This paper presents the solution of coupled radiative transfer equation with heat conduction equation in complex three-dimensional geometries. Due to very different time scales for both physics, the radiative problem ...This paper presents the solution of coupled radiative transfer equation with heat conduction equation in complex three-dimensional geometries. Due to very different time scales for both physics, the radiative problem is considered steady-state but solved at each time iteration of the transient conduction problem. The discrete ordinate method along with the decentered streamline-upwind Petrov-Galerkin method is developed. Since specular reflection is considered on borders, a very accurate algorithm has been developed for calculation of partition ratio coefficients of incident solid angles to the several reflected solid angles. The developed algorithms are tested on a paraboloid-shaped geometry used for example on concentrated solar power technologies.展开更多
The spin-dependent Andreev reflection is investigated theoretically by analyzing the electronic transport in a thin-film topological insulator(TI)ferromagnet/superconductor(FM/SC)junction.The tunneling conductance and...The spin-dependent Andreev reflection is investigated theoretically by analyzing the electronic transport in a thin-film topological insulator(TI)ferromagnet/superconductor(FM/SC)junction.The tunneling conductance and shot noise are calculated based on the Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory.It is found that the magnetic gap in ferromagnet can enhance the Andreev retro-reflection but suppress the specular Andreev reflection.The gate potential applied to the electrode on top of superconductor can enhance the two types of reflections.There is a transition between the two types of reflections at which both the tunneling conductance and differential shot noise become zero.These results provide a method to realize and detect experimentally the intra-band specular Andreev reflection in thin film TI-based FM/SC structures.展开更多
Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from one and the same camera position but under varyi...Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from one and the same camera position but under varying illumination. The vast majority of studies in this 3D reconstruction method assume orthographic projection for the camera model.In addition, they mainly use the Lambertian reflectance model as the way that light scatters at surfaces.Thus, providing reliable photometric stereo results from real world objects still remains a challenging task. We address 3D reconstruction by use of a more realistic set of assumptions, combining for the first time the complete Blinn–Phong reflectance model and perspective projection. Furthermore, we compare two different methods of incorporating the perspective projection into our model. Experiments are performed on both synthetic and real world images; the latter do not benefit from laboratory conditions. The results show the high potential of our method even for complex real world applications such as medical endoscopy images which may include many specular highlights.展开更多
In aerial images,near-specular and specular reflection often appear in water bodies.They often lead to irregular brightness or color changes in water bodies and even produce hot spots,harmful to radiometric normalizat...In aerial images,near-specular and specular reflection often appear in water bodies.They often lead to irregular brightness or color changes in water bodies and even produce hot spots,harmful to radiometric normalization.Therefore,water bodies must be eliminated when calculating radiometric differences during radiometric normalization of aerial images.In this paper,a simple method to detect water bodies in aerial images based on texture features is presented,an improved seeded region growing(SRG)method.A texture feature is calculated using the relative standard deviation index(RSDI)and a coarse-to-fine procedure is employed.The proposed method includes a multiple partition strategy and a refinement in gradient image that improves the reliability and accuracy of water body detection.By fusing water bodies detected in multiple images,hot spots in these water bodies are also detected.Experiments validate the feasibility and effectiveness of the proposed method.展开更多
Here,we introduce the first experimental proof of coherent oscillation and coupling of photoswitchable molecules embedded randomly in a polymeric matrix and acting cooperatively upon illumination with UV light.In part...Here,we introduce the first experimental proof of coherent oscillation and coupling of photoswitchable molecules embedded randomly in a polymeric matrix and acting cooperatively upon illumination with UV light.In particular,we demonstrate the specular reflection and Brewster phenomenon alteration of photochromic molecular dipole antennas.We successfully demonstrate the concept of Brewster wavelength,which is based on the dipolar interaction between radiating dipoles and the surrounding matrix possessing a net dipole moment,as a key tool for highly localized sensing of matrix polarity.We also introduce the concept of‘tailored molecular photonic coupling’while highlighting the role of interferences for the design of optically active media by adjusting the photonic response of the medium with the real and imaginary refractive index of photoswitchable molecules in the‘ON’state.Our results enhance our fundamental understanding of coherent dipole radiation and open a new vein of research based on glassy disordered dipolar composites that act as macroscopic antenna with cooperative action;furthermore,these results have important implications for new design rules of tailored photonics.展开更多
文摘This paper presents the solution of coupled radiative transfer equation with heat conduction equation in complex three-dimensional geometries. Due to very different time scales for both physics, the radiative problem is considered steady-state but solved at each time iteration of the transient conduction problem. The discrete ordinate method along with the decentered streamline-upwind Petrov-Galerkin method is developed. Since specular reflection is considered on borders, a very accurate algorithm has been developed for calculation of partition ratio coefficients of incident solid angles to the several reflected solid angles. The developed algorithms are tested on a paraboloid-shaped geometry used for example on concentrated solar power technologies.
