Equivalent Density Research Articles

An Optimal Design Method for Lightweight Heating Film of Anisotropic Heat Conduction Substrate Based on Surrogate Model.

In space missions, heating films are crucial for uniformly heating onboard equipment for precise temperature control. This study develops an optimization method using surrogate models for lightweight anisotropic substrate thermal conductive heating films, meeting the requirements of uniform heating in thermal control for space applications. A feedforward neural network optimized by particle swarm optimization (PSO) was employed to create a surrogate model, mapping design parameters to the temperature uniformity of the heating film. This model served as the basis for applying the NSGA-II algorithm to quickly optimize both temperature uniformity and lightweight characteristics. In this study, the PSO-BP surrogate model was trained using heating film thermal simulation data, and the surrogate model demonstrated an accurate prediction of the mean square error (MSE) of the predicted temperature difference within 0.0168 s. The maximum temperature difference in the optimal model is 1.188 ℃, which is 30.5 times lower than before optimization, and the equivalent density is only increased by 3.9%. In summary, this optimization design method effectively captures the relationships among various parameters and optimization objectives. Its superior computational accuracy and design efficiency offer significant advantages in the design of devices such as heating films.

Modal analysis of taipei 101 building

In this paper, a multi-stage modeling and simulation approach incorporating different deformation conditions is used to analyze the structure of the Taipei 101 building. The modeling process mainly involves the formation of an initial simplified model based on the basic geometry, the determination of an accurate model based on the actual dimensions, and finally the introduction of a hollow structure design to mimic the density and mass distribution of the real building. After the model is established, mesh creation and mesh independence study are carried out. The simulation is carried out using Ansys software, which mainly performs the process of selecting boundary conditions, determining the equivalent density, dividing the mesh for modal analysis, and obtaining the modal vibration pattern as well as the corresponding intrinsic frequency. By analyzing the intrinsic frequencies and vibration modes, the structure of Taipei 101 Building is prone to resonance under certain circumstances, and this study provides some significance to the geology of local seismic activities.

Stability of influenza A virus in droplets and aerosols is heightened by the presence of commensal respiratory bacteria.

Aerosol transmission remains a major challenge for control of respiratory viruses, particularly those causing recurrent epidemics, like influenza A virus (IAV). These viruses are rarely expelled alone, but instead are embedded in a consortium of microorganisms that populate the respiratory tract. The impact of microbial communities and inter-pathogen interactions upon stability of transmitted viruses is well-characterized for enteric pathogens, but is under-studied in the respiratory niche. Here, we assessed whether the presence of five different species of commensal respiratory bacteria could influence the persistence of IAV within phosphate-buffered saline and artificial saliva droplets deposited on surfaces at typical indoor air humidity, and within airborne aerosol particles. In droplets, presence of individual species or a mixed bacterial community resulted in 10- to 100-fold more infectious IAV remaining after 1 h, due to bacterial-mediated flattening of drying droplets and early efflorescence. Even when no efflorescence occurred at high humidity or the bacteria-induced changes in droplet morphology were abolished by aerosolization instead of deposition on a well plate, the bacteria remained protective. Staphylococcus aureus and Streptococcus pneumoniae were the most stabilizing compared to other commensals at equivalent density, indicating the composition of an individual's respiratory microbiota is a previously unconsidered factor influencing expelled virus persistence.IMPORTANCEIt is known that respiratory infections such as coronavirus disease 2019 and influenza are transmitted by release of virus-containing aerosols and larger droplets by an infected host. The survival time of viruses expelled into the environment can vary depending on temperature, room air humidity, UV exposure, air composition, and suspending fluid. However, few studies consider the fact that respiratory viruses are not alone in the respiratory tract-we are constantly colonized by a plethora of bacteria in our noses, mouth, and lower respiratory system. In the gut, enteric viruses are known to be stabilized against inactivation and environmental decay by gut bacteria. Despite the presence of a similarly complex bacterial microbiota in the respiratory tract, few studies have investigated whether viral stabilization could occur in this niche. Here, we address this question by investigating influenza A virus stabilization by a range of commensal bacteria in systems representing respiratory aerosols and droplets.

