ChatG PT,an artificial intelligence generated content (AIGC) model developed by OpenAI,has attracted worldwide attention for its capability of dealing with challenging language understanding and generation tasks in th...ChatG PT,an artificial intelligence generated content (AIGC) model developed by OpenAI,has attracted worldwide attention for its capability of dealing with challenging language understanding and generation tasks in the form of conversations.This paper briefly provides an overview on the history,status quo and potential future development of ChatGPT,helping to provide an entry point to think about ChatGPT.Specifically,from the limited open-accessed resources,we conclude the core techniques of ChatGPT,mainly including large-scale language models,in-context learning,reinforcement learning from human feedback and the key technical steps for developing ChatGPT.We further analyze the pros and cons of ChatGPT and we rethink the duality of ChatGPT in various fields.Although it has been widely acknowledged that ChatGPT brings plenty of opportunities for various fields,mankind should still treat and use ChatG PT properly to avoid the potential threat,e.g.,academic integrity and safety challenge.Finally,we discuss several open problems as the potential development of ChatGPT.展开更多
Objective: A solid understanding of levels and trends of spending on cancer is important to evaluate whether our healthcare resources were wisely spent and to prioritize future resources for cancer treatment and preve...Objective: A solid understanding of levels and trends of spending on cancer is important to evaluate whether our healthcare resources were wisely spent and to prioritize future resources for cancer treatment and prevention. However, studies on economic burden of cancers in China are scant and the results are inconsistent. Methods: The Chinese hospital information database and nearly 350 million inpatient medical record data were used. As the ratios of cancer inpatient payments to total inpatient payments were mainly influenced by the grades and sites of hospitals, the estimates of payments of cancer inpatients in this study were stratified by hospital grades and provinces. Only the payments of cancer inpatients happened in grade 2, grade 3 and specialized cancer hospitals were included in the analyses. The total medical payments of cancers in China were estimated based on the ratios of outpatient payments to inpatient payments in specialized cancer hospitals. Results: From 2011 to 2015, the payments of cancer inpatients in China have increased by 84.1% and the total inpatient payments reached 177.1 billion RMB in 2015, accounting for 4.3% of the total health expenditure in China. Based on the ratio of outpatient payments to inpatient payments, the total payments on cancer treatments in China were estimated to be 221.4 billion RMB in 2015. Among different cancer types, the highest payments were the treatment of trachea, bronchus and lung cancer. The major cancer inpatient payments (67.1% in 2015) spent in grade 3 general hospitals and this ratio increased continually from 2011 to 2015. The expenditure of cancer treatments also varies by region with the major expenditure in the eastern region of China. Conclusions: This study estimated the total payments of cancer treatments in China and analyzed how the money was spent on cancer treatments in the recent 5 years, which would provide information for decision makings on the allocation of resources to service provisioning, prevention strategies, research funding, and 展开更多
Background:Gastric cancer mortality decreased substantially over the last decades in most countries worldwide.This study aimed to assess the most recent national trend of gastric cancer mortality and examine the dispa...Background:Gastric cancer mortality decreased substantially over the last decades in most countries worldwide.This study aimed to assess the most recent national trend of gastric cancer mortality and examine the disparity of gastric cancer mortality between rural and urban areas in China.Methods:The crude mortality data of gastric cancer by sex,age group,and area were obtained from China Health Statistical Yearbooks(2003-2015)covering 10%of Chinese population.The age-standardized rates of mortality(ASRM)of gastric cancer in rural and urban areas were estimated using the 2010 Chinese Census population stratified by age,sex,and area.The trend of mortality of gastric cancer was assessed by using Joinpoint analysis.Results:During the 13-year period,the ASRM was reduced from 31.5/100,000 in 2003 to 20.9/100,000 in 2015 in rural areas and from 18.9/100,000 in 2003 to 14.5/100,000 in 2015 in urban areas.In the male population,the annual percent changes of mortality were−2.2%in urban areas(95%confidence interval[CI]−3.8%to−0.6%;P<0.001)and−3.4%in rural areas(95%CI−5.1%to−1.8%;P<0.001).In the female population,the annual percent changes of mortality were−2.7%in urban areas(95%CI−4.2%to−1.2%;P<0.001)and−4.6%in rural areas(95%CI−5.5%to−3.7%;P<0.001).Conclusions:The declining trend of mortality of gastric cancer was presented from 2003 to 2015 in both rural and urban areas in China.The decrease in gastric cancer mortality is greater in rural areas than in urban areas in China.展开更多
High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements.Although in the infant stage,the emerging ...High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements.Although in the infant stage,the emerging of this new family of materials has brought new opportunities for material design and property tailoring.Distinct from metals,the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering.Aside from strengthening,hardening,and low thermal conductivity that have already been found in high-entropy alloys,new properties like colossal dielectric constant,super ionic conductivity,severe anisotropic thermal expansion coefficient,strong electromagnetic wave absorption,etc.,have been discovered in HECs.As a response to the rapid development in this nascent field,this article gives a comprehensive review on the structure features,theoretical methods for stability and property prediction,processing routes,novel properties,and prospective applications of HECs.The challenges on processing,characterization,and property predictions are also emphasized.Finally,future directions for new material exploration,novel processing,fundamental understanding,in-depth characterization,and database assessments are given.展开更多
The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the g...The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.展开更多
Machine learning(ML) has been widely applied to the upper layers of wireless communication systems for various purposes, such as deployment of cognitive radio and communication network. However, its application to the...Machine learning(ML) has been widely applied to the upper layers of wireless communication systems for various purposes, such as deployment of cognitive radio and communication network. However, its application to the physical layer is hampered by sophisticated channel environments and limited learning ability of conventional ML algorithms. Deep learning(DL) has been recently applied for many fields, such as computer vision and natural language processing, given its expressive capacity and convenient optimization capability. The potential application of DL to the physical layer has also been increasingly recognized because of the new features for future communications, such as complex scenarios with unknown channel models, high speed and accurate processing requirements; these features challenge conventional communication theories. This paper presents a comprehensive overview of the emerging studies on DL-based physical layer processing, including leveraging DL to redesign a module of the conventional communication system(for modulation recognition, channel decoding, and detection) and replace the communication system with a radically new architecture based on an autoencoder. These DL-based methods show promising performance improvements but have certain limitations, such as lack of solid analytical tools and use of architectures that are specifically designed for communication and implementation research, thereby motivating future research in this field.展开更多
