• Journal of KIISE
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• v.44 no.7
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• pp.726-732
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• 2017

In practical distributed sensing and prediction applications over wireless sensor networks (WSN), environmental sensing activities are highly dynamic because of noisy sensory information from moving source signals. The recent distributed online convex optimization frameworks have been developed as promising approaches for solving approximately stochastic learning problems over network of sensors in a distributed manner. Negligence of mobility consequence in the original distributed saddle point algorithm (DSPA) could strongly affect the convergence rate and stability of learning results. In this paper, we propose an integrated sliding windows mechanism in order to stabilize predictions and achieve better convergence rates in cooperative detection of a moving source signal scenario.

• International Journal of Computer Science & Network Security
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• v.21 no.12
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• pp.280-292
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• 2021

Enterprise Resource Planning (ERP) is a software that manages and automate the internal processes of an organization. Process speed and quality can be increased, and cost reduced by process automation. Odoo is an open source ERP platform including more than 15000 apps. ERP systems such as Odoo are all-in-one management systems. Odoo can be suitable for small and medium organizations, but duo to efficiency limitations, Odoo is not suitable for the large ones. Furthermore, Odoo can be implemented on both local or public servers in which each has some advantages and disadvantages such as; the speed of internet, synced data or anywhere access. In many cases, there is a persistent need to have more than one synchronized Odoo instance in several physical places. We modified Odoo to support this kind of requirements and improve its efficiency by replacing its standard database with a distributed one, namely CockroachDB.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3E
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• pp.25-30
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• 2001

In angle of arrival estimation, the direction of a signal is usually assumed to be a point. If the direction of a signal is distributed due to some reasons in real surroundings, however, angle of arrival estimation techniques based on the point source assumption may result in poor performance. In this paper, we consider angle of arrival estimation when the signal sources are distributed. A parametric source model is proposed, and the estimation techniques based on the well-known maximum likelihood technique is considered under the model. In addition, Various statistical properties of the estimation errors were obtained.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.492-498
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• 2010

In this paper, a new distributed space-time coded (DS-TCed) non-orthogonal decode-and-forward (NDF) protocol with source antenna switching (SAS) is proposed, where two antennas associated with each radio frequency chain can be alternatively used in the first and second phases. Several DSTC schemes for the NDF with SAS (NDF-SAS) protocol are proposed and their average pairwise error probability for the error-free source-relay (SR) channel is also derived. The simulation results show that the NDF-SAS protocol achieves larger diversity order than the NDF protocol under the error-free and erroneous SR channels.

• Journal of Broadcast Engineering
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• v.24 no.6
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• pp.956-964
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• 2019

In the age of personal media such as YouTube and Twitch, individual media content creation and consumption have become simpler. A huge amount of media content is created and consumed through platform services. In this regard, interest in copyright of media contents is increasing. In particular, the sound source is an indispensable element in almost all media contents production. In this paper, we propose a method to store the sound source and its signature using blockchain and distributed storage system to verify the copyright of music contents. We Identify the possibility of including the audio signature extraction result of the sound source as blockchain transaction data. Through experiments, we compare the input and output speed when the sound source and its signature are stored in the distributed storage system.

• Journal of information and communication convergence engineering
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• v.15 no.1
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• pp.21-27
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• 2017

In this research, we study the outage probability for distributed space-time coding-based cooperative (DSTC) systems with amplify-and-forward relaying over Rayleigh fading channels with a high temporal correlation where the direct link between the source and the destination is available. In particular, we derive the upper and lower bounds of the outage probability as well as their corresponding asymptotic expressions. In addition, using only the average channel powers for the source-to-relay and relay-to-destination links, we propose an efficient power allocation scheme between the source and the relay to minimize the asymptotic upper bound of the outage probability. Through a numerical investigation, we verify the analytical expressions as well as the effectiveness of the proposed efficient power allocation. The numerical results show that the lower and upper bounds tightly correspond to the exact outage probability, and the proposed efficient power allocation scheme provides an outage probability similar to that of the optimal power allocation scheme that minimizes the exact outage probability.

• Journal of Broadcast Engineering
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• v.24 no.7
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• pp.1228-1236
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• 2019

Recently, media platforms such as YouTube and Twitch provide services that can generate personal revenue by utilizing media content produced by individuals. In this regard, interest in the copyright of media content is increasing. In particular, in the case of an audio source, competition for securing audio source copyright is fierce because it is an essential element for almost all media content production. In this paper, we propose a method to store the audio source and its signature using a blockchain and distributed storage system to verify the copyright of music content. To identify the possibility of extracting the audio signature of the audio source and to include it as blockchain transaction data, we implement the audio source and its signature file upload system based on the proposed scheme. In addition, we show the effectiveness of the proposed method through experiments on uploading and retrieving audio files and identify future improvements.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.491-506
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• 2015

Distributed models represent watersheds using a network of numerous, uniform calculation units to provide spatially detailed and consistent evaluations across the watershed. However, these models have a disadvantage in general requiring a high computing cost. Semi-distributed models, on the other hand, delineate watersheds using a simplified network of non-uniform calculation units requiring a much lower computing cost than distributed models. Employing a simplified network of non-uniform units, however, semi-distributed models cannot but have limitations in spatially-consistent simulations of hydrogeochemical processes and are often not favoured for such a task as identifying critical source areas within a watershed. Aiming to overcome these shortcomings of both groups of models, a hybrid watershed model STREAM (Spatio-Temporal River-basin Ecohydrology Analysis Model) was developed in this study. Like a distributed model, STREAM divides a watershed into square grid cells of a same size each of which may have a different set of hydrogeochemical parameters reflecting the spatial heterogeneity. Like many semi-distributed models, STREAM groups individual cells of similar hydrogeochemical properties into representative cells for which real computations of the model are carried out. With this hybrid structure, STREAM requires a relatively small computational cost although it still keeps the critical advantage of distributed models.

• Journal of Electrical Engineering and Technology
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• v.1 no.4
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• pp.409-413
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• 2006

This paper deals with the design and testing of a simulator system for microgrids with distributed generations. This system is composed of a Real Time Digital Simulator (RTDS) and a power amplifier. The RTDS parts are operated for real time simulation for the microgrid model and the distributed generation source model. The power amplifiers are operated fur amplification of the RTDS's simulated output signal, which is a node voltage of the microgrid and distributed generation source. In this paper, we represent an RTDS system design, specification and test results of a power amplifier and simulation results of a PV (Photovoltaic) system and wind turbine system. The proposed system is applicable for development and performance testing of a PCS (Power Conversion System) for renewable energy sources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4C
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• pp.329-336
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• 2010

Distributed source coding (DSC) system moves computational burden from encoder to decoder, so it takes higher decoding complexity. This paper explores the problem of reducing the decoding complexity of practical Slepian-Wolf coding using low-density parity check accumulate (LDPCA) codes. It is shown that the convergence of mean magnitude (CMM) stopping criteria for LDPC codes help reduce the 85% of decoding complexity under the 2% of compression rate loss, and marginal initial rate request reduces complexity below complexity minimum bound. Moreover, inter-rate stopping criterion, modified for rate-adaptable characteristic, is proposed for LDPCA codes, and it makes decoder perform less iterative decoding than normal stopping criterion does when channel characteristic is unknown.