bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallel SMO for Traffic Flow Forecasting
Authors: Wang Fan , Tan Guo Zhen , Deng Chao
Published: January 2010

Accurate traffic flow forecasting is crucial to the development of intelligent transportation systems and advanced traveler information systems. Since Support Vector Machine (SVM)have better generalization performance and can guarantee global minima for given training data, it is believed that SVR is an effective method in traffic flow forecasting. But with the sharp increment of traffic data, traditional serial SVM can not meet the real-time requirements of traffic flow forecasting. Parallel processing has been proved to be a good method to reduce training time. In this paper, we adopt a parallel sequential minimal optimization (Parallel SMO) method to train SVM in multiple processors. Our experimental and analytical results demonstrate this model can reduce training time, enhance speed-up ratio and efficiency and better satisfy the real-time demands of traffic flow forecasting.
The Application of Data Mining in the Food Manufacturing Industry
Authors: Zong Chun Mei , Wang Hong Bin , Du Xue Juan
Published: January 2010

The paper first displays the feature of food, then points out the significance of putting into practice the Customer Relationship Management and supply chain administration in selling management, thereby draws out data mining. Finally, the paper describes the application of data mining in food.
The Application of Feature Mapping in Model Transformation of Turbine Blade
Authors: Cheng Rong
Published: January 2010

A transformation technology for part model to blank model based on feature mapping of turbine blade was prompted to improve the design efficiency of investment casting mold. The definition, feature presentation and feature mapping theory were researched. The feature and the geometry structure of turbine blade’s part mold, blank model and cavity mold were analyzed, and the feature mapping technology was prompted. At last, a mold transformation system was developed based on UG. Experiment result shows that with the help of this system, designers can improve design efficiency of investment casting mold of turbine blade.
Hierarchical Process Neural Network Model within Variable-Sampling Time
Authors: Chen Lei , Liu Fei
Published: January 2010

The biochemical processes are usually described as seriously time varying and nonlinear dynamic systems. It is very costly and difficult to build their first-principle models due to the absence of inherent mechanism and efficient on-line sensors. In this paper, a hierarchical process neural network (HPNN) model within variable-sampling time has been proposed. Simulation is based on penicillin fed-batch fermentation process, shows that the model established is more accurately and efficient, and suffice for the requirements of control and optimization for biochemical processes.
Attitude Stability Determination Based on RCS Series Information Extraction for Space Objects
Authors: Fu Xiong Jun , Wang Min , Wang Cai , Gao Mei Guo
Published: January 2010

Information extraction for space objects based on narrowband radars is still a hot spot in
the field of automatic target recognition. The attitude stability of space objects can be determined by
randomicity and periodicity detection for RCS series. In this paper, a nonparametric statistics theory
called run test is adopted to perform randomicity detection. Autocorrelation function and cepstrum
analysis are used to judge periodicity and estimate the rotate speed for rotary targets. What’s more, a
novel method is proposed here for attitude stability determination according to the rule of posture
angle altering. The experiments with real data indicate the effectiveness of the methods.
Early Warning Model of Enterprise Operating Ability Using BP Neural Network
Authors: Wang Mo Yu , Chen Jie , Shen Xiao Liu , Yu Gui Lin
Published: January 2010

With the increasing risk in electric power bureaus, warning risk of enterprise operating ability in advance is an important work. However it is very difficult to establish stable functions to describe the mapping relationship between operating ability and associated causal influences. Hence, early warning of the operating ability is harder. In this paper, an early warning model based on BP neural network is designed and put forward to forecast the risk of operating ability of an electric power bureau. In addition, illustration by the experiment is given. The stable and accurate analysis result of the experiment shows that this early warning model is applicable to forecast the risk of operating ability of electric power bureaus.
Parameter Estimation of Spaceborne SAR Based on the Combination of STFT and FRFT
Authors: Bai Jin Liang , Wu Rong Gang , Wang Jun Ling , Hong Yong Bin
Published: January 2010

A method of parameters estimation of spaceborne synthetic aperture radar based on combination algorithm of STFT and FRFT is proposed in this paper. Parameters here namely frequency centroid and frequency rate characterize the transmitted signal of spaceborne SAR. Estimation the parameters of the single way SAR signal is very important in ESM system. The combination algorithm of STFT and FRFT proposed in this paper overcomes the inaccuracy of direct estimation by STFT and large computation burden of pure FRFT. Simulation results show that this method is feasible and effective in improving the accuracy and reducing computational complexity for parameters estimation of spaceborne SAR.
Design of High-Speed Decoder for New High-Speed Bus
Authors: Zhang Wei Gong , Yang Bo , Ding Rui , Hu Yong Qin
Published: January 2010

This paper presents a new type of high-speed error correction for the requirements of new high-Speed Bus. Use RS (255, 239). Not only optimization traditional algorithm, but also design bidirectional synchronous calculated adjoint form module, Fast B-M algorithm module. and full parallel Chien Search module. These design used in new high-Speed Bus, Larger than usual decoder designed to significantly shorten the critical path decoding, and achieve continuous decoding. In addition, this error correction system separated error detection and correction module modules, And after error detection module add intelligent control, which reduced the complexity and power consumption of equipment. The error correction system design for the requirements of the new bus which speed is above 400m / s.
Constructing Ontology-Based Petroleum Exploration Database for Knowledge Discovery
Authors: Ge Ji Ke , Chen Zu Qin
Published: January 2010

