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In this paper, an integrated drive converter of segmented-double-stator switched reluctance machine (SDS-SRM) with isolation and non-isolation charging capabilities for electric vehicle (EV) is presented. The proposed converter can not only reduce the number of the power switches, but also implement multiple operation modes. In non-isolation charging mode, the motor windings and existing power switches constitute a buck/boost converter to charge the battery. The appropriate rotor positions are obtained to achieve torque-free control, and the interleaved phase currents control method is introduced to reduce the charging current ripples. In isolation charging mode, the inner-stator is powered by the utility grid to drive the middle-rotor, and converts electrical energy into mechanical energy. While, the outer-stator is operated in generation mode to convert mechanical energy into electrical energy. The SDS-SRM is served as a rotating transformer to transfer the electric power to charge the battery with the galvanic isolation function. A low power proof-of-concept prototype platform is built and experiments are carried out to verify the effectiveness of the proposed integrated drive converter and the corresponding control schemes.

The motor drive system plays a significant role in the safety of electric vehicles as a bridge for power transmission. Meanwhile, to enhance the efficiency and stability of the drive system, more and more studies based on AI technology are devoted to the fault detection and diagnosis of the motor drive system. This paper reviews the application of AI techniques in motor fault detection and diagnosis in recent years. AI-based FDD is divided into two main steps: feature extraction and fault classification. The application of different signal processing methods in feature extraction is discussed. In particular, the application of traditional machine learning and deep learning algorithms for fault classification is presented in detail. In addition, the characteristics of all techniques reviewed are summarized. Finally, the latest developments, research gaps and future challenges in fault monitoring and diagnosis of motor faults are discussed.

At present, for inorganic photochromic materials, the single function limits their application level in the field of optical storage and anti-counterfeiting. Generally, the reversible modulation of photoluminescence is achieved through a photochromic process, thereby improving the ability of the photochromic material to store information. Here, we designed a Sm3+ doped perovskite oxide (SrZrO3:Sm3+) inorganic photochromic material. Combined with its red photoluminescence and photochromic properties, it can realize dual information storage and recognition functions. The fluorescence regulation function is realized by the doping of Sm3+, which is conducive to the application in the direction of optical switch. The mechanism of photoluminescence and photochromism was studied. Finally, a flexible film with SrZrO3:Sm3+ material was fabricated to demonstrate rewritable optical recording and storage and reading of dual optical information.

The security of powering systems has been a major problem over the last decade, leading to an increased interest in wireless power and data transfer. In this research paper, a new inductive Wireless Power Transfer (WPT) circuit topology has been used. In traditional WPT circuits, the inverters are used to produce an oscillation for the transmitter coils. The classic WPT system includes intrinsic energy dissipation sources due to the use of switches, necessitating the need of an extra control circuit to ensure proper switching time. Furthermore, they have limited data encryption capabilities. As a result, an unique WPT system based on memristors has been developed, eliminating the need for switches. Furthermore, because this novel topology communicates a synchronised chaotic behaviour, it becomes highly beneficial. This circuit may be used in Near Field Communication (NFC), where chaotic true random numbers (TRNG) can be generated to increase security. The results of simulations indicate the functioning of the Memristor-based WPT (M-WPT) and its ability to generate random numbers. We experimentally proved the chaotic behaviour of the circuit and statistically demonstrated the development of the TRNG, using an Arduino board and the Chua circuit to build the M-WPT circuit.

The near-infrared (NIR) light source has a huge potential for foodstuff analysis, biometric identification, physiological monitoring, and night vision technology with real-time and non-destructive advantages. Demand-led growth impels the exploration of novel NIR phosphors with broadband emission. Here we report a new kind of blue-light excitable NIR phosphor Mg7Ga2GeO12: xCr3+, in which the multi-site occupation of Cr3+ induces broadband NIR emission in the range of 600–1200 nm with a large full width at half maximum (FWHM) of ~190 nm and a NIR photoluminescence quantum yield (PLQY) of 12.06% at x = 0.02. The FWHM can be effectively adjusted from 101 to 226 nm via multisite occupancy preference of Cr3+ ions. The PL intensity remains ~50% and nearly 100% of the initial level after heated up to 400 K and immersed in hot water (100 °C) for 24 h, respectively, demonstrating good thermal stability and robust chemical stability. The broadband emission originated from multi-site PL centers of Cr3+ is discussed in detail by the temperature-dependent PL behaviors and PL decay lifetime. Finally, a broadband emission NIR-LED is fabricated, based on which a proof-of-concept application for night vision is demonstrated. This work not only provides a strategy for the design and developing of novel broadband NIR phosphors, but also indicates the potential for various advanced spectroscopy applications.

Image-guided therapies have been on the rise in recent years as they can achieve higher accuracy and are less invasive than traditional methods. By combining augmented reality technology with image-guided therapy, more organs, and tissues can be observed by surgeons to improve surgical accuracy. In this review, 233 publications (dated from 2015 to 2020) on the design and application of augmented reality-based systems for image-guided therapy, including both research prototypes and commercial products, were considered for review. Based on their functions and applications. Sixteen studies were selected. The engineering specifications and applications were analyzed and summarized for each study. Finally, future directions and existing challenges in the field were summarized and discussed.

