Rotational Distributions Research Articles

THE IMPORTANCE OF LIGAMENT PROPERTIES IN CERVICAL SPINE KINEMATICS: A FINITE ELEMENT STUDY

Rotation of the cervical spine beyond its normal range of motion is a leading cause of fall-related spinal cord injuries (SCIs) in older adults. This rotation is constrained, in part, by the spinal ligaments. The experimentally measured properties of these ligaments are tabulated in literature, including sex-specific properties; however, their influence on the rotation kinematics of the cervical spine has not been compared. We examined how different mechanical properties of spinal ligaments, including sex-specific properties, affected the rotational kinematics of the cervical spine using finite element analysis (FEA). Ligament properties most influenced the rotation of the lower cervical spine, with increased ligament stiffness reducing rotation. Ligament deformation remained mostly in the toe region of their force-displacement curves, emphasizing the need to incorporate non-linear ligament behavior in FEA. Predictions made using one set of experimental properties (Property 1) better-matched experimental kinematic data. Using sex-specific properties had a moderate effect (6% in extension, –3% in flexion) on rotation, with a greater impact on extension. Ligament properties also affected the segmental distribution of rotation, causing a variability of 3–21% at different levels. We emphasized the need to incorporate tailored approaches to FEA to obtain clinically relevant results when modeling flexion/extension rotation.

Modelling chemical clocks. Theoretical evidences of the space and time evolution of [s/α] in the Galactic disc with Gaia-ESO survey

Chemical clocks based on s-process element/α element ratios are widely used to estimate the ages of Galactic stellar populations. However, the s/α versus age relations are not universal, varying with metallicity, location in the Galactic disc, and specific s-process elements. Moreover, current Galactic chemical evolution models struggle to reproduce the observed s/α increase at young ages, particularly for Ba. Our aim is to provide chemical evolution models for different regions of the Milky Way (MW) disc in order to identify the conditions required to reproduce the observed s/H s/Fe and s/α versus age relations. We adopted a detailed multi-zone chemical evolution model for the MW including state-of-the-art nucleosynthesis prescriptions for neutron-capture elements. The s-process elements were synthesised in asymptotic giant branch (AGB) stars and rotating massive stars, while r-process elements originate from neutron star mergers and magneto-rotational supernovae. Starting from a baseline model that successfully reproduces a wide range of neutron-capture element abundance patterns, we explored variations in gas infall/star formation history scenarios, AGB yield dependencies on progenitor stars, and rotational velocity distributions for massive stars. We compared the results of our model with the open clusters dataset from the sixth data release of the Gaia -ESO survey. A three-infall scenario for disc formation aligns better with the observed trends. The models capture the rise of s/α with age in the outer regions but fail towards the inner regions, with larger discrepancies for second s-process peak elements. Specifically, Ba production in the last 3 Gyr of chemical evolution would need to increase by slightly more than half to match the observations. The s-process contribution from low-mass ( 1.1 M_⊙) AGB stars helps reconcile predictions with data but it requires a too-strong increase that is not predicted by current nucleosynthesis calculations, even with a potential i-process contribution. Variations in the metallicity dependence of AGB yields either worsen the agreement or show inconsistent effects across elements, while distributions of massive star rotational velocities with lower velocity at high metallicities fail to improve results due to balanced effects on different elements. The predictions of our model confirm, as expected, that there is no single relationship s/α versus age and that it varies along the MW disc. However, the current prescriptions for neutron-capture element yields are not able to fully capture the complexity of evolution, particularly in the inner disc.

Recent Advances in Ozone Photochemistry: A Lambda Doublet Propensity and Spin-Forbidden Channels.

Recent studies on ozone photodissociation in the Hartley and Huggins bands have provided new insights into the dissociation dynamics and product state distributions. A Λ-doublet propensity in the photodissociation has been identified through experiment and theory as the origin of the oscillatory O2(a1Δg) rotational distributions and provides a promising diagnostic for determining the relative contributions of 3A' and 3A″ states in Huggins band spin-forbidden processes. Recent experiments on spin-forbidden dissociation have provided detailed information about the vibrational and rotational distributions of the O2 products and the branching ratios between the O2 electronic states, serving as a motivation for high-level theory.

