In recent years, the ownership rate of motor vehicles has been continuously rising and their exhaust emissions have become very high. It is the main source of urban pollution at present. Therefore, in order to improve...In recent years, the ownership rate of motor vehicles has been continuously rising and their exhaust emissions have become very high. It is the main source of urban pollution at present. Therefore, in order to improve people's quality of life and achieve sustainable development, it is very important to strengthen the specific emissions and control of motor vehicle exhaust. In this way, the pollution problem can be controlled from the source and the environmental quality can be improved.展开更多
Immediate remote sensing detection and diagnosis of surface anomalies is a critical requirement to ensure the healthy development of China's social economy and national security in the new era.However,this emergin...Immediate remote sensing detection and diagnosis of surface anomalies is a critical requirement to ensure the healthy development of China's social economy and national security in the new era.However,this emerging frontier field is still in its infancy.Current researches lack not only a clear definition and analysis of concepts related to surface anomalies,but also a systematic examination of research approaches and development prospects.This study systematically summarizes the concepts and manifestation characteristics of anomaly,surface anomaly,and potential surface anomaly,and analyzes the connections and differences between them.Based on the temporal incongruence,spatial incongruence,and spatiotemporal incongruence characteristics of potential surface anomalies,three research frameworks for immediate remote sensing detection of potential surface anomalies are proposed,and the key issues and development prospects under these three research frameworks are pointed out.This study can provide research approaches and theoretical basis for immediate remote sensing detection of surface anomalies.展开更多
The objective of this study is to address semantic misalignment and insufficient accuracy in edge detail and discrimination detection,which are common issues in deep learning-based change detection methods relying on ...The objective of this study is to address semantic misalignment and insufficient accuracy in edge detail and discrimination detection,which are common issues in deep learning-based change detection methods relying on encoding and decoding frameworks.In response to this,we propose a model called FlowDual-PixelClsObjectMec(FPCNet),which innovatively incorporates dual flow alignment technology in the decoding stage to rectify semantic discrepancies through streamlined feature correction fusion.Furthermore,the model employs an object-level similarity measurement coupled with pixel-level classification in the PixelClsObjectMec(PCOM)module during the final discrimination stage,significantly enhancing edge detail detection and overall accuracy.Experimental evaluations on the change detection dataset(CDD)and building CDD demonstrate superior performance,with F1 scores of 95.1%and 92.8%,respectively.Our findings indicate that the FPCNet outperforms the existing algorithms in stability,robustness,and other key metrics.展开更多
In the field of remote sensing,the rapid and accurate acquisition of the category and location of airplanes has emerged as a prominent research.However,remote sensing fuzzy imaging and complex environmental interferen...In the field of remote sensing,the rapid and accurate acquisition of the category and location of airplanes has emerged as a prominent research.However,remote sensing fuzzy imaging and complex environmental interference affect airplane detection.Besides,the inconsistency in the size of remote sensing images and the low accuracy of small target detection are crucial challenges that need to be addressed.To tackle these issues,we propose a novel network SDaDCS(SAHI-data augmentation-dilation-channel and spatial attention)based on YOLOX model and the slicing aided hyper inference(SAHI)framework,a new data augmentation technique and dilation-channel and spatial(DCS)attention mechanism.Initially,we create a remote sensing dataset for airplane targets and introduce a new data augmentation technique based on the Rotate-Mixup and mixed data augmentation to enhance data diversity.The DCS attention mechanism,which comprises the dilated convolution block,channel attention and spatial attention,is designed to bolster the feature extraction and discrimination of the network.To address the challenges arised by the difficulties of detecting small targets,we integrate the YOLOX model with the SAHI framework.Experiment results show that,when compared to the original YOLOX model,the proposed SDaDCS remote sensing target detection algorithm enhances overall accuracy by 13.6%.The experimental results validate the effectiveness of the proposed algorithm.展开更多
