Choice Of Frame Research Articles

Understanding Coherent Turbulence and the Roll‐Cell Transition With Lagrangian Coherent Structures and Frame‐Indifferent Fluxes

AbstractWe present the first analysis of frame‐indifferent (objective) fluxes and material vortices in Large Eddy Simulations of atmospheric boundary layer turbulence. We extract rotating fluid features that maintain structural coherence over time for near‐neutral, transitional, and convective boundary layers. In contrast to traditional analysis of coherent structures in turbulent boundary layers, we provide the first identification of vortex boundaries that are mathematically defined to behave as tracer transport barriers. Furthermore, these vortices are indifferent to the choice of observer reference frame and can be identified without user‐dependent velocity field decompositions. We find a strong agreement between the geometric qualities of the coherent structures we extract using our new method and classical descriptions of horizontal rolls and convective cells arising from decades of observational studies. We also quantify trends in individual vortex contributions to turbulent and advective fluxes of heat under varying atmospheric stability. Using recently developed tools from the theory of transport barrier fields, we compare diffusive momentum and heat barrier fields with the presence of rolls and cells, and determine a strong connection between heat and momentum orthogonality with the physical drivers of roll‐cell transformation. This newly employed frame‐indifferent characterization of coherent turbulent structures can be directly applied to numerical model output, and thus provides a new Lagrangian approach to understand complex scale‐dependent processes and their associated dynamics.

How does the choice of reference frame impact the distribution of WBAM components around different anatomical axes?

How does the choice of reference frame impact the distribution of WBAM components around different anatomical axes?

A Relativistic Framework to Estimate Clock Rates on the Moon

As humanity aspires to explore the solar system and investigate distant worlds such as the Moon, Mars, and beyond, there is a growing need to estimate and model the rate of clocks on these celestial bodies and compare them with the rate of standard clocks on Earth. According to Einstein’s theory of relativity, the rate of a standard clock is influenced by the gravitational potential at its location and its relative motion. A convenient choice of local reference frames allows for the comparison of local time variations of clocks due to gravitational and kinematic effects. We estimate the rate of clocks on the Moon using a locally freely falling reference frame coincident with the center of mass of the Earth–Moon system. A clock near the Moon’s selenoid ticks faster than one near the Earth’s geoid, accumulating an extra 56.02 μs day−1 over the duration of a lunar orbit. This formalism is then used to compute the clock rates at Earth–Moon Lagrange points. Accurate estimation of the rate differences of coordinate times across celestial bodies and their intercomparisons using clocks on board orbiters at Lagrange points as time transfer links is crucial for establishing reliable communications infrastructure. This understanding also underpins precise navigation in cislunar space and on celestial bodies’ surfaces, thus playing a pivotal role in ensuring the interoperability of various position, navigation, and timing systems spanning from Earth to the Moon and to the farthest regions of the inner solar system.

Causality and stability in relativistic hydrodynamic theory - a choice to be endured

In this work, it has been indicated that the key features requisite for preserving causality and stability of the popularly existing relativistic hydrodynamic theories, can be translated into each other. It has been shown here, that a generic ‘fluid frame transformation’ including all orders of gradient corrections can recast a stable-causal hydrodynamic theory that (i) only includes fundamental fluid variables (velocity and temperature) but requires to be in a general hydrodynamic frame other than the Landau or Eckart, to a theory that is (ii) pathology free in Landau frame but needs newer degrees of freedom. Since frame choice provides the first principle field definitions and degrees of freedom indicate the number of conserved quantities, the causality and stability of a theory seem to require a consensus between the two unless the derivative correction goes to infinity. The key finding of this work is to indicate a connection between these different formalisms, that lead to a causal and stable hydrodynamic theory.

