• Macromolecular Research
• /
• v.14 no.1
• /
• pp.101-106
• /
• 2006

The transport of reactant gas, electrons and protons at the three phase interfaces in the catalytic layers of membrane electrode assemblies (MEAs) in proton exchange, membrane fuel cells (PEMFCs) must be optimized to provide efficient transport to and from the electrochemical reactions in the solid polymer electrolyte. The aim of reducing proton transport loss in the catalytic layer by increasing the volume of the conducting medium can be achieved by filling the voids in the layer with small-sized electrolytes, such as dendrimers. Generation 1.5 and 3.5 polyamidoamine (PAMAM) dendrimer electrolytes are well-controlled, nanometer-sized materials with many peripheral ionic exchange, -COOH groups and were used for this purpose in this study. The electrochemically active surface area of the deposited catalyst material was also investigated using cyclic voltammetry, and by analyzing the Pt-H oxidation peak. The performances of the fuel cells with added PAMAM dendrimers were found to be comparable to that of a fuel cell using MEA, although the Pt utilization was reduced by the adsorption of the dendrimers to the catalytic layer.

• Journal of Radiation Protection and Research
• /
• v.31 no.3
• /
• pp.149-153
• /
• 2006

An ionization chamber is still widely used in many fields by virtue of its' simple operational characteristics and the possibility of its' various shapes. A parallel type of an ionization chamber for a steel sheet thickness measurement was designed and fabricated. High pure xenon gas, which was pressurized up to 6 atm, was chosen as a filling gas to increase the current response and sensitivity for a radiation. A high pressure gas system was also constructed. The active volume and the incident window size of the fabricated ionization chamber were $30\;cm^3\;and\;12\;cm^2$, respectively. Preliminary tests with a 25 mCi $^{241}Am$ gamma-ray source and evaluation tests in a standard X-ray field were performed. The optimal operation voltage was set from the results of the collection efficiency calculation by using an experimental two-voltage method. Linearity for a variation of the steel sheet thickness, which is the most important factor for an application during a steel sheet thickness measurement, was 0.989 in this study.

• Journal of Korean society of Dental Hygiene
• /
• v.21 no.1
• /
• pp.89-98
• /
• 2021

Objectives: The purpose of this study was to investigate the perception and satisfaction of caregivers and parents after being covered by health insurance for light-curing composite resin fillings, and to contribute to the settlement of the expansion and coverage of health insurance. Methods: A survey was conducted on caregivers who visited two dental institutions in the Gyeonggi-do area, and parents who joined internet cafes (online communities) in the Gyeonggi-do area from June 2 to September 2, 2020. 225 responses were collected eventually, and 212 valid responses were used as analysis data. Results: 67.0% of the study subjects were aware of the permanent teeth resin fillings being covered by health insurance and the satisfaction was relatively high (91.5%). There was a statistically significant difference in the perception of permanent tooth resin filling benefits according to the child's oral condition (p=0.025) and the parents' own interest in oral health (p=0.039). Conclusions: Based on the results of this study, it is necessary to increase the accessibility to the initial treatment for dental care of children through active promotion of detailed items of permanent teeth resin fillings.

• Geomechanics and Engineering
• /
• v.32 no.6
• /
• pp.601-613
• /
• 2023

Low liquid limit silt, widely distributed in the middle and down reaches of Yellow River, has the disadvantages of poor grading, less clay content and poor colloidal activity. It is very easy to cause vehicle jumping at the bridge-embankment transition section when the low liquid limit silt used as the backfill at the abutment back. In this paper, a series of laboratory tests were carried out to study the physical and mechanical properties of the low liquid limit silt used as back filling. Ground granulated blast furnace slag (GGBFS) was excited by active MgO and hydrated lime to solidify silt as abutment backfill. The optimum ratio of firming agent and the compaction and mechanical properties of reinforced soil were revealed through compaction test and unconfined compressive strength (UCS) test. Scanning electron microscope (SEM) test was used to study the pore characteristics and hydration products of reinforced soil. 6% hydrated lime and alkali activated slag were used to solidify silt and fill the model of subgrade respectively. The pavement settlement regulation and soil internal stress-strain regulation of subgrade with different materials under uniformly distributed load were studied by model experiment. The effect of alkali activated slag curing agent on curing silt was verified. The research results can provide technical support for highway construction in silt area of the Yellow River alluvial plain.