Core Hole Effect to Valence Excitations: Tracking and Visualizing the Same Excitation in XPS Shake-Up Satellites and UV Absorption Spectra.

Introducing a core hole significantly alters the electronic structure of a molecule, and various X-ray spectroscopy techniques are available for probing the valence electronic structure in the presence of a core hole. In this study, we visually demonstrate the influence of a core hole on valence excitations by computing the ultraviolet absorption spectra and the shake-up satellites in X-ray photoelectron spectra for pyrrole, furan, and thiophene, as complemented by the natural transition orbital (NTO) analysis over transitions with and without a core hole. Employing equivalent core hole time-dependent density functional theory (ECH-TDDFT) and TDDFT methods, we achieved balanced accuracy in both spectra for reliable comparative analysis. We tracked the same involved valence transition in both spectra, offering a vivid illustration of the core hole effect via the change in corresponding particle NTOs introduced by a 1s core hole on a Cα, Cβ, or O atom. Our analysis deepens the understanding of the core hole effect on valence transitions, a phenomenon ubiquitously observed in general X-ray spectroscopic analyses.

Spark plasma sintering of silicon(oxy-)nitride/boron nitride composites and their subsequent thermo-physical properties

Silicon nitride and boron nitride (Si3N4/h-BN) based ceramic composites were prepared by Spark Plasma Sintering (SPS) using aluminium oxide (Al2O3) and/or yttrium oxide (Y2O3) as sintering additives. The amount of h-BN introduced varied from 0 vol.% to 20 vol.% in order to study its influence on ceramic properties. In the same way, the amount of oxide additives has been controlled and the influence of the additive's nature on the final properties has been underlined. The sintering temperature has been selected in order to obtain equivalent relative densities. The formation of β-SiAlON has been underlined by XRD and TEM analysis. Moreover, due to the fast-sintering process, amorphous secondary phase has been formed. Mechanical properties (hardness, fracture toughness, Young modulus) and thermal diffusivity have been evaluated. It appears that the nature of the oxide additive used plays an important role on the mechanical and thermal behaviour of Si3N4/h-BN composites.

Simultaneous thermal camouflage and radiative cooling for ultrahigh-temperature objects using inversely designed hierarchical metamaterial

Abstract Sophisticated infrared detection technology, operating through atmospheric transmission windows (usually between 3 and 5 μm and 8–13 μm), can detect an object by capturing its emitted thermal radiation, posing a threat to the survival of targeted objects. As per Wien’s displacement law, the shift of peak wavelength towards shorter wavelengths as blackbody temperature rises, underscores the significance of the 3–5 μm range for ultra-high temperature objects (e.g., at 400 °C), emphasizing the crucial need to control this radiation for the objects’ viability. Additionally, effective heat management is essential for ensuring the consistent operation of these ultrahot entities. In this study, based on a database with high-temperature resist materials, we introduced a material-informatics-based framework aimed at achieving the inverse design of simultaneous thermal camouflage (low emittance in the 3–5 μm range) and radiative cooling (high emittance in the non-atmospheric window 5–8 μm range) tailored for ultrahigh-temperature objects. Utilizing the transfer matrix method to calculate spectral properties and employing the particle swarm optimization algorithm, two optimized multilayer structures with desired spectral characteristics are obtained. The resulted structures demonstrate effective infrared camouflage at temperatures up to 250 °C and 500 °C, achieving reductions of 86.7 % and 63.7 % in the infrared signal, respectively. At equivalent heating power densities applied to the structure and aluminum, structure 1 demonstrates a temperature reduction of 29.4 °C at 0.75 W/cm2, while structure 2 attains a temperature reduction of 57.5 °C at 1.50 W/cm2 compared to aluminum, showcasing enhanced radiative cooling effects. This approach paves the way for attenuating infrared signals from ultrahigh-temperature objects and effectively managing their thermal conditions.

