Magnetic and electrical transport properties in GdAlSi and SmAlGe

We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crystals,which possess a LaPtSi-type structure(space group I4_(1)md).The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature(T_(N)).For GdAlSi,a hysteresis loop is observed in the magnetization and magnetoresistance curves within the ab plane when the magnetic field is applied below T_(N),which is around32 K.Notable specific heat anomalies are detected at 32 K for GdAlSi and 6 K for SmAlGe,confirming the occurrence of magnetic transitions.In addition,the extracted magnetic entropy at high temperatures is consistent with the theoretical value of Rln(2J+1) for J=7/2 in Gd^(3+) and J=5/2 in Sm^(3+),respectively.SmAlGe also exhibits Schottky-like specific heat contributions.Additionally,both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.

Linear magnetoresistance and structural distortion in layered SrCu_(4-x)P_(2) single crystals

We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at T_(p)~140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e.,?L_(c)/L_(c)~0.062%. The structural characterization confines that there is no structure transition below and above T_(p). All these results suggest that the nonmagnetic transition of SrCu_(4-x)P_(2) could be associated with structural distortion.

Characterization of rock thermophysical properties and factors affecting thermal conductivity−A case study of Datong Basin,China

Rock thermal physical properties play a crucial role in understanding deep thermal conditions,modeling the thermal structure of the lithosphere,and discovering the evolutionary history of sedimentary basins.Recent advancements in geothermal exploration,particularly the identification of high-temperature geothermal resources in Datong Basin,Shanxi,China,have opened new possibilities.This study aims to characterize the thermal properties of rocks and explore factors influencing thermal conductivity in basins hosting high-temperature geothermal resources.A total of 70 groups of rock samples were collected from outcrops in and around Datong Basin,Shanxi Province.Thermal property tests were carried out to analyze the rock properties,and the influencing factors of thermal conductivity were studied through experiments at different temperature and water-filled states.The results indicate that the thermal conductivity of rocks in Datong,Shanxi Province,typically ranges from 0.690 W/(m·K)to 6.460 W/(m·K),the thermal diffusion coefficient ranges from 0.441 mm^(2)/s to 2.023 mm^(2)/s,and the specific heat capacity of the rocks ranges from 0.569 KJ/(kg·℃)to 1.117 KJ/(kg·°C).Experimental results reveal the impact of temperature and water saturation on the thermal conductivity of the rock.The thermal conductivity decreases with increasing temperature and rises with high water saturation.A temperature correction formula for the thermal conductivity of different lithologies in the area is proposed through linear fitting.The findings from this study provide essential parameters for the assessment and prediction,development,and utilization of geothermal resources in the region and other basins with typical high-temperature geothermal resource.

Specifications of nanosecond laser ablation with solid targets,aluminum,silicon rubber,and polymethylmethacrylate(PMMA)

The ablation parameters such as threshold fluence, etch depth, ablation rate and the effect of material targets were investigated under the interaction of laser pulse with low intensity. The parameters of the laser system are： laser pulse energy in the range of 110–140 m J, wavelength1064 nm and pulse duration 20 ns. By macroscopic estimation of the outward images of the ablation and data obtained, we can conclude that the photothermal and photoionization processes have more influence for aluminum ablation. In contrast, for polymer samples, from the macroscopic observation of the border pattern at the irradiated spot, and also the data obtained from the experiment results, we deduce that both chemical change due to heating and photochemical dissociation were effective mechanisms of ablation. However, concerning the two polymer samples, apart from considering the same theoretical ablation model, it is conceived that the photomehanical specifications of PMMA are involved in the ablation parameters. The threshold fluence for an ablation rate of 30 laser shots were obtained as 12.4, 24.64, and 11.71 J cm^（-2）, for aluminum, silicon rubber and polymethylmethacrylate（PMMA） respectively.The ablation rate is exponentially decreased by the laser-shot number, especially for aluminum.Furthermore, the etch depth after 30 laser shots was measured as 180, 630 and 870 μm, for aluminum, silicon rubber and PMMA, respectively.

