Critical Point Temperature Research Articles

Preparation and flame retardant properties of new mining fireproof gel

Coal spontaneous combustion (CSC) brings great danger to mine safety. Although traditional colloidal fire-fighting materials can reside at high fire source points, their permeability and fluidity are poor, and such materials focus on their water absorption, but pay less attention to water retention and resistance, which makes their fire-fighting effect not good. This paper proposed a new type of mining fire prevention colloid material (CPS-α), which had good solid water gel formation, viscosity, fluidity, and blocking properties to compensate for traditional colloids' shortcomings. According to the single-factor experiment, polymeric polyacrylamide (PAM) as the base material, sodium carboxymethyl cellulose (CMC) as the coagulant, modified starch (SS) as the flame retardant and reduced ascorbic acid were determined. After gel treatment, compared with raw coal, the critical temperature point of spontaneous combustion of coal was increased by about 28 °C, the time to reach the critical temperature point was delayed by 190s, and the characteristic temperature points were significantly increased; the overlap area of coal and water increases by about 20 % after adding gel, and the change slope of the diffusion coefficient of water decreases, which indicated that CPS-α had good flame retardant effect.

Preparation and Properties of Composite Double-Network Gel for Inhibiting Coal Spontaneous Combustion.

In order to improve the inhibition effect of gel on coal spontaneous combustion, a chitosan (CS)/polyacrylamide (PAM)/metal ion (Al3+) composite double-network gel was developed in this study. The optimum formula of the composite double-network gel was determined using orthogonal experimentation. The microstructure, water retention, compressibility, and anti-destruction properties of the composite double-network gel were analyzed. The inhibition effect of the composite double-network gel on coal spontaneous combustion was studied via infrared spectroscopy and a synchronous thermal analyzer from the micro and macro perspectives. The results show that the composite double-network gel has a denser interpenetrating double-network structure and a larger void ratio than the ordinary gel. The water retention rate was 55% after standing at 150 °C for 12 h. The deformation memory ratio of the composite double-network gel was 78%, which was 26.8% higher than that of the ordinary gel, and the compressive strength also increased by 59.96%. In addition, the critical temperature point and the maximum thermal weight-loss rate temperature point decreased by 7.01 °C and 39.62 °C, respectively, and the composite double-network gel effectively reduced active functional groups in the treated coal sample, such as hydroxyl and aliphatic hydrocarbons. In this study, a CS/PAM/Al3+ composite double-network gel was produced, which exhibited good gel performance and inhibition effects, with physical effects such as the covering, wetting, and cementation of coal.

Adsorption Mechanism and Characteristic Temperatures of the Monolayer Adsorption of CO2 on Graphite: The Role of Graphene Dimensions.

Although simulation results for gaseous adsorption on a surface of infinite extent, modeled with periodic conditions at the boundaries of the simulation box, agree with experimental data at high temperatures, simulated isotherms at temperatures below the triple point temperature show unphysical substeps because of the compromise of interactions within the box and interactions between the box and its mirror image boxes. This has been alleviated with surfaces of finite dimensions (Loi, Q. K.; Colloids Surf., A 2021, 622, 126690 and Castaño Plaza, O.; Langmuir 2023, 39 (21), 7456-7468) to account for free boundaries at the adsorbate patch on the surface, and the critical parameter of this model substrate is the size of the finite surface. If it is too small, the adsorbate patch does not model the physical reality; however, if it is too large, the computation time is excessive, making the simulation impractical. In this study, we used carbon dioxide/graphite as the model system to explore the effects of finite dimensions on the description of experimental data of Terlain, A.; Larher, Y. Surf. Sci. 1983, 125 (1), 304-311, especially for temperatures below the bulk triple point temperature. With the appropriate choice of graphene size, we derived the 2D triple point and 2D critical point temperatures of the monolayer, and most importantly, for temperatures below the 2D critical point temperature, the adsorption mechanism for the formation of the monolayer is due to the interplay between the boundary growth process and the vacancy filling. The extent of this interplay is found to depend on the fractional coverage of the surface.

