• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.465-471
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• 2013

A steam generator in nuclear power plant is a heatexchager which is used to convert water into steam from heat produced in a nuclear reactor core, and the steam produced in steam generator is delivered to the turbine to generate electricity. Because of damage to steam generator tubing may impair its ability to adequately perform required safety functions in terms of both structural integrity and leakage integrity, eddy current testing is periodically performed to evaluate the integrity of tubes in steam generator. This assessment is normally performed during a reactor refueling outage. Currently, the eddy current testing for steam generator of nuclear power plant in Korea is performed in accordance with KEPIC & ASME Code requirements, the eddy current testing system is consists of remote data acquisition unit and data analysis program to evaluate the acquired data. The KEPIC & ASME Code require that the electrical properties of remote data acquisition unit, such as total harmonic distortion, input & output impedance, amplifier linearity & stability, phase linearity, bandwidth & demodulation filter response, analog-to-digital conversion, and channel crosstalk shall be measured in accordance with the KEPIC & ASME Code requirements. In this paper, the measurement requirements of electrical properties for eddy current testing instrument described in KEPIC & ASME Code are presented, and the measurement results of newly developed eddy current testing instrument by KHNP(Korea Hydro & Nuclear Power Co., LTD) are presented.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.85-96
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• 2000

It is necessary that fully differential operational amplifier circuit should drive an external load in the VLSI design such as SCF(Switched Capacitor Filter), D/A Converter, A/D Converter, Telecommunication Circuit and etc. The conventional CMOS operational amplifier circuit has many problems according to CMOS technique. Firstly, Capacity of large loads are not able to operate well. The problem can be solve to use class AB stages. But large loads are operate a difficult, because an element of existing CMOS has a quadratic functional relation with input and output voltage versus output current. Secondly, Whole circuit of dynamic range decrease, because a range of input and output voltages go down according as increasing of intergration rate drop supply voltage. The problem can be improved by employing fully differential operational amplifier using differential output stage with wide output swing. In this paper, we proposed new current mirror has large output impedance and good current matching with input an output current and compared with characteristics for operational amplifier using cascoded current mirror. To obtain large output swing and low power consumption we suggest a fully differential operational amplifier. The circuit employs an output stage composed new current mirror and two amplifier stage. The proposed circuit is layout and circuit of capability is inspected through simulation program(SPICE3f).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.4
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• pp.69-74
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• 2010

A new package substrate for dynamic random access memory(DRAM) devices has been developed using selective aluminum anodization. Unlike the conventional substrate structure commonly made by laminating epoxy-based core and copper clad, this substrate consists of bottom aluminum, middle anodic aluminum oxide and top copper. Anodization process on the aluminum substrate provides thick aluminum oxide used as a dielectric layer in the package substrate. Placing copper traces on the anodic aluminum oxide layer, the resulting two-layer metal structure is completed in the package substrate. Selective anodization process makes it possible to construct a fully filled via structure. Also, putting vias directly in the bonding pads and the ball pads in the substrate design, via in pad structure is applied in this work. These arrangement of via in pad and two-layer metal structure make routing easier and thus provide more design flexibility. In a substrate design, all signal lines are routed based on the transmission line scheme of finite-width coplanar waveguide or microstrip with a characteristic impedance of about $50{\Omega}$ for better signal transmission. The property and performance of anodic alumina based package substrate such as layer structure, design method, fabrication process and measurement characteristics are investigated in detail.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.813-818
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• 1998

Ultrafine powders of $\textrm{In}_{2}\textrm{O}_{3}$-doped $\textrm{SnO}_{2}$ were synthesized by a coprecipitation method and the effects of pH value and the amount of In2Q addition on particle size were investigated. The influence of pH value on particle size could be negligible, whereas the amount of $\textrm{In}_{2}\textrm{O}_{3}$ has influenced on particle size and specific surface area. The gas sensitivity to hydrocarbOn($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) increased with $\textrm{In}_{2}\textrm{O}_{3}$ addition and reached a maximum at 3wt.% addition. From the results of impedance analysis and I-V characteristics. it was showed that the agglomeration structure of particles and the boundaries between agglomerates were the important factors to determine the gas sensing mechanism.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.47-56
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• 2011

Korea Ministry of Knowledge Economy has estimated that wind power (WP) will be occupied 37% in 2020 and 42% in 2030 of the new energy sources, and also green energies such as photovoltaic (PV) and WP are expected to be interconnected with the distribution system because of Renewable Portfolio Standard (RPS) starting from 2012. However, when a large scale wind power plant (over 3[MW]) is connected to the traditional distribution system, protective devices (mainly OCR and OCGR of re-closer) will be occurred mal-function problems due to changed fault currents it be caused by Wye-grounded/Delta winding of interconnection transformer and %impedance of WP's turbine. Therefore, when Double-Fed Induction Generator (DFIG) of typical WP's Generator is connected into distribution system, this paper deals with analysis three-phase short, line to line short and a single line ground faults current by using the symmetrical components of fault analysis and PSCAD/EMTDC modeling.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.171-175
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• 2011

