bluuebunny/crossref_metadata_2025 huggingface dataset:
A penalty-free approach to PDE constrained optimization: application to an inverse wave problem
Authors: Hoffmann Alexandre , Monteiller Vadim , Bellis Cédric
Published: February 2021

Inverse wave problems (IWPs) amount in non-linear optimization problems where a certain distance between a state variable and some observations of a wavefield is to be minimized. Additionally, we require the state variable to be the solution of a model equation that involves a set of parameters to be optimized. Typical approaches to solve IWPs includes the adjoint method, which generates a sequence of parameters and strictly enforces the model equation at each iteration, and, the wavefield reconstruction inversion (WRI) method, which jointly generates a sequence of parameters and state variable but does not strictly enforce the model. WRI is considered to be an interesting approach because, by virtue of not enforcing the model at each iteration, it expands the search space, and can thus find solutions that may not be found by a typical adjoint method. However, WRI techniques generally requires the tuning of a penalty parameter until the model equation is considered satisfied. Alternatively, a fixed penalty parameter can be chosen but, in such case, it is impossible for the algorithm to find a solution that satisfies the model equation exactly. In the present work, we present a, to our knowledge, novel technique of WRI type which jointly generates a sequence of parameters and state variable, and which loosely enforces the model. The method is based on a TR-SQP method which aims at minimizing, at each iteration, both the residual relative to the linearized model and a quadratic approximation of the cost functional. Our method approximately solves a sequence of quadratic subproblems by using a Krylov method. The Hessian-vector product is computed using the second-order adjoint method. The method is demonstrated on a synthetic case, with a configuration relevant to medical imaging.
Effective theory for self-interacting dark matter and massive spin-2 mediators
Authors: Kang Yoo-Jin , Lee Hyun Min
Published: February 2021

We consider the effective theory for self-interacting dark matter with arbitrary spin and go beyond the previous discussion in the literature by introducing a massive spin-2 particle as the mediator for dark matter (DM) self-scattering. We present effective self-interactions for DM in the leading order expansions with momentum transfer and DM velocity. We compare the Born cross section and the non-perturbative cross section in the leading-order approximation of the effective Yukawa interaction. As a result, we find that there is a wide range of DM and spin-2 particle masses for velocity-dependent self-scattering to solve small-scale problems in galaxies and to satisfy the bounds from galaxy clusters at the same time.
Automated remote decision-making algorithm as a primary triage system using machine learning techniques
Authors: Kim Dohyun , Chae Jewook , Oh Yunjung , Lee Jongshill , Kim In Young
Published: February 2021

Objective. An objective and convenient primary triage procedure is needed for prioritizing patients who need help in mass casualty incident (MCI) situations, where there is a lack of medical staff and available resources. This study aimed to develop an automated remote decision-making algorithm that remotely categorize a patient’s emergency level using clinical parameters that can be measured with a wearable device. Approach. The algorithm was developed according to the following procedures. First, we used the National Trauma Data Bank data set, a large open trauma patient data set assembled by the American College of Surgeons (ACS). In addition, we performed pre-processing to exclude data when the vital sign or consciousness indicator value was missing or physiologically in an abnormal range. Second, we selected the T-RTS method, which classifies emergency levels into four classes (Delayed, Urgent, Immediate and Dead), as the primary outcome. Third, three machine learning methods widely used in the medical field, logistic regression, random forest, and deep neural network (DNN), were applied to build the algorithm. Finally, each method was evaluated using quantitative performance indicators including the macro-averaged f1 score, macro-averaged mean absolute error (MMAE), and the area under the receiver operating characteristic curve (AUC). Main results. For total sets, the logistic regression had a macro-averaged f1 score of 0.673, an MMAE of 0.387 and an AUC value of 0.844 (95% CI, 0.843–0.845), while the random forest and DNN had macro-averaged f1 scores of 0.783 and 0.784, MMAEs of 0.297 and 0.298 and AUC values of 0.882 (95% CI, 0.881–0.883) and 0.883(95% CI, 0.881–0.884), respectively. Significance. In a comprehensive analysis of these results, our algorithm demonstrated a viable approach that could be practically adopted in an MCI. In addition, it can be employed to transfer patients and to redistribute available resources according to their priorities.
4D flow MRI: impact of region of interest size, angulation and spatial resolution on aortic flow assessment
Authors: Casciaro M E , Pascaner A F , Guilenea F N , Alcibar J , Gencer U , Soulat G , Mousseaux E , Craiem D
Published: February 2021

