bluuebunny/crossref_metadata_2025 huggingface dataset:
Threat Detection in Power Grid Based on Hierarchical Feature Cloud Computing Model
Authors: Li Jing , Huang Jie , Liu Fen
Published: March 2020

The extraction of subjective features such as the authority, purpose, and opportunity of power network operators has outstanding subjectivity. It is difficult to accurately quantify subjective features due to the subjective factors of operators, resulting in fuzzy subjective features. Traditional algorithms use subjective features to detect internal threats to the power grid. Once subjective factors interfere, they will cause the defects of fuzzy main features, leading to a decrease in the accuracy of threats to the internal power grid. This paper focuses on the detection of power grid internal threats based on a hierarchical feature cloud computing model. This paper proposes a power network internal threat detection method based on the hierarchical feature cloud mapping model; calculates the hierarchical mapping relationship based on the internal threat features to complete the internal threat detection of the power grid; experiments prove that the algorithm avoids subjective factors being affected by subject characteristics, and The ambiguity of features reduces the missed detection rate to below 15.3%.
Application of Cloud Computing in Geological Exploration
Authors: Liu Pengcheng
Published: March 2020

The wide application of information technology in geological exploration will greatly improve the modernization level of geological exploration. At present, geological survey information work has entered the era of big data. How to break the limitation of independent management of geological exploration database and effectively integrate and share the accumulated massive geological exploration data has become a problem that the geological exploration information workers are eager to solve. The emergence and maturity of cloud computing technology provides a feasible solution to this problem. Firstly, from the perspective of public welfare and social service of geological exploration data, this paper summarizes and analyzes the application requirements of cloud computing in geological exploration work by studying the theoretical basis and relevant examples of cloud computing technology. Use Microsoft azure, SQL azure and other related products of Microsoft cloud computing platform azure to achieve the corresponding needs, research and clarify the relationship between geological exploration data and specific applications in geological cloud computing; use VMware vSphere virtualization platform to share existing and available hardware resources, and at the same time, research and build geoscience cloud storage mode based on virtualization technology to realize the sea Reasonable storage of quantitative geological exploration data; establishment of development environment with SDK provided by azure as the core for the development of application program of geological exploration data cloud computing; realization of data storage in the cloud for the purpose of integrating and sharing the achievement data of national mineral resource potential evaluation, and virtualization application of geoscience software.
Information Encryption Algorithm in Power Network Communication Security Model
Authors: Yang Chunyan , Ling Ying , Li Xin
Published: March 2020

With the rapid development of communication technology in power networks, data communications are facing traditional network security risks. The information encryption algorithm is a key part of power network communication security. How to ensure the acquisition of confidential data is one of the key factors for the normal operation of the power grid system. The study of encryption algorithms is of great significance to the power grid communication security. This paper mainly researches the information encryption algorithm in the power grid communication security model. The experimental simulation results in this paper show that for the key pair generation time, the SM2 algorithm can generate a 256-bit key very quickly, which is 130 times faster than the RSA algorithm in generating a 1024-bit key, and the 2048-bit key in comparison 730 times faster. Therefore, under the same security level, the encryption and decryption efficiency of the SM2 algorithm is significantly higher than that of the RSA algorithm, and with the increase of the security strength, the superiority of the SM2 algorithm is more prominent.
Research on the Quantitative Assessment and Security Measures of Hierarchical Network Security Threat Situation
Authors: Mai Rui , Wu Mingzhu
Published: March 2020

With the rapid development of modern network technology, technology not only changes people’s life, but also breeds a variety of new problems. With the popularization of network application technology, various kinds of harmful means are emerging, and network security problems emerge in endlessly, among which information network security is the most prominent. This paper mainly describes the development and response methods of information security threats, analyzes the main attack modes and the evolution of information security threats, and analyzes the development direction of vulnerability detection technology that threatens the root of information security. Aiming at the security problem of school network, through analyzing all kinds of hidden dangers of network security, the best way is the hierarchical security solution. According to the implementation of the network security deployment cycle, security strategies are proposed from the network planning, network management and the use of network individuals.
Reservoir seismic inversion method and Key problems and Countermeasures in application
Authors: Ma Yan
Published: March 2020

Although reservoir seismic inversion technology has achieved some results in reservoir prediction and description, but due to the complex seismic geological conditions and the lack of in-depth and systematic research on the application conditions of the technology, to a certain extent, it has affected the wide application of the technology. Based on the classification and description of the current inversion methods, through the theoretical model and the inversion processing practice of a large number of data, this paper studies and summarizes the applicable conditions of several inversion methods, expounds some key problems existing in the application of inversion technology, and puts forward corresponding solutions.
Study on Integrated Energy System Scheduling Optimization Based on Runoff Algorithm
Authors: Yuan Wenwei , Yuan Shuhua , Luo Jinman
Published: March 2020

