- 标题
- 摘要
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- 实验方案
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3D surface reconstruction of retinal vascular structures
摘要： We propose in this paper, a three-dimensional surface reconstruction of a retinal vascular network from a pair of 2D retinal images. Our approach attempts to address the above challenges by incorporating an epipolar geometry estimation and adaptive surface modelling in a 3D reconstruction, using three steps: segmentation, 3D skeleton reconstruction and 3D surface modelling of vascular structures. The intrinsic calibration matrices are found via the solution of simplified Kruppa equations. A simple essential matrix based on a self-calibration method has been used for the ‘fundus camera-eye’ system. The used method has eventually produced vessel surfaces that could be fit for various applications, such as applications for computational fluid dynamics simulations and applications for real-time virtual interventional.
关键词： Kruppa equations,curvature-dependent subdivision,surface reconstruction,epipolar geometry,segmentation,retinal vascular network,self-calibration
更新于2025-09-23 15:22:29
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Rapid holographic phase transition with brane-localized curvature
摘要： We study the finite-temperature properties of the Randall-Sundrum model in the presence of brane-localized curvature. At high temperature, as dictated by AdS=CFT, the theory is in a confined phase dual to the planar anti-de Sitter black hole. When the radion is stabilized, á la Goldberger-Wise, a holographic first-order phase transition proceeds. The brane-localized curvature contributes to the radion kinetic energy, which allows us to substantially decrease the critical bubble energy. Contrary to previous results, the phase transition is completed at much larger values of N, the number of degrees of freedom in the conformal field theory. Moreover, the value of the bulk scalar on the TeV brane is allowed to become large, consistent with backreaction constraints. Assisted by this fact, we find that for a wide region in the parameter space tunneling happens rather quickly, i.e., Tn=Tc ～ Oe0.1–1T. At zero temperature, the most important signature of brane-localized curvature is the reduction of spin-2 Kaluza-Klein graviton masses and a heavier radion.
关键词： holographic phase transition,Kaluza-Klein graviton,brane-localized curvature,radion,Randall-Sundrum model
更新于2025-09-23 15:21:21
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Characterization and on-line adjustment of the sagittal-bent Laue crystal profile
摘要： The sagittal-bent Laue monochromator can provide an ideal way to focus high-energy X-ray beams. However, the anticlastic curvature induced by sagittal bending has a great influence on the crystal performance. Thus, characterizing the bent-crystal shape is very important for predicting the performance of the bent-crystal monochromator. In this paper the crystal profile is measured by off-line optical metrology and on-line X-ray experiments. The off-line results showed that the bent-crystal surface could be well fitted to a saddle surface apart from a redundant cubic term which was related to the different couples applied on the crystal. On-line characterization of the meridional and the sagittal radius of the bent crystal includes double-crystal topography and ray-tracing measurement. In addition, the double-crystal topography experiment could be used as a quick diagnostic method for the bending condition adjustment. The sagittal radius of the bent crystal was characterized through a ray-tracing experiment by using a particularly designed tungsten mask. Moreover, rocking curves under different bending conditions were measured as well. The results were highly consistent with analytical results derived from the elastic theory. Furthermore, radii along different vertical positions under various bending conditions were measured and showed a quadratic relationship between the vertical positions and the meridional radii.
关键词： ray-tracing measurement,double-crystal topography,sagittal-bent Laue crystal,optical metrology,anticlastic curvature
更新于2025-09-23 15:21:21
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Influence of target curvature on the characteristics of particle beams generated by laser ion acceleration with microstructured enhanced targets at ultra high intensity
摘要： Following the advances in laser science that have been performed recently, the push to improve the quality of the laser generated particle beams has seen a lot of interest in the past decade. The work presented in this paper aims to study the role of target curvature using 2D PIC simulations to ascertain its influence on the angular spread and peak energy for the accelerated proton beam, and the characteristics of the gamma photons produced for potential usage as secondary sources. For the scope of this work we parametrically probed different curvature radii of a microstructured enhanced target impacted by a laser pulse with predetermined parameters. This paper continues past studies (Tatomirescu et al 2017 AIP Conf. Proc. 1796 020013; Tatomirescu et al 2017 AIP Conf. Proc. 1916 030002) and concentrates on determining the target curvature effect when using conical structures for pulse focusing. The results show promising enhanced focus of the accelerated particles and an enhancement of the peak energy of the accelerated particles.