Volumes of petroleum resources data are archived in different companies. Complex geospatial heterogeneous data structures complicate the accessibility and presentation of data in petroleum industries. Objectives of the current research are to integrate the data from different sources and connect them intelligently and semantically. Petroleum exploration databases provide a central focus for scientific communities as well as providing useful resources to aide research. However, such resources require constant curation and often become outdated and discontinued. In this research work, we develop an ontology-based system for managing petroleum exploration data that addresses the issues of data integration and information sharing. Ontology approach ensures petroleum data validity that will support petroleum knowledge discovery process.
The Architecture Framework with Exception Handing in SOA
Authors: Wu Qing , Ying Shi , Ni You Cong , Cui Hua
Published: January 2010

Service-oriented software systems are inherently complex and have to cope with an increasing number of exceptional conditions in order to meet the system’s dynamic requirements. This work proposes an architecture framework which has exception handling capability. This framework ensures the credibility of service-oriented software, during the architectural stage, by adding exception handling-related architecture elements and modeling exception handling process. It allows a clear separation of concerns between the business function and the exception handling unit, using reflection mechanism. It plays an important guiding role for achieving reliable service-oriented system.
Electrodeposition and Mechanical and Corrosion Resistance Properties of Tertiary Ni-W/Al2O3/CNT Nanocomposite Coatings
Authors: Aliofkhazraei Mahmood , Rouhaghdam Alireza Sabour , Ghobadi Ehsan , Mohsenian Ehsan
Published: January 2010

In this paper, the effects of the average size of nanometric particles (ASNP) from submicron scale (less than 1 µm) to nanometric scale (less than 10 nm) have been studied on the properties of nanocomposite layers which usually have not been studied or rarely studied. These properties consist of corrosion current density after long time immersion, roughness of obtained layer and distribution of nanometric particles. All of the other effective factors for fabrication of nanocomposite coatings have been fixed for better studying the effect of the ASNP. It has been seen that decreasing the ASNP will lead to lower corrosion current densities however in some cases pitting phenomena has been observed. The roughness illustrated a minimum level while the distribution of nanometric particles will be more uniform by decreasing the ASNP.
Barriers of Oxidation ans Ageing of Space Shuttle Material
Authors: Da Rold Guillaume , Guyon Cédric , Cavadias Siméon , Amouroux Jacques
Published: January 2010

During the atmospheric re-entry phase, the thermal protection of a spacecraft vehicle is submitted to air plasma. The transfer of the kinetic energy of the gases to the surface leads to an important heating of the nose cap and leading edges. The energy released from the recombination of oxygen atoms on the surface produces an additional amount of heat, increasing further the temperature. This excess of heat can damage the protection materials. This last mechanism leads to the oxidation of the surface and an accelerated ageing of the material. The oxidation produces a new surface layer of oxide such as SiO2 (Passive oxidation) and leads to the ablation of the material by the formation of CO, CO2, SiO and to the diffusion of oxygen in the bulk creating micro-cracks in the material (Active oxidation). Thus the composition of the surface and consequently the protection material properties are modified. The atmospheric re-entry conditions are created with a non equilibrium low pressure RF plasma chemical reactor. The ageing of the material and the diffusion of oxygen are studied by mass spectrometry analysis of 18O isotope for temperatures ranging from 300 – 1000 K. Silicon Carbide targets are covered with two different coatings, Chromium oxide, and Chromium oxide/ Silica. Oxygen diffusion in the material bulk for the targets was followed by Secondary Ion Mass Spectroscopy (SIMS).Mass Spectrometry shows the formation of CO and CO2 pointing out the process of ablation. This ablation is much lower in the case of polluted sample (with Chromium oxide). SIMS analyses show that Cr2O3 acts like a barrier in the oxidation of the material by limiting the diffusion of oxygen in the bulk.
Fracture Toughness of High-Performance Concrete on Three-Point Bending Notched Beams at Elevated Temperature
Authors: Djaknoun Samira , Ouedraogo Evariste , Benyahia Ali Ahmed
Published: January 2010

High-performance concrete (HPC) are advanced materials used in advances applications such as tunnels or nuclear power plant in which they can be accidentally submitted to severe stress or thermal conditions. The present study deals with the material response to thermal loading conditions. The main objective of this research is the characterization of the fracture toughness under Mode I at high temperature of high performance mortars by using notched specimens in three-point bending test in accordance with the RILEM recommendations. The mechanical loading is applied to the specimens while heated at various temperatures ranging from 25 to 900°C in isothermal conditions. The maximum applied load is found to be maximum at 300°C temperature and then to decrease sharply at higher temperatures. Analysis of SEM micrographs undertaken on the heated specimens after mechanical tests helps in the understanding of the material macroscopic behaviour. The evaluation of the material toughness during the hot testing is undertaken through analytical approach based on Fracture Mechanics. Lastly, the stress intensity factor as well as the energy of fracture evolves similarly versus temperature as the maximum applied load.
Experimental Study of Mandibular and Malar Distraction Osteogenesis Using Deos Device
Authors: Dubois Guillaume , Bonnet Anne Sophie , Lipiński Paul
Published: January 2010

