bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a WSN System for Condition Monitoring of the Mechanical Equipment with Energy Harvesting
Authors: Zheng Kai , Zhang Yun , Chen Bo , Dong Yangfang , Wang Yang , Li Tianliang
Published: April 2015

Abstract—A design of wireless sensor networks for mechanical condition monitoring system (WSN-MCM) is presented in this paper. The main purpose of this work is to develop a WSN system for mechanical condition monitoring as the existing mature wireless sensor network nodes are not suitable for the long-time monitoring of mechanical equipment due to their short working life and low acquisition accuracy. In order to realize the function of long-term working of the sensor node, we designed an energy harvesting board of the node to harvest the energy and transferred energy with high efficiency . Meanwhile, the node has the function of high-accuracy acquisition of analog signals and can access of various low-frequency and high-frequency sensors. The experiment and stimulated results demonstrate that the wireless sensor network system designed is suitable for mechanical condition monitoring.
Automatic Assessment of Progress Using Remote Laboratories
Authors: Romero Susana , Guenaga Mariluz , García-Zubia Javier , Orduña Pablo
Published: April 2015

In this paper we present an automatic assessment model for the development of competencies in a physics course using VISIR remote experiment, based on a rubric, and using learning analytics techniques to process data automatically collected from students’ activity using Weblab-Deusto platform.
Using Node-HTTP-Proxy for Remote Experiment Data Transmission Traversing Firewall
Authors: Wang Ning , Chen Xuemin , Song Gangbing , Parsaei Hamid
Published: April 2015

In this paper, a novel real time experimental data transmission solution based on a new web server software architecture that allows the traversing of network firewalls is proposed. With this new software architecture, the public network port 80 can be shared between Node.js and the Apache web server software system. With this new solution, the Apache web server application still listens to the public network port 80, but any client requests for the Node.js web server application through the port will be forwarded to a special network port which Node.js web server application is listening to. Accordingly, a new solution in which both Apache and Node.js web server applications work together via HTTP proxy developed by the Node-HTTP-Proxy software package is implemented on the server-side. With this new real time experiment control and data transmission solution, the end user can control remote experiments and view experimental data on the web browser without firewall issues and without the need of third party plug-ins. It also provides a new approach for the remote experiment control and real time data transmission based on pure HTTP protocol. The solution will significantly benefit the development of remote laboratory technology.
De-noise of Online Monitoring Basic Data Collected by Surveying Robots
Authors: Li Wei , Xiong Hongqi , Sun Houguang , Mao Yachun , Zhang Hankang
Published: April 2015

Abstract —Three-dimensional online monitoring systems based on a surveying robot (TCA2003) are widely used in the slope monitoring of various open pits. A lot of noise is contained in basic monitoring data (azimuth, vertical angle, distance) because of various factors. Thus, the accuracy of basic monitoring data is greatly reduced, and this issue has become a limitation in landslide warning. In this paper, multi-cycle monitoring data from multiple open pits are used as data source and de-noised using different filtering methods. At the same time, filtering effect is evaluated using the image and accuracy of filtered basic data. Best filtering methods of different monitoring basic data are proposed, laying the foundation for automated processing of monitoring data based on a surveying robot.
La lisière des espaces ouverts : support de densification qualitative des métropoles
Authors: Vanbutsele Séréna , Decleve Bernard
Published: April 2015

Les bords des espaces ouverts ont été reconnus dans plusieurs territoires comme des espaces stratégiques. Ils se trouvent à l’intersection entre les problématiques de développements urbains, de gestion de l’augmentation démographique et les impératifs de valorisation et de protection des espaces de nature. Le concept de lisière urbaine traite les bords en tant qu’éléments complexes, d’épaisseurs variables et porteurs de projets. Si ces espaces sont associés à l’idée d’articulation entre la ville et la nature, ils sont aussi conjointement présentés comme des supports de densification. Or, la mise en avant des bords soulève plusieurs questions. Premièrement, sur la transformation des espaces ouverts induite par une nouvelle pression urbaine. Deuxièmement, sur la requalification de zones jusque-là sous valorisées. Et troisièmement, sur le lieu même d’implantation de la lisière. L’impératif est de traiter avec attention égale tant les éléments bâtis que non bâtis pour qu’ils forment une lisière urbaine, celle-ci marquant d’une part la limite à l’urbanisation et articulant et favorisant, d’autre part, les échanges entre ville et nature. L’implantation de la lisière s’opérerait tant par l’aménagement d’espaces ouverts en bordure de sites naturels ou agricoles (pomerio) que par une densité perméable à trouver dans la partie bâtie de la lisière (ante parc).
AUTOMATIC NIPPLE DETECTION IN MAMMOGRAMS USING LOCAL MAXIMUM FEATURES ALONG BREAST CONTOUR
Authors: Jen Chun-Chu , Yu Shyr-Shen
Published: April 2015