Transition to oscillatory instability of lean methane–air flames in microchannels

Micro-flow reactors and porous media burners are prone to instability in the form of flame with repetitive extinction and ignition (FREI) near the region of a temperature gradient. Although significant progress has been made in this field, there is still a lack of understanding regarding the nature of such stable-to-unstable transition. Some studies reported a smooth and continuous instability transition in microchannels, interpreting this phenomenon as a supercritical bifurcation. Meanwhile, others have observed that the transition is subcritical, with rapid, stepwise evolution of the stable flame to FREI. This study aims to rigorously determine the transition character theoretically and numerically using a two-dimensional model with a precise resolution of the bifurcation parameter (flow velocity) near the critical point and gradual wall temperature ramp. The results indicate that the transition is a subcritical bifurcation with strong hysteresis. However, the amplitude of the limit cycle born in the bifurcation point could be small compared to FREI-like oscillations. Moreover, further development of the instability depends significantly on the channel width. In relatively wide channels, the stable regime transforms immediately into the extinction/ignition one with rapid growth in amplitude. In moderate channels, complex transitional dynamics were observed with an evident pulsating regime, which evolved into FREI through mixed-mode oscillations. In narrow channels, the amplitude of transitional pulsating flame becomes comparable to the fully-developed extinction/ignition cycles, and the bifurcation diagram has a continuous character with no significant jumps or discontinuities. Such qualitative variation of transition character provides a possible explanation for contradictory interpretations presented in the literature.Novelty and Significance StatementCurrently, there is no consensus about the character of transition between the stable and extinction/ignition regimes in microchannels. Some studies have reported a continuous instability transition with an evident pulsating regime, interpreting it as a supercritical bifurcation, while others have observed subcritical bifurcation with a rapid transition. The novelty of this research lies in the rigorous determination of the bifurcation type and further instability development in microchannels of different widths based on an accurate simulation of flame dynamics near the critical point with very small steps of the flow velocity variation, along with the bifurcation theory. The study contributes to understanding the instability transition nature and may explain the different interpretations of the transitional phenomenon found in the literature. The results offer valuable insights for designing micro-scale and porous media combustion devices.

Multi-verse optimizer for thermal error modeling approach of spindle system based on thermal image

Since the spindle thermal error of CNC machine tools has a significant impact on machining precision, this paper introduces a unique approach for modeling spindle thermal error. Several key steps are involved in the proposed approach. First, the Fluke thermal imaging camera is employed for acquiring thermal image information of the spindle system. Second, the Gaussian filter is employed to denoise the thermal image sequence. Next, the temperature values at the measurement points are extracted from the thermal image sequence according to the mapping relationship between the grayscale value and the temperature value. Subsequently, critical temperature points are identified from thermal images using the density-based spatial clustering of applications with noise (DBSCAN) algorithm and the correlation coefficient method. Finally, the multi-verse optimized NARX neural network is employed to investigate the nonlinear prediction of thermal deformation. The research is conducted on the VMC-850E vertical machining center as the subject of study. The performance of the model is validated under conditions of idle spindle and 5000 r/min, comparing prediction results against traditional algorithms. The findings demonstrate that the non-contact measurement method based on thermal imaging successfully establishes the thermal error model, achieving a prediction accuracy of 0.1517 μm for the MVO-NARX model.

Computer Simulation of Three-Phase Equilibria for Some Water/n-Alkane Binary Systems.

