Core Thickness Research Articles

Abstract 4120480: HIV-Nef extracellular vesicles utilize the novel Btk-NFκB-MerTK signaling axis to impair macrophage efferocytosis and promote atherosclerosis: A multiomics study

Background: People living with HIV (PLWH) on anti-retroviral therapy remain at risk for cardiovascular diseases, including atherosclerosis. We hypothesized that persistent viral protein (HIV-Nef) in extracellular vesicles (EVs) modulate macrophage heterogeneity to impair atheroprotective efferocytosis to accelerate cardiovascular disease. Methods and Results: Macrophage heterogeneity was characterized in human primary macrophages (50,931 cells; 4 donors) stimulated with EVs engineered to contain HIV-Nef by simultaneous scRNAseq and scATACseq. Among 16 clusters (Fig.1A), two inflammatory Nef dominant clusters were characterized using gene set enrichment analysis. Gene regulatory network analysis of scRNAseq (pySCENIC) and transcription factor footprinting analysis of sc-ATACseq (ChromVar) suggest elevated NFκB activation in these clusters. Whole cell and sub-cellular compartmentalized proteomics of nucleus, cytosol, cell surface and secreted EVs indicate changes in immune response related biological pathways. Network analysis of our multi-omics data predicts Bruton Tyrosine Kinase (Btk) signaling as a potential contributor to Nef induced macrophage dysregulation. Pathway enrichment analysis of these multiomics dataset suggest Nef influences atheroprotective efferocytosis through the Btk-NFκB signaling axis. Spectral flow cytometry, high content imaging and multiplexed qPCR showed reduction in key effector of efferocytosis, MerTK. Btk inhibition using siRNA, reversible and irreversible Btk inhibitors restored MerTK expression and rescued efferocytosis. Importantly, CRISPRa based overexpression of MerTK in human primary macrophages rescued Nef impaired efferocytosis. Injection of HIV-Nef EVs into male and female C57BL6/J mice impaired efferocytosis of peritoneal and bone marrow derived macrophages which was rescued with Btk inhibition in vivo . Critically, injection of HIV-Nef EV into male and female Ldlr -/- enhanced atherogenesis with larger aortic wall thickness and necrotic core (Fig.1B). Conclusion: Persistent Nef in EV in PLWH may modulate macrophage heterogeneity to impair efferocytosis. These findings may help develop novel atheroprotective therapies by restoring macrophage efferocytosis.

Ballistic characteristics of ceramic core sandwich structures

The ceramic core sandwich structure (CCSS) is a lightweight material with advantages of high anti-ballistic impact performance, high energy absorption and high specific strength. The ballistic performances of the CCSS with metal face plates hit vertically by projectiles with the nose shapes of conical, flat, and hemispherical are studied analytically and numerically in this paper. Based on the principle of energy conservation, an analytical model of ballistic characteristics of the sandwich ceramic core structure is developed. Numerical calculations are conducted, and the numerical model has been verified by experimental results from references by others. In addition, the analytical results agree well with finite element results. The effects of shape of projectile head, the thickness ratio of three plates of CCSS, and the ratio of shear strength of ceramic core to yield strength of metal face plates on the ballistic characteristics of the CCSS are discussed. It is shown that the conical-nosed projectile achieved the highest ballistic limit velocity (BLV) and the sharper nose increases the normal stress at the impact area thereby enhancing the BLV. The thickness of the ceramic core significantly influences the resistance of the CCSS and the thicker ceramic core enhances the ability of CCSS to absorb kinetic energy from the projectile. Furthermore, an appropriate increase in the yield strength of face plates can enhance the anti-ballistic impact performance of the CCSS. These insights have practical implications for the design of protective systems in military and civilian applications, where optimizing materials for impact resistance is crucial.

