bluuebunny/crossref_metadata_2025 huggingface dataset:
Emotion as a Significant Change in Neural Activity
Authors: Parussel Karla
Published: April 2010

It is hypothesized here that two classes of emotions exist: driving and satisfying emotions. Driving emotions significantly increase the internal activity of the brain and result in the agent seeking to minimize its emotional state by performing actions that it would not otherwise do. Satisfying emotions decrease internal activity and encourage the agent to continue its current behavior to maintain its emotional state. It is theorized that neuromodulators act as simple yet high impact signals to either agitate or calm specific neural networks. This results in what we can define as either driving or satisfying emotions. The plausibility of this hypothesis is tested in this article using feed-forward networks of leaky integrate-and-fire neurons.
Bacterial Foraging Optimization
Authors: Passino Kevin M.
Published: April 2010

The bacterial foraging optimization (BFO) algorithm mimics how bacteria forage over a landscape of nutrients to perform parallel nongradient optimization. In this article, the author provides a tutorial on BFO, including an overview of the biology of bacterial foraging and the pseudo-code that models this process. The algorithms features are briefly compared to those in genetic algorithms, other bio-inspired methods, and nongradient optimization. The applications and future directions of BFO are also presented.
Strategic Considerations for Emergency Preparedness and Management
Authors: Turoff Murray
Published: April 2010

A strategic issue is a major core issue that can rarely be resolved by any sort of fully objective approach. It is usually about the future and the alternative options that exist to “improve” the future. This article explores the critical areas of concern in strategic considerations illustrated by the topic of Emergency Preparedness and Management.
Group Support Systems and Action Research
Authors: Martz Jr. Wm. Benjamin , Sakaguchi Toru
Published: April 2010

Research in Information Systems, specifically Group Support Systems (GSS), lends itself well to Action Research. From its original definition in 1985, GSSs have included a human component, the facilitator thereby providing an excellent venue for action research. This article proposes that action research acts as a key component in the knowledge accrual process for information systems research. The article demonstrates this proposal by developing a four-phased empirical-action research cycle based on McGrath et al.’s (1982) empirical research cycle, Baskerville’s (1997) action research cycle, and the call to include the practitioner’s view in empirical research as posited by Kerlinger’s (1986) suggested goals for non-experimental studies. Finally, the proposed empirical-action research cycle is applied directly to a GSS field study wherein a group uses a GSS for a real-world problem of business process reengineering. The details of the study are discussed using the four phases in the model.
Affective Factors for Successful Knowledge Management
Authors: Smith Peter A.C.
Published: April 2010

The article proposes that any effort to successfully manage knowledge must be concerned not only with relevant technology, but also with the plethora of affective factors present in the workforce. The aim of this article is to heighten awareness of the impact of these affective factors on KM implementation, and to offer practical approaches that it is contended will assist in “getting the affective factors right”.
Designing Visionary Leadership Teams
Authors: Johnson Martin
Published: April 2010

Nigel Sykes’ 3E’s concept is examined against established theory and recent work in Organizational Behaviour. The possibility that this concept offers a way of developing social synergy in work groups is explored, and considered in the context of socio-technical systems. 3E’s is based on the categorisation of people in the workplace into roles labelled “Envisioners” “Enablers” or “Enactors”. Role theory is explored, and its relevance to organizational success. The importance of the affective component in motivation and decision-making is identified. A research study is reported testing the 3E’s concept which shows that it corresponds with measurable differences of motivational need, personality factors, and decision-making between individuals. The characteristics of successful group decision-making are linked with the 3E’s differentiation. The 3E’s model offers the possibility of improving person-role fit, and thus organisational performance. It proposes an integrated design for the selection and operation of teams, offering a person-role fit, optimal decision-making behaviour, and consequent social synergy.
Think Global, Act Local
Authors: Albert Sylvie , Flournoy Don
Published: April 2010

Being able to connect high-speed computing and other information technologies into broadband communication networks presents local communities with some of their best chances for renewal. Such technologies are now widely perceived to be not just a nice amenity among corporations and such non-profit organizations as universities but a social and economic necessity for communities struggling to find their place in a rapidly changing world. Today, citizens want and expect their local communities to be “wired” for broadband digital transactions, whether for family, business, education or leisure. Such networks have become a necessity for attracting and retaining the new “knowledge workforce” that will be key to transforming communities into digital societies where people will want to live and work. Since the Internet is a global phenomenon, some of the challenges of globalization for local communities and regions are introduced in this article and suggestions for turning those challenges into opportunities are offered. To attain maximum benefit from the new wired and wireless networks, local strategies must be developed for its implementation and applications must be chosen with some sensitivity to local needs. New Growth theory is used to show why communities must plan their development agenda, and case studies of the Intelligent Community Forum are included to show how strategically used ICTs are allowing local communities to be contributors in global markets.
The Keys to the White House
Authors: Lichtman Allan J.
Published: April 2010

The Keys to the White House are an index-based prediction system that retrospectively account for the popular-vote winners of every US presidential election from 1860 to 1980 and prospectively forecast the winners of every presidential election from 1984 through 2008. The Keys demonstrate that American presidential elections do not turn on events of the campaign, but rather on the performance of the party controlling the White House. The Keys hold important lessons for politics in the United States and worldwide. A preliminary forecast based on the Keys indicates that President Obama is a likely winner in 2012, but also reveals the specific problems at home at abroad that could thwart his re-election.
Perceiving the Social
Authors: Kryssanov Victor V. , Kumokawa Shizuka , Goncharenko Igor , Ogawa Hitoshi
Published: April 2010

