A novel inductance-free nonlinear oscillator circuit with a single bifurcation parameter is presented in this paper. This circuit is composed of a twin-T oscillator, a passive RC network, and a flux-controlled memrist...A novel inductance-free nonlinear oscillator circuit with a single bifurcation parameter is presented in this paper. This circuit is composed of a twin-T oscillator, a passive RC network, and a flux-controlled memristor. With an increase in the control parameter, the circuit exhibits complicated chaotic behaviors from double periodicity. The dynamic properties of the circuit are demonstrated by means of equilibrium stability, Lyapunov exponent spectra, and bifurcation diagrams. In order to confirm the occurrence of chaotic behavior in the circuit, an analog realization of the piecewise-linear flux-controlled memristor is proposed, and Pspice simulation is conducted on the resulting circuit.展开更多
A new twin-tungsten TIG (T-TIG) welding method was studied. This method differs from the conventional TIG method, it places two electrodes insulated from each other in the same welding torch, and a coupling arc is g...A new twin-tungsten TIG (T-TIG) welding method was studied. This method differs from the conventional TIG method, it places two electrodes insulated from each other in the same welding torch, and a coupling arc is generated from the two electrodes. The coupling arc pressure was measured and preliminary welding experiment was made. The results show that the coupling arc can keep arc pressure at a low level compared with conventional TIG arc, and welding can be achieved under higher current and high travel speed with sound appearance of weld. Therefore, this new method can applied widely in high effwiency welding.展开更多
This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring.This sensor employs a parallel plate capacitor design, with sea wate...This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring.This sensor employs a parallel plate capacitor design, with sea water serving as the medium between plates. Novalac resin and a proprietary commercial polymer (AccufloTW) were investigated as corrosion protective coatings for the copper electrodes of the capacitor. Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion inhibition of polymer coatingin sea water. A detection circuit was designed and simulated using P-spice and then implemented in Printed Circuit Board (PCB). EIS results indicate that Accuflo exhibits better corrosion inhibition in ocean water than Novolac. Further, the use of Twin-T oscillator based detection circuit resulted in enhanced sensitivity and better detection limit. Experiments performed using ocean water samples resulted in oscillator frequency shift of 410 Hertz/power supply unit (Hz/PSU). Oscillator frequency drift was reduced using frequency-to-voltage converters and sensitivity of 10 mV/PSU was achieved.展开更多
以FPGA和MSP430F6638为控制核心,主要包含信号源、被测网络、检波及显示部分。其中,测试信号源基于DDS原理,可以实现0.1∽150 k Hz的扫频,最小步进10 Hz,稳定度优于10-4,测量精度1%。并设计制作了中心频率5 k Hz,带宽±50 Hz的阻容...以FPGA和MSP430F6638为控制核心,主要包含信号源、被测网络、检波及显示部分。其中,测试信号源基于DDS原理,可以实现0.1∽150 k Hz的扫频,最小步进10 Hz,稳定度优于10-4,测量精度1%。并设计制作了中心频率5 k Hz,带宽±50 Hz的阻容双T网络。检波部分采用高性能芯片AD637测量双T网络输出信号的有效值,通过单片机计算峰值;并将输出、输入信号分别放大整形得到稳定的方波输入FPGA计算相差,从而绘制幅频特性曲线和相频特性曲线。可以通过键盘设置步进,切换幅频特性曲线、相频特性曲线的显示界面,以及其他参数的显示和查看。整个系统是单片机和FPGA的有机结合、协同控制下,工作稳定,测量精度高,人机交互灵活。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60972147 and 61176032)
文摘A novel inductance-free nonlinear oscillator circuit with a single bifurcation parameter is presented in this paper. This circuit is composed of a twin-T oscillator, a passive RC network, and a flux-controlled memristor. With an increase in the control parameter, the circuit exhibits complicated chaotic behaviors from double periodicity. The dynamic properties of the circuit are demonstrated by means of equilibrium stability, Lyapunov exponent spectra, and bifurcation diagrams. In order to confirm the occurrence of chaotic behavior in the circuit, an analog realization of the piecewise-linear flux-controlled memristor is proposed, and Pspice simulation is conducted on the resulting circuit.
文摘A new twin-tungsten TIG (T-TIG) welding method was studied. This method differs from the conventional TIG method, it places two electrodes insulated from each other in the same welding torch, and a coupling arc is generated from the two electrodes. The coupling arc pressure was measured and preliminary welding experiment was made. The results show that the coupling arc can keep arc pressure at a low level compared with conventional TIG arc, and welding can be achieved under higher current and high travel speed with sound appearance of weld. Therefore, this new method can applied widely in high effwiency welding.
文摘This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring.This sensor employs a parallel plate capacitor design, with sea water serving as the medium between plates. Novalac resin and a proprietary commercial polymer (AccufloTW) were investigated as corrosion protective coatings for the copper electrodes of the capacitor. Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion inhibition of polymer coatingin sea water. A detection circuit was designed and simulated using P-spice and then implemented in Printed Circuit Board (PCB). EIS results indicate that Accuflo exhibits better corrosion inhibition in ocean water than Novolac. Further, the use of Twin-T oscillator based detection circuit resulted in enhanced sensitivity and better detection limit. Experiments performed using ocean water samples resulted in oscillator frequency shift of 410 Hertz/power supply unit (Hz/PSU). Oscillator frequency drift was reduced using frequency-to-voltage converters and sensitivity of 10 mV/PSU was achieved.
文摘以FPGA和MSP430F6638为控制核心,主要包含信号源、被测网络、检波及显示部分。其中,测试信号源基于DDS原理,可以实现0.1∽150 k Hz的扫频,最小步进10 Hz,稳定度优于10-4,测量精度1%。并设计制作了中心频率5 k Hz,带宽±50 Hz的阻容双T网络。检波部分采用高性能芯片AD637测量双T网络输出信号的有效值,通过单片机计算峰值;并将输出、输入信号分别放大整形得到稳定的方波输入FPGA计算相差,从而绘制幅频特性曲线和相频特性曲线。可以通过键盘设置步进,切换幅频特性曲线、相频特性曲线的显示界面,以及其他参数的显示和查看。整个系统是单片机和FPGA的有机结合、协同控制下,工作稳定,测量精度高,人机交互灵活。
基金Foundation item: China National "863" High-Tech Program (2007AA100503)National Natural Science Foundation of China (No.30871722)Shanghai Science and Technology Committee Project (No. 03DZ19310 and 073158202)