Gravitational Acceleration Research Articles

Sub-parsec-scale jet-driven water maser with possible gravitational acceleration in the radio galaxy NGC 1052

Abstract We report sub-parsec-scale observations of the 321 GHz H2O emission line in the radio galaxy NGC 1052. The H2O line emitter size is constrained in <0.6 mas distributed on the continuum core component. The brightness temperature exceeding 106 K and the intensity variation indicate certain evidence for maser emission. The maser spectrum consists of redshifted and blueshifted velocity components spanning ∼400 km s−1, separated by a local minimum around the systemic velocity of the galaxy. The spatial distribution of maser components shows a velocity gradient along the jet direction, implying that the population-inverted gas is driven by the jets interacting with the molecular torus. We identified a significant change of the maser spectra between two sessions separated by 14 days. The maser profile showed a radial velocity drift of 127 ± 13 km s−1 yr−1 implying inward gravitational acceleration at 5000 Schwarzschild radii. The results demonstrate the feasibility of future very long baseline interferometry observations to resolve the jet–torus interacting region.

Improved Accuracy in Determining the Acceleration Due to Gravity in Free Fall Experiments Using Smartphones and Mechanical Switches

This study presents an innovative methodology to augment the accuracy of gravitational acceleration (g) measurements in free fall experiments. Employing smartphones and integrating mechanical switches, our approach utilizes a built-in microphone for precise time measurements during the initiation of free fall. A meticulously designed mechanical switch controls the release of a steel sphere, triggering the timer upon the initiation of descent. Our experimental outcomes showcase a commendable congruence between the calculated g value and the locally accepted reference value, pinpointing g at 9.8274 ± 0.01 m/s2. A salient feature of our method is the utilization of the smartphone’s onboard microphone sensor, offering superior convenience to conventional sensor-based methodologies that require additional equipment. Additionally, our study introduces the seamless integration of open-source software on smartphones, facilitating the direct display and analysis of sound parameters. This integration streamlines the experimental process, contributing to the ongoing endeavors aimed at enhancing accuracy in free fall experiments. Our findings underscore the potential of smartphones and mechanical switches as accessible and effective tools in advancing physics education and scientific investigations.

Direct ink writing of viscous inks in variable gravity regimes using parabolic flights

Additive manufacturing (AM) has significant utility for off-planet fabrication where dedicated infrastructure is severely limited, weight reduction and in situ resource utilization is desirable, and demands for complex systems are high. Direct ink writing (DIW) is a useful AM technique since it enables the deposition of a broad set of materials and the co-printing of multiple materials simultaneously. This allows for the fabrication of complex functional devices and systems in addition to structural objects. To evaluate this technique for space applications, this study characterized DIW in low gravity environments. Parabolic flights were used to simulate Martian, Lunar, and Micro gravity, and the effects that these 3 gravity regimes have on two critical print performance parameters, drooping and slumping, was evaluated using viscous paste inks deposited with an auger-driven extrusion head. In the drooping case, bridging structures were printed across gaps without support material, and the deformation was monitored. In the slumping case, a wall was printed through sequential layer deposition, and the vertical displacement of each layer under reduced gravity was explored. As expected, we found that a reduction in apparent gravity led to a decrease in the droop of a printed line, and as apparent gravitational acceleration is decreased its impact on the magnitude of drooping becomes less significant. For wall structures printed in simulated Lunar or Martian gravity regimes, the total structure height was found to be similar to that of a structure printed under Earth's gravitational conditions. In contrast, for prints performed in microgravity, it was found that slumping was significantly reduced and structure height was larger. These results provide experimental data to enable the design and optimization of appropriate structures and tool paths for printing objects using DIW for off-planet manufacturing.

Gravitational repulsion in an expanding ball of dust

In general relativity, there is a velocity dependent term in the gravitational acceleration of a test particle for an observer at infinity. Depending on the direction of motion and the speed, that term can be repulsive. We show that this is also the case in the Parametrized Post-Newtonian (PPN) formalism. We compute the magnitude of that repulsive term for an expanding sphere of dust observed at infinity, and find that it could mimic the effect of a cosmological constant. The time evolution of such an expanding ball of dust for an observer at infinity is calculated, and compared with the standard ΛCDM model. We find that the so-called coincidence problem does not exist for such a model as the energy density attributed to the expansion is always of the same order as the matter energy density.

