Difference scattering field properties between periodic defect particles and three-dimensional slightly rough optical surface

Based on the practical situation of nondestructive examination, the calculation model of the composite scattering is established by using a three-dimensional half-space finite difference time domain, and the Monte Carlo method is used to solve the problem of the optical surface with roughness in the proposed scheme. Moreover, the defect particles are observed as periodic particles for a more complex situation. In order to obtain the scattering contribution of defects inside the optical surface, a difference radar cross section is added into the model to analyze the selected calculations on the effects of numbers, separation distances, different depths and different materials of defects. The effects of different incident angles are also discussed. The numerical results are analyzed in detail to demonstrate the best position to find the defects in the optical surface by detecting in steps of a fixed degree for the incident angle.

Seasonal Variation of the East Asian Subtropical Westerly Jet and Its Association with the Heating Field over East Asia

The structure and seasonal variation of the East Asian Subtropical Westerly Jet （EAWJ） and associations with heating fields over East Asia are examined by using NCEP/NCAR reanalysis data. Obvious differences exist in the westerly jet intensity and location in different regions and seasons due to the ocean-land distribution and seasonal thermal contrast, as well as the dynamic and thermodynamic impacts of the Tibetan Plateau. In winter, the EAWJ center is situated over the western Pacific Ocean and the intensity is reduced gradually from east to west over the East Asian region. In summer, the EAWJ center is located over the north of the Tibetan Plateau and the jet intensity is reduced evidently compared with that in winter. The EAWJ seasonal evolution is characterized by the obvious longitudinal inconsistency of the northward migration and in-phase southward retreat of the EAWJ axis. A good correspondence between the seasonal variations of EAWJ and the meridional differences of air temperature （MDT） in the mid-upper troposphere demonstrates that the MDT is the basic reason for the seasonal variation of EAWJ. Correlation analyses indicate that the Kuroshio Current region to the south of Japan and the Tibetan Plateau are the key areas for the variations of the EAWJ intensities in winter and in summer, respectively. The strong sensible and latent heating in the Kuroshio Current region is closely related to the intensification of EAWJ in winter. In summer, strong sensible heating in the Tibetan Plateau corresponds to the EAWJ strengthening and southward shift, while the weak sensible heating in the Tibetan Plateau is consistent with the EAWJ weakening and northward migration.

Dynamic measurement of beam divergence angle of different fields of view of scanning lidar

The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.

Real-time digital image stabilization based on regional field image gray projection

Digital image stabilization technique plays important roles in video surveillance and object acquisition.Many useful electronic image stabilization algorithms have been studied.A real-time algorithm is proposed based on field image gray projection which enables the regional odd and even field image to be projected into x and y directions and thus to get the regional gray projection curves in x and y directions,respectively.For the odd field image channel,motion parameters can be estimated via iterative minimum absolute difference based on two successive field image regional gray projection curves.Then motion compensations can be obtained after using the Kalman filter method.Finally,the odd field image is adjusted according to the compensations.In the mean time,motion compensation is applied to the even field image channel with the odd field image gray projection curves of the current frame.By minimizing absolute difference between odd and even field image gray projection curves of the current frame,the inter-field motion parameters can be estimated.Therefore,the even field image can be adjusted by combining the inter-field motion parameters and the odd field compensations.Finally,the stabilized image sequence can be obtained by synthesizing the adjusted odd and even field images.Experimental results show that the proposed algorithm can run in real-time and have a good stabilization performance.In addition,image blurring can be improved.

Research on changes and circulations of sea-ice in Eurasian in recent 50 years

Using the monthly 1° × 1° sea-ice concentration data of Hadley center and the monthly NCEP geopotential height data from January 1953 to February 2003, temporal and spatial changing characters of sea-ice arc examined. The results show almost all of the sea-ice of eight regions was decreasing, especially all seasons in Europe. But in Asia part, those display some increasing trends in spring and winter, Abrupt times of sea-ice in Europe were at end of 1970＇ s and in Asia the times in summer/fall（spring/winter） were at end of 1980＇ s.

A novel spiking neural network of receptive field encoding with groups of neurons decision

Human information processing depends mainly on billions of neurons which constitute a complex neural network,and the information is transmitted in the form of neural spikes.In this paper,we propose a spiking neural network(SNN),named MD-SNN,with three key features:(1) using receptive field to encode spike trains from images;(2) randomly selecting partial spikes as inputs for each neuron to approach the absolute refractory period of the neuron;(3) using groups of neurons to make decisions.We test MD-SNN on the MNIST data set of handwritten digits,and results demonstrate that:(1) Different sizes of receptive fields influence classification results significantly.(2) Considering the neuronal refractory period in the SNN model,increasing the number of neurons in the learning layer could greatly reduce the training time,effectively reduce the probability of over-fitting,and improve the accuracy by 8.77%.(3) Compared with other SNN methods,MD-SNN achieves a better classification;compared with the convolution neural network,MD-SNN maintains flip and rotation invariance(the accuracy can remain at 90.44% on the test set),and it is more suitable for small sample learning(the accuracy can reach 80.15%for 1000 training samples,which is 7.8 times that of CNN).

Entanglement Teleportation via a Two-Qubit System with Anisotropic Couplings under a Different Nonuniform Magnetic Field

We examine entanglement teleportation,characterized by average fidelity,of two-qubit XY Z spin chain under different nonuniform magnetic field.The entanglement teleportation and the fidelity of entanglement teleportation are investigated separately.We show explicitly that the fidelity of entanglement teleportation can be enhanced by changing the direction of the magnetic field.This means that we can always get optimal fidelity by choosing the directions of magnetic field in the process of quantum teleportation.Moreover,the results show that in some cases the ferromagnetic chain also is a qualified candidate in the process of teleportation protocol.

Magnetic Field Configuration at the Magnetopause for Different Planetary Conditions

We have simulated the processes of transient reconnection at the nightside magnetopause by using a two-dimensional compressible MHD model.According to the simulation results,three types of global reconnection configuration at the magnetopause are proposed.The main results are summarized as follows.