Objectives. In cardiovascular magnetic resonance, the 3D time-resolved phase-contrast technique, also known as 4D flow, is gaining increasing attention due to applications that exploit three-directional velocity encoding throughout the cardiac cycle. Blood flow volume assessment usually requires an expert to draw regions of interest (ROI) around the vessel cross section, whereas the errors involved in this estimation have not been thoroughly investigated. Our objective is to quantify the influence of ROI sizing, angulation and spatial resolution of the reconstructed plane employed in blood flow measurements using 4D flow. Approach. Three circular ROIs were drawn around the ascending, arch and descending aorta of healthy volunteers (n = 27) and patients with a dilated ascending aorta or bicuspid valve (n = 37). We applied systematic changes of ROI diameter (up to ±10%), tilt angle (up to ±25°) and spatial resolution (from 0.25 to 2 mm) of the reconstructed oblique planes, calculating the effects on net, forward and backward blood flow volumes. Main results. Patients had a larger ascending aorta than healthy volunteers with similar ages and male sex proportion (60 ± 15 y.o. vs 58 ± 16 y.o. and 84% vs 70%, respectively). Higher forward and backward flow volumes were observed in the ascending aorta and the aortic arch of the patients with respect to controls (p < 0.001), whereas net volumes were similar: 74.0 ± 20.8 ml versus 75.7 ± 21.8 ml (p = 0.37), respectively. The ascending aorta was the most sensitive to ROI modifications. Changes of ±10% in the ROI diameter and ±25° in tilt angles produced flow volume differences of up to 9 ml (10%) and 18 ml (15%) in controls and patients, respectively. Modifying the reconstructed planes spatial resolution produced flow volume changes below 2 ml. Significance. Since the setting of the ROI size and plane angle could produce errors that represent up to 20% of the forward and/or backward aortic flow volume, a good standardization for vessel segmentation and plane positioning is desirable.
Structural parameter study of dual transducers-type ultrasonic levitation-based transportation system
Authors: Mu Guanyu , Zhao Jie , Dong Huijuan , Wu Jiang , Grattan Kenneth Thomas Victor , Sun Tong
Published: February 2021

Having a continuous mode of transportation, in the manufacturing and pharmaceutical industries, is desirable and this facilitated by the usage of dual transducer-type ultrasonic levitation-based transportation systems. It is well known that the structural and electrical parameters determine what can be transported continuously, but the relationships between these important parameters are still not clear. In this study, the vibrating plate length and the phase shift between the two transducers were investigated as both of these are key parameters for the transportation system, and affect the standing wave ratios (SWRs), the acoustic radiation forces, and consequently the way the transportation system operates. Through numerical analysis and experimental verification, it can be seen that when the sum or difference of the spatial phase difference (determined by the vibrating plate length) and the phase shift is equal to 180° × (1 + 2n) (where n is an integer), except for the spatial phase difference of 180°·m (where m is also an integer) and the SWRs approaches unity, all this implying that traveling waves (TWs) are dominantly excited on the vibrating plate. As a consequence, the TW-induced acoustic radiation force, which greatly exceeds the standing wave-induced force, causes the continuous transportation of the particle being moved in the sound field. This paper not only clarifies the requirements for generating this continuous transportation, but also provides valuable information on the practical design of such a transportation system.
Proton fraction in neutron star matter: dynamical mean-field approach
Authors: Velikanov Maksim , Rubtsov Alexey N , Krippa Boris
Published: February 2021

Dynamical mean field theory (DMFT) is used to study neutron matter, both with and without admixture of the proton fraction. The system is approximated by the lattice Hubbard model. The corresponding equation of state as a function of temperature/density/asymmetry is investigated. The results are compared with the standard mean field (MF) approach where the effect of local correlations is neglected. Whereas the influence of the correlations on the properties of a pure neutron matter is found to be moderate, it becomes strong when the proton admixture is taken into account. In particular, we calculate the proton fraction, energy density and pressure in outer core of neutron stars, taking into account the beta equilibrium condition. The DMFT predicts that the proton fraction is several times the MF based calculations, whereas the DMFT results for energy density and pressure are 30%–40% lower than the corresponding MF estimates. Physical implications of our findings for a neutron star dynamics are discussed.
Exciton radiative lifetime in a monoatomic carbon chain
Authors: Kutrovskaya Stella , Demirchyan Sevak , Osipov Anton , Baryshev Stepan , Zasedatelev Anton , Lagoudakis Pavlos , Kavokin Alexey
Published: February 2021

Linear carbon-based materials such as polyyne and cumulene oligomers provide a versatile platform for nano-physics and engineering. Direct gap quasi-1D polyyne structures are promising for the observation of strong and unusual excitonic effects arising due to the two-dimensional quantum confinement. Recently, we reported on the observation of sharp exciton peaks in low temperature photoluminescence spectra of polyyne chains (Kutrovskaya S et al 2020 Nano Lett.
20 6502–9). Here, we analyze the time-resolved optical response of this system. We extend the non-local dielectric response theory to predict the exciton radiative lifetime dependence on the band-gap value and on the length of the chain. A good agreement between the experiment and the theory is achieved.
Double-logarithmic nonlinear electrodynamics
Authors: Gullu Ibrahim , Mazharimousavi S Habib
Published: February 2021

