• Journal of the Society of Naval Architects of Korea
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• v.45 no.6
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• pp.601-610
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• 2008

This paper deals with a new geometrical surface modeling method of forebody's hull form which is fully defined by form parameters. The complex hull form in the forebody can be modeled by the combination of three parts: bare hull, bulbous bow and blending part which connects a bare hull and a bulbous bow. All these subdomain parts are characterized by each own form parameters and constructed with simple surface model. For this, we need only 2-dimensional hull form data and then the form parameters are calculated automatically from these data. Finally, the smooth hull form surfaces are generated by parametric design and fair-skinning. In the practical point of view, we show that this new method can be useful and efficient modeling tool by applying to the hull form surface modeling of Panamax container's forebody.

• Advances in concrete construction
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• v.16 no.2
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• pp.107-117
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• 2023

Textile-reinforced concrete composite (TRC) is a new alternative material that can satisfy sustainable development needs in the civil engineering field. Its mechanical behaviour and properties have been identified from the experimental works. However, it is necessary for a numerical approach to consider the effect of the parameters on TRC's behaviour with lower analysis duration and cost related to the experiment. This paper presents obtained results of the numerical modelling for TRC composite using the cracking model for the cementitious matrix in TRC. As a result, the TRC composite exhibited a strain-hardening behaviour with the cracking phase characterized by the drops in tensile stress on the stress-strain curve. This model also showed the failure mode by multi-cracking on the TRC specimen surface. Furthermore, the parametric studies showed the effect of several parameters on the TRC tensile behaviour, as the reinforcement ratio, the length and position of the deformation measurement zone, and elevated temperatures. These numerical results were compared with the experiment and showed a remarkable agreement for all cases of this study.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.422-432
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• 2013

A System Identification method to develop parametric models linking free surface elevation and wave pressure is presented and two models are built allowing for either wave pressure or free surface elevation simulation. Linear, time invariant model structures with static nonlinearities are assumed and solutions are sought in a form of autoregressive model with extra input (ARX). An arbitrary chosen free-surface elevation and wave pressure dataset is used for estimation of the models, which are subsequently verified against datasets with similar pressure gauge depth but different free-surface elevation spectra due to different meteorological conditions. It is shown that free-surface simulation using System Identification methods can perform better than traditional linear transfer function derived from linear wave theory (LTF), while wave pressure simulation quality using presented methods is generally similar to that obtained with corrected LTF.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.385-388
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• 2004

The influence of material properties and process parameters on the strain distribution of stamping parts was studied by finite element method. For the parametric study, the investigation of variation of material properties was carried out with tensile test for a dozens of different steel sheets. The friction test for each surface and lubricants conditions are also carried out because the frictional characteristic is important parameter fur sheet metal forming. The geometry of stamping parts was measured by 3D scanner to build the tool model fer the FE analysis. As a result of analysis the major process parameter fer each automotive parts was investigated.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2760-2770
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• 2020

A model for calculation of fuel temperature profile using binary gas mixture of Helium and Xenon for gap gas conductance is proposed here. In this model, the temperature profile of a fuel pencil from fuel centreline to fuel surface has been calculated by taking into account the dilution of Helium gas filled during fuel manufacturing due to accumulation of fission gas Xenon. In this model an explicit calculation of gap gas conductance of binary gas mixture of Helium and Xenon has been carried out. A computer code Fuel Characteristics Calculator (FCCAL) is developed for the model. The phenomena modelled by FCCAL takes into account heat conduction through the fuel pellet, heat transfer from pellet surface to the cladding through the gap gas and heat transfer from cladding to coolant. The binary noble gas mixture model used in FCCAL is an improvement over the parametric model of Lassmann and Pazdera. The results obtained from the code FCCAL is used for fuel temperature calculation in 3-D neutron diffusion solver for the coolant outlet temperature of the core at steady operation at full power. It is found that there is an improvement in calculation time without compromising accuracy with FCCAL.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.8
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• pp.108-115
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• 2002

In measuring step for reverse engineering of sculptured surfaces, computer vision system is used to simplify the complicated surface by boundary edge detection method that minimizes the measuring error. The measured data by Coordinate measuring machine is clouded data points of surfaces which is segmented surface using image process. In this research, the measured data is approximated as NURBS surfaces by new suggested algorithm. The position and number of control points, selection of parametric values and compensation of weight factors are proposed. Finally, surface model is simulated and improved resulting performance is obtained.

