Risk analysis of Portfolio is studied ,by comparing Copula functions and the traditional VaR methods,mixing copula is made. By backtesting ,the empirical research shows that mixing Copula method makes better VaR model .

The redox property of palladium nanoparticles (NPs) is pivotal to CeO₂ supported Pd catalysts in oxidation reactions and is closely related to the structure of Pd-CeO₂ interface. Herein, we report that low-temperature CO oxidation activity of Pd/CeO₂ highly depends on the shape and crystal plane of CeO₂ supports. Pd/CeO₂ catalysts with CeO₂ nanoocthedrons (NOCs) and nanocubes (NCs) as supports were prepared by colloidal-deposition method. Results show that Pd/CeO₂ NOCs with ceria {111} facets enclosed exhibited much higher catalytic activity than Pd/CeO₂NCs with ceria {100} facets exposed. DFT calculations revealed that the redox property of surface Pd species may play important roles in determining the reducibility and activity of catalysts. The PdO_x to Pd cycle is more facile on Pd₄@CeO₂(111) than on Pd₄@CeO₂(100), which is dictated by the Pd-ceria interaction in the end. Our results show that the redox property of surface Pd is pivotal to the reducibility and activity of Pd/ceria catalysts, which could be tuned by manipulation of the Pd-CeO₂ interaction via tuning the exposed facets of ceria support.

Light field is a representation of full four-dimensional radiance of all rays with spatial and angular information in free space, and capture of light field data enables many new development potentials for computational imaging. The historical development of light field photography is summarized, and typical light field photography devices are categorized in view of capture methods for 4D light field. Based on the principles of light field camera, computational imaging theorem, refocusing theory, synthetic aperture refocusing algorithm, and light field microscopic technology are emphatically described. Finally, the promising application perspectives and existing critical issues of light field imaging are discussed.

GH3 genes belong to a primary auxin-response gene family. The 10 promoter sequences of Arabidopsis GH3 genes were analyzed using bioinformatics method. The results show that the transcription start site of these genes is generally 65~145bp away from the start codon, and the TATA boxes are located in the (-24)-(-40)bp. MDB and MatInspector analyses show that most upstream regions of these GH3 genes contain the cis-elements required for tissue and organ-specific expression responding to phytohormones and external environment, indicating that the expressions of GH3 genes are strictly controlled by multi-factors. Gene chip data show that AuxREs is very important for GH3 genes in response to IAA treatment,but it is not the unique cis-element for auxin response.

Textual document clustering is one of the effective approaches to establish a classification instance of huge textual document set. Clustering Validation or Quality Evaluation techniques can be used to assess the efficiency and effective of a clustering algorithm. This paper presents the quality evaluation criterions from outer and inner. Based on these criterions we take three typical textual document clustering algorithms for assessment with experiments. The comparison results show that STC(Suffix Tree Clustering) algorithm is better than k-Means and Ant-Based clustering algorithms. The better performance of STC algorithm comes from that it takes accounts the linguistic property when processing the documents. Ant-Based clustering algorithm’s performance variation is affected by the input variables. It is necessary to adopt linguistic properties to improve the Ant-Based text clustering’s performance.

The micron-grade PMMA microspheres with narrow size distribution were prepared by dispersion polymerization. The mechanism of the dispersion polymerization was discussed. The factors influencing both the size and size distribution of the microspheres including initial concentrations of the initiator, monomer, stabilizer, the polarity of the medium and the reaction conditions were studied. The results indicated that the size and size distribution of microspheres both increased with initial concentrations of initiator and monomer. Increasing the amount of the stabilizer resulted in decreasing size and narrowing size distribution of microspheres. Other factors such as the polarity of medium and the reaction temperature had great influences too. By controlling these factors, the desired-size monodisperse microspheres could be obtained.

