• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.45-52
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• 2003

Detailed flowfield resulting from the secondary sonic gas injection into a divergent section of supersonic conical nozzle has been numerically investigated. The three-dimensional flowfield associated with the bow-shock/boundary-layer interaction inside the nozzle has been solved by Reynolds-averaged Navier-Stokes equations with an algebraic and $\kappa$-$\varepsilon$ turbulence model. The numerical results have been compared with the experimental results for the identical flow conditions, and it is shown that the comparison is satisfactory Effects of different injection pressures of the secondary jet on the shock/boundary-layer interactions and the overall flow structure inside the nozzle have been investigated. The vortex structures behind the shock interaction and wall pressure variations have also been studied.

• Honam Mathematical Journal
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• v.27 no.1
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• pp.131-140
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• 2005

Lower dimensional cases of Einstein's connection were already investigated by many authors for n = 2, 3, 4, 5, 6, 7. In the following series of two papers, we present a surveyable tensorial representation of 8-dimensional Einstein's connection in terms of the unified field tensor: I. The recurrence relations in 8-g-UFT II. The Einstein's connection in 8-g-UFT In our previous paper [1], we investigated some algebraic structure in Einstein's 8-dimensional unified field theory (i.e., 8-g-UFT), with emphasis on the derivation of the recurrence relations of the third kind which hold in 8-g-UFT. This paper is a direct continuation of [1]. The purpose of the present paper is to prove a necessary and sufficient condition for a unique Einstein's connection to exist in 8-g-UFT and to display a surveyable tensorial representation of 8-dimensional Einstein's connection in terms of the unified field tensor, employing the powerful recurrence relations of the third kind obtained in the first paper [1]. All considerations in this paper are restricted to the second class only of the generalized 8-dimensional Riemannian manifold $X_8$, since the case of the first class are done in [2], [3] and the case of the third class, the simplest case, was already studied by many authors.

• Journal of Communications and Networks
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• v.15 no.2
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• pp.217-221
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• 2013

Quantum low-density parity-check (LDPC) codes based on the Calderbank-Shor-Steane construction have low encoding and decoding complexity. The sum-product algorithm(SPA) can be used to decode quantum LDPC codes; however, the decoding performance may be significantly decreased by the many four-cycles required by this type of quantum codes. All four-cycles can be eliminated using the entanglement-assisted formalism with maximally entangled states (ebits). The proposed entanglement-assisted quantum error-correcting code based on Euclidean geometry outperform differently structured quantum codes. However, the large number of ebits required to construct the entanglement-assisted formalism is a substantial obstacle to practical application. In this paper, we propose a novel class of entanglement-assisted quantum LDPC codes constructed using classical Euclidean geometry LDPC codes. Notably, the new codes require one copy of the ebit. Furthermore, we propose a construction scheme for a corresponding zigzag matrix and show that the algebraic structure of the codes could easily be expanded. A large class of quantum codes with various code lengths and code rates can be constructed. Our methods significantly improve the possibility of practical implementation of quantum error-correcting codes. Simulation results show that the entanglement-assisted quantum LDPC codes described in this study perform very well over a depolarizing channel with iterative decoding based on the SPA and that these codes outperform other quantum codes based on Euclidean geometries.

• Steel and Composite Structures
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• v.34 no.2
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• pp.241-260
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• 2020

This article presented a comprehensive model to study static buckling stability and associated mode-shapes of higher shear deformation theories of sandwich laminated composite beam under the compression of varying axial load function. Four higher order shear deformation beam theories are considered in formulation and analysis. So, the model can consider the influence of both thick and thin beams without needing to shear correction factor. The compression force can be described through axial direction by uniform constant, linear and parabolic distribution functions. The Hamilton's principle is exploited to derive equilibrium governing equations of unified sandwich laminated beams. The governing equilibrium differential equations are transformed to algebraic system of equations by using numerical differential quadrature method (DQM). The system of equations is solved as an eigenvalue problem to get critical buckling loads and their corresponding mode-shapes. The stability of DQM in determining of buckling loads of sandwich structure is performed. The validation studies are achieved and the obtained results are matched with those. Parametric studies are presented to figure out effects of in-plane load type, sandwich thickness, fiber orientation and boundary conditions on buckling loads and mode-shapes. The present model is important in designing process of aircraft, naval structural components, and naval structural when non-uniform in-plane compressive loading is dominated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.11
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• pp.57-62
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• 2019

This paper describes the prediction of eigenfrequencies due to changes in stiffness and mass in the connection area of the lap joint beam in terms of linear and torsional stiffness as well as connection length. The sensitivities of mass and stiffness in the finite element model were derived by using the first-order differential and algebraic equation and were thereafter applied to obtain new natural frequencies that were compared with theoretical exact solutions. Newly predicted natural frequencies due to only a change in stiffness were in relatively good agreement with those in lower modes for rigid joints, while further investigation was needed for flexible joints. On the other hand, only the change in mass resulted in a large discrepancy in the flexible joint case. It may be strongly anticipated that this study will provide a useful tool for estimating modal parameters by change in any design variable, such as the structural dimension, material property, or connection type for a large-scale structure, even though the proposed methodology is currently limited to a jointed beam.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.29-34
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• 2020

