bluuebunny/crossref_metadata_2025 huggingface dataset:
Empirical Method of Atmospheric Refraction Error Correction in Optical Low-Level Measuring
Authors: Xiao Ying , Dong Yu Hua
Published: May 2010

This paper proposed a empirical method of atmospheric refraction error correction in optical low-level measuring. The experience attenuation coefficient was derived by using the data of previous tests, then it solved the problem of atmospheric refraction error correction under the condition does not have a sounding measurements. At the same time, this paper deduced the empirical formula of atmospheric refraction error correction in low-level measuring, using the empirical formula of atmospheric refraction error correction can overcome the stationary point problem in the traditional method when computing for the negative to positive angle(< ). The effectiveness was verified by the results of test data processing.
Vehicle Swarm Motion Coordination through Independent Local-Reactive Agents
Authors: Yu Chun Yan , Wu Ming Hui , He Xiao Sheng
Published: May 2010

Vehicle swarm refers to a group of autonomous vehicles. Vehicle swarm motion coordination is a difficult problem in Intelligent Transport System. Due to similar characteristics of reactive agents and autonomous vehicles relying on self-organization principles, this paper presents reactive agent driven motion coordination for vehicle swarm that adopts large-scale independent local-reactive agents to perform a self-organized motion coordination control mechanism, which is composed of a network of swarm collaborative agents, a set of dynamic hybrid local networks of individual swarm collaborative agent and vehicle autonomic agents, and a homogenous self-organized motion coordination control protocol for individual vehicle autonomic agent’s self-adapting motion.
Leakage Power Estimation of Adiabatic Circuits Using SPICE in Nanometer CMOS Processes
Authors: Wu Yang Bo , Hu Jian Ping , Li Hong
Published: May 2010

In deep sub-micro CMOS process, the leakage power is becoming a significant proportion in power dissipation. Hence, estimating the leakage power of CMOS circuits is very important in low-power design. In this paper, an estimation technology for the total leakage power of adiabatic logic circuits by using SPICE is proposed. The basic principle of power estimation for traditional CMOS circuits using SPICE is introduced. According to the energy dissipation characteristic of adiabatic circuits, the estimation technology for leakage power is discussed. Taken as an example, the estimation for total leakage power dissipations of PAL-2N (pass-transistor adiabatic logic with NMOS pull-down configuration) circuits is illustrated using the proposed estimation technology.
The Property of Kippenhahn Curves of Kronecker Sum and Applications
Authors: Zhao Wen Ling
Published: May 2010

In many physical applications, we must solve a system of linear equations such as . The Kronecker sum can get a convenient representation for linear equations . In this paper, let and be denoted reducible companion matrices. We study the property of the Kippenhahn curve and of the numerical rang being an elliptic disc by making use of matrices Kronecker sum and the Kippenhahn curve continually.
A Sensitive Technique of Airflow Omnibearing Level Posture
Authors: Piao Lin Hua , Li Yan Jie , Li Bai Hua , Ji Ming Ming , Zhang Xue Yan
Published: May 2010

The paper firstly introduced the sensitive mechanism of micromachined airflow omnibearing level posture. There is a non-closure annulus heat source in the airtight space, and around the heat source, there are eight parallel heat resistance wire composed omnibearing level posture sense organ. Signal processing circuit is composed by pre-signal circuit and digital circuit, to obtain voltage, omnibearing signal synthesis and resolution compensation of omnibearing tile angle signal. It is testified that: resolution<0.1°,the scope of azimuth is 360°,the scope of tile angle is 20°. The sensor is not only in small size but also in simply crafting. It is good in sensitive organ’s output consistency, and suitable for mass production.
Research on the Pressure Fluctuation in Draft Tube Based on the Sparse Bayesian
Authors: Wang Li Ying , Zhao Wei Guo , Zhang Ji Gao
Published: May 2010

Relevance Vector Machine (RVM) is a novel kernel method based on Sparse Bayesian, which has many advantages such as its kernel functions without the restriction of Mercer’s conditions, the relevance vectors automatically determined and fewer parameters. In view of the actual situation that the corresponding space curved surface which expressed the characteristics of pressure fluctuation is too complex to be analyzed, the RVM regression model for describing the characteristics which is nonlinear relationship among pressure fluctuation value，unit rotation and unit discharge is established，and it is applied to hydropower station. Comparing with Support Vector Machine (SVM), the experimental results show the final RVM model achieved is sparser, the prediction precision is higher and the prediction values are in better agreement with the real values.
A Measurement Approach for Critical Voids in Mineral Aggregate Based on AC-20
Authors: Ning Chen , Wang Ming Hui
Published: May 2010