The water body detection in high-resolution synthetic aperture radar (SAR) images is a challenging task due to the changing interference caused by multiple imaging conditions and complex land backgrounds. Inspired by the excellent adaptability of deep neural networks (DNNs) and the structured modeling capabilities of probabilistic graphical models, the cascaded fully-convolutional network (CFCN) is proposed to improve the performance of water body detection in high-resolution SAR images. First, for the resolution loss caused by convolutions with large stride in traditional convolutional neural network (CNN), the fully-convolutional upsampling pyramid networks (UPNs) are proposed to suppress this loss and realize pixel-wise water body detection. Then considering blurred water boundary, the fully-convolutional conditional random fields (FC-CRFs) are introduced to UPNs, which reduce computational complexity and lead to the automatic learning of Gaussian kernels in CRFs and the higher boundary accuracy. Furthermore, to eliminate the inefficient training caused by imbalanced categorical distribution in the training data set, a novel variable focal loss (VFL) function is proposed, which replaces the constant weighting factor of focal loss with the frequency-dependent factor. The proposed methods can not only improve the pixel accuracy and boundary accuracy but also perform well in detection robustness and speed. Results of GaoFen-3 SAR images are presented to validate the proposed approaches.

Materials exhibiting luminescent switching upon photochromic reaction have received increasing attention due to their potential applications in erasable optical storage. Nevertheless, it is still challenging to synthesize photochromic materials that selectively absorb different wavelengths of light for erasable optical storage. Herein, we report a series of fluorophosphate structure (Ca,Sr,Ba)5(PO4)3F:Eu2+ photochromic materials with tunable absorption bands upon photochromic reaction. Tunable photochromism is a phenomenon is rarely observed in inorganic materials. Thus, to fill this gap, we designed (Ca,Sr,Ba)5(PO4)3F:Eu2+ photochromic materials with highly reversible tunable photochromism by adjusting and substituting the alkaline-earth metal. The substitution of the divalent cations with a smaller ionic radius by larger cations induced a shift in the absorption band of the (Ca,Sr,Ba)5(PO4)3F:Eu2+ photochromic material to a longer wavelength. The multicolor change may pave the way for the design of photochromic materials to meet specific application requirements. All as-prepared photochromic flexible films showed excellent fatigue resistance, water resistance, flexibility and stretchability. Writing, erasing, and reading were performed using the flexible photochromic films, demonstrating their particular application in complicated environments for optical storage and rewritable flexible devices. An efficient energy transfer process was established between luminescent and photochromic units, which may open a door for the design of high-performance optical storage materials. Erasable optical storage could be excited by UV and visible light to encode and decode on the flexible film.

Laser power transmission (LPT) is considered a potentially efficient way for power delivery, especially in long-distance wireless applications and harsh hazardous environmental conditions. In contrast to other wireless power transmission (WPT) methods, LPT has many advantages such as lower device size, focused transmitting direction and high power density. With the development of technology, LPT has been widely adopted in several fields. In conservative industries, the utilisation of LPT can resolve the limitation problem in a wired connection. The adverse influence of electromagnetic interference (EMI) concerning application and high-temperature fields can be reduced. This paper will give a simple review of LPT and demonstrate the basic concept of a photoelectric emitter, transmission channel and receiver material. Based on the recent research about diode laser beam combining technology and high-efficiency multi-junction photovoltaics (PV) materials, the advised LPT devices for simple application as laser power motor will be simply discussed.

Non-lead metal halide double perovskites (MHDPs), recognized as one of the most promising alternatives to lead-based metal halide perovskites (MHPs), have received enormous attention in recent years due to their nontoxicity and good thermodynamic stability. However, the development of a broadband near-infrared (NIR) emitting MHP with high optical efficiency and robust chemical stability remains a challenge. In this work, we report a broadband NIR emitting lead-free MHDP Cs2SnCl4Br2 activated by Sb3+ with the largest full width at half maximum of 164 nm. The morphology and particle size were controllably evolved via finely adjusting the preparation temperature. Most surprising is that the high-temperature post-treatment, which is to be avoided always, was applied for the as-obtained NIR MHDP, achieving an unexpectedly great boosting of the NIR emission efficiency by 13 times. Moreover, excellent stability was achieved, which showed that the broadband NIR emission intensity retains 90% of the initial level after continuous UV irradiation for 48 h, maintains 100% of the initial level after being immersed in water for 6 h, and increases up to 102% after being stored in air for 2 months. The origin of NIR emission from Sb3+ ionoluminescence was verified with the combination of experimental and DFT studies. As a proof-of-concept, a broadband NIR light emitting diode with a radiant flux of 17.23 mW was fabricated using the as-obtained broadband NIR MHDP for NIR spectroscopy applications. This work not only provides a method for the rational design of broadband NIR MHPs and extending their applications, but also prompts the steps to develop novel MHDPs with superior chemical and optical stability.

Traditional clutter suppression methods are mainly studied under the condition that the pulse repetition frequency (PRF) of the system is not less than the Nyquist frequency. Whereas in the high-resolution and wide-swath (HRWS) multichannel synthetic aperture radar (SAR) system, a low PRF is used to break through the minimum antenna area constraint. The low PRF case brings new challenges to the traditional clutter suppression methods. In this letter, a subspace projection clutter suppression method is proposed based on the fact that moving targets and the clutter consist in different signal subspaces. This method can be directly applied to the HRWS multichannel SAR system, and it shows better performance compared to the space-time adaptive processing (STAP) when the moving target components cannot be ignored in the clutter covariance matrix calculation. Simulated data and airborne measured data are processed to verify its effectiveness.

