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In the DC distribution network, the ability of the converters to withstand overcurrent is very poor. When a fault occurs in the DC line, the converter protection and line protection cannot be easily coordinated, making it difficult to ensure selective fault removal. This paper investigates protection for the DC distribution line connected with the DAB converter. First, a fault current limiting scheme for the DAB converter using phase shifting and constant current control is proposed. Then a protection scheme for the DC distribution line based on the similarity of the fault currents flowing on both sides of the line is proposed. The effectiveness of the fault current limiting control scheme and the protection scheme is verified in PSCAD/EMTDC simulation.

In order to reasonably evaluate the effectiveness of UHF sensor arrangement in online monitoring of partial discharge of bushing, it is necessary to study the electromagnetic wave propagation characteristics of partial discharge UHF in the bushing. In this paper, a three-dimensional model of a real transformer bushing is established, the XFDTD software is used to simulate the raised seat defects and internal capacitive core defects of the bushing, field strength sensors are arranged at different locations inside and outside the bushing, and the propagation process of partial discharge UHF signals leaking from the oil-paper insulated bushing to the external free space is simulated and analyzed. The results show that the time difference between the signals received by the field strength sensors at different locations is not significant and can be neglected in practice. The partial discharge electromagnetic wave signal generated by the bushing elevated seat defect leaks from the upper porcelain sleeve to the external space, and the leaked electromagnetic wave energy is mainly gathered at the upper and lower ends of the upper porcelain sleeve. The partially discharged electromagnetic signal at the capacitor core inside the bushing will propagate along the coaxial waveguide structure formed between the capacitor screens towards the two ends of the capacitor core, the downward propagating electromagnetic wave energy is confined within the elevated seat, the upward propagating electromagnetic wave energy propagates from the top of the upper porcelain bushing to the external space, the leaked electromagnetic wave energy is mainly concentrated at the top of the upper porcelain bushing. The simulation results provide ideas for optimizing the arrangement of external antenna sensors for UHF detection of partial discharges in transformer oil-paper insulated bushings.

In this paper, we prepared titanium alloy through near-net forming green manufacturing, and then we quantitatively deformed the alloy and finally analyzed the deformation and fracture mechanism of the alloy. The result indicates that the deformation mechanism of those containing α + β lamellar structures is different from that of traditional structures. Especially, the lamellar structure can absorb the deformation energy of the alloy, thus improving the comprehensive properties of the alloy, of which the α phase mainly contributes to the plasticity of the alloy, while the β phase mainly contributes to the strength of the alloy. The two-phase combination will improve the mechanical properties of the alloy, which is completely different from the traditional strengthening mechanism of the basket structure and Widmanstatten structure.

Extrusion-based printing with soft materials is an additive manufacturing technology, which is widely used in biomedical fields such as skin reconstruction, muscle repair, and cartilage regeneration, etc. Constructing high-precision printed structures and maintaining high cellular bioactivity are key issues in the in vitro construction of tissues and organs using extrusion bioprinting. There are some printing paraments such as pressure, height, nozzle type (eg, length and inner diameter), translational speed, etc. can have a huge influence on the structural fidelity. In this work, we put forward a quantitative test method to evaluate the printing accuracy is influenced by pressure and height. The results show that higher pressure can benefit uniformity (the filament width is equal everywhere), and higher height leads to higher uniformity only in low pressure for paste. This study can provide researchers with the tunning suggestions of printing paraments, which may promote the development of printing accuracy in the future.

This paper describes an indoor location recognition device and method based on an indoor robot. The device includes a computer Raspberry Pi, a lidar, a CMOS camera, an ultrasonic sensor, a first microcontroller, and a servo motor; the lidar is connected to the computer Raspberry Pi. Pie, the lidar is driven by a servo motor, the ultrasonic sensor is connected to the computer Raspberry Pi through the first microcontroller, and the computer Raspberry Pi controls the lidar to scan the location to measure the width and length of the current location, and controls the ultrasonic sensor to the location. Perform up and down scanning to measure the distance between the ultrasonic sensor and the ground and the ceiling respectively, and obtain the height of the room; the CMOS camera is connected to the computer Raspberry Pi, and the computer Raspberry Pi sends an instruction to control the CMOS camera to take pictures of objects and places and use them Opencv and other related technologies achieve the purpose of identification. The device and method can continuously identify indoor locations under various complex conditions, and at the same time improve the accuracy and reliability of location recognition.

Event detection (ED) aims to identify events and their types from the given text, which is the vital subtask of event extraction. However, poor quality training corpus can seriously affect the validity of current dominating deep learning-based techniques. In order to improve the robustness of the model, this paper converts the ED task into the named entity recognition (NER) task, and uses the span-based NER framework to identify and classify event triggers. In addition, we ameliorate the framework through data cleaning strategy, hierarchical learning rate strategy, sentence-level loss function and model ensemble strategy. The experimental results suggest that our approach achieves state-of-the-art performance on the widely used Chinese dataset. Moreover, the deep analysis has confirmed the effectiveness of the improvement strategy in resisting data pollution.

