Kinetic Theory Research Articles

Mathematical Modeling of Fluidized Bed Magnetizing Roasting of Iron Ore Fines

The fluidized bed magnetizing roasting of low‐grade iron ore fines is employed as a beneficiation technique in iron‐making and steel‐making industries. In the present work, the unreacted shrinking core reaction kinetic model is coupled with the two‐fluid and kinetic theory of granular flow gas–solid flow model to simulate magnetizing roasting of hematite to magnetite in iron ore fines using a fluidized bed reactor. The model is validated with published experimental findings. Thereafter, the influence of different process parameters such as gas temperature, composition, velocity, and particle size on the reduction fraction and rate along with mass fraction and emission is studied. The reduction rate increases with gas temperature and mass fraction while it decreases with particle size. The emission increases with gas temperature, particle size, and mass fraction. However, the influence of gas velocity on these parameters is not significant. The reduction rate and time vary from 0.0010 to 0.0067 s−1 and 65 to 553 s, respectively, at a reduction fraction of 0.5. The mass fraction and emission range from 0.80 to 0.92 and from 0.63 to 4.14 g kg−1 ore, respectively.

Enhanced Structural VS4 Grown onto Hollow Carbon Mesoporous Spheres via Surficial Bonding for High Cycling Stability in Sodium-Ion Batteries.

Transition metal sulfides are recognized as an excellent alternative to sodium ion anodes ascribed to the outstanding theoretical capacity. The unique crystal arrangement of VS4 gives it exceptional theoretical capacity, despite challenges like insufficient electrical conductivity and undesirable volume expansion. Herein, a novel stabilized anode featuring a distinctive 3D hollow spherical structure is proposed, providing a simple strategy to synthesize such anodes for VS4-HCMSs bonded via C-O-S and V-O-C interfaces. The kinetic investigations and density functional theory reveal that the unique structure connected by interfacial bonds enhances Na+ transport rate and charge transfer efficiency, while carbon greatly mitigates the volume expansion. Unsurprisingly, the VS4-HCMSs exhibit an impressive first-cycle Coulombic efficiency of 91.31% and an ultrahigh reversible capacity of 612 mAh g-1 after 300 cycles at 0.5 A g-1, even exhibit the reversible capacity of 498.8 mAh g-1 after 1000 cycles at 5 A g-1. Additionally, the NaFePO4//VS4-HCMSs full cell is cycled for 200 cycles at 0.2 C and powered the light-emitting diodes for up to 30 minutes afterward. Overall, this work enhances the conductivity and stability of the material by combining VS4 with hollow carbon mesoporous spheres through interfacial bonding, offering an efficient strategy to anode materials in sodium-ion batteries.

Is ‘global’ warming concept consistent with thermodynamics according to ChatGPT?

Aim. Taking care of the environment on Planet Earth is still important and has be- come popular exceeding boundaries of science. Therefore description of climate changes has evolved into the concept of Global Warming since the 20th century. On the other hand, principles of thermodynamics where temperature is defined locally (not globally) are still valid. In my research I have applied tools like ChatGPT to detect possible contra- dictions and propose bridging gaps between statistical physics and the concept of global warming. Methods. The concept of temperature based on calculations of local particles’ kinetic energy in a microcanonical ensemble has been confronted with the concept of so called ‘average’ temperature in ‘global’ warming. The principles of Kinetic Theory and Statisti- cal Ensembles provided by statistical physics have been applied to ChatGPT based on natural language Results. Contradictions between the concept of average temperature in global warming and the concept of temperature based on local particle kinetic energy arise due to the different scales, heterogeneity, presence of feedback mechanisms, and boundary conditions. According to the chatGPT’s verdict, the concept of temperature based on calculations of local particles kinetic energy in the microcanonical ensemble is statistically more accurate. Conclusion. The concept of so called ‘global’ warming (confronted with the physics- based concept of temperature, providing a more accurate and nuanced understanding of temperature changes in different scales and contexts) should be replaced by the idea of local warming which is consistent with the concept of temperature based on calcula- tions of local particles kinetic energy in the microcanonical ensemble and experimental measurements provided by NASA. Therefore, talking about local (not global) warming is more reasonable when our goal is to prevent our coexistence with environment on Planet Earth from disasters.

