Core Structure Research Articles

Thermology-mechanical integrated SiC panel with triply periodic minimal surface architectures for thermal protection

In this study, a thermomechanically integrated SiC panel is fabricated using vat photopolymerization technology. A theoretical predictive model is developed for the thermodynamic integration of triply periodic minimal surfaces (TPMS). Firstly, a mathematical analysis model is established to integrate thermodynamics into TPMS architecture. Among the structures studied, the Schoen gyroid exhibits the best insulation performance, surpassing the Schwarz diamond, Neovius surface, and Schwarz W due to its superior radiation effect within the sandwich configuration's core structure. Regarding compression mechanical performance, the Schoen gyroid structure proved to be the optimal choice with yield points of 16.18 MPa and 9.8 MPa. The successful additive manufacturing of SiC ceramics with TPMS architectures is achieved by considering the integration of thermology and mechanics.

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Discovery of an Extremely Dense and Compact Object Embedded in the Prestellar Core G208.68-19.92-N2

The internal structure of the prestellar core G208.68-19.02-N2 (G208-N2) in the Orion Molecular Cloud 3 (OMC-3) region has been studied with the Atacama Large Millimeter/submillimeter Array. The dust continuum emission revealed a filamentary structure with a length of ∼5000 au and an average H2 volume density of ∼6 × 107 cm−3. At the tip of this filamentary structure, there is a compact object, which we call a nucleus, with a radius of ∼150–200 au and a mass of ∼0.1 M ⊙. The nucleus has a central density of ∼2 × 109 cm−3 with a radial density profile of r −1.87±0.11. The density scaling of the nucleus is ∼3.7 times higher than that of the singular isothermal sphere (SIS). This as well as the very low virial parameter of 0.39 suggests that the gravity is dominant over the pressure everywhere in the nucleus. However, there is no sign of CO outflow localized to this nucleus. The filamentary structure is traced by the N2D+ 3–2 emission, but not by the C18O 2–1 emission, implying the significant CO depletion due to high density and cold temperature. Toward the nucleus, the N2D+ also shows the signature of depletion. This could imply either the depletion of the parent molecule, N2, or the presence of the embedded very-low luminosity central source that could sublimate the CO in the very small area. The nucleus in G208-N2 is considered to be a prestellar core on the verge of first hydrostatic core (FHSC) formation or a candidate for the FHSC.

Penguin search with Harris-Hawk optimization algorithm to improve clustering performance in wireless network

<span>Integrating optimal search algorithm concepts across the wireless core and cluster structure enables next-generation wireless networks to effectively provide reliable low-delay communications and connectivity for internet of things (IoT) devices. This article describes penguin search with the Harris-Hawk optimization algorithm (PHHO) to improve clustering performance in wireless networks. The penguin search optimization algorithm (PSO) algorithm computes the fitness value for feature selection from the database. Harris-Hawk optimization (HHO) algorithm to reduce the time and energy required for network transmission. This mechanism builds the clusters based on node communication range. The node direction, node mobility, node bandwidth availability, and energy parameters to decide the cluster head (CH) by applying the HHO algorithm. This approach uses a PSO algorithm fitness function to select the feature subset to minimize error and overhead in the network. Using a network simulator (NS)-3, this method assesses and chooses the most efficient way for data transmission, and the result is compared to a baseline mechanism.</span>

Synthesis of labionin and avionin precursors via a nitrogen-centred-radical-triggered 1,5-HAT reaction of Tris derivatives.

Labionin and avionin are non-proteinogenic amino acids containing 2,4-diamino-2-(mercaptomethyl)pentanedioic acid that forms the core structures of spirocyclic peptides including labyrinthopeptin A2 and microvionin, respectively. We have developed a diastereoselective synthetic route to labionin and avionin precursors. This route highlights the formation of the quaternary carbon stereocenter of an α,α-disubstituted amino acid via a regioselective 1,5-HAT reaction of a Tris derivative.

