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The closed-loop fluxgate current transducer (CFCT) is the only current sensor whose measurement accuracy can reach a level of the parts per million (ppm) at present. However, the false balance, which makes the CFCT unable to work, caused by an excessive offset current is the inherent flaw of the CFCT. The high di/dt (rate of current change) of the primary current is the main factor resulting in the offset current overload. Therefore, the CFCT is currently only applied for steady-state direct-current measurements. In this article, an approach is proposed to eliminate the false balance of the CFCT in the dynamic process by adding a feedforward branch, which provides a follow-up bias point for the CFCT to make the CFCT always work in a small-signal range, where a risk of magnetic saturation does not arise. The zero-flux state of the CFCT still only depends on the feedback branch, so its high measurement accuracy is maintained. The experiments prove that the CFCT can measure a flat-top pulsed current with an accuracy of the ppm level by this method.

The negative effect of an air gap layer presented between the membrane and cooling plate on air gap membrane distillation (AGMD) performance was diminished largely by inserting a water gap membrane distillation (WGMD) module in series. The new design of air-gap–water-gap membrane distillation (AG-WG)MD was evaluated experimentally by comparing with an AGMD system under different operating conditions. In theory, mass and heat transfer in the new (AG-WG)MD and imitative AGMD systems were analyzed. Experimental outcomes showed that a new (AG-WG)MD design profoundly enhanced flux (Pd) and gained output ratio (GOR), and greatly decreased energy consumption (STEC) and heat input (EH.I). At a concentration of 5,000 mg/L, coolant temperature of 20 °C, and flow rate of 18 L/h, Pd was promoted by 76.26%, 40.84%, 35.45%, 30.91%, and GOR by 46.38%, 33.46%, 31.27%, 26.65%, in addition to STEC being reduced about 55.63%, 46.81%, 43.66%, 38.30%, and EH.I around 31.31%, 25.84%, 23.53%, 20.55%, from the AGMD to (AG-WG)MD system at feed temperatures of 50 °C, 60 °C, 70 °C, and 80 °C, respectively. The outcomes proved that the AGMD performance could be significantly promoted by integrating with WGMD in a combined MD system. This combination increased the temperature difference across the membrane and decreased thermal-concentration boundary layers for the AGMD system.

The low flux and high energy consumption problems of the conventional three-stage air-gap membrane distillation (AG-AG-AG)MD system caused by the low temperature difference between hot and cold feed at both sides of the membrane and high boundary layer thickness were solved successfully by replacing one of the three stages of air gaps by a water gap. The novel three-stage air-gap–water-gap membrane distillation (AG-AG-WG)MD system reduced energy consumption and increased flux due to efficient internal heat recycling by virtue of a water-gap module. Heat and mass transfer in novel and conventional three-stage systems were analyzed theoretically. Under a feed temperature of 45 °C, flow rate of 20 l/h, cooling temperature of 20 °C, and concentration of 340 ppm, the (AG-AG-WG)MD promoted flux by 17.59% and 211.69%, and gained output ratio (GOR) by 60.57% and 204.33% compared with two-stage (AG-WG)MD and one-stage AGMD, respectively. This work demonstrated the important role of a water gap in changing the heat and mass transfer where convection heat transfer across the water gap is faster by 24.17 times than conduction heat transfer through the air gap. The increase in flux and GOR economized the heating energy and decreased waste heat input into the system. Additionally, the number of MD stages could increase the achieving of a high flux with operation stability.

A linear bypass circuit was developed to realize the high stability flat-top pulsed magnetic field (FTMPF) powered by battery-bank at the Wuhan National High Magnetic Field Center (WHMFC) in 2018. It mainly consists of the insulated-gate bipolar transistors (IGBTs) operating in the active region and a power resistor connected in series with the IGBTs. However, the terminal voltage of the IGBTs is high due to the operation in active region, which limits their through-current capability. In this paper, an approach for injecting current to the power resistor is proposed to reduce the terminal voltage of the IGBTs. Compared with the original technology, the through-current capability of the IGBTs will be enhanced greatly and the regulation scope of the FTPMF system will be expanded with the same number of IGBT. The method is discussed in detail and the number of IGBT is reduced from 35 to 8 in achieving an FTPMF of 40 T.

The accuracy of current measurement directly determines stability of the high flat-top pulsed magnetic field (FTPMF), which is a key aspect in some scientific studies. The Direct-Current Current Transformers (DCCT) is the best choice to achieve the high accuracy of current measurement. Different from the conventional DC current measurement, the DCCT is prone to be unstable in the FTPMF system due to the nonlinearity of the open-loop characteristic of DCCT. In this paper, the cause of nonlinearity of the open-loop characteristic is analyzed in detail, and a formulation is obtained to estimate the open-loop linear range (OLR). The relationship between the response time and OLR is proposed to make the DCCT stable. Then, a small-signal model is established to optimize the control parameters of the DCCT and a prototype of 30 kA is developed.

