• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.7
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• pp.515-522
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• 2018

An orthogonal frequency division multiplexing with coded direct index modulation(OFDM-CDIM) system that can achieve higher performance and spectral efficiency than previous OFDM systems is proposed. Previous OFDM with index modulation(IM) and OFDM-IM using dual modes systems allocate additional data to indices of respective subcarriers through combining operation with high complexity and then transmit them. However, the proposed system directly allocates the mode selection information to each subcarrier without performing additional operations. Then, the system selects and transmits one symbol in the selected mode. Furthermore, only the data allocated to the index of the subcarrier is encoded, and a good performance improvement effect is obtained with a high code rate. Simulation results show quantitatively that an OFDM-CDIM system using four modes improves bit error rate performance and transmission efficiency in additive white Gaussian noise and Rayleigh fading channel environments compared with a conventional OFDM system using 4-ary quadrature amplitude modulation.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1061-1068
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• 2019

Cooperative networks transmit signals form the source node to the destination node via several relay node where the combining and demodulation of relay aided signals provide the benefit of performance enhancement and data rate increment. In general, a repetitive manner transmission scheme in which the received signal from the source node is amplified/re-generated and forward to the destination node is widely used. In this paper, we analyzed the performance of cooperative networks using the mixed transmission scheme. The conventional modulation scheme is used in the source-relay links, and space-time code is applied in the relay-destination links. To reduce the complexity of the overall system, we adopt differential modulation which bypasses channel state information. We analyze bit error rate (BER) of the proposed system by considering the number of relay nodes, and the performances depending on the strength of transmission signal in the source-relays and rely-destination links are compared. In addition, we also discuss the system performance with the signal strength and the number of relay nodes simultaneously.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.12
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• pp.2609-2618
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• 2011

Under the knowledge-based economy in 21C, the convergence and complexity in science and technology are being more active. Interoperability between heterogeneous domains is a very important point considered in the field of scholarly information service as well information standardization. Thus we suggest the systematic solution method to flexibly extend classification scheme in order for content management and service organizations. Especially, This paper shows that automatic method for interoperability between heterogeneous scholarly classification code structures will be effective in enhancing the information service system.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.33-39
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• 2016

Generally, thermal analysis of spent fuel storage cask has been conducted using the porous media and effective thermal conductivity model to simplify the structural complexity of spent fuel assemblies. As the fuel assembly is composed of two regions; active fuel region corresponding to UO2 pellets and unactive fuel region corresponding to the top and bottom nozzle, the heat transfer performance can be influenced depending on porous media application at these regions. In this study, numerical analysis on concrete storage cask of spent fuel was performed to investigate heat transfer effects for two cases; one was porous media application only to active fuel region(case 1) and the other one was porous media to whole length of fuel assembly(case 2). Using computational fluid dynamics code, the three dimensional, 1/4 symmetry model was constructed. For two cases, maximum temperatures for each component were evaluated below the allowable limits. For the case 1, maximum temperatures for fuel cladding, neutron absorber and baskets inside the canister were slightly higher than those for the case 2. In particular, even though the helium flows with low velocity due to buoyant forces occurred at the top and bottom of unactive fuel region, treating only active fuel region as the porous media was ineffective in respect of the heat removal performance of concrete storage cask, implying a conservative result.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.131-138
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• 2005

The AASHTO wheel load distribution factor (LDF) equation has been with us since 1931 and has undergone minor modifications. In 1994, an entirely new procedure was introduced in the AASHTO LRFD code based on parametric studies and finite element analyses. However, this LDF equation involves a longitudinal stiffness parameter, the design of which is not initially known. Thus, an iterative procedure is required to correctly determine the LDF value. The increased level of complexity puts undue burden on the designer resulting in a higher likelihood for misinterpretation and error. In this study, based on current AASHTO LRFD framework, a new simplified equation is developed that does not require an iterative procedure. A total of 43 representative composite steel girder bridges are selected and analyzed using a finite element model.The new simplified equation produces LDF values that are always conservative when compared to those obtained from the finite element analyses and are generally greater than the LDF obtained using AASHTO LRFD specification. Therefore, the proposed simplified equation is expected to streamline the determination of LDF for bridge design without sacrificing safety.

• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.481-490
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• 2006

The actual performance of a building during an earthquake depends on many factors. The prediction of the seismic performance of a new or existing structure is complex, due not only to the large number of factors that need to be considered and the complexity of the seismic response, but also due to the large inherent uncertainties and randomness associated with making these predictions. A central issue of this research is the proper treatment and incorporation of these uncertainties and randomness in the evaluation of structural capacity and response has been adopted in the seismic performance evaluation of steel tall buildings to account for the uncertainties and randomness in seismic demand and capacities in a consistent manner. The basic framework for reliability-based seismic performance evaluation and the key factors for statistical studies were summarized. A total of 36 target structures that represent typical tall steel buildings based on national building code (KBC-2005) were designed for the statistical studies of demand factor s and capacity factors. The incremental dynamic analysis (IDA) approach was examined through the simple steel moment frame building in determination of global drift capacity.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.594-600
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• 2014

In modern warfare, securing communication channel by combatting opponents' electromagnetic attack is a crucial factor to win the war. Military satellite digital transponder is a communication payload of the next generation military satellite that maintains warfare networks operational in the presence of interfering signals by securely relaying signals between ground terminals. The transponder in this paper is classified as a partial processing transponder which performs cost effective secure relaying in satellite communication links. The control functions of transmission security achieve immunity to hostile interferences which may cause malicious effects on the link. In this paper, we present an efficient architecture for implementing the control mechanism. Two major ideas of pipelined processing in per-group control and software processing of blocked band information dramatically reduce the complexity of the hardware. A control code sequence showing its randomness with uniform distribution is exemplified and qualification test results are briefly presented.

• Journal of Computing Science and Engineering
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• v.5 no.2
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• pp.111-120
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• 2011

Data mining algorithms should exploit new hardware technologies to accelerate computations. Such goal is difficult to achieve in database management system (DBMS) due to its complex internal subsystems and because data mining numeric computations of large data sets are difficult to optimize. This paper explores taking advantage of existing multithreaded capabilities of multicore CPUs as well as caching in RAM memory to efficiently compute summaries of a large data set, a fundamental data mining problem. We introduce parallel algorithms working on multiple threads, which overcome the row aggregation processing bottleneck of accessing secondary storage, while maintaining linear time complexity with respect to data set size. Our proposal is based on a combination of table scans and parallel multithreaded processing among multiple cores in the CPU. We introduce several database-style and hardware-level optimizations: caching row blocks of the input table, managing available RAM memory, interleaving I/O and CPU processing, as well as tuning the number of working threads. We experimentally benchmark our algorithms with large data sets on a DBMS running on a computer with a multicore CPU. We show that our algorithms outperform existing DBMS mechanisms in computing aggregations of multidimensional data summaries, especially as dimensionality grows. Furthermore, we show that local memory allocation (RAM block size) does not have a significant impact when the thread management algorithm distributes the workload among a fixed number of threads. Our proposal is unique in the sense that we do not modify or require access to the DBMS source code, but instead, we extend the DBMS with analytic functionality by developing User-Defined Functions.

• Wind and Structures
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• v.23 no.6
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• pp.505-521
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• 2016

The objective of this study is to investigate numerically the effect of building roof shaps on wind flow and pollutant dispersion in a street canyon with one row of trees of pore volume, $P_{vol}=96%$. A three-dimensional computational fluid dynamics (CFD) model is used to evaluate air flow and pollutant dispersion within an urban street canyon using Reynolds-averaged Navier-Stokes (RANS) equations and the Explicit Algebraic Reynolds Stress Models (EARSM) based on k-${\varepsilon}$ turbulence model to close the equation system. The numerical model is performed with ANSYS-CFX code. Vehicle emissions were simulated as double line sources along the street. The numerical model was validated by the wind tunnel experiment results. Having established this, the wind flow and pollutant dispersion in urban street canyons (with six roof shapes buildings) are simulated. The numerical simulation results agree reasonably with the wind tunnel data. The results obtained in this work, indicate that the flow in 3D domain is more complicated; this complexity is increased with the presence of trees and variability of the roof shapes. The results also indicated that the largest pollutant concentration level for two walls (leeward and windward wall) is observed with the upwind wedge-shaped roof. But the smallest pollutant concentration level is observed with the dome roof-shaped.

• Journal of KIISE:Software and Applications
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• v.36 no.10
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• pp.851-860
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• 2009

Recently, among the computational methods of protein-protein interaction prediction, vast amounts of domain based methods originated from domain-domain relation consideration have been developed. However, it is true that multi domains collaboration is avowedly ignored because of computational complexity. In this paper, we implemented a protein interaction prediction system based the Interaction Significance matrix, which quantified an influence of domain combination pair on a protein interaction. Unlike conventional domain combination methods, IS matrix contains weighted domain combinations and domain combination pair power, which mean possibilities of domain collaboration and being the main body on a protein interaction. About 63% of sensitivity and 94% of specificity were measured when we use interaction data from DIP, IntAct and Pfam-A as a domain database. In addition, prediction accuracy gradually increased by growth of learning set size, The prediction software and learning data are currently available on the web site.