Geometric Ratio Research Articles

Study on Coal Seam Roof Failure Based on Optical Fiber Acoustic Sensing and the Parallel Electrical Method

As China enters the stage of deep coal mining, the accidents caused by roof failure pose increasingly serious threats. Current research on roof failure zones often use single methods, but single geophysical data may result in multisolution issues during interpretation. This paper employed similar simulation experiments, exploring the strain failure characteristics and the changes in apparent resistivity caused by stress variations, taking the 11-3106 working face of a mining area as the research object. Through optical fiber strain and apparent resistivity, the locations and degrees of fracture in postmining rock strata were identified. The feasibility of using distributed optical fiber sensing and the parallel electrical method for qualitative and quantitative analysis of mining-induced fractures was verified. The results showed that optical fiber strain increased significantly at the location of rock fracture, with apparent resistivity anomalies rising correspondingly. The peak strain region corresponded well with the region of apparent resistivity anomalies. In a similar simulation with a geometric ratio of 1:100, the height of the caving zone was measured to be 31.65 cm, with a caving-to-mining ratio of 6.33. In the field working face, the caving zone height was 29.47 m, with a caving-to-mining ratio of 6.01, consistent with the actual conditions of the 11-3106 working face.

Influence of submerged impingement jet designs on solar air collector performance

The present study experimentally investigates the solar air heater performance employing submerged impinging jets (SAHSIJ). The submerged jets produce high flow velocities, leading to significant turbulence aided by shear forces at the heated surface, resulting in increased and evenly distributed heat removal rates. The study explores the impact of geometric parameters viz jet spacing ratio (Sj/Dh) from 0.108 to 0.433, jet angles (α) from 75° to 90° jet diameter ratio (d/Dh) from 0.043 to 0.076, span-wise pitch ratio (Y/Dh) from 0.43 to 1.08 and stream wise pitch (X/Dh) from 0.43 to 1.73 on the Nusselt number and friction performance to enhance the overall efficacy of the system. To evaluate the effectiveness of the new SAHSIJ design in terms of thermal and thermo-hydraulic performance, the results are compared with those from a smooth duct solar air heater. The results show that the novel solar air heater with submerged pipe jet significantly outperforms the smooth duct solar air heater in terms of heat removal from the absorber plate. SAHSIJ achieved a thermal efficiency (ηth) of 75.3 % and a thermo-hydraulic efficiency (ηeff) of 69.2 %, with a thermo-hydraulic performance parameter (η) of 3.19.

Modified Easley formula for elastic critical global shear buckling stress of corrugated steel webs considering real boundary conditions

The real juncture between corrugated steel webs (CSWs) and flanges follows a multi-segmented line, distinct from that of flat steel webs. Classic methods may yield significant deviations in predicting the elastic global shear buckling capacity of CSWs of various scales due to their failure to consider real boundary constraints. Therefore, a universally applicable formula for calculating the elastic critical global shear buckling stress of CSWs, which accounts for real boundary conditions, is proposed. This formula is pertinent to both large-scale engineering CSWs and small-scale testing CSWs. This study commenced with a comprehensive reassessment of the elastic global shear buckling calculation method. Subsequently, the influence of geometric parameter ratios on the elastic critical global buckling stress was examined. The primary parameter was identified and employed to improve the global buckling coefficient. The proposed calculation method was validated using different corrugation configurations, including 1000-type, 1200-type, 1600-type, 1800-type, and 2000-type CSWs, as well as other CSWs used in experimental settings. These results were compared with those obtained from other reference methods. Findings indicate that the accuracy of the classic theoretical method is affected by variations in both boundary conditions and geometric dimensions due to the constraint effect of real boundary conditions. Under the real boundary conditions, the elastic critical global shear buckling stress of CSWs with simply supported boundary conditions is close to that of CSWs with consolidated boundary conditions. The ratio of web height to corrugation depth primarily affects the elastic global shear buckling capacity, which decreases as the ratio increases. The Easley formula can be modified based on the web height to corrugation depth ratio. Comparisons of numerous numerical and theoretical results reveal that the proposed calculation method exhibits commendable computational precision. In comparison to alternative formulas, the proposed method demonstrates enhanced consistency for calculating CSWs with varying geometric dimensions and boundary conditions, thereby demonstrating its favorable applicability. These conclusions provide valuable reference for the shear design of CSWs.