This article describes a system developed to help people explore local communities by providing navigation services in social spaces created by the community members via communication and knowledge sharing. The proposed system utilizes data of a community’s social network to reconstruct the social space, which is otherwise not physically perceptible but imaginary, experiential, yet learnable. The social space is modeled with an agent network, where each agent stands for a member of the community and has knowledge about expertise and personal characteristics of some other members. An agent can gather information, using its social “connections,” to find community members most suitable to communicate to in a specific situation defined by the system’s user. The system then deploys its multimodal interface, which “maps” the social space onto a representation of the relevant physical space, to locate the potential interlocutors and advise the user on an efficient communication strategy for the given community.
CoPBoard
Authors: Sato Gilson Yukio , Barthès Jean-Paul A.
Published: April 2010

Symbiotic computing leads to a proliferation of computing devices that allow linking people, favoring the development of distributed Communities of Practice (CoPs). Their members, being dispersed geographically, have to rely strongly on technological means to interact. In this context, coordinating distributed CoPs is more challenging than coordinating their collocated counterparts. Hence, the increasing role of the coordination should be supported by an adequate set of coordination tools. In this article, we present an approach based on multi-agent systems for coordinating distributed CoPs. It includes analyzing the exchanges among members and translating this information into a graphical format to help the coordinators to follow the evolution of the participation and the domain of the community.
Remote Conversation Support for People with Aphasia
Authors: Aye Nilar , Ito Takuro , Hattori Fumio , Kuwabara Kazuhiro , Yasuda Kiyoshi
Published: April 2010

This article proposes a remote conversation support system for people with aphasia. The aim of our system is to improve the quality of lives (QoL) of people suffering cognitive disabilities. In this framework, a topic list is used as a conversation assistant in addition to the video phone. The important feature is sharing the focus of attention on the topic list between a patient and the communication partner over the network to facilitate distant communication. The results of two preliminary experiments indicate the potential of the system.
The Formal Design Model of an Automatic Teller Machine (ATM)
Authors: Wang Yingxu , Zhang Yanan , Sheu Philip C.Y. , Li Xuhui , Guo Hong
Published: April 2010

An Automated Teller Machine (ATM) is a safety-critical and real-time system that is highly complicated in design and implementation. This article presents the formal design, specification, and modeling of the ATM system using a denotational mathematics known as Real-Time Process Algebra (RTPA). The conceptual model of the ATM system is introduced as the initial requirements for the system. The architectural model of the ATM system is created using RTPA architectural modeling methodologies and refined by a set of Unified Data Models (UDMs), which share a generic mathematical model of tuples. The static behaviors of the ATM system are specified and refined by a set of Unified Process Models (UPMs) for the ATM transition processing and system supporting processes. The dynamic behaviors of the ATM system are specified and refined by process priority allocation, process deployment, and process dispatch models. Based on the formal design models of the ATM system, code can be automatically generated using the RTPA Code Generator (RTPA-CG), or be seamlessly transformed into programs by programmers. The formal models of ATM may not only serve as a formal design paradigm of real-time software systems, but also a test bench for the expressive power and modeling capability of exiting formal methods in software engineering.
Benefits and Challenges in the Use of Case Studies for Security Requirements Engineering Methods
Authors: Mead Nancy R.
Published: April 2010

The premise of this article is that pilot case studies in security requirements engineering provide both benefits and challenges to the underlying research, education, and technology transition effort. Over the past four years we have worked with seven development groups in five organizations in the process of refining and transitioning the Security Quality Requirements Engineering (SQUARE) and SQUARE-Lite methods into practice. These experiences have provided the opportunity to step back and assess the use of pilots in conjunction with student projects to support method refinement and technology transition. Although SQUARE and SQUARE-Lite are concerned with security requirements, the benefits and challenges that have been observed would apply to many security research and technology transition efforts. We itemize and justify these benefits and challenges and discuss their practical relevance and application to ensuring adequate information assurance protection.
A Survey of Web Services Provision
Authors: Liu An , Liu Hai , Lin Baoping , Huang Liusheng , Gu Naijie , Li Qing
Published: April 2010

Web services technologies promise to create new business applications by composing existing services and to publish these applications as services for further composition. The business logic of applications is described by abstract processes consisting of tasks which specify the required functionality. Web services provision refers to assigning concrete Web services to perform the constituent tasks of abstract processes. It describes a promising scenario where Web services are dynamically chosen and invoked according to their up-to-date functional and non-functional capabilities. It introduces many challenging problems and has therefore received much attention. In this article, the authors provide a comprehensive overview of current research efforts. The authors divide the lifecycle of Web services provision into three steps: service discovery, service selection, and service contracting. They also distinguish three types of Web services provision according to the functional relationship between services and tasks: independent provision, cooperative provision and multiple provision. Following this taxonomy, we investigate existing works in Web services provision, discuss open problems, and shed some light on potential research directions.
An Efficient and Simple Algorithm for Matrix Inversion
Authors: Farooq Ahmad , Hamid Khan
Published: April 2010