The conventional phase current reconstruction strategies utilize a dc bus current sensor to reproduce the three-phase currents during phase current sensor faults. However, no current sensor is guaranteed to be healthy in an actual drive. It means that the only survived current sensor may not be accidentally located at the dc bus side, and it can also be at the phase side. In addition, previous studies focus on a particular inverter topology for current reconstruction, whose fault-tolerant capability is threatened when the inverter topology is changed due to malfunctions. This article proposes a survivable interior permanent magnet synchronous motor (IPMSM) drive that realizes the current reconstruction purpose whichever the only survived current sensor is. Besides, inverter topology reconfiguration can be realized by not changing the wirings of the current sensors. Most important of all, the proposed strategy does not affect the normal operations of the drive when no fault occurs. The effectiveness of the proposed strategy is verified by experimental results on a 5-kW IPMSM motor prototype, which shows that the reconstructed phase currents track the actual ones accurately under different failure conditions.

With the increasing demand of applications that have two different output voltages, the single-input dual-output (SIDO) converter with fewer components is becoming the cost-effective option instead of employing two single-input single-output converters. However, the cross-regulation of different outputs is still a challenge in SIDO converters design. To save cost and obtain improved cross-regulation performance, a novel SIDO converter consisting of three active switches is proposed in this article. Owing to the use of a voltage multiplier circuit, a high step-up voltage conversion ratio is achieved with relatively low voltage stress of switches. Thanks to the independent power flow and two control variables, the cross-regulation performance is improved, and simultaneous buck as well as boost output voltages is realized. Additionally, all switches can achieve zero-voltage switching operation, which contributes to a significant switching loss reduction. The operation characteristics, design considerations, and control strategy of the proposed converter are analyzed. To verify the theoretical analysis and measure the power efficiency, a prototype circuit with 48 V input and 24 V/2 A, 200 V/1 A outputs is built.

Airborne LIDAR can flexibly obtain point cloud data with three-dimensional structural information, which can improve its effectiveness of automatic target recognition in the complex environment. Compared with 2D information, 3D information performs better in separating objects and background. However, an aircraft platform can have a negative influence on LIDAR obtained data because of various flight attitudes, flight heights and atmospheric disturbances. A structure of global feature based 3D automatic target recognition method for airborne LIDAR is proposed, which is composed of offline phase and online phase. The performance of four global feature descriptors is compared. Considering the summed volume region (SVR) discrepancy in real objects, SVR selection is added into the pre-processing operations to eliminate mismatching clusters compared with the interested target. Highly reliable simulated data are obtained under various sensor’s altitudes, detection distances and atmospheric disturbances. The final experiments results show that the added step increases the recognition rate by above 2.4% and decreases the execution time by about 33%.

Power & signal multiplex transmission (P&SMT) is a technique that uses power electronic circuits for communication signal transmission. In this paper, a three-phase cascaded multilevel inverter-based P&S MT system is proposed. The proposed method can transmit communication signals without using a Controller Area Network bus, thereby reducing the wiring cost of the conventional electric vehicle (EV) communication system. The designed system can achieve motor speed regulation and battery balance discharging for EVs. With the combined pulse width modulation scheme and frequency shift keying method, both power and communication signals are transmitted successfully in a simulation model implemented in Matlab/Simulink. By evaluating the bit error rate of the transmitted signal, the maximum signal rate of the proposed system is determined as 600 bit/s.

The missile-borne LiDAR has an essential prospect in precise guidance. However, the instability of the missile has a significant impact on the precision of LIDAR point cloud, thus modeling and analyzing the influencing factors of point cloud generation is necessary. In this investigation, the authors modeled the point cloud calculation process of missile-borne linear array scanning LiDAR under ideal conditions and analyzed the effect of position change on the field of view (FOV) in the course of platform motion. Subsequently, the authors summarized that the stability concerning the field of view and the target tracking are dependent on three limiting conditions. Finally, the authors derived an error formula and analyzed several typical errors in missile platform flight, including scanner error, POS error, system integration error, and platform vibration error. Based on theoretical analysis and simulation experiments, the model proposed in this paper can provide a theoretical basis for the design of the missile-borne LiDAR system and the selection of related instruments in practice.

Due to the wide applications of solar photovoltaic (PV) technology, safe operation and maintenance of the installed solar panels become more critical as there are potential menaces such as hot spot effects and DC arcs, which may cause fire accidents to the solar panels. In order to minimize the risks of fire accidents in large scale applications of solar panels, this review focuses on the latest techniques for reducing hot spot effects and DC arcs. The risk mitigation solutions mainly focus on two aspects: structure reconfiguration and faulty diagnosis algorithm. The first is to reduce the hot spot effect by adjusting the space between two PV modules in a PV array or relocate some PV modules. The second is to detect the DC arc fault before it causes fire. There are three types of arc detection techniques, including physical analysis, neural network analysis, and wavelet detection analysis. Through these detection methods, the faulty PV cells can be found in a timely manner thereby reducing the risk of PV fire. Based on the review, some precautions to prevent solar panel related fire accidents in large-scale solar PV plants that are located adjacent to residential and commercial areas.

This paper proposes a mutual calibration strategy for multiple current sensors in an electric vehicle motor drive. The motor drive usually consists of three current sensors, i.e., a dc-bus current sensor and two phase current sensors. Due to the aging effect and harsh operating environment, the accuracy uncertainty issue is inevitable in these crucial sensors, which results in poor driving performance. In this paper, the detection voltage injection (DV-Injection) method is proposed for mutual calibration of the aforementioned current sensors. Two opposite basic vectors are set together to detect and eliminate the offset error of the dc-bus current sensor. Then, both the directly measured phase-current values by the phase-current sensors and the indirectly measured values by the dc-bus current sensor are sampled. These values are utilized for mutual calibration of the phase-current sensor offset errors and scaling error differences among all the current sensors. Meanwhile, the DV-Injection process is only applied in the period of calibration process, whereas in the remaining intervals the space vector pulsewidth modulation technology is utilized. Finally, the effectiveness of the proposed scheme is verified by simulation study in MATLAB/Simulink and experimental results on a 5-kW interior permanent magnet synchronous motor motor prototype.

