• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.80-87
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• 2007

In this paper, link-level performance of a OFDMA technique, which has been considered as a standard for 802.16, 802.20, 3G-LTE, WiMax, and WiBro, is evaluated for next-generation wireless communication systems. While many researches have focused on uncoded forward-link performances, this paper provides a coded performance of a reverse-link OFDMA system. Performance degradation due to time offset among reverse-link users and frequency offset during FFT process is investigated. Transmitter and receiver antenna diversity techniques are used to overcome performance degradation. Performance of a OFDMA system is compared with a CDMA system in terms of FER and throughput to emphasize the advantage of OFDMA system for a reverse-link. Finally, under given specification, Eb/No required to achieve the maximum throughput of a reverse-link is proposed considering various coded rates and antenna permutations.

• Journal of Radiation Protection and Research
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• v.13 no.2
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• pp.78-87
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• 1988

This article suggests the radionuclides which should be considered more important to the offsite consequence assesment during a nuclear power plant accident. For this purpose, the relative importance to the early health effects of released radionuclides on the major organs during the accident is estimated under the assumption of the same release fraction. The inventories of the 25 elements, 54 nuclides selected in the Reactor Safety Study are calculated by ORIGEN 2 code. The organs of interest in the estimation are G. I. track, bone marrow, thyroid and lung. The result shows the relative potential importance of radionuclides as follows: For G.I. track, Np, Ce, Ru, Y, and Zr are of importance in sequence, Np, I, La, Sr, Ba for bone marrow, I and Te for thyroid, Cm, Ce, Ru, Pu, Zr for lung. In addition to iodine and noble gases, therefore, the potential contribution of those nuclides listed above to the offsite consequences should not be overlooked for some accidents of particular sequence.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.386-393
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• 1994

We have investigated output characteristics of XeCI excimer laser excited by transeverse electronbeam. We used e-beam output of 880 kV, 21 kA (70 ns, FWHM) and controlled current density of e-beam by pulsed magnetic coil (4.7 kG) which was fabricated around an e-beam diode (A-K gap is 21 mm) and laser chamber. We have obtained 35 J (4 atm) of e-beam deposition energy injected into laser media. The deposition energy was converted from an exposure area of Radcolor film and rising pressure of gas media which is measured by pressure jump method. The excited volume of $320cm^{3}$ was calculated. The maximum efficiency of 1.7% was obtained with the mixing ratio of HCllXe/Ar==0.2/ 6.3/93.5% and total pressure of 3 atm. Also laser output energy and specific energy were obtained 0.52 J and 1.7 J/I, respectively. For the analysis of experimental results we have developed computer simulation code. From the good agreements with the results of experiment and simulation we could theoretically explain the XeCI* formation channel. relaxation channel, and absorption channel of 308 nm.308 nm.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.157-170
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• 2005

The combination of multiple antennas and multi-carrier code division multiple-access (MC-CDMA) is a strong candidate for the downlink of the next generation mobile communications. The study of such systems in scenarios that model real-life trans-missions is an additional step towards an optimized achievement. We consider a realistic MIMO channel with two or four transmit antennas and up to two receive antennas, and channel state information (CSI) mismatches. Depending on the mobile terminal (MT) class, its number of antennas or complexity allowed, different data-rates are proposed with turbo-coding and asymptotic spectral efficiencies from 1 to 4.5 bit/s/Hz, using three algorithms developed within the European IST-MATRICE project. These algorithms can be classified according to the degree of CSI at base-station (BS): i) Transmit space-frequency prefiltering based on constrained zero-forcing algorithm with complete CSI at BS; ii) transmit beamforming based on spatial correlation matrix estimation from partial CSI at BS; iii) orthogonal space-time block coding based on Alamouti scheme without CSI at BS. All presented schemes require a reasonable complexity at MT, and are compatible with a single-antenna receiver. A choice between these algorithms is proposed in order to significantly improve the performance of MC-CDMA and to cover the different environments considered for the next generation cellular systems. For beyond-3G, we propose prefiltering for indoor and pedestrian microcell environments, beamforming for suburban macrocells including high-speed train, and space-time coding for urban conditions with moderate to high speeds.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.437-450
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• 1996

A set of stability equations is formulated for natural convection flows adjacent to a vertical isothermal surface melting in cold pure water. It takes account of the nonparallelism of the base flows. The melting rate is regarded as a blowing velocity at the ice surface. The numerical solutions of the linear stability equations which constitute a two-point boundary value problem are accurately obtained for various values of the density extremum parameter $R=(T_m-T_{\infty})/(T_0-T_{\infty})$ in the range $0.3{\leq}R{\leq}0.6$, by using a computer code COLNEW. The blowing effects on the base flow becomes more significant as ambient temperature ($T_{\infty}$) increases to $T_{\infty}=10^{\circ}C$. The maximum decrease of heat transfer rate is about 6.4 percent. The stability results show that the melting at surface causes the critical Grashof number $G^*$ and the maximum frequency of disturbances to decrease. In comparision with the results for the conventional parallel flow model, the nonparallel flow model has a higher critical Grashof number but has lower amplification rates of disturbances than does the parallel flow model. The spatial amplification contours exhibit that the selective frequency $B_0$ of the nonparallel flow model is higher than that of the parallel flow model and that the effects of melting are rather small. The present study also indicates that the selective frequency $B_0$ can be easily predicted by the value of the frequency parameter $B^*$ at $G^*$, which comes from the neutral stability results of the nonparallel flow model.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1308-1318
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• 2016