Subtle lattice distortion-driven phase transitions in layered ACu_(4)As_(2)(A=Eu,Sr)

The compounds composed of transition metal cations and pnictide anions provide a rich platform for studying novel physical phenomena.Here we report on the observation of a phase transition at~70 K and 145 K in layered compound EuCu_(4)As_(2)and SrCu_(4)As_(2),respectively.from both the transport and heat capacity.The thermal expansion measurements show that the variation of the lattice parameters(△L_(b)/L_(ab))around T_(P) is much less than that for a typical crystalline phase transition.Our experimental results reveal that the transition in EuCu_(4)As_(2)and SrCu_(4)As_(2)should be driven by subtle structural-distortion.

Computation of Stiffness and Damping Derivatives of an Ogive in a Limiting Case of Mach Number and Specific Heat Ratio

This work aims to compute stability derivatives in the Newtonian limit in pitch when the Mach number tends to infinity.In such conditions,these stability derivatives depend on the Ogive’s shape and not the Mach number.Generally,the Mach number independence principle becomes effective from M=10 and above.The Ogive nose is obtained through a circular arc on the cone surface.Accordingly,the following arc slopes are consideredλ=5,10,15,−5,−10,and−15.It is found that the stability derivatives decrease due to the growth inλfrom 5 to 15 and vice versa.Forλ=5 and 10,the damping derivative declines with an increase inλfrom 5 to 10.Yet,for the damping derivatives,the minimum location remains at a pivot position,h=0.75 for large values ofλ.Hence,whenλ=−15,the damping derivatives are independent of the cone angles for most pivot positions except in the early twenty percent of the leading edge.

Specific Heat Capacity of A2FeCoO6-δ (A = Ca or Sr)

A2FeCoO6-δ (A = Ca or Sr) is synthesized by the solid-state synthesis method and their specific heat capacities are evaluated at 40˚C using a heat flow meter. The effect of the A-cation size on the specific heat capacity of these compounds is observed. The specific heat capacity of Sr2FeCoO6-δ is found to be the highest, and that of Ca2FeCoO6-δ is the lowest while CaSrFeCoO6-δ shows the intermediate value. The specific heat capacity decreases with the decrease of the average A-site ionic radius, demonstrating the relationship between heat capacity and A-site ionic radius. The relationship between specific heat capacity and molar mass is also confirmed as the δ value decreases or molar mass increases from Ca2FeCoO6-δ to CaSrFeCoO6-δ to Sr2FeCoO6-δ.

Effects of crystallization on low-temperature specific heat capacity of Cu_(60)Zr_(20)Hf_(10)Ti_(10) bulk metallic glass

The specific heat capacities of Cu60Zr20Hfl0Til0 bulk metallic glass （BMG） and crystallized alloys were measured from 2 to 101 K. The effect of crystallization on the specific heat capacity of the BMG was studied. The effects of crystallization and the relationship between local modes and boson peak in the BMG were discussed. The specific heat capacity deviates from the simple Debye behaviors, showing the presence of local harmonic modes （Einstein oscillator） in the BMG and the crystallized alloy. Model calculation includes the contribution of one Debye mode and two Einstein modes for the BMG, one Debye mode and one Einstein mode for the crystallized alloy, showing an adequate description of the experimental data.

Exploration of regional surface average heat flow from meteorological and geothermal series

We attempt to compute the Surface Average Heat Flow （SAHF） from long-term temperature observations of one hundred seventy-seven observational points at the depths of 0.8, 1.6, and 3.2 m, which were relatively evenly distributed in China's Mainland. We first employ Fourier transformation to remove the influence of atmospheric temperature variations from the observation series, which are classified into the type of the steady-state temperature monotonously increasing with depth （type I） and other three types. Then we compare our results obtained from the data of type I, of which the values are thought to equal to those of the mean borehole heat flow, with those obtained from traditional heat flow observations mainly distributed in North China Craton. In computations of the SAHF at the observation stations, we deduce the thermal diffusivity and volumetric specific heat of the soil by employing harmonic solutions of the heat conduction equation for the same moisture group as the first step, and then we determine the SAHF using Fourier＇s law. Our results indicate that the SAHF derived from shallow earth geothermal data can reflect the heat flow field to a large extent.

Reconsideration on the role of the specific heat ratio in Arrhenius law applications

Arrhenius law implicates that only those molecules which possess the internal energy greater than the activation energy Ea can react. However, the internal energy will not be proportional to the gas temperature if the specific heat ratio y and the gas constant R vary during chemical reaction processes. The varying y may affect significantly the chemical reaction rate calculated with the Arrhenius law under the constant γ assumption, which has been widely accepted in detonation and combustion simulations for many years. In this paper, the roles of variable γ and R in Arrhenius law applications are reconsidered, and their effects on the chemical reaction rate are demonstrated by simulating one- dimensional C-J and two-dimensional cellular detonations. A new overall one-step detonation model with variable γ and R is proposed to improve the Arrhenius law. Numerical experiments demonstrate that this improved Arrhenius law works well in predicting detonation phenomena with the numerical results being in good agreement with experimental data.