A computational study of nematic core structure and disclination interactions in elastically anisotropic nematics.

A singular potential method in the Q tensor order parameter representation of a nematic liquid crystal is used to study the equilibrium configuration of a disclination dipole. Unlike the well studied isotropic limit (the so called one constant approximation), we focus on the case of anisotropic Frank elasticity (bend/splay elastic constant contrast). Prior research has established that the singular potential method provides an accurate description of the tensor order parameter profile in the vicinity of a disclination core of a highly anisotropic lyotropic chromonic liquid crystal. This research is extended here to two interacting disclinations forming a dipole configuration. The director angle is shown to decay in the far field inversely with distance to the dipole as is the case in the isotropic limit, but with a different angular dependence. Therefore elastic constant anisotropy modifies the elastic screening between disclinations, with implications for the study of ensembles of defects as seen, for example, in active matter in the extended system limit.

Enantioselective synthesis of 3-(N-indolyl)quinolines containing axial and central chiralities.

Quinoline and indole are important core structures in biologically active compounds and materials. Atropisomeric biaryls consisting of quinoline and indole are a unique class of axially chiral molecules. We report herein enantioselective synthesis of 3-(N-indolyl)quinolines having both C-N axial chirality and carbon central chirality by a photoredox Minisci-type addition reaction catalyzed by a chiral lithium phosphate/Ir-photoredox complex. The catalytic system enabled access to a unique class of 3-(N-indolyl)quinolines with high chemo-, regio-, and stereoselectivities in good yields through the appropriate choice of an acid catalyst and a photocatalyst. This is the first example of the synthesis of 3-(N-indolyl)quinoline atropisomers in a highly enantioselective manner.

Enhancing optical properties through zinc halide precursor selection: interfacial optimization of InZnP quantum dots

QDs with a core structure synthesized using highly reactive zinc chloride, exhibited increased Zn–O bonds, effectively reducing the inherent surface defects in InP, minimizing the lattice mismatch, and enhancing the QY of InZnP/ZnS QDs.

Conformation-controlled catalytic asymmetric synthesis of Swaminathan ketones

Besides numerous synthetic and biological applications, the catalytic construction of chiral Swaminathan ketones and their analogues possessing a bicyclo[5.4.0]undecane core structure has remained challenging for the scientific community for over four decades.

Revisiting ultrasmall phosphine-stabilized rhodium-doped gold clusters AunRh (n = 5, 6, 7, 8): geometric, electronic, and vibrational properties.

Incorporation of other transition metals in Au nanoclusters has been thriving recently due to its effect on their electronic and photophysical properties. Here, the ultrasmall phosphine-stabilized Rh-doped gold clusters AunRh (n = 5, 6, 7, 8), with metal core structures represented as fragments of a rhodium-centered icosahedron, are considered. The geometric and electronic properties of these nanoclusters are revisited and analyzed using density functional theory (DFT). Moreover, infrared spectra are simulated to identify the effects of Rh doping on the clusters through vibrational properties. Peaks are assigned to breathing-like normal modes for all AuRh clusters except for Au8Rh, likely due to the presence of bound Cl ligands. Unlike their pure gold core counterparts, the % motions of both Au and Rh atoms are lower in the mixed metal clusters, suggesting more restrained metal cores by rhodium, which could result in other novel physical and chemical properties not hitherto discovered.

Structures and energies of twist grain boundaries in Mg[formula omitted]SiO4 forsterite

In this work, we investigate twist grain boundary (GB) energies and structures in Mg2SiO4 forsterite using atomistic simulations. We first present a new bond orientational order parameter allowing to highlight disordered regions in this low-symmetry crystal for which classical visualization tools are ineffective. Then we examine three GB planes, (010), (120) and (001), corresponding to the most favorable free surfaces of this crystal. We show that twist GB follow the same energy ordering as corresponding free surfaces. In addition, except for some misorientation angles and for the (120) GB plane, GB energies and structures are quite insensitive to microscopic translational degrees of freedom. The dislocation composition of low-angle twist GB can be related to γ-surfaces in the corresponding planes, and are in good agreement with first-principle calculations. It is also shown that the dislocation core structures in low angle twist GB can strongly differ from the ones of intracrystalline dislocations.