The distributed optical fiber sensing system uses optical fiber as the sensing element and signal transmission medium at the same time, and adopts advanced Optical Time-domain Reflectometry (OTDR) technology to detect the changes of temperature and strain at different positions along the optical fiber, thus achieving a truly distributed measurement. Using the Micro-structured Optical Time-domain Reflectometry (M-OTDR) optical fiber sensing access network technology, combined with optical link components such as fault locators, can judge the operating status of optical fiber Composite phase cable (IOPPC) lines, and detect faults (such as breakpoints) in optical fiber communication location and diagnosis. The position of the lightning strike is determined by detecting the change of polarization state caused by the transmitted light in the optical fiber inside the IOPPC before and after a lightning strike, and the positioning error is less than 1%. By observing the Brillouin frequency shift chart, the ice state can be accurately identified and the positioning function can be realized. By monitoring the vibration frequency of the IOPPC cable, the line dancing phenomenon can be detected in time to prevent line faults caused by dancing. The online safety and health monitoring of the operating state of transmission lines are realized.

To reduce the cost of a flight, a calculation method is proposed in this paper, which takes the shortest distance as the goal and avoids the obstacle zone, and controls the turning angle as a constraint. Firstly, the Maklink diagram is used to build the obstacle zone model and establish the relationship between the obstacle zones. Then Dijkstra algorithm is used to construct the initial flight path to form a suboptimal path. Then the genetic ant colony algorithm is used to optimize the obtained suboptimal path. When there is a conflict risk between the two planned paths, the flight altitude of the aircraft on one path is adjusted, and the constraints are checked to form the optimal path. The simulation results show that the method can realize flight path optimization and verify the feasibility of the method.

At present, there are some problems with aero-engine, such as insufficient high-altitude point/flameout boundary, smoke in large conditions, and easy flameout in slow trains with poor oil, which seriously threaten flight safety. Aiming at the problem of insufficient high altitude stable combustion range, an intelligent control combustor of plasma-enhanced combustion is proposed in this paper. The sliding arc exciter is perfectly combined with the combustor head and the pre-burning sliding arc jet igniter is used as the technical basis of the enhanced combustion. Based on the working environment and service state of the engine, a set of the control system is designed for active control. The influence of the installation of the exciter on the combustion flow field is explored, and the feasibility of the exciter for widening the point flameout boundary and improving the combustion efficiency is verified. A set of the control scheme is proposed. The research shows that: the exciter can realize the integration of ignition and combustion support in the combustion chamber. After the exciter is started, the ignition boundary is widened by about 17.6% on average, and the flameout boundary is widened by about 45.3% on average. The combustion efficiency can be increased by 9.28%, which indicates the feasibility of the combustion chamber.

Capacity prediction of surface mount production lines is important for improving productivity, dynamic production scheduling, and optimizing production structure. An integrated mutual information-cuckoo search-extreme learning machine (MI-CS-ELM) prediction model is proposed for the impact of nonlinear and high-dimensional features of surface-mounted production lines on capacity. Firstly, the features affecting the production capacity are ranked based on the mutual information method, and the predictive input data set is reconstructed. Secondly, the input parameters of the prediction model are adjusted by the cuckoo search algorithm and the capacity prediction model is built based on an extreme limit learning machine. Finally, the rationality of the proposed method is verified by an example to guide capacity planning and production scheduling optimization.

A differential absorption lidar method utilizing the spectral and energetic properties of high-power, pulsed laser diodes for remote sensing of atmospheric humidity is reported. The laser radiation of selected complementary laser diodes is multiplexed in dual spectral channels centered at optimal wavelength of 0.86µm and 0.911µm. Humidity profiles are retrieved integrating multiple resonance lines in the tunable range within the absorption spectrum of water vapor. The integral spectrum is less affected by the variable atmospheric pressure and temperature, which is an essential advantage allowing direct and reliable DIAL measurement.

With the continuous development of the smart grid and the gradual improvement of the demand for grid reliability and power grid self-healing capability, a large number of artificial intelligence technologies have been applied to the power grid. In order to improve the automation of the power grid, realize automatic fault identification and diagnosis after a power grid failure, and improve the efficiency of fault handling by the dispatching department, it is of great practical significance to use alarm information to achieve accurate fault judgment. However, the difference between the dynamic reading of alarm information flow and static samples in engineering applications is often ignored in the research of fault diagnosis using alarm information, which makes it difficult to apply fault diagnosis methods in engineering practice. Based on the characteristics of the LSTM algorithm, such as deep knowledge extraction ability, data mining ability and time series knowledge processing ability, this paper studies the power grid fault diagnosis method based on LSTM to adapt to the data of each sampling time window in the process of online fault diagnosis, solves the problems faced by the application of traditional diagnosis methods in engineering practice, and effectively improves the reliability of fault diagnosis.