Land use reflects human activities on land.Urban land use is the highest level human alteration on Earth,and it is rapidly changing due to population increase and urbanization.Urban areas have widespread effects on lo...Land use reflects human activities on land.Urban land use is the highest level human alteration on Earth,and it is rapidly changing due to population increase and urbanization.Urban areas have widespread effects on local hydrology,climate,biodiversity,and food production[1,2].However,maps,that contain knowledge on the distribution,pattern and composition of various land use types in urban areas,are limited to city level.The mapping standard on data sources,methods,land use classification schemes varies from city to city,due to differences in financial input and skills of mapping personnel.To address various national and global environmental challenges caused by urbanization,it is important to have urban land uses at the national and global scales that are derived from the same or consistent data sources with the same or compatible classification systems and mapping methods.This is because,only with urban land use maps produced with similar criteria,consistent environmental policies can be made,and action efforts can be compared and assessed for large scale environmental administration.However,despite of the fact that a number of urban-extent maps exist at global scales[3,4],more detailed urban land use maps do not exist at the same scale.Even at big country or regional levels such as for the United States,China and European Union,consistent land use mapping efforts are rare[5,6](e.g.,https://sdi4apps.eu/open_land_use/).展开更多
Four wetland maps for all China have been produced,based on Landsat and CBERS-02B remote sensing data between 1978 and 2008 (1978,1990,2000 and 2008).These maps were mainly developed by manual interpretation and valid...Four wetland maps for all China have been produced,based on Landsat and CBERS-02B remote sensing data between 1978 and 2008 (1978,1990,2000 and 2008).These maps were mainly developed by manual interpretation and validated by substantial field investigation in 2009.Based on these maps,we analyzed the 2008 wetland distribution in China and discussed wetland changes and their drivers over the past 30 years.(i) There were about 324097 km 2 of wetlands in 2008,for which inland marshes or swamps were the most common wetland type (35%),with lakes (26%) second.Most of the wetlands were in Heilongjiang,Inner Mongolia,Qinghai and Tibet,occupying about 55% of the national wetland area.(ii) From 1978 to 2008,China's wetland area continually and significantly decreased,by about 33% based on changes in the wetland map.This was in sharp contrast to the increase in artificial wetlands,which increased by about 122%.Inland marshes accounted for the main loss of total wetlands from 1978 to 2000.From 2000 through 2008,riverine and lacustrine wetlands constituted the main wetland loss.Fortunately however,the rate of wetland loss decreased from 5523 to 831 km 2 /a.(iii) The change ratio of lost natural wetlands (including inland and coastal wetlands) to non-wetlands has decreased slightly over the past 30 years.From 1978 to 1990,nearly all natural wetlands (98%) lost were transformed into non-wetlands.However,the ratio declined to 86% from 1990 to 2000,and to 77% from 2000 to 2008.(iv) All Chinese provinces were divided into three groups according to patterns of wetland changes,which could relate to the driving forces of such changes.Tibet was completely different from other provinces,as it was one representative example in which there was a net wetland increase,because of global warming and decreased human activity since 1990.Increased economic development caused considerable wetland loss in most eastern provinces,and artificial wetlands increased.展开更多
Blockchain with these characteristics of decentralized structure, transparent and credible, time-series and immutability, has been considering as a promising technology. Consensus algorithm as one of the core techniqu...Blockchain with these characteristics of decentralized structure, transparent and credible, time-series and immutability, has been considering as a promising technology. Consensus algorithm as one of the core techniques of blockchain directly affects the scalability of blockchain systems. Existing probabilistic finality blockchain consensus algorithms such as PoW, PoS, suffer from power consumptions and low efficiency;while absolute finality blockchain consensus algorithms such as PBFT, HoneyBadgerBFT, could not meet the scalability requirement in a largescale network. In this paper, we propose a novel optimized practical Byzantine fault tolerance consensus algorithm based on EigenTrust model, namely T-PBFT, which is a multi-stage consensus algorithm. It evaluates node trust by the transactions between nodes so that the high quality of nodes in the network will be selected to construct a consensus group. To reduce the probability of view change, we propose to replace a single primary node with a primary group. By group signature and mutual supervision, we can enhance the robustness of the primary group further. Finally, we analyze T-PBFT and compare it with the other Byzantine fault tolerant consensus algorithms. Theoretical analysis shows that our T-PBFT can optimize the Byzantine fault-tolerant rate,reduce the probability of view change and communication complexity.展开更多
With the rapid development of mechanical equipment, the mechanical health monitoring field has entered the era of big data. However, the method of manual feature extraction has the disadvantages of low efficiency and ...With the rapid development of mechanical equipment, the mechanical health monitoring field has entered the era of big data. However, the method of manual feature extraction has the disadvantages of low efficiency and poor accuracy, when handling big data. In this study, the research object was the asynchronous motor in the drivetrain diagnostics simulator system. The vibration signals of different fault motors were collected. The raw signal was pretreated using short time Fourier transform （STFT） to obtain the corresponding time-frequency map. Then, the feature of the time-frequency map was adap- tively extracted by using a convolutional neural network （CNN）. The effects of the pretreatment method, and the hyper parameters of network diagnostic accuracy, were investigated experimentally. The experimental results showed that the influence of the preprocessing method is small, and that the batch-size is the main factor affecting accuracy and training efficiency. By investigating feature visualization, it was shown that, in the case of big data, the extracted CNN features can represent complex mapping relationships between signal and health status, and can also overcome the prior knowledge and engineering experience requirement for feature extraction, which is used by tra- ditional diagnosis methods. This paper proposes a new method, based on STFT and CNN, which can complete motor fault diagnosis tasks more intelligently and accurately.展开更多
