Dynamic Finite Element Modelling and Vibration Analysis of Prestressed Layered Bending–Torsion Coupled Beams

Free vibration analysis of prestressed, homogenous, Fiber-Metal Laminated (FML) and composite beams subjected to axial force and end moment is revisited. Finite Element Method (FEM) and frequency-dependent Dynamic Finite Element (DFE) models are developed and presented. The frequency results are compared with those obtained from the conventional FEM (ANSYS, Canonsburg, PA, USA) as well as the Homogenization Method (HM). Unlike the FEM, the application of the DFE formulation leads to a nonlinear eigenvalue problem, which is solved to determine the system’s natural frequencies and modes. The governing differential equations of coupled flexural–torsional vibrations, resulting from the end moment, are developed using Euler–Bernoulli bending and St. Venant torsion beam theories and assuming linear harmonic motion and linearly elastic materials. Illustrative examples of prestressed layered, FML, and unidirectional composite beam configurations, exhibiting geometric bending-torsion coupling, are studied. The presented DFE and FEM results show excellent agreement with the homogenization method and ANSYS modeling results, with the DFE’s rates of convergence surpassing all. An investigation is also carried out to examine the effects of various combined axial loads and end moments on the stiffness and fundamental frequencies of the structure. An illustrative example, demonstrating the application of the presented methods to the buckling analysis of layered beams is also presented.

Неэмпирический анализ изотопических сдвигов и резонансных эффектов в инфракрасном спектре высокого разрешения фреона-22 (CHF-=SUB=-2-=/SUB=-Cl), обогащенного -=SUP=-13-=/SUP=-C

The IR transmittance spectrum of an isotopic mixture of chlorodifluoromethane (CHF2Cl, Freon-22) with a 33% fraction of 13C and a natural ratio of chlorine isotopes was measured in the frequency range 1400-740 cm–1 with a resolution of 0.001 cm–1 at a temperature of 20C. An ab initio calculation of the structure and sextic potential energy surface and surfaces of the components of the dipole moment has been carried out by the the electronic quantum-mechanical method of Möller-Plesset, MP2/cc-pVTZ. Then the potential was optimized by replacing the harmonic frequencies with the frequencies calculated by the electronic method of coupled clusters, CCSD(T)/aug-cc-pVQZ. The fundamental and combination frequencies were calculated using the operator perturbation theory of Van Vleck (CVPTn) of the second and fourth order (n=2,4). Resonance effects were modeled using an additional variational calculation in the basis up to fourfold VCI excitation (4). The average prediction error for the fundamental frequencies of the 12C isotopologues was ~1.5 cm–1. The achieved accuracy made it possible to reliably predict the isotopic frequency shifts of the 13C isotopologues. It is shown that the strong Fermi resonance ν4/2ν6 dominates in the 12C isotopologues and is practically absent in 13C. The literature assumption [Spectrochim. Acta A, 44: 553] about the splitting of ν1 (CH) due to the resonance ν1/ν2+ν7+ν9 is confirmed. The coefficients of the polyadic quantum number are determined. The analysis made it possible to carry out a preliminary identification of the centers of the vibrational-rotational bands of isotopologues 13CHF235Cl и 13CHF237Cl in the spectrum of the mixture in preparation for individual analyzes of the vibrational-rotational structures of individual vibrational transitions.

Estimation Formula of Modal Frequency of High-Rise Buildings under Different Wind Speeds during Typhoons

On 18 October 2016, the wind-induced effects of a high-rise building with square section was measured by the monitoring system in Haikou of China during Typhoon Sarika. The wind characteristics atop the building and the time-history responses of the translational and rotational accelerations on different floors were measured by the monitoring system; the first three modal parameters were identified according to the measured acceleration. The results show that the combinations of the cross spectral density function, phase spectrum, and coherence function can clearly judge the phase of the measured floors in the frequency resonance area as well as its modal frequencies at the first three orders. The modal frequencies at the first three orders decrease linearly with the growth of mean wind speed within the range of 0~20m/s. The estimation formula of the modal frequencies of high-rise buildings considering the influences of different wind speeds is put forward, which is expected to fill the gap in the existing specification for the quantitative analysis of the influences of wind-loads on the fundamental frequencies of high-rise buildings.

Spectroscopic constants and anharmonic force field of dithioformic acid and its isomers: a theoretical study

The potential astronomical interest dithioformic acid (trans-HC(=S)SH) exists five isomers and has received considerable attention of astronomical observation in recent years. The different positions of H atoms of five isomers lead to diverse point groups, dipole moments, and spectroscopic constants. The anharmonic force field and spectroscopic constants of them are calculated using CCSD(T) and B3LYP employing correlation consistent basis sets. Molecular structures, dipole moments, rotational constants, and fundamental frequencies of trans-HC(=S)SH are compared with the available experimental data. The B3LYP/Gen=5 and CCSD(T)/Gen=Q results can reproduce them well. Molecular structures, dipole moments, relative energies, spectroscopic constants of cis-HC(=S)SH and dithiohydroxy carbene (DTHC) are also calculated. The new data obtained in this study are expected to guide the future high resolution experimental work and to assist astronomical search for CH2S2.

