Structural Dynamic Properties Research Articles

Bio-templated energy transfer system for constructing artificial light-harvesting antennae, white light generation, and photonic nanowires

Developing environmentally friendly, sustainable, and biocompatible artificial light-harvesting systems has become an essential area of research to understand natural light-harvesting processes involving multistep resonance energy transfer and building efficient energy conversion systems related to energy and optoelectronic applications. In this direction, bio-scaffolded artificial energy transfer systems for panchromatic light collection and sequential energy transfer have fascinated the scientific community. In this review, we have discussed what the dynamic structure and intrinsic physical properties of biomolecules like deoxyribonucleic acid, proteins, and peptides can provide for the development of new optical devices, sustainable and environmentally friendly white emitting materials, and cascaded energy transfer systems for energy harvesting from light. In doing so, we have highlighted some of the recent advances in bio-scaffolds as a platform for the assembly of different types of donor–acceptor chromophores involved in fluorescence energy transfer.

The stability, electronic, thermal, and optical properties of silver halide (AgX: X = F, Cl, Br, and I) semiconductors: Ab-initio study

The structural properties, mechanical and dynamic stability, electronic, thermal and optical properties of silver halide AgX (X = F, Cl, Br, and I) compounds in the rock-salt phase within GGA and HSE approximations have been studied. The calculations are performed using the QUANTUM-ESPRESSO package which is based on the density functional theory (DFT) and the pseudo-potential method. The calculated elasticity parameters illustrated that the rock-salt phase complies with the mechanical stability conditions at ambient pressure. Based on the results of the mechanical calculations, it can be concluded that AgI is more rigid than other silver halide compounds, while the AgF compound is more malleable than other silver halide compounds. Also, against other examined silver halides, the AgI compound has an isotropic nature. The phonon scattering diagram has proved the dynamic stability of silver halide compounds in the studied rock-salt phase. Evaluation of the electronic results indicates that silver halide compounds in both GGA and HSE approximations have an indirect bandgap in the L−Γ path. In comparison to GGA, the HSE calculation improves the amount of bandgap toward a better agreement with experimental results. At room temperature, the hole mobility of silver halides is much less than the electron mobility. The decreasing trend of the effective mass of electrons in silver halides with the atomic radius of halide in the rock-salt phase leads to a faster carrier transfer rate in AgI, AgBr, AgCl, and AgF compounds, respectively. Moreover, by increasing the atomic radius of halide atom X, the Debye temperature θD and stiffness decrease, and inversely the heat capacity Cv increases. The increasing entropy relative to temperature refers to the endothermic properties of silver halide compounds. In both GGA and HSE approximations, the AgF compound has the highest absorption coefficient peak with the maximum optical absorption in the ultraviolet regime of the electromagnetic spectrum. The absorption coefficients of the silver halide compounds are of the order of 105 cm−1 which is comparable to the absorption coefficient of silicon crystals. The latter property along with a high stability and high electron mobility, makes silver halides attractive photocatalytic materials in the NaCl structure.

A high-fidelity constitutive model considering hydrostatic damage for predictions of high dynamic properties of concrete structures

This paper establishes a new high-fidelity constitutive model for predicting the high dynamic responses of concrete structures. The presented model incorporates the damage caused by hydrostatic pressure into the constitutive equations of concrete, while the hydrostatic damage induced strength and stiffness degradation behaviors have not been considered in existing models. In this model, two hydrostatic damage equations are introduced respectively to quantify the strength and stiffness degradation caused by hydrostatic damage. Based on this, a shrinking failure surface method is proposed for the failure criterion to capture the strength degradation, and a novel unloading/reloading law is developed for the equation of state to describe the stiffness reduction non-linearly. The model is implemented in the hydrocode LS-DYNA through the user-defined material subroutine. Numerical hydrostatic tests using a single element are conducted to verify the accuracy of the model firstly, and the corresponding predictions are in good agreement with the experimental results. Numerical simulations of penetration tests are then performed, where the damage mechanisms including hydrostatic damage and shear damage are identified. The comparisons between simulation and test results indicate that the presented model reflects the dynamic responses of concrete structures more accurately and reproduces the damage evolution of concrete more completely.