The voids in the mineral aggregate (VMA) is considered to be the most important mix design parameter which affects the durability of the asphalt concrete mix. This has traditionally been addressed during mix design by meeting a minimum voids in the mineral aggregate (VMA) requirement, based solely upon the nominal maximum aggregate size without regard to other significant aggregate-related properties. The goal of this study is to determine the validity of the minimum VMA requirement versus nominal maximum aggregate size required in Marshall volumetric mix design. Specimens were compacted using the Superpave Gyratory Compactor (SGC), conventionally tested for bulk and maximum theoretical specific gravities and physically tested using the thiaxial creep test system under a repeated load confined configuration to identify the transition state from sound to unsound. AC-20 was classified in the light of fine, dense and coarse gradation. The AC-20C, AC-20D and AC-20F asphalt mixtures were tested as the object of study. The results clearly demonstrate that the volumetric conditions of an VMA mixture at the stable unstable threshold are influenced by a composite measure of the aggregate size gradation .The currently defined VMA criterion, while significant, is seen to be insufficient by itself to correctly differentiate sound from unsound mixtures. Under current specifications, many otherwise sound mixtures are subject to rejection solely on the basis of failing to meet the VMA requirement. Based on the laboratory data and analysis, a new paradigm to volumetric mix design is proposed that explicitly accounts for aggregate gradation factors.
On-Line Measuring System for Urban Highway Traffic Flow Based on Video Detection Technique
Authors: Ning Chen
Published: May 2010

In intelligent transportation systems (ITS) for urban highway-nets, the data of traffic flow is very important to control and lead to traffic. According to chromatic aberration between vehicles and road surfaces in images caught from moving vehicles, a new method is proposed to analyze on-line traffic states based on video detection technique. firstly video for 10 frame/second sampling, difference operation of same region of two neighbored image is used to detect moving vehicle very quickly on measurement strap; secondly the result of difference was grayed ,horizontal projection and adaptive threshold methods are adopted to recognize moving vehicle and type of vehicle by statistical analysis, which is very expedient, accurate and quick. The results of experiments show that the correct recognition rate of this system reaches up to 96%.And the combination of phase control of road control, which can intelligent lead to traffic by on-line and satisfies the requirements of practical application.
Application of Bayesian Learning Mechanism in Power System Transient Stability Assessment
Authors: Niu Lin , Zhao Jian Guo , Li Ke Jun , Zhou Zhen Yu
Published: May 2010

One of the most challenging problems in real-time operation of power system is the prediction of transient stability. Fast and accurate techniques are imperative to achieve on-line transient stability assessment (TSA). This problem has been approached by various machine learning algorithms, however they find a class decision estimate rather than a probabilistic confidence of the class distribution. To counter the shortcoming of common machine learning methods, a novel machine learning technique, i.e. ‘relevance vector machine’ (RVM), for TSA is presented in this paper. RVM is based on a probabilistic Bayesian learning framework, and as a feature it can yield a decision function that depends on only a very fewer number of so-called relevance vectors. The proposed method is tested on New England power system, and compared with a state-of-the-art ‘support vector machine’ (SVM) classifier. The classification performance is evaluated using false discriminate rate (FDR). It is demonstrated that the RVM classifier can yield a decision function that is much sparser than the SVM classifier while providing higher classification accuracy. Consequently, the RVM classifier greatly reduces the computational complexity, making it more suitable for real-time implementation.
Assessment of An Advanced Traffic State Detector
Authors: Liu Hao , Yuan Yuan , Niu Shu Yun
Published: May 2010

This paper conducts an evaluation of a new traffic state detector. Compared with traditional traffic detector, this new detector can provided traffic state directly. A comprehensive assessment of this traffic state detector is described in this paper. Microwave traffic detector is used as reference. The results collected from both traffic state detector and microwave detector are investigated. Some interesting findings will be summarized in this paper.
The Development of an Online Reading Literacy Assessment
Authors: Hung Pi Hsia , Huang Chi Jung , Yeh Ya Hsiu , Chang Kuei Lin
Published: May 2010

The purpose of this study is to develop an innovative assessment to explore the characteristics of Taiwanese eighth graders’ online reading literacy. The online reading literacy assessment (ORLA) is designed based on PISA’s Electronic Reading Assessment Framework which contains three reading processes: retrieving information, interpreting information, and reflecting on and evaluating content of texts. There are 176 eighth graders sampled from three schools in Tainan districts. The results indicate that ORLA is a valid but relatively difficult test for most of eighth graders. The internal consistency Alpha is .65. The correlation coefficient between ORLA and the computerized reading comprehension test (CRCT) is .51. In other words, online reading literacy is reasonably independent from reading comprehension. The tasks of online searching and integrating different sources of information are functioning differently from the conventional reading tasks. The correlation coefficients between ORLA and the school grades of five subjects (English, Science, Mathematics, Social Science, and Chinese) ranged from .36 to .54. The pattern of correlation coefficients demonstrates sensible supporting evidences for the convergent and discriminant validity.
Effect of Rare Earth La2O3 on Digestive System of the Red-Eared Slider
Authors: Li Xue Bin , Yu Xiao Ling , Wang Tie Gu , Su Sheng Yan , Zhao Kun , Zhang Xiao Jian
Published: May 2010

