• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.108-113
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• 2011

In this paper, we propose QAPM(Quadrature Amplitude Position Modulation) modulation scheme for improving power efficiency and we compare existing PSSK(Phase Silence Shift Keying) and QAPM. An existing PSSK Modulation is extension from PSK modulation technique. The conventional PSSK modulation technique can be regarded as an extension from PSK modulation. And this PSSK has better power efficiency than PSK modulation. The Bandwidth efficiency of PSSK is half than PSK, but improved BER(Bit Error Rate) performance. A propose QAPM scheme is build on QAM. And BER performance of QAPM is better than PSSK because BER performance of QAM is better than PSK. In this paper, we compare PSSK and QAPM regard to bit error rate and throughput.

• Journal of the Korean Chemical Society
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• v.39 no.1
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• pp.14-22
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• 1995

This paper is concerned with the design of optimal surface heating patterns that result in focusing acoustic energy inside a subsurface target volume at a specified target time. The surface of the solid is heated by an incident laser beam which gives rise to shear and compressional waves propagating into the solid. The optimal heating design process aims to achieve the desired energy focusing at the target with minimal laser power densities and minimal system disturbance away from the target. The optimality conditions are secured via the conjugated gradient method and by the finite element method along with using the half-space Green's function matrix. Good quality energy focusing is achived with the optimal designs reflecting the high directivity of the photothermally generated shear wave patterns.

• Journal of Digital Convergence
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• v.10 no.11
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• pp.371-376
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• 2012

In this paper, we propose a new data coding method and its circuits for minimizing data transition in text image. The proposed circuits can solve the synchronization problem between input data and output data in the modified LVDS algorithm. And the proposed algorithm is allowed to transmit two data signals through additional serial data coding method in order to minimize the data transition in text image and can reduce the operating frequency to a half. Thus, we can solve EMI(Electro-Magnetic Interface) problem and reduce the power consumption. The simulation results show that the proposed algorithm and circuits can provide an enhanced data transition minimization in text image and solve the synchronization problem between input data and output data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.340-350
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• 1999

In this paper, W-type reflector antennas modified from corner reflector antenna structure were proposed and the radiation characteristics were analyzed using the method of moments. The analysis results such as gain, F/B, half power beamwidth, and radiation pattern are presented as functions of dipole height h and back edge spacing d. Also, the proposed antenna was compared with corner reflector antennas in the same size of side reflectors, W-type reflector antenna was found to exhibit somewhat higher gain and larger F/B than corner reflector antennas. To verify the analysis results, W-type reflector antenna was fabricated and the radiation characteristics were measured. The measured results show good agreement with the calculated results.

• Electrical & Electronic Materials
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• v.10 no.7
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• pp.706-712
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• 1997

AlN(Aluminium Nitride) thin films were prepared using by RF sputtering method on the Si(100) and Si(111) substrates as the parameters of the substrate temperature, RF power, sputtering duration and the $N_2$/Ar ratio and investigated by X-ray diffraction, IR spectrometry, n&k analyzer. For the Si(100) substrate, the AlN thin films of (101) orientation were obtained under the conditions of room temperature and the nitrogen of 60 vol.%. For the Si(111) substrate, the (002) AlN thin films were obtained under the nitrogen of 100 vol.%. In case of the thin film prepared in the condition of above 60 vol.% of the nitrogen, the average value of the surface roughness of the film was 151$\AA$. From the changes of the half widths of E$_1$[TO] phonon bands at the wavenumber of 680$cm^{-1}$ /, it were compared of the crystallinities of the films which were grown under the different conditions. The thicknesses of AlN films were decreased dramatically in the region of the nitrogen of 40~60 vol.%. Its due to the nitridation of the Al target surface and getting low of the sputtering yield by the $N_2$/Ar ratio being increased.

• Journal of the Korean Society of Safety
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• v.36 no.1
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• pp.80-85
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• 2021

Radionuclides, particularly radioactive cesium (Cs), are a concern of human health in some nuclear power accidents. It could lead to a high level of intracellular accumulation due to its high radioactivity and long half-life. Therefore, it is imperative to develop a method to remove Cs from wastewater. Herein, we synthesized activated carbon fibers (ACFs) doped with Prussian blue (PB) via in situ methods. We classified samples by their preparation method as either physical (PB-ACF-A) or physicochemical (PB-ACF-B) syntheses for comparison. The PB-ACF-B sample showed a significant surface loss compared to PB-ACF-A but a better ¹³³Cs adsorption capacity. All samples fit well to Langmuir isotherms and the values of qmax were directly correlated to the amount of PB on the surface of the ACFs. Adsorption characteristics were further confirmed by the calculated free energy, enthalpy, and entropy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.770-776
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• 2009

We propose and demonstrate an I/Q demodulator using four-port BPSK demodulator base on additive mixing and reflection-type phase shifter using hybrid technique. Previously, the conventional I/Q demodulator base on multiplicative or additive mixing method divides I/Q signal path from mixer to parallel-to-serial converter. In this paper, we propose new I/Q demodulator without dividing I/Q baseband signal path. The proposed schematic requires half size in implementation and half power consumption in baseband path compared with the conventional receiver. Also, the proposed receiver eliminates parallel-to-serial converter after data decoding. The proposed circuit has been successfully demodulated a QPSK signal with the L-band carrier frequency and 20 Mbps data rate.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.4
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• pp.53-58
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• 2008

This paper designs sigma-delta D/A Converter with a high resolution and low power consumption. It reorganizes the input data along LJ, RJ, I2S mode and bit mode to the output data of A/D converter. The D/A converter decodes the original analog signal through HBF, Hold and 5th CIFB(Cascaded Integrators with distributed Feedback as well as distributed input coupling) sigma-delta modulation blocks. It uses repeatedly the addition operation in instead of the multiply operation for the chip area and the performance. Also, the half band filters of similar architecture composed the one block and it used the sample-hold block instead of the sinc filter. We supposed simple D/A Converter decreased in area. The filters of the block analyzed using the matlab tool. The top block designed using the top-down method by verilog language. The designed block is fabricated using Samsung 0.35um CMOS standard cell library. The chip area is 1500*1500um.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.4
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• pp.378-385
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• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.965-972
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• 2005

In this paper, we first review LDPC codes in general and a belief propagation algorithm that works in logarithm domain. LDPC codes, which is chosen for second generation digital video broadcasting standard, are required a large number of computation due to large size of coded block and iteration. Therefore, we presented two kinds of low computational algorithm for LDPC codes. First, sequential decoding with partial group is proposed. It has same H/W complexity, and fewer number of iteration's are required at same performance in comparison with conventional decoder algerian. Secondly, early detection method for reducing the computational complexity is proposed. Using a confidence criterion, some bit nodes and check node edges are detected early on during decoding. Through the simulation, we knew that the iteration number are reduced by half using subset algorithm and computational complexity of early detected method is about $50\%$ offs in case of check node update, $99\%$ offs in case of check node update compared to conventional scheme.