摘要 :
Water depth is an important marine elements, and one of the main contents of marine surveying and
mapping. Compared with traditional single-beam and multi-beam sonar measurement methods, remote sensing
method has become an importa...
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Water depth is an important marine elements, and one of the main contents of marine surveying and
mapping. Compared with traditional single-beam and multi-beam sonar measurement methods, remote sensing
method has become an important supplementary method for bathymetric data of the area that the vessel can not
be directly reached，due to its advantages of large-scale and low-cost.
Sun glitter is an interference factor of shallow water depth multispectral remote sensing, and it contains water
depth information. Therefore, how to separate the sun glitter information and water radiation information, and
improve the inversion ability of water depth using the two parts of information, is a scientific and practical
research topic.
In this study, the Lingshui Bay of Hainan Island was selected as the main study area, and the sun glitter separation
method of high resolution multispectral remote sensing images and the semi-empirical water depth inversion
models are evaluated and analyzed. And a multi-spectral remote sensing inversion method for water depth
without the support of measured water depth data was developed. The following research results are obtained:
The semi-empirical water depth inversion models were used for inversion and evaluation analysis of the water
radiation information obtained by different sun glitter separation methods. Results showed that the logarithmic
ratio depth model with blue and green bands is the best in the shallow area of 10 m. When the solar radiation of
remote sensing image is weak, the best water depth inversion results can be obtained using Martin algorithm, the
R2 is 0.94, the RMSE is 1.27m. When the solar radiation of remote sensing image is strong, the best water depth
inversion results can be obtained using Hedley algorithm, the R2 is 0.89, the RMSE is 0.94m.
A multispectral remote sensing water depth inversion algorithm without the support of measured water depth
data was developed based on sun glitter information and water radiation information. The evaluation results
showed that RMSE is 0.92m in shallow waters with depth less than 6m. Therefore, this algorithm has a certain
application potential in shallow sea area without measured data.
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摘要 :
In order to ensure the reliability of satellite data, it is necessary to test the authenticity of satellite products during the
operation of ocean color satellite in orbit. Therefore, it is significant to obtain accurate sea surfa...
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In order to ensure the reliability of satellite data, it is necessary to test the authenticity of satellite products during the
operation of ocean color satellite in orbit. Therefore, it is significant to obtain accurate sea surface field data, which can
provide source data for the authenticity test of satellite products. At present, the main means of acquiring data at sea in
China is still large-scale voyage test on board ships. This method needs high cost and requires a lot of manual operation,
and the efficiency of acquiring data is extremely limited. However, a large amount of observation data can be obtained by
establishing long-term automatic observation stations at sea, and the cost is low. In this paper, the continuous observation
data of atmospheric optical parameters obtained by CE318 solar photometer installed on Wenzhou offshore platform in
Zhejiang Province are analyzed based on the data processing method of AERONET. Combined with the actual situation,
the automatic observation data of atmospheric optical parameters at sea are qualitatively controlled and verified by satellite
data. Finally, a data quality control scheme for automatic observation of atmospheric optical parameters at sea is proposed.
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摘要 :
BEEPS(bi-exponential edge-preserving filter) is used to enhance the details of infrared image in this paper. The
original infrared image has a dynamic range of 12 or 14 bits, and the human observation range is only 8 bits. Usually...
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BEEPS(bi-exponential edge-preserving filter) is used to enhance the details of infrared image in this paper. The
original infrared image has a dynamic range of 12 or 14 bits, and the human observation range is only 8 bits. Usually, the
original infrared image needs to be compressed and displayed by gray-scale remapped for displaying. For example,
automatic gain control and histogram equalization are the most widely used image display technologies in infrared
imaging systems, but they can lead to the loss of local details, and it is difficult to control the visibility of weak details in
images. Therefore, an infrared image digital detail enhancement algorithm has emerged.Current digital enhancement
algorithms can effectively enhance image details and avoid over-amplification of noise, but there are still some
drawbacks, such as large computational load and poor application flexibility.Therefore, we use BEEPS in our algorithm
to overcome these problems. This algorithm uses a two dimensional convolution to separate the detail information from
an original infrared image, and turn the original image into the detail layer and the base layer. Detail layer processing is
to transform two-dimensional convolution into one-dimensional convolution, and to complete one-dimensional
convolution through iterative calculation. Then, the enhanced detail layer is added back to the base frequency layer of
histogram equalization. This not only improves the computational efficiency, but also improves the visual quality of the
original image. The BEEPS algorithm is proved to be excellent by image and data testing.