With the advancement of economic globalization, set energy production, supply and use of integrated energy system has become the current social indispensable material base, its advantage is to utilize the energy such as natural gas, wind energy, solar energy is transformed into each other basic conditions, based on the use of renewable function between the electric energy development model, in order to reduce harmful emissions and effectively promote the consumption of energy storage, supply and its efficiency for the development goals, finally realizes the comprehensive optimization of energy system operation and development. However, the practice based on integrated energy scheduling can not achieve the best expected results, and there is a paradox between the theoretical basis and the fact. Therefore, based on the study of integrated energy system scheduling optimization, combined with different research status at home and abroad, this paper proposes a runoff algorithm to realize the economic operation mode of energy system, in order to solve the problems in the implementation process of integrated energy system scheduling, and promote the development trend of high efficiency and stability.
AI Implementation of Freehand Ink Dynamic Modeling and Rendering Algorithm
Authors: Chen Jing
Published: March 2020

Freehand brushwork is the quintessence of Chinese culture and a business card of Chinese culture in the international cultural market. However, domestic games seldom use freehand brushwork style to make real-time dynamic rendering of game pictures. The basic reason is that the picture structure of freehand brushwork is complex, there are many elements, and the terminal computing power and rendering cycle cannot achieve more than 30 frames of game pictures per second Dyeing effect. Through the analysis of this paper, through simplifying the model and optimizing the rendering logic, we can realize the dynamic rendering of freehand ink painting style animation.
Modeling and simulation analysis of computer network defense
Authors: Wang Juan
Published: March 2020

With the continuous development of computer network, its network drawbacks are also increasingly prominent. There are more and more computer network attacks caused by computer network hackers and viruses, which have gradually attracted the attention and attention of government departments, military agencies and national security departments. In order to effectively improve the security of computer network, various computer network attack and defense technologies are constantly updated, and the network attack and defense simulation methods are proposed for the characteristics of network attack and defense technologies Analysis and experiment provide a platform for development. In this context, the computer network modeling and simulation method is born. Applying the modeling and simulation method to the network attack and defense security of the computer can effectively avoid the damage of the computer network. At the same time, this modeling and simulation method also has certain repeatability, flexibility, and does not consume a lot of time, which can effectively ensure the network security of the computer. This paper mainly analyzes this computer modeling and simulation method, in order to promote the computer network security.
Information Integrity Evaluation of Information System Integration Based on Bayesian Algorithm
Authors: Liu Liyuan , Luo Jinman , Gao Chengfang , Zhao Shanlong
Published: March 2020

Information system integration information needs safe and effective data. Ensuring the stability and integrity of data is a crucial step to realize the information integration of information system. As for data integrity, there have been a lot of studies in the academic field. Most of the research directions are based on the macro perspective, discussing what is integrity, how to guarantee technology and other theoretical studies that need to be discussed from a holistic perspective, belonging to the qualitative research provided for information integrity of information system integration, while quantitative research is a little insufficient. This research focuses on quantitative research, the Bayesian prediction algorithm compared with other prediction algorithm, the Bayesian prediction algorithm is used to calculate the integrity transition probability of quantitative evaluation model, in order to get the parameter value, to demonstrate that the Bayesian algorithm is more suitable for forecasting the integrity of the information system integration evaluation, data is used to demonstrate the Bayesian prediction algorithm for information system integration information integrity evaluation more efficient and applicable.
Visualization technology in Computer Science
Authors: Chen Kuntian
Published: March 2020

This paper focuses on the analysis of data preprocessing and data periodic regression under the condition of complex data. It includes a linear data projection technology, a nonlinear data projection technology, a data periodic regression technology and a more intuitive data visualization display technology after data periodic regression. Through the above technology, we can make the complex data more intuitive display, and show the details of the relatively dense part of the data.
Application In Communication Equipments Antiseismic Time History Analysis Based on Advanced Mass Scaling
Authors: Du Wenman , Gao Yongqiang , Zhang Shanshan , Sun Guoliang
Published: March 2020

RADIOSS is a powerful and stable explicit non-linear finite element analysis (FEA) solver in Altair HyperWorks. In this paper, the seismic time history analysis of communication equipment based on RADIOSS solver was taken as the research object. In the numerical simulation, three methods were applied in the computational efficiency enhancement: the non-timestep control method, the traditional mass scaling technology, and the advanced mass scaling technology (AMS). Calculations prove that the AMS technology in RADIOSS can not only improve the solution efficiency, but also guarante the calculation accuracy in antiseismic time history analysis.
Design and implementation of ITS Architecture based on Big Data
Authors: Long Qiong , Duan Xian-Li
Published: March 2020

