• Mass Spectrometry Letters
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• v.10 no.4
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• pp.117-122
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• 2019

This study demonstrated the sensitivity of electron capture dissociation mass spectrometry (ECD-MS) to probe subtle conformational changes in gaseous melittin ions induced by the substitution of an amino acid. ECD-MS was performed for triply and quadruply-protonated melittin and its variants obtained by a single amino acid substitution, namely, D-Pro14, Pro14Ala, and Leu13Ala. Although native triply-protonted melittin showed only a few peptide backbone cleavage products, the D-Pro14 and Pro14Ala variants exhibited extensive backbone fragments, suggesting the occurrence of a significant structural or conformational change induced by a single amino acid substitution at Pro14. On the contrary, the substitution at Leu13, namely Leu13Ala (+3), did not cause significant changes in the ECD backbone fragmentation pattern. Thus, the sensitivity of ECD-MS is demonstrated to be good enough to probe the aforementioned conformational change in melittin.

• Structural Engineering and Mechanics
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• v.33 no.6
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• pp.697-708
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• 2009

Stresses are solved for two parallel cracks in an infinite orthotropic plate during passage of incoming shock stress waves normal to their surfaces. Fourier transformations were used to reduce the boundary conditions with respect to the cracks to two pairs of dual integral equations in the Laplace domain. To solve these equations, the differences in the crack surface displacements were expanded to a series of functions that are zero outside the cracks. The unknown coefficients in the series were solved using the Schmidt method so as to satisfy the conditions inside the cracks. The stress intensity factors were defined in the Laplace domain and were inverted numerically to physical space. Dynamic stress intensity factors were calculated numerically for selected crack configurations.

• Structural Engineering and Mechanics
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• v.23 no.2
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• pp.163-175
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• 2006

In this paper, the dynamic response of a piezoelectric layer with a penny-shaped crack is investigated. The piezoelectric layer is subjected to an axisymmetrical action of both mechanical and electrical impacts. Two kinds of crack surface conditions, i.e., electrically impermeable and electrically permeable, are adopted. Based upon integral transform technique, the crack boundary value problem is reduced to a system of Fredholm integral equations in the Laplace transform domain. By making use of numerical Laplace inversion the time-dependent dynamic stress and electric displacement intensity factors are obtained, and the dynamic energy release rate is further derived. Numerical results are plotted to show the effects of both the piezoelectric layer thickness and the electrical impact loadings on the dynamic fracture behaviors of the crack tips.

• Structural Engineering and Mechanics
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• v.54 no.4
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• pp.809-827
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• 2015

In this paper, seismic energy response of inelastic steel structures under earthquake excitations is investigated. For this purpose, a numerical procedure based on nonlinear dynamic analysis is developed by considering material, geometric and connection nonlinearities. Material nonlinearity is modeled by the inversion of Ramberg-Osgood equation. Nonlinearity caused by the interaction between the axial force and bending moment is also defined considering stability functions, while the geometric nonlinearity caused by axial forces is described using geometric stiffness matrix. Cyclic behaviour of steel connections is taken into account by employing independent hardening model. Dynamic equation of motion is solved by Newmark's constant acceleration method in the time history domain. Energy response analysis of space frames is performed by using this proposed numerical method. Finally, for the first time, the distribution of the different energy types versus time at the duration of the earthquake ground motion is obtained where in addition error analysis for the numerical solutions is carried out and plotted depending on the relative error calculated as a function of energy balance versus time.

• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.341-350
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• 2020

The present investigation is concerned with two dimensional deformation in a non local thermoelastic solid with two temperatures due to time harmonic sources. The nonlocal thermoelastic solid is homogeneous with the effect of two temperature parameters. Fourier transforms are used to solve the problem. The bounding surface is subjected to concentrated and distributed sources. The analytical expressions of displacement, stress components and conductive temperature are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of nonlocal parameter and frequency on the components of displacements, stresses and conductive temperature. Some special cases are also deduced from the present investigation.

• Structural Engineering and Mechanics
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• v.57 no.1
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• pp.91-103
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• 2016

This investigation is concerned with the disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperature, in the presence of the combined effects of Hall currents and magnetic field due to normal force of ramp type. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi Theories of Type-II and Type-III. Laplace and Fourier transform technique is applied to solve the problem. The analytical expressions of displacements, stress components, temperature change and current density components are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerically simulated results are depicted graphically to show the effects of Hall current and anisotropy on the resulting quantities. Some special cases are also deduced from the present investigation.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.607-614
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• 2019

The present investigation has focus on the study of deformation due to thermomechanical sources in a thick circular plate. The thick circular plate is homogeneous, transversely isotropic with two temperatures and without energy dissipation. The upper and lower surfaces of the thick circular plate are traction free. The Laplace and Hankel transform has been used for finding the general solution to the field equations. The analytical expressions of stresses, conductive temperature and displacement components are computed in the transformed domain. However, the resulting quantities are obtained in the physical domain by using numerical inversion technique. Numerically simulated results are illustrated graphically. The effects of two temperatures by considering different values of temperature parameters are shown on the various components. Some particular cases are also figured out from the present investigation.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.245-255
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• 2019

In present research, we have considered transversely isotropic magneto thermoelastic solid with two temperature and without energy dissipation due to inclined load. The mathematical model has been formulated using Lord-Shulman theory. The Laplace and Fourier transform techniques have been used to find the solution to the problem. The displacement components, stress components and conductive temperature distribution with the horizontal distance are computed in the transformed domain and further calculated in the physical domain using numerical inversion techniques. The effect of rotation and angle of inclination of inclined load is depicted graphically on the resulting quantities.

• Wind and Structures
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• v.32 no.3
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• pp.249-265
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• 2021

As high-rise buildings become more and more slender and flexible, the wind effect has become a major concern to modern buildings. At present, wind engineering for high-rise buildings mainly focuses on the following four issues: wind excitation and response, aerodynamic damping, aerodynamic modifications and proximity effect. Taking these four issues of concern in high-rise buildings as the mainline, this paper summarizes the development history and current research progress of wind engineering for high-rise buildings. Some critical previous work and remarks are listed at the end of each chapter. From the future perspective, the CFD is still the most promising technique for structural wind engineering. The wind load inversion and the introduction of machine learning are two research directions worth exploring.

• Structural Engineering and Mechanics
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• v.77 no.3
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• pp.315-327
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• 2021

Here, in this research we have studied a two dimensional problem in a homogeneous orthotropic magneto-thermoelastic medium with higher order dual-phase-lag heat transfer with combined effects of rotation and hall current in generalized thermoelasticity due to time harmonic sources. As an application the bounding surface is subjected to uniformly distributed and concentrated loads (mechanical and thermal source). Fourier transform technique is used to solve the problem. The expressions for displacement components, stress components and temperature change are derived in frequency domain. Numerical inversion technique has been used to obtain the results in physical domain. The effect of frequency has been depicted with the help of graphs.