RESEARCH SOLUTIONS FOR PRECAST CONCRETE REVETMENTS USING ALB-REBAR TO RETAIN CORAL SAND FOR OFFSHORE ISLANDS IN VIETNAM

Gravity revetment solutions are a popular choice for shore protection at atolls under the harsh conditions of ocean waves. The precast revetment option is preferred to reduce shipping costs for materials and ensure quick construction. This article studied precast concrete revetments with ALB composite material reinforcement and conducted experimental research to determine the shear resistance characteristics of coral sand and the friction characteristics of concrete materials with coral sand. Based on the experimental parameters, the authors calculated the stability of the ALB embankment structure against the effects of wave loads during storms. With experimental data obtained from coral sand samples prepared with equivalent density in the field, the results showed that the stability coefficient of the revetment is significantly higher than the one obtained from the traditional calculation concept.

Ti–6Al–4V hybrid-strut lattice metamaterials: A design strategy for improved performance

Metal hollow-strut lattices manipulate the strut and node sections to achieve higher strength. Although these metamaterials have recently surpassed the structural efficiency of conventional solid-strut lattices of comparable density and topology, they often observe localised yielding and fragmentation through the nodes that limit their structural efficiency. To quantify the effect of this localised failure and to develop mitigating strategies, we have integrated solid and hollow strut and node sections in singular Ti–6Al–4V simple cubic hybrid-strut lattices for a deployable relative density range of 15–30%. Fabricated through laser powder bed fusion these hybrid-strut lattices are stronger (32%), stiffer (15%), and tougher (65%) than solid-strut lattices of equivalent density. Interestingly, the metamaterials with hollow beams can transition from a bending-dominated to a stretch-dominated deformation response with increasing density, while the lattices with solid beams only observed a uniformly stretch-dominated deformation response. The combination of solid and hollow strut and node sections in the hybrid-strut lattice establishes a simple yet effective strategy to enhance structural efficiency and control of failure response without increasing density or manipulating unit cell topology.

3D printed carbon fiber reinforced carbon as an energy efficient alternative to graphite for EFAS tooling

As Electric Field Assisted Sintering (EFAS) gains more industrial acceptance and use, it becomes more important to develop more efficient means to implement this technology. To this aim, 3D printed continuous carbon fiber reinforced carbon (CCC) was manufactured and fabricated into tooling for EFAS systems as an alternative to traditional graphite tooling. The impact of fiber orientation on the thermal and electrical properties of the CCC was characterized. Sample material was sintered in Tokai G535 graphite tooling, under common processing conditions and compared with CCC tooling. There was nearly 50 % energy savings compared to graphite while maintaining equivalent sample density and microstructure plus keeping ram temperatures 39 % cooler. This is due to spatial control of generated heat and thermal diffusivity within the molds, by means of fiber orientation anisotropy. Finite element modeling of the tooling design supported the experimental results as well as displays the effect of optimization of this 3D printed CCC material.

Surrogate-based multi-objective design optimization of tree-shaped fins with uniform branch end distribution for latent heat thermal energy storage

The enhancement of latent heat thermal energy storage (LHTES) systems through fin geometry optimization remains a critical challenge for leveraging the full potential of renewable energy sources. This study focuses on optimizing the geometries of tree-shaped fins to enhance power and energy densities in LHTES systems. The goal is to find branch designs with high energy and power density through a novel surrogate model-based optimization strategy that explores a broad design space. The surrogate models applied, including linear regression, principal component analysis-based linear regression, artificial neural networks, and random forest, are evaluated for their predictive performance. The random forest model demonstrates superior accuracy in predicting targets. The optimization process results in a Pareto-optimal design with a volume fraction of 33.9%. This optimal design substantially enhances the system's power density by 61.6% compared to conventional plate fins at an equivalent energy density. This optimized design improves energy and power density, achieving a uniform end-to-branch distribution, which is a pivotal factor for consistent temperature distribution and improved thermal efficiency. By integrating surrogate-based optimization with broad ranges of the tree-shaped fin design, this research has significantly improved the operational efficiency of LHTES systems. This research promises more effective thermal management and provides a methodological framework for design innovation in thermal energy storage.