DBSCAN is a classic density-based clustering algorithm. It can automatically determine the number of clusters and treat clusters of arbitrary shapes. In the clustering process of DBSCAN, two parameters, Eps and minPts,have to be specified by uses. In this paper an adaptive algorithm named SA-DBSCAN was introduced to determine the two parameters automatically via analysis of the statistical characteristics of the dataset, which enabled clustering process of DBSCAN fully automated. Experimental results indicate that SA-DBSCAN can select appropriate parameters and gain a rather high validity of clustering.

In this paper, we present a new method based on self-modification mechanism to protect softwares against illegal acts of hacking. The key idea is to converse key codes into data in the original program so as to make programs harder to analyze correctly. Then, we translate data to executable codes by enabling the virtual memory page which stores the hidden code to be executable at run-time. Our experiments demonstrate that the method is practical and efficient.

Gram-Schmidt algorithm is one of the fundamental methods in linear algebra, which is mainly used to compute QR decomposition. The classical and modified Gram-Schmidt are both based on level 1 or level 2 BLAS operations which have low cache reuse. In this paper, a new block Gram-Schmidt algorithm is proposed. The new algorithm ensures the orthogonality of resulting matrix Q is close to machine precision and improves performance because of using level 3 BLAS. Numerical experiments confirm the favorable numerical stability of the new algorithm and its effectiveness on modern computers.

A design of high resolution camera system based on DALSA’ s CCD evaluation kit EKxxxx was presented. It was composed of a pulse pattern generator (SAA8103), a vertical line driver (TDA9991), four analog-to-digital interfaces (TDA9965) and a system controller (P89LV51RD2). Camera link with medium configuration was adopted to transfer digital images. The software for controlling and debugging the camera was developed. To correct the non-uniformity of 4 outputs, a method based on two-point correction was described. The system can acquire ultra high resolution pictures at a high frame rate thus it is suitable for aero photography.

In recent years, the heavy metal pollution incidents in China were frequently reported. However, studies on pollution, sources, and control strategies of atmospheric heavy metals in China are rare. We summarize the research results reported in recent years. The features of pollution level, seasonal variation, regional differences, size distribution of the atmospheric heavy metal elements including Pb, V, As, Mn, Ni, Cr, and Cd in China are analyzed. The main sources, current control status, and control technologies of atmospheric heavy metals are discussed. Comprehensive suggestions for China's heavy metal pollution control are put forward based on the summarization of the progress and experience of the atmospheric heavy metal pollution control in other countries and regions.

A high performance CMOS sample/hold circuit is presented, which achieves the precision of 10-bit over Nyquist band in 50-MHz sampling frequency at 3.3-V supply. This circuit uses full differential circuits, bottom-plate sampling, bootstrap circuits and high performance gain-boost operational amplifier. Simulation in 0.35-μm CMOS process shows the circuit consumes 18-mW of power.

Malicious applications pose tremendous threats to Android platform. More than 90% of malicious codes are introduced in the form of Android apps. Hence, behavior monitoring scheme for Android applications are required in order to resolve the problem. However, most of the schemes are based on system customization and hard to deploy on devices for Android's fragmentation problem. In this paper, an easy-to-deploy Android application monitoring method on the basis of process hijacking is proposed after analysis of Android process model and code execution details. The method depends on Dalvik interpreter entry point and system call interception. The authors created a fully usable prototype of the system, and the evaluation results show that the system is easy to deploy, provides a whole-scale behavior of Android applications, and incurs little performance overhead.

Uranium dioxide is a kind of steady nuclear fuel that has the characteristic of high melting point and steady property. The thermal conductivity of uranium dioxide can directly influence the temperature distribution of nuclear fuel and the max temperature of the center of nuclear fuel. The experimental results and expression of thermal conductivity have been compared in the paper. The deviation between the experiment results has decreased. The non-equilibrium molecular dynamics simulation results are in good agreement with the experiment results in medium temperature region. In low temperature region, it is necessary to add the quantum correction to the kinetic energy computation of phonon. In high temperature region, it is needed to use the accurate potential model and build up the electron gas energy transport model and photon radiation energy transport to study the thermal conductivity well and truly for the nuclear reactor safety design and uranium dioxide engineering application.

