• Investigative Magnetic Resonance Imaging
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• v.15 no.1
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• pp.48-56
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• 2011

Purpose : The aim of this study is to measure the typical MR variables such as $T_1$- and $T_2$-relaxation times according to morphological characteristics of gold nanopartides as a preliminary study to perform theragnosis using local heating by gold nanopartides. Materials and Methods : Two types of gold nanoparticles were used. Spheres were synthesized by various methods and stirring speed. Rods were synthesized by adding various concentrations of sphere nanopartides. Gold nanopartides were mixed with 2% agarose gel at 1:1 ratio and then signals were acquired using a 1.5T MRI. For the measurements of $T_1$-and $T_2$-relaxation times, TR and TE were varied, respectively. The results were acquired through $T_1$ and $T_2$ curves based on the intensities of MR image using self-developed software. And Statistical analysis was performed. Results : $T_1$ times were measured 1.86 sec and 2.08 sec for sphere and rod, respectively. On the other hands, $T_2$ times were measured 57 ms and 35.45 ms for sphere and rod. Conclusion : The changes of the MR variables according to the morphological characteristics of the gold nanopartides were confirmed. Optimal MR imaging conditions can be obtained by choosing proper TR and TE according to the type of nanoparticles.

• The KIPS Transactions:PartA
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• v.17A no.3
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• pp.159-166
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• 2010

In this paper, to obtain the Minimum Spanning Tree (MST) from the graph with several nodes having the same weight, I applied both Bor$\dot{u}$vka and Kruskal MST algorithms. The result came out to such a way that Kruskal MST algorithm succeeded to obtain MST, but not did the Prim MST algorithm. It is also found that an algorithm that chooses Inter-MSF MWE in the $2^{nd}$ stage of Bor$\dot{u}$vka is quite complicating. The $1^{st}$ stage of Bor$\dot{u}$vka has an advantage of obtaining Minimum Spanning Forest (MSF) with the least number of the edges, and on the other hand, Kruskal MST algorithm has an advantage of always obtaining MST though it deals with all the edges. Therefore, this paper suggests an Hybrid MST algorithm which consists of the merits of both Bor$\dot{u}$vka's $1^{st}$ stage and Kruskal MST algorithm. When applied additionally to 6 graphs, Hybrid MST algorithm has a same effect as that of Kruskal MST algorithm. Also, comparing the algorithm performance speed and capacity, Hybrid MST algorithm has shown the greatest performance Therefore, the suggested algorithm can be used as the generalized MST algorithm.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.853-858
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• 2005

Recently, various novel numerical models based on Navier-Stokes equation have been developed for calculating wave motions in the sea with coastal or ocean structures. Among those models, Volume Of Fluid (VOF) method might be the most popular one, and it has been used for numerical simulations of wave motions including complicated phenomena of wave breakings. VOF method, however, needs enormous computation time and large computational storage memories in general, thus it is practically difficult to use this method for calculations in the case of random waves because long and stable computation (e.g for more than 100 significant wave periods) is required to obtain statistically meaningful results. On the other hand if the wave motion is potential motion, Boundary Element Method (BEM), which is a much faster and more accurate method than VOF method, can be effectively used. The aim of this study is to develop a new efficient model applicable to calculations of wave motion and/or wave-structure interactions under random waves. To achieve this, a strictly combined BEM-VOF model has been developed by making the best use of both methods' merits; VOF method is used in a restricted fluid domain around a structure where complicated phenomena of wave breakings may exist, and BEM is used in the other domains far from the disturbance where the wave motion may be assumed to be potential. The verification of the model was performed with numerical results for Stokes' 5th order wave propagation and a random wave propagation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.180-186
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• 2020

ICT convergence using smart livestock is that in the first-generation dairy smart farm model, each device made by several manufacturers uses its own communication method, limiting the mutual operation of each device. This study uses a model based on open control technology to secure interoperability of existing ICT devices and to manage data efficiently. The open integrated control derived from this process is the software interface structure of Open API. It is an observer that serves as real-time data collection according to the communication method of ICT devices and sensors located at each end. It consists of a broker that connects and transmits to the upper integrated management server. As a result of the performance analysis through verification of two first-generation dairy smart farm model sites, the average daily milk production increased compared to the previous year (farm A 5.13%, farm B 1.33%, p<0.05). Cow days open (DO) was reduced by 17.5% on farm A and 13.3% for farm B(p<0.05). Cows require an adaptation period after the introduction of the ICT device, but if continuous effects are observed, the effect of production can be expected to increase gradually.

