Nonperturbative Spontaneous Symmetry Breaking

A nonperturbative approach for spontaneous symmetry breaking is proposed. It is based on some conjectural properties of interacting field operators. As the consequences an additional terms like to m ² A ² appears in the initial Lagrangian.     

Topological Quantization of the Magnetic Flux

The quantization of the magnetic flux in superconducting rings is studied in the frame of a topological model of electromagnetism that gives a topological formulation of electric charge quantization. It turns out that the model also embodies a topological mechanism for the quantization of the magnetic flux with the same relation between the fundamental units of magnetic charge and flux as there is between the Dirac monopole and the fluxoid.     

Flux line lattice symmetries in the borocarbide superconductor LuNi2B2C

We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor LuNi₂B₂C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above 10 K the transition onset field. H ₂(T), rises sharply, bending away from H _c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H _tr=3–3.5 kOe. Below H _tr the FLL nearest neighbor direction is parallel to the b-axis, and above H _tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model.     

圆管管翅散热器肋侧主流方向绝对涡通量研究

本文以圆管管翅式散热器为研究对象,采用数值模拟的方法对圆管管翅式散热器肋侧空气通道主流方向绝对涡通量的特性进行了探讨。给出了肋侧空气通道主流方向绝对涡通量无量纲化参数,二次流雷诺数;横向管间距、肋侧空气流动雷诺数对二次流雷诺数及努塞尔数的影响。     

Embedding Spacetime via a Geodesically Equivalent Metric of Euclidean Signature

Starting from the equations of motion in a 1 + 1 static, diagonal, Lorentzian spacetime, such as the Schwarzschild radial line element, I find another metric, but with Euclidean signature, which produces the same geodesics x(t). This geodesically equivalent, or dual, metric can be embedded in ordinary Euclidean space. On the embedded surface freely falling particles move on the shortest path. Thus one can visualize how acceleration in a gravitational field is explained by particles moving freely in a curved spacetime. Freedom in the dual metric allows us to display, with substantial curvature, even the weak gravity of our earth. This may provide a nice pedagogical tool for elementary lectures on general relativity. I also study extensions of the dual metric scheme to higher dimensions.     

Numerical Investigation of Heat Transfer Characteristics of scCO2 Flowing in a Vertically-Upward Tube with High Mass Flux

In this work, the heat transfer characteristics of supercritical pressure CO₂ in vertical heating tube with 10 mm inner diameter under high mass flux were investigated by using an SST k-ω turbulent model. The influences of inlet temperature, heat flux, mass flux, buoyancy and flow acceleration on the heat transfer of supercritical pressure CO₂ were discussed. Our results show that the buoyancy and flow acceleration effect based on single phase fluid assumption fail to explain the current simulation results. Here, supercritical pseudo-boiling theory is introduced to deal with heat transfer of scCO₂. scCO₂ is treated to have a heterogeneous structure consisting of vapor-like fluid and liquid-like fluid. A physical model of scCO₂ heat transfer in vertical heating tube was established containing a gas-like layer near the wall and a liquid-like fluid layer. Detailed distribution of thermophysical properties and turbulence in radial direction show that scCO₂ heat transfer is greatly affected by the thickness of gas-like film, thermal properties of gas-like film and turbulent kinetic energy in the near-wall region. Buoyancy parameters Bu < 10⁻⁵, Bu* < 5.6 × 10⁻⁷ and flow acceleration parameter K_v < 3 × 10⁻⁶ in this paper, which indicate that buoyancy effect and flow acceleration effect has no influence on heat transfer of scCO₂ under high mass fluxes. This work successfully explains the heat transfer mechanism of supercritical fluid under high mass flux.     

圆管内自由固体相变材料定热流接触熔化

针对水平圆管内自由固体相变材料储能时的吸热熔化,运用接触熔化理论建立定热流圆管热源接触熔化模型.运用Nusselt液膜理论,建立熔化控制方程,并求解得到无量纲熔化方程组.分析讨论不同工况下熔化速度、液膜层厚度和压力分布等熔化参数的变化规律,探讨各影响因素对熔化的影响,并与温差熔化结果进行比较,研究第二类热边界条件下的接触熔化规律.发现,熔化过程中随着固体高度的减小,接触熔化液膜厚度逐渐增大,使熔化速度降低;热流密度较小时,其变化对熔化影响显著.     