In this paper, a new algorithm is proposed for finding inverse and determinant of a given matrix in one instance. The algorithm is straightforward in understanding and manual calculations. Computer implementation of the algorithm is extremely simple and is quite efficient in time and memory utilization. The algorithm is supported by an example. The number of multiplication/division performed by the algorithm is exactly; however, its efficiency lies in the simplicity of coding and minimal utilization of memory. Simple applicability and reduced execution time of the method is validated form the numerical experiments performed on test problems. The algorithm is applicable in the cases of pseudo inverses for non-square matrices and solution of system of linear equations with minor modification.
Thirst for Business Value of Information Technology
Authors: Marthandan Govindan , Meng Tang Chun
Published: April 2010

For years information technology (IT) has helped companies improve organizational efficiency and effectiveness. Today’s IT plays a more strategic role in building capabilities for sustaining and creating competitive advantages. The increasing importance of IT has led many organizations to integrate it into their daily operations. To justify the ever-increasing spending on IT, organizations have been searching for evaluation methods to prove the business value of IT. However, this is a challenging undertaking, as there are contradictory answers to questions on whether it is worthwhile to pay substantial sums for IT. To gain insight into the reasons behind the contradictory answers, this paper first reviews conflicting research results of past studies on IT business value. It then explains the term IT productivity paradox. Last, it provides five reasons why IT business value is not fully reflected in the way business managers expect it to be.
The Issues Related To Student Authentication in Distance Education
Authors: Gearhart Deb
Published: April 2010

As long as there has been distance education there has been the question how do you know the student turning in the work is the student registered for the course? As technology has been improving distance education course delivery, online education has been growing in leaps and bounds. The most recent Sloan-C report stated that in the U. S. alone there were almost 3.9 million students taking at least one online course during the fall of 2007 term (Allen and Seaman, 2008). Legislators took a hard look at the issue of student authentication in distance education with the passage of the Higher Education Opportunity Act of 2008. This paper reviews the issues related to student authentication and reviews the current forms of student authentication, reviewing one institution’s answer to student authentication in its online programs.
Enhance Students' Computing Skills via Web-Mediated Self-Regulated Learning with Feedback in Blended Environment
Authors: Lee Tsang-Hsiung , Shen Pei-Di , Tsai Chia-Wen
Published: April 2010

The vocational colleges in Taiwan regard professional certifications as a badge of skills achievement. To enhance student learning in this specific context, the authors conducted a quasi-experiment to explore effects of web-mediated self-regulated learning (SRL) with feedback, blended learning (BL) and their combinations on enhancing students’ skills of using Microsoft Word. Four classes in successive years, with a total of 190 freshmen, were divided into 2 (SRL with Feedback vs. SRL without Feedback) × 2 (Blended vs. Traditional) experimental groups. Results were generally positive. The results showed that students in the group of BL and SRL with feedback had better skills and higher pass rate on certification exams than those in the control group. It is hoped that the lesson learned is also useful for those teachers engaged in e-learning, specifically, in vocational colleges.
On the Definition and Impact of Virtual Communities of Practice
Authors: Andreatos Antonios
Published: April 2010

The evolution of the Internet has made several Communities of Practice to go online and has brought into life numerous Virtual Communities of Practice. The purpose of this article is: to define and categorize Virtual Communities of Practice; to examine their social impact in general and specifically in knowledge and technology management; also, to examine the contribution of Communities of Practice to informal learning and to relate them to Connectivism and collaborative learning. Several case studies are presented to clarify the presentation. It is expected that Virtual Communities of Practice will play an important role in both learning theory and practice as well as knowledge management during the years to come.
Using WSRP 2.0 with JSR 168 and 286 Portlets
Authors: Polgar Jana
Published: April 2010

WSRP—Web Services for Remote Portlets—specification builds on current standard technologies, such as WSDL (Web Services Definition Language), UDDI (Universal Description, Discovery and Integration), and SOAP (Simple Object Access Protocol). It aims to sol
Containers and Connectors as Elements in a Portal Design Framework
Authors: Lamantia Joe
Published: April 2010

This article defines the standardized elements used in the building blocks portal design framework in detail, as the second in a series of articles on a Portal Design Framework. This article explains the (simple) rules and relationships for combining Cont
A Model-Based Approach for Diagnosing Fault in Web Service Processes
Authors: Yan Yuhong , Dague Philippe , Pencole Yannick , Cordier Marie-Odile
Published: April 2010

Web service orchestration languages are de?ned to describe business processes composed of Web services. A business process can fail for many reasons, such as faulty Web services or mismatching messages. It is important to ?nd out which Web services are responsible for a failed business process because we could penalize these Web services and exclude them from the business process in the future. In this paper, we propose a model-based approach to diagnose the faults in a Web service-composed business process. We convert a Web service orchestration language, BPEL4WS, into synchronized automata, so that we have a formal description of the topology and variable dependency of the business process. After an exception is thrown, the diagnoser can calculate the business process execution trajectory based on the formal model and the observed evolution of the business process. The faulty Web services are deduced from the variable dependency on the execution trajectory.
Enhancing Security Modeling for Web Services Using Delegation and Pass-On
Authors: She Wei , Yen I-Ling , Thuraisingham Bhavani
Published: April 2010