Numerous studies reported that mixtures of Rare Earth Elements (REEs) could produce quite sensational growth-promoting effects in all categories of farm animals; but many people thought that REEs could affect human healthy. Therefore, experiments were done to understand the effects of La2O3 on red-eared sliders. The results showed that lower dose of La2O3 could probably improve the metabolism of Red-eared Slide turtle, and the higher dose of La2O3 could probably cause pathologic reaction. Lanthanum trichloride (La) could cause the Histological changes in tortoise livers. A very lower dosage of La2O3 could damage the livers of red-eared slides obviously though diversity pathway. The wild animal should be protected from harm in the RE diggings. If the RE is used or must be used as an additives in animal foods, an appropriate dose of RE was necessary, and the safety evaluation should be done.
Research on Resource Allocation Algorithm Based on MAS Cooperative Technology
Authors: Shi De Jia , Jiang Wei Jin , Liu Zhi Qiang , Wang Li
Published: May 2010

With MAS(Multi Agent System)coordinated technology and market bidding game rules, a grid resource allocation model based on market economy was introduced, which could show the relation between supply and demand. The utility function of consumer was given; The results of emulation test showed that the resource allocation algorithm could be a reference to resources of consumers and the approach significantly improves resource utilization, which made the allocation of the whole network resource tend to be more reasonable.
A Methodology to Assure Measurement Data Quality for Key Engineering Materials
Authors: Su Ying , Huang Jing Hua , Al-Hakim Latif
Published: May 2010

Purpose – Only limited attention has been paid to the issue of Measurement Data Quality (MDQ) in a metrology context. To address this critique of the literature a methodology to assure MDQ was proposed. Methodology – The study proposes a methodology which consists of four steps can be used to 1 identify the importance of a measurement (identification), 2 determine accuracy and precision (determination), 3 evaluate the criticality of the measurement to its impact on the final result (evaluation) and 4 record the facts that influenced the decision making process (documentation). Findings –When followed and properly documented, these four steps can help ensure our measurements are valid and worthwhile. Identifying the important measurements that are made, determining the level of accuracy required and then using the proper tools to make the measurements will yield valid, useful results.
An On-Line ANN-Based Approach for Quality Estimation in Resistance Spot Welding
Authors: El Ouafi Abderrazak , Bélanger Rudy , Méthot Jean-François
Published: May 2010

The aim of this study is to develop an effective on-line ANN-based approach for quality estimation in resistance spot welding. The proposed approach examines the welding parameters and conditions known to have an influence on weld quality, and builds a quality estimation model step by step. The modeling procedure begins by establishing relationships between welding parameters (welding time, welding current, electrode force and sheet metal thickness), welding conditions represented by typical characteristics of the dynamic resistance curve and welding quality indices (nugget diameter, nugget penetration, and indentation depth), and the sensitivity of these elements to the variation of the process conditions. Using these results and various statistical tools, three estimation models are developed. The first one is based exclusively on welding parameters. The second model is based on characteristics of the dynamic resistance curve. The third estimation model combines welding parameters and characteristics of dynamic resistance curves. In order to carry out the models building procedure, an extensive number of welding experiments are required. For this purpose, Taguchi’s efficient method of experimental planning is adopted. The results demonstrate that the developed models can provide an accurate on-line estimate of the weld quality, under different welding conditions.
Geometric and Kinematic Modelling of a New Parallel Kinematic Machine Tool: The Tripteor X7 Designed by PCI
Authors: Pateloup Sylvain , Chanal Helene , Duc Emmanuel
Published: May 2010

Today, Parallel Kinematic Machine tools (PKMs) appear in automotive and aeronautic industry. These machines propose high kinematic performances allowing a higher productivity than Serial Kinematic Machine tools (SKMs). However, this kinematic behaviour is anisotropic and a particular study is then necessary to locate the part in a workspace where the kinematic performances are well exploited. The study presented in this article deals with the determination of geometric and kinematic models of a new PKM : the Tripteor X7 designed by PCI. The inverse kinematic model expresses the joint coordinates with regard to the cartesian coordinates. The kinematic model which takes into account velocity, acceleration and jerk limits axis, allows computing the displacement time between two tool positions. Finally, this model can be used to determine the workspace where Non Effective cutting Times (TNE) are minimum. The method is applied for an automotive part machining
Control of Chatter by Spindle Speed Variation in High-Speed Milling
Authors: Seguy Sébastien , Dessein Gilles , Arnaud Lionel , Insperger Tamás
Published: May 2010

High-speed milling operations are often limited by regenerative vibrations. The aim of this paper is to analyze the effect of spindle speed variation on machine tool chatter in high-speed milling. The stability analysis of triangular and sinusoidal shape variations is made numerically with the semi-discretization method. Parametric studies show also the influence of the frequency and amplitude variation parameters. This modeling is validated experimentally by variable spindle speed cutting tests with a triangular shape. Stable and unstable tests are analyzed in term of amplitude vibration and surface roughness degradation. This work reveals that stability must be considered at period variation scale. It is also shown that spindle speed variation can be efficiently used to suppress chatter in the flip lobe area.
Study of DGEBA and Novolac Adhesive Solutions between Ceramic and Steel Substrates
Authors: Gaussens Clélia , Nassiet Valérie , Hassoune-Rhabbour Bouchra
Published: May 2010

