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As a kind of extensive sources and low cost industrial waste, fly ash has many features, such as porosity, large surface area, adsorption capacity, chemical activity and weakly alkaline, which seem a wide prospect of application in wastewater treatment. This study proposed the acid modification test on fly ash. The effect of key factors including the particle size, pH, the dosage of fly ash, adsorption time and dosage of the modifier on domestic sewage removal efficiencies were evaluated. The optimum conditions and the corresponding removal efficiency were determined. The results show that the removal efficiency is increased firstly and steady subsequently with the increase of fly ash dosage, increased firstly and decreased subsequently with the increase of adsorption time, and increased firstly and decreased subsequently with the increase of pH value. The removal efficiency can up to 95.19% when 0.7 g fly ash added in 200 mL wastewater when the pH value was adjusted to 5 at the adsorption time of 20 min. And the best particle size of fly ash is 200 meshes, when used 2mol/L hydrochloride as modifier and soaked fly ash for 2h, and the ratio of hydrochloride and fly ash is 1mL / g, the effect is best. It also finds obviously that fly ash can have a better effect on removal efficiency than raw fly ash.

The sensorless vector control method of synchronous reluctance motors (SynRMs), based on extended back electromotive force (EMF) or flux observation, has been widely applied in the medium- or high-speed range. However, in the low-speed and low-current range, the extended back-EMF and flux are nearly zero. The use of the current frequency (I-f) control method can enable the motor to pass through the low-speed region, thereby ensuring that the back-EMF and flux reach a large value. I-f control methods that are widely used in permanent magnet synchronous motors (PMSMs) may encounter many problems when applied to SynRMs. The most serious issue is the inability to adjust the current amplitude to control the rotor angle and achieve a smooth transition to sensorless control. Based on various issues, this article proposes an I-f control method with four stages that can be used in SynRMs. This method uses a simple inductance identification method to solve the flux saturation phenomenon of SynRMs and then uses high-frequency voltage injection to continuously adjust the current amplitude and rotor angle position in conjunction with this inductance identification method. The effectiveness of this method is experimentally demonstrated on a 5.5 kW SynRM. [ABSTRACT FROM AUTHOR]

For the sensorless control in a low-speed range of synchronous reluctance motors (SynRMs), injecting random high-frequency (HF) square-wave-type voltages has become a widely used and technologically mature method. It can solve the noise problem of traditional injection signal methods. However, all injection signal methods will cause problems such as torque ripple, which causes speed fluctuations. This article proposes a self-regulating random model algorithm for the random injection signal method, which includes a quantity adaptive module for adding additional random processes, an evaluation module for evaluating torque deviation degree, and an updated model module that is used to receive signals from the other two modules and complete model changes and output random model elements. The main function of this algorithm is to create a model that updates to suppress the evaluation value deviation based on the evaluation situation and outputs an optimal sequence of random numbers, thereby limiting speed bias always in a small range; this can reduce unnecessary changes in the output value of the speed regulator. The feasibility and effectiveness of the proposed algorithm and control method have been demonstrated in experiments based on a 5-kW synchronous reluctance motor. [ABSTRACT FROM AUTHOR]

Two‐dimensional transition metal dichalcogenides (TMDs) are needed in high‐performance piezoresistive sensors due to their strong strain‐induced bandgap modification and thereby large gauge factors. However, integrating a conventional high‐temperature chemical vapor deposition (CVD)‐grown TMD with a flexible substrate necessitates a transfer process that inevitably degrades the sensing properties of the TMDs and increases the overall fabrication complexity. We present a high‐performance piezoresistive strain sensor that employs large‐area PdSe2 films grown directly on polyimide (PI) substrates via plasma‐assisted selenization of a sputtered Pd film. The reliable strain transfer from the substrate to the PdSe2 film ensures an outstanding strain‐sensing capability of the sensor. Specifically, the sensors have a gauge factor of up to −315 ± 2.1, a response time under 25 ms, a detection limit of 8 × 10−6, and an exceptional stability of over 104 loading–unloading cycles. By attaching the sensors to the skin surface, we demonstrate their application for measuring physiological parameters in health care monitoring, including motion, voice, and arterial pulse vibration. Furthermore, using the PdSe2 film sensor combined with deep learning technology, we achieved intelligent recognition of artery temperature from arterial pulse signals with only a 2% difference between predicted and actual temperatures. The excellent sensing performance, together with the advantages of low‐temperature fabrication and simple device structure, make the PdSe2 film sensor promising for wearable electronics and health care sensing systems. [ABSTRACT FROM AUTHOR]