Stability and nonlinear vibrations of an inclined axially moving beam considering self-weight

The transmission device of the astronautic exploration vehicle can be regarded as an inclined beam experiencing axial motion under varying gravitational acceleration and tilt angle. Understanding the instability and vibration characteristics of this structure with axial movement is crucial for the dynamic design of the astronautic exploration vehicle. This paper discusses the stability and non-linear vibration nature of a self-weight inclined beam. The governing equations of the system are established and discretized using the hypothesized mode method and the extended Hamilton principle. The stability of the inclined beam is explored through an analysis of its natural frequency. The amplitude-frequency responses of the first four generalized coordinates of the inclined beam are analyzed by the Matcont toolkit. The influence of the axial velocity, the value of external excitation, the gravitational acceleration, and the tilt angle on the nonlinear vibration characteristics of the beam are discussed. Through the numerical discussion in this paper, a diverse range of nonlinear dynamic phenomena are observed and valuable insights for the stability design of the transmission device are provided.

State primary special standard of acceleration unit in the field of gravimetry GET 190-2023: reproduction and transmission of the unit under the influence of geophysical factors

The relevance of research on the reproduction and transmission of the acceleration unit in gravimetry is determined by the development of measuring instruments for the absolute value of the acceleration of free fall and its changes. Qualitative and quantitative changes in the instrument base are due to the requirements of applied tasks solved using gravimetric data in such fields as geodesy, navigation, geodynamics, as well as the expansion of the field of practical application of absolute gravimeters. At the same time, in order to solve applied problems, along with accuracy requirements at a level close to the maximum achievable at the current level of technology development, maximum territorial coverage of measurement sites within the entire territory of the Russian Federation is often necessary. The accuracy of the results obtained with the help of measuring instruments is determined by the level of their metrological support, the main stages of which are the reproduction of the corresponding unit by the standard and its transfer to the measuring instrument. An analysis of possible sources of errors in gravimetric equipment has shown that when reproducing and transmitting the acceleration unit in gravimetry, it is necessary to take into account the influence of geophysical factors that manifest themselves as additional accelerations of a gravitational or inertial nature. The distribution of the gravitational field within a gravimetric point can manifest itself as an additional constant acceleration. Seismic processes and lunar and solar tides manifest themselves as variable accelerations. For various stages of metrological support of gravimetric devices, the mechanisms of the effects of such accelerations have been studied, as well as methods for accounting and reducing their influence using additional equipment have been developed. An additional gravimetric point with a cryogenic relative gravimeter and a broadband seismometer, as well as transported absolute ballistic and relative quartz gravimeters, were introduced into the State primary special standard of acceleration units in the field of gravimetry GET 190-2023.

Measuring and modeling of liquid water transport in a carbon paper with the aid of centrifuge experiment

In previous macroscopic average models of proton exchange membrane fuel cells (PEMFCs), liquid water was assumed to be continuous throughout the carbon paper. The transport of disconnected water drops in carbon paper has long been neglected in these models, which tend to underestimate water saturation in carbon paper. This study proposes a two-phase flow model that considers the transport of disconnected water drops to simulate the air-water transport in carbon paper. The proposed model was established based on the relationship between capillary force and liquid water saturation, and this relationship was obtained by conducting centrifuge experiments. In the centrifuge experiment, initially, the water saturation inside the carbon paper sample was one, and the centrifugal acceleration was zero. As the centrifugal acceleration increased, the water saturation decreased owing to the centrifugal force. After twenty seconds, the water saturation no longer decreases because the centrifugal force on the liquid water is balanced by the capillary force. Centrifugal acceleration was used to evaluate the capillary force. When the centrifugal acceleration was 185 ms−2, the saturation of the water drops in the balanced state was 32.0%. As the centrifugal acceleration increases to 739 ms−2, the saturation decreases to 6.5%. According to the experimental results, a function correlating the saturation and centrifugal acceleration, that is, the capillary force, was established. Finally, the results show that the centrifugal acceleration is more than 18.5 times that of the gravitational acceleration, indicating that the effect of gravity on the motion of water drops is negligible.