The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves.In the past decade,metamaterials with effective medium parameters o...The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves.In the past decade,metamaterials with effective medium parameters or gradient phases have been studied to control terahertz waves and realize functional devices.Here,we present a new approach to manipulate terahertz waves by using coding metasurfaces that are composed of digital coding elements.We propose a general coding unit based on a Minkowski closed-loop particle that is capable of generating 1-bit coding(with two phase states of 0 and 180°),2-bit coding(with four phase states of 0,90°,180°,and 270°),and multi-bit coding elements in the terahertz frequencies by using different geometric scales.We show that multi-bit coding metasurfaces have strong abilities to control terahertz waves by designing-specific coding sequences.As an application,we demonstrate a new scattering strategy of terahertz waves—broadband and wide-angle diffusion—using a 2-bit coding metasurface with a special coding design and verify it by both numerical simulations and experiments.The presented method opens a new route to reducing the scattering of terahertz waves.展开更多
Accumulating evidence shows that cellular and acellular components in tumor microenvironment(TME)can reprogram tumor initiation,growth,invasion,metastasis,and response to therapies.Cancer research and treatment have s...Accumulating evidence shows that cellular and acellular components in tumor microenvironment(TME)can reprogram tumor initiation,growth,invasion,metastasis,and response to therapies.Cancer research and treatment have switched from a cancercentric model to a TME-centric one,considering the increasing significance of TME in cancer biology.Nonetheless,the clinical efficacy of therapeutic strategies targeting TME,especially the specific cells or pathways of TME,remains unsatisfactory.Classifying the chemopathological characteristics of TME and crosstalk among one another can greatly benefit further studies exploring effective treating methods.Herein,we present an updated image of TME with emphasis on hypoxic niche,immune microenvironment,metabolism microenvironment,acidic niche,innervated niche,and mechanical microenvironment.We then summarize conventional drugs including aspirin,celecoxib,β-adrenergic antagonist,metformin,and statin in new antitumor application.These drugs are considered as viable candidates for combination therapy due to their antitumor activity and extensive use in clinical practice.We also provide our outlook on directions and potential applications of TME theory.This review depicts a comprehensive and vivid landscape of TME from biology to treatment.展开更多
The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace eleme...The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace elements analysis shows that the granite is depleted extremely in Ba, Sr and Eu, and rich in some large-ion lithophile elements and high field strength elements. Besides, the granite has high Ga contents, the values of 104（Ga/AI） vary from 2.50 to 2.77, which is mainly greater than the lower limit of A-type granites （2.6）, and is higher than the I- and S- type granites＇ average （2.1 and 2.28, respectively）. Rare earth element （REE） is characterized by relatively high fractionations of light REE （LREE） and heavy REE （HREE） （LREE/HREE=9.3-13.60, （La/Yb）N=10.92-18.02）, pronounced negative Eu anomalies （JEn=0.08-0.13）, and exhibits right- dipping gull pattern. Major elements, rare elements and trace elements features show the granite is ascribed to A-type granite and A2 subtype in tectonic genetic type. They are plotted into post-collision or within-plate area in a variety of tectonic discriminations. Geological and geochemical data comprehensively suggest that the granite is formed in a post-collision extensive tectonic setting. Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating yields a weighted mean age of 425 Ma, belonging to Middle Silurian, which is similar to the age of the post- collision geological events in the region. The differences of magmatic rocks in formation age, rocks assemblage and rocks series systematically indicate that the regional tectonic stress regime in the East Kunlun orogenic belt experienced a major transformation from compress to extension in Middle Silurianin, and the Helegangnaren feldspar granite intruded in the early stage of tectonic transformation.展开更多
The western Noah Pacific anomalous anticyclone （WNPAC） is an important atmospheric circulation system that conveys El Nifio impact on East Asian climate. In this review paper, various theories on the formation and m...The western Noah Pacific anomalous anticyclone （WNPAC） is an important atmospheric circulation system that conveys El Nifio impact on East Asian climate. In this review paper, various theories on the formation and maintenance of the WNPAC, including warm pool atmosphere-ocean interaction, Indian Ocean capacitor, a combination mode that emphasizes nonlinear interaction between ENSO and annual cycle, moist enthalpy advecfion/Rossby wave modulation, and central Pacific SST forcing, are discussed. It is concluded that local atmosphere-ocean interaction and moist enthalpy advection/Rossby wave modulation mechanisms are essential for the initial development and maintenance of the WNPAC during El Nifio mature winter and subsequent spring. The Indian Ocean capacitor mechanism does not contribute to the earlier development but helps maintain the WNPAC in El Nifio decaying summer. The cold SST anomaly in the western North Pacific, although damped in the summer, also plays a role. An inter- basin atmosphere-ocean interaction across the Indo-Pacific warm pool emerges as a new mechanism in summer. In addition, the central Pacific cold SST anomaly may induce the WNPAC during rapid El Nifio decaying/La Nina developing or La Nifia persisting summer. The near-annual periods predicted by the combination mode theory are hardly detected from observations and thus do not contribute to the formation of the WNPAC. The tropical Atlantic may have a capacitor effect similar to the tropical Indian Ocean.展开更多
This article evaluates the performance of 20 Coupled Model Intercomparison Project phase 6(CMIP6)models in simulating temperature and precipitation over China through comparisons with gridded observation data for the ...This article evaluates the performance of 20 Coupled Model Intercomparison Project phase 6(CMIP6)models in simulating temperature and precipitation over China through comparisons with gridded observation data for the period of 1995–2014,with a focus on spatial patterns and interannual variability.The evaluations show that the CMIP6 models perform well in reproducing the climatological spatial distribution of temperature and precipitation,with better performance for temperature than for precipitation.Their interannual variability can also be reasonably captured by most models,however,poor performance is noted regarding the interannual variability of winter precipitation.Based on the comprehensive performance for the above two factors,the“highest-ranked”models are selected as an ensemble(BMME).The BMME outperforms the ensemble of all models(AMME)in simulating annual and winter temperature and precipitation,particularly for those subregions with complex terrain but it shows little improvement for summer temperature and precipitation.The AMME and BMME projections indicate annual increases for both temperature and precipitation across China by the end of the 21st century,with larger increases under the scenario of the Shared Socioeconomic Pathway 5/Representative Concentration Pathway 8.5(SSP585)than under scenario of the Shared Socioeconomic Pathway 2/Representative Concentration Pathway 4.5(SSP245).The greatest increases of annual temperature are projected for higher latitudes and higher elevations and the largest percentage-based increases in annual precipitation are projected to occur in northern and western China,especially under SSP585.However,the BMME,which generally performs better in these regions,projects lower changes in annual temperature and larger variations in annual precipitation when compared to the AMME projections.展开更多
