Polar Moment Research Articles

A Paradigm Shift for Torsional Stiffness of Nickel-Titanium Rotary Instruments: A Finite Element Analysis

IntroductionThe aim of this study was to investigate the influence of mass and the polar moment of inertia on the torsional behavior of nickel-titanium rotary instruments to understand which parameter of cross-sectional design had a key role in terms of torsional resistance. MethodsFour different instrument models were designed and meshed using computer-aided engineering software (SolidWorks; Dassault Systems, Waltham, MA). Instrument models shared the same characteristics, except for cross-sectional design; triangle, rectangle, square, and hollow square geometry was selected. Finite element analysis was performed simulating a static torsional test using the FEEPlus internal solver (Solid Works). Von Mises stress and torsional load at fracture were calculated by the software. Linear regression analysis was performed to investigate the relationship of the polar moment of inertia, cross-sectional area, inner core radius, and mass per volume on the torsional resistance of nickel-titanium rotary instruments. ResultsThe polar moment of inertia positively affected the maximum torsional load with the highest level of correlation (R2 = 0.917). It could be stated that the higher the polar moment of inertia is, the more maximum torsional load at fracture is present. Mass and cross-sectional area had a lower level of correlation compared with the polar moment of inertia (R2 = 0.5533). According to this, 2 instruments with the same mass/mm and/or cross-sectional area could have different torsional resistance. ConclusionsThe polar moment of inertia can be considered as the most important cross-sectional factor in determining the torsional resistance of rotary instruments over metal mass and cross-sectional area.

The effect of 3d states on band structure feature, optical and magnetic properties of TM-doped CdS: a theoretical insights

Based on the full-potential linearized augmented plane wave (FP-LAPW) method, we have investigated the electronic, structural, magnetic and optical properties of Cd0.9375TM0.0625S (TM = Mn, Fe, Co and Ni) compounds in the zinc-blende (ZB) ferromagnetic phase. The magnetic and electronic properties are treated using the PBE-GGA and TB-mBJ approximations. CdS is well known as a non-magnetic semiconductor. When CdS is doped with a transition metal (TM), Cd0.9375TM0.0625S (TM = Mn, Fe, Co) changes to half-semiconductors (HSC) and Cd0.9375Ni0.0625S to a half-metal (HM). It is found that the 3d-t2g states of the transition metal are responsible for generating spin polarization and magnetic moment in these compounds. All the considered compounds are ferromagnetic and the calculated total magnetic moment increases from 2 to 5 µB moving from Ni to Mn. The optical properties exhibited new peaks in the visible and ultraviolet regions due to the effect of free-carrier absorption related to the magnetic impurities. Our results show very good agreement to previous theoretical and experimental data. The results presented herein imply that TM-doped CdS has potential for applications in spintronic and optoelectronic device sectors in a wide energy range of the light spectrum from visible to ultraviolet.

Quantifying the effect of polar interactions on the behavior of binary mixtures: Phase, interfacial, and excess properties.

In this work, polar soft-Statistical Associating Fluid Theory (SAFT) was used in a systematic manner to quantify the influence of polar interactions on the phase equilibria, interfacial, and excess properties of binary mixtures. The theory was first validated with available molecular simulation data and then used to isolate the effect of polar interactions on the thermodynamic behavior of the mixtures by fixing the polar moment of one component while changing the polar moment of the second component from non-polar to either highly dipolar or quadrupolar, examining 15 different binary mixtures. It was determined that the type and magnitude of polar interactions have direct implications on the vapor-liquid equilibria (VLE), resulting in azeotropy for systems of either dipolar or quadrupolar fluids when mixed with non-polar or low polar strength fluids, while increasing the polar strength of one component shifts the VLE to be more ideal. Additionally, excess properties and interfacial properties such as interfacial tension, density profiles, and relative adsorption at the interface were also examined, establishing distinct enrichment in the case of mixtures with highly quadrupolar fluids. Finally, polar soft-SAFT was applied to describe the thermodynamic behavior of binary mixtures of experimental systems exhibiting various intermolecular interactions (non-polar and polar), not only demonstrating high accuracy and robustness through agreement with experimental data but also providing insights into the effect of polarity on the interfacial properties of the studied mixtures. This work proves the value of having an accurate theory for isolating the effect of polarity, especially for the design of ad hoc polar solvents.