In recent years, security issues in web service environments have been widely studied and various security standards and models have been proposed. However, most of these standards and models focus on individual web services and do not consider the security issues in composite services. In this article, the authors propose an enhanced security model to control the information flow in service chains. It extends the basic web service security models by introducing the concepts of delegation and pass-on. Based on these concepts, new certificates, certificate chains, delegation and pass-on policies, and how they are used to control the information flow are discussed. The authors also introduce a case study from a healthcare information system to illustrate the protocols.
Service Flavors
Authors: Jegadeesan Harshavardhan , Balasubramaniam Sundar
Published: April 2010

In a services marketplace where a particular service is provided by multiple service providers, service offerings have to be differentiated against competitor services in order to gain market share. Differentiation of services is also needed for different markets and for different consumer segments. Strategies to differentiate service offerings have to be unintrusive—without requiring major changes to the existing service realization mechanisms. In this article, the authors present Service Flavors, a strategy for service providers to differentiate services. By using this strategy, it is possible to analyze and adapt various aspects of a service that help differentiate it from that of the competitors. The authors model differentiating aspects as policies and also provide a mechanism for enforcing these policies in the middleware.
Surface Hardening of BN-Al Ceramic Composites
Authors: Li Ying , Jin Hai Yun , Wang Xiang Dong , Qiao Guan Jun
Published: April 2010

Ceramic composites containing BN and Al can be machined easily into complex shape, the hardness of the composites can also be improved by surface hardening process of in situ reaction between Al and BN. However, the reaction of Al and BN is a volume reduced one and the porosity will increase during the hardening treatment.. In order to solve this problem, a surface nitriding process was developed. Put the pre-sintering samples (with designed shapes) into a vacuum furnace in nitrogen atmosphere and reheated to high-temperature, so that the residual Al after pre-sintering would react with N2 completely, and change to AlN which has higher hardness. The phase transformation and microstructure were observed and the mechanical and other properties were also measured. The results showed that the surface nitriding process could increase the hardness, bending strength and density obviously. The porosity decreased sharply compared with the general hardening treatment.
Effect of In Situ TiC Particulate on the Wear Resistance of Spray-Deposited AZ91 Magnesium Matrix Composite
Authors: Yao Jun Ping , Zhong Sun , Zhang Lei , Zhao Huo Ping
Published: April 2010

TiC reinforced AZ91 magnesium matrix composites have been fabricated by a melt in-situ reaction spray deposition. The microstructures of spray-deposited alloys were studied by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry sliding wear behavior of the alloys was investigated by using a pin-on-disc machine under five loads, namely 10, 20, 30, 40 and 50 N. It has been found that the wear behavior of the alloys was dependent on the TiC content in the microstructure and the applied load. At a lower load (10 N), with increasing TiC content, the wear rate of the alloy was decreased, and the dominant wear mechanism was an oxidative mechanism. At a higher load (50 N), a spray- deposited AZ91/TiC composites exhibited superior wear resistance to the AZ91 magnesium alloy, the dominant wear mechanism was delamination.
Dynamics of Crack Healing and its Molecular Dynamics Simulation of Al2O3-MgAlON Composite
Authors: Yang Dao Yuan , Yuan Hui Yu , Qian Fen Ling , Wu Juan , Zhu Kai , Zhang Rui
Published: April 2010

After preparing samples (3mm long×4mm wide×36mm high) of Al2O3-MgAlON composites and sintered at 1500°C for 2 h in N2 atmosphere, samples’ cracks were carved by a Vickers hardometer’s pressing head on the center of the sample surface (4 mm×36 mm). Subsequently, the cracks were healed at 1000°C-1550°C for 6 h respectively. Effects of healing temperature on sample’s strength, crack healing dynamics and its molecular dynamics simulation were investigated. The results suggested that: the optimum range of cracks healing temperature was 1300°C-1550°C, and the healing process accelerated at 1300°C, meanwhile, the strength of samples increased significantly. Cracks completely healing finished at 1550°C. The dynamics equation of crack healing was lnν = -Q/kT+lnC. Through characterizing the crack healing rate with the recovering rate of sample’s strength, the diffusion activation energy Q = 4.264 × 10-30 J•K-1 and diffusion constant C=7.359 were claimed. The result of the molecular dynamics simulation suggested that cracks healing process was caused by diffusion could be divided into five stages: passivation of crack tips, formation of salient island, crack shrinkage, generation of secondary crack, and complete healing.
Size Dependent Thermal Expansion Coefficient of Rod-Shaped Oxide Eutectic Ceramic
Authors: Ni Xin Hua , Li Bao Feng , Zhong Guo Hui , Zhao Lei
Published: April 2010