Strain-Induced Electromagnetic Transmission Modulation via a Reconfigurable Kirigami Metasurface

Tunable three-dimensional (3D) electromagnetic (EM) metasurfaces are critical for dynamic modulation of EM responses but their construction and tuning mechanism are still complex. Here, we report a simple yet effective 3D reconfigurable EM metasurface, which was obtained from a planar kirigami polyimide substrate printed with periodically arranged copper split-ring resonator. Under mechanical stretch, the two-dimensional (2D) planar metasurface can be uniformly deformed into a 3D state, which is effective for tuning its EM transmission characteristic. By combining mechanics and EM simulations as well as experimental measurements, we revealed the deformation mode and active EM transmission modulation capability of the metasurface. It is shown that at the initial state, the planar kirigami metasurface exhibits ideal frequency selective transmission to transverse electric (TE) wave but allows for complete transmission for transverse magnetic (TM) wave. As the applied strain increases from 0% to 20%, the transmission was adjusted from −17.74[Formula: see text]dB to −9.74[Formula: see text]dB for TE wave but merely from 0[Formula: see text]dB to −3.25[Formula: see text]dB for TM wave. Meanwhile, the resonant frequency experienced a visible shift for both TE and TM waves. Finally, the equivalent circuit analysis and simulated surface current density were conducted to reveal the tuning mechanism of the proposed metasurface.

Numerical simulation of ultrasonic P-wave propagation in water-bearing coal based on gas-liquid homogeneous wave velocity model

This paper establishes the equivalent density and equivalent P-wave velocity models of coal bodies with different water saturation, and investigates the P-wave propagation evolution law of coal bodies with different water saturation from the perspective of numerical simulation. When the experimental coal samples continue to use high-pressure water after reaching the natural saturation state, the water saturation can be further increased, and the increase in water saturation is larger, and the corresponding P-wave velocity also appears to be increased more substantially, and this phenomenon also occurs in numerical simulation results, which indicates that the P-wave velocity will have an obvious increasing trend when the coal body is from nearly saturated to fully saturated. The experimental and numerical simulation results show that the P-wave velocity of coal samples increases with the water saturation degree in a similar exponential function, which further verifies the reasonableness and feasibility of the modelling based on the assumption of gas-liquid homogeneous medium. In addition, the propagation of P-wave in coal samples is affected by the pore and fracture structure, and the pore and fracture with small pore size has less influence on the P-wave, and vice versa.

Micro-Groove Optimisation of High-Speed Inner Ring Micro-Grooved Pumping Seal for New Energy Electric Vehicles

Traditional oil seals are insufficient for the high-speed and bi-directional rotation of new energy electric vehicles. Therefore, we developed a Python program focusing on micro-groove pump seals and examined the unexplored non-contact oil–air biphasic internal end-face seals. Real gas effects were described using the virial and Lucas equations. We introduced an oil–air ratio to determine the equivalent density and viscosity of the two-phase fluid in the seal. Furthermore, we solved the compressible steady-state Reynolds equation using the finite difference method. Analysing the seal’s pumping mechanisms and the effects of operating parameters on sealing performance, we assessed 17 types of hydrodynamic grooves. The results demonstrate that inverse fir tree-like grooves perform well under typical sealing conditions. Under the conditions given in this study, the pumping rate of the optimal groove type compared to other groove types even reached 633.54%. In the oil–air biphasic state, the micro-groove pump seal exerts significant dynamic pressure on the sealing surface. Seal opening force increases with rotational velocity, oil–air ratio, and inlet pressure but decreases with temperature. The pumping rate first increases and then decreases with rotational velocity, increases with oil–air ratio and temperature, and then decreases with inlet pressure. Some special working points require consideration in sealing design. Our results provide insights into designing micro-grooved pumping seals for new energy electric vehicles.