Power Analysis of Toroidal Core Electromagnetic Energy Harvesters for Transmission Lines

Introduction. As the need for energy increases, energy harvesting methods have also been intensively researched. Energy harvesting techniques which are a way of converting low amounts of energy from the environment into electrical energy can be used to meet the energy needs of low-power electronic devices and sensors. The increase in such sensors and devices with low power consumption also makes energy harvesting techniques more important. One of these harvesting techniques is energy harvesting from electromagnetic fields, which is obtained from transmission lines. Aim of the Article. The article is aimed at developing an effective electromagnetic energy harvester from energy transmission lines for unmanned aerial vehicles. Materials and Methods. The method of harvesting energy from transmission lines through magnetic field energy harvesting is reviewed. Theoretical analyses, Finite Element Analyses (FEA), and experimental studies are conducted on toroidal core structures designed in different sizes and with different materials. Results. Among the selected materials and under the specified line conditions, current of 0‒30 A and a frequency of 50 Hz, the highest power of 695.516 mW was harvested by the 60x30x20 sized ferrite core harvester at a line current of 30 A. Discussion and Conclusion. Detailed experiments were conducted based on the 60x30x20 mm ferrite core, which demonstrated the highest induced voltage. Different load resistances were used to find the resistance value for the highest power at each current value. The optimal load resistance for maximum power transmission was determined for each core using the curve fitting method at all current values.

Reconstitution of the Alzheimer's Disease Tau Core Structure from Recombinant Tau297-391 Yields Variable Quaternary Structures as Seen by Negative Stain and Cryo-EM.

The protein tau misfolds into disease-specific fibrillar structures in more than 20 neurodegenerative diseases collectively referred to as tauopathies. To understand and prevent disease-specific mechanisms of filament formation, in vitro models for aggregation that robustly yield these different end point structures will be necessary. Here, we used cryo-electron microscopy (cryo-EM) to reconstruct fibril polymorphs taken on by residues 297-391 of tau under conditions previously shown to give rise to the core structure found in Alzheimer's disease (AD). While we were able to reconstitute the AD tau core fold, the proportion of these paired helical filaments (PHFs) was highly variable, and a majority of filaments were composed of PHFs with an additional identical C-shaped protofilament attached near the PHF interface, termed triple helical filaments (THFs). Since the impact of filament layer quaternary structure on the biological properties of tau and other amyloid filaments is not known, the applications for samples of this morphology are presently uncertain. We further demonstrate the variation in the proportion of PHFs and PHF-like fibrils compared to other morphologies as a function of shaking time and AD polymorph-favoring cofactor concentration. This variation in polymorph abundance, even under identical experimental conditions, highlights the variation that can arise both within a lab and in different laboratory settings when reconstituting specific fibril polymorphs in vitro.

A comprehensive study on the effect of rock corrosion and CO2 on oil-water interfacial tension during CO2 injection in heavy oil reservoirs

This study is focused on addressing issues related to the interaction mechanism between reservoir rocks and fluids during CO2 injection in heavy oil reservoirs. The results indicate that the carbonated water formed after high-pressure CO2 injection is causing corrosion in the core structure. Furthermore, the average corrosion rate increases from 0.358% as pressure increases from 8 MPa to 16 MPa to 0.742%. The core slices exhibit corrosion pits and cracks on their surface, as well as surface particles flaking and dissolving. The dynamic IFT between decyl trimethyl ammonium bromide solution and crude oil exhibited slower stabilization and less change without CO2 injection. However, with increasing pressure post CO2 injection, the dynamic IFT decreased at a more rapid rate. Furthermore, positive correlation between equilibrium IFT and temperature was observed with low-pressure CO2. In contrast, the surfactant played a more dominant role in reducing IFT with high-pressure CO2. The findings of this study can help for better understanding of the mechanism of microscopic action on reservoir rock and oil-water interface after CO2 injection, and offer theoretical basis and reference for CO2 injection in heavy oil reservoirs to enhance the recovery rate.