Rod-shaped oxide eutectic ceramics fabricated through SHS process can acquire outstanding mechanical properties. First, Four-phase model method was used to study effective disturbance strain of rod-shaped oxide eutectic ceramics produced by nano fibers with inter-phases, then average strain of rod-shaped oxide eutectic ceramics aroused thermal inconsistency is obtained. The effective thermal expansion longitudinal strain and transverse strain of rod-shaped oxide eutectic ceramics are determined by the average strain. Rod-shaped oxide eutectic ceramics is transverse isotropy and has two independent thermal expansion coefficients. The results show that the thermal expansion coefficients of rod shaped oxide eutectic ceramics are dependent on the diameter of nano-fiber. The thermal expansion coefficients will decrease when the diameter of nano-fiber decrease.
Synthesis Nano-SiCp/MoSi2 Composites by In Situ Reaction Sintering and Low Temperature Oxidation Behavior
Authors: Kang Peng Chao , Chen Guo Qin , Wu Gao Hui
Published: April 2010

Nano-SiCp/MoSi2 composites with different SiC volume fraction have been synthesized by in situ reactive hot press sintering with the milled Mo, Si and C elements powders. The X-ray diffraction (XRD) detection shows the composites are composed of α-MoSi2 and β-SiC, and transmission electron microscopy (TEM) shows that the particle sizes of β-SiC formed by in situ reaction are in range of 20-100nm, and most of the them locate in grain boundary and some particles embed in MoSi2 grain. The isothermal oxidation and thermal cycling test of nano-SiCp/MoSi2 composites were carried out in air at temperatures of 500°C. The pest phenomenon was not found during oxidation and cyclic oxidation at 500°C for 500 hours and 50 cycles, respectively. All the composites have both excellent oxidation resistant and good cyclic oxidation resistant. The mechanisms of oxidation at low temperature were discussed also.
Application of ANN Back-Propagation for Residual Stress in an Alloy Reinforced Ceramics/Metal Composite
Authors: Duan Hong Yan , Li You Tang , Lei Chun Li , He Gui Ping
Published: April 2010

Artificial neural network (ANN) back-propagation model was developed to predict the thermal expansion behavior and internal residual strains in reinforced ceramic matrix composites (CMCS).The ANN training model has been used to predict the thermal expansion behavior and internal residual strains, exhibiting excellent comparison with the experimental results. It was concluded that predicted thermal expansion behavior and internal residual strains by the trained neural network model seem more reasonable compared to approximate methods. It is possible to claim that, ANN is fairly promising prediction technique if properly used. Training ANN model was introduced at first. And then the neural network architecture is designed. The performance of system is summarized at last. In order to facilitate the comparisons of predicted values, the error evaluation and mean relative error are obtained. The result shows that the training model has good performance, and the experimental data and predicted data from ANN are in good coherence.
High Temperature Oxidation Behavior of ZrB2-SiC-Graphite Composite Heated by High Electric Current
Authors: Chen Hong Bo , Meng Song He
Published: April 2010

High temperature oxidation testing was carried out on hot-pressed ZrB2-SiC-graphite composite by using high electric current heating. The composites oxidation behavior was investigated, the temperature of oxidized specimens was above 2000°C. The results found that the UHTC composite was ruptured at oxidized temperature 2055°C. The microstructure of surface and cross-section of posttest samples were investigated by scanning electron microscopy along with energy and X-ray diffraction. The failure mechanism of rupture was also discussed.
Thermal Conductivity and Mechanical Property of Si3N4 Ceramics Sintered with CeF3/LaF3 Additives
Authors: Bing Bai , Fu Teng , Ning Xiao Shan
Published: April 2010

In this paper, rare-earth fluorides were used as sintering additives instead of rare-earth oxides, the influence of the type and the amount of the fluoride on the thermal conductivity, hardness and strength of Si3N4 ceramics was studied. Results show that the thermal conductivity of a sample sintered with CeF3 is nearly 10% higher than that of the sample sintered with Ce2O3, while the samples sintered with LaF3 increases further 15% as comparing with the samples sintered with CeF3. The strength of the samples changes reversely. These results express that the thermal conductivity of Si3N4 ceramics can be improved by using rare-earth fluoride additives instead of the oxides, and the type of rare-earth fluorides has a significant impact on the properties of Si3N4 ceramics.
Wear Resistance of Nano-ZrO2 Ceramic for Hip Joint Head Prostheses
Authors: Wang Chen , Dong Li Min , Zan Qing Feng , Guo Pen , Tian Jie Mo
Published: April 2010

By using the ring-block friction and wear machine, the friction and wear behavior of nano-ZrO2 ceramic test block against GCr15 steel test ring has been studied. At the same time, friction and wear test of 45# steel block against GCr15 steel ring has also been conducted for comparison. By using self-made test machine for the wear ability of the hip joint, the friction test of nano-ZrO2 ceramic hip joint head against ultra-high molecular weight polyethylene (UHMWPE) acetabulum has been done, the friction test of Co-Cr-Mo alloy hip joint head against UHMWPE acetabulum has also been made for comparison. The results show that the friction factor of nano-ZrO2 ceramic test block against GCr15 steel test ring is less 37.3% than that of 45# steel block against GCr15 steel ring, the wear weight of nano-ZrO2 ceramic test block against GCr15 steel test ring is only 0.76% of that of 45# steel block against GCr15 steel ring. The wear weight of UHMWPE acetabulum against nano-ZrO2 ceramic hip joint head is 61.5% of UHMWPE acetabulum against Co-Cr-Mo alloy hip joint head. This indicates nano-ZrO2 ceramic has good wear resistance property and is the ideal materials for artificial Hip joint head Prostheses.
Oxidation Behaviors of TiB2-TiCX and TiB2-TiCX/15SiC Ceramics
Authors: Zhu De Gui , Sun Hong Liang , Wang Yu Shu , Wang Liang Hui
Published: April 2010

