Geometrical Parameters Of Structure Research Articles

Application of multi-objective optimization genetic algorithm to design terahertz metamaterials with fano resonances

In the prosperous development of terahertz (THz) metamaterials, Fano resonances have gained attention due to their potential applications in ultrasensitive systems. The performance of Fano resonance is directly influenced by the geometrical parameters of the element structure. However, the traditional design rules for Fano resonances in metamaterials rely on an empirical trial-and-error strategy, necessitating significant effort to achieve optimal results. To address this issue, we propose a design method in this study that utilizes the finite integration technique in time domain (FITD) along with a multi-objective optimization genetic algorithm for the intelligent design of metamaterial structures exhibiting the Fano resonance phenomenon. The FITD method is primarily used to calculate the Fano resonance with different metamaterial geometric structure parameters, while the genetic algorithm efficiently selects the optimal solution. Our method, characterized by high efficiency and complete independence from prior knowledge, could offer a new design technique for metamaterials with specific functions, thereby contributing to the development of THz applications.

A novel design method based onmulti–objective optimization for graded lattice structure by additive manufacturing

Purpose While performance demands in the natural world are varied, graded lattice structures reveal distinctive mechanical properties with tremendous engineering application potential. For biomechanical functions where mechanical qualities are required from supporting under external loading and permeability is crucial which affects bone tissue engineering, the geometric design in lattice structure for bone scaffolds in loading-bearing applications is necessary. However, when tweaking structural traits, these two factors frequently clash. For graded lattice structures, this study aims to develop a design-optimization strategy to attain improved attributes across different domains. Design/methodology/approach To handle diverse stress states, parametric modeling is used to produce strut-based lattice structures with spatially varied densities. The tailored initial gradients in lattice structure are subject to automatic property evaluation procedure that hinges on finite element method and computational fluid dynamics simulations. The geometric parameters of lattice structures with numerous objectives are then optimized using an iterative optimization process based on a non-dominated genetic algorithm. Findings The initial stress-based design of graded lattice structure with spatially variable densities is generated based on the stress conditions. The results from subsequent dual-objective optimization show a series of topologies with gradually improved trade-offs between mechanical properties and permeability. Originality/value In this study, a novel structural design-optimization methodology is proposed for mathematically optimizing strut-based graded lattice structures to achieve enhanced performance in multiple domains.

Low frequency bandgap and high stiffness of innovative auxetic metamaterial with negative thermal expansion

Achieving multifunctional integration is crucial in mechanical metamaterials to meet the requirements of structures and equipment serving in complex environments across various engineering fields. In this study, we propose two novel bi-material and tri-material metamaterials based on the original edge-shared quadrangle (EQ/EQO) metamaterial, which exhibit negative thermal expansion (NTE), negative Poisson's ratio (NPR), and bandgap characteristics. The effective thermoelastic properties, including coefficient of thermal expansion (CTE), Poisson's ratio (PR), and Young's modulus, are compared and analyzed through theoretical formulation based on Timoshenko beam theory and numerical simulation using continuum elements with Abaqus. Additionally, finite element analysis is employed to calculate the energy band structures of these metamaterials based on Bloch's theorem, while the transmission characteristic curve verifies the validity of the obtained band structure. We systematically discuss the bandgap characteristics, coupling relationship between bandgaps and thermoelastic properties, as well as the influence of geometrical parameters on both bandgaps and thermoelastic properties. Our results demonstrate that the effective thermoelastic properties of these metamaterials are primarily determined by their frame structure's geometrical parameters, particularly the incline angle. Furthermore, for bi-material metamaterials, their specific stiffness closely relates to their bandgaps; however, for tri-material metamaterials, only the central local resonant unit determines their bandgap behavior. Notably, planar and 3D tri-material metamaterials can concurrently achieve a low-frequency bandgap along with high stiffness as well as NTE/NPR behavior. This work presents a new design strategy for optimizing multifunctional metamaterials' bandgaps while incorporating NTE behavior.

Structure Design and Heat Transfer Performance Analysis of a Novel Composite Phase Change Active Cooling Channel Wall for Hypersonic Aircraft.

