Boundary Region Research Articles

Combustion and particulate I/SVOC characteristics of an aero-engine combustor with dual-stage under operational power and injection pressure

The combustion and particulate intermediate-volatile/semi-volatile organic compound (I/SVOC) emission characteristics of a technology of low emission stirred swirl aero-engine combustor, which was operated under dual combustion stages of diffusion and premixed-dominant combustion have been investigated. The operational conditions of the combustor were combustor power (7 %–100 %) and injection pressure (IP, 1.5–6.0 MPa). Initially, the ignition and extinction boundary regions were identified, and within the ignition region, the emitted I/SVOCs were comprehensively resolved via a two-dimensional gas chromatography-time of flight mass spectrometer (GC × GC-ToFMS). It is found that I/SVOCs were remarkable under diffusion combustion, and reduced significantly by 61 % under premixed-dominant combustion (at 3.0 MPa IP). Besides, I/SVOCs were suppressed prominently by 49 % as IP increased from 1.5 MPa to 6.0 MPa (at 30 % combustor power). Based on the Response Surface Method (RSM), a model has been established to simulate the particulate I/SVOCs. The simulation model reveals that high Power-IP (100 % power, 6 MPa IP) could reduce I/SVOCs maximally by 84 %, 78 % and 56 % for n-alkanes, cycloalkanes and PAHs, respectively in comparison with low Power-IP (30 % power, 1.5 MPa IP). The essence of the findings reveals that domination of premixed combustion with promotional atomization inhibits aviation-emitted organic particles effectively.

Phase diagram of the eutectic type LiCl-PrCl3-KCl system with wedging liquidus of binary compound

Based on the published experimental data (phase diagrams of three binary systems, four isothermal sections and DTA curves of 33 alloys), a spatial (three-dimensional – 3D) computer model of the LiCl-PrCl3-KCl phase diagram has been constructed. It is shown that, in the general case, the diagram is formed by 66 surfaces and 27 phase regions; however, due to the negligible solubility of the initial chlorides and the stoichiometry of the two binary compounds in reality, it consists of 31 surfaces and 14 phase regions. The evaluation of the quality of the obtained 3D model is a comparison of model and initial isothermal sections and calculation of response functions for 33 alloys with temperature values at the boundaries of the primary crystallization regions shown on DTA traces. The geometric structure of the LiCl-PrCl3-KCl phase diagram is also considered as an illustration of the features of ternary systems of the eutectic type, depending on the nature of the formed in them binary compounds.

Unmanned Aerial Vehicle Fire Detection Platform Based on Semantic Yolov5 and Autonomous Recognition

In recent years, as fire image detection has become a research hotspot. One class of methods is color-based methods, which are very sensitive to brightness and shadows. As a result, the number of false alarms generated by these methods is high. Aiming at the task requirements of airborne binocular vision obstacle avoidance and target tracking, this paper establishes the verification platform architecture of UAV (Unmanned Aerial Vehicle) binocular vision obstacle avoidance and target tracking. For the update and maintenance of boundary regions, we can also continuously extract richer information from the boundary, make more elaborate plans, and develop an incremental method to detect locally updated maps within the boundary. The fire point can be independently and quickly identified through deep learning to extinguish the fire accurately. Assuming that the system incorrectly identifies 2 out of 80 non-fire sources as fire sources, so the results indicate a precision of about 88%, a recall of 90%. However, the traditional fire detection is around 80%.

