Dynamic Stability Research Articles

Hyers - Ulam Stability of Ebola and Nipah Virus Co-infection Fractional Dynamics

Hyers - Ulam Stability of Ebola and Nipah Virus Co-infection Fractional Dynamics

System Tautochronic Path for Pendulum Vibration Absorber Based on Simple Harmonic Oscillator Transformation

Abstract Centrifugal pendulum vibration absorbers (CPVAs) are essentially collections of pendulums attached to a rotating component or components within a mechanical system for the purpose of mitigating the typical torsional surging that is inherent to internal combustion engines and electric motors. The dynamic stability and performance of CPVAs are highly dependent on the motion path defined for their pendulous masses. Assemblies of absorbers are tuned by adjusting these paths such that the pendulums respond to problematic orders (multiples of average rotation speed) in a way that smooths the rotational accelerations arising from combustion or other nonuniform rotational acceleration events. For most motion paths, pendulum tuning indeed shifts as a function of the pendulum response amplitude. For a given motion path, the tuning shift that occurs as pendulum amplitude varies produces potentially undesirable dynamic instabilities. Large amplitude pendulum motion that mitigates a high percentage of torsional oscillation while avoiding instabilities brought on by tuning shift introduces complexity and hazards into CPVA design processes. Therefore, identifying pendulum paths whose tuning order does not shift as the pendulum amplitude varies, so-called tautochronic paths, may greatly simplify engineering design processes for generating high-performing CPVAs. To illustrate this new approach and results, a tautochronic cutout shape producing constant period system motion is obtained for a simplified problem involving a mass sliding in the cutout of a larger mass that is free to translate horizontally without friction in a constant gravitational field, where the translating base mass replaces the rotating rotor in the centrifugal field.

Theoretical Prediction of Crystal Structure of Mo2Ga2B and Its Evolution to Layered Boride Mo2B

Conventional Mn+1AXn phases are a large family of compounds that have been limited to carbides and nitrides. Herein, the stable structure of Mo2Ga2B, a typical boron‐based ternary phase in the Mo‐Ga‐B system, using a computational structure search approach is predicted. The predicted hexagonal‐layered structure is the typical structure of traditional Mn+1AXn phases, and two Ga layers separate Mo2B blocks in Mo2Ga2B, which is different from the M2AX phases. The analysis of phonon dispersions and elastic constants confirms that the hexagonal‐layered structure exhibits both dynamical and mechanical stability, respectively. The tensile and shear stress–strain curves are obtained, and the structural stability is investigated by analyzing the stability of chemical bonds under tensile and shear deformations. Layered Mo2B can be obtained by the removal of Ga layer from the precursor Mo2Ga2B. Theoretical predictions indicate that monolayer Mo2B is metallic, and has potential applications as an anode and thermoelectric material.

Seismic stability of the famous telemly bridge-building located in Algiers

This work focuses on the static and dynamic stability of the historical irregularly shaped bridge-building located in a rocky valley at Telemly, Algiers. This work focuses on the static and dynamic stability of the famous building-bridge located in Telemely district, Algiers. The Telemly building-bridge is a structure that combines the functions of a residential building and a road/pedestrian bridge. It is located in the Telemly district of Alger-Centre, Algeria. This building-bridge of Telemely is one of two kinds in the world. This structure is composed of eight floors used for residential habitation, and the last slab supports a roadway and serves for automobile traffic. The stability study is performed simultaneously based on the Algerian seismic code for buildings RPA99 Version 2003 and the Algerian seismic code for bridges RPOA. This structure is located in a high seismic zone according to Algerian seismic codes. A three-dimensional finite elements model of this famous structure is realized using a finite elements code. Static and dynamic analyses were conducted using this finite elements model under static loads, seismic excitations and moving loads on the last floor. The responses of the different components of Telemly building-bridge were calculated and illustrated. The results of this study, represented in terms of internal efforts and displacements, demonstrate that the structure of Telemly building-bridge presents good performances under moving loads and seismic excitations.