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摘要 :
The space-dependent rate equations of passively Q-switched intracavity frequency-doubled diamond Raman lasers are
deduced for the first time. The rate equations are normalized and solved numerically to investigate the influences o...
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The space-dependent rate equations of passively Q-switched intracavity frequency-doubled diamond Raman lasers are
deduced for the first time. The rate equations are normalized and solved numerically to investigate the influences of the
normalized parameters (the normalized Raman gain coefficient, the normalized initial population inversion density, the
normalized frequency doubling factor, saturable absorber parameter, the coupling rate of the pump beam and fundamental
beam in the laser medium, the normalized loss factor, and etc) on the laser pulse parameters (pulse energy, peak power and
pulse width). The new theories and numerical results will help design passively Q-switched intracavity frequency-doubled
diamond Raman lasers of high performance.
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摘要 :
In view of the previous work, the effective radius of curvature (ERC) and Rayleigh range zR of a
general-type partially coherent beam propagating are studied in anisotropic oceanic turbulence. Based on the
extended Huygens–Fresne...
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In view of the previous work, the effective radius of curvature (ERC) and Rayleigh range zR of a
general-type partially coherent beam propagating are studied in anisotropic oceanic turbulence. Based on the
extended Huygens–Fresnel integral, we derive the formulae of the second-order moments of Wigner distribution
function (WDF) in anisotropic oceanic turbulence. The calculation results reveal that turbulent anisotropy has a
sharp impact on both the ERC and Rayleigh range for a general-type beam. In the near field, the effect of
anisotropic oceanic turbulence on the ERC is distinct. With the increase of propagation distance, these influence on
the ERC gradually weaken, and can be ignored in the far field. In addition, zR is always larger than that of the
conventional Gaussian-Shell model beam in anisotropic oceanic turbulence. And these results will be useful in
optical underwater communication.
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摘要 :
As the core component of image intensifier, the electronic multiplication performance of microchannel plate
determines the ability of the device to detect weak signals. The theoretical model of electron gain is the theoretical bas...
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As the core component of image intensifier, the electronic multiplication performance of microchannel plate
determines the ability of the device to detect weak signals. The theoretical model of electron gain is the theoretical basis
for the secondary electron multiplication of microchannel plates. It has important theoretical significance for the research
of high performance microchannel plates and image intensifiers. In this paper, the theoretical model and simulation of
electron gain in microchannel plates are reviewed. The electronic gain model and the modified theoretical model of the
"energy proportional hypothesis" are emphatically introduced. On the basis of the model, some improvements are made
and good simulation results are obtained. The behaviors of electron transport, collision and multiplication in
microchannels based on the theoretical model of electronic gain and Monte Carlo stochastic calculation method are
summarized. The differences among the three models are analyzed, and the problems existing in the theoretical model
and simulation of electronic gain at present are analyzed. Finally, aiming at the shortcomings of theoretical model and
simulation, the direction of improvement and optimization is put forward.
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摘要 :
Aiming at the characteristics that the contrast of schlieren sphere image is weak, the color of sphere
target is black, and the sphere target is surrounded by background area in the fast collimation process of
integrated diagnosti...