Advanced optimization of elastic sheets for solar parabolic trough concentrators: integrating particle swarm optimization and genetic algorithms

Abstract The fabrication of solar parabolic trough concentrators using flat elastic sheets presents a straightforward and cost-effective method. This paper introduces an optimization technique centered on stiffness adjustment, harnessing elastic buckling to attain precise parabolic shapes in these concentrators. Through an enhanced Particle Swarm Optimization-Genetic Algorithm (PSO-GA), strategically punched holes are optimized on the flat sheet, allowing for the attainment of perfect parabolic shapes by controlling the chord length with a positional rod or cable. The efficacy of this approach is showcased not only through interactive finite element analysis and ray tracing software simulations but also via experimental sunlight concentration. A geometric concentration ratio of up to 145.16 is achieved, underscoring the effectiveness of this innovative concept. This approach facilitates the simple fabrication and transportation of flat mirror elements to field sites, where they can be assembled into parabolic trough concentrators, offering potential cost reductions and highly efficient solar energy solutions.

Design of a thermoelectric cooler to control the temperature of telecom outdoor cabinet

This paper discusses the design of a thermoelectric cooler (TEC) system for controlling the temperature of telecom outdoor cabins. Traditional cooling methods, such as refrigerants, have potential negative impacts on the environment, making thermoelectric cooling systems a promising alternative due to their efficiency, environmental friendliness, and versatility. The paper reviews the current state of the art in designing thermoelectric cooler systems for absorbing heat generated from telecom electronic devices. The literature review highlights studies that have evaluated the cooling performance, energy efficiency, and cost-effectiveness of thermoelectric cooling systems for telecom electronic devices. The objective of this project is to design a TEC system that can absorb the heat generated from telecommunication cabinets. The design is generated analytically using the TE ideal equation with a heat sink or heat exchanger system. The design aims to investigate the optimum current and geometric ratio that can improve the cooling capacity of the TEC system. The paper also presents a modeling approach for thermoelectric coolers with two heat sinks. The study concludes that thermoelectric cooling systems have the potential to provide efficient and environmentally friendly cooling solutions for telecom electronic devices, and future studies should continue to investigate and optimize the design of thermoelectric cooling systems for various types of telecom electronic devices.

Study on seismic response characteristics of living stumps slope based on large-scale shaking table test

A large-scale shaking table test of a living stump slope with a geometric similarity ratio of 1:7 was designed and completed. The peak acceleration, acceleration amplification factor, and displacement response patterns of living stumps slopes under different types of seismic waves and excitation intensities were obtained. The time-frequency and energy variation characteristics were analyzed using the Hilbert-Huang Transform (HHT). The results showed that: (1) Regardless of the type of seismic wave, the peak acceleration and acceleration amplification factor of the living stumps slope surface are positively correlated with relative height and seismic excitation intensity. When the excitation intensity is ≤ 0.4 g, the acceleration amplification effect is more pronounced; when the excitation intensity is > 0.4 g, the acceleration amplification effect weakens. (2) Under the action of different seismic waves, the peak displacement of slope surface shows amplification effect along the elevation, and increases with the increase of excitation intensity. In addition, the incremental displacement gradually decreases from the toe to the top of the slope, which is expressed as D2 > D3 > D1 > D4 > D5. The peak displacement at the top of the slope is the greatest, but the incremental displacement is the smallest; the peak displacement at the toe of the slope is the smallest, but the incremental displacement is relatively large. (3) Regardless of the type of seismic wave, living stumps slope shows the characteristics of filtering the low-frequency components of the seismic waves and amplifying their high-frequency components. At the same time, the seismic Hilbert energy gradually accumulates along the elevation. PSHEA and PMSA significantly increase with elevation and excitation intensity, and they reach the maximum at the top of the slope. (4) The seismic Hilbert energy is positively correlated with the relative height and excitation intensity, and reaches the maximum at the top of the slope. With the accumulation of seismic Hilbert energy increases, the dynamic response parameters such as peak acceleration, acceleration amplification coefficient and displacement also increase synchronously, reaching the maximum at the top of the slope. The research conclusions can provide an experimental basis for the seismic design of living stumps slopes.