Efficient and stable heat dissipation structure is crucial for improving the convective heat transfer performance of thermal protection systems (TPSs) for hypersonic aircraft. However, the heat dissipation wall of the current TPS is limited by a single material and structure, inefficiently dissipating the large amount of accumulated heat generated during the high-speed maneuvering flight of hypersonic aircraft. Here, a convection cooling channel structure of TPS is proposed, which is an innovative multi-level structure inspired by the natural honeycomb. An active cooling channel (PCM-HC) is designed by using a variable-density topology optimization method and filled with phase change material (PCM). Numerical simulations are used to investigate the thermal performance of the PCM-HC wall, focusing on the influence of PCM properties, structural geometric parameters, and PCM types on heat transfer characteristics. The results demonstrate that the honeycomb-like convection cooling channel wall, combined with PCM latent heat of phase change, exhibits superior heat dissipation capability. With a heat flux input of 50 kW/m2, the maximum temperature on the inner wall of PCM-HC is reduced by 12 K to 20 K. Different PCMs have opposing effects on heat transfer performance due to their distinct thermophysical properties. This work can provide a theoretical basis for the design of high-efficiency cooling channel, improving the heat dissipation performance in the TPS of hypersonic aircraft.

Modeling and vibration analysis of bolted composite conical-conical shells with flanges

This paper proposes a general semi-analytical modeling method of bolted composite conical-conical shells with flanges based on the first-order shear deformation theory. The coupling connections between conical shells and flanges are achieved by using the penalty function method. A bolted joint model that considers the non-uniform distribution of interface pressure is proposed, which can efficiently simulate any number of bolt connections between flanges and boundaries and between flanges and flanges. The correctness and effectiveness of the proposed modeling method are confirmed through step-by-step comparisons with finite element analysis and experimental testing. Then, the influence of various parameters on the frequency trajectories and modal shapes of bolted composite conical-conical shells with flanges is analyzed, with a particular focus on frequency veering and modal coupling vibration behaviors in these structures. The analyses indicate that the proposed modeling method can flexibly adjust structural geometric parameters, material parameters, bolt parameters, fiber layer parameters, and so on, which can efficiently guide the dynamic design of bolted composite conical shell structures with flanges.

Hierarchical pore structure with a confined resonant mode for improving the solar energy utilizing efficiency of ultra-thin perovskite solar cells

The perovskite solar cell (PSC) has the benefits of flexibility, inexpensiveness, and high efficiency, and has important prospective applications. However, serious optical losing and low solar energy-utilizing efficiency remain a challenge for the ultra-thin PSCs because of the interface reflection of traditional planar structure. In this study, a hierarchical pore structure with a confined resonant mode is introduced and optimized by electromagnetic theory to improve the solar energy absorbing and utilizing efficiency of ultra-thin PSCs. The large pores in the top layer that support a whispering gallery mode can focus and guide the incident light into the solar cell. The small pores in the bottom layer enable backward scattering of the unabsorbed light and can improve the effective absorption of active layer. The finite-difference time-domain method is employed to optimize the geometric parameters of hierarchical pore structure to improve the light absorption of PSCs. The proposed resonant hierarchical pore structure can greatly improve sunlight absorption of ultra-thin PSCs, and the effective light absorption and photocurrent of PSCs with a hierarchical pore structure is 20.7% higher than that of PSCs with traditional planar structure. This work can offer a beneficial guideline for improving solar energy utilizing efficiency of various thin-film solar cells.

Dissociation Constant of Di‐ and Tri‐Basic Solvents Based on Piperazine and Its Derivatives for Post‐Combustion CO2 Capture

AbstractAmine solvents remain popular in the industries for post combustion carbon dioxide (CO2) capture. Dissociation constant of basic amine solvents plays significant role to influence the CO2 absorption. It is thus important to study the dissociation of new amine solvents for assessing their viability for CO2 capture. In the present work, potentiometric titration method is employed to determine the dissociation constants of dibasic (e. g., Piperazine (PZ), 1‐methyl piperazine (1‐MPZ) and tribasic amines (1‐(2‐aminoethyl‐piperazine) (AEPZ) which could be promising for formulating blended solvent system towards enhancing the rate of CO2 absorption. The estimated dissociation constants for the PZ and 1‐MPZ while match well with reported results, the dissociation constants for AEPZ has been determined newly here within the temperature range 298—318 K. In addition, the structural geometric parameters and Natural Bond Order (NBO) calculations of the amine solvents are performed based on Density Functional Theory (DFT). The NBO calculations predict charge distribution on the nitrogen and other elements, and envisage its effect on the pKa values of the amines. Further, potential energy surface (PES) scanning calculations are performed for AEPZ to explain it's ring inversion which is responsible for obtaining a single pKa value in experimental studies.

