Hasil untuk "Thermodynamics"

L. Martyushev, V. Seleznev

Yun-Ho Kim, In Hyoun Kim

This study derives the uniqueness of positive solutions to Brézis–Oswald-type problems involving the fractional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>(</mo><mi>r</mi><mo>,</mo><mi>q</mi><mo>)</mo></mrow></semantics></math></inline-formula>-Laplacian operator and discontinuous Kirchhoff-type coefficients. The Brézis–Oswald-type result and Ricceri’s abstract global minimum principle are critical tools in identifying this uniqueness. We consider an eigenvalue problem associated with fractional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>(</mo><mi>r</mi><mo>,</mo><mi>q</mi><mo>)</mo></mrow></semantics></math></inline-formula>-Laplacian problems to confirm the existence of a positive solution for our problem without the Kirchhoff coefficient. Moreover, we establish the uniqueness result of the Brézis–Oswald type by exploiting a generalization of the discrete Picone inequality.

Sunday C. Iweka, Jeremiah L. Chukwuneke, Emmanuel Chuka Chinwuko

ABSTRACT A unique green catalyst was derived from novel powdered Uzere tallow seeds shell calcined at 700°C for 1 h in a muffle furnace. The catalytic activity of the Uzere acidified catalyst was due to a high proportion of sulphur trioxide, calcium oxide, and potassium oxide. The Ozoro Thevetia peruviana seed oil was produced via a Soxhlet instrument using acetone as solvent. The transesterification process was optimized with rotatable central composite design and RStudio, and both tools yielded the same maximum biodiesel output of 97.12 wt.%., at time 70 min, acidified‐catalyst 3.5 wt.%, methanol: oil 7:1, and temperature at 65°C. Although both tools generated a similar R2 of 0.9989, RStudio generated a better p‐value of < 2.2e−16 as against central composite design < 0.001. In addition, RStudio generated more statistical values like kurtosis (2.46) and skewness (−0.112) which were within acceptable bounds. Furthermore, RStudio charts provided a better visual clue and demonstrated superior performance. An activation energy of 79.1 kJmol−1 with an R2 of 97.75% was computed from kinetic approach while the thermodynamics approach produced an entropy of −0.0579 kJmol−1, enthalpy of 76.297 kJmol−1, and Gibbs free energy of 95.75, 95.87, 95.98 kJmol−1, at 336, 338, and 340 K, respectively. The results were within accepted bounds. Additionally, the physiochemical and fuel qualities of the produced biodiesel agree with the recommended range. Thus, this produced eco‐friendly biodiesel can be used to power diesel engines without any issues for the betterment of the world at large.

Mohamed Essoufy, Imane El Ouahabi, Saida Benkaddour et al.

This study focuses on the potential of treated avocado seed to remove azoic organic dyes (basic yellow 28 and tartrazine). The treated avocado seed was characterized, and batch adsorption studies were carried out to evaluate the effects of several removal dye parameters (contact time, ionic strength, initial concentration, adsorbent dose, and temperature). The adsorption kinetics of the dyes examined showed that the adsorption mechanism on the two selected catalysts followed pseudo-second-order kinetics (R2 > 0.999). The adsorption process of each dye was reported to fit using five non-linear regressions. Freundlich and Temkin adsorption isotherms described well the adsorption of basic yellow 28, and Freundlich adsorption isotherms described well the adsorption of tartrazine on the Treated Avocado Seed. The results suggested that the maximum amount adsorbed was 49.30 mg/g for basic yellow 28 and 38.43 mg/g for tartrazine and a high removal rate of 89.93% for BY 28 and 93.22% for tartrazine and that a chemical, spontaneous and endothermic process of adsorption occurred. Boyd’s expression demonstrated a mechanism of film diffusion for adsorption. Based on the findings, we suggest the application of activated avocado seeds for the removal of azoic dyes in aqueous solutions.