Free vibrations and dynamic behavior of the three layered flexoelectric functionally graded microbeam under moving load

In this study, free vibrations and the dynamic responses of the three layered flexoelectric functionally graded microbeam under the effect of moving load are investigated. Using the first order shear deformation and the size-dependent piezoelectricity theories in the framework of Hamilton's principle, the governing equations of motion and the corresponding classical and non-classical boundary conditions are obtained. Next, the equations of motion were discretized and solved using the finite element method. In order to validate the governing equations and the solution method, the obtained results have been compared with the results of previous studies, which shows a good convergence between the current and previous results. The obtained results demonstrate the dynamic behavior of the microbeam is strongly influenced by the geometrical ratios, the flexoelectric layers thickness, the functionally graded power index, the flexoelectric coefficient and the load velocity. So that the escalation in the strain gradient from the augmentation of the flexoelectric layers' thickness leads to a corresponding rise in the electric potential function. Moreover, as the flexoelectric coefficient increases, the microbeam becomes more responsive to polarization, thereby generating a greater amount of electrical energy. In addition, changes in the velocity of the moving load significantly affect the dynamic behavior of the structure in such a way that with the increase in the load velocity, the dynamic deflection of the structure increases.

Projectile nose-length effect on specific cavitation energy and ballistic limit velocity and thickness

The perforation of armour plates by quasi-rigid projectiles in ductile hole growth has been demonstrated to be influenced by the ratio of plate thickness to projectile diameter, referred to as the hole slenderness ratio, h/D. Here we propose a new non-dimensional geometric ratio, termed as the target containment ratio, that uses the projectile nose-length in place of the diameter, i.e., h/L. We demonstrate that the hole slenderness ratio is a special approximation of the target containment ratio for projectiles with a nose-shape ratio (projectile nose-length normalised by projectile shank radius) on the order of 3. We validate the proposed relationship via a comprehensive numerical study and through comparison with experimental data for the 14.5 mm BS41 armour piercing bullet, for which the nose-shape ratio is about 2. We show that the new target containment ratio dependent formulation of the specific cavitation energy improves the accuracy of the model suggested in Masri and Ryan (2024). This new formulation is also used to update existing formulae for ballistic limit predictions of monolithic and multilayer ductile targets.

Modelling П-Shaped Concentrating Optics for Lcpv Solar Cells Using Fresnel Lens

Abstract Most concentrating optics do not show good performance at higher incidence angles and have low acceptance angles and, therefore, they require a high-accuracy solar tracking system, which is costly. In this study, by detailed investigation of optics of the proposed П-shaped concentrating optics, it was found that system remained high in terms of optical efficiency and its concentration ratio at certain higher incidence angles. During the work, ray path through the concentrating optics, width of the light spot at different incidence angles were calculated. Optical efficiency, geometrical concentration ratio, concentration ratio at different incidence angles were found by the results of COMSOL Multiphysics calculations. It was found that the system had a high optical efficiency of approximately 95% and its concentration ratio of 3x-5x was at the range of ±0-20 degrees of incidence angle, and it could reduce the work of a solar tracking system. As well, an increase in the optical efficiency could be seen from 0 to 5 degrees of the incidence angle and an increase in the concentration ratio could be seen from 0 to 12 degrees of the incidence angle in terms of the reflective mirrors which helped redirect the rays to the solar cells. Optical systems with such a high incidence angle could reduce the performance of the solar tracker system, and it reduced the overall cost and energy consumption of the LCPV.

