inflammation of the pleura. No definite laceration of the pleura was found. The patient was discharged on the first day after the operation without any complications. Conclusion: Surgeons should be aware that breast implants can rupture anytime and the injury to the chest wall, which may displace the breast implant into the pleural cavity, can happen during submuscular pocket dissection and implant insertion.

• Archives of Plastic Surgery
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• v.38 no.2
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• pp.166-172
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• 2011

Purpose: Facial contouring surgery for improving congenital, acquired deformity and senile change were attempt in past. Recently contouring surgery became more interested subject for improving the flat forehead and temple area. Many synthetic materials were used such as Collagen, silicon, polyacrylamide gel as liquid form and Gore-tex, silicon implant, endotine as solid form. But, these synthetic implants associate complications as foreign body reaction, infection, displacement, granuloma formation and absorption. Auto-fat injection are used for disfigurement of many part of body. We did auto-fat injection for facial contouring of forehead and temple region. Auto-fat injection is suitable without foreign body reaction, displacement, and toxic reaction. Also auto-fat is relatively simple to obtain from patient and less expensive and able to repeat surgeries. Methods: From 2006 to 2009, 150 patients were treated with Auto-fat injection for facial contouring. For follow up, we sent questionnaire to all patients but 110 patients returned answer sheets. The patients consisted of 20 male patients and 90 female patients with an age ranged from 26 to 60, and the mean 43. Fat tissue were injected 6-8 cc in forehead, 7-12 cc in temple area and fat were harvested from thigh and abdomen. Results: In follow up, all patients, showed absorption of injected fat varied degree and except two patients all patients underwent secondary fat injection. Complications were minimal and neuropraxia of facial nerve were recovered. Most of the patients were satisfied with result of procedure, and answered that they recommend same procedure to their friends and will do surgery again. Conclusion: Auto-fat injections were implemented for facial contouring in 150 patients and obtained satisfactory result. Auto-fat injection is relatively easy procedure and applicable widely. Even though, by passing time, some of the injected fats are absorbed, auto-fat injection could be choice of treatment for contouring forehead and temple. With accumulations of cases and development of surgical technique, better result could be expected.

• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.9-13
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• 2009

Fluorescence recovery after photobleaching (FRAP) has been widely used for the measurement of molecular diffusion in living cells and tissues. We developed an image-based FRAP (iFRAP) technique using a modified real-time microscope and a 488 nm Ar-ion laser. A fractional intensity curve was obtained from the time-lapse images of fluorescence recovery in the bleached spot to determine the diffusion coefficient of fluorescently labeled macromolecules in porous medium. We validated iFRAP through experiments with agar gels (0.5% and 1.5% w/v) containing FITC-Dextrans (10, 70 and 500 kDa MW). Further validation was performed by a Monte Carlo approach, where we simulated the three-dimensional random walk of macromolecules in agar gel model. Diffusion coefficients were deduced from the mean square displacement curves and showed good agreements with those measured by iFRAP.