Distraction Osteogenesis (DO) is a surgical technique used to reconstruct bone defects. In the maxillofacial specialty, it account for one of the best procedures to treat severe traumas as ballistic wounds. The evolution of forces acting during DO is known to be strongly linked with the clinical issue of the treatment. In this context, the aim of this study was to determine the time-dependent forces supported by a distraction device (DEOS, OBL, France), particularly indicated for severe traumas. Bone transport forces were evaluated for two patients undergoing respectively mandibular and malar DO following a gunshot wound. In order to evaluate the distraction forces, some fixing pins of the distraction device were equipped with strain gauges. Strain values were recorded by means of a data acquisition system (SCXI, National Instruments, USA) connected to a PC computer and executing a LabView program (National Instruments, USA). Records started about one minute before the DO activation and ended about one hour later. Eighteen measurements were done for both cases during the early phases of the treatment. An equilibrium analysis was achieved in order to determine the force and moment acting in bone regenerate from strains in the pins. This procedure was coded through a Fortran program, allowing to plot the evolution of DO force and moment. The present work confirmed the time-dependent feature of the bone regenerate mechanical behaviour. Important data have been obtained concerning forces and their evolution for both mandibular and malar DO.
High Pressure Torsion of Pure Ti: Effect of Pressure and Strain on Allotropy
Authors: Edalati Kaveh , Horita Z. , Tanaka Masaki , Higashida Kenji
Published: January 2010

High-pressure torsion (HPT) was conducted on commercial grade pure titanium (99.4%) by applying pressures in a wide range from 1.2 to 40 GPa. When the microhardness was plotted against equivalent strain, the hardness saturates to a constant level at each applied pressure. Such a level at the saturation depends on the applied pressure: for up to the pressure of 4 GPa, the saturation level is independent of the pressure but, for the pressures above 4 GPa, the hardness gradually increases with pressure because of the formation of an  phase. Bending tests showed that an excellent ductility as well as high bending strength was achieved for the sample processed at 2 GPa. The bending ductility was reduced for the sample at 6 GPa because of the  phase formation.
Elaboration of Sol-Gel Coatings from Aerogels and Xerogels of Doped Zirconia for TBC Applications
Authors: Fenech Justine , Viazzi Céline , Ansart Florence , Bonino Jean Pierre
Published: January 2010

Thermal Barrier Coatings (TBCs) are used as insulators on hot section components to reduce operating temperatures in aircraft engines and industrial gas turbine. The TBC system consists of two layers: the ceramic top coat traditionally Yttria Stabilized Zirconia (YSZ) with a low conductivity, and the bond coat generally MCrAlY, M=Ni and/or Cr or Co or Pd or Pt modified aluminides. In the industry, two dry-route processes used to deposit TBCs give quite different microstructures of coatings. In one hand, coatings resulted by plasma spraying (PS) present a lamellar microstruture with a low thermal conductivity in the range from 0.7 to 0.9 Wm−1K−1. In the other hand, Electron Beam Physical Vapour Deposition (EBPVD) coatings with columnar microstruture coatings present the best mechanical performances but perpendicular orientation of the columns makes their thermal conductivity twice higher compared to PS coatings. The present study proposes the elaboration of zirconia coatings via the sol-gel route combined with dip-coating process. It is a versatile process able to produce either thin ceramic coatings or thick deposits. The main advantage of this method is to decrease the crystallization temperature, much lower than conventional processes. Moreover, the sol-gel process is a nondirectional deposition technique, which is very different to the physical methods described above. Doped zirconia have been chosen to constitute isolating multilayers coatings. Sol formulation, slurries stability but also dip-coating conditions have been optimized in order to obtain homogeneous layers on nickel based superalloys substrates.
Plasma Surface Modification of 316L Stainless Steel for Cardiovascular Stent Coating
Authors: Gallino Enrico , Tatoulian Michael , Arefi-Khonsari Farzaneh , Mantovani Diego
Published: January 2010

Coronary stents are metallic (316L stainless steel) devices employed during balloon angioplasty to reopen and prevent the re-obstruction of a diseased narrowed area within a coronary artery. To reduce restenosis rate, bare metal stent coating is a promising solution. The coating can act as an anticorrosive barrier against the aggressive properties of biological environment, improving the long-term safety of the device. The goal of this study is to develop a dry process to isolate metallic surface from the biological environment by depositing a thin plasma polymerized allylamine (CH2=CH-CH2-NH2) film on the metallic surface. Plasma polymerized allylamine films were deposited on flat electropolished 316L stainless steel samples in a low pressure plasma reactor (70 kHz). Chemical composition of the coatings has been analysed as a function of the discharge power and treatment time. Moreover, special attention has been paid on the stability of the coating after immersion during 24 hours in D.I. water. Finally, to mimic stent expansion conditions, a “small punch test” has been used to investigate the adhesive properties of the coating. Our results demonstrate that is possible to deposit a stable, cohesive and adhesive plasma polymerized allylamine thin film which can be used as a coating for cardiovascular stents
Surface Microstructure and Texture Evolution during Interrupted Annealing in Ultra Low Carbon Steels
Authors: Gautam J. , Petrov Roumen H. , Kestens Leo A.I. , Leunis Elke
Published: January 2010

