• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.681-688
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• 2004

For use of the thermal cycle of the biochemical fluid sample, the isothermal temperature source with a large surface area was designed, fabricated and its thermal characterization was experimentally evaluated. The comprehensive overview of the technology trend on the temperature control devices was detailed. The large surface area isothermal temperature source was realized by using the vapor chamber heat spreader. The cost-effectiveness and simple manufacturing process were achieved by using the metal-etched wick structure. The temperature distribution was quantitatively investigated by using IR temperature imaging system at equivalent temperatures to the PCR thermal cycle. The standard deviation was measured to be within 0.7$^{\circ}C$ for each temperature cycle. This concludes that the presented isothermal temperature source enables no temperature gradient inside bio-sample fluid. Furthermore it can be applied to the cooling of the electronic devices due to its slimness and low thermal spreading resistance.

• Membrane Journal
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• v.25 no.2
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• pp.107-114
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• 2015

PTMSP-NaA zeolite composite membranes were prepared by adding 0~50 wt% NaA zeolite to PTMSP. The membranes were characterized by FT-IR, $^1H$-NMR, GPC, DSC, TGA, SEM. The permeabilities of $H_2$ and $N_2$ gases through PTMSP-NaA zeolite composite membranes was studied as a function of NaA zeolite contents. According to TGA measurements, when zeolite was inserted into the polymer, weight loss temperature and weight loss wt% of PTMSP-NaA zeolite composite membranes were decreased. Based on SEM observation, NaA zeolite was dispersed in the PTMSP-NaA zeolite composite membrane with the size $2{\sim}5{\mu}m$. The permeability of PTMSP-NaA zeolite composite membranes increased added as NaA zeolite content increased. On the contrary, the selectivity ($H_2/N_2$) of the composite membranes decreased as NaA zeolite content increased. PTMSP-NaA zeolite composite membrane showed better permeability and selectivity ($H_2/N_2$) of $H_2$ and $N_2$ than PTMSP-NaY zeolite composite membrane.

• Journal of the Korean Electrochemical Society
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• v.7 no.4
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• pp.179-182
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• 2004

The aim of this study is to investigate the initiation and propagation of crevice corrosion for ferritic stainless steel in artificial crevice based on micro capillary tube method. The 430 stainless steel in artificial crevice is potentiostatically polarized in different sodium chloride solutions. Potentiodynamic and potentiostatic polarization data were measured in situ. The potentials in the crevice were measured by depth profile using the 0.04 mm diameter micro capillary tube inserted in the crevice. The potentials in the crevice ranged from -220 mV to -360 mV vs SCE from opening to bottom of crevice, which are lower than the external surface potential, -200 mV vs SCE. Such a potential drop induced the change of the metal surface state from passive to active. The surface of metal is located in passive state in -200 mV but the inner surface keeps active state below -220 mV, Thus these results show that the It drop mechanism in the crevice was more objective for evaluation and the method was easier to reproduce. Therefore the potential drop is one of the reasons for crevice corrosion by measuring the potentials in narrow crevice with a new micro measuring system.

• Clean Technology
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• v.29 no.3
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• pp.172-177
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• 2023

Many studies have been conducted on the indiscriminate use of plastic due to the environment problems it has caused all over the world. This problem can be mitigated by using eco-friendly/biodegradable plastics that can be decomposed by microorganisms or enzymes. This study focused on addressing the plastic golf tees that are thrown away at golf courses. In order to replace conventional golf tees (ABS) with a more eco-friendly alternative, this study explored a biodegradable plastic and 3D printing method for producing golf tees. Among the biodegradable plastics, PLA (polylactic acid) was found to be a good candidate as an eco-friendly material because it is biodegradable by microorganisms. Thus, golf tees were prepared by using PLA via 3D printing, and the physical and chemical properties of the tees were evaluated. The amorphous region of PLA was confirmed through XRD. Also, FT-IR showed the unique peak of PLA without impurities. It was confirmed through an optical microscope that the specific surface area and roughness had increased. This structure plays a role in firmly fixing the golf tee when it is inserted into the ground. In addition, it was possible to improve the compressive load compared to ABS golf tees while also decreasing the compressive stretching.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.970-976
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• 1996

An ester-carbonate copolymer was synthesized, in which carbonate was inserted into a biodegradable aliphatic polyester, poly(butylene succinate) (PBS), to modify its mechanical properties. The synthesis was carried out by condensation reactions in two steps. In the first step, oligo(butylene succinate) was prepared by the reaction of succinic acid with 1,4-butanediol (BD). In the second step, it was reacted with oligohexamethylenecarbonate diol (OHMCG) to prepare the ester-carbonate copolymer. Titanium(IV) isopropoxide (TIP) was used as a catalyst for the reaction. The structure of the copolymer was confirmed by FT-IR and $^1H$-NMR and the thermal behavior and mechanical properties were investigated by differential scanning calorimetry (DSC) and universal testing machine (UTM), respectively. It was found that optimum amount of the catalyst for the formation of high molecular weight copolymer was 1wt% for succinic acid. When the BD:OHMCG is in the range 149:1~249:1, the copolymer with high viscosity was obtained. As the OHMCG content was increased, melting temperature ($T_m$) of the copolymer was decreased. When BD:OHMCG is 149:1, the copolymer showed a increase in ultimate strain by two times and the slight decrease in modulus compared to those of PBS.

