• Journal of Power Electronics
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• v.17 no.4
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• pp.991-1003
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• 2017

The conventional sliding mode control (CSMC) has a number of problems. It may cause dc output voltage ripple and it cannot guarantee the robustness of the whole system for a matrix rectifier (MR). Furthermore, the existence of a filter can decrease the input power factor (IPF). Therefore, a novel global sliding mode control (GSMC) based on a hyperbolic tangent function with IPF compensation for MRs is proposed in this paper. Firstly, due to the reachability and existence of the sliding mode, the condition of the matrix rectifier's robustness and chattering elimination is derived. Secondly, a global switching function is designed and the determination of the transient operation status is given. Then a SMC compensation strategy based on a DQ transformation model is applied to compensate the decreasing IPF. Finally, simulations and experiments are carried out to verify the correctness and effectiveness of the control algorithm. The obtained results show that compared with CSMC, applying the proposed GSMC based on a hyperbolic tangent function for matrix rectifiers can achieve a ripple-free output voltage with a unity IPF. In addition, the rectifier has an excellent robust performance at all times.

• Communications of the Korean Mathematical Society
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• v.20 no.3
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• pp.443-456
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• 2005

Let G be a Lie group, let L(G) be its Lie algebra, and let exp : $L(G){\rightarrow}G$ denote the exponential mapping. For $S{\subseteq}G$, we define the tangent set of S by $L(S)\;=\;\{X\;{\in}\;L(G)\;:\;exp(tX)\;\in\;S\;for\;all\;t\;{\geq}\;0\}$. We say that a semigroup S is strictly infinitesimally generated if S is the same as the semigroup generated by exp(L(S)). We find a tangent set of the semigroup of all non-singular totally positive matrices and show that the semigroup is strictly infinitesimally generated by the tangent set of the semigroup. This generalizes the familiar relationships between connected Lie subgroups of G and their Lie algebras

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.601-625
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• 2014

Based on continuum mechanics and the principle of virtual displacements, incremental total Lagrangian formulation (T.L.) and incremental updated Lagrangian formulation (U.L.) were presented. Both T.L. and U.L. considered the large displacement stiffness matrix, which was modified to be symmetrical matrix. According to the incremental updated Lagrangian formulation, small strain, large displacement, finite rotation of three dimensional Timoshenko fiber beam element tangent stiffness matrix was developed. Considering large displacement and finite rotation, a new type of tangent stiffness matrix of the beam element was developed. According to the basic assumption of plane section, the displacement field of an arbitrary fiber was presented in terms of nodal displacement of centroid of cross-area. In addition, shear deformation effect was taken account. Furthermore, a nonlinear finite element method program has been developed and several examples were tested to demonstrate the accuracy and generality of the three dimensional beam element.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.143-154
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• 2014

An improved method for evaluating effective buckling length of semi-rigid frame with inelastic behavior is newly proposed. Also, generalized exact tangential stiffness matrix with rotationally semi-rigid connections is adopted in previous studies. Therefore, the system buckling load of structure with inelastic behaviors can be exactly obtained by only one element per one straight member for inelastic problems. And the linearized elastic stiffness matrix and the geometric stiffness matrix of semi-rigid frame are utilized by taking into account 4th terms of taylor series from the exact tangent stiffness matrix. On the other hands, two inelastic analysis programs(M1, M2) are newly formulated. Where, M1 based on exact tangent stiffness matrix is programmed by iterative determinant search method and M2 is using linear algorithm with elastic and geometric matrices. Finally, in order to verify this present theory, various numerical examples are introduced and the effective buckling length of semi-rigid frames with inelastic materials are investigated.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.785-801
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• 1997

Reinforced Concrete beams with tension and compression softening material constitutive laws are studied. Energy-based and non-local regularisation techniques are presented and applied to a R.C. element. The element characteristics (sectional tangent stiffness matrix, element tangent stiffness matrix restoring forces) are directly derived from their symbolic expressions through numerical integration. In this way the same spatial grid allows us to obtain a non-local strain estimate and also to sample the contributions to the element stiffness matrix. Three examples show the spurious behaviors due to the strain localization and the stabilization effects given by the regularisation techniques, both in the case of tension and compression softening. The possibility to overestimate the ultimate load level when the non-local strain measure is applied to a non softening material is shown.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1
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• pp.26-32
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• 2008

UBSS (unde-determined blind source separation) is composed of the stages of BMMR (blind mixing matrix recovery) and BSR (blind source recovery). Generally, these two stages are executed using the sparseness of the observed data, and their performance is influenced by the accuracy of the measure of the sparseness. In this paper, as introducing the measure of the sparseness using the Gini coefficient to BSR stage, we obtained more accurate measure of the sparseness and better performance of BSR than methods using the $l_1$-norm, $l_q$-norm, and hyperbolic tangent, which was confirmed via computer simulations.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.8
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• pp.323-330
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• 1985

Dielectric loss tangent and ac dielectric strength of GFRP (Glass Fiber Reinforced Plastics, G-10)was investigated as parameters of mechanical and thermal stresses, in order to study the basic dielectrical characteristics of composite insulating materials. The dielectric loss tangent was increased and the ac dielectric strength was decreased with increase in the mechanical stresses beyond the mechanical yield point on account of fiber-matrix debonding, but the dielectric constant was not varied sigificantly. the dielectric strength of G-10 was about 2 MV/cm and the dielectric constant was about 4.8.

• Computational Structural Engineering
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• v.10 no.2
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• pp.139-148
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• 1997

A finite element method is programmed to analyse the nonlinear behavior of axisymmetric structures. The lst order Mindlin shell theory which takes into account the transversal shear deformation is used to formulate a conical two node element with six degrees of freedom. To evade the shear locking phenomenon which arises in Mindlin type element when the effect of shear deformation tends to zero, the reduced integration of one point Gauss Quadrature at the center of element is employed. This method is the Updated Lagrangian formulation which refers the variables to the state of the most recent iteration. The solution is searched by Newton-Raphson iteration method. The tangent matrix of this method is obtained by a finite difference method by perturbating the degrees of freedom with small values. For the moment this program is limited to the analyses of non-linear elastic problems. For structures which could have elastic stability problem, the calculation is controled by displacement.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Journal of the Korean Data and Information Science Society
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• v.18 no.1
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• pp.229-235
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• 2007

Measures of leverage in nonlinear regression models are discussed by extending the leverage in linear regression models. The connection between measures of leverage and nonlinearity of the models are explored. Illustrative example based on real data is presented.