• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.30-37
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• 2006

The purpose of this study is to visualize the characteristics of ER fluids as preceding step of developing 3 port ER valves. ER fluids are made with silicone oil and 3 weight fraction starch having hydrous particles. The flow visualization of ER fluids flow is obtained by CCD camera with changing the strength of electric field to ER fluids flow. As the strength of the electric field increases, more clusters in flow are made and these clusters are though to be the reasons of the load flow rate being increased and the outlet flow rate being decreased. The ER Valves and load and outlet flow rate check method are considered to be applied to the fluid power control system.

• Journal of Information Technology Services
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• v.7 no.4
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• pp.209-219
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• 2008

Recently the number of Internet firms providing useful information like weather forecast data is growing. However most of such information is not prepared in accordance with customers' demand, resulting in relatively low customer satisfaction. To upgrade the service quality, it is recommended to devise a system for customers to get involved in the process of service production, which normally requires a huge investment on supporting computer systems like clusters. In this paper, as a way to cut down the budget for computer systems but to improve the performance, we extend the HPC cluster system to include other Internet servers working independently on the same LAN, to make use of their idle times. We also deal with some issues resulting from the extension, like the security problem and a possible deadlock caused by overload on some non-dedicated nodes. At the end, we apply the technique in the solution of some 2D grid problem.

• Journal of information and communication convergence engineering
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• v.19 no.3
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• pp.136-141
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• 2021

Research on wireless sensor networks has focused on the monitoring and characterization of large-scale physical environments and the tracking of various environmental or physical conditions, such as temperature, pressure, and wind speed. We propose a stochastic mobility model that can be applied to a MANET (Mobile Ad-hoc NETwork). environment, and apply this mobility model to a newly proposed clustering-based routing protocol. To verify its stability and durability, we compared the proposed stochastic mobility model with a random model in terms of energy efficiency. The FND (First Node Dead) was measured and compared to verify the performance of the newly designed protocol. In this paper, we describe the proposed mobility model, quantify the changes to the mobile environment, and detail the selection of cluster heads and clusters formed using a fuzzy inference system. After the clusters are configured, the collected data are sent to a base station. Studies on clustering-based routing protocols and stochastic mobility models for MANET applications have shown that these strategies improve the energy efficiency of a network.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.1
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• pp.241-248
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• 2018

A Recommender System (RS) is a system that provides optimized information to users in an over-supply situation. The key to RS is to accurately predict the behavior of the user. The Matrix Factorization (MF) method was used for this prediction in the early stage, and according to the recent SNS development, social information is additionally utilized to improve prediction accuracy. In this paper, we use RS internal trust cluster, which was overlooked in previous studies, to further improve performance and analyze the characteristics of trust clusters.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.439-446
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• 2001

The main stream of parallel programming today is using synchronous algorithms, where processor synchronization for correct computation and workload balance are essential. Overall performance of the whole system is dependent upon the performance of the slowest processor, if workload is not well-balanced or heterogeneous clusters are used. Asynchronous iteration is a way to mitigate such problems, but most of the works done so far are for shared memory systems. In this paper, we suggest and implement a parallel large sparse linear system solver that improves performance on distributed memory systems like clusters by reducing processor idle times as much as possible by asynchronous iterations.

• The Journal of the Korean Society for Microbiology
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• v.21 no.3
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• pp.363-373
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• 1986

We developed a giant colony test system with rapidly growing mycobacteria by stab-culture with a loopful inoculum of cells into Middlebrook 7H10 agar medium containing soluble extracts of the fruits of Gardenia jasminoides(7H10-crocin agar medium) and assessed the significance of the giant colony test with 28 strains of 10 clusters of rapidly growing mycobacteria classified by the simple biological 5-test characters. Of the 10 clusters of mycobacteria tested, some of strains which belonged to cluster No. 1a, 5a and 11a did grow as gravis types, whereas most of other clusters gave mitis or intermedius types in their colonial sizes at 12 days culture. By this test, pathogenic strains of M. fortuitum-chelonei complex which belonged to cluster No. 5a, b, 7a and 8a, b could be divided into gravis, intermedius and mitis colony types and the gravis ones were characterized by bluish-white "mushroom-shaped" colonies with central complexes in the texture, whereas the intermedius gave grayish-white "flower-shaped" colonies with radiated folds, but without any central complexes. The mitis colonies were characterized by grayish-white smooth or smooth mucoid colonies and were common among the clusters in their shapes. The colony of M. chelonei was bluish-white mitis type and was characterized by its hilly rhizoid colony. The gravis colony of cluster No. 1a identified as M. phlei was characterized by yellow "round straw- mat-shaped" or "chrysanthemum-shaped" colony with whole complexes in the texture, and the gravis colonies of the cluster No. 11a gave grayish-white "flower-shaped" colonies with central stamens, radiating trough and fine cup-shaped strands in the texture. The four colony types of pathogenic species of M. fortuitum-chelonei complex on 7H10-crocin agar medium were distinctive from those of other clusters of rapidly growing mycobacteria and these results indicated that the giant colony test, in conjunction with the simple 5-test characters, would be of value in the differentiation of M. fortuitum complex from other clusters of rapidly growing mycobacteria.

