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Vacuum‐evaporated metal halides (MHs) scintillator thick films have received much attention in the X‐ray imaging field due to their excellent light yield and uniform large‐area preparation. However, the inevitable heteromorphic homologs in MHs (e.g., Copper‐based MHs (Cu‐MHs): CsCu2X3∖Cs3Cu2X5) and change of film structural backbone will result in spectral hybridization (phase purity), and the film eventually detaches (lattice mismatches). Herein, a single‐source vacuum evaporation method to prepare a thick film (≈10 µm) of Cu‐MHs (as an example) scintillators is realized: 1) Presynthesis of pure phase materials by solution method with a protective agent to ensure phase purity without precise control of component ratios in evaporation process; 2) One‐shot formation of film structural backbone avoids stress accumulation and utilize the longitudinal growth characteristics of crystalline films to obtain crystal orientations with better optical outputs. Finally, the films obtained have a light yield comparable to a partially single‐crystal (53 983 photons MeV−1) and an imaging resolution (14.1 lp mm−1) comparable to the partial template method. The detection system based on the prepared Cu‐MHs scintillator thick films exhibits good response speed and linearity in response to different X‐ray radiation intensities and exposure times. The method will further drive the application of MHs is believed. [ABSTRACT FROM AUTHOR]

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This paper presents a high-performance, multilevel inverter with symmetry and simplification. This inverter is a single-phase, seven-level symmetric switched-capacitor inverter based on the concept of the double voltage clamping circuit connected to the half-bridge circuit. Above all, only a single DC power supply is used to achieve a single-phase inverter with seven levels and a voltage gain of three. In addition to analyzing the operating principle of the proposed switched-capacitor multilevel inverter in detail, the stability analysis and controller design are carried out by the state-space averaging method. The feasibility and effectiveness of the proposed structure are validated by some simulated results based on the PSIM simulation tool and by some experiments using FPGA as a control kernel, respectively. However, in this study, the switches were implemented by MOSFETs to meet a high switching frequency. These MOSFETs can be replaced by IGBTs in the motor drive applications so that the used switching frequency can be reduced. [ABSTRACT FROM AUTHOR]

Multiple techniques have been suggested to achieve control balance in single-phase three-level neutral-point clamped (3L-NPC) converters. Nevertheless, there is a deficiency of quantitative calculations related to the extent of balancing. Operating beyond the balancing range may result in a sequence of safety incidents. This paper presents a conceptualization of the 3L-NPC converter as two cascaded H-bridges. By employing power conservation principles, the balancing range for the NPC converter is derived, and two novel methods are investigated to broaden the balance range in accordance with the calculated balance range. A comparison is made among the balancing ranges under different balancing control methods. This study establishes a theoretical foundation to ensure the secure and stable operation of the NPC converter. [ABSTRACT FROM AUTHOR]

In the energy sector, the application of renewable energy sources especially solar photovoltaics (PV), is expanding exponentially. Inverters find application in converting DC power from solar PV generating arrays to AC power and feeding it to grid. This study proposes a 5-level switched-capacitor multilevel inverter (SCMLI) that can be used for solar PV applications. The problem of leakage current was mitigated with the use of common ground configuration. Based on various performance parameters a comparison with recently proposed SCMLI’s has been carried out. The proposed SCMLI achieves an efficiency of 95.03% under a 2-kW load. It utilizes one input DC power source, 7 switches, and 2 capacitors only. The experimental results of the proposed inverter show better harmonic profile with reduced Total Harmonic Distortion (THD). The performance of the proposed MLI topology is validated through MATLAB/SIMULINK. Moreover, loss analysis has been carried out on PLECS platform. The hardware implementation is done on a power converter test bed.

Despite numerous studies focused on the hydrothermal (HT) synthesis of fly ash zeolites (FAZs), this method still has many limitations, the main of which is the low yield of zeolites. Hydrothermally synthesized zeolites are typically multiphase and exhibit low purity, which limits their applicability. Pure-phase zeolites have been primarily prepared from filtrates after alkaline mineralization of fly ashes, not directly in suspension. In addition, the published methodologies have not been tested in a wider set of samples, and thus their reproducibility is not confirmed. The aim of the study is to propose a reproducible methodology that overcomes the mentioned limitations. The influence of the Si/Al ratio (1.3:1–1:2), the type and concentration of the activator (2/4 M NaOH/KOH/LiOH), the reagent (30% LiCl), the duration (24–168 h), and the temperature (50–180 °C) of the synthesis phases were studied. The sequence of the synthesis phases was also optimized, depending on the type of heat transfer. The fly ashes were analyzed by wavelength-dispersive X-ray fluorescence (WD XRF), flame atomic absorption spectrometry (F-AAS), and X-ray diffraction (XRD). The energy intensity of the synthesis was reduced through the application of unique microwave digestion technology. Both microwave and combined (microwave and convection) syntheses were conducted. FAZs were identified and quantified by XRD analysis. This study presents a three-stage (TS) hydrothermal synthesis of pure-phase sodalite in suspension. Sodalite (>99 wt.%) was prepared from nine fly ashes under the following conditions: I. microwave phase: 120 °C, 150 min, solid-to-liquid ratio (S/L) 1:5, Si/Al ratio 1:1.5, and 4 M NaOH; II. convection phase: 120 °C, 24 h, S/L 1:40, and the addition of 30 mL of 30% LiCl; and III. crystallization: 70 °C for 24 h. The formation of rhombododecahedral sodalite crystals was confirmed by scanning electron microscope (SEM) images. [ABSTRACT FROM AUTHOR]

