Elasticity of the B2 phase and the effect of the B1–B2 phase transition on the elasticity of MgO

A study of the high-pressure anisotropy of MgO was conducted using first-principles calculations based on density functional theory within the generalized gradient approximations. The pressure dependence of the elastic stiffness coefficients and the anisotropy parameters, in both B1 and B2 phases, shows that for high-hydrostatic compression the easiest deformation is the shear along (100) plane and the the material's response to deformation and to shearing strains is quite the same. According to the calculations of the velocities of propagation of elastic waves, we deduced that MgO develop an elastic anisotropy, especially, in the B1 phase. We present the B2 phase elastic properties which are not already studied under high pressure.     

Experimental study of flight noise on AS350B2 helicopter

A joint flight experiment is conducted by China Aviation Establishment and German Aerospace Center on an Aerospatiale AS350B2 helicopter to investigate rotorcraft flight acoustics at Pingfang airport, Harbing City, China. This paper briefly introduces the methodologies and facilities used in the flight tests. The flight exposure noise levels for ten test flight conditions are showed in the paper and harmonic spectrum and wavelet analysis methods are used for the noise test data processing, which are measured in the flight test in taking off, climbing, forward and descent flight conditions. Results show that the flight noise levels are relatively higher in the climbing and descending flight conditions. The flight noise comes mainly from the tail rotor for the climbing and from the main rotor due to the blade vortex interaction (BVI) for the descending flight conditions. The highest noise level occurs in the forward rotating blade side when the helicopter flys at moderate speed with about 6° descending sl     

The influence of molecular structure of protein on the acoustic nonlinearity parameter B/A

I.IntroductionAcousticnonlinearityparameterB/Adescrjbesthenonlilleareffectsofasoundwavetrav-ellingthroughamedium.Withtheapplicationofhighmowerultrasonicwavetomedicine,thenonlineareffectsbecomemoreandmoreimportant.EspeciallybecauseB/Aissensitivetothepathologicalstateofbiologicaltissues[1-2])thisprovidesprospectiveapplicationinmedicaldiagnosis.Atpresent,thestudyinthisareaemphasizesontwoaspects.OneistodevelopnewmedicalimagingtechniquesbyusingthisnonlinearityparameterB/Al1'3-'];theotheristostu…     

Impacts of the Soft—Gluon Exchanges on B→ππ Decays

We have investigated the role of soft-gluon exchanges in B→ππ,using the light-cone sum rules in quantum chromodynamics,The calculations are carried out not only for the tree operators but also for the penguin operators.We conclude that soft-gluon exchanges contribute to the decay amplitudes,noticeably on some decay channels,and thus cannot be neglected.     

The effects of B/(B+A1) ratio on glass formation regions and properties of phosphate edge-cladding glasses

The glass-forming region of P2O5-Al2O3-B2O3-ZnO-Na2O-CuCl system with different Al2O3 and B2O3 contents was studied. The dependence of glasses properties on B/(B A1) ratio was investigated. The absorption coefficient of copper ion in a specific glass was measured. These results are very helpful to the designing of a cladding glass for large size neodymium phosphate glass.     

Effect of B2O3 on the structure and properties of tungsten–tellurite glasses

The elastic properties and Debye temperatures of xB₂O₃–70TeO₂–(30–x)WO₃, (0 ≤ x ≤ 30 mol%) glasses have been investigated using sound velocity measurements at 4 MHz. Ultrasonic and thermal parameters, combined with the results of IR spectroscopic analyses, were employed to explore the effect of B₂O₃ on the structure of tungsten–tellurite glasses. According to IR analysis, there is competition between WO₆ and TeO₄ units to form BO₄ units, and the vibrations of the tellurite structural units are shifted towards lower wavenumbers on the formation of non-bridging oxygens. It is assumed that B₂O₃ acts as a modifier by decreasing the glass-transition temperature T _g and increasing both the thermal stability and glass formation range of the tellurite glasses. The change in density and molar volume with B₂O₃ content reveals that the borate units are less dense than the tellurite structural units. The observed compositional dependence of elastic moduli is interpreted in terms of the effect of B₂O₃ on the coordination number of the tellurite units. A good correlation was observed between experimentally determined elastic moduli and those computed with the Makishima–Mackenzie model.     

Effect of annealing temperature on coercivity of Nd–Fe–B magnets with TbFeAl doping by process of hot-pressing

The Nd–Fe–B magnets are pre-sintered and then processed with hot-pressing, and the resulting magnets are called the hot-pressed pretreated(HPP) magnets. The coercivity of the HPP magnets increases as the annealed temperature increases.When the annealing temperature is 900℃, the coercivity of the magnet is only 17.6 kOe(1Oe = 79.5775 A·m~(-1)), but when the annealing temperature rises up to 1060℃, the coercivity of the magnet reaches 23.53 k Oe, which is remarkably increased by 33.7%. The microstructure analysis indicates that the grain surface of the HPP magnet becomes smoother as the annealed temperature increases. The microstructure factor α is changed according to the intrinsic coercivity model formula. The α of the magnet at 900℃ is only 0.578, but it is 0.825 at 1060℃. Microstructural optimization is due mainly to the increase of coercivity of the HPP magnet.     