The austenite-to-ferrite phase transformation, which is an inherent feature of low-alloyed ultra low carbon steels, has scarcely been investigated to control surface texture and microstructure evolution. This paper investigates the systematic evolution of texture and microstructure at the metal-vapour interface during interrupted annealing in vacuum. Interrupted annealing experiments were carried out on three ultra low carbon steel sheets alloyed with Mn, Al and Si. The texture and microstructures have been investigated by X-ray diffraction and SEM-EBSD techniques. These results reveal a very clear variation in the surface texture components as well as in the surface microstructure after BCC recrystallisation and double  transformation interrupted annealing. The recrystallisation texture consists mainly of a <111>//ND fibre, while the transformation texture at the surface exhibits a <100>// ND fibre in combination with components of the <110> //ND fibre. It has been revealed that the latter specific surface texture was present in a monolayer of outer surface grains which were in direct contact with the vapour atmosphere. This observed phenomenon could be explained by considering the role of surface energy anisotropy occurring during phase transformation annealing.
Synthesis and Characterization of Ti2AlC and Ti2AlN MAX Phase Coatings Manufactured in an Industrial-Size Coater
Authors: Garkas W. , Leyens Christoph , Flores-Renteria A.
Published: January 2010

Due to a nanolaminate structure, MAX phases are materials with an interesting set of properties. The present paper is focussed on the synthesis and characterization of Ti2AlC and Ti2AlN MAX phase coatings. They were deposited by dc magnetron sputtering from single elemental Ti, Al, and C targets (Ti-Al-C system); in addition to Ti and Al, nitrogen was used for the Ti-Al-N system. XRD analysis revealed the growth of cubic Ti3AlC and Ti3AlN perovskite phases in the coatings deposited at 540°C. After coating deposition an annealing treatment at 800, 1000 and 1200°C was carried out. The results indicate that annealing for 1 h in vacuum at 800°C enhances crystallization of the Ti2AlN and Ti2AlC MAX phases. It was also observed that annealing at temperatures higher than 1000°C enhances the decomposition of both phases, Ti2AlC and Ti2AlN, and gives rise to the formation of the carbide and nitride phases TiCx and TiNx, respectively.
Effect of Strain Paths on Formability Evaluation of TRIP Steels
Authors: Gutiérrez David , Lara A. , Casellas Daniel , Prado Jose Manuel
Published: January 2010

The Forming Limit Diagrams (FLD) are widely used in the formability analysis of sheet metal to determine the maximum strain, which gives the Forming Limit Curve (FLC). It is well known that these curves depend on the strain path during forming and hence on the test method used to calculate them. In this paper, different stretching tests such as the Nakajima and the Marciniak tests were performed, with different sample geometries to obtain points in different areas of the FLD. An optical analysis system was used, which allows following the strain path during the test. The increasing use of advanced high-strength steels (AHSS) has created an interest in determining the mechanical properties of these materials. In this work, FLCs for a TRIP steel were determined using Nakajima and Marciniak tests, which revealed different strain paths depending on the type of test.

Determination of the FLCs was carried out following the mathematical calculations indicated in the ISO 12004 standard and was also compared with an alternative mathematical method, which showed different FLCs. Finally, the tests were verified by comparing the strain paths of the Nakajima and Marciniak tests with a well-known mild steel.
Exact Solutions for Powder Plastic Materials
Authors: Chesnikova Olga , Pirumov Alexander , Alexandrov Sergei
Published: January 2010

A comparative study of two analytic solutions for the classical plasticity of incompressible materials and a plasticity model for powder materials is made to reveal an effect of plastic compressibility on qualitative behaviour of the velocity field in the vicinity of maximum friction surfaces.
Microstructural Evolution during Gas Tungsten Arc, Laser and Resistance Spot Welding of Al-Containing Transformation Induced Plasticity (TRIP) Steel
Authors: Amirthalingam M. , Hermans M.J.M. , Richardson I.M.
Published: January 2010

In this work, the microstructural evolution of aluminum containing commercial grade TRIP steels during gas tungsten arc (GTA), Laser beam (LB) and resistance spot (RS) welding have been studied. Microstructural analysis was carried out using optical and scanning electron microscopy. Results show that fusion zones of welded TRIP steels contain complex inclusions with similar size distribution. The energy dispersive spectroscopy analysis of inclusions indicated that these inclusions are primarily oxides of aluminum with epitaxial enrichment of manganese and phosphorous. The fusion lines of GTA and LB welded aluminum containing TRIP steel contain a zone of polygonal ferrite with a size of about 200 m and 50 m respectively. It is found that aluminum partitioned from the liquid weld to the solidified delta ferrite in the fusion line causing enrichment and resulting in ferrite stabilisation. This ferrite zone was not found in the case of resistance spot welded samples due to faster cooling rates.
Isothermal Aging Behavior in Ti-10 Cr-Al Alloys for Medical Applications
Authors: Hatanaka Shota , Ueda Masato , Ikeda Masahiko , Ogawa Michiharu
Published: January 2010

