Matching Parameters Research Articles

Hollow Gradient-Structured Iron-Anchored Carbon Nanospheres for Enhanced Electromagnetic Wave Absorption

HighlightsMicrowave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance.Outstanding reflection loss value (−62.7 dB), broadband wave absorption (6.4 dB with only 2.1 mm thickness) in combination with flexible adjustment abilities were acquired, which is superior to other relative graded distribution structures.This strategy initiates a new method for designing and controlling wave absorber with excellent impedance matching property in practical applications.In the present paper, a microwave absorber with nanoscale gradient structure was proposed for enhancing the electromagnetic absorption performance. The inorganic–organic competitive coating strategy was employed, which can effectively adjust the thermodynamic and kinetic reactions of iron ions during the solvothermal process. As a result, Fe nanoparticles can be gradually decreased from the inner side to the surface across the hollow carbon shell. The results reveal that it offers an outstanding reflection loss value in combination with broadband wave absorption and flexible adjustment ability, which is superior to other relative graded distribution structures and satisfied with the requirements of lightweight equipment. In addition, this work elucidates the intrinsic microwave regulation mechanism of the multiscale hybrid electromagnetic wave absorber. The excellent impedance matching and moderate dielectric parameters are exhibited to be the dominative factors for the promotion of microwave absorption performance of the optimized materials. This strategy to prepare gradient-distributed microwave absorbing materials initiates a new way for designing and fabricating wave absorber with excellent impedance matching property in practical applications.

An adaptive interactive multi-model navigation method based on UUV

This paper introduces an adaptive interactive multi-model algorithm for the navigation system of the unmanned underwater vehicle (UUV). The underwater environment is diverse and time-varying. Obtaining high-precision navigation is very important for the safety and effectiveness of autonomous navigation of unmanned underwater vehicles, which makes the reliability of UUV navigation-related sensors particularly demanding. When the underwater environment has absorbing substances or a deep-sea environment, the Doppler velocity log (DVL) will produce outliers or even fail. When the vehicle navigates to a flat terrain area and terrain aided navigation (TAN) performs navigation parameter matching, multiple adaptation positions will appear, resulting in abnormal measurement data. Similarly, when UUV sails to a strong magnetic area, magnetic compass (MCP) will be disturbed, etc. To improve the robustness of navigation and reduce the influence of the change of system model and measurement noise model caused by environmental factors, an adaptive interactive multi-model algorithm is proposed, which is carried out with the UUV based INS/DVL/MCP/TAN integrated navigation system. For the problem that the measurement noise of the system changes, different models are organized into a collection, and according to different situations, the corresponding model or hybrid model is selected in the collection of models to describe the measurement noise, so as to realize the seamless switching of the system model. The simulation results show that the adaptive multi-model algorithm can effectively control the impact of system noise model uncertainty on navigation accuracy, so that UUV has higher accuracy and less computation than single navigation and traditional algorithms, and has robustness and scalability.

Estimation of Harvested RF Energy Based on Survey of Ambient RF Power for Optimized Rectifier Design

This paper presents estimation of harvested RF energy by means of measurement survey and rectifier circuit simulation. The survey was done in an indoor environment in Bangkok, Thailand using a low-cost in-house developed measurement system. From the survey, channel power distribution of a signal with 950 MHz center frequency and 20 MHz bandwidth was created. The maximum time averaged channel power is -7.6 dBm whereas the mean value with maximum signal statistic is -11.1 dBm. A single stage rectifier is simulated with 5 different nominal values of RF input power which is used to optimize the rectifier for maximum RF-to-DC power conversion efficiency. The rectifier composes a Schottky diode, a matching network and a simple load consisting of a resistor and a storage capacitor. Parameters of the simplified LC matching network have been varied to match the rectifier’s input impedance to 50 Ω for various nominal values of the RF input power. In addition, the load resistance was varied according to the nominal RF input power for an optimal power conversion efficiency of the rectifier. The rectifier delivers the highest harvested RF energy with a nominal RF input power of -9 dBm which is a value between the maximum and the mean values from the survey. The DC energy converted from ambient RF energy by the rectifier can be estimated. With this information, it can be assessed what type of applications based on available RF energy can be applied for the test area. This rectifier optimization strategy can be applied to any kind of RF signal since it is based on actual measurement results. Moreover, the proposed rectifier can be designed for reconfigurability regarding nominal RF input power at the location of interest by varying the matching network parameters and the load resistance. In practical applications, the reconfigurable rectifier can maintain a high level of power conversion efficiency over a wide range of RF input power. This can be done by optimizing the rectifier’s input matching network and the load resistance for the highest possible power harvested from the environment where the rectifier is located.