When A ∈ B（H） and B ∈ B（K） are given, we denote by Mc an operator acting on the Hilbert space HΘ K of the form Me = （ A0 CB）. In this paper, first we give the necessary and sufficient condition for Mc to be a...When A ∈ B（H） and B ∈ B（K） are given, we denote by Mc an operator acting on the Hilbert space HΘ K of the form Me = （ A0 CB）. In this paper, first we give the necessary and sufficient condition for Mc to be an upper semi-Fredholm （lower semi-Fredholm, or Fredholm） operator for some C ∈B（K,H）. In addition, let σSF＋（A） = {λ ∈ C ： A-λI is not an upper semi-Fredholm operator} bc the upper semi-Fredholm spectrum of A ∈ B（H） and let σrsF- （A） = {λ∈ C ： A-λI is not a lower semi-Fredholm operator} be the lower semi Fredholm spectrum of A. We show that the passage from σSF±（A） U σSF±（B） to σSF±（Mc） is accomplished by removing certain open subsets of σSF-（A） ∩σSF＋ （B） from the former, that is, there is an equality σSF±（A） ∪σSF± （B） = σSF± （Mc） ∪＆ where L is the union of certain of the holes in σSF±（Mc） which ilappen to be subsets of σSF- （A） A σSF＋ （B）. Weyl＇s theorem and Browder＇s theorem are liable to fail for 2 × 2 operator matrices. In this paper, we also explore how Weyl＇s theorem, Browder＇s theorem, a-Weyl＇s theorem and a-Browder＇s theorem survive for 2 × 2 upper triangular operator matrices on the Hilbert space.展开更多
The contents and distribution of 20 polycyclic aromatic hydrocarbons （PAHs） and heterocyclic aromatic hydrocarbons （HAHs） were investigated in 16 soil profiles of Beijing and Tianjin region. Transport of high mole...The contents and distribution of 20 polycyclic aromatic hydrocarbons （PAHs） and heterocyclic aromatic hydrocarbons （HAHs） were investigated in 16 soil profiles of Beijing and Tianjin region. Transport of high molecular weight PAHs （HMWPAHs） and the correlation between total organic carbon （TOC） and their concentrations were also discussed. The results indicated that highly contaminated sites were located at urban or wastewater irrigation areas and pollutants mainly accumulated in topsoil （〈 40 cm）, with a sharp content decrease at the vertical boundary of 30-40 cm. Total PAHs/HAHs concentrations in soils from Tianjin were markedly greater than those from Beijing. Even the contents at bottoms of soil profiles in Tianjin were higher than those in topsoils of Beijing soil profile. HMWPAHs dominated the PAH profiles, exhibiting a uniform distribution of pyrogenic origin between topsoils and deep layers. Furthermore, the percentages of HMWPAHs remained relative constant with the depth of soil profiles, which were consistent with the distribution of particulate matter-associated PAHs in the local atmospheric environments. Therefore, HMWPAHs transport with particulates might be the predominant source found in soil profiles.展开更多
Deep Learning(DL)is such a powerful tool that we have seen tremendous success in areas such as Computer Vision,Speech Recognition,and Natural Language Processing.Since Automated Modulation Classification(AMC)is an imp...Deep Learning(DL)is such a powerful tool that we have seen tremendous success in areas such as Computer Vision,Speech Recognition,and Natural Language Processing.Since Automated Modulation Classification(AMC)is an important part in Cognitive Radio Networks,we try to explore its potential in solving signal modulation recognition problem.It cannot be overlooked that DL model is a complex model,thus making them prone to over-fitting.DL model requires many training data to combat with over-fitting,but adding high quality labels to training data manually is not always cheap and accessible,especially in real-time system,which may counter unprecedented data in dataset.Semi-supervised Learning is a way to exploit unlabeled data effectively to reduce over-fitting in DL.In this paper,we extend Generative Adversarial Networks(GANs)to the semi-supervised learning will show it is a method can be used to create a more dataefficient classifier.展开更多
Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information processing.However,the reported optical logic gates rely heavily on the precise contr...Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information processing.However,the reported optical logic gates rely heavily on the precise control of input light signals,including their phase difference,polarization,and intensity and the size of the incident beams.Due to the complexity and difficulty in these precise controls,the two output optical logic states may suffer from an inherent instability and a low contrast ratio of intensity.Moreover,the miniaturization of optical logic gates becomes difficult if the extra bulky apparatus for these controls is considered.As such,it is desirable to get rid of these complicated controls and to achieve full logic functionality in a compact photonic system.Such a goal remains challenging.Here,we introduce a simple yet universal design strategy,capable of using plane waves as the incident signal,to perform optical logic operations via a diffractive neural network.Physically,the incident plane wave is first spatially encoded by a specific logic operation at the input layer and further decoded through the hidden layers,namely,a compound Huygens’metasurface.That is,the judiciously designed metasurface scatters the encoded light into one of two small designated areas at the output layer,which provides the information of output logic states.Importantly,after training of the diffractive neural network,all seven basic types of optical logic operations can be realized by the same metasurface.As a conceptual illustration,three logic operations(NOT,OR,and AND)are experimentally demonstrated at microwave frequencies.展开更多
基金supported by National Key Research and Development Program of China (2021YFB1714300)National Natural Science Foundation of China (62293502, 61831022, 61976211)Youth Innovation Promotion Association CAS。
文摘ChatG PT,an artificial intelligence generated content (AIGC) model developed by OpenAI,has attracted worldwide attention for its capability of dealing with challenging language understanding and generation tasks in the form of conversations.This paper briefly provides an overview on the history,status quo and potential future development of ChatGPT,helping to provide an entry point to think about ChatGPT.Specifically,from the limited open-accessed resources,we conclude the core techniques of ChatGPT,mainly including large-scale language models,in-context learning,reinforcement learning from human feedback and the key technical steps for developing ChatGPT.We further analyze the pros and cons of ChatGPT and we rethink the duality of ChatGPT in various fields.Although it has been widely acknowledged that ChatGPT brings plenty of opportunities for various fields,mankind should still treat and use ChatG PT properly to avoid the potential threat,e.g.,academic integrity and safety challenge.Finally,we discuss several open problems as the potential development of ChatGPT.
