Values Of Vibrational Frequencies Research Articles

In Silico Calculations of 2-Methoxy-6-[(3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-4-yl)-iminomethyl] Phenyl Benzoate

Schiff's bases are significant compound for organic chemistry. In the last year, computational properties of Schiff bases were examined on a computer. In this study, we investigated theoretical features of 2-methoxy-6-[(3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-4-yl)-iminomethyl] phenyl benzoate with B3LYP/6-311G(d) basis set. All quantum chemical calculations were carried out using the Gaussian09W program package and the Gauss View molecular visualization program. The IR vibrational frequency values of the titled compound were calculated using B3LYP/6-311G(d) basis set. The vibrational spectral analysis was carried out using infrared spectroscopy in the range 4000-400 cm-1 for titled compound. The IR vibrational frequency values were defined using the veda4f software. The 1H-NMR and 13C-NMR spectral values of the titled compound were calculated utilizing the B3LYP/6-311G(d) basis set. To determine the 1H-NMR and 13C-NMR isotropic shift values, the gauge independent atomic orbital (GIAO) methodology was used. The UV-vis spectral calculations in the ethanol solvent of the titled compound were performed via the same basis set. TD-DFT computations in ethanol solvent were used to identify the UV-Vis spectral analyses. In addition, dipole moments, LUMO-HOMO, total energy, and electronic properties; ELUMO-EHOMO energy gap (ΔEg), electronegativity (χ), electron affinity (A), global hardness (η), softness (σ), ionization potential (I), thermodynamics properties; (thermal energies (E), thermal capacity (CV), entropy (S) were calculated.

Experimental (FT-IR, 13C/1H-NMR) and DFT (B3LYP, B3PW91) Studies of 3-n-Propyl-4-[2-(4-Methoxybenzoxy)-3-Methoxy] Benzylidenamino-4,5-Dihydro-1h-1,2,4-Triazol-5-Ones Molecule

All theoretical calculations of 3-n-propyl-4-[2-(4-methoxybenzoxy)-3-methoxy] benzylidenamino-4,5-dihydro-1H-1,2,4-triazol-5-ones has been performed with B3LYP/B3PW91 functions of DFT method using the 6-311G(d,p) basis set (Frisch et al., 2009; Wolinski et. al., 1990). Firstly, optimized to achieve the most stable form of the molecule. Then, the veda4f program was used in defining Infrared (IR) data (Jamróz, 2004). The standard error values were found via the Sigma plot with regression coefficient of a and b constants. The vibrational frequency values of this molecule have been calculated by using 6-311G(d,p) basis set with DFT (B3LYP/ B3PW91) methods. Then, these values are scaled with appropriate scala factors (Merrick et al., 2007). 1H-NMR and 13C-NMR spectral values according to GIAO method (Wolinski et al., 1990) was calculated using Gaussian G09W program package in DMSO solvent and in gas phase. Theoretical spectral values of molecule were compared with experimental values. Experimental data obtained from the literature (Alkan et al., 2014). In addition, electronic properties (electronegativity (χ), global hardness (η), electron affinity (A), ionization potential (I), softness (σ), thermodynamics properties (heat capacity CV0, entropy S0 and enthalpy H0), HOMO-LUMO energy, ELUMO-EHOMO energy gap (ΔEg), geometric properties (bond angles, bond lengths), dipole moments, Mulliken atomic charges, total energy of the molecule were calculated. Finally, the molecular surfaces such as the electron density, molecular electrostatic potential (MEP), contour and the total density maps were designated.

Relation of Natural Frequencies to Traffic Pedestrians’ Comfort of Some Steel Footbridges

Abstract In this paper several aspects regarding the dynamic behaviour of the steel footbridge structures under the action of the loads generated by the pedestrians’ displacement, correlated with the traffic comfort of the pedestrians crossing the structure are presented. The crossing pedestrians’ comfort criterion requires the values of vibration frequencies and accelerations of the structures in certain limits so that the vibration amplification or resonance is avoided. The paper takes under investigation eight footbridges on steel, composite steel-concrete girders and a cable stayed structure from the viewpoint of frequencies in vibration Mode 1 in a vertical plane, generated by their own weight - natural frequency, or from a partial pedestrian loading, as well as the resulting resonance risk and the traffic comfort.

