• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.651-659
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• 2014

In this paper, we consider a two way relay network for ship-to-ship communications in a fleet, where two communicating ships exchange the information with the help of a multi-antenna relay ship. For the network, we propose a rate-aware three-phase analog network coding to improve the reliability of the information exchange with asymmetric rates. The proposed scheme allows low-complex implementation of the relay without channel estimation by generating an improved analog network coded signal with the orthogonally received signals from two ships by using only the received signal power at each antenna. In addition, the proposed scheme reduces outages in the data exchange at asymmetric rates by adopting a rate-aware relay power allocation, which is confirmed by evaluating the outage performance via simulation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.425-429
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• 2011

In the unlikely of nuclear reactor meltdown, the leaked core melt or corium must be contained in a device called core-catcher so that the corium can be cooled and stabilized. The ex-vessel behavior of corium involves complex physical and chemical mechanisms of flow propagation, heat transfer, and reactions with sacrificial substrates. In this study, the detailed characteristics of corium flow and heat transfer were investigated by using a commercial CFD code for VULCANO VE-U7 test reported in the literature. The volume-of-fluid (VOF) model was used to predict the interfacial surface formation of corium and the surrounding air, and the discrete ordinate model was adopted to calculate radiation between corium and the surroundings. It was found that cooling via radiation through the top surface of corium had a dominant effect on the temperature and viscosity profiles at the front of the corium flow.

• The Korean Journal of Petroleum Geology
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• v.6 no.1_2 s.7
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• pp.1-7
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• 1998

A multichannel seismic profile from the southwestern margin of the Ulleung Basin, East Sea, was analysed in detail to interpret the middle to late Miocene sequence stratigraphic evolution of the area. A regressive package is overlying a transgressive package which, in turn, is underlain by older uplifted and deformed sedimentary layers. A prominent condensed section separates the regressive and transgressive packages. The transgressive package is characterized by onlapping onto the underlying uplifted and deformed strata. The regressive package contains six prograding sequences composed of seismically resolvable lowstand, highstand, and transgressive systems tracts. Most of the depositional sequences comprise lowstand systems tracts consisting of basin-floor fan, slope fan, and prograding complex. Potential reservoirs in the regressive package are turbidite sands in basin-floor fans, channel-fill sands and overbank sand sheets in slope fans, and incised valley-fill sands in the shelf. The shallow marine sands in transgressive packages are another type of reservoir. Detailed sequence stratigraphic analysis, seismic data reprocessing, and 3-D seismic survey are suggested for the successful hydrocarbon exploration in the study area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.21-40
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• 2018

In this paper, we propose the distributed robust beamforming design scheme in cognitive two-way amplify-and-forward (AF) relay networks with imperfect channel state information (CSI). Assuming the CSI errors follow a complex Gaussian distribution, the objective of this paper is to design the robust beamformer which minimizes the total transmit power of the collaborative relays. This design will guarantee the outage probability of signal-to-interference-plus-noise ratio (SINR) beyond a target level at each secondary user (SU), and satisfies the outage probability of interference generated on the primary user (PU) above the predetermined maximum tolerable interference power. Due to the multiple CSI uncertainties in the two-way transmission, the probabilistic constrained optimization problem is intractable and difficult to obtain a closed-form solution. To deal with this, we reformulate the problem to the standard form through a series of matrix transformations. We then accomplish the problem by using the probabilistic approach based on two sorts of Bernstein-type inequalities and the worst-case approach based on S-Procedure. The simulation results indicate that the robust beamforming designs based on the probabilistic method and the worst-case method are both robust to the CSI errors. Meanwhile, the probabilistic method can provide higher feasibility rate and consumes less power.

• Journal of IKEEE
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• v.4 no.2 s.7
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• pp.257-265
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• 2000

Turbo Code decoder is an iterate decoding technology, which extracts extrinsic information from the bit to be decoded by calculating both forward and backward metrics in each decoding step, and uses the information to the next decoding step. Viterbi decoder, which is for a convolutional code, runs continuous mode, while Turbo Code decoder runs by block unit. There are algorithms used in a decoder : which are MAP(maximum a posteriori) algorithm requiring very complicated calculation and SOVA(soft output Viterbi algorithm) using Viterbi algorithm suggested by Hagenauer, and it is known that the decoding performance of MAP is better. The result of this make experimentation shows that the performance of SOVA, which has half complex algorithm compare to MAP, is almost same as the performance of MAP when the SOVA decoding performance is supplemented with Robust equalization techniques.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.137-144
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• 1983

