Reference Frame Research Articles

The archerfish uses motor adaptation in shooting to correct for changing physical conditions.

The archerfish is unique in its ability to hunt by shooting a jet of water from its mouth that hits insects situated above the water's surface. To aim accurately, the fish needs to overcome physical factors including changes in light refraction at the air-water interface. Nevertheless, archerfish can still hit the target with a high success rate under changing conditions. One possible explanation for this extraordinary ability is that it is learned by trial and error through a motor adaptation process. We tested this possibility by characterizing the ability of the archerfish to adapt to perturbations in the environment to make appropriate adjustments to its shots. We introduced a perturbing airflow above the water tank of the archerfish trained to shoot at a target. For each trial shot, we measured the error, i.e., the distance between the center of the target and the center of the water jet produced by the fish. Immediately after the airflow perturbation, there was an increase in shot error. Then, over the course of several trials, the error was reduced and eventually plateaued. After the removal of the perturbation, there was an aftereffect, where the error was in the opposite direction but washed out after several trials. These results indicate that archerfish can adapt to the airflow perturbation. Testing the fish with two opposite airflow directions indicated that adaptation took place within an egocentric frame of reference. These results thus suggest that the archerfish is capable of motor adaptation, as indicated by data showing that the fish produced motor commands that anticipated the perturbation.

The length contraction paradox

Reciprocal length contraction and time dilation, as enshrined in the Lorentz transformation, are the bulwark of the special relativity theory. Reciprocal time dilation is typically discussed (in the context of its apparent contradiction) and usually explained away as the result of differing synchronization in inertial reference frames and the relativity of simultaneity. Further, it is generally suggested that time is an abstract concept, and its perceptions may differ with context. However, we suggest that regarding length measurements no such abstraction can be envisaged. In this manuscript, we examine the reciprocal length contraction in detail to assess whether it leads to any contradiction.

Experiencing an Elongated Limb in Virtual Reality Modifies the Tactile Distance Perception of the Corresponding Real Limb.

In measurement, a reference frame is needed to compare the measured object to something already known. This raises the neuroscientific question of which reference frame is used by humans when exploring the environment. Previous studies suggested that, in touch, the body employed as measuring tool also serves as reference frame. Indeed, an artificial modification of the perceived dimensions of the body changes the tactile perception of external object dimensions. However, it is unknown if such a change in tactile perception would occur when the body schema is modified through the illusion of owning a limb altered in size. Therefore, employing a virtual hand illusion paradigm with an elongated forearm of different lengths, we systematically tested the subjective perception of distance between two points [tactile distance perception (TDP) task] on the corresponding real forearm following the illusion. Thus, the TDP task is used as a proxy to gauge changes in the body schema. Embodiment of the virtual arm was found significantly greater after the synchronous visuotactile stimulation condition compared with the asynchronous one, and the forearm elongation significantly increased the TDP. However, we did not find any link between the visuotactile-induced ownership over the elongated arm and TDP variation, suggesting that vision plays the main role in the modification of the body schema. Additionally, significant effect of elongation found on TDP but not on proprioception suggests that these are affected differently by body schema modifications. These findings confirm the body schema malleability and its role as a reference frame in touch.

Fluid flow reconstruction around a free-swimming sperm in 3D.

We investigate the dynamics and hydrodynamics of a human spermatozoa swimming freely in 3D. We simultaneously track the sperm flagellum and the sperm head orientation in the laboratory frame of reference via high-speed high-resolution 4D (3D+t) microscopy, and extract the flagellar waveform relative to the body frame of reference, as seen from a frame of reference that translates and rotates with the sperm in 3D. Numerical fluid flow reconstructions of sperm motility are performed utilizing the experimental 3D waveforms, with excellent accordance between predicted and observed 3D sperm kinematics. The reconstruction accuracy is validated by directly comparing the three linear and three angular sperm velocities with experimental measurements. Our microhydrodynamic analysis reveals a novel fluid flow pattern, characterized by a pair of vortices that circulate in opposition to each other along the sperm cell. Finally, we show that the observed sperm counter-vortices are not unique to the experimental beat, and can be reproduced by idealised waveform models, thus suggesting a fundamental flow structure for free-swimming sperm propelled by a 3D beating flagellum.