Structure optimization design and magneto-mechanical characteristics analysis of amorphous alloy with oriented silicon steel composite wound core

Three-dimensional wound cores are widely used in three-phase distribution transformer due to the symmetrical magnetic circuit structure. Amorphous alloy and oriented silicon steel are two kinds of ferromagnetic materials commonly used to make distribution transformer cores, each has own advantages and disadvantages in magnetic and mechanical characteristics. The amorphous alloy and oriented silicon steel composite core can synthesize the advantages of both. In this paper, a double-layer composite wound core (DCWC) structure is proposed and the corresponding dual nonlinear electric circuit and magnetic circuit coupling model is established. A structure optimization design method for the DCWC based on the free parameter scanning method is proposed by taking the percentage of oriented silicon steel in the composite core and the structure parameters as free variables. Based on the proposed optimization design method, a DCWC is designed and the experimental prototypes are manufactured. Further, the flux density distribution, core loss and mechanical vibration displacement of the DCWC are analyzed, and the effectiveness of the proposed method is verified by comparing with the measured results.

Magneto-thermo-gravitational Rayleigh–Bénard convection of an electro-conductive micropolar fluid in a square enclosure: Finite volume computation

This article presents both a theoretical and a numerical analysis of thermo-gravitational magnetic convection in electro-conductive Eringen micropolar fluids in a two-dimensional enclosure. The computational regime is bound with cold top, hot bottoms, and adiabatic side walls. The governing equations were transformed via scaled variables into dimensionless partial differential equations. A Finite volume method (FVM) is used to get a solution of the computational regime. Validation of the FVM solutions is included for non-magnetic special case from the literature. Streamline contours, isotherm contours, iso-microrotation contours (lines of constant angular velocity) and local Nusselt number at the left hot wall is depicted graphically for the impact of Hartmann (magnetic) number (Ha), Prandtl number (Pr), micropolar parameter (K) and Rayleigh number (Ra). A significant modification in internal circulation and micro-rotation in addition to temperature distribution is observed with increasing vortex viscosity parameter. Significant warping of isotherms is induced with stronger magnetic field and the mushroom-shaped core structure encountered at weak magnetic field transitions to a sigmoidal topology.

High-temperature sealing performance and structure optimization of rubber core for conical blowout preventer

Conical blowout preventer is a vital sealing component in the process of petroleum and gas development, if it were to malfunction, which will result in extremely severe consequences. In order to investigate sealing performance of conical blowout preventer at high temperature and reduce failure rate of rubber core. Firstly, high-temperature tensile and compression experiments for the rubber were conducted, then the constitutive model parameters for rubber core material was confirmed. A numerical model for wellhead sealing of conical blowout preventer was established. Stress distribution and sealing performance of rubber core at different temperatures were investigated. Finally, structural optimization was performed of rubber core, support rib and piston. The results show that the lower end of rubber core is the primary sealing area. Stress concentration on rubber core and significant deformations are the primary reasons for the cracking and detachment of rubber core. As the temperature increases, sealing performance of rubber core gradually decreases. After optimizing structures of rubber core, support ribs and piston, sealing performance of rubber core has been improved. Those results hold significant importance in improving sealing performance of conical blowout preventer and ensuring the safety of operational processes, providing theoretical guidance for the optimization of blowout preventer structures.

