• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.392-399
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• 2009

The paper concerns the description of the step by step development process of the new fixed blade runner called "Mixer" suitable for the uprating of the Francis turbines units installed at the older low head hydropower plants. In the paper the details of hydraulic and mechanical design are presented. Since the rotational speed of the new runner is significantly higher then the rotational speed of the original Francis one, the direct coupling of the turbine to the generator can be applied. The maximum efficiency at prescribed operational point was reached by the geometry optimization of two most important components. In the first step the optimization of the draft tube geometry was carried out. The condition for the draft tube geometry optimization was to design the new geometry of the draft tube within the original bad draft tube shape without any extensive civil works. The runner blade geometry optimization was carried out on the runner coupled with the draft tube domain. The blade geometry of the runner was optimized using automatic direct search optimization procedure. The method used for the objective function minimum search is a kind of the Nelder-Mead simplex method. The objective function concerns efficiency, required net head and cavitation features. After successful hydraulic design the modal and stress analysis was carried out on the prototype scale runner. The static pressure distribution from flow simulation was used as a load condition. The modal analysis in air and in water was carried out and the results were compared. The final runner was manufactured in model scale and it is going to be tested in hydraulic laboratory. Since the turbine with the fixed blade runner does not allow double regulation like in case of full Kaplan turbine, it can be profitably used mainly at power plants with smaller changes of operational conditions or in case with more units installed. The advantages are simple manufacturing, installation and therefore lower expenses and short delivery time for turbine uprating.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2209-2215
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• 2014

This paper presents, a deinterlacing method by improving the Direction-Oriented Interpolation (DOI) technique. The technique is considered to be a very strong tool for intrafield-based deinterlacing. However, DOI has some problems such as long processing time, wrong edge detection in periodic pattern. To remedy this problem, we replace the full search in DOI by a two-step search to reduce processing time and introduces two additional processes to improve image quality. In the proposed method, the spatial direction vectors (SDVs) misread data are reconsidered to prevent them utilizing in the next interpolation step, resulting in an accurate deinterlacing method. We conduct experiments with ISO experimental images to compare the proposed method with the existing methods including line evarage (LA), edge-based line averaging (ELA), DOI, selective deinterlacing algorithm (SDA). Experimental results show the proposed method gives better performance in objective and subjective quality than existing deinterlacing methods.

• Management Science and Financial Engineering
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• v.15 no.1
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• pp.81-96
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• 2009

Data mining, specially clustering is one of exciting research areas for ant based algorithms. Ant clustering algorithm, however, has many difficulties for resolving practical situations in clustering. We propose a new grid-based ant colony algorithm for clustering of data. The previous ant based clustering algorithms usually tried to find the clusters during picking up or dropping down process of the items of ants using some stigmergy information. In our ant clustering algorithm we try to make the ants reflect neighborhood information within the storage nests. We use two ant classes, search ants and labor ants. In the initial step of the proposed algorithm, the search ants try to guide the characteristics of the storage nests. Then the labor ants try to classify the items using the guide in-formation that has set by the search ants and the stigmergy information that has set by other labor ants. In this procedure the clustering decision of ants is quickly guided and keeping out of from the stagnated process. We experimented and compared our algorithm with other known algorithms for the known and statistically-made data. From these experiments we prove that the suggested ant mining algorithm found the clusters quickly and effectively comparing with a known ant clustering algorithm.

• International Journal of Computer Science & Network Security
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• v.23 no.11
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• pp.93-98
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• 2023

Instagram is one of the fastest-growing online photo social web services where users share their life images and videos with other users. Image tagging is an essential step for developing Automatic Image Annotation (AIA) methods that are based on the learning by example paradigm. Hashtags can be used on just about any social media platform, but they're most popular on Twitter and Instagram. Using hashtags is essentially a way to group together conversations or content around a certain topic, making it easy for people to find content that interests them. Practically on average, 20% of the Instagram hashtags are related to the actual visual content of the image they accompany, i.e., they are descriptive hashtags, while there are many irrelevant hashtags, i.e., stophashtags, that are used across totally different images just for gathering clicks and for search ability enhancement. Hence in this work, Sorting instagram hashtags all the way through mass tagging using HITS (Hyperlink-Induced Topic Search) algorithm is presented. The hashtags can sorted to several groups according to Jensen-Shannon divergence between any two hashtags. This approach provides an effective and consistent way for finding pairs of Instagram images and hashtags, which lead to representative and noise-free training sets for content-based image retrieval. The HITS algorithm is first used to rank the annotators in terms of their effectiveness in the crowd tagging task and then to identify the right hashtags per image.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.10-20
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• 2002

The present paper investigates methods to control dynamic stall using an optimal approach. An unsteady aerodynamic sensitivity analysis code is developed by a direct differentiation method from a two-dimensional unsteady compressible Navier-Stokes solver including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating for a period of time. Unsteady sensitivity derivatives of the objective function are calculated by the sensitivity code, and optimization is carried out using a linear line search method at every physical time step. Numerous examples of dynamic stall control using control parameters such as nose radius, maximum thickness of airfoil, or suction show satisfactory results.