Mehmet Gümüş, Fatih Hezenci, Hüseyin Budak

This paper aims to examine an approach that studies many Euler–Maclaurin-type inequalities for various function classes applying Riemann–Liouville fractional integrals. Afterwards, our results are provided by using special cases of obtained theorems and examples. Moreover, several Euler–Maclaurin-type inequalities are presented for bounded functions by fractional integrals. Some fractional Euler–Maclaurin-type inequalities are established for Lipschitzian functions. Finally, several Euler–Maclaurin-type inequalities are constructed by fractional integrals of bounded variation.

Shuai Song, Longhang Xing, Xiaona Song et al.

This paper focuses on the fuzzy adaptive predefined-time control for fractional-order nonlinear systems with time-varying deferred constraints. First, a modified dynamic surface control technique is introduced to address the problem of computational complexity exposed in the backstepping framework, and the interval type-2 fuzzy logic systems are applied to model the unknown nonlinearities of the systems. Next, a shifting function and the barrier Lyapunov function with variational barrier bounds are formulated to deal with the constraints issue. Particularly, the constraint conditions can be satisfied within a predetermined time, even if they are transgressed initially. Furthermore, a switching threshold event-triggered controller is devised to balance the control energy and communication resources. With the help of the predefined-time stability criterion, it is proven that the presented predefined-time event-triggered controller can ensure that all the signals involved in the closed-loop system are bounded and the tracking error fluctuates to a small neighborhood of the origin in a predefined-time interval. Finally, two simulation examples are provided to confirm the effectiveness of the put-forward control algorithm.

José Figueroa, Gaston Giribet, Anibal Neira-Gallegos et al.

Abstract We study solutions of Einstein equations with negative cosmological constant in five dimensions that describe black holes whose event horizons are homogeneous, anisotropic spaces. We focus on the case where the constant-time slices of the horizon are the Nil geometry, the Thurston geometry associated to the Heisenberg group. For such spaces, we analyze the symmetries both in the asymptotic region and in the near horizon region. We compute the associated conserved charges, which turn out to be finite and admit a sensible physical interpretation. We analyze the thermodynamics of the Nil black hole, and we present a stationary spinning generalization of it in the slowly rotating approximation.

Robert E. Danczak, Robert E. Danczak, Vanessa A. Garayburu-Caruso et al.

A large amount of dissolved organic matter (DOM) is transported to the ocean from terrestrial inputs each year (~0.95 Pg C per year) and undergoes a series of abiotic and biotic reactions, causing a significant release of CO2. Combined, these reactions result in variable DOM characteristics (e.g., nominal oxidation state of carbon, double-bond equivalents, chemodiversity) which have demonstrated impacts on biogeochemistry and ecosystem function. Despite this importance, however, comparatively few studies focus on the drivers for DOM chemodiversity along a riverine continuum. Here, we characterized DOM within samples collected from a stream network in the Yakima River Basin using ultrahigh-resolution mass spectrometry (i.e., FTICR-MS). To link DOM chemistry to potential function, we identified putative biochemical transformations within each sample. We also used various molecular characteristics (e.g., thermodynamic favorability, degradability) to calculate a series of functional diversity metrics. We observed that the diversity of biochemical transformations increased with increasing upstream catchment area and landcover. This increase was also connected to expanding functional diversity of the molecular formula. This pattern suggests that as molecular formulas become more diverse in thermodynamics or degradability, there is increased opportunity for biochemical transformations, potentially creating a self-reinforcing cycle where transformations in turn increase diversity and diversity increase transformations. We also observed that these patterns are, in part, connected to landcover whereby the occurrence of many landcover types (e.g., agriculture, urban, forest, shrub) could expand DOM functional diversity. For example, we observed that a novel functional diversity metric measuring similarity to common freshwater molecular formulas (i.e., carboxyl-rich alicyclic molecules) was significantly related to urban coverage. These results show that DOM diversity does not decrease along stream networks, as predicted by a common conceptual model known as the River Continuum Concept, but rather are influenced by the thermodynamic and degradation potential of molecular formula within the DOM, as well as landcover patterns.