Equivalence condition for the best matching parameters of multiple integral operator with generalized homogeneous kernel and applications

By introducing the matching parameters $a_{1},a_{2},\ldots,a_{n}$ and using the weight function method, the inequality $~\|T(f_{1},f_{2},\ldots,f_{n-1})\|_{q_{n},\alpha_{n}(1-q_{n})}\!\leq\!~M(a_{1},a_{2},\ldots,a_{n})~\prod_{i=1}^{n-1}\|f_{i}\|_{p_{i},\alpha_{i}}$ can be obtained for the operator $T$: <disp-formula><tex-math><![CDATA[$$ T(f_{1},f_{2},\ldots,f_{n-1})(x_{n})=\int_{\mathbb{R}_{+}^{n-1}}K(x_{1},\ldots,x_{n-1},x_{n})\prod_{i=1}^{n-1}f_{i}(x_{i}) {d}x_{1}\cdots{d}x_{n-1}.$$]]></tex-math></disp-formula> If the constant factor $M(a_{1},a_{2},\ldots,a_{n})$ is the operator norm $\|T\|$ of $T:\prod_{i=1}^{n-1}L_{p_{i}}^{\alpha_{i}}(0,+\infty)\rightarrow~L_{q_{n}}^{\alpha_{n}(1-q_{n})}(0,+\infty)$, then $a_{1},a_{2},\ldots,a_{n}$ are called the best matching parameters of the operator $T$. In this paper, for the generalized homogeneous kernel, the necessary and sufficient conditions for the best matching parameters of the operator $T$ are discussed, as the method of determining that the operator $T$ is bounded and the calculation formula for the operator norm of $T$ are obtained. Finally, some special cases are given as applications.

Investigation of the Optoelectronic and Photovoltaic Properties of YxIN1-xP Alloys using First Principles Calculations

Abstract Structural stability, electronic, optical, and photovoltaic properties of pure and doped InP were evaluated by using first principles calculations via the density functional theory (DFT). The exchange-correlation potential is treated with generalized gradient approximation (GGA-PBE). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (TB-mBJ) is employed, because it gives very accurate results of the band gap in solids. Our results reveal that all compounds are energetically and mechanically stable. It is found that for Y concentrations less than 30%, the favored structure is a Zinc blende-like one, while for Y concentrations greater than 30%, the favored structure is a NaCl-like structure. The substitution of In by Y is found to be able to enlarge the direct bandgap of about 34% (from 1.43 eV to 2.17 eV) and confirms the semiconductor behavior for zinc blende stable structures. The absorption coefficient is reasonably exceeding 105 cm −1 for YxIn1-xP alloys in the case (x=0 and x=25%). The reflectivity shows less than 30% around the energy value of 2 eV and an efficiency of solar cell of 18% can be achieved for Y0.25In0.75P. Also, a thickness of L = 1μm is enough to confirm the experimental data. Regarding to the matching of lattice parameters (a mismatch &lt; 4%) of InP and Y0.25In0.75P and the band gap energy difference made Y0.25In0.75P suitable for optoelectronic and photovoltaic devices in particularity as Tandem solar cells (Y0.25In0.75P/InP) and quantum well (Y0.25In0.75P/InP/Y0.25In0.75P) applications. In the absence of experimental works, our results can be useful for further studies.

