In high-current pulsed-power accelerators, magnetically insulated transmission lines (MITLs) are used to transmit hundreds of terawatts of pulsed power from the multimodule prime sources and multilevel insulator stacks to various physical loads at the central region. At the inner-MITL (iMITL) region, whose lineal current density can reach several MA/cm, energy loss on electrodes will be severe. A variational calculus technique is used to optimize the iMITL profile to minimize the energy loss on the electrodes. The optimized iMITL is compared with the common L-shaped iMITL. The results show that the energy loss of the optimized iMITL is 40%–50% less than that of L-shaped iMITL at the same operating conditions. The effects of peak current and its rise time on the energy loss are investigated. The advantage of the optimized iMITL is greater when the peak current and rise time are higher. As the peak current is fixed at 35 MA and the rise time increases from 100 to 200 ns, the ratio of the energy loss to the input energy from the L-shaped iMITL increases from 7.85% to 19.07%, whereas the energy-loss ratio of the optimized iMITL always does not exceed 13%. As the current rise time is fixed at 150 ns and the peak varies between 25 and 45 MA, the energy-loss ratio of the L-shaped iMITL ranges from 9.80% to 19.75%, but the energy-loss ratio of the optimized iMITL is always within 14%.
The interactions between grids and power converters can easily lead to performance degradation or even instability, especially in weak grids where grid impedance can change frequently and significantly. A loop gain based auto-tuner is proposed in this work for power converters to maintain high control performance and robust grid-converter connection. The auto-tuner is designed to autonomously adjust controller's parameters (e.g., proportional gain and integral gain) of power converters based on real-time estimated loop gain. Compared with impedance reshaping methods, the proposed solution requires no additional hardware and guarantees simultaneously high control performance and sufficient stability margins. Experimental results are given for validating the effectiveness of the proposed method.
Several studies have linked gut microbiota to human brain activity. This study used Mendelian randomization (MR) to investigate the causal relationship between gut microbes and delirium.MR was used to select SNPs from large-scale GWAS summary data on 211 gut microbiota taxa and delirium. Inverse variance weighting (IVW), weighted median, and MR-Egger methods were used for statistical analyses. Outliers were assessed using the leave-one-out method. To avoid horizontal pleiotropy, we performed the MR-PRESSO and MR-Egger intercept tests. Cochran's Q and I2 values for IVW and MR-Egger were used to assess heterogeneity.IVW suggested that genetic prediction of the family Desulfovibrionaceae (1.784 (1.267-2.512), P = 0.001), order Desulfovibrionales (1.501 (1.058-2.128), P = 0.023), and genus Candidatus Soleaferrea (1.322 (1.052-1.659), P = 0.016) increased the risk of delirium, but the family Oxalobacteraceae (0.841 (0.722-0.981), P = 0.027), and genera Holdemania (0.766 (0.620-0.946), P = 0.013), Ruminococcus gnavus (0.806 (0.661-0.982), P = 0.033), and Eggerthella (0.815 (0.667-0.997), P = 0.047) reduced the risk of delirium.(1) Limited sample size, (2) inability to assess gut microbiota interactions, and (3) limited to European populations.Our results suggest that presence of the microbial family Desulfovibrionaceae, order Desulfovibrionales, and genus Candidatus Soleaferrea increased the risk of delirium, whereas the Oxalobacteraceae family, and the genera Holdemania, Ruminococcus gnavus, and Eggerthella decreased the risk of delirium. However, the potential of gut probiotic interventions in the prevention of perioperative delirium should be emphasized.