Recycled PET foam core sandwich panels with reinforced hybrid composite facesheets: A sustainable approach for enhanced impact resistance

This research explores the Low-Velocity Impact behavior of thermoplastic composite sandwich panels with 100% recycled Polyethylene Terephthalate (PET) foam sourced from post-consumer plastic water bottles. Being recognized as a reliable technique, hybridization using stainless-steel mesh layers was employed to reinforce the panels’ composite facesheets of sandwich panels accessible for modular housing, cold storage rooms and cargo trucks. Adequate impregnation of the reinforcement metallic mesh layer alongside proper skin-to-core adhesion was accomplished by optimizing a two-phase compression molding method. The effect of hybridization on impact response of sandwich panels with two different PET foam core thicknesses, and stacking sequence were evaluated. It was revealed that reinforcing the impacted surface of the composite sandwich panels significantly increased the perforation threshold. Moreover, analyzing the post-impact section view of the samples indicated that hybridization modified the damage propagation response of the PET foam core sandwich composites, through which the energy absorption capacity was improved.

Optimizing performance of hybrid fiber reinforced overwrapped pressure vessel

Composite overwrapped pressure vessels (COPVs) offer significant weight advantages over traditional all-metal vessels particularly in industries like aerospace, automotive and pharmaceutical, but pose unique challenges in mechanical design, fabrication, and testing. Despite their benefits, COPVs are susceptible to stress rupture failure, which can lead to catastrophic consequences during operation. This failure mode is not fully understood, with burst pressure-induced extreme stress concentrations and dynamic loading primarily contributing to rapid deformation and strain. To address these concerns, a comprehensive investigation was conducted, focusing on optimizing and examining the effects of optimum winding angle and lay-up pattern configuration on burst pressure in vessels under internal pressure. Finite element modeling analyzed the burst pressure behavior of COPVs with a 4 mm thick aluminum core cylinder and varying layers of carbon/fiber epoxy, each with a constant thickness. ABAQUS composite modeler generated 18 COPV models with carbon fiber/epoxy plies, ensuring uniform thicknesses while exploring different fiber orientations. The effects of ply stacking sequence were analyzed through finite element analysis for all models, comprising varying layers with uniform thicknesses. Attention was paid to failure criteria, methodically evaluating the burst strength of the Al/CFRPC COPVs This exhaustive analysis yielded an optimal COPV design profile characterized by a precisely calibrated ply stacking sequence of [24.50, −24.50] PP winding pattern and six (6) arranged layers. The stress-strain distribution analysis of the Composite Overwrapped Pressure Vessel (COPV) revealed both a uniform distribution of stress across its surface and extreme stress concentration, particularly peaking towards the polar boss region. This concentration is discernible due to variations in ply thickness induced by the overwrapped fiber orientation. This investigation provides valuable insights for optimizing COPV design and enhancing its performance and reliability in various applications.

Design and damping characterization of sandwich composite made of particle-filled hollow spheres and steel sheets

Sandwich composites made of particle-filled hollow sphere structures (PHSS) and steel sheets offer excellent lightweight and damping properties, ideal for high-speed machine tool components under dynamic loads. Previous research has focused on single particle-filled hollow sphere (PHS) and small PHSS, leaving a gap understanding of PHSS/steel sandwich composites. In this study a test rig was developed, and Design of Experiments and Response Surface Analysis were used to investigate the effects of sheet and core thickness (design parameters), filling ratio, and particle size (particle parameters) on the damping performance of PHSS/steel sandwiches. The results indicate that the design parameters have a significant influence on damping performance. The interaction between design and particle parameters also substantially affects damping. Minimizing particle size, increasing filling ratio, thinning the face layer, and thickening the core layer significantly improve structural damping. To address manufacturing tolerances, a finite element (FE) model-based optimization was developed to accurately determine PHSS material parameters. These parameters were used in an FE model of the PHSS-steel composite, with identified contact parameters minimizing measurement and simulation differences. The homogenized material model and the linear model using global damping parameters accurately reproduce the dynamic properties of the PHSS-steel sandwich composite in low vibration modes.