Alexandra Grekova, Svetlana Strelova, Anton Lysikov et al.

Adsorption energy storage is a promising resource-saving technology that allows the rational use of alternative heat sources. One of the most important parts of the adsorption heat accumulator is the adsorber heat exchanger. The parameters of heat transfer in this unit determine how fast heat from an alternative energy source, such as the Sun, will be stored. For the design of adsorption heat accumulators, plate fin heat exchangers are mainly used. In this paper, the procedure for the estimation of the global heat transfer coefficient for the adsorber heat exchanger depending on its geometry is considered. The heat transfer coefficient for a LiCl/SiO₂ sorbent flat layer under conditions of heat storage stage was measured. Based on these data, the global heat transfer coefficients for a number of industrial heat exchangers were theoretically estimated and experimentally measured for the adsorption cycle of daily heat storage. It was shown that theoretically obtained values are in good agreement with the values of the global heat transfer coefficients measured experimentally. Thus, the considered technique makes it possible to determine the most promising geometry of the plate fin heat exchanger for a given adsorption heat storage cycle without complicated experiments.

Emad Awad, Sharifah E. Alhazmi, Mohamed A. Abdou et al.

The Jeffreys-type heat conduction equation with flux precedence describes the temperature of diffusive hot electrons during the electron–phonon interaction process in metals. In this paper, the deformation resulting from ultrafast surface heating on a “nanoscale” plate is considered. The focus is on the anomalous heat transfer mechanisms that result from anomalous diffusion of hot electrons and are characterized by retarded thermal conduction, accelerated thermal conduction, or transition from super-thermal conductivity in the short-time response to sub-thermal conductivity in the long-time response and described by the fractional Jeffreys equation with three fractional parameters. The recent double-strip problem, Awad et al., <i>Eur. Phy. J. Plus</i> 2022, allowing the overlap between two propagating thermal waves, is generalized from the semi-infinite heat conductor case to thermoelastic case in the finite domain. The elastic response in the material is not simultaneous (i.e., not Hookean), rather it is assumed to be of the Kelvin–Voigt type, i.e., <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>σ</mi><mo>=</mo><mi>E</mi><mfenced separators="|"><mrow><mi>ε</mi><mo>+</mo><msub><mrow><mi>τ</mi></mrow><mrow><mi>ε</mi></mrow></msub><mover accent="true"><mrow><mi>ε</mi></mrow><mo>˙</mo></mover></mrow></mfenced></mrow></semantics></math></inline-formula>, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>σ</mi></mrow></semantics></math></inline-formula> refers to the stress, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ε</mi></mrow></semantics></math></inline-formula> is the strain, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>E</mi></mrow></semantics></math></inline-formula> is the Young modulus, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mi>ε</mi></mrow></msub></mrow></semantics></math></inline-formula> refers to the strain relaxation time. The delayed strain response of the Kelvin–Voigt model eliminates the discontinuity of stresses, a <i>hallmark</i> of the Hookean solid. The immobilization of thermal conduction described by the ordinary Jeffreys equation of heat conduction is salient in metals when the heat flux precedence is considered. The absence of the finite speed thermal waves in the Kelvin–Voigt model results in a smooth stress surface during the heating process. The temperature contours and the displacement vector chart show that the anomalous heat transfer characterized by retardation or crossover from super- to sub-thermal conduction may disrupt the ultrafast laser heating of metals.

Xiaoxia Ma, Malik Zaka Ullah, Stanford Shateyi

This work is concerned with the computational solution of the time-dependent 3D parabolic Heston–Cox–Ingersoll–Ross (HCIR) PDE, which is of practical importance in mathematical finance. The HCIR dynamic states that the model follows randomness for the underlying asset, the volatility and the rate of interest. Since the PDE formulation has degeneracy and non-smoothness at some area of its domain, we design a new numerical solver via semi-discretization and the radial basis function–finite difference (RBF-FD) scheme. Our scheme is built on graded meshes so as to employ the lowest possible number of discretized nodes. The stability of our solver is proven analytically. Computational testing is conducted to uphold the analytical findings in practice.