Grinding marks suppression strategy based on adjusting grinding traces distribution

For the grinding marks phenomenon formed in cross grinding of plane, spherical and aspheric optical elements would reduce the surface quality, surface strength and optical performance of workpiece, which would increase subsequent polishing time and wastage of polishing resources, the suppression strategies of grinding marks based on adjusting grinding traces distribution simulation was investigated. According to the distribution equations of grinding traces and the scallop height, the possibility of two grinding marks suppression strategies was discussed, one of strategy was based on matching grinding parameters and the other one was on grinding traces superposition without depth of cut. Based on the two strategies, the grinding verification experiments were carried out. The results showed that the grinding marks were suppressed by the matching parameters strategy, which cracks and deep grinding traces were less, surface roughness and its homogeneity were better, surface waviness was smaller when ground by matching parameters with the phase shift of 0.618. Besides, when grinding traces superposition strategies were used to process experiments, the morphology and surface roughness did not change much, but all homogeneity of surface roughness were fine with the increasing of superposition times. Moreover, the surface waviness significantly decreased from 90 to 30 nm after 3 superposition times, the grinding marks were also suppressed by the grinding traces superposition without depth of cut. This research would provide references and ideas for grinding aspherical surface with high surface quality and efficiency, and low energy.

Effect of different noise reduction techniques and template matching parameters on markerless tumor tracking using dual-energy imaging.

To evaluate the impact of various noise reduction algorithms and template matching parameters on the accuracy of markerless tumor tracking (MTT) using dual-energy (DE) imaging. A Varian TrueBeam linear accelerator was used to acquire a series of alternating 60 and 120kVp images (over a 180° arc) using fast kV switching, on five early-stage lung cancer patients. Subsequently, DE logarithmic weighted subtraction was performed offline on sequential images to remove bone. Various noise reduction techniques-simple smoothing, anticorrelated noise reduction (ACNR), noise clipping (NC), and NC-ACNR-were applied to the resultant DE images. Separately, tumor templates were generated from the individual planning CT scans, and band-pass parameter settings for template matching were varied. Template tracking was performed for each combination of noise reduction techniques and templates (based on band-pass filter settings). The tracking success rate (TSR), root mean square error (RMSE), and missing frames (percent unable to track) were evaluated against the estimated ground truth, which was obtained using Bayesian inference. DE-ACNR, combined with template band-pass filter settings of σlow =0.4mm and σhigh =1.6mm resulted in the highest TSR (87.5%), RMSE (1.40mm), and a reasonable amount of missing frames (3.1%). In comparison to unprocessed DE images, with optimized band-pass filter settings of σlow =0.6mm and σhigh =1.2mm, the TSR, RMSE, and missing frames were 85.3%, 1.62mm, and 2.7%, respectively. Optimized band-pass filter settings resulted in improved TSR values and a lower missing frame rate for both unprocessed DE and DE-ACNR as compared to the use previously published band-pass parameters based on single energy kV images. Noise reduction strategies combined with the optimal selection of band-pass filter parameters can improve the accuracy and TSR of MTT for lung tumors when using DE imaging.

Research on Parameter Matching of the Asymmetric Pump Potential Energy Recovery System Based on Multi-Core Parallel Optimization Method