Reversible photoluminescence switching based on photochromism has drawn considerable interest due to its widespread promising applications in photo-switching, anti-counterfeiting and optical information storage. In this paper, we reported a novel photochromic material Sr6Ca4(PO4)6F2:Eu2+ which exhibits the reversible photoluminescence switching ability. Coloration and bleaching, which are attributed to the capture and release of electrons by traps, respectively, can be efficiently converted accompanied by the color change between pink and white upon alternating UV light irradiation and visible light irradiation or thermal treatment. Sr6Ca4(PO4)6F2:Eu2+ shows photochromic properties such as high reversibility and excellent fatigue resistance. Trap engineering allows an effective way to modify the traps through changing the Eu2+ doping content and co-dopant Ln3+ (La, Y, Gd, Lu) ions, thereby purposely controlling the performance of photochromism. Photoluminescence switching strongly depends on the photochromic effect and exhibits a good reversibility after several cycles of measurements. The relative photoluminescence intensity measured from a partially thermal bleaching state indicates the highest instantaneous temperature suffered by the sample, indicating the good application prospects in instantaneous temperature recording. In addition, various patterns can be repeatedly recorded in the photochromic material Sr6Ca4(PO4)6F2:Eu2+ by alternative UV light and visible light/heat treatment, demonstrating potential application in erasable optical data storage.

The new technology solutions are playing an important role in the hardware security. One of the latest techniques is the use of the Memristor as an encryption element. In this paper, it has been introduced a two-column array inductor for Memristor-Based Wireless Power Transfer (M-WPT) systems. The traditional WPT circuits are based on switches, which do require a control circuit for timing and have low data encryption factor. By adopting the memristive Chua`s circuit with the chaotic behaviour characteristic, it is possible to create a symmetrical dual-key cryptography. Furthermore, in this innovative solution, the high inductance value of the traditional Chua circuit can be further reduced by using the dynamic effects of the coils flux linkage. The simulation results exhibit the dual-scroll attractors phase portrait, which is available for encryption features. Therefore, the data collected from the phase portrait are used as true random number generator in Python code. Instead of using algorithms, the code can create a symmetrical key for an unique chaotic cryptography. In order to build a prototype, it has been created a PCB design for the whole system. The experiment highlights the unpredictable voltage and current and validates the chaotic behaviour of the transmitter and receiver.

This paper proposes a perturbation estimation based nonlinear adaptive power decoupling controller for doubly fed induction generator based wind turbines (DFIG-WTs). Perturbation states are defined to include the nonlinearities, uncertainties of the system model, the cross-coupling between control loops, and external disturbances. Perturbation observers are designed to estimate the fast time-varying perturbation states. With perturbation estimation, the DFIG-WT system is fully decoupled, and an output feedback control can be designed for the control of rotor currents. Rotor current references are calculated based on the steady-state relation between active/reactive power and rotor current, and stator dynamic is ignored. The performance of the proposed controller is evaluated and verified via both simulation and experimental tests.

The communication system of a microgrid can transfer the information of electricity price, power consumption and so on between users and the control centre. This capability is of great significance to improve the efficiency and sustainability of power facilities. In this paper, a bidirectional DC–AC converter topology is proposed to achieve the composite transmission of power and signals in microgrids. Since the transmitted signals are modulated by power switches of converters and integrated into the currents, the cost of signal couplers can be saved and the circuit structure can be simplified. In order to verify the feasibility of the proposed method, a simulation model of the proposed converter is implemented in MATLAB/Simulink. With the power supply frequency of 50 Hz, when the converter operates in the inverter mode and rectifier mode, the data transmission rate can reach 120 bit/s and 48 bit/s, respectively.

This paper proposes a cascaded multiport switched reluctance motor (SRM) drive for hybrid electric vehicle applications, which not only allows flexible energy conversion among the generator/ac grid, the battery bank, and the motor, but also achieves battery management (BM) function for state-of-charge balance control and bus voltage regulation. By integrating the battery packs into the asymmetrical half-bridge converter, the cascaded BM modules are designed to configure multilevel bus voltage and current capacity for SRM drive, which can accelerate the excitation and demagnetization processes during the commutation region, extend the speed range, reduce the voltage stress on the switches, and improve the torque capability and system efficiency. According to the different operation requirements, the multiple driving modes, regenerative braking modes, and charging modes are equipped in the proposed converter. Moreover, with the proposed BM strategy, each battery pack can be separately connected or disconnected from the power supply, which will greatly enhance the fault-tolerance ability and easily avoid the overcharge and overdischarge issues during the motor operation. The feasibility and effectiveness of the proposed cascaded multiport SRM drive are verified by the experiments on a three-phase 12/8 SRM.

The use of noninvasive and rapid responsive spectroscopy coupled to potential applications under harsh conditions has led to an increased interest in all-optical ratiometric thermometers. In this w...

