Variation Of Physical Parameters Research Articles

Analysis of combustion and heat transfer performance in a slit-type fully premixed burner

Since most gas water heaters on the market still use diffusion or partially premixed combustion. Fully premixed combustion, with its advantages of complete combustion and low CO and NOx emissions, offers a promising alternative. In response to this, a slit-type fully premixed gas water heater with a rated power of 20kW was designed. The combustion and heat transfer performance, as well as the combustion temperature and burnout characteristics, were analyzed under ten different load conditions ranging from 100% to 8% using theoretical modeling. The study identified the variations in physical parameters and used numerical simulations to partially validate the theoretical results. Subsequently, by individually modifying structural variables, the optimal structure under single-variable conditions was determined. This optimal structure was then combined in various configurations to form a multi-variable structural design. Further theoretical analysis was conducted to assess whether the changes in the multi-variable structure, as well as the original design, met economic efficiency requirements. The results showed that the slit-type fully premixed burner achieved optimal performance when the number of burner plates was 120, with a length of 99 mm and a height of 10 mm.

Robust estimates of the ratio between S- and P-wave velocity anomalies in the Earth's mantle using normal modes

Seismic tomography allows us to image the interior of the Earth. In general, to determine the nature of seismic anomalies, constraints on more than one seismic parameter are required. For example, the ratio R between perturbations in vs and vp (dlnvs and dlnvp, respectively) is studied extensively in the lowermost mantle and interpreted in terms of thermal and/or chemical anomalies. However, to jointly interpret tomographic models of variations in vs and vp or their ratio R, it is essential for them to share the same local resolution. Most existing models do not provide resolution information, and thus cannot guarantee to honour this condition. In addition, uncertainties are typically not provided, making it difficult to robustly interpret the ratio R=dlnvs/dlnvp. To overcome these issues, we utilise the recently developed SOLA tomographic method, a variant of the linear Backus–Gilbert inversion scheme. SOLA retrieves local-average model estimates, together with information on their uncertainties, whilst it also provides direct control on model resolution through target kernels. In this contribution, we apply SOLA to normal-mode data with sensitivity to both vs and vp, as well as density throughout the mantle. Specifically, we aim to develop models of both vs and vp with the same local resolution. We test our methodology and approach using synthetic tests for various noise cases (random noise, data noise or also additional 3D Earth noise due to variations in other physical parameters than the one of interest). We find that the addition of the 3D noise increases the uncertainties in our model estimates significantly, only allowing us to find model estimates in six or four layers for vs and vp, respectively. While the synthetic tests indicate that no satisfactory density models can be obtained, we easily manage to construct models of dlnvs and dlnvp with almost identical resolution, from which the ratio R can be robustly inferred. The obtained values of R in our synthetic experiments significantly depend on the noise case considered and the method used to calculate it, with the addition of 3D noise always leading to an overestimate of R. When applying our approach to real data, we obtain values of R in the range of 2.5–4.0 in the lowest 600 km of the mantle, which are consistent with previous studies. Our model estimates with related resolving kernels and uncertainties can be used to test geodynamic model predictions to provide further insights into the temperature and composition of the mantle.

Design Simulation of Multilayer Structures for the Development of Biosensor Based on Transverse Matrix Method

Simulation of electromagnetic wave propagation on layered metal-dielectric structures using analytical methods is a study that continues to be developed because it involves strict mathematical equations with exact results. In this study, the transfer matrix method was developed to analyze the dielectric-metal-metal-dielectric structure through the reflection profile. The emergence of the Surface Plasmons Resonance (SPR) phenomenon causes a minimum reflectance whose changes are analyzed through variations in optical and physical parameters. The simulation shows that the minimum reflectance angle occurs at an angle , indicating the existence of the SPR phenomenon in the condition . The choice of metal materials, namely gold and silver, resulted in a shift in the reflectance curve, and an increase in the thickness of the adhesive layer caused a shift in the reflectance curve towards a smaller angle. Changes in the refractive index of the upper dielectric material are important for biosensor development, namely a shift in the reflectance curve with a linear response at the interval of refractive index .

