• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.9
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• pp.609-618
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• 1988

Two dimensional numericl analysis program of power VDMOSFET structure has been developed. Modeling for equipotential distribution, current flow pattern and carrier distribution are presented. I-V characteristic curves due to saturation velocity, mobility value, transconductance and on-resistance are studied by comparison of computer simulated results and exeperimental data. These are found to agree with the simulated results and experimental data.

• Bulletin of the Korean Chemical Society
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• v.19 no.2
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• pp.160-164
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• 1998

The NADH-cytochrome b5 reductase (NCBR), a mitochondrial external electron carrier, was purified from bovine heart and turnip and their properties were examined. The mitochondrial outer membranes separated were subjected to NCBR isolation through DEAE-Cellulose ion exchange, DEAE-Sephadex gel chromatography, and hydroxyapatite adsorption chromatography. These processes yielded the purification folds of 88 and 42 and the recovery percentages of 0.2%, 5.67% for turnip and bovine heart, respectively. The molecular weight of the NCBR from the two sources was estimated to be 35,000 using SDS polyacrylamide gel electrophoresis. The Michaelis constant Km and maximum velocity Vmax were determined by measuring the NADH-ferricyanide redox system as well as the NADPH-ferricyanide redox system. The kinetics showed that both NCBRs had higher affinities for NADH than artificial electron-acceptor substrate ferricyanide. Although NADPH had a lower affinity for the enzymes than NADH, this study showed the 2'-phosphate dinucleotide could be used as a substrate.

• ETRI Journal
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• v.44 no.3
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• pp.504-511
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• 2022

Monte Carlo simulations show that, as temperature increases, the average kinetic energy of channel electrons in a GaN transistor first decreases and then increases. According to the calculations, the relative energy change reaches 40%. This change leads to a reduced barrier height due to quantum coupling among the three-dimensional motions of channel electrons. Thus, an analysis and physical model of the gate leakage current that includes drift velocity is proposed. Numerical calculations show that the negative and positive temperature dependence of gate leakage currents decreases across the barrier as the field increases. They also demonstrate that source-drain voltage can have an effect of 1 to 2 orders of magnitude on the gate leakage current. The proposed model agrees well with the experimental results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.4
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• pp.65-73
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• 2003

This paper presents the implementation of an analog signal-processing ASIS to detect an angular velocity signal from a vibrator angular velocity detection sensor. The output of the sensor to be charge appeared as the variation of the capacitance value in the structure of the sensor was detected using charge amplifiers and a self oscillation circuit for driving the sensor was implemented with a sinusoidal self oscillation circuit using the resonance characteristics of the sensor. Specially an automatic gain control circuit was utilized to prevent the deterioration of self-oscillation characteristics due to the external elements such as the characteristic variation of the sensor process and the temperature variation. The angular velocity signal, amplitude-mod)Hated in the operation characteristics of the sensor, was demodulated using a synchronous detection circuit. A switching multiplication circuit was used in the synchronous detection circuit to prevent the magnitude variation of detected signal caused by the amplitude variation of the carrier signal. The ASIC was designed and implemented using 0.5${\mu}{\textrm}{m}$ CMOS process. The chip size was 1.2mm x 1mm. In the experiment under the supply voltage of 3V, the ASIC consumed the supply current of 3.6mA and noise spectrum density from dc to 50Hz was in the range of -95 dBrms/√Hz and -100 dBrms/√Hz when the ASIC, coupled with the sensor, was in normal operation.

• 전기의세계
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• v.28 no.4
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• pp.53-63
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• 1979

Interface recombination velocity in $Al_{x}$G $a_{1-x}$ As-GaAs and $Al_{0.85}$, G $a_{0.15}$ As-GaA $s_{1-y}$S $b_{y}$ heterojunction systems is studied as a function of lattice mismatch. The results are applied to the design of highly efficient III-V heterojunction solar cells. A horizontal liquid-phase epitaxial growth system was used to prepare p-p-p and p-p-n $Al_{x}$G $a_{1-x}$ As-GaA $s_{1-y}$S $b_{y}$-A $l_{x}$G $a_{1-x}$ As double heterojunction test samples with specified values of x and y. Samples were grown at each composition, with different GaAs and GaAs Sb layer thicknesses. A method was developed to obtain the lattice mismatch and lattice constants in mixed single crystals grown on (100) and (111)B oriented GaAs substrates. In the AlGaAs system, elastic lattice deformation with effective Poisson ratios .mu.$_{eff}$ (100=0.312 and .mu.$_{eff}$ (111B) =0.190 was observed. The lattice constant $a_{0}$ (A $l_{x}$G $a_{1-x}$ As)=5.6532+0.0084x.angs. was obtained at 300K which is in good Agreement with Vegard's law. In the GaAsSb system, although elastic lattice deformation was observed in (111) B-oriented crystals, misfit dislocations reduced the Poisson ratio to zero in (100)-oriented samples. When $a_{0}$ (GaSb)=6.0959 .angs. was assumed at 300K, both (100) and (111)B oriented GaAsSb layers deviated only slightly from Vegard's law. Both (100) and (111)B zero-mismatch $Al_{0.85}$ G $a_{0.15}$As-GaA $s_{1-y}$S $b_{y}$ layers were grown from melts with a weight ratio of $W_{sb}$ / $W_{Ga}$ =0.13 and a growth temperature of 840 to 820 .deg.C. The corresponding Sb compositions were y=0.015 and 0.024 on (100) and (111)B orientations, respectively. This occurs because of a fortuitous in the Sb distribution coefficient with orientation. Interface recombination velocity was estimated from the dependence of the effective minority carrier lifetime on double-heterojunction spacing, using either optical phase-shift or electroluminescence timedecay techniques. The recombination velocity at a (100) interface was reduced from (2 to 3)*10$^{4}$ for y=0 to (6 to 7)*10$^{3}$ cm/sec for lattice-matched $Al_{0.85}$G $a_{0.15}$As-GaA $s_{0.985}$S $b_{0.015}$ Although this reduction is slightly less than that expected from the exponential relationship between interface recombination velocity and lattice mismatch as found in the AlGaAs-GaAs system, solar cells constructed from such a combination of materials should have an excellent spectral response to photons with energies over the full range from 1.4 to 2.6 eV. Similar measurements on a (111) B oriented lattice-matched heterojunction produced some-what larger interface recombination velocities.ities.ities.s.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.289-301
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• 2003