Mammogram registration is an important preprocessing technique, which helps in finding asymmetrical regions in left and right breast. However, correct nipple position is the crucial key point of mammogram registration since it is the only consistent and stable landmark upon a mammogram. To locate the nipple coordinates accurately in mammogram images, this work improves previous algorithms such as maximum height of the breast border (MHBB) and proposes a novel method consisting of local spatial-maximum mean intensity (LSMMI), local maximum zero-crossing (LMZC) based on the second-order derivative, and a combined approach dependent on LSMMI and LMZC. The proposed method is tested on 413 mammogram images from MIAS and DDSM databases. Consequently, the mean Euclidean distance (MED) between the ground truth identified by the radiologist and the detected nipple position is 0.64 cm, within 1 cm of the gold standard, for estimating the proposed method. The experimental results hence indicate that our proposed method can detect the nipple positions more accurately than other previous methods. Furthermore, the proposed select visible-nipple mammograms (SVNM) algorithm with the ability of generalization has achieved a 99% selection rate for automatic clustering of nipples in a mammography database, besides automatically detecting the breast border and nipple positions in mammograms.
Optimal Kernel and Wavelet Coefficients to Support Vector Regression Model and Wavelet Neural Network for Time Series Rainfall Prediction
Authors: Rani B. Kavitha , Govardhan A.
Published: April 2015

Rainfall prediction is an active topic recently since people want to make decisions about crop and irrigation cycles to understand weather and climate patterns. Due to need of predicting this natural phenomenon, various research works has been carried out previously with different type of techniques using historical data. In this paper, a hybrid model based on support vector regression (SVR) model and wavelet neural network (WNN) for rainfall prediction is proposed. In hybridized SVR-WNN, optimal kernel and wavelet coefficients are generated using hybrid algorithm. Here, artificial bee colony (ABC) and genetic algorithm (GA) are hybridized and used to this purpose. These optimal kernel functions and wavelet coefficients are supplied to hybrid model to predict the rainfall. In hybrid model, wavelet neural network with ARX modeling and support vector regression (SVR) model is effectively hybridized to time series rainfall prediction. The performance of the hybrid model is analyzed with the help of real datasets taken from Assam, Chhattisgarh, East Rajasthan, Gangetic West Bengal, Gujarath, Haryana, Telangana, Rajalaseema regions. From the results, it can be concluded that proposed rainfall prediction model have shown the MAPE performance of 20, the RMSE performance of 2, MAD performance of 12, but existing model show the MAPE performance of 61, the RMSE performance of 3, MAD performance of 27 for Telangana dataset.
A Novel DE-PSO-DE (DPD) Algorithm for Economic Load Dispatch Problem
Authors: Das Kedar Nath , Parouha Raghav Prasad
Published: April 2015

This paper presents a hybrid algorithm of two popular heuristics namely Differential Evolution (DE) and Particle Swarm Optimization (PSO) on a tri-population environment. Initially, the whole population (in increasing order of fitness) is divided into three groups – Inferior Group, Mid Group and Superior Group. DE is employed in the inferior and superior groups, whereas PSO is used in the mid-group. It is based on the information sharing mechanism of their inherent property to overcome the shortcomings of each other. The proposed method is called DPD as it uses DE-PSO-DE on a population. Two strategies namely Elitism (to retain the best obtained values so far) and Non-redundant search (to improve the solution quality) have been employed in DPD cycle. Out of a total of 64 DPDs, Top 4 DPDs are investigated through CEC2006 constrained benchmark functions. Based on the ‘performance' analysis, best DPD is reported and further used in solving 5 engineering design problems along with economic load dispatch problem in order to confirm further the efficiency of the proposed DPD.
A Dynamic Modeling and Validation Framework for the Market Direction Prediction
Authors: Ye Xugang , Li Jingjing
Published: April 2015

There are many research papers talking about building various machine learning models to predict the market index. However, very few attention has been paid to effectively validating or calibrating the prediction results. The focus of this paper is to present a dynamic modeling and validation framework for the market direction prediction. The central idea is to calibrate the probabilistic prediction by estimating two conditional probabilities of correct forecast from the dynamic validation data set. The calibration method can be combined with any predictive model that generates probabilistic prediction of the market direction.
Should Investors Trust Equity Analysts?
Authors: Guo Xiaomin
Published: April 2015

This paper studies the holistic issue of the combination of analyst projection accuracy, diversity, and distribution. It first tracks the earnings per share and sales projections of a number of equity analysts for 17 representative U.S. companies using data from 1978 to 2012. It also compares the analysts' consensus of earnings per share, sales, rating, and price target zone to identify the degree of concentration among the opinions. It finds that the magnitudes and coefficient variations of projection errors are small, and the analysts' opinions are insignificantly diversified. Analysts' projections are not significantly skewed, but pessimistic opinions dominate. The results suggest that the projections issued by equity analysts are generally precise, and following their opinions is technically feasible. Analysts' mistakes are more due to inappropriate investment timing and less due to their abilities to pick firms with robust future performance.
A Waste Management Robot System
Authors: Matsuo Keita , Liu Yi , Elmazi Donald , Barolli Leonard
Published: April 2015

Recently, there are many problems caused by global environment warming. The limited natural resources require efficient methods and systems for recycling and processing of the wastes for a better environment. One of the problems today is the processing of the kitchen garbage, because when they become in large amounts in small areas, the natural capacity of the environment cannot assimilate them. Therefore, construction of the recycling systems is needed to save the resources and minimize the wastes. For this reason, in this paper, the authors have proposed and implemented a waste management robot system, which can change the kitchen garbage to compost. Then, the compost can be mixed with the ground and used for growing of vegetables and other plants. The proposed system uses the information network, sensor technology and robot technology. The authors present in this paper, the implementation of the proposed system and evaluate its performance by experimental results.
Students' Satisfaction from E-Learning System
Authors: Jabeen Sadia , Din Aisha Muhammad , Sadiq Muhammad Farhan
Published: April 2015