• Korean Journal of Computational Design and Engineering
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• v.11 no.3
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• pp.183-196
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• 2006

A new operation strategy. which can guarantee the data consistency of engineering information among the various intelligent information systems, is presented for engineering information of bridges, and construction methodology of integrated database is developed to support the strategy. The two core standard techniques are adopted to construct the integrated database. One is the Standard for the Exchange of Product Model Data (STEP) for CAD/CAE information and the other is the Extensible Markup Language(XML) for engineering document information. The former enabler structural engineers to handle the structural details with three-dimensional geometry-based information of bridges, and ACIS solid modeling kernel is employed to develop AutoCAD based application modules. The latter can make document files into data type for web-based application modules which assist end-users to search and retrieve engineering document data. In addition, relaying algorithm is developed to integrate the two different information, e.g. CAD/CAE information and engineering document information. The pilot application modules are also developed, and a case study subjected to the Han-Nam bridge is presented at the end of the paper to illustrate the use of the developed application modules.

• Knowledge Management Research
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• v.16 no.1
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• pp.71-93
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• 2015

With the rapid growth of the internet, electronic commerce has become accepted as one of the major purchasing channels for consumers. As more and more consumers search for and purchase products through the internet, intra-industry competition of electronic commerce has become fierce. Therefore, electronic commerce service providers pay attention to factors that prevent existing customers from leaving there services in the service failure situation. In this regard, electronic commerce service providers should make service recovery efforts for consumer recovery satisfaction after service failure. In this study, we suggest that procedural justice, interactional justice, distributive justice and authenticity have positive impacts on recovery satisfaction. In addition, we also propose that involvement plays moderating roles in the relationships between procedural justice, interactional justice, distributive justice, authenticity and recovery satisfaction. We collected empirical data for this study over a period of two weeks from subjects who had service failure recovery experiences through electronic commerce. A total of 224 complete and valid responses were obtained. We carried out data analysis using a two-step methodology with SPSS 20.0 and SmartPLS 2.0. The first step in the data analysis was to establish the internal consistency, convergent validity, discriminant validity of the constructs. In the second step, we examined the structural model. The empirical results support the proposed model and partly identify the moderating effect of involvement differences. The moderate effect results show that procedural justice, distributive justice and authenticity have different impacts on recovery satisfaction in two groups. Cognitive factor such as the procedural justice and distributive justice have stronger impacts on recovery satisfaction in the high-involvement goods than in the low-involvement goods, while emotional factor such as authenticity has a stronger impact on recovery satisfaction in the low-involvement goods than in the high-involvement goods. We expect that this result will provide researchers and managers who are interested in electronic commerce service failure recovery with useful theoretical and practical implications.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.3
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• pp.395-400
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• 2011

In this paper, we propose an study of the facial emotion recognition considering the dynamical variation of emotional state in facial image sequences. The proposed system consists of two main step: facial image based emotional feature extraction and emotional state classification/recognition. At first, we propose a method for extracting and analyzing the emotional feature region using a combination of Active Shape Model (ASM) and Facial Action Units (FAUs). And then, it is proposed that emotional state classification and recognition method based on Hidden Markov Model (HMM) type of dynamic Bayesian network. Also, we adopt a Harmony Search (HS) algorithm based heuristic optimization procedure in a parameter learning of HMM in order to classify the emotional state more accurately. By using all these methods, we construct the emotion recognition system based on variations of the dynamic facial image sequence and make an attempt at improvement of the recognition performance.

• Journal of computational fluids engineering
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• v.4 no.3
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• pp.52-62
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• 1999

The development of a parallelized aerodynamic simulation process involving moving bodies is presented. The implementation of this process is demonstrated using a fully systemized Chimera methodology for steady and unsteady problems. This methodology consists of a Chimera hole-cutting, a new cut-paste algorithm for optimal mesh interface generation and a two-step search method for donor cell identification. It is fully automated and requires minimal user input. All procedures of the Chimera technique are parallelized on the Cray T3E using the MPI library. Two and three-dimensional examples are chosen to demonstrate the effectiveness and parallel performance of this procedure.

• Journal of Korea Multimedia Society
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• v.7 no.12
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• pp.1692-1699
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• 2004

Many researchers have developed various techniques for detection of human faces in ordinary still images. Face detection is the first imperative step of human face recognition systems. The two main problems of human face detection are how to cutoff the running time and how to reduce the number of false positives. In this paper, we present frontal and near-frontal face detection algorithm in still gray images using a thick edge image and neural network. We have devised a new filter that gets the thick edge image. Our overall scheme for face detection consists of two main phases. In the first phase we describe how to create the thick edge image using the filter and search for face candidates using a whole face detector. It is very helpful in removing plenty of windows with non-faces. The second phase verifies for detecting human faces using component-based eye detectors and the whole face detector. The experimental results show that our algorithm can reduce the running time and the number of false positives.