The different influences of the two incorporation sites of B atoms on the mechanical and thermodynamic properties of B2–ZrCu compounds: a first-principle calculation

We applied a first-principle calculation to investigate the different influences of the two incorporation sites of B atoms on the mechanical and thermodynamic properties of the near-equiatomic B2–ZrCu compound. The alloying B atoms have two possible incorporation sites, namely, octahedral interstices and Cu sites. When the concentration of B atoms is lower than 5.882 at.%, interstitial B atoms will be effective at improving the bulk modulus (B), shear modulus (G) and Young’s modulus (E) of the B2–ZrCu parent. When the concentration of the substitutional B atoms is lower than 12.5 at.%, the ductility of the parent will be strengthened. The interstitial B atoms that are located at octahedral interstices in the 〈110〉 direction can remarkably improve the Debye temperature (Θ_D) of the substituted Zr₈Cu_8?zB_z phase. The prediction for the melting point shows that the high-temperature stability is strengthened with the increase of the B concentration. Interstitial B atoms are beneficial to the minimum thermal conductivity. Finally, the electronic properties are discussed in detail to further understand the mechanical properties.     

Effects of 8B size on the low-energy 7Be(p,γ)8B cross section

We calculate several “size-like” ⁸B observables within the microscopic three-cluster model and study their potential constraints on the zero-energy astrophysical S₁₇(0) factor of the ⁷Be(p,γ)⁸B reaction. We find within our three-cluster model that a simultaneous reproduction of the experimental data for the ⁸B radius and quadrupole moment and of the ⁸B⁸Li Coulomb displacement energy implies S₁₇(0) = (23–25) eV b.     

Numerical study of influence of J×B force on melt layer under conditions relevant to ITER ELMs

The influence of the J×B force on the topographical modification of W targets during a type-I-like ELM in ITER has been studied numerically. A two-dimensional(2D) fluid dynamics model is employed by solving liquid hydrodynamic Navier-Stokes equation with the 2D heat conduction equation in addition to driving forces for surface topography, such as surface tension and pressure gradient, the J×B force is particularly addressed. The governing equations are solved with the finite volume method by adequate prediction of the moving solid-liquid interface. Numerical simulations are carried out for a range of type-I ELM characteristic parameters. Our results indicate that both the surface tension and the J×B force contributes to the melt motion of tungsten plates when the energy flux is under 3000 MW·m~(-2), the surface tension is a major driving force while the pressure gradient is negligible. Our results also indicate that the J×B force makes the small hills grow at different rates at both the crater edges under a type-I-like ELM heat load with a Gaussian power density profile.     

Effect of Co on the thermal stability and impact toughness of sintered Nd–Fe–B magnets

The effect of Co on the thermal stability and impact toughness of sintered Nd–Fe–B magnets has been investigated. The results showed that the addition of Co decreased the intrinsic coercivity and the temperature coefficient of remanence (α), and increased the temperature coefficient of coercivity (β) for sintered Nd–Fe–B magnets. The impact toughness of sintered Nd–Fe–B magnets with the addition of Co first decreases, reaches a minimum, and then starts to increase. The possible reasons for increasing the temperature coefficients of coercivity (β) for sintered Nd–Fe–B magnets were analyzed, and the relations between the microstructure and impact toughness of sintered Nd–Fe–B magnets were studied.     

A note on the origin of secondary hypernuclear γ-quanta from Λ 10 B

An alternative interpretation of _Λ ¹⁰ B secondaryγ-quanta due to _Λ ¹⁰ B → _Λ ⁷ Li+³He channel is proposed. Its impact on effectiveΛN interaction properties and on understanding of (s ^?1 s _Λ) configurations is discussed and some verifying experiments are put forward.     

Influence of Inhomogeneity on Critical Behavior of Earthquake Model on Random Graph

We consider the earthquake model on a random graph. A detailed analysis of the probability distribution of the size of the avalanches will be given. The model with different inhomogeneities is studied in order to compare the critical behavior of different systems. The results indicate that with the increase of the inhomogeneities, the avalanche exponents reduce, i.e., the different numbers of defects cause different critical behaviors of the system. This is virtually ascribed to the dynamical perturbation.     

