• Biomaterials and Biomechanics in Bioengineering
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• v.5 no.1
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• pp.1-10
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• 2020

This paper investigated vibrational behavior of the osteon as bone unit in the different situations. This study can lead to increase our knowledge of our body. In this paper free vibration of the osteon with considering it as composite material has been studied. The effect of numbers of lamellae and radius of those on natural frequency of osteon are subtle; while thickness of lamellae have decreasing trend on natural frequency of osteon. The presence of nerve and blood in haversian canal change trend of natural frequency, absolutely. Using the nonlocal strain gradient theory(NSGT) leads to effectiveness of scale parameter on equations of motion and the obtained results. The governing equations are derived by Hamilton's principles. A parametric study is presented to examine the effect of various parameters on vibrational behaviour of osteon. The results can also be regarded as a benchmark in vibration analysis behavior of osteon as bone unite.

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.5 no.2
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• pp.94-98
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• 1987

Multi-Valued(MV) sequential logic circuits are proposed which are free from HAZARD. In this paper, HAZARD is classified Function and Logic HAZARD, and MV switching function in which they are eliminated is described. Also, the basic MV memory elements which can be realized without HAZARD are presented, so that suggest the realizability in the large-scale MV logic system based on these elements.

• Structural Engineering and Mechanics
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• v.3 no.5
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• pp.511-525
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• 1995

The differential equations governing in-plane free vibrations of the elastic, catenary arch with rotatory inertia are derived in Cartesian coordinates. Frequencies and mode shapes are computed numerically for such arches with unsymmetric axes, for both clamped-clamped and hinged-hinged end constraints. The lowest four natural frequency parameters are reported, with and without rotatory inertia, as a function of three nondimensional system parameters; the span to cord length ratio e, the slenderness ratio s, and the rise to cord length ratio f. Experimental measures of frequencies and mode shapes for several laboratory-scale catenary models serve to validate the theoretical results.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.37-52
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• 2020

This paper investigates the free and forced longitudinal vibration of a double nanorod system using doublet mechanics theory. The doublet mechanics theory is a multiscale theory spanning between lattice dynamics and continuum mechanics. Equations of motion and boundary conditions for the double nanorod system are obtained using Hamilton's principle. Clamped-clamped and clamped-free boundary conditions are considered. Frequencies and dynamic displacements are determined to demonstrate the effects of length scale parameter of considered material and geometry of the nanorods. It is shown that frequencies obtained by the doublet mechanics theory are bounded from above (van Hove singularity) and unlike classical elasticity theory doublet mechanics theory predicts finite number of modes depending on the length of the nanotube. The present doublet mechanics results have been compared to molecular dynamics, experimental and nonlocal theory results and good agreement is observed between the present and other mentioned results. The difference between wave frequencies of graphite is less than 10% between doublet mechanics and experimental results near to the end of the first Brillouin zone.

• Structural Engineering and Mechanics
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• v.77 no.4
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• pp.535-547
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• 2021

This paper concerns with free torsional vibration analysis of size dependent circular nanobars with von kármán type nonlinearity. Although review of the literature suggests several studies employing nonlocal elasticity theory to investigate linear torsional behavior, linear/nonlinear transverse vibration and buckling of the nanoscale structures, so far, no study on the nonlinear torsional behavior of the nanobars, considering the size effect, has been reported. This study employs nonlocal elasticity theory along with a variational approach to derive nonlinear equation of motion of the nanobar. Then, the nonlinear equation is solved using the elliptic functions to extract the natural frequencies of the structure under fixed-fixed and fixed-free end conditions. Finally, the natural frequencies of the nanobar under different nanobar lengths, diameters, nonlocal parameters, and amplitudes of vibration are reported to illustrate the effect of these parameters on the vibration characteristics of the nanobars. In addition, the phase plane diagrams of the nanobar for various cases are reported.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.35-49
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• 2021

This paper presents a direct numerical simulation of turbulent flows over a bump in an open channel to examine the turbulence characteristics near divergent waves emanating from the bump and to investigate the interaction of the turbulences with the divergent waves. To verify the reliability of the simulations, the mean velocity profile and root-mean-square of velocity fluctuations are compared with previous data. The anisotropic invariant maps show that the ratio of the streamwise to spanwise velocity fluctuations plays an important role in characterizing the anisotropic nature of the separated shear layer behind the bump in the vicinity of the free surface. The vortex identification discloses a large-scale streamwise vortical structure from the mean velocity field and a cluster of small coherent structures from the instantaneous velocity field, which are responsible for the anisotropic characteristics of the turbulence beneath the free surface.

• Steel and Composite Structures
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• v.46 no.5
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• pp.637-647
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• 2023

Nonlinear free vibration and stability responses of a carbon nanotube reinforced composite beam under temperature rising are investigated in this paper. The material of the beam is considered as a polymeric matrix by reinforced the single-walled carbon nanotubes according to different distributions with temperature-dependent physical properties. With using the Hamilton's principle, the governing nonlinear partial differential equation is derived based on the Euler-Bernoulli beam theory. In the nonlinear kinematic assumption, the Von Kármán nonlinearity is used. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The critical buckling temperatures, the nonlinear natural frequencies and the nonlinear free response of the system is obtained. The effect of different patterns of reinforcement on the critical buckling temperature, nonlinear natural frequency, nonlinear free response and phase plane trajectory of the carbon nanotube reinforced composite beam investigated with temperature-dependent physical property.

• Steel and Composite Structures
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• v.46 no.3
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• pp.335-344
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• 2023

This investigation presents nonlinear free vibration of a carbon nanotube reinforced composite beam based on the Von Kármán nonlinearity and the Euler-Bernoulli beam theory The material properties of the structure is considered as made of a polymeric matrix by reinforced carbon nanotubes according to different material distributions. The governing equations of the nonlinear vibration problem is delivered by using Hamilton's principle and the Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The nonlinear natural frequency and the nonlinear free response of the system is obtained with the effect of different patterns of reinforcement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.769-770
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• 2007

• Journal of the Korea Fashion and Costume Design Association
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• v.19 no.4
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• pp.105-121
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• 2017

This study determined the reality of how middle school students are doing with their free learning semester and what they think about it. Also, the study looked at how many parts of Home Economics and the area of clothing curriculum are being taken and, especially, how many parts of this curriculum content are being required as free learning semester activities. This study aims to not only develop free learning semester activities according to student demand but also at providing a basic resource that can help activate the area of clothing curriculum in subject of Home Economics. In short: 1) Middle school students are attending activities such as career exploration activities, student selection activities, club activities, arts activities and physical education activities thoroughly through the free learning semester. These mostly take place in school and most of the students were taught by teachers from their own school. 2) The students are aware that the free learning semester's activities are helpful for them. The most helpful part was that it reduces the load they get from the school's exam and also the fact that they can investigate areas in which they are interested. 3) The number of students who have already taken or are taking activities related to Home Economics were 145, which is about 1/3 of the 451 students overall. The area where the most of the activities were held out of those activities related to Home Economics was the domain of food while the clothing curriculum accounted for a very small part compared to it. 4) The study found that need for a clothing curriculum for middle school student free learning semesters was about 2.79 on a scale from 1 to 5. The areas of most interest in this topic were highly related to 'making and mending clothes'.