With the progress of social economy and the rapid development of transportation industry, in the face of the rapid growth of urban road traffic data, this paper puts forward the design scheme of intelligent traffic analysis system based on Hadoop. In this paper, HBase distributed database is used to store urban road static RDF data, hive data warehouse is used to store urban road traffic data, and MapReduce programming model is used to store massive and heterogeneous urban road traffic data The urban road traffic data are analyzed, and the whole scheme is verified by the prototype system.
The Application of Multimedia Network Technology in Network Technology
Authors: Li Lihui
Published: March 2020

This paper reviews the core technology system of machine translation under the condition of multimedia technology, and holds that the key links of machine translation are “sentence element” extraction, corpus selection, word selection, word order adjustment, sentence evaluation, etc., which can be realized by machine learning neural network. Corpus maintenance is not only the core work of MT, but also the key to determine the quality of Mt.
Optimization of Trajectory Design for Highly Deviated Directional Wells
Authors: Liao Xiaojia
Published: March 2020

Highly deviated directional well technology has the advantages of drilling through longer shale gas reservoir section, detecting and controlling gas bearing area in a large range, and greatly improving gas production of single well. Based on the preliminary work of vertical well and pre exploration well, through the optimization design of well bore structure, well trajectory, BHA, drill string mechanics, drilling fluid, cementing and other technologies, the drilling engineering design scheme of high angle directional well in accordance with shale gas exploration in high steep structural area is optimized, and the formation pressure profile and bit selection scheme are established to form a set of drilling technology for efficient development of shale gas The technology system can be used for reference for the exploration and development of shale gas and coalbed methane in other areas in the future.
Research on Prefabricated Structure Design Method Based on BIM Technology
Authors: Ma Cong , Wang Yu , Xu Haiqing
Published: March 2020

In recent years, with the rapid development of computer technology and continuous technological progress, it has been widely used in various industries. In the field of construction, the state advocates the development of industrialized construction and vigorously promotes prefabricated buildings. BIM (Building Information Modeling) technology is integrated into advanced computer technology. With its powerful information management and interaction capabilities, the application of prefabricated building structure design has received increasing attention. The article expounds the application and development of new prefabricated buildings and BIM technology, proposes the application of BIM technology to prefabricated building structure design methods, and analyzes the theoretical basis and main technologies that can implement the method in detail. In the end, it has prospects for its development and application in the construction industrialization.
Application of Chaos Theory in Image Encryption
Authors: Wei Yanhong
Published: March 2020

In order to protect the digital image, people have come up with many methods, digital image encryption is one of the most important means. Based on the features of chaotic mapping and the strong correlation between adjacent pixels of images, an image encryption algorithm inspired by chaos theory is proposed. In the specific operation process, chaotic mapping is used to perform chaotic encryption on the displaced image using. The image encryption algorithm is easy to operate, safe and stable, and has been confirmed by many successful examples.
Analysis of Coalbed Methane Reservoir Properties Based on Grey Correlation Prediction
Authors: Wu Jianjun , Meng Lingpeng , Li Bing , Chen Xiaoya , Lu Han
Published: March 2020

According to the grey system theory, this paper selects some logging parameters that are sensitive to the fluid properties of coalbed methane reservoirs, predicts the fluid properties of unknown coalbed methane reservoirs by using grey correlation analysis method, determines the correlation factor and correlation degree between the evaluation index of fluid properties of coalbed methane reservoirs and actual data, and quantitatively describes the categories of unknown fluid properties according to the correlation degree. By analyzing various logging data and comparing the identification result with the gas test conclusion, the accuracy rate is as high as 95%, which can accurately judge the gas-bearing property of the reservoir. This shows that the grey correlation prediction is feasible, with high accuracy and ideal effect.
RETRACTED: Accounting Information Revolution Based on Cloud Computing Technology
Authors: Xu Dong
Published: March 2020

China‘s information technology has been rapid development, cloud computing technology has been widely used in many fields. The informatization level of accounting major is one of the important factors influencing the development of enterprises. There are some problems in the traditional way of accounting work, such as low efficiency, data error and so on. Based on this, this paper puts forward the research of accounting information transformation based on cloud computing technology. This paper first analyzes the existing problems in the development of accounting informatization, and further expounds the advantages of cloud computing technology in the construction of accounting informatization, and then puts forward the transformation scheme of accounting informatization based on cloud computing technology. The results show that the scheme proposed in this paper is helpful to enhance the development strength of the company, and is widely praised by the accountants.
Computer-Aided Design is a New Manifestation of Color Composition
Authors: Zhang Dongmei
Published: March 2020