In this study, high-entropy spinel-type (Mg 0.2 Co 0.2 Ni 0.2 Li 0.4 Zn 0.2)Al 2 O 4 ceramics were synthesized by solid-state reaction method. The raw materials gradually formed spinel aluminates from 700 to 1400 °C and finally formed high-entropy (Mg 0.2 Co 0.2 Ni 0.2 Li 0.4 Zn 0.2)Al 2 O 4 ceramics after calcination at 1400 °C for 4 h. The high-configuration entropy and low average atomic-size difference were beneficial to form single-phase high-entropy ceramics. Partial lattice distortion occurred within the high-entropy (Mg 0.2 Co 0.2 Ni 0.2 Li 0.4 Zn 0.2)Al 2 O 4 ceramics structure, and its grain size gradually increased with increasing sintering temperature. The high-entropy (Mg 0.2 Co 0.2 Ni 0.2 Li 0.4 Zn 0.2)Al 2 O 4 ceramics exhibited good microwave dielectric properties when sintered at 1550 °C for 4 h: dielectric constant (ε r) = 7.4, quality factor (Qf) = 58,200 GHz, and temperature coefficient of resonance frequency (τ f) = –64 ppm/°C. The ε r values were mainly affected by the dielectric polarizability. The Qf values were highly related to the relative density and covalency of A-site bond, whereas the τ f values closely depended on the bond strength of A-site. [ABSTRACT FROM AUTHOR]

Summary: The time delay unit‐based PLLs (TD‐PLLs) are widely used in grid synchronization in single‐phase power systems. However, the TD‐PLL is vulnerable to frequency variations and harmonic disturbances, leading to grid synchronization failures. Analysis shows that the performance degradation is due to the inability to obtain the variation of the input signal frequency. This paper proposes a new time delay‐based phase‐locked loop called immune to double frequency component TD‐PLL (IDFC‐TD‐PLL) based on a feedback structure to accurately capture the variation of input signal frequency, which can improve the dynamic performance and the performance against harmonic interference. Simulations and experiments have evaluated the performance of the proposed phase‐locked loop, demonstrating its superior accuracy and dynamic performance compared to the phase‐locked loops referred in the paper. [ABSTRACT FROM AUTHOR]

A single-phase/single-loop multiple-phase-shift-keying (m-PSK) demodulator is described. The demodulator relies on a linear range of an exclusive-OR (XOR) gate employed as a phase detector. The phase controller takes the average output from the XOR gate and performs a sub-ranging/re-scaling operation to provide an input signal to a voltage-controlled oscillator (VCO). The demodulator is truly modular which theoretically can be extended for an m-PSK signal. The proposed single-phase binary-/quadrature-PSK (BPSK/QPSK) demodulators have been implemented with low-cost discrete components. The core of the phase controller simply relies on number of stages of a full-wave rectifier and a linear amplifier built from well-known op-amp-based negative feedback circuits. The demodulator prototypes operate from a single supply of 5 V. At a carrier frequency of 100 kHz, both the BPSK and QPSK demodulators achieved the maximum symbol rate of 20 ksymbol/s respectively. At these symbol rates, the BPSK and QPSK demodulators deliver symbol-error rates less than 2×10-10 and 7×10-10. [ABSTRACT FROM AUTHOR]

High and medium entropy alloys (HEAs and MEAs) exhibit superior resistance to irradiation damage: there is thus great incentive to study uranium-based HEAs and MEAs. These materials could potentially be suitable candidates for use as nuclear fuels where severe irradiation regimes prevail. In the present study, the ability to predict single phase regions in the quaternary system, Mo–Nb–U–Zr, using thermodynamic calculations was demonstrated and proven experimentally. Similarly to other known bcc HEAs systems, the bcc phase in the present MEA system was shown to exhibit high yield strength but also brittleness. It was also shown that a single phase in the MEA system, Mo–Nb–U–Zr, could be obtained only for compositions containing no more than 10 at% of Mo. [ABSTRACT FROM AUTHOR]