基金supported by National Natural Science Foundation of China (No.71403189)
文摘Objective: A solid understanding of levels and trends of spending on cancer is important to evaluate whether our healthcare resources were wisely spent and to prioritize future resources for cancer treatment and prevention. However, studies on economic burden of cancers in China are scant and the results are inconsistent. Methods: The Chinese hospital information database and nearly 350 million inpatient medical record data were used. As the ratios of cancer inpatient payments to total inpatient payments were mainly influenced by the grades and sites of hospitals, the estimates of payments of cancer inpatients in this study were stratified by hospital grades and provinces. Only the payments of cancer inpatients happened in grade 2, grade 3 and specialized cancer hospitals were included in the analyses. The total medical payments of cancers in China were estimated based on the ratios of outpatient payments to inpatient payments in specialized cancer hospitals. Results: From 2011 to 2015, the payments of cancer inpatients in China have increased by 84.1% and the total inpatient payments reached 177.1 billion RMB in 2015, accounting for 4.3% of the total health expenditure in China. Based on the ratio of outpatient payments to inpatient payments, the total payments on cancer treatments in China were estimated to be 221.4 billion RMB in 2015. Among different cancer types, the highest payments were the treatment of trachea, bronchus and lung cancer. The major cancer inpatient payments (67.1% in 2015) spent in grade 3 general hospitals and this ratio increased continually from 2011 to 2015. The expenditure of cancer treatments also varies by region with the major expenditure in the eastern region of China. Conclusions: This study estimated the total payments of cancer treatments in China and analyzed how the money was spent on cancer treatments in the recent 5 years, which would provide information for decision makings on the allocation of resources to service provisioning, prevention strategies, research funding, and
基金This work was supported in part by National Natural Science Foundation of China (Grant 31870983).
文摘Background:Gastric cancer mortality decreased substantially over the last decades in most countries worldwide.This study aimed to assess the most recent national trend of gastric cancer mortality and examine the disparity of gastric cancer mortality between rural and urban areas in China.Methods:The crude mortality data of gastric cancer by sex,age group,and area were obtained from China Health Statistical Yearbooks(2003-2015)covering 10%of Chinese population.The age-standardized rates of mortality(ASRM)of gastric cancer in rural and urban areas were estimated using the 2010 Chinese Census population stratified by age,sex,and area.The trend of mortality of gastric cancer was assessed by using Joinpoint analysis.Results:During the 13-year period,the ASRM was reduced from 31.5/100,000 in 2003 to 20.9/100,000 in 2015 in rural areas and from 18.9/100,000 in 2003 to 14.5/100,000 in 2015 in urban areas.In the male population,the annual percent changes of mortality were−2.2%in urban areas(95%confidence interval[CI]−3.8%to−0.6%;P<0.001)and−3.4%in rural areas(95%CI−5.1%to−1.8%;P<0.001).In the female population,the annual percent changes of mortality were−2.7%in urban areas(95%CI−4.2%to−1.2%;P<0.001)and−4.6%in rural areas(95%CI−5.5%to−3.7%;P<0.001).Conclusions:The declining trend of mortality of gastric cancer was presented from 2003 to 2015 in both rural and urban areas in China.The decrease in gastric cancer mortality is greater in rural areas than in urban areas in China.
基金Financial supports from the National Natural Science Foundation of China under Grant Nos.51972089,51672064,and U1435206 are also acknowledged.
文摘High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements.Although in the infant stage,the emerging of this new family of materials has brought new opportunities for material design and property tailoring.Distinct from metals,the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering.Aside from strengthening,hardening,and low thermal conductivity that have already been found in high-entropy alloys,new properties like colossal dielectric constant,super ionic conductivity,severe anisotropic thermal expansion coefficient,strong electromagnetic wave absorption,etc.,have been discovered in HECs.As a response to the rapid development in this nascent field,this article gives a comprehensive review on the structure features,theoretical methods for stability and property prediction,processing routes,novel properties,and prospective applications of HECs.The challenges on processing,characterization,and property predictions are also emphasized.Finally,future directions for new material exploration,novel processing,fundamental understanding,in-depth characterization,and database assessments are given.
基金Supported by Grants(in part)from the Major Projects Incubator Program of National Key Basic Research Program of China,No.2012CB526700National Natural Science Foundation of China,No.81370511+1 种基金Natural Science Foundation of Guangdong Province,No.S2011020002348Fundamental Research Funds for the Central Universities,No.13ykjc01 and No.82000-3281901
文摘AIM: To investigate the etiology and complications of liver cirrhosis (LC) in Southern China.
基金supported by National Key R&D Program of China (Grant Nos. 2016YFB0501700, 2016YFB0501701)National Natural Science Foundation of China (Grant No. 41374019)
文摘The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.
文摘Machine learning(ML) has been widely applied to the upper layers of wireless communication systems for various purposes, such as deployment of cognitive radio and communication network. However, its application to the physical layer is hampered by sophisticated channel environments and limited learning ability of conventional ML algorithms. Deep learning(DL) has been recently applied for many fields, such as computer vision and natural language processing, given its expressive capacity and convenient optimization capability. The potential application of DL to the physical layer has also been increasingly recognized because of the new features for future communications, such as complex scenarios with unknown channel models, high speed and accurate processing requirements; these features challenge conventional communication theories. This paper presents a comprehensive overview of the emerging studies on DL-based physical layer processing, including leveraging DL to redesign a module of the conventional communication system(for modulation recognition, channel decoding, and detection) and replace the communication system with a radically new architecture based on an autoencoder. These DL-based methods show promising performance improvements but have certain limitations, such as lack of solid analytical tools and use of architectures that are specifically designed for communication and implementation research, thereby motivating future research in this field.
基金partially supported by the National Key Research and Development Program of China(2016YFA0600104)supported by donations made by Delos Living LLC,and the Cyrus Tang Foundation+2 种基金supported by the National Natural Science Foundation of China(41471419)Beijing Institute of Urban Planningsupported by the Fundamental Research Funds for the Central Universities(CCNU19TD002).
