• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.93-99
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• 2004

According to rapid increment of demand for wireless Local Area Network (LAN), the HyperLAN of 5.1-533GHz and 5.725-5.825GHz is newly allocated for wireless LAM in many regions over the world. Also, because most of mobile communication equipments are small, the size of antenna is important factor of effective design. In this paper, the compacted and wide bandwidth antenna is designed for wireless LAN at 5GHz band. Although the structure of U-shaped slot antenna is simple, It has large bandwidth of $10-40\%$. Also, the U-slot antenna has good radiation pattern. However, in general, the size of U-slot antenna is large. Therefore, it is difficult to apply to wireless equipment such as PDA and Notebook. This proposed antenna has a wide bandwidth by U-shaped slot in rectangular patch and is compacted by using two layered dielectric substrates and foam. For the design of U-slot antenna, the Finite Difference Time Domain method is applied. Also, the method of MPI parallel program is used for the enhancement of the analyzing speed of the FDTD method.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.687-693
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• 2004

Composite membranes with a titania layer were prepared by soaking-rolling method with the titania sol of nanoparticles formed in the sol-gel process and investigated regarding the vapor permeation of various organic mixtures. The support modification was conducted by pressing $SiO_2$ xerogel of 500 nm in particle size under 10 MPa on the surface of a porous stainless steel (SUS) substrate and designed the multi-layered structure by coating the intermediate layer of ${\gamma}-Al_2O_3$. Microstructure of titania membrane was affected by heat-treatment and synthesis conditions of precursor sol, and titania formed at calcination temperature of 300$^{\circ}C$ with sol of [$H^+$]/[TIP]=0.3 possessed surface area of 210 $m^2$/g, average pore size of 1.25 nm. The titania composite membrane showed high $H_2/N_2$ selectivity and water/ethanol selectivity as 25-30 and 50-100, respectively. As a result of vapor permeation for water-alcohol and alcohol-alcohol mixture, titania composite membrane showed water-permselective and molecular-sieve permeation behavior. However, water/methanol selectivity of the membrane was very low because of chemical affinity of permeants for the membrane by similar physicochemical properties of water and methanol.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1228-1235
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• 2012

A refrigerator has many components which are made from diverse materials such as metal, polymer, plastic, and rubber. So, it generally requires much time and efforts to build up an analysis model in finite element analysis. In this work, to reduce the computational time and efforts a simplified modeling method was proposed for the analysis of a refrigerator. Occasionally, a stick-slip noise occurs in a refrigerator due to relative slip between shelf and inner-case. When we solve the problem by a FE analysis, we should model the structures with detail for considering the contact conditions; by this reason, too many efforts are consumed in the conventional analysis method. Through this work, we shows the concept of simplifying approach and a good agreement with the results of a real model analysis. And also, the evaluation of the proposed method and the application of contact analysis using the simplified model are discussed.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.219-225
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• 2013

Separate and layered transmitting and receiving spiral coil arrays had been used for the optimized individual applications of magnetostrictive type long-range ultrasonic testing. In this study, it was demonstrated that when taking advantages of the spiral coils with the leg width reduced to be half of the previous one and of the empty spaces due to the decrease of leg width, the transmitting and receiving coil array can be arranged to form a single layer structure allowing more easy use and fabrication. Because of the number of turns of the receiving coils that is proportional to their leg width, the sensitivity of the single layer coil array was about half that of the corresponding double layer coil array while it allowed the receiving amplifier to get faster recovery from a saturation due to the main bang echo. It was also found that the two types of coil arrays have almost the same performances in the view points of signal-to-noise ratio and directivity control.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.1
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• pp.1-6
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• 2016

In recent years, there were frequent exogenous contagious diseases in Eastasia like SARS(severe acute respiratory syndrome), Avian influenza, Swine influenza, MERS etc. But there are various interpretations about their pathological differentiations and lead to controversy to diagnosis and medicinal use. So there needs universal and consistent understanding methods. Several conclusions are obtained from the research on differentiation theories of various epidemic diseases. Essential elements of differential diagnostic system are pathogen, characters and matters of disease and loci, especially three yin and three yang has close affinity with constitutional features or body shape. Binding these 3 categories, an integrated differentiation 3 dimensional coordinates are made. Out of these, each elements of 3 pathogen-axial lines are related with names of exogenous disease, and those of 3 feature-axial lines are related with 8 principal patterns. And those of 3 locus-axial lines implicating therapeutic method are related with steps and location of exterior and interior, 3 yin 3 yang, Defense, Qi, Nutrient and Blood, five viscera and six bowels and tissues. Additionally, 3 lines of each axis consist of factors which have their own affinity each other, so classification of pathogen, feature, locus of disease has layered interconnectedness. This classification system is included in constitutional features of individual patient. Afterwards, these cognitive structure can be used as a general theory guiding method of therapy, prevention and aftercure healthcare.

