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.

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.

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.

Utilization of Machine Learning Methods in Modeling Specific Heat Capacity of Nanofluids

Nanofluids are extensively applied in various heat transfer mediums for improving their heat transfer characteristics and hence their performance.Specific heat capacity of nanofluids,as one of the thermophysical properties,performs principal role in heat transfer of thermal mediums utilizing nanofluids.In this regard,different studies have been carried out to investigate the influential factors on nanofluids specific heat.Moreover,several regression models based on correlations or artificial intelligence have been developed for forecasting this property of nanofluids.In the current review paper,influential parameters on the specific heat capacity of nanofluids are introduced.Afterwards,the proposed models for their forecasting and modeling are proposed.According to the reviewed works,concentration and properties of solid structures in addition to temperature affect specific heat capacity to large extent and must be considered as inputs for the models.Moreover,by using other effective factors,the accuracy and comprehensive of the models can be modified.Finally,some suggestions are offered for the upcoming works in the relevant topics.

Specific heat of superheated Al-10Sr alloy melts

The specific heat of superheated Al 10Sr melts was determined at different heating rates between 1 K/min and 20 K/min using a differential scanning calorimeter(DSC). As a whole, the specific heat increases with increasing temperature. A hump is observed on the specific heat curve at the temperature corresponding to the phase boundary temperature dependent on heating rate. Moreover, the hump shifts to higher temperature in the measured temperature range from about 840 ℃ to 890 ℃ with increasing heating rate. At certain temperature in the higher superheated zone, the specific heat of the melt as a function of temperature shows a sharp rise . The result indicates that disorder zone fraction begins to increase while atom clusters fraction decreases at the breaking temperature. [

Specific Heat of a Unitary Fermi Gas Including Particle-Hole Fluctuation

We investigate the particle-hole fluctuation correction to the specific heat of an ultracold Fermi gas at unitarity within the framework of the non-self-consistent T-matrix approximation in the normal phase. We find good agreement between our theoretical predictions and the experimental data measured by the MIT group, apart from discrepancies near the transition temperature. At high temperature, our calculated specific heat has the tendency to approach the specific heat of the Boltzmann gas.

Specific heat of the non-centrosymmetric superconductor Re_3 W

The alloys of non-centrosymmetric superconductor, Re3W, which were reported to have an ^-Mn structure [P. Greenfield and P. A. Beck, J. Metals, N. Y. 8, 265 （1959）] with Tc = 9K, are prepared by arc melting. The values of ac susceptibility and the low-temperature specific heat of these alloys are measured. It is found that there are two superconducting phases coexisting in the samples with Tc1 ≈ 9 K and Tc2 ≈ 7K, which are both non-centrosymmetric in structure as reported previously. By analysing the specific heat data measured in various magnetic fields down to a temperature of 1.8 K, we find that the absence of the inversion symmetry does not lead to an obvious deviation from an s-wave pairing symmetry in Re3W.

Thermal Behavior, Specific Heat Capacity and Adiabatic Time-to-explosion of GDN

A new compound, [（NH2）2C=NH2]＋N（NO2）2-（GDN）, was prepared by mixing ammonium dinitramide （ADN） and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy（E） and pre-exponential constant（A） of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion（Tb） of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.

Prediction of hypersonic boundary layer transition on sharp wedge flow considering variable specific heat

When the air temperature reaches 600 K or higher, vibration is excited. The specific heat is not a constant but a function of temperature. Under this condition, the transition position of hypersonic sharp wedge boundary layer is predicted by using the improved eN method considering variable specific heat. The transition positions with different Mach numbers of oncoming flow, half wedge angles, and wall conditions are computed condition, the nearer to the Mach number The results show that for the same oncoming flow condition and wall transition positions of hypersonic sharp wedge boundary layer move much leading edge than those of the flat plate. The greater the oncoming flow the closer the transition position to the leading edge.

Theory of specific heat of vortex liquid of high T_c superconductors

Superconducting thermal fluctuation(STF) plays an important role in both thermodynamic and transport properties in the vortex liquid phase of high Tsuperconductors.It was widely observed in the vicinity of the critical transition temperature.In the framework of Ginz burg-Landau-La wrence-Doniach theory in magnetic field,a self-consistent analysis of STF including all Landau levels is given.Besides that,we calculate the contribution of STF to specific heat in vortex liquid phase for high Tcuprate superconductors,and the fitting results are in good agreement with experimental data.

Quasiparticle density of states of 2H-NbSe_2 single crystals revealed by low-temperature specific heat measurements according to a two-component model

Low-temperature specific heat in a dichalcogenide superconductor 2H-NbSe2 is measured in various magnetic fields. It is found that the specific heat can be described very well by a simple model concerning two components corresponding to vortex normal core and ambient superconducting region, separately. For calculating the specific heat outside the vortex core region, we use the Bardeen-Cooper Schrieffer （BCS） formalism under the assumption of a narrow distribution of the superconducting gaps. The field-dependent vortex core size in the mixed state of 2H-NbSe2, determined by using this model, can explain the nonlinear field dependence of specific heat coefficient γ（H）, which is in good agreement with the previous experimental results and more formal calculations. With the high-temperature specific heat data, we can find that, in the multi-band superconductor 2H-NbSe2, the recovered density of states （or Fermi surface） below Tc under a magnetic field seems not to be gapped again by the charge density wave （CDW） gap, which suggests that the superconducting gap and the CDW gap may open on different Fermi surface sheets.

