The Experts below are selected from a list of 7302 Experts worldwide ranked by ideXlab platform

Sebastian J. Szybka - One of the best experts on this subject based on the ideXlab platform.

  • Light propagation in Swiss-cheese cosmologies
    Physical Review D, 2011
    Co-Authors: Sebastian J. Szybka
    Abstract:

    We study the effect of inhomogeneities on Light propagation. The Sachs equations are solved numerically in the Swiss-Cheese models with inhomogeneities modelled by the Lemaitre-Tolman solutions. Our results imply that, within the models we study, inhomogeneities may partially mimic the accelerated expansion of the Universe provided the Light Propagates through regions with lower than the average density. The effect of inhomogeneities is small and full randomization of the photons' trajectories reduces it to an insignificant level.

Lan Yang - One of the best experts on this subject based on the ideXlab platform.

  • wireless whispering gallery mode sensor for thermal sensing and aerial mapping
    Light-Science & Applications, 2018
    Co-Authors: Weijian Chen, Guangming Zhao, Lan Yang
    Abstract:

    The Internet of Things (IoT)1,2 employs a large number of spatially distributed wireless sensors to monitor physical environments, e.g., temperature, humidity, and air pressure, and has many applications, including environmental monitoring3, health care monitoring4, smart cities5, and precision agriculture. A wireless sensor can collect, analyze, and transmit measurements of its environment1,2. Currently, wireless sensors used in the IoT are predominately based on electronic devices that may suffer from electromagnetic interference in many circumstances. Being immune to the electromagnetic interference, optical sensors provide a significant advantage in harsh environments6. Furthermore, by introducing optical resonance to enhance Light–matter interactions, optical sensors based on resonators exhibit small footprints, extreme sensitivity, and versatile functionalities7,8, which can significantly enhance the capability and flexibility of wireless sensors. Here we provide the first demonstration of a wireless photonic sensor node based on a whispering-gallery-mode (WGM) optical resonator, in which Light Propagates along the circular rim of such a structure like a sphere, a disk, or a toroid by continuous total internal reflection. The sensor node is controlled via a customized iOS app. Its performance was studied in two practical scenarios: (1) real-time measurement of the air temperature over 12 h and (2) aerial mapping of the temperature distribution using a sensor node mounted on an unmanned drone. Our work demonstrates the capability of WGM optical sensors in practical applications and may pave the way for the large-scale deployment of WGM sensors in the IoT.

Pierre Fleury - One of the best experts on this subject based on the ideXlab platform.

  • Swiss-cheese models and the Dyer-Roeder approximation
    Journal of Cosmology and Astroparticle Physics, 2014
    Co-Authors: Pierre Fleury
    Abstract:

    In view of interpreting the cosmological observations precisely, especially when they involve narrow Light beams, it is crucial to understand how Light Propagates in our statistically homogeneous, clumpy, Universe. Among the various approaches to tackle this issue, Swiss-cheese models propose an inhomogeneous spacetime geometry which is an exact solution of Einstein's equation, while the Dyer-Roeder approximation deals with inhomogeneity in an effective way. In this article, we demonstrate that the distance-redshift relation of a certain class of Swiss-cheese models is the same as the one predicted by the Dyer-Roeder approach, at a well-controlled level of approximation. Both methods are therefore equivalent when applied to the interpretation of, e.g., supernova obervations. The proof relies on completely analytical arguments, and is illustrated by numerical results.

Chunle Guo - One of the best experts on this subject based on the ideXlab platform.

  • emerging from water underwater image color correction based on weakly supervised color transfer
    IEEE Signal Processing Letters, 2018
    Co-Authors: Jichang Guo, Chunle Guo
    Abstract:

    Underwater vision suffers from severe effects due to selective attenuation and scattering when Light Propagates through water. Such degradation not only affects the quality of underwater images, but limits the ability of vision tasks. Different from existing methods that either ignore the wavelength dependence on the attenuation or assume a specific spectral profile, we tackle color distortion problem of underwater images from a new view. In this letter, we propose a weakly supervised color transfer method to correct color distortion. The proposed method relaxes the need for paired underwater images for training and allows the underwater images being taken in unknown locations. Inspired by cycle-consistent adversarial networks, we design a multiterm loss function including adversarial loss, cycle consistency loss, and structural similarity index measure loss, which makes the content and structure of the outputs same as the inputs, meanwhile the color is similar to the images that were taken without the water. Experiments on underwater images captured under diverse scenes show that our method produces visually pleasing results, even outperforms the state-of-the-art methods. Besides, our method can improve the performance of vision tasks.

  • emerging from water underwater image color correction based on weakly supervised color transfer
    arXiv: Computer Vision and Pattern Recognition, 2017
    Co-Authors: Jichang Guo, Chunle Guo
    Abstract:

    Underwater vision suffers from severe effects due to selective attenuation and scattering when Light Propagates through water. Such degradation not only affects the quality of underwater images but limits the ability of vision tasks. Different from existing methods which either ignore the wavelength dependency of the attenuation or assume a specific spectral profile, we tackle color distortion problem of underwater image from a new view. In this letter, we propose a weakly supervised color transfer method to correct color distortion, which relaxes the need of paired underwater images for training and allows for the underwater images unknown where were taken. Inspired by Cycle-Consistent Adversarial Networks, we design a multi-term loss function including adversarial loss, cycle consistency loss, and SSIM (Structural Similarity Index Measure) loss, which allows the content and structure of the corrected result the same as the input, but the color as if the image was taken without the water. Experiments on underwater images captured under diverse scenes show that our method produces visually pleasing results, even outperforms the art-of-the-state methods. Besides, our method can improve the performance of vision tasks.

Min Huang - One of the best experts on this subject based on the ideXlab platform.

  • The influence of Light propagation direction on the stress-induced polarization dependence of silicon waveguides
    IEEE Photonics Technology Letters, 2006
    Co-Authors: Min Huang
    Abstract:

    This letter studies the effects of Light propagation direction on the stress-induced polarization dependence of silicon-based waveguides. Silicon is an anisotropic material, so the stresses and the corresponding change of polarization dependence vary with the Light propagation directions. The analyses show that when the Light Propagates in lang010rang directions on (100) silicon, the stress-induced changes of refractive index and the birefringence in effective index are about 20% more sensitive to the stresses than those when the Light Propagates in lang011rang directions