Optimization and performance assessment of Ag@SiO2 core–shell nanofluids for spectral splitting PV/T system: Theoretical and experiment analysis

Ag@SiO2 nanofluid is widely used in spectral splitting PV/T system. Its core–shell structure has great influence on the optical properties. In this work, we focus on the comprehensive analysis and structure optimization of Ag@SiO2 nanofluid to achieve its optimal spectral performance. DDA method is used to predict the optical properties of Ag@SiO2 nanofluid and an optimization model based on filter efficiency is proposed. The effect of the SiO2 shell thickness and Ag core mass concentration is analyzed. It indicates that the spectral performance of Ag@SiO2 nanofluid can be improved with SiO2 shell thickness of 15–40 nm and Ag core mass concentration of 81–135 mg/L. To achieve the same theoretical merit function of 1.46, the usage of Ag mass can be reduced by 25/33/44/62 % with SiO2 coating of 10/20/40/70 nm. The optimal structure to achieve the highest filter efficiency η of 37.8 % is with a shell thickness of 20 nm and a mass concentration of 113.9 mg/L. An indoor PV/T operation testing is conducted to verify the optimization results. The merit function of Ag-based nanofluids increases from 1.58 to 1.598 and a reduction in Ag usage of 17 % is achieved with a SiO2 coating shell of 17.8 nm. Operation stability is also enhanced with no aggregation observed during the working cycle and 7-day static experiment.

Nonlinear dynamic characteristics of smart FG-GPLRC sandwich varying thickness truncated conical shell with internal resonance for first three order modes

This paper examines the 1:1:1 internal resonant nonlinear dynamic characteristic of the simply supported varying thickness functionally graded graphene platelets reinforced composite (FG-GPLRC) smart truncated sandwich conical shell subject to the combined effects of transverse load and in-plane force. The truncated smart sandwich conical shell is composed of an FG-GPLRC varying thickness core and two magneto-electro-elastic face layers, whose material properties and constitutive relations are individually identified by the rule of mixture, improved Halpin-Tsai approach and generalized Hooke's law. Utilizing the first-order shear deformation theory (FSDT), von Karman's geometrical nonlinearity, Hamilton's principle and Galerkin technique, the 3DOF dimensionless nonlinear dynamic formulations for the truncated smart FG-GPLRC conical shell are established. The multiple-scale technique is applied to developing the averaged equations for the truncated smart FG-GPLRC conical shell under combined resonance. The frequency-response and force-response curves, Poincare maps, phase portraits, time history diagrams, bifurcation and maximum Lyapunov exponent diagrams can be portrayed by the nonlinear equation solver and Runge-Kutta approach. The effects of the damping and tuning parameters, transverse and in-plane forces on the 1:1:1 internal resonant nonlinear dynamic characteristic of truncated smart varying thickness FG-GPLRC sandwich conical shell are examined.

Impact responses of steel–concrete–steel–gradient aluminum foam energy absorbing panels: Experimental and numerical studies

A novel steel–concrete–steel–gradient aluminum foam energy absorbing panel (SCSGF-EAP) has been proposed for improving the impact resistance of existing structures. The impact resistant performances of the SCSGF-EAP were evaluated through the drop weight impact tests and numerical simulations. The varying thickness of gradient aluminum foam and concrete core was considered in the drop weight impact tests. All the specimens presented a consistent failure mode, which included local indentation and global flexure of SCS panel and crushing of gradient aluminum foam. The Finite Element (FE) model was developed through adopting LS-DYNA for studying the impact resistance of SCSGF-EAP, and the comparisons exhibited that numerical results agreed well with experimental data. The internal energy of different components of specimen was determined by numerical model, and the gradient aluminum foam absorbed the majority of the impact energy. Finally, parametric studies were adopted to determine influences of the initial momentum and kinetic energy of impactor, as well as the density of gradient aluminum foam and impact location on the impact response of SCSGF-EAP.