Exploring the Degradation Mechanism on PtxCoy Alloy Catalysts for Oxygen Reduction Reaction by Operando X-Ray Absorption Spectroscopy

At present, alloying the Pt with 3d-transition metal, such as Co, has been demonstrated as an efficacious approach in enhancing the activity of the cathodic catalysts and diminishing the cost of Pt through ligand effect and strain effect. However, these catalysts were facing with a substantial challenge of the limited durability, primarily attributed to the leaching of the 3d-transition metal under the rigorous electrochemical conditions for the proton exchange membrane fuel cells (PEMFCs)[1]. Herein, we applied both operando conventional XAS and high energy resolution fluorescence detection (HERFD) XAS to identify the electro-chemical behaviors of subsize (about 2.5 nm) PtxCoy alloy catalysts with different Co content and associated with the Pt1Co3@Pt core-shell (CS) nanostructure catalysts obtained by simple displacement reaction. We find that the introduction of Co helps to modify the structure of PtCo alloy catalysts and benefit the activity, however, the increase content of Co brings to the heavier oxidation of Pt, which accelerate the degradation of the PtCo alloy catalysts. While the structure with Pt-rich shell suggested a high tolerance to the Pt oxidation which benefits both stability and activity. Based on these findings, we demonstrate the significance of designing PtCo CS nanostructure with high Co content to achieve optimal performance in PEMFCs. Our research provides valuable insights in designing the catalysts combined with operando XAS analysis and paves the way for the development for the large-scale application for PEMFCs. For the typical synthesis of PtCox alloy catalysts, the Pt(acac)2 and Co(acac)3 were used as Pt and Co precursors. 4mL ethanol was added to the pre-mixed Pt and Co precursors and heated up to 60 °C with magnetic stirring. After the precursors completely dissolved, certain amount of Vulcan 72 was added into the solution. Then repeat ultrasonication and magnetic stirring in 60 °C until the solution converted into slurry statement, dried the product in 30 °C over night. Next, the above well-milled products were treated at 700 °C for 2h in Ar atmosphere to transfer into alloy particles. According to the introduced ratio between Pt and Co, the catalysts were noted as Pt3Co1, Pt1Co1, and Pt1Co3. The contribution of CS nanostructure of Pt1Co3 was applied by simple displacement reaction using H2PtCl6 solution as Pt source. The production was annealed in H2 for 30 min. Operando conventional XAS (at BL36XU in Spring 8) was performed to investigate the electronic statement and structure changes during the operation. Operando HERFD XAS (at BL39XU in Spring 8) further identified the formation of metal Pt with chemisorbed O and Pt oxidation during the polarization varying different Co content and Pt-rich shell. The electronic performance of PtCo alloy catalysts was evaluated in rotating disk electrode, gas diffusion electrode, and membrane electrode assembly, which exhibited a higher performance (about 5 times higher than Pt/C) for Pt1Co3@Pt catalyst. Fig. 1a shows the STEM mapping results for Pt1Co3@Pt catalysts, the linear scanning profile is shown in the mix-image, and the signal intensity between the Pt L-edge and Co K-edge indicates the Pt-rich shell and Pt and Co core structure, which suggested the successful synthesis of Pt-rich shell with high Co content. To further analyze the electronic-behavior for the catalysts, the operando HERFD-XAS analysis was performed on Pt1Co3 and Pt1Co3@Pt catalysts, which provides a higher signal-to-noise ratio and detailed information about the electronic statement of Pt atom[2]. As shown in Figure 1b and c, the main Pt L3-edge white line intensity continuously increased and positively shifted, which suggested the increasing coverage of chemisorbed O or OH onto the Pt surface and the generation of oxidic component at high polarization potential for Pt1Co3 catalyst. While less changes were shown in Pt1Co3@Pt catalyst, which implied the formation of Pt-rich shell could help to suppress the oxidation of Pt in PtCo alloy catalysts and benefit the catalytic performance.