Experimental identification of longitudinal and vertical lift aerodynamic admittance functions of thin sections

Previous studies of two-dimensional (2D) aerodynamic admittance function (AAF) identification methods have basically ignored the effects of different turbulence components, which may lead to unpredictable errors for practical engineering applications. This paper presents pressure measurement experiments on thin sections with a geometric ratio of 1:50 in various turbulent fields. Based on the three-dimensional (3D) two-wavenumber theoretical analytical framework, the two-wavenumber coherence function is obtained by fitting the measured spanwise root-coherence function at the effective spacing with an empirical model. A new method is proposed, assuming that the ratio relationship between the lift AAFs due to longitudinal and vertical turbulence components of the measured model section satisfies its corresponding theoretical solution ratio relationship. The 2D lift AAFs of the airfoil section induced by different turbulence components are identified following the proposed identification framework. Consistent with the previous research, force correlation is significantly larger than turbulence correlation, and the traditional 3D one-wavenumber AAFs obtained are different in different turbulent fields. The separated 2D lift AAFs demonstrate that the contributions of u- and w- turbulence to the buffeting lift force are significantly different, and are more precise, according to the ratio between the Horlock function and Sears function. Then, the method is successfully extended to estimate the AAFs with respect to the u- and w-turbulence components of a streamlined box girder section, further validating the applicability of the identification method to the streamlined box girder. Furthermore, comparing the separated 2D lift AAFs under different turbulence fields reveals their independence from turbulence characteristics.

Analysis of compact tension specimens with deflected cracks for orthotropic materials

Anisotropic materials, such as alloy, wood and fiber-reinforced composites, are widely used in load-bearing components. Accurately obtaining its fracture performance is crucial for safety assessment. However, existing testing methods based on compact tension (CT) specimen have not taken into account material anisotropic characteristics and crack deflection. In this work, the systematic finite element analysis (FEA) was conducted for CT specimens with deflected cracks made of orthotropic materials. A wide range of geometric (crack deflection angle, β, and ratio of crack length to width, ap/W) and orthotropic material (λ and ρ) parameters were discussed. Complete solutions of the stress intensity factor (KI and KII) and load-line compliance (C) were determined for the first time. The results showed that the geometric dimensions and material parameters have a significant coupling influence on the fracture parameters. The influence of the λ is generally greater than that of the ρ. Changes of material parameters can make fracture parameters’ dependence on β vary. The variation of β and ap/W could enlarge or minish even dismiss the impact of λ and ρ. In addition, to further verify the importance of the obtained fracture parameters, the CT fracture tests of carbon fiber-reinforced epoxy resin under various orientations were conducted. The solutions will promote the optimization of the fracture toughness testing standards for CT specimens made of anisotropy materials.

Flexible Single-Crystal Perovskite Photodetectors via Polymer-Controlled Transfer.

The large-sized perovskite single-crystal sheet (SCS) serves as the ideal research platform for perovskite photodetectors due to its outstanding carrier photophysics, pronounced geometric aspect ratio, and ultrahigh material utilization rate. However, its performance in flexible device applications is relatively lackluster due to the rigid and brittle nature of the three-dimensional cubic lattices. In this work, the indium tin oxide (ITO)-based multimillimeter-sized MAPbBr3 SCS is transformed into MAPbI3 SCS via ion exchange strategy. Significantly, we proposed and implemented a polymer-controlled transfer strategy─utilizing the dichloromethane (DCM) solution of poly(methyl methacrylate) (PMMA)─to nondestructively transfer the whole perovskite SCS off the ITO substrates and subsequently adhere it onto a flexible polyethylene terephthalate (PET) substrate of interdigital electrode, thereby fabricating a lateral-structured photodetector with a PMMA-SCS-Au-PET multilayer configuration. The tight self-encapsulation between the top PMMA membrane and the bottom PET substrate imparts excellent waterproof stability and concurrently excellent mechanical flexibility to these devices; additionally, the MAPbI3 device exhibits comprehensively superior performance to the MAPbBr3 one. This work represents a proactive attempt and exploration of the high-performance advancement of large-sized SCS photodetectors, undoubtedly introducing novel momentum and solutions to this domain.