Aiming at the parameters of the different displacements and related components of the variable-displacement asymmetric axial piston pump (VAPP) required by the energy-recovery system of excavator booms of different tonnages, a rapid multi-process parallel optimization method of complex hydraulic products based on a multi-core CPU was proposed for parameter matching. The parameter matching was used to reasonably select relevant parameters so that the excavator’s boom energy-recovery and utilization system can improve operational efficiency and energy-saving efficiency under the premise of satisfying the normal working conditions of the working mechanism, and achieving the purpose of serializing VAPP products. A multi-objective optimization model was put forward according to energy-saving efficiency and operational efficiency. First, the accuracy of the acceleration method of the CVODE, a solver for stiff and non-stiff ordinary differential equation (ODE) systems, was verified by a physical prototype test. The results showed that the test and simulation results were in good agreement. A particle swarm optimization algorithm (PSO) was used to optimize the main parameters of the boom energy-recovery system to obtain the appropriate energy-saving efficiency and obtain the VAPP displacement and related component parameters required by the energy-recovery system of excavator booms of different tonnages. The simulation results showed that a motor working condition was necessary in the guaranteed descending stage, and the process of lifting–descending–lifting was completed under the condition that the total time did not exceed a certain value. The energy-saving rates of the 7-ton (7T), 12-ton (12T), 20-ton (20T), and 30-ton (30T) excavator boom energy-recovery systems reached 29.8%, 35.3%, 31.25%, and 27.88%, respectively. In the eight-core CPU workstation under the simulation conditions, compared with the Simulation X platform simulation method, the simulation efficiency of the multi-core CPU parallel method was improved by more than 80 times.

An Effective Force-Temperature-Humidity Coupled Modeling for PEMFC Performance Parameter Matching by Using CFD and FEA Co-Simulation

High-performance proton exchange membrane fuel cell (PEMFC) vehicles are important for realizing carbon neutrality in transportation. However, the optimal power density of the fuel cell performance is difficult to achieve due to the internal complex operating conditions of a fuel cell stack. Moreover, there is a lack of effective models to solve the coupled multi-physical fields (force, temperature and humidity, etc.) in the PEMFC, particularly considering the gas diffusion layer (GDL) compression. Thus, a force-temperature-humidity coupled modeling method is introduced to evaluate the effects of key operating conditions for the fuel cell performance parameter matching. Firstly, the interfacial contact resistance and GDL porosity are obtained by a force-temperature coupled simulation using a finite element analysis (FEA) modeling, then the obtained results are introduced into a temperature-humidity coupled simulation using a computational fluid dynamics (CFD) modeling. An iteration algorithm is proposed to realize the force-temperature-humidity coupled simulation for the PEMFC performance. The main characteristics of the PEMFC performance parameters are revealed and the optimum matching criteria of the main performance parameters (temperature, stoichiometric ratio and relative humidity) are determined. The presented co-simulation method is significant and effective for realizing the PEMFC performance parameter matching condition, and it provides a design direction for an optimal power density of a fuel cell stack.

Research on Intelligent Decision Method of Optimal Production Planning and AGV In-time Delivery in Mixed-Model Assembly Line

An automated guided vehicle (AGV) system is an indispensable part of a mixed-model assembly line (MMAL) for flexible and efficient production, which is utilized for the material delivery. With the urgent needs of industry digitalization and market customization, along with the trend of corporate smart decision management, MMAL has been widely adopted in the manufacturing process of modularized products. To address the parameter matching and energy consumption optimization of the AGV system in MMAL, the overall architecture of an intelligent MMAL (IMMAL) is firstly proposed. And the model of this problem is constructed. Then, the research methodology is proposed, which comprehensively adopts the dispatching rule, genetic algorithm, design of experiment, BP neural network, and simulated annealing. Eventually, a real-life case is used to validate the practicality of the proposed solutions. The results show that the optimal solutions of MMAL production and AGV system delivery at the minimum energy consumption are obtained successfully. Furthermore, three factors: the quantity, capacity, and velocity of AGVs greatly impact the energy consumption of the AGV system, where the quantity of AGVs has the most negligible significance, while the capacity of AGVs has the most significance.

