Parameter Design Research Articles

Engineering of N doped carbon@FeCo alloy hollow spheres: Remarkable mid-frequency electromagnetic wave absorption performance exhibited by unique porous and wrinkled surface structure

The modulation of the shape and design of microstructures plays a crucial role in enhancing the efficient absorption of electromagnetic waves in absorbers. The electromagnetic parameters and scattering effects of these materials are directly influenced by their morphological characteristics. In this study, polystyrene microspheres were used as templates for a two-step in-situ growth process: Initially, Fe₃O₄ was coated onto the surfaces of these microspheres, followed by the in-situ growth of Fe-Co Prussian blue analogs. The rational design of electrical parameters during the conversion process was calculated and analyzed using Density Functional Theory. The precursor was calcined at various temperatures to generate a unique porous wrinkled surface hollow nanostructure. This nanostructure not only facilitates multiple reflections and scattering of incident electromagnetic waves but also promotes the occurrence of multiple interface polarizations. Doping with nitrogen and oxygen elements introduced abundant dipole polarization, thereby enhancing the electromagnetic wave attenuation capability of the composite material. The Fe3O4@PBA composite material synthesized at 600°C achieved a minimum reflection loss of −57.01 dB and a maximum effective absorption bandwidth of 4.58 GHz (7.52–12.1 GHz) at a thickness of 4 mm, covering nearly the entire X-band. This method provides a means to enhance magnetic loss by temperature adjustment to control the magnetic components in composite materials, providing a systematic approach to designing the microstructure of materials used for absorbing electromagnetic waves.

DEVELOPMENT OF DUAL-SWITCHES BRIDGELESS PFC TOTEM-POLE SEPIC CONVERTER FOR LED DRIVER APPLICATION

This paper presents a Dual-Switch Bridgeless Power Factor Correction (DSBPFC) Single Ended Primary Inductor Converter (SEPIC) with Totem-Pole circuit structure for LED Driver Application. The conventional Full-Bridge Rectifier (FBR) SEPIC converter has five diodes, four in the rectifier bridge and one in the SEPIC. In addition, the FBR SEPIC converter has several drawbacks, including low power factor (PF), high current harmonics (THDi), and high output voltage ripple, due to the combination of two operation circuits in a single converter structure. The proposed DSBPFC SEPIC converter with Totem-Pole method improves PF and reduces THDi and output voltage ripple compared to the conventional FBR SEPIC. Additionally, it only requires three diodes instead of five. The optimization parameter design minimizes the THDi and output voltage ripple. In addition, to improve the quality of the AC source, the inductors are designed to operate in DCM and CCM based on the ripple-balancing concept between input and output inductors. As to reduce output voltage ripple, a high capacitance of output capacitor is used. The simulation result of the THDi is 3.8% whereas the experimental result shows that the THDi is 23.5%; which can be attributed to the parasitic elements at the passive components. Furthermore, the experimental results of the output voltage ripple are 2 V with output capacitance of 3300 μF, compared to the output voltage ripple of 4.40 V for 470 μF. Therefore, the proposed converter's design is confirmed with an output power of approximately 14.4 W.

Automatic optimization design of laser triangulation ranging sensors using an improved genetic algorithm

Optical system parameter design is of great importance to ensure the accuracy of asymmetry systems such as laser triangulation ranging systems. However, the system parameter determination often depends on the experience and manual attempts of designers, which is not only time-consuming but also inevitable to introduce human errors. Therefore, in this paper an automatic optimization design method based on nonlinear programming genetic algorithm with elitism strategy (E-NPGA) is proposed, to accurately and fast determine the optimal system parameters of laser triangulation ranging systems assisting in improving the measurement accuracy. Firstly, an optimization model of system parameters is developed under the Scheimpflug rule establishing the constraints for various measurement resolutions and ranges. An image size constraint is constructed for the first time to improve and evaluate the parameter optimization. Secondly, the E-NPGA is proposed with nonlinear optimization and elitism strategy, which can determine the optimal system parameters in 15 iterations avoiding local extremum. In design examples, using the E-NPGA determined system parameters ZEMAX simulation and experimental results of the parameters depended image spot size show a slight relative difference below 0.6%. Moreover, the experiment results demonstrate the sensor system designed by using the E-NPGA enables a distance measurement with submicron absolute error and 10−4 relative uncertainty. The automatic optimization method proposed in this paper is compared with the conventional GA method and PSO method, and it is validated that the convergence accuracy of the proposed method is much higher than the conventional ones.