For the operation and maintenance management of Power Lines, this paper uses laser scanners to collect data from the research lines, and proposes a method combining random sampling consistency with Euclidean clustering to extract the traverse point cloud data. Firstly, the idea of random sampling consistency is used to eliminate a large number of ground points unrelated to target points. Secondly, Euclidean clustering is used to extract traverse and tower points, and then the tower and traverse are divided by combining tower coordinates and threshold. Finally, the polynomial model is used to construct a fitting traverse. The results show that this method can effectively extract the traverse points and accurately fit the traverse model, and it has certain applicability.

Unsupervised person re-identification (re-ID) aims to match pictures of target pedestrians from some other cameras without any labels. The existing methods usually adopt a cluster-based pipeline to generate false labels for training. However, because of the differences in camera configuration, taking pictures Angle, illumination intensity and pedestrian background, unlabeled pedestrian training samples captured by different cameras are hard to classify into a cluster. To solve this problem, the paper proposes a camera-irrelevant feature learning framework, which learns camera-irrelevant features and camera-irrelevant distances through network training and clustering. Specifically, during training, images of other camera styles are generated, which enriches cross-camera learning. During clustering, we propose a camera-irrelevant distance matrix, which reduces the inter-class variance caused by camera variance.

Compared with traditional inverters, line voltage cascade quasi-Z source inverter (LVC-QZSI) has many advantages, but its power quality problems limit its wide application to some extent. In this paper, voltage ripple and power loss of LVC-QZSI are selected as the optimization objectives to build a multi-objective optimization model of LVC-QZSI. In the optimization process, it is found that the dimension of decision variables is too high, which belongs to a kind of large-scale multi-objective optimization problem. To solve this problem, this paper proposes the dimension reduction and optimization strategy of particle swarm optimization based on gray relation analysis and principal component analysis (GRA-PCA-PSO). GRA-PCA is used to realize the dimension reduction of decision variables, and then PSO based on information entropy is used to optimize the multi-objective optimization model after dimension reduction. Finally, the original optimization parameter values are derived from the eigenvalue matrix obtained from PCA. Compared with the traditional method of decision variable grouping and co-evolution, it reduces the calculation cost and improves the optimization accuracy. Finally, we verify the reliability of the algorithm.

In multiphase motors, the consumption of stator copper and the output of torque are a pair of constraints affecting motor control performance. According to the constraint relationship between the them, this paper proposes a method to balance the consumption of copper and the output of torque by using the weight coefficient. Through this method, the efficient control of fault-tolerant motors can be realized, and the balance of output torque and efficiency can be realized. Finally, the accuracy of the control strategy is verified by the motor loading platform.

With the continuous development of power systems, the number of non-linear loads is increasing. When harmonics flow through wires, transformers, filters, and other devices, additional harmonic losses will be generated, which will cause power loss and safety problems such as equipment overheating. However, there are few studies on loss in complex power quality environments. Considering the influence of skin effect when harmonics flow through the conductor, this paper studies the distribution of current density, explores the influence of conductor material, radius, and frequency of the current flowing through the metal on the current distribution, and proposes a calculation method of conductor harmonic resistance considering the influence of skin effect. Furthermore, the electrical energy consumption of typical devices in the distribution network is considered. Based on the theoretical calculation model, a simulation platform was established to carry out the equipment loss measurement experiment under each harmonic current, and the mutual verification between the theoretical calculation model and the experimental measurement was realized.

To accurately count densely stacked rebars belongs to semantic segmentation in image. Various methods have been proposed to segment the objects in single image. However, widely and densely stacking scene such as warehouse or vehicle stacking of rebars is always faced. For these scenes, clear image of end faces of rebars cannot be obtained through a single camera. Generally, multiple cameras are often used to take clear images to count rebars. One strategy is to stitch multiple images into a single image at pixel level first, and then count rebars in this stitched image. Various methods have been proposed to stitch images, but it is extremely difficult to stitch two images at pixel level accurately for parallax distortion or partially hidden. A topological stitching strategy is proposed in this paper to count the rebars in whole scene. In the method, rebars in each image are identified and counted first, and then the identification and counting results in the adjacent images are stitched so as to esitmate the total number of rebars. The perfomance of the method is evaluated on real datasets, and the counting accuracy exceeds 99%. Experiments show that the proposed method is effective on widely and densely stacked rebars identification.