Organic pollutants are harmful and toxic chemical substances that adversely threaten human health and the living environment all over the world.More and more studies have been investigating the relationship between lo...Organic pollutants are harmful and toxic chemical substances that adversely threaten human health and the living environment all over the world.More and more studies have been investigating the relationship between low level of human exposure of organic compounds and various internal diseases.For the sake of assessing disease risk due to organic compounds contact in a particular location,it is imperative for relevant government departments to make a human health risk assessment in view of the organic pollutants'bioavailability and their dosage-response correlations.It is inevitable to make use of an efficient method to detect organic pollutants,which is significant for public health and safety.Fluorescent assays based on carbon dots thus would provide a very plausible candidate method.After consulting a large number of literatures,we offer a comprehensive review of the sensing applications of carbon dots for organic pollutants.展开更多
In this study,the interaction between TPE-Ph COF and ammonia molecules,as well as the mechanism of fluorescence detection of ammonia,were comprehensively investigated using density functional theory(DFT)and time-depen...In this study,the interaction between TPE-Ph COF and ammonia molecules,as well as the mechanism of fluorescence detection of ammonia,were comprehensively investigated using density functional theory(DFT)and time-dependent density functional theory(TD-DFT).It was found that the binding between TPE-Ph COF and ammonia molecules occurs primarily through coordination bonds or hydrogen bonds.Specifically,the formation of coordination bonds significantly changes the intramolecular charge transfer of TPE-Ph COF,leading to fluorescence quenching.Computational analysis revealed the changes in electron and hole distributions upon the binding of ammonia to TPE-Ph COF,as well as the competition between nonradiative and radiative transitions during the photophysical processes,thereby elucidating the intrinsic mechanism of fluorescence response.展开更多
In the edge detection of Remote Sensing (RS) image, the useful detail losing and the spurious edge often appear. To solve the problem, the authors uses the dyadic wavelet to detect the edge of surface features by comb...In the edge detection of Remote Sensing (RS) image, the useful detail losing and the spurious edge often appear. To solve the problem, the authors uses the dyadic wavelet to detect the edge of surface features by combining the edge detecting with the multi-resolution analyzing of the wavelet transform. Via the dyadic wavelet decomposing, the RS image of a certain appropriate scale is obtained, and the edge data of the plane and the upright directions are respectively figured out, then the gradient vector module of the surface features is worked out. By tracing them, the authors get the edge data of the object, therefore build the RS image which obtains the checked edge. This method can depress the effect of noise and examine exactly the edge data of the object by rule and line. With an experiment of an RS image which obtains an airport, the authors certificate the feasibility of the application of dyadic wavelet in the object edge detection.展开更多
The spontaneous burning has been lasting for thousands of years in the coal fields in the north of China. It spreads from the west (Tianshan coal field) to the east (Huolinhe coal field). Its E-W extension is up to 37...The spontaneous burning has been lasting for thousands of years in the coal fields in the north of China. It spreads from the west (Tianshan coal field) to the east (Huolinhe coal field). Its E-W extension is up to 3750km, concentrating in N35°toN45°, its vertical depth up to 260m, and the surface temprature locally up to 270℃. Annually, it burns out 0, 250-300 million tones of coal, causing economic loss equivalent to 2-3 billion R.M.B. Yuan.It destroies coal resources and causes hazards in coal mines. In order to locate the extent and the direction in coal burning areas, the remote sensing technique has heen used and has produced an obvious benefit.展开更多
Hydrazine hydrate(DH)is an important fine chemical intermediate and as fuel for rockets,however,it also has serious toxic for humans and environment.Developing novel materials and methods for sensitive detection of DH...Hydrazine hydrate(DH)is an important fine chemical intermediate and as fuel for rockets,however,it also has serious toxic for humans and environment.Developing novel materials and methods for sensitive detection of DH in water and air is an important task.In order to effectively detect DH,a novel conductive supramolecular polymer metallogel(PQ-Ag)has been constructed by the coordination of bis-5-hydroxyquinoline functionalized pillar[5]arene(PQ5)with Ag+.The metallogel PQ-Ag could realize the multi-channel sensitive detection of DH through naked-eye,fluorescence,and electrochemical methods.The lowest limit of detection(LOD)is 0.1 mg/m^(3)in air and 2.68×10^(−8)mol/L in water,which is lower than the standard of the US Environmental Protection Agency(EPA)for DH of maximum allowable concentration in drinking water.More importantly,an electronic device for DH detection based on the metallogel PQ-Ag was designed and prepared,which can realize conveniently and efficiently multi-channel detection and alert of DH through sound and light alarms not only in water but also in air.展开更多