• Journal of Korean Society of Forest Science
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• v.103 no.2
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• pp.264-269
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• 2014

The aim of this study was to determine the current distribution area of Robinia pseudoacacia habitat and to estimate its stand yield as well as its carbon stocks. In order to do so, the area of R. pseudoacacia distribution is obtained based on the large-scaled forest type map (1:5,000). Also, Weibull diameter distribution model is used to predict the yield of R. pseudoacacia stands. In addition, carbon emission factor is applied to calculate carbon stocks and removals. To obtain the stand yield of R. pseudoacacia, we developed estimation equation considering growth factors of the stand, e.g. mean diameter, the basal area, maximum and minimun diameter and etc. and tested it to ensure accuracy. Consequently, estimation equation derived from all growth factors have shown significance that could also be used for analysis. Site index was also established to determine the productivity of the forestland that later turned out to be ranging from 16 to 22. Based on these results, stand yield tables were drawn up. R. pseudoacacia is widely distributed in inland areas of Gyeongsang, Chungcheong and Gyeonggi provinces which covers total area of 26,770 ha. And when it is converted into carbon stocks, it amounts to 2,517,598tC with annual carbon uptake of 3.76tC/ha which is comparable to Querqus species that is known to storer large amounts of carbon. Therefore, R. pseudoacacia is also expected to serve as a viable carbon pool that would contribute to the mitigation of climate change. Furthermore, stand yield tables, an outcome of this survey would assist not only in proper management but also in sustainable management policy of R. pseudoacacia.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.582-594
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• 2004

In school PC labs or other educational purpose PC labs with a few dozens of PCs, computers are configured in a distributed architecture so that they are set up, maintained and upgraded separately. As an alternative to the distributed architecture, we can consider a thin-client computing environment. In a thin-client computing environment, client side devices provide mainly I/O functions with user friendly GUI and multimedia processing support whereas remote servers called terminal server provide computing power. In order to support many clients in the environment, a cluster of terminal servers can be configured. In this architecture, it is difficult due to the characteristics of terminal session persistence and different pattern of computing usage of users so that the utilization of terminal server resources becomes low. To overcome this disadvantage, we propose an adaptive terminal cluster where terminal servers ,ire partitioned into groups and a terminal server in a light-loaded group can be dynamically reassigned to a heavy-loaded group at run time. The proposed adaptive scheme is compared with a generic terminal service cluster and a group based non-adaptive terminal server cluster. Experimental results show the effectiveness of the proposed scheme.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.975-988
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• 2017

Since 2000, about 750 cubesats have been launched as of August 2017 and development and the launch of cubesat increased exponentially. Since standard of cubesat has been proposed in 1999, cubesats have grown considerably beyond the scope of education and technology verification to commercial use in the area of space exploration and earth observation, and the variety of cubesat mission and type has increased recently. In Korea, some universities and individuals have independently developed cubesats since 2000, and cubesat contests which were organized by KARI and sponsored by Ministry of Science and ICT from 2012 highly contributed to cubesat development in Korea. In addition, domestic institutes such as KARI, KASI started to develop cubesats for space science and exploration mission. Nineteen cubesats have been progressed or completed in development until now. In this paper, we present the technical trend and describe all cubesats in Korea.

• Composites Research
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• v.18 no.1
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• pp.45-54
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• 2005

The delamination in the filament-wound composite flywheel rotor often lowers the performance of the flywheel energy storage system. A conventional ring type hub usually causes tensile stresses on the inner surface of the composite rotor, resulting in lowering the maximum rotational speed of the rotor. In this work, the stress and strain distributions within a hybrid composite rotor were derived from the two-dimensional governing equation with the specified boundary conditions, and an optimum pressure at the inner surface of the rotor was proposed to minimize the strength ratio and maximize the storage energy. A split type hub was introduced to apply the calculated optimum pressure at the inner surface, and a spin test was performed up to 40,000 rpm to demonstrate the performance of the split type hub with radial and circumferential strains measured using a wireless telemetry system. From the analysis and the test, it was found that the split type hub successfully generates a compressive pressure on the inner surface of the rotor, which can enhance the performance of the composite rotor by lowering the strength ratio within the rotor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.527-534
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• 2015

This paper presents an integrated chassis control with electronic stability control (ESC) and active front steering (AFS) under lateral force constraint on AFS. The control yaw moment is calculated using a sliding mode control. The tire forces generated by ESC and AFS are determined using weighted pseudo-inverse based control allocation (WPCA) in order to generate the control yaw moment. On a low friction road, AFS is not effective when the lateral tire forces of front wheels are easily saturated. To solve problem, the lateral force of AFS is limited to its maximum and the braking of ESC is applied with WPCA. To evaluate the effectiveness of the proposed method, a simulation was performed on the vehicle simulation package, $CarSim^{(R)}$. From the simulation, it was verified that the proposed method could enhance the maneuverability and lateral stability if the lateral force of AFS exceeds its maximum.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.423-428
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• 2015

To identify locations and causes of interference among parts of an indoor air-conditioning unit, a 3D tolerance analysis was performed and optimized with respect to assembly gaps and the tolerance of each part. The maximum value of the defect rate resulting from the tolerance analysis was found to be 72.6 at the assembly portion of the body and drain. The maximum displacement caused by the thermal deformation during a heating operation was calculated to be approximately 1 mm by using finite element analysis (FEA). Therefore, it is possible that an interference among the assembled parts occurs. The tolerance of the drain was modified by the results of the sensitivity analysis. As a result, the defect rate was greatly reduced to 0.03. Through the FEA results of the indoor air-conditioning unit, it was shown that the improved tolerance of the drain decreased the interference among the assembled parts even though thermal deformation occurs during operation.