A Bioequivalence Trial of Lenvatinib Mesylate Capsules in Healthy Subjects Under Fasting and Postprandial Conditions.

The aim of this study was to evaluate the comparative effectiveness and safety profiles of generic lenvatinib mesylate capsules and the reference product in a cohort of healthy Chinese individuals. The research design consisted of a randomized, open-label trial with a single-dose regimen, 2 crossover periods, and 2 distinct phases involving participants from the Chinese population. A total of 24 individuals were enrolled in the fasting study, with an additional 27 participants included in the postmeal study. Each participant received a single dose of either 4mg of the reference product or the study product per cycle. The washout period was 14days between each period. Bioequivalence was assessed through the analysis of geometric mean and ratio of pharmacokinetic parameters, while the safety of both drugs was evaluated by monitoring adverse events (AEs). Following a single oral administration of lenvatinib (4mg), linear pharmacokinetics were observed. The rate of absorption was found to be significantly faster under fasting conditions (median time to maximum concentration, 2.3-2.5hours), while the presence of a high-fat diet resulted in delayed absorption (median tmax, 5.3-6.1hours). Furthermore, the 90% confidence intervals for the reference and test pharmacokinetic parameters under both fasting and postprandial conditions fell within the bioequivalence standard range of 80%-125%. AEs were reported in 34.78% of cases during fasting and in 48.15% of cases after eating. There was no significant difference in AE rates between the reference and study products. The study determined that both the study product and the reference product were bioequivalent and well tolerated by healthy Chinese participants in both fasting and postprandial conditions.

Exposure levels and maternal transfer of emerging organophosphate flame retardants (OPFRs) in pregnant women: Comparison with traditional OPFRs

Prenatal exposure to organophosphorus flame retardants (OPFRs) has been linked with adverse effects on reproductive health, and new OPFRs are continually emerging. In this study, emerging OPFRs, such as bis(2-ethylhexyl) phenyl phosphate (BEHPP), triamyl phosphate (TAP), tris(4-tert-butylphenyl) phosphate (T4tBPPP), oxydi-2,1-ethanediyl phosphoric acid tetrakis(2 chloro-1-methylethyl) ester (RDT905), cresyl diphenyl phosphate (CDP), and 2-isopropylphenyl diphenyl phosphate (2IPPDPP), were detected in 84 %, 100 %, 100 %, 52 %, 40 %, and 40 % of 25 decidua samples with average concentrations of 2.36, 6.21, 1.5, 2.6, 1.07, and 0.09 ng/g of dry weight (dw), respectively. Six of the aforementioned emerging OPFRs (BEHPP, T4tBPPP, RDT905, 2IPPDPP, CDP, and TAP) were simultaneously detected in paired chorionic villus samples, and their average concentrations were 11.3, 1.77, 3.64, 0.11, 0.58, and 3.34 ng/g, which were significantly higher than and positively correlated with those in decidua samples. The geometric mean concentration ratios between chorionic villus and decidua samples for BEHPP, T4tBPPP, RDT905, 2IPPDPP, CDP, and TAP were 4.02, 1.61, 1.73, 1.48, 0.82, and 0.69, respectively, consistent with transthyretin binding-dependent behavior. Prenatal exposure to such emerging OPFRs, especially for BEHPP with relatively high concentration and maternal transfer, is of high concern from the view of women’s reproductive health.

Test on progressive collapse of steel moment-resisting frame with upper-and-lower flange angle steel connection

Both of test and numerical simulation methods are employed to study the vertical progressive collapse and collapse assessment methods of steel frame under accidental loads. Firstly, a steel frame collapse test model with a geometric similarity ratio of 1:1.5 is designed and manufactured. The ends of column of test model is fixed. The upper and lower flange angle steel connection is used. The far end of the beam is constrained by a controllable sliding hinge support. The various stages of vertical progressive collapse of structures are simulated by a large displacement loads applied at the far end of the beam. The main focus of the testing is to examine the stress and deformation of beam and joint at various stages, particularly the development of stress and deformation in the angle steel attached to the beam-column connection. The development law of collapse load-displacement curve, joint rotation, beam strain, and angle steel strain are analyzed. The structural resistance mechanism and the transformation relationship between resistance mechanisms during collapse are studied. Subsequently, the relationship between the structural dynamic increase factor curve and the structural collapse process is analyzed using finite element method. The results show that the strain of angle steels can better reflect the destruction and deformation process of substructure during the collapse, the collapse resistance mechanism of structure, and the transition between resistance mechanisms.With the help of the characteristic points on the structural dynamic increase factor curve, the collapse limit state of structure can be reliably determined.