关键词： variable target curvature,particle-in-cell,ultra high intensity laser pulse,microstructured target
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Economically sustainable growth of small-scale perovskite manufacturing in alternative PV markets
摘要： This paper proposes a new computational method for retrieving shapes under unpredictable conditions such as when occlusion, geometric distortion, and differences in image resolution occur simultaneously. The human visual system retrieves shapes from incomplete information in the real world, and it has inspired a lot of computational methods of retrieving shapes. In order to retrieve shapes, the observed shapes are decided to be alike or unlike remembered shapes in memory after the comparison of these shapes. To compare the observed and remembered shapes, they must first be appropriately represented so that the points on each shape can be mapped and compared. For this reason, the shape retrieval process needs an appropriate shape representation and shape mapping methods. Moreover, the shape representations should be normalized before the mapping process. However, a normalization process for representations under unpredictable conditions has not yet been established. In this paper, we describe a shape retrieval method that enables us to retrieve shapes under unpredictable conditions with a suitable normalization process. Using curvature partition and angle-length profile, our shape retrieval method normalizes the shape representation before it does the mapping. As a result, unlike the previously proposed methods, it can be used under unpredictable conditions such as when occlusion, geometric distortion, and differences in image resolution occur simultaneously.
关键词： occlusion,Shape recognition,shape retrieval,curvature partition,geometric parameter
更新于2025-09-23 15:19:57
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Machine learning-based mapping of micro-topographic earthquake-induced paleo Pulju moraines and liquefaction spreads from a digital elevation model acquired through laser scanning
摘要： The advent of public open source airborne laser scanning-produced digital elevation models (ALS DEM) has provided new perspectives on glacial geomorphology in the Nordic countries. Seismically-induced micro-topographic paleo-landforms can now be identified and mapped throughout the former Fennoscandian Ice Sheet, allowing spatial safety assessment for nuclear waste disposal. Automated machine learning techniques enable recognition of these fine-scale geomorphological features efficiently and in a consistent way nationwide. The current study focuses on automated recognition of paleo liquefaction spreads and Pulju moraines in northern Finland. Geomorphometric variables in different cell sizes were first derived from the 2 m ALS DEM by Gabor and principal curvature filtering to emphasize the elevational multi-scale texture of these paleo-seismic landforms. The Gabor textural variables were considered as a baseline method and the principal curvature features, including maximum and minimum curvature, were used because they have previously been proven critical in recognition of concave and convex elongated features. Both sets of raster variables were then turned into histogram-based features and input into a non-linear supervised multilayer perceptron early-stop committee which is a neural network classifier. The leave-one-out cross-validation performance results indicated principal curvature features to be highly successful with 94% accuracy. Principal curvatures provided a clear improvement to Gabor based features which provided significantly lower accuracies between 83?85%. The study demonstrates the high success of supervised neural network-based classification of ALS DEM data and derived textural features capturing the multi-scale nature of the micro-topographic liquefaction spreads and Pulju moraines. The approach could be utilized for time-efficient mapping of these paleo-seismic geomorphologies to complete paleo-seismic databases in formerly glaciated regions.
