• Journal of Information Processing Systems
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• v.13 no.3
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• pp.573-589
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• 2017

Cloud computing is an attractive solution that can provide low cost storage and powerful processing capabilities for government agencies or enterprises of small and medium size. Yet the confidentiality of information should be considered by any organization migrating to cloud, which makes the research on relational database system based on encryption schemes to preserve the integrity and confidentiality of data in cloud be an interesting subject. So far there have been various solutions for realizing SQL queries on encrypted data in cloud without decryption in advance, where generally homomorphic encryption algorithm is applied to support queries with aggregate functions or numerical computation. But the existing homomorphic encryption algorithms cannot encrypt floating-point numbers. So in this paper, we present a mechanism to enable the trusted party to encrypt the floating-points by homomorphic encryption algorithm and partial trusty server to perform summation on their ciphertexts without revealing the data itself. In the first step, we encode floating-point numbers to hide the decimal points and the positive or negative signs. Then, the codes of floating-point numbers are encrypted by homomorphic encryption algorithm and stored as sequences in cloud. Finally, we use the data structure of DoubleListTree to implement the aggregate function of SUM and later do some extra processes to accomplish the summation.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.421-429
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• 2010

In this paper, in order to analyze the dynamic response of a floating crane when it lifts a heavy cargo, the boom of the floating crane is considered as an elastic beam. The boom is divided into elements based on finite element formulation and the floating frame of reference formulation and nodal coordinates are employed to model the boom as a flexible body. As an extension of the previous study, in order to consider spatial motion in waves, the coupled equations of motions of the 6 degree of freedom (DOF) floating crane and 6 DOF cargo are developed based on the flexible multibody system dynamics. The 3 dimensional deformation of the elastic boom is considered with 18 DOF. The dynamic simulation of the floating crane and the cargo is performed under regular wave conditions with various cargo weights. Finally, the effects of the elastic boom on lifting cargo are discussed by comparing the simulation results between the elastic boom and a rigid boom.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.3
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• pp.623-632
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• 2018

The object of this study is the effective utilizations of river environment management technology in the area of river reservoir water by using the technique to detect locations, and to develop algorithms on floating debris. In the floating debris detection areas(The section between the stanks of Dalsung and Gangjung-Goryeong), spectral reflections were measured on floating debris around the river: vegetation(grassland, trees), artifact(concrete, structure etc.), stream water(fresh water, turbid water, algal bloom), and simultaneously characteristics of spectral library were analyzed to river floating debris, respectively.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.230-236
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• 2001

The numerical investigations on the wave-screening characteristics of floating breakwaters are presented. The fluid motion is idealized as linearized, two dimensional potential flow. A finite element model is adopted to analyze the performance of floating breakwaters. Numerical experiments are carried out for two type floating breakwater. One is a conventional pontoon type breakwater with rectangular cross-section, and the other is a side float breakwater which consists of two rectangular shaped floats connected to each other by a frame. To improve the performance of the floating breakwaters, especially for long-period wave conditions, numerical experiments are carried out for the cases attaching the thin plates at the bottom of folats in the vertical direction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.621-627
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• 2014

In this paper, a possibility of controlling the motion of a floating wind turbine with the tuned liquid damper(TLD) is numerically investigated. First, motion of the scale model of a floating wind turbine without the TLD is predicted and its results are compared to the measured data. There are reasonably good agreements between two results, which confirms validity of the present numerical methods. Then, the effect of TLD is quantitatively assessed by comparing the prediction results for the floating wind turbine with and without the TLD. It is shown that the motion of the scale model derived by external forces can be reduced by using the TLD. On a basis of this result, a multi-layer TLD is proposed to generate larger reaction force of the TLD at the fixed target frequency. The motions of the scale model with the multi-layer TLDs are computed and compared with that of the single-layer TLD. It is shown that the multi-layer TLD generate stronger reaction force and thus more reduce the motion of the floating body than the single-layer TLD.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.28-35
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• 2011

