Physical Solution Research Articles

Problematic Analysis of Assessment Standards in Physical Education

Improving the quality of the assessment is needed because with an assessment process that meets the standards, student learning outcomes will be measured accurately. This article aims to analyze several studies on the problem of assessment standards in the physical education (PE) learning process so that knowing what factors have a relationship and influence on the occurrence of problems in physical education assessment standards and solutions that can be implemented in these problems. The method in this article is a literature review using flow chart PRISMA to identify articles through process filtering and data extraction. The results were obtained from 15 articles that meet the criteria, such as the subjects used are teachers and students in educational institutions and articles used in at least the last ten years. A total of 15 articles stated that the assessment process in physical education learning still needs a lot to meet the educational assessment standards. This is due to a lack of understanding of performance appraisal because teachers usually only see and use pre-existing assessments without evaluation and need to be adjusted to the character of student achievement and teachers' critical thinking without pedagogy.

Chemical evolution of fluorine in the Milky Way

ABSTRACT Fluorine has many different potential sites and channels of production, making narrowing down a dominant site of fluorine production particularly challenging. In this work, we investigate which sources are the dominant contributors to the galactic fluorine by comparing chemical evolution models to observations of fluorine abundances in Milky Way stars covering a metallicity range of −2 < [Fe/H] < 0.4 and upper limits in the range of −3.4 < [Fe/H] < −2.3. In our models, we use a variety of stellar yield sets in order to explore the impact of varying both asymptotic giant branch (AGB) and massive star yields on the chemical evolution of fluorine. In particular, we investigate different prescriptions for initial rotational velocity in massive stars as well as a metallicity-dependent mix of rotational velocities. We find that the observed [F/O] and [F/Fe] abundance ratios at low metallicity and the increasing trend of [F/Ba] at [Fe/H] ≳ −1 can only be reproduced by chemical evolution models assuming, at all metallicities, a contribution from rapidly rotating massive stars with initial rotational velocities as high as 300 km s−1. A mix of rotational velocities may provide a more physical solution than the sole use of massive stars with vrot = 300 km s−1, which are predicted to overestimate the fluorine and average s-process elemental abundances at [Fe/H] ≳ −1. The contribution from AGB stars is predicted to start at [Fe/H] ≈ −1 and becomes increasingly important at high metallicity, being strictly coupled to the evolution of the nitrogen abundance. Finally, by using modern yield sets, we investigate the fluorine abundances of Wolf–Rayet winds, ruling them out as dominant contributors to the galactic fluorine.

Two-dimensional Lifshitz-like AdS black holes in F(R) gravity

Two-dimensional (2D) Lifshitz-like black holes in special F(R) gravity cases are extracted. We indicate an essential singularity at r = 0, covered by an event horizon. Then, conserved and thermodynamic quantities, such as temperature, mass, entropy, and the heat capacity of 2D Lifshitz-like black holes in F(R) gravity, are evaluated. Our analysis shows that 2D Lifshitz-like black hole solutions can be physical solutions, provided that the cosmological constant is negative (Λ < 0). Indeed, there is a phase transition between stable and unstable cases by increasing the radius of AdS black holes. In other words, the 2D Lifshitz-like AdS black holes with large radii are physical and enjoy thermal stability. The obtained 2D Lifshitz-like AdS-black holes in F(R) gravity turn into the well-known 2D Schwarzschild AdS-black holes when the Lifshitz-like parameter is zero (s = 0). Moreover, correspondence between these black hole solutions and the 2D rotating black hole solutions is found by adjusting the Lifshitz-like parameter.