• Smart Structures and Systems
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• v.20 no.5
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• pp.573-581
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• 2017

A vibrating double-layered nanoscale piezoelectric plate is developed accounting for the flexoelectricity and surface effects. The flexoelectricity is due to the coupling between electrical polarization and strain gradient. Applying Hamilton's principle, the governing equations and related boundary conditions are derived. Assuming suitable approximate functions, the governing equations are numerically solved for simply-supported and clamped boundary conditions. Obtained results indicate that both the flexoelectricity and surface effects possess notable impact on the vibration frequencies of the system. Only flexoelectricity yields a considerable difference between the present model and previous investigations on conventional piezoelectric nanoplates. Generally, a parametric study has been performed to examine the effects of surface elasticity, flexoelectricity, applied electric voltage, interlayer stiffness, geometrical parameters and boundary conditions on vibration frequencies of piezoelectric nanoplates.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.161-172
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• 2018

The passive control of structures using a pendulum tuned mass damper has been extensively studied in the technical literature. As the frequency of the pendulum depends only on its length and the acceleration of gravity, to tune the frequency of the pendulum with that of the structure, the pendulum length is the only design variable. However, in many cases, the required length and the space necessary for its installation are not compatible with the design. In these cases, one can replace the classical pendulum by a virtual pendulum which consists of a mass moving over a curved surface, allowing thus for a greater flexibility in the absorber design, since the length of the pendulum becomes irrelevant and the shape of the curved surface can be optimized. A mathematical model for a building with a pendular tuned mass damper and a detailed parametric analysis is conducted to study the influence of this device on the nonlinear oscillations and stability of the main system under harmonic and seismic base excitation. In addition to the circular profiles, different curved surfaces with softening and hardening characteristics are analyzed. Also, the influence of impact on energy dissipation is considered. A detailed parametric analysis is presented showing that the proposed damper can not only reduce sharply the displacements, and consequently the internal forces in the main structure, but also the accelerations, increasing user comfort. A review of the relevant aspects is also presented.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.935-937
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• 1993

This paper presents a three dimensional automatic mesh generation scheme for the boundary element method, and this scheme can be applicable to practical problems of complex shape. The geometry of the problem is expressed as an assemblage of linear Coon's surfaces, and each surface is made up of four edge curves which are defined in the form of a parametric function. Curves are automatically segmented according to their characteristics. With these segments of curves, interior points and triangular mesh elements are generated in the parametric plane using Lindholm's method, and then their projection on the real surface forms the initial mesh. The refinement of initial mesh is performed so that the discrete triangular planes are close to the real continuous surfaces. The bisection method is used for the refinement. Finally, interior points in the refined mesh are rearranged so as to make each element be close with an equilateral triangle. An attempt has been made to apply the proposed method to a DY(Deflection Yoke) model.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.343-352
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• 2016

In this study, a pre-swirl duct for the 180,000 DWT bulk carrier has been designed from a propulsion standpoint using CFD. The stern duct - designed by NMRI - was selected as the initial duct. The objective function is to minimize the value of delivered power in model scale. Design variables of the duct include duct angle, diameter, chord length, and vertical and horizontal displacements from the center. Design variables of the stators are blade number, arrangement angle, chord length, and pitch angle. A parametric design was carried out with the objective function obtained using CFD. Reynolds averaged Navier-Stokes equations have been solved; and the Reynolds stress model applied for the turbulent closure. A double body model is used for the treatment of free-surface. MRF and sliding mesh models have been applied to simulate the actuating propeller. A self-propulsion point has been obtained from the results of towing and self-propelled computations, i.e., form factor obtained from towing computation and towing forces obtained from self-propelled computations of two propeller rotating speeds. The reduction rate of the delivered power of the improved stern duct is 2.9%, whereas that of the initial stern duct is 1.3%. The pre-swirl duct with one inner stator in upper starboard and three outer stators in portside has been designed. The delivered power due to the designed pre-swirl duct is reduced by 5.8%.