The domestic academic degree certification is inefficent in complicated process, long time and high certification fees, which makes it difficult to satisfy the needs of graduates and employers for quick, fair and accurate verification of information. It is impossible to achieve innovative application. Blockchain technology is characterized by decentralization, tamper resistance, traceability, and information change, which can effectively solve the problems existing in current domestic academic degree certification. After analyzing the foreign projects of issuing education diplomas in blockchain technology, this paper proposes an academic degree certificate platform based on the alliance chain Hyperledger Fabric, and carries out the architecture design, including the business system layer, block layer, service layer and application layer. The platform nodes are divided into four categories: education management department, trusted colleges, students and employers. It also describes the three functional processes of digital identity register, digital academic degree certificates issuing, and academic degree certificates verification. Platform technology uses an authorization-based consensus mechanism to improve performance and stores only the hash of the digital diploma, which can effectively protect personal privacy. This research attempts to innovate in the academic degree certification model and technology.

With the global industrial information security incidents occurring frequently, the security vulnerabilities of industrial control systems are increasing, the ways of network attacks in industrial areas are becoming diverse, and the security concerns of industrial Internet are increasing. This paper describes the status and market scale of security in industrial Internet industry, analyses the current security situation of industrial Internet and security elements, specifies the progress of standards at home and abroad, classifies the security technology system, and looks forward to the development trend of industrial Internet security.

In this paper we studied the relationship between partial shadowing property and transitivity. We proved that a map which has 0.5ergodic shadowing property with dense minimal points is syndetic transitive; a map which has 0.5 average shadowing property with dense minimal points is syndetic transitive.

Both sorting and inductive type play a key role in theory itself and its applications in Bigraphical Reactive Systems (BRS). The progress of research on sorting and inductive type is introduced in detail and expressiveness and confinement of them are illuminated respectively. Finally, the future research directions related to type description in bigraph theory are discussed.

SiO₂ microspheres, a new functional material, are widely used in many fields with non-toxic, harmless, size-controlled and easy-functionalized characteristics. At present, sol-gel method is one of the most available preparation methods, it has simple operation, less side reactions and dimensional homogeneity. The reaction mechanism is that under the catalytic action of ammonia water, TEOS undergoes hydrolysis and condensation reactions, forming SiO₂ microspheres finally. The synthetic effect is affected by many factors, such as the concentration of TEOS and ammonia water, the variety and dosage of solvent, reaction temperature, synthesis time,etc.Traditional sol-gel method has disadvantages of easy agglomeration, poor monodispersity and long synthesis time, etc. And many researchers have made a lot of improvements on it, deriving new methods such as continuous titration and stepwise titration,etc. Lack of unified standards makes it difficult to achieve large-scale industrial production, and the complex optimization process and high cost limit a wide spread of the functional SiO₂ microspheres. Therefore, it is important to establish a mature theoretical model and develop a sol-gel method with fixed formula and large-scale controllable production in the future.

Topological graph belongs to graph theory, a branch of mathematics. In this paper, the theory and technique of graph theory are applied in networks research, but only for networks descript. This paper focuses on new concepts such as Graph Network and Graph Matching Network, scale-free graph definition, definition of “Internet of Things”, new cumulative distributions, and splitting connectivity in artificial intelligence. The review emphasis is placed on the construction of high-quality networks and special properties of networks, the establishment of new algorithms such as spanning tree count, dominating set, dominating graph, and collapse degree; the applications of dynamic partial differential equations, probability, graph theory and other mathematical techniques in network research are highlighted.

With the continuous expansion and rapid development of the Internet, it has brought great convenience to network users. But along with the development of the Internet, the network security situation is becoming more and more serious. Traditional signature-based intrusion detection methods are difficult to deal with the increasing problem of encryption attack detection and zero-day attack detection. By contrast,deep learning based network intrusion detection has shown great potential in solving these problems. Through extensive literature review, this paper introduces the latest work of network anomaly detection using deep learning technology. Firstly, this paper summarizes the most commonly used features for network intrusion detection and relevant pre-processing operations. Then, this paper summarizes several common deep learning models and discusses how to select a suitable model. On these basis, this paper summarize several kinds of intrusion detection tasks that can be achieved by deep learning methods. Finally, some existing problems and challenges of applying deep learning for intrusion detection are discussed.