study of human-earth system is the most important content in geography; regional sustainable development relies on the reasonable structure optimal model and effective regulation of regional human-earth system. County region is a complex and opening human-earth system, taking Huangling county as an example, the environment, resources exploitation, economic development and structure evolvement of industry were systematically analyzed. And the systematical dynamic model was established and multi-projects were simulated with the theory and method of system dynamic. Optimized regulation models of human-earth system evolvement were educed based on three projects: (1) Traditional evolvement method. The intensity of resource exploitation and environment pollution is the least, but the speed of its economy development is the lowest, which restrict social sustainable development and economic reproduction. (2) Economy development method. The intensity of resource exploitation and environment pollution is the worst, economic development mostly depends on higher investment and pollution, which is a traditional mode of unsustainable development. (3) Harmonious development mode. The mode considers not only economic sustainable development and natural recourses utilizing reasonably, but also gives more attention to environment protection and harmonious development of industry, agriculture, tourism and so on. It is the optimized mode of the human-earth system evolvement.

The total polyphenols(TP)content of Quercus mongolicus Fisch leaves extracts was analyzed by Folin-ciocalteu colorimetry,with gallic acid as standard.The method was improved and verified in the aspects of stability, linearity,precision and accuracy.The results showed that the total polyphenols content of Quercus mongolicus Fisch leaves extracts could be well calculated according to their colorimetric absorption at 760nm by applying Folin-ciocalteu reagent (1mol/L) 0.15mL and 10% volume fraction of Na₂CO₃ 0.15mL at 25℃ for 80min. The (TP)content in Quercus mongolicus Fisch leaves determinated by the method was 6.39% and RSD was 1.90%.

K-means is an important clustering algorithm. It is widely used in Internet information processing technologies. Because the procedure terminates at a local optimum, K-means is sensitive to initial starting condition. An improved algorithm is proposed, which searches for the relative density parts of the database and then generates initial points based on them. The method can achieve higher clustering accuracies by well excluding the effects of edge points and outliers, as well as adapt to databases which have very skewed density distributions.

Because of the unique characteristics over wireless mesh networks, such as multi-radio multi-channel and static nodes, traditional Ad hoc network routing protocols can not work very well, which are based on the condition of “shortest path”. This paper presents a novel routing protocol named MEIL for wireless mesh networks. It designs routing metrics according to the wireless link loss, interference between channels and the load of wireless mesh nodes. MEIL chooses the route with lower loss, smaller interference and lighter load, so it can improve the throughput of the network efficiently. The simulation results show that MEIL performs much better than the AODV routing protocol and the DSDV+ETX algorithm under the circumstances of various services, and it is suitable for wireless mesh networks.

Poly (vinyl alcohol) (PVA) and its derivatives,the excellent water-soluble polymers,have attracted more and more attention,as they show the usability in many processes,as well as possess the promise of degradation in the presence of some specific microbials.In the present paper,the recent advances in the biodegradation of PVA and its derivatives,including the mechanism,influential factors,evaluation method and degradation environment etc,have been reviewed.Moreover,the latest development of PVA-based blendsPcomposites and their biodegradation is also introduced in the present article.

With the development of 3D data acquisition technology, point cloud wins the favor of researchers for it's simple but effective representation and it is widely used in the fields of remote sensing, scene reconstruction, 3D modeling, etc. Considering that the data acquisition process is easily disturbed by many factors such as equipment, environment and material, raw point cloud is often corrupted with noise and so it is of great significance to explore robust and efficient denoising algorithms. This paper firstly investigates the relevant research works of point cloud denoising and divides them into traditional algorithms based on the optimization idea and denoising algorithms based on the deep learning idea according to the implementation principles. Secondly, the research progress of each kind of algorithm is discussed and a detailed analysis of representative algorithms is presented. Thirdly, the data sets, the evaluation metrics and experimental results are summarized with an in-depth comparison. Finally, the problems and possible development directions and trends of point cloud denoising are prospected.