A novel thermometer, qualified with miniaturization, real-time monitoring, non-invasion, remote-control, and high spatio-temporal resolution, is urgently required for temperaturedetecting of sub-micrometric objects and in specific harsh conditions. Herein, we report an adaptable dual-mode optical thermometry platform LiTaO3:Ti4+, Eu3+@PDMS. A proof-of-concept implementation based on fluorescence thermometer (FT) demonstrates outstanding temperature sensing performance with excellent reversibility. The maximum Sa and Sr are as high as 0.671 and 5.425% K−1, respectively, with minimal temperature resolution of 0.14 K. Whilst, the maximum Sa and Sr based on lifetime thermometer (LT) are determined to be 0.122 and 3.637% K−1, respectively, with superior temperature resolution of 0.027–0.058 K. Finally, flexible phosphor films and 3D micro-rod arrays with handily encrypted information are fabricated for the unclonable multi-modal/multi-dimensional anti-counterfeiting application by exploiting light, temperature and time-domains as the “key” to decrypt the “locked” ciphertext, which indicates the promising prospect in temperature sensing and anti-counterfeiting. This work not only paves a way for developing novel spatial/temporal dual-mode real-time thermometer based on synergetic luminescence of lanthanide (Ln) and transition-metal (TM) ions with high temperature sensitivity and resolution, but also opens a new “window” for extending the thermometer as a flexible device in advanced multi-mode multi-dimensional high-level secure anti-counterfeiting.

High brightness and precise adjustment of luminescence colour of phosphors are two main targets in the research of phosphor-converted white LEDs. However, few feasible strategy can be employed to achieve the multicolor-tunable luminescence under the premise of maintaining high quantum efficiency. Here, we demonstrate a high-efficiency energy-transfer process from Tb3+ to Eu3+ ions with a higher luminescent quantum efficiency (64.5% and 53.4%, respectively), and green-red multicolor emission in Lu2GeO5 host via varying the doping content of Tb3+ and Eu3+ ions. Besides, Lu2GeO5:Tb3+, Lu2GeO5: Eu3+ and Lu2GeO5: Tb3+, Eu3+ all exhibit weak thermal quenching which ensures the stable use of white LED device in the high temperature environment. This paper provides a novel multicolor-tunable phosphor with high brightness, efficient energy transfer and weak thermal quenching, which presents a potential application for UV-converted white LEDs.

Deep learning has achieved much in image and natural language processing, and related research has also expanded into the field of point cloud processing, and deep networks dedicated to point clouds have emerged; however, in many points cloud applications, networks with fewer parameters and lower computational burdens are required to satisfy the requirements of miniaturisation of devices, so research into lightweight point cloud deep networks is justified. In this letter, we described the design of a lightweight point cloud classification deep learning architecture, lightweight point cloud classification network, with the self-designed block structure as a unit, using a novel index fully dense connectivity method that interconnects all convolutional layers of the network, improving the utilisation of features, thereby reducing the parameter size of each layer; at the same time, the network applies grouping convolution and pruning to the convolutional layer and the fully connected layer, further reducing the amount of parameters and calculation burden. The experimental results show the effectiveness of the network that can achieve comparable results with existing large networks, such as PointNet++, with a smaller amount of parameters. The proposed network offers great promise in mobile device deployment and real-time processing.

With the increasing demands for detection range and accuracy in heterodyne lidars, precise analyses of system efficiency are of growing importance. An extended system efficiency model is established for the detection of heterodyne lidar returns backscattered by aerosols in turbulent atmosphere; the extended Huygens–Fresnel integral and the Tatarskii spectrum are used in the derivations of system efficiency and effective coherent solid angle(ECSA). The impacts of beam truncation, optical aperture, atmospheric turbulence and laser source coherence on the performance of a monostatic heterodyne lidar are analyzed in detail. Numerical results suggest that the optimal system efficiency and beam truncation change with laser coherence, turbulence and distance for a collimated system. Lidars with larger optical apertures may have worse system efficiencies which can be below 5.5% with the aperture of 160 mm when C n 2 is 1 0 − 14 m − 2 ∕ 3 . Moreover, similar ECSAs can be obtained with both small and large optical apertures. When C n 2 is 1 0 − 18 m − 2 ∕ 3 and 1 0 − 14 m − 2 ∕ 3 , the ECSAs with the laser source coherence factor of 101 have extra attenuations of 16.52dB and 4.83dB within 30 km, which indicates that the partial coherence of laser source should be considered in the performance analyses.

Near-infrared (NIR) long-persistent phosphors (LPPs) have emerged as a potential solution for bio-imaging applications over the past few years. However, there are enormous challenges regarding their in situ application based on their dependence on short-wavelength excitation. In this paper, we report a multi-spectral excited NIR LPP, Li5 Zn8 Ga5 Ge9 O36 : 1.5 % Cr3+ , 0.5 % Ti4+ , which overcomes the limitations of functional processes in biological tissues and other complex systems. This LPP exhibits a high luminescent intensity and a long emission duration in the NIR region (700-800 nm). The applicability of this phosphor to tissue imaging is demonstrated experimentally. Its persistent luminescence (PersL) can easily penetrate approximately 2 mm of pork flesh. More importantly, this phosphor can be re-charged in situ using a red LED or laser diode array to provide renewed NIR PersL for biological tissues, which is beneficial for long-term biological tissue imaging applications with high signal-to-noise ratios. Systematic investigations of the nature of energy traps and PersL mechanisms are also reported in this paper.

Bioaerosol, an important constituent of the atmosphere, can directly affect light radiation characteristics due to absorption and scattering effects. Current research lacks a reasonable explanation for the extinction abilities of bioaerosols in a broadband. Herein, we measured the reflectance spectra of 12 common biomaterials and calculated their complex refractive indexes. The peaks of the imaginary part of the complex refractive indexes are located at wavelengths of approximately 0.7, 2.7, 6.1 and 9.5 μm. Based on photographs of the floating structures of bioaerosols, we constructed a model for calculating the extinction abilities of bioaerosols in the wavelength range of 240 nm to 14 μm . Taking AN02 spores as an example, absorption was found to account for more than 90% of the total extinction. In addition, the theoretical calculations and experimental data of transmittance corresponding to the smoke box show that bioaerosol exhibits significant broadband extinction ability from UV to IR bands, which provides new directions for the development of broadband light attenuation materials.