Semianalytical Model of Unloading-Induced Pore-Water Pressure and Consequent Consolidation Settlement of Surcharge Preloading Railway Subgrade

Surcharge preloading is a suitable foundation treatment for high-speed railways in soft soil regions. As a temporary preload on the foundation, the surcharge load must be removed before track construction. In this process, rebound deformation of the foundation and variation in the pore-water pressure have been widely observed. These phenomena significantly influence the further evolution process of foundation consolidation. Although Biot’s consolidation theory is suitable for unloading-induced soil consolidation, the conventional Laplace transform method for solving Biot’s equations entails a time-consuming procedure and cannot reflect the time-dependent characteristics of the preloading and unloading process. To address these issues, a time difference method is proposed in this work. The ordinary differential equation in the transformation domain is obtained using the backward two-step difference method, and a physical analytical solution of the plane strain problem of overloaded subgrade is obtained via the Fourier inverse transform method. The proposed solution is validated through a comparison with existing literature data and actual engineering practices. Finally, based on this calculation method, the influence of the surcharge preloading amount, loading time, and soil properties on pore-water pressure dissipation and distribution after surcharge preloading removal is investigated.

Secure UAV-to-Ground MIMO Communications: Joint Transceiver and Location Optimization

Unmanned aerial vehicles (UAVs) are foreseen to constitute promising airborne communication devices as a benefit of their superior channel quality. But UAV-to-ground (U2G) communications are vulnerable to eavesdropping. Hence, we conceive a sophisticated physical layer security solution for improving the secrecy rate of multi-antenna aided U2G systems. Explicitly, the secrecy rate of the U2G MIMO wiretap channels is derived by using random matrix theory. The resultant explicit expression is then applied in the joint optimization of the MIMO transceiver and the UAV location relying on an alternating optimization technique. Our numerical results show that the joint transceiver and location optimization conceived facilitates secure communications even in the challenging scenario, where the legitimate channel of confidential information is inferior to the eavesdropping channel.

Heat Conduction Plate Layout Optimization Using Physics-Driven Convolutional Neural Networks

Optimizing heat conduction layout is essential during engineering design, especially for sensible thermal products. However, when the optimization algorithm iteratively evaluates different loading cases, the traditional numerical simulation methods usually lead to a substantial computational cost. To effectively reduce the computational effort, data-driven approaches are used to train a surrogate model as a mapping between the prescribed external loads and various geometry. However, the existing model is trained by data-driven methods, which require intensive training samples from numerical simulations and do not effectively solve the problem. Choosing the steady heat conduction problems as examples, this paper proposes a physics-driven convolutional neural networks (PD-CNNs) method to infer the physical field solutions for randomly varied loading cases. After that, the particle swarm optimization (PSO) algorithm is used to optimize the sizes, and the positions of the hole masks in the prescribed design domain and the average temperature value of the entire heat conduction field is minimized. The goal of reducing heat transfer is achieved. Compared with the existing data-driven approaches, the proposed PD-CNN optimization framework predicts field solutions that are highly consistent with conventional simulation results. However, the proposed method generates the solution space without pre-obtained training data. We obtained thermal intensity results for holes 1, hole 2, hole 3, and hole 4 with 0.3948, 0.007, 0.0044, and 0.3939, respectively, by optimization PD-CNN model.

Loading and releasing behavior of carboxymethyl cellulose and chitosan complex beads

The complex beads of carboxymethyl cellulose (CMC) and chitosan (CHI) that are fabricated by interfacial complexation have a core-shell structure composed of a thin skin layer and a 3D entangled internal structure, which endows the beads with adsorption possibilities toward anionic and cationic molecules via electrostatic interaction. However, the loading and releasing behavior of such a system is essential and fundamental for their application yet has not been studied systematically. In this work, the influences of beads physical state, adsorbent dosage, agitation speed, solution pH and temperature on the loading behavior were investigated. The CMC@CHI beads demonstrated different loading efficiency to three typical dyes of methylene blue (MB), acid blue-113 (AB), and methyl orange (MO) with different charge status. The adsorption rate followed an order of MB ˃ AB ˃ MO, giving 97.4%, 73.3% and 20.2%, respectively. The releasing of three dyes from CMC@CHI beads also exhibited different rates, and MB release was found to be prolonged compared to AB and MO. The loading mechanism of dyes was further investigated via X-ray photoelectron spectroscopy. These CMC@CHI beads may have possible applications in mixed dye removal as well as encapsulating systems of drugs or sensitive chemicals with different charges.