Optimal decay of the Boltzmann equation

The Boltzmann equation is a typical example of partially dissipative equations, where the linearized collision operator is positive definite with respect to the microscopic part and the dissipation of the hydrodynamic part is discovered from the coupling structure between the transport operator and the linearized collision operator. Guo and Wang (Comm. Partial Differential Equations, 37, 2012) developed a general energy method for proving the optimal time decay rates of the solution to such type of equations in the whole space; however, the decay rate of the highest order spatial derivatives of the solution is not optimal. In this paper, by incorporating the high‐low frequency decomposition in the energy estimates, both linearly and nonlinearly, we prove the optimal decay rates of any high order spatial derivatives of the low frequency part of the solution to the Boltzmann equation and the almost exponential decay rate of the high frequency part, which imply in particular the optimal decay rate of the highest order spatial derivatives of the solution. Moreover, the velocity‐weighted assumption of the initial data required in Guo and Wang (Comm. Partial Differential Equations, 37, 2012) is removed by capturing the time‐weighted dissipation estimates via the time‐weighted energy method. The method can be applied to the compressible Navier–Stokes equations and many partially dissipative equations in kinetic theory and fluid dynamics.

Spin‐Crossover and Liquid Crystal Property in Fe(II) Complexes: Impact of Alkyl Chain Lengths

AbstractMaterials that combine spin‐crossover (SCO) and liquid crystal (LC) behavior have gained significant attention due to their potential applications in technological devices, attributed to their easy processability. Herein, we report three neutral heteroleptic Fe(II) complexes: [Fe(dpa‐C4)2(NCS)2] (1), [Fe(dpa‐C6)2(NCS)2] (2), and [Fe(dpa‐C16)2(NCS)2] (3) (dpa‐Cn=N‐alkyl‐N‐(pyridin‐2‐yl)pyridin‐2‐amine; n=4, 6 and 16), which exhibit thermal‐induced spin transition behavior. The transition profiles and temperatures are effectively modulated by the length of the alkyl chains. Longer alkyl chains result in gradual and higher T1/2 values, while the shorter chains lead to abrupt SCO with lower T1/2 (i. e. T1/2=259 K (3) >237 K (2) >211 K (1)). Crystallographic studies reveal the impact of hydrophobic and hydrophilic packing in the crystal lattice, contributing to cooperativity and thereby affecting the SCO behavior. Complex 3 with long alkyl chain substitution, displayed non‐synchronized SCO‐LC behavior due to the thermal motion of the alkyl chains.

Non-Classical Heat Transfer and Recent Progress

Abstract Heat transfer in solids has traditionally been described by Fourier's law, which assumes local equilibrium and a diffusive transport regime. However, advancements in nanotechnology and the development of novel materials have revealed non-classical heat transfer phenomena that extend beyond this traditional framework. These phenomena, which can be broadly categorized into those governed by kinetic theory and those extending beyond it, include ballistic transport, phonon hydrodynamics, coherent phonon transport, Anderson localization, and glass-like heat transfer, among others. Recent theoretical and experimental studies have focused on characterizing these non-classical behaviors using methods such as the Boltzmann transport equation, molecular dynamics, and advanced spectroscopy techniques. In particular, the dual nature of phonons, exhibiting both particle-like and wave-like characteristics, is fundamental to understanding these phenomena. This review summarizes state-of-the-art findings in the field, highlighting the importance of integrating both particle and wave models to fully capture the complexities of heat transfer in modern materials. The emergence of new research areas, such as chiral and topological phonons, further underscores the potential for advancing phonon engineering. These developments open up exciting opportunities for designing materials with tailored thermal properties and new device mechanisms, potentially leading to applications in thermal management, energy technologies, and quantum science.

