bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of the Laser Surface Treatments on the Wear Resistance
Authors: Bitay Enikő , Kovács Tünde
Published: May 2010

In case of traditional surface-hardening processes (e.g. carburization), the wear resistance usually correlates with hardness, which means optimising these technologies could be based on testing the achieved hardness. In case of modern laser treatment technologies however – e.g. surface melting combined with surface alloys or laser scanning surface treatment followed by nitridation – it is unlikely to conclude wear resistance from the value of hardness. The reasons are the following: the hardness of surface melting combined with surface alloys (especially if alloyage is made using high hardness compound powders) depends on the remelting of the material and the particle size and distribution of the dispersed alloy. These same properties define wear resistance, but the values don’t necessarily correlate. In case of a compound phase dispersion in a softer base material, we can have outstanding wear resistance with moderate hardness. (e.g. bearing metals) The case is similar with scanning treatment combined with nitridation, which results in complicated structures. Due to the above, it is possible that in order to optimise these aforementioned technologies, we have to rely on examining wear resistance. In order to back this statement, we show the results of two typical experiments concerning these technologies.
Influence of Undercooling on the Kinetics of the Peritectic Transition in an Fe-4.2wt%Ni Alloy
Authors: Phelan Dominic
Published: May 2010

In-situ Laser Scanning Confocal Microscopy observations are presented that assess the influence of undercooling before the initiation of the peritectic transition in a Fe-4.2wt%Ni alloy on the resulting kinetics of the peritectic reaction and transformation. In a series of experiments varying the cooling rate, increasing the cooling rate led to a lower temperature at the L/ interface. The resulting peritectic reaction changed from slow 840m/s - 1500m/s, with limited growth into the  to rapid ~11mm/s with significant growth into . In continuous cooling experiments when the nucleation temperature was low, growth into  was high and the reacting species was observed to propagate along the liquid/delta-ferrite interface at a rate of ~11mm/s. The peritectic reaction rate did not appear to be a function of temperature over a measured nucleation temperature range of 5 K. Conversely, the growth rate of austenite into the delta-ferrite in the first 0.03 seconds was observed to increase from 1.5mm/s to 8mm/s as the measured temperature at nucleation decreased.
In Situ Investigation of Liquid-Liquid Phase Separation in Hypermonotectic Alloys
Authors: Schaffer Paul L. , Mathiesen Ragnvald H. , Arnberg Lars
Published: May 2010

Hypermonotectic alloys are distinguished by a temperature region for which the homogeneous melt decomposes into two liquid phases. In Al-based hypermonotectics, the minority phase is much higher in density than the matrix melt phase and consequently macro-segregation due to sedimentation is an inherent problem when casting these alloys. However, under the correct solidification conditions, it may be feasible to counteract sedimentation by thermocapillary forces that arise due to the thermosolutal dependence of the surface tension between the two liquid phases.
The current investigation involved in-situ X-ray video microscopy studies during directional solidification of Al-Bi samples of various compositions employing a Bridgman furnace. It was found that large undercoolings were required to initiate the L  L1 + L2 reaction and L2 nucleation occurred heterogeneously on the monotectic front. L2 droplets were then set in collective size-dependent motion by hydrodynamic forces coupled to external fields (i.e. temperature gradient and gravity) and internal fluctuations. The resulting flow fields are superimposed onto the short range coagulation mechanisms, such as diffusion coupling, and are all crucial in determining the final size distribution and dispersion of the Bi-rich phase in the cast material.
A Meshless Approach in Solution of Multiscale Solidification Modeling
Authors: Šarler Božidar , Kosec Gregor , Lorbicka Agnieszka , Vertnik Robert
Published: May 2010

