A compact pulsed power driver with precisely shaped current waveforms for magnetically driven loading experiments.

Magnetically driven loading techniques based on high current pulsed power drivers are very important tools for researching material dynamic behaviors and high-pressure physics. Based on the technologies of a Marx generator energy storage and low impedance coaxial cable energy transmission, a compact high current pulsed power driver CQ-7 was developed and established at the Institute of Fluid Physics, China Academy of Engineering Physics, which can generate precisely shaped current waveforms for magnetically driven loading experiments. CQ-7 is composed of 256 two-stage Marx generators in parallel with low impedance, high voltage coaxial cables for current output. The 256 Marx generators are divided into 16 groups, and each separate group can be individually triggered to discharge and shape currents in sequence by a low jitter, high voltage pulse trigger with 16 output signals. The electrical parameters of CQ-7 are a capacitance of 20.48 µF, an inductance of 4.12 nH, and a resistance of 3.35 mΩ in a short circuit. When working at the charging voltage of ±40-±60 kV, CQ-7 can deliver a peak current from 5 to 7 MA to the short-circuit loads with a rising time of 400-700 ns at different discharging time sequences. Two different experiments were conducted to test the performance of CQ-7: magnetically driven high velocity flyer plates and solid liner implosion. The results show that CQ-7 can accelerate the aluminum flyer plate with a size of 12 × 8 × 1 mm3 to more than 7.5 km/s and uniformly drive the aluminum liner with an inner diameter of 6.2 mm and a thickness of 0.4 mm to more than 9.5 km/s. Furthermore, these experiments indicate that CQ-7 is a robust platform for material dynamics and high-pressure physics.

Adaptive Neural Dynamic Surface Control With Prespecified Tracking Accuracy of Uncertain Stochastic Nonstrict-Feedback Systems.

This article addresses the adaptive neural tracking control problem for a class of uncertain stochastic nonlinear systems with nonstrict-feedback form and prespecified tracking accuracy. Some radial basis function neural networks (RBF NNs) are used to approximate the unknown continuous functions online, and the desired controller is designed via the adaptive dynamic surface control (DSC) method and the gain suppressing inequality technique. Different from the reported works on uncertain stochastic systems, by combining some non-negative switching functions and dynamic surface method with the nonlinear filter, the design difficulty is overcome, and the control performance is analyzed by employing stochastic Barbalat's lemma. Under the constructed controller, the tracking error converges to the accuracy defined a priori in probability. The simulation results are shown to verify the availability of the presented control scheme.

Fine-mapping and identification of a candidate gene controlling seed coat color in melon (Cucumis melo L. var. chinensis Pangalo).

KEY MESSAGE: MELO3C019554 encoding a homeobox protein (PHD transcription factor) is a candidate gene that involved in the formation of seed coat color in melon. Seed coat color is related to flavonoid content which is closely related to seed dormancy. According to the genetic analysis of a six-generation population derived from two parents (IC2508 with a yellow seed coat and IC2518 with a brown seed coat), we discovered that the yellow seed coat trait in melon is controlled by a single dominant gene, named CmBS-1. Bulked segregant analysis sequencing (BSA-Seq) revealed that the gene is located at 11,860,000-15,890,000 bp (4.03 Mb) on Chr 6. The F2 population was genotyped using insertion-deletions (InDels), from which cleaved amplified polymorphic sequence (dCAPS) markers were derived to construct a genetic map. The gene was then fine-mapped to a 233.98 kb region containing 12 genes. Based on gene sequence analysis with two parents, we found that the MELO3C019554 gene encoding a homeobox protein (PHD transcription factor) had a nonsynonymous single nucleotide polymorphism (SNP) mutation in the coding sequence (CDS), and the SNP mutation resulted in the conversion of an amino acid (A → T) at residue 534. In addition, MELO3C019554 exhibited lower relative expression levels in the yellow seed coat than in the brown seed coat. Furthermore, we found that MELO3C019554 is related to 12 flavonoid metabolites. Thus, we predicted that MELO3C019554 is a candidate gene controlling seed coat color in melon. The study lays a foundation for further cloning projects and functional analysis of this gene, as well as marker-assisted selection breeding.

A compact platform for the investigation of material dynamics in quasi-isentropic compression to ~ 19 GPa.

This paper reports on the development of a magnetically driven high-velocity implosion experiment conducted on the CQ-3 facility, a compact pulsed power generator with a load current of 2.1 MA. The current generates a high Lorentz force between inner and outer liners made from 2024 aluminum. Equally positioned photonic Doppler velocimetry probes record the liner velocities. In experiment CQ3-Shot137, the inner liner imploded with a radial converging velocity of 6.57 km/s while the outer liner expanded at a much lower velocity. One-dimensional magneto-hydrodynamics simulation with proper material models provided curves of velocity versus time that agree well with the experimental measurements. Simulation then shows that the inner liner underwent a shock-less compression to approximately 19 GPa and reached an off-Hugoniot high-pressure state. According to the scaling law that the maximum loading pressure is proportional to the square of the load current amplitude, the results demonstrate that such a compact capacitor bank as CQ-3 has the potential to generate pressure as high as 100 GPa within the inner liner in such an implosion experiment. It is emphasized that the technique described in this paper can be easily replicated at low cost.

Comprehensive Analysis of Transcriptome and Metabolome Reveals the Flavonoid Metabolic Pathway Is Associated with Fruit Peel Coloration of Melon.

The peel color is an important external quality of melon fruit. To explore the mechanisms of melon peel color formation, we performed an integrated analysis of transcriptome and metabolome with three different fruit peel samples (grey-green 'W', dark-green 'B', and yellow 'H'). A total of 40 differentially expressed flavonoids were identified. Integrated transcriptomic and metabolomic analyses revealed that flavonoid biosynthesis was associated with the fruit peel coloration of melon. Twelve differentially expressed genes regulated flavonoids synthesis. Among them, nine (two 4CL, F3H, three F3'H, IFS, FNS, and FLS) up-regulated genes were involved in the accumulation of flavones, flavanones, flavonols, and isoflavones, and three (2 ANS and UFGT) down-regulated genes were involved in the accumulation of anthocyanins. This study laid a foundation to understand the molecular mechanisms of melon peel coloration by exploring valuable genes and metabolites.

A 200 kJ electrical gun for hypervelocity launch.

In order to meet the requirements of hypervelocity launch in the context of defending against space debris and deflecting asteroids, an electrical gun with 200 kJ of storage energy was recently built. The electrical gun is composed of 16 gas spark switch-capacitor modules, and pulse current is transmitted by parallel aluminum plates that are insulated by polyester foils. The capacitance, inductance, and resistance of the RLC circuit of the 200 kJ electrical gun are 80 µF, 10.3 nH, and 2.6 mΩ, respectively. It can generate pulse current with a rise time of 1.33 µs and an amplitude of 5.2 MA when short-circuited at a charging voltage of 70 kV. Hypervelocity flyer launch experiments were carried out on the 200 kJ electrical gun, in which a ϕ20 × 0.5 mm2 Mylar flyer (0.22 g) was accelerated to 10 km/s.

A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments.

A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 µF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10(-2) Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak current of new generators can be increased to 5-6 MA and about 100 GPa ramp stress can be produced on the metallic samples for high pressure physics, and a conceptual design of CQ-5-MMAF was given.