Universal density shift coefficients for the thermal conductivity and shear viscosity of a unitary Fermi gas

We measure universal temperature-independent density shifts for the thermal conductivity κT and shear viscosity η, relative to the high temperature limits, for a normal phase unitary Fermi gas confined in a box potential. We show that a time-dependent kinetic theory model enables extraction of the hydrodynamic transport times τη and τκ from the time-dependent free decay of a spatially periodic density perturbation, yielding the static transport properties and density shifts, corrected for finite relaxation times. Published by the American Physical Society 2024

Demonstrating Brownian motion and estimating Avogadro’s number using simple tools: a practical guide for students

Abstract Brownian motion provides crucial observational evidence for the kinetic molecular theory by demonstrating the random perpetual movement of small particles. This phenomenon underscores the existence and behaviour of atoms and molecules, fundamentally supporting our current understanding of molecular kinetic theory. Remarkably, in 1905 Albert Einstein was able to predict this motion exactly purely from a theoretical point of view and in 1908 Jean Perrin provided experimental proof. This provided experimental proof of the existence of atoms and molecules. This paper outlines a method to demonstrate and record Brownian motion using a drop of homogenised low fat milk, a microscope and a mobile phone. The captured video files can be analysed with Physics Tracker software, allowing for the estimation of Avogadro’s number.

Ultrafast Synthesis of MXenes in Minutes via Low-Temperature Molten Salt Etching.

Developing green and efficient preparation strategies is a persistent pursuit in the field of 2D transition metal nitrides and/or carbides (MXenes). Traditional etching methods, such as HF-based or high-temperature Lewis-acid-molten-salt etching route, require harsher etching conditions and exhibit lower preparation efficiency with limited scalability, severely constraining their commercial production and practical application. Here, an ultrafast low-temperature molten salt (LTMS) etching method is presented for the large-scale synthesis of diverse MXenes within minutes by employing NH4HF2 as the etchant. The increased thermal motion and improved diffusion of molten NH4HF2 molecules significantly expedite the etching process of MAX phases, thus achieving the preparation of Ti3C2Tx MXene in just 5minutes. The universality of the LTMS method renders it a valuable approach for the rapid synthesis of various MXenes, including V4C3Tx, Nb4C3Tx, Mo2TiC2Tx, and Mo2CTx. The LTMS method is easy to scale up and can yield more than 100g Ti3C2Tx in a single reaction. The obtained LTMS-MXene exhibits excellent electrochemical performance for supercapacitors, evidently proving the effectiveness of the LTMS method. This work provides an ultrafast, universal, and scalable LTMS etching method for the large-scale commercial production of MXenes.

Inconsistences persisting in the conceptual structure of thermal physics and the nature of fundamental constants

AbstractConceptual structure of contemporary thermal physics is by no means simple, understandable and free of contradictions or ambiguities. As many students claim, it is a rather complicated doctrine which is far from to be easy comprehensible (Meltzer in Am J Phys 72:1432–1446, 2004). Therefore, in this polemic contribution, originally the summer school lecture, we will address some lesser-known points, which are likely responsible for such a situation. We start with Black’s path breaking discovery of two aspects of heat, namely the “matter of heat” and the “intensity of heat,” which were later identified with the quantities known as entropy (S) and temperature (T). It can be shown that the product of these two quantities can enter the energy balance equation, which is apt to interconnect various parts of physics. The genesis of these key concepts was, however, not straightforward. An original hypothetical model of heat, a subtle imponderable fluid, caloric (ς), was abandoned after the non-critical acceptance of the “milestone of thermodynamics,” Mayer–Joule’s postulate claiming the equivalence of heat and work. Heat then became a pure energy without any material carrier, but with seriously limited transformation abilities. In addition, the situation is also complicated by the very fact that the definition of Kelvin absolute thermodynamic temperature scale (T) is fully based on the caloric theory. Partial reconciliation brought about only introduction of Clausius’ entropy. This, however, was afterward recognized to be practically identical with the Carnot’s caloric. Furthermore, by analogy identification of phenomenological variables S and T with statistical parameters appearing in the kinetic theory has not withstand extension to the domain of special relativity. Thus, the full equivalence between thermodynamics and statistical physics is not feasible. Another realm of problems is generated by the recent tendency in metrology to define units by means of defining constants with fixed numerical values instead of materialized étalons. In case of thermal physics, one can be skeptic about such an approach, because the universal constancy of entropy and its unit, Boltzmann constant k = 1.380649 × .10−23 J K-1, are only unjustified assumptions, which can be a potential source of future difficulties.

