Explore the vast range of titles available.

Field uniformity is one of the most important parameters for evaluating the uncertainty of electromagnetic reverberation chambers. In this paper, the field uniformity is divided into intrinsic and tuning sample component, and an assumption is proposed to clarify the relationship between the total field uniformity and two decomposed components. Standardized field uniformity is conducted in experiment. Then experimental results indicate that the intrinsic component is related to the design and change with frequency, while the tuning sample uncertainty component is related to the number of stirring paddles and independent of frequency.

High-temperature superconducting (HTS) magnets are applied across MRI, NMR, and fusion, and particle accelerators are likewise advancing toward higher magnetic fields, creating a need for high-field magnets. In synchrotrons, high-field dipole magnets of saddle geometry are required, and REBCO has drawn attention as a promising material to realize them. For these applications, the magnetic field must be spatially homogeneous along the beam line and temporally stable. However, for REBCO dipole magnets, there are few studies that rigorously report field uniformity and temporal stability on the beam line, and efforts to improve the uniformity itself remain scarce. Here we demonstrate improved field uniformity in a conduction-cooled, no-insulation (NI) REBCO saddle dipole magnet engineered to produce a 0.5 T central field. Two strategies to mitigate magnetic field uniformity due to screening-current-induced field (SCIF) or fabrication errors were assessed: current sweep reversal (CSR) and passive shimming using an AISI 1008 ferroshim. CSR produced 0.4 of improvement in spatial uniformity, while the ferroshim improved uniformity 4.5 . Harmonics are sextupole-dominant with small skew residuals, and temporal drift is 0.38 . Our results demonstrate the impact of each magnetic-field improvement technique on field uniformity using numerical simulations and experimental validations. These results outline a practical route to low-temperature-superconducting(LTS)-class field uniformity in a compact and cryogen-free dipole magnet with the NI HTS technique.

Aiming at the electromagnetic compatibility testing requirements of slender equipment, this paper proposes a design scheme for a cylindrical reverberation chamber. Through numerical simulation, the lowest usable frequency and field uniformity of the cylindrical reverberation chamber were analyzed. The results show that the cylindrical reverberation chamber has good field uniformity when the frequency is greater than , meeting the stringent requirements of IEC 61000‐4‐21. Utilizing this cylindrical structure for the reverberation chamber can effectively reduce testing costs and improve testing efficiency and accuracy. This research provides a foundation for further optimization of cylindrical reverberation chamber design, and it is expected to become an important tool for effective electromagnetic compatibility testing of equipment.

The use of metasurfaces to increase the number of modes, lower the operating frequency, and improve the field uniformity in reverberation chambers (RCs) is investigated in this paper. The method used to improve the field uniformity and decrease the resonance frequencies is based on increasing the number of modes by using the concept of subwavelength cavities. The resonance frequencies of a RC with metasurface wall are derived and expressed analytically in terms of macroscopic characteristics. Simulation of the reflection phase of the unit cell is then given as a guideline to choose the required microscopic parameters of the designed metasurface. The mode density in such subwavelength RCs is then obtained using a numerical eigenmode solver. Compared to traditional RCs, a much higher modal density is obtained at low frequencies. The standard deviation of the field uniformity in the test volume of the RC corresponding to different types of metasurface walls is finally compared. It is shown that by increasing the number of modes in the RC at the lower band, the operating frequency decreases and the field uniformity of the RC is improved.

To power the fast kicker magnet for releasing ions from the booster accelerator into the Booster–Nuclotron channel of the NICA accelerator complex (JINR, Dubna), generators based on TPI1-10k/75 pseudospark switches were developed, manufactured, and tested. The choice of the switch was due to the unique requirements for the parameters of the output pulse and the impossibility of using solid-state high-voltage switches due to the high radioactive background in the beam bypass areas at the complex. To ensure a front of 500 ns and a pulse plateau duration of 500 ns in order to reduce the influence of the inductance of the magnet conductors of 650 nH, a decision was made to use its bipolar “counter” power supply. Thanks to this, currents of more than 30 kA were obtained at a charging voltage of the forming line of up to 50 kV. The article describes the generator circuits and presents the results of their tests at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, and directly at the workplace at the NICA complex.

In order to improve the uniformity of the flow field, the processing stability, and the machining accuracy of the electrochemical machining (ECM) of cross groove structure, in this work, the flow field simulation model of the ECM of cross groove was established, and a flow field analysis was carried out based on the cathodes with different holes. Further, an experimental device was designed for the ECM of the cross groove. The results show that the uniformity of the flow field in the machining gap can be improved by adopting the symmetrical and uniform placement of the cathode hole, and the design of the connecting groove at the outlet of the cathode. In the ECM experiment, the reasonable selection of processing parameters such as the cathode feed velocity and the machining voltage can effectively improve the process stability and machining accuracy. When the diameter of the cathode hole is smaller, the cross groove with better machining effect can be obtained.