Fully dense samples of TiB2-TiCX and TiB2-TiCX/15SiC ceramic composites were fabricated by in-situ synthesis under hot isostatic pressing from TiH2, B4C and SiC powders. Their oxidized behaviors at different temperatures were tested. Optical micrograph studies and thermo-gravimetric analyses show that the highest effective temperature of oxidation resistance is 700°C for TiB2-TiCX, and 1100°C for TiB2-TiCX/15SiC. The weight gain of TiB2-TiCX/15SiC below 1100°C is quite low, and it rises up suddenly when the temperature reaches 1200°C. Thus, the highest effective temperature of oxidation resistance is 1100°C for TiB2-TiCX/15SiC. The oxidation dynamic curves of TiB2-TiCX/15SiC ceramics accord with the parabola’s law. The activation energy of TiB2-TiCx/15SiC (189.87kJ.mol-1) is higher than that of TiB2-TiCx (96.44kJ.mol-1). In the oxidation process of TiB2-TiCx/15SiC, TiB2 reacts with oxygen and generates TiO2 and B2O3 at first. A layer of whole homogeneous oxide film cannot be formed, in the mean time, the oxidation of TiC begins. When temperature goes up to 1000°C, TiC phase is totally oxidized. SiC is oxidized to SiO2 at about 900°C, Meanwhile, TiO2 forms denser film than B2O3, which grows and covers the surface of the material, and gives better property of oxidation resistance.
Hot-Pressing Sintering Behavior and Properties of AlON/SiC Composites
Authors: Zhao Xiao Jun , Zhang Ning , Ru Hong Qiang , Wang Xiao Yang , Kan Hong Min
Published: April 2010

AlON/SiC composites were synthesized by hot-pressing sintering technology using SiC and prepared AlON powder as raw materials. The influence of SiC content on relative density, hardness, bend strength and microstructure of multiphase material was studied by several testing methods, such as XRD and SEM. The strengthening mechanism of SiC was also explored in this paper. The experimental results indicated that with the addition of SiC, the bend strength of the multiphase material was obviously enhanced, comparing with AlON single phase material, and ultimately it reached 310 MPa. The best adding mass content of SiC was 8% and its strengthening mechanism was mainly thermal expansion mismatch and fine grain strengthening. As the adding mass content of SiC increased, the hardness of AlON/SiC ceramic matrix composite was increased gradually, the bend strength firstly increased and then decreased, and the main fracture way of composite was changed from intergranular fracture to transgranular fracture and finally both of the two modes of fracture occurred. This research had positive significance on deep popularization and application of AlON ceramic material.
Preparation and Properties of Ti5Si3 Matrix Composites Reinforced by Carbon Nanotube
Authors: Cui Xin Fang , Fang Shuang Quan , Qiao Ying Jie , Jia Qi
Published: April 2010

Ti5Si3 matrix composites reinforced by carbon nanotubes were fabricated by vacuum hot pressing sintering. X-ray diffraction and scanning electron microcopy were carried out to analyze the phase and microstructure of the composites. The effects of carbon nanotubes on mechanical properties were investigated. Experimental results showed that the nanotubes partly reacted with Ti and Si powders to obtain Ti5Si3 and Ti3SiC2, TiSi2 when the sintering temperature is about 1380oC. The mechanical properties of composites can be affected by carbon nanotubes. Meanwhile, the maximal increments of Vickers hardness, bending strength and fracture toughness of the composites, compared with the Ti5Si3 matrix, were 62.9%, 160.9% and 159.3%, respectively. Both of transgranular and intergranular fracture in the composites were the main fracture mode. The fracture manners of composites mainly include “bridging” of CNTs, “deflection” of minor phases and the evolution of grain.
Sintering of High-Strength Dense Al2O3 Using Rod-Like Submicron Al2O3 as Sintering Aid
Authors: Wang Yong Qing , Chang Qi Bing , Zhou Jian Er
Published: April 2010

Rod-like submicron Al2O3 powder was prepared by the controllable hydrolyzation of aluminium isopropoxide in streams atmosphere. XRD data show the rod-like Al2O3 has a γ- Al2O3 structure. TEM images display the length of the submicron Al2O3 is in the range of 100-300 nm and the slenderness ratio is above 10. The rod-like Al2O3 powder was added into the submicron Al2O3 (D50 = 0.5 μm, purity > 99.99%) to increase the bending strength of the sintered body and to decrease the sintering temperature. SEM images display that the Al2O3 sintered at 1450 °C with rod-like Al2O3 added has a higher density than the virgin Al2O3 and the Al2O3 grains have the trans-crystalline fracture. The bending strength of the sintered Al2O3 with 5 wt% rod-like Al2O3 added is 205 MPa, which increases 241%. A sharp shrinkage in 1300-1400 °C appeared in the sintering shrinkage curves characterized by DIL show the rod-like Al2O3 also acts as the sintering aid.
Effect of B4C on the Mechanical Properties and Microstructure of ZrB2-SiC Based Ceramics
Authors: Liu Xuan , Xu Qiang , Zhu Shi Zhen
Published: April 2010