This paper presents a high-performance, multilevel inverter with symmetry and simplification. This inverter is a single-phase, seven-level symmetric switched-capacitor inverter based on the concept of the double voltage clamping circuit connected to the half-bridge circuit. Above all, only a single DC power supply is used to achieve a single-phase inverter with seven levels and a voltage gain of three. In addition to analyzing the operating principle of the proposed switched-capacitor multilevel inverter in detail, the stability analysis and controller design are carried out by the state-space averaging method. The feasibility and effectiveness of the proposed structure are validated by some simulated results based on the PSIM simulation tool and by some experiments using FPGA as a control kernel, respectively. However, in this study, the switches were implemented by MOSFETs to meet a high switching frequency. These MOSFETs can be replaced by IGBTs in the motor drive applications so that the used switching frequency can be reduced.

Natural circulation loops are thermohydraulic circuits used to transport heat from a source to a sink in the absence of a pump, using the forces induced by the thermal expansion of a working fluid to circulate it. Natural circulation loops have a wide range of engineering applications such as in nuclear power plants, solar systems, and geothermic and electronic cooling. The Lattice Boltzmann Method was applied to the simulation of this thermohydraulic system. This numerical method has several interesting features for engineering applications, such as parallelization capabilities or direct temporal convergence. A 2D model of a single-phase natural circulation mini-loop with a small inner diameter was implemented and tested under different operation conditions following a double distribution function approach (coupling a lattice for the fluid and a secondary lattice for the thermal field). An analytical relationship between the Reynolds number and the modified Grashof number was used to validate the numerical model. Two regimes were found for the circulation, a laminar regime for low Reynolds numbers and a non-laminar regime characterized by a traveling vortex near the heater and cooler’s walls. Both regimes did not present flux inversion and are considered stable. The recirculation of the fluid can explain some of the heat transfer characteristics in each regime. Changing the Prandtl number to a higher value affects the transient response, increasing the temperature and velocity oscillations before reaching the steady state.

Natural circulation loops are thermohydraulic circuits used to transport heat from a source to a sink in the absence of a pump, using the forces induced by the thermal expansion of a working fluid to circulate it. Natural circulation loops have a wide range of engineering applications such as in nuclear power plants, solar systems, and geothermic and electronic cooling. The Lattice Boltzmann Method was applied to the simulation of this thermohydraulic system. This numerical method has several interesting features for engineering applications, such as parallelization capabilities or direct temporal convergence. A 2D model of a single-phase natural circulation mini-loop with a small inner diameter was implemented and tested under different operation conditions following a double distribution function approach (coupling a lattice for the fluid and a secondary lattice for the thermal field). An analytical relationship between the Reynolds number and the modified Grashof number was used to validate the numerical model. Two regimes were found for the circulation, a laminar regime for low Reynolds numbers and a non-laminar regime characterized by a traveling vortex near the heater and cooler's walls. Both regimes did not present flux inversion and are considered stable. The recirculation of the fluid can explain some of the heat transfer characteristics in each regime. Changing the Prandtl number to a higher value affects the transient response, increasing the temperature and velocity oscillations before reaching the steady state. [ABSTRACT FROM AUTHOR]

Multiple techniques have been suggested to achieve control balance in single-phase three-level neutral-point clamped (3L-NPC) converters. Nevertheless, there is a deficiency of quantitative calculations related to the extent of balancing. Operating beyond the balancing range may result in a sequence of safety incidents. This paper presents a conceptualization of the 3L-NPC converter as two cascaded H-bridges. By employing power conservation principles, the balancing range for the NPC converter is derived, and two novel methods are investigated to broaden the balance range in accordance with the calculated balance range. A comparison is made among the balancing ranges under different balancing control methods. This study establishes a theoretical foundation to ensure the secure and stable operation of the NPC converter.

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+. [ABSTRACT FROM AUTHOR]

