Different Frequency Synchronization Theory and Its Frequency Measurement Practice Teaching Innovation Based on Lissajous Figure Method

According to the requirement of multi-parameter time and frequency measurement without frequency normalization,a different frequency synchronization theory is proposed based on Lissajous figure method and the variation lawof Lissajous figure which are used in practice teaching of frequency measurement. The theory can achieve high-precision transmission and comparison of time and frequency and precise locking and tracking of phase and frequency,improve the level of scientific research on time and frequency for postgraduate,and promote practice teaching innovation of time frequency measurement for undergraduate. Utilizing the ratio of horizontal and vertical inflection point of the Lissajous figure,the nominal frequency of the measured signal is precisely calculated.The frequency deviation between the measured frequency and its nominal frequency can be obtained by combining the turning cycle of the Lissajous figure. By observing the phase relationship between the frequency standard signal and the measured signal,the accurate measurement of the frequency is implemented. Experimental results showthat the direct measurement and comparison better than the 10-11 order of magnitude with common frequency source can be finished between any signal frequencies.The frequency measurement method based on the theory has the advantage of simple operation,quick measurement speed,small error,lownoise and high measurement precision. It plays an important role in time synchronization,communications,metrology,scientific research,educational technology practice and equipment and other fields.

基于STM32的简易数字逻辑分析仪设计与研究

文章以电子设计大赛简易数字信号分析装置为背景,给出了该系统的整体设计方案及具体软硬件设计。重点论述项目中信号的产生、信号的检测与分析、时间标志线功能等内容。最后基于设计方案完成了实物制作与相关实验,通过实验验证了本项目设计的合理与有效性。

Effect of insulating oil covering electrodes on the characteristics of a dielectric barrier discharge

In this study,the effects of the fluid cooling and electric field line deformation were investigated in a dielectric barrier discharge(DBD)plasma source.The DBD plasma jet is improved by covering the ground electrode and a power electrode with insulating oil.We obtained positive results as insulating oil prevents arc formation,while it improved the supplied power and plasma jet length,and increased radical production.Radical production of this nonthermal plasma jet is studied with polyvinyl alcohol-potassium iodide liquid.

Application of DBD and DBCD in SO_2 Removal

The dielectric barrier corona discharge(DBCD) in a wire-cylinder configuration and the dielectric barrier discharge(DBD) in a coaxial cylinder configuration are studied. The discharge current in DBD has a higher pulse amplitude than in DBCD. The dissipated power and the gas-gap voltage are calculated by analyzing the measured Lissajous figure. With the increasing applied voltage, the energy utilization factor for SO2 removal increases in DBCD but decreases in DBD because of the difference in their electric field distribution. Experiments of SO2 removal show that in the absence of NH3 the energy utilization factor can reach 31 g/kWh in DBCD and 39 g/kWh in DBD.

Electrical and thermal characterization of near-surface electrical discharge plasma actuation driven by radio frequency voltage at low pressure

The electrical and thermal characterization of near-surface electrical discharge plasma driven by radio frequency voltage are investigated experimentally in this paper. The influences of operating pressure, electrode distance, and duty cycle on the discharge are studied. When pressure reaches 60 Ton. （1 Torr= 1.33322 x 102 Pa） the transition from diffuse glow mode to constricted mode occurs. With the operating pressure varying from 10 Tort to 60 Torr, the discharge energy calculated from the charge-voltage （Q-V） Lissajous figure decreases rapidly, while it remains unchanged between 60 Torr and 460 Torr. Under certain experimental conditions, there exists an optimized electrode distance （8 mm）. As the duty cycle of applied voltage increases, the voltage-current waveforms and Q-V Lissajous figures show no distinct changes.

Electrical and optical characteristics of the radio frequency surface dielectric barrier discharge plasma actuation

Electrical characteristics and optical emission spectrum of the radio frequency （RF） surface dielectric barrier discharge （SDBD） plasma actuation are investigated experimentally in this paper. Influences of operating pressure, duty cycle and load power on the discharge are analyzed. When the operating pressure reaches 30 kPa, the discharge energy calculated from the Charge-Voltage （Q-V） Lissajous figure increases significantly, while the effective capacitance decreases remarkably. As the duty cycle of the applied voltage increases, the voltage-current waveforms, the area of Q-V loop and the capacity show no distinct changes. Below 40 W, effective capacitance increases with the increase of load power, but it almost remains . peak peak unchanged when load power is between 40 W and 95 W. The relative intensity Ipeak 91.4/Ipeak380.5 changes little as the operating pressure varies from 4 kPa to 100 kPa, while it rises evidently with the pressure below 4 kPa, which indicates that the RF discharge mode shifts from filamentary discharge to glow discharge at around 4 kPa. With the increase of load power, the Ipeak371.1/Ipeak380.5 relative intensity Ipeak91.4/Ipeak380.5 rises evidently Additionally, the relative intensity Ipeak91.4/Ipeak380.5 is insensitive to the pressure, the duty cycle, and the load power.

