Thermodynamic properties of refrigerants R11, R12, R13, R14, R22, R23, R113, R114, R500 and R502

The publication presents a set of equations and constants for calculating thermodynamic properties of refrigerants. State equation, equation of saturated vapor pressure, equation of liquid volume, equation of specific heat capacity, enthalpy and entropy for R11, R12, R13, R14, R22, R23, R113, R114, R500 and R502 are presented. High accuracy of results was achieved in comparing with ASHRAE tables. All equations are in SI units.     

Flow condensing heat transfer of R410A,R22, and R32 inside a micro-fin tube

An experimental study of condensation heat transfer characteristics of flow inside horizontal micro-fin tubes is carried out using R410A, R22, and R32 as the test fluids. This study especially focuses on the influence of heat transfer area upon the condensation heat transfer coefficients. The test sections were made of double tubes using the counter-flow type; the refrigerants condensation inside the test tube enabled heat to exchange with cooling water that flows from the annular side. The saturation temperature and pressure of the refrigerants were measured at the inlet and outlet of the test sections to defined state of refrigerants, and the surface temperatures of the tube were measured. A differential pressure transducer directly measured the pressure drops in the test section. The heat transfer coefficients and pressure drops were calculated using the experimental data. The condensation heat transfer coefficient was measured at the saturation temperature of 48°C with mass fluxes of 50–380 kg/(m²s) and heat fluxes of 3–12 kW/m². The values of experimental heat transfer coefficient results are compared with the predicted values from the existing correlations in the literature, and a new condensation heat transfer coefficient correlation is proposed.     

Supergravity,R invariance and spontaneous supersymmetry breaking

We show that in order for a U(1) gauge theory with a Fayet-Illiopoulos term to be consistently coupled to supergravity, preserving gauge invariance, the superpotential must be R invariant. A supersymmetric cosmological term and therefore an explicit mass-like term for the gravitino is forbidden by gauge invariance. This result severely constrains the possible models for non-gravitational interactions. We comment on possible mass term the gauginos induced by gravitational effects.     

Solitons and SL(2, R)

The known relationship between non-linear partial differential equations which have soliton solutions, and SL (2, R), is developed to the point where it provides a framework for discussing Bäcklund transformations, and equations for the inverse scattering method.     

Electronic structure and magnetism of R(Fe,Si)12 (R = Y, Nd)

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)12 compounds (R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic moments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total magnetic moments of RFe10Si2 (R = Y, Nd) are larger than those of RFe10M2 (M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the magnetic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduction of Si atoms according to spin fluctuation of DOS at Fermi level.     

Magnetic phase diagrams of R2RhIn8 (R = Tb, Dy, Ho, Er and Tm) compounds

We have grown and characterized single crystals of R(2)RhIn(8) (R=Tb, Dy, Ho, Er and Tm) compounds crystallizing in the tetragonal Ho(2)CoGa(8)-type crystal structure. Their magnetic properties were studied by specific heat and magnetization measurements. All the investigated compounds order antiferromagnetically with Néel temperatures of 43.6, 25.1, 10.9, 3.8 and 4.1 K, respectively. Magnetic phase diagrams were constructed.     

Thermal vibrations and the structure of quasi-two-dimensional R 2CuO4 crystals (R=La, Pr, Nd, Sm, Eu, and Gd)

Thermal vibrations of ions in R ₂CuO₄ crystals (R=La, Pr, Nd, Sm, Eu, Gd) were studied by x-ray diffractometry. A comparative analysis of thermal displacements of the copper and rare-earth ions permitted a conclusion as to the main interactions responsible for the structural state of the CuO₂ sheets and of a crystal as a whole. The structural properties were found to correlate with the magnitude of the ionic radius and with the ground state of the rare-earth ions.     

Spontaneous magnetostriction in R2Fe14B (R=Y,Nd, Gd,Tb, Er)

Thermal expansion anomalies of R₂Fe₁₄B (R=Y, Nd, Gd, Tb, Er) stoichiometric compounds were studied by X-ray diffraction with high-energy synchrotron radiation using a Debye–Scherrer geometry in temperature range of ∼10–1000 K. A large invar effect with a corresponding large temperature dependence of lattice parameters ∼10–15 K above their Curie temperatures (T_c) are observed. The a-axes show a larger invar effect than the c-axes in all compounds. The spontaneous magnetostrain of the lattices and bonds are calculated. The iron sublattice is shown to dominate the volumetric spontaneous magnetostriction of the compounds and the contribution from the rare-earth sublattice is roughly proportional to the spin magnetic moment of the rare earths. The bond-length changes are consistent with the theoretical spin-density calculation. The average bonds magnetostrain around Fe sites is approximately proportional to their magnetic moments.     

Dative versus electron-sharing bonding in N-imides and phosphane imides R3ENX and relative energies of the R2EN(X)R isomers (E = N,P; R = H,Cl, Me,Ph; X = H,F, Cl)*

ABSTRACT

Quantum chemical calculations using density functional theory BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have been carried out on the title molecules. The calculation results reveal that the N-imides R₃NNX are always clearly higher in energy than the imine isomers R₂NN(X)R. In the case of phosphane imides R₃PNX and the isomers R₂PN(X)R, the substituent R plays a critical role in determining their relative stabilities. When R is hydrogen or phenyl group, R₃PNX are always higher in energy than R₂PN(X)R but the former are more stable than the latter when R = Cl. Interestingly, the Me₃PNX and Me₂PN(X)Me are quite close in energy. The energy decomposition analysis suggests that the P–N bond in the phosphane imides R₃PNX (R = H, Cl, Me, Ph; X = H, F, Cl) should be described in terms of an electron-sharing single bond between two charged fragments R₃P⁺-NX^? that is supported by (R₃P)⁺←(NX)^? π-backdonation. The π-bond contributes 14–21% of the total orbital interactions while the σ-bond provides 60–68% of ΔE_orb.