Switch Capacitor–Based High Step‐Up Three‐Port DC–DC Converter for Fuel Cell/Battery Integration

ABSTRACTAddressing issues of low input voltage in new energy generation systems such as fuel cells, a high step‐up three‐port DC–DC converter for fuel cell/battery hybrid power supply system is proposed. The proposed converter is evolved from Boost three‐port converter, and switch capacitor structure and diode capacitor voltage doubling unit are employed to achieve high voltage gain and low voltage stress. The three ports are connected to fuel cell, battery and load respectively, among which the flow of energy is realized. The steady state performance of this converter in various operating states and design of parameter are presented. Primary competitive advantages compared to similar converters include high voltage gain, continuous input current and its feature of common ground. Moreover, control strategy and compensators under three operating modes are designed to achieve stable output voltage and battery protection. Finally, a 100 W experimental prototype with 15 V input voltage and 24 V battery voltage is established to verify the stable and dynamic performance of the proposed converter.

System Structural Error Analysis in Binocular Vision Measurement Systems

A binocular stereo vision measurement system is widely used in fields such as industrial inspection and marine engineering due to its high accuracy, low cost, and ease of deployment. An unreasonable structural design can lead to difficulties in image matching and inaccuracies in depth computation during subsequent processing, thereby limiting the system’s performance and applicability. This paper establishes a systemic error analysis model to enable the validation of changes in structural parameters on the performance of the binocular vision measurement. Specifically, the impact of structural parameters such as baseline distance and object distance on measurement error is analyzed. Extensive experiments reveal that when the ratio of baseline length to object distance is between 1 and 1.5, and the angle between the baseline and the optical axis is between 30 and 40 degrees, the system measurement error is minimized. The experimental conclusions provide guidance for subsequent measurement system research and parameter design.

A Multi-Functional Reactive Power Compensation Device with the Capability of Grounding Fault Regulation and Its Parameter Design Method

Aiming at the problems of low equipment utilization and the high-capacity requirements of existing arc-suppression devices, a multi-functional reactive power compensation device with the capability of grounding fault regulation (MF-RPCD) is proposed. Firstly, the topology and operation mechanism of MF-RPCD are introduced in this paper. MF-RPCD works in a reactive power compensation mode when a power grid is under normal operation to ensure the unit power factor operation of the power-grid side. When a single line-to-ground fault occurs in the power grid, MF-RPCD works in a fault-regulation mode to effectively suppress the ground-fault current. Secondly, the parameters of the active and passive parts of MF-RPCD are optimally designed to ensure the stable operation of MF-RPCD. Finally, the correctness, feasibility and effectiveness of the proposed topology and functions are verified using simulations and experiments.

Investigation into the shear effect of torsion extrusion process

Torsion extrusion (TE) is a severe plastic deformation (SPD) technique with the potential to be used for the preparation of large bulk materials with enhanced mechanical properties. Shear deformation is the key factor for SPD to enhance the materials properties. However, it is not clear by far that what shear strains are dominant in torsion extrusion process and how they distribute in the extruded materials. These issues are crucial to the working parameters design of the torsion extrusion process for maximizing the shear effect. To this end, a plasticine billet with two colors was applied as experimental material, and the material flow pattern was revealed by measuring the twisted bicolor interfaces. The torsion extrusion was implemented using a die with a wavy cross-sectional bearing segment (W-TE), which is able to prevent the circumferential sliding of the materials against the die. Flow velocities were re-built according to the bicolor interfaces at each section in a cylindrical system. Strain rates and shear strains induced by torsion deformation along the radius of the material were formulated based on the velocity field and Eulerian variable derivatives, from which the dominant shear strain can be recognized. A shear effect index (SEI) was proposed to evaluate the contribution of the shear strains induced by torsion, and the distribution of SEI was analyzed. Furthermore, the W-TE experiments on the as-cast TiB2/2026 Al composite were carried out to demonstrate the positive correlation between the shear effect and the microstructural improvement, and finite element simulation for such experiments showed the consistency of the simulated deformation patterns with the plasticine measured ones. The evaluation method and the experimental results deepened the understanding to the shear effect of torsion extrusion process.