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Aiming at the characteristics that the contrast of schlieren sphere image is weak, the color of sphere
target is black, and the sphere target is surrounded by background area in the fast collimation process of
integrated diagnostic system, a method for calculating the schlieren sphere center based on gray stretching
and digital morphology is proposed in this paper. Firstly, the original image is transformed by linear gray
scale to enhance the contrast between the schlieren sphere target and the background area, and then the linear
gray scale image is binarized by using the OTSU method. Secondly, the background area is transformed into a
continuous connected region by using digital morphological operations such as corrosion and expansion, and
search for the maximal connected area is the background area. Thirdly, the image of using digital morphology
method and the image of background area are processed NOR operation to obtain the schlieren sphere target.
Finally, on the basis of edge detection by sobel operation, the least square method is used to fit the center and
radius of the schlieren sphere. The experimental results show that the algorithm can calculate the center of the
schlieren sphere whose gray level difference between the sphere area and the background area is greater than
10( the max gray level is 4095). The error between the center coordinate obtained by circle fitting method and
the real center coordinate is less than 2 pixels, which meets the requirement of the integrated diagnostic beam
fast automatic collimation system that the accuracy of the schlieren sphere center is less than 3 pixels.
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摘要 :
Reaction-sintered silicon carbide (RS-SiC) has been widely applied in space telescope mirrors, reflector, microelectronic
mechanical systems due to its excellent properties. These applications require high surface accuracy and qua...
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Reaction-sintered silicon carbide (RS-SiC) has been widely applied in space telescope mirrors, reflector, microelectronic
mechanical systems due to its excellent properties. These applications require high surface accuracy and quality, but
traditional mechanical contact polishing methods are hard to process this material due to the hardness and poor
machinability. In this paper, atmospheric pressure plasma processing (APPP) which is a non-contact optical manufacturing
technique with highly efficient and subsurface damage-free has been proposed to process this material, and optimal process
parameter mainly about influence on removal function for machining processing RS-SiC have been found. The sample
was observed and analyzed by scanning white-light interferometer (SWLI), which showed the calculated Peak- Maximum
removal rate (MRR) and Volume-MRR were 12.526μm/min and 0.1298mm3 /min. Meanwhile, the surface chemical
composition of RS-SiC was also investigated by XPS to reveal the plasma etching processes. The results illustrated that
small number of radicals CxFy were introduced onto the RS-SiC surface during the plasma process which could be
generated during the process of the reaction gas CF4 being excited. The process parameters and analysis of surface
chemical composition in this paper will guide the further processing of RS-SiC.
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摘要 :
The optical-mechanical model of the off-axis optical system with oscillating mirror is established. The stray light path is
analyzed on the basis of the simulation results. According to various types of stray light paths, the main...
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The optical-mechanical model of the off-axis optical system with oscillating mirror is established. The stray light path is
analyzed on the basis of the simulation results. According to various types of stray light paths, the main path of stray
light are determined and the influence of important surfaces and illumination surfaces on stray light of the camera are
clarified. Effective restraint measures are proposed without blocking the imaging light. After re-simulation, the veiling
glare indexes of the two imaging channels are greatly reduced. PST (Point Source Transmittance) is used as an index to
test the validity of stray light suppression measures. When the off-axis angle is 30 degrees, the PST of the camera
reaches 10-8, which meets the design requirements.
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摘要 :
Simultaneous localization and mapping (SLAM) had been developed in the robotics community initially, and gradually
applied to indoor positioning. The monocular visual SLAM lacks metric distances information due to scale ambiguity,...
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Simultaneous localization and mapping (SLAM) had been developed in the robotics community initially, and gradually
applied to indoor positioning. The monocular visual SLAM lacks metric distances information due to scale ambiguity, so
cannot be used in many application scenarios. This paper proposed a precision co-positioning and mapping algorithm
based on WLAN and mono vision. This method can estimate the scale factor of monocular VSLAM and get the position
in real scale space. Furthermore, the WLAN localization and monocular vision is fused by factor graph model to realize
accurate positioning and sparse mapping. Experiment results show that the algorithm can estimate scale factor well and
reached positioning accuracy of decimeter, which has good theoretical research and practical value in the field of mobile
robot navigation in indoor and outdoor environment.
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