• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.47-48
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• 2012

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4044-4062
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• 2016

We investigate the optimization of energy consumption in Mobile Cloud environment in this paper. In order to optimize the energy consumed by the CPUs in mobile devices, we put forward using the asymptotic time complexity (ATC) method to distinguish the computational complexities of the applications when they are executed in mobile devices. We propose a multi-scale scheme to quantize the channel gain and provide an improved dynamic transmission scheduling algorithm when offloading the applications to the cloud center, which has been proved to be helpful for reducing the mobile devices energy consumption. We give the energy estimation methods in both mobile execution model and cloud execution model. The numerical results suggest that energy consumed by the mobile devices can be remarkably saved with our proposed multi-scale scheme. Moreover, the results can be used as a guideline for the mobile devices to choose whether executing the application locally or offloading it to the cloud center.

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.24-34
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• 2009

The latest trend of development for submarine oil field is caused by the drained oil and gas for ground field, and FPSO is a keyword as the development for submarine oil field. FPSO (Floating Production Storage Offloading) is a kind of vessel type have a topside system for production of oil and gas and store them until the oil or gas can be offloaded onto a tanker or transported through a pipeline. Prior to the introduction of reinforcement under the pull-in winch on the STP extended top as the object of this paper, the technical background shall be introduced such as FPSO and the system and main equipments for STP as follows. The original structural concept for reinforcement of pull-in winch on the STP top and extended structure on moonpool was proposed by buyer's engineering team but it was much modified and improved in accordance with builder's fabrication and construction method.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.153-160
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• 2010

This paper deals with the topology optimized design of the riser support structures for floating production storage and offloading units (FPSOs) under global and local loading conditions. For a preliminary study and validation of the numerical approach, a simplified plate under static loading is first evaluated with the representative topology optimization methods, the Homogenization Design Method (HDM) and Density Method (DM) or Simple Isotropic Material with Penalization (SIMP). In the context of the corresponding riser support structures, the design problem is formulated such that structure shapes based on design domain variables are determined by minimizing the compliance subject to a mass target, considering the stress criterion. An initial design model is generated based on an actual FPSO riser support configuration. The topology optimization results present improved design performances under various loading conditions, while staying within the allowable limit of the offshore area.

• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.20-33
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• 2010

The paper deals with strength design of a riser support installed on floating production storage and offloading (FPSO) vessel under various loading conditions - operation, extreme, damaged, one line failure case (OLFC) and installation. The design problem is formulated such that thickness sizing variables are determined by minimizing the weight of a riser support structure subject to stresses constraints. The initial design model is generated based on an actual FPSO riser support specification. The finite element analysis (FEA) is conducted using MSC/NASTRAN, and optimal solutions are obtained via moving least squares method (MLSM) in the context of response surface based approximate optimization. For the meta-modeling of inequality constraint functions of stresses, a constraint-feasible moving least squares method (CF-MLSM) is used in the present study. The method of CF-MLSM, compared to a conventional MLSM, has been shown to ensure the constraint feasibility in a case where the approximate optimization process is employed. The optimization results present improved design performances under various riser operating conditions.

• Journal of Ocean Engineering and Technology
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• v.32 no.1
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• pp.51-61
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• 2018

In this study, the operability of an FLBT (floating LNG bunkering terminal) was evaluated experimentally. Model tests were conducted in the KRISO (Korea Research Institute of Ships and Ocean Engineering) ocean engineering basin. An FLBT, an LNG carrier, and two LNG bunkering shuttles were moored side by side with mooring ropes and fenders. Two white-noise wave cases, one irregular wave case, and various regular wave cases were generated. The relative local motions between each LNG loading arm and its corresponding manifold in the initial design configuration were calculated from measured 6-DOF motions at the center of gravity of each of the four vessels. Furthermore, the locations of the LNG loading arms and manifolds were varied to minimize the relative local motions.

• Journal of Ocean Engineering and Technology
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• v.23 no.5
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• pp.9-14
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• 2009

The green water on deck has many harmful effects on the vessel in rough seas such as damages to hull structures, damages to cargos, increase of the downtime, decrease of the stability, and so on. Floating Production Storage and Offloading vessels (FPSOs) are operated in a specific location and are normally positioned to meet mostly head or bow waves in order to reduce the roll motions. But this makes FPSOs more vulnerable to green water around the bow region therefore the bow shape should be properly designed to mitigate the green water damage. In this paper, experimental results in regular head waves for three kinds of bow shapes are compared and some design considerations are proposed, with the building a database for computational fluid dynamics (CFD) validation in mind.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.32-38
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• 2015

In this paper, we propose a smallcell local caching algorithm under user's context in smallcell environment. The proposed system reduces traffic to core network and the network cost, but increases it's performance. The proposed algorithm precache suitable files using smallcell's regional characteristics and target's personality. It can adjusts a storage allocation to make effective usage of our limited cache storage capacity. In order to evaluate the performance of the proposed cache algorithm, we define the cache efficiency, the decrement of core network traffic. The simulation results show that the proposed algorithm can improve performance by about 200% compared to existing web cache scheme.

• KIISE Transactions on Computing Practices
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• v.20 no.10
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• pp.555-560
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• 2014

This paper proposes the data security technology for the desktop virtualization environment using the separated software execution method. In the virtual environment where allocates separate VMs to the users, there is a benefit that the programs in one guest machine are isolated from the programs running in another guest machine, whereas in the separated execution environment that supports application virtualization, the isolation is not offered and it causes the data security problem because the applications are executed by the one root privilege in the server. To solve this problem, we provides the data security method using the server storage filter, the viewer filter, and the file mapping table in this paper.

• Journal of Broadcast Engineering
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• v.19 no.1
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• pp.24-30
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• 2014

This study investigates computing offloading effect of cloud in real-time video personal broadcast service, whose server is mobile device. Mobile device does not have enough computing resource for encoding video. The computing burden is offloaded to cloud, which has abundant resources in terms of computing, power, and storage compared to mobile device. By reducing computing burden, computation energy can be saved while transmission data amount increases because of decreasing compression efficiency. This study shows that the optimal operation point can be found adaptively to time-varying LTE communication condition result of tradeoff analysis between offloaded computation burden and increase in amount of transmitted data.