Photovoltaic power generation is one of the main forms of new energy utilization, and the reliable operation of a photovoltaic inverter, as the main component of a photovoltaic power generation system, is of great significance. Studying and mastering the faults of photovoltaic inverter and taking preventive measures is very important to ensure the stable and efficient operation of the photovoltaic power generation system. This paper expounds on the development of photovoltaic power generation and the composition of the photovoltaic power generation system, summarizes the typical faults of a photovoltaic inverter, analyzes the causes of the faults, and on this basis, puts forward the improvement measures to avoid the faults.

In the present study, TiN and VN surface coatings are applied on copper substrates, and their influence on the electrical contact resistance (ECR) of the primary material is studied. The coatings are deposited using reactive magnetron sputtering in an Ar/N2 environment. The formed TiN and VN thin films have a thickness of 600 nm and 350 nm, respectively. The preferred crystallographic orientation of both coatings is in the (311) plane. This corresponds to a high crystallite size, high plastic deformations, and high mobility of any structural defects. The I(200)/I(111) ratios of the coatings indicate that the deposited TiN coating is perfectly stoichiometric, and the VN one is hyper stoichiometric, resulting in its’ slightly higher electrical contact resistance. The electrical contact resistance of both coatings is significantly lower compared to that of the pure copper substrate due to their excellent corrosion resistance.

With the rapid development of electric vehicles, more and more electric vehicles are entering people’s lives. However, the large-scale access of electric vehicles to the grid brings harm to the stability of grid operation, and the problem of how to guide the staggered charging of electric vehicles needs to be solved. In this paper, we consider the travel characteristics and charging characteristics of three different types of EVs: private cars, buses, and cabs, and set up a time-of-use tariff to guide EV users to charge reasonably, thus reducing the impact of charging load on the grid by cutting peaks and filling valleys. Since the charging load of EVs is an interval value, this paper introduces interval optimization theory, establishes an optimistic model and a pessimistic model, calculates the upper and lower bound of the interval respectively, and finds out the interval value of grid load after peak and valley reduction.

All-optical vacuum birefringence experiments will get increasingly closer to feasibility as multi-petawatt laser facilities become operational around the World. Thus, the availability of focused laser intensities in the order of IL ∼ 1022 −1024 W/cm2 are to be expected in a focused spot size ∼ 3 − 5 μm. With these values, vacuum refraction indices in the order of Δn ∼ 10−11 − 10−9 are possible with an induced phase delay on a counterpropagating optical probe beam in the order of Δφ ∼ 10−9 −10−7 radians. We discuss two all-optical interferometric schemes and detail the Mach-Zender interferometric proposal. We consider this interferometric scheme fed by both classical and non-classical input light and with two detection schemes. We outline scenarios that are likely to lead to a feasible experimental implementation.

It has recently been shown both theoretically and experimentally that a significant modification of the aC:H films is possible using UV irradiation even with a very low irradiation fluence. Some initial results on the modification of aC:H films with thickness of about 40 nm with UV laser irradiation are presented here. The fourth harmonic (λ = 266 nm) of a Nd:YAG laser system (the fundamental wavelength λ = 1064 nm) was used in our experiments. The modified areas of the aC:H films were characterized by optical microscopy, Raman spectroscopy as well as by atomic force microscopy (AFM). A significant modification of aC:H films under certain conditions (laser irradiation fluence and modification modes) to multi-layer graphene accompanied by ablation of a part of the film was established. It was also found that similar aC:H films deposited on 330 nm SiO2/Si substrates did not undergo significant modification under these conditions.

The present study proposes to design, fabricate and investigate a miniature supersonic wind tunnel at an affordable cost, safe to operate, and reliable for education purposes. The configuration consists of a high pressure reservoir, and mini tunnel which will be used for providing the supersonic flow over aerodynamic models. To design the mini supersonic wind tunnel, the method of characteristics is used to ensure that any shocks that arise in contact with the surface do not impact the uniformity and velocity of the flow through the duct. To achieve the supersonic flow, the nozzle contour of the supersonic portion of the wind tunnel is built in such a way that the shocks nullify each other and have zero effect on the velocity of the flow. For compressible flow visualization, an affordable Schlieren setup consisting of a torch, mirrors, and a mobile camera is used for flow visualization. Finally, the visualization results of the present study is in good relation with the theoretical calculations. The present facility is also calibrated by measuring the oblique shock angle in the test section, in the range of Mach number 1.6 to 1.8.

According to the findings of the article, researchers looked at graphene-based hexagonal microstrip patch antennas. In place of a U-shaped slot and an elliptical slot, an ellipse-shaped slot was cut into the surface of the hexagonal radiators that were used in the designs that were recommended. This helped to improve the radiation performance of the radiators. A frequency known as ultra-wideband (UWB) is used in the modelling process for the anticipated structures. Through the use of comparative studies, an investigation into the effect of U-shaped and elliptical-shaped slots on the radiation performance of proposed graphene antenna designs has been carried out. The use of ellipsoidal slot-loaded structures results in considerable enhancements and advancements in directivity. The impedance bandwidths for S11 antennas with a gain of 10 dB range from 0.68 to 1.63 terahertz for U-shaped and elliptical-shaped slot loaded hexagonal printed antennas, respectively. Extensive research is presented for the various characteristics of the proposed THz antenna types. The designs that were offered provide excellent impedance matching over the full operating range. This is made possible by the high reflection and VSWR values that they possess. The cutting-edge antenna design may be used for spectrum imaging, the detection of explosives, medical diagnostics, radio transmission, and the monitoring of the weather.

