• The KIPS Transactions:PartD
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• v.10D no.6
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• pp.1033-1040
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• 2003

In order to provode information services on M-Commerce, a payment solution with security function should be required. User's mobile terminals for using M-Commerce services are diversifying to cellular phone, PDA, Smart phone etc. Among them, intergration of PDA's interface and mobile connection overcomes the weak point of existing cullular phone depending on information via the internet. In this paper, the protocol for a credit card transaction on PDA using ECC is presented. Secure Card module on this protocol encrypts user's information such as private information, delivery information and credit card information and store them on PDA in order to free from inputting information whenever it is used. This scheme also offers security services on M-Commerce including authentication, confidentiality, integration, non-repudiation and so on.

• Composites Research
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• v.16 no.6
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• pp.23-32
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• 2003

Applications of advanced composite material in construction field are tending upwards and development of all composite material bridges is making progress rapidly in home and abroad due to their high strength to weight ratio. This paper formulated the dynamic responses of the laminated composite structures subjected to moving load and analyzed the various dynamic behaviors using the finite element method. The nondimensionalized natural frequencies of a simply supported square-laminated composite plate are considered for verifications. Mode superposition and Newmark direct integration method are applied for moving load analysis. For structural models, dynamic magnification factor calculated for various velocities of the moving load and displacements characteristics of laminated composite structures due to the moving load are investigated theoretically Numerical results are presented to study the effects of lamination scheme, stacking sequence, and fiber angle for laminated composite structures during moving load. The various results on moving load and lamination through numerical analysis will present an important basic data for development and grasp the behavior of all composite material bridges.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.33-42
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• 2003

This paper deals with the FEM analysis of nonlinear sloshing of incompressible, invicid and irrotational flow in two dimensional rectangular tank. We use laplace equation based on potential theory as governing equation. For large amplitude sloshing motion, kinematic and dynamic free surface conditions derived from Bernoulli equation are applied. This problem is solved by FEM using 9-node elements. For the time integration and accurate velocity calculation, we introduce predictor-corrector time marching scheme and least square method. Also, numerical stability in tracking of free surface is obtained by direct calculation of free surface location to time variation. Numerical results of sloshing induced by harmonic excitations, while comparing with those of linear theory and references, prove the accuracy and stability. After verification of our program, we analyze sloshing response characteristics to the fluid height and the excitation amplitude.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.311-320
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• 2005

In this paper an enhanced quadratic finite element for static and dynamic analysis of plate structures is presented. The performance of a proposed plate element is improved by the coupled use of non conforming displacement modes, the selective integration scheme, and the assumed shear strain fields. An efficient direct modification method is also applied to this element to solve the problem such as failure of the patch test due to the adoption of non conforming modes. The proposed quadratic finite element does not show any spurious mechanism and does not produce shear locking phenomena even with distorted meshes. It is shown that the results obtained by this element converged to analytical solutions very rapidly tough numerical tests for standard benchmark problems. It is also noted that this element is applicable to transient dynamic analysis of Mindlin plates.

• Structural Engineering and Mechanics
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• v.24 no.6
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• pp.709-725
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• 2006

In this paper the buckling and post-buckling behavior of slender bars under self-weight are studied. In order to study the post-buckling behavior of the bar, a geometrically exact formulation for the non-linear analysis of uni-directional structural elements is presented, considering arbitrary load distribution and boundary conditions. From this formulation one obtains a set of first-order coupled nonlinear equations which, together with the boundary conditions at the bar ends, form a two-point boundary value problem. This problem is solved by the simultaneous use of the Runge-Kutta integration scheme and the Newton-Raphson method. By virtue of a continuation algorithm, accurate solutions can be obtained for a variety of stability problems exhibiting either limit point or bifurcational-type buckling. Using this formulation, a detailed parametric analysis is conducted in order to study the buckling and post-buckling behavior of slender bars under self-weight, including the influence of boundary conditions on the stability and large deflection behavior of the bar. In order to evaluate the quality and accuracy of the results, an experimental analysis was conducted considering a clamped-free thin-walled metal bar. As this kind of structure presents a high index of slenderness, its answers could be affected by the introduction of conventional sensors. In this paper, an experimental methodology was developed, allowing the measurement of static or dynamic displacements without making contact with the structure, using digital image processing techniques. The proposed experimental procedure can be used to a wide class of problems involving large deflections and deformations. The experimental buckling and post-buckling behavior compared favorably with the theoretical and numerical results.