Elastic Investigation of Piers Numbers Effects in Transverse Direction on the Stiffness of Continuous and Simply Supported Bridges

Piers were important structural members between superstructure and foundation of bridge which were designed to transfer and resist the vertical loads and horizontal loads (dead load of structure, traffic loads, water pressure, ice, and wind) to the foundation. The objective of this study was to evaluate the effect of number of piers in transverse direction (horizontal distance or spacing) between piers on the static and dynamic responses for two types of bridges structure which they include continuous and simply supported bridges. Static and dynamic analysis methods were adopted to analyse the bridges structures by using CSI-bridge software. The results of static analysis for two types of bridges models (continuous and simply supported) showed that the increasing of piers numbers had significant effects on the increasing of bridge structure stiffness by decreasing the downward vertical deflection due to service loads, increasing of the resistance of prestressed loads to service loads, and increasing of compression stresses. The results of time history analysis for two types of bridges models showed that the values of natural frequency were increased when the piers numbers were increased. Traffic load frequency (vibration frequency) values were decreased with increasing of bridge piers number because of the bridge structure had more stability. It can be concluded that the values of natural frequency were more than values of traffic load frequency, indicating that the bridges structures had enough stiffness and stability.

Dynamic characteristics assessment of the Denis‐Perron dam (SM‐3) based on ambient noise measurements

AbstractStanding at a height of 171 m in a narrow valley, the Denis‐Perron dam is the highest embankment dam in Québec, Canada. Between 1998 and 2002, the structure was equipped with three‐component digital strong‐motion accelerometers. The seismic data recorded during three small earthquakes allowed for the estimation of the fundamental vibration frequency (fn) values of the dam in three directions. As part of the present research study, 10 sets of ambient noise measurements were acquired at the dam using six velocimeters, aiming to evaluate the possible 3D site effects and determine the fn values. The first analyses of these experimental data consisted of processing the individual signals with the simple “reference‐dependent spectral” and “ambient vibration horizontal‐to‐vertical spectral ratio (HVSR)” methods. A more advanced modal analysis combining synchronized measurements led to the establishment of additional higher vibration frequency modes and modal shapes. The consistency between the fn values obtained using the simple methods and those from the advanced modal analysis was noticeable. The seismic data provided an exceptional opportunity to validate the experimental data. A comprehensive analysis was thus conducted to compare the dynamic parameters calculated from the processed experimental data with those resulting from the seismic data and proved the values to be similar. In addition, a numerical modal analysis of the 3D valley‐dam system corroborated the plausibility of the vibration modes obtained from the experimental synchronized ambient noise modal analysis. All of these analyses demonstrate the potential of the ambient noise technique for identifying the dynamic characteristics of large rockfill dams built in narrow valleys, without the need for the costly installation and maintenance of accelerometers in low‐seismicity areas.

Optimization of an EMU train carbody by the value of the natural bending frequency

Finding ways to optimize the body structure is an important point in the design of new electric train cars. Reducing the mass of the body leads to a lightening of the parts of the rolling stock associated with it, a reduction in energy consumption for operation and a decrease in wear in the “wheel — rail”system. Reducing the weight of the body is possible by assigning optimal rigidity to its main load-bearing elements. Increasing the rigidity of the body with a constant mass is also an important task to obtain the standard dynamic properties of the car body.The article presents method for optimizing the body structure based on calculating the value of its first frequency of natural bending vibrations. The calculation was carried out by the finite element method using a simplified beam-shell parametric model. Within the optimization calculations, 3125 working versions of sections of the main load-bearing structural elements with different rigidity were considered — bracing and cross-beams of the frame, inter-window racks and cross-beams of the roof. The sensitivity of the value of the natural vibration frequency to the change in the rigidity of the main bearing elements without taking into account the change in mass is analyzed. It was found that the rigidity of the frame bracing and cross beams has the greatest influence on the frequency value. It is shown that the ratio of the rigidity of the main bearing elements does not remain constant for optimal design options and depends on the design of the body, the target values of its mass and rigidity. When mass is limited, it is possible to choose designs that are characterized by the greatest overall body rigidity and are the most optimal in terms of manufacturability. By limiting the values of natural vibration frequency, it is possible to choose a body structure with the lowest metal mass. The presented approach allows making decisions on body modification based on the required parameters of mass and (or) the frequency of natural bending vibrations. This approach can be used in pre-design studies of the bodies of new passenger rolling stock.