Factors influencing the selection of spectacle frames and lenses – Knowledge, attitude, and practice study

Background: This study evaluated the knowledge, attitude, and practice (KAP) of patients toward the selection of frames and glasses and factors that influence selection options. Patients and Methods: In this questionnaire-based study comprising closed-end questions, consenting patients aged over 18 years were recruited. The association between family income and age on KAP was analyzed using Fisher’s exact test. Results: The mean (standard deviation) age of the cohort (n = 200, 97 males) was 44.6 ± 16.2 years. A majority (85%) stated that spectacles improved vision; 9% believed it would make eyes weaker. Only 39% were aware of alternate options for refractive error. The durability of the frame was a key factor in selecting frames in 47%; 44% stated they would change spectacles every year. Expensive frames, celebrity endorsement, fashion, and branding influenced choice in 35%, 13.5%, 12%, and 7.5% of the respondents, respectively. Higher annual family income (>Rs. 50,000) when compared with low income (<50,000), was associated with awareness of alternate options for refractive error (P < 0.001) and preference for celebrity-endorsed frames (P = 0.007). There was no association between income and choice of expensive frames (P = 0.16). A higher proportion of older patients (≥40 years) preferred to change glasses only on doctor’s recommendations when compared with younger patients (P = 0.006). Conclusion: Knowledge on alternate options for refractive error was poor. Celebrity endorsement, costly, fashionable, or branded frames did not appear to play an influential role in the choice of frames. High annual income families preferred celebrity-endorsed frames and were more aware of alternative options for refractive error.

Perception and Reality: How the Depths of the High Waters in Venice Apparently Change with the Reference System

Over the centuries, the depths of the most severe storm surges that have flooded Venice have been measured using different reference frames, i.e., related to the algae belt (CM), mean sea level (MSL), local land (ZMPS), large-scale leveling (IGM), and satellite altimetry (SA). Some reference frames, i.e., IGM and SA, are absolute, while the others are relative and represent two different physical points of view, i.e., CM and MSL refer to the sea that is rising and ZMPS refers to the land that is subsiding. The perceptions derived from the different systems are contradictory. This paper discusses and compares surges from 1821 to 2021 measured with these frames, also including the commemorative plaques that report the flood depths on walls in Venice. The paper explains the consequences of a change in frame and zero reference, and it transforms the flooding depths from the original systems to make them homogeneous. The severity of flooding changes in terms of rating with the choice of frame. In the 19th century, five storm surges exceeded the famous level of 1966 and, if they were to recur today or in the future, the sea level rise and the local land subsidence that have occurred in the meantime would greatly exacerbate the situation.

Effect of Relative Mass on Ion Velocity Cross-Correlations in Ionic Liquids and Molten Salts: Different Perspectives in Different Reference Frames.

In electrolytes, the self- and interdiffusion coefficients, transport numbers, and electrical conductivity can be used to determine velocity cross-correlation coefficients (VCC) that are also accessible through molecular dynamics simulations. In an ionic liquid or molten salt, there are only three, corresponding to correlations between the velocities of distinct ion pairs (cation-anion, cation-cation, and anion-anion) averaged over both the ensemble and time, calculable from experimental ion self-diffusion coefficients and the electrolyte conductivity. Most usually, the mass-fixed frame of reference (with velocities relative to that of the center of mass of the system) is used to discuss the VCC and the distinct diffusion coefficients (DDC) derived from them. Recent work in the literature has suggested a dependence of the DDC on the ratio of the anion to cation mass. Here, we demonstrate, using our own and literature transport property data for a large number of ionic liquids and molten salts, that the trends observed depend on the particular choice of velocity reference frame, mass-, number-, or volume-fixed. The perception of ion-ion interactions may be distorted in the mass- and volume fixed frames when the co-ions have very different masses or volumes, particularly for systems containing light lithium ions.

Three Puzzles with Covariance and Supertranslation Invariance of Angular Momentum Flux and Their Solutions.

We describe and solve three puzzles arising in covariant and supertranslation-invariant formulas for the flux of angular momentum and other Lorentz charges in asymptotically flat spacetimes: (i)Supertranslation invariance and covariance imply invariance under spacetime translations; (ii)the flux depends on redundant auxiliary degrees of freedom that cannot be set to zero in all Lorentz frames without breaking Lorentz covariance; (iii)supertranslation-invariant Lorentz charges do not generate the transformations of the Bondi mass aspect implied by the isometries of the asymptotic metric. In this Letter, we solve the first two puzzles by presenting covariant formulas that unambiguously determine the auxiliary degrees of freedom and clarify the last puzzle by explaining the different roles played by covariant and canonical charges. Our construction makes explicit the choice of reference frame underpinning seemingly unambiguous results presented in the current literature.