A Monte Carlo Simulation on Resonant Scattering of X-Ray Line Emission in Supernova Remnants

Resonant scattering (RS) of X-ray line emission in supernova remnants (SNRs) may modify the observed line profiles and fluxes and has a potential impact on estimating the physical properties of the hot gas and hence on understanding the SNR physics, but has not been theoretically modeled ever. Here we present our Monte Carlo simulation of the RS effect on X-ray resonant-line emission, typified by the O vii Heα r line, from SNRs. We employ the physical conditions characterized by the Sedov–Taylor solution and some basic parameters similar to those in Cygnus Loop. We show that the impact of the RS effect is most significant near the edge of the remnant. The line profiles are predicted to be asymmetric because of different temperatures and photon production efficiencies of the expanding gas at different radii. We also predict the surface brightness of the line emission would decrease in the outer projected region but is slightly enhanced in the inner. The G-ratio of the O vii Heα triplet can be effectively elevated by RS in the outer region. We show that the RS effect of the O vii Heα r line in the southwestern boundary region of Cygnus Loop is nonnegligible. The observed O vii G-ratio of ∼1.8 of the region could be achieved with RS taken into account for properly elevated O abundance from the previous estimates. Additional simulation performed for the SNRs in ejecta-dominated phases like Cas A shows that RS in the shocked ejecta may have some apparent effects on the observational properties of oxygen-resonant lines.

Connection density based clustering: A graph-based density clustering method

In this paper, a graph-based density clustering framework is proposed that detects the boundary points of clusters rather than cluster exemplars in high density regions. The framework introduces the connection density to measure the density relationship between points, which depends on both a density metric and a distance metric, and a weighted graph is constructed based on the connection density. By cutting off edges with low connection density, points located at the boundary region become isolated points from the rest of the weighted graph, and each connected subgraph forms an initial cluster. For the generated isolated points, a graph-based label propagation strategy is designed, the stable point in initial clusters with higher connection density with an isolated point preferentially propagate labels. Finally, a novel connection density based clustering algorithm is proposed, called CDBC, which can automatically identify clusters of arbitrary shapes. The experimental results show that the proposed method outperforms other advanced clustering algorithms on several synthetic and real-world datasets.

Modeling the phase boundaries in Cu(100)-(2√2 × √2)R45°-O missing row reconstruction (MRR) structure

Although the structure of Cu(100)-(22×2)R45°-O missing row reconstruction (MRR) has been well-established for decades, the detailed structure of its various boundaries remains an untilled area due to the difficulties in obtaining atomically resolved images. Herein, atomic arrangement of the phase boundaries existing in MRR structure was modeled on the basis of scanning tunneling microscopy (STM) investigations. By determining the periodicity and unit structure of MRR in STM images and extending them to boundary region, several types of phase boundaries were identified, resulted respectively from: (1) the mismatch between c(2 × 2)-O patches, (2) the regulation by step edges, and (3) the mismatch between Cu missing rows (MRs). With the modeled structure, it was revealed that the types of the c(2 × 2)-O mismatch induced phase boundaries (OMIPBs) are mainly dominated by the oxygen exposure and in-diffusion barrier. The step edge regulated phase boundaries (SERPBs) are always terminated with Cu-O chain and may represent an intermediate growth stage to larger MRR structure. Comparatively, Cu MRs mismatch is often reconciled by the differently oriented domains between them. As a result, the Cu MRs mismatch induced phase boundaries (CMRMIPBs) are only occasionally observed as Cu-O chains between mismatched Cu MRs that encounter shoulder-to-shoulder. For all studied boundaries, the surrounding MRR domains exhibit obvious orientation preference through inclined packing along the SP direction with the degree closely related with the width of the boundaries.

Island of Reissner-Nordström anti–de Sitter black holes in the large D limit

We study the information paradox of Reissner-Nordström anti–de Sitter black holes in the large dimension limit by using the island formula. The entanglement entropy of Hawking radiation is calculated both for the nonextremal and the extremal cases, in which the boundary of the radiation region is close to the outer horizon. For the nonextremal case, the entanglement entropy of Hawking radiation obeys the Page curve, i.e., the entanglement entropy of Hawking radiation increases with time and reaches saturation about twice Bekenstein-Hawking entropy at the Page time. For the extremal case, the entanglement entropy of Hawking radiation becomes ill defined in the absence of the island due to the appearance of the singularity at the origin of the radial coordinate, while when the island exists, the entanglement entropy is found to be equal to the Bekenstein-Hawking entropy. In addition, for the case where the boundary of the radiation region is close to the horizon, there are some obvious constraints required by the existence of the island solution for both nonextremal and extremal cases, which can be utilized to put constraints on the size of the black hole. These results reveal new features of the semiclassical large D black holes from the island perspective. Published by the American Physical Society 2024