A new model of nonlinear electrodynamics is introduced and investigated. The theory carries one dimensionful parameter β as in Born-Infeld electrodynamics. It is shown that the dual symmetry and dilatation (scale) symmetry are broken in the proposed model. The electric field of a point-like charge is derived for this model, showing that it is non-singular at the origin. Using this electric field, the static electric energy of a point-like charge is calculated. In the presence of an external magnetic field, the theory shows a phenomenon known as vacuum birefringence. The refraction index of two polarizations, parallel and perpendicular to the external magnetic induction field, are calculated. The canonical and symmetrical Belinfante energy-momentum tensors are obtained. Using the causality and unitarity principles, the regions where the theory becomes causal and unitary are found.
Modeling and analysis of high shear viscoelastic Ellis thin liquid film phenomena
Authors: Alam M Kamran , Memon K N , Siddiqui A M , Shah S F , Farooq Muhammad , Ayaz Muhammad , Nofal Taher A , Ahmad Hijaz
Published: February 2021

In this paper, the Steady state thin layer flow of a viscoelastic Ellis fluid in contact with a vertical cylinder for drainage and lift problems is examined. Closed form solutions are obtained from the resulting differential equation using the well known binomial series technique. Furthermore, during the analysis of high shear viscoelastic Ellis liquid film, special cases including power law, Bingham plastic and Newtonian fluid film have been retrieved. The Physical quantities such as vorticity vector, thickness about the fluid film, flow rate and average velocity have been investigated for both the lift and drainage physical phenomena. The Thickness of the Ellis fluid film on cylindrical surfaces has been calculated. The velocity profiles for the phenomena are graphically sketched and during the study it is investigated that at the high shear rates the model reduces to the power law model and adequately low shear stress the model reduces to a Newtonian model. From the results it is noticed that, with increase in α and R, velocity increases for drainage case while decreases for lift case. Velocity profile for Newtonian and Bingham plastic fluids is calculated and it is observed that, the drainage velocity profile has increasing effect with the increase of r and has reverse effect for lift case with increasing r. The variation of n for power law model in drainage and lift have been plotted, where it is investigated that velocity of fluid layer grow up.
Photocurrent improvement of an ultra-thin silicon solar cell using cascaded cylindrical shape plasmonic nanoparticles
Authors: Heidarzadeh Hamid , Bahador Hamid
Published: February 2021

The main aim of this research work is to significantly improve the photocurrent of an ultra-thin silicon solar cell. Here, cylindrical shape cascaded plasmonic nanoparticles are used to design an ultra-thin silicon solar cell. The main idea is to manipulate the absorption spectra of a thin absorber by applying four cascaded cylindrical shape nanoparticles from different materials with different radii and heights. At first, a cell with one nanoparticle at the surface and another one with a nanoparticle at the bottom side are simulated, and their photocurrents are determined. Then, a cell with four cascaded Ag, Al, Ag-Al, and Al-Ag nanoparticles is simulated. The maximum photocurrent density and efficiency of 23.46 mA cm−2 and 13.95%, respectively, are obtained for a cell in which Ag and Al’s nanoparticles are used alternatively from top to bottom. The photocurrent density is 8.2 mA cm−2 for a cell without any nanoparticles. The simulated results show that cascaded nanoparticles significantly enhance the photocurrent. Finally, the generation rate is presented at different wavelengths.
Decay of negativity of randomized multiqubit mixed states
Authors: Mansour M , Oulouda Y , Sbiri A , El Falaki M
Published: February 2021

In this paper, we investigate the decay of entanglement of multiqubit randomized entangled states. We start by introducing separable states of collection of n independent qubits. The randomized entangled mixed states are generated from factorisable initial states by coupling the qubits through randomized entangling operators. The bipartite and multipartite entanglement of randomized states are analyzed by employing respectively the concepts of the negativity and the genuine multiparticle negativity as measures of amount of entanglement. The decreases of the amount of entanglement of randomized entangled mixed states is studied in terms of the noisy parameter p.
Industrial 6 kW high-stability single-stage all-fiber laser oscillator based on conventional large mode area ytterbium-doped fiber
Authors: Ye Yun , Yang Baolai , Wang Peng , Zeng Lingfa , Xi Xiaoming , Shi Chen , Zhang Hanwei , Wang Xiaolin , Zhou Pu , Xu Xiaojun
Published: February 2021

We have demonstrated an industrial 6 kW single-stage end-pumped all-fiber laser oscillator based on a conventional large mode area ytterbium-doped fiber (YDF) with 30 μm core diameter and 600 μm inner-cladding diameter. As a result, the fiber oscillator achieved a maximum output power of 6.07 kW at a central wavelength of ∼1080 nm with a slope efficiency of ∼65.8%. The power of Raman Stoke light was 21.6 dB smaller than the signal light at the output power of 6.07 kW. For industrial application, the stimulated Raman scattering effect was further suppressed by employing a 50 μm-core delivery fiber, and no sign of dynamic transverse mode instability comes into view during the whole experiment. The power stability measurement at ∼6 kW operation was carried out for continuous 2 h, and the power fluctuation was within 0.31%. To the best of our knowledge, this is the first detailed demonstration of industrial 6 kW high-stability single-stage all-fiber laser oscillator based on conventional YDF. The results provide a significant guidance for the construction of more than 6 kW output power single-stage end-pumped all-fiber laser systems.
The advanced tokamak path to a compact net electric fusion pilot plant
Authors: Buttery R.J. , Park J.M. , McClenaghan J.T. , Weisberg D. , Canik J. , Ferron J. , Garofalo A. , Holcomb C.T. , Leuer J. , Snyder P.B.
Published: February 2021