In this work, novel equiatomic high entropy (Dy 1/4 Ho 1/4 Tm 1/4 Yb 1/4) 2 Si 2 O 7 or (4RE 1/4) 2 Si 2 O 7 ceramic pyrosilicate was fabricated through a single solid solution method to use as environmental barrier coating. The SEM analysis of high entropy powders shows the homogenous mixing and XRD proves the formation of single β-phase after milling and sintering. The coefficient of thermal expansion was reported as (2.3–4.8 × 10−6 K−1) from 400 K−1 to 1723 K−1. The ultra-low thermal diffusivity (0.4 mm2 s−1) and thermal conductivity (0.8 W/m°C) were reported at 1500 °C for this novel HE ceramic disilicate. The as fabricated (4RE 1/4) 2 Si 2 O 7 pyrosilicate shows an excellent CMAS resistant for even up to 48 h and negligible amount of Ca is able to penetrate in the substrate. Rare earth disilicate species with intermediate radii such as Tm3+ helps in maintaining phase stability along with passive element Yb3+ of smaller radii which also protect the interface from severe CMAS attack. However, the rare earth species with larger radii such as Dy3+ and Ho3+ actively take part in apatite formation leading to reduced corrosion activity of CMAS melt by changing its composition. This result confirms the application of (4RE 1/4) 2 Si 2 O 7 as a potential candidate to be used as protecting coating material in harsh combustion environments. [ABSTRACT FROM AUTHOR]

Low‐temperature co‐fired ceramics technology (LTCC) exhibits enormous superiorities in packaging, integration, and interconnection. However, the complex compositions of low‐melting point sintering aids may react with ceramic matrix, which increases the difficulties of phase control and tape casting. In this work, the Li2CO3–B2O3–Bi2O3–SiO2 (LBBS) sintering aid was adopted to sinter ZnZrNb2O8 ceramics with single phase at low temperatures. The LBBS glass could be used to fabricate pure‐phase ZnZrNb2O8 ceramics at a low sintering temperature, promote the grain growth, and increase the densification of ZnZrNb2O8 ceramics. Furthermore, the unit cell volume, NbO6 octahedral distortion, Raman shift, and FWHM changed along with LBBS addition, thereby affecting the microwave dielectric properties. Remarkably, ZnZrNb2O8 ceramics doped with 0.75 wt.% LBBS at 950°C were chemically compatible with the silver electrode and exhibited excellent microwave dielectric characteristics: εr = 27.1, Q × f = 54 500 GHz, and τf = −48.7 ppm/°C, providing candidates for LTCC applications. [ABSTRACT FROM AUTHOR]

Despite numerous studies focused on the hydrothermal (HT) synthesis of fly ash zeolites (FAZs), this method still has many limitations, the main of which is the low yield of zeolites. Hydrothermally synthesized zeolites are typically multiphase and exhibit low purity, which limits their applicability. Pure-phase zeolites have been primarily prepared from filtrates after alkaline mineralization of fly ashes, not directly in suspension. In addition, the published methodologies have not been tested in a wider set of samples, and thus their reproducibility is not confirmed. The aim of the study is to propose a reproducible methodology that overcomes the mentioned limitations. The influence of the Si/Al ratio (1.3:1–1:2), the type and concentration of the activator (2/4 M NaOH/KOH/LiOH), the reagent (30% LiCl), the duration (24–168 h), and the temperature (50–180 °C) of the synthesis phases were studied. The sequence of the synthesis phases was also optimized, depending on the type of heat transfer. The fly ashes were analyzed by wavelength-dispersive X-ray fluorescence (WD XRF), flame atomic absorption spectrometry (F-AAS), and X-ray diffraction (XRD). The energy intensity of the synthesis was reduced through the application of unique microwave digestion technology. Both microwave and combined (microwave and convection) syntheses were conducted. FAZs were identified and quantified by XRD analysis. This study presents a three-stage (TS) hydrothermal synthesis of pure-phase sodalite in suspension. Sodalite (>99 wt.%) was prepared from nine fly ashes under the following conditions: I. microwave phase: 120 °C, 150 min, solid-to-liquid ratio (S/L) 1:5, Si/Al ratio 1:1.5, and 4 M NaOH; II. convection phase: 120 °C, 24 h, S/L 1:40, and the addition of 30 mL of 30% LiCl; and III. crystallization: 70 °C for 24 h. The formation of rhombododecahedral sodalite crystals was confirmed by scanning electron microscope (SEM) images.

Currently, most photovoltaic (PV) sources are connected to the grid. This research discusses single-phase on-grid PV inverters. A two-stage inverter which consisted of a boost-type DC-DC converter and a single-phase inverter, was used. In addition, the inverter improved the power quality to deliver PV maximum power. The entire power generated by PV was to be delivered to PCC, and power quality in PCC was also improved. In this system, the grid only drew or supplied active power. The P&O algorithm, as a simple algorithm, was used to control the boost converter to obtain the maximum PV power. In a single-phase inverter, the DC link voltage regulation was carried out using the PI control (outer loop), while the hysteresis control was used to control the output current (inner loop). The voltage control regulated the power delivered from the PV to the PCC by maintaining a constant DC bus voltage at the specified value. With the current control, a single-phase inverter provided two compensations: reactive power and harmonics. In this research, a simulation to control a two-stage inverter was created by using PSIM. Irradiation for PV was varied between 0-1000 W/m2 for 5 seconds. The simulation results showed that the controls performed could work well, as shown by the maximum power injection from the PV to the PCC in which the grid current was sinusoidal (harmonic mitigation) and reactive power compensation was performed. [ABSTRACT FROM AUTHOR]