A LATTICE BOLTZMANN MODEL FOR COMPRESSIBLE PERFECT GAS

A new lattice Boltzmann model for compressible perfect gas is proposed. The numerical example shows that it can be used to simulate shock wave and contact discontinuity. The results are comparable with those obtained by traditional methods. The ratio of specific heats gamma may be chosen according to the requirement of problems.

A New Model for the Characterization of Frozen Soil and Related Latent Heat Effects for the Improvement of Ground Freezing Techniques and Its Experimental Verification

The correct determination of thermal parameters,such as thermal conductivity and specific heat of soil during freezing,is the most important and basic problem for the construction of an appropriate freezing method.In this study,a calculation model of three stages of soil temperature was established.At the unfrozen and frozen stages,the specific temperatures of dry soil,water,and ice are known.According to the principle of superposition,a calculation model of unfrozen and frozen soils can be established.Informed by a laboratory experiment,the latent heat of the adjacent zone was calculated for the freezing stage based on different water contents in the temperature section.Both the latent and specific heat of water,ice,and particles were calculated via superposition of the weight percentage content.A calculation model of the specific heat of the freezing stage was built,which provides both guidance and theoretical basis for the calculation of the specific heat of frozen soil.

Synthesis,Crystal Structure and Thermal Analysis of N-(2,3-Dimethyl-phenyl)-N'-(methoxyl formyl)thiourea

N-（2,3-Dimethyl-phenyl）-N＇-（methoxyl formyl）thiourea was synthesized by the reacting of 2,3-dimethylaniline,potassium thiocyanate（KSCN） and methyl chloroformate（ClCOOCH 3）.Single crystal was obtained by slowly evaporation solvent at room temperature.The structure was characterized by elemental analysis,IR and X-ray crystalography.The compound crystallized：a triclinic system with space group Pī,a=0.83440（12） nm,b=0.89113（13） nm,c=0.93015（13） nm,α=76.548（2） o,β=63.906（2） o,γ=82.538（2） o,V=0.60379（15） nm 3,Z=2,D c =1.311 mg/m 3,F（000）=252,μ=0.256 mm-1,R 1 =0.0379,wR 2 =0.0919.The specific heat capacity of the title compound was determined by a Micro-DSC method,and the specific heat capacity was 1.25 J·g-1 ·K-1 at 298.15 K.Thermodynamic functions,relative to those at the standard temperature of 298.15 K,were calculated via thermodynamic relationship.The thermal behavior of the title compound under a non-isothermal condition was studied by differential scanning calorimetry/thermogravimetric（DSC/TG） method.There was an obvious endothermic peak in the DSC curve,the peak temperature was 479.43 K.The compound mass loss was 89.94% observed from the TG curve.

Magnetocaloric and magnetic properties of La_2NiMnO_6 double perovskite

The magnetic effect and the magnetocaloric effect in La_2NiMnO_6（LNMO） double perovskite are studied using the Monte Carlo simulations.The magnetizations,specific heat values,and magnetic entropies are obtained for different exchange interactions and external magnetic fields.The adiabatic temperature is obtained.The transition temperature is deduced.The relative cooling power is established with a fixed value of exchange interaction.According to the master curve behaviors for the temperature dependence of △S_m^（max） predicted for different maximum fields,in this work it is confirmed that the paramagnetic-ferromagnetic phase transition observed for our sample is of a second order.The near room-temperature interaction and the superexchange interaction between Ni and Mn are shown to be due to the ferromagnetism of LNMO.

The effects of variable specific heat on the stability of hypersonic boundary layer on a flat plate

The gas temperature within hypersonic boundary layer flow is so high that the specific heat of gas is no longer a constant but relates to temperature. How variable specific heat influences on boundary layer flow stability is worth researching. The effect of the variable specific heat on the stability of hypersonic boundary layer flows is studied and compared with the case of constant specific heat based on the linear stability theory. It is found that the variable specific heat indeed has some effects on the neutral curves of both the first-mode and the second-mode waves and on the maximum rate of growth also. Therefore, the relationship between specific heat and temperature should be considered in the study of the stability of the boundary layer.