Physics-based simulations project a compact net electric fusion pilot plant with a nuclear testing mission is possible at modest scale based on the advanced tokamak concept, and identify key parameters for its optimization. These utilize a new integrated 1.5D core-edge approach for whole device modeling to predict performance by self-consistently applying transport, pedestal and current drive models to converge fully non-inductive stationary solutions, predicting profiles and energy confinement for a given density. This physics-based approach leads to new insights and understanding of reactor optimization. In particular, the levering role of high plasma density is identified, which raises fusion performance and self-driven ‘bootstrap currents’, to reduce current drive demands and enable high pressure with net electricity at a compact scale. Solutions at 6–7 T, ∼4 m radius and 200 MW net electricity are identified with margins and trade-offs possible between parameters. Current drive comes from neutral beam and ultra-high harmonic (helicon) fast wave, though other advanced approaches are not ruled out. The resulting low recirculating power in a double null configuration leads to a divertor heat flux challenge that is comparable to ITER, though reactor solutions may require more dissipation. Strong H-mode access (x2 margin over L–H transition scalings) and ITER-like heat fluxes are maintained with ∼20%–60% core radiation, though effects on confinement need further analysis. Neutron wall loadings appear tolerable. The approach would benefit from high temperature superconductors, as higher fields would increase performance margins while potential for demountability may facilitate nuclear testing. However, solutions are possible with conventional superconductors. An advanced load sharing and reactive bucking approach in the device centerpost region provides improved mechanical stress handling. The prospect of an affordable test device which could close the loop on net-electric production and conduct essential nuclear materials and breeding research is compelling, motivating research to validate the techniques and models employed here.
Cramér moderate deviations for the elephant random walk
Authors: Fan Xiequan , Hu Haijuan , Ma Xiaohui
Published: February 2021

We establish some limit theorems for the elephant random walk (ERW), including Berry–Esseen’s bounds, Cramér moderate deviations and local limit theorems. These limit theorems can be regarded as refinements of the central limit theorem for the ERW. Moreover, by these limit theorems, we conclude that the convergence rate of normal approximations and the domain of attraction of normal distribution mainly depend on a memory parameter p which lies between 0 and 3/4.
Research on Improvement of Temperature Rise of New Energy Vehicle Generator
Authors: Bing Xu
Published: February 2021

New energy vehicles have gradually become one of the key parts in the development of the automotive field under the background of the new era. It is also to comply with the requirements for environmental protection. Therefore, this article analyzes the reasons for the excessive temperature of the generators of new energy vehicles, and proposes targeted improvement strategies in combination with the actual situation. While ensuring that the output torque of the new energy vehicle generator itself can be effectively increased, it can ensure that the basic requirements of the new energy vehicle to the greatest extent.
Improved droop control of DC microgrid based on virtual impedance
Authors: Yuan Yizhe , Deng Yanni
Published: February 2021

In order to solve the problem of distributed energy generation, microgrid has been proposed as one of the options. Compared with AC microgrid, DC microgrid is more suitable for many current distributed power equipments. In order to ensure the stable operation of the DC microgrid, it is necessary to develop an effective energy management strategy. As a typical method of current distribution, droop control has been widely studied and discussed. Traditional droop control has inherent limitations, so this paper proposes an improved method for droop control.
Research of pulsed Xenon lamp power supply based on STM32
Authors: Liu Danni , Ma Mengfei , Zhang Yanjin
Published: February 2021

Novel coronavirus pneumonia affects the health of people all over the world. In this study, UV pulse high-light sterilization technology was used to combat coronavirus. The light source of the ultraviolet pulsed high-light disinfection robot is a kind of high-brightness flash light source using pulsed xenon lamps as the output load. This paper developed a pulsed xenon lamp power supply with a high-voltage pulse synchronous trigger function, a DC charging voltage of 1kV-3kV, an output pulse current range of 1kA-3kA, and a pulse width of 50μS for a pulsed xenon lamp with a 196mm×Φ10mm and a resistivity of 12Ω⋅A1/2. This paper presented the experimental results of charging voltage of 1kV, output pulse current peak value of 1kA, and pulse width of 50μS. The power supply design was based on the phase-shifting voltage regulation mode of UC3825 control power MOS tube, through the sampling isolation module and the closed-loop feedback formed by STM32 control, the energy storage capacitor was linearly charged through the DC voltage sampling and voltage regulation control module; the trigger pulse signal was generated by the SCR switch, and the xenon lamp was turned on and emits flash light after the pulse transformer was boosted. The sample test results verified the feasibility of the power supply design principles and technical solutions.
Design of DC Regulated Power Supply Based on Buck Circuit
Authors: Shuang Wang Xiao , Jing Zhao , Wei Li Hong , Hai Liu Yi
Published: February 2021