A three-dimensional text image watermarking model based on multilayer overlapping of extracted two-dimensional information

Aiming at the problem that watermark information is easy to be lost in two-dimensional text image watermarking, a three-dimensional text image watermarking model is proposed based on multilayer overlapping of extracted two-dimensional information, and a specific method is accordingly realized by means of embedding, extracting and overlapping of multiple watermarks in sequence. We discuss the influence of the sequence order, positional distancing and color difference of the extracted multiple two-dimensional information on displaying a three-dimensional text watermark image. In addition, considering the crucial evaluation indices of the invisibility and robustness for the watermarking algorithm, the selection method for superior embedding regions of multiple watermarks is also constructed to enhance the robust performance of watermarks under the premise of effective invisibility. Moreover, we embed the multiple two-dimensional information into the host image by using the undecimated dual-tree complex wavelet transforms - bidiagonal singular value decomposition algorithm. In this way, the extracted multiple two-dimensional information is automatically overlapped to generate the three-dimensional text watermarking according to the optimal matching parameters. We use standard image processing data set to carry out experiments, the results show that the peak signal to noise ratio before and after embedded watermarks is higher than 39 dB, and the peak signal to noise ratio between the original watermarks and the extracted watermarks is more than 37 dB, which is superior to the current reported watermark model. Therefore, it is suggested that the proposed model shows good invisibility and robustness and can reduce the loss of watermark during transmission and attack as much as possible.

Mechanism investigation for the influence of laser power on droplet transfer behaviors in laser-MIG hybrid welding

The stability of droplet transfer plays an important role in the weld formation and spatters suppression during the laser-MIG hybrid welding. However, a debate exists on whether increased laser power improves or suppresses the droplet transfer. In this study, the role of laser heat source was investigated in a wide range of laser power. The transfer frequency was firstly improved by increasing laser power, and then it was decreased once the laser power proceeded a critical value. The variation of droplet transfer frequency was determined by the competition between electromagnetic force and metal vapor reaction force. With increasing laser power, the arc conductivity was better and the arc current was improved, leading to increase of the electromagnetic force. As a result, the droplet transfer was promoted and the deposition rate of wire metal was increased. However, rapid increase of metal vapor reaction force was obtained when the laser power exceeded the critical value, producing a greater resistance on droplet transfer. Furthermore, the critical value of laser power was mainly determined by the characteristics of laser source, materials, laser focusing distance and laser-arc distance. This work will provide more guidance on matching processing parameters of the laser-MIG hybrid welding to improve weld formation and suppress spatters by stabilizing the droplet transfer.

Cardiovascular risk following cannabinoid treatment for patients with chronic pain

Abstract Background Treatment with medical cannabis for chronic pain is in popular demand, and a rising number of countries allow physicians to prescribe medical cannabis for pain management. However, data on drug-safety is scarce. Studies have showed a risk of cardiovascular side effects following use of recreational cannabis warranting further investigations into the safety of prescribing medical cannabis. Purpose We investigated risk of new-onset arrhythmias (tachy- or bradyarrhythmia and conduction disorders), acute coronary syndrome (ACS) and heart failure (HF) following use of prescribed medical cannabis compared with no use in a nationwide cohort of patients with chronic pain. Methods Using nationwide Danish registers, a cohort of patients with chronic pain and without prior history of arrhythmias, ACS, HF or prescribed medical cannabis (cannabinoid, cannabidiol or dronabinol) use were followed from 2018–2021. Any patient from the cohort initiating first-time treatment with medical cannabis was identified and matched 1:10 to corresponding controls within the cohort using incidence density sampling. Matching parameters were age group, sex, and chronic pain diagnosis. Follow-up was initiated at the date of the first claimed prescription of medical cannabis or the corresponding date among controls. We reported 180-day standardized absolute risks (AR) with 95% confidence intervals (CI) and risk ratios (RR) from fitted multivariable logistic regression models comparing patients exposed to medical cannabis with patients not exposed. Separate analyses for each chronic pain group were conducted as well. Results Among 1.6 million patients with chronic pain, 4,562 patients claimed at least one prescription of medical cannabis (exposed) and were each matched to 10 controls (non-exposed). Exposed and non-exposed patients were identical in relation to matching parameters; however, exposed patients were slightly more comorbid, and a larger proportion was concomitantly treated with other pain medication (Table). The risk of new-onset arrhythmia was elevated among exposed patients with 180-day AR of 0.71% (95% CI 0.47%–0.94%) compared with 0.43% (95% CI 0.37%–0.49%) yielding a RR of 1.64 (95% CI 1.04–2.23). The risk of new-onset ACS and HF was not increased comparing exposed to non-exposed with corresponding 180-day ARs of 0.13% (95% CI 0.03%-0.23%) vs 0.11% (95% CI 0.08%–0.14% and 0.13% (95% CI 0.03%–0.24%) vs 0.14% (95% CI 0.11%–0.17% (corresponding RRs of 1.2 [95% CI 0.3–2.1] and 0.9 [95% CI 0.2–1.7]) (Figure). Subgroup analyses of each chronic pain group yielded similar results. Conclusion In a nationwide cohort of patients with chronic pain, use of medical cannabis was associated with a 64% risk increase of arrhythmias compared with no use. This poses a potential health concern and is vital knowledge for any physician prescribing medical cannabis. Use of medical cannabis was not associated with an elevated risk of ACS or HF. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Ib Mogens Kristiansens Almene FondHelsefonden

