• Journal of Communications and Networks
• /
• v.6 no.2
• /
• pp.163-172
• /
• 2004

Ultra Wide Bandwidth (UWB) spread-spectrum techniques will playa key role in short range wireless connectivity supporting high bit rates availability and low power consumption. UWB can be used in the design of wireless local and personal area networks providing advanced integrated multimedia services to nomadic users within hot-spot areas. Thus the assessment of the possible interference caused by UWB devices on already existing narrowband and wideband systems is fundamental to ensure nonconflicting coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. In this paper, we study the coexistence issues between an indoor UWB-based system (hot-spot) and outdoor point to point (PP) links and Fixed Wireless Access (FWA) systems operating in the 3.5 - 5.0 GHz frequency range. We consider a realistic UWB master/slave system architecture and we show through computer simulation, that in all practical cases UWB system can coexist with PP and FWA without causing any dangerous interference.

• Journal of Power Electronics
• /
• v.15 no.1
• /
• pp.106-115
• /
• 2015

This paper proposes a novel direct power control (DPC) strategy for neutral-point-clamped (NPC) three-level rectifiers, to directly control the active power, the reactive power and the neutral point potential of the rectifiers by referring to three pre-calculated vector influence tables and minimizing an objective function. In the three vector influence tables, the influences of different voltage vectors on the active power, the reactive power and the neutral-point potential are shown explicitly. A conceptual description and control algorithm of the proposed controller are presented in this paper. Then, numerical simulations and experiments are carried out to validate the proposed method. Both the simulation and experimental results show that good performances during both the steady-state and transient operating conditions are achieved. As a result, the proposed strategy has been proven to be effective for NPC three-level rectifiers.

• Journal of Power Electronics
• /
• v.6 no.4
• /
• pp.356-365
• /
• 2006

This paper presents an improved three-phase PFC power rectifier with a three-phase diode rectifier cascaded four-switch boost converter. Its operating principle contains the operating principle of two conventional three-phase PFC power rectifiers: one switch boost converter type and a two switch boost converter type. The operating characteristics of the four switch boost converter type three-phase PFC power rectifier are evaluated from a practical point of view, being compared with one switch boost converter type and two switch boost converter topologies.

• Korean Journal of Agricultural Science
• /
• v.31 no.2
• /
• pp.161-174
• /
• 2004

This study is aimed at identifying China's land operating system in the great leap periods. the findings are as follows. For one thing, though the landownership in China was basically performed in public, a portion of private management was allowed. The more this kind of private management allowed, the more the life standard of farmers enhanced. For another thing, the conversion from agricultural cooperatives to people's commune happened swiftly, and the problems according to the conversion arose instantly, which made the operation system changed partially. The last, but not the least, even in the point of the rapid communistic movement, private management was locally accepted in the name of three self and one private management. Besides, as we can recognize from the case study of Daichai village, the operation of a large working group and a small working group was done in political context.

• Proceedings of the KSME Conference
• /
• 2001.06d
• /
• pp.703-707
• /
• 2001

A performance analysis of a SOFC/MGT hybrid system has been carried out for concept design. Thermo-dynamic models for each component being able to describe electrochemical characteristics and heat and mate-rial balance are proposed. Estimated is the power capacity of a SOFC suitable for the hybrid operation with a 5kW class MGT. Effects of current density and operating pressure are also investigated. Electric efficiency showed weak dependence on operating pressure and current density. It is desirable that the SOFC operates at high current density in manufacturing cost's point of view though operating with high current density slightly decreases the electric efficiency find specific power.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.507-510
• /
• 2008

Characteristics of an autothermal reformer at various operating parameters have been studied in this paper. Numerical method has been used, and simulation model has been developed for the analysis. Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction are assumed as dominant chemical reactions in the autothermal reformer. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Veolcity(GHSV). SR reaction rate decreases with low inlet temperature. If OCR is increased, $H_2$ yield is increased but optimal point is suggested. WGS reaction is activated with high SCR. When GHSV is increased, reforming efficiency is increased but pressure drop may decrease the system efficiency.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.58 no.7
• /
• pp.1424-1434
• /
• 2009

DNA computing-inspired pattern classification based on the hypernetwork model is a novel approach to pattern classification problems. The hypernetwork model has been shown to be a powerful tool for multi-class data analysis. However, the ordinary hypernetwork model has limitations, such as operating sequentially only. In this paper, we propose a efficient implementing method of DNA computing-inspired pattern classifier using GPU. We show simulation results of multi-class pattern classification from hand-written digit data, DNA microarray data and 8 category scene data for performance evaluation. and we also compare of operation time of the proposed DNA computing-inspired pattern classifier on each operating environments such as CPU and GPU. Experiment results show competitive diagnosis results over other conventional machine learning algorithms. We could confirm the proposed DNA computing-inspired pattern classifier, designed on GPU using CUDA platform, which is suitable for multi-class data classification. And its operating speed is fast enough to comply point-of-care diagnostic purpose and real-time scene categorization and hand-written digit data classification.

• International Journal of Fluid Machinery and Systems
• /
• v.4 no.2
• /
• pp.243-254
• /
• 2011

In the present paper, we focus on the flow computation of a low head Propeller turbine at a wide range of design and off-design operating conditions. First, we will present the results on the efficiency hill chart prediction of the Propeller turbine and discuss the consequences of using non-homologous blade geometries for the CFD simulation. The flow characteristics of the entire turbine will be also investigated and compared with experimental data at different measurement planes. Two operating conditions are selected, the first one at the best efficiency point and the second one at part load condition. At the same time, for the same selected operating points, the numerical results for the entire turbine simulation will be compared with flow simulation with our standard stage calculation approach which includes only guide vane, runner and draft tube geometries.

• Proceedings of the KIEE Conference
• /
• 1999.07b
• /
• pp.709-711
• /
• 1999

In this paper, Fuzzy Logic Controller was Designed for the Degree control of Arago's disk system. Arago's disk system is an application of Arago's disk phenomenon which is the operating principle of induction motor. Since the Arago's disk system varies to stable region. maginally stable region, unstable region according to the degree of bar respectively, it is a sutable system which can be evaluate an efficiency of the system. While an existing controller which was designed using linearized system modeling could control the system on only one operating point, fuzzy logic controller has the advantage in showing good response for multi-operating points because it does not need system modeling.

• Journal of Power System Engineering
• /
• v.20 no.6
• /
• pp.64-70
• /
• 2016

The unsteady-state, incompressible and three-dimensional large-eddy simulation(LES) was carried out to evaluate the vorticity distribution of a small-size axial fan(SSAF). The X-component vorticity profiles developed around blade tips turn from axial to radial, and diminish the density of distribution according to the increase of static pressure. Otherwise, the Z-component vorticity profiles evenly develop at the region larger than the half radial distance of blade at the operating points of A and B, partly at the trailing-edge region of blade and radially over bellmouth according to the increase of static pressure.