Fundamental effective temperature measurements for eclipsing binary stars – II. The detached F-type eclipsing binary CPD-54 810

ABSTRACT CPD-54 810 is a double-lined detached eclipsing binary containing two mid-F type dwarfs on an eccentric 26-d orbit. We perform a combined analysis of the extensive photometry obtained by the TESS space mission along with previously published observations to obtain a full orbital and physical solution for the system. We measure the following model-independent masses and radii: $M_1=1.3094\pm 0.0051\, {M_\odot }$, $M_2=1.0896\pm 0.0034\, {M_\odot }$, $R_1=1.9288\pm 0.0030\, {R_\odot }$, and $R_2=1.1815\pm 0.0037\, {R_\odot }$. We employ a Bayesian approach to obtain the bolometric flux for both stars from observed magnitudes, colours, and flux ratios. These bolometric fluxes combined with the stars’ angular diameters (from R1, R2 and the parallax from Gaia EDR3) lead directly to the stars’ effective temperatures: Teff, 1 = 6462 ± 43 K, and Teff, 2 = 6331 ± 43 K, with an additional systematic error of 0.8 per cent (13 K) from the uncertainty in the zero-point of the flux scale. Our results are robust against the choice of model spectra and other details of the analysis. CPD-54 810 is an ideal benchmark system that can be used to test stellar parameters measured by large spectroscopic surveys or derived from asteroseismology, and calibrate stellar models by providing robust constraints on the measured parameters. The methods presented here can be applied to many other detached eclipsing binary systems to build a catalogue of well–measured benchmark stars.

Close relationship between the dressed metric and the hybrid approach to perturbations in effective loop quantum cosmology

The dressed metric and the hybrid approach to perturbations are the two main approaches to capture the effects of quantum geometry in the primordial power spectrum in loop quantum cosmology. Both consider Fock quantized perturbations over a loop quantized background and result in very similar predictions except for the modes which exit the horizon in the effective spacetime in the Planck regime. Understanding precise relationship between both approaches has so far remained obscured due to differences in construction and technical assumptions. We explore this issue at the classical and effective spacetime level for linear perturbations, ignoring backreaction, which is the level at which practical computations of the power spectrum in both of the approaches have so far been performed. We first show that at the classical level both the approaches lead to the same Hamiltonian up to the second order in perturbations and result in the same classical mass functions in the Mukhanov-Sasaki equation on the physical solutions. At the effective spacetime level, the difference in phenomenological predictions between the two approaches in the Planck regime can be traced to whether one uses the Mukhanov-Sasaki variable $Q_{\vec k}$ (the dressed metric approach) or its rescaled version $\nu_{\vec k}=aQ_{\vec k}$ (the hybrid approach) to write the Hamiltonian of the perturbations, and associated polymerization ambiguities. It turns out that if in the dressed metric approach one chooses to work with $\nu_{\vec{k}}$, the effective mass function can be written exactly as in the hybrid approach, thus leading to identical phenomenological predictions in all regimes. Our results explicitly show that the dressed metric and the hybrid approaches for linear perturbations, at a practical computational level, can be seen as two sides of the same coin.

Inclusion of STEAM Innovation Spaces: A Critical Issue for Learners with Disabilities

The fourth industrial revolution has provided a wide range of flexible physical and digital technologies that continue to enhance the teaching and learning of STEAM. Incorporating STEAM and building makerspaces, Fablabs (Fabrication Labs), and STEAM labs as part of the educational curriculum can serve as the right environment to empower learners to transform their ideas into tangible digital or physical solutions. However, the standards way of development of spaces such as FabLabs does not always guarantee accessible learning opportunities for learners with disabilities as they may require additional accommodations to be able to access and use the technology tools. This article confirms that children with disabilities face multiple challenges with inclusivity and accessibility. Creating inclusive innovation spaces that support, promote, and accelerate learning is essential and requires an understanding of the application of user-centered design, universal design, and utilization of local and global networks to create solutions that increase accessibility and create an inclusive environment.