Kiran Siddappaji, Mark Turner

Propellers for electric aviation are used in solo- and multirotor applications. Multifidelity analysis with reduced cycle time is crucial to explore several designs for energy minimization and range maximization. A low-fidelity design tool, py_BEM, is developed for design and analysis of a reverse-engineered solo 2-bladed propeller using blade-element momentum theory with physics enhancements including local Reynolds number effect, boundary-layer rotation, airfoil polar at large AoAs and stall delay. Spanwise properties from py_BEM are converted into 3D blade geometry using T-Blade3. S809 and NACA airfoil polar are utilized, obtained by XFOIL. Lift, drag, performance losses, wake analysis, comparison of 3D steady CFD with low fidelity tool, kinetic energy dissipation, entropy and exergy through irreversibility are analyzed. Spanwise thrust and torque comparison between low and high fidelity reveals the effect of blade rotation on the polar. Vorticity dynamics and boundary-vorticity flux methods describe the onset of flow separation and entropy rise. Various components of drag and loss are accounted. The entropy rise in the boundary layer and downstream propagation and mixing out with freestream are demonstrated qualitatively. Irreversibility is accounted downstream of the rotor using the second-law approach to understand the quality of available energy. The performance metrics are within 5% error for both fidelities.

Lucas A. Pressley, Dave Edey, Romy Hanna et al.

Abstract The presence of inclusions, twinning, and low-angle grain boundaries, demanded to exist by the third law of thermodynamics, drive the behavior of quantum materials. Identification and quantification of these structural complexities often requires destructive techniques. X-ray micro-computed tomography (µCT) uses high-energy X-rays to non-destructively generate 3D representations of a material with micron/nanometer precision, taking advantage of various contrast mechanisms to enable the quantification of the types and number of inhomogeneities. We present case studies of µCT informing materials design of electronic and quantum materials, and the benefits to characterizing inclusions, twinning, and low-angle grain boundaries as well as optimizing crystal growth processes. We discuss recent improvements in µCT instrumentation that enable elemental analysis and orientation to be obtained on crystalline samples. The benefits of µCT as a non-destructive tool to analyze bulk samples should encourage the community to adapt this technology into everyday use for quantum materials discovery.

Mohammad Faisal Khan, Anjali Goswami, Shahid Khan

In our present investigation, we extend the idea of <i>q</i>-symmetric derivative operators to multivalent functions and then define a new subclass of multivalent <i>q</i>-starlike functions. For this newly defined function class, we discuss some useful properties of multivalent functions, such as the Hankel determinant, symmetric Toeplitz matrices, the Fekete–Szego problem, and upper bounds of the functional <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mfenced separators="" open="|" close="|"><msub><mi>a</mi><mrow><mi>p</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>−</mo><mi>μ</mi><msubsup><mi>a</mi><mrow><mi>p</mi><mo>+</mo><mn>1</mn></mrow><mn>2</mn></msubsup></mfenced></semantics></math></inline-formula> and investigate some new lemmas for our main results. In addition, we consider the <i>q</i>-Bernardi integral operator along with <i>q</i>-symmetric calculus and discuss some applications of our main results.

