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Yuchen Shao, Xiuyou Han, Ming Li, Mingshan Zhao
Low-power radio frequency (RF) signal detection is highly desirable for many applications, ranging from wireless communication to radar systems. A tunable optoelectronic oscillator (OEO) based on a phase-shifted fiber Bragg grating for detecting low-power RF signals is proposed and experimentally demonstrated. When the frequency of the input RF signal is matched with the potential oscillation mode of the OEO, it is detected and amplified. The frequency of the RF signal under detection can be estimated simultaneously by scanning the wavelength of the laser source...
March 15, 2018: Optics Letters
Qiang Shen, Hansheng Wang, C K Shum, Liming Jiang, Hou Tse Hsu, Jinglong Dong
We constructed Antarctic ice velocity maps from Landsat 8 images for the years 2014 and 2015 at a high spatial resolution (100 m). These maps were assembled from 10,690 scenes of displacement vectors inferred from more than 10,000 optical images acquired from December 2013 through March 2016. We estimated the mass discharge of the Antarctic ice sheet in 2008, 2014, and 2015 using the Landsat ice velocity maps, interferometric synthetic aperture radar (InSAR)-derived ice velocity maps (~2008) available from prior studies, and ice thickness data...
March 14, 2018: Scientific Reports
Manoochehr Shirzaei, Roland Bürgmann
The current global projections of future sea level rise are the basis for developing inundation hazard maps. However, contributions from spatially variable coastal subsidence have generally not been considered in these projections. We use synthetic aperture radar interferometric measurements and global navigation satellite system data to show subsidence rates of less than 2 mm/year along most of the coastal areas along San Francisco Bay. However, rates exceed 10 mm/year in some areas underlain by compacting artificial landfill and Holocene mud deposits...
March 2018: Science Advances
Ning Li, Shilin Niu, Zhengwei Guo, Yabo Liu, Jiaqi Chen
For accurate motion compensation (MOCO) in airborne synthetic aperture radar (SAR) imaging, a high-precision inertial navigation system (INS) is required. However, an INS is not always precise enough or is sometimes not even included in airborne SAR systems. In this paper, a new, raw, data-based range-invariant motion compensation approach, which can effectively extract the displacements in the line-of-sight (LOS) direction, is proposed for high-resolution sliding spotlight SAR mode. In this approach, the sub-aperture radial accelerations of the airborne platform are estimated via a well-developed weighted total least square (WTLS) method considering the time-varying beam direction...
March 12, 2018: Sensors
Young-Duk Kim, Guk-Jin Son, Chan-Ho Song, Hee-Kang Kim
Recently, radar technology has attracted attention for the realization of an intelligent transportation system (ITS) to monitor, track, and manage vehicle traffic on the roads as well as adaptive cruise control (ACC) and automatic emergency braking (AEB) for driving assistance of vehicles. However, when radar is installed on roads or in tunnels, the detection performance is significantly dependent on the deployment conditions and environment around the radar. In particular, in the case of tunnels, the detection accuracy for a moving vehicle drops sharply owing to the diffuse reflection of radio frequency (RF) signals...
March 11, 2018: Sensors
Bing Han, Chibiao Ding, Lihua Zhong, Jiayin Liu, Xiaolan Qiu, Yuxin Hu, Bin Lei
The Gaofen-3 (GF-3) data processor was developed as a workstation-based GF-3 synthetic aperture radar (SAR) data processing system. The processor consists of two vital subsystems of the GF-3 ground segment, which are referred to as data ingesting subsystem (DIS) and product generation subsystem (PGS). The primary purpose of DIS is to record and catalogue GF-3 raw data with a transferring format, and PGS is to produce slant range or geocoded imagery from the signal data. This paper presents a brief introduction of the GF-3 data processor, including descriptions of the system architecture, the processing algorithms and its output format...
