Changes In Physical Quantities Research Articles

The first boundary value problem for the fractional diffusion equation in a degenerate angular domain

This article addresses the problems observed in branching fractal structures, where super-slow transport processes can occur, a phenomenon described by diffusion equations with a fractional time derivative. The characteristic feature of these processes is their extremely slow relaxation rate, where a physical quantity changes more gradually than its first derivative. Such phenomena are sometimes categorized as processes with “residual memory”. The study presents a solution to the first boundary problem in an angular domain degenerating into a point at the initial moment of time for a fractional diffusion equation with the RiemannLiouville fractional differentiation operator with respect to time. It establishes the existence theorem of the problem under investigation and constructs a solution representation. The need for understanding these super-slow processes and their impact on fractal structures is identified and justified. The paper demonstrates how these processes contribute to the broader understanding of fractional diffusion equations, proving the theorem’s existence and formulating a solution representation.

Instrumentation for measurement: A case study on conceptual versus problem-solving knowledge

The problem under analysis looks at the overall comparison of about 1300 students’ performance considering separately their conceptual and problem-solving knowledge over 7 academic years of the course of Instrumentation for Measurement within the Mechanical Engineering Department, Faculty of Engineering, University of Porto . This course gives the relevant background for later content courses on Automation, Control, Mechatronics, Smart Factories, etc., in that Mechanical Engineering master's degree. It is important to note that such content deals with basic concepts in different science and technology topics, incorporating today's cyber systems and the Internet of Things (IoT). This content includes fundamental principles spanning traditional topics as physics, statistics, mechanical, dynamics, design, and electrical, foundational, technical, and technological knowledge, and informatics. Together, they permit access to very small changes in physical quantities making possible their measurement, interpreting them, and providing data in the cloud. Also, aspects related to a variety of specific prepared questions to motivate students to improve and enhance their comprehension instead of a pure sequence of memorization activities for a perfect “how-to-respond” are explained. The work describes details on the instructional course design, and the actions used to improve the difference in both performances, from the point of view of pedagogical strategies and their sequence of results. The main outcomes of the analysis performed on data from those 7-course editions indicate large differences between the scores of conceptual (/theoretical) and problem-solving components; steady improvement in student performance in conceptual knowledge over the years; stable performance concerning the problem-solving component; clear disruption in conceptual performance in the academic year disturbed by the pandemic situation, followed by great recovery in the following academic year. The results are discussed in the framework of the regulations and conditions in which the instruction takes place and the pedagogical strategies employed to balance conceptual and problem-solving knowledge. Finally, some suggestions are put forward to investigate further possible reasons behind the large gap in theoretical and problem-solving results. The authors hope to contribute with some helpful discussion and outcomes and to foster later feedback from the community.

An adaptive global–local generalized FEM for multiscale advection–diffusion problems

This paper develops an adaptive algorithm for the Generalized Finite Element Method with global–local enrichment (GFEMgl) for transient multiscale PDEs. The adaptive algorithm detects a subset of global nodes with trivial enrichments, which are exactly or close to linearly dependent from the underlying coarse FEM basis, at each time step, and then removes them from the global system. It is based on the calculation of the ratio between the largest and smallest singular values of small sub-matrices extracted from the global system of equations which introduces little overhead over the non-adaptive GFEMgl for transient PDEs. Compared to existing adaptive multiscale approaches, where either an a-posterior error estimate, a change in physical quantities, or a local problem residual is calculated, the proposed approach provides an innovative framework based on singular values. The proposed approach is shown to be robust for solving advection–diffusion problems that require detecting initial conditions with spikes and capturing moving/morphing/merging mass plumes in heterogeneous media and non-uniform flow with sharp fronts. Specific examples are provided for applications in groundwater contaminant and heat dissipation. The accuracy of the proposed adaptive GFEMgl closely matches reference fine-scale FEM solutions in the L∞ norm.

Efficient scheme for time-dependent thermal pure quantum state: Application to the Kitaev model with armchair edges

We consider the time-dependent thermal pure quantum state method and introduce the efficient scheme to evaluate the change in physical quantities induced by the time-dependent perturbations, which has been proposed in our previous paper [H. Taguchi et al., Phys. Rev. B 105, 125137 (2022)]. Here, we treat the Kitaev model to consider the Majorana-mediated spin transport, as an example. We demonstrate how efficient our scheme is to evaluate spin oscillations induced by the magnetic field pulse.