A high-stability flat-top pulsed magnetic field (FTPMF) is strongly needed for some scientific studies, such as nuclear magnetic resonance and specific heat measurement. This paper presents a new linear flat-top regulation bypass circuit to generate a high-stability FTPMF based on a battery bank power supply. The bypass circuit consists of insulated-gate bipolar transistors (IGBTs) in parallel that operate in the active region and are free of switch ripples. To achieve precise control of the IGBT current, the influence of the Miller effect and the nonlinearity of the IGBT's transfer characteristic are studied in detail. Then, a dual-feedback loop is designed and analyzed. A prototype consisting of a 1000 V/30 kA battery bank and a bypass circuit of 1700 V/3600 A IGBTs is developed. An FTPMF with a field/duration of 23.370 T/100 ms and a stability of 64.2 ppm has been achieved.

The phased-array ultrasonic levitation is a convenient technique to manipulate particles. In order to provide convenience for both professional and nonprofessional users to use the ultrasonic phase array levitation technique, we designed a man-machine interactive levitation system. It consists of a man-machine interaction module, a multi-channel transmitting circuit module, and an ultrasonic transducer array module. The man-machine interaction module can calculate the corresponding phase sequence according to user-defined position and angle. The transmitter module provides electrical excitation for the transducer array according to the calculated phase sequence. They can consequently generate the required sound field. Then, the man-machine interaction levitation module can control the particle position and rotation angle in real-time. In this paper, we described the man-machine interaction module and levitation module in detail and also demonstrated an example of realtime particle manipulation using the system.

In view of the problems of various types, frequent upgrades and inconsistent standards of WTDS on-board protocols and fault dictionaries of EMU, sort out various on-board protocol documents and fault dictionaries of EMU on the whole railway. Analyse the differences of various on-board protocols and fault dictionaries of multiple units of different vehicle types and batches, and study the unified and standardized management method. Design a EMU on-board data protocol management system with complete business functions, standard specifications, safety and reliability, and realize the functions of structuring the content of the protocol file, version of the protocol file, process management, etc., so as to provide data support for EMU data mining and PHM application.

Interferometric inverse synthetic aperture radar (InISAR) has received significant attention in three-dimensional (3D) imaging due to its applications in target classification and recognition. The traditional two-dimensional (2D) ISAR image can be interpreted as a filtered projection of a 3D target’s reflectivity function onto an image plane. Such a plane usually depends on unknown radar-target geometry and dynamics, which results in difficulty interpreting an ISAR image. Using the L-shape InISAR imaging system, this paper proposes a novel 3D target reconstruction algorithm based on Dechirp processing and 2D interferometric ISAR imaging, which can jointly estimate the effective rotation vector and the height of scattering center. In order to consider only the areas of the target with meaningful interferometric phase and mitigate the effects of noise and sidelobes, a special cross-channel coherence-based detector (C3D) is introduced. Compared to the multichannel CLEAN technique, advantages of the C3D include the following: (1) the computational cost is lower without complex iteration and (2) the proposed method, which can avoid propagating errors, is more suitable for a target with multi-scattering points. Moreover, misregistration and its influence on target reconstruction are quantitatively discussed. Theoretical analysis and numerical simulations confirm the suitability of the algorithm for 3D imaging of multi-scattering point targets with high efficiency and demonstrate the reliability and effectiveness of the proposed method in the presence of noise.

Bulk metallic glasses (BMGs) are a special kind of metastable complex metallic alloys with important potential applications. The ability of plastic deformation is of vital importance for the industrial application of BGMs, which can be improved by pulse current. In order to study the electroplastic effect in BMGs and prevent its crystallization caused by the high temperature in experiment, we design a power supply system with the function of real time adaptive adjustment of pulse current amplitude through feedback control to achieve precise temperature control of the specimen. It is proved by experiments that system has a high temperature control accuracy and meets the requirements of experiment for BMGs.

Recently a series of new topological materials, such as topological insulator, topological semimetal, topological superconductor have been discovered through a large number of magneto-transport measurements in high magnetic field, which greatly promotes the research process of topological quantum materials. The physical properties such as SdH oscillations can be observed from accurately measuring the magnetoresistance effect. The experimental environment puts higher requirements for data acquisition and processing procedures in topological materials measurements for the characteristics of high noise and short discharge time in pulsed high magnetic field. However, the references rarely mentions the related solutions. In this paper, a complete set of detection methods and data processing strategies for topological materials in pulsed high magnetic field environment are proposed. Here we introduce a digital lock-in amplifier and optimize the parameters of FIR filters. Based on NI-PXI-5105 and Labview, the model of fast auto-detection digital lock-in system is carried out. Taking the WTe 2 sample to experiment, the magneto-resistance detection and data analysis were performed in 65T pulsed magnetic field. A clear magnetoresistance curve with the significant SdH quantum oscillation at different temperatures was obtained. The results proved that this method is effective and applicable to complete the measurement technology of topological quantum materials in high magnetic field.

