Quantum Dynamical Phase Transition in a Spin-Orbit Coupled Bose Condensate

Spin-orbit coupled bosons can exhibit rich equilibrium phases at low temperature and in the presence of particle-particle interactions. In the case with a 1D synthetic spin-orbit interaction, it has been observed that the ground state of a Bose gas can be a normal phase, stripe phase, or magnetized phase in different experimentally controllable parameter regimes. The magnetized states are doubly degenerate and consist of a many-particle two-state system. In this work, we investigate the nonequilibrium quantum dynamics by switching on an external perturbation to induce resonant couplings between the magnetized phases, and predict the novel quantum spin dynamics which cannot be obtained in the single-particle systems. In particular, due to particle-particle interactions, the transition of the Bose condensate from one magnetized phase to the other is forbidden when the strength of external perturbation is less than a critical value, and a full transition can occur only when the perturbation exceeds such critical strength. This phenomenon manifests itself a quantum dynamical phase transition, with the critical point behavior being exactly solvable. From the numerical simulations and exact analytic studies we show that the predicted many-body effects can be well observed with the current experiments.Comment: 9 pages, 4 figures, plus supplementary materia

Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials - A general bond polarizability model

2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences (e.g. ABAB, ABCABC), leading to different physical properties. Here, we show that regardless of the space group of the 2D material, the Raman frequencies of the interlayer shear modes observed under the typical configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials.Comment: 30 pages, 8 figure

Testing System Optimization and Design for Slurry Pipeline Transportation

Abstract: This study aims to introduce the design and optimization of a testing system for the on the slurry pipeline transportation in dredging projects. Due to characteristics of slurries such as high concentration, irregular particles and complex ingredients, slurry transportation often subjects to huge pipe resistance, high energy consumption, pipe blockage and short transportation distance. Literature review indicates that the gas injection to pipeline can effectively improve slurry flow state and reduce pipeline resistance. However, the research on design and optimization of slurry pipeline transportation in dredging projects is scarce. Hence, this study has designed a new air-injected pipeline system for dredging projects. The general structure of the new system and new features of subsystems have been introduced in details. In the design process, key parameters have been monitored, including the inner pressure, quantity of flow and flow state. These parameters have been used in measurement and control subsystems, which are suitable for the dredging projects. The optimization and design results demonstrate that the designed air-injected pipeline system are reasonable in design, inclusive in functions and reliable in accuracy and can be applied to simulation of real conditions in slurry translation in dredging projects

N-Methyl-4-(4-pivalamido­phenyl­sulfan­yl)picolinamide hemihydrate

In the title compound, C18H21N3O2S·0.5H2O, the benzene ring makes dihedral angles of 88.59 (6) and 40.74 (8)° with the pyridine ring and the amide group, respectively. The water O atom lies on a twofold axis. In the crystal, the organic mol­ecules and the water mol­ecules are linked via O—H⋯O hydrogen bonds, while the organic mol­ecules are connected to each other via N—H⋯O hydrogen bonds, forming a three-dimensional network

A generic theory for Majorana zero modes in 2D superconductors

It is well known that non-Abelian Majorana zero modes (MZM) harbor at vortex cores in a $p_{x}+\text{i}p_{y}$ topological superconductor, which can be realized in a 2D spin-orbit coupled system with a single Fermi surface and by proximity coupling to an $s$-wave superconductor. Here we show that existence of non-Abelian MZMs is unrelated to the bulk topology of a 2D superconductor, and propose that such exotic modes can be resulted in much broader range of superconductors, being topological or trivial. For a generic 2D system with multiple Fermi surfaces and gapped out by superconducting pairings, we show that at least a single MZM survives if there are only odd number of Fermi surfaces of which the corresponding superconducting orders have vortices, and such MZM is protected by an emergent Chern-Simons invariant, irrespective of the bulk topology of the superconductor. This result may enrich new experimental schemes for realizing non-Aelian MZMs. In particular, we propose a minimal scheme to realize the MZMs in a 2D superconducting Dirac semimetal with trivial bulk topology, which can be well achieved based on the recent cold atom experiments.Comment: 5 pages, 3 figures, plus Supplementary Materia

Steam Condensation Cooled by Piezoelectric Driven Oscillating Air Flow

The piezoelectric (PE) fan is first put forward to use in the air-cooled condenser, and to enhance the exhaust steam condensation of large thermal power plants. The cooling performance of such a method is evaluated through numerical simulations. The study shows that the surface heat transfer coefficient with PE fan at the air side is higher than that of a conventional axial flow (AF) fan. While at the steam side of the tube, the surface heat transfer coefficient is also enhanced owing to the obvious fluctuation of liquid film caused by the vibration of the piezoelectric fan.Key words: Piezoelectric fan; Air-cooling condenser; Numerical simulation; Surface heat transfer coefficien

Inverse Problem Approach for Non-Perturbative QCD: Foundation

We propose a novel theoretical framework to calculate the non-perturbative QCD quantities. It starts from the dispersion relation of quantum field theory, separating the high-energy and low-energy scales and using the known perturbative theories to solve the unknown non-perturbative quantities by the inverse problem. We prove that the inverse problem of dispersion relation is ill-posed, with unique but unstable solutions. The regularization methods must be used to get the stable approximate solutions. The method is based on the strict mathematics, without any artificial assumptions. We have test some toy models to vividly show the main features of the inverse problem. It can be found that this approach can systematically improve the precision of the solutions.Comment: 23 pages, 8 figure

Impact of Facebook usage on firm’s performances among Malaysian Chinese retailers

Social media including Facebook has been acknowledged to play a vital role in firms achieving superior performance. Malaysia is a multicultural country in which the Malaysian Chinese are considered to be the most successful entrepreneurs. There is, however, a lack of research regarding the influence of Facebook usage on firm performance among Malaysian Chinese retailers. As such, this study had two aims. Firstly, the study investigated the influence of compatibility, cost effectiveness, trust, and interactivity on Facebook usage among Malaysian Chinese retailers. Secondly, the study assessed the impact of these retailers’ Facebook usage on their perceived financial performance, perceived non-financial performance, perceived business growth, and perceived performance relative to competitors under the moderating impact of market turbulence. This study developed a conceptual model based on the Strategic Contingency Theory (SCT) and Diffusion of Innovation (DOI) theory, and used a structured survey instrument to gather data. Using non-probability sampling techniques, 129 Malaysian Chinese retailers from Kuala Lumpur and Selangor were recruited for the study. Data was analysed using PLS-SEM techniques. The results showed that only compatibility, cost effectiveness, and interactivity have a statistically significant positive influence on Facebook usage, which in turn has a statistically significant positive influence on the retailers’ perceived financial performance, perceived non-financial performance, perceived business growth, and perceived performance relative to competitors. Moreover, market turbulence was only found to be a moderator that improves the impact of Facebook usage on perceived financial performance, perceived business growth, and perceived performance relative to competitors, but not perceived non-financial performance. These findings contribute to current literature and provide insights into the role and importance of Facebook usage on firm performance among Malaysian Chinese retailers, possibly encouraging more retailers to deploy social media in their business processe