Lithium secondary batteries using lithium metal count electrode are easy to use and to analyze the specific characteristics of working electrode. Nevertheless, during the charge operation internal electrical short circuit could be caused by the dendritic growth of lithium. The cell failure by the short circuit depends on the condition of separator such as constitutive material and thickness. To prevent the cell failure caused by the dendritic growth of lithium, the electrochemical properties of the cell of lithium metal count electrode were evaluated for four different kinds of separator. Among the tested separators, GMF (glass micro-fiber filter, $300{\mu}m$) was the most promising one because it could effectively prevent the cell failure during the charge. The cell using GMF separator had relatively low impedance. Generally the cell using thicker separator than $50{\mu}m$ could effectively avoid the cell failure by internal short circuit and had the good cycleability. The highest rate capability by the signature method was acquired in the case of GMF separator.

• Korean Journal of Community Nutrition
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• v.23 no.2
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• pp.102-115
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• 2018

Objectives: Although breakfast is important to nutrition balance, prevention of overeating, and weight control, people in their 20s (males: 55.1%, females: 49.9%) were reported to have the highest rate of skipping breakfast in 2016 Korea Health Statistics. This study aims to examine dietary habits and nutrient intake depending on breakfast frequency among young women in Seoul. Methods: The subjects were 655 young women in Seoul from August to October 2016, and the survey was performed by using a questionnaire that included general characteristics, dietary habits, and eating behavior. Body composition was determined by bioelectric impedance analysis. Nutritional status was examined by the 24-hour recall method. Results: The participants were classified by breakfast intake frequency; '${\geq}5times/week$ (n=160)', '1-4 times/week (n=327)', and 'breakfast skipping (n=168)'. The 'breakfast skipping' group had lower frequency and regularity of meals. In addition, the 'breakfast skipping' group had a higher frequency of eating-out and late-night meals. There was no difference in total calories between the 'breakfast skipping' group and other groups, but the 'breakfast skipping' group had significantly low carbohydrate and fiber intakes. The participants showed lower intakes of calories, fiber, vitamin A, vitamin C, niacin, folic acid, calcium, potassium, and zinc in comparison with recommended intakes. Especially, the 'breakfast skipping' group had significantly lower fiber, vitamin A, vitamin C, calcium, potassium levels compared to the '${\geq}5times/week$' group. For Mean Adequacy Ratio (MAR), the 'breakfast skipping' group recorded a ratio of 0.60, which was lower than those of other groups. Index of Nutritional Quality (INQ) including fiber, vitamin C, calcium and phosphorus were significantly lower in the breakfast skipper group, compared to the breakfast eater group. Conclusions: The 'breakfast skipping' group showed low regularity of meals and a high frequency of eating-out and late-night meals. The breakfast regular eater group showed high intake of micronutrients and quality of meals was high in general. Skipping breakfast could lower nutrient intake and quality of meals, which requires attention.

• Journal of Life Science
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• v.20 no.6
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• pp.894-901
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• 2010

The purpose of this study was to examine obstetrical & gynecological health status and body composition for married female immigrants. The participants were 154 immigrant women living in Busan. Data were collected from July 2008 to July 2009 using a questionnaire and a bioelectrical impedance analysis tool (Inbody 720) for analysis of body composition. Most subjects were in the normal range for body composition, but some of those who answered the questionnaire had experienced some gynecological problems such as dysmenorrhea, or irregular menstruation. There was a significant difference in experiences with in vitro fertilization, pregnancy and abortion according to age and in premensturaion syndrome, as well as differences in regulation of menstruation during the past year, leukorrhea odor, experiences in in vitro fertilization, and delivery and breastfeeding according to nationality. There were significant differences in body mass index and waist-hip ratio according to age, as well as differences in percent body fat, body mass index and waist-hip ratio according to nationality. There were also significant differences in body mass index and waist-hip ratio according to period of stay in Korea. Procreative care protocols concerning married female immigrants' characteristics should be developed.

• Journal of the Korean Electrochemical Society
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• v.17 no.3
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• pp.149-155
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• 2014

In this study, a positive-electrode material in a lithium secondary battery $Li[Ni_{0.575}Co_{0.1}Mn_{0.325}]O_2$ was synthesized as precursor by co-precipitation. Cathode material was synthesized by adding iron. The synthesized cathode material was analyzed by scanning electron microscope and x-ray diffraction. The analysis of x-ray diffraction showed that the a-axis and c-axis is increased by doping iron. And $I_{(003)}/I_{(104)}$ is increased and $I_{(006)}+I_{(102)}/I_{(101)}$ is decreased. Through this result, it was confirmed that the structural stability is improved. And impedance measurements show that the charge transfer resistance ($R_{ct}$) is lowered by doping iron. Consequently, electrochemical properties are improved by doping iron. In particular, the cycle characteristics are improved at a high temperature condition (328 K). Structural stabilities are contributing to the cycle properties.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.68.1-68.1
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• 2012

The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.