• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.116-121
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• 2016

The amount of carbon dioxide ($CO_2$) released while producing building materials is substantial and has been targeted as a leading contributor to global climate change. One of the most typical methods of reducing $CO_2$ in building materials is the addition of slag and fly ash, like pozzolan material another method is to reduce $CO_2$ production by developing carbon negative cement. MgO-based cement from the low-temperature calcination of magnesite required less energy and emitted less $CO_2$ than the manufacturing of Portland cements. It is also believed that adding reactive MgO to Portland-pozzolan cements can improve their performance and also increase their capacity to absorb atmospheric $CO_2$. In this study, basic research on magnesia cement using $MgCO_3$ and magnesium silicate ore (serpentine) as the main starting materials, as well as blast furnace slag for the mineral admixture, was carried out for industrial waste material recycling. In order to increase the overall hydration activity, $MgCl_2$ was also added. In the case of the addition of $MgCl_2$as accelerating admixture, there was a promoting effect on the compressive strength. This was found to be due to the production of needle-like dense Mg-Cl hydrates. Mgnesia cement has a high viscosity due to its high specific surface area therefore, when the PC-based dispersing agent was added at a level of more than 1.0%, it had the effect of improving fluidity. In particular, the addition of $MgCl_2$ in magnesia cement using $MgCO_3$and magnesium silicate ore (serpentine) as main starting materials led to a lower expansion ratio and an increase in the freeze-thaw resistance finally, the addition of $MgCl_2$ as accelerating admixture led to good overall durability.

• Journal of Korean Medicine for Obesity Research
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• v.16 no.1
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• pp.19-26
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• 2016

Objectives: The prevalence of obesity continues rise and obesity and metabolic syndrome is a major problem in global health care. Animal models are used in the drug discovery of novel treatment for obesity. One of common models of obesity is a high fat diet induced obesity in a C5BL/6 mouse, and the development of obesity and glucose tolerance in mouse model is different according to period of diet. Therefore, this study was performed to observe the development of obesity and glucose tolerance during a high fat diet (HFD). Methods: Male C57BL/6 mice, 5 weeks of age, were fed on a standard chow diet as a normal diet (18 kcal% fat) or a HFD (60 kcal% fat) for up to 16 weeks. The various factors related with obesity and insulin resistance were measured at 8, 12, and 16 weeks. Results: The weights of body and epididymal fat were gradually increased for 8~16 weeks, however the change of hyperglycaemia and glucose tolerance have shown different with that of body weight. Blood glucose, oral glucose tolerance and insulin tolerance were increased more clearly at week 12 and 16 than week 8. Lipid accumulation of liver and body temperature were also significantly increased at week 16, compared with normal group. Conclusions: The developments of obesity and related factors were different by a HFD period in a C57BL/6 obese mice. This result suggests that the development of obesity with glucose tolerance and liver lipid may induce clearly by a HFD for 16 weeks.

• Applied Chemistry for Engineering
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• v.21 no.6
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• pp.621-626
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• 2010

Anion exchange membranes can be used for reverse electrodialysis for electric energy generation, and capacitive deionization for water purification, as well as electrodialysis for desalination. In this study, anion exchange membranes of poly((vinylbenzyl) trimethylammonium chloride-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) were prepared through the polymerization of (vinylbenzyl)trimethylammonium chloride and 2-hydroxyethyl methacrylate in aqueous poly(vinyl alcohol) solutions, esterification with glutaric acid, and cross-linking reaction with glutaraldehyde. We investigated electrochemical properties for the anion exchange membranes prepared according to experimental conditions. Ion exchange capacity and electrical resistance for the membranes were changed with a variation in the monomer ratio in polymerization. Water uptake and conductivity for the membranes decreased with an increase in the content of glutaric acid in esterification. The change in the time of crosslinking reaction with the formed film and glutaraldehyde affected electrochemical properties such as water uptake, conductivity, or transport number for the membranes. Chronopotentiometry and limiting current density for the anion exchange membranes prepared were measured.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.492-498
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• 2012

A hyper branched 10-butylphenothiazine with in-situ thermally curable methacrylate (1,3,5-tris-[$\{$10-Butyl-3-(4-(2-methyl-acryloyloxy)-phenyl)-7-yl-10H-phenothiazine$\}$]-benzene, (tris-PTMA)) was synthesized successfully. From the TGA thermogram of tris-PTMA was thermally stable up to $336^{\circ}C$. In the first heating scan of DSC thermogram, tris-PTMA showed glass transition temperature (Tg) at $140^{\circ}C$ and broad endothermic process in the region of $144-179^{\circ}C$, which is thermally curing temperature. In the second heating process, $T_g$ exhibited at $158.7^{\circ}C$ and endothermic process was not observed. Thermally cured tris-PTMA showed no big change in the UV-visible spectrum after washing with organic solvent such as methylene chloride, chloroform, toluene, indicating that thermally cured film was very good solvent resistance. Thermally cured tris-PTMA was electrochemically stable and the HOMO energy level of tris-PTMA was -5.54 eV. The maximum luminance efficiency of double layer structured polymer light-emitting diode based on in-situ thermally cured tris-PTMA was 0.685 cd/A at 16.0 V, which was higher than that of the device without thermally cured tris-PTMA (0.348 cd/A at 15.0 V).