Can Small States Reshape Their Regional Identities? Examining Georgia’s Cognitive Dissonance between South Caucasus and Eastern Europe

Abstract Georgia represents an interesting case to study the agency of small states in reshaping their regional identity and external environment. Although much of the world has considered Georgia as politically part of the South Caucasus region, the country’s political elites themselves have long attempted to escape the geographic boundaries of the South Caucasus region and relocate their country into Eastern Europe. We argue that Georgian elites were partially successful in their quest for foreign political identity change. Although they did not manage to entirely change the international perception about Georgia’s geographic belonging, the country has politically moved closer to Eastern Europe and is considered to be part of “Associated Trio” together with Ukraine and Moldova—and recently became an EU candidate. From a theoretical perspective, we argue that Georgia’s quest for foreign policy identity recalibration fits the constructivist paradigm of international relations well. It can be argued that Georgia’s political elites were partially driven by ideational factors and were ignorant of the balance of power in their external environment, which cost the country the lost wars and compromised territorial sovereignty.

Integrating Raiffa and Nash approaches to bargaining using interim agreements

Raiffa's solution to the bargaining problem, outlined in Luce and Raiffa (1957), is the point where the negotiation curve - a sequence of points that constitute step-by-step improvements from the status quo in the feasible payoff space - meets (possibly in the limit) the efficient boundary of the feasible region. A bargaining model with interim agreements yields a negotiation curve in equilibrium (in the spirit of Raiffa), and as the bargaining frictions disappear, the Raiffa path of payoffs converges to the Nash solution.

Addressing incomplete tile phenomena in image tiling: Introducing the grid six-intersection model

Abstract With the continuous development of Earth Observation technology, resolution of imagery and gridded data has significantly increased, leading to a rapid increase in data volume. To efficiently acquire and analyze these vast amounts of imagery and gridded data, image tiling technology has been developed to effectively access data of interested areas. Tiling technology divides large-scale image data into smaller tiles, providing fast, accurate, and efficient access support for imagery and gridded data. The spatial grid model, as the foundational framework of the new generation of geographic spatial information, plays a critical role in the retrieval, integration, services, and applications of imagery and gridded data resources. When tiling image data based on the spatial grid model, it always generates both complete and incomplete tiles. Particularly, when conducting image tile retrieval using the same rule-based grid in the retrieval area, incomplete tile phenomena along the boundary regions of the retrieved images often occur, resulting in gaps within the retrieval area. To tackle this issue, in this study, we present a new topological model called the Grid Six-Intersection Model (G-6IM), specifically designed for regular rectangular grids, to accurately represent boundary issues in image tiling. Through a practical case study, we demonstrate the effectiveness and practical application potential of the proposed G-6IM model, providing new insights and guidance for the improvement and optimization of imagery and gridded data tiling technology.

Generating grid maps via the snake model

Generating grid maps via the snake model

Boundary-Repairing Dual-Path Network for Retinal Layer Segmentation in OCT Image with Pigment Epithelial Detachment.