The effect of Al addition on the elastic modulus and aging behavior in Ti-10 Cr alloys was investigated by means of electrical resistivity, X-ray diffractometry and Vickers hardness measurements. All of the alloys used were formed from solutions treated at 1173 K for 3.6 ks and then quenched into ice water (STQ). Following STQ, all Al-containing specimens exhibited a  phase, with the athermal  appearing only for alloys with zero Al addition. The elastic modulus was found to decrease with addition of Al from approximately 80 to 70 GPa, due to the suppression of the athermal . The specimens following STQ were isothermally aged at 573 K, 673 K and 773 K. The addition of Al was found to retard the onset of precipitation of the isothermal  phase and decrease the upper limit temperature for precipitation of this phase. On the other hand, as the Al content was increased, precipitation of the  phase was accelerated in the presence of an existing isothermal  phase. By contrast, this precipitation was suppressed under single  phase conditions. Surface modification for osteointegration was also performed. When the modified specimens were immersed in simulated body fluid, the surface modification was found to promote the deposition of HAp.
An Assessment of Bulk and Local Stored Energy Measurements in Ultrafine Grained Interstitial Free Steel
Authors: Hazra Sujoy S. , Gazder Azdiar , Pereloma Elena V.
Published: January 2010

The evolution of stored energy and associated thermal behaviour was investigated for an ultrafine grained Ti-IF steel severely deformed by Equal Channel Angular Pressing (ECAP) followed by cold rolling at ambient and liquid nitrogen temperatures. Bulk stored energy measurements by Differential Scanning Calorimetry (DSC) returned 350-600 whereas local stored energy estimates from microhardness, Electron Back-Scattering Diffraction (EBSD) and X-ray line profile analysis resulted in 5-140 . Higher bulk stored energy values correspond to the enthalpy release from all sources of strain in the material volume as well as Ti precipitation during annealing while the lower local stored energy range alludes only to dislocation content or internal stresses. An apparent activation energy of 500-550 suggests sluggish recrystallisation due to excess of Ti in solid solution.
Numerical Modelling of the Compression Behaviour of Single-Crystalline MAX-Phase Materials
Authors: Jiang Janna , Nylén Per
Published: January 2010

In this article a numerical model to describe the mechanical behaviour of nanophased singlecrystalline Ti3SiC2 is proposed. The approach is a two dimensional finite element periodic unit cell consisting of an elastic matrix interlayered with shear deformable slip planes which obey the Hill’s yield criterion. The periodic unit cell is used to predict compression material behaviour of Ti3SiC2 crystals with arbitrary slip plane orientations. Stress strain relationships are derived for Ti3SiC2, and the effect of slip plane volume fraction as well as orientation of the slip planes are investigated. The two main deformation mechanisms of the material namely; ordinary slip and so called kinking are considered in the study.
Numerical and Experimental Study of Residual Stresses in a Linear Friction Welded Al-SiCp Composite
Authors: Jun Tea Sung , Song Xu , Rotundo Fabio , Ceschini Lorella , Morri Alessandro , Threadgill Philip L. , Korsunsky Alexander M.
Published: January 2010

In the present study, the process modelling of AMCs linear friction weldment was carried out. Four major stages of the process (Part 1: Warm-Up; Part 2: Osci-Forging; Part 3: Forging; Part 4: Cool-Down) were identified and simulated consecutively to generate the temperature field and residual strains distribution within the model. An eigenstrain model calibrated by the neutron diffraction results was also employed to capture the permanent deformation distribution. Good agreement between the process modelling and the experimental measurements was found.
Predicting the Effect of Compressive and Tensile Residual Stresses in Fracture Mechanics Specimens
Authors: Kamel S. , Wimpory Robert C. , Hofmann Michael , Nikbin Kamran M. , O'Dowd N.P.
Published: January 2010

This paper considers the prediction of the effects of tensile and compressive residual stress in fracture mechanics specimens by the application of a mechanical pre-load. This is considered in the context of a ‘C’ shape specimen which is mechanically pre-tensioned or pre-compressed to produce, respectively, a compressive or tensile residual stress in the region where the crack is introduced. Finite-element analysis is performed to simulate the pre-loading and the subsequent fracture loading of the cracked specimens. The finite-element predictions are compared with experimental data including residual stress measurements using neutron diffraction. A discussion is presented on modelling and material issues pertaining to the use of mechanical pre-loading as a means for introducing residual stress.
Density Gradient Materials by Direct Metal Laser Sintering
Authors: Kang Hyun Goo , Osada Toshiko , Miura Hideshi
Published: January 2010