Effect of aspect ratio and geometric defects on the stability performance of U-rib stiffened plates

As an important component of steel-box beams, the stability of stiffened plates is a key factor that affects the safety of bridge structures. The geometric dimensions, such as the width-to-thickness ratio of the motherboard, stiffening rib thickness, and ratio of stiffening rib area to motherboard area, of stiffened plates have been considered in existing studies. However, the impact of the aspect ratio has not been reported in the literature. This study systematically investigated the effect of the aspect ratio on the stability performance of U-rib stiffened plates. Five sets of stiffened plate specimens with different aspect ratios were designed and manufactured. After testing the initial geometric defects of the specimens, axial compressive stability tests were conducted. Rotational hinge supports were placed at both ends of the specimens in order to simulate simply supported boundary conditions. The influence of geometric defects and aspect ratio on the stability of stiffened plates was discussed through numerical simulation. The results reveal that as the width of the stiffened plate increases, the initial geometric defects are distributed in a half-wave form along both the longitudinal and transverse directions, exhibiting an overall hemispherical distribution. The instability mode of a single-rib stiffened plate is characterized by local instability, whereas multi-rib stiffened plates exhibit global instability. The buckling mode is significantly influenced by the distribution of initial geometric defects. As the aspect ratio of the specimen decreases, the average stress at instability decreases and the stiffened plate gradually undergoes a biased compression state during the compression process. Failure of the specimen typically results in pure bending deformation when the aspect ratio is relatively large, whereas when the aspect ratio is relatively small, failure may result in bending and twisting deformation. Finally, a reasonable aspect ratio recommendation value was given.

Flexural Behavior of Self-Compacting PVA-SHCC Bridge Deck Link Slabs

This paper studied the flexural behavior of bridge deck link slabs made with polyvinyl alcohol–strain-hardening cementitious composites (PVA-SHCC). The tensile and flexural properties of the self-compacting PVA-SHCC with four volume fractions, i.e., 0%, 1%, 1.5%, and 2%, were evaluated first. Next, using the similarity theory, composite models with a geometric similarity ratio of 1:5 were designed to represent the bridge deck with the link slabs. The models considered three materials for link slabs, including concrete, cement mortar, and self-compacting PVA-SHCC, and two different curing ages at 7 and 56 days. Bending tests were performed to investigate the flexural behavior of the models. Based on the fractal theory, the cracking characteristics of the models with different types of link slabs were compared, and the relationship between fractal dimensions and the flexural behavior of the models was studied. Numerical models were built to correlate with the results from the bending tests. It was illustrated that the flexural behavior of the self-compacting PVA-SHCC link slab is better than that of concrete and cement mortar link slabs, where the crack initiation and propagation can be postponed. The results can provide theoretical support and design guidance for the self-compacting PVA-SHCC bridge deck.

A Data-Driven DNN Model to Predict the Ultimate Strength of a Ship’s Bottom Structure

Plates and curved plates are essential components in ship construction. In the design stage, the methods used to evaluate the ultimate strength required to confirm the structural safety of plates include prediction through analytical methods, finite-element analysis (FEA), and empirical formulas. However, with nonlinear buckling, the results of the empirical formula and the FEA differ for small flank angles (1~9). As a result, the prediction of the nonlinear ultimate strength of flank angle (1~9) plates still requires significant computation time and cost. To compensate for this, this study performed an ultimate strength prediction method utilizing a deep neural network together with the 4050 curved plate analysis. In addition, this paper presents the analysis results of the nonlinear finite-element method and the geometric shape and ratio of curved plates as training data. Based on the results of this study, designers can more efficiently design appropriate curved plate members by considering the ultimate strength.