This review aims to guide the future development of related research in the field of learning path planning through the analysis of the current research status of learning path planning. Specifically, this review first introduces the definition of learning path planning and the commonly used parameters in learning path planning methods; then, it classifies in detail according to the algorithms used to generate learning path planning and summarizes the advantages and disadvantages of various learning path planning methods. In addition, the data set and evaluation method used by the learning path planning method is introduced. Finally, the challenges faced by the learning path planning method are summarized and the future development trend is predicted.

The quadratic assignment problem (QAP) is one of the NP-hard combinatorial optimization problems and is known for its diverse applications in real life. The current relatively mature heuristic algorithms are usually problem-oriented to design customized algorithms and lack the ability to transfer and generalize. In order to provide a unified QAP solution strategy, this paper abstracts the flow matrix and distance matrix of QAP problem into two undirected complete graphs and constructs corresponding correlation graphs, thus transforming the assignment task of facilities and locations into node selection task on the association graph. Based on actor-critic framework, this paper proposes a new algorithm ACQAP(actor-critic for QAP). Firstly, the model uses a multi-headed attention mechanism to construct a policy network to process the node representation vectors from the graph convolutional neural network; Then, the actor-critic algorithm is used to predict the probability of each node being output as the optimal node. Finally, the model outputs an action decision sequence that satisfies the objective reward function within a feasible time. The algorithm is free from manual design and is more flexible and reliable as it is applicable to different sizes of inputs. The experimental results show that on QAPLIB instances, the algorithm has stronger transfer and generalization ability under the premise that the accuracy is comparable to the traditional heuristic algorithm, while the assignment cost for solving is less compared to the latest learning-based algorithms such as NGM, and the deviation is less than 20% in most instances.

Recently, a major feature of global warming is asymmetrical temperature increase during day and night, i.e., the rate of warming at night is greater than that during the day. However, effects of asymmetrical warming have not yet attracted widespread attention. In this study, by collecting historical observation data of 838 meteorological stations in China, and using methods such as trend estimation, the characteristics of the temporal and spatial variation of diurnal temperature range (DTR) and the long-term trends of DTR from 1952 to 2018 were analyzed. The results indicated that:spatially, the regions with the highest average annual DTR in the country were distributed in the northwest and southwest, followed by the northeast and north China, and the areas with lowest DTR located in central, eastern, and southern China. The average monthly DTR in the year was generally multimodal. Among four seasons, DTR in spring and autumn was higher than in summer. From 1952 to 2018, the annual average DTR decreased significantly (τ=-0.396; p<0.01). Long-term changes in DTR were positively correlated with evaporation, sunshine hours, latitude and altitude, and negatively correlated with wind speed, precipitation, relative humidity, station pressure, total cloudiness, and longitude.

The estimation of forest biomass at individual tree scale is the basis for the estimation of forest biomass at the regional scale. This paper aims at developing a reliable and effective allometric equation for Eucalyptus in Fujian in order to improve the estimation accuracy of Eucalyptus biomass in this area and to provide basic supporting data for the sustainable forestry development of Eucalyptus. This study takes Eucalyptus, a major fast-growing and productive tree species in Southern China, as the research object. Using 90 Eucalyptus woods harvested in the field, the partitioning of Eucalyptus biomass among organs are studied, the optimal allometric equations are constructed, and the Eucalyptus root/shoot ratios are calculated and applied to estimate Eucalyptus root biomass. Results show Eucalyptus has the following biomass allocation strategies: the biomass proportion of trunks increases with increasing stand age, while that of branches, leaves, and roots decreases. The most feasible and effective way to estimate Eucalyptus root biomass is to use root/shoot ratio data with stand age. In the construction of the allometric equation for Eucalyptus biomass, the multiplicative power equation is better than the linear equation, and the optimal independent variable varied by organ type. This paper provides data and theoretical support for the accurate estimation of Eucalyptus plantation biomass, and has implications for species growth patterns, survival strategies, and even forest ecological management.

