• Steel and Composite Structures
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• 제49권1호
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• pp.31-45
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• 2023

The network theory studies interconnection between discrete objects to find about the behavior of a collection of objects. Also, nanomaterials are a collection of discrete atoms interconnected together to perform a specific task of mechanical or/and electrical type. Therefore, it is reasonable to use the network theory in the study of behavior of super-molecule in sport nano-scale. In the current study, we aim to examine vibrational behavior of spherical nanostructured composite with different geometrical and materials properties. In this regard, a specific shear deformation displacement theory, classical elasticity theory and analytical solution to find the natural frequency of the spherical nano-composite sport structure equipment. The analytical results are validated by comparison to finite element (FE). Further, a detail comprehensive results of frequency variations are presented in terms of different parameters. It is revealed that the current methodology provides accurate results in comparison to FE results. On the other hand, different geometrical and weight fraction have influential role in determining frequency of the structure.

• Coupled systems mechanics
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• 제12권6호
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• pp.519-530
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• 2023

This paper presents a mathematical model suitable for the calculation of laminated glass, i.e. glass plates combined with an interlayer material. The model is based on a beam differential equation for each glass plate and a separate differential equation for the slip in the interlayer. In addition to slip, the model takes into account prestressing force in the interlayer. It is possible to combine the two contributions arbitrarily, which is important because the glass sheet fabrication process changes the stiffness of the interlayer in ways that are not easily predictable and could introduce prestressing of varying magnitude. The model is suitable for reformulation into an inverse procedure for calculation of the relevant parameters. Model consisting of a system of differential-algebraic equations, proved too stiff for cases with the thin interlayer. This novel approach covers the full range of possible stiffnesses of layered glass sheets, i.e., from zero to infinite stiffness of the interlayer. The comparison of numerical and experimental results contributes to the validation of the model.

• Advances in nano research
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• 제16권2호
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• pp.175-186
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• 2024

Dynamical behaviors of one-dimensional (1D) nano-sized structures are of great importance in nanotechnology applications. Therefore, the torsional dynamic response of functionally graded nanorods which could be used to model the nano electromechanical systems or micro electromechanical systems with torsional motion about the center of twist is examined based on the theory of strain gradient nonlocal elasticity in this work. The mathematical background is constructed based on both strain gradient theory and Eringen's nonlocal elasticity theory. The equation of motions and boundary conditions of radially functionally graded nanorods are derived using Hamilton's principle and then transformed into the eigenvalue analysis by using Fourier sine series. A general coefficient matrix is obtained to assemble the Stokes' transformation. The case of a restrained functionally graded nanorod embedded in two elastic springs against torsional rotation is then deeply investigated. The effect of changing the functionally graded index, the stiffness of elastic boundary conditions, the length scale parameter and nonlocal parameter are investigated in detail.

• Smart Structures and Systems
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• 제33권3호
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• pp.243-251
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• 2024

Modeling of vibrations of a rotating pendulum with working shape memory alloy rod has been performed in the frames of a microstructural model taking into account the latent heat release, absorption and the heat exchange during direct and reverse martensitic transformation. It has been shown that the influence of the latent heat, the rate of preliminary deviation of the pendulum from the equilibrium, the rate of heating and cooling can have a significant impact on the vibrations and damping characteristics of the system.

• Earthquakes and Structures
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• 제26권3호
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• pp.219-228
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• 2024

This study examines damping modification factors (DMFs) of elastic input energy spectra corresponding to a set of 116 earthquake ground motions. Mean input energy per mass spectra and mean DMFs are presented for both considered ground motion components. Damping ratios of 3%, 5%, 10%, 20%, and 30% are used and the 5% damping ratio is considered the benchmark for DMF computations. The geometric mean DMFs of the two horizontal components of each ground motion are computed and coefficients of variation are presented graphically. The results show that the input energy spectra-based DMFs exhibit a dependence on the damping ratio at very short periods and they tend to be nearly constant for larger periods. In addition, mean DMF variation is obtained graphically for also the damping ratio, and mathematical functions are fitted as a result of statistical analyses. A strong correlation between the computed DMFs and the ones from predicted equations is observed.

• Smart Structures and Systems
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• 제33권2호
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• pp.133-143
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• 2024

Piezoelectric (PZT) actuators have been widely used in precision positioning fields for their excellent displacement resolution. However, due to the inherent characteristics of piezoelectric actuators, hysteresis has been proven to greatly reduce positioning performance. In this paper, five mathematical hysteretic models based on activation function are proposed to characterize the nonlinear hysteresis characteristics of piezoelectric actuators. Then the performance of the proposed models is verified by particle swarm optimization (PSO) algorithm and the experiment data. Thirdly, the fitting performance of the proposed models is compared with the classical Bouc-Wen model. Finally, the performance of the five proposed models in modelling hysteresis nonlinearity of piezoelectric drivers is compared, in terms of RMSE, MAPE, SAPE and operation efficiency, and relevant suggestions are given.