In this work, the vapor-liquid-liquid equilibrium (VLLE) of the water/n-pentane, water/n-hexane, water/n-octane, and water/n-decane binary systems is calculated by computer simulation using the NVT-Gibbs ensemble (in the version of three simulation boxes) combined with the configurational bias Monte Carlo method. The combination of both methods, the molecular potential models used, and the simulation details allowed us to calculate the triphasic equilibrium properties of the systems studied: the densities of the three phases in equilibrium, their compositions, and potential energies. In previous works, these simulations were not carried out at a temperature range nor water/n-alkanes systems simulated in this work, probably because they are highly nonideal systems; so, to the best of our knowledge, this is the first time that this phenomenon is studied in detail. The results from VLLE simulations of the water/n-pentane system for temperatures from 343.2 to 435 K, the water/n-hexane system for temperatures from 373.11 to 473.15 K, the water/n-octane system for temperatures from 310.9 to 500 K, and for the water/n-decane system for temperatures from 374.15 to 525 K are reported here. The temperature range was selected in concordance with the experimental data available for an adequate study of the VLLE simulation results. The subcritical densities (vapor and liquid rich in n-alkane phases) at various temperatures fit well with the scaling law and the law of rectilinear diameters, allowing the estimation of upper critical end point temperature and density of the VLLE. The simulation results show a good prediction with experimental data reports in the literature.

Influence of PEG-PPG-PEG Block Copolymer Concentration and Coagulation Bath Temperature on the Structure Formation of Polyphenylsulfone Membranes.

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5-15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18-20 L·m-2·h-1 for the reference PPSU membrane up to 38-140 L·m-2·h-1 for 20 wt.% PPSU/10-15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5-7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR-81-89%, DRr-26-32%, DRir-10-20%, DT-33-45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR-29-38%, DRr-6-14%, DRir-74-89%, DT-88-94%).

Phase Diagrams of Anthracene Derivatives in Pyridinium Ionic Liquids.

Crystal engineering for single crystallization of π-conjugated molecules has attracted much attention because of their electronic, photonic, and mechanical properties. However, reproducibility is a problem in conventional printing techniques because control of solvent evaporation is difficult. We investigated the phase diagrams of two anthracene derivatives in synthesized ionic liquids for non-volatile crystal engineering to determine the critical points for nucleation and crystal growth. Anthracene and 9,10-dibromoanthracene were used as representative π-conjugated molecules that form crystal structures with different packing types. Ionic liquids with an alkylpyridinium cation and bis(fluorosulfonyl)amide were good solvents for the anthracene derivatives from ca. 0 °C to 200 °C. The solubilities (critical points for crystal growth) of the anthracene derivatives in the ionic liquids reached the 100 mM level, which is similar to those in organic solvents. Ionic liquids with phenyl and octyl groups tended to show high-temperature dependence (a high dissolution entropy) with 9,10-dibromoanthracene. The precipitation temperature (critical point for crystal nucleation) at each 9,10-dibromoanthracene concentration was lower than the dissolution temperature. The differences between the dissolution and precipitation temperatures (supersaturated region) in the ionic liquids were greater than those in an organic solvent.

Numerical study of CO2 trans-critical process inside micromodel based porous structures under supercritical pressures

Understanding the flow, heat transfer, and trans-critical process of carbon dioxide in porous media is crucial for various applications, including CO2 sequestration, soil remediation and oil and gas recovery, due to its unique physical properties in the critical region. In this study, a porous media model on a microfluidic chip structure was simulated to emphasize the heat transfer and trans-critical process of CO2 under supercritical pressure in porous media. The study aims to observe the behaviors of CO2 during its transition from subcritical to supercritical temperature under supercritical pressure. The main objective is to observe the temperature distribution and pressure change of CO2 in a porous media model under the influence of bottom heating. At the same time, we observe the changes in the position of the critical temperature point of CO2 in porous media and analyze its heat exchange process in porous media. After the flow reaches a steady state, the temperature span near the grains is 1.6 K, and the pressure drop per unit length is 1480.3 Pa/mm. As the flow time progresses, the critical temperature line migrates from outlet region to inlet region, the range of sCO2 narrows from 81.7 % to 84.7 % in the porous media region. Finally, the influence of different working conditions on the trans-critical region is studied. It is hoped that this study will contribute to the understanding of the trans-critical process of CO2 in porous media.