Noninferior Immunogenicity and Consistent Safety of Respiratory Syncytial Virus Prefusion F Protein Vaccine in Adults 50-59 Years Compared to ≥60 Years of Age.

The adjuvanted respiratory syncytial virus (RSV) prefusion F protein-based vaccine (RSVPreF3 OA) is approved in adults aged ≥60 years. We evaluated RSVPreF3 OA immunogenicity and safety in adults aged 50-59 years without or with increased risk for RSV disease due to specific chronic medical conditions. This observer-blind, phase 3, noninferiority trial included adults aged 50-59 years, stratified into 2 subcohorts: those with and those without predefined, stable, chronic medical conditions leading to an increased risk for RSV disease. Participants in both subcohorts were randomized 2:1 to receive RSVPreF3 OA or placebo. A control group of adults aged ≥60 years received RSVPreF3 OA. Primary outcomes were RSV-A and RSV-B neutralization titers (geometric mean titer ratios and sero-response rate differences) 1 month post-vaccination in 50-59-year-olds versus ≥60-year-olds. Cell-mediated immunity and safety were also assessed. The exposed population included 1152 participants aged 50-59 years and 381 participants aged ≥60 years. RSVPreF3 OA was immunologically noninferior in 50-59-year-olds versus ≥60-year-olds; noninferiority criteria were met for RSV-A and RSV-B neutralization titers in those with and those without increased risk for RSV disease. Frequencies of RSVPreF3-specific polyfunctional CD4+ T cells increased substantially from pre- to 1 month post-vaccination. Most solicited adverse events had mild-to-moderate intensity and were transient. Unsolicited and serious adverse event rates were similar in all groups. RSVPreF3 OA was immunologically noninferior in 50-59-year-olds compared to ≥60-year-olds, in whom efficacy was previously demonstrated. The safety profile in 50-59-year-olds was consistent with that in ≥60-year-olds. ClinicalTrials.gov: NCT05590403.

Thermodynamic cycle performance modeling and numerical simulation of higher Mach scramjet with inlet pre-injection

This paper focuses on the thermodynamic cycle performance modeling and numerical investigation of a high Mach number scramjet with inlet pre-injection of hydrogen. The scramjet model used in this study was the Hyshot-Ⅱ engine model. Flight experiments using this model at high Mach number have been conducted previously, which provides a unique testbed for validating the computational prediction of supersonic combustion. A thermodynamic cycle performance model with inlet pre-injection was developed for operating characteristics studies of the scramjet engine. A set of three-dimensional Reynolds average Navier-Stockes (RANS) simulations of the reactive flow was performed with a 9-specie and 19-step kinetic mechanism for hydrogen combustion. The turbulence is modeled by k-ω shear stress transport (SST) turbulence model. The thermodynamic cycle performance analysis results indicate that inlet pre-injection can enhance the hydrogen mixing efficiency, and a small amount of advanced heat release can improve the overall thermal cycle efficiency. Detailed flow analysis from the three-dimensional simulation results indicates flow can be ignited in the first shock wave induced boundary layer separation (SIBLS) region. Inlet pre-injection enables the propagation of the flame toward the core flow compared to the throat injection. The inlet fuel pre-injection proved to be a promising injection method due to the higher combustion efficiency, elevated from 0.75 to 0.85, and higher specific impulse potential, increased from 1570 s to 1810 s. As the ER of inlet pre-injection increases within the examined range, the performance curve exhibits an optimal point. As the geometric compression ratio increases, the entire combustion process advances, leading to a significant increase in the performance potential of the engine. The comparative analysis of the thermodynamic cycle performance modeling and computational fluid dynamics (CFD) modeling indicates the model shows a good prediction on the performance of the scramjet engine with the inlet pre-injection, with the same trend of performance curves and an error of less than 10 % compared to the numerical simulation.