Optimal design of vibration resistance of fiber-reinforced composite sandwich plates embedded in a viscoelastic square honeycomb core

This work focuses on investigating the optimal design of composite sandwich plates (FCSPs) with a viscoelastic square honeycomb core (VSHC). Firstly, using the cross-fill theory, the complex modulus technique, the first-order shear deformation theory, the minimum strain energy principle, and the Newmark-β method, a theoretical model of the VSHC-FCSPs under half-sine pulse excitation is formulated to calculate the inherent frequencies, the peak and vibration decay time of the transient response in time domain. The peak and vibration decay time are taken as the indexes of the anti-vibration performance. Considering an index of structural stiffness performance, the average value of the inherent frequencies is adopted to calculate the overall stiffness. After a set of literature validations and optimization validations, the multi-objective genetic algorithm is employed to study the optimization issue of VSHC-FCSPs. The optimization objectives are to minimize the three design variables of the transient response peak, vibration decay time, and reciprocal of overall stiffness. Then, the fiber laying angle of each layer, the core thickness ratio and the modulus ratio are assumed as optimization variables. Finally, the results with good vibration resistance and structural stiffness in the Pareto front are chosen as references, and these corresponding variations of the design variables and optimization objectives are obtained. The optimization results have revealed that the optimization variables corresponding to the intermediate points should be selected as references to improve the anti-vibration capacity and ensure the structural stiffness performance.

3D-Printing Functional Ceramic for One-Step Fabrication of Pd/C Catalytic Reactor

Catalysts are widely used in the chemical industry because of their environmental friendliness and low energy consumption. However, integrated fabrication of catalytic reactors (CRs) remains challenging. In this study, we propose the integrated manufacturing of a palladium-carbon (Pd/C) CR for the first time. The outer shell ink comprises Al2O3 powder and aluminum dihydrogen phosphate (AP), whereas the inner core ink consists of activated carbon powder, AP, and polymethylmethacrylate (PMMA). By integrating with the coaxial 3D printing strategy, the Pd/C CR can be freeform-designed with different core thicknesses, lengths, and shapes (W-type, L-type, and U-type). Based on this, a CR with excellent catalytic properties was further developed by loading palladium (Pd) particles. Typically, the resultant Pd/C CR with a length of 2.5 cm exhibits a catalytic efficiency of up to 97.6% after 60 min. This method of preparing Pd/C CR using coaxial 3D printing combines multimaterial 3D printing, integrated molding, and complex biomimetic structure fabrication. This offers a feasible and cost-effective solution that uses a simple fabrication process.

Effect mechanism of low-velocity impact loading rate on the failure modes transition of steel-UHPC-steel composite plates

This study delved into the transition mechanism of loading rate on the failure mode transition in steel-ultra-high performance concrete-steel (SUHPCS) composite plates under concentrated low-velocity impact loads. A series of drop-weight tests elucidated that, as impact velocity escalated, the composite plate shifts from local punching failure, characterized by circumferential cracks, to overall flexural failure, marked by radial cracks resembling yield lines. Given the constraints in capturing strain data in drop-weight test, a 3D nonlinear structural analysis using Abaqus software was conducted. This numerical simulation method was validated by drop-weight test results in terms of crack patterns and impact force time histories. Moreover, structural dynamic punching and flexural loads at a specific loading rate were obtained with the assistance of the dynamic increase factor (DIF). Failure mode could be judged through comparison between the two critical loads. The discrepancy in strain sensitivity exhibited by steel plates and UHPC accounted for the transition in failure modes of the SUHPCS composite plates. DIFs for UHPC compressive strength and steel plate strength were lower than DIF for UHPC tensile strength, as these factors were around 1.5, 1.7 and 2.6, respectively. Parameter analysis showed that the critical transition impact velocity for a composite plate with a core thickness of 80 mm was 11 m/s, surpassing the 13 m/s threshold for a composite plate with a 100 mm-thick core. Moreover, changes in DIFs of UHPC and steel strengths were less than 2 % with various impact masses and the composite plate maintained the same failure mode.

