By making a comparison between the acoustic equations and the 2-dimensional(2D) Maxwell equations,we obtain the material parameter equations(MPE) for acoustic elliptical cylindrical cloaks.Both the theoretical results and the numerical results indicate that an elliptical cylindrical cloak can realize perfect acoustic invisibility when the spatial distributions of mass density and bulk modulus are exactly configured according to the proposed equations.The present work is the meaningful exploration of designing acoustic cloaks that are neither sphere nor circular cylinder in shape,and opens up possibilities for making complex and multiplex acoustic cloaks with simple models such as spheres,circular or elliptic cylinders.
Dipoles with Lorentz-type resonant electromagnetic responses can realise negative effective parameters in their negative resonant region.The electric dipole and magnetic dipole can realise,respectively,negative permittivity and negative permeability,so both the field distribution forms of electric and magnetic dipoles are fundamentals in designing left-handed metamaterial.Based on this principle,this paper studies the field distribution in high-permittivity dielectric materials.The field distributions at different resonant modes are analysed based on the dielectric resonator theory.The origination and influence factors of the electric and magnetic dipoles are confirmed.Numerical simulations indicate that by combining dielectric cubes with different sizes,the electric resonance frequency and magnetic resonance frequency can be superposed.Finally,experiments are carried out to verify the feasibility of all-dielectric left-handed metamaterial composed by this means.
FSM(Finite State Machine,有限状态机)的核心功能是能描述一系列具有逻辑顺序的事件,并能有效管理各个事件执行的步骤,它是一种较为特殊的时序电路。本文分析了LDPC码译码器的主控程序的结构,结合有限状态机的设计思想,采用了两个状态机交替工作的机制,在FPGA上实现了译码器的主控模块,使初始信息存储模块、校验消息处理模块、变量消息处理模块、累加模块及校验模块有序工作,实现了模块间的无缝链接,使译码器工作稳定可靠。