Specific heat in superconductors

Specific heat is a powerful tool to investigate the physical properties of condensed materials.Superconducting state is achieved through the condensation of paired electrons,namely,the Cooper pairs.The condensed Cooper pairs have lower entropy compared with that of electrons in normal metal,thus specific heat is very useful in detecting the low lying quasiparticle excitations of the superconducting condensate and the pairing symmetry of the superconducting gap.In this brief overview,we will give an introduction to the specific heat investigation of the physical properties of superconductors.We show the data obtained in cuprate and iron based superconductors to reveal the pairing symmetry of the order parameter.

A Study on the Specific Heat of the Lanthanide Oxides

In this paper,we report the measurements of the specific heat of the lanthanide oxides(La_2O_3,CeO_2, Pr_6O_(11),Nd_2O_3,Sm_2O_3,Eu_2O_3,Gd_2O_3,Tb_4O_7,Dy_2O_3,Ho_2O_3,Er_2O_3,Tm_2O_3,Yb_2O_3,Lu_2O_3)from-150℃ to 800℃ by using adiabatic scanning calorimeter.We found that chemical reactions occur during the heating pro- cess of initial La_2O_3 and Nd_2O_3 materials by using DTA and X-ray diffraction.The results of specific heat measurement show that except CeO_2 and Tb_4O_7,other twelve lanthanide oxides were accompanied with endothermal change and weight loss to a certain degree during the heating process.

Prediction of Thermal Conductivity and Specific Heat of Native Maize Starch and Comparison with HMT Treated Starch

Specific heat(Cp)and effective thermal conductivity(λ)of native maize starch(NS)were measured by DSC and transient heat transfer method,respectively,at different moisture contents and temperatures.The dependency of temperature(T)and moisture content(W)on the two parameters were investigated.The thermophysical properties of treated starch(TS)by four hydrothermal processes(RP-HMT,IV-HMT,DV-HMT and FV-HMT)were measured and compared to native strach.Hydrothermal treatments were performed at 3 bars(133°C)for 10 min.For Cp andλmeasurements,moisture content varied for NS from 5 to 21.5%d.b.and from 8.8 to 25%d.b.,respectively,and was fixed at 6%d.b.for TS.Empirical models were developed to specific heat and effective thermal conductivity,using a multiple regression algorithm with subsequent statistical analysis.The proposed models for NS based on T and W predict Cp andλwith a mean absolute error of 3.5%and 1.3%,respectively.Large differences in specific heat were observed between TS and NS.In a temperature range of 40 to 160°C,Cp values varied from 1.964 to 2.699 for NS and 1.380 to 2.085(J.g-1.°C-1)for TS.In contrast,the conductivity of NS was almost identical to that of treated starch by FV-HMT,followed in an increasing order by those treated by DV-HMT,RP-HMT,and IV-HM processes.

A Study of the Specific Heats of the Compounds in the Sm_2O_3-BaO-CuO System

By means of X-ray diffraction and adiabatic scanning calorimeter,the specific heats of five compounds in the Sm_2O_3-BaO--CuO system,such as Sm_2BaO_4,Sm_2CuO_4,BaCuO_4, Sm_2BaCuO_5,SmBa_2Cu_3O_(7-x),from -150℃ to 800℃ have been measured.It is found that the specific heats of these compounds increase smoothly with the increase of temperature.

Effects of anisotropy and magnetic fields on the specific heat of a quasi-two-dimensional Boltzmann gas in an elliptical parabolic quantum dot

We investigate the effects due to anisotropy and magnetic field interaction for a quasi-two-dimensional Boltzmann gas in an elliptical parabolic quantum dot. The specific heat is studied with varying temperature, anisotropy, and magnetic field strength. The cases without and with the inclusion of the spin Zeeman interaction are considered.

A Calorimetric Study Assisted with First Principle Calculations of Specific Heat for Si-Ge Alloys within a Broad Temperature Range

Calorimetric measurements are performed to determine the specific heat of Si-xat.% Ge(where x = 0, 10, 30,50, 70, 90 and 100) alloys within a broad temperature range from 123 to 823 K. The measured specific heat increases dramatically at low temperatures, and the composition dependence of specific heat is evaluated from the experimental results. Meanwhile, the specific heat at constant volume, the thermal expansion, and the bulk modulus of Si and Ge are investigated by the first principle calculations combined with the quasiharmonic approximation. The negative thermal expansion is observed for both Si and Ge. Furthermore, the isobaric specific heat of Si and Ge is calculated correspondingly from OK to their melting points, which is verified by the measured results and accounts for the temperature dependence in a still boarder range.

Characteristic of specific heat capacity of NiTi alloy phases

The specific heat capacity of NiTi alloy at constant pressure using MDSC (Modulated differential scanning calorimeter) was determined. It was found that the variation tendencies of the specific heat capacity for different phases are different. The fitting equations of the specific heat capacity for martensite and austenite phases were presented. Then, a reason, based on thermodynamic point of view, was proposed to explain the difference of the specific heat capacity between martensitic and austenitic phases. Finally, compared with the specific heat capacity of pure Ni and Ti, it was found that the specific heat capacity of NiTi alloy is inherent to that of pure Ti. When the specific heat capacity of NiTi alloy is calculated by Neuman Kopp, in the temperature region of phase transformation and the temperature higher than 400 K, the results are not desirable.[

Fluctuating specific heat in two-band superconductors

Theory of thermal fluctuations in two-band superconductors under an essentially homogeneous magnetic field is developed within the framework of the two-band Ginzburg-Landau theory. The fluctuating specific heat is calculated by using the optimized self-consistent perturbation approach and the results are applied to analyze the thermodynamic data of the iron-based superconductors Ba（1-x）KxFe2As2 with x -0.4, which have been suggested to have a two-band structure by recent experiments. We estimate the fluctuation strength in this material and find that the specific heat is described well with the Ginzburg number Gi = 4 · 10^-4. The influence of interband coupling strength is investigated and the result of the two-band Gaussian approximation approach is compared.