Asymmetric bi-level dual-core mode converter for high-efficiency and polarization-insensitive O-band fiber-chip edge coupling: breaking the critical size limitation

Abstract Efficient coupling between optical fibers and on-chip photonic waveguides has long been a crucial issue for photonic chips used in various applications. Edge couplers (ECs) based on an inverse taper have seen widespread utilization due to their intrinsic broadband operation. However, it still remains a big challenge to realize polarization-insensitive low-loss ECs working at the O-band (1,260–1,360 nm), mainly due to the strong polarization dependence of the mode coupling/conversion and the difficulty to fabricate the taper tip with an ultra-small feature size. In this paper, a high-efficiency and polarization-insensitive O-band EC is proposed and demonstrated with great advantages that is fully compatible with the current 130-nm-node fabrication processes. By introducing an asymmetric bi-level dual-core mode converter, the fundamental mode confined in the thick core is evanescently coupled to that in the thin core, which has an expanded mode size matched well with the fiber and works well for both TE/TM-polarizations. Particularly, no bi-level junction in the propagation direction is introduced between the thick and thin waveguide sections, thereby breaking the critical limitation of ultra-small feature sizes. The calculated coupling loss is 0.44–0.56/0.48–0.61 dB across the O-band, while achieving 1-dB bandwidths exceeding 340/230 nm for the TE/TM-polarization modes. For the fabricated ECs, the peak coupling loss is ∼0.82 dB with a polarization dependent loss of ∼0.31 dB at the O-band when coupled to a fiber with a mode field diameter of 4 μm. It is expected that this coupling scheme promisingly provides a general solution even for other material platforms, e.g., lithium niobate, silicon nitride and so on.

The aeroelastic stability characteristics of a ring-stiffened conical three-layered sandwich shell with an FG auxetic honeycomb core utilizing zig-zag shell theory

This paper is devoted to the supersonic flutter analysis of a ring-stiffened conical three-layered sandwich shell consisting of an auxetic honeycomb (AH) core fabricated from functionally graded material (FGM). The face sheets are manufactured of FGM as well in which the volume fraction of the ceramic increases from zero at the inner surface to one at the outer surface based on a power-law function. The sandwich shell is mathematically modeled based on the Murakami's zig-zag shell theory and the aerodynamic pressure is modeled utilizing piston theory. The derivation of governing equations along with compatibility and boundary conditions are performed using Hamilton's principle and are solved through a semi-analytical solution consisting of an exact solution in the circumferential direction followed by an approximate solution in the meridional direction. The flutter boundaries are attained to investigate the variations of the natural frequencies and damping ratios to find the critical aerodynamic pressure (CAP). The impacts of several factors on the CAP are examined such as the power-law index, geometric characteristics of the cells in the FGAH, thickness of the honeycomb core, location of the ring, and boundary conditions. It is observed that an optimal location can be found for the ring support somewhere between the middle length and large radius of a conical shell that provides the best aeroelastic stability.

Optimization of precursor structure by dispersants to promote nitrogen reduction process to prepare high-quality VN

In this study, three dispersants of polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG) and citric acid (CA) are used to optimize the structure of the precursor in order to prepare high quality VN. Under optimum condition, the VN with nitrogen content of 17.94 % is prepared by adding 5 % PVP. The sequence of phase evolution from the precursor to VN is: APV → V2O5 → V6O13 → V7O13 → VO2 → V3O5 → V2O3 → (VC) → VN. The precursors of adding 5 % PVP have lower Ea of 0.17 kJ mol−1, 20.51 kJ mol−1 and 62.70 kJ mol−1 during reduction and nitration process, which is easier to be reduced and nitridated. PVP not only promotes the uniform dispersion of the carbon powders in the vanadium rich solution but also enhance the hydrogen bonding of APV ions to promote their nucleation and growth. The precursor with uniform and concentrated particle size distribution, complete and stable encapsulation of shell of APV and core of carbon powder, and uniform and moderate thickness of APV shell is successfully prepared by adding PVP. The precursor has a larger phase reaction interface and more reactive sites during the nitriding reduction process, which results in a faster reduction and nitriding rate. In comparison with the current process, the nitriding reaction temperature has been reduced from 1400 ∼ 1500 °C to 1150 ∼ 1200 °C, the reaction time has been shortened by 75 %, and the N2 consumption has been reduced by 40 %.

