Abstract:This paper describes algorithm improvements for FY-2 meteorological satellite at image navigation and wind vector derivation.From which,the pathways on solving problems at mission implementation are summarized.

Abstract:This study aims to examine change features from the early years of the Nanjing University of Information Science and Technology (NUIST) to present using satellite images.A total of five cloud-free images acquired between November 1964 and December 1970 have been analyzed.The image positional accuracy after georeferencing is in the range of 4.8 and 7.8 m.Buildings,road structures,and water bodies are clearly discernible in these images.A comparison has been made between these black and white spy satellite images and color images from the Google Earth collection for the period between 2006 and 2018.The present-day campus is considerably larger than the old campus.Additionally,the old track field has expanded from a total track length of 298 m according to a 1968 spy image to 406.5 m according to a Google Earth 2006 image,and the center of the field has moved east by 9 m and south by 47 m.The spy and Google Earth images are georeferenced to a common coordinate and are archived as online supplements to this paper.

Abstract:This paper presents an overview on the studies of pinning control for complex networks over the past decade.Firstly,we summarize the pinning control algorithms for synchronizing complex networks.Then,based on network topology and node dynamics,some necessary or sufficient conditions for the pinning control of complex networks are discussed.For the pinning-controlled complex networks,we address the strategies for selecting the pinned nodes in detail,and comprehensively analyze the effects of the pinned-node number,the coupling strength,the pinning feedback gains and the node dynamics on the pinning control of complex networks.Moreover,we discuss the progress in the pinning control of signed networks where exist both cooperative and competitive relationships and provide some brief introduction for the application of the pinning control of complex networks.Finally,some suggestions are given to address the future research trends for the pinning control of complex networks.

Abstract:With rapid development of the Internet and social media platforms,hundreds of millions of users have created and shared information as a large quantities of text,image,audio,and video data.Given this large volume of heterogeneous,multi-source,and complex social multimedia content,the challenge of providing effective content understanding and knowledge representation to users with more efficient and high-quality service has become the key to realizing the value of big social media data.This paper reviews research on social multimedia content analysis,knowledge extraction and representation,and on user modeling applications in recent years.In addition,research on social multi-modal feature fusion,cross-modal knowledge extraction and representation,and user modeling based on social media has been presented in detail.We then discuss development trends in social multimedia content knowledge representation,and review research into and application of user modeling.Finally,we summarize likely research directions for multimedia knowledge representation and user modeling.

Abstract:Wireless covert communication is the technology of hiding messages in wireless communication data frames and signals for covert transmission,which belongs to the cross-field of wireless communication and information hiding technology.This paper analyzes the system model and main ability factors of wireless covert communication,summarizes the theory of noise-type covert channel capacity and the research progress of wireless covert communication technology in link layer,coding layer,modulation layer and signal layer,and gives the problems that need further study.

Abstract:Atmospheric gravity wave is an important atmospheric dynamic disturbance widely existing in the Earth's atmosphere.It is of great significance to study its distribution and variations for understanding atmospheric physics,atmospheric structure and atmospheric dynamics.Traditional methods of atmospheric gravity wave detection,such as radar and sounding balloon,have the weaknesses of short detection time and low effective detection altitude.The Global Navigation Satellite System (GNSS) Radio Occultation with the advantages of all-weather,low cost and high accuracy has been widely used in the earth's atmosphere detection and research,which provides new observation data for the study of regional or global gravity wave variation and activity characteristics.In this paper,the occultation data of the first Chinese GNSS radio occultation satellite-Fengyu-3C (FY-3C) are used to obtain the atmospheric temperature profile from August 2014 to December 2016,and then the spatial and temporal distribution of gravity wave parameters is estimated and analyzed for the first time.The results show that the potential energy of gravity wave in winter and summer is stronger than that in spring and autumn due to seasonal convection between the land and the sea.Equatorial convection leads to stronger gravity wave in the equatorial region than in the two polar regions.In summer,gravity wave activity is frequent in the middle and low latitudes of the southern hemisphere,and in winter,gravity waves in the middle and low latitudes of the northern hemisphere are active.With the increase of altitude,the potential energy of gravity wave decreases gradually.In addition,the topography is the main source of gravity waves in the lower atmosphere.

Abstract:The setting of socio-economic scenarios is the basis of climate change research and the key point of climate change impact assessment.In this paper,we review the development process of socio-economic scenarios,provide the description of the main characteristics and the latest development trend of shared socio-economic pathways,and introduce the construction of regional socio-economic scenarios and its applications in the field of disaster risk.Finally the prospects for shared socio-economic pathways are discussed.

Abstract:Due to the intensification of human activities,the pattern of global atmospheric circulation is significantly affected.The increase of global average temperature leads to the increase of the magnitude,frequency and duration of drought events,which has a significant effect on the forest ecosystem.Based on the existing research,this paper systematically summarizes the effects of drought events on the geographical distribution pattern,community structure reconstruction,plant growth and physiological characteristics,death and extinction,plant productivity,and carbon cycle function of forest ecosystems.To this end,future research should focus on the long-term effects of drought events and the mechanisms of action at different time scales on forest ecosystems.It has important guiding significance for the research field of forest ecosystem response mechanism to drought events in the context of global change.