Preliminary Observations on Historical Castle Trakošćan (Croatia) Performance under Recent ML ≥ 5.5 Earthquakes

Trakošćan Castle, built on a rocky peak in the late 13th century, is a cultural heritage site protected as a historical entity by the Republic of Croatia. The Castle is constructed as a highly irregular masonry structure with timber or shallow masonry arches, vaults or dome floors. It was substantially renewed, upgraded and partially retrofitted from the 16th century until the year 2000. The M5.5 (VIII EMS) and M6.2 (VIII-IX EMS) earthquakes, which struck the city of Zagreb on 22 March 2020 and the Pokupsko-Petrinja area on 29 December 2020, strongly shook the Castle’s structure. Earthquake damage was observed and assessed by visual inspection accompanied by ambient vibration measurements. The slight cracks that appeared on masonry arches were found to be critically positioned, and can likely lead to the arches’ collapse if their spreading is not prevented. Ambient vibration measurements, which were compared to pre-earthquake ones, revealed the decrease in the fundamental frequencies of the Castle’s central tower unit and the second floor, thus possibly indicating the loss of structural stiffness as a consequence of the earthquake damage.

Harmonics Analysis of Inverter Circuits on Smart Grid System

Smart Grid System has Harmonics Distortions. Caused when switching inverters convert DC current into AC that lowers power quality and affects power generation system. Interference occurs in sinusoidal wavelengths of voltage or system currents that have frequency multiples of fundamental frequencies. Therefore, analysis is required based on IEEE Std 519-2014 standard which is for 20kV Bus voltage has a limit value of 3% for VIHD and 5% for VTHD, using ETAP software was conducted simulating the condition of the non-grid bus system has a VTHD value of 4.9%, while the on-grid system conditions that have inverters for buses have a VTHD value of 5.81%, and simulations before passive filters are installed in the 5th order (f = 250 Hz) with a VTHD value of 6.33%; VIHD 4.82% after installing passive filter VTHD value 1.88 %; VIHD 0.00 %, while in the 7th order (f=350 Hz) the VTHD value is 6.33%; VIHD3.33 % after installing passive filter VTHD value 1.88%; VIHD 0.00%. The passive filter used is a single tuned passive filter. Change the PF (Power Factor) value before filtering is installed on the distribution bus = 82.9%, after the passive filter installed is 88.1%.

The impact of physician empathy on patient outcomes: A gender analysis

Background: Empathy in primary care settings has been linked to improved health outcomes. However, the operationalisation of empathy differs between studies, and no study concurrently compared affective, cognitive, and behavioural components of empathy regarding patient outcomes. Moreover, it is unclear how gender interacts with the studied dimensions. Aim: To examine the relationship between several empathy dimensions and patient-reported satisfaction, consultation’s quality and trust in physician, and to determine whether this relationship is moderated by physician’s gender. Design and setting: Analysis of 61 primary care physicians’ empathy in relation to 244 patient experience questionnaires in French-speaking part of Switzerland. Method: Sixty-one physicians were videotaped with two male and two female patients. Six different empathy measures were assessed: two self-reported measures, a facial recognition test, two external observational measures, and a Synchrony of Vocal Mean Fundamental Frequencies (SVMFF), measuring vocally coded arousal. After the consultation, patients indicated their satisfaction, trust, and quality of the consultation. Results: Female physicians self-rated their empathic concern above their male counterparts, whereas male physicians were more synchronised to their patients. SVMFF was the only significant predictor of all patient outcomes. Verbal empathy statements were linked to higher satisfaction when the physician was a man. Conclusion: Gender differences were observed more often in self-reported measures of empathy than in external measures, indicating a probable social desirability bias. SVMFF significantly predicted all patient outcomes and could be used as a cost-effective proxy of relational quality.

Compact Tri-band Bandpass Filter Based on Asymmetric Step Impedance Resonators for WiMAX and RFID Systems

In this article, a simple method is developed to design a highly miniaturized tri-band bandpass filter (BPF) utilizing two asymmetric coupled resonators with one step discontinuity and one uniform impedance resonator (UIR) for worldwide interoperability for microwave access (WiMAX) and radio frequency identification (RFID) applications. The first and second passbands located at 3.7 GHz and 6.6 GHz are achieved through two asymmetric coupled step impedance resonators (SIRs), while the third passband, centered at 9 GHz, is achieved using a half-wavelength UIR, respectively. The fundamental frequencies of this BPF are implemented by tuning the physical length ratio (α) and impedance ratio (R) of the asymmetric SIRs. The proposed filter is designed and fabricated with a circuit dimension of 13.69 mm × 25 mm (0.02 λg × 0.03 λg), where λg represents the guided wavelength at the first passband. The experimental and measured results are provided with good matching.