This paper describes an overview of a new meshless solution procedure for calculation of one-domain coupled macroscopic heat, mass, momentum and species transfer problems as well as phase-field concepts of grain evolution. The solution procedure is defined on the macro [1] as well as on the micro levels [2] by a set of nodes which can be non-uniformly distributed. The domain and boundary of interest are divided into overlapping influence areas. On each of them, the fields are represented by the multiquadrics radial basis functions (RBF) collocation on a related sub-set of nodes. The time-stepping is performed in an explicit way. All governing equations are solved in their strong form, i.e. no integrations are performed. The polygonisation is not present and the formulation of the method is practically independent of the problem dimension. The solution can be easily and efficiently adapted in node redistribution and/or refinement sense, which is of utmost importance when coping with fields exhibiting sharp gradients. The concept and the results of the multiscale solidification modeling with the new approach are compared with the classical mesh-based [3] approach. The method turns out to be extremely simple to code and accurate, inclusion of the complicated physics can easily be looked over. The coding in 2D or 3D is almost identical.
Numerical Simulation of TiAl-Nb Alloy Solidification Experiment in TEM 01-3M Facility Aboard MAXUS 8
Authors: Kartavykh A.V. , Ganina S. , Grothe Dieter , Lemoisson Fabienne , Herfs W.
Published: May 2010

The problem of numerical modeling of directional solidification of TiAl refractory intermetallics aboard the MAXUS 8 sounding rocket is considered. The research is of relevance to the FP6 Integrated project IMPRESS (Intermetallic Materials Processing in Relation to Earth and Space Solidification). Attention is paid to columnar-to-equiaxed microstructure transition (CET) phenomenon and mushy zone evolution in Ti-45.9Al-8Nb (at %) alloy being processed in TEM 01-3M high-temperature (up to 17000C) furnace. In this three-zone resistive furnace the “bent” temperature profile is applied with two strongly different axial thermal gradients, presumably allowing the achieving of CET conditions along the sample of 160 mm length. Temperature profile evolution is defined by power-down furnace operation. 2D-numerical study of heat transfer and realtime-scale solidification dynamics of TiAl-Nb under zero gravity approximation is performed. The approaches used for solution of Navier-Stokes equations and phase transition (Stefan) problem are briefly described. The solidification time is shown to be satisfying the 12-minute microgravity limit aboard a MAXUS. The position and the time at which CET may be triggered are predicted and confirmed in line with the Hunt diagram. The comparison is performed of model predictions with the real microstructure of TiAl-Nb reference sample solidified on-ground in TEM 01-3M facility.
Microstructure Formation in AlSi6Cu4 Alloy with Forced Melt Flow Induced by a Rotating Magnetic Field
Authors: Zimmermann Gerhard , Vitusevych Viktor T. , Sturz Laszlo
Published: May 2010

The objective of this paper is the experimental investigation of the microstructure in Al-6wt%Si-4wt%Cu alloy, directionally solidified without and with forced melt flow, induced by a rotating magnetic field. The flow leads to reduced primary dendrite spacing and to strong radial segregation of silicon and copper. As a consequence the local solidification conditions change, resulting in different types of Al2Cu phase formation. This outcome is explained by ThermoCalc calculations predicting the corresponding solidification behavior.
Role of Oxide Particles in Aluminum Melt toward Aluminum Foam Fabrication by the Melt Route
Authors: Kadoi Kota , Babcsán Norbert , Nakae Hideo
Published: May 2010