Achieving bandgaps and double negative properties with single‐phase metamaterial in the low‐frequency range remains a challenge. Currently, acoustic metamaterials with double negative parameters are made of different materials, which can limit their application and design. Herein, a single‐phase multiple re‐entrant star‐shaped honeycomb (MRSSH) is designed and the double negative parameters and bandgaps are simulated. The numerical results show that the MRSSH exhibits three bandgaps and double negative characteristics (negative effective mass density and negative effective modulus) within a certain frequency range. The formation mechanics of bandgaps are investigated by analyzing the vibration modes. Moreover, the effects of geometry parameters such as internal concave angle and re‐entrant on the bandgaps and vibration modes of the MRSSH are investigated. By adjusting the geometry parameters, the dispersion curves and bandgap distribution can be tuned simultaneously. This study provides a new idea for designing a single‐phase lightweight metamaterial that can apply to noised reduction, vibration control, and super‐resolution imaging. [ABSTRACT FROM AUTHOR]

In this study, we presented two reliable methods, the sol–gel and autocombustion, to synthesis a high purity BiFeO3 single phase with low calcination time using glycine as chelating agent. The glycine-autocombustion method produced a high purity BiFeO3 phase using either low or high concentrations of the reactants (Bi(NO3)3 + Fe(NO3)3), while the glycine-sol–gel method delivered a high purity BiFeO3 phase using low concentrations of reactants. In the case of using tartaric acid and urea as chelating agents, mixtures of BiFeO3 and Bi25FeO40 phases were formed. The morphology, size, and porosity of the particles were obviously changed by varying the synthesis method and chelating agents. The high purity BiFeO3 samples exhibit a visible light band gap of 2.05 eV with long absorption tail extending to the infrared region, suggesting the suitability of the synthesized powders in the solar photocatalytic applications. A weak hysteresis ferromagnetic loop was observed for BiFeO3 (glycine method) and BiFeO3/Bi25FeO40 (urea method) with large contribution from the paramagnetic behavior. On contrast, robust ferromagnetic loops were found for BiFeO3/Bi25FeO40 sample synthesized by tartaric acid with saturation magnetization reaching to 2.5 emu/g. Remarkably, the pure single phase BiFeO3 powders synthesized by sol–gel and auto-combustion methods using glycine possess room temperature dielectric constant values of 622 and 845 respectively at a frequency of 42 Hz. In the case of BiFeO3 powders prepared by using tartaric acid, the dielectric constant exhibits values of 401 and 1118 for sol–gel and auto-combustion assisted samples, at the same frequency, respectively. At low frequency, the values of the real part of the complex permittivity tend to be zero which confirms a negligibly small contribution of the electrode effect. [ABSTRACT FROM AUTHOR]

Single-phase Power Factor Correction (PFC) rectifiers with sinusoidal grid currents are inherently subject to an input power fluctuating at twice the mains frequency. In order to potentially mitigate bulky, heavy and failure-prone electrolytic dc-link capacitors, active Power Pulsation Buffer (PPB) concepts are proposed in the literature. For converter systems employing Flying Capacitor (FC) multilevel bridge-legs, the FCs can be utilized as a twice-mains frequency energy storage, i.e., as an integrated active PPB without the need for additional power components. Such ac-dc-stage-integrated FC PPBs capable of buffering the complete input power variation are known in literature which, however, require sophisticated control strategies with varying switching frequency and discontinuous conduction mode. This paper presents a novel ac-dc-stage-integrated FC-PPB approach which is compatible with standard PFC control concepts and enables a significant reduction in dc-link voltage variation. First, a control concept cycling the FC voltage in a wide range without interfering with the grid current controller is derived step by step and verified by means of circuit simulations. Design guidelines for the calculation of suitable FC capacitance values are presented and the limits in buffering capability are discussed. The concept is then experimentally verified with a 2.2 kW three-level FC single-phase PFC rectifier employing 600 V GaN power semiconductors where the dc-link voltage variation is reduced by 28% compared to conventional operation. Last, the applicability of the ac-dc-stage-integrated FC-PPB concept to other FC converter topologies is discussed.