Enhancing the energy absorption capability of auxetic metamaterials through auxetic cells within re-entrant circular units

Re-entrant circular (REC) auxetic metamaterials have garnered significant attention in structural engineering due to their enhanced energy absorption capability and reduced stress concentration compared to traditional re-entrant auxetic configurations. However, there is considerable potential for further enhancing their design to achieve even greater energy absorption capabilities. This study introduces three novel REC auxetic structures (REC-S, REC-Star and REC-Flower) specifically designed to enhance energy absorption capabilities compared to traditional REC configurations. These structures are formed by deploying an S-shaped, a star, and a newly designed auxetic unit-cell (UC) named Flower into the REC framework and fabricated through 3D printing by using fused deposition modeling (FDM) techniques. Their deformation behavior and mechanical performance are assessed through quasi-static compressive experimental tests and finite element analysis (FEA), with good agreement obtained between the two sets of results. Based on the validated FEA, the effects of the geometrical parameters of the structures on specific stiffness (Es), specific energy absorption (SEA), and Poisson's ratio are further investigated. The results show that the newly designed structures outperform the traditional REC structure with equivalent relative densities (∆ρ) and the REC-Flower has the highest SEA for all relative densities, positioning it as a promising candidate for the next generation of REC structures.

Impact of CT tube voltage variation on calculated dose radiotherapy: A simulation and phantom study

BackgroundAdvanced radiotherapy techniques necessitate the use of precise treatment planning systems (TPSs) that account for tissue density differences. Modern TPSs require electron density to be defined for every tissue type and that is usually provided from computed tomographic images. ObjectiveChanging the tube voltage used during CT acquisition can affect the CT number which consequently changes the derivation of tissue electron densities. This study measures the radio-therapeutic dose deviation caused by such variations. MethodsA phantom with different tissue equivalent densities of material plugs is used in the study. We investigated the tube voltage influence on the dose attenuation coefficients percent (DACP) and equivalent path length (EPL) within the tissue phantom plugs. Monte Carlo was used to explore the influence of the tube voltage used in imaging on the dose distributions in a pelvic phantom. ResultsOur calculations show that the attenuation percentage in each phantom plug was highest in high-density materials. The maximum difference was 3.5% when comparing the attenuation percentage of 80 KV to 140 KV, while field size had no significant impact. Our simulation of a pelvic case revealed that switching from 140 KV to 80 KV could result in a 3% difference in a patient plan. However, it is highly dependent on the proximity to high-density materials. The study demonstrated that 140 KV images yield a much closer match between measured and theoretical equivalent path lengths compared to 80 KV images in high-density materials. ConclusionsCT tube voltage variation has an impact on the dose calculations especially for high-density structures. The CT voltage variations influence can be small in most cases, but care should be taken in high dense bone situations especially in the vicinity of critical structures.

Intelligently optimized arch-honeycomb metamaterial with superior bandgap and impact mitigation capacity

Engineering applications concurrently face challenges related to vibration, impact, load-bearing and energy absorption. Here, an arch-honeycomb metamaterial with split-ring resonators is proposed for wave attenuation and impact mitigation, with better energy absorption and lower initial peak stress. The split-ring resonators effectively induce bandgaps below 3 kHz, and the mechanisms of bandgap generation and polarization are studied through mode shapes, frequency contours and equivalent mass densities. Subsequently, a machine learning-based optimization framework is introduced to tailor the bandgaps, leading to a 155.59% increase in bandgap width. Furthermore, superior vibration isolation and impact mitigation are confirmed through experiments. Obvious attenuation peaks are observed in the bandgaps of the acceleration transmission spectrum in frequency domain. In time domain, the impact test demonstrates peak weakening and delay. The metamaterials offer advantages in wave attenuation, impact mitigation, load-bearing and energy absorption, providing valuable insights for the advancement of multifunctional metamaterials and their practical engineering applications.

