• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1875-1879
• /
• 2004

This paper deals with the evaluation of several boundary conditions which are commonly used in the lattice Boltzmann equation method. 2-D channel flow(poiseui1le flow) and lid-driven cavity flow was selected as a test problem of this study, because there exist an analytic solution and previous study which could be used for a benchmarking test. It was found that lattice Boltzmann method still needs more considerations of stability and physical consistency, though it could predict the flow patterns both qualitatively and quantitatively.

• Journal of the Korean Chemical Society
• /
• v.15 no.4
• /
• pp.165-169
• /
• 1971

A general method of calculating the frequency shift due to lattice defects is developed for a one dimensional lattice with an arbitrary number of lattice points. The method is based on the Fourier transform of the equation of motion. It is shown that the frequency spectrum is determined by the roots of 5${\times}$5 secular equation, the coefficients of which depend on defects in the mass and the force constant as well as the number of the lattice points. For the limiting case of infinite lattice, the dimension of the secular equation reduces to three and the result agrees with that of Montroll and Potts.

• Steel and Composite Structures
• /
• v.24 no.2
• /
• pp.249-264
• /
• 2017

In this paper free linear vibration of lattice composite conical shells will be investigated. Lattice composite conical shell consists of composite helical ribs and thin outer skin. A smeared method is employed to obtain the variable coefficients of stiffness of conical shell. The ribs are modeled as a beam and in addition to the axial loads, endure shear loads and bending moments. Therefore, theoretical formulations are based on first-order shear deformation theory of shell. For verification of the obtained results, comparison is made with those available in open literature. Also, using FEM software the 3D finite element model of composite lattice conical shell is built and analyzed. Comparing results of analytical and numerical analyses show a good agreement between them. Some special cases as variation of geometric parameters of lattice part, effect of the boundary conditions and influence of the circumferential wave numbers on the natural frequencies of the conical shell are studied. It is concluded, when mass and the geometrical ratio of the composite lattice conical shell do not change, increment the semi vertex angle of cone leads to increase the natural frequencies. Moreover for shell thicknesses greater than a specific value, the presence of the lattice structure has not significant effect on the natural frequencies. The obtained results have novelty and can be used for further and future researches.

• The Journal of Engineering Geology
• /
• v.22 no.3
• /
• pp.323-330
• /
• 2012

The use of lattice girder is increased rapidly as a substitute for H-steel ribs at the tunnel sites in Korea. Ground loads acting on the tunnel are supported by shotcrete and lattice girders. To assess the safety of the tunnel, it is essential to obtain field measurements for the lattice girders; however, lattice girder measurements have rarely been performed at tunnel sites, and the method of measurement is not well established. In the present study we suggest a load cell method for the instrumentation of tunnels with lattice girders. Actual measurements of ground loads acting on lattice girders are presented for a specific tunnel under construction.

• Korean Journal of Materials Research
• /
• v.25 no.12
• /
• pp.713-718
• /
• 2015

A new method is proposed for the calculation of the unrelaxed surface energy of spinel ferrite. The surface energy calculation consists of (1) setting the central and computational domains in the semi-infinite real lattice, having a specific surface, and having an infinite real lattice; (2) calculation of the lattice energies produced by the associated portion of each ion in the relative domain; and (3) dividing the difference between the semi-infinite lattice energy and the infinite lattice energy on the exposed surface area in the central domain. The surface energy was found to converge with a slight expansion of the domain in the real lattice. This method is superior to any other so far reported due to its simple concept and reduced computing burden. The unrelaxed surface energies of the (100), (110), and (111) of $ZnFe_2O_4$ and $Fe_3O_4$ were evaluated by using in the semi-infinite real lattices containing only one surface. For the normal spinel $ZnFe_2O_4$, the(100), which consisted of tetrahedral coordinated $Zn^{2+}$ was electrostatically the most stable surface. But, for the inverses pinel $Fe_3O_4$, the(111), which consisted of tetrahedral coordinated $Fe^{3+}$ and octahedral coordinated $Fe^{2+}$ was electrostatically the most stable surface.

• Tunnel and Underground Space
• /
• v.15 no.4 s.57
• /
• pp.243-249
• /
• 2005

Structural behavior of lattice girders of different loading conditions, loading patterns and shapes was analyzed by MIDAS, the finite element method. Optimal condition for lattice girders was represented.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.16 no.4
• /
• pp.255-262
• /
• 2013

The boltzmann equation is based on the particle distribution function while the Navire-Stokes equation based on the continuum theory. In order to simulate free surface flow, this paper used the Lattice Boltzmann Method of which is the discretized form. The detail study on the characteristics of the Lattice Boltzmann Method for the free surface simulation was investigated. The developed code was validated with the traditional dam breaking problem by tracking the front position of the water. A basic roles of density functions in the Lattice Boltzmann Method is discussed. To have an engineering applications, the simulation is also conducted the free surface behavior with an arbitrary wall geometry.

• Journal of the Korean Society of Safety
• /
• v.7 no.2
• /
• pp.71-79
• /
• 1992

This paper presents a least-square algorithms of lattice structures and their use for adaptive prediction of time series generated from the dynamic system. As the view point of adaptive prediction, a new method of Identification of dynamic characteristics by means of estimating the parameters of linear auto regressive model is proposed. The fast convergence of adaptive lattice algorithms is seen to be due to the orthogonalization and decoupling properties of the lattice. The superiority of the least-square lattice is verified by computer simulation, then predictor coefficients are computed from the linear sequential time data. For the application to the dynamic characteristic analysis of unknown system, the transfer function of ideal system represented in frquency domain and the estimated one obtained by predicted coefficients are compared. Using the proposed method, the damping ratio and the natural frequency of a dynamic structure subjected to random excitations can be estimated. It is expected that this method will be widely applicable to other technical dynamic problem in which estimation of damping ratio and fundamental vibration modes are required.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.19 no.2
• /
• pp.171-188
• /
• 2015

In this paper, the efficient column-wise/row-wise lattice reduction (LR) updating and downdating methods are developed and their complexities are analyzed. The well-known LLL algorithm, developed by Lenstra, Lenstra, and Lov${\acute{a}}$sz, is considered as a LR method. When the column or the row is appended/deleted in the given lattice basis matrix H, the proposed updating and downdating methods modify the preconditioning matrix that is primarily computed for the LR with H and provide the initial parameters to reduce the updated lattice basis matrix efficiently. Since the modified preconditioning matrix keeps the information of the original reduced lattice bases, the redundant computational complexities can be eliminated when reducing the lattice by using the proposed methods. In addition, the rounding error analysis of the proposed methods is studied. The numerical results demonstrate that the proposed methods drastically reduce the computational load without any performance loss in terms of the condition number of the reduced lattice basis matrix.

• Proceedings of the Korea Institute of Convergence Signal Processing
• /
• 2001.06a
• /
• pp.45-48
• /
• 2001

In this paper, the characteristic of the equalizer using Lattice filter was investigated in channel ISI (Inter-Symbol Interference) in OFDM (orthogonal frequency division multiplexing) system. The equalizer using lattice filter has more fast convergence and little equalization error characteristic in two number of tap by orthogonal effect of each tap than another equalizers. The filter coefficient convergency and static BER (bit error ratio) characteristic was analysed by computer simulation. In this paper, it is shown that the equalizer using lattice filter has the better performance than a equalizer which makes use of another equalization method.