Molecular Distributions and Abundances in the Binary-shaped Outflow of V Hya

Binaries are known to play a key role in the mass loss and dynamical environments of evolved stars. Stellar and substellar companion interactions produce complex wind morphologies including rotating/expanding disks, bipolar outflows, and spiral wind patterns; however, the connection between these many structures and the gas-phase chemistry they harbor is not well constrained. To expand the sample of chemical inventories in interacting systems, we present a detailed spectroscopic case study of the binary C-rich asymptotic giant branch (AGB) star V Hya. Using spatially resolved Atacama Large Millimeter/submillimeter Array observations at Bands 3, 6, and 7, we characterize the rotational emission lines and distributions of molecules in its surrounding disk undergoing dynamical expansion (DUDE). We detect emission from over 15 molecules and isotopologues toward this source, and present resolved maps for the brightest tracers of carbonaceous chemistry (e.g., CCH, C4H, HC5N, HNC, and CH3CN ). Employing LTE and non-LTE models of emission from the DUDE, we estimate the abundance distributions for optically thin species, and compare them with prototypical carbon-rich AGB envelopes. We find that the average abundances of detected species are within a factor of ∼5 from sources with similar mass-loss rates; however, the distribution of daughter species in V Hya is much more compact, with carbon chain species (CCH, C4H, and HC3N) appearing with abundances >10−7 even in the innermost sampled regions (200 au) of the disk.

Disk-locking Regulates Stellar Rotation in Young Clusters: Insights from NGC 2264

Abstract Many young clusters possess extended main sequences, a phenomenon commonly ascribed to stellar rotation. However, the mechanism behind their very wide stellar rotation distributions remains unclear. A proposed explanation is that magnetic star–disk interaction can regulate stellar rotation, i.e., protostars with longer disk lifetimes will eventually evolve into slow rotators, and vice versa. To examine this hypothesis, we took the star-forming region NGC 2264, as a test bed. We have studied its high-mass pre-main-sequence and zero-age main-sequence (ZAMS) stars. We find that, on average, diskless pre-main-sequence stars rotate faster than their disk-bearing counterparts. The stellar rotation distribution of the ZAMS stars is similar to evolved young clusters. We conclude that disk-locking may play a crucial role in the rotational velocity distribution of intermediate-mass early-type stars. We suggest that the observed wide stellar rotation distributions in many young clusters can occur in their early stages.

Investigation of the Gas-Phase N2+ + CH3CN Reaction at Low Temperatures.

Rate coefficients for ion-polar-molecule reactions between acetonitrile molecules (CH3CN) and nitrogen molecular ions (N2+), which are of importance to the upper atmospheric chemistry of Saturn's moon Titan, were measured for the first time at low translational temperatures. In the experiments, the reaction between sympathetically cooled N2+ ions embedded in laser-cooled Ca+ Coulomb crystals and velocity-selected acetonitrile molecules generated using a wavy Stark velocity filter was studied to determine the reaction rate coefficients. Capture rate coefficients calculated by the Su-Chesnavich approach and by the perturbed rotational state theory considering the rotational state distribution of CH3CN were compared to the experimental rate coefficients. The results indicate that the present reaction is barrierless and that the rate coefficients are consistent with the capture rate coefficients. The potential energy surface of the reaction product CH3CN+ was calculated by the CCSD(T)/aug-cc-pVQZ level theory to explore possible isomerization and dissociation pathways. Several locally stable structures leading to H2CCN+, HCCNH+, HCNCH+, and H2CNC+ were found, while no intrinsic reaction coordinate leading to the CHCN+ formation pathway accompanied by H2 abstraction has been identified. The H2CCN+ + H dissociation channel is a major pathway of the reaction product, though theoretical calculations suggest the CHCN+ + H2 dissociation channel is energetically feasible. The present experimental and theoretical studies will contribute to the accurate modeling of nitrile chemistry in interstellar matter and in the upper atmosphere of Titan.