2-Acetyl-5-chloro-thiophene thiosemicarbazone and its nickel(II) and zinc(II) complexes: Hirshfeld surface analysis and Density Functional Theory calculations for molecular geometry, vibrational spectra and HOMO-LUMO studies

In this work, the theoretical studies on the molecular structure are presented for 2-Acetyl-5-chloro-thiophene thiosemicarbazone and its Ni(II) and Zn(II) complexes. The optimized molecular geometry and fundamental vibrational frequency values have been investigated with the help of DFT/B3LYP method using 6-31G(d,p) basis set and they are found to be in agreement with the experimental values. Additionally, frontier molecular orbital energies (HOMO, LUMO) and their energy gaps (∆E) are calculated by the same method. The HOMO and LUMO analysis are used to determine some molecular properties such as chemical potential, hardness, softness and electronegativity. Furthermore, Hirshfeld surface analyses and fingerprint plots have been used for visualizing and exploring intermolecular interactions in the crystal structure and for determining the percentage contribution of these interactions on the surface. The Hirshfeld surface analysis and the 2D fingerprint plots indicate that the crystal packing of the compounds is dominated by Cl···H/H···Cl, S···H/ H···S, N···H/ H···N and H···H contacts.

Determination of the dynamic load of the carrying structure of the hopper wagon with the actual dimensions of structural elements

The object of research is the supporting structure of the pellet wagon with the actual dimensions of the supporting elements. One of the most problematic areas is the determination of the indicators of dynamics and strength of the supporting structure of the hopper wagon with the actual dimensions of the structural elements.
 A study of the dynamic loading of the supporting structure of the hopper wagon was carried out. At the same time, the actual dimensions of the structural elements were determined by means of field studies. Mathematical modeling of the dynamic loading of the load-carrying structure of a hopper wagon with the actual dimensions of structural elements was carried out by means of mathematical modeling. The studies were carried out in a flat coordinate system. The presence of three degrees of freedom of the supporting structure of the hopper wagon was taken into account: vibrations of twitching, bouncing and galloping. Differential equations were solved in the MathCad software package. In doing so, they were reduced to the Cauchy normal form, and then integrated using the Runge-Kutta method. It was found that the maximum value of the acceleration acting on the supporting structure of the hopper wagon is 38.5 m/s2, which is 2.7% higher than the acceleration of the supporting structure with nominal dimensions.
 Computer simulation of the dynamic loading of the supporting structure of the hopper wagon was carried out. The calculation was carried out using the finite element method in the SolidWorks Simulation (CosmosWorks) software package. It was found that the maximum accelerations are concentrated in the middle part of the supporting structure of the hopper wagon and amount to 36.2 m/s2. The F-criterion was used to verify the developed model. The calculations showed that the calculated value of the criterion is Fc = 1.09 and is less than the table value Ft = 3.29. The adequacy hypothesis is not rejected.
 The natural frequencies and vibration modes of the hopper wagon supporting structure were determined. It has been established that the values of natural vibration frequencies of the hopper wagon bearing structure with the actual dimensions of the structural elements are within the permissible limits.
 The research will contribute to the creation of relevant developments to extend the service life of wagons that have exhausted their standard resource, as well as to increase the efficiency of railway transport operation.