Liver transcriptome analysis reveal the metabolic and apoptotic responses of Trachinotus ovatus under acute cold stress

Trachinotus ovatus is an economically important fish and has been recommended as a high-quality aquaculture fish breed for the high-quality development of sea ranches in the South China Sea. However, T. ovatus shows intolerance to low temperature, greatly limiting the extension of farming scale, reducing production efficiency in winter, and increasing farming risks. In this study, liver transcriptome analysis was investigated in T. ovatus under acute low temperature conditions (20 and 15 °C) using RNA sequencing (RNA-Seq) technology. Inter-groups differential expression analysis and trend analysis screened 1219 DEGs and four significant profiles (profiles 0, 3, 4, and 7), respectively. GO enrichment analysis showed that these DEGs were mainly related to metabolic process and cell growth and death process. KEGG enrichment analysis found that DEGs were mainly associated with lipid metabolism, carbohydrate metabolism, and cell growth and death, such as gluconeogenesis, glycolysis, fatty acid oxidation, cholesterol biosynthesis, p53 signaling pathway, cell cycle arrest, and apoptotic cell death. Moreover, protein–protein interaction networks identified two hub genes (FOS and JUNB) and some important genes related to metabolic process and cell growth and death process, that corresponding to enrichment analysis. Overall, gluconeogenesis, lipid mobilization, and fatty acid oxidation in metabolic process and cell cycle arrest and apoptotic cell death in cell growth and death process were enhanced, while glycolysis, liver glycogen synthesis and cholesterol biosynthesis in metabolic process were inhibited. The enhancement or attenuatment of metabolic process and cell growth and death process is conducive to maintain energy balance, normal fluidity of cell membrane, normal physiological functions of liver cell, enhancing the tolerance of T. ovatus to cold stress. These results suggested that metabolic process and cell growth and death process play important roles in response to acute cold stress in the liver of T. ovatus. Gene expreesion level analysis showed that acute cold stress at 15 °C was identified as a critical temperature point for T. ovatus in term of cellular metabolism alteration and apoptosis inducement, and rewarming intervention should be timely implemented above 15 °C. Our study can provide theoretical support for breeding cold-tolerant cultivars of T. ovatus, which is contributed to high-quality productions fish production.

Digital Fracture Surface Morphology and Statistical Characteristics of Granite Brazilian Tests after Non-Steady-State Thermal Disturbance

With the widespread advent of digital technologies, traditional perspectives in rock mechanics research are poised for further expansion. This paper presents a Brazilian test conducted on granite after non-steady-state thermal disturbance at 25 °C, 200 °C, 400 °C, and 600 °C, with detailed documentation of the damage process and failure response using an acoustic emission (AE) apparatus and a digital image correlation (DIC) system. Subsequently, utilizing point cloud data captured by a three-dimensional (3D) laser scanning system, a digital reconstruction of the failed specimen’s fracture surface was accomplished. The 3D fractal characteristics and roughness response of the digitized fracture surface were studied using the box-counting method and least squares approach. Furthermore, texture information of the digitized fracture surface was calculated using the Gray Level Co-occurrence Matrix (GLCM), and statistical characteristics describing the elevation distribution were analyzed. The results elucidate the influence of thermal disturbance temperature on the mechanical parameters of the specimen, acoustic emission behavior, surface strain field evolution, and digital fracture morphology characteristics. The findings indicate a non-linear degradation effect of temperature on the specimen’s tensile strength, with a reduction reaching 80.95% at 600 °C, where acoustic emission activity also peaked. The rising thermal disturbance temperature inhibited the crack initiation load at the specimen’s center but expanded the high-strain concentration areas and the growth rate of horizontal displacement. Additionally, varying degrees of linear or non-linear relationships were discovered between thermal disturbance temperature and the 3D fractal dimension of the fracture surface, average roughness (Ra), peak roughness (Rz), and root mean square roughness (Rq), confirming the potential of Rsm in predicting the 3D fractal dimension of Brazilian test fracture surfaces. The study of the GLCM of the digitized 3D fracture surface demonstrated a high dependency of its four second-order statistical measures on thermal disturbance temperature. Finally, the statistical parameters of the fracture surface’s elevation values showed a significant non-linear relationship with thermal disturbance temperature, with a critical temperature point likely existing between 400 and 600 °C that could precipitate a sudden change in the fracture surface’s elevation characteristics.