The aim of this work is to elucidate the role and contribution of oxide particles to aluminum foam fabrication. The melts were internally oxidized by a thickening process in which pure aluminum melt was stirred with or without the addition of 1.5 wt.% calcium for maximum 25 min. After this, each thickened samples were melted again and mixed for 100 s by introducing 1.5 wt.% TiH2 as a blowing agent. In order to investigate the foam evolution, the foam samples were hold in the furnace for 50 to 500 s. The stirring torque (viscosity) of the calcium containing melt increases with thickening time and achieves the stationary value after 17 min. However, the torque of pure aluminum melt does not change during stirring. Oxides have been found on the microstructures of both stirred samples, although the content of oxides of calcium added sample is significantly more than that of pure aluminum. SEM observation results of samples thickened by calcium addition show that the melt contains calcium oxide and Al4Ca in addition to equiaxed aluminum, and the morphology of formed oxide is not granulous but wrinkled bifilm containing calcium and aluminum oxides. The oxides formed in the pure Al melt has less effect on the viscosity thus the foamability of the aluminum melt. It is found that the calcium oxides formed by stirring are responsible for the effective increase of melt viscosity. The foams using oxidized pure Al melt have dense layer at the bottom caused by drainage and coarse foam structure due to strong coalescence. In case of the Al-Ca alloy, uniform pore distribution, lack of the dense layer and homogeneous time dependent increase of the cell size were observed. Besides, the sample held for longer time has thicker cell wall at the bottom compared with that at the top. We confirmed that the oxide bifilms of Al and Ca contributes to decreased drainage rate and coalescence, namely stabilization. The insufficient amount of oxide particles in pure aluminum is the reason for the lack of stabile foam (significant drainage) in that case.
Foam Evolution and Stability at Elevated Gravity Levels
Authors: Somosvári Béla M. , Bárczy Pál , Szirovicza Péter , Szőke János , Bárczy Tamás
Published: May 2010

Foaming experiments in order to understand the evolution of the foam structure blown in different directions and levels of gravity have been carried out. The key elements of the experiment are the foam generator body (henceforth FG) and the controlled blowing apparatus. The FG was a polymer foam infiltrated with a suspension (distilled water, pure tenside (SDS, 0.05m%) and SiO2 nanoparticles (2m%)) Foams were blown out at 1.5, 2, 4, 6, 10 and at 15g levels in three different directions (0, 90 and 180o, measured to the direction of the gravity vector). The elevated gravity condition was implemented in a hyper-g centrifuge (ZARM Bremen). Results show that foams can be created even at high gravity levels though the foamability and foam structure alters a lot by varying gravity level and foaming direction. At higher g-levels, under fixed gas flow rate and blowing time less foam could be produced. The average cell size varied with the blowing directions but proved constant on any gravity levels. On base of the gravity direction dependent pressure curves the foaming process was interpreted in detail. It was found that the sedimentation ruled capillary clogging is the main process by causing the gravity direction dependent foaming phenomena. The unexpected observation is that the foam stability does not depend on the gravity level.
Permeability in the Mushy Zone
Authors: Erdmann R.G. , Poirier D.R. , Hendrick A.G.
Published: May 2010

When modeled at macroscopic length scales, the complex dendritic network in the solid-plus-liquid region of a solidifying alloy (the “mushy zone”) has been modeled as a continuum based on the theory of porous media. The most important property of a porous medium is its permeability, which relates the macroscopic pressure gradient to the throughput of ﬂuid ﬂow. Knowledge of the permeability of the mushy zone as a function of the local volume-fraction of liquid and other morphological parameters is thus essential to successfully modeling the ﬂow of interdendritic liquid during alloy solidiﬁcation.
In current continuum models, the permeability of the mushy zone is given as a deterministic function of (1) the local volume fraction of liquid and (2) a characteristic length scale such as the primary dendrite arm spacing or the reciprocal of the speciﬁc surface area of the solid-liquid interface. Here we ﬁrst provide a broad overview of the experimental data, mesoscale numerical ﬂow simulations, and resulting correlations for the deterministic permeability of both equiaxed and columnar mushy zones.
A extended view of permeability in mushy zones which includes the stochastic nature of permeability is discussed. This viewpoint is the result of performing extensive numerical simulations of creeping ﬂow through random microstructures. The permeabilities obtained from these simulations are random functions with spatial autocorrelation structures, and variations in the local permeability are shown to have dramatic eﬀects on the ﬂow patterns observed in such microstructures. Speciﬁcally, it is found that “lightning-like” patterns emerge in the ﬂuid velocity and that the ﬂows in such geometries are strongly sensitive to small variations in the solid structure.
We conclude with a comparison of deterministic and stochastic permeabilities which suggests the importance of incorporating stochastic descriptions of the permeability of the mushy zone in solidiﬁcation modeling.
Flow Effects on Mush Coarsening
Authors: Kasperovich Galina , Steinbach Sonja , Ratke Lorenz
Published: May 2010