Through the traditional methods of bibliometrics and Cite-Space software, the paper analyzes the literature output time, keywords, authors and agencies of the “Life-Production-Ecological Space” study. Finally, the paper summarizes the research hotspots and status quo of the existing “three-life space” literature. It draws the results: ①Domestic research on “three-life space” first appeared at the end of the 20th century. In 2012, it became a research hotspot. The number of documents has increased rapidly and has remained stable in recent years. ②There are many researchers in this field, and Fan Jie has published the most literature. ③The Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences has the highest frequency of publication, and it is at the center of the cooperation network of scientific research institutions. There are more cooperations with institutions in the same city or in the same sector, and there is less cross-regional and interdisciplinary cooperation. ④In recent years, the “three-life space” research has the characteristics of multi-disciplinary and multi-scale research methods. The research content mainly focuses on the construction of the theoretical framework, classification, evaluation and optimization of “three-life space.”

The total coloring of a graph is the generalization of its vertex coloring and edge coloring, whose requirement is to assign colors to both its vertices and edges such that any adjacent elements (adjacent vertices and adjacent edges) and incident elements (vertices and edges) do not receive the same color. The total chromatic number of a graph is the minimum integer for which the graph admits a total coloring. In terms of this graph parameter, Vizing (1964) and Behzed (1965) independently proposed an identical conjecture: every graph has a total coloring using at most Δ+2 colors, where Δ denotes the maximum degree of the graph. This conjecture is still open. This paper will present a comprehensive survey on this topic.

The paper begins with an introduction to the existing RSSI ranging conversion equations and an analysis on the basic principle and application scope of various signal propagation theoretical models. By constructing experimental platform based on TI CC2530 SoC, the intensity of 2.4GHz RF signal in indoor environment is measured. This paper also analyzes the quantitative relationship between RSSI and inter-node distance, and illustrates the parameter estimation process of 5 common curve fitting models with measured data. Finally, goodness of fit is examined for each fitting model and a comparison analysis is performed. Verification test results show that Single Gaussian Curve Fitting Model performs well as a RSSI-based indoor ranging fitting model with high accuracy and wide applicability.

The emergence of cryptocurrency bitcoin has driven the vigorous development of blockchain technology, and smart contract technology is a technical highland of blockchain technology. At present, smart contract applications in ethereum have received a lot of attention, creating a lot of value applications, and at the same time bringing intensive attack activities.With the increasing number of intelligent contracts, especially the code loopholes in intelligent contracts have been gradually discovered by many researchers and malicious attackers, which has caused a series of serious economic losses.In order to provide theoretical research basis for the stable development of intelligent contract technology, this paper introduces, classifies and summarizes the known intelligent contract vulnerabilities in ethereum, and elaborates the principle and scene code of intelligent contract security vulnerabilities in detail.

The task computing offloading technology is generated to solve the problem of limited local computing resources. It has mainly appearing in the cloud and mobile scenes for a long time. With the advent of edge computing, are the task offloading technology of the mobile edge computing end (MEC) has also received extensive attention and research. This paper first introduces the network architecture and deployment scheme of MEC, and analyzes and compares different deployment scenarios. Then it studies from the perspectives of mobile computing offload decision, resource allocation and offloading system. Finally, it summarizes challenges faced by the current MEC's mission calulation in mobility management, security management, and service management.

