• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.120-127
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• 2005

The design method of the transversal filter using continuously cascaded directional couplers is presented. The coupler can be treated for a continuously varying nonuniform coupled transmission line. The design method is based on the optimum extraction of desired coupling factor by the control of null positions which are inherent to the coupling spectra pattern. In the optimization process, the improved Woodward-Lawson sampling method is applied to easily synthesize the distributed delay and weighting elements for transversal filter properties. For application, the microstrip transversal filter is fabricated and optimum dielectric overlay is introduced for the mode phase velocity compensation for non-TEM coupler nodes by using SDA(Spectral Domain Approach). Experiment results confirm the validity of the proposed method.

• Journal of Korean Biological Nursing Science
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• v.2 no.1
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• pp.49-63
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• 2000

Aflatoxin $B_1(AFB_1)$ is a potent hepatotoxic and hepatocarcinogenic mycotoxin in human beings. It is accumulated in animal tissues and injured cell through variable metabolic pathway. This study was conducted to determine the effect of antioxidant vitamins on liver function enzymes and hepatic damage of $AFB_1$ treated mice. The 6 weeks old male ICR mice were randomly separated 6 groups, vehicle solvent or vitamin C(10 mg/kg/day) and vitamin E(63.8 mg/kg/day) were administered by intraperitoneal(i.p.) injection and 1 hr later, vehicle solution(DMSO) or $AFB_1$(0.4 mg/kg) were injected. The results obtained as follow ; The levels of liver function enzymes such as GOT, GPT, LDH, and alkaline phosphatase, in sera of mice were remarkably elevated by treatment with $AFB_1$ only. However, those enzymes were significantly alleviated by co-treatment with antioxidant vitamins(p<0.01). Especially the levels of LDH and ALK phosphatase were similar to those of control groups(p<0.01). The transmission electron microscopy(TEM) image of intracellular microrganelles on the liver cell of mice was also degenerated extremely by treatment with $AFB_1$, but vitamin C and vitamin E gave good effects on cellular deformation. The intracellular microrganelles such as mitochondria, endoplasmic reticulum, nucleus and nucleic membrane were nearly disappeared the cellular deformation by antioxidant vitamins co-administration. With above results, we could estimated that antioxidant vitamins blocked AFB1 induced hepatic cell damage.

• Journal of Korea Foundry Society
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• v.17 no.2
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• pp.158-163
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• 1997

Properties of $Al_{86}Ni_6Ce_4Mg_4$ alloy powder produced by helium gas atomization process were investigated by using DSC, XRD, SEM and TEM. The powders below 32 ${\mu}m$ in diameter were identified as an amorphous phase mixed with a ${\alpha}-Al$ phase. $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy was manufactured by hot extruding the alloy powders at various temperatures, and the estimation of its mechanical properties was carried out subsequently. As a result, the bulk alloy extruded at the temperature below $450^{\circ}C$ exhibited the microstructure in which the near-spherical shape of some powders below 20 ${\mu}m$ were nearly unchanged and fine voids between matrix and powders were formed during extrusion process. On the other hand, the tensile strength and elongation at room temperature for $Al_{86}Ni_6Ce_4Mg_4$ bulk alloy extruded at $450^{\circ}C$ were 750 MPa and 7.5%, respectively.

• Journal of Power System Engineering
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• v.17 no.1
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• pp.110-115
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• 2013

The electrochemical performance and microstructure of Al-Si, Al-Si/C was investigated as anode for lithium ion battery. The Al-Si nano composite with 5 : 1 at% ratio was prepared by arc-discharge nano powder process. However, some of problem is occurred, when Al nano composite was synthesized by this manufacturing. The oxidation film is generated around Al-Si particles for passivating processing in the manufacture. The oxidation film interrupts electrical chemistry reaction during lithium ion insertion/extraction for charge and discharge. Because of the existence the oxidation film, Al-Si first cycle capacity is very lower than other examples. Therefore, carbon synthsized by glucose ($C_6H_{12}O_6$) was conducted to remove the oxidation film covered on the composite. The results showed that the first discharge cycle capacity of Al-Si/C is improved to 113mAh/g comparing with Al-Si (18.6mAh/g). Furthermore, XRD data and TEM images indicate that $Al_4C_3$ crystalline exist in Al-Si/C composite. In addition the Si-Al anode material, in which silicon is more contained was tested by same method as above, it was investigated to check the anode capacity and morphology properties in accordance with changing content of silicon, Si-Al anode has much higher initial discharge capacity(about 500mAh/g) than anode materials based on Aluminum as well as the morphology properties is also very different with the anode based Aluminum.

• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.523-527
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• 2002

Partition coefficient related composition of LPG are studied. Analysed sulfur compounds are ethyl mer-captan,n-propyl mercaptan and n-butyl mercaptan. The composition of liquid phase and gas phase in LPG are deter-mined by gas chromatography. The partition coefficient to related the boiling point of sulfur compounds, the temperature and the compositions of solvents, determined by using MLR(multiple linear regression) of SAS is follows; Kpc= $0.61222({\pm}0.6578)-0.04670({\pm}0.000959)Bp+0.26984(\pm0.06504)C4+0.003803(^{\circ}ae0.0019993)Tk,$ N=24, F=14.851, $R^2_{adj}$=0.6437. The boiling points of sulfur compounds at atmospheric pressure and the compositions of LPG effect mostly on partition coefficients. It is presumed that the gas odor elevating effects should be increased, where being on high tem-perature and larger amounts of n-butane.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.115-120
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• 2003

We have developed laser micro-machining technology for fabrication of the micro thin-film inductors. After the thin layers of FM/M/FM films were coated to the silicon substrate by using the conventional sputtering method, the new laser machining was applied to the patterning process that used to be carried out by the semiconductor lithography procedure. A CW Nd:YAG laser operating in TEM$\sub$00/ mode was actively Q-switched to obtain the very short pulse of 200 ns. The laser micro-machining process with pulse energy and repetition rate have been optimized as 5 mJ/pulse and 5 kHz, respectively, to obtain the line resolution as fine as 20 $\mu\textrm{m}$.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.91-96
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• 2003

Cross-geometrical Cr/Co/Al-Ox/Co/Ni-Fe tunnel junctions were fabricated by magnetron sputtering. To form an insulating layer, The Al layer was oxidized in an atmosphere of oxygen-argon mixture at low power after deposition. To enhance the coercivity of the bottom Co layer, The Cr seed layer was deposited on the glass and it led to increase in coercivity. The coercivity increase is due to the increase of roughness through the Cr thickness. In over oxidation time, the oxidation of Co bottom layer and flat interface of insulator can increase the bottom Co coercivity. But TMR ratio gradually decrease. TMR ratio is relevant with Cr thickness, insulator thickness, and oxidation time. The maximum TMR ratio was 14% at room temperature and the TMR ratio was decreased to half at 0.51 V.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.233-245
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• 2001

With the advent of super-conducting magnet, NMR spectroscopy becomes a very important tool in geology as well as in chemistry. $^{29}Si$ and $^{27}Al$ which are the main components of minerals and contain structural informations, are useful major targets for the NMR study in geology, but some other elements including alkali cations such as $^{23}Na$ are also one of them. NMR can be applied to many different fields. For example, it can be applied to study smaller range of structure (in molecular level) than XRD and TEM. NMR provides us with structural informations such as order-disorder in Al and Si distribution, oxygen coordination number, and distribution of other cations. Another important information that we can obtain from NMR is not only the static structural informations, but also the molecular dynamics. This dynamic informations of molecules also enable us to figure out the frequency of molecular motion and activation energy. Structure of amorphous minerals and chemistry and structure of natural organic materials are also studied by NMR.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.8
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• pp.1020-1031
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• 1998

This study was done to investigate thermal reponses and to obtain the basic information of thermal comfort by sex and posture under the Ondol heating system. Six healthy males and females were exposed to Ondol(Room Temp.: 25$\pm$1$^{\circ}C$, 50$\pm$10%R.H, Floor Temp.:30$\pm$1$^{\circ}C$) on the of posture such as sitting, lying aside and supine on the floor for 30 minutes after 30 minutes' control phase. During the experiment, rectal temperature, skin temperature of 10 areas, local sweating rate, clothing microclimate, subjective sensation were measured. Rectal temperature gradually decreased and mean skin temperature grad-ually increased both male and female in any posture. There was not significant difference between male and female in rectal temperature and mean skin temperature. There were significant difference among the postures in rectal temperature(p<0.001) and mean skin temperature(p<0.001). In lying aside and supine on the floor, appearances of change and changes in rectal temperature and mean skin temperature were large, changes of weight were small. In sitting on the floor, appearances of change and changes in rectal temperature and mean skin temperature were small, changes of weight were large. The trunk skin tem-perature was higher in female than in male, but the extremity skin temperature was higher in male than in female. In sitting on the floor, foot skin temperature(p<0.001) was higher than any other local skin temperature. In supine on the floor, back skin temperature(p<0.001) was higher than any other local skin temperature.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.2
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• pp.91-98
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• 2005

Both commercially pure titanium and Ti-6Al-4V alloy have been widely used as biomaterials because of their excellent biocompatibility, corrosion resistance and mechanical properties. However, in recent years, vanadium has been found to cause cytotoxic effects and adverse tissue reactions, while aluminium has been associated with potential neurological disorders. A newly designed ${\alpha}+{\beta}$ type Ti alloy, Ti-10Ta-10Nb alloy showed superior properties to CP Ti and Ti-6Al-4V alloy in the point of biomaterial, and elucidated the future uses as a biomaterial. Microstructural changes of Ti-10Ta-10Nb alloy after hot-rolling, warm-rolling, solution and aging treatment were investigated. According to TEM results, the microstructures after solution treatment were composed of mostly ${\alpha}$ phase with a trace of ${\beta}$ phase due to adding ${\beta}$-phase stabilizer tantalum and niobium. The microstructures after warm-rolling is coarse and elongated ${\alpha}$ phase and hot rolling resulted in very fine ${\alpha}$ widmanst$\ddot{a}$tten. The highest value of hardness was obtained by aging treatment at $400^{\circ}C$ for 20hr in which microstructure consisted of very fine ${\alpha}$ phase in ${\beta}$ matrix.