Deciphering carbon–sulfur rotational distribution in a crystalline host for enhanced red persistent organic phosphorescence

Deciphering carbon–sulfur rotational distribution in a crystalline host for enhanced red persistent organic phosphorescence

Novel Energy-efficient Modified LEACH Routing Protocol for Wireless Sensor Networks

Introduction: In wireless sensor networks (WSNs), hierarchical clustered routing protocols play a crucial role in minimizing energy consumption. The Low Energy Adaptive Clustering Hierarchy (LEACH) architecture is commonly employed for application-specific protocols in WSNs. However, the LEACH protocol may lead to increased energy consumption within the network if the rotational distribution of cluster heads (CHs) is not considered. Methods: A novel average energy, residual energy-based modified LEACH (aerem-LEACH) routing protocol for improving the WSN’s energy efficiency is proposed. This approach simultaneously considers the average energy of the networks and the residual node energy for routing, thereby reducing overall power consumption. Results: The suggested approach in aerem-LEACH accounts for optimal CHs numbers, and nodes in close proximity to the sink are forbidden from participating in cluster formation in order to achieve sufficient performance in the form of reduced sensor node energy consumption. Furthermore, a new threshold is employed in the proposed approach for selecting CHs for the network, and the aerem-LEACH uses free space, multiple hopping, and a hybrid communicating model for an energy-efficient network. Conclusion: The simulation result demonstrates that there is a substantial reduction in the consumption of energy in WSNs with the proposed aerem-LEACH routing protocol compared with existing routing protocols, namely Stable Energy Efficient Network (SEEN), Energy Efficient LEACH (EE LEACH), Optical LEACH (O-LEACH), LEACH-Mobile (LEACH-M), LEACHCentralized (LEACH-C), and LEACH for small-scale as well as large-scale sensor field.

Photodesorption of CO ices: Rotational and translational energy distributions.

This study investigates the translational and rovibrational energy of vacuum-ultraviolet (VUV) photodesorbed CO molecules from a CO polycrystalline ice (15K) at ∼8eV. The electronic excitation was produced by a pulsed VUV laser, and the photodesorption of CO molecules in their ground and first vibrational states was observed using resonance enhanced multiphoton ionization. Time-of-flight and rotationally resolved spectra were measured, and the kinetic and internal energy distribution were obtained. Vibrationally cold CO molecules were observed, with little energy in rotation and translation (≤300meV). Ab Initio Molecular Dynamics (AIMD) simulations focusing on the description of the vibrational energy redistribution within an aggregate of 50 CO molecules were performed. The measured energy distributions are in very good agreement with those predicted by AIMD simulations. The rotational energy was found to slightly increase with translational energy, a trend also predicted by theory. This confirms the validity of the indirect desorption mechanism triggered by the excitation of CO in a high vibrational state.

Systematic study on the hydrogen abstraction reactions from oxygenated compounds by H and HO2

AbstractTo extend the rule‐based approach for hydrogen abstraction reactions from oxygenated compounds, a systematic investigation was performed to examine the reactivity of gas‐phase hydrogen abstraction reactions from alkyl groups (methyl and ethyl groups) bound to oxygen atoms in five types of oxygenated compounds (alcohols, ethers, formate esters, acetate esters, and carbonate esters) by H atoms and HO2 radicals comprehensively considering rotational conformers. Quantum chemical calculations were conducted at the CBS‐QB3 level for stationary points. Rate constants were determined employing conventional transition state theory (TST). For hydrogen abstraction reactions by H, the rotational conformer distribution partition function was employed to approximate partition functions, owing to the similarity in vibrational energy‐level structures among conformers. In hydrogen abstraction reactions by HO2, the vibrational structures of transition‐state (TS) conformers varied significantly due to the hydrogen bonding, leading to an inappropriate evaluation of rate constants when using the lowest‐energy conformer as a representative. Therefore, the rate constants were calculated by the multi‐structural TST. It was revealed that the differences in functional groups containing O atoms mainly affect the bond dissociation energies of the C–H bonds and the activation energies of hydrogen abstraction reactions only when the C atoms are adjacent to the O atoms. Additionally, it was found that hydrogen bonds formed in the TSs show minor effect on rate parameters for the overall rate constants, apart from the reduction of the pre‐exponential factors for the H‐abstraction reactions from the methylene position of ethyl groups. The comparison with the rate constants from previous studies showed reasonable results, indicating that the rate constants in this study, which thoroughly consider rotational conformers, can be the current best estimates.