The coherent magneto-optical resonances on the potassium D2 line are investigated from the point of view of magnetometry applications. The measurements are performed in Hanle configuration with potassium excited by circularly polarized laser beam in cell with dimensions 8 mm and buffer gas 30 Torr Ne. The parameters of the resonances registered in fluorescence and transmission are compared. The capability of the laser system to work with magnetically unshielded cell is demonstrated. The registration of bright and dark magneto-optical resonances detected in fluorescence by controlling the optical thickness of potassium vapor is discussed. The influence of the laser power and transverse magnetic field are considered. The experimental results show the potential of the system for magnetic field sensing and calibration.

Ultra-thin amorphous carbon (a-C) films are well established protective coatings of optical fibers. These coatings allow one to prevent degradation of the SiO2 fiber, which occurs due to diffusion of the water and hydrogen molecules into cladding and core. The a-C films typically contain impurities, such as oxygen and hydrogen, which are attached to organic moieties via chemical bonding. The formation of hydrogen- and oxygen-containing functional groups reduces the hermeticity of a-C coatings, and therefore, monitoring these impurities is of great importance. In this work, we develop a method for probing O- and H- containing moieties based on resonance anti-Stokes Raman spectroscopy. We measured Raman spectra of a-C films and observed that anti-Stokes to Stokes ratios of Raman peaks differ from those predicted by Boltzmann law. This effect caused by resonance enhancement of the anti-Stokes Raman scattering in defects of graphite-like crystals. To quantify this effect, we used a resonance factor, which is defined as a ratio of the anti-Stokes and Stokes scattering cross sections. We show that this indicator can be used to assess degree of enrichment/depletion of a-C with O- and H- containing functional groups. Understanding the physical mechanisms of the anomalous anti-Stokes Raman scattering will improve Raman thermometry.

Thrust eccentricity refers to the phenomenon that the thrust vector deviates from the axis of symmetry. This phenomenon will produce lateral force and torque around the aircraft, which affects the normal flight of the aircraft, increases the required control torque, and reduces the density of uncontrolled rockets. There are three sources of thrust eccentricity: mass eccentricity, geometric eccentricity, and aerodynamic eccentricity. The aerodynamic eccentricity is caused by the asymmetrical flow of combustion gas in the nozzle. This paper uses FLUENT software to carry out a numerical simulation of a cone-shaped nozzle. By changing different factors such as the structure of the inner surface of the nozzle and the convergence radius, the influence law of the inner surface structure of different nozzles on the lateral force of the pneumatic eccentricity of the nozzle is explored. The following conclusions were drawn: With the expansion of the expansion half-angle, the second zero point moves toward the nozzle outlet. The relative radius of curvature has little effect on the main thrust of the nozzle but has a certain influence on the eccentricity of its thrust, and as the relative radius of curvature increases, the first and second zeros move toward the throat.

The expansion of laser sources operating at 2-3 μm is motivated in large by strong absorption in atmospheric gases, liquid water, and plastics, critical for applications in remote sensing, soft and hard tissue surgery, and materials processing. 2-μm novel solid-state lasers based on Tm3+-doped ceramics (Lu2O3 or Y2O3) or YAP crystals in-band pumped by a fiber laser at 1670 nm are presented in this report. CW, actively or passively Q-switch operations of the Tm3+-doped lasers are described. The Tm3+ laser characteristics are compared with parameters of an in-band fiber-laser-pumped Ho3+:YAG laser. The 2-μm output of the lasers are used to pump the Cr2+-doped ZnSe or CdSe crystals. The lasers based on the Tm3+:Lu2O3 ceramics and the Tm3+:YAP crystal are also used as pump sources for mid-IR optical parametric oscillators (OPOs) or second-harmonic generators (SHGs). The high-efficiency oscillations are obtained at 3.8-4.1 μm in the OPOs based on a fun-out PPMg:LN; the SHGs provided the repetitively-pulsed radiations at 970-983 nm.