Improving the YOLOV7 Algorithm for Object Detection within Recorded Videos

Object detection algorithms play an important role in detecting people in surveillance videos. In recent years, with the rapid development of deep learning, the performance of object detection has improved by leaps and bounds, and the scheme of object detection by the YOLOV7 algorithm has also been born. Traditional object detection methods often fail to achieve a balance between speed and accuracy. To address these issues, in this research, an improved YOLOv7 algorithm performance is proposed to get the best speed-to-accuracy balance compared to state-of-the-art object detection within recorded videos using an effective compression method. This method calculates the difference between frames of video, and by using the zero difference approach by removing the duplicate frames from the recorded video and choosing only the meaningful frames based on many variables, including frame size, frame details, and the distance of the frames, influence the choice of a meaningful frame, and this will reduce the size of the video by eliminating the frames comparable to those chosen. Additionally, any other datasets or pre-trained weights have not been used; YOLOv7 has been exclusively trained on the MS COCO dataset from scratch. In order to ensure the effectiveness of this approach, numerous detection systems are used in this work. Additionally, positive performance results to reduce the processing time required for object detection have been attained.

Quantum Euler angles and agency-dependent space-time

Abstract Quantum gravity is expected to introduce quantum aspects into the description of reference frames. Here we begin exploring how quantum gravity induced deformations of classical symmetries could modify the transformation laws among reference frames in an effective regime. We invoke the quantum group SUq(2) as a description of deformed spatial rotations and interpret states of a representation of its algebra as describing the relative orientation between two reference frames. This leads to a quantization of one of the Euler angles and to an aspect of agency dependence: space is reconstructed as a collection of fuzzy points, exclusive to each agent, which depends on their choice of reference frame. Each agent can choose only one direction in which points can be sharp, while points in all other directions become fuzzy in a way that depends on this choice. Two agents making different choices will thus observe the same points with different degrees of fuzziness.

Reframing Whole-body Angular Momentum: Exploring the Impact of Low-Pass Filtered Dynamic Local Reference Frames during Straight-line and Turning Gaits.

Accurately estimating whole-body angular momentum (WBAM) during daily activities may benefit from choosing a locally-defined reference frame aligned with anatomical axes, particularly during activities involving body turns. Local reference frames, potentially defined by pelvis heading angles, horizontal center of mass velocity (vCoM), or average angular velocity (Aω), can be utilized. To minimize the impact of inherent mediolateral oscillations of these frames, such as those caused by pelvis or vCoM rotation in the transverse plane, a low-pass filter is recommended. This study investigates how differences among global, local reference frames pre- and post-filtering affect WBAM component distribution across anatomical axes during straight-line walking and various turning tasks, which is lacking in the literature. Results highlighted significant effects of reference frame choice on WBAM distribution in the anteroposterior (AP) and mediolateral (ML) axes in all tasks. Specifically, expressing WBAM in the vCoM-oriented local reference frame yielded significantly lower (or higher) WBAM in the AP (or ML) axes compared to pelvis-oriented and Aω-oriented frames. However, these significant differences disappeared after employing a low-pass filter to local reference frames. Therefore, employing low-pass filtered local reference frames is crucial to enhance their applicability in both straight-line and turning tasks, ensuring more precise WBAM estimates. In applications that require expressing anatomical axes-dependent biomechanical parameters in a local reference frame, pelvis- and vCoM-oriented frames are more practical compared to the Aω-oriented frame, as they can be determined by a reduced optical marker set or inertial sensors in future applications when the whole-body kinematics is not available.