Experimental investigation on impact and after-impact compression (AIC) behavior of foam core composite panels

This study investigates the impact and after-impact compression behavior of sandwich structures with carbon fiber composite face-sheets consisting of various polymeric core structures. In particular, the performance of polypropylene foam core with closed cell structure, which is new to engineering applications, against other polymeric core structures was investigated. Sandwich panels were subjected to three different impact energies and after-impact compression tests were conducted on each sample to reveal their damage tolerances and load-carrying capabilities. In-situ acoustic measurements were made to fully understand the damage and evolution mechanisms in the after-impact compression tests. Honeycomb polypropylene (PP) foam, polyvinyl chloride (PVC), and extruded polystyrene (XPS) foam were used as core materials. As a result of the tests, it was obtained which damage types occurred at which force levels. PP core panels exhibited different impact behavior compared to conventional sandwich core structures and were successful in preventing damage to the face sheets.

Finite-temperature screw dislocation core structures and dynamics in α-titanium

A multiscale approach based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) methods is developed to simulate the dynamics of an 〈a〉 screw dislocation in α-Ti. The free energy barriers for the core dissociation transitions and Peierls barriers for dislocation glide as a function of temperature are extracted from the MD simulations (based on machine learning interatomic potentials and optimization); these form the input to kMC simulations. Dislocation random walk trajectories from kMC agree well with those predicted by MD. On some planes, dislocations move via a locking-unlocking mechanism. Surprisingly, some dislocations glide in directions that are not parallel with the core dissociation direction. The MD/kMC multiscale method proposed is applicable to dislocation motion in simple and complex materials (not only screw dislocations in Ti) as a function of temperature and stress state.

Development of Novel Star-Like Branched-Chain Acrylamide (AM)-Sodium Styrene Sulfonate (SSS) Copolymers for Heavy Oil Emulsion Viscosity Reduction and Its Potential Application in Enhanced Oil Recovery.

Injecting water with chemicals to generate emulsions in the reservoir is a promising method for enhancing heavy oil recovery because oil-in-water (O/W) emulsions significantly reduce oil viscosity. To enhance heavy oil recovery efficiency, we developed new star-like branched AM-SSS copolymers (SB-PAMs) with reduction in the viscosity of the heavy oil emulsion, which was synthesized by reversible addition-fragmentation chain transfer (RAFT) controlled radical polymerization. The core structure of the branched polymer was RAFT polymerization of acrylamide (AM) and N,N'-methylene bis-acrylamide (BisAM), in the presence of 3-(((benzylthio)carbonothioyl)thio)propanoic acid as a chain transfer agent, followed by chain extension with AM and SSS. The core structures were achieved by incorporation of total monomer ratios [BisAM]/[AM] of 1:11. The expansion of the core structures by copolymerization of AM and SSS resulted in star-like branched polymer SB-PAM-co-SSS with apparent molecular weights ranging from 240 to 2381 kDa. 1H-nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) confirmed the synthesized polymer structure. The molecular weight was determined by gel permeation chromatography (GPC). The polydispersity coefficient was between 1 and 7, which has a broad molecular weight distribution. The polymer dissolves only 0.75 h in deionized water, faster than conventional polyacrylamide. At 50 °C, the viscosity of the 1000 mg/L SB-polymer solution can reach up to 45 mPa·s. First, heavy oil viscosity reduction by 800 mg/L SB polymer can reach 91.7%, at a water dehydration rate of 90.4%; second, with 0.6 PV injection, 800 mg/L SB polymer improved oil recovery up to 23.66% after water flooding; and third, SB-polymer-assisted hot water flooding shows that heavy oil recovery improved by 19.46% at 110 °C with 0.6 pore volume (PV) SB-polymer injection. This novel branched chain polymer with heavy oil emulsion capability will shed light on high-temperature polymer flooding and the development of a new candidate structure for heavy oil viscosity reduction.