• Journal of Biomedical Engineering Research
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• v.38 no.6
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• pp.277-284
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• 2017

This paper presents an implantable pH measurement electrode for wireless gastroesophageal reflux measurement. Usually, gastroesophageal reflux is diagnosed by a catheter-type wire connection between the esophagus and the diagnostic device which brings many side effects such as restriction of daily living, pain, and discomfort in the nasal cavity and pharynx of patients. In order to solve these issues, researchers have been studied a wireless measurement method and a micro-sized pH electrode for human body insertion is necessary. Commercial glass packaged pH meter is formed by a sensing and a reference electrodes in a KCl solution. However, if the glass meter is inserted into the human body, there are risks of leakage of the solution, breakage of the glass package, injury of the body elements. Therefore, the solution should be solidified on the micro-sized noble metal wire which has a characteristic of biocompatible. After solidified wire fabrication, the designed meter was tested for feasibility of measurement and the result was well agreed with pH values of commercial pH meter. Potentials in pH 1 to 12 solution was measured to obtain the sensitivity of the sensor with linearity. And we have designed a simulation of gastroesophageal reflux with symptom frequency, interval, and duration time in pH 2 solution. The proposed sensor has capable to get the same potential for 24 measurements in 3 days, and it has sensed same pH values of 2 for one hour with every 10 minutes. Furthermore, the sensor was survived for 48 hours with reasonable potentials in the acid solution.

• Membrane Journal
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• v.24 no.4
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• pp.285-291
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• 2014

The PTMSP[Poly(1-trimethylsilyl-1-propyne)]-NaY zeolite composite membranes were prepared by adding 0~50 wt% NaY zeolite to PTMSP. In order to investigate the characteristics of these membranes, we used the analytical methods such as FT-IR, $^1H$-NMR, GPC, DSC, TGA, and SEM. Gas permeation experiments were carried out at $23{\sim}26^{\circ}C$, $2kgf/cm^2$, and the permselectivity of $H_2$ and $N_2$ gases through the composite membranes was studied as a function of the NaY zeolite contents. According to TGA measurements, when NaY zeolite was inserted within the PTMSP, thermal stability of PTMSP was enhanced. Based on SEM observation, NaY zeolite was dispersed in the PTMSP-NaY zeolite composite membrane with a size of $1.5{\mu}m$. The permeability of $H_2$ and $N_2$ through the PTMSP-NaY zeolite composite membranes increased as NaY zeolite content increased. On the contrary, the selectivity($H_2/N_2$) of the PTMSP-NaY zeolite composite membranes decreased as zeolite content increased.

• Korean Journal of Materials Research
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• v.10 no.10
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• pp.665-670
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• 2000

Linear annealing method was developed to increase the bond strength of Si wafer pair mated at room tem­perature instead of conventional furnace annealing method. It has been known that the interval of the two mating wafer surfaces decreases and the density of gaseous phases generated at the interface increases with increase in an-nealing temperature. The new annealing method consisting of one heat source and light reflecting mirror used these two phenomena and was applied to Si$\mid$$\mid$Si and Si$\mid$$\mid$$SiO_2/Si$ bonding. The bonding interface observed directly by using IR camera and HRTEM showed clear bonding interface without any unbonded areas except the area generated by the dusts inserted into the mating interface at the room temperature. Crack opening method and direct tensile test was ap­pplied to measure the bond strength. The two methods showed similar results. The bond strength increased continuous­tly with the increase of annealing temperature.

• Journal of the Korean Society of Radiology
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• v.16 no.4
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• pp.405-410
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• 2022

In brachytherapy, a radiation source is inserted into the body to kill tumor tissue. Therefore, it is important to accurately measure the location of the source and the dose distribution. In this study, a dosimeter that can be used for brachytherapy was developed using CsPbBr₃ which is cheaper than the existing detector materials and has a simpler manufacturing process. The CsPbBr₃ dosimeter performance was evaluated by analyzing reproducibility, linearity, and distance dependence in ¹⁹²Ir source. As a result of reproducibility evaluation, the RSD was 1.36%, which satisfies the standard value of 1.5%. As a result of the linearity evaluation, the R² value was 0.9993, which satisfies the standard R² of 0.9990. The distance dependence evaluation showed a signal value that decreased exponentially as the distance increased. The evaluation results show that the CsPbBr₃ dosimeter satisfies the evaluation criteria and can be used as a brachytherapy quality assurance dosimeter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.402-403
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• 2007

High-efficiency white organic light-emitting diodes (WOLEDs) were fabricated with two emissive layers and a spacer was sandwiched between two phosphorescent dyes which were, bis(3,5-Difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (FIrpic) as the blue emission and bis(5-acetyl-2-phenylpyridinato-N,C2') acetylacetonate $((acppy)_2Ir(acac))$ as the red emission. This spacer effectively prevented a triple-triple energy transfer between the two phosphorescent emissive layers with blue and red emission that was showed a improved lifetime. The white device showed Commission Internationale De L'Eclairage $(CIE_{x,y})$ coordinates of (0.33, 0.42) at $22400\;cd/m^2$, a maximum luminance of $27300\;cd/m^2\;at\;0.388\;mA/cm^2$, and a maximum luminous efficiency of 26.9 cd/A.