Photodetectors with tunable responsivity are highly desirable for intelligent light sensors. The charge carrier transport properties of two-dimensional materials can be easily tuned by electrostatic doping due to their ultrathin thickness, meeting the requirement of deep optical sensing. In this study, we present the tunable temperature coefficient of resistance (TCR) in palladium diselenide (PdSe2) nanosheet-based field effect transistors (FETs) via gate voltage modulation. By applying a gate voltage to a FET with SiO2 (285 nm) dielectric, the TCR can be finely tuned from −1 to −3% K–1. Substituting the thick SiO2 with a thin h-BN dielectric further allows for TCR tuning from −2 to −0.06% K–1. The tunable TCR is attributed to the control of activation energy by the gate voltage. In addition, we demonstrate that a PdSe2 nanosheet-based FET, fabricated on a PI substrate, can act as a bolometric photodetector whose responsivity to infrared illumination (9.3 μm) can be electrically tuned. By modulation of the gate voltage, the responsivity can be adjusted from 21 to 245 mA/W. These findings suggest promising applications of PdSe2 nanosheet-based bolometers in next-generation intelligence infrared optoelectronic devices. [ABSTRACT FROM AUTHOR]

Atomically thin narrow-bandgap layered PdSe2 has attracted much attention due to its rich and unique electrical properties. For silicon-compatible device integration, direct wafer-scale preparation of high-quality PdSe2 thin film on a silicon substrate is highly desired. Here, we present the low-temperature synthesis of large-area polycrystalline PdSe2 films grown on SiO2/Si substrates by plasma-assisted metal selenization and investigate their charge carrier transport behaviors. Raman analysis, depth-dependent x-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy were used to reveal the selenization process. The results indicate a structural evolution from initial Pd to intermediate PdSe2– x phase and eventually to PdSe2. The field-effect transistors fabricated from these ultrathin PdSe2 films exhibit strong thickness-dependent transport behaviors. For thinner films (4.5 nm), a record high on/off ratio of 104 was obtained. While for thick ones (11 nm), the maximum hole mobility is about 0.93 cm2 V−1 S−1, which is the record high value ever reported for polycrystalline films. These findings suggest that our low-temperature-metal-selenized PdSe2 films have high quality and show great potential for applications in electrical devices. [ABSTRACT FROM AUTHOR]

In this study, an interior permanent magnet synchronous motor (IPMSM) for single-rotor air conditioner compressors with small inertia is studied, which adopts a sensorless control based on the phase-locked loop (PLL). Owing to the large periodic motor speed fluctuations, the speed and rotor angle of these compressors calculated by the PLL have inherent lagging phase shift and amplitude attenuation, which deteriorates the field weakening control performance and leads to larger speed fluctuations and current oscillations. In this study, a novel phase lead compensated PLL (PLC-PLL) was proposed to reduce the angle error between the real rotor position and estimated rotor position as well as to improve the performance of field weakening control. This method compensates the phase shift of the calculated angle and then reduces the angle error and speed fluctuations. Furthermore, the method of setting parameters for the PLC-PLL is also given. The experimental results confirm that this scheme can greatly reduce the angle error and the fluctuations of speed and currents, which improves the performance of the controller. [ABSTRACT FROM AUTHOR]

Pure Fe2O3 microspheres and Gd2O3/Fe2O3 loose microspheres were synthesized successfully by a facile hydrothermal method and followed with calcined. The structure and elemental composition were provided by the X-ray powder diffraction (XRD) and energy-dispersive spectroscopy (EDS). Additionally, the morphology was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), which show the loose surface state of Gd2O3/Fe2O3 microspheres. Finally, the property of the gas-sensing sensor based on Gd2O3/Fe2O3 loose microspheres was investigated systematically. It exhibits ultrahigh sensitivity of 268.6 to 100 ppm acetone at low operating temperature 220 °C, which is 9.8 times higher than the pure Fe2O3 microspheres sensor (27.5/100 ppm). Remarkably, the response of Gd2O3/Fe2O3 loose microspheres sensor to 0.1 ppm acetone is 2.3. Furthermore, the sensor shows fast response and recovery time (6/36 s) and splendid selectivity to acetone. [ABSTRACT FROM AUTHOR]

The pure and Tb-doped In2O3 beaded-porous nanotubes (BPNTs) are fabricated by simple electrospinning method. The crystal phase, morphology and chemical composition of the obtained samples were analyzed by characteristic techniques (XRD, FE-SEM, TEM, EDS, XPS, etc.). The mechanism of forming BPNTs structure was studied, and phase separation plays a key role in the process of formation. A series of sensing tests toward formaldehyde gas showed that 6 mol% Tb-doped In2O3 BPNTs exhibited the best sensing performance: high response (75-50 ppm), shorter response and recovery times (2 s and 12 s), low limit of detection (LOD, 1.27-100 ppb), good selectivity and long-term stability, etc. The significantly improved gas sensing properties were mainly resulted from their high surface basicity, enriched defects (oxygen vacancies), small crystallite size and complex porous structures. [ABSTRACT FROM AUTHOR]