• Pediatric Infection and Vaccine
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• v.6 no.2
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• pp.261-266
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• 1999

Vancomycin-resistant enterococcus(VRE) was first isolated from various specimens of patients with renal failure or leukemia in 1988. Thereafter VRE has been increasing gradually and became one of the clinically important palhogenic organisms currently. We experienced a case of E. faecalis sepsis in a 4 day old neonate. She was born at 39 weeks gestational age with 2,900gm weight by Cesarean section delivery due to breech presentation. She had had swelling and motion limitation of the left knee joint with fever for one day at age of 4 day and was transfered to our hospital. Ultrasonographic examination of her left knee joint showed some inflammatory change. E. faecalis was isolated from the blood. The organism showed resistance to vancomycin on drug susceptibility test using BHI agar screening test and disk diffusion method. After treatment with ampicillin-sulbactam for 3 weeks the baby was improved. Although VRE infection has been considered rare in Korea. considerable number of demonstrative studies about VRE isolation have been reported recently thus adequate countermeasures are needed to reduce the emergence and prevent nosocomial spreading of this organism.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.6
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• pp.553-559
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• 2015

The purpose of this research is to develop a gait assistive device to enhance the gait stability and training efficiency of stroke patients. The configuration of this device is mainly composed of a motored wheel and a single cane whose lower end is attached to a motored wheel frame. A patient can feel haptic information from continuous ground contact from the wheel while walking through the grip handle. In addition, the wheeled cane can avoid using excessive use of the patient's upper limb for weight support and motivate the patient to use a paralyzed lower limb more actively. Moreover, the proposed device can provide intuitive and safe user interaction by integrating a force sensor and a tilt sensor equipped to the cane frame, and a switch sensor at the cane's handle. The admittance control has been implemented for the patient to change the walking speed intuitively by using the interaction forces at the handle. A hemi-paretic stroke patient participated in the walking assistive experiments as a pilot study to verify the effectiveness of the proposed haptic cane system. The results showed that the patient could improve walking speed and muscle activations during walking with a constant speed mode of the haptic cane. Moreover, the patient could maintain the preferred walking speeds and gait stability regardless of the magnitude of resistance forces with the admittance control mode of the haptic cane. The proposed robotic gait assistive device with a simple and intuitive mechanism can provide efficient gait training modes to stroke patients with high possibilities of widespread utilizations.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.9-19
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• 2002

By using the thermionic emission model, the L-I-V(power-current-voltage) characteristics of a SCH(seperate confinement heterostructure) QW(quantum well) laser diode is analytically derived. We derived the relationships between the bulk carrier density of SCH regions and the confined carrier density of QW. The L-I-V characteristics is derived analytically by using current continuity equations. Solving the ambipolar diffusion equation under the condition of high level injection and charge neutrality, the current distribution in the SCH regions is considered. Results showed that the major factor affecting the laser I-V characteristics was the change of potential barrier at the cladding-SCH interface. Also the series resistance of a laser diode was decreased and the carrier injection was increased by increasing the forward flux of injection current from cladding to SCH region.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.8
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• pp.1-9
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• 1999

Timing-level circuit analyses are used to obtain fast and accurate results, and the analysis of gate and interconnect delay is necessary to validate the correctness of circuit design. This paper proposes an efficient algorithm which simultaneously calculates the gate delay and the transition time of linearized voltage source for subsequent interconnect delay calculation. The notion of effective capacitance is used to calculate the gate delay and the transition time of linearized voltage source which considers the on-resistance of driving gate. The procedure for obtaining the gate delay and the transition time of linearized voltage source has been developed through an iterative operation using the precharacterized data of gates. While previous methods require extra information for the transition time calculation of linearized voltage sources, our method uses the derived data during the gate delay calculation process, which does not require any change in the precharacterization process.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.53-57
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• 2017

The most representative transparent electrode in the modern society is ITO (Indium Tin Oxide). ITO is widely used in general for touch panels and displays due to its high electrical and optical properties. However, in general, mechanical deformation causes deterioration and destruction of device properties because ITO is basically vulnerable to mechanical deformation. Therefore, the in-depth understanding on the stability of ITO film during various mechanical deformations is necessary. In this study, the reliability and mechanical properties ITO sample having different length, width, and area were investigated. The electrical stability was estimated according to electrical resistance change. The stability was dropped as the sample length, and width increased and the sample area decreased. The electrical stability of ITO film was correlated with twisting strain including tensile, compressive and shear stress.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.205-209
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• 2015

The economic losses resulted from the accident in the power cables at the power station is not only huge but also requires a great amount of time and expenses to restore to the former condition. In order to prevent these, it is necessary to invent and apply a technique to expect and prevent the accidents. In order to measure insulation resistances of power cables in operation, we derived the relations between load current and temperature. By analyzing data obtained from our measuring equipments, we showed the expected time to change deteriorated cables before accident occurs. We present a result of our study on the effects of the load current on lifetime of 6.6 kV cable systems in operation. With the current flowing through the load of the cable a heat is generated reducing the lifetime of the cable. In order to find out the effect of load current on the lifetime of cable systems, we applied the lifetime theory to the development of two equipments to measure insulation resistance and current of cable systems in operation.