Dendrite to symmetry-broken dendrite transition in directional solidification of non-axially oriented crystals

In this paper, the morphological transition from dendrite to symmetry-broken dendrite is investigated in the directional ;olidification of non-axially-oriented crystals using a quantitative phase-field model. The effects of pulling velocity and zrystal orientation on the morphological transition are investigated. The results indicate the orientation dependence of the ;ymmetry-broken double dendrites. A dendrite to symmetry-broken dendrite transition is found by varying the pulling telocity at different crystal orientations and the symmetry-broken multiple dendrites emerge as a transition state for the ;ymmetry-broken double dendrites. The state region during the transition can be well characterized through the variations ff the characteristic angle and the average primary dendritic spacing.     

An Exact Interior Solution of a Static Charged Sphere in Higher Dimensional Spacetime

By assuming "p = Aρ" and the total intrinsic energy density εr^k (k + D - 1 > 0), we strictly solve the higher dimensional Einstein-Maxwell field equations in a static charged sphere, resulting in an exact interior solution of the equations.     

Flux trapping in a macroscopic cylinderical hole drilled in Bi-Sr-Ca-Cu-O

The flux dynamics in a polycrystalline sample of Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O_x with a macroscopic cylindrical hole (CH) drilled was investigated by slow transport relaxation (V-t curves) and magnetovoltage measurements (V-H curves). It was monitored that there are several discontinuities in the time evolution of quenched state in V-t curves, which was attributed to the leaving of quantized flux lines trapped through CH together with surface superconducting effects. We observed that asymmetric V-H curves demonstrate unusual remarkable counter clockwise hysteresis effects upon cycling of field. This interesting result was correlated mainly to the flux trapping inside the CH that acts as a macroscopic attractive pinning center for flux lines. Further, the hysteresis effects in V-H curves for a fixed transport current provide a direct evidence that the number of flux lines, measured dissipation and relative decrease/increase in irreversibilities could be determined by sweeping rate of external magnetic field (dH/dt) which leads also to peculiar time effects.     

Role of electronic nematicity in the interplay between s- and d-wave broken-symmetry states

To understand the role of electronic nematic order in the interplay between s- and d-wave particle-particle or particle-hole condensate states, relations between various s- and d-wave order parameters are studied. We find that the nematic operator transforms two independent six-dimensional vectors. The d-wave superconducting, d-density wave, and antiferromagnetic orders are organized into one vector, and the s-wave superconducting, charge density wave, and spin-triplet d-density wave orders into the other vector. Each vector acts as a superspin and transforms under the action of SO(6) where charge, spin, η- and π-pairing, spin-triplet nematic operators satisfy the SO(6) Lie algebra. Electronic nematic order is not a part of the SO(6) group. It commutes with all 15 generators. Our findings imply that nematic order does not affect the competition among the order parameters within the same superspin, while it strongly interferes the interplay between two order parameters that belong to different superspins. For example, nematicity allows a linear coupling between d- and s-wave superconducting order parameters which modifies the superconducting transition temperature. A generalized Ginzburg-Landau theory and further physical implications are discussed.     

氧化物超导体的磁通动力学

考虑到氧化物高温超导体与传统超导体磁性质之间的不同之处，文章从不可逆线的解释，Ａｎｄｅｒｓｏｎ模型的一种修正方案以及对Ｓ－Ｔ关系曲线的解释等三个方面对高温超导体的磁通动力学行为作了简要的介绍。     

Gauged supergravities in various spacetime dimensions

In this review article we study the gaugings of extended supergravity theories in various space‐time dimensions. These theories describe the low‐energy limit of non‐trivial string compactifications. For each theory under consideration we review all possible gaugings that are compatible with supersymmetry. They are parameterized by the so‐called embedding tensor which is a group theoretical object that has to satisfy certain representation constraints. This embedding tensor determines all couplings in the gauged theory that are necessary to preserve gauge invariance and supersymmetry. The concept of the embedding tensor and the general structure of the gauged supergravities are explained in detail. The methods are then applied to the half‐maximal (N = 4) supergravities in d = 4 and d = 5 and to the maximal supergravities in d = 2 and d = 7. Examples of particular gaugings are given. Whenever possible, the higher‐dimensional origin of these theories is identified and it is shown how the compactification parameters like fluxes and torsion are contained in the embedding tensor.     