The present study was conducted to explore the students' satisfaction level from Virtual University of Pakistan e-learning system. This paper aimed at bringing the underlying factors which determine and affect students' satisfaction from e-learning. The method adopted for the present study was survey. In order to measure students' satisfaction a questionnaire with 25 items was deployed. The sample of current study comprised 240 students from different study programs. Descriptive statistics, regression analysis and one sample t-test were applied to measure students' satisfaction from the system. Results showed that students prefer this system due to its teaching standards. Regression analysis explained interactivity pattern as an important indicator of overall satisfaction from the system. One sample t-test revealed that students were highly satisfied from e-learning system. The results concluded that unconventional mode of learning is as powerful tool of education as conventional. Findings of the study lead to the practical implications and identify the need of face to face communication and betterment in interactivity patterns between instructors and students to enhance students' satisfaction from the system.
A Roadmap to Implement Rapid Transition as a Proposal of e-Learning Model
Authors: Balaban M. Erdal , Kartal Elif
Published: April 2015

Digital age (information/computer age) offers many opportunities. Many transforms and changes have been made in public and private sectors. It is clear to say that education is one of the most important areas that has been trying to use IT tools. Today, e-learning is an important way of removing time and place constraints between students and instructors. In addition, it is the best way to make education sustainable in every organization. Many organizations can face problems during their e-learning experience. Having enough knowledge about e-learning is not a must for every organization in every sector. Therefore, in this study, the authors aim to provide a rapid transition for organizations that wants to set up an e-learning system. This paper gives some hints related to transition process. Therefore, theoretical framework of an e-learning system, selection of learning management system (LMS) and content management system (CMS), designing of a virtual classroom, online course implementation, controlling the project are explained, future works related to the framework are discussed.
Intelligent Decision Making and Risk Analysis of B2c E-Commerce Customer Satisfaction
Authors: Mohammadian Masoud
Published: April 2015

Customer satisfaction and relationship is complex, demanding, and yet crucial to an organization success and its competitive position in the marketplace. Due to rapid changes in emerging technologies there is a need for constant improvement and adjustment of product and services offered using e-commerce systems. Customer satisfaction is dependent on a large number of organizational as well as product and services attributes. These attributes require continuous development, improvement and monitoring. The interdependencies of these attributes make it very difficult for managers and product and services development teams to comprehend and be aware of effect (, Rohm et al 2004, , ) of inefficiencies that may exist in development and offering of their products and services. This paper considers the implementation of an intelligent decision making system using Fuzzy Cognitive Maps (FCMs) to provide facilities to capture and represent complex relationships in a customer satisfaction management and modelling to improve the understanding of managers and product developers about their customers and associated risks related to products and services that are offered online using e-commerce sites. By using FCMs, customer satisfactions can regularly be reviewed and improved. Managers can perform what-if analyses to better understand vulnerabilities and pitfalls in the way their product and services are provided to customers.
Selecting Significant Process Parameters of ECG Process Using Fuzzy-MCDM Technique
Authors: Bose Goutam Kumar
Published: April 2015

The present paper highlights selection of significant machining parameters during Electrochemical grinding while machining alumina-aluminum interpenetrating phase composites by MCDM techniques. The conflicting responses like higher material removal rate, lower surface roughness, lower overcut and lower cutting force are ensured simultaneously by a single parametric combination. Control parameters like electrolyte concentration, voltage, depth of cut and electrolyte flow rate have been considered for experimentation. VIKOR is one of the multiple criteria decision making (MCDM) models to determine the reference ranking from a set of alternatives in the presence of conflicting criteria. Finally Grey Relational Analysis is performed to optimize multiple performances in which different levels combinations of the factors are ranked based on grey relational grade. Surface roughness is given more importance than other responses, using Fuzzy Set Theory considering basic objective of the process. It is observed that substantial improvement in machining performance takes place following this technique. The study highlights the effects of different process variables on multiple performances for complex process like ECG.
Shale Gas and Import Dependency
Authors: Moorlag Ruben , Pruyt Erik , Auping Willem L , Kwakkel Jan H.
Published: April 2015

Today, many governments are considering the exploration and production of unconventional resources, shale gas in particular, for reasons of security of supply and reduction of import dependency. Large-scale development of these resources promises to significantly lower import dependency of gas supply of many countries. Whether the promise will be met remains uncertain though, not only because of uncertain resources, technological challenges, and environmental concerns, but also because of the interdependence, complexity and uncertainty of gas markets. Modelling and simulation may therefore be required to assess the resulting economic implications of global shale gas development. In this study, System Dynamics and Agent-Based models are simultaneously deployed under deep uncertainty to discover and explore plausible scenarios for the development of shale gas and the effects on regional gas markets and regional import dependency. Among else, it is shown that regional economic growth is likely to have a larger impact on gas import dependency than the actual size of shale gas resources.
Efficacy of the Technology Satisfaction Model (TSM)
Authors: Islam A.Y.M. Atiquil , Leng Chin Hai , Singh Diljit
Published: April 2015

