Electric characteristic and cavitation bubble dynamics using underwater pulsed discharge

Underwater pulsed discharge is widely applied in medicine, machining, and material modification.The induced cavitation bubble and subsequent cavitation collapse are considered the major motivations behind these applications. This paper presents an underwater pulsed discharge system.The experimental setup is established to induce and investigate the cavitation bubble assisted with a high-speed camera. Three aspects, including the characteristic of the discharge with different applied voltages and conductivities, the evolution of the cavitation bubble profile, and the energy efficiency of cavitation bubble inducing, are investigated, respectively. Especially, the mechanism of pre-discharge time delay in the low field intensity case is explained using the Joule heat effect.The results show the validity of the underwater pulsed discharger and experimental setup. The present underwater pulsed discharger is proved to be a simple, portable, and easy-to-implement device for the investigation of cavitation bubble dynamics.

Characteristics of water volatilization and oxides generation by using positive and negative corona

The physical and chemical properties have significant differences for the positive and negative charged particles generated by discharge.In this work,a positive and negative corona discharge system was established,and two discharge reactors for charged particles restraining and acting were designed by a needle electrode covered with a quartz tube and a plate electrode filled with water.The corona discharges happened within the needle-plate electrodes were excited by a positive and negative high voltage source,and the characteristics of both water volatilization and oxides generation were examined within influence of the distances of both quartz tube inside and outside.The results show that the characteristics of both the water volatilization and oxides generation can be affected by the distances of both quartz tube inside and outside.When the distances of tube inside were increased from 5.00 to 13.00 mm,the water volatilizations decreased under negative corona,and increased firstly and declined immediately under positive corona.The maximum value of the water volatilization appeared in the distances of tube inside with 6.00–8.00 mm.In addition,the concentrations of the HNO_(x) and H_(2)O_(2)in treated water decreased with increasing the distances of tube inside.Moreover,with increasing the distances of tube outside from 4.00 to 14.00 mm,the change trends of both the water volatilizations and oxides presented the same as the distances of tube inside,and the maximum value of the water volatilization and oxides appeared in the distance of tube outside with about 9.00 mm.Overall,the positive corona can generate more water volatilizations and oxides in water than negative corona,and non H_(2)O_(2)can be produced by negative corona.The results reflect the difference between positive and negative corona interaction with water,which can provide reference for plasma application.

IGIgram:An Improved Gini Index-Based Envelope Analysis for Rolling Bearing Fault Diagnosis

The transient impulse features caused by rolling bearing faults are often present in the resonance frequency band which is closely related to the dynamic characteristics of the machine structure.Informative frequency band identification is a crucial prerequisite for envelope analysis and thereby accurate fault diagnosis of rolling bearings.In this paper,based on the ratio of quasi-arithmetic means and Gini index,improved Gini indices(IGIs)are proposed to quantify the transient impulse features of a signal,and their effectiveness and advantages in sparse quantification are confirmed by simulation analysis and comparisons with traditional sparsity measures.Furthermore,an IGI-based envelope analysis method named IGIgram is developed for fault diagnosis of rolling bearings.In the new method,an IGI-based indicator is constructed to evaluate the impulsiveness and cyclostationarity of the narrow-band filtered signal simultaneously,and then a frequency band with abundant fault information is adaptively determined for extracting bearing fault features.The performance of the IGIgram method is verified on the simulation signal and railway bearing experimental signals and compared with typical sparsity measures-based envelope analysis methods and log-cycligram.The results demonstrate that the proposed IGIs are efficient in quantifying bearing fault-induced transient features and the IGIgram method with appropriate power exponent can effectively achieve the diagnostics of different axle-box bearing faults.

Performance projections for ballistic carbon nanotube FinFET at circuit level

A novel three-dimensional device structure for a carbon nanotube （CNT） fin field-effect transistor （FinFET） is proposed and evaluated. We evaluated the potential of the CNT FinFET compared with a Si FinFET at a 22-nm node at the circuit level using three performance metrics including propagation delay, total power dissipation, and energy-delay product （EDP）. Compared with a Si FinFET, the CNT FinFET presents obvious advantages in speed and EDP arising from its almost much larger current density but also results in a higher total power dissipation, especially at a low threshold voltage （V~ = 1/3Vaa）. A suitable improvement in Vth can effectively contribute to a significant suppression of leakage current and power dissipation, and then an obvious optimization is obtained in the EDP with an acceptable sacrifice in speed. In particular, CNT FinFETs with optimized threshold voltages can provide an EDP advantage of approximately 50 times over Si FinFETs under a low supply voltage （Vdd -- 0.4 V）, suggesting great potential for CNT FinFET-based integrated circuits.