Gradient annealing experiments of a near-eutectic AlCu30 alloy with artificial stirring induced by a rotating magnetic field (RMF) of 6 mT were performed. The specific surface area of the primary phase was measured on metallographic sections perpendicular to the sample axis with a fixed amount of fraction solid. The variation of the specific surface area with fluid flow is compared to flow free experiments: the specific surface area varies as the inverse cube root of annealing time if no RMF is applied, but varies as an inverse forth root at 6 mT. The experimental procedure and results are presented in detail and discussed with models of convective coarsening of dendrites.
The Influence of the Solidification Process to the Dimensional Accuracy of Castings
Authors: Molnár Dániel , Dúl Jenő
Published: May 2010

The real system under consideration comprises of a solidifying casting with the casting mould, environment and other external influences. The process observed begins with the introduction of liquid metal to the channels of the runner system and filling of the mould cavity. This is connected with the contact of liquid metal with the atmosphere and also, with the walls of the mould. During the filling of the mould cavity heat transfer between the metal surface and the walls of the mould takes place (by radiation and conduction), which in practice can lead to mould cracking, and next to the formation of casting surface defects. In this stage of the process of great significance are the hydrodynamic conditions. These are dependent on the metal itself (its viscosity), and also on the runner system (rate of flow, resistances). During this time in the volume of the casting and mould, a pseudo-initial temperature fields is generated which is significant for the filling of the mould cavity and also for further cooling and solidification of the casting.
Experimental and Simulation Researches about „U” Section Castings Solidification
Authors: Munteanu Sorin Ion , Ciobanu Ioan , Crişan Aurel , Masnita M.
Published: May 2010

There are presented the results of an experimental research developed by authors referring to „U” section bars solidification. The U bars represent a special case of castings. Their solidification and the hot spots position is much influenced by the crossing piece length respective of the distance between the parallel walls. There were realised simulation researches and experimental researches that consist in casting parts and simulating their solidification. The case of casting parts in grey cast iron was analyzed. There were compared the shrinkage positions evidenced in experiments with the hot spots position obtained by solidification simulation on computer. Some conclusions about the validity of the results obtained by solidification simulation are revealed.
Solidification Time Estimation and Simulation - In Case of HPDC
Authors: Leranth Gabor
Published: May 2010

Since cast parts are used by the mankind -and the casting method should be one of the oldest metal forming technologies- the foundrymen struggle with various kind of difficulties. The most elementary ones are thermal problems during pouring. The basic condition, filling the mould before the metal solidifies to get the whole required shape, underlies primarily the thinnest wall within the casting and the thermal conditions. The empiric, experience-based knowledge was for a long time the single clue at the practical work with castings. Chvorinov, in German-speaking publications also written as Chworinoff, summarized and through his theoretical as well as experimental work complemented the knowledge of his time concerning the estimation of solidification development in sand-casted steel parts. His theory –expressed with the certainly best known formula in this speciality- was later expanded, modified and adapted to new scientific informations, although in a different way regarding the German-speaking respectively Anglo-Saxon technical literature. Nowadays, in time of more correct predictions supported through modern tools, estimation formulas are still very useful, acting as a preliminary stage of the design and development. Numerical simulation, in effect the efficient instrument for the subsequent steps of the processing, can also help to make the basic approximations more accurate, but it has his own possible traps as well.
Comparison of Thermal Analysis and Differential Thermal Analysis for Evaluating Solid Fraction Evolution during Solidification of Al-Si Alloys
Authors: Fernández-Calvo Ana Isabel , Niklas Andrea , Lacaze Jacques
Published: May 2010

Both thermal analysis (TA) and differential thermal analysis (DTA) have been used since long to evaluate latent heat release and solid fraction evolution during solidification of metallic alloys. TA makes use of cooling curves recorded under "natural" cooling while DTA consists in recording the temperature difference between the sample temperature and an inert reference during a controlled cooling, i.e. at imposed constant cooling rate. In both cases, the solid fraction evolution is deduced from a calculation of the latent heat release as estimated by means of a heat transfer model. This paper provides a comparison of such evaluations performed on one Al-Si alloy.
The Effects of Solidification Conditions and Heat Treatment on the Microstructure and Mechanical Properties of EN-AC 44400 Alloy
Authors: Mohsen Sadrossadat S. , Johansson Sten
Published: May 2010

