Accurate Design Research Articles

Accelerating the Hydrogen Production via Modifying the Fermi Surface.

The design of catalysts has attracted a great deal of attention in the field of electrocatalysis. The accurate design of the catalysts can avoid an unnecessary process that occurs during the blind trial. Based on the interaction between different metal species, a metallic compound supported by the carbon nanotube was designed. Among these compounds, RhFeP2CX (R-RhFeP2CX-CNT) was found to be in a rich-electron environment at the Fermi level (denoted as a flat Fermi surface), beneficial to the hydrogen evolution reaction (HER). R-RhFeP2CX-CNT exhibits a small overpotential of 15 mV at the current density of 10 mA·cm-2 in acidic media. Moreover, the mass activity of R-RhFeP2CX-CNT is 21597 A·g-1, which also demonstrates the advance of the active sites on R-RhFeP2CX-CNT. Therefore, R-RhFeP2CX-CNT can be an alternative catalyst applied in practical production, and the strategies of a flat Fermi surface will be a reliable strategy for catalyst designing.

Explicit analytical solutions for the full plane-stress field in sandwich beams under flexure governed by zigzag warping

We provide analytical solutions for the full stress field of straight sandwich beams with identical skins subject to linear elastic flexure governed by zigzag warping, where all layers obey Timoshenko’s kinematics. As a main novelty, we make use of an equilibrium equation for the Cauchy continuum to recover of the through-the-thickness normal stress component, σy. The new estimates are accurate for a wide range of relative stiffness between skins and core and suitable boundary conditions, as it can be demonstrated through the comparison with detailed finite element simulations where the sandwich is modelled as a two-dimensional continuum. As a main practical result concerned with the study of delamination, we find that at a core–skin interface of a cantilever sandwich subjected to a uniformly distributed load, in a region close to the fully-clamped cross-section, σy is a tensile stress of magnitude larger than that of the shear stress. On this basis, we infer that the availability of good estimates for σy, along with those for the longitudinal and shear stresses, may be important for the accurate design of sandwich panels.

Traffic input module for mechanistic-empirical pavement design with weigh-in-motion data

• Weigh-in-motion data provides large quantity of traffic information for pavement design. • Reliability of pavement design highly depends on the quality of truck traffic data. • The weigh-in-motion recorded traffic data may not be sufficiently accurate for satisfactory pavement design. • The accuracy of weigh-in-motion traffic data can be improved through machine learning algorithms. The success of the mechanistic-empirical pavement design guide implementation depends largely on a high level of accuracy associated with the information supplied as design inputs. Truck axle load spectra play a critical role in all aspects of the pavement structure design. Inaccurate traffic information will yield an incorrect estimate of pavement thickness, which can either make the pavement fail prematurely in the case of under-designed thickness or increase construction cost in the case of over-designed thickness. The primary objective of this study was to create an accurate traffic design input module, and thus to improve the quality of pavement designs. The traffic input module was created with the most recent data to better reflect the axle load spectra for pavement design. The unclassified vehicles by weigh-in-motion devices were analyzed and a neural-network-model-based classification method was utilized to determine the appropriate allocations of unclassified vehicles to truck classes. The updated truck traffic information includes average annual daily truck traffic, truck volume monthly adjustment factors, truck volume lane distribution factors, truck volume directional distribution factors, truck volume class distributions, traffic volume hourly distribution factors, distributions of for single-axle, tandem-axle, tridem-axle, and quad-axle loads, average axle weight, average axle spacing, and average number of axle types.

Designing RNA switches for synthetic biology using inverse-RNA-folding

RNA switches respond to specific ligands to control gene expression. They are widely used in synthetic biology applications and hold potential for future RNA-based therapeutic breakthroughs. However, the crux is their precise design. Here, we will discuss how inverse-RNA-folding could be utilized for the accurate design of RNA switches.

Macroscopic model and statistical model to characterize electromagnetic information of a digital coding metasurface.