Youjiang basin (Nanpanjiang basin) experienced a complex tectonic evolution of Paleozoic prototype basin-superimposed basin, and finally, it appears as a residual basin. According to the tectonic setting, sedimentary series and magmatic rocks, the evolution of Youjiang basin after Caledonian movement can be divided into six stages:intracontinental extensional basin (early rift valley) evolution stage (D²₁-D¹₂), oceanic extensional basin (rift ocean basin) evolution stage (D₂-T₁), ocean basin extinction and foreland flexure basin evolution stage (T²₁-T¹₃), fold orogeny and post collisional extension stage (T¹₃-J₁), NW trending compression orogeny stage (J₂-K²₁), and local extension stage (K³₁-E). There are a large number of Carlin-type gold deposits in the basin, and most ore bodies occur in thrust-fold belts. The Carlin-type gold deposit has multi-stage metallogenic characteristics, large-scale mineralization mainly began in the compressive background and continued to the post orogenic extension stage, and there are two concentrated metallogenic periods. The first stage was formed in the evolution stage of foreland flexure basin related to collision orogeny to post collisional extension (235-193 Ma, Carlin-type gold deposit in the central and southern part of the basin). The mineralization in this stage was controlled by metamorphic hydrothermal fluids or hydrothermal fluids relate to magmatic melting which induced by the superposition of collision orogeny of the Yangtze Block and the Indochina Block and the subduction of the Paleo-Pacific plate to the Eurasian continent. The second stage was formed in the stage of NW trending compression orogeny to local extension (148-103 Ma, Carlin-type gold deposit in the whole Youjiang basin). The mineralization in this stage was mainly affected by the magmatic hydrothermal activities during the superposition and transformation of the pre-existing structures by the NW trending compression orogeny. Magmatic or metamorphic hydrothermal activities under extensional background before the Early Triassic has the effect of initial enrichment, and it has the effect of superimposed and reformation post mineralization after the Early Cretaceous. The ore-forming fluid of Carlin-type gold deposit has the characteristics of mixed sources. It is mainly metamorphic hydrothermal solution in the central and southern part of the basin, and mostly mixed source hydrothermal solution in the central part of the basin. While, the ore-forming fluid is mainly magmatic hydrothermal solution in the northern part of Youjiang basin. Through comparative analysis, it is considered that the ages obtained by different dating methods can represent the metallogenic age to a certain extent. And the combined application of multiple methods should be used to limit the metallogenic age of Carlin-type gold deposits.

Beijing synchrotron radiation facility (BSRF) 4B7B soft X-ray endstation is an ultra-high vacuum system, which is connected to the upstream beamline through an electromagnetic plug-in valve. Scientific research users are prone to misoperation when changing samples in experiment. When valve is not closed, vacuum system is vented and equipment is damaged. In order to avoid vacuum accidents, this article proposes to optimize the original manual protection measures and design vacuum safety interlock protection systems. Vacuum gauge, pneumatic angle valve, and electromagnetic flapper valve are interlocked and controlled by electrical components, aiming to improve the convenience and reliability of user's operation on the basis of ensuring the vacuum safety of endstation when user changes samples. The safety interlocking protection system control cabinet was confirmed to meet the expected design requirements after many commissioning inspections and trial runs after landing, and was formally applied in soft X-ray calibration experiment, effectively ensuring the safety and reliability of equipment during user operation. In addition, application prospect of the safety interlock protection system in beamline of high energy photon source (HEPS) in the future is discussed in this article, and engineering design experience is provided for construction of vacuum interlocking protection system of HEPS beamline.

In this paper, we express the Mahler measure of a two-variable polynomial P(x,y)=(x²+1)y²+2(x²+x)y+x(x²+1) as a linear sum of some Bloch-Wigner Dilogarithm functions. and prove that the Mahler measure of P(x,y) is rationally proportional to L'(χ_-3,-1):m(P(x,y))=5/2L'(χ_-3,-1).