March 10, 2018: Sensors
Tom Margham, Natalie Symes, Sally A Hull
BACKGROUND: Identifying patients at risk of harm in general practice is challenging for busy clinicians. In UK primary care, trigger tools and case note reviews are mainly used to identify rates of harm in sample populations. AIM: This study explores how adaptions to existing trigger tool methodology can identify patient safety events and engage clinicians in ongoing reflective work around safety. DESIGN AND SETTING: Mixed-method quantitative and narrative evaluation using thematic analysis in a single East London training practice...
March 12, 2018: British Journal of General Practice: the Journal of the Royal College of General Practitioners
Junxiang Wang, Xianpeng Wang, Dingjie Xu, Guoan Bi
This paper deals with joint estimation of direction-of-departure (DOD) and direction-of- arrival (DOA) in bistatic multiple-input multiple-output (MIMO) radar with the coexistence of unknown mutual coupling and spatial colored noise by developing a novel robust covariance tensor-based angle estimation method. In the proposed method, a third-order tensor is firstly formulated for capturing the multidimensional nature of the received data. Then taking advantage of the temporal uncorrelated characteristic of colored noise and the banded complex symmetric Toeplitz structure of the mutual coupling matrices, a novel fourth-order covariance tensor is constructed for eliminating the influence of both spatial colored noise and mutual coupling...
March 9, 2018: Sensors
Isahar Gabay, Amir Shemer, Ariel Schwarz, Zeev Zalevsky
In this paper, we present an advanced two-dimensional (2D) novel microwave photonic approach to super-resolved radar imaging. Unlike synthetic aperture radar that requires movement to improve resolution by synthetically increasing the antenna's dimensions, our super-resolved imaging solution not only does not require movement to synthetically increase the antenna's dimensions, it also allows this super-resolved sensing with only a single (mono) detector. The operation principle is based upon phased array antennas, which consist of four radiating horn antennas that generate a projected plane at the far field zone...
March 1, 2018: Applied Optics
Thibault Catry, Zhichao Li, Emmanuel Roux, Vincent Herbreteau, Helen Gurgel, Morgan Mangeas, Frédérique Seyler, Nadine Dessay
The prevention and control of mosquito-borne diseases, such as malaria, are important health issues in tropical areas. Malaria transmission is a multi-scale process strongly controlled by environmental factors, and the use of remote-sensing data is suitable for the characterization of its spatial and temporal dynamics. Synthetic aperture radar (SAR) is well-adapted to tropical areas, since it is capable of imaging independent of light and weather conditions. In this study, we highlight the contribution of SAR sensors in the assessment of the relationship between vectors, malaria and the environment in the Amazon region...
March 7, 2018: International Journal of Environmental Research and Public Health
Sha Jiang, Xiaolan Qiu, Bing Han, Wenlong Hu
The GaoFen-3 (GF-3) satellite, launched on 10 August 2016, is the first C-band polarimetric synthetic aperture radar (PolSAR) satellite in China. The PolSAR system of GF-3 can collect a significant wealth of information for geophysical research and applications. Being used for related applications, GF-3 PolSAR images must be of good quality. It is necessary to evaluate the quality of polarimetric data and achieve the normalized quality monitoring during 8-year designed life of GF-3. In this study, a new quality assessment method of PolSAR data based on common distributed targets is proposed, and the performance of the method is analyzed by simulations and GF-3 experiments...
March 7, 2018: Sensors
Zhengyan Zhang, Jianyun Zhang, Qingsong Zhou, Xiaobo Li
In this paper, we consider the problem of tracking the direction of arrivals (DOA) and the direction of departure (DOD) of multiple targets for bistatic multiple-input multiple-output (MIMO) radar. A high-precision tracking algorithm for target angle is proposed. First, the linear relationship between the covariance matrix difference and the angle difference of the adjacent moment was obtained through three approximate relations. Then, the proposed algorithm obtained the relationship between the elements in the covariance matrix difference...
March 7, 2018: Sensors
Min Liu, Zhou Li, Lu Liu
Sidelobe reduction is a very primary task for synthetic aperture radar (SAR) images. Various methods have been proposed for broadside SAR, which can suppress the sidelobes effectively while maintaining high image resolution at the same time. Alternatively, squint SAR, especially highly squint SAR, has emerged as an important tool that provides more mobility and flexibility and has become a focus of recent research studies. One of the research challenges for squint SAR is how to resolve the severe range-azimuth coupling of echo signals...