Mid-Century Modern Design as a Cinematic Vision of Dystopia Based on Selected Examples of the 21st-Century Films and TV Series

The text aims to investigate various uses of the mid-century modern period pieces in the production design of films and TV series developed after the year 2000 and presenting various visions of a dystopic future. The choice of time frame for the analysis was motivated by the desire to showcase the connotations between the mid-century modern and 21st-century visions of the future which can be broadly described as retrofuturistic. On account of its primary focus on progressive ideas, new materials and forms, mid-century modern has always been broadly associated with the design of the future. The author discusses various takes on set design to highlight a wide spectrum of narrations regarding the future and its cultural dimension in selected productions incorporating iconic mid-century design pieces and, more importantly, the non-verbal message they carry.

Angle Rigidity for Multiagent Formations in 3-D

This paper establishes the notion and properties of angle rigidity for 3D multi-point frameworks with angle constraints, and then designs direction-only control laws to stabilize angle rigid formations of mobile agents in 3D. Angles are defined using the interior angles of triangles within the given framework, which are independent of the choice of coordinate frames and can be conveniently measured using monocular cameras and direction-finding arrays. We show that 3D angle rigidity is a local property, which is in contrast to the 3D bearing rigidity as has been proved to be a global property in the literature. We demonstrate that such angle rigid and globally angle rigid frameworks can be constructed through adding repeatedly new points to the original small angle rigid framework with carefully chosen angle constraints. We also investigate how to merge two 3D angle rigid frameworks by connecting three points of one angle rigid framework simultaneously to the other. When angle constraints are given only in the surface of a framework, angle rigidity of convex polyhedra is studied, in which the cases of triangular face and triangulated face are considered, respectively. The proposed 3D angle rigidity theory is then utilized to design decentralized formation control strategies using local direction measurements for teams of mobile agents. Simulation examples are provided to validate the convergence of the formations.

Switching quantum reference frames in the N-body problem and the absence of global relational perspectives

Given the importance of quantum reference frames (QRFs) to both quantum and gravitational physics, it is pertinent to develop a systematic method for switching between the descriptions of physics relative to different choices of QRFs, which is valid in both fields. Here we continue with such a unifying approach, begun in [Quantum 4, 225 (2020)], whose key ingredient is a symmetry principle, which enforces physics to be relational. Thanks to gauge related redundancies, this leads to a perspective-neutral structure which contains all frame choices at once and via which frame perspectives can be consistently switched. Formulated in the language of constrained systems, the perspective-neutral structure is the constraint surface classically and the gauge invariant Hilbert space in the Dirac quantized theory. By contrast, a perspective relative to a specific frame corresponds to a gauge choice and the associated reduced phase and Hilbert space. QRF changes thus amount to a gauge transformation. We show that they take the form of `quantum coordinate changes'. We illustrate this in a general mechanical model, namely the relational N-body problem in 3D space with rotational and translational symmetry. This model is especially interesting because it features the Gribov problem so that globally valid gauge fixing conditions, and hence relational frame perspectives, are absent. The constraint surface is topologically non-trivial and foliated by 3-, 5- and 6-dimensional gauge orbits, where the lower dimensional orbits are a set of measure zero. The N-body problem also does not admit globally valid canonically conjugate pairs of Dirac observables. These challenges notwithstanding, we exhibit how one can construct the QRF transformations for the 3-body problem. Our construction also sheds new light on the generic inequivalence of Dirac and reduced quantization through its interplay with QRF perspectives.

Special theory of relativity for a graded index fibre

The speed of light (c) in a vacuum is independent of the choice of frames to describe the propagation, according to the theory of relativity. We consider how light is characterised in a material, where the speed of light is different from that in a vacuum due to the finite dielectric constant. The phase velocity in a material is smaller thanc, such that the speed of a moving frame can be larger than the phase velocity, such that the frame can move faster than the speed of light in a material. Consequently, an unusual Doppler effect is expected, and the wavelength in the moving frame changes from the red-shift to the blue-shift upon increasing the speed of the frame. The corresponding energy of the light also changes sign from positive to negative, while momentum is always positive, leading to the changes of signs for the phase velocity and the helicity. In a graded index fibre, where the exact solution is available, even more complicated phenomena are expected, due to the finite effective mass of photons. Upon the increase of the energy gap, generated by optical confinements and optical orbital angular momentum, the effective mass of photons increases. If the gap is large enough, momentum starts to change the sign upon increasing the frame velocity, while the energy of photons is always positive. In this case, the phase velocity diverges if momentum is in agreement with the fame velocity. Contrary to the unusual behaviours of the phase velocity, the group velocity is always belowc. This thought experiment might be useful for considering insight into the polarisation state of light.