Online social networks have become the disaster areas where rumors grow. It is of great significance to identify core rumor spreaders for rumor prevention and control. The traditional rumor control model is mainly based on the dynamics of rumor propagation, and it is mainly focused on in-event or post-event control. In view of the timeliness of rumor control, this paper proposes a multi-stage graph convolutional network based on multi-dimensional features (MSF-GCN) deep learning model to accurately locate core rumor spreaders as early as possible and block rumor diffusion from the source. This work compares the MSF-GCN method with other three baseline methods on rumor data set, and the experimental results verify that our method is more efficient.

Unmanned aerial vehicles (UAV) controlled by autonomous control algorithms often have greater advantages than manned aircraft in the execution of directional strikes and other dangerous tasks. When performing blasting tasks, the robustness of the UAV detection algorithm in different scenarios is often not guaranteed, which greatly affects the UAV's positioning of the target, thus reducing the success rate of the mission. In order to solve the above problems, the crossdomain-based object detection algorithm is used to improve the robustness of the UAV detection algorithm in different scenarios, and the online GPS clustering algorithm is used to improve the robustness of object positioning. At the same time, in view of the impact of the object blasting position on the blasting result, the system uses an algorithm for locating weak parts to improve the accuracy and success rate of blasting.

High frequency Sharpe ratio, a measure of return and risk, is commonly used in current portfolio construction method since it can avoid covariance matrix in high dimensional analysis. The newly proposed D-SEV measures the correlation between stock's return and high frequency Sharpe ratio index to further construct portfolio. However, there are some problems with the measure used in D-SEV, such as its lack of robustness and slow computational speed. In this paper, we propose to use a new correlation coefficient proposed by Sourav Chatterjee instead. The new correlation coefficient guarantee robustness, specifically it can reduce the impact of abnormal data on correlation, such as significant events that have a large impact on the asset prices. It is also extremely fast in its calculations. Extensive simulation demonstrate that new correlation coefficient outperforms D-SEV and other traditional methods in several different models. Actual Shanghai Securities Exchange (SSE) and Shenzhen Securities Exchange (SZSE) stock market data for 2019 and 2020 also show that the assets selected by new correlation coefficient earns 8% more excess annualized return than D-SEV, while it also owns a higher Sharpe ratio.

In recent years, multi-agent reinforcement learning has received a lot of attention from researchers. In the study of multi-agent reinforcement learning, the question of how to perform ad-hoc cooperation, i.e., how to adapt to a changing variety and number of teammates, is a key problem. Existing methods either have strong prior knowledge assumptions or use hard-coded protocols for cooperation, which lack generality and can not be generalized to more general ad-hoc cooperation scenarios. To address this problem, this paper proposes a local observation reconstruction algorithm for ad-hoc cooperation, which uses attention mechanisms and sampling networks to reconstruct local observations, enabling the algorithm to recognize and make full use of high-dimensional state representations in different situations and achieve zero-shot generalization in ad-hoc cooperation scenarios. In this paper, the performance of the algorithm is compared and analyzed with representative algorithms on the StarCraft micromanagement environment and ad-hoc cooperation scenarios to verify the effectiveness of the algorithm.

Subgroup analysis of heterogeneous groups is a crucial step in the development of individualized treatment and personalized marketing strategies. Regression-based approaches are one of the main schools of subgroup analysis, a paradigm that divides predictor variables into two parts with heterogeneous and homogeneous effects and divides the sample into subgroups based on the heterogeneous effects. However, most of the existing regression-based subgroup analysis methods have two major limitations: First, they still consider the sample homogeneous within subgroups and do not fully consider individual effects; Second, the common contamination phenomenon of homogeneous effect variables is not taken into account, which will lead to large bias in the model results. To address these challenges, we propose a robust individualized subgroup analysis. We use a multidirectional separation penalty function to achieve individualized effects analysis for the heterogeneous part of the model and use γ-divergence to obtain robust estimates for the contaminated homogeneous part. We also propose an efficient alternating iterative two-step algorithm, combining coordinate descent and alternating direction method of multipliers (ADMM) techniques to implement this process. Our proposed method is further illustrated by simulation studies and analysis of a skin cutaneous melanoma dataset.