In this paper,an energy-harvesting cognitive radio(CR) is considered,which allows the transmitter of the secondary user(SU) to harvest the primary signal energy from the transmitter of the primary user(PU) when the pr...In this paper,an energy-harvesting cognitive radio(CR) is considered,which allows the transmitter of the secondary user(SU) to harvest the primary signal energy from the transmitter of the primary user(PU) when the presence of the PU is detected.Then the harvested energy is converted into the electrical power to supply the transmission of the SU at the detected absence of the PU.By adopting the periodic spectrum sensing,the average total transmission rate of the SU is maximized through optimizing the sensing time,subject to the constraints of the probabilities of false alarm and detection,the harvested energy and the interference rate control.The simulation results show that there deed exists an optimal sensing time that maximizes the transmission rate,and the maximum transmission rate of the energy-harvesting CR can better approach to that of the traditional CR with the increasing of the detection probability.展开更多
In order to improve the throughput of cognitive radio(CR), optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing was investigated in a CR network that includes multiple ...In order to improve the throughput of cognitive radio(CR), optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing was investigated in a CR network that includes multiple users and one fusion center. The frame structure of cooperative spectrum sensing was divided into multiple transmission time slots and one sensing time slot consisting of local energy detection and cooperative overhead. An optimization problem was formulated to maximize the throughput of CR network, subject to the constraints of both false alarm probability and detection probability. A joint optimization algorithm of sensing time and number of users was proposed to solve this optimization problem with low time complexity. An allocation algorithm of cooperative users was proposed to preferentially allocate the users to the channels with high utilization probability. The simulation results show that the significant improvement on the throughput can be achieved through the proposed joint optimization and allocation algorithms.展开更多
Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure....Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure. Therefore the hydrocarbon must spread and move vertically to the surface along the pressure gradient orientation. Hydrocarbons in the reservoir along some small rifts, cracks, joints and cleavages penetrate the overlying strata and seepage onto the surface. Thus the hydrocarbons become unvisble oil and gas signs. This process is called the phenomena of hydrocarbon microseepage of reservoir. Hydrocarbons microseepage in the process展开更多
The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe Riv...The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1：50,000 topographic map data, Landsat TM/ETM＋ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963–2007/ 2011 were also analyzed. The results show that：（1） In the period 1956/1963–2007/2011, the Heihe River Basin＇s glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km^2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km^2; the total number of the glaciers decreased from 967 to 800.（2） Glaciers in this basin are mainly distributed at elevations of 4300–4400 m, 4400–4500 m and 4500–4600 m; and there are significant regional differences in glaciers distribution and glaciers change.（3） Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate.（4） Analysis of the six meteorological stations＇ annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to some extent.展开更多
Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in...Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in the Yellow River Delta（YRD） region using moderate resolution imaging spectroradiometer（MODIS） time-series data. The normalized difference vegetation index（NDVI） was obtained by calculating the surface reflectance in red and infrared. We used the Savitzky-Golay filter to smooth time series NDVI curves. We adopted a two-step classification to identify winter wheat. The first step was designed to mask out non-vegetation classes, and the second step aimed to identify winter wheat from other vegetation based on its phenological features. We used the double Gaussian model and the maximum curvature method to extract phenology. Due to the characteristics of the time-series profiles for winter wheat, a double Gaussian function method was selected to fit the temporal profile. A maximum curvature method was performed to extract phenological phases. Phenological phases such as the green-up, heading and harvesting phases were detected when the NDVI curvature exhibited local maximum values. The extracted phenological dates then were validated with records of the ground observations. The spatial patterns of phenological phases were investigated. This study concluded that, for winter wheat, the accuracy of classification is 87.07%, and the accuracy of planting acreage is 90.09%. The phenological result was comparable to the ground observation at the municipal level. The average green-up date for the whole region occurred on March 5, the average heading date occurred on May 9, and the average harvesting date occurred on June 5. The spatial distribution of the phenology for winter wheat showed a significant gradual delay from the southwest to the northeast. This study demonstrates the effectiveness of our proposed method for winter wheat classification and phenology detection.展开更多