Hydraulic fracturing can effectively increase reservoir productivity, and the effect depends on proppant behavior. Crushing of proppant during fracturing induces a series of changes in fracture width and the pore space formed between proppant particles, affecting reservoir fluid flow. For exploring the flow law of oil and water in proppant fractures, the discrete element method (DEM) and Tavares crushing model were combined to simulate the proppant crush process. At the same time, based on the formed pore space, the flow law of two phase fluid under the influence of such factors as the number of proppant placement, combination of particle size, closing pressure, and particle wettability was studied by fluid volume method(VOF). A series of data obtained through simulation show that with the increase of the average particle radius of single-layer and multilayer proppant is, the fracture conductivity and fracture width increase at the same closure pressure,. In the pore space formed by surface water-wet proppant, the ability of pore to transport oil phase increases; the higher of the number of closure pressure is, the larger the ability of pore to transport oil phase is.

Li-Fi (Light Fidelity) is a new wireless communication technology that is comparable to Wireless Fidelity (Wi-Fi). However, Li-Fi is supposed to be better than Wi-Fi, and this has been theoretically verified. Li-Fi is also thought to make a significant contribution to wireless networks. The practical application of Li-Fi will be discussed in this study. In this paper we chose NOMA because of its ability and efficiency in simultaneously transporting data, as well as its application in 5G cellular networks. VLC stands for visible light communication, as the name implies. In this section, we will investigate how the data transporting capabilities of Li-Fi make use of the visible light emitted by light emitting diodes (LEDs). In this paper, the effectiveness of a non-orthogonal multiple access (NOMA) protocol used in a downlink visible light communication (VLC) system is evaluated for two distinct situations. On a two-user paired NOMA, we create an analytical expression of the system coverage probability for QoS provisioning and show that optimum power allocation coefficients do exist. Additionally, we establish the existence of optimal power allocation coefficients. Last but not least, the numerical and analytical results illustrated in our work show that the VLC single-cell system throughput obtained with our technique is better than that obtained with the earlier strategy. Additionally, it is shown that the suggested alternative lower bound fits the original NOMA-VLC GRPA objective asymptotically using indoor VLC channels.

The aim of this work is to gain an insight on the effect of the wall heating on the aeroacoustic sound radiated by bluff bodies in laminar flows. In particular, the local thermal treatment of the wall boundary was investigated as a possible method for active controlling the emitted noise. This technique was studied performing direct numerical simulations of the aeroacoustic noise produced by an isolated square cylinder operating at a Reynolds and Mach numbers equal to 150 and 0.2, respectively. In the considered case, the Karman vortex street deriving by the flow/cylinder interaction, produces a lift and drag pulsation on the body surface, leading to a dipolar-like noise emission. In this context, different local thermal fluxes were applied to the cylinder wall in order to reduce its aerodynamic forces fluctuation and, consequently, the associated pressure disturbance that produces the radiated sound. The computations are performed using an OpenFOAM solver that adopts an explicit Runge-Kutta scheme for time integration and a second-order, energy conserving scheme for the convective part of the Eulerian flux. Moreover, the spurious numerical waves reflections at the far-field boundary are damped adopting a sponge-layer approach.

The aircraft gun firing will cause serious impact on airframe structure. According to the gun firing principle, the muzzle blast wave is simulated by chemical explosion. ALE method is used to deal with the fluid-structure interaction between high-pressure flowing air and the surface of the cabin. Then the expression model of the impact load is established. The numerical calculation is completed to analyse the dynamic response of the cabin structure under the impact load. The parameters of load and cabin model are modified by using the experiment results. Comparing the calculated dynamic response with the experiment results, the error is within acceptable range. Multiaxial stress equivalence and rain-flow counting method are used to process the simulation impact response data to estimate the impact fatigue life. In conclusion, the paper provides a feasible method for analysing dynamic response and fatigue life of gun cabin structure.

In this paper, we report a numerical study of the thermal effects within both a-cut crystals Nd: YVO4 (1.5 at.%) and Nd: GdVO4 (1.5 at.%) end-pumped by a diode laser emitting at 914 nm. The temperature, stresses distributions and thermal lensing parameters were calculated by finite element method using LASCAD© software. The obtained results show that the Nd:GdVO4 is the best candidate for high power diode laser end-pumped solid-state lasers because of its lower thermal effects.

This paper briefly analyzed the operation mechanism and construction strategy of source grid load storage under the access of renewable energy, and discussed the method of constructing the source-grid-load-storage model under the access of renewable energy. The results of the study show that an economic efficiency of active distribution network operation can be improved by the coordinated optimisation of source network load storage.

To meet the demand for carbon emission prediction, it is necessary to master the measurement criteria and influencing factors of carbon emission and improve the accuracy of prediction results in the form of a combined application of multiple algorithmic models. This paper proposes a carbon emission impact factor decomposition model based on LMDI and a carbon emission prediction model based on the EEMD-BSO-GPR model. The study of carbon emission forecasting within the study region allows the study of the stage in which carbon emissions are located, the relationship between emissions and influencing factors such as industrial structure, affluence, energy structure, technology level, degree of openness to the outside world, and population size. The combined forecasting model can also meet the demand for carbon emission forecasting in the region with higher forecasting accuracy.

