A spatiotemporal evolution model of a short-circuit arc to a secondary arc based on the improved charge simulation method

The initial shape of the secondary arc considerably influences its subsequent shape.To establish the model for the arcing time of the secondary arc and modify the single-phase reclosing sequence,theoretical and experimental analysis of the evolution process of the short-circuit arc to the secondary arc is critical.In this study,an improved charge simulation method was used to develop the internal-space electric-field model of the short-circuit arc.The intensity of the electric field was used as an independent variable to describe the initial shape of the secondary arc.A secondary arc evolution model was developed based on this model.Moreover,the accuracy of the model was evaluated by comparison with physical experimental results.When the secondary arc current increased,the arcing time and dispersion increased.There is an overall trend of increasing arc length with increasing arcing time.Nevertheless,there is a reduction in arc length during arc ignition due to short circuits between the arc columns.Furthermore,the arcing time decreased in the range of 0°-90°as the angle between the wind direction and the x-axis increased.This work investigated the method by which short-circuit arcs evolve into secondary arcs.The results can be used to develop the secondary arc evolution model and to provide both a technical and theoretical basis for secondary arc suppression.

Development of a Novel Noise Reduction Algorithm for Smart Checkout RFID System in Retail Stores

This paper presents a smart checkout system designed to mitigate the issues of noise and errors present in the existing barcode and RFID-based systems used at retail stores’checkout counters.This is achieved by integrating a novel AI algorithm,called Improved Laser Simulator Logic(ILSL)into the RFID system.The enhanced RFID system was able to improve the accuracy of item identification,reduce noise interference,and streamline the overall checkout process.The potential of the systemfor noise detection and elimination was initially investigated through a simulation study usingMATLAB and ILSL algorithm.Subsequently,it was deployed in a small-scale environment to validate its real-world performance.Results show that RFID with the proposed new algorithm ILSL and AI basket is capable of accurately detecting the related itemswhile eliminating noise originating fromunrelated objects,achieving an accuracy rate of 88%.

PERFORMANCE IMPROVEMENT OF CENTRIFUGAL FAN BY MEANS OF NUMERICAL SIMULATION

Numerical simulation is used to investigate the flow field in a model centrifugal fan for steam power stations in order to improve the performance. During testing the model fan, it is found that the efficiency is only 62.5% with inlet box, without it the efficiency is 83%. In addition, the strong vibration of test rig is observed with inlet box. It would be highly desirable if the aerodynamics of the fan could be studied. Therefore, numerical simulation is carried out to investigate the internal flow characteristics of a model fan with inlet box. The results from CFD analysis show that the whole region of the inlet box is occupied by a spiral vortex rotating inversely as the rotor＇s direction, which significantly affect the most flow＇region inside the fan. For this reason, a dummy plate is arranged in the inlet box to impede the generation of the spiral vortex, the results from CFD after the reform demonstrate that the modification is quiet effective, the former large spiral vertex has been destroyed effectively, the large one is superseded in favor of two small vortexes. However, two small vortexes have little effect on the inner flow of the rotor and the following parts. Finally, the efficiency of the model fan is improved by the test and the strong vibration of the test rig disappears. This type of modification has been used in steam power stations, the fan efficiency raises to 84% successfully.

Simulation study on the starting characteristics of a kind of improved direct torque control system

Analyzed working principle and starting process of asynchronous motor direct torque control system. In order to solve the problem of serious fluctuation of starting current in traditional control scheme, the author puts forward a new kind of starting method which can limit voltage value to achieve the goal of reducing fluctuation of the current by increasing zero voltage vectors during the stage of starting. The author has also carried on simulation study on the system, and the result of simulation study shows that this method is effectual.

Improving the efficiency of transport systems using simulation

The article describes the possibilities of application of simulation modeling for the analysis of infrastructure and technology of transport services of enterprises. The main technological and possible economic effects for the enterprises arising at performance of modeling of a transport component of their work are resulted.