Structural, electronic, optical, mechanical, and phononic bulk properties of tetragonal trirutile antimonate MSb2O6 (M = Fe, Co, Ni, or Zn): a first-principles prediction for optoelectronic applications

Abstract This work does an extensive analysis of the optoelectronic and mechanical properties of the tri rutile structure type 3d transition metal Antimonate MSb2O6 (M = Fe, Co, Ni, or Zn), for the first time, utilizing the pseudo-potential plane wave approach within the density functional theory framework. When calculating the structural, optical, and mechanical properties, the exchange–correlation interactions were studied using the GGA-PBE functional, whereas when computing electronic, it is analyzed using the HSE06 hybrid functional. The equilibrium lattice parameters exhibit good agreement with the available experimental results. The electronic properties were estimated using the GGA-PBE and HSE06 functionals. Based on the calculated electronic properties with the GGA-PBE functional, the FeSb2O6, CoSb2O6, and NiSb2O6 materials exhibit metallic behavior with energy gap values of 0 eV, while ZnSb2O6 is a semiconductor with a narrow direct band gap (Γ–Γ) of 0.5 eV. Furthermore, the computed band gaps using the HSE06 functional are 0 eV, 0 eV, 1 eV (Γ–Γ), and 4 eV (Γ–Γ) for FeSb2O6, CoSb2O6, NiSb2O6, and ZnSb2O6, respectively. Density of states diagrams were used to gain deeper insights into the characteristics of the energy bands. The optical properties of these compounds, such as the dielectric function, energy loss function, conductivity, reflectivity, refractive index, and absorption coefficient were investigated over the energy range of 0 to 40 eV. The materials exhibited a high absorption coefficient and a significantly low reflectivity within the UV–vis energy spectrum. The negative cohesive energy Ecoh implies the chemical (thermodynamic) stability of the trirutile MSb2O6 (M = Fe, Co, Ni, or Zn). Mechanical stability is confirmed by applying the Born stability criteria using elastic constants (Cij). The absence of imaginary frequencies in the phonon spectrum calculations confirms the dynamic stability of the studied compounds. These results are consistent with previous experimental research on these materials in photocatalysis and gas sensor applications. On the other hand, these compounds possess exceptional high and broad optical absorption UV range, making them suitable for use in next-generation ultraviolet photodetectors.

Risk factors for screw loosening in patients with lumbar degenerative spondylolisthesis treated with Dynesys dynamic stabilization.

Posterior decompression with Dynesys dynamic stabilization (DDS) is an effective treatment option for degenerative spondylolisthesis. However, postoperative pedicle screw loosening (PSL) often results in poor outcomes. Determining possible risk factors may aid in making informed decisions. This study aimed to evaluate the incidence and risk factors for PSL in patients who underwent elective DDS. We conducted a retrospective analysis of 94 patients with L4-L5 grade I degenerative spondylolisthesis who underwent DSS at a single academic institution between May 2008 and February 2015. Screw loosening was defined as a halo or double halo sign on plain radiography. The screw loosening rate was 4.8% among screws and 11.7% among patients. Multivariate analysis revealed that age >65 years, smoking, segmental ROM >13°, and L1 vertebral body (VB) Hounsfield unit (HU) <110 were risk factors for PSL after DDS. Five reoperations were performed; however, no screw breakage was observed. The Oswestry Disability Index and visual analog scale scores did not differ significantly at the final follow-up between the screw loosening and no screw loosening groups. Our study suggests that patients with age >65 years, smoking, segmental ROM >13°, and L1 VB HU <110 had a higher risk of PSL after DDS.

Computational insights into transition metal-based BaCoX3 (X = Cl, Br, I) halide perovskites for spintronics, photovoltaics, and renewable energy devices

Ab-initio simulations using density functional theory (DFT) were employed to investigate the structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of halide perovskites \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoX}_3$$\\end{document} (X = Cl, Br, I). Structural optimization and mechanical stability assessments confirm the reliability of these perovskites in a hexagonal P\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$6_3$$\\end{document}mc symmetry. The stability of the ferromagnetic phase was validated through total crystal energy minimization via Murnaghan’s equation of state. Electronic band structures and density of states, derived from the generalized gradient approximation (GGA), reveal a semiconducting ferromagnetic nature in the spin up channel, spotlighting their potential in semiconductor spintronic applications. Phonon dispersion analysis of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoCl}_3$$\\end{document} and \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoBr}_3$$\\end{document} revealed positive phonon modes throughout the entire Brillouin zone, confirming their dynamical stability. In contrast, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoI}_3$$\\end{document} demonstrated dynamical instability. The elastic constants confirm the mechanical stability and ductile nature of the perovskites. Optical and dielectric properties of these perovskites show significant UV absorption and photoconductivity, making them highly suitable for optoelectronic and solar cell applications. Finally, transport properties, such as the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit (ZT) unveil their exceptional thermoelectric performance. Combining half-metallic ferromagnetic traits with superior thermoelectric and optoelectronic performance positions \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {BaCoX}_3$$\\end{document} compounds as exceptional candidates for applications in spintronics, optoelectronics, and thermoelectrics. This comprehensive investigation demonstrates their ability to excel across a diverse array of advanced technological applications.