The color composition is a designer to design must pay attention to the problem, the traditional color composition mainly through the form of printing, this way due to backward technology, appear very big error, often makes the constitute of the color affect the accurate color performance, thereby affect the colour of the designer cognition and learning. With the rapid development of information technology in China, computer-aided design emerges as The Times demand, and is gradually applied to the parts related to color composition. The purpose of this paper is to make an in-depth study of the new manifestation of color composition in computer-aided design, to help designers establish a new cognition of color composition, and to promote the further development of design work. Firstly, this paper gives an overview of the computer-aided design and color composition of computer aided design. With the help of color reduction algorithm, experiments on the color composition of computer aided design are carried out. Through the analysis of the experimental results, several new manifestations of the color composition of computer aided design are obtained. The experimental results show that computer aided design (cad) gives a new expression to color composition.
Improvement on the Representation and Fusion Method of Fragmented Knowledge Structure
Authors: Jia Lili , Yang Jinhua
Published: March 2020

With the rapid development of Internet, cloud computing, Internet of things and other new technologies, information is growing exponentially, and human society has entered a new stage of fragmented knowledge. Fragmentation is flexible, random, and contains rich information, but fragmented information is fragmented, disordered, incomplete, large in size and fast in updating, so it is difficult to form effective knowledge. To resolve the problem of extracting and mining fragmented knowledge, firstly, this paper studies the fragmented knowledge map and he integration method of fragmented knowledge. secondly, we study the integration method of fragmented knowledge, from the aspects of incomplete and redundant fragmented information; Finally, we put forward several points of fragmented knowledge processing methods Key scientific issues and challenges.
Impact of Cloud Computing on Agricultural Product E-commerce
Authors: Zhang Chengwei , Rao Weiqi
Published: March 2020

With the development of technology, all parts of the world have gradually entered the 5G era. The advent of the 5G era enables “cloud computing” to complete the processing of tens of thousands of data in a short period of time, helping users to perform data mining and achieve powerful network services. In order to solve the current problems of agricultural product supply, marketing and logistics in China. This paper uses the literature survey method and data analysis to analyze the role of cloud computing technology in data mining. And apply this technology to e-commerce platforms. The application of this technology to e-commerce platforms can promote the development of agricultural e-commerce. It can be seen that under the influence of cloud computing technology, agricultural e-commerce is about to enter a new era.
Application of Cloud Teaching in Higher Vocational English Teaching—Take the MosoInk Cloud Class as an Example
Authors: Yang Guolan
Published: March 2020

Big data bring revolutionary changes to education in the Internet +education era. This paper analyzes the current teaching situation of higher vocational English teaching, and proposes Cloud teaching mode based on the MosoInk Cloud Class platform. The teaching practice shows that Cloud teaching mode can stimulate students’ interest in autonomous learning, transform passive learning into active learning, and make teaching fun, simple and efficient, improve the students’ language skills.
Application Research of English Scoring Based on TF-IDF Clustering Algorithm
Authors: Saihanqiqige
Published: March 2020

In recent years, with the promotion and application of artificial intelligence technology in all fields, English has also had a lot of attention and automatic grading areas, but not much in the text of the characterization of breakthrough, the traditional technology based on latent semantic analysis of the text said, more latent semantic analysis technology can extract thematic information, and information is ignored. The purpose of this paper is to better reflect the content of the text, evaluate the English level more accurately, and improve students’ English level better. This paper proposes a text representation method based on word vector clustering and a text representation method based on vector space model. A TF-IDF algorithm based on word vector is proposed. It is verified that the quadratic weighted Kappa value of the prediction results of the multi-model fusion algorithm based on word vector is better than the first place in Kaggle international English composition scoring competition, which verifies the effectiveness of the algorithm.
Railway Safety Vehicle Detection Method Based on Information Technology
Authors: Gao Shuang
Published: March 2020

Safety is the top priority in railway development. At present, the rapid progress of economy and science and technology makes the speed of China’s railway operation and the density of the railway network are increasing, which have a direct impact on China’s railway safety. The research on railway safety detection technology can quickly realize the detection and elimination of related safety hidden dangers and prevent the occurrence of safety accidents, which not only ensures the safety of people’s lives and property, but also is conducive to the establishment of a harmonious and safe railway environment in China and can promote further economic development. The emergence and development of information technology provides a relatively new technical means for railway safety detection, which can realize the rapid progress of detection technology. Based on the information technology and with the help of the security location algorithm, this paper briefly analyzes the problems encountered in railway safety detection, and puts forward the specific components and Suggestions of railway safety technology. On the one hand, it promotes the improvement of railway safety detection technology and ensures the safety of railway operation. On the other hand, it provides a certain theoretical basis for future research.
Key Information Recognition Algorithm for Mobile Network Video Propagation based on Discrete GMM-HMM
Authors: Xu Aixi
Published: March 2020