文摘Land use reflects human activities on land.Urban land use is the highest level human alteration on Earth,and it is rapidly changing due to population increase and urbanization.Urban areas have widespread effects on local hydrology,climate,biodiversity,and food production[1,2].However,maps,that contain knowledge on the distribution,pattern and composition of various land use types in urban areas,are limited to city level.The mapping standard on data sources,methods,land use classification schemes varies from city to city,due to differences in financial input and skills of mapping personnel.To address various national and global environmental challenges caused by urbanization,it is important to have urban land uses at the national and global scales that are derived from the same or consistent data sources with the same or compatible classification systems and mapping methods.This is because,only with urban land use maps produced with similar criteria,consistent environmental policies can be made,and action efforts can be compared and assessed for large scale environmental administration.However,despite of the fact that a number of urban-extent maps exist at global scales[3,4],more detailed urban land use maps do not exist at the same scale.Even at big country or regional levels such as for the United States,China and European Union,consistent land use mapping efforts are rare[5,6](e.g.,https://sdi4apps.eu/open_land_use/).
基金supported by the National High-tech R&D Program of China(2009AA122003)
文摘Four wetland maps for all China have been produced,based on Landsat and CBERS-02B remote sensing data between 1978 and 2008 (1978,1990,2000 and 2008).These maps were mainly developed by manual interpretation and validated by substantial field investigation in 2009.Based on these maps,we analyzed the 2008 wetland distribution in China and discussed wetland changes and their drivers over the past 30 years.(i) There were about 324097 km 2 of wetlands in 2008,for which inland marshes or swamps were the most common wetland type (35%),with lakes (26%) second.Most of the wetlands were in Heilongjiang,Inner Mongolia,Qinghai and Tibet,occupying about 55% of the national wetland area.(ii) From 1978 to 2008,China's wetland area continually and significantly decreased,by about 33% based on changes in the wetland map.This was in sharp contrast to the increase in artificial wetlands,which increased by about 122%.Inland marshes accounted for the main loss of total wetlands from 1978 to 2000.From 2000 through 2008,riverine and lacustrine wetlands constituted the main wetland loss.Fortunately however,the rate of wetland loss decreased from 5523 to 831 km 2 /a.(iii) The change ratio of lost natural wetlands (including inland and coastal wetlands) to non-wetlands has decreased slightly over the past 30 years.From 1978 to 1990,nearly all natural wetlands (98%) lost were transformed into non-wetlands.However,the ratio declined to 86% from 1990 to 2000,and to 77% from 2000 to 2008.(iv) All Chinese provinces were divided into three groups according to patterns of wetland changes,which could relate to the driving forces of such changes.Tibet was completely different from other provinces,as it was one representative example in which there was a net wetland increase,because of global warming and decreased human activity since 1990.Increased economic development caused considerable wetland loss in most eastern provinces,and artificial wetlands increased.
基金supported by Nature Key Research and Development Program of China (2017YFB1400700)the National Natural Science Foundation of China (61602537, U1509214)+1 种基金the Central University of Finance and Economics Funds for the Youth Talent Support Plan (QYP1808)First-Class Discipline Construction in 2019,open fund of Key Laboratory of Grain Information Processing and Control (KFJJ-2018-202)
文摘Blockchain with these characteristics of decentralized structure, transparent and credible, time-series and immutability, has been considering as a promising technology. Consensus algorithm as one of the core techniques of blockchain directly affects the scalability of blockchain systems. Existing probabilistic finality blockchain consensus algorithms such as PoW, PoS, suffer from power consumptions and low efficiency;while absolute finality blockchain consensus algorithms such as PBFT, HoneyBadgerBFT, could not meet the scalability requirement in a largescale network. In this paper, we propose a novel optimized practical Byzantine fault tolerance consensus algorithm based on EigenTrust model, namely T-PBFT, which is a multi-stage consensus algorithm. It evaluates node trust by the transactions between nodes so that the high quality of nodes in the network will be selected to construct a consensus group. To reduce the probability of view change, we propose to replace a single primary node with a primary group. By group signature and mutual supervision, we can enhance the robustness of the primary group further. Finally, we analyze T-PBFT and compare it with the other Byzantine fault tolerant consensus algorithms. Theoretical analysis shows that our T-PBFT can optimize the Byzantine fault-tolerant rate,reduce the probability of view change and communication complexity.
基金Supported by National Natural Science Foundation of China(Grant No.51405241,51505234,51575283)
文摘With the rapid development of mechanical equipment, the mechanical health monitoring field has entered the era of big data. However, the method of manual feature extraction has the disadvantages of low efficiency and poor accuracy, when handling big data. In this study, the research object was the asynchronous motor in the drivetrain diagnostics simulator system. The vibration signals of different fault motors were collected. The raw signal was pretreated using short time Fourier transform （STFT） to obtain the corresponding time-frequency map. Then, the feature of the time-frequency map was adap- tively extracted by using a convolutional neural network （CNN）. The effects of the pretreatment method, and the hyper parameters of network diagnostic accuracy, were investigated experimentally. The experimental results showed that the influence of the preprocessing method is small, and that the batch-size is the main factor affecting accuracy and training efficiency. By investigating feature visualization, it was shown that, in the case of big data, the extracted CNN features can represent complex mapping relationships between signal and health status, and can also overcome the prior knowledge and engineering experience requirement for feature extraction, which is used by tra- ditional diagnosis methods. This paper proposes a new method, based on STFT and CNN, which can complete motor fault diagnosis tasks more intelligently and accurately.
基金This work was supported by the National High Tech Projects(2012AA030402 and 2011AA010202)the National Science Foundation of China(61138001,61171024,61171026,61371035 and 11227904)+2 种基金the 111 Project(111-2-05)the Natural Science Foundation of Jiangsu Province(BK2012019)and the 973 Program(2014CB339800).
文摘The terahertz region is a special region of the electromagnetic spectrum that incorporates the advantages of both microwaves and infrared light waves.In the past decade,metamaterials with effective medium parameters or gradient phases have been studied to control terahertz waves and realize functional devices.Here,we present a new approach to manipulate terahertz waves by using coding metasurfaces that are composed of digital coding elements.We propose a general coding unit based on a Minkowski closed-loop particle that is capable of generating 1-bit coding(with two phase states of 0 and 180°),2-bit coding(with four phase states of 0,90°,180°,and 270°),and multi-bit coding elements in the terahertz frequencies by using different geometric scales.We show that multi-bit coding metasurfaces have strong abilities to control terahertz waves by designing-specific coding sequences.As an application,we demonstrate a new scattering strategy of terahertz waves—broadband and wide-angle diffusion—using a 2-bit coding metasurface with a special coding design and verify it by both numerical simulations and experiments.The presented method opens a new route to reducing the scattering of terahertz waves.
