• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.5
• /
• pp.2177-2193
• /
• 2018

This paper studies resource allocation schemes for the relay-aided cooperative system consisting of multiple source-destination pairs and decode-forward (DF) relays. Specially, relaying selection, multisubcarrier pairing and assignment, and power allocation are investigated jointly. We consider a combinatorial optimization problem on quality of experience (QoE) and energy consumption based on relay-aided cooperative system. For providing better QoE and lower energy consumption we formulate a multi-objective optimization problem to maximize the total mean opinion score (MOS) value and minimize the total power consumption. To this end, we employ the nondominated sorting genetic algorithm version II (NSGA-II) and obtain sets of Pareto optimal solutions. Specially, two formulas are devised for the optimal solutions of the multi-objective optimization problems with and without a service priority constraint. Moreover, simulation results show that the proposed schemes are superior to the existing ones.

• Journal of applied mathematics & informatics
• /
• v.8 no.3
• /
• pp.1021-1026
• /
• 2001

In this paper, we give an improvement of Carleman’s inequality by using the strict monotonicity of the power mean of n distinct positive numbers.

• Journal of Embryo Transfer
• /
• v.23 no.3
• /
• pp.203-209
• /
• 2008

To estimate the genetic characteristics and cumulative power of discrimination (CPD) existing among Hanwoo (Korean cattle) and exotic foreign population (Angus, Herford, Charolais, Holstein) we used a total of 414 genomic DNAs from five breeds population (Hanwoo, Angus, Hereford, Charolais, Holstein). Genetic characteristics indices including mean allele number among loci, unbiased heterozygosity ($h_i$) within locus and polymorphic information content (PIC) and unbiased average heterozygosity (H) among loci in four breeds were calculated using the generated allele frequencies by each marker. The mean allele numbers for all loci ranged between 5 and 7 while heterozygosity (H) ranged from 0.75 (HW) to 0.64 (HF) among loci and across breeds heterozygosity (H) was 0.69. The generated unbiased average heterozygosity among loci in each breed was integrated to the global formula of CPD resulting in 99.71 % within the populations. The genetic variation of HW (Hanwoo) showed highest estimates among the analyzed breeds.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.8
• /
• pp.2722-2742
• /
• 2014

We propose methods of linear transceiver design for two different power constraints, sum relay power constraint and per relay power constraint, which determine signal processing matrices such as base station (BS) transmitter, relay precoders and user receivers to minimize sum mean square error (SMSE) for multi-relay multi-user (MRMU) networks. However, since the formulated problem is non-convex one which is hard to be solved, we suboptimally solve the problems by defining convex subproblems with some fixed variables. We adopt iterative sequential designs of which each iteration stage corresponds to each subproblem. Karush-Kuhn-Tucker (KKT) theorem and SMSE duality are employed as specific methods to solve subproblems. The numerical results verify that the proposed methods provide comparable performance to that of a full relay cooperation bound (FRCB) method while outperforming the simple amplify-and-forward (SAF) and minimum mean square error (MMSE) relaying in terms of not only SMSE, but also the sum rate.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1804-1814
• /
• 2015

In order to explore the characteristics of electrons in DC negative corona discharge, an improved plasma chemical model is presented for the simulation of bar-plate DC corona discharge in dry air. The model is based on plasma hydrodynamics and chemical models in which 12 species are considered. In addition, the photoionization and secondary electron emission effect are also incorporated within the model as well. Based on this model, electron mean energy distribution (EMED), electron density distribution (EDD), generation and dissipation rates of electron at 6 typical time points during a pulse are discussed emphatically. The obtained results show that, the maximum of electron mean energy (EME) appears in field ionization layer which moves towards the anode as time progresses, and its value decreases gradually. Within a pulse process, the electron density (ED) in cathode sheath almost keeps 0, and the maximum of ED appears in the outer layer of the cathode sheath. Among all reactions, R1 and R2 are regarded as the main process of electron proliferation, and R₂₂ plays a dominant role in the dissipation process of electron. The obtained results will provide valuable insights to the physical mechanism of negative corona discharge in air.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.1
• /
• pp.19-23
• /
• 2000

Partial discharges(PD)in air insulated electric power apparatus often lead to deterioration of solid insulation by electron bombardments and electrochemical reaction. The PD caused to reduce the life time of power apparatus and to increase power losses. Thus understanding and classification of PD patterns in air are very important to discern sources of PD. In this paper, PD in air by using statistical methods was investigated. We classified air discharges, corona, surface discharges and cavity discharges by Kohonen network. For classification of PD patterns, we used statistical operators and parameters such as skewness$(S^+,\; S^-),\; kurtosis(K^+, K^-),\; mean phase(AP^+, AP^-)$, cross-correlation factor(CC) and asymmetry derived from the mean pulse-height phase distribution$(H_{avg}(\phi))$, the max pulse-height phase distribution $(H_{qmax}(\phi))$, the pulse count phase distribution $(H_n(\phi))$ and the pulse height vs. Repetition rate $(H_q(n))$.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.541-544
• /
• 2002