Seismic performance investigation of new buckling-restrained steel plate for resilient rocking column foot joint

Seismic damage-controllable components and design approaches are crucial for achieving the seismic resilience and post-earthquake recovery of building structures. To improve the seismic resilience of reinforced concrete (RC) frame structures, this study proposed a novel assembled replaceable rocking column foot joint. The column foot joint is composed of a concrete foundation, short steel-tube concrete column in the center, and four new buckling-restrained steel plates (BRSPs) on the periphery. A detailed design method for the BRSPs was developed, and six BRSP specimens were designed with different core weakening forms and thicknesses. The specimens were cyclically tested and the failure mode and hysteresis behavior were examined. The test results confirmed that the proposed BRSPs exhibit satisfactory energy-dissipation capacity and achieve damage control. The refined numerical models were developed using ABAQUS and verified using the test results. Parametric analyses were conducted for the BRSPs to examine the influence of core plate thickness, gap size, and restraint plate thickness. A numerical analysis model of the column foot joint was established, and the influence of the axial compression ratio and BRSP bearing capacity on the seismic performance of the column foot was investigated. This study provides a reference for the construction of resilient RC frame structures.

Thermal performance assessment of sandwich wall panel fabricated with polyurethane foam and natural husk

The demand for enhancing thermal efficiency in building construction has accelerated the evolution of sandwich wall panels in recent years. In this study, the novel sandwich panel is developed using Polyurethane (PU) as core and PU replaced with Rice husk (RH) and Coconut Husk (CH) at varying percentage (10, 20, 30, 40 and 50 %) with calcium silicate board as outer material. Dimension of sandwich panel is 30 × 30 cm with 3 cm as a core thickness is tested for compressive strength. The panel owing highest compressive load with combination of Polyurethane foam Coconut Husk panel at 20 % (PUC3–20 %) and polyurethane foam Rice husk panel at 30 % (PUR3–30 %) was taken further for thermal analysis. The temperature study was carried out on a prototype model using IR thermographic camera showing the temperature difference of indoor and outdoor of the sandwich panel. The PUR3–30 % shows the thermal conductivity of 0.28 w/mk and the difference of thermal heat flux was 10.42 W/m2. Regression analysis was carried out to validate the experimental results and the correlation accuracy of R2 > 0.90 was obtained. A residential building (G+3) was created in Autodesk Revit to conduct an energy analysis audit, where all the data of fabricated sandwich panel was added as new material and the analysis was carried out in green building studio. The annual energy and annual fuel end use for Heating Ventilation and Air Conditioning (HVAC) has been decreased by 3.5 and 4.5 % using PUC3–20 % and PUR3–30 % panels compared to the base material.

Test methods for determination of shear properties of sandwich panels

This paper presents analysis and comparison of test methods for determining transverse shear strength and shear modulus of steel-faced sandwich panels commonly used in construction. The test methods are taken from the governing European standard EN 14509:2013. Two-point loading and four-point loading test methods as well as a full-scale test method are examined. Based on extensive experimental work on sandwich panels with varying core thickness, comprising mineral wool (MW) and polyisocyanurate (PIR) and encompassing both roof and wall panels, this study provides details of the test setup for the four-point loading and vacuum box methods with which a pure shear failure is obtained. Such details are missing from EN 14509. This paper highlights that the two-point loading method fails to consistently produce shear failure, especially in thicker panels, indicating it does not accurately measure transverse shear strength. The results of the experiments conducted in this study indicate that the four-point loading and full-scale test methods provide consistent shear failure for thicker panels while yielding greater transverse shear strength than the two-point loading test in general.