DC stabilized power supplies are widely used in automotive, aviation and DC speed control fields. This article introduces the method of applying buck circuit design to realize 5V switching DC power supply. The designed switching power supply has the advantages of small ripple, continuously adjustable, good stability, etc, and can be used in low-voltage and highpower power supply situations.
Research on damping addition and vibration reduction technology of frame aerospace electronic chassis
Authors: yu Zhang , bolin Zhang
Published: February 2021

This paper poses a box instrumentation in aerospace electronic chassis TO-5 encapsulation relay under the action of impact environmental load state of reverse fault mode, by reasonable single frames of viscoelastic damping materials added, increasing box style structure between the PCB mechanical installation interface damping ratio and frequency ratio, finally realizes the transfer rate is reduced, achieve instrumentation relay PCB, lower impact acceleration response. By adding damping cushion to the frame machine installation interface, the load transfer path of impact mechanics is optimized to reduce the installation stiffness and change the fundamental frequency characteristics of the whole machine.
Analysis and Simulation Research on Radial Electromagnetic Force Wave of Permanent Magnet Synchronous Motor
Authors: Sun Zhen , Xu Yufa , Zhao Xinliang
Published: February 2021

Aiming at the problems of vibration and noise of permanent magnet synchronous motors, based on the principle of radial air gap magnetic density generation, a model of radial electromagnetic force waves is constructed, and the radial air gap magnetic density and diameter of permanent magnet synchronous motors are derived by analytical analysis Analytical expression of the electromagnetic wave, to obtain the main order, frequency and amplitude of the radial electromagnetic wave. Using Maxwell 2D simulation software to establish a simulation model, verify it, prove the correctness of the proposed method, and provide a theoretical basis for further research on the vibration and noise of permanent magnet synchronous motors.
Design and Realization of Intelligent Vehicle Based on Embedded System
Authors: Guanghong Song , Tai hu Zuo , Li li Zhao
Published: February 2021

The paper takes the STM32F103ZET6 development board as the core to design a smart car with a PC-side real-time monitoring system and infrared wireless remote control. It is equipped with a small OLED display to monitor the running state of the necessary services in the car and the system network in real time through Wi-Fi monitoring video transmission and display, using infrared receiver and remote control to achieve NEC protocol communication, and control the wireless movement and the steering of a two-degree-of-freedom camera.
EMC hardware design of intelligent watt-hour meter
Authors: Liu Xingzhi , Zheng Ke , Lv Fengbao , Wei Changming , Tian Juan
Published: February 2021

Electromagnetic compatibility (EMC) is very important for intelligent instruments, and it is an important guarantee for its reliable operation. The complexity of EMC is mainly reflected in how to quickly and accurately locate the disturbance source, effectively suppress the disturbance source, and correctly judge the disturbance coupling path. Intelligent instruments have similar hardware characteristics. In this paper, the characteristics of common hardware characteristics of disturbance source and coupling path are analyzed, the equivalent antenna model of disturbance is analyzed, and the disturbance suppression method is given. Finally, the correctness of the method is verified by experiments.
Research on Test Method of Radio Frequency Radiation Antiinterference of Road Vehicles
Authors: Cao Changping , Tao Hu , Chuan Yang , Pan Yuehong , Yuan Shengjun
Published: February 2021

Based on the comparison and analysis of ISO11452-2 (2004 and 2019), the differences in the testing of radiation immunity Absorber-lined shielded enclosure method are sorted out, and the testing requirements of the newly added High voltage electronic parts components are interpreted.
MOSFETS Power Consumption and Power Dissipation Calculation
Authors: Wang Junkai
Published: February 2021

Metal oxide semiconductor field effect transistors are usually called MOSFET. Nowadays, MOSFET is one of the most crucial electrical components that engineers usually use when constructing laptops and desktop computers. A large number of MOSFETS are usually integrated together to form control and logic functions of computers CPU. Thus, it is essential for electrical engineers to know what type of MOSFETS is appropriate for them to use when designing the integrated circuits. Engineers can seek the answer through calculating two of the most basic and important components of MOSFET power consumption and power dissipation. This article walks through the steps of calculating the power consumption and power dissipation of MOSFETS to provide electrical engineers, students and circuit designers with a clear thought of how to do the calculation under some complex circumstances. MOSFETS power consumption calculation is different under 3 different modes which are cutoff mode, saturation mode and triode mode. Under cutoff mode, the power consumption is zero. Under saturation mode, power consumption is calculated by MOSFETS consume certain amount of power and the total amount of power can be calculated by finding integral of the IV curve. For triode mode, power consumption can be determined by the equation derived later in the article. As for power dissipation, in this article, total power dissipation is divided into two parts which are switching power dissipation and resistive power dissipation. Then, each part of power dissipation is calculated by equations listed in the article and then added together which is the total power dissipation of MOSFETS.
3D reconstruction method of inner surface of pipeline
Authors: Chen Xu , Zhang Yan , Zhao Kang , Guo Jinyu , Luo Ruiliang
Published: February 2021