Post-Earthquake Dynamic Performance of Intact Masonry Building Based on Finite Element Model Updating

The recent seismic activity in Croatia has inflicted significant damage upon numerous buildings, with masonry structures being particularly affected. Consequently, experimental investigations and structural condition assessments’ have garnered increased attention, as they have become integral to the renovation process for such buildings. Additionally, assessing the structural condition prior to seismic events is vital for determining the extent to which earthquakes impact the stiffness of systems, such as masonry structures. This paper presents the results of experimental investigations and numerical analysis conducted on a damaged high school building in Sisak, Croatia. The experimental investigation involved shear testing, flat jack analysis, and operational modal analysis. Utilizing the available drawings and mechanical properties determined experimentally, an initial numerical model was developed. Subsequently, through the iterative process of finite element model updating, the initial numerical model was refined based on the structural dynamic properties. The updated numerical model was then employed to assess the structural condition prior to the earthquake event. This study contributes to the field by providing insights into the post-earthquake estimation of dynamic properties in intact masonry buildings, utilizing a comprehensive approach that combines experimental investigations and finite element model updating. By quantifying the changes in dynamic parameters, such as natural frequencies and mode shapes, the study provides valuable insights into the response characteristics of damaged masonry building. The observed differences in natural frequencies between the damaged and undamaged states are as follows: 9% for the first mode shape, 6% for the second mode shape, and 2% for the third mode shape.

Ab initio calculated dynamic structural factors and optical properties of beryllium along the Hugoniot

Beryllium is an ablator material used in inertial-confinement fusion and hypervelocity impact studies. The thermoelastic properties, structural factors, and optical properties of beryllium are important in these studies. In this paper, the static structural factors, ion–ion dynamic structural factors, adiabatic velocity, and optical properties of beryllium along the Hugoniot were calculated by ab initio simulations. The static structural factors show that beryllium atoms were randomly distributed. The dynamic structural factors extracted the dispersion relation for collective excitation via the scattering function. By collecting the peak position of the dynamic structural factors, the dispersion relation and adiabatic sound velocity were derived by definition. Using the calculated equation of state, the thermoelastic properties and adiabatic sound velocity have been derived. The two calculated methods for adiabatic sound velocity were verified to be equivalent.

Electromechanical coupling enriched finite element method for dynamic characteristic of piezoelectric materials structures

To improve the application depth and breadth of intelligent unit devices made from piezoelectric structures, their kinetic properties shall be urgently studied. Herein, based on the basic equations and boundary conditions of piezoelectric materials, an interpolation coverage function of node displacement was introduced into the displacement shape function and potential shape function of coupling electromechanical finite element method (FEM), forming an electromechanical coupling enriched FEM generalized shape function. Together with the variation principle, an electromechanical coupling enriched FEM was put forward, and its motion equations were deduced. Next, the free vibration and transient response of the piezoelectric structure were analyzed, and the accuracy and validity of the new method were validated with numerical cases. Results show this method has high application prospects for analyzing the dynamic properties of piezoelectric material structures.

Dynamic Spillovers between Carbon Price and Power Sector Returns in China: A Network-Based Analysis before and after Launching National Carbon Emissions Trading Market

The launch of the national carbon emissions trading (CET) market has resulted in a closer relationship between China’s CET market and its electricity market, making it easy for risks to transfer between markets. This paper utilizes data from China’s CET market and electric power companies between 2017 and 2023 to construct the spillover index model of Diebold and Yilmaz, the frequency-domain spillover approach developed by Barun’ik and Křehl’ik, and a minimum spanning tree model. The comparison is made before and after the launch of the national CET market. Subsequently, this paper examines the market spillover effects, as well as the static and dynamic properties of network structures, considering both the time domain and frequency-domain perspectives. The research findings suggest the following: (1) There is a strong risk spillover effect between China’s CET market and the stock prices of electric power companies; (2) There is asymmetry in the paired spillover effects between carbon trading pilot markets and the national CET market, and differences exist in the impact of risk spillovers from power companies between the two; (3) The results of the MST model indicate that the risk contagion efficiency is higher in the regional CET pilot stage compared to the national CET market launch stage, with significant changes occurring in key nodes before and after the launch of the national CET market; (4) Both the dynamic spillover index and the standardized tree length results demonstrate that crisis events can worsen the risk contagion between markets. Besides offering a theoretical foundation and empirical evidence for the development of China’s CET and electricity markets, the findings of this paper can provide recommendations for financial market participants as well.

The footbridge Jesípek – application of radar interferometry for dynamic response evaluation

Recent advances in radar systems have led to the development of radar interferometry (RI) methods for contactless vibration monitoring of large-scale structures, i.e. bridges, water tower reservoirs, and factory chimneys. Interferometric radars are devices capable to measure with 200 Hz sampling frequency and relative movement precision of 0.1 mm up to 0.01 mm. The major part of this paper describes an in-situ footbridge experiment near Hradec Králové. Radar interferometry devices were deployed along with ordinary techniques compounded by accelerometers, wiring, and acquisition station. Experiment was focused on the evaluation of basic dynamic structural properties such as natural frequencies and mode shapes. A lot of attention was also given to the result comparison of these measurement methods. Test results have confirmed the applicability of RI for bridge vibration monitoring.

