• Interaction and multiscale mechanics
• /
• v.4 no.2
• /
• pp.155-164
• /
• 2011

The lattice strain evolution within polycrystalline solids is influenced by the crystal orientation and grain interaction. For multi-phase polycrystals, due to potential large differences in properties of each phase, lattice strains are even more strongly influenced by grain interaction compared with single phase polycrystals. In this research, the effects of the grain interaction and crystal orientation on the lattice strain evolution in a two-phase polycrystals are investigated. Duplex steel of austenite and ferrite phases with equal volume fraction is selected for the analysis, of which grain arrangement sensitivity is confirmed in the literature through both experiment and simulation (Hedstr$\ddot{o}$m et al. 2010). Analysis on the grain interaction is performed using the results obtained from the finite element calculation based on the model of restricted slip within crystallographic planes. The dependence of lattice strain on grain interactions as well as crystal orientation is confirmed and motivated the need for more in-depth analysis.

• Journal of the Korean Institute of Navigation
• /
• v.14 no.3
• /
• pp.15-33
• /
• 1990

In recent years, propellers with various blade configurations such as highly skewed propellers are often fitted to ships from the viewpoint of reduction of vibration and noise. In the design of such propellers, design charts based on methodical series tests are to be complemented by theoretical calculations for accurate estimation of propeller open-water characteristics. The author intended to develop a method to estimate propeller open-water characteristics based on Quasi -Vortex - Lattice Method originally developed by Lan for solving planar thin wings, The Quasi - Vortex - Lattice Method has the simplicity and flexibility of Vortex - Lattice Method. Its accuracy is comparable to that of the Vortex - Lattice Method. Converged solution can be obtained with a small number of control points and further, leading edge suction force can be calculated directly. In the present paper, a numerical method to estimate propeller open-water characteristics based on the Quasi - Vortex - Lattice Method is reviewed and its application to marine propellers is described in detail. Comparison of propeller open-water characteristics obtained by the present method with experimental data showed good agreement for a wide variety of propellers including highly skewed propellers.

• Journal of the Korean Physical Society
• /
• v.73 no.10
• /
• pp.1541-1545
• /
• 2018

We study lattice thermal conductivity of $Sb_2Te_3$ using molecular dynamics simulations. The interatomic potentials are fitted to reproduce total energy and elastic constants, and phonon properties calculated using the potentials are in reasonable agreement with first-principles calculations and experimental data. Our calculated lattice thermal conductivities of $Sb_2Te_3$ decrease with temperature from 150 K to 500 K. The in-plane lattice thermal conductivity of $Sb_2Te_3$ is higher than cross-plane lattice thermal conductivity of $Sb_2Te_3$, as in the case of $Bi_2Te_3$, which is consistent with the anisotropy of the elastic constants.

• Journal of information and communication convergence engineering
• /
• v.20 no.4
• /
• pp.242-249
• /
• 2022

Classical cryptography with complex computations has recently been utilized in the latest computing systems to create secret keys. However, systems can be breached by fast-measuring methods of the secret key; this approach does not offer adequate protection when depending on the computational complexity alone. The laws of physics for communication purposes are used in quantum computing, enabling new computing concepts to be introduced, particularly in cryptography and key distribution. This paper proposes a quantum computing lattice (CQL) mechanism that applies the BB84 protocol to generate a quantum key. The generated key and a one-time pad encryption method are used to encrypt the message. Then Babai's algorithm is applied to the ciphertext to find the closet vector problem within the lattice. As a result, quantum computing concepts are used with classical encryption methods to find the closet vector problem in a lattice, providing strength encryption to generate the key. The proposed approach is demonstrated a high calculation speed when using quantum computing.

• 한국초전도학회:학술대회논문집
• /
• v.15
• /
• pp.38-38
• /
• 2005

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.3
• /
• pp.450-466
• /
• 2017

This paper defines the modified effective membrane stiffness, bending stiffness considering the directionally dependent mechanical properties and mode shape function of a composite lattice rectangular plate, which is assumed to be a Kirchhoff-Love plate. It subsequently presents an approximate method of conducting a buckling analysis of the composite lattice rectangular plate with various boundary conditions under uniform compression using the Ritz method. This method considers the coupled buckling mode as well as the global and local buckling modes. The validity of the present method is verified by comparing the results of the finite element analysis. In addition, this paper performs a parametric analysis to investigate the effects of the design parameters on the critical load and buckling mode shape of the composite lattice rectangular plate based on the present method. The results allow a database to be obtained on the buckling characteristics of composite lattice rectangular plates. Consequently, it is concluded that the present method which facilitates the calculation of the critical load and buckling mode shape according to the design parameters as well as the parametric analysis are very useful not only because of their structural design but also because of the buckling analysis of composite lattice structures.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.10a
• /
• pp.623-628
• /
• 2002

A meshfree formulation for the calculation of energy band structure is presented. The conventional meshfree shape function is modified to handle the periodicity of Bravais lattice, and applied to the calculation of real-space electronic-band structure. Numerical examples include the Kronig-Penney model potential and the empirical pseudopotentials of diamond and zinc-blonde semiconductors. Results demonstrate that the meshfree method be a promising one as a real-space technique for the calculations of diverse physical band structures.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05a
• /
• pp.65-70
• /
• 1997

Computational benchmark calculations have been performed for CANDU DUPIC fuel lattice and core using a Monte Carlo code MCNP-4B with ENDF/B-V library. The eigenvalues of the DUPIC fuel lattice have been predicted by an integral transport code WIMS-AECL using ENDF/B-V library for different burnup steps and lattice conditions. The comparison has shown that the eigenvalues match those of MCNP-4B within 0.20% $\Delta$k difference between WIMS-AECL and MCNP-4B results. The calculation of a 2-dimensional CANDU core loaded with DUPIC fuel has shown that the eigenvalue predicted by a diffusion code RFSP using lattice parameters generated by WIMS-AECL matches that of MCNP-4B within 0.12%Δk and the largest bundle power prediction error is around 7.2%.

• Journal of Mechanical Science and Technology
• /
• v.16 no.10
• /
• pp.1327-1335
• /
• 2002

The shock wave process represents an abrupt change in fluid properties, in which finite variations in pressure, temperature, and density occur over the shock thickness which is comparable to the mean free path of the gas molecules involved. This shock wave fluid phenomenon is simulated by using the finite difference lattice Boltzmann method (FDLBM). In this paper, a new model is proposed using the lattice BGK compressible fluid model in FDLBM for the purpose of speeding up the calculation as well as stabilizing the numerical scheme. The numerical results of the proposed model show good agreement with the theoretical predictions.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.561-564
• /
• 2002

For the reduction of fuel consumption of high speed, the aerodynamic drag must be reduced. In early vehicle design process, it is very important to have information about aerodynamic characteristics of design models. In this phase CFD methods are usually used to predict the aerodynamic forces. But commercial programs using turbulence models cannot give a good agreement with experimental result and have also problems with convergence. PowerFLOW employs a new technology called DIGITAL PHYSICS, which provides a different approach to simulating fluids. DIGITAL PHYSICS uses a lattice-based approach (extended from lattice-gas and lattice-Boltzmann methods) where time, space and velocity are discrete. This discrete system represents the Wavier-Stokes continuum behavior without the numerical instability Issues of traditional CFD solvers, such as convergence. In this paper, aerodynamic performance of vehicles are simulated using PowerFLOW by Exa and results are compared with experimental wind tunnel data.