As a wide band gap semiconductor, Aluminum Nitride ( AlN) has excellent physical and chemical properties and has been widely used in the field of Light Emitting Diode ( LED) . Similarly,Gallium Nitride ( GaN) , which is well developed, also plays an irreplaceable role in this field. High performance devices need a good epitaxial layer. The traditional preparation method of AlGaN based ultraviolet LED( UV LED) epitaxy layer is Metal Organic Chemical Vapor Deposition ( MOCVD) .However, due to the strong pre reaction and slow migration rate of Al atoms in this method, a large number of defects appear in the epitaxial layer, which reduces the performance of UV LED devices.In addition, due to the difference in the refractive index of different materials and the difference in the refractive index of materials and air, light has difficulty escaping to the outside world, and most of the light is localized in the chip, thus reducing the light extraction efficiency and light intensity. In order to improve the optical performance of the device, a new UV LED structure is proposed. In this paper, Finite Difference Time Domain ( FDTD) software is used to simulate the light extraction efficiency and light intensity of the epitaxial structure. It is found that compared with the traditional LED structure, the light extraction efficiency of the new UV LED structure in transverse magnetic wave ( TM) mode and transverse electric wave ( TE) mode is increased by 19 1% and 29 3% , respectively, and the maximum light intensity is increased by 42 78% and 47 18% , respectively, which significantly improves the optical performance of the device. In addition, the influence of the structure parameters of the epitaxial layer of the new UV LED on the overall optical properties of the device is also studied in this paper. Under the constant conditions of light source, physical model size, simulation conditions and other factors, the optimal structural parameters of the optical performance are obtained.

Gable culture is one of the characteristics of the Chaoshan ancient architectures. By describing the decorative pattern, morphology and spiritual connotation of the gable, the applying law of the gable is revealed; its design is mostly decided by outside environment, building orientation and some of the mystery strength, such as the hosts Mingge.

Urban housing is a typical heterogeneous commodity, whose price is determined by the utility of all characteristics. For heterogeneous commodities, this paper is based on the sample data of commercial housing transactions in Shenzhen in 2016.Based on the related theory of Hedonic model, we use stepwise regression algorithm, Lasso penalty algorithm respectively to build housing price model. The results show that the most influential factor on the housing price of Shenzhen is the greening rate. Finally, the housing price quantile regression model is constructed with the 5%, 25%, 50%, 75% and 95% points of the housing price in Shenzhen. It is found that the coefficients of significant characteristic variables vary greatly at different housing price points, which is reflected in the different preferences of people on residential properties at different housing prices.

With the popularity of IoT devices, security issues of these devices have become serious concerns. Many reports have confirmed that there exist a large number of attacks targeting IoT devices. This paper surveys existing works concerning the software security of IoT devices. In particular, we first introduce works that leverage HoneyPot to capture real attacks, and then describe the software analysis systems of IoT devices. At last, we illustrate possible ways to enhance the software security of IoT devices, and then discuss possible research directions.

With the complexity of software increasing year by year, software security vulnerability has become one of the root factors of cyber-security threats. However, it is hard to meet the needs of vulnerability analysis and exploitation on labor. To analyze and exploit the vulnerabilities automatically in time, researchers have proposed several techniques, some of which can get good results. This paper presents a summary of the recent advances in four aspects, which include: control flow hijacking vulnerabilities automatic exploitation, heap-oriented vulnerabilities automatic analysis and exploitation, security mechanism automatic countermeasure, and the comprehensive framework of vulnerability automatic exploitation. Finally, we conclude the tendency of software vulnerability automatic exploitation to shed lights on potential future directions.

Although big data analysis has shown great value in some fields, the current development of big data is still faced with many problems. Among others, privacy preserving is recognized as a key issue. In the context of big data, there is an intricate relevance among data. To prevent an attacker from acquiring privacy by using a priori knowledge, Dwork proposed the concept of differential privacy. In recent years, differential privacy has been broadly concerned and has become an important research field to solve the privacy problem in the context of big data. However, it is worth noting that, in some systems such as Airavat performing MapReduce computations, the differential privacy technology is only used in some components. Clearly, preserving the privacy of components is not sufficient for the privacy preserving of an entire system. To this end, some scholars have made many efforts to ensure privacy at the system level. In this paper, after briefly reviewing the background, definition, and theoretical progress of the classical differential privacy, we survey the latest developments and research directions of differential privacy in probabilistic systems from the perspective of formal methods, with a view to promoting further research in this field.