Soft-gluon exchange matters: Isotropic screening in QCD kinetic theory

Soft-gluon exchange matters: Isotropic screening in QCD kinetic theory

Molecular Insights into CO2 Diffusion Behavior in Crude Oil

CO2 flooding plays a significant part in enhancing oil recovery and is essential to achieving CCUS (Carbon Capture, Utilization, and Storage). This study aims to understand the fundamental theory of CO2 dissolving and diffusing into crude oil and how these processes vary under reasonable reservoir conditions. In this paper, we primarily use molecular dynamics simulation to construct a multi-component crude oil model with 17 hydrocarbons, which is on the basis of a component analysis of oil samples through laboratory experiments. Then, the CO2 dissolving capacity of the multi-component crude was quantitatively characterized and the impacts of external conditions—including temperature and pressure—on the motion of the CO2 dissolution and diffusion coefficients were systematically investigated. Finally, the swelling behavior of mixed CO2–crude oil was analyzed and the diffusion coefficients were predicted; furthermore, the levels of CO2 impacting the oil’s mobility were analyzed. Results showed that temperature stimulation intensified molecular thermal motion and increased the voids between the alkane molecules, promoting the rapid dissolution and diffusion of CO2. This caused the crude oil to swell and reduced its viscosity, further improving the mobility of the crude oil. As the pressure increased, the voids between the internal and external potential energy of the crude oil models became wider, facilitating the dissolution of CO2. However, when subjected to external compression, the CO2 molecules’ diffusing progress within the oil samples was significantly limited, even diverging to zero, which inhabited the improvement in oil mobility. This study provides some meaningful insights into the effect of CO2 on improving molecular-scale mobility, providing theoretical guidance for subsequent investigations into CO2–crude oil mixtures’ complicated and detailed behavior.

Modeling chemical bioaccumulation in snakes, part 1: Model development

Environmental chemical emission influences ecological health to some extent. Predators (e.g., snakes) could bioaccumulate chemicals along the food chain, which also leaves potential health implications on their reproduction. For the difficulty of collecting related biomatrices for exposure assessment, part 1 of this study proposed a modeling method relying on physiologically based kinetic (PBK) theory to estimate snake chronic exposure to environmental chemicals. In the steady state, the biotransfer factors of chemicals produced by the PBK model can indicate a snake’s chronic internal exposure to environmental chemicals and their potential for bioaccumulation at this level of the food web. Specifically, 3074 organic chemicals were compelled into the dataset for PBK modeling (part 2 of the study). The modeling framework covered the physiological process of the skin to consider shed snakeskin as a potential biomarker for future study. The proposed modeling approach was integrated into a spreadsheet, enabling the modification of input values to simulate outcomes for a wide range of chemical and snake species. The proposed model can help assess the ecological risks of environmental chemicals and quantify their behavior in the food web.