Structural, Elastic, Electronic, Dynamic, and Thermal Properties of SrAl2O4 with an Orthorhombic Structure Under Pressure

Its outstanding mechanical and thermodynamic characteristics make SrAl2O4 a highly desirable ceramic material for high-temperature applications. However, the effects of elevated pressure on the structural and other properties of SrAl2O4 are still poorly understood. This study encompassed structural, elastic, electronic, dynamic, and thermal characteristics. Band structure calculations indicate that the direct band gap of SrAl2O4 is 4.54 eV. In addition, the Cauchy pressures provide evidence of the brittle characteristics of SrAl2O4. The mechanical and dynamic stability of SrAl2O4 is evident from the accurate determination of its elastic constants and phonon dispersion relations. In addition, a comprehensive analysis was conducted of the relationship between specific heat and entropy concerning temperature variations.

Dynamic instabilities and turbulence of merged rotating Bose–Einstein condensates

We present the simulation results of merging harmonically confined rotating Bose–Einstein condensates in two dimensions. Merging of the condensate is triggered by positioning the rotation axis at the trap minima and moving both condensates toward each other while slowly ramping their rotation frequency. We analyze the dynamics of the merged condensate by letting them evolve under a single harmonic trap. We systematically investigate the formation of solitonic and vortex structures in the final, unified condensate, considering both nonrotating and rotating initial states. In both cases, merging leads to the formation of solitons that decay into vortex pairs through snake instability, and subsequently, these pairs annihilate. Soliton formation and decay-induced phase excitations generate sound waves, more pronounced when the merging time is short. We witness no sound wave generation at sufficiently longer merging times that finally leads to the condensate reaching its ground state. With rotation, we notice off-axis merging (where the rotation axes are not aligned), leading to the distortion and weakening of soliton formation. The incompressible kinetic energy spectrum exhibits a Kolmogorov-like cascade [E(k)∼k−5/3] in the initial stage for merging condensates rotating above a critical frequency and a Vinen-like cascade [E(k)∼k−1] at a later time for all cases. Our findings hold potential significance for atomic interferometry, continuous atomic lasers, and quantum sensing applications.

Anticipatory postural adjustment deficits in children with developmental coordination disorder during a self-induced prehension task while standing on one leg

Effective postural control is essential for motor skill development, yet the specific nature of anticipatory control in children with Developmental Coordination Disorder (DCD) remains poorly understood for complex or dynamic stability tasks. This study investigated anticipatory postural adjustments (APA) during a self-initiated dynamic stability task. The Can Placement Task (CPT)—a self-initiated dynamic stability task—was performed by 23 children with DCD and 30 typically developing (TD) children aged 9–12 years. The task involved standing on one leg while also repositioning a can on the floor. Center of pressure (COP) movement was recorded by two force platforms during the five phases of the movement. The ground reaction force measured external support during both descent to pick up the can and ascent after replacing the can. The study used a mixed-design approach with group (DCD, TD) as a between-subject factor and condition (can position close or far) and phase of movement as within-subject. Distinct movement control characteristics were shown for children with DCD including a greater range of COP movement and higher COP velocity in the anterior-posterior direction prior to movement initiation compared with TD. The DCD group also relied more on external support during both the downward and upward phases of the CPT and needed more trials to complete the task. Only two significant interaction effects involving Group and the within-subject factors emerged. Children with DCD swayed significantly more at specific phases of the task, especially when coming up and restoring balance, and did not adapt COP velocity as a function of reaching distance. Dynamic control of posture in children with DCD is impaired as they struggle to generate the effective APAs necessary to maintain dynamic stability which leads to greater reliance on external support and more corrective movements. The CPT provides a valuable assessment of posture and dynamic balance control during a complex prehension movement performed on one leg; the task highlights distinct movement patterns between children with and without DCD.