An investigation of the multi-mode Richtmyer-Meshkov instability at a gas/HE interface using Pagosa

In this work, we present a hydrocode Pagosa and explore the Richtmyer-Meshkov Instability (RMI) at an air/high explosive (HE) interface for the first time that is important but has not received much attention yet in the high explosive safety field. Thus, the presented Pagosa can be expected to predict the whole deflagration-to-detonation transition (DDT) process in future. In Pagosa, spatial discretization is implemented on cubic staggered grids by computing different variables at the vertex and the cell center, respectively, a special operator-splitting technique is employed to reduce the computational cost, and an artificial viscosity is added to handle the discontinuous shock waves in our simulations. To quantitatively evaluate the capability of Pagosa to solve these kinds of instabilities, the single mode Rayleigh-Taylor instability (RTI) and the multimode RMI at an air/SF 6 interface are first performed, respectively. The Pagosa results are compared with the related numerical solutions in the existing references and the experimental result. Moreover, a theoretical derivation of growth of RTI is also provided based on our numerical method. Subsequently, we explore the multi-mode RMI at an air/HE interface as well as the effects of several factors using Pagosa. Numerical results show that Pagosa is a powerful toolset to generate the right structures and the amplitude of RTI and RMI at an air/SF 6 interface. The solid HE can be penetrated by a strong shock wave and forms RMI deformations. The RMI at an air/HE interface behaves very different than at an air/SF 6 interface, periodic, decreased oscillation is observed due to material character, and is very sensitive to the initial simulation settings, that is, a tiny change in physical quantities will lead to a remarkable RMI structure, which is also observed in a shock bubble interaction [41] . The findings in this work are significant, and will present a new insight for the high explosive field. • An enhanced model Pagosa is presented with some special techniques. • Pagosa's capability to accurately capture the RTI at an air/SF 6 interface. • Pagosa's ability to accurately predict the RMI at an air/SF 6 interface. • The RMI at an air/HE interface is different from that at an air/SF 6 interface. • Effects of several factors on RMI at an air/HE interface.

Unsteady thin film flow with ohmic heating and chemical reactions

In this study, we have analyzed magnetohydrodynamic (MHD) consequences on the heat and mass transmission within unsteady dissipated liquid film flow. Flow is generated due to stretchable surface accompanied with effects of ohmic heating, chemical reaction and heat absorption. Moreover, the flow governing partial differential equations (PDEs) are further modified into equivalent ordinary differential equations (ODEs) by applying regular perturbation method to get its analytical solution after that we have applied sixth-order Runge–Kutta technique to get its numerical solution. These two solutions are validating each other in the simulations. Figures are plotted to study the changes in physical quantities like skin friction coefficient, concentration, velocity, temperature, Sherwood and Nusselt number with the variations of Prandtl numbers Pr, parameters of chemical reaction [Formula: see text], Eckert numbers Ec, magnetic parameter Ha (also known as Hartman number) Schmidt number and coefficient of heat absorption [Formula: see text].

ST – ELEMENTS APPLICATIONS FOR SOME TASKS

Using elements of the mathematics of St1, we introduce the concept of St – the change in physical quantity B: . Then the mean St - velocity will be vcpst(t, Δt) =, and St is the velocity at time t:. St – acceleration .

Arc-Extinguishing Research on Semi-Closed Multi-Compression Tube Structures

Using lightning energy to extinguish the arc is a new lightning protection method. On this basis, the semi-closed multi-compression tube structures (SMTS) combined with the arc extinguishing structure studied in this paper can suppress the power frequency arc at the initial stage of arc establishment by using the coupling effect of current and gas. Firstly, through the simulation comparison method, the promotion effect of the semi-closed tube on the arc discharge was found. Furthermore, the two-dimensional impulse power frequency current coupling discharge model was established to obtain changes in physical quantities, such as temperature and conductivity. The conductivity decreased to the initial value in about 1 ms. Finally, the impulse power frequency combined arc extinguishing test was carried out. The test results show that the arc extinguishing structure can effectively extinguish power frequency freewheeling within 1 ms. It proves the effectiveness of the arc extinguishing structure.

