大功率4K脉管制冷机模拟和实验研究

提高液氦温区脉管制冷机的制冷量对于冷却超导磁体和氦液化具有重要意义。本文将已成功应用于单级脉管制冷机和4 K G-M制冷机模拟的回热器模拟软件REGEN用于液氦温区脉管制冷机二级回热器的模拟。计算结果显示,脉管制冷机在4.2 K的制冷量一定程度上随着二级质量流量的增加而增大。在此基础上,我们在实验中采用不同质量流量的压...     

An improved progressive preconditioning method for steady non‐cavitating and sheet‐cavitating flows

An improved progressive preconditioning method for analyzing steady inviscid and laminar flows around fully wetted and sheet‐cavitating hydrofoils is presented. The preconditioning matrix is adapted automatically from the pressure and/or velocity flow‐field by a power‐law relation. The cavitating calculations are based on a single fluid approach. In this approach, the liquid/vapour mixture is treated as a homogeneous fluid whose density is controlled by a barotropic state law. This physical model is integrated with a numerical resolution derived from the cell‐centered Jameson's finite volume algorithm. The stabilization is achieved via the second‐and fourth‐order artificial dissipation scheme. Explicit four‐step Runge–Kutta time integration is applied to achieve the steady‐state condition. Results presented in the paper focus on the pressure distribution on hydrofoils wall, velocity profiles, lift and drag forces, length of sheet cavitation, and effect of the power‐law preconditioning method on convergence speed. The results show satisfactory agreement with numerical and experimental works of others. The scheme has a progressive effect on the convergence speed. The results indicate that using the power‐law preconditioner improves the convergence rate, significantly. Copyright © 2010 John Wiley & Sons, Ltd.     

FPGA and ASIC implementation of robust invisible binary image watermarking algorithm using connectivity preserving criteria

Digital watermarking is the process of hiding information into a digital signal to authenticate the contents of digital data. There are number of watermarking algorithm implemented in software and few in hardware. This paper discusses the implementation of robust invisible binary image watermarking algorithm in Field Programmable Gate Array (FPGA) and Application Specific Integrated Circuits (ASIC) using connectivity preserving criteria. The algorithm is processed in spatial domain. The algorithm is prototyped in (i) XILINX FPGA (ii) 130 nm ASIC. The algorithm is tested in Virtex-E (xcv50e-8-cs144) FPGA and implemented in an ASIC.     

SOFC/GT/ST三重复合动力系统特性研究

本文研究SOFC/GT/ST三重复合动力系统.首先基于Aspen Plus建立了SOFC/GT/ST的性能分析模型,分析了各主要参数对SOFC/GT/ST复合动力系统性能的影响规律.研究结果表明:复合动力系统尽量在高的压力,温度在900℃左右的条件下,有较高系统效率;较高的燃料利用率(Ut)有利于提高系统效率.本文研究...     

大功率LED驱动电路研究设计

根据大功率LED的供能要求,从EMI滤波、功率因素校正、半桥谐振转换三个方面着手,以FAN6961和FSFR2100为控制芯片,设计了一款大功率的高效率LED驱动电路,在90～264VAC的线路输入和满载下,功率因数高于93%,效率高于85%,并具有低输入电流谐波失真和低EMI.     

PLC、人机界面结合变频器在纯净水再生装置中自动恒压控制的设计

本文详细介绍了用OMRON CQM1系列PLC、OMRON线性传感控制模块及NT31系列人机界面在纯净水再生装置中的硬件配置和软件设计。     

Correlation receiver of below-noise pulsed signals based on parametric interactions of spin waves in magnetic films

A correlation receiver capable of receiving pulsed microwave signals having amplitudes substantially below the noise level is proposed and experimentally realized. The device is based on the parametric interaction of two contra-propagating spin waves excited by the received microwave signal and the reference pulsed signal, containing information about the received signal shape, in a ferrite film waveguide. The output nonlinear correlation signal having the doubled carrier frequency and the signal-to-noise ratio enhanced by several orders of magnitude is received by a dielectric resonator coupled to an output microwave transmission line.     

A Strong Anti-Jamming Algorithm Based on FPGA for Estimating Loop Delay in Digital Predistortion System

At present what are the key points focused in the research of loop-delay estimation for the digital predistorter in the radio frequency (RF) power amplifier system is reducing its complexity of engineering realization and improving anti-jamming ability and computational speed. Besides, opening up its application scope should be contained. For these targets, a novel method including integer loop delay estimation and fractional part is proposed. The integer part applies amplitude-difference summation function and the fractional one adopts the method of finite impulse response (FIR) linear interpolation. The algorithm finds wide applications. What is more, strong anti-jamming ability and low complexity are also its merits. Simulation results support the above opinion. Digital predistortion (DPD) system based on this algorithm achieves good performance.     

Efficient Heck cross-coupling of 3-iodo-benzopyrones with olefins under microwave irradiation without phosphine

An efficient and effective microwave-assisted Heck cross-coupling of different terminal olefins with various 3-iodo-benzopyrones including sterically hindered, electron-rich, electron-neutral, and electron-deficient is developed. It proceeded faster and generally gave good to excellent yields under microwave irradiation, phosphine-free, and air condition. The reaction could render this method particularly attractive for the efficient preparation of biologically and medicinally interesting molecules.