Improved mechanical and physical properties of an Al-Si alloy as a well-known casting alloy is strongly dependent upon the morphology of silicon particles, Al grains and also type of intermetallics which are in turn a function of alloy composition, solidification rate and heat treatment. This study aims at investigating the influence of the different solidification conditions (high pressure die, gradient and sand cast) and heat treatment on the microstructure (dendrite parameters, silicon particle morphology, intermetallic compounds), mechanical properties and fracture surface appearance of Al- 9Si- 4Mn alloy. To identify the features of microstructure and fracture surface analysis, a combination of optical metallography, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) have been employed. The results show that the cooling rate has a strong effect on the evolution of intermetallics, morphology of the silicon and dendrite parameters.
Heat Balance of the Model Ingot Head
Authors: Krajewski Witold K.
Published: May 2010

The paper brings data about heat balance of the killed steel ingot head. The balance is obtained on basis of the temperature measurement in the system: ingot body - ingot head - ingot mould - insulating sleeves – radiation shield - ambient. The measurements were performed using model sys-tem (1:5) of the 20000 kg flat ingot. The balance shows that about 86% of the heat issued during solidification of the ingot head is transferred to the ingot mould through the insulating sleeves. In order to decrease this heat, insulating sleeves of low thermal conductivity are required, which should allow reducing dimensions of the ingot head and increasing the metal yield.
Analysis of Cu-Zr-Al Amorphisable Alloys Produced by Centrifugal Casting
Authors: Tomolya Kinga , Janovszky Dóra , Svéda Mária , Hegman Norbert , Roósz András
Published: May 2010

In this paper CuZrAl amorphous alloys with different Al content were prepared by centrifugal casting. The master alloy ingots were prepared by arc melting the mixture of the constituents on a water cooled copper boat in argon atmosphere. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mold. The microstructure of the samples was examined by Scanning Electron Microscope (SEM) and the phases were analyzed by X-ray diffractometry (XRD) to define the amorphous fraction.
The Research and Development of Novel Magnetic Material and Magnetic Core Used in Planar Transformer
Authors: Lou Jian Yong , Wang Ji Ping , Chen Yi Tong , Gao Lin
Published: May 2010

The novel soft magnetic materials and magnetic core structure used in planar transformer have been studied. The frequency, electrical and structure feature of the planar transformer with matrix structure was described. Then the novel magnetic materials used in the planar transformer were discussed, which were very different from ferrite block. The silicon steel strip was first represented, the magnetic characteristic of which was related to its geometric dimension, working frequency and the component. The microcrystallite alloy and amorphous alloy magnetic materials were then indicated, including iron-base nanocrystal and cobalt-base amorphous alloy. The magnetic materials of the above amorphous alloy and microcrystallite alloy were compared respectively. These soft magnetic materials could be used as the magnetic core in planar transformer, and the magnetic core could be composed of thin strip and line. The structure of magnetic core was flexible, which could benefit the planar transformer to reduce its volume. The development and trendy of novel magnetic materials and magnetic core in planar transformer were analyzed and discussed in this paper.
Effect of FAPAS Process on the Thermoelectric Properties of β-FeSi2
Authors: Meng Qing Sen , Fan Wen Hao , Wang L.Q. , Ding L.Z.
Published: May 2010

