• Journal of Korea Water Resources Association
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• v.32 no.2
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• pp.99-110
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• 1999

The method of moments, a Lagrangian scheme, considers the zeroth, first, and second moments of the grid cell spatial distributions of the concentration and then advects the concentration by maintaining conservation of the moments. The reasonable inital description of the first and second moments as well as the mean concentration, the zeroth moments, in grid element is important in the method of moments. In this study, the description methods of each initial moment are reviewed, and the method of moments is extended to overcome the restrictions of Courant number. Its performance is compared with those of available Eulerian and Lagrangian schemes. As the results, the method is successfully extended to overcome the stability restriction and is an accurate scheme for the advection simulation of concentration distribution, especially of which the gradient is steep. In addition, the method is very promising scheme in terms of computational efficiency when the mixing is confined in a relatively small region to the entire domain in two-dimensional problem.

• Korean Journal of Mathematics
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• v.16 no.2
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• pp.123-134
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• 2008

In the present article, we give a description of a chain complex of a cyclic cohomology type proposed by Grayson, which is constructed from the double exact sequences of an exact category. We also provide some results which relate it with motivic cohomology of a smooth scheme over a field.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.429-441
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• 2011

In large-scale problem, a huge size of computational resources is needed for a reliable solution which represents the detailed description of dynamic behavior. Recently, eigenvalue reduction schemes have been considered as important technique to resolve computational resource problems. In addition, the efforts to advance an efficiency of reduction scheme leads to the development of the multi-level system condensation (MLSC) which is initially based on the two-level condensation scheme (TLCS). This scheme was proposed for approximating the lower eigenmodes which represent the global behavior of the structures through the element-level energy estimation. The MLSC combines the multi-level sub-structuring scheme with the previous TLCS for enhancement of efficiency which is related to computer memory and computing time. The present study focuses on the implementation of the MLSC on the direct time response analysis and the frequency response analysis of structural dynamic problems. For the transient time response analysis, the MLSC is combined with the Newmark's time integration scheme. Numerical examples demonstrate the efficiency of the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1354-1359
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• 2013

With the development of multimedia and network technology, the production of multimedia contents is rapidly increasing. Meanwhile, the technology to search and use the contents is still insufficient. There are standards for multimedia contents to address the problem, but they cannot fully support diverse multimedia data types or ensure their interoperability. In this paper, an ontology-based content search system is proposed to ensure the interoperability of multimedia contents. The ontology is configured by presenting the rules for it using the schema structure of the multimedia description scheme (MDS) of MPEG-7. Based on this ontology, This paper extend multimedia relationship based on ontology, thus established the semantic retrieval system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.491-508
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• 2010

In peer-to-peer (P2P) on-demand streaming networks, the alleviation of server load depends on reciprocal stream sharing among peers. In general, on-demand video services enable clients to watch videos from beginning to end. As long as clients are able to buffer the initial part of the video they are watching, on-demand service can provide access to the video to the next clients who request to watch it. Therefore, the key challenge is how to keep the initial part of a video in a peer's buffer for as long as possible, and thus maximize the availability of a video for stream relay. In addition, to address the issues of delivering data on lossy network and providing scalable quality of services for clients, the adoption of multiple description coding (MDC) has been proven as a feasible resolution by much research work. In this paper, we propose a novel caching scheme for P2P on-demand streaming, called Dynamic Buffering. The proposed Dynamic Buffering relies on the feature of MDC to gradually reduce the number of cached descriptions held in a client's buffers, once the buffer is full. Preserving as many initial parts of descriptions in the buffer as possible, instead of losing them all at one time, effectively extends peers’ service time. In addition, this study proposes a description distribution balancing scheme to further improve the use of resources. Simulation experiments show that Dynamic Buffering can make efficient use of cache space, reduce server bandwidth consumption, and increase the number of peers being served.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.307-312
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• 2006

Protection to the multimedia contents is inevitable to ensure that only authorized users be able to access the protected contents for consumption. Since protection mechanisms need to be designed efficiently by exploiting the type of the contents, we propose a protection scheme for the video bitstream encoded by Scalable Video Coding (SVC) technique. Our scheme exploits the property of SVC in which a video is encoded into spatial, temporal, and quality scalability layers. By applying our proposed protection scheme to the appropriate scalability layers we can effectively control the SVC contents completely or partially. Each layer can be flexibly protected with different encryption keys or even with different encryption algorithms. The algorithms that are used to protect each layer are described by the standardized protection description tool, which is the MPEG-21 Intellectual Property Management and Protection (IPMP) Components. In this paper, we present the design of the proposed layered SVC protection scheme, its implementation and experimental results. The experiment result shows that the proposed layered SVC protection scheme is very effective and can easily be applied.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.36.1-36.1
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• 2013

I present a simple scheme for the treatment of gravitational interactions on galactic scales. In analogy with known mechanisms of quantum field theory, I assume ad hoc that gravitation is mediated by virtual exchange particles - gravitons - with very small but non-zero masses. The scheme predicts the asymptotic flattening of galactic rotation curves, the Tully-Fisher/Faber-Jackson relations, the mass discrepancy-acceleration relation of galaxies, and the surface brightness-acceleration relation of galaxies correctly; additional (dark) mass components are not required. The well-established empirical scaling laws of Modified Newtonian Dynamics follow naturally from the model. The scheme I present is not a consistent theory of gravitation; rather, it is a toy model providing a convenient scaling law that simplifies the description of gravity on galactic scales.

• The Journal of Korea Robotics Society
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• v.14 no.2
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• pp.104-113
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• 2019

Object manipulation in cluttered environments remains an open hard problem. In cluttered environments, grasping objects often fails for various reasons. This paper proposes a novel task and motion planning scheme to grasp objects obstructed by other objects in cluttered environments. Task and motion planning (TAMP) aims to generate a sequence of task-level actions where its feasibility is verified in the motion space. The proposed scheme contains an open-loop consisting of three distinct phases: 1) Generation of a task-level skeleton plan with pose references, 2) Instantiation of pose references by motion-level search, and 3) Re-planning task based on the updated state description. By conducting experiments with simulated robots, we show the high efficiency of our scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.12
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• pp.3118-3134
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• 2013

This paper deliberates for a multimedia transmission scheme combining multiple description coding (MDC) and network coding (NC). Our goal is to take advantage from the property of MDC to provide quantized and compressed independent and identically distributed (iid) descriptions and also from the benefit of network coding, which uses network resources efficiently to recover lost data in the network. Recently, p-cycle NC has been introduced to recover and protect any lost or distorted descriptions at the receiver part exactly without need of retransmission. So far, MDC have not been explored using this type of NC. Compressed and coded descriptions are transmitted through the network where p-cycle NC is applied. P-cycle based algorithm is proposed for single and multiple descriptions lost. Results show that in the fixed bit rate, the PSNR (Peak Signal to Noise Ratio) of our reconstructed image and also subjective evaluation is improved significantly compared to previous work which is averaging method joint with MDC in order to conceal lost descriptions.

• Journal of Internet Computing and Services
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• v.10 no.4
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• pp.13-23
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• 2009

In this paper we propose an approach for localizing objects in satellite images. Our method exploits matching features based on description vectors. We applied Scale Invariant Feature Transform (SIFT) to object localization. First, we find keypoints of the satellite images and the objects and generate description vectors of the keypoints. Next, we calculate the similarity between description vectors, and obtain matched keypoints. Finally, we weight the adjacent pixels to the keypoints and determine the location of the matched object. The experiments of object localization by using SIFT show good results on various scale and affine transformed images. In this paper the proposed methods use Google Earth satellite images.