In this paper, the wave-induced motion characteristics of a floating pendulor are investigated numerically. A floating pendulor is a movable-body-type wave energy converter. This device consists of three main parts (floater, pendulum, and damping plates). In order to obtain the hydrodynamic coefficients and wave exciting forces acting on floating bodies, a higher-order boundary element method (HOBEM) using a wave Green function is applied to the present problems. The hinged motion of a pendulum is simulated by applying the penalty method. In order to obtain a more realistic motion response for a pendulor, numerical body damping is included. First, the wave force and motion characteristics of just a floater are observed with respect to different shape parameters. Then, a coupled analysis of a floater, pendulum, and damping plates is carried out. The relative pitch velocity and wave forces acting on the floating pendulor are compared with those of a fixed pendulor.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.62.1-62.1
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• 2011

The wind can be stronger and steadier further from shore, but water depth is also deeper. Then bottom-mounted towers are not feasible, and floating turbines are more competitive. There are additional motions in an offshore floating wind turbine, which results in a more complex aerodynamics operating environment for the turbine rotor. Many aerodynamic analysis methods rely on blade element momentum theory to investigate aerodynamic load, which are not valid in vortex ring state that occurs in floating wind turbine operations. So, vortex lattice method, which is more physical, was used in this analysis. Floating platform's prescribed positions were calculated in the time domain by using floating system RAO and waves that are simulated using JONSWAP spectrum. The average value of in-plane aerodynamic force increase, but the value of out-of-plane force decrease. The maximum variation aerodynamic force abruptly increases in severe sea state. Especially, as the pitch motion of the barge platform is large, this motion should be avoided to decrease the aerodynamic load variation.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.1
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• pp.16-26
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• 2010

In this paper, we present the result of investigations pertaining to the development of the floating type photovoltaic energy generation system. Pultruded FRP has superior mechanical and physical properties compared with those of conventional structural materials. Since the FRP has an excellent corrosion-resistance and high specific strength and stiffness, the FRP material may be highly appreciated for the development of the floating type photovoltaic energy generation system. In the paper, we discussed the development concepts of the floating type photovoltaic energy generation system, briefly. The mechanical properties of the FRP structural member used in the development are investigated through the tensile and compression tests. Test results are used in the finite element analysis and the design of the system. In addition, bolted connections of the members are briefly discussed and the strengths of FRP bolted connections are estimated based on the results of experiments. The experimental results are compared with the finite element analysis results and discussed briefly. The floating type photovoltaic energy generation system is designed, fabricated, and installed successfully in site.

• Journal of the Korea Society of Computer and Information
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• v.3 no.2
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• pp.77-84
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• 1998

The continuous time signal system by development of CMOS technology have been receiving consideration attention. In this paper, Low pass filter using CMOS floating resistor have been designed with cut off frequency for speech signal processing. Especially a new floating resistor consisting entirely of CMOS devices in saturation has been developed. Linearity within $\pm$0.04% is achieved through nonlineartiy via current mirrors over an applied range of $\pm$1V. The frequency response exceeds 10MHz, and the resistors are expected to be useful in implementing integrated circuit active RC filters. The low pass filter designed using this method has simpler structure than switched capacitor filter. So reduce the chip area. The characteristics of the designed low pass filter using this method are simulated by pspice program.

• Journal of The Korean Digital Architecture Interior Association
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• v.11 no.3
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• pp.43-51
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• 2011

Currently the locations of Unpleasant Facilities, especially surrounding the site selections, have been causing conflicts among the national government, many local governments and local residents. These Unpleasant Facilities must be necessary facilities for people's modern cultural lives, but there is no obvious solution that will make us all pleasant for the locations of them until now. In this study, we'll focused on applying the Floating architecture, one of the variety of marine structures, as an alternative location of Public service facilities accommodating Unpleasant Facilities which are classified as public service facilities. Of course, there should be beforehand studies in which we can define Unpleasant Facilities and analyse the conflicts surrounding the locations of them, and we can suggest that applying the Floating architecture should be the very solution to solve all these problems together. And as our main study, we should research and develop the structure and construction, maintenance and management of the Floating architecture which will be applied to the Unpleasant Facilities, together with the environmental considerations of their emergence on the waters. In future, to secure Unpleasant Facilities sites will become more and more difficult, and so Various kinds of public service facilities will have to be the subject to the floating construction.