Role of nonthermal solar wind protons in the excitation of electromagnetic proton-cyclotron instability: a kinetic theory based exact numerical investigation

Free transverse kinetic energy i.e. perpendicular temperature anisotropy of protons excite the electromagnetic ion/proton cyclotron instability which is pertained to waves associated with prevalent electromagnetic ion/proton cyclotron emissions in various natural regions of plasmas. The transverse dielectric response function of left hand circularly polarized electromagnetic proton cyclotron (EPC) instability is calculated for two models of nonthermal Cairns distributed plasmas. These models are distinguished according to the effective thermal velocities of protons. For the energetic nonthermal protons populations, nonthermality dependent effective temperature model is proposed which significantly contributes in the excitation of aforementioned plasma mode and cause an appreciable enhancement in the instability growth rate. Exact numerical solution of dispersion relation yields oscillatory real frequency and growth rate of instability. A comparative analysis is also carried out to examine the instability behavior in distinct nonthermal and thermal plasma models. Contemporary numerical investigations are highly beneficial to understand the intricate dynamics of space plasmas.

Ultrafast Structural Transition and Electron-Phonon/Phonon-Phonon Coupling in Antimony Revealed by Nonadiabatic Molecular Dynamics.

Real-time time-dependent density-functional theory molecular dynamics (rt-TDDFT-MD) reveals the nonadiabatic dynamics of the ultrafast photoinduced structural transition in a typical phase-change material antimony (Sb) with Peierls distortion (PD). As the excitation intensity increases from 3.54% to 5.00%, three distinct structural transition behaviors within 1 ps are observed: no PD flipping, nonvolatile-like PD flipping, and nonstop back-and-forward PD flipping. Analyses on electron-phonon and phonon-phonon couplings indicate that the excitation-activated coherent A1g phonon mode by electron-phonon coupling drives the structural transition within several hundred femtoseconds. Then, the energy of coherent motions are transformed into that of random thermal motions via phonon-phonon coupling, which prevents the A1g-mode-like coherent structure oscillations. The electron-phonon coupling and coherent motions will be enhanced with increasing the excitation intensity. Therefore, a moderate excitation intensity that can balance the coherent and decoherent thermal movements will result in a nonvolatile-like PD flipping. These findings illustrate important roles of nonadiabatic electron-phonon/phonon-phonon couplings in the ultrafast laser-induced structural transitions in materials with Peierls distortion, offering insights for manipulating their structures and properties by light.

Thermodynamics and Kinetics-Directed Regulation of Nucleic Acid-Based Molecular Recognition.

Nucleic acid-based molecular recognition plays crucial roles in various fields like biosensing and disease diagnostics. To achieve optimal detection and analysis, it is essential to regulate the response performance of nucleic acid probes or switches to match specific application requirements by regulating thermodynamics and kinetics properties. However, the impacts of thermodynamics and kinetics theories on recognition performance are sometimes obscure and the relative conclusions are not intuitive. To promote the thorough understanding and rational utilization of thermodynamics and kinetics theories, this review focuses on the landmarks and recent advances of nucleic acid thermodynamics and kinetics and summarizes the nucleic acid thermodynamics and kinetics-based strategies for regulation of nucleic acid-based molecular recognition. This work hopes such a review can provide reference and guidance for the development and optimization of nucleic acid probes and switches in the future, as well as for advancements in other nucleic acid-related fields.

Thermostatted Kinetic Theory Structures in Biophysics: Generalizations and Perspectives

The mathematical modeling of multicellular systems is an important branch of biophysics, which focuses on how the system properties emerge from the elementary interaction between the constituent elements. Recently, mathematical structures have been proposed within the thermostatted kinetic theory for the modeling of complex living systems and have been profitably employed for the modeling of various complex biological systems at the cellular scale. This paper deals with a class of generalized thermostatted kinetic theory frameworks that can stand in as background paradigms for the derivation of specific models in biophysics. Specifically, the fundamental homogeneous thermostatted kinetic theory structures of the recent literature are recovered and generalized in order to take into consideration further phenomena in biology. The generalizations concern the conservative, the nonconservative, and the mutative interactions between the inner system and the outer environment. In order to sustain the strength of the new structures, some specific models of the literature are reset into the style of the new frameworks of the thermostatted kinetic theory. The selected models deal with breast cancer, genetic mutations, immune system response, and skin fibrosis. Future research directions from the theoretical and modeling viewpoints are discussed in the whole paper and are mainly devoted to the well-posedness in the Hadamard sense of the related initial boundary value problems, to the spatial–velocity dynamics and to the derivation of macroscopic-scale dynamics.