A large-eddy simulation study on the similarity between free vibrations of a flexible cylinder and forced vibrations of a rigid cylinder

The strip theory in hydrodynamics has been widely used for predicting complex vortex induced vibrations (VIV) behind bluff bodies, but the question of how accurate such predictions are has not been addressed adequately before. In order to corroborate the application of strip theory in VIV, we present a comparative study between free mono-frequency vibrations of a long flexible cylinder in both uniform and linearly sheared flow and corresponding forced vibrations of a rigid cylinder with prescribed sinusoidal motions. We employ the entropy–viscosity large-eddy simulation (LES) to resolve the vortical flow and the coupled cylinder response, which we validate by companion experiments of the same configuration. We then extract from LES, at the same Reynolds number, the values of the sectional vibration amplitude, frequency, and phase angle (between inline and crossflow motions), and use them as input parameters for the forced vibration case, for which we perform two-dimensional simulations. We show here by systematic simulation studies that the hydrodynamic coefficients exhibit strong similarities between the two cases, and the forced vibration closely resembles the sectional near wake of the free vibration.

The dynamical problem for the infinite elastic layer with a cylindrical cavity

The wave field of an infinite elastic layer weakened by a cylindrical cavity is constructed. The ideal contact conditions are given on the upper layer’s face and bottom face is rigidly fixed. The normal dynamic tensile load is applied to a cylindrical cavity’s surface at the initial moment of time. The Laplace and finite sin- and cos- Fourier integral transforms are applied successively directly to axisymmetric equations of motion and to the boundary conditions, on the contrary to the traditional approaches, when integral transforms are applied to solutions’ representation through harmonic and biharmonic functions. This operation leads to a one-dimensional vector inhomogeneous boundary value problem with respect to unknown displacements’ transformations. The problem is solved using a matrix differential calculus, which leads to an integral equation solved with a method of orthogonal polynomials. The field of initial displacements is derived after application of inverse integral transforms. The case of the steady-state oscillations was investigated. The normal stress on the rigidly fixed face of the elastic layer is constructed and investigated depending on the mechanical and dynamic parameters. Formulas for determining the normal stress for large values ​​of natural vibration frequencies were constructed.

Hybrid cross-tie system with passive dampers study

The authors have investigated the use of passive vibration dampers through the implementation of concentrated masses in the hybrid cross-tie system of a cable-stayed bridge. A 3D model of a cable-stayed bridge was built in ANSYS suite. The authors have studied the stress-strain behavior and dynamic characteristics of the model under the gravity load. The study has shown that the most effective model appears to be the one with passive dampers implemented by means of six concentrated masses. The increased stiffness of links of the concentrated masses had stronger effect on the model with passive dampers implemented by means of ten concentrated masses, however the model where passive dampers were implemented by six concentrated masses displayed comparable values of natural vibration frequencies with deflections in the spans being 3% lower, displacements of the towers being 8% lower, and longitudinal forces in the main cable being 6% lower. The results obtained by the authors allow for the conclusion that all models of a hybrid cross-tie system with passive dampers reviewed have high aerodynamic stability.

Numerical algorithm for searching for layouts of electroelastic bodies with external electric circuits for obtaining the best damping properties

This paper presents an algorithm which allows finding such layouts of electromechanical systems that provide the best vibration damping whether for one mode or a set of vibration modes within some continuous frequency ranges. The basis for the algorithm is the problem solution about natural vibrations. An elastic structure with a piezoelectric element located on its surfaces, which electrodes are connected to a passive external electric circuit, is treated as an electromechanical system. The piezoelectric elements shunted with an electric circuit are the devices where energy dissipation occurs, thus leads to damping of vibrations. A change in damping properties of such systems can be reached by a proper choice of parameters of the electric circuits and corresponding location of the piezoelectric element, which provides the highest energy withdrawal into the electric circuit. The paper presents the mathematical formulation of the natural vibrations problem for piecewise-homogeneous electroelastic bodies shunted with passive external electric circuits. Within the proposed mathematical statement, the problem solution of natural vibrations for such objects is based on values of complex natural vibration frequencies. Real parts of the complex natural vibration frequencies are the circular frequency of vibrations, and the imaginary parts are the damping indices of vibrations. We proposed techniques aimed at determining the location of the piezoelectric element and selecting parameters of shunting the external electric circuit. These approaches are based on values of the complex natural vibration frequencies obtained as results of solving the natural vibrations problem. The proposed approach is demonstrated using a specimen of a thin-walled shell in the semi-cylinder form. The piezoelectric element has a form of a segment of a ring made of PZT-4 piezoceramics. Electrodes of the piezoelectric element are connected to the series resonant RL -circuit. The formulated problem is solved numerically using the finite element method and ANSYS commercial package.

