• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.504-514
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• 2014

An MMIC multi-function chip with a low DC power consumption for an X-band active phased array radar system has been designed and fabricated using a 0.5 ${\mu}m$ GaAs p-HEMT commercial process. The multi-function chip provides several functions: 6-bit phase shifting, 6-bit attenuation, transmit/receive switching, and signal amplification. The fabricated multi-function chip with a compact size of $16mm^2(4mm{\times}4mm)$ exhibits a gain of 10 dB and a P1dB of 14 dBm from 7 GHz to 11 GHz with a DC low power consumption of only 0.6 W. The RMS(Root Mean Square) errors for the 64 states of the 6-bit phase shift and attenuation were measured to $3^{\circ}$ and 0.6 dB, respectively over the frequency.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2185-2190
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• 2018

Methane activation through oxychlorination is in the spotlight due to the relatively mild reaction conditions at atmospheric pressure and in the temperature range of $450-550^{\circ}C$. Although $CeO_2$ is known to exhibit good activity for methane oxychlorination, significant amounts of by-products such as $CO_2$, CO and carbon deposits are produced during the reaction over $CeO_2$. We investigated the effect of iron in $FeO_x/CeO_2$ catalysts on methane oxychlorination. $FeO_x/CeO_2$ with 3 wt% iron shows the maximum yield at $510^{\circ}C$ with 23% conversion of methane and 65% selectivity of chloromethane. XRD and $H_2$ TPR results indicate that iron-cerium solid solution was formed, resulting in the production of more easily reduced cerium oxide and the suppression of catalysts sintering during the reaction. Furthermore, the selectivity of by-products decreased more significantly over $FeO_x/CeO_2$ than cerium oxide, which can be attributed to the facilitation of HCl oxidation arising from the enhanced reducibility of the former sample.

• Elastomers and Composites
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• v.56 no.2
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• pp.92-99
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• 2021

Microstructure-dependent changes in the crystalline properties of poly(ethylene-co-vinyl acetate) (EVA) was investigated using various EVAs at different VA contents via X-ray diffraction (XRD). The parameters analyzed herein were percentage crystallinity (X_c), interplanar crystal spacing (d_hkl), crystal stack size (D_hkl), and the number of crystal plane piles (N_hkl). The X_cs of [110] and [200] crystals were 21.0-4.1 and 6.7-1.4%, respectively, and they decreased by approximately 2.3 and 0.7% for every mol% of the VA content, respectively. The X_c ratios of the [110] and [200] crystals were approximately 3. The d₁₁₀s and d₂₀₀s values were 0.41-0.42 and 0.37-0.38 nm, respectively. The D₁₁₀s and D₂₀₀s values were 9.56 -21.92 and 7.00-16.42 nm, respectively. The d_hkls increased with an increase in the VA content, whereas the D_hkls decreased. The N₁₁₀s and N₂₀₀s were 22.7-51.3 and 18.3-43.2, respectively, and they decreased by increasing the VA content. EVA with the same VA content showed different crystalline properties as per the suppliers, and some EVAs deviated from the average trends. This could be explained by the difference in their microstructures such as the sizes and distribution uniformity of the ethylene sequences in EVA chains.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.513-517
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• 2003

In this paper, a VCDRO(Voltage Control Dielectric Resonator Oscillator} applied to X-band as stable source is implementea and constructed with a MESFET for low noise, a dielectric resonator of high frequency selectivity and high Q varactor diode to obtain a good phase noise performance and stable sweep characteristics. The designed circuits is simulated through the harmonic balance simulation technique to provide the optimum performance. The measured results of a fabricated VCDRO show that output is 2.22dBm at 12.05GHz. harmonic suppression -30dBc. phase noise -130dBc at 100kHz offset. and sweep range of varactor diode $\pm$18.7MHz. respectively. This oscillator will be available to X-band application.