Exact solutions for MHD and radiative wall jet hybrid nanofluid flow over a permeable surface with velocity slip and convective boundary conditions

AbstractIn this research, we investigated the wall jet problem for a hybrid nanofluid with MHD, thermal radiation, velocity slip, and convective boundary conditions. After converting the governing partial differential equations into nonlinear ordinary ones, by using the proper similarity transformations, they were theoretically solved in view of the hypergeometric function. Comparing the present results with those in the literature, a very good agreement was obtained for fixed values of the included parameters. For some included parameters, regions of physical solutions were presented. By deducing the critical and terminated values of the suction/injection parameter, dual solutions for the reduced skin friction coefficient have been determined. It was found that the hybrid nanofluid temperature is efficiently heated by increasing values of the moving wall, absolute value of the Biot number, and thermal radiation parameters. However, it is cooled by enlarging values of the velocity slip and suction parameters.

Optimal threshold padlock systems

In 1968, Liu described the problem of securing documents in a shared secret project. In an example, at least six out of eleven participating scientists need to be present to open the lock securing the secret documents. Shamir proposed a mathematical solution to this physical problem in 1979, by designing an efficient k-out-of-n secret sharing scheme based on Lagrange’s interpolation. Liu and Shamir also claimed that the minimal solution using physical locks is clearly impractical and exponential in the number of participants. In this paper we relax some implicit assumptions in their claim and propose an optimal physical solution to the problem of Liu that uses physical padlocks, but the number of padlocks is not greater than the number of participants. Then, we show that no device can do better for k-out-of-n threshold padlock systems as soon as k ⩾ 2 n , which holds true in particular for Liu’s example. More generally, we derive bounds required to implement any threshold system and prove a lower bound of O ( log ( n ) ) padlocks for any threshold larger than 2. For instance we propose an optimal scheme reaching that bound for 2-out-of-n threshold systems and requiring less than 2 log 2 ( n ) padlocks. We also discuss more complex access structures, a wrapping technique, and other sublinear realizations like an algorithm to generate 3-out-of-n systems with 2.5 n padlocks. Finally we give an algorithm building k-out-of-n threshold padlock systems with only O ( log ( n ) k − 1 ) padlocks. Apart from the physical world, our results also show that it is possible to implement secret sharing over small fields.

Secure Transmission in Cellular V2X Communications Using Deep Q-Learning

Cellular vehicle-to-everything (V2X) communication is emerging as a feasible and cost-effective solution to support applications such as vehicle platooning, blind spot detection, parking assistance, and traffic management. To support these features, an increasing number of sensors are being deployed along the road in the form of roadside objects. However, despite the hype surrounding cellular V2X networks, the practical realization of such networks is still hampered by under-developed physical security solutions. To solve the issue of wireless link security, we propose a deep Q-learning-based strategy to secure V2X links. Since one of the main responsibilities of the base station (BS) is to manage interference in the network, the link security is ensured without compromising the interference level in the network. The formulated problem considers both the power and interference constraints while maximizing the secrecy rate of the vehicles. Subsequently, we develop the reward function of the deep Q-learning network for performing efficient power allocation. The simulation results obtained demonstrate the effectiveness of our proposed learning approach. The results provided here will provide a strong basis for future research efforts in the domain of vehicular communications.

Nucleation in situ of perylene crystal by femtosecond laser induced cavitation

Organic semiconductor single crystal materials have broad application prospects in the field of high-performance optoelectronic devices because of their highly ordered structure, few defects, and high carrier mobility. However, it is difficult to control the nucleation location of crystal formation in the current commonly used crystal growth methods including physical vapor transport and solution processing, which makes it difficult to manufacture organic crystal devices. Laser-induced crystallization technology is expected to solve this problem. In this study, we demonstrated nucleation in situ of a perylene crystal by femtosecond laser induced cavitation. The results show that the crystallization of perylene crystals induced by the femtosecond laser is mainly due to the aggregation effect by laser cavitation bubbles caused by multiphoton absorption. This strategy facilitates the application of organic single crystals to optoelectronic devices.