The Improved Design of Multi-channel Thin Gap Chamber Simulation Signal Source for the ATLAS Detector Upgrade

We develop an improved design of thin gap chamber （TGC） simulation signal source. To further simulate the feature of TGC detector, a novel thought is proposed. The TGC source has 256 channels. Every channel can randomly output the signal in 25 ns. The design is based on true random number generator （TRNG）. Considering the electrical connection between the TGC source and the developing trigger electronics, the GFZ connector is used. The experimental results show that the improved TGC simulation signal source can uniformly output the random signal in every channel. The output noise is less than 3 mVrms.

Effect of car-body lower-center rolling on aerodynamic performance of a high-speed train

The interaction between the car-body vibration and aerodynamic performance of the train becomes more prominent motivated by the vehicle’s light-weighting design.To address this topic,this study firstly analyzes the posture characteristics of the car-body based on the previous full-scale test results.And then the aerodynamic performance under different vibration cases(different car-body roll angles)is studied with an improved delayed detached eddy simulation(IDDES).The results revealed that car-body rolling had a significant impact on the aerodynamic behavior of bogies,which significantly increased the lateral force and yaw moment of a bogie and further may have aggravated the operational instability of the train.The unbalanced distribution of the longitudinal pressure on both sides of the bogie caused by the car-body rolling motion was the primary cause for the bogie yaw moment increase.The tail vortex of the train was also affected by the car-body rolling,resulting in vertical jitter.

Improvement of light uniformity by lighting arrangement for standardized crop production

In a commercialized, fully artificial plant factory, artificial luminaire is arranged in a unified way using a general illumination theory, an actual measurement, or an empirical methodology. However, with these methods, lightings are implemented without considering specific optical characteristics of lighting or material characteristics of each component that constructs a cultivation system, resulting in an amount of light that becomes irregular. The amount of lighting is closely related with the growth and quality of crops, and the deviation between points where cultivated crops are located causes quality difference in the produced crops, thus impairing the economic feasibility of a plant factory. In this regard, a simulation to figure out an optimum lighting layout was performed. Arrangements based on the spectrum distribution of light source and reflector materials were implemented to ascertain the distance between lighting and height of lighting and gather information in the pre-treatment process to improve the uniformity of light in the plant cultivation system. Improvement of around 15% in light uniformity is achieved compared with the existing system after the simulation is carried out. This result would reduce the deviation in crop growth to make uniform quality crop production possible.

Clinical application of improved 2D computer-assisted fluoroscopic navigation through simulating a 3D vertebrae image to guide pedicle screw internal fixation

Objective To study the effect of using improved 2D computer-assisted fluoroscopic navigation through simulating 3D vertebrae image to guide pedicle screw internal fixation.Methods Posterior pedicle screw internal fixation,distraction

Effect of low operating temperature on the aerodynamic characteristics of a high-speed train

In this study,an improved delayed detached eddy simulation(IDDES)method based on the shear-stress transport(SST)k-ωturbulence model has been used to investigate the underbody flow characteristics of a high-speed train operating at lower temperatures with Reynolds number Re=1.85×10^(6).The accuracy of the numerical method has been validated by wind tunnel tests.The aerodynamic drag of the train,pressure distribution on the surface of the train,the flow around the vehicle,and the wake flow are compared for four temperature values:+15℃,0℃,−15℃,and−30℃.It was found that lower operating t emperatures significantly increased the aerodynamic drag force of the train.The drag overall at low temperatures increased by 5.3%(0℃),11.0%(−15℃),and 17.4%(−30℃),respectively,relative to the drag at+15℃.In addition,the low temperature e nhances the positive and negative pressures around and on the surface of the car body,raising the peak positive and negative pressure values in areas susceptible to impingement flow and to rapid changes in flow velocity.The range of train-induced winds around the car body is significantly reduced,the distribution area of vorticity moves backwards,and the airflow velocity in the bogie cavity is significantly increased.At the same time,the temperature causes a significant velocity reduction in the wake flow.It can be seen that the temperature reduction can seriously disturb the normal operation of the train while increasing the aerodynamic drag and energy consumption,and significantly interfering with the airflow characteristics around the car body.