Internal structural properties of the humeral diaphyses in an early modern human from Tianyuan Cave, China

Since the cross-sectional geometries of long bone diaphyses preserve evidence of a bone's mechanical loading history, examination of a bones' cross-sectional properties can be used to inform its loading history. Here, we use a novel colormap method to quantitatively visualize the topography of cortical bone, second moment of areas, and polar moment of areas along the humeral diaphyses to shed light on the potential manipulative behaviors of the Tianyuan 1 fossil human (Homo sapiens). We compare both humeri of Tianyuan 1 to two Holocene Chinese populations. Our results show that the standardized cortical bone thickness, standardized second moment of areas, and standardized polar moment of areas of Tianyuan 1's right humeral diaphysis are greater than those of the left diaphysis. This evidence supports the hypothesis that the individual was right-handed. The greater medial and lateral cortical reinforcement in the right midshaft humerus, relative to that of the left humerus, may be related to increased unilateral physical activity of the right arm. Unlike the lower humeral asymmetry of recent human agriculturalists, the relatively higher bilateral asymmetry, combined with the relatively larger femoral robusticity, indicate that Tianyuan 1 lived an activity lifestyle compared to the agriculturalists investigated in this study. The bilateral asymmetry of the right and left humeri may be more informative for discriminating between fossil and recent modern human samples than cortical thickness or rigidity values in only one side. This study also indicates that upper limb internal structures can provide important information for inferring the behavior of ancient hominins.

Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait

Although both the petiole and lamina of foliage leaves have been thoroughly studied, the transition zone between them has often been overlooked. We aimed to identify objectively measurable morphological and anatomical criteria for a generally valid definition of the petiole–lamina transition zone by comparing foliage leaves with various body plans (monocotyledons vs. dicotyledons) and spatial arrangements of petiole and lamina (two-dimensional vs. three-dimensional configurations). Cross-sectional geometry and tissue arrangement of petioles and transition zones were investigated via serial thin-sections and µCT. The changes in the cross-sectional geometries from the petiole to the transition zone and the course of the vascular bundles in the transition zone apparently depend on the spatial arrangement, while the arrangement of the vascular bundles in the petioles depends on the body plan. We found an exponential acropetal increase in the cross-sectional area and axial and polar second moments of area to be the defining characteristic of all transition zones studied, regardless of body plan or spatial arrangement. In conclusion, a variety of terms is used in the literature for describing the region between petiole and lamina. We prefer the term “petiole–lamina transition zone” to underline its three-dimensional nature and the integration of multiple gradients of geometry, shape, and size.

Spontaneous electric polarization of high-valance-ion-doped lead-free ferroelectric KSr2Nb5O15 by first-principles calculations

The polarizability and spontaneous polarization of high-valent cations (La3+, Bi3+, Y3+, Ti4+, Ta5+ and W6+) doped KSr2Nb5O15 lead-free tetragonal tungsten bronze ferroelectrics are calculated by using the first principles and experimental results. The cation dopants give different results, mainly due to the shortage of the additivity rule that ignores the ion polarizability of the missing atoms and the polarizability caused by the interaction of the atoms. The polarizability based on the dielectric constants is in good agreement with experimental values, especially for the structures with trivalent cation doping. And the spontaneous polarization calculated by the polar moment by using first principles result is consistent with that based on the polar moment from experiment. This shows the reliability of the prediction, and the spontaneous polarization of high-valent cations doped KSr2Nb5O15 are confirmed. This work paves a way for the spontaneous polarization of the ferroelectric materials with tetragonal tungsten bronze structure.

Secular changes in length of day: Effect of the mass redistribution

In this paper the secular change in the length of day due to mass redistribution effects is revisited using the Hamiltonian formalism of the Earth rotation theories. The framework is a two-layer deformable Earth model including dissipative effects at the core–mantle boundary, which are described through a coupling torque formulated by means of generalized forces. The theoretical development leads to the introduction of an effective time-averaged polar inertia moment, which allows us to quantify the level of core–mantle coupling throughout the secular evolution of the Earth. Taking advantage of the canonical procedure, we obtain a closed analytical formula for the secular deceleration of the rotation rate, numerical evaluation of which is performed using frequency-dependent Love numbers corresponding to solid and oceanic tides. With this Earth modeling, under the widespread assumption of totally coupled core and mantle layers in the long term response, a secular angular acceleration of − 1328.6′′ cy−2 is obtained, which is equivalent to an increase of 2.418 ms cy−1 in the length of day. The ocean tides and the semidiurnal band of the mass-redistribution-perturbing potential, mostly induced by the Moon, constitute the main part of this deceleration. This estimate is shown to be in very good agreement with recent observational values, and with other theoretical predictions including comparable modeling features.