Exploring the thermodynamics and dynamics of lithium ions inserted into Li1-xMn2O4 electrode at different temperatures

Efficient lithium extraction via electrochemical adsorption holds great promise for resource utilization and energy storage. However, the mechanism of how temperature influences the electrochemical adsorption process, particularly the thermodynamics and dynamics in the liquid, liquid–solid interface, and solid remains unclear. To address this challenge, we explored the impact of temperature (273.15 to 328.15 K) using Li1-xMn2O4 as an adsorbent. For the liquid phase, the conductivity increased from 0.89 to 0.95 S/m following lnΛ = -0.11(1000/T) + 0.27 in thermodynamics; the solution viscosity decreased from 1.71 × 10-3 to 5.15 × 10-4 Pa·s conforming lnη = 1.96(1000/T) − 13.54 in dynamics. For the liquid–solid interface, the charge transfer resistance (Rct) decreased from 42.03 to 25.17 ohm obeying ln(1/Rct) = -0.82(1000/T) − 0.69 in thermodynamics; the exchange current (i0) showed a positive correlation with temperature in fitting Logi0 = -0.50(1000/T) − 1.40 in dynamics. For the solid phase, the increase in reduction peak voltage (ERP) and the decrease in Gibbs free energy (G), entropy (S), and enthalpy (H) all indicate that the increase of temperature promotes lithium ions to inserted into Li1-xMn2O4 in thermodynamics; the increased diffusion coefficient (DLi+(S)) and higher reduction peak current (IRP) suggest that higher temperature strengthens lithium ions diffusion and insertion in dynamics. In the temperature range, the adsorption capacity gradually increased from 1.15 to 7.37 mg/g, the initial current enhanced from −3.40 × 10-4 to −1.85 × 10-3 A, the terminal current raised from −1.59 × 10-4 to −7.40 × 10-4 A, and the current efficiency improved from 31.28 % to 66.11 % in the temperature range. This work provides a deeper understanding of the impact of temperature on the electrochemical lithium adsorption process from thermodynamics and dynamics. This work also offers crucial guidance for the upgrading of electrochemical lithium adsorption technology and can be applied to other fields such as energy storage, catalysis, and synthesis, providing a valuable reference for optimizing reaction parameter design in thermodynamics and dynamics.

A Novel Single-Stage Boost Single-Phase Inverter and Its Composite Control Strategy to Suppress Low-Frequency Input Ripples

Low-frequency pulsating ripples exist on the input side of a single-phase inverter, which bring some adverse effects and harm to the inverter and photovoltaic power generation system. In order to suppress the low-frequency pulsating ripple and reduce the filter circuit parameters, a novel single-stage boost single-phase inverter is proposed, which can suppress low-frequency ripple. And a three-closed-loop compound control strategy that can suppress input low-frequency ripples under the limitation of an energy storage inductor current and buffer capacitor voltage is proposed. The circuit topology, control strategy, key circuit parameters design, system modeling, and simulation of the inverters are deeply analyzed and studied. Simulation and experimental results show that the inverter has a good ability to suppress input low-frequency ripples.

Optimization-based design of structure and operation parameters simultaneously for real-world distillation column based on rate-based model

Simultaneously optimizing the structure and operating parameters of distillation columns based on rigorous rate-based models is critical for various process intensification technologies to achieve their intended purpose in real-world distillation columns. However, efficiently optimizing a distillation column based on rate-based models while considering the column hydraulics is far from practical. The biggest obstacle in using rigorous models for distillation columns in an equation-oriented environment is ensuring a robust solution for large-scale, strongly coupled nonlinear models, along with the simultaneous optimization of integer and continuous variables. In this study, a new optimization framework was introduced. It incorporated a pseudo-transient simulation method to ensure convergence of the simulation in equation-oriented environment. Additionally, an efficient relaxation method transformed the mixed integer nonlinear programming problem into a nonlinear programming problem, facilitating simultaneous optimization of both the integer variable representing column structure and the continuous variables governing column operation. Three examples, including a complex intensified catalytic distillation column, were optimized to demonstrate the efficiency of the proposed framework. Specifically, its advantages in terms of mathematical optimality and industrial feasibility were illustrated.