Core walls for tall building is one of the structures to support lateral load. Since most structural elements used for resisting which ate relatively weak against torsion, it is important to investigate tosional effects in the analysis and design of tall buildings. Rutenberg proposed a more refined theory on the torsional analysis of core walls which can be used when the stiffness of lintel beams are small or large. In this paper a more refined method to analysis the torsion of core wall structures with variable cross sections and being subjected to arbitrarilly distributed load was suggested. To reduce complex and a great number of calculations and to enhance the generality and flexibility of application of this method, the discrete method using transfer matrix formulation was used. Then this method can be easily applied to irregular and variational sections, has no necessity to get particular solution for each of loading conditions, and the maximum size of matrix calculated is $4{\times}4$, which makes this approach more appropriate for design office calculations using comuters of any sizes or even desk calculators.

• Composites Research
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• v.31 no.4
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• pp.145-150
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• 2018

Various structural health monitoring (SHM) systems have been suggested for aerospace industry in order to increase its life-cycle and economic efficiency. In the case of aircraft structure madden with metal, a major concern was hot spots, such as notches, bolts holes, and where corrosion or stress concentration occurs due to moisture or salinity. However, with the increasing use of composites in the aerospace industry, further advanced SHM systems have been being required to be applied to composite structures, which have much complex damage mechanism. In this paper, a method of acoustic emission localization for composite structures using Q-switched laser and multiple Amplifier-integrated PZTs have been proposed. The presented technique aims at localization of the AE with an error in distance of less than 10 mm. Acoustic emission simulation and the localization attempt were conducted in the composite structure to validate the suggested method. Localization results, which are coordinates of detected regions, grid plots and color intensity map have been presented together to show reliability of the method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1640-1649
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• 2001

The present study investigates the effects of various rib arrangements on heat/mass transfer in the cooling passage of gas turbine blades. A complex flow structure occurs in the cooling passage with rib turbulators which promote heat transfer on the wall. It is important to increase not only the heat transfer rates but also the uniformity of heat transfer in the cooling passage. A numerical computation is performed using a commercial code to calculate the flow structures and experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. A square channel (50 mm $\times$ 50 mm) with rectangular ribs (4 mm $\times$ 5 mm) is used fur the stationary duct test. The experiments focus on the effects of rib arrangements and gap positions in the discrete ribs on the heat/mass transfer on the duct wall. The rib angle of attack is 60°and the rib-to-rib pitch is 32 mm, that is 8 times of the rib height. With the inclined rib angle of attack (60°), the parallel rib arrangements make a pair of counter rotating secondary flows in the cross section, but the cross rib arrangements make a single large secondary flow including a small secondary vortex. These secondary flow patterns affect significantly the heat/mass transfer on the ribbed wall. The heat/mass transfer in the parallel arrangements is 1.5 ∼2 times higher than that in the cross arrangements. However, the shifted rib arrangements change little the heat/mass transfer from the inline rib arrangements. The gap position in the discrete rib affects significantly the heat/mass transfer because a strong flow acceleration occurs locally through the gap.

• Proceedings of the Korea Contents Association Conference
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• 2005.05a
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• pp.458-463
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• 2005

OFDM communication system is effective for the high data rate transmission in the frequency selective fading channel. Since OFDM has high PAPR, OFDM signal may be distorted by the nonlinear HPA. In this paper, we propose an combined SLM and PTS method for reducing the PAPR in OFDM communication system. Proposed method increased some system complex in comparison with exiting method. But we made sure of high efficiency in the case of reducing the PAPR. As a result of using the 16-QAM modulation and increasing the carrier number in the SLM, PTS method and the SLM-PTS combined method, SLM-PTS combined method is more an effective method of reducing 3.5 dB PAPR than exiting OFDM system when this method is M, L=3, D=128, 256 in 10-3 BER.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.79-84
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• 1996

In this paper, adaptive correlator model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of adaptive correlator uswing backpropagation neural network improved than that of adaptive transversal filter of direct sequence spread spectrum considering of co-channel and narrow-band interference. Bit error ratio of adaptive correlator using backpropagation neural network is reduced about $10^{-1}$ than that of adaptive transversal filter where interference versus signal ratio is 5 dB.