A new near-infrared phosphor Mg4Ga4Ge3O16: Cr3+ with multi-photo-functionalities has been developed. Such phosphors can act as luminescent down-shifting materials converting UV and visible photons into NIR light (600–850 nm). UV irradiation induced strong NIR long persistent luminescence (LPL) can persist for more than 10 h. With the prolonged decay time, the extinguished NIR LPL can be rejuvenated by external photo stimulus including not only 980 nm light but also visible light. Such NIR photostimulated persistent luminescence (PSPL) presents separated write-in and read-out wavelength ranges. Meanwhile, photochromism (PC), that the material surface undergoes reversible change between white/pale green and ronbrown when triggered alternatively by UV and visible irradiation/heating, was also observed. Several recycle measurements demonstrate the robust fatigue resistance of PC property. Owning to the multi-photo-functionalities of Mg4Ga4Ge3O16: Cr3+, the fabrication of flexible phosphor membranes endows their application for optical information storage and repeatable optical recording. The electron motion in traps was studied by thermoluminescence (TL) and the color center formation was verified with electron spin resonance (ESR) spectra, based on which an energy level diagram was proposed for the illustration of the multifunctional mechanism. The revealing of multi-photo-functional mechanism and fabrication of flexible phosphor membranes may promote the development of a universal design principle for further study.

Heterodyne lidar echoes in atmospheric detection are greatly affected by the shapes of aerosols. With the aid of T-matrix and vector Monte Carlo simulation, we investigated the properties of lidar echoes backscattered by randomly oriented polydisperse aerosols, including the soot, sea salt and mineral aerosols. The degree of polarization (DoP) and backscattered photon numbers in different range bins are calculated when the launched laser pulses are linearly polarized light and circularly polarized light at 1.55 μm. There are reductions of DoP along the 10 km detection path, which vary with aspect ratios (AR) and aerosol types. The ARs are chosen within 0.5–2.0 for cylinders and 0.3–1.0 for spheroids. The lidar echoes in soot aerosols have the largest DoP which is higher than 0.8. Moreover, the shape fading factor and polarization fading factor are defined and calculated based on the effective backscattered photon numbers, which shows that the mineral aerosols in nuc.mode (MINM) is less affected by aerosol shapes and laser polarization states, and that the LPL is suitable for the heterodyne detection of nonspherical atmospheric aerosols. The results provide echo characteristic deviations from the spherical particle scattering, which can be used in the practical modeling of atmospheric echoes and designs of heterodyne lidars.

With the wide use of electromagnetic information equipment, a large number of wireless radiation systems coexisting in the same region produce intentional or unintentional interference on electronic receivers. For the purpose of intentional electromagnetic interference, it is necessary to realise the efficient suppression of other receivers at little cost. When multiple transmitting sources are used to interfere with multiple receivers, the parameters of multiple transmitting sources are required to be comprehensively optimised and set so as to achieve a desired high-efficiency interference. Therefore, we propose a novel method to optimise the setting of parameters of a multi-source, multi-object and multi-domain (M-SOD) interference system based on intelligent optimisation approaches. Furthermore, this study also builds an intelligent optimisation model, which contains multiple transmitters and receivers which involved many parameters include position, direction of space domain, frequency, bandwidth, and power. Then the model is abstracted to the problem of single-objective optimisation with constraints and optimised through a traditional GA and an improved FWA method. The extensive experiments and comparisons show that the proposed algorithm is an effective approach for setting the parameters of an M-SOD electromagnetic interference system and superior to the conventional method.

In this paper, a new color tunable long persistent phosphor (Ca, Sr)Ga4O7:Mn2+,Bi3+ has been successfully synthesized via a high-temperature solid-state reaction. Crystal field modulation and band gap engineering controlled by Sr2+ substitution for Ca2+ realizes the color tunable Mn2+ emission from 580 to 556 nm. Guided by the tailoring of traps distribution, the long persistence luminescence (LPL) performance of CaGa4O7:Mn2+ is greatly enhanced to 33 times higher brightness and much longer persistent time through Bi3+ co-doping. Furthermore, aided by the Rietveld refinement method, steady/transient-state fluorescence and thermoluminescence (TL) techniques with the combination of DFT calculations, the crystal structure evolution, electronic structure, trap distribution tailoring, self reduction of Mn4+, and the related color tunable Mn2+ photoluminescence/enhanced LPL properties are systematically characterized. Finally, a schematic diagram is proposed for a detailed illustration of the photoluminescence and LPL mechanisms.

Condition monitoring (CM) is widely used in wind turbines (WTs) to reduce operation and maintenance (O&M) costs. Bearings are crucial components in WT and many bearing CM approaches have focused on vibration analysis. Statistical theory and artificial intelligence-based WT bearings evaluation methods require mass data for training, which makes the detection of incipient failures barely possible. In this paper, a WT bearing performance evaluation method is proposed based on the similarity analysis of fuzzy k-principal curves (FKPCs) in manifold space. For a start, 38 features are extracted from bearing vibration signals to constitute high-dimensional feature matrices. The feature matrices for the healthy samples and the samples to be evaluated are then transformed into 3-D space. Afterward, the FKPCs are extracted and the similarities among the curves of samples are calculated based on the Hausdorff distance to evaluate the performance of the bearing. Bearing degradation experiments are investigated to verify the efficiency of the proposed method. The results indicate that the proposed FKPC method can portray the degradation trend of bearings accurately with the capability of detecting incipient failures. The proposed method can be applied in the case of small-size training samples with stable performance.