基金supported by funding from the Project Nn10 of Harbin Medical University Cancer Hospital(Grant Number Nn102017-02)National Natural Science Foundation of China(Grant Number 81602323,81872149)+3 种基金Outstanding Youth Project of Heilongjiang Provincial Natural Science Foundation(Grant Number YQ2019H027)Distinguished Young Scholars of Harbin Medical University Cancer Hospital(Grant Number JCQN2018-03)Yong Elite Training Foundation Grant of Harbin Medical University Cancer Hospital(Grant Number JY2016-02)Haiyan Fund Project of Harbin Medical University Cancer Hospital(Grant Number JJQN 2018-10).
文摘Accumulating evidence shows that cellular and acellular components in tumor microenvironment(TME)can reprogram tumor initiation,growth,invasion,metastasis,and response to therapies.Cancer research and treatment have switched from a cancercentric model to a TME-centric one,considering the increasing significance of TME in cancer biology.Nonetheless,the clinical efficacy of therapeutic strategies targeting TME,especially the specific cells or pathways of TME,remains unsatisfactory.Classifying the chemopathological characteristics of TME and crosstalk among one another can greatly benefit further studies exploring effective treating methods.Herein,we present an updated image of TME with emphasis on hypoxic niche,immune microenvironment,metabolism microenvironment,acidic niche,innervated niche,and mechanical microenvironment.We then summarize conventional drugs including aspirin,celecoxib,β-adrenergic antagonist,metformin,and statin in new antitumor application.These drugs are considered as viable candidates for combination therapy due to their antitumor activity and extensive use in clinical practice.We also provide our outlook on directions and potential applications of TME theory.This review depicts a comprehensive and vivid landscape of TME from biology to treatment.
基金financially supported by National Natural Science Foundation of China (Grant Nos. 41172186, 40972136 and 40572121)Special Fund for Basic Scientific Research of Central Colleges, Chang’an University, China (Grant Nos.CHD2011TD020, CHD2009JC070, CHD2009JC053 and CHD2009JC046)the Commonweal Geological Survey,the Aluminum Corporation of China and the Land-Resources Department of Qinghai Province (Grant No.200801)
文摘The Helegangnaren feldspar granite exposed in the eastern part of East Kunlun, is characterized by high concentrations of SiO2 and alkaline, low abundances of Fe, Mg and Ca, metaluminous-weak peraluminous. Trace elements analysis shows that the granite is depleted extremely in Ba, Sr and Eu, and rich in some large-ion lithophile elements and high field strength elements. Besides, the granite has high Ga contents, the values of 104（Ga/AI） vary from 2.50 to 2.77, which is mainly greater than the lower limit of A-type granites （2.6）, and is higher than the I- and S- type granites＇ average （2.1 and 2.28, respectively）. Rare earth element （REE） is characterized by relatively high fractionations of light REE （LREE） and heavy REE （HREE） （LREE/HREE=9.3-13.60, （La/Yb）N=10.92-18.02）, pronounced negative Eu anomalies （JEn=0.08-0.13）, and exhibits right- dipping gull pattern. Major elements, rare elements and trace elements features show the granite is ascribed to A-type granite and A2 subtype in tectonic genetic type. They are plotted into post-collision or within-plate area in a variety of tectonic discriminations. Geological and geochemical data comprehensively suggest that the granite is formed in a post-collision extensive tectonic setting. Laser ablation inductively coupled plasma mass spectrometry （LA-ICP-MS） zircon U-Pb dating yields a weighted mean age of 425 Ma, belonging to Middle Silurian, which is similar to the age of the post- collision geological events in the region. The differences of magmatic rocks in formation age, rocks assemblage and rocks series systematically indicate that the regional tectonic stress regime in the East Kunlun orogenic belt experienced a major transformation from compress to extension in Middle Silurianin, and the Helegangnaren feldspar granite intruded in the early stage of tectonic transformation.
基金Supported by the National Key Research and Development Program(2017YFA0603802,2015CB453200)National Natural Science Foundation of China(41630423,41475084,41575043,41375095)+3 种基金United States National Science Foundation(AGS-1565653)Jiangsu Province Natural Science Foundation Key Project(BK20150062)Jiangsu Shuang-Chuang Team Fund(R2014SCT001)Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The western Noah Pacific anomalous anticyclone （WNPAC） is an important atmospheric circulation system that conveys El Nifio impact on East Asian climate. In this review paper, various theories on the formation and maintenance of the WNPAC, including warm pool atmosphere-ocean interaction, Indian Ocean capacitor, a combination mode that emphasizes nonlinear interaction between ENSO and annual cycle, moist enthalpy advecfion/Rossby wave modulation, and central Pacific SST forcing, are discussed. It is concluded that local atmosphere-ocean interaction and moist enthalpy advection/Rossby wave modulation mechanisms are essential for the initial development and maintenance of the WNPAC during El Nifio mature winter and subsequent spring. The Indian Ocean capacitor mechanism does not contribute to the earlier development but helps maintain the WNPAC in El Nifio decaying summer. The cold SST anomaly in the western North Pacific, although damped in the summer, also plays a role. An inter- basin atmosphere-ocean interaction across the Indo-Pacific warm pool emerges as a new mechanism in summer. In addition, the central Pacific cold SST anomaly may induce the WNPAC during rapid El Nifio decaying/La Nina developing or La Nifia persisting summer. The near-annual periods predicted by the combination mode theory are hardly detected from observations and thus do not contribute to the formation of the WNPAC. The tropical Atlantic may have a capacitor effect similar to the tropical Indian Ocean.
基金the National Key Research and Development Program of China(2018YFA0606301)the National Natural Science Foundation of China(42025502,41991285,42088101).