Alfvén Wing‐Like Structures in Titan's Magnetotail During T122‐T126 Flybys

AbstractIn this paper, we study Titan's magnetotail using Cassini data from the T122‐T126 flybys. These consecutive flybys had a similar flyby geometry and occurred at similar Saturn magnetospheric conditions, enabling an analysis of the magnetotail's structure. Using measurements from Cassini's magnetometer (MAG) and Radio and Plasma Wave System/Langmuir probe (RPWS/LP) we identify several features consistent with reported findings from earlier flybys, for example, T9, T63 and T75. We find that the so‐called ’split’ signature of the magnetotail becomes more prominent at distances of at least 3,260 km (1.3 RT) downstream of Titan. We also identify a specific signature of the sub‐alfvenic interaction of Titan with Saturn, the Alfvén wings, which are observed during the T123 and T124 flyby. A coordinate transformation is applied to mitigate variations in the upstream magnetic field, and all the flybys are projected into a new reference frame—aligned to the background magnetic field reference frame (BFA). We show that Titan's magnetotail is confined to a narrow region of around ∼4 RT YBFA. Finally, we analyze the general draping pattern in Titan's magnetotail throughout the TA to T126 flybys.

Efficient random-access GPU video decoding for light-field rendering

Compression method for GPU streaming of discrete light fields is proposed in this paper. Views on the scene are encoded with video codec to enable streaming in real time. Instead of using a classic scheme, all frames are encoded according to one reference frame. Any frame is decoded directly, in a random-access manner that is suitable for light-field rendering methods, where only few frames are necessary on the GPU. The proposed scheme reaches the best decoding quality/time ratio in comparison to other schemes, where all preceding frames need to be decompressed, and all-key-frame video that supports random access, but is extremely large. The proposed method solves the space-requirements and streaming-bandwidth issues using the GPU accelerated decoding, and enables incorporating light-field assets in real-time 3D simulations. Compared to existing methods, the proposal is easy to implement, does not depend on specific video format or extension and is efficient on consumer GPUs.

The ways of creating a trust

This article explores the ways of creating a trust, according to Article 2074 of the Civil Code of the Republic of Moldova. To shed light on the legislative inspiration and the distinct characteristics of various methods of establishment, a comparative analysis is conducted concerning the provisions outlined in Book X (Trusts) of the Draft Common Frame of Reference, as well as the Civil Codes of the Province of Quebec, France, Romania, and the Republic of Moldova. The discussion emphasizes the ways for voluntarily creating a trust, namely by contract, unilateral declaration, and will, all of which are comprehensively regulated. Additionally, the article addresses the mechanism of creating a trust through administrative act or court decision, situations that necessitate explicit legislative regulation before implementation. The paper also delves into the relationship between ‘law’ and ‘administrative act’ as sources of trusts, presenting a hypothesis that the legislator intentionally substituted this term in the legislation of the Republic of Moldova.

On Bell's dynamical route to special relativity

This paper develops the approach to special relativity put forward by John S. Bell. The classical dynamics of an electron orbiting a nucleus in uniform motion is solved analytically and compared to numerical simulations for an accelerated nucleus. The relativistic phenomena of length contraction and time dilation are shown to result from the electric and magnetic forces on the electron when its motion is analyzed in a single frame of reference. The relevance of these results for understanding the theory of special relativity is discussed.

Theory of Everything

Our Theory of Everything is made possible by the discovery of a closed fluid dynamic principle, working in a closed fluid space-time system, (the universe). Through the principle of fluid space-time, almost all of the unexplained mysteries of the universe are revealed. How the universe came into being, with matter and the most basic force, Gravity. Newton’s law of gravity in particular, the inverse square law with distance. (the reason is for appearance of the inverse square law, simultaneously in gravitation and electromagnetism, not a coincidence). Special Relativity is an account of how space contracts, time dilates and mass increases, with velocity. General Relativity is an account of how space-time curves. According to Muhammad’s closed fluid dynamic principle, space actually consists of an extremely fluid substance which we call aether. It is therefore fitting that through the closed fluid dynamic principle, we can arrive at an explanation for one major thorn in the side of Special Relativity, the twin paradox. The problem is, it is the twin who accelerates that gets it wrong. Because his assessment of the age of his brother was done without consideration of the fact that when he turned around, made the return journey, he felt his acceleration but did not employ this in Einstein’s time dilation, which was based on inertial reference frames. The task we are confronted with in this paper is to find out how the time dilation addressed in special relativity comes into proceedings in an accelerated frame. We achieve this.

