关于克劳修斯方法对可逆和不可逆过程(循环)的处理

介绍了克劳修斯方法对可逆和不可逆过程(循环)的处理,提出了处理不可逆过程的方法,论证了处理方法与克劳修斯方程的一致性,论述了克劳修斯方法的实质和意义;简单介绍了熵的另一个导出方法,比较了两种方法对绝热过程的处理,指出克劳修斯方法存在一个假设条件.     

轴对称非静态电荷电流分布轴外场的交替迭代

在轴对称非静态电荷电流分布的情况下,利用麦克斯韦方程组和轴对称性,给出了计算轴外电磁场的交替迭代法.     

Recent progress on RF superconducting cavities

RF superconducting (SRF) cavities can work in continuous wave mode or long pulse mode.SRF technology has been developing rapidly since the end of the last century.RF superconducting technology is widely used in particle accelerators around the world.As the key elements, research on superconducting cavities is carried out worldwide.Besides Europe, the United States and Japan, many countries have already started SRF projects, such as Canada, India, Korea, etc.Great improvements on SRF technology have been made in China in recent years.Progress in SRF cavities is introduced in this paper.     

一类Riccati矩阵方程广义自反解的双迭代算法

本文研究了一类Riccati矩阵方程广义自反解的数值计算问题.利用牛顿算法将Riccati矩阵方程的广义自反解问题转化为线性矩阵方程的广义自反解或者广义自反最小二乘解问题,再利用修正共轭梯度法计算后一问题,获得了求Riccati矩阵方程的广义自反解的双迭代算法.拓宽了求解非线性矩阵方程的迭代算法.数值算例表明双迭代算法是有效的.     

Spectral characterization of diffusion with chemical shift resolution: Highly concentrated water-in-oil emulsion

We present a modulated gradient spin-echo method, which uses a train of sinusoidally shaped gradient pulses separated by 180° radio-frequency (RF) pulses. The RF pulses efficiently refocus chemical shifts and de-phasing due to susceptibility differences, resulting in undistorted, high-resolution diffusion weighted spectra. This allows for the simultaneous spectral characterization of the diffusion of several molecular species with different chemical shifts. The technique is robust against susceptibility artifacts, field inhomogeneity and imperfections in the gradient generating equipment. The feasibility of the technique is demonstrated by measuring the diffusion of water, oil, and water-soluble salt in a highly concentrated water-in-oil emulsion. The diffusion of water and salt reveal precise information about the droplet size distribution below the μm-range. Common droplet size distribution explains both the data for water with finite long-range diffusion and the data for salt with negligible long-range diffusion. The results of water diffusion show that the technique is efficient in deconvolving the effects of molecular exchange between droplets and restricted diffusion within droplets. The effects of water exchange suggest that droplets of different sizes are uniformly distributed within the sample.     

T1 and T2 effects during radio-frequency pulses in spoiled gradient echo sequences

Finite pulse durations in diverse pulse schemes lead to the reduction of the magnitude of the magnetization vector due to T₁ and T₂ effects during the radio-frequency pulses. This paper presents an analysis of the steady state signal in the presence of relaxation effects during radio-frequency pulses in MRI spoiled gradient echo sequences. It is shown that minor attenuations of the magnetization vector can have dramatic consequences on the measured signal, and may thus entail a loss in SNR benefits at high static magnetic fields if a careful analysis is not performed. It is emphasized that it is the time-integrated magnetization vector trajectory that matters for these effects and not only the pulse duration. Some experimental results obtained on a phantom at 3 T verify this analysis.     

High-spin excitations of 81, 82, 83, 85Se : Competing single-particle and collective structures around N = 50

The ^{81, 82, 83, 85}Se nuclei have been produced as fission fragments in the fusion reaction ¹⁸O + ²⁰⁸Pb at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the triple -ray coincidence data and - angular correlations have been analyzed in order to assign spin and parity values to many observed states. The lowest-spin states of the two-neutron and three-neutron configurations are strongly mixed with two-proton excitations among the fp orbits. On the other hand, the highest-spin states of these neutron configurations are found to remain almost pure. Neutron excitation across the N = 50 gap is observed both in ⁸³Se₄₉ and in ⁸⁵Se₅₁ .     

Lattice chiral effective field theory with three-body interactions at next-to-next-to-leading order

We consider low-energy nucleons at next-to-next-to-leading order in lattice chiral effective field theory. Three-body interactions first appear at this order, and we discuss several methods for determining three-body interaction coefficients on the lattice. We compute the energy of the triton and low-energy neutron-deuteron scattering phase shifts in the spin-doublet and spin-quartet channels using Lüscher’s finite-volume method. In the four-nucleon system we calculate the energy of the -particle using auxiliary fields and projection Monte Carlo.     

Ab initio study of structural,electronic, and elastic properties of M<Subscript>2</Subscript>SbP (M = Ti,Zr, and Hf)

This study predicts the structural behaviour of selected M₂SbP compounds with the same structure as MAX phases. Zero pressure results of the lattice parameters, equilibrium volume, and the internal parameter Z_M are calculated with an error less than 3%. Band structure, total and partial density of states were calculated and show the metallic character of these phases. Moreover we observed strong hybridising states; M d–P p, and M d–Sb p. The pressure dependence of the volume, and the lattice parameters were studied. The stiffness of M–P, and M–Sb bonds was discussed in term of relative length change under hydrostatic pressure. Hf₂SbP present the highest bulk modulus and the unidirectional elastic modulus C₃₃ is slightly greater than C₁₁.     

Blackbody radiation shift of the Al<Superscript>+</Superscript> clock transition

The blackbody radiation shift of the Al⁺ 3s^{2 1}S^e ₀ ↦ 3s3p ³P^○ ₀ clock transition is evaluated. The polarizabilities of the two states are determined by means of configuration interaction calculations in conjunction with oscillator strength sum rules. The ground state polarizability was 24.14 ±0.12 a.u. while the metastable state polarizability was 24.62 ±0.25 a.u. The derived frequency shift at 300 K was Δν= -0.0042 ±0.0032 Hz. Some auxiliary sum rules are evaluated that allow for the conversion of a finite frequency polarizability difference to a static polarizability difference.