Broadband energy harvesting via magnetic coupling between two movable magnets

Harvesting energy from ambient mechanical vibrations by the piezoelectric effect has been proposed for powering microelectromechanical systems and replacing batteries that have a finite life span. A conventional piezoelectric energy harvester （PEH） is usually designed as a linear resonator, and suffers from a narrow operating bandwidth. To achieve broadband energy harvesting, in this paper we introduce a concept and describe the realization of a novel nonlinear PEH. The proposed PEH consists of a primary piezoelectric cantilever beam coupled to an auxiliary piezoelectric cantilever beam through two movable magnets. For predicting the nonlinear response from the proposed PEH, lumped parameter models are established for the two beams. Both simulation and experiment reveal that for the primary beam, the introduction of magnetic coupling can expand the operating bandwidth as well as improve the output voltage. For the auxiliary beam, the magnitude of the output voltage is slightly reduced, but additional output is observed at off-resonance frequencies. Therefore, broadband energy harvesting can be obtained from both the primary beam and the auxiliary beam.     

Electronic structures and magnetocrystalline anisotropy energies of ordered Co1-xNix alloys: a first principles study

The electronic structures and magnetocrystalline anisotropy(MA) of ordered hexagonal close-packed(hcp) Co1-xNix alloys are studied using the full-potential linear-augmented-plane-wave(FLAPW) method with generalized gradient approximation(GGA).Great changes of magnetocrystalline anisotropy energy(MAE) are gained with different Ni compositions.Also,in-plane magnetocrystalline anisotropy is obtained for Co 15 Ni in which the Snoek’s limit is exceeded.It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions,which plays an important role in modulating the magnetization direction,where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states.The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition,and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.     

复习教学中“一题多解”策略的运用

"一题多解"不是盲目地追求物理问题的多解,更不是学生或教师炫耀自己的解题能力.在笔者看来,"一题多解"作为高中物理总复习期间的一种复习策略,如果运用恰当,对夯实学生物理基础知识和方法,提高学生分析解决物理问题的能力大有裨益.在复习的不同阶段,应该采取不同类型的"一题多解"策略.在第一轮复习中,我们更关注学生对基础物理知识和基本方法的掌握,不急于要求学生从整体上把握高中物理知识体系.所以,针对第一轮复习的特点,我们应多采取"知识点"内的"一题多解"策