文摘This article evaluates the performance of 20 Coupled Model Intercomparison Project phase 6(CMIP6)models in simulating temperature and precipitation over China through comparisons with gridded observation data for the period of 1995–2014,with a focus on spatial patterns and interannual variability.The evaluations show that the CMIP6 models perform well in reproducing the climatological spatial distribution of temperature and precipitation,with better performance for temperature than for precipitation.Their interannual variability can also be reasonably captured by most models,however,poor performance is noted regarding the interannual variability of winter precipitation.Based on the comprehensive performance for the above two factors,the“highest-ranked”models are selected as an ensemble(BMME).The BMME outperforms the ensemble of all models(AMME)in simulating annual and winter temperature and precipitation,particularly for those subregions with complex terrain but it shows little improvement for summer temperature and precipitation.The AMME and BMME projections indicate annual increases for both temperature and precipitation across China by the end of the 21st century,with larger increases under the scenario of the Shared Socioeconomic Pathway 5/Representative Concentration Pathway 8.5(SSP585)than under scenario of the Shared Socioeconomic Pathway 2/Representative Concentration Pathway 4.5(SSP245).The greatest increases of annual temperature are projected for higher latitudes and higher elevations and the largest percentage-based increases in annual precipitation are projected to occur in northern and western China,especially under SSP585.However,the BMME,which generally performs better in these regions,projects lower changes in annual temperature and larger variations in annual precipitation when compared to the AMME projections.
文摘When A ∈ B（H） and B ∈ B（K） are given, we denote by Mc an operator acting on the Hilbert space HΘ K of the form Me = （ A0 CB）. In this paper, first we give the necessary and sufficient condition for Mc to be an upper semi-Fredholm （lower semi-Fredholm, or Fredholm） operator for some C ∈B（K,H）. In addition, let σSF＋（A） = {λ ∈ C ： A-λI is not an upper semi-Fredholm operator} bc the upper semi-Fredholm spectrum of A ∈ B（H） and let σrsF- （A） = {λ∈ C ： A-λI is not a lower semi-Fredholm operator} be the lower semi Fredholm spectrum of A. We show that the passage from σSF±（A） U σSF±（B） to σSF±（Mc） is accomplished by removing certain open subsets of σSF-（A） ∩σSF＋ （B） from the former, that is, there is an equality σSF±（A） ∪σSF± （B） = σSF± （Mc） ∪＆ where L is the union of certain of the holes in σSF±（Mc） which ilappen to be subsets of σSF- （A） A σSF＋ （B）. Weyl＇s theorem and Browder＇s theorem are liable to fail for 2 × 2 operator matrices. In this paper, we also explore how Weyl＇s theorem, Browder＇s theorem, a-Weyl＇s theorem and a-Browder＇s theorem survive for 2 × 2 upper triangular operator matrices on the Hilbert space.
基金supported by the National NaturalScience Foundation of China (No. 40473045)
文摘The contents and distribution of 20 polycyclic aromatic hydrocarbons （PAHs） and heterocyclic aromatic hydrocarbons （HAHs） were investigated in 16 soil profiles of Beijing and Tianjin region. Transport of high molecular weight PAHs （HMWPAHs） and the correlation between total organic carbon （TOC） and their concentrations were also discussed. The results indicated that highly contaminated sites were located at urban or wastewater irrigation areas and pollutants mainly accumulated in topsoil （〈 40 cm）, with a sharp content decrease at the vertical boundary of 30-40 cm. Total PAHs/HAHs concentrations in soils from Tianjin were markedly greater than those from Beijing. Even the contents at bottoms of soil profiles in Tianjin were higher than those in topsoils of Beijing soil profile. HMWPAHs dominated the PAH profiles, exhibiting a uniform distribution of pyrogenic origin between topsoils and deep layers. Furthermore, the percentages of HMWPAHs remained relative constant with the depth of soil profiles, which were consistent with the distribution of particulate matter-associated PAHs in the local atmospheric environments. Therefore, HMWPAHs transport with particulates might be the predominant source found in soil profiles.
基金This work is supported by the National Natural Science Foundation of China(Nos.61771154,61603239,61772454,6171101570).
文摘Deep Learning(DL)is such a powerful tool that we have seen tremendous success in areas such as Computer Vision,Speech Recognition,and Natural Language Processing.Since Automated Modulation Classification(AMC)is an important part in Cognitive Radio Networks,we try to explore its potential in solving signal modulation recognition problem.It cannot be overlooked that DL model is a complex model,thus making them prone to over-fitting.DL model requires many training data to combat with over-fitting,but adding high quality labels to training data manually is not always cheap and accessible,especially in real-time system,which may counter unprecedented data in dataset.Semi-supervised Learning is a way to exploit unlabeled data effectively to reduce over-fitting in DL.In this paper,we extend Generative Adversarial Networks(GANs)to the semi-supervised learning will show it is a method can be used to create a more dataefficient classifier.
基金sponsored by the National Natural Science Foundation of China(NNSFC)under Grants Nos.61625502,11961141010,and 61975176the Top-Notch Young Talents Programme of China+4 种基金the Fundamental Research Funds for the Central UniversitiesNanyang Technological University for NAP Start-Up Grantthe Singapore Ministry of Education(Grant Nos.MOE2018-T2-1-022(S),MOE2016-T3-1-006 and Tier 1 RG174/16(S))supported by the Chinese Scholarship Council(CSC No.201906320294)Zhejiang University Academic Award for Outstanding Doctoral Candidates.
文摘Optical logic operations lie at the heart of optical computing,and they enable many applications such as ultrahighspeed information processing.However,the reported optical logic gates rely heavily on the precise control of input light signals,including their phase difference,polarization,and intensity and the size of the incident beams.Due to the complexity and difficulty in these precise controls,the two output optical logic states may suffer from an inherent instability and a low contrast ratio of intensity.Moreover,the miniaturization of optical logic gates becomes difficult if the extra bulky apparatus for these controls is considered.As such,it is desirable to get rid of these complicated controls and to achieve full logic functionality in a compact photonic system.Such a goal remains challenging.Here,we introduce a simple yet universal design strategy,capable of using plane waves as the incident signal,to perform optical logic operations via a diffractive neural network.Physically,the incident plane wave is first spatially encoded by a specific logic operation at the input layer and further decoded through the hidden layers,namely,a compound Huygens’metasurface.That is,the judiciously designed metasurface scatters the encoded light into one of two small designated areas at the output layer,which provides the information of output logic states.Importantly,after training of the diffractive neural network,all seven basic types of optical logic operations can be realized by the same metasurface.As a conceptual illustration,three logic operations(NOT,OR,and AND)are experimentally demonstrated at microwave frequencies.