Evaluation of orthogonal composite designs for second‐order model in presence of missing observation

AbstractOrthogonal‐array composite designs (OACDs) and orthogonal‐uniform composite designs (OUCDs) are orthogonal composite designs that combine two‐level full or fractional factorial and three‐level orthogonal‐array/uniform designs for estimation of the linear, bilinear, and quadratic effects in a second‐order response surface model. In this study, the effects of missing one observation in the various design portions (factorial (f) axial (a) and center (c)), on the precision of parameter estimates, prediction variance and design efficiency of OACDs and OUCDs for 5 ≤ k ≤ 9 factors at different values of α (the distance of a non‐zero co‐ordinate in an additional design point from the center) are evaluated. The results showed that missing a factorial and an axial point have adverse effect on the precision of parameter estimates of OACDs and OUCDs, while missing a center point has little effect. Missing an axial point caused the highest effect on the prediction variance and design efficiencies. The FDS plots showed OACDs to be better designs for k ≤ 7 and OUCDs for k = 8 and 9 factors.

Bayesian modeling and optimization for split-plot experiments with multiple responses

In many industrial processes, cost or time constraints make some input variables harder to change or control than others. An appropriate experimental design method is restricted randomization, which results in split-plot experiments. Empirical models that connect multiple quality characteristics with input variables play a crucial role in robust parameter design for split-plot experiments. At present, many modeling methods typically adopt the single response model for analyzing industrial processes in the split-plot experiments without considering correlation among multiple responses, correlation among whole plots, and uncertainty of model parameters. However, ignoring these issues can lead to poor product or process design. To solve these issues, this paper suggests a novel Bayesian modeling and optimization approach. We first construct a Bayesian multi-response linear mixed-effects model and obtain the posterior distribution for model parameters by employing Bayesian theorem. Then, the Gibbs sampling procedure is employed for the estimation of model parameters. Finally, the overall weighted desirability optimization function meeting the specification is developed to avoid acquiring ideal input settings with outliers. A simulation and an engineering case study demonstrate the validity of the proposed method. In comparison to existing methods, the optimization results given the proposed method are more robust and reliable.

Effect of PGV/PGA ratio on seismic-induced vibrations of structures equipped with parallel tuned mass dampers considering SSI

Tuned mass damper is one of the effective methods used to reduce dynamic loads in structures under the influence of environmental loads such as earthquakes, wind, and traffic loads. In the current TMD design, the fixed base approach is mostly considered when determining the dynamic properties of the structure. However, in cases where the structure-soil interaction (SSI) is important, the frequency values of the structure are significantly different from those obtained for the fixed foundation approach. This situation negatively affects the performance of TMD operating in a narrow frequency range. Therefore, using a control system consisting of multiple TMDs connected in parallel (MTMD) instead of a single TMD may be a promising solution for the control of structural vibrations. In this study, a parameter design and efficiency assessment of MTMD for reducing the seismic responses of the structure considering SSI is studied. The particle swarm optimization (PSO) algorithm is adopted to obtain the optimum parameters (i.e., damping ratio, frequency ratio, and frequency bandwidth) of the MTMD. The effects of different support conditions, number of TMD units, and peak ground velocity (PGV) / peak ground acceleration (PGA) ratio on the performance of MTMD are also evaluated comprehensively. The dynamic responses of the structure are obtained under 42 near -fault ground motions from the time history analysis. The results reveal that ground motions with low PGV/PGA ratio can significantly increase the responses of the structure for both with and without SSI cases. Moreover, it has been observed that optimized TMDs placed parallel to the top floor of the structure are effective in reducing the seismic responses of a ten-story building considering SSI.