Tool-straw-paddy soil coupling model of mechanical rotary-tillage process based on DEM-FEM

The working conditions involving rotary-tillage processes in the paddy fields are complex and dynamic, and certain parameters are difficult to measure in real-time. Owing to the lack of applicable analytical methods, the interactions among knife rollers, wheat straw, and paddy soil are not well understood, which prevents improvements to the rotary tillage quality in paddy fields. A dynamics model of the tool-straw-soil coupling system was established in this work using finite and discrete element methods to analyze the paddy rotary-tillage process. Soil bin test is crucial for verifying the reliability of simulation models and the accuracy of simulation results, the reliability and accuracy of the numerical model were verified based on a soil tank test. The results indicate that in terms of blade roller torque, mud disturbance, and straw embedment rate, for a single group of knife rollers throughout the three soil bin tests, the average torque was 11.99 N∙m, significantly lower than the 19.32 N∙m obtained from previous studies. The mud disturbance rate was 71.09%, and the wheat-straw burial rate was 85.64%, wheat-straw burial rate is slightly better than 83% obtained from previous studies. The errors between the simulations and the soil tank test regarding the knife roller torque, mud disturbance, and wheat-straw burial rate were 0.75%, 2.21%, and 4.83%, respectively. The proposed numerical simulation method reflected the variations in physical and mechanical parameters during the paddy field rotary-tillage. The proposed approach provides an effective method for visualizing and analyzing the rotary-tillage interactions and mechanisms in complex paddy field working systems.

Hydromorphodynamics modeling of dredging and dumping activities in Mirim lagoon, RS, Brazil

This study aims to employ a combination of numerical models to simulate bed evolution under various operational strategies within two navigation channels in Mirim Lagoon, Brazil. The model simulations accurately represent the water levels within the lagoon. These findings suggest that river discharge plays a pivotal role in shaping the temporal patterns of sediment transport within the system. The morphodynamic model reveals that sediment transport and bed evolution primarily occur in a southwest-to-northeast direction, following the flow of water. The greatest sediment accumulation is observed in the central and southern regions of the lagoon. Our results confirm that channel dredging induces significant variations in lagoon physical parameters, such as current velocity. The bed evolution results indicate that rapid siltation of the channel follows dredging, suggesting a substantial increase in bottom evolution within the navigation channels compared to the unaltered scenario. Our findings highlight that the utilization of hydromorphodynamic modeling, with a particular emphasis on dredge-and-dump strategies, can serve as a precise methodology to enhance natural mechanisms that positively influence channel depth and stability. This approach also enables us to predict unfavorable changes in physical parameters over both the medium and long term.

First-principles analysis of the structural, thermodynamic, elastic and thermoelectric properties of LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler alloys

We used the pseudopotential plane wave approach, as implemented in the Quantum Espresso program, to investigate the impact of X atoms (V, Nb, and Ta) on the physical properties of LuXCo2Sb2 double half Heusler alloys. We determined the equilibrium structural parameters, including the crystal lattice parameters, atomic position coordinates, and bulk modulus, with and without including the spin-orbit effects. The predicted single-crystal elastic constants (Cij) show that the title compounds are mechanically stable with a pronounced elastic anisotropy. The bulk modulus, shear modulus, Young's modulus, Poisson coefficient, Debye temperature, and Vickers hardness coefficient were deduced from Cij via the Voigt-Reuss-Hill approximations. We also determined the variations of some macroscopic physical parameters as functions of temperature and pressure, namely the thermal expansion coefficient, lattice thermal conductivity, heat capacity at constant volume, Debye temperature and entropy. The considered alloys demonstrate special thermal properties under pressure and heat conditions, specifically, their low thermal expansion coefficient and lattice thermal conductivity; their thermal expansion coefficient is lower than 4.5 × 10−5 K−1 at 1000 K, and lattice thermal conductivity don’t exceed 1 W.m−1 K−1 for temperatures higher than 300 K. Furthermore, we investigated the temperature and charge carrier concentration dependencies of some thermoelectric coefficients. The results of this study reveal the potential of the considered compounds for achieving a figure of merit greater than 0.5 at a temperature of 500 K and a doping concentration of 1020 cm−3.