There is a great market demand for positive-charged membrane used to treat wastewater containing positive-charged pollutants. Based on the fact that the C–Cl bond energy in the molecular chain of the PVDF-based poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) copolymer membrane is significantly lower than the C–F bond. Herein, the method of controllable positive-charged modification of PVDF-CTFE membrane surface has been successfully realized by using diethylenetriamine (DETA) a small molecule polyamine compound under mild conditions. The modified membranes were characterized by X-ray photoelectron spectroscopy (XPS), zeta potential and water contact angle, and the best condition for positive-charged modification were explored. The results show that the modified membrane has an excellent positively charged effect, changing from an original membrane which is completely negative to the positive-charged membrane whose isoelectric point value is 7.63, the content of N element is as high as 6.31 at% and the water contact angle decreased by 42.8%. After 7 cycles of treatment of polycationic acrylamide solution, the recovery rate of feed-liquid flux is still above 97.5%, indicating that the ability to resist positively charged pollutants is significantly improved. More importantly, the mechanical strength is not adversely affected. The method proposed in this paper may provide a good idea for the graft modification of chlorinated polymers.

The ability to effectively manipulate magnetic particles is of great importance for biological and chemical applications. To achieve improved controllability of magnetic particles in a microsystem, this paper proposed a hybrid magnet system consisting of integrated microconductors and external permanent magnets for producing a special gradient magnetic field. Finite-element numerical simulations were carried out to map the magnetic force distribution in the region of interest around microconductors for eight configurations of the hybrid magnet system. Then, these simulation predictions were qualitatively illustrated by microscopic visualizations of the concentrated positions of magnetic particles in the experiments. Results show that either attracting or repelling forces acting on magnetic particles can be generated by use of the hybrid magnet system and magnetic particles can be captured toward different regions, which are relevant to both directions of currents flowing in the microconductors and external uniform magnetic fields generated by permanent magnets.

Fully understanding the dynamics of particles induced by magnetic fields with considering particle-particle interaction is an interesting and important issue for delivering magnetic particles to a target site with a high efficiency. For this purpose, permanent magnets with horizontal and vertical magnetization directions respectively have been taken for generating two types of gradient magnetic fields, which are applied to produce similar gradient magnetic forces while with different magnetic interaction forces between particles. On this basis, the distributions of particles under the two gradient magnetic fields are investigated and compared using Monte Carlo simulations. The results show that the concentrated particles have chainlike structures and their distributions are configuration dependent with the magnetization direction of permanent magnets: parallel and perpendicular to the bottom line for horizontal and vertical magnetization directions, respectively. Above all, a detailed microscopy study reveals that the movement trajectories of magnetic particles are affected by both transport and aggregation behavior of particles and the microscopic visualizations of particle distributions in the target region are in agreement with simulation predictions.

In this paper, a kind of poly(vinylidene fluoride) (PVDF) porous heat exchange tube (HET) was prepared via non-solvent induced phase separation (NIPS) method. This porous HET possessed an ultra-thin dense skin layer of 2 μm. Since the thermal conductivity of water is higher than that of PVDF, filling the pores with water can significantly improve the heat performance of the porous HET. A full plastic double-pipe air gap membrane distillation (AGMD) module was fabricated with the porous HETs and PVDF hollow fiber membranes. In the AGMD process, the wetting treatment can make the membrane distillation flux (J) and the gained output ratio (GOR) increased by 30%. During the long-term stability test, the maximum conductivity of distillate water was only 17.2 μS/cm. The experimental results demonstrated that the porous HET can be applied for the AGMD process to treat high saline brine, and the ultra-thin dense layer can prevent the leakage of saltwater.

In this paper, an innovative method for generating high stability flat-top pulsed magnetic field (FTPMF) based on battery power supply is proposed. The system including a bypass circuit and a divider resistor is developed. The bypass circuit is in parallel with the magnet to form a parallel branch, with which the divider resistor is in series. Different from traditional application, the IGBT in bypass circuit work in linear area, as a controllable constant current source, rather than in the switch mode. The current of bypass circuit can be adjusted by the driving voltage of IGBTs to achieve the continuously regulation of the voltage division ratio between divider resistor and magnet. The current of magnet can maintain stability with feedback control, and high stability flat-top pulsed magnetic field can be obtained. The prototype has been developed, and the experiment was conducted, which proved that the high stability current can be achieved by this way.