As a class of functional crystalline porous materials,metal-organic frameworks(MOFs)gained rapid development in the past three decades and a large number of MOFs with ordered structures,high surface areas,and function...As a class of functional crystalline porous materials,metal-organic frameworks(MOFs)gained rapid development in the past three decades and a large number of MOFs with ordered structures,high surface areas,and functionalized channels have been investigated.MOFs and MOF-derived/composite materials show great potential in many application fields.In this review,we discussed the main applications of MOFs and MOF-derived/composite materials in small molecule storage,separation,luminescence,sensing,multitype catalysis,and energy storage.In addition,challenges and problems in the future research of MOFs-related fields are also discussed.展开更多
Can WiFi signals be used for sensing purpose？ The growing PHY layer capabilities of WiFi has made it possible to reuse WiFi signals for both communication and sensing. Sensing via WiFi would enable remote sensing wit...Can WiFi signals be used for sensing purpose？ The growing PHY layer capabilities of WiFi has made it possible to reuse WiFi signals for both communication and sensing. Sensing via WiFi would enable remote sensing without wearable sensors, simultaneous perception and data transmission without extra communication infrastructure, and contactless sensing in privacy-preserving mode. Due to the popularity of WiFi devices and the ubiquitous deployment of WiFi networks, WiFi-based sensing networks, if fully connected, would potentially rank as one of the world＇s largest wireless sensor networks. Yet the concept of wireless and sensorless sensing is not the simple combination of WiFi and radar. It seeks breakthroughs from dedicated radar systems, and aims to balance between low cost and high accuracy, to meet the rising demand for pervasive environment perception in everyday life. Despite increasing research interest, wireless sensing is still in its infancy. Through introductions on basic principles and working prototypes, we review the feasibilities and limitations of wireless, sensorless, and contactless sensing via WiFi. We envision this article as a brief primer on wireless sensing for interested readers to explore this open and largely unexplored field and create next-generation wireless and mobile computing applications.展开更多
文摘In recent years, the ownership rate of motor vehicles has been continuously rising and their exhaust emissions have become very high. It is the main source of urban pollution at present. Therefore, in order to improve people's quality of life and achieve sustainable development, it is very important to strengthen the specific emissions and control of motor vehicle exhaust. In this way, the pollution problem can be controlled from the source and the environmental quality can be improved.
基金supported by the National Natural Science Foundation of China(Grant Nos.42192580,42192581)。
文摘Immediate remote sensing detection and diagnosis of surface anomalies is a critical requirement to ensure the healthy development of China's social economy and national security in the new era.However,this emerging frontier field is still in its infancy.Current researches lack not only a clear definition and analysis of concepts related to surface anomalies,but also a systematic examination of research approaches and development prospects.This study systematically summarizes the concepts and manifestation characteristics of anomaly,surface anomaly,and potential surface anomaly,and analyzes the connections and differences between them.Based on the temporal incongruence,spatial incongruence,and spatiotemporal incongruence characteristics of potential surface anomalies,three research frameworks for immediate remote sensing detection of potential surface anomalies are proposed,and the key issues and development prospects under these three research frameworks are pointed out.This study can provide research approaches and theoretical basis for immediate remote sensing detection of surface anomalies.
文摘The objective of this study is to address semantic misalignment and insufficient accuracy in edge detail and discrimination detection,which are common issues in deep learning-based change detection methods relying on encoding and decoding frameworks.In response to this,we propose a model called FlowDual-PixelClsObjectMec(FPCNet),which innovatively incorporates dual flow alignment technology in the decoding stage to rectify semantic discrepancies through streamlined feature correction fusion.Furthermore,the model employs an object-level similarity measurement coupled with pixel-level classification in the PixelClsObjectMec(PCOM)module during the final discrimination stage,significantly enhancing edge detail detection and overall accuracy.Experimental evaluations on the change detection dataset(CDD)and building CDD demonstrate superior performance,with F1 scores of 95.1%and 92.8%,respectively.Our findings indicate that the FPCNet outperforms the existing algorithms in stability,robustness,and other key metrics.