The direct metal laser sintering process was applied to produce density gradient materials of stainless steel 316L. In order to understand the mechanism of forming porous structure, the influence of laser power, scan rate and scan pitch on the porosity were investigated by measuring density of produced samples and observing cross-sectional microstructures. Laser power greatly affected to the porosity by forming clusters of melted metal powders. It was found that the size change of clusters plays a role in forming porous structure. Eventually, three dimensional sample owing density gradient structures was manufactured.
Effect of Heat Treatment on Mechanical Properties of Super Duplex Stainless Steel
Authors: Kim Sun Mi , Kim Kwang Tae , Lee Yong Deuk , Lee Chong Soo
Published: January 2010

A study was made to investigate the precipitation behavior of sigma phase via various heat treatments and corresponding mechanical properties of super duplex stainless steels. Isothermal heat treatment was performed at temperature range of 600~1000°C to draw TTT diagram for sigma phase. Tensile and Charpy impact tests were performed at room temperature and the results were analyzed in relation with the microstructure. The effect of lattice misfit strains due to the precipitation of sigma phase on the mechanical properties was also discussed.
Effect of Cold Deformation upon Ageing of Superaustenitic Stainless Steels
Authors: Koutsoukis T. , Zormalia S. , Kokkonidis P. , Papadopoulou E. , Tsakiridis P. , Fourlaris G.
Published: January 2010

Cold rolling followed by ageing in two grades of superaustenitic stainless steel was performed in order to assess the effect of cold deformation on the precipitation characteristics of these steels. Samples were cold rolled from 20% to 60% reduction in thickness and aged within the temperature range of 650οC to 950οC for times up to 120h. Following ageing precipitation of secondary phases took place, with sigma (σ) phase formation being the predominant precipitate species forming. Secondary phases have been reported to form following isothermal exposure to high temperatures, yet the precipitation behaviour of cold deformed samples has received less attention. When compared to the ageing characteristics of undeformed samples, cold deformation was found to accelerate precipitation during ageing. This study helped clarify a time-temperature-transformation regime relating isothermal ageing of cold deformation that could be applied to these steels in order to avoid occurrence of undesirable microstructural constituents with the associated reduction of mechanical and corrosion properties.
The Optimization of Calciothermic Reduction-Diffusion Process for Preparation of High-Performance Sm2Fe17Nx Magnetic Powder
Authors: Lee Jung Goo , Yun J.C. , Lee Jai Sung , Choi C.J.
Published: January 2010

Calciothermic reduction-diffusion (CRD) method was employed to prepare the Sm2Fe17 powder. By using CRD method, single-phase Sm2Fe17 powders were successfully made and no α-Fe phase detected. And Subsequent suitable nitrogenation treatment after CRD process enabled us to obtain Sm2Fe17Nx magnetic powders. However, the magnetic performance of the powders was below expectation due to their large particle size. Further study on effective milling process is needed.
Evaluation of the Work-Hardening of Brass Sheets Following Strain Path Changes
Authors: Lopes Wellington , Siqueira Corrêa Elaine Carballo , Béria Campos Haroldo , Paulino Aguilar Maria Teresa , Cetlin Paulo Roberto
Published: January 2010

The strain paths followed by metals during sheet forming can be quite complex, especially when successive forming steps are involved. The work hardening of metals associated with these strain paths differs from that caused only by monotonic straining, such as simple tension or compression. It is important to have an adequate description of the work hardening of the material under processing, especially when numerical simulations of the forming are used. The experimental evaluation of the effect of strain path changes on the material work hardening is usually performed through tensile testing following the strain path changes. This technique, however, demands complex machining operations of the formed sheets and the imposed strain is severely limited by impending necking. The present paper utilizes simple shear as a tool for the determination of the work hardening of CuZn34 brass sheets following various strain path changes associated with combinations of different modes of deformation such as rolling, tension, cyclic and forward shears. The results indicate that the cyclic shearing delays the occurrence of plastic instabilities for brass previously tensioned, occurring the opposite for final monotonic shearing. These phenomena were correlated with the probable microstructural evolution of the CuZn34 brass.
Quantitative Analysis of Variant Selection and Orientation Relationships during the γ-to-α Phase Transformation in Hot-Rolled TRIP Steels
Authors: Malet Loïc , Jacques Pascal J. , Godet Stéphane
Published: January 2010

The orientation relationships that apply to the fcc (γ) – bcc (α) phase transformation in high-performance hot-rolled TRIP-aided steels were characterised by EBSD techniques. A statistical treatment of the experimental data allows the mean orientation relationship to be determined. This mean orientation relationship was compared to the models commonly proposed in the literature and confronted qualitatively to the predictions of the phenomenological theory of martensite crystallography (PTMC). The variant selection phenomenon was also characterized quantitatively at the level of individual austenite grains. The reconstruction of the EBSD maps evidences that bainite grows by packets in which the bainite laths share a common {111}γ plane in the austenite. This growth mechanism is not influenced by the prior hot deformation of the austenite. The hot deformation has a critical influence on the number of packets that forms. The analysis of the crystallographic features of the bainite packets reveals that all possible variants are formed in a packet, though in different proportions.
Effect of High Pressure Torsion on Crystal Orientation to Improve the Thermoelectric Property of a Bi2Te3-Based Thermoelectric Semiconductor
Authors: Ashida Maki , Hamachiyo Takashi , Hasezaki Kazuhiro , Matsunoshita Hirotaka , Horita Z.
Published: January 2010

