• Ocean and Polar Research
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• v.25 no.spc3
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• pp.423-426
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• 2003

The seawater exchange breakwater equipped with an oscillating water channel and water transmitting pipes has a very spectacular function that seawater supply can be greatly increased due to the upsurge of the water surface inside the channel at resonance condition which can be reached when the incident wave period becomes close to the natural period of the channel. The variations of the water level and period inside the channel are very important factors in enhancing the efficiency of sea water exchange, especially when designing the breakwater cross-section in shallow water zone which requires longer resonance period with the elongated horizontal projection of the channel. In the present study, a hydraulic experiment was performed varying the length of the oscillating channel, and the resonance periods and water surface variations are analyzed in terms of water transmission through the pipes.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.6
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• pp.487-493
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• 2013

As the spread of smart devices that service variety of content, limited mobile terminal channel assignment problem has intensified. In the channel assignment in mobile networks mobile switching center at the request belongs to each base station allocates the channel to the mobile station. This effectively allocate the limited channels of various methods have been proposed for, in this case a hybrid channel allocation using genetic algorithms UHGA (Universal Hybrid Channel Assignment using Genetic Algorithm) in rural areas or urban areas, such as universal network applied to a variety of environments that the efficiency is verified through simulation.

• Kyungpook Mathematical Journal
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• v.13 no.2
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• pp.153-156
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• 1973

• The Research Journal of the Costume Culture
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• v.26 no.1
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• pp.109-124
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• 2018

As fashion and distribution companies have increasingly turned to implementing marketing activities that use omni-channel strategies, it is imperative to explore consumer-oriented evaluations of omni-channel shopping for fashion products. Through contributing to the growing research flow of consumer behavior within omni-channel contexts, the current study explores consumer motivations for omni-channel fashion shopping and their impacts on the decision-making stages of fashion products. The authors first performed in-depth interviews with six Korean consumers and confirmed the four types of consumer motivation for omni-channel shopping, and how decision-making processes react to fashion companies' omni- channel marketing strategies. These findings were used to set survey items for the main study. Based on the results and findings of previous literature, an online survey was conducted with 300 participants who had actual experience with omni-channel shopping for fashion products. The statistic results from the survey revealed the following: First, the in-depth interviews allowed the authors to confirm four factors of omni-channel shopping motivation (ubiquity, efficiency, convenience, and impulsiveness). Second, the survey showed the authors that among the four factors of omni-channel shopping orientation, impulsiveness had the greatest effect on consumer behaviors at the preand on-purchase stages, while the ubiquity factor had the greatest effect at the post-purchase stage. As such, the study empirically tested the omni-channel-specific factors of shopping orientation and motivation. In addition, it showed the effect of omni-channel marketing on various stages of the decision- making process and the study's limitations and implications were discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1837-1860
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• 2020

We propose a general framework for studying resource allocation problem and the tradeoff between spectral efficiency (SE) and energy efficiency (EE) for downlink traffic in power domain-non-orthogonal multiple access (PD-NOMA) and device to device (D2D) based heterogeneous cloud radio access networks (H-CRANs) under imperfect channel state information (CSI). The aim is jointly optimize radio remote head (RRH) selection, spectrum allocation and power control, which is formulated as a multi-objective optimization (MOO) problem that can be solved with weighted Tchebycheff method. We propose a low-complexity algorithm to solve user association, spectrum allocation and power coordination separately. We first compute the CSI for RRHs. Then we study allocating the cell users (CUs) and D2D groups to different subchannels by constructing a bipartite graph and Hungrarian algorithm. To solve the power control and EE-SE tradeoff problems, we decompose the target function into two subproblems. Then, we utilize successive convex program approach to lower the computational complexity. Moreover, we use Lagrangian method and KKT conditions to find the global optimum with low complexity, and get a fast convergence by subgradient method. Numerical simulation results demonstrate that by using PD-NOMA technique and H-CRAN with D2D communications, the system gets good EE-SE tradeoff performance.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.4
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• pp.277-288
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• 2005