ZrB2-SiC-B4C is sintered at 1700°C by spark plasma sintering process. The effect of B4C content on the mechanical properties and microstructure of ZrB2-SiC based ceramics is studied. The results show that, with the content of B4C increases, the relative density and room-temperature strength decrease in the ZrB2-SiC-B4C composite. The fracture toughness rises at first and then falls down. The high temperature strength increases.
High Temperature Properties of Ti3SiC2-SiC Composites
Authors: Zhu De Gui , Tang Hui Yi , Sun Hong Liang , Guo Shuang Quan
Published: April 2010

Fully dense Ti3SiC2-64vol.%SiC(0.5m) composite materials are successfully fabricated by in situ synthesis under hot isostatic pressing. The high temperature flexure, tension and creep of Ti3SiC2-SiC composites were studied, and the results indicated that the composite had a high tensile strength under high temperature. Above 1000°C the composite were displayed a good high temperature plastic. The creep behavior is characterized by two regimes: an initial transient regime, where έ(dε/dt) decreases with t (time); a secondary creep regime in which έ is more or less constant with time.
Interfacial Microstructure and Strength of Vacuum Brazed Joints of Ternary Ceramics Ti3SiC2
Authors: Shi Li Ping , Zhong Ye Sheng , Yu Jia , He Xiao Dong
Published: April 2010

Ti3SiC2 is one of the nano-layered ternary ceramics Mn+1AXn, where M is a transition metal, A is an A-group (mostly IIIA or IVA) element, and X is C or N. With the filler of Ag-Cu-Ti, the brazing of Ti3SiC2 has been conducted at 800°C–950°C for 5-10min under 3.5×103Pa in a vacuum. The phase composition and microstructure of the joints were investigated by XRD, SEM AND EPMA. The diffusion of Cu element in fillers through the reaction zone toward Ti3SiC2 is the main controlling step in the bonding process. Joint strengths were evaluated by three point bending test. The maximum flexural strength of joints reaches is 306±11MPa, which is lower than the bending strength of Ti3SiC2, obtained under the same condition.
A New Technique for Testing Abrasion Resistance of Refractories at Elevated Temperatures
Authors: Peng Xi Gao , Sun Jia Lin , Shi Gan , Huang Shao Ping
Published: April 2010

Based on an extensive comparison of test methods for abrasion resistance from home and abroad, a new technique for abrasion resistance at elevated temperature has been developed with some improvements. Two connected airtight chambers are designed to prevent compressed air from entering the sample chamber, so that heat loss of the sample chamber can be reduced and the chamber temperature is less disturbed. The sample surface temperature can reach stable within 5 min and the temperature fluctuation on sample surface can be less than 20°C in the course of inleting the compressed air at working temperatures up to1400°C. The repeatability was tested using float-glass plate as reference sample at ambient temperature and using high alumina bricks for elevated temperature. A variation coefficient under 7% at ambient temperature has been achieved. Comparison of abrasion resistance at elevated temperature was tested respectively on a high alumina brick and on a silicon nitride bonded silicon carbide brick and the results could be significantly distinguished. Nitrogen can be blown into sample chamber during heating the furnace to prevent nonoxide bearing samples from being oxidized.
Microwave Dielectric Properties of Ca1-x(Li1/2Sm1/2)xTiO3 Ceramics
Authors: Li Yue Ming , Song Ting Ting , Hu Fei , Liao Run Hua , Zhang Bin
Published: April 2010

Ca1-x(Li1/2Sm1/2)xTiO3 microwave dielectric ceramics in the x range of 0.70 ~ 0.80 were prepared by conventional ceramics fabrication technique. The crystal structure, microstructure and microwave dielectric properties were investigated. The results showed that a single orthorhombic perovskite structure formed within this x range, and the substitution of (Li1/2Sm1/2)2+ ion for Ca2+ ion in A-site has a significant influence on the microwave dielectric properties of the ceramics. With the increase of substitution of (Li1/2Sm1/2)2+ ion with 0.75, the temperature coefficient of resonant frequency τf reaches zero, and it could be attributed that the Sm and Li have a polarizability effect according to its microstructure. The Ca0.25(Li1/2Sm1/2)0.75TiO3 ceramic had a good performance with microwave dielectric properties of τf = 0 ppm/°C, εr = 105.83, and Qf = 3170 GHz.
Ferroelectric and Dielectric Properties of Vanadium-Doped Bismuth Layer Sr2Bi4Ti5O18 Ceramics
Authors: Zhang Yan Jie , Xu Zhi Jun , Chu Rui Qing , Hao Ji Gong , Li Guo Rong , Yin Qing Rui , Zhu Pei Ying , Wu Xin , Lu Qing Jun , Ding Lei
Published: April 2010

Sr2Bi (4-x/3) Ti (5-x) VxO18 (x = 0.0-0.06) (SBTV) ceramics were prepared by a solid-state reaction method, and the ferroelectric and dielectric properties of the ceramics were investigated with respect to the amount of V deficiency. XRD analysis indicated that the oxide compounds were Aurivillius phases. The Curie temperature of SBTV ceramics was improved by doping of certain amount of V. The V deficiency also led to a steady increase in the density together with a decrease in the coercive field. For the ceramics with x = 0.06, the properties become optimum: d33 = 19 pC/N, Tc = 306oC, Ec = 43.7 KV/cm.
Structure and Dielectric Behavior of La-Doped BaTiO3 Ceramics
Authors: Li Wei , Xu Zhi Jun , Chu Rui Qing , Fu Peng
Published: April 2010