• Structural Engineering and Mechanics
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• v.15 no.1
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• pp.83-114
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• 2003

A new simple 3-node triangular flat-shell element with standard nodal DOF (6 DOF per node) is proposed for the linear and geometrically nonlinear analysis of very thin to thick plate and shell structures. The formulation of element GT9 (Long and Xu 1994), a generalized conforming membrane element with rigid rotational freedoms, is employed as the membrane component of the new shell element. Both one-point reduced integration scheme and a corresponding stabilization matrix are adopted for avoiding membrane locking and hourglass phenomenon. The bending component of the new element comes from a new generalized conforming Kirchhoff-Mindlin plate element TSL-T9, which is derived in this paper based on semiLoof constrains and rational shear interpolation. Thus the convergence can be guaranteed and no shear locking will happen. Furthermore, a simple hybrid procedure is suggested to improve the stress solutions, and the Updated Lagrangian formulae are also established for the geometrically nonlinear problems. Numerical results with solutions, which are solved by some other recent element models and the models in the commercial finite element software ABAQUS, are presented. They show that the proposed element, denoted as GMST18, exhibits excellent and better performance for the analysis of thin-think plates and shells in both linear and geometrically nonlinear problems.

• Coupled systems mechanics
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• v.9 no.2
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• pp.163-182
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• 2020

Coupled thermo-mechanical analysis of reinforced concrete slab at elevated temperatures from a fire accounting for nonlinear thermal parameters is carried out. The main focus of the paper is put on a one-way continuous reinforced concrete slab exposed to fire from the single (bottom) side as the most typical working condition under fire loading. Although contemporary techniques alongside the fire protection measures are in constant development, in most cases it is not possible to avoid the material deterioration particularly nearby the exposed surface from a fire. Thereby the structural fire resistance of reinforced concrete slabs is mostly influenced by a relative distance between reinforcement and the exposed surface. A parametric study with variable concrete cover ranging from 15 mm to 35 mm is performed. As the first part of a one-way coupled thermo-mechanical analysis, transient nonlinear heat transfer analysis is performed by applying the net heat flux on the exposed surface. The solution of proposed heat analysis is obtained at certain time steps of interest by α-method using the explicit Euler time-integration scheme. Spatial discretization is done by the finite element method using a 1D 2-noded truss element with the temperature nodal values as unknowns. The obtained results in terms of temperature field inside the element are compared with available numerical and experimental results. A high level of agreement can be observed, implying the proposed model capable of describing the temperature field during a fire. Accompanying thermal analysis, mechanical analysis is performed in two ways. Firstly, using the guidelines given in Eurocode 2 - Part 1-2 resulting in the fire resistance rating for the aforementioned concrete cover values. The second way is a fully numerical coupled analysis carried out in general-purpose finite element software DIANA FEA. Both approaches indicate structural fire behavior similar to those observed in large-scale fire tests.

• Journal of Digital Convergence
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• v.9 no.3
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• pp.213-223
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• 2011

Today, information resource management is key task in the data-centre as like as NCIA(National computing integration Agency of Korea). In IRM, the server's performance is one of the core elements, it must be importantly managed during whole of system life cycle. As first step of such management is in purchase phase, it is very important that the optimum specification is determined. The server's specification contains such as performance of core, criteria for performance verification, minimum cores, etc. There is constant controversy concerning the minimum cores. In this article, we present criteria for determination of the minimum cores that considered three aspects: (1) Costly aspect as TCO(Total Cost of Ownership, (2) Environmental aspect as Green IT (3) Technical aspect as RAS(Reliability, Availability, Serviceability) functionality. Finally, we propose scheme to ideally determinate the minimum cores.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.24-30
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• 2007

Latching optical switches and optical logic gates with AND or OR, and the INVERT functionality are demonstrated, for the first time, by the monolithic integration of a differential typed vertical cavity laser with depleted optical thyristor (VCL-DOT) structure with a low threshold current of 0.65 mA, a high slope efficiency of 0.38 mW/mA, and high sensitivity to input optical light. Many kinds of logic functions (AND, OR, NAND, NOR, and INVERT) are experimentally demonstrated using a differential switching operation scheme changing the intensity of a reference input beam without any changes of electrical circuits.

• Journal of the Korea Society of Computer and Information
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• v.19 no.5
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• pp.27-35
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• 2014

The characteristics of today's health care industry, based on the state of the art IT can be represented as a paradigm of human-oriented ubiquitous and accessible as possible by U-Health care. In addition, the healthcare industry is information and communication technologies (ICT) developments regarding the many advances and applications based on the research being carried out actively. Medical information system has been developed toward combining information systems of medical IT and it sets its sights on the fusion of developed IT and u-healthcare system. So changing distributed medical information systems into a safe PHR integrated system based on IaaS cloud computing is suggested in order to forge u-healthcare system with the times in this paper. Our experimental results show that our proposed system increased the data access time by about 24% and reduces the waiting time for processing service by about 4.3% over the web-based PHR.