Prospects of GENESIS and Galileo joint orbit and clock determination

The European Space Agency (ESA) is preparing a satellite mission called GENESIS to be launched in 2027 as part of the FutureNAV program. GENESIS co-locates, for the first time, all four space geodetic techniques on one satellite platform. The main objectives of the mission are the realization of the International Terrestrial Reference Frames and the mitigation of biases in geodetic measurements; however, GENESIS will remarkably contribute to the determination of the geodetic parameters. The precise GENESIS orbits will be determined through satellite-to-satellite tracking, employing two GNSS antennas to observe GPS and Galileo satellites in both nadir and zenith directions. In this research, we show results from simulations of GENESIS and Galileo-like constellations with joint orbit and clock determination. We assess the orbit quality of GENESIS based on nadir-only, zenith-only, and combined nadir–zenith GNSS observations. The results prove that GENESIS and Galileo joint orbit and clock determination substantially improves Galileo orbits, satellite clocks, and even ground-based clocks of GNSS receivers tracking Galileo satellites. Although zenith and nadir GNSS antennas favor different orbital planes in terms of the number of collected observations, the mean results for each Galileo orbital plane are improved to a similar extent. The 3D orbit error of Galileo is improved from 27 mm (Galileo-only), 23 mm (Galileo + zenith), 16 mm (Galileo + nadir), to 14 mm (Galileo + zenith + nadir GENESIS observations), i.e., almost by a factor of two in the joint GENESIS + Galileo orbit and clock solutions.

The Universe Never Had the So-Called Gravity

This paper challenges conventional gravity theories by revisiting Galileo's discoveries and presenting a counterintuitive perspective. Recent experiments, such as the hammer and feather drop on the moon and vacuum demonstrations on Earth, prompt a reevaluation of our current scientific understanding of gravity. The paper argues that celestial bodies, including Earth, move towards objects, challenging the traditional concept of gravity. Drawing on the equivalence principle and dark matter effects, it contends that objects become stationary when disconnected from their original reference frame. Addressing criticisms, the paper asserts that Earth's perpetual movement ensures uniform gravitational effects globally. Exploring the expanding universe and dark matter's influence, it concludes that objects released in space do not fall but become stationary, prompting a reassessment of established scientific principles. This paradigm shift invites readers to reconsider their understanding of gravity and the universe. The paper is written as a letter to stimulate thought and discussion.

The nucleosome reference frame and standard geometries for octasomes.

There are over 533 nucleosome structures in the Research Collaboratory for Structural Bioinformatics (RCSB). Collectively, numerous variants and species are present, as are sub-nucleosomal and super-nucleosomal assemblies within the nucleosome family. The organization of the histones and DNA is highly conserved in all standard octasomes containing 145, 146, or 147 base pairs. This observation is used to establish a nucleosome reference frame that enables us to describe and compare the gross structure and organization of all nucleosomes. We observe that cumulative sums of Rise, Twist, and DNA arc length are linear functions of the base pair index with values exceeding 0.999 for almost all octasome structures. These relationships enable us to readily compare the location and orientation of DNA director frames extracted from the crystal structures to ideal superhelix values. Such comparisons reveal that the DNA superhelix extracted from X-ray structures exhibits a sinusoidal variation with an amplitude of approximately 5Å about a constant superhelix radius of Å, in agreement with early descriptions of nucleosome organization as tripartite. There is also a distinct straightening of the nucleosomal DNA over the outermost turn of DNA's double helix. The straightening of the DNA superhelix marks the transition to linker DNA and is easily recognized as a rapid increase in superhelix radius and is concomitant with a change in pitch. This provides a rigorous means of separating nucleosomal DNA from linker DNA. For all X-ray structures, we find that near the dyad, there exists a set of DNA director frames for which the spatial location and orientation are highly conserved. Away from the dyad, the DNA superhelix exhibits "singletrack" and "multipath" regions. In the singletrack region, all structures exhibit a single highly conserved pathway along which all base pairs must track, but at varying rates. In the multipath regions, the base pairs are allowed to map out a limited number of different pathways along the surface of the histone octamer. To demonstrate the utility of the proposed reference geometries, standard and distorted octasome structures, super-nucleosomal structures, nucleosomes with linker DNA, and nucleosomes in closed circular DNA are analyzed. The online version contains supplementary material available at 10.1007/s12551-024-01206-5.