In view of the problem that mobile network video transmission is prone to traffic congestion, the key information identification is carried out to improve the mobility of mobile network video transmission. A key information recognition method for mobile network video transmission is proposed based on Gaussian Mixture Model (GMM-HMM). The key information after feature separation is input into the neural network classifier to detect and process the key information of mobile network video transmission, and the key information identification of mobile network video transmission is completed. The simulation results show that the proposed method has strong anti-jamming ability, high probability of accurate recognition and good convergence of GMM-HMM Model, which improves the recognition efficiency.
Under the Background of “Internet +” Applied Undergraduate Research of Tourism Management Talents Training--Take Hainan Higher Vocational and Undergraduate Joint Training 4+0 Pilot as an Example
Authors: Du Changchun
Published: March 2020

With the continuous progress of economic level, China’s tourism in recent years has made rapid development. However, with the rapid development of tourism, a series of problems have emerged, among which the most significant one is the imbalance between tourism management talents and tourism development. The current tourism management personnel simply cannot adapt to the needs of the rapid development of tourism. In particular, the rapid development of the Internet has given birth to the “Internet + tourism” model and promoted the reform of the tourism industry. The rapid change of tourism industry means that tourism industry has entered a new period of development, but it also puts forward higher requirements. Tourism management talents are related to the development quality of tourism industry. Under the background of “Internet +”, it has become an urgent problem to study the cultivation of application-oriented undergraduate tourism management professionals. Based on this, this article - to hainan vocational college and undergraduate cultivation 4 + 0 pilot project as an example, the first “Internet +” and “4 + 0” model for the relevant interpretation, on the basis of the information data algorithm and combined with the related experiment, analyzes the current status of tourism management talents cultivation, and puts forward some strategies on the cultivation of the tourism management specialized talented person.
Methods of Teachers’ Personal Privacy Security Protection Based on Big Data Analysis
Authors: Zhang Haichao
Published: March 2020

With the advent of the era of big data, these diverse, maritime and high-speed terminal data will be calculated through cloud-based storage, sharing, and mining of information, cheaply, efficiently, and quickly. The creation and driving of new industries, new products, new services, and big data are constantly emerging, which has profoundly changed people’s daily lives. The value of data in the era of big data is constantly being discovered and developed to provide a convenient and comfortable life. It brings unprecedented challenges to privacy protection. The collection of personal information is throughout life. The preservation of information is vulnerable to online attacks and leads to large-scale disclosure of personal information. During the operation of big data, problems such as illegal collection of privacy information, excessive analysis and illegal transactions occurred, which constantly threatened the stability of personal life and the security of personal property. The purpose of this article is to study teachers’ privacy protection methods based on big data analysis. This paper uses the fusion technology of ORAM and group signatures to study the privacy protection of teachers. It aims to better protect the privacy of teachers in a big data environment. It also provides reference suggestions for other researchers and contributes to the protection of teachers’ privacy.
Group composition analysis of the Shubarkol deposit coal-tar resin fraction
Authors: Smagulova N T , Kairbekov Zh K , Maloletnev A C , Kairbekov A Zh , Zhanabaev D , Kanatkyzy A
Published: March 2020

Coke-chemical resin is used for the production of sulfur-free naphthalene, benzene, and tetralin. In this study, physico-chemical characteristics of the coke-chemical resin and the tar fraction were examined using gas chromatography and mass spectrometry. Three fractions of initial resin were analyzed with boiling point up to 180, 180-230, and 230-280°C. The results showed that the chemical composition of distillate fractions of resin consists of alkyl derivatives and aromatic hydrocarbons with the number of aromatic rings of 1-4.
Compressive behavior of rice straw-reinforced concrete for rigid pavements
Authors: Ahmed T , Farooqi M U , Ali M
Published: March 2020

Micro-shrinkage cracking in concrete is normally observed at early stages. The cracking increases with the passage of time and affects the serviceability. The micro-shrinkage cracking can be avoided if its initiation is controlled by use of fibers. The utilization of natural fibers gains popularity in developing countries, including Pakistan, where vast resources of natural fibers are available as by-products with a low economic use. This paper primarily focuses on the utilization of locally available rice straw in concrete for rigid pavement application. The compressive behavior of rice straw-reinforced concrete (RSRC) is explored as per ASTM standard. The mix proportion of 1:2:4:0.6 (cement, sand, aggregate, and water, respectively by their weight) is considered for plain cement concrete (PCC) which is taken as reference. For RSRC, the length and content of rice straw are 25 mm and 1% (by wet volume weight), respectively. In addition to compressive strength, elastic modulus, absorbed energy, and toughness index of PCC and RSRC are experimentally determined and compared. The modulus of rupture is determined through empirical relation. Rigid pavements for PCC and RSRC are designed and compared using these parameters. The proposed rigid pavement design is discussed in detail.
Analyzing the contact resistance for the penetration brazing of Cu/Ni metal wires
Authors: Gao Y Z , Liu X F , Feng Z G , Tian P F
Published: March 2020