Chang-Na Lu, Cun-Juan Hou, Ning Zhang

In this paper, a (4+1)-dimensional nonlinear integrable Fokas equation is studied. It is rarely studied because the order of the highest-order derivative term of this equation is higher than the common generalized (4+1)-dimensional Fokas equation. Firstly, the (4+1)-dimensional time-fractional Fokas equation with the Riemann–Liouville fractional derivative is derived by the semi-inverse method and variational method. Further, the symmetry of the time-fractional equation is obtained by the fractional Lie symmetry analysis method. Based on the symmetry, the conservation laws of the time fractional equation are constructed by the new conservation theorem. Then, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mfenced separators="" open="(" close=")"><mfrac><msup><mi>G</mi><mo>′</mo></msup><mi>G</mi></mfrac></mfenced></semantics></math></inline-formula>-expansion method is used here to solve the equation and obtain the exact traveling wave solutions. Finally, the spectral method in the spatial direction and the Gr<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mover accent="true"><mi>u</mi><mo>¨</mo></mover></semantics></math></inline-formula>nwald–Letnikov method in the time direction are considered to obtain the numerical solutions of the time-fractional equation. The numerical solutions are compared with the exact solutions, and the error results confirm the effectiveness of the proposed numerical method.

Peter Styring, George R. M. Dowson, Isabel O. Tozer

In this review we consider the important future of the synthetic fuel, dimethyl ether (DME). We compare DME to two alternatives [oxymethylene ether (OMEx) and synthetic diesel through Fischer-Tropsch (FT) reactions]. Finally, we explore a range of methodologies and processes for the synthesis of DME.DME is an alternative diesel fuel for use in compression ignition (CI) engines and may be produced from a range of waste feedstocks, thereby avoiding new fossil carbon from entering the supply chain. DME is characterised by low CO2, low NOx and low particulate matter (PM) emissions. Its high cetane number means it can be used in CI engines with minimal modifications. The key to creating a circular fuels economy is integrating multiple waste streams into an economically and environmentally sustainable supply chain. Therefore, we also consider the availability and nature of low-carbon fuels and hydrogen production. Reliable carbon dioxide sources are also essential if CO2 utilisation processes are to become commercially viable. The location of DME plants will depend on the local ecosystems and ideally should be co-located on or near waste emitters and low-carbon energy sources. Alternative liquid fuels are considered interesting in the medium term, while renewable electricity and hydrogen are considered as reliable long-term solutions for the future transport sector. DME may be considered as a circular hydrogen carrier which will also be able to store energy for use at times of low renewable power generation.The chemistry of the individual steps within the supply chain is generally well known and usually relies on the use of cheap and Earth-abundant metal catalysts. The thermodynamics of these processes are also well-characterised. So overcoming the challenge now relies on the expertise of chemical engineers to put the fundamentals into commercial practice. It is important that a whole systems approach is adopted as interventions can have detrimental unintended consequences unless close monitoring is applied. This review shows that while DME production has been achieved and shows great promise, there is considerable effort needed if we are to reach true net zero emissions in the transport sector, particularly long-haul road use, in the require timescales.

M. Ijaz Khan, Seifedine Kadry, Yu-Ming Chu et al.

In this present communication, we proposed the mathematical model for non-Newtonian liquid (Ree-Eyring model) towards a stretched surface. The Buongiorno model is used in the modelling of flow problem subject to magnetohydrodynamics, entropy generation, nonlinear thermal radiation, homogeneous-heterogeneous reactions, Brownian motion, Joule heating and thermophoresis diffusion. Convective boundary conditions are implemented at the stretched surface. With the assistance of rheological expression of Ree-Eyring model, we construct the governing flow expressions. The energy equation is developed via Brownian diffusion, nonlinear thermal radiation, Joule heating and thermophoresis. Two different types of species (homogeneous-heterogeneous reactions) are considered for the analysis of mass transport. The flow is solely induced due to a nonlinear stretched surface. The electrical conducting and chemically reactive fluid is considered for the analysis towards a stretched surface. The appropriate transformations are implemented to transform governing PDEs into a set of coupled ODEs. Shooting method has been applied to get the solutions of obtained highly non-linear ODEs. The thermodynamics second law is employed to model and calculate total entropy rate. Impact of influential variables on the flow field (velocity), gradient of velocity, temperature, gradient of temperature, concentration and entropy generation rate are studied. The engineering quantities like velocity, temperature gradients are numerical discussed in tabular form. Furthermore, the entropy rate and Bejan number show contrast impact versus larger Brinkman number.