With the rapid development of China, there is a huge demand for PE pipelines. At present, the detection methods in pipeline production are mainly manual sampling testing and ultrasonic testing, which cannot display the internal surface characteristics of the pipeline comprehensively and visually, so as to facilitate the subsequent non-destructive testing. To solve this problem, this paper proposes a method to capture the three-dimensional feature data in the pipe with a depth camera, and transmit the collected point cloud data into PC for processing, identification and reconstruction, so as to realize the non-destructive testing of the inner surface of PE pipe.
Analysis of small signal model of DC/DC converter without source and load effects
Authors: Zhang Wenjie
Published: February 2021

The small signal model of DC/DC converter without source and load effects is established and analyzed in detail. Characteristics of input and output impedance of converter in frequency domain in the model are applicable to the stability analysis and design in DC multi-converter power system. Investigation shows that the resonant characteristics of input and output impedance under closed-loop control are closely related to the crossover frequency and phase margin of control loop. The input impedance resonant valley and output impedance resonant peak locate at the same frequency as the loop crossover frequency. Furthermore, when the phase margin decreases, the resonance valley of the input impedance becomes lower and the resonance peak of the output impedance becomes higher. Finally, the accuracy of the model is verified by MATLAB Simulink time domain simulation.
A Method to Reduce Torque Ripple of Brushless DC Motor
Authors: Liu Sihao , Yao Xiaodong , Shen Yali
Published: February 2021

In order to improve the accuracy of the commutation of the brushless DC motor rotor, considering that the traditional modulation method will be affected by the conduction voltage drop of the switch tube and the freewheeling diode, resulting in the non-conduction phase freewheeling during the non-commutation period Torque ripple, which is also the main cause of torque ripple. Therefore, it is a positionless control method that controls the non-conducting phase torque ripple PWM_ON_PWM modulation. However, due to PWM modulation, off-phase freewheeling will inevitably occur. For this, the resonant DC link soft-switching inverter topology is used to suppress the off-phase freewheeling. Through experiments and simulations, it is proved that these combined methods can effectively reduce the size of torque ripple.
Multi-target charging strategy for smartphones based on laser wireless power transmission and machine vision technology
Authors: Yu Huiling , jin Ke
Published: February 2021

A novel method of multi-target charging is proposed in this paper, in the context of charging multiple indoor mobile phones simultaneously. Based on the laser wireless power transmission system, combined with machine vision technology, the traditional two-stage circuit is turned into a single-stage type, which realizes longer distance and more convenient charging. This article analyzes the working mode and circuit topology of the dc-dc converter in the multi-target charging mode, and analyzes the positioning and charging strategies for multi-targets based on machine vision. Under the strategy, the output voltage of the photovoltaic panel can be adjusted by modulating the pulsed light, so as to achieve the maximum power control for mobile phone charging. The simulation results are provided in this paper to validate the effectiveness of the proposed approach.
Research on Robotic Arm Movement Grasping System Based on MYO
Authors: Wei Ye , Jia Danping
Published: February 2021

This paper studies the continuous motion capture system of a robotic arm based on MYO. The MYO sensor can collect the electromyographic signal (sEMG) and the motion signal (IMU) of the arm during exercise, and filter the electromyographic signal, extract the features, and return the features. After the first transformation, the machine learning algorithm is used for model training. In order to verify the effect of the recognition of the EMG signal on the deep learning method, the accuracy comparison experiment with the BP neural network is also added. In addition, a two-link arm model was built, and the pose information of the end of the arm was obtained through Euler angle transformation, and then the end pose information of the robotic arm was obtained through coordinate mapping, and the end pose simulation was performed using Matlab software. The simulation results prove that the performance of the system meets expectations, and points out the direction for subsequent research.
Research on Intelligent Technology of CNC Machine Tool Industrial Design
Authors: Guiming Qian
Published: February 2021

The level of economic development of a country can be demonstrated by the development of the machinery manufacturing industry. At present, the industrial design of CNC machine tool in China is progressing in the direction of intelligence, providing more efficient processing technology to meet the needs of the times and social development. However, there are still many challenges, which are the key research of the current intelligent industrial design technology. The article will analyze the significance of industrial design intelligence technology to CNC machine tool, analyze the current research status and propose the application strategies.
Research on Natural Scene Text Detection and Recognition
Authors: Wang Jieming , Wu Wei
Published: February 2021

In recent years, as the importance of scene text detection and recognition in real life has gradually become prominent, its research methods have become mature, and more attention has been placed on improving accuracy. Due to the complex background in natural scenes, different font arrangements, lighting, etc., various methods are difficult to meet the requirements of the application. In this paper, the detection and recognition of curved text are studied, and the research method based on the ESIR framework[1] is improved, specifically in the following two aspects: (1) TPS transform fiducial points are predicted by the positioning network, and the positioning network uses CNN to return to the required fiducial points[2] The x and y coordinates. (2) Using ACE (aggregated cross entropy) method for sequence recognition, its loss function is realized faster and it occupies less memory than CTC and attention mechanism, and it performs well in the one-dimensional prediction of scene text recognition. In this paper, the irregular data set is sampled by reference points, and the parameter matrix T of TPS is calculated to transform the points in the picture, and cyclically transform until the image text is level, and then use the CNN-BLSTM model to perform one-dimensional prediction and output the recognition results. The selected data set is irregular text data set: for example, SVT-Perspective, CUTE80.
Global maximum power tracking algorithm for solar photovoltaic array under uneven illumination
Authors: Guo Jianlong
Published: February 2021