Microphase separation in active filament systems maintained by cyclic dynamics of cluster size and order

The onset of polar flocking in active matter is discontinuous, akin to gas-liquid phase transitions, except that the steady state exhibits microphase separation into polar clusters. While these features have been observed in theoretical models and experiments, little is known about the underlying mesoscopic processes at the cluster level. Here we show that emergence and maintenance of polar order are governed by the interplay between the assembly and disassembly dynamics of clusters with varying size and degree of polar order. Using agent-based simulations of propelled filaments in a parameter regime relevant for actomyosin motility assays, we monitor the temporal evolution of cluster statistics and the transport processes of filaments between clusters. We find that, over a broad parameter range, the emergence of order is determined by nucleation and growth of polar clusters, where the nucleation threshold depends not only on the cluster size but also on its polar moment. Growth involves cluster self-replication, and polar order is established by cluster growth and fragmentation. Maintenance of the microphase-separated, polar-ordered state results from a cyclic dynamics in cluster size and order, driven by an interplay between cluster nucleation, coagulation, fragmentation and evaporation of single filaments. These findings are corroborated by a kinetic model for the cluster dynamics that includes these elementary cluster-level processes. It consistently reproduces the cluster statistics as well as the cyclic turnover from disordered to ordered clusters and back. Such cyclic kinetic processes could represent a general mechanism for the maintenance of order in active matter systems.

Quaternary Heusler alloys a future perspective for revolutionizing conventional semiconductor technology

Computational methods are infallible in predicting the ground state and numerous other properties of materials. There have been copious efforts to design high spin-polarized ferromagnetic materials for utilizing the electron spin to revolutionize conventional electronics. Our investigation relies on designing new quaternary half-metallic Heusler alloys CoFeXSn (X = Ru, Zr, Hf, Ta) with 100% spin polarization and high magnetic moment. Also, we have analyzed the effect of 3-d and 4-d transition metal electrons on electronic structures, mechanical and thermoelectric properties. The origin of the half-metallic gap and magnetism is conferred in detail using schematic representation. Mechanical parameters elucidate the brittle, ductile, and anisotropic nature of alloys. Based on the criteria of mechanical stability the alloys CoFeRuSn, and CoFeTaSn exhibit ductile nature whereas CoFeZrSn, and CoFeHfSn evinces brittle nature. The various elastic parameters authenticate the mechanical stability of the alloys. In addition to this, the thermoelectric parameters affirm the possible application of these materials in green energy harvesting.

Juvenile Body Mass Estimation from the Femur Using Postmortem Computed Tomography Data.

Skeletal estimation methods to reconstruct the juvenile biological profile are largely limited to those estimating age and, to a lesser extent, sex. While body mass is not generally estimated as part of the biological profile in forensic investigations, this is a logical candidate for inclusion in the forensic biological profile, as it has long been of interest in paleoanthropology and several methods to estimate juvenile body mass currently exist. To explore the performance of body mass estimation for juveniles, the authors tested the accuracy and precision of previously published panel regression formulae using two femoral measurements: the breadth of the distal metaphysis and the cross-sectional polar moment of inertia (J). The test sample consisted of measurements of 94 individuals from birth to 12.5 years of age, taken from postmortem computed tomography scans housed at the Office of the Medical Investigator, New Mexico, USA. Results indicate that body mass estimates are more accurate when estimated from cross-sectional than from metaphyseal measures. Both formulae, however, consistently underestimated weight, and the magnitude of the underestimation increased exponentially with age. This suggests that, contrary to what others have argued, body mass estimation is complicated by population variation in body composition. This study reinforces the importance of documenting and investigating the ontogeny of human variation. The global increase in medical imaging in clinical settings can be leveraged to obtain skeletal data for juveniles from a wide range of ontogenic environments, marking an exciting time for the study of human variation.