The turbine performance test of an axial-type turbine is carried out with various axial gap distances between the stator and rotor. The turbine is operated at the low pressure and speed, and the degree of reaction is 0.373 at the mean radius. The axial-type turbine consists of ons-stage and 3-dimensional blades. The chord length of rotor is 28.2mm and mean diameter of turbine is 257.56mm. The power of turbo-blower for input power is 30kW and mass flow rate is $340m^3/min\;at\;290mmAq$ static-pressure. The RPM and output power are controlled by a dynamometer connected directly to the turbine shaft. The axial gap distances are changed from a quarter to two times of stator axial chord length, and performance curves are obtained with 7 different axial gaps. The efficiency is dropped about $5{\%}$ of its highest value due to the variation of axial gap on the same non-dimensional mass flow rate and RPM, and experimental results show that the optimum axial gap is 1.0-1.5Cx.

• Wind and Structures
• /
• v.31 no.2
• /
• pp.165-183
• /
• 2020

The first step of performance-based design for transmission lines is the determination of wind fields as well as wind loads, which are largely depending on local wind climate and the surrounding terrain. Wind fields in a mountainous area are very different with that in a flat terrain. This paper firstly investigated both mean and fluctuating wind characteristics of a typical mountainous wind field by wind tunnel tests and computational fluid dynamics (CFD). The speedup effects of mean wind and specific turbulence properties, i.e., turbulence intensity, power spectral density (PSD) and coherence function, are highlighted. Then a hybrid simulation framework for generating three dimensional (3D) wind velocity field in the mountainous area was proposed by combining the CFD and proper orthogonal decomposition (POD) method given the properties of the target turbulence field. Finally, a practical 220 kV transmission line was employed to demonstrate the effectiveness of the proposed wind field generation framework and its role in the performance-based design. It was found that the terrain-induce turbulence effects dominate the performance-based structural design of transmission lines running through the mountainous area.

• Wind and Structures
• /
• v.31 no.4
• /
• pp.299-309
• /
• 2020

In this study, wind data such as speeds, loads and potential of Muğla which is located in the southwest of Turkey were statistically analyzed. The wind data which consists of hourly wind speed between 2010 and 2013 years, was measured at the 10-meters height in four different ground stations (Datça, Fethiye, Marmaris, Köyceğiz). These stations are operated by The Turkish State Meteorological Service (T.S.M.S). Furthermore, wind data was analyzed by using Log-Normal and Gamma distributions, since these distributions fit better than Weibull, Normal, Exponential and Logistic distributions. Root Mean Squared Error (RMSE) and the coefficients of the goodness of fit (R²) were also determined by using statistical analysis. According to the results, extreme wind speed in the research area was 33 m/s at the Datça station. The effective wind load at this speed is 0.68 kN/㎡. The highest mean power densities for Datça, Fethiye, Marmaris and Köyceğiz were found to be 46.2, 1.6, 6.5 and 2.2 W/㎡, respectively. Also, although Log-normal distribution exhibited a good performance i.e., lower AD (Anderson - Darling statistic (AD) values) values, Gamma distribution was found more suitable in the estimation of wind speed and power of the region.

• Ocean and Polar Research
• /
• v.38 no.4
• /
• pp.315-324
• /
• 2016

In this study, we investigated changes in the macrobenthic community in Sihwa tidal flat before and after the operation of a Tidal Power Plant (TPP). In order to investigate changes in the macrobenthic community structure, field surveys were conducted at eighteen stations in 4 transect lines every September from 2011 to 2015. Mean density of macrobenthos decreased to $116ind./m^2$ in 2015 from $1,602ind./m^2$ in 2011. While the mean density of macrobenthos has decreased, species richness and biomass have gradually increased. The species diversity and SEP (Shannon-wiener Evenness Proportion) have also gradually increased over time since the operation of the TPP. The macrobenthic community in Sihwa tidal flat was divided into 4 groups on a yearly base. Before the operation of TPP, opportunistic species such as Neanthes succina and Polydora cornuta largely contributed to the structure of the macrobenthic community, while equilibrium species such as Periserrula leucophryna and Scopimera globosa contributed after the operation. With the operation of TPP, the macrobenthic community has rapidly recovered and this might be related to improvement in the quality of water and sedimentary environments as a result of an increase in water mass volume exchanged through the TPP gate.