Torque ripples cause acoustic noise, fluctuation in speed, vibration, and reduce lifetime of the motor. The double salient structure of Flux Switching Motor (FSM) has a high air-gap permeance variation that produces high torque ripples. This paper presents an analytical model to reduce air-gap permeance variation and torque ripples of the proposed octane modular stator 8slots-6poles single-phase Electrically Excited (EE) FSM. Furthermore, the rotor pole shaping technique is used to minimize the air-gap permeance variation and therefore, torque ripples of the proposed design are reduced. The electromagnetic performance of EEFSM is analyzed via the Finite Element Analysis (FEA) method. For the proposed design magnetic flux harmonics are reduced by 71% and back-EMF harmonics are suppressed by 48.5%. Torque ripples of the proposed EEFSM are reduced by 20%, cogging torque is diminished by 42.7% and average torque is enhanced by 5.8%. Finally, the prototype is fabricated and tested experimentally. Calculated values and experimental results are in good agreement and the difference is 3.5%-5%.

Elucidation of the intrinsic catalytic principle of iron carbides remains a substantial challenge in iron-catalyzed Fischer-Tropsch synthesis (FTS), due to possible interference from other Fe-containing species. Here, we propose a facile approach to synthesize single-phase θ-Fe3C via the pyrolysis of a molecularly defined Fe-C complex (Fe4[Fe(CN)6]3), thus affording close examination of its catalytic behavior during FTS. The crystal structure of prepared θ-Fe3C is unambiguously verified by combined XRD and MES measurement, demonstrating its single-phase nature. Strikingly, single-phase θ-Fe3C exhibited excellent selectivity to light olefins (77.8%) in the C2-C4 hydrocarbons with less than 10% CO2 formation in typical FTS conditions. This strategy further succeeds with promotion of Mn, evident for its wide-ranging compatibility for the promising industrial development of catalysts. This work offers a facile approach for oriented preparation of single-phase θ-Fe3C and provides an in-depth understanding of its intrinsic catalytic performance in FTS. [ABSTRACT FROM AUTHOR]

The Phase-Locked-Loop (PLL) based on quadrature signal generation (QSG) is widely used in the synchronization units of power systems. Being one of the most popular QSG-PLLs, the time delay unit-based PLL (TD-PLL) is simple and easy to implement. However, when the frequency of the input signal deviates from its rated value, the orthogonality of the QSG output signal and the original input signal cannot be guaranteed, which leads to the generation of double frequency components. To solve this problem, this paper analyzes the generation mechanism for the double frequency component of the TD-PLL. Then, a quadrature signal generation and processing module is built based on a DQ transform and time delay unit to eliminate the double frequency component. This ability is the key part of the proposed PLL (DQ-TD-PLL). Finally, the performance of DQ-TD-PLL is evaluated with simulations and experiments. The obtained results show that the proposed DQ-TD-PLL can eliminate the influence of double frequency component. It can also be seen that the proposed method has better dynamic performance when compared with other methods in the literature. [ABSTRACT FROM AUTHOR]

This paper proposes an intelligent control scheme (ICS) for optimum efficiency and reduced emission operation in small marine transportation systems such as tugs, research vessels, and small scale cruiser ships. The diesel engines used in marine and other transport related applications are designed to provide optimum efficiency at a specific value of mechanical loading. Generally, these engines provide the best fuel efficiency near 80% of their rated load and also the break specific emission of CO (carbon mono oxide) and other harmful greenhouse gases are found to be lowest at this specific amount of mechanical loading. The proposed controller makes the diesel engine to operate continuously at 80% of loading in order to ensure an optimum efficiency operation even if the mechanical load is kept changing due to the variations and fluctuations in the ship propulsion load or electrical load. The intelligent control scheme (ICS) uses a battery bank as an energy balancing element to maintain a constant total mechanical loading on the engine shaft using a bidirectional power flow control through the battery bank thus changing effective mechanical loading on the engine for optimum efficiency operation of the marine transportation system. The output mechanical power (P) delivered by the engine on its shaft is sensed using a power sensor and compared with its optimum value in order to calculate the error. Thereafter, based on the information about the error in engine shaft power, the ICS regulates the power flow to the SPAG (single phase asynchronous generator) in such a manner that the mechanical load on the engine is restored to its optimum value immediately. The optimum efficiency operation is maintained under randomly varying mechanical power demanded by the ship propulsion system and it is also maintained under varying electrical loads in the marine transportation system. This ICS scheme has been implemented in the laboratory using a DSP controller. The detailed test results are presented to validate the claims. [ABSTRACT FROM AUTHOR]