An Improved Artificial Electric Field Algorithm for Determining the Maximum Length of Gravel Packing in Deep-Water Horizontal Well

Gravel packing in deep-water horizontal wells is an effective and practical sand control method, which is a key technical method to ensure efficient exploitation of deep-water oil and gas. To ensure the successful implementation of gravel packing in deep water horizontal wells, it is crucial to carry out effective optimization design of packing parameters. This paper proposes a novel optimization design approach for gravel packing in deep-water horizontal wells. In the proposed approach, an optimization model is proposed for gravel packing in deep-water horizontal wells, in which the gravel packing length is regarded as the objective function. Then, an improved artificial electric field algorithm (IAEFA) is introduced for optimizing the key gravel packing parameters so as to determine the maximum gravel packing length. For a specific case study, we conducted optimization calculations for gravel packing in a deep-water horizontal well. Results of the case study demonstrate that the optimization design approach based on the IAEFA algorithm can effectively address the parameter optimization problem of deep-water horizontal well gravel packing. For the target well of the case study, the maximum packing length obtained by the IAEFA algorithm could reach 1000.22 m, and the corresponding 3 sets of optimal packing parameters were also obtained. In the scenario of optimal packing parameters, the total time of gravel packing in target well is 566.6 min, and the total amount of sand consumption is 54,050.94 lbs. The bottom hole pressure during the injection stage remains stable with about 9780 psi, then slowly rises from 9788 psi to 9837 psi in the α-wave packing stage, and rapidly increases from 9837 psi to 9986 psi in the β-wave packing stage. The proposed approach provides an efficient and practical optimization tool for the optimal design of gravel packing in deep water horizontal wells.

Simulation and study of the flow field in a kettle-type reactor for ethylene polymerization

Abstract Addressing the complexities inherent in the polymerization process for solution method polyethylene production, particularly the challenges in describing the turbulent three-dimensional flow field within the reactor and the precise design of reactor structural parameters, this research leverages computational fluid dynamics (CFD) methods integrated with polymerization reaction kinetics equations. We have formulated User-Defined Functions (UDFs) for a quantitative representation of the polymerization process. Employing the Realizable k-epsilon turbulence model and Sliding Grid (SG) technique, we analyzed the flow dynamics and field distribution within the reactor, elucidating the distribution patterns of temperature, pressure, and concentration fields. A comparative assessment of simulation outcomes against experimental data revealed that the average deviation of the simulated temperature field from actual operating conditions falls within the permissible error range, thereby affirming the simulation model’s validity. Utilizing local sensitivity analysis, we investigated the impact of impeller structural parameters on mixing time and stirring power. Our analysis of the most sensitive structural parameters indicated that impeller diameter and the number of impellers are pivotal in reducing mixing time and stirring power, respectively. Notably, the stirring power escalates with an increase in the number of impellers, while the mixing time exhibits a trend of initial decrease followed by an increase with varying impeller diameters. The methodologies and patterns discerned in this study provide insightful design references for the design and optimization of reactors across different tonnages.

Parameter Design for Suppressing Current Distortion Caused by DC Bias in Dual-Active-Bridge Converters

Parameter Design for Suppressing Current Distortion Caused by DC Bias in Dual-Active-Bridge Converters

Enhancing spontaneous and continuous liquid directional transport on peristome-mimetic surface with hierarchical microgrooves

Directional liquid transport function discovered on the peristome of Nepenthes alata has attracted considerable attention for its diverse potential applications. Despite the extensive efforts made for the peristome-mimetic surface fabrication and the anisotropic liquid spreading regulation, it remains a daunting challenge to reveal the synergistic effect of hierarchical structures on the liquid spreading and pinning dynamics. Here, we demonstrate the first-tier microgroove morphology, as well as the presence of second-tier microgrooves, play an important role in homogenous film formation and the directional liquid transport control. Through experimental investigation and theoretical analysis, the enhanced spreading and pinning effect is validated. Moreover, the preferential directional liquid spreading will collapse on the peristome-mimetic surface without a rational parameter design, and the threshold value for the transition of liquid propagation dynamics is determined. Spontaneous directional liquid transport from the cold region to the hot region and smart liquid transport regulation was also realized on the peristome-mimetic surface. This work will provide guidance to the design of effective open microfluidic systems, and open a new way for thermal management and lab-on-chip applications.