Nanometer refractive index sensor based on water droplet cavity structure with rectangular short rod

In this paper, a novel nano sensor structure is proposed, which consists of a metal-insulator-metal waveguide (MIM) with rectangular baffles and a water droplet cavity with rectangular stubs (WDCRS). The WDCRS structure optimizes the sensitivity of a single water droplet cavity and makes the transmission curve clearer and smoother. The transmission characteristics of WDCRS structure were simulated using finite element method (FEM). The transmission characteristics of the exported structure were analyzed in detail. In addition, the influence of structural geometric parameters on sensing performance was also studied, and it was found that the size of the water droplet cavity is a key factor in improving sensitivity. When applied to a refractive index sensor, the structure achieves a sensitivity of up to 2,300 nm/RIU with a corresponding figure of merit (FOM) of 60.5. These works provide some ideas for the design of high-performance nanostructures and multiple Fano resonance excitation structures.

Synthesis and performance of a nanosensing platform for homocysteine detection: A series of iridium(III) complexes containing aldehyde group as probe and MOF as supporting substrate

The low cost and simple detection method for Hcy (homocysteine) is highly desired in analytical and biological fields since Hcy has been regarded as a bio-marker for multiple diseases. In this work, five Ir(C^N)2(N^N)+ compounds having –CHO group in their C^N or N^N ligand were synthesized and tried for Hcy sensing. Electron-donating groups such as –NH2 and –CH3 were incorporated into the C^N or N^N ligand. Their geometric structure, electronic structure, and optical parameters (with or without Hcy) were analyzed and compared carefully to explore their Hcy sensing potential. The sensing mechanism was revealed by NMR titration and theoretical simulation as a cyclization reaction between the –CHO group and Hcy. The optimal compounds, which showed increased emission quantum yield (2.5-fold) and emission blue-shift (by ∼ 100 nm) upon Hcy, were then covalently grafted into a porous host bio-MOF-1. Linear working plots were fitted, with good selectivity, LOD of 0.15 μM, and response time of 33 s. The novelty of this work was the eye-sensitive emission color change of this nanosensing platform from red (without Hcy) to green (with Hcy).

Comparative study of 4-((4-aminophenyl)diazenyl)-2-((2-phenylhydrazono)methyl)phenol and N-(4-((4-hydroxy-3-((2-phenylhydrazono)methyl)phenyl)diazenyl)phenyl)acetamide - DFT method

Theoretical calculation of 4-((4-aminophenyl)diazenyl)-2-((2-phenylhydrazono)methyl) phenol (1) and N-(4-((4-hydroxy-3-((2-phenylhydrazono)methyl)phenyl)diazenyl)phenyl) acetamide (2) was studied by DFT/B3LYP/6-311+G(d,p) basis set. The calculated values of geometric structural parameters, Fourier transform infrared spectral data, highest occupied molecular orbital and lowest unoccupied molecular orbital, natural bond orbital, nucleus-independent chemical shifts, Fukui function, polarizability, hyperpolarizability, and UV data of compounds 1 and 2 clearly indicate that substitution of the amino group alters the physical properties of compound 2. The nucleus-independent chemical shift values of the amino-substituted phenyl ring reduces the aromatic character due to the lone pair electron on nitrogen involved in inductive and conjunction effects, as well as due to OH, NH2 and OH, NHCOCH3 in compounds 1 and 2, respectively. The effect of the solvent on different parameters was studied, and it was found that increasing the dielectric constant increased the parameter studied. The stability and planarity of the molecule’s effects on dipole moment, energy, polarizability, and hyperpolarizability were studied extensively.

Operating Properties of Deep Hole Boring Tools with Modified Design.