Coupling of radiation and magnetospheric accretion flow in ULX pulsars: radiation pressure and photon escape time

ABSTRACT The accretion flow within the magnetospheric radius of bright X-ray pulsars can form an optically thick envelope, concealing the central neutron star from the distant observer. Most photons are emitted at the surface of a neutron star and leave the system after multiple reflections by the accretion material covering the magnetosphere. Reflections cause momentum to be transferred between photons and the accretion flow, which contributes to the radiative force and should thus influence the dynamics of accretion. We employ Monte Carlo simulations and estimate the acceleration along magnetic field lines due to the radiative force as well as the radiation pressure across magnetic field lines. We demonstrate that the radiative acceleration can exceed gravitational acceleration along the field lines, and similarly, radiation pressure can exceed magnetic field pressure. Multiple reflections of X-ray photons back into the envelope tend to amplify both radiative force along the field lines and radiative pressure. We analyse the average photon escape time from the magnetosphere of a star and show that its absolute value is weakly dependent on the magnetic field strength of a star and roughly linearly dependent on the mass accretion rate being $\sim 0.1\, {\rm s}$ at $\dot{M}\sim 10^{20}\, {\rm g\, s^{-1}}$. At high mass accretion rates, the escape time can be longer than free-fall time from the inner disc radius.

Numerical study and optimization of battery thermal management systems (BTMS) Based on Fin-Phase change material (PCM) in variable gravity environments

Phase change materials (PCMs) are widely employed in electronic thermal control systems for spacecraft because of their substantial energy storage competencies. Hence, the impact of gravitational acceleration (GA) on PCM thermal performance holds particular significance. Moreover, given considerations for spacecraft center of gravity, attitude control, and structural design, choosing an optimal battery placement orientation becomes pivotal for maximizing available space utilization. This study employs the enthalpy-porosity method to simulate and assess the heat transfer efficiency of PCM and the thermal behavior of cooling battery thermal management system (BTMS) under different gravity environments (0.05 g, 0.1 g, 1 g, 10 g, and 20 g) and different inclination angles (θ = 90°, 45°, 0°). The research findings indicate that when θ = 90°, as gravity increases from 0.05g to 20g, the complete melting time of PCM at GA = 20g is shortened by 95.05 s (15.00 %) compared to GA = 0.05g. Particularly, when GA = 10 g, increasing θ from 45° to 90° reduces PCM melting time by 59.05 s (9.66 % reduction) compared to θ = 45°, while at θ = 0°, it decreases by 65.75 s (10.75 % reduction). Notably, at θ = 45°, some unmelted solid PCM accumulates in the lower right corner of the enclosure hindering the BTMS heat transfer. Based on PCM melting characteristics, three optimization structures for different θ are proposed. At t = 240 s, PCM melting significantly improves with fins. Comparing Convective Heat Transfer Coefficients (CHTC) curves before and after optimization reveals reduced accumulated effects. However, more fins aren't always better due to BTMS weight considerations. Investigating enhanced CHTC, fin mass, and volume ratio(γ), the optimized model impacts BTMS weight differently for θ values. θ = 45°, a combination of annular and straight fins, is determined optimal using entropy-weighted TOPSIS. This paper innovatively studies PCM melting in BTMS under varied gravitational environments and θ, proposing an enhanced heat transfer scheme for aerospace BTMS design.

The Radcliffe Wave is oscillating.