The industrial application (under a confidential clause) concerns a ceramic/steel assembly. This PhD research is concerned with providing a reliable industrial bonding between ceramic and steel using structural adhesive. This industrial joint shall withstand a wide range of temperatures with brutal thermal changes. This paper focuses on the adhesive formulation. Indeed, we needed to compromise the adhesive flexibility: soft enough to resist the thermal stresses and compensate the coefficient of thermal expansion mismatch between the two substrates. We find this good compromise with DGEBA and Novolac epoxy based adhesive separated or blended. The influence of the different formulation parameters on the initial properties was studied by chemical, rheological and thermal tests on adhesive samples. Depending on those formulations, we observed different behaviours in term of glass transition temperature, cross-linking time and flexibility.
Failure Mechanisms of Thin Hard Coatings Submitted to Repeated Impacts: Influence of the Film Thickness
Authors: lamri Salim , Langlade Cecile , Kermouche Guillaume
Published: May 2010

Thin films produced by sputtering methods are used in many practical applications. This work aims at studying the failure mechanisms of thin hard coatings submitted to repeated impact conditions, with a special focus on the influence of the film thickness. Impact tests were carried out using a cyclic loading system developed in our laboratory. Steel balls (100Cr6) were used as impacting bodies. After tests, samples were observed by optical and scanning electron microscopy in order to investigate coating failure. The experimental work has permitted to identify blistering phenomena that has been related to the film mechanical properties and residual stress level. The influence of the film thickness is discussed and measurements of the residual stress in the buckled coatings have been performed using Raman spectroscopy to check the validity of our mechanical approach.
Numerical Modeling of Chemical and Thermal Coupling in a Silicon Carbide Based Heat Exchanger Reactor
Authors: Boniface Benjamin , Caperaa Serge , Dalverny Olivier
Published: May 2010

The objective of this paper is to present the solution developed to model the chem- ical and thermal coupling occurring in an intensied heat exchanger reactor. The results of this modeling are all the properties of the chemical uid along the conduit, and the temperature distribution in the structure. This will be used to manage a thermal and mechanical reliability study of the heat exchanger reactor.
Investigation on Fabrication of W-Cu Nanocomposite via a Thermochemical Co-Precipitation Method and its Consolidation Behavior
Authors: Hashempour M. , Rezaie Hamid Reza , Razavizadeh Hekmat , Salehi M.T. , Mehrjoo H. , Ardestani M
Published: May 2010

W-25%Cu nanocomposite was produced via a thermochemical co-precipitation procedure. Copper nitrate and sodium tungstate salts were used as Cu and W containing precursors respectively. Aqueous solutions of these salts were reacted under controlled pH condition prepared by ammonia addition and the resulting precipitates were then calcined at 450oC and hydrogen reduced at 800oC. The products of each step were characterized by XRD and Electron Microscope. Using a basic medium with a pH of 13 which caused the formation of complex Cu(NH3)42+ was found to provide suitable condition for precipitation of nanosized composite powders. Cu2WO4(OH)2 and CuWO4.2H2O as raw precipitates, CuWO4-x , CuO, and WO3 as calcined powders, and W-Cu reduced composite powders, all were seen to keep nanosize dimensions through high temperature treatments of fabrication. Sintering of the reduced powders at the temperature of 1150oC led in a density of about 98% theoretical density.
Cost Affordable Developments in Titanium Technology and Applications
Authors: Froes F.H. , Imam M. Ashraf
Published: May 2010

Titanium is the “wonder” metal, which makes sense as the material of choice for a wide variety of applications. However, because of its relatively high price- a result of extraction and processing costs- it is used basically only when it is the only choice; with the caveat that titanium has a bright “image” which can lead to use even when the economics are unfavorable. The major thrust in the area of titanium technology has been aimed at achieving cost reduction rather than developing alloys with enhanced properties. This paper will overview the potential areas which are amenable to cost reduction and present some applications of titanium and it’s alloys.
Microstructure and Mechanical Properties of α’ Martensite Type Ti-V-Al Alloy after Cold- or Hot Working Process
Authors: Matsumoto Hiroaki , Yoneda Hiroshi , Sato Kazuhisa , Konno Toyohiko J. , Kurosu Shingo , Fabrègue Damien , Maire Éric , Chiba Akihiko
Published: May 2010

Ti alloys are widely utilized for industrial applications due to their excellent mechanical properties combined with low density. In general, Ti alloys are classified as , + and  alloys, with further subdivision into near  and metastable  alloys. Quite recently, we have presented new type structural ’ martensite (H.C.P.) Ti alloys with low Young’s modulus, high strength and excellent ductility at room temperature. In this work, we examined the microstructure and mechanical properties of ’ martensite type Ti-V-Al alloy after cold- or hot working process. Then, we found that deformation behavior of ’ initial microstructure as compared with (+) initial microstructure was different based on the results of stress-strain curves and Processing Maps under the hot working process. Further, cold rolled ’ martensite microstructure exhibited the refined equiaxed dislocation cell structure, thereby resulting in high strength. This result suggests the new type deformation processing (for both cold- and hot work processing) utilizing ’ martensite in industrial Ti alloys.
Direct Electrochemical Reduction of Titanium Dioxide in Molten Salts
Authors: Dring Kevin
Published: May 2010