The electrical contact resistance behavior of the interface between the copper electrode and the graphite welding pool plays an important role in penetration brazing of Cu/Ni metal wires. Based on the fractal contact resistance model, the contact resistance between the copper electrode and the graphite welding pool is established by taking the oxide ablation of the graphite surface into account. The influences of the graphite ablation on the contact resistance for different pressure and different graphite materials are experimentally investigated. The ablation phenomenon on the surface of the graphite welding pool is observed during the welding process. It is found that the contact resistance slowly increases as the ablation degree of the graphite welding pool surface increases. The present work shows that the impact of the common graphite ablation on the interface contact resistance is more obvious than that of fine graphite.
The application of a Morlet wavelets bandpass filter in the fault diagnosis of rolling bearings
Authors: Wei R , Ming T F , Xu W , Zhao H
Published: March 2020

An improved demodulation approach is proposed for the construction of a bandpass filter and determination of its parameters. An envelope analysis of the relationship among the central frequency, bandwidth and the system’s damping coefficient was conducted and it was demonstrated that to extract the fault features effectively, the quality factor of the bandpass filter should remain constant and the bandwidth should be determined according to the damping coefficient of the system, the central frequency of the filter, and the fault frequency of the bearing. A combined wavelet bandpass filtering function was constructed based on the Morlet wavelet function. The capture of fault signals from the rolling bearing was optimized in virtue of excellent bandpass filtering properties of the combined wavelet’s better response and the strong sensitivity of the correlated kurtosis to periodic pulse signals. The experimental test data and the simulation results demonstrated that the proposed approach is an effective method for fault diagnosis of rolling bearings.
Investigation on the microstructural evolution and mechanical properties of semi-solid Al-5Zn-3Mg-2Cu alloy based on recrystallization and partial remelting
Authors: Tao J Q , Zhao G Z , Huang Z W , Li M , Xing Z H
Published: March 2020

The present research envisages the investigation of the optimized semi-solid process parameters of the Al-5Zn-3Mg-2Cu alloy. The effects of remelting temperature and holding time on the microstructure and mechanical properties of modified Al-5Zn-3Mg-2Cu alloy were studied by the recrystallization and partial remelting (RAP) process. The results reveal that with an increase in the semi-solid holding temperature, there was an increase in the average grain size of the Al-5Zn-3Mg-2Cu alloy, but when the temperature was increased to 635°C, the grain roundness decreased owing to the grain coalescence and growth. After holding at 635°C for 32 min, the grains were partially transformed into dendrites. Further, with the prolongation of the holding time, the grain size of alloy gradually grew and the roundness increased, and after holding 32 min at 625°C, the grain roundness began to decrease. The optimum semi-solid process parameters were: 615°C × 32 min and 625°C × 16 min. The Al-5Zn-3Mg-2Cu alloy parts were prepared by thixoforming process. Under the conditions of 615°C × 32 min and 625°C × 16 min, the parts were formed completely and the surface of the parts was smooth and clean. Under the condition of holding 32 min at 615°C, the tensile strength and elongation at the break of the parts correspondingly reached 576 MPa and 9.5% respectively, while they reached 589 MPa and 11%, respectively under the condition of holding 16 min at 625°C.
Experimental research on high-speed dry milling performance of large-area nodular cast iron
Authors: Yan P , Wang Y B , Chen K J , Ma B X , Xiao Y L , Wang X B
Published: March 2020

Nodular cast iron was with excellent casting performance, abrasion resistance, strength, and toughness, and successfully applied in large components with high requirements of complex load, strength, etc. While high-efficiency precision machining of large-size plane nodular cast iron was difficult in actual production. In this study, the influence of cutting parameters on cutting performance in the precision milling of large size nodular cast iron was systematically investigated. The spindle peak-power ratio increased linearly as the increase of cutting speed and cutting depth, while it was the lowest at a feed rate of 0.10 mm on account of the minimum cutting depth effect. The surface roughness Ra was decreased linearly as the increase of cutting speed, while the change trend of Ra was not significant as feed rate and cutting depth. As the cutting speed increased, the flaky chips shortened and the helical chip crimped intensity; as the increase of feed rate or longitudinal cutting depth, the length of the foil or ribbon chips increased and the crimp of the helical chip increased. The results could be the guide of the actual machining process of nodular cast iron engine box and cover to improve the machining efficiency and surface quality.
Intermetallic formation and characterization of Sn-Cu-Mn-Ag lead-free soldering alloys
Authors: Padmanaban D A , Sunderraj D A J , Geethan K A V
Published: March 2020