文摘The spin-dependent Andreev reflection is investigated theoretically by analyzing the electronic transport in a thin-film topological insulator(TI)ferromagnet/superconductor(FM/SC)junction.The tunneling conductance and shot noise are calculated based on the Dirac-Bogoliubov-de Gennes equation and Blonder-Tinkham-Klapwijk theory.It is found that the magnetic gap in ferromagnet can enhance the Andreev retro-reflection but suppress the specular Andreev reflection.The gate potential applied to the electrode on top of superconductor can enhance the two types of reflections.There is a transition between the two types of reflections at which both the tunneling conductance and differential shot noise become zero.These results provide a method to realize and detect experimentally the intra-band specular Andreev reflection in thin film TI-based FM/SC structures.
基金supported by the Deutsche Forschungsgemeinschaft under grant number BR2245/4–1
文摘Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from one and the same camera position but under varying illumination. The vast majority of studies in this 3D reconstruction method assume orthographic projection for the camera model.In addition, they mainly use the Lambertian reflectance model as the way that light scatters at surfaces.Thus, providing reliable photometric stereo results from real world objects still remains a challenging task. We address 3D reconstruction by use of a more realistic set of assumptions, combining for the first time the complete Blinn–Phong reflectance model and perspective projection. Furthermore, we compare two different methods of incorporating the perspective projection into our model. Experiments are performed on both synthetic and real world images; the latter do not benefit from laboratory conditions. The results show the high potential of our method even for complex real world applications such as medical endoscopy images which may include many specular highlights.
基金This work was supported by the National Basic Research Program of China(973 Program)[grant number 2012CB719901]the National Natural Science Foundation of China(grant number 91438112)the Foundation for the Author of National Excellent Doctoral Dissertation of China(FANEDD)[grant number 201249].
文摘In aerial images,near-specular and specular reflection often appear in water bodies.They often lead to irregular brightness or color changes in water bodies and even produce hot spots,harmful to radiometric normalization.Therefore,water bodies must be eliminated when calculating radiometric differences during radiometric normalization of aerial images.In this paper,a simple method to detect water bodies in aerial images based on texture features is presented,an improved seeded region growing(SRG)method.A texture feature is calculated using the relative standard deviation index(RSDI)and a coarse-to-fine procedure is employed.The proposed method includes a multiple partition strategy and a refinement in gradient image that improves the reliability and accuracy of water body detection.By fusing water bodies detected in multiple images,hot spots in these water bodies are also detected.Experiments validate the feasibility and effectiveness of the proposed method.
基金We gratefully acknowledge financial support from the German Research Foundation(DFG)through SFB677(C09)and partial financial support from SFB677(C01)as well as the German Academic Exchange Service(DAAD)ME thanks the Initiative and Networking Fund of the Helmholtz Association(Grant no.VH-NG-523)for providing the financial support to start his research group.
文摘Here,we introduce the first experimental proof of coherent oscillation and coupling of photoswitchable molecules embedded randomly in a polymeric matrix and acting cooperatively upon illumination with UV light.In particular,we demonstrate the specular reflection and Brewster phenomenon alteration of photochromic molecular dipole antennas.We successfully demonstrate the concept of Brewster wavelength,which is based on the dipolar interaction between radiating dipoles and the surrounding matrix possessing a net dipole moment,as a key tool for highly localized sensing of matrix polarity.We also introduce the concept of‘tailored molecular photonic coupling’while highlighting the role of interferences for the design of optically active media by adjusting the photonic response of the medium with the real and imaginary refractive index of photoswitchable molecules in the‘ON’state.Our results enhance our fundamental understanding of coherent dipole radiation and open a new vein of research based on glassy disordered dipolar composites that act as macroscopic antenna with cooperative action;furthermore,these results have important implications for new design rules of tailored photonics.