Strategic Influence in Focus: Assessing the Roles of Defense Expenditures, Foreign Capital, Political Stability, and Energy Sustainability in Geopolitical Dynamics

Strategic Influence in Focus: Assessing the Roles of Defense Expenditures, Foreign Capital, Political Stability, and Energy Sustainability in Geopolitical Dynamics

Effect of Chiropractic Intervention on Oculomotor and Attentional Visual Outcomes in Young Adults With Long-Term Mild Traumatic Brain Injury: A Randomized Controlled Trial.

This study aimed to establish if chiropractic care can improve oculomotor and cognitive symptoms in individuals with persistent postconcussion syndrome (PPCS). A single-blind, randomized controlled intervention study recorded baseline computerized eye-tracker assessment (CEA) outcomes in 40 young adults with PPCS following mild traumatic brain injury. Participants were randomly allocated to either a chiropractic or age-matched active control intervention, and the change in CEA outcomes following intervention was compared between the chiropractic and control groups. A battery of CEAs including egocentric localization, fixation stability, pursuit, saccades, Stroop, and the vestibulo-ocular reflex, were used to assess oculomotor function, visual attention/processing, and selective attention. Relative to the control group, participants receiving the chiropractic intervention scored better in the Stroop test (P < .001), had improved gaze stability during both vestibulo-ocular reflex (P < .001) and fixation stability (P = .009), and a lower vertical error in egocentric localization (P < .001). However, performance was poorer in pursuits, where they had an increased tracking error (P < .001). Chiropractic care in participants with PPCS significantly improved static and dynamic gaze stability, and performance in the Stroop test, compared with a control intervention. These results suggest that chiropractic care can offer a novel avenue for alleviating certain visual and cognitive symptoms in patients with PPCS. It also adds to the growing evidence that suggests that some longstanding PPCS visual symptoms may have a spinal or proprioceptive basis.

Ca-decorated holey graphyne for reversible hydrogen storage: Insights from DFT analysis

We theoretically examine the hydrogen storage capabilities of a newly synthesized carbon allotrope known as holey graphyne (HGY). HGY exhibits weak interaction with H2, making it unsuitable for storage, thus prompting surface modification. Ca binds to HGY with a binding energy of −2.03 eV and experiences a diffusion energy barrier of 1.49 eV. The supercell of HGY accommodates six Ca atoms, and each Ca atom binds five H2 with an average binding energy of −0.27 eV, resulting in an uptake capacity of 12.07 wt% and desorption temperature of 331K at 5 bar. AIMD simulation and positive phonon frequencies confirms thermal and dynamic stability of Ca-decorated HGY. RDG analysis reveals electrostatic interactions between Ca and HGY, and van der Waals interactions between H2 and Ca. Thus, Ca-decorated HGY shows exceptional uptake capacity, desirable adsorption energy and desorption temperature, making it a suitable material for on-board reversible hydrogen storage in light vehicles.

Ab initio investigation of structural, elastic, dynamic, and electronic properties of YN binary rare earth nitride in ZB cubic phase

This research employs ab initio calculations, utilizing the FP-LAPW method as implemented in WIEN2k and the PP-PW method in QUANTUM ESPRESSO, within the framework of the GGA-PBE approximation, to investigate the physical properties of the rare earth nitride binary YN. Structural parameters of YN are determined, yielding predictive results consistent with recent calculations. Furthermore, a comprehensive investigation into mechanical behavior and elastic properties confirms the mechanical stability of YN in its cubic ZB structure. An analysis of the anisotropy coefficient reveals its elastic anisotropy. The dynamic stability of YN is investigated through PW-scf calculations using DFPT theory, enabling the calculation of phonon spectra, frequencies, and polarization vectors. These findings affirm the stability of YN material in the B3 structure, which can be experimentally synthesized. Electronic properties are probed, showing semiconductor behavior, utilizing GGA mBJ, and YS PBE0 methods to ascertain band gap values in the B3 structure. This suggests its potential for adoption in optoelectronic and photonic devices.