Thermal analysis for hydromagnetic flow of Darcy-Forchheimer hybrid nanofluid with velocity and temperature slip effects: Scrutinization of stability and dual solutions

This article explores heat transfer characteristics of magnetohydrodynamics water-base silver (Ag) and iron oxide (Fe3O4) hybrid nanomaterials flow in a Darcy-Forchheimer porous medium induced by a stretching/shrinking surface with impacts of heat sink/source. Moreover, thermal radiation effects and the slip boundary conditions are also incorporated in the given problem. Governing partial differential equations (PDEs) are first altered into the ordinary differential equations (ODEs) using suitable similarity transformations. These achieved ODEs are solved by the well-known shooting technique in Maple software to get the required numerical solutions for the variation in different physical parameters. Here, the numerical findings show duality in solutions in case of stretching/shrinking parameter over different ranges of the comprised distinguished parameters. In this regard, the stability analysis is done and the first solution is found stable and physically acceptable, while the second one unstable and physically infeasible. Besides, the skin friction increases for the case of shrinking but it decreases for case of stretching parameter due to the greater impacts of the mass transfer parameter while the heat transfer phenomenon upsurges for the case of shrinking parameter. Moreover, the skin friction, and the heat transfer rise with variation of the suction parameters when the quantity of solid nanoparticles volume fraction is increased.

Comparative Characterization of Water Source Flowing in Ultapani Drain and Water Samples of other nearby Sources

Water quality is a critical aspect of environmental health, impacting both human and ecological well-being. This study aims to compare and characterize the water source flowing in Ultapani drain with water samples collected from other nearby sources. The objective is to assess the variations in physical and chemical parameters, providing insights into the overall water quality in the study area.

Field assessment of the potential for small scale co-cultivation of seaweed and shellfish to regulate nutrients and plankton dynamics

The co-cultivation of seaweed alongside shellfish has the potential to regulate local dissolved nutrient concentrations and consequently affect plankton dynamics. Evidence for this has until now come largely from computational modelling and laboratory studies, rather than field studies. Here we report on weekly/bi-weekly profiling of inorganic nutrient concentrations (nitrate, nitrite, ammonium, phosphate, and silicate) over two years (2019–2020) at three sampling stations across a small-scale (16 ha) kelp and mussel farm in Porthallow Bay, Cornwall, UK. Nutrient concentrations were measured in conjunction with a range of related environmental variables, including water temperature, salinity, clarity, and phyto- and zoo- plankton abundance, biomass and community composition. These environmental data were also supplemented with river discharge data. Our results indicate typical seasonal variations in chemical (nutrient), physical (hydrographic), and biological (plankton) parameters across all three sampling stations and no significant reductions in inorganic nutrient concentrations in the water column downstream from the integrated kelp and shellfish farm. We conclude that the effectiveness of nutrient regulation by integrating seaweed and shellfish aquaculture will depend on local climatic and hydro-geochemical conditions (affecting background nutrient inputs), as well as the design and scale of integrated multi–trophic aquaculture (IMTA) systems.

Electronic Localized States Behaviour in a GaAs/GaAlAs Multi-Quantum Wells with a Geo-Material and a Material Defects

This paper represents a theoretical study of the transmission and the electronic band structure for a GaAs/GaAlAs Multi-quantum wells, containing two defect layers: a geo-material and a material defect layer. The variation of the different physical parameters ( i.e the transmission rate and the energy of the eigen states) as a function of the defect layers nature, is carefully investigated using the Green’s function method. Due to the presence of the defect layers, localized electronic states appeared and their properties have been studied. Our results show that both the position and the thickness of the defect layers can play an important role in the creation of well-defined localized electronic states inside the band gaps, in order to favor the transfer of electrons, without using a higher energy. Furthermore, we were able to identify the origin of each of the states appearing inside the band gaps, whether they are induced by the geo-material or by the material defect.