Female patients with coronary artery disease and aortic stenosis undergoing a surgical or interventional treatment in terms of revascularization and valve replacement

Abstract Background Coronary artery disease (CAD) in female patients undergoing a Transcatheter Aortic Valve Implantation (TAVI) is accompanied with a worse outcome compared to those without CAD. Nevertheless, it is still unclear whether a complete revascularization and outcome are achieved similarly in women treated with an interventional (PCI plus TAVI) or surgical (CABG plus SAVR) treatment strategy. Purpose This study aims to compare the completeness of revascularization in terms of residual SyntaxScore and to evaluate the differences in 30-days (short-term), one-year and three-years (intermediate term) mortality in women with CAD and AS undergoing a surgical or catheter-based treatment. Methods Patients were recruited at one tertiary center in Germany between 2016 and 2019. Initially the surgical group contained 932 patients and the interventional cohort 360 patients as a result of setting a maximum time interval of 3 months between PCI and TAVI. The surgical group (CABG+SAVR) and the interventional group (PCI+TAVI) were compared by using a propensity score analysis. Age, left ventricular function, EuroSCORE II and degree of CAD served as matching parameters so that the matched female cohort finally consisted of 114 patients (57 patients treated interventionally, 57 treated surgically). Syntax Score was measured before and after revascularization. As a primary endpoint all-cause mortality was analyzed at 30 days, one and three years after the procedure. Results Median age was 80 years both in the interventional and surgical cohort (p=0.298). Both groups represented a moderate to high-risk population (EuroScore II in PCI+TAVI: 4.39 [2.83–8.82] vs 6.18 [3.43–8.6] in CABG+SAVR (p=0.279) and showed no significant difference in median pre-interventional/preoperative SyntaxScore I (PCI+TAVI: 16.00 [9–26.5] vs CABG+SAVR: 18 [9.5–25.5]; p=0.719). In the interventional group coronary physiology was measured more frequently (6.8% vs 1.8%, p=0.024). There was no significant difference in the presence of an aortoostial lesion, heavy calcification and a length of the lesion &amp;gt;20mm between PCI+TAVI and CABG+SAVR before therapy (PCI+TAVI vs CABG+SAVR: 11.1% vs 13.0%, p=0.581; 60.5% vs 55.1%, p=0.289; 20.4% vs 25.1%, p=0.316). The main stem as target lesion was present in both groups with no significant difference (PCI+TAVI vs CABG+SAVR: 8.8% vs 19.3%, p=0.106). Median residual SyntaxScore I was significantly higher in PCI+TAVI than in CABG+SAVR (5.0 [0.0–13.0] vs 0.0 [0.0–8.5], p=0.03). No significant difference in 30-days, 1-year and 3-years mortality was observed between the interventional and surgical group (PCI+TAVI vs CABG+SAVR: 3.5% vs 8.8%, p=0.242; 10.5% vs 14%, p=0.568; 22.8% vs 15.8%, p=0.342). Conclusion Female patients with AS and CAD with low SyntaxScore undergoing CABG+SAVR reach a more complete revascularization than those treated interventionally. Nevertheless, this fact seems to have no influence on short and intermediate term mortality. Funding Acknowledgement Type of funding sources: None.

