Anomalous magneto-structural behavior of MnBi explained: a path towards an improved permanent magnet

Low-temperature MnBi (hexagonal NiAs phase) exhibits anomalies in the lattice constants (a, c) and bulk elastic modulus (B) below 100 K, spin reorientation and magnetic susceptibility maximum near 90 K, and, importantly for high-temperature magnetic applications, an increasing coercivity (unique to MnBi) above 180 K. We calculate the total energy and magneto-anisotropy energy (MAE) versus (a, c) using DFT+U methods. We reproduce and explain all the above anomalies. We predict that coercivity and MAE increase due to increasing a, suggesting means to improve MnBi permanent magnets.Comment: 4 pages, 5 figure

The application of Han Dynasty cultural elements to modern product design

Chinese Han Culture, as Chinese nation's "core culture", is the cultural symbol of Chinese nation, and played an important role in the history of Chinese cultural development, even in the history of world cultural development. Designing in the Han Dynasty, while inheriting Chinese traditional culture, but also having its unique style, are appreciated and respected by the people nowadays. In a modern society where the design is becoming more diversified, the innovative design based on traditional culture and art has its unique charm and vitality. This paper presented our recent research on the application of Han Dynasty cultural elements to modern product design, reflected the local design connotation of Han Dynasty cultural elements

Particle swarm optimization with composite particles in dynamic environments

This article is placed here with the permission of IEEE - Copyright @ 2010 IEEEIn recent years, there has been a growing interest in the study of particle swarm optimization (PSO) in dynamic environments. This paper presents a new PSO model, called PSO with composite particles (PSO-CP), to address dynamic optimization problems. PSO-CP partitions the swarm into a set of composite particles based on their similarity using a "worst first" principle. Inspired by the composite particle phenomenon in physics, the elementary members in each composite particle interact via a velocity-anisotropic reflection scheme to integrate valuable information for effectively and rapidly finding the promising optima in the search space. Each composite particle maintains the diversity by a scattering operator. In addition, an integral movement strategy is introduced to promote the swarm diversity. Experiments on a typical dynamic test benchmark problem provide a guideline for setting the involved parameters and show that PSO-CP is efficient in comparison with several state-of-the-art PSO algorithms for dynamic optimization problems.This work was supported in part by the Key Program of the National Natural Science Foundation (NNSF) of China under Grant 70931001 and 70771021, the Science Fund for Creative Research Group of the NNSF of China under Grant 60821063 and 70721001, the Ph.D. Programs Foundation of the Ministry of education of China under Grant 200801450008, and by the Engineering and Physical Sciences Research Council of U.K. under Grant EP/E060722/1

Optical Modulation in the X-Ray Binary 4U 1543-624 Revisited

The X-ray binary 4U 1543$-$624 has been provisionally identified as an ultracompact system with an orbital period of $\simeq$18~min. We have carried out time-resolved optical imaging of the binary to verify the ultra-short orbital period. Using 140\,min of high-cadence $r'$-band photometry we recover the previously-seen sinusoidal modulation and determine a period $P=18.20\pm0.09$\,min. In addition, we also see a 7.0$\times 10^{-4}$\,mag\,min$^{-1}$ linear decay, likely related to variations in the source's accretion activity. Assuming that the sinusoidal modulation arises from X-ray heating of the inner face of the companion star, we estimate a distance of 6.0--6.7\,kpc and an inclination angle of 34$^{\circ}$--61$^{\circ}$ (90\% confidence) for the binary. Given the stability of the modulation we can confirm that the modulation is orbital in origin and 4U 1543$-$624 is an ultracompact X-ray binary.Comment: 6 pages, 3 figures, accepted for publication in Publications of the Astronomical Society of Australia (PASA

Origin of sawtooth domain walls in ferroelectrics

Domains and domain walls are among the key factors that determine the performance of ferroelectric materials. In recent years, a unique type of domain walls, i.e., the sawtooth-shaped domain walls, has been observed in BiFeO$_{3}$ and PbTiO$_{3}$. Here, we build a minimal model to reveal the origin of these sawtooth-shaped domain walls. Incorporating this model into Monte-Carlo simulations shows that (i) the competition between the long-range Coulomb interaction (due to bound charges) and short-range interaction (due to opposite dipoles) is responsible for the formation of these peculiar domain walls and (ii) their relative strength is critical in determining the periodicity of these sawtooth-shaped domain walls. Necessary conditions to form such domain walls are also discussed

Optical wavelength conversion of quantum states with optomechanics

An optomechanical interface that converts quantum states between optical fields with distinct wavelengths is proposed. A mechanical mode couples to two optical modes via radiation pressure and mediates the quantum state mapping between the two optical modes. A sequence of optomechanical $\pi/2$ pulses enables state-swapping between optical and mechanical states as well as the cooling of the mechanical mode. Theoretical analysis shows that high fidelity conversion can be realized for states with small photon numbers in systems with experimentally achievable parameters. The pulsed conversion process also makes it possible to maintain high conversion fidelity at elevated bath temperatures.Comment: 4 pages, 4 figures, Fig. 4 looks weird (possible latex style problem