Our Sun lies within 300 parsecs of the 2.7-kiloparsecs-long sinusoidal chain of dense gas clouds known as the Radcliffe Wave1. The structure's wave-like shape was discovered using three-dimensional dust mapping, but initial kinematic searches for oscillatory motion were inconclusive2-7. Here we present evidence that the Radcliffe Wave is oscillating through the Galactic plane while also drifting radially away from the Galactic Centre. We use measurements of line-of-sight velocity8 for 12CO and three-dimensional velocities of young stellar clusters to show that the most massive star-forming regions spatially associated with the Radcliffe Wave (including Orion, Cepheus, North America and Cygnus X) move as though they are part of an oscillating wave driven by the gravitational acceleration of the Galactic potential. By treating the Radcliffe Wave as a coherently oscillating structure, we can derive its motion independently of the local Galactic mass distribution, and directly measure local properties of the Galactic potential as well as the Sun's vertical oscillation period. In addition, the measured drift of the Radcliffe Wave radially outwards from the Galactic Centre suggests that the cluster whose supernovae ultimately created today's expanding Local Bubble9 may have been born in the Radcliffe Wave.

Physical strength, body composition, and G-test results of air force cadets based on nutrition knowledge differences

The Gravitational Acceleration Test (G-test) is a demanding, and sophisticated high-intensity physical activity, greatly influenced by individual body composition and physical strength. This study analyzed the general nutrition knowledge questionnaire (GNKQ) responses of Air Force cadets to identify the relationship between nutrition knowledge, body composition, physical activity, physical strength, and gravity-induced loss of consciousness. Based on the G-test results, 105 fourth-year Air Force cadets were divided into two groups: GP (G-test pass group) and GF (G-test fail group). The analysis items were GNKQ responses, body composition, and physical strength analysis, based on which independent sample t-tests , and logistic regression analysis were conducted. Physical activity according to the G-test results was statistically higher in the GP compared to the GF (vigorous activity reps/week, p = 0.017; mins/day, p = 0.011). The GP Group showed a statistically high GNKQ score compared to the GF Group: Overall (p = 0.003), Section 1 (p < 0.001), and Section 2 (p = 0.002). Based on this study, it can be deduced that analyzing the effect G-test through continuous research over the next years and applying them to physical training will have a greater impact on the cadets’ increased physical strength and their success on the G-test.

Quantum Gravitational Acceleration

In this study, we present the quantum gravitational acceleration. By having something in common All modern theoretical physics equations. Therefore, we can connect the theory of relativity General Einstein with quantum physics, we discuss the physics of black holes from one side and theory Information We show that it is natural to introduce the concept of black hole entropy as a metric Information about the inner parts of a black hole that cannot be accessed by Monitor outside. All equations have physical variables and variables, which express the values of certain, and these values are preserved that preserve all equations and information in theoretical physics modernity.

Remote physics experiment Mathematical pendulum as an attractive alternative to traditional laboratory exercises

Traditional laboratory exercises are usually not popular among students, especially the processing and submission of protocols. Students are used to using digital technologies, prefer active participation in the learning process, and love visualisations. To improve motivation and make laboratory practices more attractive to students, remote laboratories with the real time control and available anytime and anywhere can be offered. In this paper, we present the remote experiment Mathematical Pendulum, which is physically located at the Department of Physics, Faculty of Science, Jan Evangelista Purkyně University (UJEP) in Ústí nad Labem. Using it we can study physical laws such as the dependence of the pendulum’s period of oscillation on its length and determine the value of the gravitational acceleration. The remote pendulum is interactively controlled through a web browser from a computer or mobile phone, provides live video stream and experimental data downloadable via Internet. This single remote laboratory task is complemented by remote measurements of the acceleration of gravity at different latitudes through a group of ten identical mathematical pendulums created within the WorldPendulum WP@ELAB project. In this paper, we present not only the results of the measurements made, but also a pilot investigation of the use of this complex remote experiment.

Characterization of Sensitivity of Time Domain MEMS Accelerometer.

This paper characterizes the sensitivity of a time domain MEMS accelerometer. The sensitivity is defined by the increment in the measured time interval per gravitational acceleration. Two sensitivities exist, and they can be enhanced by decreasing the amplitude and frequency. The sensitivity with minor nonlinearity is chosen to evaluate the time domain sensor. The experimental results of the developed accelerometer demonstrate that the sensitivities span from -68.91 μs/g to -124.96 μs/g and the 1σ noises span from 8.59 mg to 6.2 mg (amplitude of 626 nm: -68.91 μs/g and 10.21 mg; amplitude of 455 nm: -94.51 μs/g and 7.76 mg; amplitude of 342 nm: -124.96 μs/g and 6.23 mg), which indicates the bigger the amplitude, the smaller the sensitivity and the bigger the 1σ noise. The adjustable sensitivity provides a theoretical foundation for range self-adaption, and all the results can be extended to other time domain inertial sensors, e.g., a gyroscope or an inclinometer.