Analyses of non-clean surface compressor blade cascades’ aerodynamic performance deterioration

Abstract The efficiency and dependability of the engine are directly impacted by the compressor’s performance, which is a crucial part of gas turbines. The blade cascade is significantly influenced by surface roughness in terms of flow characteristics and aerodynamic performance. In this study, the NACA65-410 airfoil is selected as the research object to investigate the variations in blade cascade performance and flow characteristics under different inflow and roughness conditions. The results show that the smooth surface blade cascade performs optimally when the Reynolds number increases from 120,000 to 200,000. As the angle of attack increases from -5° to 8°, the blade cascade performance deteriorates, and the degree of performance degradation increases with the increase in angle of attack. For the roughened blade cascade surface, the performance initially improves and then decreases as the equivalent sand grain density increases, and there exists a critical equivalent sand grain density that maximizes the blade cascade performance. When the Reynolds number is 120,000, the critical equivalent sand grain density is 225 μm, and when the Reynolds number is 160,000, the critical equivalent sand grain density is 111 μm. Based on the findings of this study, the degradation pattern of blade cascade performance can be predicted, and it can be utilized to enhance the overall performance of the compressor.

Comparison of analytical and numerical methods for estimating notch strains**

AbstractIn fatigue assessments, local strains and stresses can be easily evaluated using accurate finite element analysis in a case of an individual fatigue‐critical notch or structural detail. In practical design and analysis of global models, the consideration of local notch effects using suitable estimation rules in the combination with linear elastic analysis is reasonable. Various notch rules exist but the current knowledge lacks understanding how applicable different notch rules are for estimating notch strains from elastic stresses. This work studies the Neuber′s rules for sharp and mild notches, Glinka′s equivalent strain energy density method, the correction of Neuber′s rule proposed by Sonsino for mild notches, as well as the Seeger‐Beste method. The application of different estimation rules for notch strains, applied to the elastic‐perfectly plastic steel material and to Ramberg‐Osgood material model for the aluminum material, including work hardening effect, was studied in this work by comparing the estimations with the corresponding experimental data and finite element analysis results. The Neuber′s rule for mild notches and Sonsino′s averaging method gave best correlations with the experimental data and numerical (finite element analysis) results and can be thus recommended for such analyses in compatible cases studied in this work.

Equivalent power densities model for multi-pulse ultrashort pulsed laser processing

Equivalent power densities model for multi-pulse ultrashort pulsed laser processing

Stabilization of Morphotropic Phase Boundary in Hafnia via Microwave Low‐Temperature Crystallization Process for Next‐Generation Dynamic Random Access Memory Technology

The morphotropic phase boundary (MPB), which arises from the combination of antiferroelectric and ferroelectric phases, demonstrates the highest dielectric constant (κ) compared to other phases. This emphasizes its potential as a leading contender for dielectric films in future dynamic random access memory (DRAM) capacitors. MPB‐based high‐κ materials using hafnia have shown a trade‐off between equivalent oxide thickness (EOT) and leakage current density (Jleak) when the crystallization temperature increases with scaling the thickness. Herein, a microwave annealing (MWA) method that can achieve low‐temperature crystallization below 350 °C is employed. The purpose of this method is to mitigate the trade‐off relationships and achieve the strict criteria of current DRAM capacitors. These criteria include low EOT (less than 4 Å) and Jleak (less than 10−7 A cm−2 at 0.8 V) characteristics. The MWA is capable of relatively low‐temperature annealing by supplying energy to the films through both thermal energy and dipole vibration energy. As a result, a record‐low EOT of 3.76 Å and a low leakage current characteristic of 4.2 × 10−8 A cm−2 at 0.8 V are achieved concurrently. It is confident that the research can be important in addressing the challenges associated with reducing the size of next‐generation DRAM capacitors.