A new multi-field coupled dynamic analysis method for fracturing pipes

In petrochemical, marine, and other fields, high-concentration solid-liquid two-phase flow induced pipe vibration has always been a problem worthy of attention. Especially when the oil pipe transports solid-liquid two-phase flow, researchers have introduced the equivalent density of the two-phase flow into the fluid momentum equation to consider the influence of the two-phase flow on pipes with vibrations. This method ignores the influence of particle collision and accumulation in the pipe on fluid flow and pipe vibration, which makes it impossible to fully predict the dynamic state of the pipes. Therefore, this paper presents the fluid-particle-pipe multi-field coupling analysis method (CFD-DEM-FEM method) for the first time to analyze the pipe vibration induced by the two-phase flow. The analysis found that when the velocity of the two-phase flow and the sand ratio increase, at the same time the diameter ratio decreases, the more significant the collision and accumulation of particles at the location where the pipe diameter changes, as well as the vibration amplitude of the pipe are all getting bigger. In addition, high fluid velocity can produce high-amplitude and high-frequency vibrations, while high sand ratio can produce low-amplitude high-frequency vibrations. For the pipe vibration amplitude and frequency values, the relative errors between the current computational results and those from experiments are less than 15%, indicating that our multi-field coupling calculation method can be used in the pipe vibration induced by solid-liquid two-phase flow. Our research results can be used to guide the structural design and process design of high-concentration solid-liquid two-phase flow pipe, and reduce the chance of two-phase flow-induced pipe vibration damage.

A novel method for the synthesis and characterization of 10-hexyl-3-(1-hexyl-4, 5-diphenyl-1H-imidazol-2-yl)-10H-phenothiazine: DFT computational, in vitro anticancer and in silico molecular docking studies

This study aimed to newly synthesized compound 10-hexyl-3-(1-hexyl-4, 5-diphenyl-1H-imidazol-2-yl)-10H-phenothiazine (abbreviated as HHDIP) by direct and thermal condensation methods, which were characterized by different spectral analysis. The optimized geometry completed the theoretical calculation; the Fourier-transform infrared spectroscopy (FTIR) vibrational frequency studies of HHDIP were found by using the (density functional theory) ab initio calculation with B3LYP/6-311++G (d,p) level. The computed and scaled vibrational frequency values were well matched with the experimental FTIR and Fourier-transform Raman spectroscopy (FT-Raman) spectra. A particular understanding of the FTIR spectra of this title compound was performed by the computed potential energy distribution. The UV–Vis, 1H, and 13C NMR investigations were completed as well as observed; these theoretical outcomes have been seen as in good concurrence with the experimental value. The mass spectroscopy investigation was completed to this compound. In addition to this title compound, the computed (HOMO and LUMO) energy values have been revealed with the charge transfer inside the organic molecules. Nonlinear optics and Mulliken population studies were completed for this title compound. Finally, intensive studies on their anticancer properties were studied through in vitro as well as in silico approaches, suggesting our title compound exhibited tremendous anticancer activity at the concentration value of 250 µg/mL. The in silico docking and adsorption, distribution, metabolisms, excretion and toxicity (ADMET) studies were executed through commercial docking software Discovery Studio, version 4.0 against the protein target c-Met kinase (hepatocyte growth factor; PDB ID: 3F66). The results showed a ligand–receptor interaction energy value of − 64.494 KCal/mol against 3F66 protein (standard anticancer drug tivantinib exhibited − 57.804 KCal/mol). In the ADMET study, it gives good results of nonmutagenic and noncarcinogenic activities. However, in vitro studies exposed more significant antioxidant activity at the range of hydrogen peroxide (H2O2) scavenging activity as 66.31% and 52.877% which showed a vigorous DPPH radical scavenging antioxidant activity concentration value of 500 µg/mL. Further studies are desired to explore its promising anticancer, clinical research and other pharmacological aspects.