With the rapid uptake of the Internet and e-learning systems worldwide, online research databases have become necessary, even indispensable, tools for research and learning. The International Islamic University Malaysia (IIUM) recognizes the huge potential of databases in improving educational outcomes, and in promoting research among its students and academic staff. In line with its aim to become a research university and centre for educational excellence, the IIUM introduced its online database system in 2000 as part of its e-library services. However, despite a decade of existence, the database was found to be underutilized, especially by postgraduate students. As such, the prime objective of this study is to validate the Technology Satisfaction Model (TSM) to assess its efficacy on students' satisfaction in using online research databases in higher education. A total of 180 postgraduate students from four faculties (Education, Human Sciences, Engineering and Economics) were selected using stratified random sampling procedure. The questionnaires' reliability and validity were performed through a Rasch model using Winsteps version 3.49. The data were analyzed applying the Structural Equation Modeling to test the hypotheses of TSM. The results of this study revealed that computer self-efficacy had a statistically significant direct influence on perceived ease of use and perceived usefulness. Subsequently, students' perceived ease of use and perceived usefulness had statistically significant positive direct influence on their satisfaction in using online research databases. On the other hand, computer self-efficacy had a significant indirect influence on satisfaction mediated by perceived ease of use. Finally, computer self-efficacy also demonstrated a statistically significant indirect influence on satisfaction mediated by perceived usefulness of databases. The findings contributed that the TSM is viable to examine the successful integration of online research databases among postgraduate students in higher education.
The Impact of Information Visualisation on the Quality of Information in Business Decision-Making
Authors: Zabukovec Alenka , Jaklič Jurij
Published: April 2015

The visualisation of information for business decision-making is a relatively understudied area despite the promising benefits. Previous research confirms the value of information visualisation. Still, the mechanisms of the impacts on the quality of information are poorly understood. Therefore, the authors examine the impact of the quality and quantity of information visualisation on the quality of the content and access to information among different types of users and for various types of use. The results show the varying importance of the quality and quantity of visualisation for the quality of information and that there are statistically significant differences between groups of decision-makers and decision-making in various situations. Information visualisation adjustments for different user perceptual types and for various business decision-making situations can increase the quality of information and potentially lead to the faster and more accurate receipt and processing of business information.
Influence of Hot Extrusion on Microstructure and Hardness of SiC Particle Reinforced Al-Zn-Mg-Cu Alloy Matrix Composite
Authors: Wang Xiao Hong , Guo Jun , Luo Liang , Ye Min , Lin Yuan Hua , Peng Jian , Han Xiong
Published: April 2015

In this paper, the microstructure and mechanical property of the Al-Zn-Mg-Cu aluminum matrix composite reinforced by SiC particles with the contents of 2.5, 4.5, and 6.5wt% through vacuum casting are studied. The homogenization treatment was conducted at 465°C heat insulation for 24h. The purpose of this study is to analyze hot extrusion influence on the microstructure and hardness of the Al-Zn-Mg-Cu aluminum matrix composite. SiCp under pre-processing possesses good wetability with the analysis of Laser Particle Sizer and XRD. Metallurgical microscope, XRD, SEM and EDS is applied to analyze the microstructure of the Al-Zn-Mg-Cu aluminum matrix composite. It has proved that the hot extrusion can effectively improve the homogenization of SiCp and dissolve the second rough phases to reinforce the dispersal of CuAl2 and MgZn2 phase. The hardness of Al/SiCp composite rises as the increase of the SiCp content. It is shown that when the SiCp content is above 5%, its hardness obviously reinforced as well as that of the Al/SiCp composite.
Effect of Curing Methods on the Mechanical Property of SiC Fiber Prepared via Hydrogenation
Authors: Wang Yi Fei , Xing Zhong Fang , Liu Cheng Ming
Published: April 2015

Two different polycarbosilane (PCS) fibers were prepared by a new oxygen-free curing method and Chemical Vapor Curing (CVC), respectively. Nearly stoichiometric SiC fiber was prepared via hydrogenation in H2-N2 mixture and subsequent sintering in inert gases. The green PCS fiber and nearly stoichiometric SiC fiber were characterized by FT-IR, XRD, SEM etc. Meanwhile, the effect of hydrogenation on the thermal stability of SiC fibres cured by CVC method was studied. It was found that the oxygen-free curing method can effectively decrease the content of oxygen in the final SiC fiber, while the hydrogenation treatment can dramatically diminish the content of free carbon, so the nearly stoichiometric SiC fiber with C/Si atomic ratio being 1.06 can be obtained. After the heat-treated at 1600°C in inert gases, the strength retaining ratio of the oxygen-free cured SiC achieved 68%, demonstrating that the nearly stoichiometric SiC fiber possesses excellent high-temperature stability and higher anti-oxidation property.
Effect of the Ball Milling on the Microstructure and Mechanical Properties of AlN/Cu Composite
Authors: Yu Qian , Song Mei Hui , Li Yan , Zhang Xiao Chen
Published: April 2015