Automatic retinal layer segmentation in optical coherence tomography (OCT) images is crucial for the diagnosis of ocular diseases. Currently, automatic retinal layer segmentation works well with normal OCT images. However, pigment epithelial detachment (PED) dramatically alters the retinal structure, causing blurred boundaries and partial disappearance of the Bruch's Membrane (BM), thus posing challenges to the segmentation. To tackle these problems, we propose a novel dual-path U-shaped network for simultaneous layer segmentation and boundary regression. This network first designs a feature interaction fusion (FIF) module to strengthen the boundary shape constraints in the layer path. To address the challenge posed by partial BM disappearance and boundary-blurring, we propose a layer boundary repair (LBR) module. This module aims to use contrastive loss to enhance the confidence of blurred boundary regions and refine the segmentation of layer boundaries through the re-prediction head. In addition, we introduce a novel bilateral threshold distance map (BTDM) designed for the boundary path. The BTDM serves to emphasize information within boundary regions. This map, combined with the updated probability map, culminates in topology-guaranteed segmentation results achieved through a topology correction (TC) module. We investigated the proposed network on two severely deformed datasets (i.e., OCTA-500 and Aier-PED) and one slightly deformed dataset (i.e., DUKE). The proposed method achieves an average Dice score of 94.26% on the OCTA-500 dataset, which was 1.5% higher than BAU-Net and outperformed other methods. In the DUKE and Aier-PED datasets, the proposed method achieved average Dice scores of 91.65% and 95.75%, respectively.

Gauging Centrifugal Instabilities in Compressible Free-Shear Layers via Nonlinear Boundary Region Equations

Curved free shear layers emerge in many engineering problems involving complex flow geometries, such as the flow over a backward-facing step, flows with wall injection in a boundary layer, the flow inside side-dump combustors, or wakes generated by vertical axis wind turbines, among others. Previous studies involving centrifugal instabilities have mainly focused on wall-flows where Taylor instabilities between two rotating concentric cylinders or Görtler vortices in boundary layers are generated. Curved free shear layer flows, however, have not received sufficient attention, especially in the nonlinear regime. The present work investigates the development of centrifugal instabilities in a curved free shear layer flow in the nonlinear compressible regime. The compressible Navier–Stokes equations are reduced to the nonlinear boundary region equations (BREs) in a high Reynolds number asymptotic framework, wherein the streamwise wavelength of the disturbances is assumed to be much larger than the spanwise and wall-normal counterparts. We study the effect of the freestream Mach number M∞, the shear layer thickness δ, the amplitude of the incoming disturbance A, and the relative velocity difference across the shear layer ΔV on the development of these centrifugal instabilities. Our parametric study shows that, among other things, the kinetic energy of the curved shear layer flow increases with increasing ΔV and A decreases with increasing delta. It was also found that increasing the disturbance amplitude of the incoming disturbance leads to significant growth in the mushroom-like structure’s amplitude and renders the secondary instability structures more prominent, indicating increased mixing for all Mach numbers under consideration.

Improved Smoothed Particle Hydrodynamics for the Three-Dimensional Solid Impact Problems

Total Lagrangian-Smoothed Particle Hydrodynamics (TL-SPH) method is an important method to improve the tensile instability of traditional SPH, but it still faces some defects, such as insufficient accuracy at boundary region, difficulty in obtaining damage and applying interface conditions. Therefore, the high-order TL-SPH is applied for the elastic–plastic solid. A damage model is proposed by adaptively transforming the type of kernel function. Furthermore, a Riemann contact algorithm is introduced for different solids. The advantages of the methods in improving tensile instability and simulating damage are verified by the cases of the plates and the notched beams with an impact load.

New source model for the 1771 Meiwa tsunami along the southern Ryukyu Trench inferred from high-resolution tsunami calculation