The proliferation of the internet technologies and applications has intensified business activities on the Internet. This study considered the price competition between two shopping channels, one on-line seller and the other traditional off-line retailer. Based on the Hotelling's linear market model, we derive the Nash and Stackelberg equilibria as a function of the cost parameters which represent the characteristics of the online and off-line channels. By analyzing the equilibrium solutions, the following significant findings were obtained. First, pricing by Stackelberg equilibrium always outperformed that of Nash equilibrium. However the value of the cost parameters played a crucial role in determining both channels' preferred position (price leader or follower). Second, the online seller could benefit more in terms of profit by lowering its efficiency when its efficiency belongs to a certain interval. Third, when the online seller's efficiency is low, lowering its delivery cost has no contribution to its profit. To benefit more from lowering its delivery cost, increasing its channel efficiency to a certain level should be preceded.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.286-289
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• 2003

We investigated the influence of the properties of substrate material on the separation efficiency in microchip electrophoresis. We fabricated the various microchips and studied separation efficiency in microchannels composed of a single material such as quartz, glass, polydimethylsiloxane (PDMS), and polymethylmetha crylate (PMMA), as well as hybrid micro channels composed of different materials. New fabrication process for glass chip was suggested and some treatment is added to improve fabrication process in other chip. Separation efficiency was compared by measuring migration times and bandwidths of EOF and analytes in each microchip. The efficiency is the function of migration time, which is affected by the electroosmotic flow (EOF), and bandwidth of an analyte. EOF is highly dependent upon the characteristics of a microchannel wall surface. Migration time was more reproducible in silica chips than that of PDMS chip and more band broadening was observed in the microchip composed of hybrid material due to non-uniformity of surface charge density at the walls of the channel.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.509-528
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• 2010

The random access systems, with retransmission diversity (RD) employment, over large random spreading code division multiple access (CDMA) channel subject to fading is investigated, under the assumption of infinite number of users and infinite spreading gain with their ratio converging to a constant. The low bound of the signal to interference and noise ratio (SINR) is shown to converge almost surely to a constant. The throughput, spectrum efficiency and energy efficiency in the dominating systems are obtained. The analytical results are confirmed by simulations. We find that in high traffic loads the throughput with fading is higher than that without. When the energy efficiency increases, the spectrum efficiency tends to two contrary values due to SNR increases or decreases. For the ordinary stable systems, the stability region is shown to shrink as the traffic increases and enlarge with RD employment.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.517-520
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• 2006

The Korean peninsula has a number of coastal sites where the rhythmic rising and lowering of water surface due to tides results in strong tidal current. The kinetic energy of these currents can be efficiently exploited by use of tidal current turbines. The pilot tidal current power plant is to be constructed at the Uldolmok narrow channel between J info and Haenam, Our ins next Year, and extensive coastal engineer ing research works have been carried out. This paper describes and analyzes some observation results of field test about the efficiency of Helical turbine for tidal current power plant. The efficiency of turbine, which is diameter 2.2m and height 2.5m, is evaluated meximum RPM, torque, and current velocity. The tested turbines had the maximum efficiencies of the bounds of 25 to 35% in the current velocity range between 1.4 and 2.6 m/s. This result shows that the pilot tidal current power plant needs three helical turbines with diameter 3.0m and height 3.6m to produce electric power 500kW.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.141-149
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• 1999

If signal time duration of MC-CDMA method which has studied for next-generation high-speed data transmission is not sufficiently large compared to delay spread of channel, the performance is degraded by generation of intersymbol interference. In this paper, this problem will solve through serial to parallel convertor and make large sufficiently time duration of signal compared to delay spread of channel and rise variable spectral efficiency through the number of serial to parallel convertor subchannel we will add to parallel frequency diversity block for improve the performance in mobile Communication. Spectral efficiency of the proposed system is counted and compared to spectral efficiency of MC-CDMA and investigated through computer simulations by using multipath Rayleigh fading channel.