Hybrid Scheme of Kinematic Analysis and Lagrangian Koopman Operator Analysis for Short-Term Precipitation Forecasting

With the accumulation of meteorological big data, data-driven models for short-term precipitation forecasting have shown increasing promise. We focus on Koopman operator analysis, which is a data-driven scheme to discover governing laws in observed data. We propose a method to apply this scheme to phenomena accompanying advection currents such as precipitation. The proposed method decomposes time evolutions of the phenomena between advection currents under a velocity field and changes in physical quantities under Lagrangian coordinates. The advection currents are estimated by kinematic analysis, and the changes in physical quantities are estimated by Koopman operator analysis. The proposed method is applied to actual precipitation distribution data, and the results show that the development and decay of precipitation are properly captured relative to conventional methods and that stable predictions over long periods are possible.

An experimental and numerical study of turbulent heat transfer enhancement for graphene nanofluids produced by pulsed discharge

• Time and cost-effective production of graphene nanofluids by pulsed discharge is tried and tested. • A new two-step method for producing graphene nanofluids has been developed. • Graphene nanofluids generated by pulsed discharge and ultrasound, like other graphene nanofluids, have high turbulent heat transfer performance (35% higher than water). • The numerical results show considerable increase in turbulent kinetic energy (8%) and velocity gradients near the wall due to physical interaction between continuous phase(water) and dispersed phase (graphene nano-particles). • The exchange of momentum and energy due to the movement of particles is considered as a cause-and-effect relationship between the aggregation of particles and the change in physical quantities in the continuous phase. Developing production methods for graphene nanofluids that can produce them in large quantities at once in a short time and at a low cost will contribute to the development of a wide range of industries that use nanofluids, and understanding their properties through mathematical modeling and experiments will lead to the development of new nanofluids. In this study, the new production method of graphene nanofluids is proposed and experimental and numerical investigations of the turbulent heat transfer performance of graphene nanofluids in a horizontal circular tube subjected to constant heat flux are conducted. The experimental investigation is conducted to evaluate the turbulent heat transfer performance of graphene nanofluids which are made by a new method using pulsed discharge and to compare them with numerical results. In the numerical investigation, the finite volume method with a Realizable k-ε model and Two-layer model is employed to solve the continuity, momentum, and energy conservation in two-dimensional domains. The Lagrangian two-phase model is applied to consider the physical interaction between the dispersed phase and continuous phase. In this model, the particles are tracked in a Lagrangian manner and coupled with the Eulerian flow description. Since the computational burden would be tremendous if individual nanoparticles were tracked in a Lagrangian manner, we defined a cluster of particles, called a parcel and treated it statistically. This concept of parcels allowed the average behavior of nanoparticles to be established as an analytical parameter. As a result, graphene nanofluids are not produced by pulsed discharge alone but are successfully produced by applying ultrasonic. Experimental investigations show a 33% increase in the Nu number of graphene nanofluid produced by pulsed discharge compared to water as the flow velocity increased. Numerical investigations confirm changes in the properties (Turbulent kinetic energy, Velocity distribution, Temperature distribution) of the continuous phase due to physical interactions between the dispersed and continuous phases. It is also shown that these changes contribute to the improved turbulent heat transfer performance of the nanofluid and that the aggregation of particles into the center of the tube is responsible for these changes.

Novel Surface Acoustic Wave Temperature-Strain Sensor Based on LiNbO3 for Structural Health Monitoring.

In this paper, we present the design of an integrated temperature and strain dual-parameter sensor based on surface acoustic waves (SAWs). First, the COMSOL Multiphysics simulation software is used to determine separate frequencies for multiple sensors to avoid interference from their frequency offsets caused by external physical quantity changes. The sensor consists of two parts, a temperature-sensitive unit and strain-sensitive unit, with frequencies of 94.97 MHz and 90.05 MHz, respectively. We use standard photolithography and ion beam etching technology to fabricate the SAW temperature–strain dual-parameter sensor. The sensing performance is tested in the ranges 0–250 °C and 0–700 μԑ. The temperature sensor monitors the ambient temperature in real time, and the strain sensor detects both strain and temperature. By testing the response of the strain sensor at different temperatures, the strain and temperature are decoupled through the polynomial fitting of the intercept and slope. The relationship between the strain and the frequency of the strain-sensitive unit is linear, the linear correlation is 0.98842, and the sensitivity is 100 Hz/μԑ at room temperature in the range of 0–700 μԑ. The relationship between the temperature and the frequency of the temperature-sensitive unit is linear, the linearity of the fitting curve is 0.99716, and the sensitivity is 7.62 kHz/°C in the range of 25–250 °C. This sensor has potential for use in closed environments such as natural gas or oil pipelines.