Isogeometric Analysis for Buckling and Wrinkling of Variable-Stiffness Sandwich Plates Under Compression

In this paper, an isogeometric analysis (IGA) framework based on the high-order sandwich plate theory is developed for the first time to deal with both buckling and wrinkling problems of variable-stiffness sandwich plates under compression. The present sandwich plate model is formulated based on the extended high-order sandwich plate theory (EHSAPT). The weak-form governing equations are firstly derived from the principle of virtual work, and afterward the IGA formulations based on the Non-Uniform Rational B-Splines (NURBS) are applied to predict the instability loads and the corresponding instability modes. Both the membrane and non-membrane conditions are integrated into the linear buckling analysis. The novelty of this work lies in that the employment of high-order continuous NURBS basis functions can directly fulfill the [Formula: see text] continuity requirement inherent in the EHSAPT theory, which enables the EHSAPT-based IGA model to be formulated with fewer degrees of freedom. Besides, the developed EHSAPT-based IGA model has also the ability to capture the overall buckling or wrinkling modes of the sandwich plates. The accuracy and effectiveness of the proposed EHSAPT-based IGA model are verified by comparison with previously published results and those obtained using ABAQUS. Effects of the core thickness and fiber angle on the buckling behaviors of the sandwich plates are also studied in numerical examples. It is observed that the non-uniform in-plane pre-stress over the skin layers is the main reason for the non-periodic wrinkling of constant-stiffness sandwich constructions, whereas the non-uniformity of both the in-plane pre-stress and out-of-plane bending stiffness is responsible for the non-periodic wrinkling of variable-stiffness sandwich constructions. The results presented herein may be beneficial for the design of variable-stiffness sandwich constructions under compression.

Optically Thick Jet Base and Explanation of Edge Brightening in Active Galactic Nucleus Jets

The jet cores in active galactic nuclei (AGNs) are resolved and found to harbor an edge-brightened structure where the jet base appears extended at the sides compared to its propagation axis. This peculiar phenomenon invites various explanations. We show that the photosphere of an optically thick jet base in AGNs is observed edge brightened if the jet Lorentz factor harbors an angular dependence. The jet assumes a higher Lorentz factor along the jet axis and decreases following a power law along its polar angle. For an observer near the jet axis, the jet has a lower optical depth along its propagation axis compared to off-axis regions. Higher optical depth at the outer region makes the jet photosphere appear to extend to larger radii compared to a deeper photosphere along its propagation axis. We tackle the problem both analytically and numerically, confirming the edge brightening through Monte Carlo simulations. Other than the edge brightening, the outcomes are significant as they provide a unique tool to determine the jet structure and associated parameters by their resolved observed cores. The study paves the way to explore the spectral properties of optically thick cores with structured Lorentz factors in the future.

Traveling wave vibration characteristic analysis of FRC sandwich cylindrical shells with FGP-GPLRC core under discontinuous elastic boundary conditions

In this study, a fiber-reinforced composite (FRC) sandwich cylindrical shell with a functionally graded porous graphene platelet reinforced composite (FGP-GPLRC) core is investigated, and the traveling wave vibration characteristics of this new sandwich cylindrical shell under discontinuous elastic boundary conditions are analyzed for the first time. The influences of centrifugal and Coriolis forces are introduced into the model. By employing the first-order shear deformation theory (FSDT) and the continuity assumption of the layerwise theory, the governing equations of the rotating sandwich shell are obtained. The artificial springs are implemented at the ends of the sandwich shell to represent the discontinuous elastic boundary conditions. The natural frequency of the shell is solved via the Rayleigh-Ritz method and the state space method. Then, the approach proposed is validated by comparing the present results with those reported in the literature and the finite element method. Finally, the effects of various parameters on the traveling wave frequency of the shell are evaluated. It was found that in practical engineering, the appropriate thickness of the FGP-GPLRC core should be selected according to the boundary conditions and other factors, and the ply angle should be adjusted to obtain more stability of vibration.