Don’t Forget to Water Your Antennas! [Editor’s Comments

Everyone with just a bit of a green thumb will tell you that water can do miracles for a well-maintained lawn. Sometimes, however, water can also do great things for antennas. Please check out the article by Kong et al. focusing on a frequency-selective structure that can be controlled using water channels. The article starts with an introduction that reviews the concept of frequency-selective surfaces. Then it turns to the new design concept, providing both analytic and numerical evidence in support of the new idea. Finally, the contribution is enriched with experimental results confirming the performance of the technology, showing its practical interest. This issue of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IEEE Antennas and Propagation Magazine</i> also features many other interesting articles. Surender et al. presents a nice review of rectennas for applications in wireless technologies. The work starts with a rich bibliographic analysis. It then reviews the primary elements of a rectenna system, examining the main solutions available in literature. Finally, attention is turned to applications, with a detailed list of relevant scenarios analyzed in large detail. The article by Notaros <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ˇ</small> is an excellent review of polarimetric weather radars. The article starts by illustrating the principles of radar polarimetry, then it proceeds with technical analyses of specific devices, and finally the contribution turns to applications, showing the data richness that can be provided by polarimetry and its applicability to weather analysis and forecasts. Finally, the article by Loghmannia and Manteghi presents a broadband strategy for small-antenna matching by an amplifier. After a bibliographic review and a section summarizing the relevant background material, the article reviews the principles of broadband parametric matching and presents an antenna design enriched with validating simulations. Finally, a prototype with experimental validations is presented showing achievable performance of the technology.

Research Progress of High-Speed Wheel–Rail Relationship

The research on wheel–rail relationship includes the basic theoretical models and corresponding numerical methods of wheel–rail in rolling contact, geometric parameter matching and material matching of them, friction and wear, wheel–rail rolling contact fatigue, wheel–rail adhesion and noise. They are also key theoretical and technical problems of the high-speed train/track coupling system. The basic theoretical models of wheel–rail in rolling contact and the corresponding numerical methods are the basis and one of the basic means for solving other wheel–rail relationship problems. The other is the experimental means. Moreover, the modeling and analysis of coupling behavior of the train and track can only be realized by means of the wheel–rail rolling contact mechanics model and its corresponding numerical method. This paper mainly discusses some research work and achievements on high-speed wheel–rail relationship problems since China opened a high-speed railway system on a large scale. The discussions in this paper include the classic wheel–rail rolling contact theoretical models (analytical forms) and the modern wheel–rail rolling contact theories (numerical methods), their advantages and disadvantages, their application and future development direction of them. The reviewed research progress on the other wheel–rail relationships mainly expounds the thorny problems of the wheel–rail relationship encountered in the operation of China’s high-speed railway, how to adopt new theoretical analysis methods, test means and take effective measures to solve these problems. It also includes research results of similar important reference values performed by international peer experts in related fields. Challenging and unsolved problems in high-speed wheel–rail relationship research are also reviewed in the full text.