Temperature Monitoring of Through-Thickness Temperature Gradients in Thermal Barrier Coatings Using Ultrasonic Guided Waves

Ultrasonic guided waves offer a promising method of monitoring the online temperature of plate-like structures in extreme environments, such as aero-engine nozzle guide vanes (NGVs), and can provide the resolution, response rate, and robust operation that is required in aerospace. Previous investigations have shown the potential of such a system but the effect of the complex physical environment on wave propagation is yet to be considered. This article uses a numerical approach to investigate how thermal barrier coatings (TBCs) applied to the surface of many components designed for extreme thermal conditions will affect ultrasonic guided wave propagation, and how a system can be employed to monitor through-thickness temperature changes. The top coat/bond coat boundary in NGVs has been shown to be a temperature critical point that is difficult to monitor with traditional temperature sensors, which highlights the potential of ultrasonic guided waves. Differences in application method and layer thickness are considered, and analysis of through-thickness displacement profiles and dispersion curves are used to predict signal response and determine the most suitable mode of operation. Heat transfer simulations (COMSOL) have been used to predict temperature gradients within a TBC, and dispersion curves have been produced from the temperature dependant material properties. Time dependant simulations of wave propagation are in good agreement with dispersion curve predictions of wave velocity for the two lowest order modes in three thicknesses of TBC top coat (100, 250, and 500 μm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu \\hbox {m}$$\\end{document}). When wave velocity measurements from the simulations are compared to dispersion curves generated at isotropic temperatures, the corresponding temperature represents the average temperature of a gradient system well. Such a measurement system could, in principle, be used in conjunction with surface temperature measurement systems to monitor through-thickness temperature changes.

High-temperature strain sensor based on sapphire fiber Bragg grating.

Sapphire fiber Bragg grating (SFBG) is a promising high-temperature strain sensor due to its melting point of 2045°C. However, the study on the long-term stability of SFBG under high temperature with an applied strain is still missing. In this paper, we reported for the first time to our knowledge on the critical temperature point of plastic deformation of the SFBG and demonstrated that the SFBG strain sensor can operate stably below 1200°C. At first, we experimentally investigated the topography and the spectral characteristics of the SFBG at different temperatures (i.e., 25°C, 1180°C, and 1600°C) with applied 650 µε. The reflection peak of the SFBG exhibits a redshift of about 15 nm and broadens gradually within 8 h at 1600°C, and the tensile force value decreases by 0.60 N in this process. After the test, the diameter of the SFBG region decreases from 100 to 88.6 µm, and the grating period is extended from 1.76 to 1.79 µm. This indicates that the plastic deformation of the SFBG happened indeed, and it was elongated irreversibly. Moreover, the stability of the Bragg wavelength of the SFBG under high temperature with the applied strain was evaluated. The result demonstrates the SFBG can be used to measure strain reliably below 1200°C. Furthermore, the strain experiments of SFBG at 25°C, 800°C, and 1100°C have been carried out. A linear fitting curve with high fitness (R2 > 0.99) and a lower strain measurement error (<15 µε) can be obtained. The aforementioned results make SFBG promising for high-temperature strain sensing in many fields, such as, power plants, gas turbines, and aerospace vehicles.

Preparation of tough and stiff ionogels via phase separation.

Ionogels have the advantages of thermal stability, non-volatility, ionic conductivity and environmental friendliness, and they can be used in the field of flexible electronics and soft robotics. However, their poor mechanical strength and complex preparation methods limit their practical application. Herein, we propose a simple strategy to improve the performance of ionogels by adjusting their phase separation behavior. In a polymer-ionic liquid (IL) binary system with an upper critical solution temperature (UCST) and Berghmans' point, the phase separation behavior will be frozen below the temperature corresponding to the Berghmans' point, and thus, the degree of phase separation can be adjusted by controlling the cooling rate. We found that a polyacrylamide (PAM)-IL binary system possessed a UCST and Berghmans' point and the resulting ionogels had excellent mechanical properties. Their tensile strength, tensile modulus, compressive strength and compressive modulus reached 31.1 MPa, 319.8 MPa, 122 MPa and 1.7 GPa, respectively, while these properties of the other ionogels were generally less than 10 MPa. Furthermore, they were highly transparent, stretchable, stable and multifunctional.