基金supported in part by National Natural Science Foundation of China(No.62471034)Hebei Natural Science Foundation(No.F2023105001)。
文摘In the field of remote sensing,the rapid and accurate acquisition of the category and location of airplanes has emerged as a prominent research.However,remote sensing fuzzy imaging and complex environmental interference affect airplane detection.Besides,the inconsistency in the size of remote sensing images and the low accuracy of small target detection are crucial challenges that need to be addressed.To tackle these issues,we propose a novel network SDaDCS(SAHI-data augmentation-dilation-channel and spatial attention)based on YOLOX model and the slicing aided hyper inference(SAHI)framework,a new data augmentation technique and dilation-channel and spatial(DCS)attention mechanism.Initially,we create a remote sensing dataset for airplane targets and introduce a new data augmentation technique based on the Rotate-Mixup and mixed data augmentation to enhance data diversity.The DCS attention mechanism,which comprises the dilated convolution block,channel attention and spatial attention,is designed to bolster the feature extraction and discrimination of the network.To address the challenges arised by the difficulties of detecting small targets,we integrate the YOLOX model with the SAHI framework.Experiment results show that,when compared to the original YOLOX model,the proposed SDaDCS remote sensing target detection algorithm enhances overall accuracy by 13.6%.The experimental results validate the effectiveness of the proposed algorithm.
基金financially supported by Natural Science Foundation of Zhejiang Province(Nos.LY22B050001 and LR18R050001)the National Natural Science Foundation of China(Nos.21675143,21775139,82100376 and 21705120)+4 种基金the Natural Science Foundation of Shandong Province,China(Nos.ZR2023MB001,ZR2017LB016 and ZR2022QH108)the Project of Shandong Province Higher Educational Outstanding Youth Innovation Team(No.2019KJM008)Shandong Province Medicine and Health Science and Technology Development Plan Project(No.202113050530)Special Fund for Taishan Scholar Project(No.tsqn202211231)Foundation of Yuandu Scholar。
文摘Organic pollutants are harmful and toxic chemical substances that adversely threaten human health and the living environment all over the world.More and more studies have been investigating the relationship between low level of human exposure of organic compounds and various internal diseases.For the sake of assessing disease risk due to organic compounds contact in a particular location,it is imperative for relevant government departments to make a human health risk assessment in view of the organic pollutants'bioavailability and their dosage-response correlations.It is inevitable to make use of an efficient method to detect organic pollutants,which is significant for public health and safety.Fluorescent assays based on carbon dots thus would provide a very plausible candidate method.After consulting a large number of literatures,we offer a comprehensive review of the sensing applications of carbon dots for organic pollutants.
文摘In this study,the interaction between TPE-Ph COF and ammonia molecules,as well as the mechanism of fluorescence detection of ammonia,were comprehensively investigated using density functional theory(DFT)and time-dependent density functional theory(TD-DFT).It was found that the binding between TPE-Ph COF and ammonia molecules occurs primarily through coordination bonds or hydrogen bonds.Specifically,the formation of coordination bonds significantly changes the intramolecular charge transfer of TPE-Ph COF,leading to fluorescence quenching.Computational analysis revealed the changes in electron and hole distributions upon the binding of ammonia to TPE-Ph COF,as well as the competition between nonradiative and radiative transitions during the photophysical processes,thereby elucidating the intrinsic mechanism of fluorescence response.
基金Supported by the National Natural Science Foundation of China (No.40071061).
文摘In the edge detection of Remote Sensing (RS) image, the useful detail losing and the spurious edge often appear. To solve the problem, the authors uses the dyadic wavelet to detect the edge of surface features by combining the edge detecting with the multi-resolution analyzing of the wavelet transform. Via the dyadic wavelet decomposing, the RS image of a certain appropriate scale is obtained, and the edge data of the plane and the upright directions are respectively figured out, then the gradient vector module of the surface features is worked out. By tracing them, the authors get the edge data of the object, therefore build the RS image which obtains the checked edge. This method can depress the effect of noise and examine exactly the edge data of the object by rule and line. With an experiment of an RS image which obtains an airport, the authors certificate the feasibility of the application of dyadic wavelet in the object edge detection.