High intensity dynamic stability gait training for people with multiple sclerosis: a pilot study

High intensity dynamic stability gait training for people with multiple sclerosis: a pilot study

Enhanced dynamical stability of rotating composite pipes conveying fluid by a smart piezoelectric design

Enhanced dynamical stability of rotating composite pipes conveying fluid by a smart piezoelectric design

Dynamics of Binary Planets within Star Clusters

We develop analytical tools and perform three-body simulations to investigate the orbital evolution and dynamical stability of binary planets within star clusters. Our analytical results show that the orbital stability of a planetary-mass binary against passing stars is mainly related to its orbital period. Critical flybys, defined as stellar encounters with energy kicks comparable to the binary binding energy, can efficiently produce a wide range of semimajor axes (a) and eccentricities (e) from a dominant population of primordially tight Jupiter-mass binary objects (JuMBOs). The critical flyby criterion we derived offers an improvement over the commonly used tidal radius criterion, particularly in high-speed stellar encounters. Applying our results to the recently discovered JuMBOs by the James Webb Space Telescope (JWST), our simulations suggest that to match the observed ∼9% wide binary fraction, an initial semimajor axis of a 0 ∼ 10–20 au and a density-weighted residence time of χ ≳ 104 Myr pc−3 are favored. These results imply that the JWST JuMBOs probably formed as tight binaries near the cluster core.

Research on a New Topology and Reactive Power Compensation Application of Reinjection Multilevel Voltage Source Converter

Based on the principles of reinjection converter technology and submodule operation, a novel topology for a reinjection multilevel voltage source converter (RMVSC) is proposed. In this topology, submodules are dynamically connected in series as the reinjection circuit. This new topology retains all the functions of the RMVSC while offering flexible control of the reinjection circuit and ease of modularization, making it highly suitable for high-voltage, high-power applications. A circulating drive pulse sequence was developed for the 7-level serial submodule RMVSC, ensuring dynamic stability of the submodule voltage and maintaining low harmonic distortion when interfaced with the grid. Building on this, a double-loop control strategy—comprising an outer power loop and an inner current loop—was proposed for the static synchronous compensator (STATCOM) of RMVSC. A simulation model was constructed in PSCAD/EMTDC, and the simulation results confirm the excellent performance of the proposed topology and the effectiveness of both the modulation strategy and the double-loop control strategy. The RMVSC-STATCOM demonstrates continuous and bidirectional reactive power regulation, with high control accuracy and superior compensation current quality.

Comparison of dynamic neuromusuclar stabilisation and Maitland’s mobilisation on nerve conductivity in subjects with cervical radiculopathy

Aim. To compare the effect of Dynamic Neuromuscular Stabilisation and Maitland mobilisation in improving nerve conductivity and muscle activity in patients with cervical radiculopathy Methodology. A pilot study done on 34 subjects with unilateral cervical radiculopathy was conducted based on selection criteria. Subjects were divided into 2 groups. Group DNS received Dynamic neuromuscular stabilisation exercise. Group MM received Maitland mobilisation. Pre-test was done using NCV for median nerve conductivity and EMG for pronator teres muscle activity. Following the intervention’s termination, a post-test was conducted using the same measurements. The gathered data was put to use in statistics. Result. The statistics revealed that there is no significant difference between two groups. But group DNS who were treated with Dynamic neuromuscular stabilisation showed a better improvement in nerve conductivity and muscle activity than the subjects treated with Maitland mobilisation in cervical radiculopathy.

The Influence of high kinesiophobia on dynamic postural stability among females with patellofemoral pain syndrome during a single-leg squat test

Objective. The purpose of this study was to examine the effect of Kinesiophobia level on postural stability during Single Leg Squat Test (SLST) in females with patellofemoral pain syndrome (PFPS). Methods. Forty women with PFPS were divided into a High Kinesiophobia level group (HK), a Low Kinesiophobia level group (LK), and a pain-free control group of twenty participants. Postural stability was measured during the performance of the Single Leg Squat Test (SLST) on a force platform. The centre of pressure (COP) excursion and velocity were recorded. Results. The HK group had a significantly higher mean medial–lateral and anterior-posterior COP displacement compared to the LK and control groups. However, the results showed no significant differences in COP variables (velocity and displacement) between LK and healthy subjects. Muscle strength of participants with PFPS presented a significant deficit compared to healthy control group. Conclusions. High Kinesiophobia negatively affects postural stability during the SLST. Kinesiophobia should be considered during the assessment and management of PFPS.