The characteristics of heterodyne lidar echoes are related to both the polydisperse aerosols and the polarization state of emitted laser. Based on the database of optical properties of aerosols and clouds(OPAC), we have numerically simulated the backscattering process of photons in different polydisperse aerosol environments using the semi-analytic Monte Carlo method. Then, the backscattering properties of five typical aerosol components in four environments are analyzed within the wavelength range of 1.4–2.1 μm, and the emitted lasers are linear polarized light (LPL) and circular polarized light (CPL). The simulation results show that the degree of polarization (DoP) of lidar echoes is larger by using LPL in the four typical aerosol environments and that the returned photon numbers are less affected by the polarization state of emitted laser pulses. Finally, to achieve the same detection performance, the required laser power ratios are discussed in detail under typical humidities, which is of reference value to the designs and performance analyses of heterodyne lidar systems for atmospheric environment observations with long range and high accuracy.

The impact of electromagnetic interference (EMI) is an increasingly important aspect of the performance of switching inverters. The challenges of managing EMI continue to grow with the emergence of wide bandgap (WBG) devices, the trend towards ever-greater integration and higher power rating. This paper reviews suppression methods for the conductive common-mode (CM) EMI in inverter fed motor drives. In order to span EMI suppression across the full system design process, the review considers both mitigation from the sources and suppression along the conduction paths. Furthermore, the shortcomings and merits of the reviewed publications are discussed, and their attenuation frequency range and attenuation level are compared. It is demonstrated that the CM EMI at low frequency is mainly determined by the PWM strategies and can be reduced or even theoretically eliminated through zero common-mode control. On the other hand, the CM EMI at high frequency is markedly influenced by the switching transients of the power devices. Thus, various drive circuits are reviewed which improve the switching behavior. Finally, the deployment of passive and active filters to suppress or compensate for the EMI is discussed.

Persistent-luminescence phosphors (PLPs) have a wide variety of applications in the fields of photonics and biophotonics due to their ultralong afterglow lifetime. However, the existing PLPs are charged and recharged with short-wavelength high-energy photons or inconvenient and potentially risky X-ray beams. To date, deep tissue penetrable NIR light has mainly been used for photostimulated afterglow emission, which continues to decay and weaken after each cycle, Herein, a new paradigm of trap energy upconversion-like near-infrared (NIR) to near-infrared light rejuvenateable persistent luminescence in bismuth-doped calcium stannate phosphors and nanoparticles is reported. In contrast to the existing PLPs and persistent-luminescence nanoparticles, the materials enable the occurrence of a reversed transition of the carriers from a deep-level energy trap to a shallow-level trap upon excitation by low-energy NIR photons. Thus these new materials can be charged circularly via deep-tissue penetrable NIR photons, which is unable to be done for existing PLPs, and emit afterglow signals. This conceptual work will lay the foundation to design new categories of NIR-absorptive-NIR-emissive PLPs and nanoparticles featuring physically harmless and deep tissue penetrable NIR light renewability and sets the stage for numerous biological applications, which have been limited by current materials.

Switched reluctance generator (SRG) have unavoidable application potential in power generation because of good high reliability, simple structure, high fault tolerance, and therefore attract increasing research attentions. Due to the intelligentization demands, reliable communication is of great significance for fault monitoring and remote control among power converters integrated in microgrid systems. In this paper, an improved new SRG power converter is discussed, which is able to reduce the number of switching devices, as well as the cost of SRG system. The power and signal synchronous transmission (PSST) is also realized by using the modified power converter without requirement of extra coupling equipment. The signals are embedded by modulating the output voltage ripples and FFT method is adopted on the receiver side to demodulate the signals. Simulation verification are carried out to confirm the feasibilities of the proposed converter and power line communication method.

The modular multilevel converter (MMC) becomes attractive in the medium- and high-power application with high modularity. In this paper, the MMC and cycloconverter based machine drive system is proposed. The six-phase MMC is used as the grid-side converter, which produces six-phase medium-frequency ac voltage for the machine side converter. The six-phase to three-phase cycloconverter is used as the machine-side converter, which converts the medium-frequency ac voltage to the low-frequency ac voltage to drive the machine. In addition, the corresponding control for the grid-side converter and the machine-side converter are also proposed. The proposed MMC and cycloconverter based machine drive system can effectively realize the control for the high-voltage, high-power and low-speed machine. What is more, the SM capacitance is significantly reduced owing to the medium-frequency ac output voltage of the MMC. The simulation studies of the proposed MMC and cycloconverter based machine drive system and control are conducted with a detailed PSCAD/EMTDC model, and the results show their effectiveness.