Abstract:Over the past few decades,the research into and application of hyperspectral images has made significant progress,with interest levels progressing from very little to intense.Among the many aspects of this research,hyperspectral image classification has become one of the most-studied topics,with experiments showing that the spatial spectral joint classification method can achieve better classification results than the pixel-by-pixel classification method that relies on spectral information alone.Here,we classified and analyzed a number of spatial spectral joint classification methods.First,we introduced two kinds of spatial dependence relations between adjacent pixels in hyperspectral images;using these,we were able to classify existing spatial-spectral classification methods into fixed-dependent neighborhood-based and adaptive neighborhood-based types.In addition,we were able to further divide existing methods into two types,single-dependency and double-dependency,based on whether or not we used two types of dependencies at the same time.We were also able to divide existing classification methods into three types:preprocessing,integration,and post-processing,according to the different fusion stages of the spatial and spectral information.Finally,we showed the classification results achieved from the application of several representative spatial-spectral classification methods to real hyperspectral datasets.

Abstract:In this paper,new boundary differential equations for the two-dimensional exterior scattering problem have been derived.It has been shown that the Helmholtz equation can be reduced to an inhomogeneous Bessel's equation in a body-fitted coordinate system.By imposing the Sommerfeld radiation condition to the general solution of the Bessel's equation,an integro-differential equation,which is equivalent to the original Helmholtz equation,can be obtained.The boundary differential equation can then be established by use of the integration by parts to get rid of the integral in the integro-differential equation for high frequency problems.Numerical examples have been presented to demonstrate the validity of the new boundary differential equations.

Abstract:In this study,we examined the influence of low temperature and low light intensity stress on the soluble sugar,soluble protein,and free amino acid content in different organs and on dry matter distribution in greenhouse tomato seedlings.We used Photosynthetically Active Radiation (PAR) at 800 μmol·m^-2·s^-1 and temperature of 25℃ as control(CK),and set up an experiment involving six treatments[L1T1 (PAR 200 μmol·m^-2·s^-1,4℃),L1T2 (PAR 200 μmol·m^-2·s^-1,6℃),L1T3 (PAR 200 μmol·m^-2·s^-1,8℃),L2T1 (PAR 400 μmol·m^-2·s^-1,4℃),L2T2 (PAR 400 μmol·m^-2·s^-1,6℃),and L2T3 (PAR 400 μmol·m^-2·s^-1,8℃)] that were monitored for 6,12,24,48,and 72 h,respectively.The results showed that the dry matter distribution ratio in the underground part of the plant was lower than that in the ground-level parts and opposite to that in the aboveground part.Low temperature and low light intensity stress significantly reduced the soluble sugar,soluble protein,and free amino acid content of the stems and leaves.The soluble sugar content in the roots was not consistent with the aboveground parts but was highest in the roots,stems,and leaves (94.88 mg·g^-1,77.09 mg·g^-1 and 41.62 mg·g^-1,respectively) after 72 h in the L2T3 treatment.The soluble protein content in the roots was not consistent with the aboveground part but was highest in both the stems and leaves after 12 h in the L2T3 treatment and lowest after 72 h in the L1T1 treatment.The free amino acid content in different organs showed an effect opposite to that of the soluble protein content when the stress exposure time was prolonged.Low light had less of an effect on dry matter and nutrient content than low temperatures did.The results showed that dry matter and nutrients were distributed to the ground-level part of the plant during the early stages of exposure to stress,and then to the root system after 24 h of stress exposure.The results provide a theoretical basis for improved loss prevention due to low temperature or low light stress in crops grown in facilities such as greenhouses.

Abstract:With the development of 5G communication technology and its diverse application scenarios,the requirements for access flexibility in optical fiber communication systems have increased.Probabilistic shaping is a new modulation and coding technology with lower complexity and higher flexibility.Currently,this technology has mobilized research across the world and attracted the attention of many researchers.Probabilistic shaping not only enables flexible broadband optical access,but also optimizes quadrature amplitude modulation signals at the scale of large constellations.In this study,we will discuss a series of research achievements by our team in the field of probabilistic shaping,and hope to provide guidance and references for future optical fiber communication systems.

Abstract:In this study,we proposed a low-loss microwave negative group delay circuit with a waveshape.The proposed circuit is composed mainly of four identical microstrip transmission lines,two identical coupled microstrip lines,and a T-shaped connector.After describing the equivalent circuit topology,the S-parameter model and the negative group delay formula of the circuit were derived using microwave circuit theory.The circuit structure was optimized using ADS simulation,and the fabrication and measurement were carried out.Test results showed that at a center frequency of 1.017 GHz,the maximum group delay of the circuit was -2.46 ns,the insertion loss was -2.1 dB,and the reflection loss was -13 dB.The measured results were in good agreement with results from both simulations and theoretical calculations.