The effect of doping Mn2+ ions with cobalt ferrite (CoFe3O4) is examined. The photoelectric and optoelectronic behaviors of manganese cobalt ferrite (MnxCo1-xFe3O4) nanomagnetic samples grown by co-precipitation were examined. The effect of cation redistribution on octahedral sublattice site-B and tetrahedral sublattice site-A was investigated. X-ray analysis revealed the formation of Fe-phase in trivalent state and single-phased cubic spinel framework that exhibit a preferred orientation along (311) reflection plane. The crystallite size was determined by Scherer equation with values ranging between 9.02 nm and 32.64 nm. The Mn2+-rich Mn–CoFe2O4 nanoparticles exhibit low optical losses, whereas Mn2+-poor Mn–CoFe2O4 samples exhibit high optical losses. FTIR analysis revealed the presence of metal oxide, hydroxyl group and carboxylic group in the ferrite samples. The EDX plot provides evidence of the presence of Mn2+, Co2+, Fe3+, and O2− ions in proper ratio confirming the desired stoichiometric composition. Mn2+-rich Mn–CoFe2O4 samples showed the formation of enhanced photoelectric conductivity and photodiode characteristics. Optical analysis showed that Mn2+-rich Mn–CoFe2O4 nanoparticles are suitable as infrared (IR) detectors, optoelectronic devices and ultraviolet detectors. VSM measurements showed an increase in magnetic saturation and decrease in coercivity as Mn2+ ion composition is increased. Photoluminescence (PL) spectroscopy revealed the emission of a series of colors, such as violet, green and yellow at different wavelengths. Mn–Co ferrite exhibits multi-magnetic domain structure and is hard magnetic material due to Hc > Mr/2, and it is useful for high-frequency device applications. [ABSTRACT FROM AUTHOR]

Nowadays, several HTS cable projects around the world have been demonstrated and operated in real grids. Due to the AC HTS cables have the advantages of high current capacity, small size and low loss, it is beneficial to improve the reliability and economic competitiveness of the power grid. However, the current-carrying capacity of the HTS cables is limited, which is difficult to meet the power supply demands of some short-distance high-current occasions. This paper designs a novel structure of multi-layer cable based on the principle of uniform current, in which the conductor and shielding layers are arranged alternately. The influence of the magnetic field between the superconducting layers is greatly reduced so that the degradation of J c and hysteresis loss is decreased. A 2D simulation model is built to analyze and compare magnetic field distribution and hysteresis loss between the conventional and proposed HTS cables. Consequently, the magnetic field distribution and hysteresis loss of the proposed structure are lower and uniform. Meanwhile, as the number of layers increases, the difference in hysteresis loss keeps increasing gradually. The proposed cable is suitable for mid- and low-voltage and high-current application, which has great significance to improve the stability of the power grid and reduce the cost. [ABSTRACT FROM AUTHOR]

To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+.

Recent developments of fast-charging power delivery protocols are driving ac–dc adapters to 100-W power ranges. Conventional solutions in this power range employing a two-stage topology and a big twice-line frequency buffer capacitor are generally costly and bulky. This article presents a patent-pending modulation method for an active-clamp flyback converter, allowing for a single-stage adapter design with reduced capacitance requirements and higher efficiency. This is achieved by exploiting the inherent energy storage capability of the clamping capacitor while turning it into an active power buffer. No hardware modifications are needed, while all salient features of active-clamp flyback converter, i.e., soft switching and leakage recycling, are retained. Operating principles and detailed controller design are discussed, and a 100-W laboratory prototype is built. The prototype achieves 94% peak efficiency and up to 92% size reduction of the buffer capacitor. The experimental evaluation shows that the new single-stage solution enabled by the proposed modulation method is superior to the conventional two-stage and single-stage solutions in terms of cost, conversion efficiency, and power density. [ABSTRACT FROM AUTHOR]

The single-phase isolated quasi-single-stage AC-DC converter has many virtues, such as high power density and efficiency; however, its grid current closed-loop control has not been solved. This paper aims to solve the remaining gap based on a large-signal model. In this paper, the large-signal model of this converter under triple-phase-shift modulation is built for the first time. It is verified that the built model is a zero-order linear system. Based on this built model, the effect of grid harmonics on this converter grid current is analyzed. The theoretical analysis reveals that the grid voltage low-order harmonics will cause the same order grid current harmonics and only varying the parameters of the filter is not an effective method to solve this problem. For the purpose of eliminating the effect of grid voltage harmonics on the grid current and realizing the zero-error control of the fundamental component of the grid current, a grid current closed-loop control strategy based on the proportional-resonant compound odd-mode repetitive controller is proposed. The operation principle, parameter constraint, and design rule of the proposed compound control strategy are analyzed comprehensively. The theoretical analysis and the compound control strategy put forward in this paper are tested, with detailed experimental results. [ABSTRACT FROM AUTHOR]