Traditional synthetic aperture radar (SAR) image change detection methods have some problems, such as big impact by speckle noise, difficult to use deep information of the image, and low detection accuracy. To solve above problems, this paper presents an SAR amplitude image change detection algorithm based on convolution neural network and fuzzy clustering. Firstly, a hierarchical FLICM algorithm based on Gabor texture is used to pre-classify the difference images, and reliable training samples are automatically selected based on the pre-classification results without manual labeling. Then, a multiscale channel attention mechanism is introduced, and a MSCA_WCNN is used to complete the second classification, and the result of change detection is obtained. This algorithm extracts the different scale features of SAR images while suppressing the irrelevant feature channels to effectively utilize the image features. The wavelet convolution neural network achieves the denoising function while preserving the useful information of the image and enhances the robustness of the algorithm. The comparison experiments using real spaceborne SAR image data show that the algorithm has high detection accuracy and the effectiveness of the algorithm is verified.

The fine particulate matter PM_2.5 could be harmful to human health and the atmospheric environment. Beijing-Tianjin-Hebei is one of the most serious regions in China in terms of atmospheric PM_2.5 pollution. Based on PM_2.5 concentrations data, natural factors data, and human activity factors data, this study used kriging interpolation and statistical analysis to explore the spatial and temporal distribution characteristics of atmospheric PM_2.5 pollution in 13 cities of Beijing-Tianjin-Hebei in 2017 and then used correlation analysis models and factor analysis models to explore its influential factors. The results show that in Beijing-Tianjin-Hebei, 1) PM_2.5 concentrations are low in the north and high in the south. The gradient of annual average concentrations between the southern and northern cities can reach up to 64μg/m³. 2) PM_2.5 concentrations are high in winter and low in summer, high in the morning and evening, and low in the afternoon. PM_2.5 concentration in winter is 1.3-2.8 times higher than in summer, and the daily differences in PM_2.5 concentrations in all seasons are between 11-29μg/m³. 3) Atmospheric PM_2.5 pollution is closely related to natural factors. Terrain and topography affect the processes of PM_2.5 aggregation, transport, and dispersion. Wind speed, sunshine hours, and relative humidity are the dominant meteorological factors affecting atmospheric PM_2.5 pollution, and PM_2.5 concentrations have the strongest correlation with meteorological factors in winter. 4) Atmospheric PM_2.5 pollution is closely related to human activities, which can be summarized into social economy factor, industrial pollutant discharge factor, and urban construction factor. The results of this study will help fill the gaps in air pollution prevention and control in Beijing-Tianjin-Hebei.

The physical unclonable function (PUF) implemented on SRAM and other schemes exists inherent demerit of poor reproducibility for environmental factors such as voltage changes and thermal noise. This disadvantage greatly restricts functional application in cryptography, communication and other fields. In this paper, a fuzzy extractor with large error correction capacity is designed to reconstruct the original data of SRAM by means of BCH codes (Bose-Chaudhuri-Hocquenghem Codes). The SRAM PUF chip applying this design is manufactured on the Hua Hong Grace 0.11 μm CMOS platform with area of 306 267 μm². The original BCH code has a code length of 127 bits and an error correction capability of 27 bits, which achieves the practical requirements of PUF applications.

The first measured high-precision data on the differential cross sections and polarization observable beam asymmetry Σ for the γp→π^-Δ⁺⁺ reaction from the LEPS collaboration are analyzed within a tree-level effective lagrangian approach. In addition to the t-channel π and ρ exchanges, the u-channel Δ exchange, the s-channel N exchange, and the interaction current that is required by the gauge invariance, the s-channel nucleon resonance exchanges are further taken into account to reproduce the data of LEPS. Numerical results show that, the data on Σ can not be well reproduced when no contributions from the s-channel resonance exchanges are introduced. Further analyses show that, by including the contribution from the resonance N(1860)5/2⁺, both the data on the differential cross sections and beam asymmetry Σ can be well reproduced.

