• Journal of computational fluids engineering
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• v.6 no.1
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• pp.14-20
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• 2001

The CFD analysis of the three-dimensional turbulent flow in the impeller and diffuser of an axial flow pump was performed. Not only the design point but also the off-design points were computed. The results were compared with available experimental data in terms of head generated. At the design point, the analysis accurately predicted the experimental head value. In the range of the higher flow rates, the results were also in very good agreement with the experimental data, not only in absolute value but also in term of slope. Although experimental data to be compared were not available in the range of the lower flow rates, the results well described the S-shape performance curve of the axial pump characteristic.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.780-783
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• 1999

This paper gives channel estimation of W-CDMA reverse link using 2-point second-order algorithm over Rayleigh fading channels. The proposed algorithm is compared with the existing interpolation algorithms, i.e., WMSA, linear and second-order Gaussian interpolation, by obtaining HER performance through computer simulations. The BER performance of 2-point second-order interpolation is superior to other algorithms in fading channels. The proposed algorithm also has relatively-simple structure and similar processing delay in comparison to the existing algorithm, Therefore, this algorithm is more suitable for high speed mobile communication environments.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.12
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• pp.1234-1239
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• 2011

The scan matching is widely used in localization and mapping of mobile robots. This paper presents a probabilistic scan matching method. To improve the performance of the scan matching, a direction of data point is incorporated into the scan matching. The direction of data point is calculated using the line fitted by the neighborhood data. Owing to the incorporation, the performance of the matching was improved. The number of iterations in the scan matching decreased, and the tolerance against a high rotation between scans increased. Based on real data of a laser range finder, experiments verified the performance of the proposed direction augmented probabilistic scan matching algorithm.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.671-690
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• 2004

A meshless method with novel variation of point collocation by finite mixture approximation is developed in this paper, termed the meshless finite mixture (MFM) method. It is based on the finite mixture theorem and consists of two or more existing meshless techniques for exploitation of their respective merits for the numerical solution of partial differential boundary value (PDBV) problems. In this representation, the classical reproducing kernel particle and differential quadrature techniques are mixed in a point collocation framework. The least-square method is used to optimize the value of the weight coefficient to construct the final finite mixture approximation with higher accuracy and numerical stability. In order to validate the developed MFM method, several one- and two-dimensional PDBV problems are studied with different mixed boundary conditions. From the numerical results, it is observed that the optimized MFM weight coefficient can improve significantly the numerical stability and accuracy of the newly developed MFM method for the various PDBV problems.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.92-96
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• 2012

This paper presents return link demodulation algorithm designed for hardware implementation using HDL that include complex signal processing work reliably even in low SNR. Simulation results show that performance of Es/$N_0$ has improved within 0.5dB at the point of uncoded BER $10^{-3}$ compared to the ideal QPSK signal. In addition, fixed-point simulation and HDL implementation performance compared to the simulation we can see that there is no difference.

• Proceedings of the KSR Conference
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• 1999.11a
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• pp.280-287
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• 1999

An automatic train operation(ATO) system executes the operation of constant speed travelling and fixed point parking by using microprocessors instead of drivers manual operation. This paper describes the mathematical model for the train considering unknown disturbances which consist of start resistance, travelling resistance, slope resistance, curve resistance, and so on. The speed controller of ATO system is designed by considering the disturbances. The simulation is executed to verify the speed control and fixed point parking performance and to compare its performance with that of a PID-type ATO control system under disturbances. Simulation results show that the control performance of gain scheduled control scheme fur ATO system is better than that of the conventional PID controller.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.27-33
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• 2013

In this paper, we design and analyze the performance of Coordinated Multi-Point (CoMP) techniques to the number of users for next-generation cellular systems. We perform Monte Carlo simulations with Long Term Evolution-Advanced (LTE-Advanced) and confirm the performance from the graph of the Cumulative Distribution Function (CDF). From simulation results, we show the significant performance gain when CoMP technique is used and also show better performance when we apply the various schemes additionally as scheduling and precoding.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.55-62
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• 2012

Centrifugal compressors are widely used and each operating condition is different. However, it cannot be manufactured according to the every operating condition. In the this study, performance of compressor was evaluated with various rotational speeds of impeller and various stagger angles of diffuser in order to apply a typical model widely. A centrifugal compressor was designed and manufactured based on the design point. On this machines, an experiment was conducted and the performance was predicted at off-design point. The performance prediction was validated with the experimental result and the numerical result. Although the isentropic efficiency on the prediction was slightly lower than that on the experimental result due to the heat loss in the experiment, the pressure ratio was predicted well and also the predicted results were matched well with the numerical results. When the rotational speed of the impeller and the stagger angle of the diffuser were changed together, the compressor can be worked in the high efficiency region and avoided operating in the stall region.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.662-668
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• 2011

This paper analyzes the performance of the Ad hoc On-demand Distance Vector (AODV) routing protocol and Optimized Link State Routing (OLSR) for Mobile Ad hoc Networks (MANETs) using node mobility models. Mobility affects the performance of a routing protocol as it causes changes to network topology. Thus, evaluating the performance of a MANET routing protocol requires mobility models that can accurately represent the movements of mobile nodes. Therefore, this paper evaluates the performance of the AODV and OLSR routing protocols using the random way point model and the Levy walk model by the ns-2 simulations.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.2
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• pp.121-137
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• 2013

Now days, firm's technology capability is recognized as important factor to forecast and to evaluate firm's business performance. There are many efforts to develop useful indicators by applying patent information that includes concrete description about technology. Many previous studies analyzed relationship between patent indicators and firm's performance. But they didn't consider time gap between a point of firm's invention activity and a point of firm's performance improvement. They didn't considered a character of industrial fields either. To overcome these limitations, we selected IT industry for target analysis industry. Time-series patent data and financial data from 41 American IT firms between 2000 and 2011 were used to analyze. In this study, We empirically analyzed subsequent effect of patent indicators on firm's business performance by using correlation analysis and regression analysis.