To develop a chemical-looping combustion technology, conceptual design of 50 kW thermal chemical-looping combustor, which is composed of two interconnected pressurized circulating fluidized beds, was performed by means of mass and energy balance calculations. A riser type fast fluidized bed was selected as an oxidizer and a bubbling fluidized bed was selected as a reducer by mass balance for the chemical-looping combustor. Calculated values of bed mass, solid circulation flux, and reactor dimension by mass and energy balance calculations were suitable for construction and operation of chemical-looping combustor. It is concluded from the comparison of the design results and operating values of commercial circulating fluidized bed that the process outline is realistic. Moreover, the previous results support that oxygen carrier particle, NiO/bentonite, fulfills the conversion rates needed for the proposed design. The effects of system capacity, metal oxide content in a oxygen carrier particle, amount of steam input, gas velocity, and solid depth on design values were investigated and the changes in the system performance can be estimated by proposed design tool.

• Tribology and Lubricants
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• v.32 no.2
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• pp.61-66
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• 2016

Total thickness variation (TTV), BOW, and surface roughness are essential characteristics for high quality sapphire substrates. Many researchers have attempted to increase removal rate by controlling the key process parameters like pressure and velocity owing to the high cost of consumables in sapphire chemical mechanical polishing (CMP). In case of the pressure approach, increased pressure owing to higher deviation of pressure over the wafer leads to significant degradation of the TTV. In this study, the authors focused on reducing TTV under the high-pressure conditions. When the production equipment polishes multiple wafers attached on a carrier, higher loads seem to be concentrated around the leading edge of the head; this occurs because of frictional force generated by the combination of table rotation and the height of the gimbal of the polishing head. We believe the skewed pressure distribution during polishing to be the main reason of within-wafer non-uniformity (WIWNU). The insertion of a hub ring between the polishing head and substrate carrier helped reduce the pressure deviation. Adjusting the location of the hub ring enables tuning of the pressure distribution. The results indicated that the position of the hub ring strongly affected the removal profile, which confirmed that the position of the hub ring changes the pressure distribution. Furthermore, we analyzed the deformation of the head via finite element method (FEM) to verify the pressure non-uniformity over the contact area Based on experiment and FEM results, we determined the optimal position of hub ring for achieving uniform polishing of the substrate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.676-684
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• 2008

In digital video broadcasting-terrestrial (DVB-T), which is the European digital terrestrial television standard, the orthogonal frequency division multiplexing (OFDM) has been adopted for signal transmission. The main reasons using OFDM are to increase the robustness against the frequency selective fading and impulse noise, and to use available bandwidth efficiently. However, channel variation within an OFDM symbol destroys orthogonality between subcarriers, resulting in inter-carrier interference (ICI), which increases an error floor in proportional to maximum Doppler spread. This paper provides an ICI analysis in both time and frequency domains while existing literatures analyze the ICI effects mainly in frequency domain and proposes the algorithms that estimate the channel impulse response and channel variation using least square (LS) algorithm which is the most simple channel estimation technique. And we propose adaptive channel estimation algorithm that estimates the velocity of terminals. The simulation results show that proposed algorithm has similar performance with about 1.5% computational complexity of noise and ICI reduction LS algorithm in low speed environments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.5233-5241
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• 2014

This study analyzed the system level performance of the Mobile WiMAX-based TICN, and the effects of the use of BS-OTM in terms of the throughput of individual users as well as the overall system, assuming that other stationary BSs are distributed randomly. When BS-OTM is used, the CINRs decrease due to the additional interference from the BS-OTM from the perspective of SSs that are served by the same BS as when OTM BS is not used. On the other hand, from the perspective of SSs that had low CINRs, the CINRs increase significantly due to the new service from BS-OTM. Considering both effects, the cell throughput can be increased using BS-OTM. The CINR distribution and throughput of the overall system, changing the carrier frequency, position and velocity of the BS-OTM were also evaluated.

• 연구논문집
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• s.30
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• pp.101-110
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• 2000

Weft insertion mechanism is for completing the structure of yarn and weft yarn and its driving method is screw type. In the high speed rapier loom, weft yarn is thrown by insert rapier and carrier rapier into the shed which make divide two parts of upper part ant lower part for warp yarn. It is possible for this mechannism to reduce the size of rapier and wheel, and directly connected to the main shaft without gear belt. Therefore, exact rapier motion through realization of arbitrary acceleration diagram requested rapier and optimal design for high speedization and operating rate increasing are necessary. In this study, with a view to exact system analysis for understanding of overall trace and high speedization of rapier loom through computer simulation. we report not only deduction of displacement, velocity, and acceleration components of rapier for analysis theory establishment, of weft insertion mechanism and exact motion induction according to screw rotation, but also development of simulation program for realization these on the monitor.