AlN/Cu composite powder was prepared by ball milling method. Laser particle size analyzer, X-ray diffraction and scanning electron microscopy analysis were performed to study AlN/Cu composite powders. The effects of rotation speed, mixing time, and ball to powder weight ratio (BPR) on the particle size distribution, composition, and morphology were investigated. Results showed that the best ball milling parameters were the rotation speed of 200r/min, mixing time of 6 hours and BPR 10:1. In this best condition, AlN/Cu composite powders would be obtained with optimum particle size distribution and morphology. Then composite powders were pressed at 500MPa and sintered at 1000°C in N2 atmosphere. Finally, the composite with an AlN content of 33wt% showed the bending strength of 370MPa, Vikers hardness HV154, thermal conductivity of 182.7W/m°C and electrical conductivity of 3.08MS/m. However, the composite with an AlN content of 25wt% showed the bending strength of 329MPa, Vikers hardness HV122, thermal conductivity of 195W/m°C and electrical conductivity of 6.54MS/m.
Flexural Properties of T700 2D Cf/SiC Composites via Precursor Infiltration and Pyrolysis
Authors: Ma Xin , He Xin Bo , Hu Hai Feng , Zhang Yu Di , Li Yong
Published: April 2015

2D Cf/SiC composites were prepared by precursor infiltration and pyrolysis (PIP) process with spreaded T700-12K plain weave carbon clothes as the reinforcement. The mechanical properties and microstructures were investigated. The composites are compact with few internal defects since the precursor could infiltrate the preform effectively. CVD-PyC interface modified the surface of T700 carbon fiber, a rough surface is helpful for the interfacial combination and the load transfer. For the Cf/PyC/SiC composites, the flexural strength and flexural modulus were 425±23.2 MPa and 36.3±3.1 GPa, respectively.
Preparation of Graphene and Graphene/Al Composites
Authors: Leng Jin Feng , Teng Xin Ying , Jiang Fu Lei , Hu De Jiang , Geng Hao Ran
Published: April 2015

Metal matrix composites reinforced by graphene particles exhibit physical and mechanical property and are developed and qualified for use in aerospace structure, bioengineering, energy storage material and photoelectric device. In the present paper, graphene was fabricated by modify Hummers method, and then was surface modified by chemical plating copper. The graphene/Al composites were fabricated by powder metallurgic method. Morphology characterization of graphene and composites were detected by XRD and SEM,the fabrication parameters of composites were optimized by testing harness and density. The volume fraction of graphene particles was 3%, the density of composites was maximum of 96.5%. The hardness had a maximum of HB 42.6, and the hardness of graphene/Al composites increased by 33.5%.
Influence of Temperatures on the Formation of SiBCN Powders Prepared by CVD Using Borazine and Liquid Polycarbosilane
Authors: Sun Xun , Li Jun Sheng , Cheng Hai Feng
Published: April 2015

SiBCN powders have been prepared by chemical vapor deposition using borazine and liquid polycarbosilane as source precursors in the deposition temperature range from 800 °C to 1100 °C, with the pressure of 10 kPa. The effect of the temperatures on the surface morphologies of the as-received powders was investigated by SEM. FTIR analysis of the powders was used to obtain the composition of the powders, and the XRD analysis was used to determine the crystalline state of the deposits. The results showed the powders were amorphous and composed of normally spherical grains.
Preparation of BN Coating on KD-II Silicon Carbide Fiber by Dip-Coating Process
Authors: Yang Bei , Zhou Xin Gui , Yu Jin Shan , Wang Hong Lei
Published: April 2015

Boron nitride (BN) coating on KD-II silicon carbide fiber was prepared from boric acid and urea by a 4-circle dip-coating process. SiCf/SiC composites were prepared from the precursor LPVCS by a HP(heat pressure) assisted PIP(precursor infiltration and pyrolysis) process. The microstructure and crystal structure of the coatings were characterized by SEM and XRD. XPS was adapted to analysis the composition and contents of different elements on the surface of BN coating. The influence of dip-coating process to the fibers was studied by the monofilament strength test. As the results, the monofilament strengths of the dip-coated fibers decreased firstly and increased subsequently. The strengths were slightly higher (3.4%) than the original fiber after 4 circles. The average flexural strength and fracture toughness of the composites with BN coating are respectively 290.8 MPa and 12.09 MPa⋅m1/2, while those of composites without coating are 144.1 MPa and 6.72 MPa⋅m1/2, respectively.
Effect of N2H4 on Electrodeposition of Ni-Graphene Composite Coatings and their Corrosion Resistance Property
Authors: Yu Quan Yao , Zhang Ying Xin , Liu Zhen Zhen , Zeng Zhi Xiang , Wu Xue Dong , Xue Qun Ji
Published: April 2015

The Ni-graphene composite coatings were prepared by electrochemical deposition method, using nickel sulfate and graphene as primary reagents. Pure Ni coatings, Ni-graphene coatings with N2H4 and Ni-graphene coatings without N2H4 were prepared from three different but similar electrolytes. The N2H4 added into the solution is for complexation with NiSO4 to settle the Ni ions. Graphene used in this work is characterized by TEM and HRTEM. The reaction of N2H4 with NiSO4 is characterized by XRD and optical graphs. The composite coatings’ morphology, structure and corrosion resistance were characterized by SEM and Potentiodynamic polarization test, respectively. The results show that well dispersed graphene–nickel coatings can be prepared with N2H4 in the electrolyte. By comparison with the situation that electrolyte without N2H4, graphene agglomerated at the surface of nickel coatings. The grain of the coatings prepared with and without N2H4 shows similar sizes. Ni-graphene coatings exhibit poor anticorrosion property by comparison with pure Ni coatings because of the defects (cracks and roughness on composite coatings with and without N2H4 in the solution, respectively) on the surface of graphene nickel coatings. These results provide a basis viewpoint for the further research of graphene-metallic composite coatings’ anticorrosion effect.
Microstructure and Mechanical Property of Ti3AlC2/TiAl3 Composite Synthesized by Hot Pressing
Authors: Chen Wei Ping , Zeng Yong , Li Xiao Mei , Xiao Hua Qiang
Published: April 2015