The structural behavior of liquid sloshing in a rectangular Tuned Liquid Damper ( TLD) water tank with built in vertical screens under external horizontal excitation is investigated by Computational Fluid Dynamics ( CFD) method, the mechanical properties of liquid sloshing are numerically simulated by FLUENT software. The CFD simulation results in this paper are also compared with the experimental data with a similar configuration of water tank with vertical screens, which further verifies the effectiveness of the proposed CFD numerical simulation method. The numerical simulation results show that with the increase in the amplitude of the horizontal external excitation at the bottom of the tank, the nonlinearity of the liquid sloshing gradually intensifies. Meanwhile the amplitude of wave height of free surface and damping ratio of TLD system increase, but the amplitude of nondimensional horizontal control force gradually decreases. Setting the vertical screen at the location of the maximum amplitude of the first sloshing mode was found to effectively suppress the nonlinear phenomenon of liquid sloshing. The closer the vertical screen is placed near to the middle location of the water tank, the more value in the damping ratio of TLD system could produce. Numerical analyzed results show that the increase in water depth ratio of TLD system could result in the decrease in the damping ratio of TLD system gradually.

Arches are structures mainly subjected to compressive loads which will be out of balance in-plane or out-of-plane owing to the load reaching its critical value. The instability of arches always occurs suddenly without any omen, which is similar to brittle fracture. There will be disastrous consequences once these structures lose stability, which will endanger the life and property safety. Hence, it is particularly important to explore the stability of the arch from a deeper perspective. In this paper, the research progress of in-plane and out-of-plane static and dynamic stability of single arch and arch bridges are systematically reviewed, the theoretical and experimental research on static and dynamic stability of single arch and arch bridge are summed up, the limitation of arch stability analytical methods are summarized, the development trend of research on stability of arch is forwarded, and the guidance for the future arch research is given.

A CPAM-MMT hybrid polymer was synthesized through dispersing polymerization with Acrylamide (AM), the organic modified montmorillonite (O-MMT), 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) and its flocculation performance was also studied. The experimental results showed that morphology of the CPAM-MMT hybrid polymer was a multi-branched structure which helps to entrap more suspended colloidal-particles and gives a better bridging capacity, the flocculation ability of the CPAM-MMT hybrid polymer on the kaolin suspensions was better than that of CPAM and its optimum dosage was about 10 mg·L^-1, the CPAM-MMT hybrid polymer possessed the adsorption function on Cr(VI) ions, which made the decolorization rate on Cr(VI) larger than that of the CPAM, the CPAM on Cr(VI)was 18%. However, the CPAM-MMT(1) hybrid polymer was 28%.

A PVA-SA hydrogel biocarrier was prepared by solution blending method with boric acid as crosslinking agent. Then the carrier was characterized by using specific surface area/aperture distribution, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopic methods. Furthermore, its biological activity and treatment efficiency in the wastewater treatment were investigated. The results show that the most suitable PVA and SA concentrations are 7% and 1% respectively. Under these conditions, the specific surface area of gel beads is 24.233 m²·g^-1. The average pore size is 60.895nm, and these pores are dominated by large and mesoporous pores. It is observed that the network of the gel beads is stable and has abundant pore structure under the scanning electron microscopy. With the formation of biofilm in the gel beads, the surface and internal of the gel beads effectively produce lots of microorganisms, which results in excellent biological activity. The batch test showed that the oxygen uptake rate of the carriers is 8.95 μgO²·(min·stars)^-1 and COD removal efficiency can reach 89%. Thus, the PVA-SA hydrogel gel bead can serve as an ideal biological carrier to speed up the biofilm formation and improve the efficiency of wastewater treatment.

The population characteristics of naturally regenerated Sonneratia apetala under the edges and gaps of the five-year man-made S. apetala forest at the Erxiewan of Qi’ao, Zhuhai was surveyed by using the quadrat method, so as to provide basic data for investigating the ecological adaptability and potential damage of natural population of S. apetala. The results showed that the seedling population of S. apetala at Er’xiewan has a total of 299 individuals, with average density of 7.475 individuals·m^-2. The current-year seedling accounted for 72.24%, while the last-year seedling took up 27.76% of the whole population. The size structure of base diameter and plant height showed an increasing population type, and there was a significant linear relationship between base diameter and plant height. The population has a clump distribution type. The growth of native mangrove species such as Kandelia obovata, even the invasive plant species Spartina alterniflora were affected by this plantation trees through competing light and habitat, suggesting the Sonneratia apetala has an ecological damage to the other mangrove species. The structure of this plantation forest of S. apetala should be changed with native mangrove species and the S. apetala should not be planted anymore for the bare beaches.