Iron disilicide (-FeSi2, and -FeSi2+Cu0.1wt%) were prepared by a field-activated pressure assisted synthesis(FAPAS) method from elemental powders and the thermoelectric properties were investigated. The average grain size of these products is about 0.3m. The thermal conductivity of these materials is 3-4wm-1K-1in the temperature range 300-725K. These products’ figure of merit is 28.50×10-4 in the temperature range 330-450K. The additions of Cu promote the phase transformation of -Fe2Si5 + -FeSi → β-FeSi2 and shorten the annealing time. It is proved that FAPAS is a benign and rapid process for sintering of -FeSi2 thermoelectric materials.
Phase Structure and Hydrogen Storage Characterization of the As-Cast Mg-10Ni-2Mm Alloy
Authors: Xing N. , Bai P.C. , Wu Ying , Lu Z.C. , Han W. , Zhou S.X.
Published: May 2010

The microstructural revolution of non-hydrogenated and hydrogenated Mg-based Mg-10Ni-2Mm alloy was studied. PCT and H-absorption/desorption kinetics were performed to evaluate the hydrogen storage properties. Storage capacities of 4.75, 5.03 and 5.27wt.%H for the alloy were obtained at 300, 325 and 350°C, respectively. The phases in the hydrogenated samples are mainly MgH2 and Mg2NiH4. Two absorption/desorption plateau existed in the PCT curves at each isothermal temperature. The values of ΔH and ΔS of the Mg2NiH4-formation was respectively -61.5 kJ/mol H2 and -118.6 J/mol H2 K which is lower compared with literature values. The kinetics of the H-absorption/desorption reactions for the alloy was improved by increasing the temperature. The alloy at 350°C showed the best kinetics performance of the H-absorption/desorption among the three temperatures. It is suggested that metallic particles and Mm may be mainly responsible for the improvement of the H-absorption/desorption kinetics, and Ni for the enhancement of hydrogen absorption capacity of the alloys.
A Simple and Low Cost Approach for Texturing on CZ-Silicon Solar Cell
Authors: Gou Xian Fang , Li Xu Dong , Xu Ying , Song Shuang , Cui Yin Fang , Fan Hong Yan
Published: May 2010

Silicon solar cell surface texture was effective to reduce reflectance and improve light collection. Alkaline etchants was a conventional process in monocrystalline silicon texturing.However, isopropyl alcohol(IPA) as buffer solution was expensive and high consumption, which increased the cost of solar cell. In the paper, It has been found that a cheaper surfactant as buffer solution decrease silicon surface interfacial force and increase etchant infiltrating of silicon wafer, so a large number of very small and uniform texture appeared on the silicon surface. pyramids size of about 3µm formed after etching of 15min. A new process to reduce the production cost and form the high quality pyramids texturization has been developed by this investigation.
Effect of Welding Parameters and Post-Weld Heat Treatment on the Cracking Sensitivity of Weldments in Electron Beam Welded Rene 41 with Incoloy907
Authors: Li Xiao Li , Liang Yang Min , Kang Wen Jun , Li Huan Xi , Ma Zhao Li
Published: May 2010

The cracking sensitivity of weldments in electron beam welded (EBW) Rene 41 with Incoloy 907 superalloy was studied under various welding and post-weld heat treatment condition. The results revealed that the optimum heat input for the weldments was about 714 J/cm. The weldments exhibited relatively higher cracking sensitivity when the post-weld heat treatments were carried out at 760°C for 16hrs. In this case, the carbides in the grain boundaries commonly distributed as thin film. It is found that the lower heating rate is favor to the formation of thin carbide film, which results in the increased cracking sensitivity in the heat affected zone (HAZ). When the weldments were heated at 950°C for 12h followed with furnace cooling to 620°Cand holding for 12hrs, then air cooling to room temperature, no cracks were observed in the HAZ of Rene 41. In this case, the carbides precipitated as stagger and refined granules in the grain boundaries. When the heat treatment temperature was up to 1040°C, some overfiring cracks occurred on the grain boundary of HAZ.
Phase Diagram Calculation and Experimental Study on the New Type Mg-Al-Zn-Ca-Sr Alloy in the Mg-Rich Region
Authors: Luo Su Qin , Tang Ai Tao , Pan Fu Sheng , Chen Yi , Feng Zhong Xue
Published: May 2010