Evolution of grinding energy and particle size during dry ball-milling of silica sand

The energy efficiency of dry fine grinding process of powders dramatically declines with decreasing particle size, and represents a growing concern in various cutting-edge technical applications for pharmaceutical and cosmetic products, advanced-ceramics, and food industry. In this paper, we report on a detailed experimental analysis of the long-term grinding behavior of silica sand as a model material in an oscillatory ball mill for a broad range of the values of vibration frequency and amount of powder. We show that the re-agglomeration of fine particles unambiguously explains the anomalous increase of grinding power consumption. We also find that the agglomeration phenomena are correlated with the volume fraction of the class of finest particles. A nonlinear comminution model is shown to capture this effect for the prediction of the evolution of the specific surface area.

Estimation of Vibration Frequency of Structural Floors Using Combined Artificial Intelligence and Finite Element Simulation

Floor vibration due to human activities (walking, running, etc.) and operating machines generally makes inconveniences for residents. The natural vibration frequency of beams is determined as the main source and also the controlling parameter of such the phenomenon. Many studies have been conducted on determining the natural frequency of beams in recent years; however, the proposed formulations in many of them are not very practical for vibration control of tall building floors. In this paper, the finite element method (FEM), nonlinear (NL) dynamic analyses, and artificial intelligence (AI) techniques were adopted to constitute the simple frequency equations of the fixed ends and cantilever steel beams for controlling floor vibration. The input data required for training the AI based model are simulated in a NL-FE platform considering various cases of the steel moment connections. The analysis outcome of several hundred beams with different properties indicated that the calculated vibration frequency values of the fixed ends and cantilever beams were respectively 2.07 and 0.33 times larger than the frequency value of the simply supported beams with similar conditions. To this, the implemented soft computing technique was determined as an effective approach to improve the computational efficiency of the NL-FE simulations.

Crystal growth, structural, nonlinear optical and theoretical investigations of Benzilic acid crystals

Organic single crystals of Benzilic Acid (BA) were grown by slow solvent evaporating method by using acetone as solvent. The unit cell parameter values and the crystal system are recognized by using single crystal XRD technique. The optical assessment of BA molecules is observed by with UV-Vis spectral analysis as the ultraviolet range between 200 and 400 nm and the visible region between 400 and 800 nm. The nonlinear optical (NLO) properties such as second harmonic efficiency nature of BA crystal were analyzed using Nd:YAG laser. The laser-induced damage threshold assessment of BA crystal is measured as 2.76 GW/cm2. From the Density Functional Theory (DFT), the molecular structural feature and vibrational frequencies were defined by using the Gaussian system along with comparisons of experimental frequencies. Using the DFT method, the derived vibrational frequency values showed an admirable accord with experimental frequencies. The charge interactions within the BA molecules are confirmed by HOMO and LUMO energy value. The first-order molecular hyperpolarizabilities, dipole moment, polarizability and Mulliken charge analysis of the BA molecule are also evaluated.