Non-Contact Global Measurement of the Engine in Working Condition

Vibration measurements are essential for studying the dynamic properties of structures, as they can better capture the global characteristics of the structure. This paper proposes a three-dimensional measurement method based on projected structured light to address the challenge of measuring the vibration information of engine pipes during operation. By using the data obtained from this method and applying the time domain analysis method for modal analysis, the modal parameters of the engine under operating conditions can be obtained. The feasibility of this method is demonstrated by comparing it with different measurement methods, and it provides an effective solution for modal identification of engines under operating conditions.

Modal sensitivity analysis of acoustic metamaterials for structural damage detection

Metamaterials have garnered significant research interest over the past few decades, primarily due to their unique properties not found in naturally occurring materials. However, when integrated into operational engineering structures, metamaterials can sustain damage, compromising their extraordinary attributes and potentially leading to structural failure. This work marks a novel advancement in the field of metamaterials research, providing an in-depth analysis into the impact of damage on the structural dynamic properties of finite acoustic metamaterials (AMMs) consisting of periodic locally resonant mass-in-mass units. A modal sensitivity analysis is formulated based on equations of motion of a damaged AMM, along side with associated eigenvalue problem and frequency response functions. The critical role of the internal spring is analytically revealed in determining the effective mass of a damaged unit. To evaluate the effects of damage on AMMs, an extensive numerical investigation is conducted on a finite AMM; an damage index is proposed for measuring the modal deformation of each spring. It is unequivocally demonstrated that frequency response functions, eigenvalues, and mode shapes of damaged AMMs undergo substantial changes at frequencies near bandgaps and these changes diminish as frequencies move away from the bandgaps. This behavior directly corresponds to the frequency-dependent changes in the effective mass of a mass-in-mass unit due to damage. Hence, this work constitutes a leap forward in our understanding of the structural dynamics of damaged metamaterials and offers valuable insights that could facilitate the development of more effective damage identification techniques and the realization of resilient metamaterial-based structures.

Magnetic Resonance Velocimetry for porous media: sources and reduction of measurement errors for improved accuracy

Nuclear Magnetic Resonance (NMR) is a powerful tool for noninvasively investigating static and dynamic properties of fluids inside complex and opaque structures. Thus, Magnetic Resonance Velocimetry (MRV) allows for the in situ analysis of the local flow velocity of fluids. Such an analysis characterises mass transport properties and helps to validate or improve numerical predictions for porous media. The benefit of such validations is lowered by several problems worsening the measurement accuracy. This publication addresses systematic errors and the influence of noise, which may reduce the accuracy of MRV measurements. Techniques are described to minimise or correct displacement and phase errors. A new multi-echo MRV-sequence is proposed as a compromise between Velocity-to-Noise Ratio (VNR), total measurement time, spatial resolution and displacement errors. For improved VNR, a dual-VENC encoding scheme was used and repetition time T_{text{R}} was optimised. As an example, the proposed MRV sequence was used to measure the three-directional flow velocity of water in an Open Cell Foam (OCF) with 10 pores per inch with three-dimensional isotropic spatial resolution.

Poisson’s ratio influence on structural dynamic properties of 3D printed bio-based sandwich with an anti-trichiral core

The main interest of this study is to analyze the effect of Poisson’s ratio (negative for auxetic materials) on the dynamic behavior of anti-trichiral structures: an experimental and numerical study is proposed. Using three-dimensional printing technology, anti-trichiral structures (cores and sandwiches) with different geometric parameters were produced with a bio-based composite material. The material used was polylactic acid (PLA) with flax fibers. The structure geometry (anti-trichiral) is the main factor that has an influence in determining its auxetic behavior. In this study, we show the effect of the elementary cell size of the anti-trichiral structure on the auxetic behavior and its impact on the static and dynamic properties of the materials. Initially, experimental tensile tests were used to establish the static characteristics of all specimens, including Poisson’s ratio values. From these results concerning Poisson’s ratios, experimental vibration tests were also carried out to determine their dynamic properties and this is to understand the field of application of these structures and to analyze their behavior in practical use. To validate experimental results, finite element studies were carried out. In this study of the dynamic properties, we observe close agreement convergence between the results of the experimental tests and the numerical analysis.