This paper theoretically analyzes the performance changes of the measuring winding and protective winding of the current transformer behind the iron core of the DC ice melting current magnetized transformer. According to the actual ice melting situation, a finite element simulation model is established to calculate the electromagnetic field distribution inside the transformer, quantify the remanence generated by the ice melting, and design a verification test to measure the remanence and transmission characteristics of the current transformer after the ice melting current is magnetized. Based on theory, simulation, and experiment, suggestions for the treatment after ice melting are put forward.

Cobalamins are cobalt corrin complexes (vitamin B12) with typical porphyrinoid structure and absorption which partly overlaps with the solar spectrum of irradiation. This highly conjugated structure is assumed to have not only the well-known curative action as co-factor and vitamin, but also phototoxicity on dysfunctional, and, in a low extent, on normal cells. Moreover, the cobalamin can have properties as a photosensitizer at appropriate light conditions. The present study aims at characterization of the cyanocobalamin (CNCbl) as a synthetic cobalamin under solar-spectrum irradiation. The photo- and dark cytotoxicity studies were carried out on a normal cell line (BALB/c 3T3, A31) showing no effect due to light application. The photodynamic action of CNCbl due to its porphyrinoid-like structure was not observed. The results on two breast cancer cell lines (MDA-MB-231 and MCF-7) versus a non-tumorigenic cell line (MCF-10) showed similar values for cytotoxicity. A complete loss of viability was observed at approx. 10-4 M CNCbl after 24-hs incubation and soft irradiation (10 J/cm2) for the spectral range 360-960 nm of a LED Helios-iO solar simulator. The cobalt corrin complex showed non-photodynamic ability to reduce the viability of both breast tumor cells depending on the nature of the cell line but not on the light application.

The premise of the system reliability analysis is to effectively discern the patterns of product failures at all levels. To deal with the problem that the diversity of failure modes of complex products represented by LED systems cannot be analyzed comprehensively, in this paper, a key failure mode identification method based on Fuzzy TOPSIS is proposed. First, the construction method of the failure relevance tree is given to support the comprehensive identification of potential failure modes. Then, the decision rule of node failure weight is mined by the rough set method, the systematic evaluation of the node failure weight is realized with the TOPSIS method, and the key failure modes are identified. Finally, a case validation of the proposed method in this paper is performed.

The application of PVT (Photovoltaic-thermal) technology is discussed based on R-CELLS, which is a zero-energy solar energy house at Solar Decathlon China 2021. Combined with the actual data, the simulation model of the PVT system, which supplies domestic hot water and heating bathroom, is established in TRNSYS, and the performance evaluation of the whole year and heating season and economic analysis of the whole life cycle is carried out at the same time. Comparing and analyzing the system with or without auxiliary heating in the water tank, the simulation results show that the annual average electrical efficiency of the system is 15.35% and 15.52%, the annual average thermal efficiency is 3.36% and 9.52%, and the payback period is 13.87 years and 12.12 years. By increasing the number of PVT panels, 4 PVT panels can achieve zero energy consumption of the system, and the payback period of the PVT system can be reduced to 6.5 years after continuing to increase. The small-scale PVT system is systematically analyzed based on a case, and the importance of water tank auxiliary heating design and supply-demand matching design in the PVT energy supply system is found through data comparison, which has reference significance for the promotion of PVT building energy supply system in the future.

Based on the current situation of frequent wind deflection faults of 500 kV transmission line jumpers caused by typhoons in coastal areas, this paper proposes a new sectional wind deflection proof post insulator transformation measure by analyzing the advantages and disadvantages of conventional jumper wind deflection transformation measures, which effectively improves the anti typhoon and wind resistance of 500 kV transmission line jumpers. It can save the amount of steel for tower transformation and greatly shorten the transformation outage time. It provides a solution for future coastal transmission line construction and wind deflection prevention reconstruction.

Aiming at the debris hazard area caused by the explosion and disintegration of the suborbital vehicle, the plane convex hull divide and conquer method is used to process the physical boundary which is in accordance with the air traffic control rules. On this basis, a new method of civil aircraft rerouting planning based on reinforcement learning DDPG algorithm is proposed. According to the state-action space DDPG algorithm, the reward function is optimized to achieve the effect of reasonable routing. With the increase in training times, the reward curve gradually becomes stable and converges in a certain time step, which verifies the effectiveness of the route change planning method.

The purpose of this paper is to solve the problem of the helicopter load factor limit exceeding caused by inappropriate pilot control in vertical maneuvering flight. Through the collective stick control power restriction, an load factor limit protection method based on a load factor predictive algorithm is proposed. First, the load factor prediction is realized by the change rate of the collective stick position given by the actuator and the control derivative of the collective stick position to vertical acceleration, and then the vertical control power is restricted according to the predicted load factor, so as to achieve the purpose of helicopter load factor protection.