A Bi2Te3-based thermoelectric semiconductor was subjected by high pressure torsion (HPT). Sample disks of p-type Bi0.5Sb1.5Te3.0 were cut from sintered compacts that were made by mechanically alloying (MA) followed by hot pressing. Disks were subjected by HPT with 1, 5 and 10 turns at 473 K under 6.0 GPa of pressure. Crystal orientation was investigated by X-ray diffraction. Microstructures were characterized using scanning electron microscopy. Results indicated that HPT disks after 5 turns had a preferred orientation and a fine grain compared with pre-HPT disks while the orientation factor was decreased after HPT using 10 turns. The power factor had a maximum value at 5 turns as determined by measuring its thermoelectric properties. A maximum power factor of 4.30×10-3 Wm-1K-2 was obtained for HPT disks after 5 turns. This value was larger than that for the pre-HPT disk. The over-HPT of 10 turns was found to have caused a decrease in the preferred orientation leading to a low power factor.
Iron Oxide Nanoparticles: Novel Drug Delivery Materials for Treating Bone Diseases
Authors: Tran Nhiem , Pareta Rajesh A. , Taylor Erik , Webster Thomas J.
Published: January 2010

Magnetic nanoparticles have been used extensively as drug delivery materials in recent years [1,2]. The present research goal is to treat bone diseases (such as osteoporosis and infection) by using surface modified magnetic nanoparticles. Magnetite (Fe3O4) and maghemite (Fe2O3) were synthesized and coated with calcium phosphate (CaP). The resulting nanoparticles were treated hydrothermally to change the crystalline properties of CaP. Nanoparticles were characterized via transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). TEM was also used to study the uptake of nanoparticles into osteoblasts (OB) and bacteria. OB proliferation experiments were conducted after 1, 3 and 5 days in the presence of the various iron oxide nanoparticles alone and CaP coated iron oxide magnetic nanoparticles. OB proliferation experiments were also conducted after 1, 3 and 5 days in the presence of various concentrations of CaP coated nanoparticles to examine a possible concentration dependent trend on OB density. Staph epidermidis were incubated with different doses of Fe3O4 to determine the effect of these nanoparticles on bacteria activity. Results of this in vitro study demonstrated greater OB functions and inhibited bacteria functions in the presence of select magnetic nanoparticles. In summary, the results of this study showed that magnetic nanoparticles should be further studied for various orthopedic applications.
Effect of Weld Tip Geometry on Ultrasonic Welding between Steel and Aluminum Alloy
Authors: Nishihara Kosuke , Watanabe Takehiko , Sasaki Tomohiro
Published: January 2010

In this study, authors investigated the effect of horn tip geometry on the mechanical properties of a joint ultrasonically welded between a mild steel sheet and an aluminum alloy sheet. Two types of weld tips with the different contact face geometries were employed. One type of a tip has a cylindrical contact face without knurl. The other type of a tip has flat contact face with knurl. The main results obtained in this study are as follows.
Authors successfully welded the mild steel sheet to the aluminum alloy sheet using both of the weld tips. However, the strength of the joint welded by the tip with cylindrical geometry was higher than that welded by the flat tip with knurl under the same welding condition, and the strength of the joint by the tip with cylindrical geometry was twice larger than that by the flat tip with knurl under the optimal welding condition.
The strength of the joint increased with increasing the welding time and the clamping force, and showed the maximum under the reasonable welding condition. Excessively long welding time and large clamping force damaged the workpiece surface contacted the horn side tip, resulting in the decrease of the joint strength.
It was possible to improve the joint strength using commercially pure aluminum foil with suitable thickness as insert metal.
Long-Term Corrosion Resistance of Biomedical Grade Stainless Steel ISO 5832-1 ("316LVM") under External Anodic Electrical Pulsing Conditions
Authors: Rebentisch Ronald , Lange Regina , Beck Ulrich
Published: January 2010

For medical implant application of metals or alloys, one major prerequisite is the absence of release of metal ions to the surrounding tissue. In the case of stainless steel, this prerequisite can be achieved by modifying the surface by chemical and electrochemical passivation pre-treatments so that the general corrosion-rate will be reduced and pitting corrosion will not occur. In a first step, the surface of the test specimens (10 mm diam.) were chemically pre-treated with nitric acid using different concentrations and duration. In the second step, the passivation effect was tested by applying voltage-scans reaching from hydrogen to oxygen evolution in a 3-electrode CV-measurement using phosphate buffered saline (PBS) (pH7.4) as electrolyte. It turned out that after the 2nd of a total of five scans all CV-diagrams looked almost the same and the chemical passiva-tion treatment was of minor effect; none of the CV-diagrams showed effects of pitting corrosion. The third step was to apply external electrical anodic pulses (n=5.3x106) on the surface of the specimen (+4.5V, 0.5ms, 740Hz). In the forth step, the passive behaviour again was tested using the same CV-measurement setup. Again, no effect of pitting corrosion was seen and in parts of the CV-diagrams the measured current signal was less than before.
Recrystallization and Grain Growth Behavior of SPD Deformed 316L Stainless Steel
Authors: Scheriau Stephan , Schöberl Thomas , Kleber Siegfried , Pippan Reinhard
Published: January 2010

