• Journal of Nutrition and Health
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• v.41 no.4
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• pp.307-316
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• 2008

The purpose of the study was to investigate nutritional status of chronic obstructive pulmonary disease (COPD) patients and to find out the differences according to the stages of disease. From March to October, 2006, 41 stable male patients of mild to severe COPD patients were recruited from Seoul National University hospital. The patients' of body weight and fat free mass were assessed by bioelectrical impedance analysis. The nutritional status of the patients was also assessed by 3-day recall, index of nutritional quality (INQ), dietary diversity score (DDS), dietary variety score (DVS), food group index pattern and dietary quality index (DQI). The total of 41 patients were classified into three groups, stage I, stage II and stage III groups according to the classification of Global Initiative for Chronic Obstructive Lung Disease (GOLD) standard. The mean age of the patients in each stage were 67.2-66.9 years showing no significant difference. The ratio of $FEV_1$/FVC were $57.5{\pm}7.3$, $46.9{\pm}7.6$ and $38.2{\pm}6.8%$, respectively showing significant differences according to the stages of disease. The fat free mass of the stage II ($48.2{\pm}4.7kg$) and III ($47.3{\pm}4.5kg$) was significantly lower than that of stage I ($53.1{\pm}6.9kg$) patients. There were significant correlation of fat free mass with $FEV_{1}$, and BMI (body mass index) with $FEV_{1}$/FVC ratio (p < 0.05). COPD patients showed the diet-related clinical symptoms of anorexia, dyspnea, dyspepsia, and chewing difficulty. Daily intakes of calorie, K, vitamin $B_2$ and folate of the patients were very low ($83.8{\pm}20.7%$, $58.9{\pm}14.4%$, $70.7{\pm}19.6%$ and $74.4{\pm}10.2%$, respectively) however, they did not significantly different according to the stages of disease. Daily intake of calcium was significantly lower in the stage III patients (p < 0.05). The mean scores of dietary variety score was significantly lower in the stage III patients (p < 0.001). Dietary quality index of the patients were not different among the stages of disease and the scores indicated poor quality of diet. As a summary, we found that body fat free mass, regularity of exercise, frequency of having snacks and dietary variety score were significantly associated with the severity of chronic obstructive pulmonary disease.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1125-1132
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• 2000

The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.508-517
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• 2004

We described a near-field scanning microwave microscope which uses a high-quality dielectric resonator with a tunable screw. The operating frequency is f=4.5 5GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator We developed a hybrid tip combining a reduced length of the tapered part with a small apex. In order to understand the function of the probe, we fabricated three different tips using a conventional chemical etching technique and observed three different NSMM images for patterened Cr films on glass substrates. We measured the reflection coefficient of different metal thin film samples with the same thickness of 300m and compared with theoretical impedance respectly. By tuning the tunable screw coming through the top cover, we could improve sensitivity, signal-to-noise ratio, and spatial resolution to better than $1{\mu}m$. To demonstrate the ability of local microwave characterization, the surface resistance of metallic thin films has been mapped.

• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.543-548
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• 2015

Si/C/CNF composites as anode materials for lithium-ion batteries were examined to improve the capacity and cycle performance. Si/C/CNF composites were prepared by the fabrication process including the synthesis and magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling and the carbonization of phenol resin with CNF and HCl etching. Prepared Si/C/CNF composites were then analysed by BET, XRD, FE-SEM and TGA. Among SBA-15 samples synthesized at reaction temperatures between 50 and $70^{\circ}C$, the SBA-15 at $60^{\circ}C$ showed the largest specific surface area. Also the electrochemical performances of Si/C/CNF composites as an anode electrode were investigated by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of LiPF6 dissolved in mixed organic solvents (EC : DMC : EMC = 1 : 1 : 1 vol%). The coin cell using Si/C/CNF composites (Si : CNF = 97 : 3 in weight) showed better capacity (1,947 mAh/g) than that of other composition coin cells. The capacity retention ratio decreased from 84% (Si : CNF = 97 : 3 in weight) to 77% (Si : CNF = 89 : 11 in weight). It was found that the Si/C/CNF composite electrode shows an improved cycling performance and electric conductivity.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.251-259
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• 2005

In order to characterize the influence of the reaction-site density on the cathodic polarization property of LSCF, we chose the porosity of LSCF as a main controlling variable, which is supposed to be closely related with active sites for the cathode reaction. To control the porosity of cathodes, we changed the mixing ratio of fine and coarse LSCF powders. The porosity and pore perimeter of cathodes were quantitatively analyzed by image analysis. The electrochemical half cell test for the cathodic polarization was performed via 3-probe AC-impedance spectroscopy. According to the investigation, the reduction of oxygen at LSCF cathode was mainly controlled by following two rate determining steps; i) surface diffusion and/or ionic conduction of ionized oxygen through bulk LSCF phase, ii) charge transfer of oxygen ion at cathode/electrolyte interface. Moreover, the overall cathode polarization was diminished as the cathode porosity increased due to the increase of the active reaction sites in cathode layer.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.269-275
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• 2005

We analyzed the unit cell performance against the cathode porosity, which is supposed to be closely related with active sites for the cathode reaction. In order to fabricate the unit cells with different porosity in the cathode layer we changed the mixing ratio of fine and coarse LSCF cathode powders. The final porosity of each cathode layer was 14, 23, 27, $39\%$ respectively. According to the electrochemical analysis of unit cell performance via DC current interruption and AC impedance method, the electrodic polarization resistance was diminished as the cathode porosity increased. The decrease of polarization resistance was attributed due to the increase of active reaction sites and the enhancement of overall unit cell performance could be explained in the same line.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.42-49
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• 2018