Two lead-free soldering alloys, namely 87Sn-7Cu-3Mn3Ag and 87.5Sn-7.5 Cu-2.5 Mn-2.5 Ag, were prepared and the effect of Mn addition to Sn-Cu-Ag alloys was studied. The alloy was characterized using XRD, DSC, and metallurgical microscopy. Hardness of the former alloy exceeded that of the latter, due to higher intermetallic formation, according to XRD studies. The DSC curves for both alloys have melting points of 219.4 and 219.7°C, with a range of melting close to 10 °C. The microstructure of both alloys contains Cu6Sn5, Ag3Sn, and MnSn2 present in dendritic Sn-rich solid solution.
A study of the fracture behavior of ballistic gelatin based on wire-cutting tests
Authors: Liu L , Fan Y R , Lu Q Q
Published: March 2020

The present study explores fracture properties of ballistic gelatin at different loading rates. Wire-cutting fracture tests were undertaken, and a new analysis method was proposed, in order to delineate the fracture force from the total cutting force. The new method was proved to be effective in obtaining the fracture toughness of ballistic gelatin at different cutting rates. It was found that the fracture toughness of 10% ballistic gelatin at 4°C increases almost linearly from 3.1 N/m at a cracking velocity of 10 mm/min to 19.4 N/m at 200 mm/min.
Metallurgical modeling of intergranular HAZ liquation cracking during laser welding newly developed crystallography-dependent aerospace materials. Part I: Spontaneous microcrack repair of microstructure development
Authors: Gao Z G
Published: March 2020

Metallurgical modeling of microcrack self-repair during laser welding of nickel-based superalloys has been properly established. Metallurgical mechanism of crystallographic control self-repair intergranular liquation cracking of heat-affected zone (HAZ) through spontaneous feed of interdendrite liquid beneath the surface is proposed. Self-repair of arterial crack network with dendrite substructure of backfill enables crack resistance amelioration and is dependent on alloying element and heat input. Microstructure development and solidification behavior are controlled to minimize the severe liquation cracking near the fusion boundary by optimization of laser welding conditions through numerical analysis. Liquid healing of incipient cracking in the HAZ through available feeding fluid flow due to accessible to weld pool are sensitive to grain size and weld pool geometry to metallurgically suppress liquation crack, stabilize the primary solidification path and improve the weld integrity, simultaneously. It is revealed that optimum low heat input is favored to reduce liquation cracking. Theoretical predictions are in satisfactory agreement with microanalysis of measurement result indirectly. In addition, this metallurgical modeling is also applicable to other nickel-based superalloys with similar metallurgical properties.
Characteristics of Ni/Au/Ni/Au ohmic contact in a p-AlGaN/GaN semiconductor
Authors: Hu Z F , Li X Y , Zhang Y
Published: March 2020

The low-resistance NiAu/Ni/Au ohmic contact in p-type AlGaN/GaN semiconductor was carefully investigated by electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) after two-step annealing at 550 and 750°C. It is shown that complicate double-direction diffusion and reaction occurred in the metal layer and underlying GaN layer. The four metal stacks of Ni/Au/Ni/Au turned into almost one layer and an intimate relationship established at NiAu/GaN boundary, which should play a primary role in ohmic contact to reduce the contact barrier. At the intimate interface, the metal layer close to the contact was enriched with Ga and Au, and the GaN upper layer was metalized by Au and Ni. Numerous Ni atoms were oxidized and formed dispersive NiO nanoclusters in the metal layer, which might have a hindering effect on upward migration of Ga atoms. Dislocations connected with the contact boundary absorbed interstitial atoms of Au or Ni may serve as channels for current carrier transportation. Thus, a low-resistance p-GaN ohmic contact can be obtained by the above combination of these microstructural characteristics.
Steric hindrance effects of phenoxyimine nickel catalysts in ethylene/propylene polymerization
Authors: Xu D , Dai L , Li F Y , Zhu J X , Chai J K , Zhang Y W
Published: March 2020

A new mononuclear phenoxyimine nickel (II) catalyst with a xanthene skeleton was synthesized and applied to polymerization of ethylene/propylene. Higher activities were achieved in comparison with the catalyst lacking the axial steric hindrance and the catalyst with a synergistic effect. Moreover, the synthetic method was easier than that for the bimetallic catalyst.
Effect of prestrain on storage life for HTPB coating in solid rocket motor
Authors: Du Y Q , Zheng J , Yang Y , Yang T C , Tu X
Published: March 2020