The past and future obliquity of Saturn as Titan migrates

Context. Giant planets are expected to form with near-zero obliquities. It has recently been shown that the fast migration of Titan could be responsible for the current 26.7°-tilt of Saturn’s spin axis. Aims. We aim to quantify the level of generality of this result by measuring the range of parameters allowing for this scenario to happen. Since Titan continues to migrate today, we also aim to determine the obliquity that Saturn will reach in the future. Methods. For a large variety of migration rates for Titan, we numerically propagated the orientation of Saturn’s spin axis both backwards and forwards in time. We explored a broad range of initial conditions after the late planetary migration, including both small and large obliquity values. Results. In the adiabatic regime, the likelihood of reproducing Saturn’s current spin-axis orientation is maximised for primordial obliquities between about 2° and 7°. For a slightly faster migration than expected from radio-science experiments, non-adiabatic effects even allow for exactly null primordial obliquities. Starting from such small tilts, Saturn’s spin axis can evolve up to its current state provided that: (i) the semi-major axis of Titan changed by more than 5% of its current value since the late planetary migration, and (ii) its migration rate does not exceed ten times the nominal measured rate. In comparison, observational data suggest that the increase in Titan’s semi-major axis exceeded 50% over 4 Gyr, and error bars imply that the current migration rate is unlikely to be larger than 1.5 times its nominal value. Conclusions. If Titan did migrate substantially before today, tilting Saturn from a small obliquity is not only possible, but it is the most likely scenario. Saturn’s obliquity is still expected to be increasing today and could exceed 65° in the future. Maximising the likelihood would also put strict constraints on Saturn’s polar moment of inertia. However, the possibility remains that Saturn’s primordial obliquity was already large, for instance as a result of a massive collision. The unambiguous distinction between these two scenarios would be given by a precise measure of Saturn’s polar moment of inertia.

Development of Methodology for Calculation of Discontinuous Circular Welds in Torsion

The main criterion for the performance of welds is the strength. The least durable ones are the corner joints used to perform various types of welded joints. In the literature, the methods of calculating the strength of welded joints with solid welds are considered in sufficient details. Methods of calculation of connection interrupted sutures absent. In this case, the greatest difficulty is the calculation of connections using circular intermittent welds, which are often performed in welded drums and pulleys; they work on torsion. Therefore, the development of methods for calculating circular intermittent welds for torsion is quite important.Shear stresses in welds from torque are determined depending on the value of the polar moment of resistance of its dangerous section. When determining the polar moment of resistance of the dangerous section of a circular discontinuous weld, it was represented by a set of sections in the form of a sector of a circular ring. The method of calculation of the polar moment of resistance of the rotated dangerous section of a circular discontinuous weld, which takes into account the relative length of the weld areas and their number, as well as the method of accurate and approximate calculation of shear stresses in the weld.

Invariant Image Representation Using Novel Fractional-Order Polar Harmonic Fourier Moments.

Continuous orthogonal moments, for which continuous functions are used as kernel functions, are invariant to rotation and scaling, and they have been greatly developed over the recent years. Among continuous orthogonal moments, polar harmonic Fourier moments (PHFMs) have superior performance and strong image description ability. In order to improve the performance of PHFMs in noise resistance and image reconstruction, PHFMs, which can only take integer numbers, are extended to fractional-order polar harmonic Fourier moments (FrPHFMs) in this paper. Firstly, the radial polynomials of integer-order PHFMs are modified to obtain fractional-order radial polynomials, and FrPHFMs are constructed based on the fractional-order radial polynomials; subsequently, the strong reconstruction ability, orthogonality, and geometric invariance of the proposed FrPHFMs are proven; and, finally, the performance of the proposed FrPHFMs is compared with that of integer-order PHFMs, fractional-order radial harmonic Fourier moments (FrRHFMs), fractional-order polar harmonic transforms (FrPHTs), and fractional-order Zernike moments (FrZMs). The experimental results show that the FrPHFMs constructed in this paper are superior to integer-order PHFMs and other fractional-order continuous orthogonal moments in terms of performance in image reconstruction and object recognition, as well as that the proposed FrPHFMs have strong image description ability and good stability.