The microstructural evolution, the changes in microhardness and the recrystallization behavior of a modified 316L stainless steel were investigated during high pressure torsion (HPT) and subsequent annealing. To study the impact of the governing process parameters on the evolving microstructures, the applied strain, the strain path and the annealing temperatures were varied. In contrast to ordinary single phase steels, which showed a decrease in the structural size ending in a saturation of the microstructural refinement between an equivalent strain eq of 10 and 15, HPT of the modified 316L results in a steep increase in shear stress at very small strains and the saturation region is reached far before eq = 10. Studies using the transmission electron microscope (TEM) revealed that at large strains the original coarse grains are converted by the massive intersection and fragmentation of twins into a nanometer-scaled microstructure. In the case of monotonic HPT, shock annealing of the deformed discs results in rows of fine and coarse grains. In the cyclic deformed discs a homogenous, fine-grained and almost fully recrystallized microstructure was observed. The results clearly show that both the strength and ductility of the material can be significantly influenced by SPD and subsequent annealing. Possible reasons for the observed differences in the deformation and annealing behavior are discussed.
In Situ X-Ray Diffraction Investigations during Diffusion Anneals of Ni-Cu Thin Film Diffusion Couples
Authors: Sheng J. , Welzel U. , Mittemeijer Eric Jan
Published: January 2010

The stress evolution during diffusion annealing of Ni-Cu bilayers (individual layer thicknesses of 50 nm) was investigated employing ex-situ and in-situ X-ray diffraction measurements. Annealing at relatively low homologous temperatures (about 0.3 - 0.4 Tm) for durations up to about 100 hours results in considerable diffusional intermixing, as demonstrated by Auger-electron spectroscopy investigations (in combination with sputter-depth profiling). In addition to thermal stresses due to differences of the coefficients of thermal expansion of layers and substrate, tensile stress con-tributions in the sublayers arise during the diffusion anneals. The obtained stress data have been discussed in terms of possible mechanisms of stress generation. The influence of diffusion on stress development in the sublayers of the diffusion couple during heating and isothermal annealing was investigated by comparing stress changes in the bilayer system with corresponding results obtained under identical conditions for single layers of the components in the bilayer system. The specific residual stresses that emerge due to diffusion between the (sub)layers in the bilayer could thereby be identified.
Analysis of Surface and Subsurface Layers after Shot Peening of Various Aluminium Alloys
Authors: Žagar Sebastjan , Grum Janez
Published: January 2010

In the paper two aluminium alloys, i.e. 6082 and 7075, which were cold hardened by shot peening under different conditions, are treated. Surface hardening was carried out with S170 steel shot of the same diameter, particle hardness being 56 HRC. Other conditions were the operating pressure, mass flow, which provide different Almen intensities. The hardened layer was described by surface integrity. Macroscopic and microscopic analyses consisted in analyses of hardened profiles of hardness, and residual stresses in the thin surface layer. Research results indicated that there were significant differences among the characteristics chosen to describe surface integrity and that they had an important influence on the final condition of the surface layer. With too severe settings of the peening parameters, the surface properties got worse because of damages, which resulted in crack initiation and growth of the existing cracks.
Nucleation at Cube Bands during Recrystallisation in Commercial Al Alloy
Authors: Sukhopar Olga , Schäfer C. , Gottstein Günter
Published: January 2010

In the present study, nucleation at Cube bands during annealing of a cold rolled commercial aluminium alloy AA8079 was investigated. The main goal of this work was to provide experimental data for subsequent modelling. By studying the deformed material the geometrical parameters of Cube bands were determined. The Cube band spacing in the deformed state was measured experimentally and accordingly calculated with a simple geometric model, taking the initial Cube fraction in the pre-deformed state and the deformation degree into account. The nucleation frequency during subsequent annealing of the cold deformed material was estimated from the geometry and size of deformed Cube bands prior to deformation. From investigations of the orientation relationship between the Cube oriented nuclei and the adjacent deformed matrix with S orientation, the fraction of 40°<111> grain boundaries having optimum growth conditions, was established.
Effect of Substrate Constraint on Stress-Induced Deformation Mechanism of Tungsten Thin Film
Authors: Sun H.L. , Ma Fei , Song Zhong Xiao , Li Yan Huai , Xu Ke Wei
Published: January 2010

The deformation process of sputtered tungsten films were investigated according to the morphological characteristics and residual stress analysis. Results show that there are four characteristics depending on the substrates and stress state. For thin films on polyimide, the localized plastic deformation is mediated by the alignment of grain boundaries in the case of tension or line bulges in the case of compression. It results from both in-plane and out-of-plane grain rotation. For thin films on silicon substrate, wedge cracks in the case of tension or regular hillocks in the case of compression become the typical morphology. From this point of view, the deformation behaviors of films depended on the substrate constraint and residual stress states.