Electrical Characteristics of Dielectric-Barrier Discharges in Atmospheric Pressure Air Using a Power-Frequency Voltage Source

Dielectric-barrier discharges （DBDs） in atmospheric pressure air have been studied by using a power-frequency voltage source. In this paper the electrical characteristics of DBDs us- ing glass and alumina dielectrics have been investigated experimentally. According to the Lissajous figures of voltage-charges, it is discovered that the discharge power for an alumina dielectric is much higher than that for a glass dielectric at the same applied voltage. Also~ the voltage-current curves of the glass and alumina dielectrics confirm the fact that the dielectric barriers behave like semiconducting materials at certain applied voltages.

A comparison of power measurement techniques and electrical characterization of an atmospheric pressure plasma jet

In the last two decades a growing interest has been shown in the investigation of atmospheric pressure plasma jets(APPJs)that operate in contact with liquid samples.In order to form a complete picture about such experimental systems,it is necessary to perform detailed diagnostics of plasma jets,as one step that will enable the adjustment of system properties for applications in different areas.In this work,we conducted a detailed electrical characterisation of a plasma system configuration used for water treatment.A helium plasma jet,with a pin electrode powered by a continuous sine wave at a frequency of 330 k Hz,formed a streamer that was in contact with a distilled water sample.An electrical circuit allowed the monitoring of electrical signals supplied to the jet and also to the plasma itself.An electrical characterisation together with power consumption measurements was obtained by using two different methods.The first method was based on the direct measurements of voltage and current signals,while in the second method we used'Lissajous figures'.We compared these two methods when used for discharge power estimation and addressed their advantages and limitations.The results showed that both of these methods could be used to successfully determine power consumed by a discharge in contact with water,but only when taking into account power dissipation without plasma.

Grounding fault location method of overhead line based on dual-axis magnetic field trajectory

To address the challenges in fault location in distribution networks,the distribution of magnetic field under overhead line and its relationship with three-phase currents are explored in this paper.At the same time,considering the influ-ence of sensor installation position,line sag and galloping on magnetic field,a grounding fault location method of an overhead line based on dual-axis magnetic field trajectory is proposed.The analytical expressions of the magnetic field on the x-axis and y-axis under the overhead line are obtained by least squares fitting.The Lissajous figure synthe-sized by dual-axis is then compared with the general equation of an ellipse,and the characteristic quantity expression characterizing the magnetic field trajectory structure is obtained.Finally,a fault location criterion is constructed using the difference of the characteristic quantities of the ellipses synthesized by x-axis and y-axis magnetic fields upstream and downstream of the fault point,i.e.,the difference of the length of the major axis and the minor axis,and the sign for the ratio of the cosine value of the inclination angle.Compared with other location methods based on electrical quantity,the principle of this method is simpler and it can locate faults more quickly and accurately.A large number of simulation results show that the proposed method is suitable for different types of fault conditions.

Experimental study of an anti-icing method over an airfoil based on pulsed dielectric barrier discharge plasma

Aircraft icing has long been a plague to aviation for its serious threat to flight safety. Even though lots of methods for anti-icing have been in use or studied for quite a long time, new methods are still in great demand for both civil and military aircraft. The current study in this paper uses widely used Dielectric Barrier Discharge（DBD） plasma actuation to anti-ice on a NACA0012 airfoil model with a chord length of 53.5 cm in a closed-circuit icing wind tunnel. An actuator was installed at the leading edge of the airfoil model, and actuated by a pulsed low-temperature plasma power source. The actuator has two types of layout, a striped electrode layout and a meshy electrode layout.The ice accretion process or anti-icing process was recorded by a CCD camera and an infrared camera. Instantaneous pictures and infrared contours show that both types of DBD plasma actuators have the ability for anti-ice under a freestream velocity of 90 m/s, a static temperature of -7℃,an Median Volume droplet Diameter（MVD） of 20 lm, and an Liquid Water Content（LWC） of 0.5 g/m^3. The detected variations of temperatures with time at specific locations reveal that the temperatures oscillate for some time after spraying at first, and then tend to be nearly constant values.This shows that the key point of the anti-icing mechanism with DBD plasma actuation is to achieve a thermal equilibrium on the model surface. Besides, the power consumption in the anti-icing process was estimated in this paper by Lissajous figures measured by an oscilloscope, and it is lower than those of existing anti-icing methods. The experimental results presented in this paper indicate that the DBD plasma anti-icing method is a promising technique in the future.

Fluence rate linear response limit of a scintillators to γ-rays

Scintillation detectors based on LSO, CeF and PbWO are the main candidates for measuring T- rays in a mixed γ/n pulsed radiation field with high intensity. An experiment using the Lissajous figure method to study the high fluence rate response behavior of three kinds of commonly used scintillators is introduced in this paper. The result shows that the fluence rate linear response limit of LSO and CeF is 1.9×10^19 and 2.1 × 10^18MeV/（cm^2·s）, respectively, and the PbWO scintillator still maintains linear response when the fluence rate of T-ray is up to 2.0×10^20 MeV/（cm^2·s）.