Frequency response control strategy of wind farm based on wind turbine state

Abstract With the development of new power systems, the inertia of the power system generated by connecting the air power generation to the high power network is gradually decreasing. First, the proposed piecewise element is to determine the production frequency of the wind electric field classification based on the operating state and average velocity of the wind electric field. On the other hand, the inertia and frequency during the parameter operation decrease as a function of the rotational air dynamic ability, while monitoring the rotational air distribution dynamics closely and monitoring the change in the reference power. This allows power to be used to convey unit rotor energy at higher frequencies to avoid the lower unit speed involved in frequency control. Simulation results show that the strategy can fix the active effects of power based on the fan, the state of the wind electric field, and the possible kinetic energy during rotation.

Spin–Orbit Alignment of Early-type Astrometric Binaries and the Origin of Slow Rotators

The spin–orbit alignment of binary stars traces their formation and accretion history. Previous studies of spin–orbit alignment have been limited to small samples, slowly rotating solar-type stars, and/or wide visual binaries that not surprisingly manifest random spin–orbit orientations. We analyze 917 Gaia astrometric binaries across periods P = 100–3000 days (a = 0.5–5 au) that have B8-F1 IV/V primaries (M 1 = 1.5–3 M ⊙) and measured projected rotational velocities v sin i. The primary stars in face-on orbits exhibit substantially smaller v sin i compared to those in edge-on orbits at the 6σ level, demonstrating significant spin–orbit alignment. The primaries in our astrometric binaries are rotating more slowly than their single-star or wide-binary counterparts and therefore comprise the slow-rotator population in the observed bimodal rotational velocity distribution of early-type stars. We discuss formation models of close binaries where some of the disk angular momentum is transferred to the orbit and/or secondary spin, quenching angular momentum flow to the primary spin. The primaries in astrometric binaries with small mass ratios q = M 2/M 1 < 0.3 possess even smaller v sin i, consistent with model predictions. Meanwhile, astrometric binaries with large eccentricities e > 0.4 do not display spin–orbit alignment or spin reduction. Using a Monte Carlo technique, we measure a spin–orbit alignment fraction of F align = 75% ± 5% and an average spin reduction factor of 〈S align〉 = 0.43 ± 0.04. We conclude that 75% of close A-type binaries likely experienced circumbinary disk accretion and probably formed via disk fragmentation and inward disk migration. The remaining 25%, mostly those with e > 0.4, likely formed via core fragmentation and orbital decay via dynamical friction.

A study of the effects of welding parameters on macrostructure properties and heat distribution in FSW of aluminium metal matrix composite

Abstract The objective of this study is to present the effects of welding variables, specifically traverse speed and rotational speed, on the macrostructure of an aluminium metal matrix composite. This investigation includes comprehensive thermal monitoring and measurements within the weld joint area, utilizing infrared thermography to track the primary stages of friction stir welding (FSW). By examining different areas of the weld, to study aims to elucidate how temperature is distributed across the aluminium metal matrix composite in relation to the specific parameters of the FSW process, and to determine the subsequent impact on weld quality. Using infrared thermography, the researcher not only maps the thermal profile during welding, but also correlates these thermal variations with macrostructural changes in the aluminium metal matrix composite. This method allows for precise detection of temperature fluctuations and provides a detailed understanding of how traverse speed and rotational speed influence thermal distribution. Moreover, the study demonstrates the efficacy of thermography as a valuable tool for assessing weld quality. By capturing real-time thermal images, this technique enables the identification of potential defects and inconsistencies within the weld zone, facilitating a more thorough investigation into the integrity and performance of the welded joints. Ultimately, the findings aim to contribute to optimizing welding parameters on enhance the structural integrity and reliability of aluminium metal matrix composites in various applications.

