• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.47-52
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• 2003

Ferromagnetic tunnel junctions were fabricated by dc magnetron sputtering and plasma oxidation process. The local transport properties of the ferromagnetic tunnel junctions were studied using contact-mode Atomic Force Microscopy (AFM) and the local current-voltage analysis. Tunnel junctions with the structure of sub./Ta/Cu/Ta/NiFe/Cu/Mn$\_$75/Ir$\_$25//Co$\_$70/Fe$\_$30//Al-oxide were prepared on thermally oxidized Si wafers. Al-oxide layers were formed with microwave excited plasma using radial line slot antenna (RLSA) for 5 and 7 sec. Kr gas was used as the inert gas mixed with $O_2$ gas for the plasma oxidization. No correlation between topography and current image was observed while they were measured simultaneously. The local current distribution was well identified with the distribution of local barrier height. Assuming the gaussian distribution of the local barrier height, the ferromagnetic tunnel junction with longer oxidation time was well fitted with the experimental results. As contrast, in the case of the shorter time oxidation junction, the current mainly flow through the low barrier height area for its insufficient oxygen. Such leakage current might result in the decrease of tunnel magnetoresistance (TMR) ratio.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.2
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• pp.54-61
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• 1999

This paper describes the design of a 4-Mbps wireless infrared data transceiver chip. The receiver consits of the analog front-end, clock recovery and frame generator, and demodulator. The transmitter consists of the demodulator and LED driver. The versatile analog front- end consisting of multiple amplifiers makes it possible for the chip to be applied to various infrared environments by compensating DC and offset signal components. A 4PPM (pulse position modulation) scheme is used for data transfer in order to meet the IrDA standards. The chip was fabricated in a $0.8-{\mu}m$ 2-poly, 2-metal CMOS technology and dissipates 122mW for ${\pm}2.5V$ supply.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.33-38
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• 2015

Energy storage systems (ESSs) have been utilized widely in the world to optimize the power operation system and to improve the power quality. As lithium secondary batteries are the main power supplier for ESSs, it is very important to predict its cycle and power degradation behavior. In particular, the power, one of the hardest electrochemical properties to measure, needs lots of resources such as time and facilities. Due to these difficulties, computer modelling of lithium secondary batteries is applied to predict the DC-IR and power value during charging and discharging as a function of state of charge (SOC) by using pulse-based measurement methods. Moreover, based on the hybrid pulse power characteristics (HPPC) and J-Pulse (JEVS D 713, Japan Electric Vehicle Association Standards) methods, their electrochemical properties are also compared and discussed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.2
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• pp.167-173
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• 2016

This study investigated the effects of green tea polyphenol and vitamin C on type 2 diabetes mellitus by administering polyphenon 60 (P60) and sodium ascorbate (SA) to diabetic rats induced by high fat diet/low-dose streptozotocin. The experimental group was divided into five different groups: non-diabetic control group (NC), diabetes control group (DC), diabetes+P60 group (DM+P60), diabetes+SA group (DM+SA), and diabetes+P60+SA group (DM+P60+SA). P60 and SA were dissolved in 0.1% drinking water. After P60 and SA were administered for 16 weeks, fasting blood glucose, plasma insulin, serum triglyceride, blood urea nitrogen (BUN), and creatinine levels as well as kidney alkaline phosphatase (AP) and ${\gamma}$-glutamyltranspeptidase (GGT) activities were measured. Fasting blood glucose level increased 5-fold in the DC group compared to the NC group. In the DM+P60 group, fasting blood glucose level decreased by 14%. In the DM+P60+SA group, fasting blood glucose level decreased by 28% compared to the DC group, whereas the DM+SA group did not show any significant difference. The homeostasis model assessment for insulin resistance index increased in the DC group and decreased in the DM+P60+SA group compared to the DC group. Serum creatinine level increased in the DC group, but decreased by 17% in the DM+P60 group and by 43% in the DM+P60+SA group compared to the DC group. The serum BUN level increased in the DC group, but decreased by 41% in the DM+P60+SA group compared to the DC group. Kidney GGT and AP activities decreased in the DC group compared to the NC group; however, they were reversed by DM+P60+SA group. These results show that combined administration of both green tea polyphenol and vitamin C had better effects on improving blood glucose level, insulin resistance, serum triglyceride level, and protecting kidneys than administration of either green tea polyphenol or vitamin C alone in the context of type 2 diabetes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.439-444
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• 2012

For the application of photo-detector as active layer, we have studied how to deposit SiGe thin film using an independent Si target and Ge target, respectively. Both targets were synthesized by purity of 99.999%. Plasma generators were generated by radio frequency (rf, 13.56 MHz) and direct current (dc) power. When Ge and Si targets were sputtered by dc and rf power, respectively, we could observe the growth of highly crystalline Ge thin film at the temperature of $400^{\circ}C$ from the result of raman spectroscopy and X-ray diffraction method. However, SiGe thin film did not deposit above method. Inversely, we changed target position like that Ge and Si targets were sputtered by rf and dc power, respectively. Although Ge crystalline growth without Si target sputtering deteriorated considerably, the growth of SiGe thin film was observed with increase of Si dc power. SiGe thin film was evaluated as microcrystalline phase which included (111) and (220) plane by X-ray diffraction method.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.5
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• pp.630-637
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• 2012