The Stability Analysis of Coupled Differential Equations in Stellar Structure

Astrophysical and Mathematical Models usually describes the evolutionary processes of life cycle of stellar structure. The process of star formation undergoes various stages during its life cycle. In human time scale it is not possible to observe whole of the evolution of stellar structure. From the birth of star to the death of star, different complex cosmological phenomenon occurs in the galactic region. In general theory of astrophysics stars are assumed to be static and spherical in nature. This nature results from hydrostatic and thermostatic equilibrium. Self-gravitating forces makes the star to collapse gradually and intermittently. At the same time thermal nature of chemical composition inside the star develops the pressure and hinders the sudden collapse. As a result, there is change in physical quantities like temperature, density, mass, radius, luminosity opacity and many more structural behaviours of star. These quantities are taken as variable in differential equation which are evolved in due process of star evolution. During the evolution of star, hydrostatic equilibrium and thermal equilibrium remains the major areas of study, therefore emphasis is laid on the stability of stellar structure with main focus on the hydrostatic and thermal equilibrium.

EFFECT OF STRESS CAUSED BY INSUFFICIENT SLEEP ON HUMAN BIOEFFLUENTS AND PERCEIVED AIR QUALITY

To improve indoor air quality, it’s necessary to accurately control the body odor emitted by humans living under various environmental conditions and lifestyles. The purpose of this study was to obtain a better understanding of the effects of changes in physical quantities due to insufficient sleep on the emission of human bioeffluents causing body odor and the perceived air quality. The experiment involved two conditions of sleep time. Different biogenic substance concentrations and sensory evaluations of the odor in the chamber were obtained when the occupants' sleep times was different, even for the same CO2 concentration in the room.

Lorentz symmetries and primary constraints in covariant teleparallel gravity

In this article we explore local Lorentz transformations in theories of gravity based on the teleparallel formalism. For the teleparallel equivalent of general relativity (TEGR), the spin connection plays no role in the equations of motion, and therefore it is possible to simply put it equal to zero with no change in physical quantities, and then the theory is formulated purely in terms of the tetrad field which can be freely chosen in any way. In nonlinear modifications of TEGR, this is a more intricate issue, and vanishing spin connection is then the Weitzenb\"{o}ck gauge choice which imposes restrictions on the choice of tetrad. This has led to considering the so-called covariant formulation of $f(T)$ gravity. We examine the primary constraints arising when passing to the Hamiltonian framework, and compute their algebra. We show that the problems of local Lorentz symmetry breaking still appear in this formulation, even if in a different disguise.

CFD Simulation of Kaplan Turbine Rotating Union and the Development of a Real Time Diagnostic System

Obtaining energy from low-emission sources is extremely important currently. The use of hydropower plants for electrical energy production proves to be advantageous. The most commonly used type of water turbines are Kaplan machines due to the highest efficiency they offer in a wide range of operation. There is a need to increase the reliability of operating machines due to the failure of the oil heads performing the task of supplying hydraulic oil to the interior of the rotating turbine shaft to control the Kaplan turbine rotor blades. An in-depth analysis of physical phenomena such as friction, mechanical vibrations, and heat transfer has been carried out. The assumptions for the construction of the FDHC early diagnostics system have been created. Methods of measuring the parameters have been defined, which have consequently assisted in creating an algorithm for the testing method of a working machine in real time. The 3D CFD simulation method has been applied and physical phenomena have also been implemented in order to enable the reconstruction of the actual processes taking place inside the working element. This has enabled the observation of changes in physical quantities in any cross-section and point of the component tested. These activities have made it possible to determine the critical measurement points of physical quantities in the model that can be applied to a real object. In order to confirm the correctness of the assumptions made for the construction of the FDHC system, the 3D CFD simulation has been compared with the results obtained during measurements carried out on a working hydro unit. The results of the measurements carried out with the thermal imaging camera have partly coincided with the results obtained in the computational model.