Insights into the dynamic induction in FOWT surge motion using an actuator-line model

This research investigates the impact of surge motion on Floating Offshore Wind Turbines (FOWTs) through dynamic inflow analyses using an in-house Actuator Line Model (ALM). The study explores surge reduced frequencies in the range from 1 to 10 to analyse the returning wake phenomenon occurring at blade passage frequency. The findings highlight the dampening effect of the rotor thrust and torque by 25% due to induction field inertia. Noteworthy observations include the filter-like effect on the span-wise induced velocity trends: with the frequency increment, the induction field is ’synchronised’ with the apparent wind and forces. The results of the analyses evidence the suitability of the induction parsed in the absolute reference frame to capture the induction field features, amplitude and phase shift, at increasing surge frequencies.

Aerodynamic and Structural Assessment of Floating Wind Turbine Rotor Under Varying Tilt Angle

Predicting the aerodynamic performance of floating offshore wind turbines (FOWTs) proves challenging due to platform motion induced by waves. The effect of wind and waves results in a six-degree-of-freedom motion of the platform, directly influencing turbine performance. Understanding the impact of specific degrees of freedom (DOF) motions on aerodynamics and structural response is crucial for effective wind turbine design. This research examines the impact of rotor tilt on both aerodynamic performance and structural response. The investigation employs computational fluid dynamics (CFD) analysis and mapping aerodynamic loads onto the finite element (FE) mesh for structural analysis. The study employs a comprehensive 3D simulation, utilizing the moving reference frame (MRF) method for the NREL 5 MW reference wind turbine CFD simulations. It explores different rotor tilt angles (5°, 10°, 15°, and 20°) encountered by offshore structures during their operation and examines their impact on aerodynamic performance. Predicted aerodynamic loads were mapped onto the blade FE mesh using the radial basis function (RBF) interpolation technique and solved using the open-source FE solver CalculiX. The analysis shows that the turbine performance is relatively unaffected up to a tilt angle of 10°. However, further increase in rotor tilt angle adversely impacts turbine performance, leading to notable reductions in thrust and power output. The fluid-structure coupled analysis provided insights into the deformations and stresses experienced by the turbine blade, indicating a notable increase in flap-wise displacement for larger tilt angles, while edge-wise displacement is not as significantly affected. The maximum stress location on the blade generally correlates well with actual observations.

Distributed voltage unbalance mitigation in islanded microgrid using moth flame optimization and firebug swarm optimization

In recent trends, hybrid renewable energy sources (HRES) provide a better solution to meet energy demand, maximizing the productivity of electricity network. Due to the above-mentioned features, several researchers have given more attention to PV-wind-based HRES systems. A stable energy supply must be added, including batteries, diesel generator (DG), to meet demand in the event of a grid failure. To meet the voltage unbalance in islanded mode, the sizes of DG have need to be selected sensibly and HRES requires additional energy storage. To examine the voltage unbalance problems of an islanded microgrid, a hybrid optimization approach known as moth flame optimization (MFO) and firebug swarm optimization (FSO) is introduced. Due to various loads, harmonic distortion causes the voltage to unbalance, which can result in voltage collapse. To deliver a quick response in an island mode, a comprehensive algorithm called MFO-FSO control is proposed. MATLAB software is used to validate the results which demonstrate that the proposed MFO-FSO outperforms the conventional decoupling double synchronous reference frame (DDSRF) methods by reducing total harmonic distortion (THD) up to 1.21% and voltage unbalance factor (VUF) up to 1.427%.

Intensity patterns of a focused electromagnetic spherical wave with aberration

The laser pulse focused by a relativistic flying parabolic mirror can exceed the laser intensity focused by conventional physical focusing optics. Depending on the Lorentz γ-factor, the focal length of the relativistic flying mirror in the boosted frame of reference becomes much shorter than the incident beam size. The 4π-spherical focusing scheme is applied to describe such a focused field configuration. In this paper, a theoretical formalism has been developed to describe the field configuration focused by the 4π-spherical focusing scheme with an arbitrary phase error of an incident electromagnetic wave. The focused field configuration is described by the linear combination of the product of the spherical Bessel function and the spherical harmonics, resulting in the same expression as the multipole radiation. The mathematical expression showing the focused field for the femtosecond laser pulse, as well as the continuous wave, has been derived for the application to the femtosecond high-power laser. We show the three-dimensional intensity distribution near focus for the 4π-spherically focused electromagnetic field with phase error.