Based on the analysis of the shortcomings of the existing maximum power point tracking (MPPT) method, a multi-peak MPPT tracking strategy is proposed based on the geometric characteristics of the output curve of photovoltaic array. This method takes advantage of the fact that the pv array U-I output curve has the characteristics of "the left slope changes slowly and the right slope changes quickly" at the local extrema point, quickly locates the voltage interval including the global maximum power point, and converts it into a perturbation observation method (perturb and observe, P&O) with higher tracking accuracy within this interval. Thus, the global maximum power point can be tracked. By comparing this algorithm with improved disturbance observation (Perturb, observe and check, POC), its application range was determined and applied flexibly. The algorithm is fast and can avoid missing peak value effectively.
Summary of Recommendation Algorithm Research
Authors: Yan Jie , Zeng QingTao , Zhang FuQian
Published: February 2021

In order to solve the problem of information overload caused by the rapid expansion of information, it is particularly difficult for users to select the information they are interested in when faced with massive amounts of information. Traditional search has some drawbacks and cannot solve the problem of information overload. The recommendation algorithm provided by the recommendation system is a good strategy to deal with. This article mainly introduces two recommendation algorithms and their principles, content-based recommendation algorithms and collaborative filtering-based recommendation algorithms. And their advantages and disadvantages are compared.
Study of Solar Radiation Effect on Radio Signal Using Plasma Antenna
Authors: Dagang A N , Azmi F S , Umar R
Published: February 2021

Plasma antenna can be formed by energizing glass tubes which are filled with neutral gases. It works similarly as metal antenna where it can transmit and receive wireless signal. This study aims to investigate the effect of weather focused on solar radiation towards the performance of plasma antenna represented by signal strength. Fluorescent lamp was set as plasma because it used ionized gas as its conducting element instead of metal. Execution of electrical properties measurements need to be done first, in order to obtain discharge current and voltage values, that need to be used into Glomac programming for the generation of electron temperature and electron density. Next, calculations of the plasma properties was performed to derive the value of plasma and collision frequencies. The plasma properties are important parameters to design and simulate plasma antenna using Computer Simulation Technology (CST). Antenna parameters in terms of return loss, gain, directivity and radiation pattern can be simulated using CST. Signal strength experiment was conducted to evaluate plasma antenna performance in terms of its capability to capture the signals and analyse the effect of solar radiation on that particular moment through the rate of power level over time versus solar radiation data. It was observed at the highest solar radiation rate which is 920 V/m, the power level recorded is the lowest value at-172.93 dBm. Therefore, the signal strength received by the plasma antenna shows remarkable changes under the influence of solar radiation.
The Implementation of Log Periodic Dipole Antenna (LPDA) and CALLISTO system on Solar Radio Bursts Observation
Authors: Mohamad Ansor N , Hamidi Z S , Shariff N N M
Published: February 2021

Solar activity is very important to be observed in order to study its effects to Earth’s climate and space weather generally. In order to understand the behavior of the Sun and its activity, developing ground-based instruments is one of the ways to record the occurrence of the activity other than satellites data. We present in this paper our work on the implementation of Log Periodic Dipole Antenna (LPDA). The LPDA has been successfully set up at UiTM Shah Alam, Malaysia in 2016 with high performance with 8.4-meter height and it has achieved gain as high as 7.28 dB. It mainly records solar radio bursts during the occurrence of solar activity and has been operating at frequency range of 45-870 Hz. This project is done under International Space Weather Initiative (ISWI) by using CALLISTO spectrometer at the same frequency range to monitor solar observations in supporting developing countries with latest technologies of instrument. Beneficially in Malaysia, our station contributes half of the data on e-CALLISTO website due to 12 hours Sun exposure compared to other stations in different countries. All types of solar bursts obtained by e-CALISTO are presented in this paper.
A Design of “Postsecondary Options” Android Application for Junior High school Student
Authors: Putra Bhakti Caraka , Ummi Noviriska Hasan Sitti , Wulidatin Noor Khilda , Aminur Rahman Fuad , Alfarizqi Nizamuddin Ghiffari Muhammad
Published: February 2021

The purpose of this study is to develop a postsecondary option-based android application that is used by junior secondary students in determining plans for further study. Planning further studies from junior to senior high school and beyond, certainly requires a consideration. All preparations both externally (school, facilities, environment) and internally (academic ability, understanding of learning), and all of that include in postsecondary options. Postsecondary options are awareness the opportunity to obtain a career and develop experts using various abilities such as grouping careers, the ability to assess themselves, and many more. Optimizing postsecondary options can be applied in technology. The research method used is research and development, which develops Android applications based on postsecondary options in helping student’s postsecondary option. In this application, it contains information about the requirements, curriculum, job opportunities in a number of options for further study of students after junior high school and beyond.
Particle Swarm Optimization based modelling of a surface ship using free running experimental approach
Authors: Wang Y , Chai S , Nguyen H D , Liu J , Ma F
Published: February 2021