A digital coding metasurface is a platform connecting the digital space and electromagnetic wave space, and has therefore gained much attention due to its intriguing value in reshaping wireless channels and realizing new communication architectures. Correspondingly, there is an urgent need for electromagnetic information theory that reveals the upper limit of communication capacity and supports the accurate design of metasurface-based communication systems. To this end, we propose a macroscopic model and a statistical model of the digital coding metasurface. The macroscopic model uniformly accommodates both digital and electromagnetic aspects of the meta-atoms and predicts all possible scattered fields of the digital coding metasurface based on a small number of simulations or measurements. Full-wave simulations and experimental results show that the macroscopic model is feasible and accurate. A statistical model is further proposed to correlate the mutual coupling between meta-atoms with covariance and to calculate the entropy of the equivalent currents of digital coding metasurface. These two models can help reconfigurable intelligent surfaces achieve more accurate beamforming and channel estimation, and thus improve signal power and coverage. Moreover, the models will encourage the creation of a precoding codebook in metasurface-based direct digital modulation systems, with the aim of approaching the upper limit of channel capacity. With these two models, the concepts of current space and current entropy, as well as the analysis of information loss from the coding space to wave space, is established for the first time, helping to bridge the gap between the digital world and the physical world, and advancing developments of electromagnetic information theory and new-architecture wireless systems.

Data-driven inverse design of mode-locked fiber lasers

The diverse applications of mode-locked fiber lasers (MLFLs) raise various demands on the output of the laser, including the pulse duration, energy, and shape. Simulation is an excellent method to guide the design and construction of an MLFL for on-demand laser output. Traditional simulation of an MLFL uses the split-step Fourier method (SSFM) to solve the nonlinear Schrödinger (NLS) equation, which suffers from high computational complexity. As a result, the inverse design of MLFLs via the traditional SSFM-based simulation method relies on the design experience. Here, a completely data-driven approach for the inverse design of MLFLs is proposed, which significantly reduces the computational complexity and achieves a fast automatic inverse design of MLFLs. We utilize a recurrent neural network to realize fast and accurate MLFL modeling, then the desired cavity settings meeting the output demands are searched via a deep-reinforcement learning algorithm. The results prove that the data-driven method enables the accurate inverse design of an MLFL to produce a preset target femtosecond pulse with a certain duration and pulse energy. In addition, the cavity settings generating soliton molecules with different target separations can also be located via the data-driven inverse design. With the GPU acceleration, the time consumption of the data-driven inverse design of an MLFL is less than 1.3 hours. The proposed data-driven approach is applicable to guide the inverse design of an MLFL to meet the different demands of various applications.

STEAM Experimental Facility: A Step Forward for the Development of the EU DEMO BoP Water Coolant Technology

Within the EUROfusion roadmap for the technological development of the European-DEMOnstration (EU-DEMO) reactor, a key point has been identified in the discontinuous operation (pulse-dwell-pulse) of the machine. Water Cooled Lithium Lead (WCLL) Breeding Blanket (BB) Primary Heat Transfer Systems (PHTSs) adopt technology and components commonly used in nuclear fission power plants, whose performances could be negatively affected by the above mentioned pulsation, as well as by low-load operation in the dwell phase. This makes mandatory a full assessment of the functional feasibility of such components through accurate design and validation. For this purpose, ENEA Experimental Engineering Division at Brasimone R.C. aims at realizing STEAM, a water operated facility forming part of the multipurpose experimental infrastructure Water cooled lithium lead -thermal-HYDRAulic (W-HYDRA), conceived to investigate the water technologies applied to the DEMO BB and Balance of Plant systems and components. The experimental validation has the two main objectives of reproducing the DEMO operational phases by means of steady-state and transient tests, as well as performing dedicated tests on the steam generator aiming at demonstrating its ability to perform as intended during the power phases of the machine. STEAM is mainly composed of primary and secondary water systems reproducing the thermodynamic conditions of the DEMO WCLL BB PHTS and power conversion system, respectively. The significance of the STEAM facility resides in its capacity to amass experimental data relevant for the advancement of fusion-related technologies. This capability is attributable to the comprehensive array of instruments with which the facility will be equipped and whose strategic location is described in this work. The operational phases of the STEAM facility at different power levels are presented, according to the requirements of the experiments. Furthermore, a preliminary analysis for the definition of the control strategy for the OTSG mock-up was performed. In particular, two different control strategies were identified and tested, both keeping the primary mass flow constant and regulating the feedwater mass flow to follow a temperature set-point in the primary loop. The obtained numerical results yielded preliminary feedback on the regulation capability of the DEMO steam generator mock-up during pulsed operation, showing that no relevant overtemperature jeopardized the facility integrity, thanks to the high system responsivity to rapid load variations.