Electrochemical methods and electrowinning of titanium have been promoted, unsuccessfully, for many years as a replacement for the current Kroll process, which has not achieved the same economies of scale as other light metals (eg. Al, Mg) have. One such method is the direct electrochemical reduction of titanium dioxide, which encompasses a range of processes involving the electrolysis of a molten salt and the subsequent reduction of titanium via the metal of the salt cation. Norsk Titanium AS, in a collaboration with Norsk Hydro, SINTEF, and NTNU through a Norwegian Research Council grant, has been actively involved in the development of such a process and the focus of this presentation is to give a summary of the research activities. Particular emphasis will be given to the fundamental reactions underlying the process.
The Production of Ti Alloy Powder from Chloride Precursors
Authors: Withers James , Laughlin John , Elkadi Yasser , DeSilva Jay , Loutfy Raouf O.
Published: May 2010

It has long been a goal to produce Ti Alloy powder directly to eliminate the standard processing of melting sponge, alloying, producing a billet/ingot and then reducing to powder by one of several techniques. The batch Kroll process where reaction occurs at the reactor wall interface from TiCl4 vapor and molten magnesium, limits the potential to directly form alloys. Any batch processing has the limitation of alloy compositional control from batch to batch. A unique continuous processing approach permits the gaseous mixing of chloride precursors with metallothermic reduction that directly produces an alloy powder in a size that is useable for standard powder metallurgy. Discussion will include producing Ti-6Al-4V and other alloy powder.
Electromigration Reliability of the Contact Hole in SiC Power Devices Operated at Higher Junction Temperatures
Authors: Tanimoto Satoshi , Nishio Naoki , Suzuki Tatsuhiro , Murakami Yoshinori , Ohashi Hiromichi , Yamaguchi Hiroshi , Okumura Hajime
Published: May 2010

It is strongly desired to operate SiC power devices at higher junction temperatures (Tj), but that often entails problems because they contain a variety of materials with thermal activity or weakness. An example of such troubles is the steep increase in resistance of the Al electrode in the source (or emitter) contact holes, caused by electromigration (EM). In this work, EM reliability of the contact hole in SiC power devices was evaluated for an improved Al electrode sandwiched between thin TaN layers. An estimated mean time to failure (MTTF) of approximately 3400 years was achieved under conditions of Tj = 300°C and J = 104 A/cm2.
2DEG HEMT Mobility vs Inversion Channel MOSFET Mobility
Authors: Pérez-Tomás Amador , Placidi Marcel , Baron N. , Chenot Sébastien , Cordier Yvon , Moreno J.C. , Millan José , Godignon Philippe
Published: May 2010

Channel mobility properties of SiC and GaN based MOSFETs and AlGaN/GaN HEMTs
are compared in this paper. For a similar active area, the specific on-resistance of the MOSFET is
much larger than the on-resistance for the HEMT, which is depending on the electron mobility in
their respective channels. Physically-based models are used to fit this experimental transistor
mobility.
Control of the Single Crystal Reinforcement by the Intermetallic Compound Layers
Authors: Wołczyński Waldemar , Mikułowski Borys , Boczkal Grzegorz
Published: May 2010

. An improvement of the Brody & Flemings theory has been proposed to study not only the solute segregation but the solute redistribution during the single crystal growth as well. The redistribution is treated as a phenomenon superposed upon the segregation phenomenon. The crystal growth has been performed by the closed Bridgman system with a constant growth rate and an imposed temperature gradient. A hypo-eutectic Zn-Ti alloy has been subjected to oriented growth and precipitation of the Zn-16Ti intermetallic compound was observed. The precipitates have been placed as some layers distributed within the single crystal with a constant spacing. Some data from the Zn-Ti binary phase diagram was introduced into the theory to show possibility of the control the phenomenon of the reinforcement by precipitation during a single crystal growth.
Alignment of Primary Al3Ni Phases in Hypereutectic Al-Ni Alloys with Various Compositions under High Magnetic Field Gradients
Authors: Liu Tie , Wang Qiang , Wang Zhong Ying , Li Dong Gang , He Ji Cheng
Published: May 2010

The microstructural changes of the primary Al3Ni phases in hypereutectic Al-Ni alloys solidified under various high magnetic field gradients were investigated. It was found that the application of a magnetic field gradient induced an aligned structure of the primary Al3Ni phases similar to those in a high uniform magnetic field. However, the high magnetic field gradient showed more obvious effect on the alignment of the primary Al3Ni phases than the uniform magnetic field, although this effect strongly depended on the alloy composition.
Effect of Alloying Elements on Graphite Morphology in CGI
Authors: Selin Martin , Holmgren Daniel , Svensson Ingvar L.
Published: May 2010

Understanding how alloying elements and amounts affect the shape and size of graphite in compacted graphite cast irons could be of great importance. Some important material properties that are affected by the graphite shape are tensile strength and thermal conductivity. Knowing the effect of alloying additions could be of assistance when trying to optimise material for a specific application. In order to determine how graphite changes depending on alloying additions the microstructure of nineteen CGI materials were investigated. All melts were based on one chemical composition and alloying elements were added to obtain melts with variation in magnesium, silicon, copper, tin, chromium and molybdenum. Some of the more important microstructure features that were analysed are the amount and size of different graphite particles. The result from this analysis should give an indication on what features each alloying element affect and how these features varies with alloying amount.
Modeling of Heat and Solute Interactions upon Grain Structure Solidification
Authors: Gandin Charles-André , Blaizot J. , Mosbah Salem , Bellet Michel , Zimmermann Gerhard , Sturz Laszlo , Browne David J. , McFadden Shaun , Jung H. , Billia Bernard , Mangelinck-Noël Nathalie , Nguyen-Thi Henri , Fautrelle Yves , Wang Xiao Dong
Published: May 2010

