• Coupled systems mechanics
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• v.7 no.1
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• pp.5-25
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• 2018

A fully-coupled thermodynamic-based transient finite element formulation is proposed in this article for electric, magnetic, thermal and mechanic fields interactions limited to the linear case. The governing equations are obtained from conservation principles for both electric and magnetic flux, momentum and energy. A full-interaction among different fields is defined through Helmholtz free-energy potential, which provides that the constitutive equations for corresponding dual variables can be derived consistently. Although the behavior of the material is linear, the coupled interactions with the other fields are not considered limited to the linear case. The implementation is carried out in a research version of the research computer code FEAP by using 8-node isoparametric 3D solid elements. A range of numerical examples are run with the proposed element, from the relatively simple cases of piezoelectric, piezomagnetic, thermoelastic to more complicated combined coupled cases such as piezo-pyro-electric, or piezo-electro-magnetic. In this paper, some of those interactions are illustrated and discussed for a simple geometry.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.69-77
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• 1998

Linear displacement accuracy is one of the most important factors that determine machine tool accuracy The laser interferometer has been usually recommended for the measurement of linear displacement accuracy. In this paper, microcomputer aided measurement and compensation system has been developed for the pitch error in a CNC machine tool. For accurate pitch error calculation. the analysis code for the pitch error has been also implemented according to the international standards (ISO). The PC based automatic compensation system for the pitch error is also implemented. A new algorithm for calculating optimum value for pitch error compensation is proposed, minimizing the deviation at each target points. The development system has been applied to a practical CNC maching center and the performance has been demonstrated.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1231-1238
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• 2015

In this paper, we proposed an efficient algorithm using Node monitoring (NM) and Piecewise Linear Function Approximation(: NP) for reducing the complexity of LDPC code decoding. Proposed NM algorithm is based on a new node-threshold method together with message passing algorithm. Piecewise linear function approximation is used to reduce the complexity of the algorithm. This new algorithm was simulated in order to verify its efficiency. Complexity of our new NM algorithm is improved to about 20% compared with well-known methods according to simulation results.

• Bulletin of the Korean Mathematical Society
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• v.57 no.1
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• pp.37-50
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• 2020

Linear complementary dual (LCD) codes are linear codes that intersect with their dual trivially. LCD cyclic codes have been known as reversible cyclic codes that had applications in data storage. Due to a newly discovered application in cryptography, interest in LCD codes has increased again. Although LCD codes over finite fields have been extensively studied so far, little work has been done on LCD codes over chain rings. In this paper, we are interested in structure of LCD codes over chain rings. We show that LCD codes over chain rings are free codes. We provide some necessary and sufficient conditions for an LCD code C over finite chain rings in terms of projections of linear codes. We also showed the existence of asymptotically good LCD codes over finite chain rings.

• Steel and Composite Structures
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• v.4 no.6
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• pp.453-469
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• 2004

In this article, a genetic algorithm based optimum design method is presented for non-linear steel frames with semi-rigid connections. The design algorithm obtains the minimum weight frame by selecting suitable sections from a standard set of steel sections such as European wide flange beams (i.e., HE sections). A genetic algorithm is employed as optimization method which utilizes reproduction, crossover and mutation operators. Displacement and stress constraints of Turkish Building Code for Steel Structures (TS 648, 1980) are imposed on the frame. The algorithm requires a large number of non-linear analyses of frames. The analyses cover both the non-linear behaviour of beam-to-column connection and $P-{\Delta}$ effects of beam-column members. The Frye and Morris polynomial model is used for modelling of semi-rigid connections. Two design examples with various type of connections are presented to demonstrate the application of the algorithm. The semi-rigid connection modelling results in more economical solutions than rigid connection modelling, but it increases frame drift.

• Bulletin of the Korean Mathematical Society
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• v.60 no.5
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• pp.1237-1252
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• 2023

A fundamental problem in coding theory is to find n_q(k, d), the minimum length n for which an [n, k, d]_q code exists. We show that some q-divisible optimal linear codes of dimension 4 over 𝔽_q, which are not of Belov type, can be constructed geometrically using hyperbolic quadrics in PG(3, q). We also construct some new linear codes over 𝔽_q with q = 7, 8, which determine n₇(4, d) for 31 values of d and n₈(4, d) for 40 values of d.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.457-466
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• 2003

In this paper, the numerical finite element formulations were derived for the linearized Navier-Stokes' equations with assumptions of two-dimensional incompressible, homogeneous viscous fluid field, and small oscillation and the FAMD (Fluid Added Mass and Damping) code was developed for practical applications calculating the fluid added mass and damping. In formulations, a fluid domain is discretized with C$\^$0/-type quadratic quadrilateral elements containing eight nodes using a mixed interpolation method, i.e., the interpolation function for the velocity variable is approximated by a quadratic function based on all eight nodal points and the interpolation function for the pressure variable is approximated by a linear function based on the four nodal points at vertices. Using the developed code, the various characteristics of the fluid added mass and damping are investigated for the concentric cylindrical shell and the actual hexagon arrays of the liquid metal reactor cores.

• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.176-182
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• 2000

This paper presents methods for dynamic stall control utilizing an optimization approach. Unsteady aerodynamic sensitivity code is developed using a direct diffentiation method from a discrete two-dimensional unsteady compressible Navier-Stokes code including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating a response for a period of time. Unsteady sensitivity derivative of the objective function is calculated by the sensitivity code, and optimization is conducted using a linear line search method at every physical time level. Examples of dynamic stall control utilizing airfoils nose radius or maximum thickness variation show very satisfactory results.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.127-135
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• 1994

In this paper we propose an EWLD(Enhanced Weighted Levenshtein Distance) algorithm to organize code-string pattern matching linear array processor based on the mappting to an one-dimensional array from a two-dimensional matching matrix, and design a processing element(PE) of the processor, N PEs are required instead of NS02T in the processor because of the mapping. Data input and output between PEs and all internal operations of each PE are performed in bit-serial fashion. The bit-serial operation consists of the computing of word distance (WD) by comparison and the selection of optimal code transformation path, and takes 22 clocks as a cycle. The layout of a PE is designed based on the double metal $1.5\mu$m CMOS rule. About 1,800 transistors consistute a processing element and 2 PEs are integrated on a 3mm$\times$3mm sized chip.

• Journal of Ocean Engineering and Technology
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• v.10 no.2
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• pp.13-19
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• 1996

For fatigue analsis of offshore structures, existing methods have been reviewed and a computer code has been developed on PC. As methods to estimate the probabillity distribution of the fatigue stress, three methods(the deterministic method, the stochastic method, and the simplified method) are used in this code, to choose the appropriate method according to the situations. This code estimates damage ratios, fatigue lives, and probabilities of fatigue failure considering scatterness of SN-data, based on linear damage rule and SN-curves. Also, allowable stress for the design extreme wave can calculated by the simplified method.