Drift–Diffusion Simulation of Intermediate Band Solar Cell: Effect of Intermediate Band Continuity Constraint

Self-consistent drift–diffusion model has been widely employed to simulate the device performance of intermediate band solar cell (IBSC) under practical device configuration. However, one of the remained issues in the drift–diffusion modeled-based works is the difficulty to reach the IB carrier continuity through the self-consistent manner. In most of the previous reports the constraints were relaxed or just partially satisfied; which render the unreliable performance results and misguide the device design strategy. In this work, in order to solve this issue and to validate our results, we performed extensive simulations to fully disclose the significant effect of the IB continuity constraints by taking InAs/GaAs quantum dot-based IBSC as a model device using the semiconductor modules in COMSOL Multiphysics combined with the Fortran codes. We found that under rigorous satisfaction of IB continuity constraint, the band potential profiles for the IBSC with either doped or nondoped IB under various light illumination conditions are nearly identical to those under the dark conditions. Moreover, from the simulated current–voltage curve dependence on the light concentration ratio, we found the device performance based on drift–diffusion under rigorous IB continuity constraint showed similar tendency to the features simulated based on detailed balance principle except the much-lowered power conversion efficiency. Our work demonstrated here, serves as an accurate and reliable IBSC device design approach toward better IB material screening, efficiency improvement, optical management, and extended application in the emerging field such as the perovskite material-based IBSC.

Measurement and characterization of aging-induced gradient properties inside asphalt mixture by composite specimen method

Measurement and quantitative characterization of aging-induced gradient properties for the asphalt mixture is an important theoretical basis for the accurate mechanical behavior analysis and design of asphalt pavement. In this research, the composite specimen method is proposed to obtain asphalt binders at different depths inside the asphalt mixture. Aging-induced gradient properties have been measured by dynamic shear rheometer (DSR) tests to reveal the internal mechanism. G* master curves for asphalt binders in different depths have been constructed by a generalized logistic sigmoidal model (GLSM) to investigate the gradient aging effects in a wide range. It is found that the composite specimen method can restore the boundary conditions of asphalt binders through the process of specimen preparation, core drilling, core shifting, asphalt injecting, gradient aging test, and layered cutting. It is feasible to study gradient aging characteristics inside the asphalt mixture. Asphalt binder samples obtained from the surface of the composite specimen with the most serious aging degree have the maximum G* value and the minimum δ value. Under the same aging condition, the variation of G* of the asphalt binder along the depth is more pronounced than that of δ. The change behavior of G* and δ are generally the same, and there are only differences in G* and δ values and the depth range of gradient aging effects for different aging levels. At the same temperature and loading frequency, values for G* under the Aging-L3 condition are the largest, and values for δ are the smallest in this aging state. The aging influence depth range inside the composite specimens is about 3 cm, 4.5 cm, and 5.5 cm after oven aging at 85 °C for 5 days, 10 days, and 15 days, respectively. GLSM is well suited for constructing G* master curves of asphalt binders. The distinction between G* master curves is most obvious in the depth of 0 ∼ 1 cm and changes the most from the depth of 0 ∼ 1 cm to 1 ∼ 2 cm. Under the condition of Aging-L3, G* master curves are most differentiated at different depths, indicating the most significant gradient aging state inside the asphalt mixture composite specimen.

Real-Time Remote Patient Monitoring and Alarming System for Noncommunicable Lifestyle Diseases.