Uncovering the universality of critical phenomenon in a ferromagnet Gd5Si4 prepared under high pressure

Manipulation of phase transition is of great interest not only because it can enhance the application ability of accompanying physical effects, but also because it allows us to uncover the physical connotations near the critical temperature point. In this work, we systematically examine the influence of high-pressure annealing (HPA) on critical phenomena in Gd5Si4 ferromagnet. A second-order magnetic phase transition is determined in the annealed sample under 3 GPa with a reduced Curie temperature. Various techniques including modified Arrott plot, Kouvel-Fisher method, and critical isotherm analysis are adopted to calculate critical exponents β, γ, and δ of HPA compound. Using the obtained parameters, we employ the renormalization group theory to calculate the spin exchange range, which satisfies J(r) ∼ r−4.454, exhibiting a longer-range-ordered ferromagnetic interaction. Our work indicates that HPA can manipulate the degree of order inside matter with a novel universality class, thus acquiring desired functionality through reasonable HPA treatment.

Preparation of functional nanoparticles of mPEG‐b‐P(DMA‐co‐HA) copolymers via polymerization‐induced thermal self‐assembly

AbstractSelf‐assembled polymeric nanoparticles have been of great interest for various biological applications such as drug delivery, catalysis, and biosensing. In this regard, polymerization‐induced self‐assembly (PISA) has been widely explored as a more efficient technique than conventional self‐assembly methods as it can be conducted in one pot and does not require harsh conditions. Recently, a method known as polymerization‐induced thermal self‐assembly (PITSA) has emerged, exploiting the inherent phase transition behavior of thermoresponsive polymers at a critical temperature point to generate thermoresponsive nanoparticles in situ. However, the narrow range of monomers suitable for PITSA limits the design of diverse thermoresponsive nanoparticles, and therefore this process has not yet been explored to its fullest capacity. In this study, we demonstrate the preparation of thermoresponsive nanoparticles based on hydrophilic N,N‐dimethyl acrylamide (DMA) and hydrophobic hexyl acrylate (HA) monomers. This is particularly interesting as these monomers produce non‐responsive homopolymers but display thermoresponsive behavior when copolymerized. The nanoparticles obtained were crosslinked to enable their characterization at room temperature, and further functionalized with a short synthetic antibacterial peptide (WR)3 to demonstrate proof‐of‐concept potential as antimicrobial agents. Overall, this work expands the library of monomers amenable to PITSA for the production of thermoresponsive nanoparticles, contributing to the design of new functional nanoparticles for therapeutic purposes.

Effect of surface roughness on phase transition timing in megaampere pulsed-power–driven exploding conductors

An understanding of material phase transitions in megaampere pulsed-power–driven exploding conductors is important for predicting the growth of hydrodynamic instabilities in magneto-inertial fusion concepts. This study analyzes phase transitions in electrical conductor explosions using 1D Lagrangian and 2D arbitrary Lagrangian–Eulerian resistive magnetohydrodynamic simulations to show that micrometer-scale surface roughness can lead to the electrothermal instability (ETI), a feedback effect that concentrates resistive heating and leads to early melting and ablation. Simulations of the Mykonos electrothermal instability II (METI-II) experiment show melting begins 19% sooner for machined rods with micrometer-scale surface roughness than for rods without these features. The surface magnetic field is 41 T around the initial region of melt, representing a lower magnitude than both the 86 T from 1D simulations and the 85 T threshold reported elsewhere. In 2D simulations with micrometer-scale surface roughness, temperature measurements indicate the critical point temperature of aluminum is reached 17% faster in comparison with 1D simulations. Values from 2D simulations with surface roughness align with predictions from ETI theory, and the observed temperature redistribution further supports the ETI as an underlying mechanism. Simulation results are validated against experimental photonic Doppler velocimetry data. This study shows 1D simulations are adequate to model conductors with sub-micrometer-scale surface roughness in this high-energy-density regime; however, 2D or 3D simulations are required to capture the full range of physics for accurately describing phase transitions in conductors with micrometer-scale or larger surface roughness.