Simulations of several laboratory experiments developed for the study of structure and segregation in casting are presented. Interaction between the development of dendritic grain structure and segregation due to the transport of heat and mass by diffusion and convection is modeled using a Cellular Automaton - Finite Element model. The model includes a detailed treatment of diffusion of species in both the solid and liquid phases as presented elsewhere in this volume [1]. Applications deal with prediction of columnar and equiaxed grain structures, as well as inter-dendritic and inter-granular segregations induced by diffusion and macrosegregation induced by thermosolutal buoyancy forces.
Meshless Approach to Solving Freezing with Natural Convection
Authors: Gregor Kosec , Šarler Božidar
Published: May 2010

This paper for the first time explores the application of the meshless approach, structured on the Local Radial Basis Function Collocation Method (LRBFCM), for solving the freezing process with convection in the liquid phase for a metals-like material in a closed rectangular cavity. The enthalpy one-domain formulation is used to avoid inclusion of additional boundary conditions at the fluid-solid interface. To avoid numerical instabilities, the freezing of a pure substance is modeled by a narrow phase change interval. The fluid flow is solved by a local pressure-velocity coupling, based on the mass continuity violation [1-3], and the explicit time stepping is used to drive the system to the free boundary solution. The results are presented through temperature and streamfunction contours and the liquid-solid interface position at the steady state, as well as the time development of the average Nusselt number and the time development of the cavity average liquid fraction. Results are validated with already benchmarked melting example [3]. The paper represents first steps in solution of the Hebdich and Hunt experiment by an alternative numerical technique, different from the classical finite volume or finite element methods [4].
Detailed Numerical Simulation of Short-Term Microgravity Experiments to Determine Heat Conductivity of Melts
Authors: Bánhidi Viktor , Szabo Tamas J.
Published: May 2010

In the frame of an international cooperation a 4 year long project was executed to determine thermal conductivity in metallic melts. During the project, the University of Miskolc designed and developed unique apparatus which was capable to perform measurements under microgravity conditions. The experiments were carried out at the Drop Tower „Bremen” where the conditions of reduced gravity could be provided for 4.7 s and a gravity level of 10-5g was achieved. The registered temperature distribution data of the examined melts always show a clear difference between the experiments measured in the normal and in the low gravity environment. During the evaluation of the datasets it was proven, that the well known canonical evaluations could not be used with high reliability for all the measurements, for all the materials and for all the geometry used. Besides of the understanding of the underlying physics and evaluating the measured data, the Crank-Nicolson method and error function analysis were used at the beginning, some numerical analyses were also initiated to simulate the system in FEM (Marc). The results showed acceptable results, but also pointed out a need for further study, so a detailed numerical analysis on a specialized FVM (Fluent) system was started. The code used for the numerical simulation (Fluent) was able to handle the heat conductivity, the liquid flow, the complex material parameters changes and the used geometries as well. With this technique, from the data of the drop experiments, the pure - free from the effect of the liquid flow - thermal conductivity could be separated. The results show that after these simulations, using different conditions (temperature, gravity level, etc.) for one material the same thermal conductivity value could be determined, within acceptable tolerance.
Undercooling of Pure Cu and Ge Melts in a Static Magnetic Field
Authors: Zhang Y.K. , Zhou Y.L. , Gao J.R. , He J.C.
Published: May 2010

The glass fluxing technique was used to undercool melts of pure Cu and Ge in the presence of a static magnetic field generated by a superconducting magnet. It was found that the mean undercooling of liquid Cu increased with increasing magnetic field, whereas the mean undercooling of liquid Ge did not show any significant changes with increasing magnetic field. Such a difference in the undercooling behavior can be related to the Lorentz force imposed by the magnetic field, which was larger for liquid Cu because of a larger electrical conductivity than that of liquid Ge.
Refinement of Solidification Microstructures by the MCAST Process
Authors: Fan Z. , Xia M. , Bian Zan , Bayandorian I. , Cao L. , Li H. , Scamans Geoff M.
Published: May 2010

MCAST (melt conditioning by advanced shear technology) is a novel processing technology developed recently for conditioning liquid metal under intensive forced convection prior to solidification processing. The MCAST process uses a twin screw mechanism to impose a high shear rate and a high intensity of turbulence to the liquid metal, so that the conditioned liquid metal has uniform temperature, uniform chemical composition and well-dispersed and completely wetted oxide particles with a fine size and a narrow size distribution. The microstructural refinement is achieved through an enhanced heterogeneous nucleation rate and an increased nuclei survival rate during the subsequent solidification processing. In this paper we present the MCAST process and its applications for microstructural refinement in both shape casting and continuous casting of light alloys. Discussions will be made on the effect of intensive forced convection on the enhanced heterogeneous nucleation. The concept of physical grain refinement will be proposed and discussed in contrast to the conventional chemical grain refinement by addition of grain refiners.
In Situ Observation of Solidification in Horizontal Centrifugal Casting Process
Authors: Esaka Hisao , Hiramoto Jun-Nichi , Miyahara Shota , Shinozuka Kei
Published: May 2010