METHOD FOR IDENTIFYING THE EQUIVALENT FRAME OF A SOLUTION BY ANALYZING TITRATION VIDEO IMAGES USING AN AUTOMATIC APPROACH

Determination of equivalence in inorganic chemistry can be achieved by various methods, such as colorimetric titration, conductimetric titration and pH-metric titration. However, these traditional methods often require repetition to guarantee reliable results, increasing the time and cost of the experiment. In response to this limitation, some authors have suggested a semi-automatic approach based on colorimetric titration, although this also has subjective aspects. The aim of this article is to propose a new method based on intuitive observation to identify the equivalent frame in a titration video. This approach relies on the use of the KNN classifier to automate the detection of the reference frame within a predefined confidence interval. To facilitate this automation, a dataset was built up from experiments at the Groupe Chimie de lEau et Substances Naturelles (GCESNA) laboratory at the Institut National Polytechnique HouphouetBoigny (INP-HB).The performance of the KNN algorithm was effectively assessed by evaluating it against the performance indicators of precision, recall and F-measure. The results obtained are as follows: Precision: 92.2%, Recall: 91.7% and F-measure: 92.0%. These experimental results demonstrate the effectiveness of the KNN algorithm in frame classification.

MILITARY-EYES: A Real-Time Hyper-Tuned and Optimised Object Detection Approach Tailored for Military Dataset

Accurately identifying all objects of interest inside the specified frame of reference is crucial for object identification techniques to allow machine vision to interpret images successfully. Theoretical frameworks from computer vision and deep learning have informed many potential solutions to this problem. However, current approaches frequently fail when faced with objects going through random geometric changes and continually show shortcomings when identifying small, dense objects. This research looks at state-of-the-art object detection methods, compares them, and then suggests a convolutional object detection network that has been tweaked to fix the problems with the existing methods. Comparing our research to existing approaches, we find that they perform better. We accomplish this by training deep convolutional networks to detect geometric transformations and adjusting the networks to handle multi-scaled features. The results achieved after the optimization of the You only look once (YOLO) V5 & V7 are stated in this paper. The experiments demonstrated that YOLO v8 achieved higher accuracy than the hyper-tuned YOLO V5 and V7, with an average Precision (mAP) score of 52.8% on the customized military dataset running at 60 Frames Per Second (FPS). Object detection using deep neural networks (DNNs) poses a significant challenge due to the high computational and power requirements, mainly when deployed on general-purpose platforms such as CPUs and GPUs. However, addressing these limitations becomes crucial for efficient edge computing tasks like object detection, where faster, smaller, and energy-efficient solutions are essential. To overcome these challenges, system-on-chip (SoC) designs emerge as a promising solution.

Монгол хэлний “дээр” хэмээх үгийн танин мэдэхүйн утга зүйн судалгаа

Cognitive linguistics regards the meaning of language as humans' subjective interpretation of the world. As men communicate with the world through their bodies, their views are self-centered. Those views are reflected in languages. Therefore, it is possible to reveal the unique way of thinking reflected in a language by analyzing the semantic system related to words. This research examines some spatial semantic characteristics of the spatial term “дээр” in the Mongolian language. For this, the study determines its fundamental meanings and schemas related to them based on the basic concepts of spatial semantics of Zlatev (2007) among the cognitive semantics. According to the frame of reference, the word “дээр” spatially indicates a level of height between two things and certain location on a thing. Due to these schematic characteristics, this word does not indicate active or directional motions but static situations.

Verbal behavior and the future of social science.

Natural language processing (NLP)-previously the domain of a select few language and computer scientists-is undergoing an unprecedented surge in popularity across disciplines. The ubiquity of language data, alongside extremely rapid methodological innovations, has magnetized the field, attracting researchers with the promise of measuring, forecasting, and understanding the most central questions in business, psychology, biology, sociology, the humanities, and beyond. The power of language analysis to reveal insights into human thought, feeling, and behavior has become a core interest emerging from recent technological advances, which are being probed to unearth deeply embedded truths about the human condition. However, NLP research has reached a critical juncture, sitting at the cusp of societal transformation in many aspects of daily life. The details of how NLP research develops over the next 3-5 years will define this transformation. In this emerging, near-infinite space of NLP-driven research, we provide a critical frame of reference for how, when, and why these technologies should evolve in a particularly transdisciplinary manner. Specifically, we discuss (a) the urgency of pairing existing and emerging NLP research with existing scientific knowledge, theory, and principles from the behavioral sciences; (b) the coevolution of NLP technologies; and (c) the practical implications and ethical consequences of expanding language analysis using broader psychosocial theories of the human condition. While our discussion focuses principally on using language as a window in the individual mind, this topic holds substantial implications for other disciplines and lines of inquiry, including the dynamics of social interaction and beyond. (PsycInfo Database Record (c) 2024 APA, all rights reserved).