March 5, 2018: Sensors
Bonan Jin, Xiaosu Xu, Tao Zhang
Finding the position of a radiative source based on time-difference-of-arrival (TDOA) measurements from spatially separated receivers has been widely applied in sonar, radar, mobile communications and sensor networks. For the nonlinear model in the process of positioning, Taylor series and other novel methods are proposed. The idea of cone constraint provides a new way of solving this problem. However, these approaches do not always perform well and are away from the Cramer-Rao-Lower-Bound (CRLB) in the situations when the source is set at the array edge, the noise in measurement is loud, or the initial position is biased...
March 4, 2018: Sensors
Lei Wang, Xin Xu, Hao Dong, Rong Gui, Fangling Pu
Convolutional neural networks (CNN) have achieved great success in the optical image processing field. Because of the excellent performance of CNN, more and more methods based on CNN are applied to polarimetric synthetic aperture radar (PolSAR) image classification. Most CNN-based PolSAR image classification methods can only classify one pixel each time. Because all the pixels of a PolSAR image are classified independently, the inherent interrelation of different land covers is ignored. We use a fixed-feature-size CNN (FFS-CNN) to classify all pixels in a patch simultaneously...
March 3, 2018: Sensors
Antonio-Javier Gallego, Pablo Gil, Antonio Pertusa, Robert B Fisher
In this work, we use deep neural autoencoders to segment oil spills from Side-Looking Airborne Radar (SLAR) imagery. Synthetic Aperture Radar (SAR) has been much exploited for ocean surface monitoring, especially for oil pollution detection, but few approaches in the literature use SLAR. Our sensor consists of two SAR antennas mounted on an aircraft, enabling a quicker response than satellite sensors for emergency services when an oil spill occurs. Experiments on TERMA radar were carried out to detect oil spills on Spanish coasts using deep selectional autoencoders and RED-nets (very deep Residual Encoder-Decoder Networks)...
March 6, 2018: Sensors
C Yuan-Yuan, Z Guo-Ding, G U Ya-Ping, X U Xiang-Zhen, J Xiao-Lin, Z Hua-Yun, W Jie, L You-Sheng, Y Kun, C Jun
Objective To understand the integrated ability of parasitic disease prevention and control of professional personnel of Jiangsu Province through the contest. Methods Totally 56 players from the whole province were selected, and all the players participated in the contest. The theory knowledge and skill scores were collected and the statistical analyses were conducted. Results The average theoretical score of the participants was 88.86±15.56 and the passing rate was 91.1%. The average skill operating score was 69...
March 21, 2017: Zhongguo Xue Xi Chong Bing Fang Zhi za Zhi, Chinese Journal of Schistosomiasis Control
Maria Gabrielsen Jumbert
The matter of boat migrants crossing the Mediterranean Sea, seeking to reach Europe, is interchangeably defined as a 'security issue', requiring stricter border controls, and as a humanitarian issue with corresponding rescue and protection requirements. This paper seeks to understand what role various surveillance technologies, such as radar, satellites, and unmanned aerial vehicles, can play in this respect (legally and technically), in comparison to the role that they are assigned (that is, political expectations)...
March 5, 2018: Disasters
Rui Wang, Cheng Hu, Xiaowei Fu, Teng Long, Tao Zeng
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
March 1, 2018: Scientific Reports
Zhao Liu, Chaorong Zheng, Yue Wu
Recently, the government installed a boundary layer profiler (BLP), which is operated under the Doppler beam swinging mode, in a coastal area of China, to acquire useful wind field information in the atmospheric boundary layer for several purposes. And under strong wind conditions, the performance of the BLP is evaluated. It is found that, even though the quality controlled BLP data show good agreement with the balloon observations, a systematic bias can always be found for the BLP data. For the low wind velocities, the BLP data tend to overestimate the atmospheric wind...
February 2018: Review of Scientific Instruments
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