• Advances in nano research
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• v.10 no.3
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• pp.271-280
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• 2021

The present work deals with an investigation on longitudinal wave propagation in nanobeams made of graphene sheets, for the first time. The nanobeam is modelled via a higher-order shear deformation theory accounts for both higher-order and thickness stretching terms. The general nonlocal strain gradient theory including nonlocality and strain gradient characteristics of size-dependency in order is used to examine the small-scale effects. This model has three-small scale coefficients in which two of them are for nonlocality and one of them applied for gradient effects. Hamilton supposition is applied to obtain the governing motion equation which is solved using a harmonic solution procedure. It is indicated that the longitudinal wave characteristics of the nanobeams are significantly influenced by the nonlocal parameters and strain gradient parameter. It is shown that higher nonlocal parameter is more efficient than lower nonlocal parameter to change longitudinal phase velocities, while the strain gradient parameter is the determining factor for their efficiency on the results.

• Advances in nano research
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• v.13 no.3
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• pp.297-312
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• 2022

Coughing and breath shortness are common symptoms of nano (small) cell lung cancer. Smoking is main factor in causing such cancers. The cancer cells form on the soft tissues of lung. Deformation behavior and wave vibration of lung affected when cancer cells exist. Therefore, in the current work, phase velocity behavior of the small cell lung cancer as a main part of the body via an exact size-dependent theory is presented. Regarding this problem, displacement fields of small cell lung cancer are obtained using first-order shear deformation theory with five parameters. Besides, the size-dependent small cell lung cancer is modeled via nonlocal stress/strain gradient theory (NSGT). An analytical method is applied for solving the governing equations of the small cell lung cancer structure. The novelty of the current study is the consideration of the five-parameter of displacement for curved panel, and porosity as well as NSGT are employed and solved using the analytical method. For more verification, the outcomes of this reports are compared with the predictions of deep neural network (DNN) with adaptive optimization method. A thorough parametric investigation is conducted on the effect of NSGT parameters, porosity and geometry on the phase velocity behavior of the small cell lung cancer structure.

• Advances in concrete construction
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• v.16 no.5
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• pp.243-254
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• 2023

Microtubules in the cell are influenced by internal and external stimulation and play an important part in conveying protein substances and in carrying out medications to the intended targets. Waves are produced during these functions and in order to control the biological cell functions, it is important to know the wave velocities of microtubules. Owing to cylindrical shell shaped and mechanically elastic and orthotropic, cylindrical shell model based on gradient elasticity theory has been used. Wave velocities of the protein microtubule are carried out by considering Love's thin shell theory and Navier solution. Also the effect of size parameter and other variables on the results are investigated.

• Current Optics and Photonics
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• v.7 no.5
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• pp.537-544
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• 2023

Differential phase contrast (DPC) microscopy, a central quantitative phase imaging (QPI) technique in cell biology, facilitates label-free, real-time monitoring of intrinsic optical phase variations in biological samples. The existing DPC imaging theory, while important for QPI, is grounded in paraxial diffraction theory. However, this theory lacks accuracy when applied to high numerical aperture (NA) systems that are vital for high-resolution cellular studies. To tackle this limitation, we have, for the first time, formulated a nonparaxial DPC imaging equation with a transmission cross-coefficient (TCC) for high NA DPC microscopy. Our theoretical framework incorporates the apodization of the high NA objective lens, nonparaxial light propagation, and the angular distribution of source intensity or detector sensitivity. Thus, our TCC model deviates significantly from traditional paraxial TCCs, influenced by both NA and the angular variation of illumination or detection. Our nonparaxial imaging theory could enhance phase retrieval accuracy in QPI based on high NA DPC imaging.

• Journal of the Korean Institute of Gas
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• v.14 no.3
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• pp.46-52
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• 2010

Flame propagation velocity is the one of the main mechanism of the stabilization of triple flame. To quantity the triple flame propagation velocity, Bilger presents the triple flame propagation velocity, depending on the mixture fraction gradient, based on the laminar jet flow theory. However, in spite of these many analyses, there has not been any attempt to quantify the triple flame propagation velocity with the flame radius of curvature and scalar dissipation rate. In the present research, there was discussion about the radius of flame curvature and scalar dissipation rate, through the numerical study. As a result, we have known that the flame propagation velocity was linear with the nozzle exit velocity and scalar dissipation rate decreases nonlinearly with the flame propagation velocity and radius of curvature of flame increases linearly. Also radius of curvature of flame decreases non-linearly with the scalar dissipation rate. Therefore, we ascertained that there was corelation among the scalar dissipation rate, radius of flame curvature and flame propagation velocity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.267-273
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• 2008