In this paper, a dual-band microstrip-fed monopole antenna with a DGS(defected ground structure) for WLAN(wireless local area network) applications is presented. The antenna consists of a monopole and a defected ground, which were etched on both sides of the FR-4 substrate. The defected ground structure was used to obtain the dual band, while the step-by-step reduction in the monopole width was used to improve the impedance matching of the antenna. The antenna has an overall compact size of $44{\times}51{\times}1.6mm^3$, which was optimized by varying the size of the monopole and the ground plane such that it may resonate at the 2.4 GHz and 5 GHz bands of the WLAN. The measurement results showed that the antenna operates in the frequency band of 210 MHz(2.29~2.50 GHz) and 900 MHz(5.05~5.95 GHz) for a VSWR under 2, and showed omnidirectional radiation pattern at all desired frequencies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4165-4170
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• 2012

In this paper, a method for the improvement in the gain and bandwidth of a microstrip-fed broadband planar quasi-Yagi antenna (QYA) is studied. The broadband characteristics of the QYA are achieved from the coplanar strip-fed planar dipole driver and a parasitic director close to the driver. In order to obtain stable gain variation over the required frequency band, a director and a ground reflector are appended to the driver having a nearby parasitic director. The QYA is fed through an integrated balun composed of a microstrip line and a slot line which are terminated in a short circuit. By adjusting the feeding point, a broadband impedance matching is obtained. A QYA with an operating frequency band of 1.75-2.7 GHz and a gain > 4.5 dBi is designed and fabricated on an FR4 substrate with dielectric constant of 4.4 and thickness of 1.6mm. The experimental results show that the fabricated antenna has good performance such as a broad bandwidth of 59.7%(1.55-2.87 GHz), a stable gain between 4.7-6.5 dBi, and a front-to-back ratio > 10 dB. The measured data agree well with the simulation, which validates this study.

• Journal of the Korean Society of School Health
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• v.7 no.2
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• pp.125-133
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• 1994

This study was conducted to identify the relationship between body fat percent/serum lipid level and obesity index among school children. The study subjects were 277 boys and 266 girls aged between 10 and 11 years old in a selected elementary school in Taegu City. The survey was conducted for the period of two months from May 1 to June 30, 1993. A $R{\ddot{o}}hrer$index(weight/height3) was calculated for each individual as a measure of obesity. Three groups were classified as underweight($R{\ddot{o}}hrer$ index < 109), normal($109{\leq}$ $R{\ddot{o}}hrer$ index < 140), and overweight ($R{\ddot{o}}hrer$ index ${\geq}140$). As for the body fat percent, fat weight, lean body mass were measured by impedance fat, meter(Model SIF-891). Serum total cholesterol. high-density lipoprotein, and triglyceride were measured by automated clinical chemistry analyzer(Astra system). Obesity was found 18.1% in boys and 14.7% in girls. Body weight, fat percent, fat weight, and lean body mass were significantly different among three groups classified by $R{\ddot{o}}hrer$ index in both sexes. Serum total cholesterol, triglyceride, atherogenic index and T-CHO/HDL ratio were also significantly different among three groups in both sexes. Serum total cholesterol, low-density lipoprotein, trigylceride, atherogenic index of boys were positively correlated with height, weight. $R{\ddot{o}}hrer$ index, fat weight, lean body mass, and triglyceride. The negative correlation was found in high-density lipoprotein against height, weight, Rohrer index, fat percent, fat weight, lean body mass. Triglyceride and atherogenic index of the girls were positively correlated with height, weight, $R{\ddot{o}}hrer$ index, fat percent, fat weight, lean body mass. The negative correlation was found in high-density lipoprotein against height, weight, $R{\ddot{o}}hrer$ index, fat percent, fat weight, lean body mass. These findings suggest that the prevention of obesity and hyperlipidemia among school children is very important. Thus adoption of healthy life-style is strongly recommended in school health programs in order to prevent the obesity and hyperlipidemia.

• Journal of Nutrition and Health
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• v.47 no.1
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• pp.23-32
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• 2014

Purpose: This study was conducted in order to investigate the effect of Sargassum confusum extracts on the reduction of body fat for eight weeks in overweight women ($BMI{\geq_-}23kg/m^2$). Methods: Subjects were classified by double-blind randomized trial as the control group (C group, n = 14) and the Sargassum confusum extract supplementation group (SC group, n = 16), which consumed 12 tablets per day. Questionnaires related to their health status were assessed twice (week 0 and week 8). Their dietary intake status was evaluated by 24-recall method and body compositions were measured using a bioelectrical impedance analyzer. In addition, we assessed the anti-obesity effect and the occurrence possibility of health risk factors during the supplementation periods by hematological and clinical analysis of blood. Results: Waist circumference and body fat (%) were significantly decreased in the SC group. Serum leptin level was also significantly decreased in the SC group. Defecation frequency was significantly increased in the SC group. The above results indicate that Sargassum confusum extract supplementation improves overweight on visceral fat and blood leptin level by increasing bowel movement. These results imply a decrease of health risk factors in overweight women. Seven subjects withdrew from the study due to adverse events; however, no differences regarding adverse events were observed between the control and treatment group. Conclusion: Therefore, Sargassum confusum extract is a plausible effective agent for body fat reduction in humans.