This study was performed to investigate the effects of puffed and fermented red ginseng on blood glucose-related biomarkers in streptozotocin-induced diabetic rats. Male Sprague-Dawley diabetic rats were orally injected with 0.85% NaCL as a diabetic control (DC), 300 mg/kg general red ginseng (RG), 300 mg/kg puffing red ginseng fermented by mixed strain culture of $Bifidobacterium$ $breve$ and $Lactobacillus$ $delbrueckii$ (BL), and 300 mg/kg puffing red ginseng fermented by $Enterococcus$ $faecalis$ (EF) for 5 weeks. The blood glucose level of group BL was significantly lower maintained than in groups DC and RG for the experimental period (p<0.05). It was also significantly lower than in groups DC, RG, and EF at the 5th week (p<0.05). In the oral glucose tolerance test, the blood glucose of group BL was maintained the lowest level (p<0.05), and the area under the blood glucose curve (AUC) was also significantly lower in group BL than in group DC (p<0.05). The fasting blood glucose and insulin levels after the experiment were significantly low in group BL (p<0.05), and the HOMA-IR was more significantly low in groups BL and EF than in group DC (p<0.05). Also, the HbA1c content of group BL was significantly low than in groups DC and RG (p<0.05). The serum TC level was significantly decreased in groups RG, BL, and EF than in group DC (p<0.05), and the LDL-C content was significantly low in group BL than in group DC (p<0.05). From the findings, it was shown that the puffed and fermented red ginseng made using a mixed strain culture of $B.$ $breve$ and $L.$ $delbrueckii$ could improve blood glucose-related biomarkers.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.15-21
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• 1988

The Polarographic behavior of 1-(2-thiazolylazo)-2-naphthol (TAN) in acetonitrile solution was studied. From the DC polarograms of TAN in acetonitrile solution, the type of reduction current and the effect of proton donor such as water have been investigated. In order to explain the reduction mechanism, the number of the electrons for each reduction step was measured by controlled potential coulometric technique and the electrolysis products were identified by UV-Vis spectroscopy and IR spectroscopy. The results were shown that the reduction of TAN in acetonitrile solution occurred with four-one electron steps. In addition, each reduction step was considerably reversible and the reduction current was diffusion controlled.

• Journal of Magnetics
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• v.8 no.1
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• pp.32-35
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• 2003

Magnetic funnel Junctions (MTJs) were fabricated on thermally oxidized Si (100) wafers using DC magnetron sputtering. The film Structures were Ta(50 ${\AA}$)/CU(100 ${\AA}$)$Ni_{80}Fe_{20}(20 $ ${\AA}$)/Cu(50 ${\AA}$)/$Mn_{75}Ir_{25}(100 $ ${\AA}$)/$Co_{70}Fe_{30}(25$ ${\AA}$)/Al-O(15 ${\AA}$)/$Co_{70}Fe_{30}(25 $ ${\AA}$)/$Ni_{80}Fe_{20}(t)/Ta(50 $ ${\AA}$), with t=0 ${\AA}$, 100 and 1000 ${\AA}$, respectively. X-ray diffraction has shown improvement of (111) texture of IrMn$_3$ and Cu by annealing. The exchange-biased energy is almost inversely proportional to temperature. The difference between the coercivity H$_c$ and the exchange biased field H$_E$ for t = 0 $_3$ sample is smaller than that for t = 1000 ${\AA}$. For the pinned layer, the decreasing rate of the coercivity with the temperature is higher compared to that of the exchange field, but variation of H$_c$ is similar to that of the exchange field for free layer.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.1
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• pp.19-29
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• 2003

This paper proposes a CMOS readout circuit for uncooled micro-bolometer arrays adopting a four-point step calibration technique. The proposed readout circuit employing an 11b analog-to-digital converter (ADC), a 7b digital-to-analog converter (DAC), and an automatic gain control circuit (AGC) extracts minute infrared (IR) signals from the large output signals of uncooled micro-bolometer arrays including DC bias currents, inter-pixel process variations, and self-heating effects. Die area and Power consumption of the ADC are minimized with merged-capacitor switching (MCS) technique adopted. The current mirror with high linearity is proposed at the output stage of the DAC to calibrate inter-pixel process variations and self-heating effects. The prototype is fabricated on a double-poly double-metal 1.2 um CMOS process and the measured power consumption is 110 ㎽ from a 4.5 V supply. The measured differential nonlinearity (DNL) and integrat nonlinearity (INL) of the 11b ADC show $\pm$0.9 LSB and $\pm$1.8 LSB, while the DNL and INL of the 7b DAC show $\pm$0.1 LSB and $\pm$0.1 LSB.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.967_968
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• 2009

For lighting application, high-power LED nowadays is driven at 350mA and a sensing resistor is used to provide feedback for LED-current regulation. This method adds an IR drop at the output branch, and limits power efficiency as LED current is large and keeps increasing. In this paper, a power efficient LED-current sensing circuit is proposed. The circuit does not use any sensing resistor but extracts LED-current information from the output capacitor of the driver. Controlling the brightness of LEDs requires a driver that provides a constant, regulated current. In one case, the converter may need to step down the input voltage, and, in another, it may need to boost up the output voltage. These situations often arise in applications with wide-ranging ""dirty"" input power sources, such as automotive systems. And, the driver topology must be able to generate a large enough output voltage to forward bias the LEDs. So, to provide this requirements, 13W prototype Buck-Boost Converter is used.