Telemedicine and remote patient monitoring (RPM) systems have been gaining interest and received adaptation in healthcare sectors since the COVID-19 pandemic due to their efficiency and capability to deliver timely healthcare services while containing COVID-19 transmission. These systems were developed using the latest technology in wireless sensors, medical devices, cloud computing, mobile computing, telecommunications, and machine learning technologies. In this article, a real-time remote patient monitoring system is proposed with an accessible, compact, accurate, and low-cost design. The implemented system is designed to an end-to-end communication interface between medical practitioners and patients. The objective of this study is to provide remote healthcare services to patients who need ongoing care or those who have been discharged from the hospital without affecting their daily routines. The developed monitoring system was then evaluated on 1177 records from MIMIC-III clinical dataset (aged between 19 and 99 years). The performance analysis of the proposed system achieved 88.7% accuracy in generating alerts with logistic regression classification algorithm. This result reflects positively on the quality and robustness of the proposed study. Since the processing time of the proposed system is less than 2 minutes, it can be stated that the system has a high computational speed and is convenient to use in real-time monitoring. Furthermore, the proposed system will fulfil to cover the lower doctor-to-patient ratio by monitoring patients from remote locations and aged people who reside in their residences.

A Comparative Study on Accurate Parameter Estimation of Solar Photovoltaic Models Using Metaheuristic Optimization Algorithms

Fossil fuel prices are increasing day by day due to growing demand and resource limitations. This situation shifts conventional electricity generation to renewable power generation. Among renewables, solar photovoltaic (PV) energy is very promising as the third fastest growing one. However, PV system modeling requires the estimation of unknown parameters of PV cells and modules. This problem remains a compelling task due to its multi-dimensional, multi-model and non-linear characteristics. In order to contribute to the solution of this optimization problem, this work makes a detailed comparison of artificial hummingbird algorithm, artificial rabbits optimization, enhanced Jaya algorithm, flow direction algorithm and artificial gorilla troops optimizer for determining the unknown parameters of PV models. Experimental results demonstrate that artificial hummingbird algorithm in single diode modeling of PV cell, flow direction algorithm in double diode modeling of PV cell and artificial rabbits optimization in single diode modeling of PV module are found to be capable of estimating accurate and efficient design coefficients for PV systems. In addition, the mentioned metaheuristic algorithms show reasonable convergence characteristics for the corresponding PV models.

Mechanism of physical hardening on the fracture characteristics of polymer-modified asphalt binder

This article aims to reveal the physical hardening mechanism of polymer-modified asphalt binder (PMA) and accurately assess its impact on the low-temperature fracture properties of asphalt binders. Base asphalt binder (BA), styrene–butadiene–styrene modified asphalt binder (SBSMA), and crumb rubber modified asphalt binder (CRMA) were used as the research objects. Molecular dynamics (MD) simulation and differential scanning calorimetry (DSC) test were used to investigate the physical hardening mechanism of PMA at the microscopic level. The fracture characteristics of PMA under physical hardening were analyzed based on the single-edge notched beam (SENB) test. The results show that under prolonged cold service conditions, the asphalt molecular mobility is weakened, the non-bond energy and the free volume are reduced, and the molecules undergo aggregation state transformation, leading to the physical hardening of asphalt materials. In the process of physical hardening of asphalt molecules in the micro-Brownian motion of the main active force from the aromatic and saturate fractions. Considering the effect of physical hardening, it is recommended that the method used to test the low temperature properties of asphalt binders should ensure a constant temperature for at least 24 h. The crack tolerance (Ct) is recommended as the evaluation index of low-temperature cracking resistance of PMA in cold regions. The Ct of BA, SBSMA, and CRMA are reduced by 52.88 %, 12.04 %, and 35.24 %, respectively, after 24 h of constant low temperature. This indicating that the polymer modifiers can improve the fluidity of asphalt molecules, inhibit molecular aggregation, and reduce the effect of physical hardening on asphalt binders. Thermo-oxidative aging can aggravate the physical hardening phenomenon of asphalt binder, and the higher the degree of thermo-oxidative aging, the more severe the physical hardening of asphalt binder. The related research results provide the theoretical basis and technical support for the accurate design and development of the low-temperature performance of asphalt binders for roads in cold regions.