Thermal Progress of Unsteady Separated Stagnation Point Flow with Magnetic Field and Heat Generation in Hybrid Ferrofluid.

This paper examines the unsteady separated stagnation point (USSP) flow and thermal progress of Fe3O4–CoFe2O4/H2O on a moving plate subject to the heat generation and MHD effects. The model of the flow includes the boundary layer and energy equations. These equations are then simplified with the aid of similarity variables. The numerical results are generated by the bvp4c function and then presented in graphs and tables. The magnetic and acceleration (strength of the stagnation point flow) parameters are the contributing factors in the augmentation of the skin friction and heat transfer coefficients. However, the enhancement of heat generation parameter up to 10% shows a reduction trend in the thermal rate distribution of Fe3O4–CoFe2O4/H2O. This finding reveals the effectiveness of heat absorption as compared to the heat generation in the thermal flow process. From the stability analysis, the first solution is the physical solution. The streamline for the first solution acts as a normal stagnation point flow, whereas the second solution splits into two regions, proving the occurrence of reverse flow.

Positioning and power optimisation for UAV-assisted networks in the presence of eavesdroppers: a multi-armed bandit approach

Unmanned aerial vehicles (UAVs) are becoming increasingly attractive for the ambitious expectations for 5G and beyond networks due to their several benefits. Indeed, UAV-assisted communications introduce a new range of challenges and opportunities regarding the security of these networks. Thus, in this paper we explore the opportunities that UAVs can provide for physical layer security solutions. Particularly, we analyse the secrecy performance of a ground wireless communication network assisted by N friendly UAV jammers in the presence of an eavesdropper. To tackle the secrecy performance of this system, we introduce a new area-based metric, the weighted secrecy coverage (WSC), that measures the improvement on the secrecy performance of a system over a certain physical area given by the introduction of friendly jamming. Herein, the optimal 3D positioning of the UAVs and the power allocation is addressed in order to maximise the WSC. For that purpose, we provide a reinforcement learning-based solution by modelling the positioning problem as a multi-armed bandit problem over three positioning variables for the UAVs: angle, height and orbit radius. Our results show that the proposed algorithm improves the secrecy of the system over time in terms of the WSC, and it converges into a stable state close to the exhaustive search solution for discretised actions, where there is a trade-off between expediency of the positioning of the UAVs to positions of better secrecy outcome and energy consumption.

Effect of a Three-Month HOPSports Brain Breaks® Intervention Program on the Physical Fitness Levels of Grade 6-Learners in South Africa.

Despite the numerous health benefits of being physically active, children are not active enough. Various researchers have indicated that intervention programs improve physical fitness levels. Still, only a few have focused on improving physical fitness levels by incorporating technology. HOPSports Brain Breaks® are designed and presented as physical activity solutions with online videos requiring the participants to imitate the movements. These videos are 2–5-min classroom activity breaks. This study determined the effect of a three-month HOPSports Brain Breaks® intervention program on the physical fitness levels of Grade 6-learners. Physical fitness was measured with the EUROFIT test battery. The experimental group consisted of 79 children (26 boys and 47 girls) and the control group of 47 children (16 boys and 33 girls). The mean age for the entire group was 11.92 (±0.36) years. The results indicated that there was a statistically (p ≤ 0.05) and practically (d ≥ 0.20) significant difference between the experimental and control group for percentage body fat; stork balance; plate tapping; sit-and-reach; standing jump; sit-ups; and 10 × 5 m shuttle run and 20 m shuttle run between the pre-and post-test. Therefore, considering the results mentioned above, the HOPSports Brain Breaks® intervention program can indeed contribute to the improvement of physical fitness, and motor skills of children. Therefore, future studies should be conducted to determine the effect of HOPSports Brain Breaks® between genders as well as what impact it will have on academic performance.