Abstract Since uranium carbide (UC) fuel has higher thermal conductivity and uranium density than UO2 fuel, good inherent safety and economy can be achieved by UC dispersion fuel. This paper focuses on the research of UC phase control during sol-gel preparation of UC ceramic microsphere. Using nano-carbon black powder as carbon source, UC ceramic microspheres were prepared by sol-gel process combined with carbothermal reaction process. Specific amount of carbon black was uniformly added into the glue solution, which was then dispersed to prepare carbon ADU gel spheres. With heat treatment of carbon ADU gel spheres subject to carbothermic reaction, ceramic microspheres containing UC phase were obtained. During the experiment, the effects of different carbon black addition ratio, thickener addition level and dispersion process on the chemical composition, sphericity and surface morphology on UC ceramic microspheres were investigated. The effects of heat treatment temperature, atmosphere and pressure on the preparation of UC microspheres were also studied during the carbothermic experiment. The process parameters for UC phase control were determined through the experiment and XRD, and the ceramic microsphere samples containing the UC phase were obtained as well. Analysis results show that crack-free UC microspheres with smooth surface can be obtained after drying when sol solution C/U is 2.5∼6.0 and thickener addition level is 1.2∼2.0 kg/kgU. By reaction treatment at high temperature, ceramic microspheres with good sphericity, compact structure and UC phase composition were obtained. A preparation method of UC ceramic microspheres was developed as a result.
The fast linear transformer driver (FLTD) utilizes a water-insulated transmission line as its secondary. To monitor the fast pulsed current and locate the fault, a compact self-integrating current sensor is developed. Print circuit board (PCB) coils and PCB integrating resistors are used to form the current sensor. By soldering a large number of chip resistors, PCB integrating resistors with various resistance and low inductance can be obtained. The current sensor is designed in a coaxial structure to reduce its inductance and size and can be installed on the inner conductor of the FLTD’s secondary water-insulated transmission line with a small opening. The principle and matching schemes for the current sensor are theoretically analyzed with the circuit principle. Both simple matching and two-stage division can be used to obtain signals without oscillation. The time constant of the two schemes is the same. However, the sensitivity of the current sensor with two-stage division is lower than that with simple matching. A 100 kV step pulse generator is used as the pulsed high current generator to verify the properties of the current sensor. The designed current sensor could respond to the step current pulse with the rise time of 4 ns. The matching scheme is verified to be effective with step response experiments. Finally, the influence of the parameters, which are the coil type, the angle between the PCB coil and the magnetic flux, the resistance of the integrating resistor, and the length of the measuring cable, on the output signal of the current sensor is studied.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Cold hole expansion is a crucial technology for enhancing the fatigue life of hole structures. This paper presents the design and optimization of a novel multi-convex hulls expansion tool for deep small holes in Inconel 718 superalloy using the finite element method (FEM) and experimental techniques. The results from the FEM model, which was used to investigate the compressive residual stress (CRS) distribution and contact force during the expansion process, indicate that the curved single convex hull(CSCH) structure is more suitable for deep small hole expansion (DSHE). However, accounting for the strength limitations of the actual expansion tool, a multi-convex hulls expansion tool structure was proposed. The FEM model was employed to compare the effects of various tool structures on the hole wall CRS distribution and the contact force during the expansion process. The obtained optimal parameters for enhancing deep small holes in Inconel 718 superalloy under high temperature and high load conditions are as follows: expansion section hull spacing l 1 = 0.4 mm, taper ratio C = 0.008, number of convex hulls in the sizing section n = 10, and sizing section hull spacing l 2 = 1 mm. Moreover, an optimized convex hull expansion amount allocation scheme was obtained through an experimental study. The results of the FEM simulations and experimental study demonstrate that the optimized multi-convex hulls expansion tool (with an expansion rate of 1.92%) can induce the formation of a high CRS layer and a refined surface without causing significant microcracks in the hole walls.
Stretchable electroluminescent device is a compliant form of light-emitting device to expand the application areas of conventional optoelectronics on rigid wafers. Currently, practical implementations are impeded by the high operating voltage required to achieve sufficient brightness. In this study, we report the fabrication of an intrinsically stretchable electroluminescent device based on silver nanowire electrodes and high-k thermoplastic elastomers. The device exhibits a bright emission with a low driving voltage by using polar elastomer as a dielectric matrix of the electroluminescent layer. Highly stretchable silver nanowire electrodes contribute to the exceptional elasticity and durability of the device in spite of bending, stretching, twisting, puncturing, and cutting. Stretchable electroluminescent devices developed here may find potential uses in wearable displays, deformable lightings, and soft robotics.
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