文摘The spontaneous burning has been lasting for thousands of years in the coal fields in the north of China. It spreads from the west (Tianshan coal field) to the east (Huolinhe coal field). Its E-W extension is up to 3750km, concentrating in N35°toN45°, its vertical depth up to 260m, and the surface temprature locally up to 270℃. Annually, it burns out 0, 250-300 million tones of coal, causing economic loss equivalent to 2-3 billion R.M.B. Yuan.It destroies coal resources and causes hazards in coal mines. In order to locate the extent and the direction in coal burning areas, the remote sensing technique has heen used and has produced an obvious benefit.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.22065031,22061039)the Top Leading Talents Project of Gansu Province,the Key R&D program of Gansu Province(No.21YF5GA066)+1 种基金Gansu Province College Industry Support Plan Project(No.2022CYZC-18)Natural Science Foundation of Gansu Province(Nos.2020-0405-JCC-630,20JR10RA088).
文摘Hydrazine hydrate(DH)is an important fine chemical intermediate and as fuel for rockets,however,it also has serious toxic for humans and environment.Developing novel materials and methods for sensitive detection of DH in water and air is an important task.In order to effectively detect DH,a novel conductive supramolecular polymer metallogel(PQ-Ag)has been constructed by the coordination of bis-5-hydroxyquinoline functionalized pillar[5]arene(PQ5)with Ag+.The metallogel PQ-Ag could realize the multi-channel sensitive detection of DH through naked-eye,fluorescence,and electrochemical methods.The lowest limit of detection(LOD)is 0.1 mg/m^(3)in air and 2.68×10^(−8)mol/L in water,which is lower than the standard of the US Environmental Protection Agency(EPA)for DH of maximum allowable concentration in drinking water.More importantly,an electronic device for DH detection based on the metallogel PQ-Ag was designed and prepared,which can realize conveniently and efficiently multi-channel detection and alert of DH through sound and light alarms not only in water but also in air.
基金supported by the National Natural Science Foundation of China under Grant Nos.61201143,61402416,611301132and 61471194the Natural Science Foundation of Jiangsu Province under Grant No.BK20140828+2 种基金the Natural Science Foundation of Zhejiang Province under Grant No.LQ14F010003the Chinese Postdoctoral Science Foundation under Grant No.2015M580425the Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry
文摘In this paper,an energy-harvesting cognitive radio(CR) is considered,which allows the transmitter of the secondary user(SU) to harvest the primary signal energy from the transmitter of the primary user(PU) when the presence of the PU is detected.Then the harvested energy is converted into the electrical power to supply the transmission of the SU at the detected absence of the PU.By adopting the periodic spectrum sensing,the average total transmission rate of the SU is maximized through optimizing the sensing time,subject to the constraints of the probabilities of false alarm and detection,the harvested energy and the interference rate control.The simulation results show that there deed exists an optimal sensing time that maximizes the transmission rate,and the maximum transmission rate of the energy-harvesting CR can better approach to that of the traditional CR with the increasing of the detection probability.
基金Project(61471194)supported by the National Natural Science Foundation of ChinaProject(BK20140828)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,China
文摘In order to improve the throughput of cognitive radio(CR), optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing was investigated in a CR network that includes multiple users and one fusion center. The frame structure of cooperative spectrum sensing was divided into multiple transmission time slots and one sensing time slot consisting of local energy detection and cooperative overhead. An optimization problem was formulated to maximize the throughput of CR network, subject to the constraints of both false alarm probability and detection probability. A joint optimization algorithm of sensing time and number of users was proposed to solve this optimization problem with low time complexity. An allocation algorithm of cooperative users was proposed to preferentially allocate the users to the channels with high utilization probability. The simulation results show that the significant improvement on the throughput can be achieved through the proposed joint optimization and allocation algorithms.
文摘Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure. Therefore the hydrocarbon must spread and move vertically to the surface along the pressure gradient orientation. Hydrocarbons in the reservoir along some small rifts, cracks, joints and cleavages penetrate the overlying strata and seepage onto the surface. Thus the hydrocarbons become unvisble oil and gas signs. This process is called the phenomena of hydrocarbon microseepage of reservoir. Hydrocarbons microseepage in the process
基金Funds for Creative Research Groups of China,No.41121001 Project for Incubation of Specialists in Glaciology and Geocryology of National Natural Science Foundation of China,No.J1210003/J0109+1 种基金 National Natural Science Foundation of China,No.41340014 National Basic Research Program of China,No.2013CBA01801
文摘The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1：50,000 topographic map data, Landsat TM/ETM＋ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963–2007/ 2011 were also analyzed. The results show that：（1） In the period 1956/1963–2007/2011, the Heihe River Basin＇s glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km^2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km^2; the total number of the glaciers decreased from 967 to 800.（2） Glaciers in this basin are mainly distributed at elevations of 4300–4400 m, 4400–4500 m and 4500–4600 m; and there are significant regional differences in glaciers distribution and glaciers change.（3） Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate.（4） Analysis of the six meteorological stations＇ annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to some extent.
