• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.702-713
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• 1998

The characteristics of flow and particle collection for an electrocyclone with a central wire inside a high efficiency Stairmand cyclone was numerically analysed. Turbulent flow field was modeled by the Reynolds stress model and solved with an FVM code FLUENT. Particle motion and in-situ charging were simultaneously solved by a Lagrangian integration with time. The flow field obtained was in good agreement with experiments in the outer region. The characteristics of collection enhancement due to electric force were well manifested and well explained based on first principles. The effect of the in-situ charging process was very similar to the case of a simplified assumption of saturated charging, and the effect of the hopper was proved negligible.

• Proceedings of the Safety Management and Science Conference
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• 2009.04a
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• pp.351-364
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• 2009

As well as the development of the measurement of service quality, various kinds of service measurements are also being developed. Especially the mobile telecommunication service being representative to the mobile telecommunication company would be the mostly developed area. Its development can be understood along with the development of the telecommunication companies as well as cellular companies, not only the service alone. It is a differentiated phenomenon in the current research, such as the organic influence between the service quality and product. Of course there are such products placed on sale and enjoyed the common service, but at present there is another case that the product is on the market exclusively with the mobile company in here. This article is to estimate service efficiency for Mobile Communication and Cellular company. In this paper, We tried to measure the service quality and overall satisfaction by using Data Envelopment Analysis(DEA), degree of combination and top2box which is a little bit different methodology from traditional ones. This paper uses CCR model in DEA to measure service efficiency in the Mobile Communication.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.852-857
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• 1988

In induction motor control, power efficiency as well as high dynamic performance is important. We attempt to achieve both of them by decoupled control of rotor speed and flux. A nonlinear feedback controller with a well-known rotor flux observer is proposed with its stability analysis. Experimental results demonstrate that the proposed control method based on recently developed nonlinear feedback control theory is of practical use.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.1041-1046
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• 1989

In this paper, we attempt to control induction motors with high power efficiency as well as high dynamic performance by utilizing the recently developed theories: singular perturbation technique and noninteracting feedback control. Our controller does not need the transformation between a d-q synchronously rotating frame and a x-y stator-fixed frame. It is computationally quite simple. Furthermore, it does not depend on the rotor resistance. To illuminate the practical significance of our results, we present simulation and experimental results as well as mathematical performance analysis.

• Computers and Concrete
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• v.12 no.4
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• pp.443-498
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• 2013

A detailed finite element modeling is presented for the simulation of the nonlinear behavior of reinforced concrete structures which manages to predict the nonlinear behavior of four different experimental setups with computational efficiency, robustness and accuracy. The proposed modeling method uses 8-node hexahedral isoparametric elements for the discretization of concrete. Steel rebars may have any orientation inside the solid concrete elements allowing the simulation of longitudinal as well as transverse reinforcement. Concrete cracking is treated with the smeared crack approach, while steel reinforcement is modeled with the natural beam-column flexibility-based element that takes into consideration shear and bending stiffness. The performance of the proposed modeling is demonstrated by comparing the numerical predictions with existing experimental and numerical results in the literature as well as with those of a commercial code. The results show that the proposed refined simulation predicts accurately the nonlinear inelastic behavior of reinforced concrete structures achieving numerical robustness and computational efficiency.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.17-22
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• 1999

Convergence characteristics and efficiency of three implicit approximate factorization schemes(ADI, DDADI and MAF) are examined using 2-Dimensional compressible upwind Navier-Stokes code. Second-order CSCM(Conservative Supra Characteristic Method) upwind flux difference splitting method with Fromm scheme is used for the right-hand side residual evaluation, while generally first-order upwind differencing is used for the implicit operator on the left-hand side. Convergence studies are performed using an example of the flow past a NACA0012 airfoil at steady transonic flow condition, i. e. Mach number 0.8 at $1.25^{\circ}$ angle of attack. The results were compared with other computational results in order to validate the current numerical analysis. The results from the implicit AF algorithms were compared well in low surface with the other computational results; however, not well in upper surface. It might be due to lack of the grid around the shock position. Because the algorithm minimizes the errors of the approximate decomposition, the improved convergence rate with MAF were observed.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.215-222
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• 2002

It has been well acknowledged that intake system plays great role in the performance of reciprocating engine. Well-designed intake system is expected to not only increase engine efficiency but also decrease engine emission, which is one of the most urgent issues in the automotive society. Thorough understanding of the flow in intake system helps great to design adequate intake system. Even though both experimental and numerical methods are used to study intake flow, numerical analysis is more widely used due to its merits in time and economy. Intake system of In-line 6-Cylinder CNG engine was chosen for the analysis ICEM CFD HEXA was used to create 3-D structured grid and FIRE code was used for the flow analysis in the intake system. Due to the complexity of the geometry standard ${\kappa}-{\varepsilon}$ turbulence model was applied. Numerical analysis was performed for various inlet and outlet boundary conditions under both steady and transient flow. Inlet mass flow rate and outlet pressure variation were changing parameters with respect to engine speed. Flow parameters, such as velocity, pressure and flow distribution, were evaluated to provide adequate data of this intake system.

• Journal of Information Technology Applications and Management
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• v.16 no.1
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• pp.97-113
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• 2009

Collaborative filtering(CF) has been a very successful approach for building recommender system, but its widespread use has exposed to some well-known problems including sparsity and scalability problems. In order to mitigate these problems, we propose two novel models for improving the typical CF algorithm, whose names are ISCF(Item-Selected CF) and USCF(User-Selected CF). The modified models of the conventional CF method that condense the original dataset by reducing a dimension of items or users in the user-item matrix may improve the prediction accuracy as well as the efficiency of the conventional CF algorithm. As a tool to optimize the reduction of a user-item matrix, our study proposes genetic algorithms. We believe that our approach may relieve the sparsity and scalability problems. To validate the applicability of ISCF and USCF, we applied them to the MovieLens dataset. Experimental results showed that both the efficiency and the accuracy were enhanced in our proposed models.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.1-5
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• 2012

By using LED optical devices and improving the efficiency of optical devices as well as lighting apparatus for humans, LED lighting industry puts the purpose of manufacturing the main products related with information, electric, large-sized LCD BLU, automobile, shipbuilding, agriculture, medical treatment, environment, and telecommunications, etc. Moreover, the main products and the industrial lighting products are manufactured with fusion, as the result, LED lighting industry provides various effects as well as sources of technology based on practical use of LED technology in order to develop the industry from the perspective of the lower price, the higher efficiency, the higher function, the deeper reliance. In the future, not only the development of new LED technology but also the fusion and combination of digital IT technologies using wire-wireless communication, sensor, controller, and artificial intelligence will be expected to create new industrial fields.

• The KIPS Transactions:PartA
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• v.18A no.2
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• pp.69-74
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• 2011

The minimum dominating set problem of a graph G is to find a smallest possible dominating set. The minimum dominating set problem is a well-known NP-complete problem such that it cannot be solved in polynomial time. Heuristic or approximation algorithm, however, will perform well in certain area of application. In this paper, we suggest three different simulated annealing algorithms and experimentally show better efficiency improvement by applying these algorithms to the graph instances developed by DIMACS.