BaTiO3 ceramics doped with 1, 2, 3 and 4 mol% La were prepared by sol-gel method. The effects of La doping on structure and dielectric characteristics of Ba1−xLaxTiO3 were investigated. The results show that: All the powders calcined at 800°C were found to be perovskite structure with cubic phase. Ba1−xLaxTiO3 were sintered at 1300°C, phase transition behavior appeared from tetragonal phase to cubic phase with increasing La-doping level. As the doping concentration increases, the grain growth of the Ba1−xLaxTiO3 ceramics was controlled efficiently and Curie point shifted to lower temperature. The grain size decreased from 20μm with 0 mol% La doped to 0.5μm with 4 mol% La doped. The Curie point shift rate was 22 °C/ mol% with increasing La content. The dielectric constant of La doped Ba1−xLaxTiO3 ceramics increased with increasing La content and a maximum value of 8900 was attained with 4 mol% La doped.
Influence of Slight Bismuth Additive on the Properties of Calcium Copper Titanate Ceramic
Authors: Luo Feng Chao , He Jin Liang , Hu Jun , Lin Yuan Hua
Published: April 2010

The CaCu3Ti4O12 samples with slight amount of doped bismuth were prepared and tested in this research. No second phase with bismuth was found in the doped samples. It was inferred that the bismuth ions has entered the lattice and take the place of the calcium ions. The grain size was diminished with the increase of the bismuth content. The bismuth atoms can inhibit the grains from growing large, and it could be used to modify the microstructure of CaCu3Ti4O12 ceramic. The reduction of the grain size resulted in the decrease of the relative dielectric constant, according to the “internal barrier layer capacitance (IBLC)” theory. The impedance measurements showed that the doped samples have less conductivity and lower potential barrier at the grain boundaries, and the substitution of the bismuth ions on the calcium cites might be the reason for it. As a result of the lowered potential barrier, the non-ohmic I-V property of the CaCu3Ti4O12 ceramic almost disappears in the doped ones.
Electrical Properties of Bismuth-Layered Structural CaxSr2-xBi4Ti5O18 Ceramics
Authors: Fan Su Hua , Zhang Feng Qing , Che Q.D. , Yu R. , Hu W. , Tian Qing Bo
Published: April 2010

Effects of amount of Ca on crystal structure, microstructure, ferroelectric properties, and dielectric properties of the CaxSr2-xBi4Ti5O18 (CSBTi-x) ferroelectric ceramics were investigated. The results show that single-phase layered perovskite ferroelectrics were obtained and no appreciable secondary phase was found.Ca-doping results in a notable enlargement of remnant polarization 2Pr. The 2Pr of CSBT-0.15 reaches a large value, the remnant polarization 2Pr and coercive field 2Ec were 18.1µC/cm2 and 120.2kV/cm, respectively. Dielectric constant and dielectric loss of CSBT-0.15 was also measured, showing dielectric constant εr=199~194 and dielectric loss tanδ=0.02~0.014 over the range of 100 kHz~1MHz, respectively.
Co-Precipitation Synthesis of BiFeO3 Powders
Authors: Bo Hai Yang , Tan Guo Qiang , Miao Hong Yan , Xia Ao
Published: April 2010

Bismuth ferrite powders were synthesized by a simple citric acid complexing co-precipitation method at much lower temperature of 600°C. The work studies the calcination temperature and molar ratio of Fe and Bi on the structure and morphology. The as-prepared BiFeO3 powder was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope and Fourier transform infrared spectrophotometer. The result shows that the phase pure BiFeO3 powders with cubic morphology were prepared as the calcination temperature was 600°C and molar ratio of Fe and Bi was 1:1. The nanoparticles was uniform with the size of about 200nm.
SrTiO3 Functional Ceramics Thin Film Prepared by Self-Assembled Monolayers with PTCS Substrate Functionalization
Authors: Qin Bo , Tan Guo Qiang , Miao Hong Yan , Liu Jian , Xia Ao , Liu Ya Ya
Published: April 2010

This article used PTCS to dispose the self-assembled substrate, and prepared the precursor by the ratio of AHFT / SN / BA = 1:1:3 and then immersed the functionalized substrate into the precursor supersaturated solution. With the colloidal particles absorption induced by SAMs, SrTiO3 thin film was prepared by the self-assembled monolayers with liquid phase deposition method. The effects of the time of UV radiation and the time of PTCS immersion on the substrate contact angle were studied and the time of UV radiation had an effect on the substrate functionalization after PTCS immersion. The results showed that the first UV radiation for 25 min, PTCS immersion for 7 min and the second UV radiation for 30 min were beneficial to the crystallization of SrTiO3. XRD and AFM were used to characterize the thin film physical phase and surface morphology at 600oCwith annealing and heat retaining for 2 hours. The results also showed that under the same condition, the SrTiO3 crystals on the thin film surface had the clear outline and the spherical crystals were distributed regularly and evenly.