• ETRI Journal
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• v.46 no.3
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• pp.432-445
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• 2024

This paper demonstrates improved throughput and energy efficiency of wireless communications by exploiting nonorthogonal multiple access (NOMA), multiple input-multiple output (MIMO), and radio frequency energy harvesting (EH) technologies. To assess the performance of NOMA MIMO communications with EH (MMe), we consider the nonlinear characteristics of EH devices and propose explicit expressions for throughput and outage probability. Based on our results, the system performance is significantly mitigated by EH nonlinearity and is considerably improved by increasing the number of antennas. Additionally, by appropriately adjusting the system parameters, our NOMA MMe innovation can avert complete outages while optimizing system performance. Moreover, the results demonstrate the superiority of the NOMA MMe over its orthogonal multiple access MMe counterparts.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.13-15
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• 2006

When we use multilayer perceptron model for pattern classification probmems, we allocate one output node for each class. In this paper, we increase the number of output nodes for each class and investigate the performance of multilayer perceptrons through the simulation of isolated-word recognition problems.

• New & Renewable Energy
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• v.2 no.2 s.6
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• pp.81-85
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• 2006

The output performance characteristics for surveyed sites were analyzed, using developed model. It consists of two main parts, the deciding flow duration characteristic of river and performance prediction model to estimate the output characteristics of small hydropower plants. As a result, It was found that the flowrate concerning with 25% of time ratio on flow duration curve can be selected to design flowrate of small hydropower plants, and the output characteristics of small hydropower plants having overflow dam are different from large scale hydropower plants.

• Journal of the Optical Society of Korea
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• v.6 no.2
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• pp.48-54
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• 2002

Experimental study is performed on flashlamp-pumped Ti: sapphire lasers with single, double, and four-partial-ellipse-pump cavities aiming at improving the performance of the lasers. The output energy of 604 mJ per pulse with a width of 25 $\mu$s at a total laser efficiency of 0.13% is achieved in the laser pumped by a light pulse of 45$\mu$s without a fluorescent converter The laser output energy versus its Ti: sappy ire rod length, pumping-light pulse duration, and electrical input energy are discussed with or without using a fluorescent converter. The result shows that much more output energy is obtained il a longer Ti: sapphire-rod laser pumped by a shorter light pulse when its output coupler has an optimized transmittance. In addition, an enhancement of output energy by a factor of 7 is achieved. in the laser using a fluorescent converter LD490.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.491-494
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• 2006

The output performance characteristics for surveyed sites were analyzed, using developed model. It consists of two main parts, the deciding flow duration characteristic of river and performance prediction model to estimate the output characteristics of small hydropower plants. As a result, it was found that the flowrate concerning with 25% of time ratio on flow duration curve can be selected to design flowrate of small hydropower plants, and the output characteristics of small hydropower plants having overflow dam are different from large scale hydropower plants.

• Journal of Energy Engineering
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• v.28 no.2
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• pp.47-54
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• 2019

As absorption type heat pump for waste heat recovery is installed in combined cycle power plant for Energy Service Company, performance test is implemented to confirm the operation data on partial load. The operation data changes according to the heat pump operation on partial load are as follows. Total heat output increases, because waste heat of closed cooling water and a portion of LP steam from HRSG is supplied. But electric power output of steam turbine is reduced, because LP steam to steam turbine is reduced. And heat output from HP district heater and LP district heater is reduced, because HP turbine exhaust steam to HP district heater and LP district heater is reduced. On partial load operation, turbine output reduction is higher than the base load operation. Therefore, on partial load, heat pump should be operated in consideration of the heat output increase and electric power output reduction.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.1-9
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• 1998

ATM was adopted as the switching and multiplexing technique for BISDN which aims at transmitting traffics with various characteristics in a unified network. To construct these ATM networks, the most important aspect is the design of the switching system with high performance and different service capabilities. In this paepr, we analyze the performance of an input and output queueing switch with preemptive priority which is considered to be most suitable for ATM networks. For the analysis of an input queue, we model each input queue as two separate virtual input queues for each priority class and we approximage them asindependent Geom/Geom/1 queues. And we model a virtual HOL queue which consists of HOL cells of all virtual input queues which have the same output address to obtain the mean service time at each virtual input queue. For the analysis of an output quque, we obtain approximately the arrival process into the output queue from the state of the virtual HOL queue. We use a Markov chain method to analyze these two models and obtain the maximum throughput of the switch and the mean queueing delay of cells. and analysis results are compared with simulation to verify that out model yields accurate results.

• Journal of Powder Materials
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• v.22 no.5
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• pp.331-336
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• 2015

We report on the succesful fabrication of ZnO nanorod (NR)-based robust piezoelectric nanogenerators (PNGs) by using Cu foil substrate. The ZnO NRs are successfully grown on the Cu foil substrate by using all solution based method, a two step hydrothermal synthesis. The ZnO NRs are grown along c-axis well with an average diameter of 75~80 nm and length of $1{\sim}1.5{\mu}m$. The ZnO NRs showed abnormal photoluminescence specrta which is attributed from surface plasmon resonance assistant enhancement at specific wavelength. The PNGs on the SUS substrates show typical piezoelectric output performance which showing a frequency dependent voltage enhancement and polarity dependent charging and discharging characteristics. The output voltage range is 0.79~2.28 V with variation of input strain frequency of 1.8~3.9 Hz. The PNG on Cu foil shows reliable output performance even at the operation over 200 times without showing degradation of output voltage. The current output from the PNG is $0.7{\mu}A/cm^2$ which is a typical out-put range from the ZnO NR-based PNGs. These performance enhancement is attributed from the high flexibility, high electrical conductivity and excellent heat dissipation properties of the Cu foil as a substrate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.756-760
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• 1995

Optimal design of a hybrid parallel robot is investigated. In order to optimize the mechanism, new performance measures are introduced since use of the previous methods suffer form lack of the physical meaning due to the dimensional inhomogeneity. To overcome the problem, an Euclidean norm definition of each output space with homogeneous dimension is used to find input-output norm relation and derive new performance measures for each output spaces, that is, translational and rotational velocity, and derive new torque space. For illustion,the derived performance measures is applied to find the isotropic design of a Stewart platform robot which has condition number measures equal to one.

• The KSFM Journal of Fluid Machinery
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• v.11 no.4
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• pp.45-51
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• 2008

The purpose of this study is to examine the effect of nozzle shape on the performance and internal flow of a cross-flow hydro turbine. CFD analysis for three kinds of nozzle shape is conducted to simulate the effect of nozzle shape. The results reveal that relatively narrow nozzle width is effective to increase the turbine efficiency and output power. Almost output power is achieved at Stage 1. Therefore, optimum design of the nozzle shape is necessary to improve the turbine performance. Recirculation flow in the runner passage decreases the turbine efficiency and output power because the flow make hydraulic loss and collision loss in the region. Air should be put into the runner passage and the recirculating flow should be suppressed by the air layer in the runner.