This study primarily simulates the flashover phenomenon between the metal fittings (rods) and the skirt surface (plates) of insulators when water droplets traverse between them under heavy rain conditions. High-speed cameras recorded droplet deformation and breakdown processes, while electric field simulation software modeled the air gap’s electric field distribution. The effects of air gap length, axial position of the water droplet, droplet conductivity, droplet diameter, and voltage polarity on the DC breakdown voltage were analyzed. Results indicate that a larger air gap leads to a greater reduction in droplet breakdown voltage and lower electric field uniformity. The breakdown voltage is essentially independent of changes in the axial position of the droplet and the droplet’s conductivity. The breakdown voltage exhibits no significant correlation with droplet diameter. Droplets rarely break down when voltage is applied to the electrodes, indicating that flashover at the low-voltage end of insulators during rainfall occurs infrequently. This research holds significant importance for elucidating the flashover mechanisms of water droplets at both ends (high-voltage and low-voltage) of the insulators and for guiding the design of external insulation for power equipment.

The uniformity of the excitation magnetic field is an important factor affecting the measurement accuracy of the electromagnetic flowmeter and its adaptability to different flow states of the complex multiphase flow. The main purpose of this paper is to improve the measurement accuracy of electromagnetic flowmeter by improving the uniformity of magnetic field excitation of electromagnetic flowmeter sensor. Firstly, an evaluation index system based on area weight magnetic field deviation degree is established, and the concept of flow state adaptability is put forward. According to this evaluation system, the excitation structure of the conventional electromagnetic flowmeter sensor is improved and optimized, and an excitation model with high uniformity is designed. Meanwhile, the ANSYS software is used for numerical simulation, and normalized standard deviation is used to compare between the new and the traditional electromagnetic flowmeter models. Finally, according to the requirements of the index function, the magnetic pole detection angle of the improved excitation model is simulated and analyzed, and the optimal magnetic pole detection angle is determined to be 45°. On this basis, a new electromagnetic flowmeter is designed for complex multiphase flow at oil wellhead. The field test proves that the measurement error of this flowmeter can reach less than 5%. Compared with the traditional electromagnetic flowmeter, the measurement accuracy has been greatly improved.

The Circulating Water Channel (CWC) is a device commonly utilized in maritime engineering for hydrodynamic experiments. The ability to generate a high-quality flow field is a critical criterion for evaluating the device, and thus, improving key parts of the CWC device can significantly increase this ability. In this paper, a numerical model based on the RANS method is established to investigate the hydrodynamic performance of the circulating water channel’s finite section. First, associated analyses and optimizations for the turning vanes and contraction section are performed. Following confirmation that adding a honeycomb can greatly improve the flow field, the hole type and length diameter ratio are investigated further. After integrating the components, the flow field properties are examined at various flow velocities. The main findings demonstrate that flow field’s uniformity can be enhanced using the right number of turning vanes. Applying the Witozinsky transition curve to the contraction section can produce a better pressure gradient and increase the efficiency of contraction selection. The best rectification result is achieved by a honeycomb with a square shape and a slenderness ratio of 9. By varying flow velocities, the most uniform flow field area occurs at 4 m to 16 m from the outlet of the contraction section. This model can better simulate the dynamic characteristics of the flow field in the 3D CWC and serve as the foundation for the design of multifunctional CWC equipment for wind, wave, and flow.

By combining a transmission line system (TLS) and a reverberation chamber (RC), a hybrid electromagnetic compatibility (EMC) testing facility is designed and constructed. Generally, the lowest usable frequency (LUF) of an RC is limited by its dimension, which limits the application of RCs for EMC testing at low frequencies. Therefore, to improve the field uniformity (FU) of an RC at frequencies lower than the LUF, a TLS is integrated into the RC. After optimizing the load resistance, length, and width of the TLS, the resonant frequency and electric field spikes of the hybrid system are eliminated. The FU of the E-field in the system is greatly improved in the frequency range of 0-30 MHz. Moreover, using an oscillating wall stirrer in the RC, the FU satisfies the standard (IEC 61000-4-21) above 80 MHz. Results show that combining the TLS and the RC testing system could be widely used for EMC testing in the frequency range of 0-30 MHz and 80 MHz-6 GHz.