The method of using radiochemical separation and purification technology and alpha-spectrometer measuring technology,using was built for measuring ²¹⁰Po activity in inhalable particulate matter (PM).By self-made small-scale radon chamber to carry out simulation experiment using PTFE membrane filter in the small seal chamber after 60 d, this paper measured radon concentration and membrane after dealing with the acid wet digestion, as ²¹⁰Po was deposited on the silver piece, and used alpha spectrometer to analyze sedimentary finished silver strip measurement. The results showed that the indoor radon concentration quickly reached more than 2×10⁵ Bq·m^-3 and maintain a long time, ²¹⁰Po through the deposition, the ²¹⁰Po activity of radon decay progeny can check out on the filter paper, high parallelism. It is proved that the small radon chamber can completely satisfy the radon measurement and simulation experiment.

The field measurements of outdoor air temperature,relative humidity, surface temperature, wind velocity, solar radiation and physiological equivalent temperature(PET) were conducted in Guangzhou University in typical summer days, the relationship between some impact factors and thermal comfort indices were quantified. The result indicated that the air temperature and mean radiation temperature of different hard underlying surfaces made little difference without effective shade, while higher than those under the tree about 2.4 ℃ and 20 ℃ respectively. The distribution trend of PET: tree shade<pavilion<grass<grass permeable brick<dark colored concrete<white tile.

In this paper, asset pricing models based on investor sentiment are briefly reviewed. Based on many empirical research achievements,the existing six methods for measuring investor sentiment are systematically summarized: direct investigation, indirect representation, principal component analysis, partial least squares, dynamic factor model, test mining. Future development direction is finally pointed out according to the limitations of the research methods about investor sentiment analysis.

Let n be an integer, and k is a prime number with 2 being its primitive root. We give the formula of the k-th cyclotomic matrix over finite field F_2ⁿ. This result can be used to compute the number of the corresponding class of de Bruijn sequences.

The modeling of the inlet fluctuated wind velocity in large eddy simulation plays an important effect on the precision of computational fluid dynamics numerical simulation of wind loads on buildings. Along with the application of DSRFG method in turbulence wind velocity, the study on selecting the reasonable numerical values of some main parameters in this method was conducted in this paper. These key parameters mainly include: the discretized sampling number for the simulated energy spectrum of fluctuated wind speed, the number of triangular function series in modeling the energy spectrum, the spatial and time scale parameter. The effect of these parameters on the simulated power spectrum and vertical spatial correlation of fluctuated wind speed were studied by an example of inlet fluctuated wind velocity simulation for the CFD application. Simulated results showed that the more scattered numerical values in spatial scale parameter were found to fit the empirical vertical spatial correlation of fluctuated wind speed. Finally a numerical simulation of inlet fluctuated wind velocity was conducted in this study through DSRFG method with the proposed values for these four parameters, and the simulated results could represent the von Karman spectrum and its vertical spatial correlation with considerable precision.

Since fiber reinforced polymer (FRP) excels in mechanical properties and constructional convenience, the way of bonding FRP to strengthen the reinforced concrete beams has been widely used in bridge engineering. The FRP-concrete bonding interfacial fracture property is a key issue of this technology. Based on the numerical simulation of ABAQUS, the FRP-concrete interfacial fracture was analyzed, and the mechanical parameters of interfacial crack and their key influence factors were determined. Then the theoretical formulas of the strain energy release rate and stress intensity factor for the interfacial crack were given. This paper provides technical support for the technology of concrete structures strengthened with FRP.

This paper aims to study the modal analysis on Timoshenko multispan uniform beams with intermediate elastic bearing. For the equivalent system of continued beams which support reaction force as a substitution for elastic bearing, Laplace transformation is used to obtain the frequency characteristic equations under the boundary conditions of continued beams and the deformation compatibility conditions at the elastic bearing. Frequency from the frequency characteristic equations and corresponding mode of continued beams are obtained. Based on numerical example, the result of this paper and its theoretical value are verified for validity. The frequency and mode of continued beams under different boundary conditions are tackled in the end.