In order to prevent the maritime accident, all seafarers who work on fishing vessels over G/T 20 tons are required to undergo the basic safety training by the Seafarer's Act. 45% of domestic crews have boarded on the fishing vessels. However, the fishermen have been trained in accordance with the STCW(International convention on standards of training certification and watch-keeping for seafarers) Convention. But safety training courses for seaman do not reflect on the safety equipment and the limitation of the fishing vessel in the training contents which is organized in accordance with the merchant ship by STCW convention and code. Most of the fishing vessels are small fishing boat of less than G/T 80 tons. Small fishing vessels are operating with only a minimum of safety equipment that has been defined by the fishing vessel safety equipment standard. Due to the safety training that does not fit the situation of the fishing boat, the level of satisfaction by the crews onboard is low for the training. Furthermore, there is a difficulty in achieving the goal of safety education. In order to carry out the safety training that is suitable for fishermen, it is required to provide appropriate standards for the safety education of workers of small fishing boat, by understanding the current state of the domestic fishing vessels. The purpose of this study is to define the aforementioned problems and to provide the standard for the safety education of fishermen. In order to complete the purpose, the research team has conducted a analyzation for registered domestic fishing vessel and safety equipment standard.

• KSBB Journal
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• v.26 no.5
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• pp.427-432
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• 2011

In this study, a EXGA gene code for exo-β-1,3-glucanase from Aspergillus oryzae was overexpressed and secretory produced in Saccharomyces cerevisiae. To overexpress the β-1,3-glucanase, pGInu-exgA and pAInu-exgA plasmids having GAL10 and ADH1 promoter, respectively, and exoinulinase signal sequence (Inu s.s) were constructed and introduced in S. cerevisiae SEY2102 and 2805. The recombinant β-1,3-glucanase was successfully expressed and secreted into the medium and the β--1,3-glucanase activity in 2102/pGInu-exgA and 2102/pAInu-exgA strain were 5.01 unit/mL and 4.09 unit/mL, respectively. In the 2805/pGInu-exgA and 2805/pAInu-exgA strain, the β-1,3-glucanase activity showed 3.23 unit/mL and 3.22 unit/mL, respectively. Secretory efficiency in each strain reached 95% to 98%. Subsequently, the recombinant β1,3-glucanase was used for ethanol production. Ethanol productivity in 2102/pAInu-exgA strain was 0.83 g/L when pre-treated Laminaria japonica which has initial reducing sugar of 1.4 g/L was used as substrate. It is assumed that the polysaccharides of Laminaria japonica was effectively saccharified by recombinant β-1,3-glucanase, resulting in increase of ethanol productivity. These results suggested that recombinant β-1,3-glucanase was efficiently overexpressed and secreted in S. cerevisiae SEY2102 as host strain by using ADH1 promoter-Inu s.s system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6C
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• pp.625-631
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• 2002

This paper presents a MSB-first digit-serial systolic array for computing modular multiplication of A(x)B(x) mod G(x) in finite fields $GF(2^m)$. From the MSB-first multiplication algorithm in $GF(2^m)$, we obtain a new data dependence graph and design an efficient digit-serial systolic multiplier. For circuit synthesis, we obtain VHDL code for multiplier, If input data come in continuously, the implemented multiplier can produce multiplication results at a rate of one every [m/L] clock cycles, where L is the selected digit size. The analysis results show that the proposed architecture leads to a reduction of computational delay time and it has much more simple structure than existing digit-serial systolic multiplier. Furthermore, since the propose architecture has the features of unidirectional data flow and regularity, it shows good extension characteristics with respect to m and L.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.173-180
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• 2006

The seismic responses of a building are affected by the base soil conditions. In this study, linear time-history seismic analysis and nonlinear pushover static seismic analysis were performed to estimate the base shear forces of 3-, 5-, and 7-story steel buildings, considering the rigid and soft soil conditions. Foundation soil stiffness, based on the equivalent static stiffness formula, is used for the damper, one of the Link elements in SAP 2000. The base shear forces of the steel buildings, estimated through time-history analysis using the general-purpose structural-analysis program of SAP 2000, were compared with those calculated using the domestic seismic design code, the UBC-97 design response spectrum. and pushover static nonlinear analysis. The steel buildings designed for gravity and wind loads showed elastic responses with a moderate earthquake of 0.11 g, while the elastic soft-soil layer increased the displacement and the base shear force of the buildings due to soil-structure interaction and soil amplification. Therefore, considering the characteristics of the soft-soil layer, it is more reasonable to perform an elastic seismic analysis of a building's structure during weak or moderate earthquakes.

• Journal of the Korean Geotechnical Society
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• v.35 no.2
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• pp.5-17
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• 2019

Dynamic centrifuge model test was conducted to evaluate the dynamic stability of the pile-supported slab track method during dynamic railway loading and earthquake loading. The centrifuge tests were carried out for various condition of embankment height and soft ground depth. Based on test results, we found that the bending moment was increased with embankment height and decreased with soft ground depth. In addition, it was confirmed that the pile-supported slab track system could have dynamic stability for short-period seismic loading. However, in case of long-period seismic loading, such as Hachinohe earthquake, the observed maximum bending moment reached to pile cracking moment at the return period of 2,400 year earthquake. The criterion of ratio between embankment height and soft ground depth was suggested for dynamic stability of pile-supported slab track system.