Theoretical and experimental assesment of structural, spectroscopic, electronic and nonlinear optical properties of two aroylhydrazone derivative

Two aroylhydrazone, N'-(pyridine-4-ylmethylene)nicotic acid hydrazide (1) and N'-(pyridine-3-ylmethylene)nicotic acid hydrazide (2), were synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The X-ray analysis indicated that the compound 1 was crystallized in triclinic crystal system with P -1 space group a = 8.7899 (2) Å, b = 10.8983 (3) Å, c = 11.7726 (3) Å, α= 89.952 (3)°, β = 88.684 (3)°, γ= 75.293 (2)°, V = 1090.50 (5) Å3 and Z = 4 and compound 2 was crystallized in monoclinic crystal system with P21/c space group, a = 11.9239 (3) Å, b = 8.6495 (2) Å, c = 11.1021 (3) Å, α= 90 (3)°, β = 111.664 (3) (3)°, γ= 90°, V = 1064.14 (5) Å3 and Z = 4. Intermolecular interactions of the compounds were determined by Hirhfeld Surface Analysis. The H ··· H interactions with 37.9% (for compound 1) and 37.5% (for compound 2) contributions are the most important interactions to the overall crystal packings. FT-IR, Raman, 1H and 13C NMR and UV–Vis spectroscopy methods were used for spectroscopic characterization of the compounds. The spectroscopic properties of the compounds were calculated theoretically by using Density Functional Theory (DFT) with B3LYP and ab initio Hartree-Fock (HF) methods at different basis sets. A correlation was found between the theoretical and experimental values for the spectroscopic results. Moreover, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), electric dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the compounds were computed both DFT/B3LYP/6–311++G(d,p) and ab initio HF/6–311++G(d,p) methods. The calculated first hyperpolarizability value at the DFT/B3LYP/6–31++G (d,p) level of compound 1 with dimer structure is 18.14 times larger than urea, the standard nonlinear optical material. So, this value implies that compound 1 considered have potential candidates for designing high quality nonlinear optical materials. The energy gap (ΔEgap) and Molecular Electrostatic Potential (MEP) of the compounds were investigated. The structural and vibration frequency values calculated theoretically were compared with the experimental values.

Influence of Foundation Quality on the Stress in the Elements of Steel Façade Scaffolding

The purpose of this paper is to show the influence of incorrect scaffolding foundations on the stress in their elements. Static stress analysis was performed for exemplary steel façade scaffolding. The scaffolding was formed using the Plettac 70 system and was composed of 16 modules and 13 working levels. The total dimensions of the scaffolding were 45.0 × 26.36 × 0.74 m. The scaffolding was set up partly on concrete and partly on a created ground classified as coarse sand with discontinuous graining. The boundary conditions modelling the foundation considered the heterogeneity of the ground both along the scaffolding and in the direction perpendicular to the façade. The effect of uneven subsidence on the scaffolding frames was checked, adopting a constant stiffness of 3500 kN/m in half of the supports, while in the rest of them the stiffness varied from 35 to 3500 kN/m. Due to additional bending moments, normal stresses in stands and transoms of the frames increased. Incorrect scaffolding foundation has the greatest negative effect on normal forces in anchors and bracings. Because these elements are responsible for the stability of the scaffolding, their damage may result in scaffolding failure and would certainly lead to a reduction of the values of free vibration frequencies, thus resulting in the discomfort of the workers on the scaffolding and a lack of safety.

Nonlinear dynamic characteristics of nonlocal multi-phase magneto-electro-elastic nano-tubes with different piezoelectric constituents

Analysis of exact nonlinear dynamic behavior of multi-phase magneto-electro-elastic (MEE) nanoshells has been presented in this paper using Jacobi elliptic functions. Multi-phase MEE material is constructed form piezoelectric and piezo-magnetic constituents for which the material properties can be controlled based on the percentages of the constituents. Nonlinear governing equations are established for MEE nanoshell based on nonlocal elasticity theory and an exact solution is provided using Jacobi elliptic function method. This method gives an exact value of vibration frequency in nonlinear regime and overcomes the shortcomings of several approximate solutions applied in the studies on nanostructures. It will be shown that nonlinear vibration behavior of MEE nanoshell in electro-magnetic field depends on the constituent’s percentages. Influences of nonlocal scale factor, piezoelectric reinforcement, magnetic field intensity, and electrical voltage on vibration frequencies of the nanoshell are also investigated.