This paper presents the results of research work on the revised design of a deep hole boring tool. The study was divided into three stages: theoretical, experimental and operational. In the theoretical part, a 3D model of the actual boring bar was created, which was subjected to strength tests using the Finite Element Method (FEM), and then prototypes of new deep hole boring tools were made with structural modifications to the shank part of the tool. For the polymer concrete core of a shank, there was a 14.59% lower displacement, and for the rubber-doped polymer concrete (SBR-styrene butadiene rubber) core of a shank there was a 4.84% lower displacement in comparison to the original boring bar. In the experimental part of the study, the original boring bar and the prototypes were subjected to experimental modal analysis and static analysis tests to compare dynamic and static properties. In the operational part of the study, boring tests were carried out for various workpiece materials, during which the basic parameters of the surface geometric structure (SGS), such as roughness Ra and Rz, were studied. Despite the promising preliminary results of the theoretical and experimental studies, using the described modifications to the boring bar is not recommended.

Structural optimization design of ice abrasive water jet nozzle based on multi-objective algorithm

To enhance the cleaning efficiency of the ice abrasive water jet (IAWJ), the nozzle in the jet structure was optimized. The cleaning effect of nozzle with different structural design is different. The design variables include the geometric parameters of the nozzle's structure and the flow process parameters of the jet. The maximum wall static pressure, outlet velocity and wash width are the optimization objectives. Based on the Optimal Latin Hypercube Sampling (OLHS) method, 50 sets of sample capacity were designed for simulation calculation. The parameter functions associated with the three objectives were fitted by MATLAB. The Competitive mechanism multi-objective particle swarm optimizer (CMOPSO) algorithm was used to optimize the nozzle to improve the cleaning effect, which was verified with the test results. The inlet pressure and outlet diameter are critical factors influencing the cleaning effect of the IAWJ. The maximum wall static pressure produced by the optimized nozzle is about 4.5% higher than that of the ordinary cosine nozzle. The cleaning effect of the optimized nozzle is 10% higher than that of the ordinary cosine nozzle, which is verified by the experiments. The optimization of the nozzle serves as a valuable reference for the nozzle structure design of the cleaning machine.

Multi-objective parameter optimization of the Z-type air-cooling system based on artificial neural network

The performance of electric vehicles is significantly influenced by the battery thermal management system (BTMS). In this article, the Z-type air cooling BTMS is studied, and a method combining an artificial neural network (ANN) model as a surrogate model with non-dominated sorting genetic algorithm II (NSGA-II) for multi-objective optimization is proposed to enhance the heat dissipation performance. The ANN model is trained by using 1529 sets of numerical simulation data of Z-type air cooling system, and the fast and high-precision prediction of heat dissipation performance is realized, which effectively avoids the repeated calculation of CFD. The design variables studied include geometric structure parameters and inlet wind speed (vinlet), and the target variables are maximum temperature (Tmax), temperature difference (ΔTmax) and pressure loss (ΔP). From the new perspective of genetic evolution process of NSGA-II, it is proved that the design of tapered inlet and outlet is better than that of flat and expansion outlet, the wide channel near the inlet and narrow channel near the outlet are more conducive to the improvement of heat dissipation performance. Further analysis shows that there is a linear relationship among vinlet, Tmax and ΔP in the Pareto solution set of Z-type air-cooling system, which simplifies the Pareto model effectively, and engineers can predict the optimal performance of BTMS by this relationship. In addition, through sensitivity analysis, it is found that in the Z-type BTMS, the operating parameter vinlet has the greatest influence on the heat dissipation performance and pressure loss, while the geometric parameters have less influence. Compared with the benchmark case, the optimized design scheme reduces Tmax, ΔTmax and ΔP by 1.97 K, 6.32 K and 2.82 Pa, respectively, which significantly improves the heat dissipation performance.