The circular cylinder pipes are used in the many industrial areas. In this paper, the acoustic wave propagation in the pipe containing a gas is researched. First of all, the theory for the coupled acoustic wave propagation in a pipe is investigated. Acoustic wave propagation in pipe can not be occurred independently between the wave of the fluid and the shell. It requires complicated analysis. However, as a special case, the coupled wave in a high density pipe containing a light density medium is corresponded closely to the uncoupled in-vacuo shell waves and to the rigid-walled duct fluid waves. The coincidence frequencies of acoustic and shell modes contribute to the predominant energy transmission. The coincidence frequency means the frequency corresponding to the coincidence of the wavenumber in both acoustic and shell. In this paper, it is assumed that the internal medium is much lighter than the pipe shell. After the uncoupled acoustic wave in the internal medium and uncoupled shell wave are considered, the coincidence frequencies are found. The analysis is successfully confirmed by the verification of the experiment using the real long steel pipe. This work verifies that the coupled wave characteristic of the shell and the fluid is occurred as predominant energy transmission at the coincidence frequencies.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.1 no.1
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• pp.35-39
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• 2008

In this paper, we have developed a propagation loss prediction software with GUI (Graphic User Interface) functions, based on the geometrical ray optics model, which can predict radio parameters for the deployment of wireless indoor network. The program has two numerical modules consisted with electrical image and ray launching methods to implement UTD theory. The simulated results are compared with reported data measured in the foreign building environments for office and '一' type corridor, and measured and simulated results for the propagation loss agree with each other quite well. Simulation results for '一' type corridor and 'T' type corridor propagation environment are shown for reference.

• Geotechnical Engineering
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• v.10 no.3
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• pp.119-134
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• 1994

In order to assess the possibility of using steel fibers in the fissured ciays, uniaxial compression tests were performed on both unreinforced and reinforced clay samples containing a pre-existing crack. Test results showed that the steel fiber reinforcement increased resistance to cracks initiation and their propagation, and therefore increased both stress at crack growth initiation and peak stress at failure. The increase in resistance to cracks initiation and their propagation was related to the arresting or deflecting the crack propagation in clay samples by steel fibers. A theoretical interpretation of experimental results was made using fracture mechanics theory and pull-out mechanisms in fiber reinforced materials. It was revealed that the steel fibers had bridging effect through their pull-out action that caused an increased resistance to the propagation of the cracks in the samples. The predicted pull-out force based on theoretical analyses agreed reasonably well with the measured values obtained from pull-out tests.

• Steel and Composite Structures
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• v.42 no.3
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• pp.397-405
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• 2022

The existing researches on the dynamics of the fluid-conveying pipes only focus on stability and vibration problems, and there is no literature report on the wave propagation of the fluid-conveying pipes. Therefore, the purpose of this paper is to explore the propagation characteristics of longitudinal and flexural waves in the fluid-conveying pipes. First, it is assumed that the material properties of the fluid-conveying pipes vary based on a power function of the thickness. In addition, it is assumed that the material properties of both the fluid and the pipes are closely depended on temperature. Using the Euler-Bernoulli beam equation and based on the linear theory, the motion equations considering the thermal-mechanical-fluid coupling is derived. Then, the exact expressions of phase velocity and group velocity of longitudinal waves and bending waves in the fluid-conveying pipes are obtained by using the eigenvalue method. In addition, we also studied the free vibration frequency characteristics of the fluid-conveying pipes. In the numerical analysis, we successively studied the influence of temperature, functional gradient index and liquid velocity on the wave propagation and vibration problems. It is found that the temperature and functional gradient exponent decrease the phase and group velocities, on the contrary, the liquid flow velocity increases the phase and group velocities. However, for vibration problems, temperature, functional gradient exponent parameter, and fluid velocity all reduce the natural frequency.

• Structural Engineering and Mechanics
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• v.85 no.6
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• pp.729-742
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• 2023

It is a recent attraction to the mechanical scientists to investigate state of wave propagation, buckling and vibration in the sport balls to observe the importance of different parameters on the performance of the players and the quality of game. Therefore, in the present study, we aim to investigate the wave propagation in handball game ball in term of mass of the ball and geometrical parameters wit incorporation of the viscoelastic effects of the ball material into account. In this regard, the ball is modeled using thick shell structure and classical elasticity models is utilized to obtain the equation of motion via Hamilton's principle. The displacement field of the ball model is obtained using first order shear deformation theory. The resultant equations are solved with the aid of generalized differential quadrature method. The results show that mass of the ball and viscoelastic coefficient have considerable influence on the state of wave propagation in the ball shell structure.