The Densities in Diffuse and Translucent Molecular Clouds: Estimates from Observations of C2 and from Three-dimensional Extinction Maps

Newly computed collisional rate coefficients for the excitation of C2 in collisions with H2, presented recently by Najar & Kalugina, are significantly larger than the values adopted previously in models for the excitation of the C2 molecule, a widely used probe of the interstellar gas density. With these new rate coefficients, we have modeled the C2 rotational distributions inferred from visible and ultraviolet absorption observations of electronic transitions of C2 toward a collection of 46 nearby background sources. The inferred gas densities in the foreground interstellar clouds responsible for the observed C2 absorption are a factor 4–7 smaller than those inferred previously, a direct reflection of the larger collisional rate coefficients computed by Najar & Kalugina. These lower-density estimates are generally in good agreement with the peak densities inferred from 3D extinction maps for the relevant sight lines. In cases where H3+ absorption has also been observed and used to estimate the cosmic-ray ionization rate (CRIR), our estimates of the latter will also decrease accordingly because the H3+ abundance is a function of the ratio of the CRIR to the gas density.

High-Temperature Mechanical–Conductive Behaviors of Proton-Conducting Ceramic Electrolytes in Solid Oxide Fuel Cells

Proton-conducting solid oxide fuel cells (P-SOFCs) are widely studied for their lower working temperatures than oxygen-ion-conducting SOFCs (O-SOFCs). Due to the elevated preparation and operation temperatures varying from 500 °C to 1500 °C, high mechanical stresses can be developed in the electrolytes of SOFCs. The stresses will in turn impact the electrical conductivities, which is often omitted in current studies. In this work, the mechanical–conductive behaviors of Y-doped BaZrO3 (BZY) electrolytes for P-SOFCs under high temperatures are studied through molecular dynamics modeling. The Young’s moduli of BZY in fully hydrated and non-hydrated states are calculated with different Y-doping concentrations and at different temperatures. It is shown that Y doping, oxygen vacancies, and protonic point defects all lead to a decrease in the Young’s moduli of BZY at 773 K. The variations in the conductivities of BZY are then investigated by calculating the diffusion rates of protons in BZY at different triaxial, biaxial, and uniaxial strains from 673 K to 873 K. In all cases, the diffusion rate present a trend of first increasing and then decreasing from compression state to tension state. The variations in elementary affecting factors of proton diffusion, including hydroxide rotation, proton transfer, proton trapping, and proton distribution, are then analyzed in detail under different strains. It is concluded that the influences of strains on these factors collectively determine the changes in proton conductivity.

Influence of tool rotational speed in butt-joint friction stir welding (FSW): a thermo-mechanical simulation of AA6061

Friction Stir Welding (FSW) is a solid-state welding technique that involves joining two pieces of material by rotating a non-consumable pin at high RPM. This rotation generates heat through friction between the tool and the plates, enabling the welding process without the need for filler metal. Invented by the British Welding Institute (TWI) in 1991, FSW is renowned for creating strong welds and is widely used in the automotive and aerospace industries, in those industries the aluminum alloys are indispensable due to their unique combination of properties. This study focuses on how variations in rotational speed influence temperature distribution, the width of the heat-affected zone, and Von-Mises stress distribution in welded aluminum alloy 6061 sheets, this research aims to provide a comprehensive understanding of these effect, therefore the findings are expected to contribute to optimizing FSW parameters and enhancing weld quality. The analysis was conducted using the finite element method and ALTAIR software.

Torsion of end-bearing pile foundations in layered anisotropic geomaterials

ABSTRACT An analysis for the torsional dynamic response of end-bearing pile foundations embedded in a layered transversely isotropic geomaterial (soil/rock) is presented. The deformation of the transversely isotropic soil or rock is described by the method of separation of variables. The elasticity theory for a viscoelastic medium with frequency independent hysteretic material damping, and the Extended Hamilton’s Principle are utilised to derive the differential equations describing pile and soil motions. The differential equations are solved analytically in an iterative algorithm. The accuracy of the analysis is verified with existing studies reported in the literature for pile foundations embedded in a homogeneous and layered soil deposit. The effect of the degree of anisotropy on the pile-soil response – dynamic pile-head stiffness, distribution of pile rotation and torque with depth, dimensionless soil displacement function for various values of pile slenderness and pile-soil stiffness ratios in a homogenous soil deposit is investigated. Design charts of static pile-head stiffness in a homogeneous soil deposit for a wide range of pile-soil stiffness and pile slenderness ratios, and degree of anisotropy are also reported. The effect of soil layering for a pile embedded in a two-layered soil deposit is also studied.