• Journal of Electrochemical Science and Technology
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• v.5 no.1
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• pp.32-36
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• 2014

The $0.3Li_2MnO_3{\cdot}0.7LiMn_{0.55}Ni_{0.30}Co_{0.15}O_2$ cathode material was prepared via a co-precipitation method. The vapor grown carbon fiber (VGCF) was used as a conductive material and its effects on electrochemical properties of the $0.3Li_2MnO_3{\cdot}0.7LiMn_{0.55}Ni_{0.30}Co_{0.15}O_2$ cathode material were investigated. From the XRD pattern, the typical complex layered structure was confirmed and a solid solution between $Li_2MnO_3$ and $LiMO_2$ (M = Ni, Co and Mn) was formed without any secondary phases. The VGCF was properly distributed between cathode materials and conductive sources by a FE-SEM. In voltage profiles, the electrode with VGCF showed higher discharge capacity than the pristine electrode. At a 5C rate, 146 mAh/g was obtained compared with 232 mAh/g at initial discharge in the electrode with VGCF. Furthermore, the impedance of the electrode with VGCF did not changed much around $9-10{\Omega}$ while the pristine electrode increased from 21.5${\Omega}$ to $46.3{\Omega}$ after the $30^{th}$ charge/discharge cycling.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.299-310
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• 2003

In the evaluation of the subgrade stiffness structure by the SASW method, the calculation of the phase velocities is the important task controlling the reliability of the result. The interpretation of the phase spectrum should precede the phase-velocity calculation in the current practice of the SASW method. The difficulty involved in the interpretation prohibited the SASW method from being spread over to the industry. This study proposed a new method called the frequency-wave number technique, which is based on the frequency-wave number relationship of the surface wave in the multi-layered system. The frequency-wave number technique eliminates the expertise in the interpretation of the phase spectrum, automates the phase-velocity calculation and expedites the determination of the phase-velocity dispersion curve. To verify the validity of the proposed frequency-wave number method, the transfer function determined from the numerical simulation of the SASW measurements was used fir the calculation of the automatic calculation of the phase velocities and compared with the phase velocities by WinSASW employing the phase-unwrapping method. Also, the proposed method was applied to the real SASW measurements performed at$\bigcirc$$\bigcirc$area in GyeongGi-Do to see how the proposed method works with the real measurements.

• International Commerce and Information Review
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• v.3 no.2
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• pp.215-233
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• 2001

Nowadays, the international economic environment has been improved by the World Trade Organization based on UR trade negotiation. In such state, the international commerce cooperation, which means trade liberalization through relaxation or abolition of customs and noncustoms harrier, is necessary a country's policy for overseas strategy. To the view point of international commerce order, there co-exist the globalism represntatived by GATT/WTO and the regionalism operated by European Community including 15 countries, or North American Zone with canada, Maxico. The former expands the trade liberalization through the most favoured nation treatment of WTO among whole world nations and the latter takes the differential trade policy to other countries. For extreme dependence on foreign natural resources and raw materials, Our country should strengthen it' comming prospect for the world economy. To put it more concrete, We must enforce in advance the legal basis of convention and norm which in adopted by WTO. Also we are desirable to cooperate with Asia and pacific economy area or APEC. Finally, under the direction of international commerce environment and world economy, we must take the commerce cooperation in global order considering the tendency of regionalism and bloc economy.

• Applied Science and Convergence Technology
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• v.26 no.5
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• pp.110-113
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• 2017

The two-dimensional layered $MoS_2$ has high mobility and excellent optical properties, and there has been much research on the methods for using this for next generation electronics. $MoS_2$ is similar to graphene in that there is comparatively weak bonding through Van der Waals covalent bonding in the substrate-$MoS_2$ and $MoS_2-MoS_2$ heteromaterial as well in the layer-by-layer structure. So, on the monatomic level, $MoS_2$ can easily be exfoliated physically or chemically. During the $MoS_2$ field-effect transistor fabrication process of photolithography, when using water, the water infiltrates into the substrate-$MoS_2$ gap, and leads to the problem of a rapid decline in the material's yield. To solve this problem, an epoxy-based, as opposed to a water-based photoresist, was used in the photolithography process. In this research, a hydrophobic $MoS_2$ field effect transistor (FET) was fabricated on a hydrophilic $SiO_2$ substrate via chemical vapor deposition CVD. To solve the problem of $MoS_2$ exfoliation that occurs in water-based photolithography, a PPMA sacrificial layer and SU-8 2002 were used, and a $MoS_2$ film FET was successfully created. To minimize Ohmic contact resistance, rapid thermal annealing was used, and then electronic properties were measured.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.48.2-48.2
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• 2010

The effect of additives as rare-earth in dielectric materials has been studied to meet the development trend in electronics on the miniaturization with increasing the capacitance of MLCCs (multi-layered ceramic capacitors). It was reported that the addition of rare-earth oxides in dielectrics would contribute to enhance dielectric properties and high temperature stability. Especially, dysprosium and thulium are well known to the representative elements functioned as selective substitution in barium titanate with perovskite structure. The effects of these additives on microstructure and electric properties were studied. The 0.8 mol% Dy doped $BaTiO_3$ and the 1.0 mol% Tm doped $BaTiO_3$ had the highest electric properties as optimized composition, respectively. According to the increase of rare-earth contents, the growth of abnormal grains was suppressed and pyrochlore phase was formed in more than solubility limits. Furthermore, the effect of two rare-earth elements co-doped $BaTiO_3$ on the dielectric properties and insulation resistance was investigated with different concentration. The dielectric specimens with $BaTiO_3-Dy_2O_3-Tm2O_3$ system were prepared by design of experiment for improving the electric properties and sintered at $1320^{\circ}C$ for 2h in a reducing atmosphere. The dielectric properties were evaluated from -55 to $125^{\circ}C$ (at $1KHz{\pm}10%$ and $1.0{\pm}0.2V$) and the insulation resistance was examined at 16V for 2 min. The morphology and crystallinity of the specimens were determined by microstructural and phase analysis.