Parameter Matching, Optimization, and Classification of Hybrid Electric Emergency Rescue Vehicles Based on Support Vector Machines

Based on the requisition for an ideal precise power source for a hybrid electric emergency rescue vehicle (HE-ERV), we present an optimistic parameter matching and optimization schemes for the selection of a HE-ERV. Then, given a set of optimized power source components, they are classified into different types of HE-ERV. In this study, due to the different design objectives of different types of emergency rescue vehicles and the problems of hybrid electric vehicle parameter matching, a multi-island genetic algorithm (MIGA) and non-linear programming quadratic Lagrangian (NLPQL) is proposed for the matched parameters. The vehicle dynamic model is established based on the AVL Cruise simulation platform. The power source performance parameters are matched by theoretical analysis and coupled to the simulation platform. Finally, the optimized matched parameters are classified based on the support vector machines classification model to determine the category of the HE-ERV. The classification results showed that there is an unprecedented level for categorizing several factors of the power source parameters. This research showed that its more logical and reasonable to match HE-ERVs with medium motor/engine power output and battery capacity, as these can attain dynamic performance, extended driving range, and reduced energy consumption.

Powertrain Design and Energy Management Strategy Optimization for a Fuel Cell Electric Intercity Coach in an Extremely Cold Mountain Area

Facing the challenge that the single-motor electric drive powertrain cannot meet the continuous uphill requirements in the cold mountainous area of the 2022 Beijing Winter Olympics, the manuscript adopted a dual-motor coupling technology. Then, according to the operating characteristics and performance indicators of the fuel cell (FC)–traction battery hybrid power system, the structure design and parameter matching of the vehicle power system architecture were carried out to improve the vehicle’s dynamic performance. Furthermore, considering the extremely cold conditions in the Winter Olympics competition area and the poor low-temperature tolerance of core components of fuel cell electric vehicles (FCEV) under extremely cold conditions, such as the reduced capacity and service life of traction batteries caused by the rapid deterioration of charging and discharging characteristics, the manuscript proposed a fuzzy logic control-based energy management strategy (EMS) optimization method for the proton exchange membrane fuel cell (PEMFC), to reduce the power fluctuation, hydrogen consumption and battery charging/discharging times, and at the same time, to ensure the hybrid power system meets the varying demand under different conditions. In addition, the performance of the proposed approach was investigated and validated in an intercity coach in real-world driving conditions. The experimental results show that the proposed powertrain with an optimal control strategy successfully alleviated the fluctuation of vehicle power demand, reduced the battery charging/discharging times of traction battery, and improved the energy efficiency by 20.7%. The research results of this manuscript are of great significance for the future promotion and application of fuel cell electric coaches in all climate environments, especially in an extremely cold mountain area.

Parameter Matching and Structural Optimization Design of H-SFCL in MMC Ship MVDC System

As a high-density and high-load system, ship DC system has the characteristics of short power supply line, low system damping. When a short-circuit fault occurs, it will cause serious damage and the direct current circuit breaker (DCCB) is required to cut off the fault current quickly. In our previous paper, a hybrid-type superconducting fault current limiter (H-SFCL) has been proposed, which can help DCCB reliably remove faults and realize fast reclosing. On this basis, the H-SFCL is selected and applied in ship medium voltage direct current (MVDC) system. In this paper, not only the current limiting principle of H-SFCL is introduced, but also its current limiting characteristics in modular multilevel converter (MMC) ship MVDC system are simulated and analyzed. In addition, the paraments selection and coil structural design of H-SFCL are optimized to improve the economy and ensure the safety and stability of the coil. Firstly, the parameter matching method is proposed based on the optimization algorithm in Matlab, and then the electromagnetic force coupling model in COMSOL is built to complete the structural optimization of the superconducting coil. The effectiveness of the optimization results is verified by stress analysis.

Study on dynamic characteristics of flexible feed system by mechanical parameters

The dynamic characteristics of CNC feed system are determined by the dynamic characteristics of mechanical drive and control parameters. The dynamic characteristics of transmission link are closely related to the mechanical characteristic parameters. The designer must find the matching control parameters by analyzing the law of mechanical characteristic parameters and dynamic characteristics. In this paper, the relationship between inertia ratio, resonant frequency and velocity loop control gain is analyzed by using the established three-inertia system model, and the parameters are input into the system model for simulation. It provides a method for the designers of CNC machine tools to adjust the internal control parameters, which has important theoretical and practical value.