• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1272-1290
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• 2013

Privacy-preserving collaborative filtering schemes are becoming increasingly popular because they handle the information overload problem without jeopardizing privacy. However, they may be susceptible to shilling or profile injection attacks, similar to traditional recommender systems without privacy measures. Although researchers have proposed various privacy-preserving recommendation frameworks, it has not been shown that such schemes are resistant to profile injection attacks. In this study, we investigate two memory-based privacy-preserving collaborative filtering algorithms and analyze their robustness against several shilling attack strategies. We first design and apply formerly proposed shilling attack techniques to privately collected databases. We analyze their effectiveness in manipulating predicted recommendations by experimenting on real data-based benchmark data sets. We show that it is still possible to manipulate the predictions significantly on databases consisting of masked preferences even though a few of the attack strategies are not effective in a privacy-preserving environment.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.118-125
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• 1995

This paper presents the result of a computational study on the wake characteristics of two tanker models. i.e HSVA and DYNE hull forms. The focus of the study is on the distributions of axial. radial and tangential velocities of the two hull forms in way of the propeller, especially over the propeller disk. The effect of bilge vortices on the velocity distribution is also concerned. For the computation of stern and wake flows of the two hull forms. the incompressible Reynolds-Averaged Navier-Stokes(RANS) equations are numerically solved by the use of a second order finite difference method, which employs a four stage Runge-Kutta scheme with a residual averaging technique and the Baldwin-Lomax model. The calculated pressure distributions on the hull surface and the axial. radial and tangential velocity distributions over the propeller disk are presented for the two hull forms. Finally, the result of wake analysis for the computed wake distribution over the propeller disk is given in comparison with those for the experimental wake distribution for the both hull forms.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.132-133
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• 2005

A study to evaluate the fire extinguishing performance of the water mist system inside simulated machinery spaces according to IMO MSC/Circ.668 was performed. Fire tests were conducted inside a compartment having a area 100$m^2$(10m${\times}$10m) with a ceiling height of 10m and door opening of 2m${\times}$2m in size. Test fuels were used heptane, diesel, wood crib and mineral oil. Water mist nozzles were installed downward at ceiling and horizontally at bilge area. All fires in the test were extinguished within 15minutes of system activation and there was no reignition or fire spread.

• Structural Engineering and Mechanics
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• v.51 no.2
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• pp.267-276
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• 2014

Wharfs are essential to shipping and support very large gravity loads on both a short-term and long-term basis which cause quite large seismic internal forces. Therefore, these structures are vulnerable to seismic activities. As they are supported on vertical and/or batter piles, soil-pile interaction effects under earthquake events have a great importance in seismic resistance which is not yet fully understood. Seismic design codes have become more stringent and suggest the use of new design methods, such as Performance Based Design principles. According to Turkish Code for Coastal and Port Structures (TCCS 2008), the interaction between soil and pile should somehow be considered in the nonlinear analysis in an accurate manner. This study aims to explore the lateral load carrying capacity of recently designed wharf structures considering soil-pile interaction effects for different soil conditions. For this purpose, nonlinear structure analysis according to TCCS (2008) has been performed comparing simplified and detailed modeling results.

• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.21-38
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• 2009

The use of multi scale modeling concepts and simulation techniques to study the destabilization of an ultrathin layer of oxide interface between a metal substrate and the surrounding environment is considered. Of particular interest are chemo-mechanical behavior of this interface in the context of a molecular-level description of stress corrosion cracking. Motivated by our previous molecular dynamics simulations of unit processes in materials strength and toughness, we examine the challenges of dealing with chemical reactivity on an equal footing with mechanical deformation, (a) understanding electron transfer processes using first-principles methods, (b) modeling cation transport and associated charged defect migration kinetics, and (c) simulation of pit nucleation and intergranular deformation to initiate the breakdown of the oxide interlayer. These problems illustrate a level of multi-scale complexity that would be practically impossible to attack by other means; they also point to a perspective framework that could guide future research in the broad computational science community.

• Journal of Korean Neurosurgical Society
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• v.57 no.3
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• pp.211-214
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• 2015

Ganglioneuromas are benign tumors. Surgical excision is the treatment of choice with very good prognosis. However, neuroblastomatous malignant transformation of ganglioneuromas was previously reported. We report a patient with spinal neuroblastoma recurrent from a ganglioneuroblastoma after disease free survival of 13 years. This is one of the rare examples of spinal neuroblastoma and to our knowledge the second case report with malignant transformation from a ganglioneuroblastoma or a ganglioneuroma. The present case is the only report in the literature with further genetic investigations.

• Natural Product Sciences
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• v.5 no.4
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• pp.177-180
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• 1999

The ethanolic extracts of two shallow water sponge species collected from the Aegean Sea afforded thirteen terpenoids in total, two of which were determined to be new. The structure elucidation of the terpenoids was carried out by spectroscopic techniques and comparison with related authentic compounds. The terpenoids have also been assayed for antibacterial activity. This is the first report about the metabolites isolated from the marine sponges of the Aegean Sea in Turkey.

• Journal of KSNVE
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• v.6 no.1
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• pp.27-34
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• 1996

In this paper, design sensitivity of vibration displacement and acceleration is computed and design sensitivity, the derivative information of responses with respect to design perameters, is used as a design guidance tool to reduce the vibration. First, the harmonic vibration analysis of deck and simplified ship structures is performed by finite element method and secondly continuum disign sensityivity for excessive dynamic response is computed by continuum method. Both the direct and modal frequency response methods for the finite element analysis are adopted. Sensitivities of structural components such as upper plate, side wall, bilge, bottom plate are compared and the reductionof vibration is obtained by the proper increase of thickness of each component.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.425-432
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• 2012

Viscous flow fields of side-by-side arranged two-dimensional floating bodies are numerically simulated by a Navier-Stokes equation solver. Two identical bodies with a narrow gap are forced to heave and sway motions. Square and rounded bilge hull forms are compared to find out the effects of vortex shedding on damping force. Wave height, force RAOs, added mass and damping coefficients including non-diagonal cross coefficients are calculated and a similarity between the wave height and force RAOs is discussed. CFD which can take into account of viscous damping and vortex shedding shows better results than linear potential theory.

• Bulletin of the Society of Naval Architects of Korea
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• v.25 no.3
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• pp.13-18
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• 1988

Three-dimensional turbulent flows over ship sterns are measured by using the hot-wire anemometer and static holes in the wind tunnel. A conventional stern and a barge-type stern are adopted for the present study. Three components of mean velocities, pressures on the hull and six components of Reynolds stresses are measured. Longitudinal velocity contours are more parallel to the hull surface and weak bilge vortices appear on the barges type stern rather than the conventional stern. Those viscous flow patterns may have close relations to improvements of the resistance and propulsion performance, which have been verified in the towing tests. Measured data files are valuable for the ensuing numerical studies.