Study of low-cost, flexible graphite-based sensor for human finger movement

Paper-based sensor devices have grown prominently in recent decades owing to their flexibility, light weight, biodegradability, and low cost. Pencil traces on the paper are the protuberant component to sense the physical parameter variation, and the geometry on the paper substrate plays a vital role in sensing applications. This study used the commercially available pencil as an electrode on a paper substrate that senses the mechanical strain on human finger movements. Two different geometries of the paper substrate were considered, and the optimized geometry was identified. Two different grades (HB and 8B) pencils were used as the drawing instrument to draw the graphite on the paper. The repeated experimental results show a better version of the proposed sensor for measuring human finger movements. The grade HB pencil provides excellent results compared to the other grade pencils.

Seasonal and depth variation of soil physical parameters irrigated with treated wastewater in the case of light textured soil

In places with scarce water supplies, treated wastewater (TWW) can be used for irrigation. This is the case in many places on the Mediterranean coast. In order to examine changes in soil physical proprieties irrigated with secondary-treated wastewater for >38 years, a study was conducted under real agricultural conditions and three different sampling seasons (Summer, autumn and winter). Five soil depth distribution (0-20, 20-40, 40-60, 60-80 and 80-100 cm was also investigated. The soil parameters studied were: salinity (EC), permeablity (K) and structural stability (IS). The results demonstrate that K and IS depended significantly on the season and varied throught the soil profile. However, only the depth had an impact on the EC. The maximum EC and K were observed in summer at 0-60 and 0-20 cm, respectively. The highest IS, although, was detected during the winter at 40–60 cm depth layer. More interstingly, to take into consideration the interactions of both factors, a positive correlations were shown between K and EC, and IS (r =0.56***, r = 0.62***, respectively) and between EC and IS (r = 0.44**) in summer. In contrast, only K and EC showed a negative correlation (r = -0.35*) in the autumn, but no correlation was detected between all parameters in winter. The results indicate that treated wastewater is a suitable alternative during hot seasons, especially in sandy soils. Further research is required to investigate the effect of this wastwater on crops responses.

Modal analysis of concrete filled steel tubular structure under lateral impact loading

In this paper, deformation mode and the large deflection of the concrete filled steel tubular (CFST) structural member with fixed ends under lateral impact loading was studied by rigid-plastic modal approximation method and finite element analysis by ABAQUS. Using the yield criterion and beam-on-foundation model, the modal analytical solution for plastic behavior of CFST member under lateral impact is obtained considering the interaction of bending and axial stretching. The rigid-plastic modal solution captures the FE results and the deformation mode is accordance with the available experimental results. It shows that lateral deformation of CFST member can be effective predicted by the modal solution consisting of geometric and physical parameters variations. The influence of steel tube thickness, cross-section diameter, effective length, strength and density of concrete and steel, and initial impulsive are discussed in detail. The results show that deflection of the CFST member increase with the increase of the length to diameter ratio, initial impulse and smaller thickness to diameter ratio. Finally, the relationship between lateral deformation and geometric variations are established by optimal sets of modal solution.