Ti3AlC2/TiAl3 composite was successfully fabricated by ball milling and in-situ reaction/hot-pressing of Ti, Al and graphite powders mixture at 1200 °C and 30 MPa for 30 min. The phase composition and microstructure of the milled powders and synthesized composite were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), the mechanical properties and the toughening mechanism of 20%vol Ti3AlC2/TiAl3 composite was also studied. The results show that no new phase is detected during 50 h of milling process. The in-situ synthesized samples are fully dense and composed of 72%vol TiAl3, 24%vol Ti3AlC2 and 4%vol Al2O3/TiC. The Vickers Hardness, three-point bending strength and fracture toughness of the composite is ~5.2 GPa, ~243 MPa and ~4.3 MPa/m1/2, respectively. Analysis of microstructure reveals that crack deflection, crack bridging and delamination of Ti3AlC2 are the main mechanism responsible for the toughening.
Structure of B-Modified MoSi2 Coating on C103 Alloy Prepared through Glow Plasma Deposition and HAPC Combined Method
Authors: Tian Xiao Dong , Guo Xi Ping , Sun Zhi Ping , Qu Jiang Long , Wang Li Jie
Published: April 2015

Glow plasma deposition (GPD) and halide activate pack cementation (HAPC) methods were combined to prepare B-modified MoSi2 coatings on C103 alloy. The pure Mo layer was firstly deposited on the substrate through GPD process, and then Si and B were co-deposited into the Mo layer through HAPC process to form the B-modified MoSi2 coating. Experimental results revealed that the Mo layer exhibited metallurgical bonding with the substrate. Two typical coatings were produced through the above combined method. One consisted of the MoSi2 outer layer, the MoSi2+MoB two-phase middle layer and the Mo5Si3 inner layer, the other consisted of an outer deposits layer composed of MoSi2 matrix and MoB dispersions, and an inner diffusion layer composed of NbSi2, NbB2 and Nb5Si3 phases. The latter coating was oxidized at 1250 °C, and it has been found that the protective scale can form on the coating surface, which indicates the good oxidation resistance of such B-modified MoSi2 coating prepared through the combined method.
Effect of Mullite Content on the Properties of Silica-Based Ceramic Cores
Authors: Fan Hong Na , Ji Hui Ming , Tang Ding Zhong , Liu Xiao Guang , Yao Jian Sheng , Li Xin , Gu Guo Hong , Wang Li Li , Niu Shu Xin
Published: April 2015

In this study, mullite was used as the addition to prepare silicon based ceramic cores, and the effect of mullite content on the mechanical and chemical properties was investigated. The phase composition and the morphology of the ceramic cores were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. The results indicated that the shrinkage was induced by the addition of mullite and contaminations. The intensity of pre-heated cristobalite increased sharply with the mullite content increasing, which could improve the high temperature deformation simultaneously. However, mullite was difficult to remove by reacting with KOH which decreased the leaching rate of ceramic core. When mullite content was 15 wt%, the shrinkage of ceramic core was 0.78%, the creep at 1540 °C for 1 h was 0.3 mm and the leaching rate was 0.1 g/min, which meets the need of ceramic core of hollow turbine blades.
Microstructures and Mechanical Properties of Three-Dimensional Braided Carbon Fiber Reinforced Mullite Composites with Different Sols as Raw Materials
Authors: Liang Song Lin , Ma Qing Song , Liu Hai Tao
Published: April 2015

In order to efficiently fabricate dense three-dimensional carbon fiber reinforced mullite matrix composites (3D C/mullite), two kinds of Al2O3-SiO2 sols with high solid content were used as raw materials. The ceramic yield and mullitization behavior of the sols and the densification process were investigated. It is indicated that the two sols have proper solid content and ceramic yield and can be completely transformed into mullite at 1573K, which make them be able to prepare composites. 3D C/mullite composites with a porosity of ∼25% were prepared by repeating less than 20 cycles of infiltration-drying-heating of sols, and the microstructures and mechanical properties were examined. The results suggest that the sol with smaller particle size derived composites exhibit well-sintered dense matrix and physically stronger interfacial bonding, which are beneficial to improve load-bearing and load-transferring capacity of matrix. As a result, this composites show much higher mechanical properties. The flexural strength and modulus are 2.4 times and 1.3 times as those of the sol with larger particle size derived composites, respectively.
Effect of Al Content on Microstructure and Creep Behavior of Low Density Ni3Al-Base Single Crystal Superalloy
Authors: Fu Hao , Li Shu Suo , Pei Yan Ling , Gong Sheng Kai
Published: April 2015