Gravity theories with local energy-momentum exchange: a closer look at Rastall-like gravity

Einstein’s famous equivalence principle is certainly one of the most striking features of the gravitational interaction. In a strict reading, it states that the effects of gravity can be made to disappear locally by a convenient choice of reference frame. As a consequence, no covariantly-defined net gravitational (point-wise) force should exist and energy-momentum of all matter and interaction fields combined, with gravity excluded, should be locally conserved. Although elegant, this represents a strong constraint on the dynamics of a gravitating system and it is only logical to question its naturality and observational basis. This is the purpose of the present work. For concreteness sake, we analyze, in the context of metric (torsion-free) theories of gravity, the simplest phenomenological model which allows for local energy-momentum exchange between the spacetime and matter/interaction fields while preserving the seemingly more natural principle of general covariance. This concrete model turns out to be a generalization of the socalled Rastall’s theory, with one important advantage: criticisms made to the latter, which are often used to dismiss it as a viable or interesting model, do not apply to the former in a Universe containing ‘dark’ ingredients, such as ours—a connection which seems to have been overlooked thus far. We conclude by exploring the consequences of our Rastall-like model to standard (astrophysical and cosmological) gravitational scenarios.

Statistical Analysis and Forecasting of Gender Asymmetry Indexes in the Labor Market of the Orenburg Region

The labor market in Russia and its regions operates in an unstable socio-economic situation, which can contribute to the emergence of gender disproportion. The study of gender asymmetry is considered the most popular direction during periods of “economic shocks”, since this kind of instability increases the inequality of men and women in various spheres of life. The state of turbulence in which the labor market of Russia as a whole and each of its regions is located contributes to the adaptation of each of its segments to new forms of work. This study examines the results of an analysis of the structure and trends in the dynamics of indexes of employment and unemployment of the male and female population in the Orenburg region for 2016-2021. The choice of the time frame is justified by the uneven development of both the world and the Russian economy. Modern economic realities, in which the labor market exists and develops as a country as a whole and its regions, experiencing a number of shocks, determine the scientific novelty of the issues under consideration.Purpose of the study. The main idea of the work done is the possibility of using the methods of economic and statistical analysis to study dynamic differences in gender structures according to various characteristics, development directions that determine gender asymmetry in the labor market of the Orenburg region, and predict its main indexes for the medium term.Materials and methods. The information base of the study was the statistical information of Orenburgstat, which characterizes gender asymmetry in the labor market of the Orenburg region. To achieve this goal, a set of methods of economic and statistical analysis was applied, including the calculation of indexes of the structure and structural differences, dynamics, identifying trends, forecasting, as well as presenting the results of the study using tables and figures.Results. According to the results of the study, an average portrait of a busy and carefree person by gender was compiled. The characteristics of the male and female population in the labor market of the Orenburg region in 2021 compared to 2016 are highlighted. The study of structural differences was carried out according to the criterion of V. Ryabtsev, during which it was noted that there were no significant changes in the structures of employed men and women. A significant level of differences characterizes the age structure of unemployed men and women in 2021 compared to 2016, as well as the structure of unemployed men by level of education.The study made it possible to assert that in the dynamics of indexes characterizing gender inequality in the labor market of the Orenburg region, unstable changes are observed. The study tested the hypothesis of the presence/absence of trends in the time series of indexes characterizing gender asymmetry in the labor market of the region. For this purpose, one of the modifications of the series criterion was used. The assumption that there is no trend in the dynamics series under consideration has not been confirmed, therefore, the trend exists. Taking into account this circumstance, trend models were constructed, among which, according to the best statistical characteristics, secondorder polynomial models were selected. With the help of the selected polynomials of the second degree, it was determined that in the dynamics of employment and unemployment indexes of the male and female population, downward trends of change prevail. Further, their prospective indexes were calculated.Conclusion. The study made it possible to analyze the main vectors that are emerging in the field of employment and unemployment in the regional labor market by gender, and to predict their main indexes for the medium term. In the dynamics of the number of both male and female labor force in the Orenburg region, unstable trends will be observed in the future. The number of women employed in the region’s economy will grow; the number of unemployed women will decrease. In the forecast period, the number of employed men in the economy of the Orenburg region will change under the influence of a downtrend. The number of unemployed men in the period from 2023 to 2025 will tend to decrease.