A mathematical model for cilia actuated transport of Gold–Silver hybrid nanofluid EMHD flow with activation energy phenomena

The advancement of nanobiotechnology is happening with leap and bound and the maneuvering in application of nanofluids in medical field is emerged as major research topic in recent times. Motivated by key applications in this direction, the current investigation embarks to explore the hybrid nanofluid dynamics in a ciliated inclined microchannel with various physical impacts, electromagnetohydrodynamic (EMHD), gyrotactic microorganisms, activation energy, and solar radiation. The pertinent equations of motion are tackled with low Reynolds number, long wavelength, and Debye–Huckel linearization approximations. The resulting equations of motion after simplifications tackled with the implementation numerical computations in Mathematica. The variations of pivotal physical parameters on the flow dynamics and thermal axiom are exhibited with graphical illustrations. It is worth mention here that the Hartmann, Grashof, electroosmotic, buoyancy, bioconvection parameters surged the hybrid nanofluid velocity adjacent to right wall. The temperature goes down with the thermal radiation and thermophoresis parameters. The radiation, Brownian motion, thermophoresis parameters reinforce the nanoparticle volume fraction, and motile microorganisms. The reported investigation has great significance for physiological fluid transport in the gastrointestinal tract, managing the bleeding by manipulating the magnetic field and in drug infusion mechanism.

Modeling and numerical handling of viscous dissipation in second order viscoelastic fluid flow in a nonparallel channel

This work gives an insight into the viscous effects of a viscoelastic fluid on the flow and heat transfer when it is put to flow between two nonparallel plates via some source/sink. Modeling of the problem is presented in detail with focus on the viscous dissipation effect. Afterwards, the problem is solved numerically by Keller Box method and bvp4c routine using MATLAB. The comparative analysis of the two techniques has been drawn on the basis of numerical values of Nusselt number. Alongside this, a comprehensive detail of the impact of pertinent parameters on the flow and temperature profiles have been given. The numerical results give an insight about the fluid characteristics like velocity, temperature, heat transfer and skin friction with variations in pertinent physical parameters.

The Effects of a 1-Year Recreational Kung Fu Protocol on Bone Health Parameters in a Group of Healthy Inactive Young Men

The main aim of the current study was to explore the effects of a 1-year recreational Kung Fu protocol on bone health parameters (bone mineral content (BMC), bone mineral density (BMD), femoral neck geometry and composite indices of femoral neck strength) in a group of healthy inactive young men. 54 young inactive men voluntarily participated in this study, but only 51 of them completed it. The participants were assigned to 2 different groups: control group (n=31) and Kung Fu group (n=20). The Kung Fu group performed two sessions of recreational Kung Fu per week; the duration of each session was 45 minutes. The current study has demonstrated that whole body (WB) BMC, ultra-distal (UD) radius BMD, 1/3 radius BMD, total radius BMD, total forearm BMD, maximal strength, maximum oxygen consumption and jumping performance increased in the Kung Fu group but not in the control group. The percentages of variations in WB BMC, forearm BMD and physical performance parameters were significantly different between the two groups. In conclusion, this study suggests that recreational Kung Fu is an effective method to improve WB BMC, forearm BMD and physical performance parameters in young inactive men.

The slippery slope of dust attenuation curves

Aims. We investigate the dust attenuation of 122 heavily dust-obscured galaxies detected with the Atacama Large Millimeter Array (ALMA) and Herschel in the COSMOS field. We search for correlations between dust attenuation recipes and the variation of physical parameters, namely, the effective radii of galaxies, their star formation rates, and stellar masses. We aim to understand which of the commonly used laws best describes dust attenuation in dusty star-forming galaxies (DSFGs) at high redshift. Methods. We made use of the extensive photometric coverage of the COSMOS data combined with highly resolved dust continuum maps from ALMA. We used CIGALE to estimate various physical properties of these dusty objects, namely: their star formation rates (SFR), their stellar masses, and their attenuation at short wavelengths. We inferred the effective radii (Re) of galaxies using GALFIT in the Y band of HSC and ALMA continuum maps. We used these radii to investigate the relative compactness of the dust continuum and the extension of the rest-frame UV/optical Re(y)/Re(ALMA). Results. We find that the physical parameters calculated from our models strongly depend on the assumption of the dust attenuation curve. As expected, the most impacted parameter is the stellar mass, which leads to a change in the “starburstiness” of the objects. We find that taking into account the relative compactness of star-to-dust emission prior to SED fitting is crucial, especially when studying dust attenuation of dusty star-forming galaxies. Shallower attenuation curves do not show a clear preference of compactness with attenuation, while the Calzetti attenuation curve is shown to prefer a comparable spatial extent of unattenuated stellar light and dust emission. The evolution of the Re(UV)/Re(ALMA) ratio with redshift peaks around the cosmic noon in our sample of DSFGs, showing that this compactness is correlated with the cosmic SFR density of these dusty sources.