The influence of Al content on microstructure and creep behavior of Ni3Al-Base single crystal superalloy was investigated. Two Ni3Al-Base single crystal alloys with different Al contents were prepared in a vacuum induction furnace by screw selection crystal method.Optical microscope (OM), differential scanning calorimetry (DSC),scanning electron microscope (SEM),energy dispersive spectrometer (EDS),and X-ray diffraction (XRD) were used to observe the microstructure of the alloys.The experimental results showed thatthe volume fraction, mean size of the eutectic phase γ-γ′, γ′before and after heat treatment display differences with the Al content. It has been found that the stress-rupture lives increased with theAl content.The reasons may be as follows.Firstly, as content of Al increases, the reinforcing phaseγ′increases, resulting in the improvement of the precipitation strengthening.And secondly, the increasing of Al content leadsthe decreasing lattice mismatch of γ/γ′ phase, which enhances the coherent strain field around theγ′ phase and the hence increase the strengthening effect to the alloy.
Influences of Thermal Molding Process on the Flexural Properties of SiC/SiC Composites with a New Precursor Polymer
Authors: Luo Zheng , Zhou Xin Gui , Yu Jin Shan , Wang Fei
Published: April 2015

Silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC) were fabricated by precursor impregnation and pyrolysis (PIP) process with a new precursor polymer, liquid polyvinylcarbosilane (LPVCS). The molding process was conducted during the cross-linking reactions of LPVCS for the first PIP cycle. The influences of molding pressure and molding time on the flexure properties of the SiC/SiC composites were studied. The results indicated that the optimal molding pressure and molding time were 3MPa and 5h respectively due to the fine interfacial bonding between fiber and matrix. The density of the SiC/SiC composites was 2.16g/cm3. The flexural strength and fracture toughness of the SiC/SiC composites were 637.5MPa and 29.8MPa·m1/2 respectively.
Effect of Al-5Zr-1.1B Grain Refiner on Microstructure and Mechanical Properties of AZ91D Magnesium Alloy
Authors: Wang Shun Cheng , Huang Zheng Hua , Qi Wen Jun , Zheng Kaihong
Published: April 2015

An Al-5Zr-1.1B grain refiner was prepared by in-situ synthesis from Al melt and K2ZrF4+KBF4 mixed powder. The microstructure of Al-5Zr-1.1B grain refiner was analyzed by XRD, SEM and EDS. The effect of Al-5Zr-1.1B grain refiner on the microstructure and mechanical properties of AZ91D magnesium alloy were studied. Results show that a large number of fine ZrB2 particles were observed in the Al-5Zr-1.1B grain refiner and the ZrB2 particles could act as the heterogeneous nuclei of α-Mg grains. With the increase of the addition amount of Al-5Zr-1.1B grain refiner, the α-Mg grains of AZ91D magnesium alloy were refined from coarse dendrites to equiaxed grains. When the addition amount of Al-5Zr-1.1B grain refiner increased to 0.6%, the α-Mg grains of AZ91D magnesium alloy were refined to fine equiaxed grains with an average diameter of 45 μm, and the tensile strength and elongation of AZ91D magnesium alloy were improved to 195.3 MPa and 3.94%, respectively. The α-Mg grains average diameter of AZ91D magnesium alloy decreased by 73.5% and the tensile strength and elongation improved by 25.9% and 27.9% compared with that of AZ91D magnesium alloy without adding the Al-5Zr-1.1B grain refiner. It is concluded that the Al-5Zr-1.1B is an effective grain refiner to refine the α-Mg grains of AZ91D magnesium alloy.
Microstructure and Properties of Friction Stir Welded Mg-1Al-xSn-0.3Mn Magnesium Alloys
Authors: Xu An Lian , Pan Fu Sheng , Jiang Xian Quan , Li Cheng , Ran Yang
Published: April 2015

For the study of the weldability of new-typed Mg-1Al-xSn-0.3Mn (x=1,3) magnesium alloys, the plates of extruded Mg-1Al-xSn-0.3Mn (x=1,3) magnesium alloys with a thickness of 2.8 mm were friction stir welded by butt. And the microstructure and properties were tested and analyzed by X-ray non-destructive test, OM, SEM, EDS, microhardness and tensile test. The results show that the above-mentioned magnesium alloys could be successfully butt-welded without any defect by friction stir welding, the microstructure in the NZ was fine and equiaxed, and some grains in the TMAZ were elongated in the form of bars. Moreover, the tensile strength of the friction stir weld could reached over 85% that of the base material and the HAZ at advancing side of the weld had the lowest hardness.
Tensile Behavior of Mg-Nd-Zn-Zr Alloy at Medium and High Temperature
Authors: Wang W.H. , Wu D. , Chen Rongshi , Lou Chang Sheng
Published: April 2015