Transient Behavior in Variable Geometry Industrial Gas Turbines: A Comprehensive Overview of Pertinent Modeling Techniques.

Generally, industrial gas turbines (IGT) face transient behavior during start-up, load change, shutdown and variations in ambient conditions. These transient conditions shift engine thermal equilibrium from one steady state to another steady state. In turn, various aero-thermal and mechanical stresses are developed that are adverse for engine’s reliability, availability, and overall health. The transient behavior needs to be accurately predicted since it is highly related to low cycle fatigue and early failures, especially in the hot regions of the gas turbine. In the present paper, several critical aspects related to transient behavior and its modeling are reviewed and studied from the point of view of identifying potential research gaps within the context of fault detection and diagnostics (FDD) under dynamic conditions. Among the considered topics are, (i) general transient regimes and pertinent model formulation techniques, (ii) control mechanism for part-load operation, (iii) developing a database of variable geometry inlet guide vanes (VIGVs) and variable bleed valves (VBVs) schedules along with selection framework, and (iv) data compilation of shaft’s polar moment of inertia for different types of engine’s configurations. This comprehensive literature document, considering all the aspects of transient behavior and its associated modeling techniques will serve as an anchor point for the future researchers, gas turbine operators and design engineers for effective prognostics, FDD and predictive condition monitoring for variable geometry IGT.

Hydrodynamic study of hyperon spin polarization in relativistic heavy ion collisions

We perform a systematic study of the spin polarization of hyperons in heavy-ion collisions using the MUSIC hydrodynamic model with A Multi-Phase Transport (AMPT) pre-equilibrium dynamics. Our model calculations nicely describe the measured collision-energy, centrality, rapidity, and $p_T$ dependence of $\Lambda$ polarization. We also study and predict the global spin polarization of $\Xi^-$ and $\Omega^-$ as a function of collision energy, which provides a baseline for the studies of the magnetic moment, spin, and mass dependence of the spin polarization. For the local spin polarization, we calculate the radial and azimuthal components of the transverse $\Lambda$ polarization and find specific modulating behavior which could reflect the circular vortical structure. However, our model fails to describe the azimuthal-angle dependence of the longitudinal and transverse $\Lambda$ polarization, which indicates that the hydrodynamic framework with the spin Cooper-Frye formula under the assumption of thermal equilibrium of spin degree of freedom needs to be improved.

The Influence of a Fluid Core and a Solid Inner Core on the Cassini State of Mercury

AbstractWe present a model of the Cassini state of Mercury that comprises an inner core, a fluid core, and a mantle. Our model includes inertial and gravitational torques between interior regions, and viscous and electromagnetic (EM) coupling at the boundaries of the fluid core. We show that the coupling between Mercury's interior regions is sufficiently strong that the obliquity of the mantle spin axis deviates from that of a rigid planet by no more than 0.01 arcmin. The mantle obliquity decreases with increasing inner core size, but the change between a large and no inner core is limited to 0.015 arcmin. EM coupling is stronger than viscous coupling at the inner core boundary and, if the core magnetic field strength is above 0.3 mT, locks the fluid and solid cores into a common precession motion. Because of the strong gravitational coupling between the mantle and inner core, the larger the inner core is, the more this coprecessing core is brought into an alignment with the mantle, and the more the obliquity of the polar moment of inertia approaches that expected for a rigid planet. The misalignment between the polar moment of inertia and mantle spin axis increases with inner core size, but is limited to 0.007 arcmin. Our results imply that the measured obliquities of the mantle spin axis and polar moment of inertia should coincide at the present‐day level of measurement errors, and cannot be distinguished from the obliquity of a rigid planet.

The large obliquity of Saturn explained by the fast migration of Titan

The obliquity of a planet is the tilt between its equator and its orbital plane. Giant planets are expected to form with near-zero obliquities. After its formation, some dynamical mechanism must therefore have tilted Saturn up to its current obliquity of 26.7{\deg}. This event is traditionally thought to have happened more than 4 Gyrs ago during the late planetary migration because of the crossing of a resonance between the spin-axis precession of Saturn and the nodal orbital precession mode of Neptune. Here, we show that the fast tidal migration of Titan measured by Lainey et al. (2020) is incompatible with this scenario, and that it offers a new explanation for Saturn's current obliquity. A significant migration of Titan would prevent any early resonance, invalidating previous constraints on the late planetary migration set by the tilting of Saturn. We propose instead that the resonance was encountered recently, about 1 Gyr ago, forcing Saturn's obliquity to increase from a small value (possibly less than 3{\deg}), up to its current state. This scenario suggests that Saturn's normalised polar moment of inertia lies between 0.224 and 0.237. Our findings bring out a new paradigm for the spin-axis evolution of Saturn, Jupiter, and possibly giant exoplanets in multiple systems, whereby obliquities are not settled once for all, but continuously evolve as a result of the migration of their satellites.