The Black Hole Universe, Part I

The original Friedmann (1922) and Lemaitre (1927) cosmological model corresponds to a classical solution of General Relativity (GR), with the same uniform (FLRW) metric as the standard cosmology, but bounded to a sphere of radius R and empty space outside. We study the junction conditions for R to show that a co-moving observer, like us, located anywhere inside R, measures the same background and has the same past light-cone as an observer in an infinite FLRW with the same density. We also estimate the mass M inside R and show that in the observed universe R<rS≡2 GM, which corresponds to a Black Hole Universe (BHU). We argue that this original Friedmann–Lemaitre model can explain the observed cosmic acceleration without the need of Dark Energy, because rS acts like a cosmological constant Λ=3/rS2. The same solution can describe the interior of a stellar or galactic BHs. In co-moving coordinates the BHU is expanding while in physical or proper coordinates it is asymptotically static. Such frame duality corresponds to a simple Lorentz transformation. The BHU therefore provides a physical BH solution with an asymptotically deSitter metric interior that merges into a Schwarzschild metric exterior without discontinuities.

Analysis of Water Quality Improvement Effect of Controlled River by Multi-Functional Weir Operation

In this study, the water quality change in a stagnant controlled river containing hard management structures due to pulsed flow was simulated. The Environmental Fluid Dynamics Code (EFDC) model was used for the water quality change simulation, and the water quality improvement effect caused by pulsed flow was simulated for multiple scenarios. Based on Case 1, in which 274.2–291.8 CMS was discharged for five hours, other scenarios, in which the gate was opened by 0.5 m and 1.0 m while the discharge time was doubled, were simulated. On comparing the water level results with the observed data, a relatively positive result of R2 = 0.82 was obtained. The water quality simulation results showed that the concentrations of Chl-a, COD, and T-P were, respectively, approximately 7.7%, 4.5%, and 4.0% higher in Case 2 than in Case 1, 24 h after the start of discharge. Cases 3 and 4, on the other hand, exhibited decreased concentrations of Chl-a, COD, and T-P 24 h after the start of discharge. These results confirm that pulsed flow leads to different water quality improvement effects depending on the discharge amount and duration. Furthermore, the water quality improvement effect was recorded at close to 0% after 72 h in all scenarios. As the water quality improvement effect due to pulsed flow appears within 24 h and almost disappears after 72 h depending on the scenario, a physical solution to this problem is required.

Large-scale influence of numerical noises as artificial stochastic disturbances on a sustained turbulence

We investigate the large-scale influence of numerical noises as tiny artificial stochastic disturbances on a sustained turbulence. Using two-dimensional (2-D) turbulent Rayleigh–Bénard convection (RBC) as an example, we solve numerically the Navier–Stokes equations, separately, by means of a traditional algorithm with double precision (denoted RKwD) and the so-called clean numerical simulation (CNS). The numerical simulation given by RKwD is a mixture of the ‘true’ physical solution and the ‘false’ numerical noises that are random and can be regarded as a kind of artificial stochastic disturbances; unfortunately, the ‘true’ physical solution is mostly at the same level as the ‘false’ numerical noises. By contrast, the CNS can greatly reduce the background numerical noise to any a required level so that the ‘false’ numerical noises are negligible compared with the ‘true’ physical solution, thus the CNS solution can be used as a ‘clean’ benchmark solution for comparison. It is found that the numerical noises as tiny artificial stochastic disturbances could indeed lead to large-scale deviations of simulations not only in spatio-temporal trajectories but also even in statistics. In particular, these numerical noises (as artificial stochastic disturbances) even lead to different types of flows. The shearing convection occurs for the RKwD simulations, and its corresponding flow field turns to a kind of zonal flow thereafter; however, the CNS benchmark solution always sustains the non-shearing vortical/roll-like convection during the whole process of simulation. Thus we provide rigorous evidence that numerical noises as a kind of small-scale artificial stochastic disturbances have quantitatively and qualitatively large-scale influences on a sustained turbulence, i.e. the 2-D turbulent RBC considered in this paper.