Horizontal centrifugal casting is widely used for production of water pipes, rolls and so on. Advantage of this process is to press molten metal against the permanent mold due to centrifugal force. Thanks to this, one can obtain fine structure and sound castings1). On the other hand, macroscopic segregation on tangential direction sometimes forms. The formation mechanism of macroscopic segregation has not well understood. This is because the solidification process itself is still uncertain since it is very complex2-4). Thus, in order to understand the solidification process in horizontal centrifugal casting an in-situ observation has been made in this study. Transparent organic substance has been used to simulate the metal solidification.
Deformation Behavior of Aluminum Alloys during Solidification
Authors: Dahle Arne K. , Suéry Michel
Published: May 2010

This paper is concerned with the rheological behavior of aluminum alloys during solidification and the modeling aspects of this behavior. The whole range of solid fractions is considered and it is shown that the rheology can be divided into several domains exhibiting quite well-defined characteristics in terms of shear and tensile properties. Modeling based either on suspension approaches for small solid fractions or on porous medium approaches when the crystals mechanically interact is also considered.
Martensite and Nanocrystalline Phase Formation in Rapidly Solidified Ni2MnGa Alloy by Melt-Spinning
Authors: Prasad R.V.S. , Phanikumar G.
Published: May 2010

Microstructure of rapidly solidified Ni2MnGa ferromagnetic shape memory alloy has been investigated experimentally by melt-spinning technique. At a constant ribbon width of 3 mm, two speeds of melt spinning 17m/sec and 30m/sec at the extrema of conditions for a good quality of ribbon resulted in two thicknesses of the ribbon, viz., 62 μm and 44 μm, respectively. TEM and AFM analysis reveals the formation of very fine clusters of Ni2MnGa at lower wheel speeds. However at higher wheel speeds nanocrystalline Ni2MnGa particles of size about 10-20 nm and martensitic phases were confirmed.
Analysis of a Microgravity Solidification Experiment for Columnar to Equiaxed Transitions with Modeling Results
Authors: McFadden Shaun , Browne David J. , Sturz Laszlo , Zimmermann Gerhard
Published: May 2010

This paper studies the Columnar to Equiaxed Transition (CET) in an Al-7wt%Si binary alloy with and without Al-Ti-B grain refiner. A microgravity experiment was designed to produce a CET in this alloy system. The experiment was flown onboard the MAXUS-7 sounding rocket platform, which achieved twelve minutes of microgravity. Examples of CET were successfully produced during the unmanned flight. Temperature data were recorded from thermocouples in the crucible walls of the furnace. Post-mortem material characterization of the grain structure was also performed. Subsequently a model of the furnace, which used a front-tracking model of solidification and an inverse heat calculation method, was developed. In this paper, results from the model are compared to the experimental findings; agreement is found with the CET predictions. The results from the model are then used to compare findings with the CET criterion of Hunt from the literature. Agreement is found between the model predictions and the Hunt criterion.
Effect of Two-Liquid Casting on the Microstructure of Sn-Pb Alloys
Authors: Kim Y.K. , Qin Rong Shan
Published: May 2010

Traditional casting usually solidifies one homogeneous liquid by removing heat from liquid surface, by which the microstructure solely depends on the heat removal rate for the given alloy composition. The newly developed two-liquid composite simultaneous casting concept raises an alternative to control microstructure. The concept introduces the solidification while mixing technique so that the microstructure depends not only on the heat-removing from liquid surface but also the heat transfer from one liquid to another. The paper reports the experimental validation of the concept by two-liquid casting of Sn-Pb alloys. Reduced grain size, increased microhardness, rougher and more fractal grain surfaces are observed for the alloy solidified by two-liquid casting in comparison of the microstructure obtained by conventional solidification techniques.
Micro-Segregation: Issues of Growth Rate and the Peritectic
Authors: Howe A.A.
Published: May 2010

Simplified models of micro-segregation are in common use in academia and industry. An issue regarding the accuracy of these approaches is addressed, before describing extensions required for the sponsor (Corus/Tata). It is shown that the adopted growth rate law of the solid is of equal importance as the diffusivity and the partition coefficient. By making the growth rate part of the solution rather than arbitrarily imposed (e.g. parabolic growth), dramatic errors are avoided. This approach has now been extended to the peritectic transformation in steel. Also included are dendrite arm coarsening and predictions of the solute profiles across the solid and their sub-solidus homogenization. The results of this streamlined model compare very well with experimental data and Finite Difference model calculations despite operating orders of magnitude more quickly.
Crystallization of Iron Slags Found in Eraly Medieval Bloomery Furnaces
Authors: Török Béla , Kovács Árpád
Published: May 2010