关键词： rotation invariant,histogram-based features,leave-one-out cross-validation,principal curvature,area invariant,multilayer perceptron,landforms,paleo-seismology,geomorphology,Gabor filter,Pulju moraine,liquefaction spreads
更新于2025-09-23 15:19:57
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Development of Method Enhanced Laser Ablation Efficiency According to Fine Curvature of the Polymer through the Preliminary Preparation Process Using UV Picosecond Laser
摘要： In processes using the ultrashort pulsed laser, the phenomenon that the ablation efficiency is reduced due to the increase of the shielding effect of the generated plume is increasingly caused by the use of the high power and high repetition rate. A new method is needed to prevent a decrease in ablation efficiency in processing using an ultrashort pulsed laser. In this study, the proposed a processing method that can improve the ablation efficiency by providing an efficient escape path of plume, and examine the feasibility of a new processing method. The new method we proposed is a method of laser processing after generating a fine curvature in the polymer as a preliminary preparation. The fine curvature of the polymer produced by the preliminary preparation induces an artificial chimney-like opening along the path of the incident beam during laser processing, thereby enabling the plume to be effectively removed. The experiment for examine the feasibility through a new method was conducted using a 10-picosecond laser of UV wavelength with two optical systems. As a new processing method, when processing with ultrashort pulse laser, it was observed that the ablation efficiency improved.
关键词： fine curvature of polymer,picosecond pulse laser,artificial chimney,laser ablation,enhanced laser ablation efficiency
更新于2025-09-23 15:19:57
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Strongly Enhanced Berry Dipole at Topological Phase Transitions in BiTeI
摘要： Transitions between topologically distinct electronic states have been predicted in different classes of materials and observed in some. A major goal is the identification of measurable properties that directly expose the topological nature of such transitions. Here, we focus on the giant Rashba material bismuth tellurium iodine which exhibits a pressure-driven phase transition between topological and trivial insulators in three dimensions. We demonstrate that this transition, which proceeds through an intermediate Weyl semimetallic state, is accompanied by a giant enhancement of the Berry curvature dipole which can be probed in transport and optoelectronic experiments. From first-principles calculations, we show that the Berry dipole—a vector along the polar axis of this material—has opposite orientations in the trivial and topological insulating phases and peaks at the insulator-to-Weyl critical points, at which the nonlinear Hall conductivity can increase by over 2 orders of magnitude.
关键词： Berry curvature dipole,Weyl semimetallic state,BiTeI,nonlinear Hall conductivity,topological phase transitions
更新于2025-09-23 15:19:57
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Curvature-Induced Twist in Homeotropic Nematic Tori
摘要： We confine a nematic liquid crystal with homeotropic anchoring to stable toroidal droplets and study how geometry affects the equilibrium director configuration. In contrast to the case of cylindrical confinement, we find that the equilibrium state is chiral—a twisted and escaped radial director configuration. Furthermore, we find that the magnitude of the twist distortion increases as the ratio of the ring radius to the tube radius decreases; we confirm this with computer simulations of optically polarized microscopy textures. In addition, numerical calculations also indicate that the local geometry indeed affects the magnitude of the twist distortion. We further confirm this curvature-induced twisting using bent cylindrical capillaries.
关键词： twist distortion,nematic liquid crystal,curvature-induced twisting,chiral,toroidal droplets,homeotropic anchoring
更新于2025-09-23 15:19:57
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A micro MMF layer embedded in LPFG for simultaneous measurement of curvature and temperature
摘要： A micro multimode fiber (MMF) layer embedded in long period fiber grating (ME-LPFG) has been developed and experimentally investigated for the simultaneous measurement of curvature and temperature. The LPFG is written by using high-frequency CO2 laser pulses. The transmission spectrum of the novel LPFG can show the wavelength shift and splitting characteristics relative to the original LPFG. The wavelengths of the two resonant peak changes are used to monitor the variations of the curvature and temperature due to different responses. The experimental results show that the curvature sensitivities of the two peaks are -7.056 nm/m-1 and -21.080 nm/m-1, respectively. The curvature sensitivity is bigger than that of the common LPFG. And the temperature sensitivities of the two peaks reach 60 pm/°C and 58 pm/°C, respectively. Therefore the ME-LPFG has the potential to measure the curvature and temperature simultaneously with the resolutions of 4.7 × 10-5 m-1 and 0.3 °C.
关键词： Long period fiber grating,Temperature,Simultaneous measurement,Curvature
更新于2025-09-19 17:15:36