基金supported by the National Natural Science Foundation of China (41471335, 41271407)the National Remote Sensing Survey and Assessment of Eco-Environment Change between 2000 and 2010, China (STSN-1500)+2 种基金the National Key Technologies R&D Program of China during the 12th Five-Year Plan period (2013BAD05B03)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA05050601)the International Science and Technology (S&T) Cooperation Program of China (2012DFG22050)
文摘Accurate winter wheat identification and phenology extraction are essential for field management and agricultural policy making. Here, we present mechanisms of winter wheat discrimination and phenological detection in the Yellow River Delta（YRD） region using moderate resolution imaging spectroradiometer（MODIS） time-series data. The normalized difference vegetation index（NDVI） was obtained by calculating the surface reflectance in red and infrared. We used the Savitzky-Golay filter to smooth time series NDVI curves. We adopted a two-step classification to identify winter wheat. The first step was designed to mask out non-vegetation classes, and the second step aimed to identify winter wheat from other vegetation based on its phenological features. We used the double Gaussian model and the maximum curvature method to extract phenology. Due to the characteristics of the time-series profiles for winter wheat, a double Gaussian function method was selected to fit the temporal profile. A maximum curvature method was performed to extract phenological phases. Phenological phases such as the green-up, heading and harvesting phases were detected when the NDVI curvature exhibited local maximum values. The extracted phenological dates then were validated with records of the ground observations. The spatial patterns of phenological phases were investigated. This study concluded that, for winter wheat, the accuracy of classification is 87.07%, and the accuracy of planting acreage is 90.09%. The phenological result was comparable to the ground observation at the municipal level. The average green-up date for the whole region occurred on March 5, the average heading date occurred on May 9, and the average harvesting date occurred on June 5. The spatial distribution of the phenology for winter wheat showed a significant gradual delay from the southwest to the northeast. This study demonstrates the effectiveness of our proposed method for winter wheat classification and phenology detection.
基金supported by the National Key Research and Development Program of China(2022YFA1502901)the National Natural Science Foundation of China(22035003,22201137,22371137)the Fundamental Research Funds for the Central Universities(63243115)。
文摘As a class of functional crystalline porous materials,metal-organic frameworks(MOFs)gained rapid development in the past three decades and a large number of MOFs with ordered structures,high surface areas,and functionalized channels have been investigated.MOFs and MOF-derived/composite materials show great potential in many application fields.In this review,we discussed the main applications of MOFs and MOF-derived/composite materials in small molecule storage,separation,luminescence,sensing,multitype catalysis,and energy storage.In addition,challenges and problems in the future research of MOFs-related fields are also discussed.
文摘Can WiFi signals be used for sensing purpose？ The growing PHY layer capabilities of WiFi has made it possible to reuse WiFi signals for both communication and sensing. Sensing via WiFi would enable remote sensing without wearable sensors, simultaneous perception and data transmission without extra communication infrastructure, and contactless sensing in privacy-preserving mode. Due to the popularity of WiFi devices and the ubiquitous deployment of WiFi networks, WiFi-based sensing networks, if fully connected, would potentially rank as one of the world＇s largest wireless sensor networks. Yet the concept of wireless and sensorless sensing is not the simple combination of WiFi and radar. It seeks breakthroughs from dedicated radar systems, and aims to balance between low cost and high accuracy, to meet the rising demand for pervasive environment perception in everyday life. Despite increasing research interest, wireless sensing is still in its infancy. Through introductions on basic principles and working prototypes, we review the feasibilities and limitations of wireless, sensorless, and contactless sensing via WiFi. We envision this article as a brief primer on wireless sensing for interested readers to explore this open and largely unexplored field and create next-generation wireless and mobile computing applications.
