The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This paper deals with the computer modeling of a low-current vacuum arc with an external axial magnetic field taking into account the secondary plasma occurred due to anode sputtering by fast ions from cathode spot. The described hybrid model treats the electrons as a massless fluid and ions as macroparticles. The macroparticle dynamic is calculated with the use of PIC method. Ion-ion and ion electron...
A two-dimensional (2D) rotary axisymmetric model has been developed to describe the formation and development of cathode spot in vacuum arc. The model includes hydrodynamic equations and thermal conductivity equation. Parameters used in this model come from experiments and other researchers' work. The simulation results show that when the energy flux density is 1.5∼3×1012W, discharge current is 1∼6A...
In order to improve the breaking capacity of contacts, it is very important to find a better contact material. In this paper, the triggering experiments of plate contact with different material are studied to investigate the characteristics of vacuum arc. The current range is from 1kA to 9kA (rms). The gap distance is 3mm and 5mm. The arc appearance and the behavior of cathode spots are captured by...
Using magnetic fields to control the vacuum arc is a major way to improve the breaking capacity of vacuum interrupters. Besides the single transverse magnetic field (TMF) and single axial magnetic field (AMF), new type of TMF-AMF contact structure has been put forward to control the vacuum arc in recent years. In this paper, two different structure contacts are used in experiments. The arc evolution...
A lot of work had been made in the vacuum arc in power frequency. But there are few research reports about high-frequency vacuum arc. In this paper, the arc appearance and development process have been studied under 250 kHz. A compact resistance-inductance-capacitance (RLC) series resonant circuit was designed to generate high-frequency vacuum arc between plate electrodes in a detachable vacuum chamber...
The circuit breaker is an important part of control and protection in the power system. Mechanical failure is the main fault of circuit breakers, and the loosening of fasteners is one of the typical mechanical faults. The self-loosening of bolted joints is closely related to the vibration, especially transverse vibration. There is strong vibration while the circuit breakers are opened and closed....
The ICP (inner corona protection) of the stator coil is to reduce the concentrated electric field at the corner and to release the electrical stress in the filler. With these functions the life of the coil can be extended and the tip-up values can be lowered. But the properties of itself such as resistivity and length (the distance between two high voltage touch points) also have influence on performances...
Metal-stripe surface grating structure presents a stable single-mode operation for THz quantum cascade lasers due to its strong coupling mechanism and easy tuning. We use sampled metal-stripe gratings to establish a distributed feedback and scale the single-mode power by tune the grating parameters. Record single-mode power more than 500 mW at 10 K is achieved.
Deep Neural Networks (DNNs) have substantially improved the state-of-the-art in salient object detection. However, training DNNs requires costly pixel-level annotations. In this paper, we leverage the observation that image-level tags provide important cues of foreground salient objects, and develop a weakly supervised learning method for saliency detection using image-level tags only. The Foreground...
We report a novel method for multichannel transmission delay measurement in optical fibers. The fiber transfer delay measurement is converted into frequency measurement. As a key technique, a simple ambiguity resolving process based on phase discrimination and frequency locking is used to overcome the contradiction between measurement accuracy and system complexity. A real-time calibration method...
High performance compact microwave atomic clocks are on great demand in many areas. Different schemes are proposed to improve the performance and minimize the size of an atomic clock. Vapor cell atomic clocks based on Ramsey-CPT (coherent population trapping) are very promising due to its simple all optical configuration. In this paper, we report an integrated electronic controller based on a FPGA...
The Dick effect is one of the main limits for a passive atomic frequency standard to reach its frequency instability limit due to quantum projection noise. In this paper, we report on the reduction of Dick effect of a Ramsey-CPT vapor cell clock using interleaving lock. Three parameters are investigated in the process of optimizing sensitivity function in details. By optimizing the sensitivity function,...
The Android application is part of people's lives, however the functionality required by various user has greatly exceeded its original design. As a result, one must seek other ways to gain permission that is not directly available to the user. A typical approach is using the Android Debug Bridge (ADB), a developer tool that is used to grant permission to critical system resources. There are millions...
Based on the distinguishing features of multi-tier millimeter wave (mmWave) networks such as different transmit powers, different directivity gains from directional beamforming alignment and path loss laws for line-of-sight (LOS) and non-line-of-sight (NLOS) links, we introduce a normalization model to simplify the analysis of multi-tier mmWave cellular networks. The highlight of the model is that...
GIS (Gas Insulated Switchgear) is extensively used in the power grid to switch lines and protect the system. The higher requirements are proposed due to the increasing voltage level when comes to its internal over-heating problems. In this paper, the temperature rise of 40.5kV high voltage switchgear is researched with the help of ANSYS APDL and CFX. Firstly, the electromagnetic loss and generated...
In this paper, a displacement monitoring system is developed for regional high-precision monitoring tasks. This system locates the positions of target points by using hyperbolic positioning principle, and monitors displacements by continuously locating. To form the hyperbolas, the system works as a microwave interferometer to solve the phase difference of arrival. Composed by software defined radio...
Vacuum arc descaling technique is a dry and green substitute for the traditional acid-washing and mechanical cleaning technique widely used in the metallurgical industry. It mainly utilizes the high energy density property and the selective motion property of cathode spots. In this paper, the influences of different factors, mainly the vacuum arc circuit, the protect gas pressure, and the electrode...
Vacuum arc descaling technology is a new dry and green descaling technology that was put forward in recent years. The technology, which is environmental friendly, takes advantages of the high energy density and the selective movement of cathode spots to remove the oxide layer on cathode surface. In this paper, the characteristics of cathode surface in descaling are studied experimentally. Experimental...
In this paper, a 3D model for vacuum arc controlled by transverse magnetic field (TMF) is built and simulation on its parameters is calculated. In the simulation, only the external TMF is taken into consideration and arc is assumed to contracts itself. Arc is not neutral so that ions and electrons are calculated respectively. According to the simulation results, both ions and electrons are deflected...
In recent years high-speed electromagnetic repulsion mechanism (ERM), which is produced based on the eddy-current effect, has been widely applied to vacuum circuit breakers. One of the challenges for the design of ERM is to improve the speed of ERM by optimization design. In this paper, a novel co-simulation model is proposed. The related electromagnetic field, mechanical field and structural field...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.