• Bulletin of the Korean Space Science Society
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• 2001.11a
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• pp.16-16
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• 2001

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.4
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• pp.16-25
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• 2003

A parallel computing environment based on Windows operating system was constructed and a performance test was mode in comparison with Linux based systems. The Windows 2000 cluster was composed with servers and clients connected by Fast-ethernet, within which two sub-clusters may operates together or separately. Compaq Visual Fortran complier and two MPI libraries, MPICH.NT.1.2.2 and NT-MPICHNT.1.2 were installed as computing tools. Parallel computing performance tests were carried out using two-dimensional preconditioned Navier-Stokes code to examine the dependency on the number of processors, problem size and MPI libraries, those were compared with results from Linux clusters. Results shows that a cluster based on the user-friendly Windows operating system is also useful for the parallel computing and has good performance comparable to the previous Linux clusters.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.83.1-83.1
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• 2010

Recent observations of Sloan Digital Sky Survey (SDSS) for the ugriz filters have provided the largest and the most homogeneous photometric database. Especially, the ugriz systems have been used in many telescopes, such as SDSS, CFHT, and Gemini, and will be applied next generation large telescopes. In addition, many stellar evolution models, like as PADOVA, BaSTI and DSEP, have introduced theoretical isochrones in ugriz system, to apply the isochrones into the photometry of stars in globular clusters. In this study, we transformed Yonsei-Yale($Y^2$) isochrones to ugriz photometric system and fit the isochrones to the (g-r, r), (g-i, r), and (r-i, r) CMDs of 13 globular clusters (Chun et al. 2009, Clem et al. 2008, An et al. 2008). We found that the derived ages from $Y^2$-isochrones are 1~3Gyr younger and the estimated distance moduli are 0.3mag larger than the values inferred from the other isochrones in r-band. Also, the E(B-V) are 0.02~0.04mag less than those estimated from the other models. The ages of each globular cluster estimated from $Y^2$-isochrones are 12~14Gyr and distance moduli show good agreement with previous studies. From this result, we confirmed the availability of the $Y^2$-isochrones in gri filters. However, it is a problem which will improve that E(B-V) values obtained from $Y^2$-isochrones are too small. Finally, the result of this study is expected to be used research of globular cluster in ugirz photometric system.

• Journal of The Korean Astronomical Society
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• v.48 no.6
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• pp.333-341
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• 2015

A search for hot and bright white dwarfs (WDs) in the Milky Way globular clusters M13 (NGC 6205) and M22 (NGC 6656) is carried out using the deep and homogeneous V I photometric catalog of Anderson et al. and and Sarajedini et al., based on data taken with the ACS/WFC aboard the Hubble Space Telescope (HST). V versus V − I color-magnitude diagrams (CMDs) of M13 and M22 are constructed and numerous spurious detections are rejected according to their photometric quality parameters qfit(V ) and qfit(I). In the case of M13, further radial restriction is applied to reject central stars with higher photometric errors due to central crowding. From each resultant V versus V −I CMD, sixteen and thirteen WD candidates are identified in M13 and M22, respectively. They are identified as stellar objects in the accompanying ACS/WFC images and are found to be randomly distributed across the central regions of M13 and M22. Their positions in the CMDs are in the bright part of the DA WD cooling sequences indicating that they are true WDs. In order to confirm their nature, follow-up spectroscopic observations are needed.