Numerical simulation of nozzle flow based on Euler equation

In this paper, the Euler-based numerical simulation method is employed to investigate the flow characteristics inside the Laval nozzle. In detail, the central difference method is used to discretize the flow field of the nozzle. And two kinds of flow conditions are simulated numerically: the isentropic flow from subsonic to supersonic, and the isentropic flow at full subsonic speed. The results show that the velocity increases and then decreases slowly, reaching the peak point near the nozzle throat. The pressure decreases non-linearly, and the density increases at first and then drops, following by a sharp rise later. The shock wave oscillation also appears in the flow from subsonic to supersonic, and this is because the artificial viscous term is not enough in discrete solution. Then we analyze the law of change of physical quantity by changing the shape of the nozzle. The results demonstrate that the larger the nozzle’s curvature, the faster the change rate of a physical quantity is. And the velocity at the nozzle inlet approaches zero when the area at the inlet and outlet approaches infinity.

Readout Circuits for Capacitive Sensors.

The development of microelectromechanical system (MEMS) processes enables the integration of capacitive sensors into silicon integrated circuits. These sensors have been gaining considerable attention as a solution for mobile and internet of things (IoT) devices because of their low power consumption. In this study, we introduce the operating principle of representative capacitive sensors and discuss the major technical challenges, solutions, and future tasks for a capacitive readout system. The signal-to-noise ratio (SNR) is the most important performance parameter for a sensor system that measures changes in physical quantities; in addition, power consumption is another important factor because of the characteristics of mobile and IoT devices. Signal power degradation and noise, which degrade the SNR in the sensor readout system, are analyzed; circuit design approaches for degradation prevention are discussed. Further, we discuss the previous efforts and existing studies that focus on low power consumption. We present detailed circuit techniques and illustrate their effectiveness in suppressing signal power degradation and achieving lower noise levels via application to a design example of an actual MEMS microphone readout system.

Numerical analysis of suction and blowing effect on boundary layer slip flow of Casson fluid along with permeable exponentially stretching cylinder

The present study is about the numerical analysis of Casson fluid’s boundary layer slip flow beneath the impact of suction/blowing past a permeable cylinder stretching exponentially. The modeled partial differential equations are transformed to nonlinear ordinary differential equations by applying the appropriate nonlinear transformation. The Keller box procedure, a tool famous for its numerical achievements, is used. The impact of relevant physical parameters like suction, Casson fluid, and Reynolds number and slip parameters on temperature and velocity distribution is studied and shown through graphs. The change in physical quantities like the Nusselt number and the skin friction coefficient with respect to variation of the parameters mentioned earlier was also examined. Their values are given in the form of a table. To ensure authenticity of the numerical procedure, outcomes of the present investigations are compared with previous works, and strong agreement is noticed.

Optical method for determination of fatigue damage in organic glass

The features of nucleation, start, and propagation of a crack inside a transparent organic sample are investigated. The distribution of the refractive index and density around the crack was studied by changing of speckle images and ellipsometry method. It was found that the maximum value of the relative change in density is near the crack. This value before the crack start is greater than 0.003. It is proved that the speckle method we offer can be the basis for the creation of various techniques. Using these techniques will allow us to estimate the time before the crack start by the rate of change of physical quantities in small areas of the order of 50 μm and their limiting values. The results of experimental investigations are presented.

OPTIMASI PENGUKURAN LAJU AIR PADA SUSUNAN PERALATAN EKSPERIMEN DINAMIKA FLUIDA SEDERHANA

The research objective is to determine the results of optimization of water rate measurements in the arrangement of simple fluid dynamics experimental equipment. The study used an experimental method based on 5 theoretical equations. The research shows that the optimization of measurements can only be done on the study of changes in water surface position, differences in diameter pairs, differences in the diameter of the second pipe, and differences in pump conditions. The results of water rate measurements for references 0, 1, and 2, respectively, have a specific tendency for the study of changes in physical quantities and, or differences in the associated physical conditions. The mean coefficient of determination by the surface height to the reference rate of 0 is 58%, with respect to the reference rates 1 and 2, respectively 76% and 73%. By the difference in diameter with reference rate 2 based on equations (3) and (5), they are 94% and 74%, respectively.