Calculated phase diagram reveals important phase details for a new type muti-component magnesium alloy. Isothermal sections at 25°C of Mg-Ca-Sr, , Mg-2.74Al-Ca-Sr, Mg-2.74Al-0.79Zn-Ca-Sr system in the Mg-rich region were calculated using CALPHAD method, Thermo-Calc software and Mg-Al-Zn-Ca-Sr quinary database. The equilibrium phase composition in the Mg-rich region was analyzed. The equilibrium phases and solidification process of Mg-2.74Al-0.79Zn-0.68Ca-0.03Sr quinary alloy was calculated. The calculation results were consistent with the experimental results of SEM-EDX analysis and DSC spectrum. The solidification process of Mg-2.74Al-0.79Zn-0.68Ca-0.03Sr quinary alloy is as follow : α-Mg precipitates at 621°C, secondary phase C15-Al2(Ca, Sr) and Gamma-Mg17Al12 precipitate at around 520°C and 160°C in sequence, A4B-(Al4Ca,Al4Sr) may precipitate at around 460°C.
Effects of Yttrium Addition on Microstructure and Mechanical Properties of Extruded Mg-Zn-Y-Zr Magnesium Alloys
Authors: Chen Mei Bao , Pan Fu Sheng , Wang Jing Feng , Peng Jian , Tang Ai Tao
Published: May 2010

The effects of yttrium addition on microstructure and mechanical properties of extruded Mg-Zn-Y-Zr magnesium alloys were investigated by using optical microscope(OM), X-ray diffraction(XRD) and scanning electron microscope(SEM) et al. It was shown that the addition of yttrium resulted in the formation of the new phase, Mg3Zn3Y2, which distributed both on the grain boundaries and inside the grains. With the increasing of Y content, the amount of Mg3Zn3Y2 phase increases and the size becomes uniform. Grain refinement was found especially with 5.92%Y addition and a certain amount of coarse grains were formatted in the alloy with 3.95% Y addition, which led to the decline of the mechanical properties. The yield strength of the Mg-Zn-Y-Zr alloys was improved with the addition of Y, but the tensile strength was not changed obviously.
Study on the Mass Transfer Process in Pan Wet-Spinning
Authors: Ji Bao Hua
Published: May 2010

In order to reveal the formation mechanism in PAN wet-spinning process, the Magnifying Method was used to determine the mass transfer rate difference between solvent and coagulant by measuring the weight loss percent of the spinning dope at different interval in the coagulation bath. Then the effect of coagulation condition on and on structure and properties of as-spun fibers was discussed. It was found that increased along with hoist of the molecular volume of coagulants or the coagulation bath temperature but decreased with the increase of the dope solid content or coagulation bath concentration. When the coagulation condition was very moderate（high solid content, low bath temperature or high bath concentration）, the was smaller, the counter-diffusion took place slowly and peacefully, and sequentially an even and compact meshwork microstructure was obtained, thus the density and breaking tenacity of as-spun fibers increased gradually.
Study on Chloride Diffusion in Concrete with Non-Homogenous Coefficient Using Meshless Boundary Element Method
Authors: Guo Li , Chen Tang , Hong Jun , Qiao Ling , Guo Xiao Ming
Published: May 2010

A new robust numerical technique was proposed for analyzing chloride transient diffusion in concrete with non-homogenous coefficient. The method was based on a meshless boundary element method which results in an integral equation for explicitly evaluating field chloride quantities. Weighted residual method and Green’s function were adopted to derive domain and boundary integral equations. A radial integration method coupling with radial basis function approximation technology was used to convert domain integral into equivalent boundary integral. With central finite difference method, an explicit time iteration scheme was established for solving transient diffusion equation. Two numerical examples for 2D diffusion problem were given to demonstrate the robustness of the proposed method. Numerical results show that the non-homogenous diffusion coefficient causes the chloride distribution non-uniform, and the diffusion process is nonlinear with respect to time.
A Novel Constitutive Model for Concrete under Uniaxial Compression
Authors: Pan Jin Long , Zhou Jia Jia , Li Zong Jin , Leung Christopher K.Y.
Published: May 2010