Bogeun Gwak

We investigate the energy of the gravitational wave from a binary black hole merger by the coalescence of two Kerr black holes with an orbital angular momentum. The coalescence is constructed to be consistent with particle absorption in the limit in which the primary black hole is sufficiently large compared with the secondary black hole. In this limit, we analytically obtain an effective gravitational spin&#8722;orbit interaction dependent on the alignments of the angular momenta. Then, binary systems with various parameters including equal masses are numerically analyzed. According to the numerical analysis, the energy of the gravitational wave still depends on the effective interactions, as expected from the analytical form. In particular, we ensure that the final black hole obtains a large portion of its spin angular momentum from the orbital angular momentum of the initial binary black hole. To estimate the angular momentum released by the gravitational wave in the actual binary black hole, we apply our results to observations at the Laser Interferometer Gravitational-Wave Observatory: GW150914, GW151226, GW170104, GW170608 and GW170814.

C. L. Latune, I. Sinayskiy, F. Petruccione

Rich quantum effects emerge when several quantum systems are indistinguishable from the point of view of the bath they interact with. In particular, delocalized excitations corresponding to coherent superposition of excited states (reminiscent of double slit experiments or beam splitters in interferometers) appear and change drastically the dynamics and steady state of the systems. Such phenomena, which are central mechanisms of superradiance, present interesting properties for thermodynamics and potentially other quantum technologies. Indeed, a recent paper [C. L. Latune, I. Sinayskiy, and F. Petruccione, Phys. Rev. A 99, 052105 (2019)2469-992610.1103/PhysRevA.99.052105] studies these properties in a pair of indistinguishable two-level systems and points out surprising effects of mitigation and amplification of the bath's action on the energy and entropy of the pair. Here, we generalize the study to ensembles of arbitrary number of spins of arbitrary size (i.e., dimension). We confirm that the previously uncovered mitigation and amplification effects remain, but also that they become more and more pronounced with growing number of spins and growing spin size. Moreover, we find that the free energy variation and the entropy production associated with the bath-driven dissipation are systematically reduced, formalising the idea of mitigation of the bath's action. Most remarkably, the combination of mitigation effects from two baths at different temperatures can result in amplifying their action. This is illustrated with cyclic thermal machines, and leads to large power enhancements. The reduction of irreversibility is also an interesting aspect since irreversibility is known to limit the performance of thermodynamic tasks. The above findings might also lead to interesting applications in collective work extraction, quantum battery charging, state protection, light harvesting devices, quantum biology, but also for the study of entropy production. Moreover, some experimental realisations and observations suggest that such effects are within reach.

Xiao-dong Li, Qing-zhou Zhai

Nano mesocellular foam silica (MCFs) was synthesized through the hydrothermal method in this study. Powder X-ray diffraction and scanning electron microscopy were used to characterize the MCFs sample. The sample presented spherical particles and regular morphology. The results of transmission electron microscopy showed that synthesized MCFs has a three-dimensional honeycomb pore structure, which aids in the adsorption of nickel ion (Ni2+). The results of low-temperature nitrogen gas adsorption-desorption showed that the pore diameter of the synthesized MCFs was 19.6 nm. The impacts of pH, temperature, amount of adsorbent, initial concentration of Ni2+, and contact time on the adsorption effect of Ni2+ by MCFs were studied. Under the optimized adsorption conditions, the adsorption rate reached 96.10% and the adsorption capacity was 7.69 mg/g. It has been determined through the study of kinetics and adsorption isotherms that the adsorption of Ni2+ by MCFs follows the pattern of the pseudo-second-order kinetic model, simultaneously belonging to the Freundlich adsorption type. The thermodynamic results of adsorption showed that, when the temperature is between 25°C and 45°C, the adsorption is a spontaneous exothermic reaction. Keywords: Nickel ion, Adsorption, MCFs, Kinetics, Thermodynamics, Hydrothermal method, Wastewater treatment