Coulomb Corrections for Bose–Einstein Correlations from One- and Three-Dimensional Lévy-Type Source Functions

In the study of femtoscopic correlations in high-energy physics, besides Bose–Einstein correlations, one has to take final-state interactions into account. Amongst them, Coulomb interactions play a prominent role in the case of charged particles. Recent measurements have shown that in heavy-ion collisions, Bose–Einstein correlations can be best described by Lévy-type sources instead of the more common Gaussian assumption. Furthermore, three-dimensional measurements have indicated that, depending on the choice of frame, a deviation from spherical symmetry observed under the assumption of Gaussian source functions persists in the case of Lévy-type sources. To clarify such three-dimensional Lévy-type correlation measurements, it is thus important to study the effect of Coulomb interactions in the case of non-spherical Lévy sources. We calculated the Coulomb correction factor numerically in the case of such a source function for assorted kinematic domains and parameter values using the Metropolis–Hastings algorithm and compared our results with previous methods to treat Coulomb interactions in the presence of Lévy sources.

Standard of living in European Union countries

Motivation: Researchers have been concerned with the issues related to the differences among economies for many years. The level of differentiation is an important matter as excessive economic and social differences among the states may lead to limited scope of integration processes, which in turn determine the development rate of regions. Due to how significant this issue is, it was decided that the level differentiation of the standard of living of the population in selected European Union countries ought to be investigated.Aim: The purpose of the article is to compare the standard of living in the countries of the European Union, with particular emphasis placed on the countries that joined the Union in 2004. The authors try to answer the question whether the economic policy pursued by the EU achieves the intended effect. A synthetic measure was constructed to measure the standard of living, taking into account various aspects of life. The time scope of the study covers the period of 2005–2020. The choice of a specific time frame was dictated by the expansion of the number of European Union members in 2004 and the availability of data. Therefore, the analysis covered the countries of the European Union post 2005 (excluding Great Britain). Data were obtained from Eurostat.Results: Taking into account the values of the synthetic variable, it may be claimed that one the one hand, the standard of living in the countries is increasing, and on the other hand, the disparity between countries is decreasing. Therefore it should be noticed, that the economic policy pursued by the European Union achieves the intended effect.

The choice of reference frame alters interpretations of turning gait and stability

Humans regularly follow curvilinear trajectories during everyday ambulation. However, globally-defined and locally-defined reference frames fall out of alignment during turning gait, which complicates spatiotemporal and biomechanical analyses. Thus, the choice of the locally-defined reference frame is an important methodological consideration. This study investigated how different definitions of reference frame change the results and interpretations of common gait measures during turning. Nine healthy adults completed two walking trials around a circular track. Kinematic data were collected via motion capture and used to calculate step length, step width, anteroposterior margin of stability, and mediolateral margin of stability using three different locally-defined reference frames: walkway-fixed, body-fixed, and trajectory-fixed. Linear-mixed effects models compared the effect of reference frame on each gait measure, and the effect of reference frame on conclusions about a known effect of turning gait – asymmetrical stepping patterns. All four gait measures differed significantly across the three reference frames. A significant interaction of reference frame and step type (i.e. inside vs outside step) on step length (p < 0.001), anteroposterior margin of stability (p < 0.001), and mediolateral margin of stability (p < 0.001) indicated conclusions about asymmetry differed based on the choice of reference frame. The choice of reference frame will change the calculated gait measures and may alter the conclusions of studies investigating turning gait. Care should be taken when comparing studies that used different reference frames, as results cannot be easily harmonized. Future studies of turning gait need to justify and detail their choice of reference frame.