Five different rare‐earth‐based nanocrystalline high entropy oxides (HEOs) with fluorite structure and average crystallite sizes between 6 and 8 nm are prepared and their photocatalytic behavior toward azo dye degradation and photoelectrochemical water splitting for hydrogen generation is examined. The cationic site in the fluorite lattice consists of five equimolar elements selected from the group of rare‐earth elements including La, Ce, Pr, Eu, and Gd and second‐row transition metals, Y and Zr. The studied HEOs exhibit bandgaps in the range from 1.91 to 3.0 eV and appropriate valence and conduction bands for water splitting. They reveal high photocatalytic activity that is mostly attributed to the accessibility of more photocatalytic active sites, which provide radicals responsible for the azo dye degradation. The materials successfully produce hydrogen by photocatalytic water splitting, suggesting the potential of HEOs as new photocatalysts. The photocatalytic performances of all studied HEOs outperform the single fluorite oxides or equivalent mixed oxides. The Ce0.2Zr0.2La0.2Pr0.2Y0.2O2 (CZLPY) engender hydrogen in 9.2 µmol mg−1 per hour that is much higher content than for pristine CeO2 material which amounts to 0.8 µmol mg−1 per hour. [ABSTRACT FROM AUTHOR]

Abstract Cobalt carbides nanoparticles have great potential as novel materials in magnetic fields. However, it is difficult to synthesize single phase cobalt carbides, especially Co3C. In this paper, we propose a one‐pot wet‐chemistry approach to synthesize single phase ferromagnetic Co3C without using any alkali as nucleation solvent. The particle size of Co3C nanoparticle is about 3 nm. The magnetic properties of Co3C nanoparticles are measured at 300 K from –30 to 30 kOe. Compared with Co2C, Co3C exhibits a large saturation magnetization of 46.1 emu g–1 and a high coercivity of 1.5 kOe. Small amount of carbon and small particle size of the Co3C nanoparticle are believed to contribute to large magnetization and high coercivity. Magnetic measurements also reveal the spin glass behavior caused by the small Co3C nanoparticle at the spin freezing temperature of 43 K. This work provides a facile method to synthesize single phase Co3C nanoparticle which is applicable in magnetic field.

Synergistic effects of the co-doping of rare earth and transition metals on the structural, electrical and optical, in multi-ferroic BiFeO 3 nanoferrites (NFs) combined with reduced graphene oxide (r-GO) nanosheets, photocatalytic degradation properties can be boosted. In this current study gadolinium and nickel-co-doped Bi 1-x Gd x Fe 1-y Ni y O 3 were synthesised via the tartaric acid-assisted sol-gel method and their composite Bi 1-x Gd x Fe 1-y Ni y O 3 /r-GO with 10 % reduced graphene oxide (r-GO) via the ultra-sonication route. Phase and structural investigation were carried out using x-ray diffraction (P-XRD), Raman scattering, and Fourier transform infrared (FTIR) analysis, which confirms the successful fabrication of co-doping in the rhombohedral geometry of the perovskite-type Bi 1-x Gd x Fe 1-y Ni y O 3. Electrical conductivity of the fabricated composite material was observed to increase because of the co-doping and the addition of r-GO. Photoluminescence (PL) spectra of co-doped and r-GO composite material exhibited a decline in PL intensity because optical bandgap energies exhibited narrowing of 1.99 eV and 1.91 eV respectively, which indicates the excellent separation and stabilization of photo-excited charge pairs. Special conduction properties of r-GO nanosheets improved electrical and optical properties, a well-porous nature, large surface area, lower bandgap, and increased dye degradation in the Bi 1-x Gd x Fe 1-y Ni y O 3 /r-GO photocatalyst showing excellent photo-degradation of cationic malachite green (M.G.) dye, achieving a degradation efficiency of 96.4 % under natural solar light. Hence, the photocatalyst shows excellent stability where quenching of radicals using selective scavengers shows that OH* radicals and e−/h+ pairs are primarily involved in the mechanism of photo-degradation in a basic pH medium, making the as-fabricated material a potential material for photo-catalytic environmental remediation. [Display omitted] [ABSTRACT FROM AUTHOR]

Double perovskite Ba 2 FeMoO 6 (BFMO) substituted with monovalent Ag ions was synthesized using the sol-gel method, and its structure and magnetic properties were systematically studied. Rietveld refinement showed that the samples had a single phase with a cubic structure and an Fm-3m space group. With Ag substitution, the lattice parameter and unit cell of BFMO increased linearly, and the morphology of the samples was altered. X-ray photoelectron spectroscopy (XPS) examination showed mixed valence in the sample with x = 0.025 due to the Ag doping. The doped samples exhibited a decrease in magnetization, an increase in transition temperature, and anti-site (AS) defects. The AC magnetic susceptibility of the sample with x = 0.025 showed two peaks attributed to the two critical temperatures. [ABSTRACT FROM AUTHOR]