System modelling of the surface ship, which could be regarded as a multi-variable parameter estimation problem, has attracted tremendous interests from researchers since it is of key importance to development of ships’ control system. The aim of this study is to utilize the Particle Swarm Optimization (PSO) algorithm to get the optimized solution of hydrodynamic coefficients in the presence of ship’s mathematical model using the space search principle. The motion equations of the ship in four degrees of freedom are formulated to clarify the scheme of the model. After expressing the theory of the PSO method, the system identification of the ship’s motions is conducted to estimate the hydrodynamic coefficients. By using the identified parameters, the mathematical motion model of the free-running ship, namely ‘P and O Nedlloyd Hoorn’, is developed. The comparison between the experiment measurements and simulation trails and attitudes have indicated that the developed mathematical is sufficient and effective to response the ship’s motions. Therefore, it is demonstrated that the PSO based system identification algorithm is capable of conducting system identification and system modelling for the surface ship through free running approach.
Projected changes in wind power potential over China and India in high resolution climate models
Authors: Sherman Peter , Song Shaojie , Chen Xinyu , McElroy Michael
Published: February 2021

As more countries commit to emissions reductions by midcentury to curb anthropogenic climate change, decarbonization of the electricity sector becomes a first-order task in reaching this goal. Renewables, particularly wind and solar power, will be predominant components of this transition. How availability of the wind and solar resource will change in the future in response to regional climate changes is an important and underdiscussed topic of the decarbonization process. Here, we study changes in potential for wind power in China and India, evaluating prospectively until the year 2060. To do this, we study a downscaled, high-resolution multimodel ensemble of CMIP5 models under high and low emissions scenarios. While there is some intermodel variability, we find that spatial changes are generally consistent across models, with decreases of up to 965 (a 1% change) and 186 TWh (a 2% change) in annual electricity generation potential for China and India, respectively. Compensating for the declining resource are weakened seasonal and diurnal variabilities, allowing for easier large-scale wind power integration. We conclude that while the ensemble indicates available wind resource over China and India will decline slightly in the future, there remains enormous potential for significant wind power expansion, which must play a major role in carbon neutral aspirations.
Topography not tenure controls extent of wildfire within Mountain Ash forests
Authors: Adams Mark A , Bell Tina L , Gharun Mana
Published: February 2021

Two high intensity wildfire events, 70 years apart, burnt large areas of Mountain Ash forests in the Central Highlands, Victoria, Australia. Both resulted in Royal Commissions (the strongest form of judicial inquiry in Australia) as to their cause(s) owing to large losses of life and property. Here we tested the hypothesis that site ‘wetness’—determined using a Topographic Wetness Index—is a major determinant of the extent of fire (% of sample points that burnt) within high intensity wildfire events and across tenures. We show that wetness dominated the extent of fire in these forests in both the 1939 and 2009 wildfire events. Mountain Ash forests are now strongly skewed in their distribution, with wetter and older forests favored by protected tenures (e.g. National Parks) designed to meet needs for water and conservation. In 2009, the extent of fire at the stand scale in water catchments and conservation tenures was twice that in 1939. In land tenures with multiple uses (e.g. State Forests), the extent of fire was one-third less in 2009 than it was in 1939. Topographic controls on water availability, and major droughts, will likely continue to dominate the extent and likelihood of fire in these forests.
Lorentz- and permutation-invariants of particles
Authors: Gripaios Ben , Haddadin Ward , Lester Christopher G
Published: February 2021

Two theorems of Weyl tell us that the algebra of Lorentz- (and parity-) invariant polynomials in the momenta of n particles are generated by the dot products and that the redundancies which arise when n exceeds the spacetime dimension d are generated by the (d + 1)-minors of the n × n matrix of dot products. We extend the first theorem to include the action of an arbitrary permutation group P ⊂ S

n
on the particles, to take account of the quantum-field-theoretic fact that particles can be indistinguishable. Doing so provides a convenient set of variables for describing scattering processes involving identical particles, such as pp → jjj, for which we provide an explicit minimal set of Lorentz- and permutation-invariant generators. Additionally, we use the Cohen–Macaulay structure of the Lorentz-invariant algebra to provide a more direct characterisation in terms of a Hironaka decomposition. Among the benefits of this approach is that it can be generalized straightforwardly to when parity is not a symmetry and to cases where a permutation group acts on the particles. In the first non-trivial case, n = d + 1, we give a homogeneous system of parameters that is valid for the action of an arbitrary permutation symmetry and make a conjecture for the full Hironaka decomposition in the case without permutation symmetry. An appendix gives formulæ for the computation of the relevant Hilbert series for d ⩽ 4.