Effect of Rotating Channel Turning Section Clearance Size on Heat Transfer Characteristics of Supercritical Pressure Hydrocarbon Fuel

For the problem of power generation turbine blade ablation in hypersonic vehicles, hydrocarbon fuel carried by the vehicle is used to cool the turbine blades. In order to fully utilize the cooling capacity of hydrocarbon fuel, the structure of the cooling channels needs to be optimized. In this study, a variable clearance hydrocarbon fuel cooling channel is applied for the first time to the rotating turbine blades of a hypersonic vehicle to enhance the heat transfer ability of hydrocarbon fuel. The effect of clearance size on the heat transfer performance of hydrocarbon fuel under rotating conditions is investigated. The accuracy of the calculations is verified by comparison with experimental data. The results of the study show that the heat transfer performance can be significantly improved by changing the clearance of the turning section. The clearance size 2.5 D channel has the highest thermal performance with a maximum improvement of 1.8 times. The law of change of thermal performance is affected by crossing the critical temperature point, as it is different before and after the crossing. Thermal performance changes from decreasing then increasing to increasing then decreasing as the clearance size increases for high rotation speed conditions as the temperature of the entrance straddles the critical temperature. The Nusselt number first increases and then decreases for all channels with different clearance sizes with an increasing rotational speed. The friction factor changes from first increasing and then decreasing to decreasing and then increasing as the clearance size increases for high rotation speed conditions as the temperature of the entrance straddles the critical temperature.

Disturbance of oxidation/antioxidant status and histopathological damage in tsinling lenok trout under acute thermal stress.

The tsinling lenok trout (Brachymystax Lenok tsinlingensis) is a typical land-locked cold salmon. In this study, through the acute high temperature stress (16, 24, and 26°C), samples were taken at multiple temperature points to analyze the dynamic changes of serum non-specific immune indexes and histopathological changes of tissues of tsinling lenok trout. The histopathological investigation of different studied tissues revealed an increase of histological lesions' frequency and severity with increasing water temperature. The activity of T-SOD, GSH-Px, CAT, ACP, and LZM and MDA concentration are all impacted by high temperature stress. The activities of T-SOD, GSH-Px, and ACP are significantly lower in temperatures higher than 16°C (P<0.05). However, with the increase of water temperature, MDA content increased significantly. The activities of CAT and LZM were the highest at 24°C, which were significantly higher than those at 26°C (P<0.05). The above results indicate that 24°C is a "critical high temperature point" for tsinling lenok trout under heat stress, and this temperature point may be the critical point for tsinling lenok trout to enter "damaged" from adaptive adjustment. Our results can provide a theoretical basis for the development of genetic breeding, improvement, and control measures of heat stress in tsinling lenok trout in the future.

Monte-Carlo simulation of phase transition in 2D and 3D ising model

In this work, Markov Chain-Monte Carlo technique was used to study the phase transition in two and three dimensional Ising Model (IM) in a square and cubic lattice. The study of temperature dependence of average magnetization and specific heat in different magnetic fields has been carried out in the 3x3 and 3x3x3 lattice with periodic boundary. Critical temperature point kBTc / J for 2D and 3D Ising Model has been observed at around 2.2 and 4.3 respectively at zero field. Our work satisfies Onsager’s critical value in 2D IM. The simulation suggests bifurcation in average magnetization below critical temperature Tc. Temperature plays the role of increasing randomness of spins. We found that Ising Model in small lattice size still retains interesting features like spontaneous magnetization and symmetry breaking below Tc at B = 0. At a non-zero field, the likelihood of spins to prefer certain alignment depends on the direction of the external field and magnitude of magnetization depends on magnitude of field ±B. Specific heat Cv, which gives us fluctuation of energy at particular temperature, has been found to attain maximum value at critical regions.