The tensile deformation behavior and microstructure evolution of Mg-Nd-Zn-Zr alloys at solid solution condition was studied during the tensile tested at medium and high temperature. The result showed that, in medium temperature range (≤250οC), serrated flow was observed. With the temperature increasing, the critical strain decreased, the serration became more intensive, and the type of serration changed from type A to type A+B, finally to type B. At temperature of 250 οC, where serrated flows become most obvious, a large number of precipitated phases in slip band were found in micrographs. The strength reached a high peak and the ductility stay at low ebb in mechanical perspective. When tensile tested at high temperature ranging from 300 οC to 400οC, serrated flow disappeared and the ductility increased profoundly with the temperature increasing, and then approached to super-plasticity. In addition, the deformation mechanism, at medium and high temperature, has been discussed by calculating the activation energy.
Constitutive Modeling of Magnesium Alloys with Distortional Hardening
Authors: Shi Bao Dong , Peng Yan , Pan Fu Sheng
Published: April 2015

Anisotropic mechanical behavior is one of the key factors restricting the processing procedure of magnesium alloys. This pronounced anisotropy, however, cannot be characterized by classical isotropic or kinematic hardening due to the constant shape of yield surfaces during plastic deformation. Therefore, the shape evolution of yield surfaces, also known as distortional hardening is the main way to capture the anisotropic behavior. Based on elasto-plasticity theory at finite strain, constitutive model with distortional hardening for Mg alloys is proposed. The thermodynamical consistency is proved. The anisotropic mechanical behavior of AZ31 sheet is demonstrated after material parameters calibration.
Progress on Hydrothermal Synthesis of Biomedical Coatings on Magnesium Alloy
Authors: Guo Guang Hui , Jiang Jing Hua , Song Dan , Ma Ai Bin , Zhang Li Li , Yan Hui
Published: April 2015

Hydrothermal synthesis as a new coating technique has been developed to produce biomedical coating in Mg alloys in recent years. This paper summarized the process feature and corrosion resistance of hydrothermal synthesis coating in Mg alloys, and then reviewed the synthesis process, microstructure, corrosion behavior and corrosion mechanism of the Mg (OH)2 biomedical coatings. Finally, the current problems and research prospect of this technique in biomedical Mg alloys were discussed.
Investigation on the Physical and Chemical Grain Refinement of the Mg-10Sm Alloy
Authors: Wang Guang Zong , Li Da Quan , Zhu Qiang
Published: April 2015

In this paper the physical and chemical grain refining of the Mg-10Sm alloy was investigated. Physical grain refinement was achieved by strongly shearing the melt above the liquidus temperature using a twin-screw string device and then cast at the near liquidus temperature. Chemical grain refiner was added into Zr master alloy in the melt. Casting the Mg-10Sm alloy at 730°C produced an extremely coarse microstructure consisting of huge dendritic grains. The physical grain refinement greatly refined the dendritic grains to smaller rosette grains, being reduced from several millimeters to about 200μm. Chemical grain refinement produced fine and equiaxed grain structure with size of approximated 111μm. Combination of the physical and chemical grain refinement creates more significant refining effect than either of the two methods.
Effects of Different Species of Sr Additives on as Cast Microstructure and Tensile Properties of AS31 Alloy
Authors: Zhou Ji Xue , Wang Jin Wei , Zhang Yi , Tang Shou Qiu , Li Wei Hong , Yang Yuan Sheng
Published: April 2015

Effects of different species of Sr additives (pure Sr, cast Mg-10Sr block, Ф10mm extruded Al-10Sr bar) on as-cast microstructure and tensile properties both at ambient temperature and elevated temperature of AS31 alloy were studied. The experimental results showed that pure Sr, Mg-10Sr, Al-10Sr additions all could refine the grains of AS31 alloy obviously, modify the eutectic Mg2Si particles and strengthen AS31 alloy. Al-10Sr is most effective to refine microstructure and improve mechanical properties of AS31 alloy.
Preparation of Al2O3/Al-Si Composites by In Situ Reaction of Fe2O3+MnO2/Al System
Authors: Zhang Jing , Yu Hua Shun , Shuai Xin Ting , Chen Hong Mei , Min Guang Hui
Published: April 2015

Al2O3 particles reinforced ZL109 composites were prepared by in-situ reaction between Fe2O3+MnO2 and Al in this paper. The influence of ratio of Mn to Fe on the morphologies of Al-Si-Mn-Fe phase and mechanical properties of the composites was investigated. The microstructure was studied by electron probe micro-analyzer (EPMA) and transmission electron microscopy (TEM). The results show that the Al2O3 particles displaced by the Fe2O3+MnO2/Al system are in nanosize. The acicular Al-Si-Fe phases change from acicular to polygonal shape and become smaller with the increase manganese content. The hardness test results have no big difference on the composites. However, the ultimate tensile strength at room temperature and 350°C enhance evidently with the increasing of Mn/Fe.
Effect of Titanium on Solidification Behavior of IC10 Directionally Solidified Superalloy
Authors: Liu Li Yu , Fan Ying Wei , Wan Qi
Published: April 2015

Solidification behaviors of IC10 alloy with different titanium content were investigated by isothermal solidification method. Volume percentage of liquid and precipitation temperature of primary MC type carbide, eutectic and secondary γ′ phase were investigated. The results showed that with the increase of Ti content in the alloy, the liquidus, solidus and MC carbide formation temperatures decreased, on the contrary, the formation of γ+γ′ eutectic and secondary γ′ increased. For the IC10 alloy with 1.5% titanium content, it is earlier for the interdendritic pools to be divided into the parts. At this condition, melted portion of the alloy resided during isothermal process. As a result, the castability of the IC10 with 1.5% titanium is thus the lowest.