COMPUTER TECHNOLOGIES IN THE CALCULATION OF GEOMETRIC CHARACTERISTICS OF COMPLEX SECTIONS

None of the calculations for machine parts, structure elements and constructions for strength, rigidity and stability can be performed without using the geometric cross-section characteristics. These include: cross-sectional area, axial, centrifugal and polar moments of inertia, radius of gyration, axial and polar resistance moments of cross-section, etc. The article discusses the problem of technical specialties students` training quality improvement with information technologies aids. There is a review and proposed methodology of usage the software for calculating the geometric cross-sections properties. There are two groups of software: 1) software developed by teachers of higher educational institutions to use in the educational process; 2) industrial software for design engineers, which can also be used during the educational process. Using as an example the calculation of the geometric cross-sections properties of a complex section formed from several rolled profiles, it is demonstrated that the usage of programs "Geom 2006", "Compass 3D", "Consul" and "Constructor of sections" has the following advantages: decrease the costs of effort and time for routine mathematical calculations, makes it easier to find and correct errors made by manual calculations during individual study, which has a positive effect on the learning process; the implementation of calculation and graphic tasks using computer software significantly increases the interest of students for the discipline that is being studied and contributes to the better consolidation of theoretical knowledge and practical skills; students acquire skills in creating design schemes, preparing initial data, analyzing the obtained results, which are necessary for their further work with software systems for structures calculations during the course and for diploma design; it is especially useful to use the proposed programs for distance learning as an effective tool to organize individ-ual study.

Understanding and navigating the repercussions of the politically polarized climate in mental health.

The world is experiencing a moment of political polarization between liberal and conservative ideas, which has aggravated since the arrival of the Covid-19. Many countries (Brazil included) have been experiencing the generalized occurrence of people fighting over politics, in contexts including family, workplace, friendships, and romantic relationships. Over the past 2 years, it has been possible to observe an unexpected and overwhelming effect of the political climate on psychotherapy patients, some of whom have started to actively look for therapists who share their convictions. Brazil is experiencing a moment of severe sanitary, economic, social, and political crisis, which is directly affecting our patients. Nevertheless, the impact of the political climate on our population has not been systematically investigated. However, as the political environment is an inherent part of the social component of the psychosocial model, it is important that mental health professionals be prepared to have this conversation with their patients. This highlights the need to address these difficulties in supervision, rounds, and clinical discussions.

Optimal design and experiment study of the double spherical rotor of the MSCSG.

The magnetically suspended control and sense gyroscope (MSCSG) integrates spacecraft attitude measurement and control function; this paper proposes a double spherical rotor (DSR) for MSCSG. The DSR realizes the five degrees of freedom (DOFs) full active control and full channel magnetic path decoupling by the following design: the spherical axial/radial reluctance magnetic bearings are adopted to control the 3DOFs translation of rotor in the range of double spherical envelope, Lorentz force magnetic bearing (LFMB) is used to precisely drive the 2DOFs universal deflection of rotor. The optimization model is established based on the structural mechanical analysis, taking the deviation between rotor centroid and shape center as the optimization objective, choosing the first order resonance frequency, maximum equivalent stress, rigid body displacement, polar moment of inertia and inertia ratio as constraints. Then the DSR is optimized and simulated by the finite element, the MSCSG principle prototype based on DSR is successfully developed, the online dynamic balance experiment and modal test of the DSR are conducted, where the vibration amount of the DSR decreases from 20 μm before the experiment to 0.14 μm after the experiment, which decreases by 99.3%, the first test modal is 2881 Hz which is 5% different from the finite element simulation value of 3034 Hz. The results show that the DSR has the good mechanical properties and magnetic circuit decoupling characteristics.