A real-time ranging lidar with 0.1 Mega Hertz update rate and few-micrometer resolution incorporating dispersive Fourier transformation and instantaneous microwave frequency measurement is proposed and demonstrated. As time-stretched femtosecond laser pulse passing through an all-fiber Mach-Zehnder Interferometer, where the detection light beam is inserted into the optical path of one arm, the displacement is encoded to the frequency variation of the temporal interferogram. To deal with the challenges in storage and real-time processing of the microwave pulse generated on a photodetector, we turn to all-optical signal processing. A carrier wave is modulated by the time-domain interferogram using an intensity modulator. After that, the frequency variation of the microwave pulse is uploaded to the first order sidebands. Finally, the frequency shift of the sidebands is turned into transmission change through a symmetric-locked frequency discriminator. In experiment, A real-time ranging system with adjustable dynamic range and detection sensitivity is realized by incorporating a programmable optical filter. Standard deviation of 7.64 {\mu}m, overall mean error of 19.10 {\mu}m over 15 mm detection range and standard deviation of 37.73 {\mu}m, overall mean error of 36.63 {\mu}m over 45 mm detection range are obtained respectively., Comment: 7 pages, 8 figures In press

Herein, multiple Fano resonances with excellent ability to be tuned independently are produced in a sub-wavelength metal-insulator-metal system. The input and output waveguides are separated by a metal gap, and a stub and an end-coupled cavity are placed below and to the right side of the input waveguide, respectively, as discrete states. Owing to the mode interferences, double ultra-sharp and asymmetric Fano resonant peaks are observed in the transmission spectrum. Successfully, the basic structure is extended by two extra rectangular cavities, giving rise to four Fano resonances with high refractive index sensitivity and figure of merit. Due to the discrete modes of Fano resonances from different coupling cavities, their resonant wavelengths can be controlled independently, which can provide greater flexibility for tuning Fano resonances. The performances of the proposed structure are investigated by both the finite-difference time-domain method and the multimode interference coupled-mode theory. It is believed that the research can provide important guidance in designing Fano resonance structures, and the proposed structure has a wide application in sensors, switches, and nano-photonic integrated circuit devices.

The development of current technology imposes more and more requirements for measurement techniques, where one of the most important is temperature measurement. In recent years, non-contact optical thermometry based on fluorescence intensity ratio (FIR) technique has received tremendous attention in inorganic compounds for its promising applications in the electromagnetic field, micro-temperature field and thermally harsh environments. In this work, the current advancement of optical thermometry is reviewed in detail. Herein, the FIR thermometers are classified into two types: thermally coupled levels (TCLs) and non-TCLs based on the different energy level pairs. We investigate the relationship between the absolute sensitivity Sa and relative sensitivity Sr, temperature T and energy difference ∆E based on the TCLs of lanthanide ions. The most important results obtained in each case are summarized, which indicates that some new strategies can extend the temperature operating range, improve the sensitivity and enhance signal discriminability. It is expected that this review will provide important guidance in exploring novel FIR optical thermometry with excellent properties in the future.

Nowadays, the optical data storage (ODS) has already become one of the most promising data storage technologies in this digital era. Optically stimulated luminescence (OSL) material has recognized as a considerable potential candidate for the new-generation ODS. The improvement of volatile memory performance and the increase of storage capacity are two critical challenges to be solved. In this work which is reporting on, a new novel Eu2+-doped orthosilicate phosphor has been studied showing both persistent luminescence and OSL. The trap density is significantly enhanced by 10-fold via Dy3+ codoping. Information can be reversibly written into the traps by UV light illumination and then read out by optical or thermal stimulus. The capture and release dynamics of electrons by traps are studied in detail to reveal the OSL-based ODS mechanism. Moreover, as a proof-of-concept, ODS flexible medium is fabricated using the as-obtained OSL material to certify the application feasibility for erasable optical data write-in and read-out.

Bi3+-activated phosphor with ultraviolet-visible persistent luminescence and photo-stimulated luminescence is synthesized via high temperature solid phase reaction. This phosphor shows a broad emission band from 300 nm to 700 nm, a bright persistent luminescence over 12 h after ceasing the excitation and the photo-stimulated luminescence under the excitation of visible to near-infrared light. This paper reports that the operational waveband of long persistent phosphor, CaZnGe2O6: Bi3+, has been extended into the short-wavelength spectral region.

An all fiber coherent differential absorption lidar (CDIAL) system working in the 1.57 μm wavelength region was developed and the research on fast retrieval of atmospheric CO2 concentration is experimentally demonstrated. Two narrow-linewidth fiber lasers are used and controlled by an optical switch to achieve time division multiplexing. The feasibility of polarization diversity reception (PDR) is analyzed based on randomly oriented elliptically polarized light to improve the polarization matching between the lidar return and local oscillator (LO); moreover, the performance of pulse coherent accumulation is simulated on the grounds of random initial phase correction of laser pulses. Detection experiments show that the relative fluctuations of intermediate frequency (IF) signal could be reduced to 0.41% with PDR; the minimum detection limit of this CDIAL system is better than 4 ppm in less than 1 s in 1 km and it can be used to monitor the short-term changes of atmospheric CO2 concentration. Due to the capability of polarization matching and coherent accumulation, our CDIAL system is promising to improve the temporal resolution of range resolved lidars for atmospheric CO2 detection when there is a more powerful emitter.

Plug-in hybrid electrical trucks (PHETs) are a kind of emerging transport solution to reduce greenhouse gas emissions. Switched reluctance motors (SRMs) are one of the popular choices for PHETs applications due to characteristics of rear-earth free, high starting torque, wide-speed range, and good fault tolerance. Usually, more than two converters are needed to achieve flexible energy conversion among multiple electrical energy components on board, i.e., generator, battery bank, and motor. High-power converters should be used to drive the trucks that occupy the limited on-board space. Furthermore, an extra converter is also needed to achieve ac grid connecting charging. All these converters make the on-board power electronics converter complicated. In this paper, a modular tri-port high-power converter for SRM based PHETs is proposed to combine the multiple electrical energy components into one converter. The modular tri-port high-power converter can not only support flexible energy flow, but also support parallel and series winding connections according to different conditions. Furthermore, ac grid connecting nodes are also developed in the drive, which allows the proposed converter to work as a grid connecting charger without extra facilities. The simulation and experiments are employed to verify the feasibility of the proposed converter and corresponding control strategies.