A rapid performance prediction method for Two-Phase liquid metal MHD generators based on Quasi-One-Dimensional model

Liquid metal magnetohydrodynamic (LMMHD) power generation is a novel and highly efficient technology with broad application prospects. In our previous study, a novel LMMHD enhanced Closed-Brayton-Cycle power generation system for hypersonic vehicles was proposed, and its excellent power generation performance was demonstrated by thermodynamic analysis. The most important component of LMMHD system is the power generation channel, and the rapid and accurate performance prediction and optimization design methods of which are the prerequisites for further research. In this study, a quasi-one-dimensional modeling method for LMMHD power generation channels based on a two-fluid model is developed. The performance variation laws with the geometric structure, magnetic field and boundary conditions, as well as the potential loss mechanisms are investigated. Results indicate that the most optimal or appropriate design can be achieved by optimizing the channel geometry and magnetic field, such as the optimal aspect ratio of 1 and the optimal Hartmann number of 2000. But it is difficult to balance the power output and efficiency through the boundary condition optimization. The gas–liquid slip can lead to approximately 20–40% of energy losses, making the elimination and suppression of slip effects a significant research focus in the relevant field.

Design and implementation of a near-field focused metasurface for microwave power transmission

In this paper, a near-field focused (NFF) metasurface composed of sub-wavelength structures for microwave power transmission is designed and implemented. Through full-wave simulations, a phase-shifting unit is proposed, which covers a transmission phase range of 360°, maintains a transmission amplitude better than −1.5 dB in most regions. Accurate design of the units at different positions in the array is achieved using phase compensation theory, forming the near-field focusing metasurface. By adjusting the transmission phase of the central unit in the metasurface to 30°, higher transmission efficiency can be achieved. Simulation results indicate that the designed near-field focused metasurface has the properties of high transmission efficiency, polarization insensitivity and distance insensitivity. To verify the transmission performance of the near-field focusing metasurface, a near-field focusing experimental platform is built and the microwave power transmission efficiency is calculated. Experimental results demonstrate that the proposed metasurface enhances the power received at the receiver, increasing the transmission efficiency by 433 %. The proposed near-field focusing metasurface holds potential for applications in high-power wireless power transfer and microwave intracavity focusing.

Finite-difference solution for dissipation of excess pore water pressure within liquefied soil stabilized by stone columns with consideration of coupled radial-vertical seepage

The implementation of stone columns is a widely accepted method for improving the stability of liquefiable soil. A comprehensive understanding of the behavior of the composite ground is crucial for accurate design and calculation in practical applications. Several existing mathematical models were established to assess characteristics of the stone column-improved ground by typically ignoring the vertical seepage within liquefiable soil. This negligence will inevitably lead to significant calculation errors, particularly when the vertical permeability of liquefiable sites is high or the installation spacing of stone columns is large. In this context, a new mathematical model which accounts for coupled radial-vertical seepage within liquefiable soil is proposed to determine the reinforcement performance of stone columns. The equal strain assumption and new boundary conditions are incorporated to obtain numerical solutions with the finite difference method. Then the present solution is degenerated to the conventional calculation model to verify the reasonability of the proposed model. Finally, a parametric analysis is conducted to investigate the impacts of crucial parameters on the performance of stone columns for excess pore water pressure variation during soil liquefaction. The results reveal that the peak value of the maximum excess pore water pressure ratio increases with the increment of both the column spacing and cyclic stress ratio. Moreover, the increasing radial and vertical consolidation parameters Tb and Th will accelerate the dissipation rate of the excess pore water pressure of liquefiable sites. Furthermore, the conventional model neglecting the vertical seepage will underestimate the variation rate of the excess pore water pressure, and the calculation error will become larger with the increase of Th.

Accurate Design and Layout of Landscape Elements Based on Improved Particle Swarm Optimization

Accurate Design and Layout of Landscape Elements Based on Improved Particle Swarm Optimization

Cryogenic Comminution of Subsea Cables and Flowlines: A Pathway for Circular Recycling of End-of-Life Offshore Infrastructure

Hundreds of thousands of kilometers of communication and power (umbilical) cables and flowlines lie undersea worldwide. Most of these offshore cables and flowlines have reached or will soon be nearing the end of their service life, prompting the need for a viable recycling approach to recover some valuable material, e.g., copper. However, separation into constituent materials has proven very challenging due to the highly robust design of the composite cables (and flowlines) to withstand service conditions and the tough external plastic sheaths that protect against seawater corrosion. This study aims at promoting sustainable practices in the offshore energy sector. Here, we summarize the findings of the cryogenic comminution of subsea cables and flowlines for an effective separation and recovery of component materials. Heat transfer analyses of complex multilayer flowlines and umbilicals were conducted to evaluate the time required for these structures to reach their respective critical brittle-transition temperatures. Subsequently, the time was used as a guide to crush the flowline and umbilical cables under cryogenic conditions. The results show that the flowlines and umbilical cables will reach the brittle-transition temperature after approximately 1000s (i.e., 17 min) of submergence in liquid nitrogen (LN). Comminution of the materials at temperatures near the brittle-transition temperature was proven relatively efficient compared to room-temperature processing. The present evaluation of heat transfer and lab-scale crushing will afford accurate process modelling and design of a pilot cryogenic comminution of decommissioned subsea cables and flowlines, enabling the sustainable recovery of valuable materials that can provide a new stream of waste-to-wealth economy.