• Korean Journal of Food Science and Technology
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• v.21 no.2
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• pp.212-217
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• 1989

The shrinking and overall drying rate equations which can accomodate experimental date and the rate of initial drying ratio were investigated. The results obtained from hot air drying experiments of radish and sweet potatoes were as follow. The drying rate constant and the order were affected by the thickness of sample and temperature. The empirical drying rate and shrinking equations at constant drying conditions (d=4mm, $Ta=50^{\circ}C$, RH=10%, U=0.8m/s) for radish and sweet potatoes were found to $dx/dt=0.112{\times}10^{-2}\;A(1-x)^{0.43}$, A=Ao(-0.480x+1) and rates of initial drying ratio were expressed of sample thickness, relative humidity and air velocity; for radish $dx/dt=0.0648(RH)^{-0.31}\;(d)^{-0.75}\;(U)^{0.39}$ and for sweet potatoes $dx/dt=0.0547(RH)^{-0.28}\;(d)^{-0.63}\;(U)^{0.37}$

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.5
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• pp.518-528
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• 2014

In this paper, we propose a method to recognize the action direction of human by developing 4D space-time (4D-ST, [x,y,z,t]) features. For this, we propose 4D space-time interest points (4D-STIPs, [x,y,z,t]) which are extracted using 3D space (3D-S, [x,y,z]) volumes reconstructed from images of a finite number of different views. Since the proposed features are constructed using volumetric information, the features for arbitrary 2D space (2D-S, [x,y]) viewpoint can be generated by projecting the 3D-S volumes and 4D-STIPs on corresponding image planes in training step. We can recognize the directions of actors in the test video since our training sets, which are projections of 3D-S volumes and 4D-STIPs to various image planes, contain the direction information. The process for recognizing action direction is divided into two steps, firstly we recognize the class of actions and then recognize the action direction using direction information. For the action and direction of action recognition, with the projected 3D-S volumes and 4D-STIPs we construct motion history images (MHIs) and non-motion history images (NMHIs) which encode the moving and non-moving parts of an action respectively. For the action recognition, features are trained by support vector data description (SVDD) according to the action class and recognized by support vector domain density description (SVDDD). For the action direction recognition after recognizing actions, each actions are trained using SVDD according to the direction class and then recognized by SVDDD. In experiments, we train the models using 3D-S volumes from INRIA Xmas Motion Acquisition Sequences (IXMAS) dataset and recognize action direction by constructing a new SNU dataset made for evaluating the action direction recognition.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.2
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• pp.36-46
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• 1984

The Ga1-xInxSe single crystals for 0.0 < x < 0.1 and 0.8 < 1.0 were grown by the Bridgman method. The crystal structure of Ga1-xInxSe is found to be hexagonal for 0.0 < X < 1.0. The Ga1-xInxSesingle crystals have indirect energy gap with a temperature coefficient dEg/dT= -(2.4 - 4.3) $\times$ 10-4 eV/K in the range 60-250K. The temperature dependence of the energy gap can be explained by the electron-Phonos interaction model.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.229-232
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• 1999

We have measured the temperature dependence of thermoelectric power (TEP) and resistivity for the Sr$_{1-x}K_xBiO_3$ superconductor (x=0.45-0.6). At T=10.2K, the resisitivity starts to increase from zero and a rather broad superconducting phase transition (${\Delta}$T ${\sim}$ 2.3K) is observed. TEP at room temperature has a small negative value ( S =-1.96${\mu}$V/K), characteristic of metallic-like TEP. The temperature dependence of TEP shows two distinct features. With decreasing temperature from room temperature, the absolute value of TEP decreases and the sign of TEP changes from negative to positive around 200k. Also, the negative slope of TEP(dS/dT) decreases substantially and becomes rather flat at around 160k, which is a feature already noted in Ba$_{1-x}K_xBiO_3$[1].

• Kyungpook Mathematical Journal
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• v.56 no.4
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• pp.1125-1133
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• 2016

In this paper we introduce h(x)-B-Tribonacci and h(x)-B-Tri Lucas polynomials. We also obtain the identities for these polynomials.

• Journal of the Chungcheong Mathematical Society
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• v.20 no.4
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• pp.411-418
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• 2007

Let $X_1$, ${\cdots}$, $X_n$ be nondegenerate and positive independent identically distributed(i.i.d.) random variables with common absolutely continuous distribution function F(x) and $E(X^2)$ < ${\infty}$. The random variables $X_1+{\cdots}+X_n$ and $\frac{X_1+{\cdots}+X_m}{X_1+{\cdots}+X_n}$are independent for 1 $1{\leq}$ m < n if and only if $X_1$, ${\cdots}$, $X_n$ have gamma distribution.