A Novel Fast Fixed-Time Backstepping Control of DC Microgrids Feeding Constant Power Loads

Nonlinear behavior of constant power loads (CPLs) and their negative incremental impedance, which impose adverse effects on system damping and stability margins, necessitate developing proper strategies for efficient implementation framework of DC microgrid. In this paper, a fixed-time sliding mode disturbance observer (SMDO) is first addressed to provide an estimation of the instantaneous power flow moving along the uncertain CPLs with time-varying nature within a fixed time. It not only expedites the estimation rate but also improves the robustness against physical parameter variation. The fast fixed-time backstepping technique is then developed based on the estimated load power to control the duty cycle of the boost converter such that the entire power grid becomes stable and the desired voltage of the DC bus is tracked within a fixed time irrespective of the initial conditions. A rigorous Lyapunov-based approach is represented to guarantee the fixed-time stability of the proposed scheme. Finally, to validate the merits and implementation feasibility of the proposed methodology, the experimental realization is represented under various operating case studies.

Time Expansion in Distributed Optical Fiber Sensing

Distributed optical fiber sensing (DOFS) technology has recently experienced an impressive growth in various fields including security, structural monitoring and seismology, among others. This expansion has been accompanied by a speedy development of the technology in the last couple of decades, reaching remarkable performance in terms of sensitivity, range, number of independent sensing points and affordable cost per monitored point as compared with competing technologies such as electrical or point optical sensors. Phase-sensitive Optical Time-Domain Reflectometry (ϕOTDR) is a particularly interesting DOFS technique, since it enables real-time monitoring of dynamic variations of physical parameters over a large number of sensing points. Compared to their frequency-domain counterparts (OFDR), ϕOTDR sensors typically provide higher dynamics and longer ranges but significantly worse spatial resolutions. Very recently, a novel ϕOTDR approach has been introduced, which covers an existing gap between the long range and fast response of ϕOTDR and the high spatial resolution of OFDR. This technique, termed time-expanded (TE) ϕOTDR, exploits an interferometric scheme that employs two mutually coherent optical frequency combs. In TE-ϕOTDR, a probe comb is launched into the fiber under test. The beating of the backscattered light and a suitable LO comb produces a multi-heterodyne detection process that compresses the spectrum of the probe comb, in turn expanding the detected optical traces in the time-domain. This approach has allowed sensing using ϕOTDR technology with very high resolution (in the cm scale), while requiring outstandingly low detection and acquisition bandwidths (sub-MHz). In this work, we review the fundamentals of TE-ϕOTDR technology and describe the recent developments, focusing on the attainable sensing performance, the existing trade-offs and open working lines of this novel sensing approach.

Photothermal effects of semiconducting medium with non-local theory

A generalized magnetothermoelastic half-space problem is considered for a homogeneous, isotropic and semiconducting medium under the non-local heat equation with dual-phase-lag model. The boundary surface of the medium is subjected to a prescribed time-dependent and exponential order compression along with a prescribed temperature and carrier intensity gradient. Two integral transformations, Laplace transform for time variable and Fourier transform for space variable, are employed to the equations of motion and the heat conduction equation for formulation of a vector-matrix differential equation which is then solved by using eigenvalue approach. Inversion processes for the two integral transforms are carried out numerically. Finally, the effects of physical field variables and stress components are analyzed and illustrated graphically under the variation of different physical parameters.