In this study, a sensitivity formulation was applied to analyze the dynamic response due to the effect of the excitation force for the undamped vibration of the cantilever beam. The theoretically fundamental formulations were derived considering an eigenvalue problem and its modal analysis to govern the second order algebraic differential equation in terms of the change in the modal coordinate with respect to the design parameters. A representative physical quantity pertaining to the dynamic response, that is, the rate of change in the dynamic displacement, was observed by changing the design variables, such as the cross-sectional area of the beam. The numerical results were obtained at various locations, considering the application of the external forces and observation of the dynamic displacement. When the detection position was closer to the free end of the cantilever beam, the sensitivity of the dynamic displacement was higher, as predicted through the oscillating motion of the beam. The presented findings can provide guidance to compute the dynamic sensitivity for a flexibly connected structure under dynamic excitations.

• Journal of applied mathematics & informatics
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• v.41 no.5
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• pp.1037-1046
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• 2023

The reason behind to investigate axiom systems with fewer axioms into investigate what types of results still hold, and what results become more general. Seminearrings obtained by the generalisation of nearrings and semirings. Clearly, seminearrings are common abstraction of semirings and nearrings. The aim of this work is to carry out an extensive study on algebraic structure of seminearrings and the major objective is to further enhance the theory of seminearrings in order to study the special structures of seminearrings, this work addresses some special structures of seminearrings such as right duo seminearrings. The right ideal of a seminearring need not be a left ideal. We focused on those seminear-rings which demonstrate this property. A seminearring S is right duo if every right ideal is two sided. Here we have concentrated on the seminearring which are right duo and regular. Main aim of this paper is to deal with properties of regularity in right duo seminearring. We have given some results on right duo seminearring. Followed by that, we have derived some theorems on the relation between the properties of seminearring such as regularity, semi simplicity and intra-regularity in right duo seminearring. We also illustrate this concept with suitable examples.

• Steel and Composite Structures
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• v.51 no.6
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• pp.601-617
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• 2024

This work aims to explore the static behaviour of a tapered functionally graded porous plate (FGPP) with even and uneven porosity distributions resting on two parametric elastic foundations. The plate under investigation is subjected to bi-sinusoidal loading and the edges of the plate are exposed to different combinations of edge restrictions. In order to examin the static behaviour, bending factors (BF) related to bending and normal stresses have been evaluated using classical plate theory. To achieve this, the governing equations have been derived employing the energy concept. And to solve it, the Rayleigh-Ritz method with an algebraic function has been utilised; it is simple, precise, and computationally intensive. After convergence and validation analyses, new findings are made available. The BF of the plate have been exhaustively examined to explain the influence of aspect ratios, material property index, porosity factor, taper factor, and Winkler and Pasternak stiffness. It is observed that the BF of an elastically supported FGPP are influenced by the index of material propery and the aspect ratio. Findings also indicate that the impact of porosity is more when it is spread evenly, as opposed to when it is unevenly distributed. Further, the deformed plate's structure is significantly influenced by the different thickness variations. Examination of bending characteristics of FGPP having different new cases of thickness variations with different types of porosity distribution under fifteen different mixed edge constraints is the prime novality of this work. Results presented are reliable enough to be taken into account for future studies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5A
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• pp.426-435
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• 2005

this paper, we made out blocking probability analysis for a new authentication structure for reducing the certificate acquisition time which is one of the factors that should be improved in a conventional wireless PKI. A conventional key exchange method simply performs the key exchange setup step based on discrete algebraic subjects. But the mutual-authentication procedure of wireless PKI for reducing authentication time uses an elliptical curve for a key exchange setup step. Besides, we proposed advanced handover method and blocking probability analysis for wireless PKI. Proposed handover method shows reduced handover processing time than conventional method since it can reduce CRL retrieval time. Also, we compared proposed authentication structure and conventional algorithm, and simulation results show that proposed authentication method outperforms conventional algorithm in all environment regardless of call arrival rate, queue service rate, queue size

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.657-666
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• 1998

This study presents an effective dual algorithm for the optimal design of steel structures with displacement constraints. The dual method can replace a primary optimization problem with a sequence of approximate explicit subproblems with a simple algebraic structure. Since being convex and separable, each subproblem can be solved efficiently by the dual method. Specifically, this study uses the principle of virtual work to obtain the displacement constraint equations with an explicit form and adds the linear regression equation expressing the relationships between the cross-section properties to the dual algorithm to reduce the number of design variables. Furthermore, this study deals with the discrete optimization problem to select members with the standard steel sections. Through numerical analyses, the proposed method will be compared with the conventional optimality criteria method.