A technical comment on “A decade of thermostatted kinetic theory models for complex active matter living systems”. New fascinating perspectives of research

A technical comment on “A decade of thermostatted kinetic theory models for complex active matter living systems”. New fascinating perspectives of research

A magnetohydrodynamic flow of a water-based hybrid nanofluid past a convectively heated rotating disk surface: A passive control of nanoparticles

Abstract One of the basic fluid mechanics problems of fluid flows over a revolving disk has both theoretical and real-world applications. The flow over a rotating disk has been the subject of numerous theoretical studies because it has many real-world applications in areas like rotating machinery, medical equipment, electronic devices, and computer storage. It is also crucial for engineering processes. Therefore, this article deals with a time-independent water-based hybrid nanofluid flow containing copper oxide and silver nanoparticles past a spinning disk. The Newtonian flow is taken into consideration in this analysis. The influence of magnetic field, thermophoresis, nonlinear thermal radiation, Brownian motion, and activation energy has been considered. The present analysis is modeled in a partial differential equation form and is then converted to ordinary differential equations using appropriate variables. A numerical solution using the bvp4c technique is accomplished using MATLAB software. The current results are matched with the previous literature and established a close relationship with previous studies. The purpose of this investigation is to numerically investigate the time-independent hybrid nanofluid flow comprising copper oxide and silver nanoparticles over a rotating disk surface. The results show that the increased magnetic parameters increase the friction force at the surface, which decreases the radial and azimuthal velocity distribution. At the sheet surface, the radial velocity of the hybrid nanofluid shows dominant performance compared to the nanofluid. On the other hand, the magnetic factor has dominant behavior on the azimuthal velocity component of the nanofluid flow compared to the hybrid nanofluid flow. The higher volume fraction and magnetic factor enhance the skin friction at the disk surface. Furthermore, greater surface drag is found for the hybrid nanofluid flow. The higher solid volume fraction, temperature ratio, and Biot number enhance the rate of heat transmission. Also, a higher rate of heat transmission is observed for the hybrid nanofluid flow.

Thermally stable thin-film composite nanofiltration membranes derived from 3,3′-diaminobenzidine

The rapid development of modern industrialization has put forward high demands on separation and purification technologies. To reduce energy consumption, improve efficiency, and enhance process flexibility, nanofiltration membranes for high temperature separation have become more and more important. Herein, we report the use of 3,3′-diaminobenzidine (DAB) as the aqueous phase monomer and trimesoyl chloride (TMC) as the organic phase monomer to engineer thermally resistant nanofiltration membranes via interfacial polymerization. The incorporation of DAB enhances the rigidity of the cross-linked polyamide network, reduces segmental thermal motion at high temperature, and improves the thermal stability of the composite membrane. The variations in fractional free volumes of the nanofiltration membranes were analyzed at different temperatures by molecular dynamics (MD) simulation, which have also been confirmed by experiments. The findings reveal that incorporating a rigid monomer into the polyamide layer can significantly enhance the thermal resistance. The resultant composite membrane exhibits outstanding resistance to high-temperature feed solutions, boasting a highly stable rejection rate (97.0 %) to Na2SO4 between 25–85 °C. Remarkably, even under sustained operation at 85 °C for 12 h, the rejection rate is consistently stable. This work presents a novel system for the design of thermally stable nanofiltration membranes for high temperature separation.