In the last few years iron slag finds from the Late Avar Period (7-9th cent.), the Period of Hungarian conquest (10th cent.) and the Árpáds (11-13th cent.) uncovered in sites of excavation in the Carpathian Basin had been examined. The pieces of slags are by-products of the metallurgical process of bloomery and forming procedure of iron blooms. The structure of the examined slags was very heterogeneous from the metallographic point of view. The amorphous phase as well as panelled and dendritic crystallization can be found, which was the more frequent. Secondary, nay, tertiary branch of dendrite often can be studied, which was the result of gradual cooling. It was typical for its microstructure that minerals formed from oxides of elements with lower atomic number than iron (Al, Mg, Ca, etc.) surround the fayalite-rich parts. These minerals sometimes also have a high quantity of Fe, sometimes those have a very low Fe-content. The examination of microstructure can help to determine the type of the slag, whether it comes from metallurgical (as a tap-slag or cinder) or forming process, and to specify and reconstruct the metallurgical and physicochemical processes in the medieval bloomery.
Centreline Segregation of CC Slabs
Authors: Réger Mihály , Kytönen Heli , Verő Balázs , Szélig Árpád
Published: May 2010

Industrial data set with 400 CC (continuous casting) steel slabs were analysed by a statistical method for revealing the real connections between the technological parameters, heat transfer model results and the precisely determined centerline segregation index. Because of the poor correlations a new model was developed in which the shrinkage and deformations of the shells of the slabs can also be taken into account. It has been proved that the stopping of liquid movement below about 30 % liquid ratio plays an important role in the centerline segregation formation. The conclusions of the calculations are in good accordance with the results of the metallographical analysis.
Effect of Temperature on the Properties of High Pressure Die Casting
Authors: Dúl Jenő , Szabó Richárd , Simcsák Attila
Published: May 2010

Quality of high pressure die castings is influenced by a lot of factors. Among them, the most important ones are the melt-, and die temperatures. This paper shows a data acquisition system, developed for measuring the melt and die temperatures and the results of the temperature measurements obtained under variable conditions. Evaluation of the relationship between the interrelated temperatures and the casting properties is based on analyzing the structure of the castings.
Fracture Mechanics of Gray Cast Iron
Authors: Diószegi Attila , Fourlakidis Vasilios , Svensson Ingvar L.
Published: May 2010

The fracture mechanism of gray cast iron was investigated on tension loaded samples produced under different conditions. The parameters studied included the graphite morphology, the carbon content, the inoculation and the cooling condition. The observations made reveal the role of the microstructure on crack propagation. The cracks were found to always propagate parallel with the graphite flakes. The interaction between the metallic matrix precipitated as primary austenite and graphite has been interpreted by a simplified model of the austenite reinforced eutectic cell.
The geometrical transcription gave a standard crack component configuration with known mathematical solution. The microstructure observed in the experiments has been analysed by means of a novel interpretation. The fictitious stress intensity at yield and the fictitious maximum stress intensity at failure are strongly related to the relative shape of the eutectic cell and the fraction primary austenite. A different slope is observed for the material cooled at high rate when the precipitation of primary carbide reduces the stress intensity. The observed relations indicate that the tensile strength of the grey cast iron is the result of the collaboration between the toughness of the metallic matrix precipitated as primary austenite and the brittleness of the graphite phase. The shape and distribution of the primary austenite and graphite can be influenced by chemical composition, by inoculation or by the cooling condition, but they will maintain equilibrium with respect to the stress intensity.
Dilatometer Study of Aluminium-Silicon Based Alloys with Metastabile Structures
Authors: Varga Béla , Fazakas Eva , Varga L.K.
Published: May 2010

Aluminum-Silicon alloys are sought in a large number of automotive and aerospace applications due to their low coefficient of thermal expansion and high wear resistance. The fine structure of Si precipitates is controlled by forced solid solution structure obtainable by rapidly solidification techniques [1, 2, 3]. Present study focuses on precipitation of silicon in Al88Si12 as a function of temperature by dilatometer analysis. Different structures out of equilibrium have been obtained after casting in sand, black-lead and steel mould and by melt spinning. The average value of the activation energy for the precipitation of Si in steel mould casting of eutectic composition was found to be 47 kJ/mol. Our dilatometer studies were complemented by metallographic microscopy and XRD measurements.
Analysis of Cu-Zr-Ag Amorphisable Alloys Produced by Centrifugal Casting
Authors: Janovszky Dóra , Svéda Mária , Tomolya Kinga , Sólyom Jenő , Hegman Norbert , Roósz András
Published: May 2010

Bulk Metallic Glasses (BMGs) have been widely investigated due to their excellent physical and chemical properties [1]. The copper based BMG occupies a special place in the family of BMGs since they are relatively low priced. The Cu-Zr-Ag ternary system has been examined on the basis of the ternary phase diagram [2]. We have changed the concentration of the alloys from the Cu58Zr42 to the concentration of the deep eutectic point. Wedge-shaped samples have been cast from the master alloys by centrifugal casting into a copper mould, consequently analyse the influence of the cooling rate on the crystallization. The cooling rate has been estimated from the secondary dendrite arm distances by using a Cu-Sn crystalline alloy. Near the tip of the wedge the samples were amorphous and near the base of the wedge the samples were fully or partially crystallized. The structures of the samples have been characterized by scanning electron microscope and X-ray diffraction.