• Geomechanics and Engineering
• /
• v.37 no.5
• /
• pp.443-452
• /
• 2024

The use of sand-tire chip mixtures in construction industry is a sustainable and environmentally friendly approach that addresses both waste tire disposal and soil improvement needs. However, the addition of tire chip particles to natural soils decreases maximum shear modulus (G_max), but increases compressibility, which can be potential drawbacks. This study examines the effect of overconsolidation stress history on the maximum shear modulus (G_max) of rigid-soft mixtures with varying size ratios (SR) and tire chip contents (TC) by measuring the wave velocity through a 1-D compression test during loading and unloading. The results demonstrate that the G_max of tested mixtures in the normally consolidated state increased with increasing SR and decreasing TC. However, the tested mixtures with a smaller SR exhibited a greater increase in G_max during unloading because of the active pore-filling behavior of the smaller rubber particles and the consequent increased connectivity between sand particles. The SR-dependent impact of the overconsolidation stress history on G_max was verified using the ratio between the swelling and compression indices. Most importantly, this study reveals that the excessive settlement and lower G_max of rigid-soft mixtures can be overcome by introducing an overconsolidated state in sand-tire chip mixtures with low TC.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.31 no.3
• /
• pp.207-215
• /
• 2009

Purpose: The aim of the present study is to evaluate the long term bone healing after horizontal ridge augmentation using auto block bone graft for implant installation timing. Materials and Methods: Five Beagle dogs(which were 14 months old and weighted approximately 10kg). In surgery 1(extraction & bone defect), premolars(P2, P3,P4) were extracted and the buccal bone plate was removed to create a horizontally defected ridge. After three months healing, in surgery 2(ridge augmentation). Auto block bone grafts from the mandibular ramus were used in filling the bone defects were fixed with stabilizing screws. The following fluorochrome labels were given intravenously to the beagle dogs: oxytetracycline 1week after the surgery, alizarin red 4 weeks after the surgery, calcein blue 8 weeks after the surgery. The tissue samples were obtained from the sacrificed dogs of 1, 4, 8, 12, 16 weeks after the surgery. Non-decalcified sections were prepared by resin embedding and microsection to find thickness of $10{\mu}m$ for the histologic examination and analysis. Results: 1. We could achieve the successful reconstruction of the horizontal bone defect by auto block bone graft. The grafted bone block remained stable morohologically after 16 weeks of the surgery. 2. In the histologic view. We observed osteoid tissue from the sample $4^{th}$ week sample and active capillary reconstruction in the grafted bone from the $12^{th}$ week sample. Healing procedures of auto bone grafts were compared to that of the host bone. 3. Bone mineralization could be detected from the $8^{th}$ week sample. 4. Fluorochrome labeling showed active bony changes and formation at the interface of the host bone and the block graft mainly. Bony activation in the grafted bone could be seen from the $4^{th}$ week samples. Conclusions: Active bone formation and remodeling between the grafted bone and host bone can be seen through the revascularization. After the perfect adhesion to host bone, Timing of successful implant installation can be detected through the ideal ridge formation by horizontal ridge augmentation.

• Journal of the Korea Convergence Society
• /
• v.11 no.10
• /
• pp.163-169
• /
• 2020

The purpose of this study was to identify the degree of awareness and need for dental health insurance of parents with children under 12 years of age, and provide it as basic data for the development of the dental health insurance system in the future. It was conducted with 158 parents who are raising children under the age of 12 in Busan and Gyeongnam areas. In the case of mothers(p=.001), the higher the age (p=.005), the higher the experience of sealant. In the case of mothers, the knowledge of sealant (p=.012) was high. When the gender was female (p=.026), the parenting relationship was mother (p=.006), and regularly engaged in vocational activities (p=.003), the awareness of resin filling was high, and the experience was the child's age (p=. 004) was higher, the higher the knowledge was when the parenting relationship was mother (p=.024). The factors influencing the satisfaction of sealant were found to be the parents education level (p=.004), the awareness of the sealant (p=.003), and the experience (p=.011). From the above research results, more active publicity is needed to increase the awareness and experience of parents' health insurance.