Linear Time-Periodic theory-based novel stability analysis method for voltage-source converter under unbalanced grid conditions

Small-signal stability analysis is essential for the safe operation and parameter design of power electronic-dominated grids. Unbalanced conditions introduce more frequency-coupling terms, which are unneglectable in the stability assessment. This paper proposes a novel Linear Time-Periodic (LTP) theory-based stability analysis method and focuses on grid-connected voltage-source converters (VSCs) without improved unbalancing controls. Firstly, the analysis of fundamental solutions of the LTP system reveals that each LTP mode is characterized by a unique damping factor and multiple oscillation frequencies, defined by LTP eigenvalues and related transformation vectors, i.e., (λi,Vi(t)). Then, a method for calculating (λi,Vi(t)) is proposed using the characteristic matrix of the Harmonic State-Space (HSS) model. An iterative sorting method based on the time-domain interpretation of HSS eigenvalues/eigenvectors is proposed to determine accurate (λi,Vi(t)) in the case of the minimum truncation order. Finally, generalized definitions and calculation methods of the widely used indicators for modal analysis are presented to assess system stability and guide the parameter design. Numerical and simulation results verify the proposed stability analysis method and indicate its advantages compared to the existing Floquet and HSS methods.

Gated parametric neuron for spike-based audio recognition

Spiking neural networks (SNNs) aim to simulate real neural networks in the human brain with biologically plausible neurons. The leaky integrate-and-fire (LIF) neuron is one of the most widely studied SNN architectures. However, it has the vanishing gradient problem when trained with backpropagation. Additionally, its neuronal parameters are often manually specified and fixed, in contrast to the heterogeneity of real neurons in the human brain. This paper proposes a gated parametric neuron (GPN) to process spatio-temporal information effectively with the gating mechanism. Compared with the LIF neuron, the GPN has two distinguishing advantages: (1) it copes well with the vanishing gradients by improving the flow of gradient propagation; and, (2) it learns spatio-temporal heterogeneous neuronal parameters automatically. Additionally, we use the same gate structure to eliminate initial neuronal parameter selection and design a hybrid recurrent neural network-SNN structure. Experiments on two spike-based audio datasets demonstrated that the GPN network outperformed several state-of-the-art SNNs, could mitigate vanishing gradients, and had spatio-temporal heterogeneous parameters. Our work shows the ability of SNNs to handle long-term dependencies and achieve high performance simultaneously.

Design and Experiments of a Roll-Knife Pickup for a Buckwheat Pickup Harvester

To reduce grain loss during pickup and prevent stalk entanglement in buckwheat harvesters, thereby improving the quality of mechanized harvesting, a three-stage pickup conveyor roll with a ground-level rotary knife-type pickup header was designed and tested. This paper, based on the growth characteristics of buckwheat, determined the three-stage pickup conveying process and the overall structure of the ground-level rotary knife-type pickup header. Kinematic analysis and parameter design of the rotary knife-type pickup roll were conducted. Finally, a physical prototype was fabricated, and field performance tests were carried out, using machine forward speed and pickup roll rotational speed as influencing factors and pickup loss rate as an evaluation metric. Results showed that the interaction between pickup roll rotational speed and forward speed had a significant effect on the pickup loss rate, with forward speed having a greater impact than pickup roll rotational speed. Under consideration of their interaction, when the pickup roll rotational speed was within the range of 396–457 r/min, and the forward speed was between 0.9–1.0 m/s, the pickup loss rate was minimized. Based on the regression equation model, the predicted optimal conditions were a forward speed of 1.0 m/s and a roll pickup speed of 396 rpm. Under these conditions, the test results showed a pickup loss rate of 5.235%, indicating good pickup performance. This research provides a reference for the design of pickup devices in grain combine harvesters.