• Korean Journal of Mathematics
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• 제32권2호
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• pp.195-211
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• 2024

In this paper, we introduce the concept of a fuzzy lattice ordered group, which is based on a fuzzy lattice that Chon developed in his paper "Fuzzy Partial Order Relations and Fuzzy Lattice". We will also discuss fuzzy lattice-ordered groups in detail, provide several results that are analogous to the classical theory of lattice-ordered groups, and characterize the relationship between a fuzzy lattice-ordered group using its level set and support. Moreover, we define the concepts of fl-subgroups, quotients, and cosets of fl-groups and obtain some fundamental results for these fuzzy algebraic structures.

• 대한수학교육학회지:수학교육학연구
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• 제24권4호
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• pp.555-572
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• 2014

본 고는 초등 교사를 위한 한국의 12개 교사교육대학과 미국의 9개 대학의 교육과정을 비교하여, 전문직 교육으로서 한국의 수학교사교육을 위한 시사점을 찾는 것을 목적으로 한다. 교사교육의 목적, 교육과정 구성의 원리, 대학이 제공하는 강좌 구성, 그리고 수학 교수의 학습 기회의 네 가지 관점에서 교육과정을 비교 분석하였다. 두 나라의 교육과정은 교과목 지도를 특히 강조하며, 궁극적으로 초등학생들의 학력신장을 목적으로 한다. 이러한 목적하에 두 나라의 초등교사 교육과정을 전체 구조는 유사하지만, 수학교수의 학습기회라는 관점에서 교육과정이 제공하는 내용은 매우 상이한 양상을 보이고 있었다. 두 나라의 교육 및 교사에 관한 매우 다른 사회문화적 관점과 상황 때문에 다른 교사교육과정을 실행하는 것은 당연한 결과이다. 그러나, 여러 연구 결과에서 증명하듯 교수를 위한 수학지식은 학생들의 수학 성취도 및 교사들의 교수와 결정적 관련이 있다. 따라서 체계적이고 안정된 체계로서 운영되고 있는 한국의 교사교육과정의 운영에 있어서 교수를 위한 수학 지식을 중요한 요소로서 고려해야할 필요가 있다.

• 대한수학교육학회지:수학교육학연구
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• 제13권2호
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• pp.159-178
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• 2003

본 연구는 초등 수학 교재에서 정당화 과점이나 문제 해결 과정에서 활용되는 추론을 분석한 것이다. 본 연구의 분석 결과, 한 가지 전형적인 예에 대한 국소적 연역 추론이 가장 전형적인 특징으로 드러났으며, 사각형에 대한 몇 가지 명제는 연역 추론으로 정당화할 뿐 아니라 일반성을 요구하고 있는 것으로 드러났다. 또한, 열거에 의한 귀납 주론은 그리 많이 활용되고 있지 않으며, 구체물을 통한 유추가 밭이 활용되고 있음을 알 수 있었다. 전형적인 한 가지 예에 대한 설명은 Miyazaki가 제시한 예에 의한 설명이나 Semadeni가 제시한 활동 증명과 유사한 면을 지니고 있지만, 학생들의 학년 단계가 높아지더라도 계속 낮은 수준 머물러 있는 점이 문제점으로 부각되었다. 또한, 사각형의 일반적인 성질을 다루는 몇몇 명제는 Piaget의 이론에 비추어 너무 어려운 것으로 분석되었다. 본 연구에서는 이러한 문제점을 해결할 수 있는 방한으로서 보다 점진적인 추론의 지도를 제안하였는바, 전형적인 예에 대한 경험적 정당화, 전형적인 예에 대한 경험으로부터 추측의 구성, 다양한 예에 대한 추측의 타당성 조사, 일반성에 대한 스키마 형성, 함의 관계의 이해를 위한 기초 경험의 다섯 가지 수준이다.

• 대한수학회지
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• 제54권4호
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• pp.1121-1148
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• 2017

Go is an ancient game of great complexity and has a huge following in East Asia. It is also very rich mathematically, and can be played on any graph, although it is usually played on a square lattice. As with any game, one of the most fundamental problems is to determine the number of legal positions, or the probability that a random position is legal. A random Go position is generated using a model previously studied by the author, with each vertex being independently Black, White or Uncoloured with probabilities q, q, 1 - 2q respectively. In this paper we consider the probability of legality for two scenarios. Firstly, for an $N{\times}N$ square lattice graph, we show that, with $q=cN^{-{\alpha}}$ and c and ${\alpha}$ constant, as $N{\rightarrow}{\infty}$ the limiting probability of legality is 0, exp($-2c^5$), and 1 according as ${\alpha}$ < 2/5, ${\alpha}=2/5$ and ${\alpha}$ > 2/5 respectively. On the way, we investigate the behaviour of the number of captured chains (or chromons). Secondly, for a random graph on n vertices with edge probability p generated according to the classical $Gilbert-Erd{\ddot{o}}s-R{\acute{e}}nyi$ model ${\mathcal{G}}$(n; p), we classify the main situations according to their asymptotic almost sure legality or illegality. Our results draw on a variety of probabilistic and enumerative methods including linearity of expectation, second moment method, factorial moments, polyomino enumeration, giant components in random graphs, and typicality of random structures. We conclude with suggestions for further work.