On the collapse stress of tubular enhanced anti-tetra-missing rib structure

In the contemporary landscape of engineering, escalating demands for advanced material and structural performance have brought metamaterials to the forefront. Among them, the enhanced anti-tetra-missing rib structure has gained prominence owing to its auxetic behavior under significant strain. However, the lack of research on its quasi-static and dynamic mechanical performance have hindered its practical application. To address this, we introduce the tubular enhanced anti-tetra-missing rib structure (TEATMRS) and derive its collapse stress expression under various conditions. Through extensive simulations and experiments, we explore its deformation mechanisms and assess the influence of the structural geometric parameters and impact velocity on collapse stress. The results demonstrate excellent agreement among theoretical description, numerical analysis, and experimental tests, establishing the feasibility of the proposed collapse stress expression. These findings provide a theoretical foundation and design guidance for TEATMRS in engineering applications.

Molecular structural, vibrational spectra, dual descriptor, electronic transition and biological evaluations of ethyl 4‑hydroxy-3-methoxycinnamate using density functional theory

Quantum chemical, spectroscopic and bioactivity studies of pharmacologically active Ethyl 4‑hydroxy 3‑methoxy ethyl cinnamate (EHMC) were investigated. By optimizing the geometric structural parameters, it was theoretically possible to obtain the FTIR &UV–Vis absorbance of the EHMC in both protic and aprotic solvents. PED values were computed, and vibrational assignments were identified. The TD-DFT approach and the IEFPCM model were used for simulating the UV spectra of the EHMC chemical. This study presents a comprehensive analysis of molecular parameters, including topological features of electron density, Reduced density gradient (RDG), NBO hyperconjugative interaction energies, frontier molecular energies (FMO) energies, and chemical reactivity descriptors across various solvents. MEP distinguishes between nucleophilic & electrophilic locations and determines a molecule's 3D charge distribution. Electrophilic and nucleophilic strength inside a molecule explained by Fukui function and Mullikan's charge. Furthermore, drug likeness and ADMET analysis were conducted to ascertain the biological characteristics and molecular docking investigation was also performed to explore the biological function of the title substance.

Predicting carbonate rock dissolution using multi-scale residual neural networks with prior knowledge

The factors that affect carbonate dissolution are complex, and it is crucial to acquire efficient and accurate knowledge of carbonate dissolution characteristics for CO2 capture and storage (CCS) projects. In current research, the most precise outcomes can be achieved through experimental or simulation techniques, but they are frequently computationally demanding and time-consuming. Data-driven machine learning methods can efficiently perform regression prediction tasks. In this paper, we propose a multi-scale hierarchical regression model for the dissolution problem based on residual neural networks, incorporating prior knowledge. We have developed new equations for carbonate rock dissolution and have incorporated the factors that influence this process into 3D image data by introducing Dissolution Degree (Dd) parameters. This allows the image data to include both the pore space structure and dissolution information with physical meaning. We utilize the pore phase and matrix phase grayscale thresholds (Pt, Mt) to eliminate voxel noise in the characteristic maps obtained from the model. This ensures that the predicted characteristics of carbonate rock dissolution are consistent with practical physics knowledge. We selected a total of 5 core samples to test the model. Among them, three samples are from the test set, and the additional two core samples selected have strong and weak correlations with the training set samples, respectively. The predictions were evaluated using semantic segmentation evaluation parameters, porosity, geometrical and topological structure parameters, Péclet and Damköhler numbers, porous media flow field simulations, and absolute permeability. The results of both visual comparisons and quantitative analyses demonstrated a high degree of consistency between predicted and experimental results, and the trained multi-scale hierarchical regression residual neural network with prior knowledge (MSR-Net) demonstrates good accuracy and generalization ability. The results of this study demonstrate that model based on MSR-Net can be utilized to predict the dissolution properties of the pore space in the formation where the core was extracted, along with the related formation.

Absorption spectrum of magnetically structured emulsions in the centimeter range

The high degree of absorption of microwave radiation by composite materials with developed morphology can be significantly improved by directly changing the geometrical parameters of the subwavelength structure, which is difficult in the case of solid-state materials. In this work, a new composite liquid material with controlled absorption properties, a magnetodielectric emulsion, is investigated. The control of microgeometry parameters is accomplished through exposure to a magnetic field. The experimental studies have shown that the formation of chain structures from spherical water droplets in the composite leads to a significant change in the absorption coefficient. Thus, for an emulsion with 10% water content, exposure to a magnetic field of 25 kA m−1 increases the absorption coefficient by 400% at a radiation frequency of 10 GHz. It is noteworthy that the efficiency of the absorption properties control depends on the volume concentration of droplets in the sample and has a non-monotonic character. To interpret the obtained results, numerical modeling of the studied system in the effective medium approximation was carried out.