Numerical modelling and vibration serviceability assessment of a steel footbridge with a significant 3D dynamic behaviour

This paper focuses on the vibration serviceability assessment and numerical modelling of an existing steel truss footbridge located in the outskirts of Castellón, Spain. The footbridge is rather slender and composed by a main span and two access ramps supported on three 4-arm piers of different heights. Due to the connection between the main span and the ramps at the top of the tall piers, longitudinal and lateral bending/torsion natural coupled modes of vibration coexist at low frequencies, with a relevant contribution of the piers and access ramps deformation. This leads to a significant three-dimensional and rather complex dynamic response under service conditions. With the aim of characterising the structural dynamic properties and assessing the level of vibrations induced by crossing pedestrians, two in-situ experimental test programmes are conducted. On the one hand, the structural response is measured during several hammer tests and the modal properties are identified and used to update a detailed 3D numerical model by means of a Genetic Algorithm. Due to the lack of information regarding the detailing of the piers foundations, two alternative models are analysed. The relevance of the pier-foundation system rotational stiffness is highlighted for the particular configuration. On the other hand, the footbridge main span response is recorded under different pedestrian activities: walking, running and vandal simulated actions. Finally, the vibration serviceability of the structure is assessed based on current codes and regulations.

Dynamic Rheological, Thermal, and Structural Properties of Starch from Modified Cassava Flour (MOCAF) with Two Cultivars of Cassava

The objectives of this study were to investigate alteration in the starch properties of modified cassava flour from two different local cassava cultivars from Indonesia at different fermentation times, provide structural information for starch molecules, and characterize the dynamic rheological and thermal properties. Resistant starch, non-resistant starch, and total starch levels in the cassava cultivars were also evaluated. Changes in the starch properties of Cimanggu and Kaspro (local cultivars of cassavas from Indonesia) were compared following different fermentation times (0, 12, and 24 hours). The properties of starch from modified cassava flour were influenced by the fermentation time, although both cassava varieties showed the same general characteristics. Their levels of resistant starch, non-resistant starch, and total starch were 33.28% to 51.74%, 20.51% to 23.72%, and 53.81% to 72.25% (g/100 g dry sample), respectively. The starch granules for the non-fermented samples were oval, polygonal, and round shapes; however, during fermentation, the starch granules became more porous and developed cracks of various sizes. The starches of both varieties showed an onset temperature between 67.85 and 70.17 °C, a peak temperature of 69.33 °C to 71.62 °C, and an end set temperature of 68.62 °C to 70.95 °C, with enthalpy values ranging from 1.25 mJ/mg to 1.74 mJ/mg.

Effect of post annealing process on structural, magnetic and spin dynamics properties of MnFe2O4 nanoparticles

The present research work focuses on the one-step and cost-effective hydrothermal synthesis and characterization of manganese ferrite (MnFe2O4) magnetic nanoparticles (MNPs). To investigate the effect of different annealing temperatures on the structural, magnetic and spin dynamics properties of the as-synthesized MNPs, samples were annealed at 200°C, 400°C, and 600°C. X-ray diffraction (XRD) analysis showed that all samples had a cubic spinel phase structure with space group Fd-3 m (227), with minor impurities of α-Fe2O3 and α-Mn2O3 phase are present. The average crystallite size of the MNPs increased with increasing annealing temperature, due to grain growth. The molecular dynamics, bond stretching, and cubic spinel phase of all samples were analyzed through IR spectroscopy. Furthermore, the post-annealing process resulted in a decrease in saturation magnetization from 44.04 emu/g to 29.01 emu/g, which increased to 33.79 emu/g as the annealing temperature was raised from 200°C to 400°C and further to 600°C. Ferromagnetic resonance spectroscopy was utilized to validate the magnetic characteristics, unveiling the presence of unpaired electrons and assessing the resonant magnetic field, g-factor and peak-to-peak line width.The broad resonance signal observed in the room temperature spin dynamics indicated a strong dipolar-dipolar interactions interaction between magnetic ions through oxygen ions. The obtained results indicate that the synthesized MnFe2O4 MNPs have the potential to be used in various biomedical applications, including targeted drug delivery and magnetic hyperthermia treatment, owing to their biocompatibility, excellent magnetic properties, and facile synthesis method. This study paves the way for further research on the applications of MnFe2O4 MNPs in the field of nanomedicine.

Structural Dynamics Predominantly Determine the Adaptability of Proteins to Amino Acid Deletions.