Gravity-induced seismicity modulation on planetary bodies and their natural satellites

Ground-based monitoring of seismicity and modulation by external forces in the field of planetary seismology remains equivocal due to the lack of natural observations. Constrained by the natural observations (including Earthquakes, Moonquakes, and Marsquakes) and theoretical models, we present the variation in gravitational acceleration “g” of different solar system objects, combined with external harmonic forcings that are responsible for seismicity modulation on the planetary bodies and their natural satellites. From the global diversity in seismicity modulation, it has been observed that the plate-boundary regions on the Earth exhibit both short and long-period seismicity modulation. In contrast, the stable plate interior regions appear to be more sensitive to long-period seismicity modulation, however, lacking in short-period modulation. The deep Moonquakes are susceptible for both the lunar tidal period (13.6 days and 27 days) and long-period pole wobble modulation (206 days), whereas shallow emergent type moonquakes show a seismic periodicity at the lunation period (29.5 days). Further, the seasonal variation with an annual seismicity burst and seismic periodicity at polar wobble periods for high-frequency Marsquakes captured by InSight lander indicate a natural origin. Whereas diurnal and semi-diurnal periodicity along with Phobos’ tidal period, indicate possible artifacts due to different detection probabilities and non-seismic noise in the Martian environment. We argue that, in the context of rate-state-dependent fault friction, the gravity-induced resonance destabilization model appears to be better agreement with the contrast and relative diversity in seismicity modulation linked to the Earth, Moon, and Mars.

Continuum modelling of a just-saturated inertial column collapse: capturing fluid-particle interaction

This work presents a simple two-phase flow model to analyse a series of axisymmetric granular column collapse tests conducted under elevated gravitational accelerations. These columns were prepared with a just-saturated condition, where the granular pores were filled with a Newtonian fluid up to the column’s free surface. In this configuration, unlike the fully submerged case, air-water-grain contact angles may be important to flow dynamics. The interaction between a Newtonian fluid phase and a monodispersed inertial particle phase was captured by an inter-phase interaction term that considers the drag between the two phases as a function of the particle phase porosity. While this experimental setup has broad applications in understanding various industrial processes and natural phenomena, the focus of this study is on its relevance to predicting the motion of debris flows. Debris flows are challenging to model due to their temporally evolving composition, which can lead to the development of complex numerical models that become intractable. The developed numerical scheme in this study reasonably reproduces the particle-size and gravitational acceleration dependencies observed within the experimental runout and basal fluid pressure dissipation data. However, discrepancies between the model and physical experiments primarily arise from the assumption of modelling the granular phase as a continuum, which becomes less appropriate as particle size increases.Graphical

Experimental study on binary solids drying in a vibro-fluidized bed

Vibro-fluidized beds can improve the solids drying characteristics by enhancing the gas–solid contacting. In this study, experiments in a pseudo-2D vibro-fluidized bed setup are performed in order to better understand this improved drying behavior of binary solids mixtures. A coupled particle image velocimetry-infrared thermography technique is applied. Furthermore, a machine learning algorithm is used to characterize the bed segregation and mixing dynamics under the influence of mechanical vibration. Significant changes in bed hydrodynamics and various impacts on segregation and mixing characteristics were observed for vibrational oscillations corresponding to low values of acceleration compared to gravitational acceleration. Larger vibration accelerations result in significantly increased solids mixing compared to a non-vibrating gas-fluidized bed due to enhanced meso-scale particle agitation.