There might be great differences in spatiotemporal variation in leaf area index (LAI) of different grassland types; the responses of LAI with different annual variations to climate change are probably distinct. To explore these differences, from the long-term LAI data and meteorological data and the grassland type data, we obtained the temporal and spatial varying characteristics of the maximum LAI of different types of temperate grassland in northern China from 1981 to 2017, and explored the responses of LAI with different annual variations to the changes of air temperature and precipitation. The results showed that the average annual maximum LAI of temperate grassland was (0.76±1.07) m²/m², the higher in the east and the lower in the west. The meadow steppe had the highest LAI ((2.73±1.20) m²/m²) and the steppe desert had the lowest LAI ((0.13±0.17) m²/m²). From 1981 to 2017, the average annual maximum LAI showed a significantly increasing trend. The maximum LAI increased significantly for 32.52% of the area and decreased significantly for 6.31% of the area. The areas with a significantly increasing LAI were greater than those with a significantly decreasing LAI for all the grassland types. The annual average maximum LAI was positively correlated with the annual total precipitation from January to August and the annual mean air temperature for July and August. Both the significant decrease and increase of the maximum LAI was mainly affected by the significant increase of annual mean air temperature for July and August. There existed a critical threshold of the rising rate of air temperature for July and August that influenced the variation in LAI; for the grassland types that accounted for the larger areas, this threshold was 0.042-0.043 ℃/a. LAI increased with the rising air temperature as the rising rate of air temperature was lower than this threshold; conversely, LAI decreased. These results are expected to provide important scientific basis for grassland utilization, protection and restoration in the context of climate change.

Thermal stress of the moon due to cooling process is non-negligible in lunar evolution. We calculate the accumulation of thermal stress with 3-D viscoelastic model, and explore the influence of viscosity parameters on thermal stress through comparative experiments. Numerical results suggest that the thermal stress of lithosphere is utterly distinct from deep mantle. The lithosphere is under tangential compression that concentrates at the bottom of the crust because of unevenly distributed cooling rate and elastic strength; on the other hand, the accumulation and relaxation of thermal stress in deep mantle is balanced due to low viscosity, and the thermal stress is in a “hydrostatic” state, which is mainly controlled by the elastic surface. Under the assumption that viscosity of lunar lithosphere is greater than 10²⁸ Pa·s, the tangential compressive stress in lithosphere accumulates to several hundreds of MPa in the present day, while the tensile stress in deep mantle reaches up to 100 MPa. Consequently, part of the shallow moonquake events can be explained by thermal stress. However, the focal mechanism of deep moonquakes is still unclear. We speculate that the tensile thermal stress in deep mantle helps to develop pore structures, and the melting layer provides pore fluid with high pressure, which reduces the fracture strength of mantle medium.

On the basis of the previous work, considering the solar heat absorbed by the lunar surface inward and the lunar thermal radiation heat released outward, as well as the nonlinearities of the thermodynamic parameters of the lunar soil related to the temperature and depth, we have developed a thermo-elastic coupled finite element parallel program suitable for the study of the temporal and spatial evolutions of the temperature, deformation, and thermal stress of the lunar soil, and have utilized the four sets of finite element models to investigate the effects of the characteristic thicknesses of the lunar soil on the temporal and spatial evolutions of the temperature, deformation and thermal stresses of the lunar surface. The computational results show that the temperature of the lunar surface varies periodically over one lunar day (29.5 Earth days), and the temperature of the equatorial lunar surface varies from 100 to 385 K, with the variation decaying exponentially with the increase of the depth, and the depth of influence reaches to about 50 cm. The temperature cyclic changes also cause the vertical displacement of the lunar surface to rise and fall, and the horizontal normal stress of the lunar surface in the form of compression and tension. In general, the horizontal stresses are compressed during the day and tensile during the night, with the fastest increase in tensile stress at 18:00 and the highest tensile stress at 06:00. The characteristic thickness of the lunar soil has a strong influence on the temporal and spatial distributions of the temperature and the horizontal positive stresses. The magnitude of thermal stresses may reach the tensile strength of the lunar surface. The fastest growth of tensile stress and the period of maximum amplitude coincide with the observed high frequency of thermal events on the lunar surface in the morning and evening.