The 1771 Meiwa tsunami which struck the southern Ryukyu Islands (Sakishima Islands) had greater than 22 m run-up height, leaving about 12,000 casualties in its wake. At many places, the tsunami inundation or lack of inundation is well recorded in historical documents. Several tsunami source models have been proposed for this event using historical records as constraints of tsunami calculations. Nevertheless, the source model remains under discussion. This study re-evaluated the tsunami wave source model of the 1771 Meiwa tsunami using high-resolution (10 m mesh) bathymetric and topographical data for tsunami calculation, the latest historical record dataset, and seismological knowledge. Results demonstrated that a tsunami earthquake along the southern Ryukyu Trench was the likely cause of the 1771 event. However, it is noteworthy that assumption of a large slip with 30 m is necessary for a shallow and narrow region (fault depth = 5 km, fault width = 30 km, Mw = 8.49) of the plate boundary in the Ryukyu Trench, which is far larger than previously thought. This requirement of very large initial water level change at the source might involve not only the fault rupture along the plate boundary but also deformation by splay faults, inelastic deformation of unconsolidated sediments near the trench axis, and/or giant submarine landslides. Results also show that the effects of fault parameters on the run-up were quite different depending on the offshore coral reef width. This phenomenon strongly constrained the fault width to 30 km. Our tsunami ray tracing analysis further revealed the effects of bathymetry on tsunami propagation. It is noteworthy that meter-long huge tsunami boulders tend to be distributed along the specific coasts at which the tsunami was concentrated by bathymetric effects. This finding suggests that past tsunamis, including the 1771 event, might have affected the specific coral reefs on Sakishima Islands repeatedly, which is crucially important for understanding the heterogeneous distribution of tsunami boulders. This feature might also be useful to elucidate the effects of large tsunamis on the corals and reefs because a direct comparison of coral reefs that are damaged and not damaged by tsunami waves is testable in narrow areas in the case of the Sakishima Islands.

Advancing electromagnetic field modeling in axially anisotropic media with conformal method in 3D cylindrical coordinate systems

A conformal methodology for solving electromagnetic fields in axially anisotropic media in 3D cylindrical coordinate systems is proposed for the investigation of high-power microwave devices filled with such media. This method leverages the material properties of axially anisotropic media and employs the finite integral technique for solution. A simplified conformal algorithm is utilized for the boundaries of the computational region, extending the traditional conformal method for axially anisotropic media in 3D cylindrical coordinates. The proposed methodology is validated through simulations of TM01 and TE01 mode propagation in a circular waveguide filled with the medium. Subsequently, the method is integrated into particle-in-cell simulations, and an X-band relativistic backward wave oscillator filled with an axially anisotropic medium exhibiting azimuthal conductivity is numerically modeled. The results demonstrate that the medium with azimuthal conductivity effectively mitigates asymmetric modes in the relativistic backward wave oscillator, aligning with published literature. This study offers technical insights for research on high-power microwave devices incorporating axially anisotropic media, potentially facilitating the development of innovative microwave devices with enhanced performance characteristics.

The influence mechanism of periodic heterogeneous distribution of microstructure on fracture behavior in the 2319 aluminum alloy of wire-arc directed energy deposition

The microstructure of aluminum alloy components fabricated by wire-arc directed energy deposition (wire-arc DED) has typical periodic heterogeneous distribution characteristics, which will directly affect the fracture behavior of the components. Therefore, in this study, 2319 aluminum alloy components were additively manufactured by Cold Metal Transfer wire-arc DED (CMT wire-arc DED) system. Viewing the cross sections of fracture morphology from horizontal and vertical directions, the influence mechanism of periodic heterogeneous distribution of microstructure on fracture behavior of aluminum alloy components was analyzed. The results show that the mechanical properties of the additive components have obvious anisotropy. The tensile strength and elongation of the transverse tensile specimens are better than those of the longitudinal tensile specimens, and the former have better mechanical properties. With the metallographic structure and electron back scatter diffraction (EBSD) test results, it can be confirmed that the fracture location of the tensile specimens is located at the boundary region between the inter-layer area and the inner-layer area. Meanwhile, the fracture form is typical intergranular fracture. They are mainly due to the easy generation of porosity aggregation and precipitation of a large number of θ(Al2Cu) phases in the inter-layer and inner-layer junctions.