Simulation Study of Dynamic Rotation and Deformation for Plasmonic Electric Field-Skyrmions

The topological properties of optical skyrmions in confined electromagnetic fields are perfectly presented through spin vectors and electric-field vectors. However, currently, electric-field optical skyrmions in surface plasmon polaritons are mostly presented in the form of a Néel type. Most control strategies involve linear directional movement, and topological manipulation methods are monotonous. We specifically propose a multi-arc symmetric slit array, which generates skyrmions from the surface plasmon polariton (SPP) field under excitation of a linearly polarized Gaussian light-source array and exhibits strong dependence processes on the rotation, deformation, and phase distribution of the incident light source. We also discuss the independence and synthesis of deformation and rotation related to phase difference and positions of regulation, respectively, which provide the possibility for rich deformations under different rotation states. Our work extends new ideas for the dynamic control of plasmonic skyrmions, which is of great significance to fields such as spin photonics and nano-positioning.

Real-space imaging for discovering a rotated node structure in metal-organic framework

Resolving the detailed structures of metal organic frameworks is of great significance for understanding their structure-property relation. Real-space imaging methods could exhibit superiority in revealing not only the local structure but also the bulk symmetry of these complex porous materials, compared to reciprocal-space diffraction methods, despite the technical challenges. Here we apply a low-dose imaging technique to clearly resolve the atomic structures of building units in a metal-organic framework, MIL-125. An unexpected node structure is discovered by directly imaging the rotation of Ti-O nodes, different from the unrotated structure predicted by previous X-ray diffraction. The imaged structure and symmetry can be confirmed by the structural simulations and energy calculations. Then, the distribution of node rotation from the edge to the center of a MIL-125 particle is revealed by the image analysis of Ti-O rotation. The related defects and surface terminations in MIL-125 are also investigated in the real-space images. These results not only unraveled the node symmetry in MIL-125 with atomic resolution but also inspired further studies on discovering more unpredicted structural changes in other porous materials by real-space imaging methods.

An Internal-State-Variable-Based Continuous Dynamic Recrystallization Model for Thermally Deformed TC18 Alloy.

Continuous dynamic recrystallization (CDRX) is widely acknowledged to occur during hot forming and plays a significant role in microstructure development in alloys with moderate to high stacking fault energy. In this work, the flow stress and CDRX behaviors of the TC18 alloy subjected to hot deformation across a wide range of processing conditions are studied. It is observed that deformation leads to the formation of new low-angle grain boundaries (LAGBs). Subgrains rotate by absorbing dislocations, resulting in an increase in LAGB misorientation and the transition of some LAGBs into high-angle grain boundaries (HAGBs). The HAGBs migrate within the material, assimilating the (sub)grain boundaries. Subsequently, an internal state variable (ISV)-based CDRX model is developed, incorporating parameters such as the dislocation density, adiabatic temperature rise, subgrain rotation, LAGB area, HAGB area, and LAGB misorientation angle distribution. The values of the correlation coefficient (R), relative average absolute error (RAAE), and root-mean-square error (RMSE) between the anticipated true stress and measured stress are 0.989, 6.69%, and 4.78 MPa, respectively. The predicted outcomes demonstrate good agreement with experimental findings. The evolving trends of the subgrain boundary area under various conditions are quantitatively analyzed by assessing the changes in dynamic recovery (DRV)-eliminated dislocations and misorientation angles. Moreover, the ISV-based model accurately predicts the decreases in grain and crystallite sizes with higher strain rates and lower temperatures. The projected outcomes also indicate a transition from a stable and coarse-grained microstructure to a continuously recrystallized substructure.