• Journal of agriculture & life science
• /
• v.43 no.3
• /
• pp.27-34
• /
• 2009

Green tea was prepared by soaking 1.5 g of green tea leaves into 100 mL of distilled water at $75^{\circ}C$ for 5 min. The green tea was stored at three different conditions - (A) green tea was stored at not-artificially excluding natural light condition, at natural air condition, and without addition of vitamin C; (B) green tea was stored at artificially excluding natural light condition by wrapping a vial with aluminium foil, at nitrogen filling up condition, and with addition of 30 mg/100 mL of vitamin C; and (C) green tea was stored at artificially excluding natural light condition by wrapping a vial with aluminium foil, at nitrogen filling up condition, and without addition of vitamin C. After 28 days of storage at $4^{\circ}C$, the chemical quality of the green tea was evaluated. Total phenolic contents of (A), (B), and (C) green tea decreased to 71.50, 73.88 and 75.07%, respectively, after storing for 28 days compared to those of beginning state. DPPH radical scavenging activities of (A), (B), and (C) green tea were 87.87, 92.93 and 88.39%, respectively. Epigallocatechin gallate (EGCG), the main active compounds of green tea, contents of (A), (B), and (C) green tea were 130.61, 136.47 and 4.34%, respectively. The results indicated that light, air condition, and vitamin C were significantly important to the chemical quality of green tea during storage.

• Proceedings of the KOSOMBE Conference
• /
• v.1995 no.11
• /
• pp.216-218
• /
• 1995

A new atrial pressures balancing method for moving actuator total artificial heart(TAH) without an extra compliance chamber is developed. The structural characteristics of the pendulous moving actuator have made it possible to compensate the left and right pump output difference by utilizing the interventricular air space as an internal compliance chamber in a pump housing. Furthermore, the balancing performance is increased through the improvement of the flexibility of part of the polyurathane housing. However, the increase of the flexibility of the housing causes a little loss of the cardiac output due to the reduction of active filling performance. In this paper, a good condition between the balance and pump output performance is evaluated by adjusting the air volume in the interventricular space through a series of in vitro experiment.

• Journal of Environmental Science International
• /
• v.21 no.5
• /
• pp.597-603
• /
• 2012

Non-thermal plasma processing using a dielectric barrier discharge (DBD) has been investigated as an alternative method for the degradation of non-biodegradable organic compounds in wastewater. The active species such as OH radical, produced by the electrical discharge may play an important role in degrading organic compound in water. The degradation of N, N-Dimethyl-4-nitrosoaniline (RNO) was investigated as an indicator of the generation of OH radical. The DBD plasma reactor of this study consisted of a plasma reactor, recycling pump, power supply and reservoir. The effect of diameter of external reactor (15 ~ 40 mm), width of ground electrode (2.5 ~ 30 cm), shape (pipe, spring) and material (copper, stainless steel and titanium) of ground electrode, water circulation rate (3.1 ~ 54.8 cm/s), air flow rate (0.5 ~ 3.0 L/min) and ratio of packing material (0 ~ 100 %) were evaluated. The experimental results showed that shape and materials of ground were not influenced the RNO degradation. Optimum diameter of external reactor, water circulation rate and air flow rate for RNO degradation were 30 mm, 25.4 cm/s and 4 L/min, respectively. Ground electrode length to get the maximum RNO degradation was 30 cm, which was same as reactor length. Filling up of glass beads decreased the RNO degradation. Among the experimented parameters, air flow rate was most important parameters which are influenced the decomposition of RNO.