Specific Heat and Charge Density of Quasi-One-Dimensional Interchain Coupling Organic Ferromagnets

On the basis of a generalized SSH model, an organic polymer ferromagnet theory is proposed at the finite temperature in the self-consistent mean field approximation, and the specific heat and charge density of the quasione-dimensional interehain coupling organic ferromagnets are presented. We find that an obvious feature is to present itself the round peak for the specific heat with the temperature. This indicates unambiguously the presence of the phase transition in the system. The transition temperature plays down with increasing of the interchain coupling t2 or decreasing of the electron repulsion u. The curves of charge density with the temperature debase monotonously. This result illustrates that the higher the temperature is, the more electrons are excited.

Determination of Thermal Properties of Cuts and Residue Streams Obtained in the Molecular Distillation Process

A real-time sensing of the molecular distillation process temperature by a FLUKE brand thermograph Ti50 IR FlexCam and thermography technique was realized. After completion of the molecular distillation, three properties of heat transport chain cuts and residues obtained in the process were estimated by Differential Scanning Calorimetry （DSC） （specific heat, enthalpy, thermal conductivity）. These properties are of great importance for improving oil characterization and for future modeling and simulation of the molecular distillation process. The results show that through the method of Differential Scanning Calorimetry, profiles have been obtained from the variation of specific heat, enthalpy and thermal condutivity as a function of temperature for samples of cuts from the distillation （ASTM D-2892） and fractions of distillate and residue from the process of molecular distillation.

Thermal conductivity of Al-Gd-TM glass-forming alloys

Thermal diffusivity, specific heat capacity and thermal conductivity of AI86Gd6TM8 （TM = Cu, Ni, Co, Fe, Mn, Cr, Ti, Zr, Mo, Ta） glass-forming alloys in the temperature range of 300-880 K were determined by laser flash method. The temperatures of endothermic and exothermic reactions of the alloys were determined by differential scanning calorimetry method. The alloys were prepared by conventional arc-melting technique under helium atmosphere. All the alloys studied exhibit strong supercooling of the liquidus temperatures up to 80 K, which indicates their good glass-forming ability. The specific heat capacity of the alloys achieves the Dulong-Petit＇s value in the temperature range of 350-550 K except Als6CrsGd6 and Als6ZrsGd6 compositions. The values of both thermal diffusivity and thermal conductivity of the alloy studied are significantly lower than those for pure aluminum. It is found that embedding 14% （mole fraction） of transition elements （Gd＋TM） in the aluminum matrix leads to significant decrease in the absolute magnitudes of both thermal diffusivity and thermal conductivity in crystalline state. The thermal conductivity of glass-forming Als6Gd6TMs alloys is strongly affected by directed chemical bonding between alloy components.

Investigation on specific heat capacity and thermal behavior of sodium hydroxyethyl sulfonate

The thermal decomposition process was studied by the TG–DTA analyzer. The results show that the decomposition process of sodium hydroxyethyl sulfonate consisted of three stages: the mass loss for the first, the second and third stages may be about the groups of CH_3CH_2OH, CH_3CHO and SO_2 volatilized, respectively. The decomposition residuum of three stages was analyzed by FT-IR, and the results of FT-IR agreed with the decomposition process predicted by theoretical weight loss. The specific heat capacity of sodium hydroxyethyl sulfonate was determined by differential scanning calorimetry(DSC). The melting temperature and melting enthalpy were obtained to be 465.41 K and 25.69 kJ·mol^(-1), respectively. The molar specific heat capacity of sodium hydroxyethyl sulfonate was determinated from 310.15 K to 365.15 K and expressed as a function of temperature.

Thermal properties of single-walled carbon nanotube crystal

In this work, the thermal properties of a single-walled carbon nanotube （SWCNT） crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak （658 W/mK） is found at a temperature of about 100.0 K. The thermal conductivity decreases gradually to a value of 480 W/mK and keeps almost a constant in the temperature range from 100.0 K to 300.0 K. Meanwhile, the specific heat shows an obvious linear relationship with temperature in the temperature range from 1.9 K to 300.0 K. We discuss the possible mechanisms for these unique thermal properties of the single-walled carbon nanotube crystal.