In this paper, the three-dimensional numerical method is used to study the change of the internal flow field distribution characteristics of a RDC with a deflector installed at the outlet, using the premixed gas of kerosene and air as reactants. It is found that the total pressure in the front section of the combustor has been improved. Different configurations of deflectors were designed. It was found that the flow field in the combustion chamber could not be significantly changed by changing the number of blades, but the maximum average total pressure and the total pressure loss in the mixing section could be effectively improved by adjusting the angle of incidence. Because the propagation direction of rotating detonation wave and the deflector blade have directionality, the study found that when the two directions are opposite, the reflected shock wave formed at the inlet of the deflector changes greatly, the working environment of the fixed blade is worse, the uniformity of gas after passing the deflector decreases, the flow field along the axial average total pressure loss increases significantly, and the peak value of the total pressure shifts significantly downstream. The study of the interaction between NGV and RDC provides a basis for the design of the rotaing detonation turbine engine.

This paper studies a new simulation test system, which integrates the satellite management and attitude track control software test system, realizes the test configuration and equipment generalization, improves the system universality and automation capability, effectively saves human resources, and equipment costs, shortens the test cycle, avoids quality problems caused by human uncertainty, and improves the efficiency of software development on the satellite.

Photovoltaic output has strong randomness and volatility. Research on the scenario reduction method of PV output is of great significance for the planning, design, and operation of power grids. This paper proposes Nonlinear Brain Storm Optimizer (NBSO) to improve the k-means algorithm, and uses the Standard Deviation Based Index (STDI) to evaluate the effectiveness of clustering. The simulation results show that the clustering method proposed in this paper can effectively reduce the PV output scenes, and the generated typical scene set can fit the output volatility and diversity of the initial scenes.

To solve the problem of nonlinear coupling with longitudinal and lateral tire forces in the integrated control of distributed driving electric vehicles, an improved SAC reinforcement learning algorithm is proposed to coordinate the control method of active front steering (AFS) and torque distribution. The coordinated control adopts a layered structure, and the upper layer adopts the LQR controller to determine the additional front wheel rotation angle and yaw moment required for stability control. The three-level reward function is designed with the goal of vehicle stability and state tracking and is determined by the reinforcement learning algorithm. For the weight factors of the two optimization objectives, the SAC reinforcement learning algorithm is used to coordinate the decision-making of the active front wheel steering and the additional yaw moment; the lower controller uses the comprehensive utilization rate of the tire as the objective function to perform the optimal torque distribution. A co-simulation platform is established in MATLAB/Simulink and CarSim software. The results show that compared with AFS control, SAC coordinated control can not only ensure the stability of the vehicle and achieve accurate tracking of the reference state but also effectively reduces the comprehensive utilization rate of tires and the effectiveness of coordinated control.

Pneumatic lift train together is the concept of under the background of further accelerate the speed of high-speed train running speed, in order to under higher speed train the whole life cycle cost, the researchers put forward the concept of aerodynamic lift high-speed train together, break through the traditional high-speed train aerodynamic shape design concept, combined with high speed trains and aircraft their respective advantages, hope that through increasing train aerodynamic lift, It is hoped that by increasing the aerodynamic lift of the train, the overall energy saving and consumption reduction of the high-speed train can be achieved. In this paper, a high lift airfoil is optimized to improve the lift coefficient as much as possible while the drag coefficient is basically unchanged. The thickness and drag coefficient of the optimized airfoil are almost unchanged at the designed Angle of attack, and the lift coefficient is increased by 13%. A flat wing is designed based on the optimized airfoil, and the influence of wall effect and tandem wing layout on the lift drag coefficient of the wing is studied. A better aerodynamic lift cooperative train tandem wing layout is obtained, which can reduce the weight of a single train by 17%.

This paper analyses the main factors affecting the accuracy of double-end traveling wave ranging for high precision fault ranging on cable lines in DC distribution networks, and points out that the double-end traveling wave method for DC segmented cables based on uniform wave velocity is the main source of fault ranging errors. Then, an improved double-end traveling wave ranging method based on the refined wave velocity of segmented cables is proposed. Based on the linear relationship between the fault traveling wave time difference and the fault location at both ends of the cable, the measured cable segmental wave velocity is used to form a ranging function to derive accurate ranging results. PSCAD simulation experiments demonstrate that the proposed method significantly improves the segmental cable fault ranging accuracy.

After running for a long time, isolator switches are prone to be covered with dirt and corrosion. Switch cleaning is necessary for good operation and safety. Laser cleaning technology for rust removal is emerging in recent years. This paper introduces the technical principles of laser cleaning for rust removal in detail, designs a specific process scheme and takes a steel plate sample cleaning and rust removal as a case. The application effect of laser cleaning and rust removal technology is tested and shows that the technology analyzed in this paper can play a great cleaning effect without damaging the equipment base.