Penentuan Percepatan Gravitasi Bumi Menggunakan Bandul Sederhana Di Daerah Kampus UPI

Many people assume that the value of gravitational acceleration always has a fixed value. However, if we look closely, the value of gravitational acceleration always changes in each place. This research aims to compare differences in Earth's gravitational acceleration in various locations. Through this research, researchers can identify the causes of differences in gravity, one of which is differences in height. The method used in this research is a simple pendulum experimental method, with a quantitative approach to collecting data from various places. The results obtained for g in the JICA building on the 5th floor were 9,47 m/s², g in the FIP building on the 10th floor was 9,72 m/s², g in the FPTK 9,59 m/s², and g at the National Museum of Education is 9,72 m/s². Apart from that, it can be found the average magnitude of the gravitational acceleration from these four places is 9,62 m/s². From these results it can be concluded that the magnitude of the Earth’s gravitational acceleration is different in each place. Apart from height, this difference can also occur due to uncertainty in measuring gravity.

Development of constitutive relations for predicting film boiling crisis in bare and inner wall coated cryogenic tubes with a low-thermal conductive layer for heat transfer enhancement

Closure models for transient cryogenic quench flow boiling heat transfer prediction are finding significant attention to support the design of energy-efficient, cost-effective, and reliable cryogenic fluid management systems. In this regard, the characterization of the film boiling crisis, which indicates the beginning of transient wetting of the wall by liquid, is essential due to the significant heat transfer change past this stage. In the current work, a new rewetting database is developed from 112 chill-down experiments conducted using LCH4, LOX, LAr, and LN2 in feed lines having 0.11 m to 11 m length, 0.4 cm to 2.2 cm inner diameter, 0.5 mm to 5 mm wall thickness, and low-thermal conductive coating thickness up to 157 μm, under several pipe orientations. Additionally, the dataset comprises a mass flux from 10.5 kg/m2s to 1805 kg/m2s, pressure from 109.8 kPa to 1153.8 kPa and gravitational acceleration from terrestrial condition to ±0.01 g. Subsequently, 30 existing seminal rewetting correlations are analyzed for their applicability to transient cryogenic rewetting prediction. Moreover, the importance of feed line and flow parameters in this phenomenon is also studied. Accordingly, a new correlation for rewetting temperature is proposed with 4.15% mean absolute percentage error (MAPE). Further, applying a low-thermal conductive coating to the feed line inner wall surface has already been proven to enhance the chill-down efficiency up to 80%. For modeling such feed systems, determining bulk wall rewetting point is necessary. Hence, a new apparent rewetting temperature correlation to characterize the film boiling crisis in cryogenic coated tubes is proposed for the first time with a MAPE of 4%. Finally, the paper presents the predictions from a non-homogeneous two-phase thermal-hydraulic code, employing the previously reported film boiling correlations and the rewetting correlations from the present work. The obtained model performance indicates considerable improvement in prediction while using the proposed closure models. This shows their potential to support optimization tasks to achieve higher chill-down efficiency.

Chaotic motion behaviors of liquid crystal elastomer pendulum under periodic illumination

The active material of liquid crystal elastomer (LCE) is capable of harvesting energy directly from the surroundings and sustaining continuous motion in the presence of light and heat. It is extensively employed in active machinery, soft robotics, biomedicine, and other fields. To date, there is barely any research on the sustained chaotic motion system of LCE pendulum. The main objective of this paper is to put forward a sustained motion system of a simple pendulum comprising photosensitive LCE. In accordance with the LCE dynamic model, a nonlinear dynamic model of the LCE simple pendulum is established, and its motion behavior characteristics under periodic illumination are examined. The numerical outcomes demonstrate that apart from the in-situ vibration mode, the LCE pendulum experiences two types of displacement motion modes as well, namely periodic oscillation mode and chaotic motion mode. The mechanism underlying the sustained periodic oscillation and chaotic motion is revealed by compensating for the damping dissipation with work done by the LCE contraction. Moreover, the discussion also covers how the system parameters affect the motion modes of the LCE simple pendulum. Through altering the parameters such as illumination period, contraction coefficient, light intensity, damping coefficient and gravitational acceleration, it is possible to realize the distinct motion modes of the LCE simple pendulum. This research may deepen the comprehension on the motion behavior of the simple pendulum, and provide scientific guidance for the design and exploration of chaotic systems based on active materials.