Significant nuclear quantum effect of proton in the reaction of phenol and hydroxyl radical

The reaction between phenol and hydroxyl radical, leading to the formation of phenoxy radicals, is analyzed using DFT calculations at the multi-component M06-2X level that accounts for the nuclear quantum effects (NQEs) of hydrogen nuclei. The NQEs affect not only the relative energy diagram of the reaction but also the geometric parameters of the stationary point structures. In the energy minimum structures, the OH covalent bonds have lengthened, while the OH…O hydrogen bonds have shortened due to the NQEs. Furthermore, the NQEs also affect the transition state structure, where the distance between carbon and oxygen atoms is strongly influenced by the NQEs of hydrogen nuclei through a hydrogen bond network formed by surrounding water molecules. Different NQEs of hydrogen nuclei have been observed in the ipso/ortho and the para stepwise reaction pathways due to differences in the driving force of the reaction.

A new cutting tool filled with metallic lattice and design method for vibration suppression in milling

Enhancing the vibration suppression performance of cutting tools is crucial for achieving high-performance cutting of difficult-to-machine materials. This paper presents a novel cutting tool as well as its design method for vibration suppression in milling process. By incorporating a high-damping lattice structure into the cutting tool, the dynamic stiffness of the spindle-holder-tool system can be effectively increased based on the dynamic absorber effect. To achieve this goal, the natural frequency of the cutting tool filled with metallic lattice is tuned with the spindle-holder subassembly by altering the geometric parameters of the metallic lattice. A comprehensive dynamic model of the spindle-holder-tool system, considering the complex tool geometries, is developed to accurately analyze this system’s behavior and a design procedure is proposed to optimize the cutting tool. The geometric parameters of the lattice structure in the cutting tool are optimized based on the dynamic model, while the cell type of the high-damping lattice is selected by experiments. The proposed cutting tool is additively manufactured using the selective laser melting technique, and a comparison is made with a conventional indexable cutting tool with a solid tool body. Both simulations and impact hammer tests demonstrate an increase of 18.3% in the dynamic stiffness of the proposed cutting tool filled with metallic lattice compared with the conventional indexable cutting tool. Furthermore, a large number of milling tests are carried out on titanium alloy Ti-6Al-4V to validate the vibration suppression performance of the cutting tool filled with metallic lattice. Experimental results show that the stability limit corresponding to the proposed cutting tool can be doubled compared with the conventional indexable cutting tool.

A MEMS Electrochemical Angular Accelerometer with Silicon-Based Four-Electrode Structure.

This paper presents a MEMS electrochemical angular accelerometer with a silicon-based four-electrode structure, which was made of thousands of interconnected microchannels for electrolyte flow, anodes uniformly coated on structure surfaces and cathodes located on the sidewalls of flow holes. From the perspective of device fabrication, in this study, the previously reported multi-piece assembly was simplified into single-piece integrative manufacturing, effectively addressing the problems of complex assembly and manual alignment. From the perspective of the sensitive structure, in this study, the silicon-based four-electrode structure featuring with complete insulation layers between anodes and cathodes can enable fast electrochemical reactions with improved sensitivities. Numerical simulations were conducted to optimize the geometrical parameters of the silicon-based four-electrode structure, where increases in fluid resistance and cathode area were found to expand working bandwidths and improve device sensitivity, respectively. Then, the silicon-based four-electrode structure was fabricated by conventional MEMS processes, mainly composed of wafer-level bonding and wafer-level etching. As to device characterization, the MEMS electrochemical angular accelerometer with the silicon-based four-electrode structure exhibited a maximum sensitivity of 1458 V/(rad/s2) at 0.01 Hz and a minimum noise level of -164 dB at 1 Hz. Compared with previously reported electrochemical angular accelerometers, the angular accelerometer developed in this study offered higher sensitivities and lower noise levels, indicating strong potential for applications in the field of rotational seismology.