A digital orthodontic arch wire design system with interactive adjustment and intelligent optimization

The design of orthodontic arch wires is a prerequisite for orthodontic treatment that determines the subsequent orthodontic effects. Current methods for designing orthodontic arch wires are often based on traditional manual techniques, which suffer from problems such as low accuracy and efficiency. To address these issues, a digital orthodontic arch wire design system has been developed using Unity 3D and C#. This system allows for the interactive adjustment and intelligent optimization of the shape of digital orthodontic arch wires. The developed system includes modules for curve design, contour construction, and collision detection of orthodontic arch wires, which can be customized interactively to meet the personalized needs of patients. In addition, an energy-constrained method is employed to optimize the shape of certain regions of the arch wire, which helps overcome distortion and interference issues caused by unreasonable interaction. The effectiveness of the developed system has been evaluated through experiments on digital design and optimization of orthodontic arch wires. Results demonstrate that the system can achieve accurate and efficient digital design of orthodontic arch wires, effectively reduce distortion, and is expected to improve the orthodontic effect.

Elastic local buckling coefficients of I-shaped beams considering flange–web interaction

Since using high–strength and high–performance steels has become a more common structural design practice in building and bridge construction, there is an increased potential for designing extremely thin-walled I-shaped beam members to enhance the efficiency of the steel beam design. For a more accurate design approach for these thin-walled I-beam members, particularly when they are near noncompact limits, it is necessary to explore more rational methods for determining the elastic local buckling strength of I-beams. This study aimed to investigate the local buckling behavior and strength of I-shape structural sections by considering flange-web interactions through three-dimensional finite element analysis. The goal was to provide a more reasonable estimation of local buckling strength under uniform bending. To evaluate the local buckling behavior of flange and web panels and explain it reasonably, this study adopted the ratio of flange-web slenderness (λf/λw) and height-to-width ratio (H/bf) of I-shaped beams which can affect buckling mode shapes and local buckling strength of I-shaped beams induced by flange local and web bend bucklings. Finally, this study presented design equations for both flange local and web-bend buckling coefficients considering λf/λw and H/bf. It was expected that the presented local buckling coefficients (kf) for flanges and webs could lead to a more reasonable design, as compared to the existing AISC design provisions.

Experimental Study on Optimum Design of Aircraft Icing Detection Based on Large-Scale Icing Wind Tunnel

Icing detection is the premise and basis for the operation of aircraft icing protection system, and is the primary issue in flight safety assurance. At present, there is a lack of research methods and design reference for the layout optimization of ice detectors. Therefore, in order to simulate the real icing environment encountered by the aircraft more accurately, a large-scale icing wind tunnel was used to carry out experimental research on the icing characteristics of the sensor probes. A closed-loop experimental method including the typical condition selection, sensor array interference examination and ice shape repeatability verification was initially proposed. A stepwise optimization process and a sensitivity analysis on ambient conditions were combined to determine the optimal distribution for sensor installation. It is found that the water collection coefficient on the cylinder surface of the probe first increases and then decreases along the axial direction, reaching the extreme value at a certain position. The height of this extreme point will gradually increase with the development of the wall boundary layer, showing a variation range of 2~30 mm. Improper design may cause the sensor probe to fail to capture the point with the maximum icing thickness, affecting the sensitivity of icing detection. In addition, each probe position has different sensitivity to changes in flow parameters; the points with larger icing mass and lower sensitivity to changes in attack angle will have better detection effect. The measured data and analysis in the present work can provide a basis for the accurate design of icing sensor probes.