Remote sensing image semantic segmentation via class-guided structural interaction and boundary perception

Existing remote sensing semantic segmentation methods generally ignore the structural information of objects that is vital in the human visual recognition system. The absence of overall structural information often results in weak perceptions of subtle textures and fragmented predictions, especially for complex and variable ground object scenarios. Besides, they still suffer from the semantic ambiguity caused by the unclear object boundary features in remote sensing images. In this paper, we propose a novel remote sensing semantic segmentation framework, called CSBNet, which aims to enhance the capacity of class-guided structural interaction and boundary perception simultaneously. It consists of a class-guided structure interaction module (CSIM), a Transformer-based context aggregation module (TCAM) and a class-guided boundary supervision module (CBSM). The CSIM has the ability to progressively extract the class-specific structural features, i.e., refining the structural information of each class by iteratively exchanging information between initial coarse class tokens and contexts. Meanwhile, the TCAM is constructed to provide CSIM with more discriminative multi-scale contexts without losing spatial features. In particular, the CBSM plays an auxiliary role, which applies the boundary information obtained from the class tokens to supervise the segmentation of boundary regions. When tested on the ISPRS dataset, LoveDA dataset, UAVid dataset, our method significantly outperforms the state-of-the-art remote sensing semantic segmentation approaches.

Doxycycline protects against sepsis-induced endothelial glycocalyx shedding

Endothelial glycocalyx (eGC) covers the inner surface of the vessels and plays a role in vascular homeostasis. Syndecan is considered the “backbone” of this structure. Several studies have shown eGC shedding in sepsis and its involvement in organ dysfunction. Matrix metalloproteinases (MMP) contribute to eGC shedding through their ability for syndecan-1 cleavage. This study aimed to investigate if doxycycline, a potent MMP inhibitor, could protect against eGC shedding in lipopolysaccharide (LPS)-induced sepsis and if it could interrupt the vascular hyperpermeability, neutrophil transmigration, and microvascular impairment. Rats that received pretreatment with doxycycline before LPS displayed ultrastructural preservation of the eGC observed using transmission electronic microscopy of the lung and heart. In addition, these animals exhibited lower serum syndecan-1 levels, a biomarker of eGC injury, and lower perfused boundary region (PBR) in the mesenteric video capillaroscopy, which is inversely related to the eGC thickness compared with rats that only received LPS. Furthermore, this study revealed that doxycycline decreased sepsis-related vascular hyperpermeability in the lung and heart, reduced neutrophil transmigration in the peritoneal lavage and inside the lungs, and improved some microvascular parameters. These findings suggest that doxycycline protects against LPS-induced eGC shedding, and it could reduce vascular hyperpermeability, neutrophils transmigration, and microvascular impairment.

Effects of 1:5H-type Cu-rich phase around grain boundary on cell boundary phase and squareness of the demagnetization curve in sintered Sm2Co17-type magnets

The unique cellular structure of Sm2Co17-type magnets is responsible for their outstanding magnetic properties. However, the cell boundary phase around grain boundaries is few, and cannot form a complete cellular structure. This study explores the microstructure and microchemistry of the grain interiors and grain boundary regions in both the solid solution precursor and the final magnet. The Cu-rich phase precipitates around grain boundaries in the solid solution precursor, and it remains present in the final magnet. The Cu-rich phase is not present as a standalone grain boundary phase, rather, it possesses a hexagonal CaCu5-type crystal structure and demonstrates a coherent orientation relationship with the surrounding matrix. The Cu-rich phase inhibits cellular structure formation nearby, while boosting Cu content in the cell boundary phase at the grain boundary regions in the final magnet. The formation of a Cu-rich phase around the grain boundary increases the heterogeneity of the domain wall pinning field in the final magnet, becoming an unfavorable factor for the improvement of the squareness of the demagnetization curve. These discoveries enhance our comprehension of the precipitated phase surrounding the grain boundary and its impact on the cellular structure and magnetic characteristics of the magnet.