Effect of optimized aging processing on properties of the sintered Dy-doped Nd–Fe–B permanent magnet

We investigate the effect of the optimized aging processing on magnetism and mechanical property of the sintered Dydoped Nd–Fe–B permanent magnet. The experimental results show that the magnetism, especially intrinsic coercivity, of the optimized aged Dy-doped Nd–Fe–B magnet is more excellent than that of the sintered one, but the former's strength and hardness are lower than that of the latter. It was observed that the optimized aged Dy-doped Nd–Fe–B magnet have more uniform grain size, thinner(Nd, Dy)-rich boundary phase. By means of the EBSD technology, the number of larger angle grain boundaries in the optimized aged Dy-doped Nd–Fe–B magnet is more than that of the sintered one. The reasons for the increased intrinsic coercivity and decreased mechanical properties of the optimized aged Dy-doped Nd–Fe–B magnet are also discussed.     

Effect of composition on properties of reactive Al·B·I2 powders prepared by mechanical milling

Metal-based fuels producing halogen-containing combustion products are being developed to enable rapid inactivation of harmful aerosolized spores and bacteria. Ternary reactive materials containing aluminum, boron, and iodine were prepared by mechanical milling with systematically varied Al:B ratio. The aluminum mass fraction varied from 0% to 70%, and most materials included 20 wt% of iodine. Prepared powders were inspected by electron microscopy; particle size distributions were measured using low angle laser light scattering. Stability of materials was studied using thermo-gravimetry and differential scanning calorimetry. As-prepared as well as pre-heated and quenched samples were analyzed using x-ray diffraction. Iodine was released upon heating in several stages. Low-temperature iodine release was relatively small. It overlapped with decomposition of B(OH)₃ releasing water. The most significant amounts of iodine were released when the samples were heated to 400–500 °C, when AlB₂ formed. Both AlB₂ formation and iodine release were further accelerated by melting of aluminum. For the boron-rich samples, in which boron remained after all aluminum was used to form AlB₂, an additional, high-temperature iodine release stage was observed near 900 °C. The results show that both boron and aluminum are capable of stabilizing substantial quantities of iodine in the metal matrix. The iodine is released at temperatures much greater than its boiling point. The mechanism by which iodine is retained in boron and aluminum remains unclear.     

Effect of B2O3 on Judd—Ofelt parameters of Er^3＋—doped tellurite glasses

We have prepared Er^3 -doped borotellurite glasses using conventional melting and quenching method.The absorption spectrum analysis is performed on the basis of Judd-Ofelt theory.The effects of B2O3 on the spectroscopic parameters such as intersity parameters,line strengths of electric-dipole transitions,and sopontaneous emission probability are discussed.     

Effects of ⅢB transition metals on optoelectronic and magnetic properties of HoMnO_3: A first principles study

The optoelectronic and magnetic properties of pure Ho Mn O3 and Ho0.67T0.33 Mn O3(T = La, Y) alloys in hexagonal phase are theoretically investigated by using the first-principles calculations. The investigations are performed by means of the density functional theory through using the spin polarized generalized gradient approximation plus the Hubbard potential(SPGGA + U, U eff= 3 eV). The studied material Ho MnO3 exhibits two indirect band gaps: 1.58 eV for the spinup state and 0.72 eV for the spin-down state along the S–G direction within the SPGGA + U approximation. It is found that the band gap of pure Ho Mn O3 for the spin-up state increases with increasing La and Y dopants. The results show that all of the studied materials have semi-metallic behaviors for the spin-up state and semiconducting character for the spin-down state. The substitutions of La and Y for Ho in Ho MnO3 cause the static dielectric constant(ε0) to increase in the x direction but to decrease in the z direction. The calculated optical conductivity spectrum of Ho MnO3 in a low energy range is in good agreement with the recent experimental data.     

Analysis and Correction of Diffraction Effect on the B／A Measurement at High Frequencies

A numerical method is developed to analyse and to correct the diffraction effect in the measurement of acoustic nonlinearity parameter B/A at high frequencies. By using the KZK nonlinear equation and the superposition approach of Gaussian beams, an analytical model is derived to describe the second harmonic generation through multi-layer medium SiO2/liquid specimen/SiO2. Frequency dependence of the nonlinear characterization curve for water in 110-155 MHz is numerically and experimentally investigated. With the measured dip position and the new modal, values of B/A for water are evaluated. The results show that the present method can effectively correct the diffraction effect in the measurement.     

Texture in NdFeB magnets analysed on the basis of the determination of Nd2Fe14B single crystals easy growth axis

We have shown by X-ray analysis and magnetic measurements, that the easy growth axis of Nd₂Fe₁₄B crystals corresponds to the “a” axis of the tetragonal structure while the easy magnetization axis is the “c” axis at temperatures above 135K. This correlation allows to understand some interesting features in NdFeB magnets:

• •-anisotropic contraction during sintering in magnets obtained by classical powder metallurgy,
• •-orientation mechanism during hot pressing (“die upset”) of magnets based on melt spun ribons.