Numerical investigation of unsteady vortex breakdown past 80°/65° double-delta wing

An improved delayed detached eddy simulation （IDDES） method based on the k-x-SST （shear stress transport） turbulence model was applied to predict the unsteady vortex breakdown past an 80o/65o double-delta wing （DDW）, where the angles of attack （AOAs） range from 30° to 40°. Firstly, the IDDES model and the relative numerical methods were validated by simulating the massively separated flow around an NACA0021 straight wing at the AOA of 60°. The fluctuation properties of the lift and pressure coefficients were analyzed and compared with the available measurements. For the DDW case, the computations were compared with such mea-surements as the mean lift, drag, pitching moment, pressure coefficients and breakdown locations. Furthermore, the unsteady properties were investigated in detail, such as the frequencies of force and moments, pressure fluctuation on the upper surface, typical vortex breakdown patterns at three moments, and the distributions of kinetic turbulence energy at a stream wise section. Two dominated modes are observed, in which their Strouhal numbers are 1.0 at the AOAs of 30°, 32° and 34° and 0.7 at the AOAs of 36o, 38° and 40°. The breakdown vortex always moves upstream and downstream and its types change alternatively. Furthermore, the vortex can be identified as breakdown or not through the mean pressure, root mean square of pressure, or even through correlation analysis.

Numerical study on the flow field characteristics of the new high-speed maglev train in open air

With the increasing demand of higher travelling speed,a new streamlined high-speed maglev train has been designed to reach a speed of 600 km/h.To better capture the flow field structures around the maglev train,an improved delayed detached eddy simulation(IDDES)is adopted to model the turbulence.Results show that the new maglev train has good aerodynamic load performance such as small drag coefficient contributing to energy conservation.The main frequencies of aerodynamic forces for each car have a scattered distribution.There are two pairs of counter-rotating large vortices in the non-streamlined part of the train that make the boundary layer thicker.Many high-intensity vortices are distributed in the narrow space between skirt plates or train floor and track.In the gap between the train floor and track(except near the tail car nose),the main frequency of vortex shedding remains constant and its strength increases exponentially in the streamwise direction.In the wake,the counter-rotating vortices gradually expand and reproduce some small vortices that move downward.The vortex has quite random and complex frequencydomain distribution characteristics in the wake.The maximum time-averaged velocity of the slipstream occurs near the nose of the head car,based on which,the track-side safety domain is divided.

Effect of a transverse plasma jet on a shock wave induced by a ramp

We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2 mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found： the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation（IDDES） method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets.

Performance calculation and improved model research of direct-drive permanent magnet generator based on FEM

In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,are generally neglected.To solve this problem,this paper utilizes the frozen element permeability method to compute the armature self-and mutual-inductance,permanent magnet d-and q-axis flux varying with d-axis and q-axis current,then an improved model is presented in which the core saturation and cross-saturation between d-axis and q-axis are considered effectively.Based on this model,the method for computing the performance of the generators is also proposed.Taking a 1.5-MW DDPMG as an example,the time-stepping finite element method(T-S FEM) is adopted to analyze the performance with no-load and loaded conditions,the results show a good agreement with the ones obtained by the improved model.Compared with the simplified model,it is demonstrated that the presented model has the high efficiency and reliability and can provide a good reference for optimization design of DDPMG and other PM motors.

Unsteady aerodynamic performance of a maglev train:the effect of the ground condition

The effect of ground condition on unsteady aerodynamic performance of a maglev train was numerically investigated with an IDDES(Improved Delayed Detached Eddy Simulation) method. The accuracy of the numerical method has been validated by wind tunnelexperiments. The flow structure, slipstream and aerodynamic force around the train under stationary and moving ground conditionswere compared. Track and ground play a leading role in the influence of wake vortex structure;the flow structure around the trainis more complex under the stationary ground boundary condition. Near the nose point of the head and tail vehicles, the peak valueof the slipstream under the condition of moving ground is slightly higher than that under stationary ground. In the wake area, theeffect of themain vortex structure on both sides of the tail vehicle and the trackmakes the vortex structure in the wake area strongerthan that under moving ground, the slipstream peak is larger and the locus thereof is further forward. In the horizontal direction, thevortex desorption energy near the nose tip of the train is higher on stationary ground, while the vortex desorption energy far fromthe nose tip of the train is higher on moving ground. Compared with the static ground boundary condition, the resistance coefficientof the head and tail of a maglev train increases by 3.45% and 3.31% respectively under the moving ground boundary condition. Thelift coefficient decreases by 157.78% and 5.13%, respectively.