The insertion or deletion (indel) of amino acids has a variety of effects on protein function, ranging from disease-forming changes to gaining new functions. Despite their importance, indels have not been systematically characterized towards protein engineering or modification goals. In the present work, we focus on deletions composed of multiple contiguous amino acids (mAA-dels) and their effects on the protein (mutant) folding ability. Our analysis reveals that the mutant retains the native fold when the mAA-del obeys well-defined structural dynamics properties: localization in intrinsically flexible regions, showing low resistance to mechanical stress, and separation from allosteric signaling paths. Motivated by the possibility of distinguishing the features that underlie the adaptability of proteins to mAA-dels, and by the rapid evaluation of these features using elastic network models, we developed a positive-unlabeled learning-based classifier that can be adopted for protein design purposes. Trained on a consolidated set of features, including those reflecting the intrinsic dynamics of the regions where the mAA-dels occur, the new classifier yields a high recall of 84.3% for identifying mAA-dels that are stably tolerated by the protein. The comparative examination of the relative contribution of different features to the prediction reveals the dominant role of structural dynamics in enabling the adaptation of the mutant to mAA-del without disrupting the native fold.

Identification of dynamic properties of thin-walled welded structures

Predicting the dynamic properties of welded machine tool frames of is of key importance at the design stage. However, it is a complex issue, especially when damping is concerned. The paper presents the method of modeling welded structures based on finite element method and model updating. According to proposed procedure the finite element model of the welded structure is obtained by coupling its updated components. The model updating process is based on a substructural identification algorithm. The parameters of the weld model are extracted based on the isolated welded joints present in the modeled structure. The application of the method is presented on the steel welded frame example. Model verification consisting in comparing the results of the finite element analysis with the results of the experimental modal analysis carried out in the form of an impulse test showed that the relative error for natural frequencies did not exceed 4.1 %, on average 1.1 %. In addition, an average relative error determined for dominant resonances amplitudes for receptance was 16.5 %.

Energy absorption and vibration mitigation performances of novel 2D auxetic metamaterials

This paper proposes novel unit cells that can be arranged periodically constructing disparate auxetic metamaterials with negative Poisson’s ratio for engineering applications. The two-dimensional auxetic unit cells are designed utilizing the mathematical model of the modified Solid Isotropic Material with Penalization (SIMP) topological optimization method with the objective of maximizing the magnitude of the negative Poisson’s ratio. The deformation mechanisms of the auxetic structures are controlled effectively by straight and oblique struts attached at rotation joints since the optimum designs are a combination of chiral and re-entrant unit cells. Three structures with optimum auxetic designs are chosen to verify the modified SIMP method using numerical simulation. Additionally, the energy absorption and vibration mitigation of auxetic metamaterials have been extensively studied. The results showed a significant impact of negative Poisson’s ratio on the considered dynamic properties of the auxetic structures.

Benchmarking dynamic properties of structures using non-contact sensing

Benchmarking dynamic properties of structures using non-contact sensing

Shaking Table Tests of Seismic Response of Multi-Segment Utility Tunnels in a Layered Liquefiable Site

Damage to underground structures caused by liquefaction is one of the important types of hazards in the field of geotechnical engineering. Utility tunnels are the lifeline projects of cities. To ensure the sustainable and safe operation of utility tunnels over a design life of 100 years, this paper investigates the seismic response pattern of utility tunnels in the liquefied site. In this paper, shaking table tests were carried out on the utility tunnel in a layered liquefiable site. Based on the test data, the distribution law of acceleration field and pore pressure field in the model and the deformation of the soil were analyzed first. Then the soil-structure interaction, the strain and uplift of the structure were investigated. The results show that liquefaction of sand layers under strong earthquakes, resulting in seismic energy loss. The acceleration of the upper clay layer is attenuated by the seismic isolation of the liquefied soil. The utility tunnel affects the propagation of soil acceleration, which decays faster beneath the structure for the same height. The process of pore water pressure growth is a process of energy accumulation and the pore water pressure ratio curve and Arias intensity are significantly correlated. During the test, the phenomenon of sand boil appeared, and the cracks appeared on the ground surface and developed continuously. The utility tunnel in liquefied soil is lifted under the action of excess pore water pressure. There are vertical and horizontal displacement differences at the deformation joints. The strain in the utility tunnel at the stratigraphic junction is mainly influenced by the action of the bending moment, large shear deformation in the transverse section. The strain at the connection between the partition wall and the top slab is the largest and is the weak position of the structure, followed by the connection between the side walls and the top slab, and the bottom slab of the structure have a smaller strain. The results provide insights into the dynamic properties of soils and structures in liquefaction sites.