脉冲管制冷研究进展

简要介绍了脉冲管制冷机的产生和发展，特别是近年来取得的突破性进展，揭示了脉冲管制冷原理，并且指出了脉冲管制冷机的应用前景。     

Photo-Detached Electron Flux Distribution in a Gradient Electric Field

This paper investigates the flux distributions of the electron photo-detached from H-ion localized in a gradient electric field. In contrast with the photodetachment in the uniform electric field [Phys. Rev. A 40(1989) 4983],where only two electron trajectories interfere at each given point on a detector, for the photodetachment in a gradient electric field, the electrons waves can travel along multiple paths from the negative ion to a given point on the detector plane, which makes the electron flux distributions on the detector plane become much complex. Using the semi-classical theory, we put forward a formula for calculating the electron flux. Our calculation results suggest that the electron flux distributions on a given detector plane is not only related to the propagation time of the detached electron, but also related to the detached electron's energy. With the increase of the detached electron's energy, the oscillating region in the electron flux distributions becomes enlarged and the oscillating structure in the flux distributions becomes much more complicated. This study will guide future experiment research on the photodetachment microscopy of the negative ions in the presence of non-uniform external fields.     

Directed transport of coupled systems in symmetric periodic potentials

In this paper, we discuss the damped unidirectional motions of a coupled lattice in a periodic potential. Each particle in the lattice is subject to a time-periodic ac force. Our studies reveal that a directed transport process can be observed when the ac forces acting on the coupled lattice have a phase shift (mismatch). This directed motion is a collaboration of the coupling, the substrate potential, and the periodic force, which are all symmetric. The absence of any one of these three factors will not give rise to a directed current. We discuss the complex relations between the directed current and parameters in the system. Results in this paper can be accomplished in experiments. Moreover,our results can be generalized to the studies of directed transport processes in more complicated spatially extended systems.     

铁磁-d波超导结中的自旋极化隧道谱

考虑到铁磁层中准粒子输运的自旋极化效应以及 d波超导表面时间反演对称态的破缺效应 ,在 Blonder-Tinkham-Klapwijk散射理论框架下 ,研究铁磁 -d波超导隧道结中的隧道谱 ,所得结果能展示一些新奇特征 ,并能解释一些实验现象     

多级脉管制冷机的最新研究进展

介绍了最近几年来多级脉管制冷机 ,特别是液氦温区脉管制冷机研究与应用的进展情况 ,讨论了目前限制多级脉管制冷机应用的主要问题 ,同时指出了多级脉管制冷机的主要发展方向。     

超声辅助盐酸提取-电感耦合等离子体发射光谱法测定焊接药剂中磷

熔炼焊剂、烧结焊剂等焊接药剂由多种硅酸盐、碳酸盐、氧化物、氟化物、铁合金、金属粉等无机物及有机物经熔炼、烧结、粘结或混合制成,在钢铁和镍基合金的熔化焊接过程中起到造渣、脱氧、造气、稳弧、合金化等作用,广泛应用于船舶、海工、能源、冶金、化工、机械等行业领域。磷是焊接药剂及钢铁材料的有害元素,引发冷脆,降低熔敷金属和焊缝的力学性能。准确和快速地测定磷含量对焊接药剂的性能评价、质量控制等具有重要意义。研究了超声辅助盐酸提取—电感耦合等离子体发射光谱法测定焊接药剂中磷的方法,并优化确定了射频功率、雾化气流量、辅助气流量、等离子体气流量与分析谱线等仪器参数。确定的工作参数如下,射频功率：1.2 kW,雾化气流量：0.75 L·min-1,辅助气流量：1.0 L·min-1,等离子体气流量：12 L·min-1,选择P 213.617 nm为分析谱线。称取0.5 g试样,于20 mL盐酸中超声浸取30 min;加入2 mL硝酸,加热煮沸溶液,冷却后定容至100 mL,干过滤取滤液待测。以20 mL盐酸和2 mL硝酸为基体配制系列校准曲线溶液,线性相关系数大于0.999 9。方法定量限为0.001 2%。按实验方法测定磷含量为0.003%~0.03%的实际样品和标准样品,测定结果与标准方法的测定值或标准样品的认定值相符,相对标准偏差（n=6~10）不大于8%,加标回收率为93%~110%。该方法快速准确、简便可行,适用于焊接药剂中磷的快速检验。