The prestrain thermal accelerated aging tests of HTPB coating at 0%, 3%, 6% and 9% levels were carried out. The variation of maximum elongation of HTPB coating at different aging stages was analyzed. The maximum elongation was selected as the performance characterization parameter, and the aging model of HTPB coating was established. According to the time-temperature equivalence principle, the time conversion relationship between prestrain thermal accelerated aging and effective storage at room temperature was obtained, and the storage life of HTPB coating at room temperature was predicted using this model. The results show that the predicted storage life of HTPB coating at room temperature is 18.64a, 18.08a, 9.24a and 7.44a, respectively, under the aging conditions with prestrains of 0, 3, 6, and 9%. The existence of prestrain will have a significant impact on the storage life of HTPB coating, which should be avoided in actual storage.
Synthesis and testing of defected g-C3N4 with improved photocatalytic activity
Authors: Zheng Y , Li C H , Cai Y Y
Published: March 2020

Graphitic carbon nitride samples with defected structure but larger surface areas were synthesized by adding urea as additive to the thermal decomposition (pyrolysis) of melamine. The pyrolysis was carried out at 600°C in ope-air conditions for 2 hours. The as-prepared samples were compared through detailed characterizations such as SEM, BET, XRD, XPS, FTIR and DRS. It was found out that the addition of urea functioned against the perfection of polymerization, and led to defected structure, which were suggested to be g-C3N4 segments in small crystalline domains. As a result, the formation of the defected structure led to blue-shifts in the optical transitions in the UV-Vis spectral range, as well as larger surface areas. In addition, the photocatalytic activities of the samples were measured by degrading Rhodamine B (RhB) with a concentration of 10 mg/L. It was found out that the samples with defected structure exhibited improved photocatalytic activity.
Cyclic deformation behavior of gradient structured austenitic stainless steels
Authors: Zhou W L , Liu K K , Li Y , Ho H S
Published: March 2020

The cyclic deformation behavior of gradient structured 316L austenitic stainless steels produced by shot-peening is investigated. The experimental results show that for all specimens, the cyclic response exhibits a similar fundamental evolutionary character, i.e., first cyclic hardening then followed by cyclic softening. The presence of a gradient structured surface layer is observed to be capable of accelerating the cyclic hardening process but decelerating the cyclic softening process. It is further suggested that the former can be related to the restricted cyclic hardening ability and the latter to the high plastic deformation uniformity.
The Taguchi orthogonal analysis of Ti6Al4V titanium alloy chip morphology in micro-milling
Authors: Zhang X , Pan X D , Wang G L
Published: March 2020

Micro-milling is an efficient machining method, which is suitable for machining miniaturized titanium alloy parts. In this paper, chip morphology in micro-milling of Ti6Al4V titanium alloy was studied experimentally. An orthogonal experiment was established, in which cutting speed, feed per tooth, and axial depth of cut were chosen as the main influencing factors. The effect of milling parameters on chip morphology was analysed via the Taguchi method. The results strongly indicate that the degree of serration of the chip sharply increases with cutting speed, and then is saturated. The calculations of cooling and formation times of adiabatic shear bands under steady-state cutting conditions implied that the dynamic recrystallization occurred in these bands during the Ti6Al4V titanium alloy in micro-milling.
Study on pervious recycled aggregate fiber-reinforced concrete for airfield pavement
Authors: Novak J , Kohoutkova A , Chylik R , Trtik T
Published: March 2020

For the last several years, the attention has been devoted to the development of eco-friendly construction materials with the aim to reduce the environmental impact of construction. The integral part of this development is to find applications for which the recycled materials could be used efficiently. The presented study deals with the development of recycled aggregate fibre reinforced concrete which is going to be used for an innovative precast concrete pavement system. The system is being developed recently at Czech Technical University in Prague with the aim to provide a system for airfield pavement with rapid construction and recycled material utilization. The investigated material is going to be used for construction of a sub-base course which is underneath a surface course of precast concrete elements. Within the scope of the work, standard laboratory tests were conducted with the aim to observe mechanical properties of recycled aggregate fibre reinforced concrete. The obtained findings showed that the material exhibits ductile behaviour likely due to very long polypropylene fibres used for strengthening concrete matrix. On the contrary, the tested material has low modulus of elasticity in comparison with conventional concrete. Subsequently, the pilot construction of the sub-base course was carried out in order to examine both concrete mixture preparation and concrete course installation in practice. The obtained findings showed that a compaction ratio of the material is about 20%. Moreover, a flat surface of the sub-base course was hard to achieve considering the used manufacturing technology.