In this paper, a novel constitutive model of concrete has been proposed by introducing a new parameter, namely, cracking Poisson’s ratio (νcr), to account for the effect of localization due to cracking. By fitting the curve between the dimensionless strain (ε/εpr) and cracking Poisson’s ratio (νcr), νcr can be expressed as an 3rd order polynomial function of dimensionless longitudinal strain (ε/εpr). The constitutive model for the softening regime can then be proposed with the parameters of dimensionless strain and cracking Poisson’s ratio. Finally, Validity of the proposed model is verified by the test results of cylinder specimens of C30.
Effect of Ag Particles on Wettability and Creep Rupture Life of SnCu Based Composite Solders
Authors: Yan Yan Fu , Wang Guo Xin , Song Ke Xing , Zhao Kuai Le
Published: May 2010

Particle-enhanced is the way to improve properties of solder alloys. In the present work, the influence of Ag particle-enhanced on the wettability and creep rupture life of 99.3Sn0.7Cu eutectic solder with Ag content of 1vol% to 10vol% were investigated. It was indicated that the wettability of the composite solders could be improved by adding minute amount of Ag particles. With increasing the amount of Ag particles, the spreading areas of the composite solders increased when Ag was below 5vol%. When Ag was above 5vol%, the spreading areas started decreasing. When Ag content was up to 10vol%, the wettability of the composite solder sharply deteriorated. In addition, the creep rupture lives of the composite solders were longer than that of 99.3Sn0.7Cu eutectic solder at the same condition. When Ag content was 5vol%, the creep rupture life of the composite solder was the longest among the investigated composite solders and about 23 times of that of 99.3Sn0.7Cu eutectic solder.
Sn-2.5Ag-0.7Cu-0.1Re-xNi Lead-Free Solder Alloy and its Creep Properties of Solder Joints
Authors: Zhang Ke Ke , Wang Yao Li , Fan Yan Li , Zhao Guo Ji , Yan Yan Fu , Zhang Xin
Published: May 2010

The effects of Ni on the properties of the Sn-2.5Ag-0.7Cu-0.1Re solder alloy and its creep properties of solder joints are researched. The results show that with adding 0.05wt% Ni in the Sn-2.5Ag-0.7Cu-0.1Re solder alloy, the elongation can be sharply improved without decreasing its tensile strength and it is 1.4 times higher than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. Accordingly the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints is the longest, which is 13.3 times longer than that of Sn-2.5Ag-0.7Cu-0.1Re and is also longer than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. In the same environmental conditions, the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints can sharply decrease with increasing the temperature and stress.
Congenital Trypanosoma cruzi Infection. Efficacy of Its Monitoring in an Urban Reference Health Center in a Non-Endemic Area of Argentina
Authors: De Rissio Ana María , Riarte Adelina Rosa , García Miriam Martín , Esteva Mónica Inés , Quaglino Marta , Ruiz Andrés Mariano
Published: May 2010

Congenital transmission (CT) has acquired relevance in Chagas disease (CHD). A cohort of pregnant CHD women (4,355) and their babies were studied in the period 1994–2004. Children were excluded when they had received blood transfusions, or were born or had been in endemic areas; CT rate was 6.1%. Babies were diagnosed between months 1 and 5 in 68.9% of the cases and between months 6 and 12 in 31.1%. In the latter group, parasitemia was detected in 94% and serology in 74.7%. Between months 6 and 9, parasitemia diagnosed 36.2% (P = 0.000) more cases than serology. If serology had been the diagnosis method, those children would have been considered CT free. Taking the overall outcomes, 38.1% of babies were CT free, and 55.8% did not complete the follow-up. Establishing CT as a public health priority and improving first-line health service, congenital CHD coverage could be more efficient in endemic countries.
Risk Factors for Antibiotic-Resistant Escherichia coli Carriage in Young Children in Peru: Community-Based Cross-Sectional Prevalence Study
Authors: Kalter Henry D. , Gilman Robert H. , Moulton Lawrence H. , Cullotta Anna R. , Cabrera Lilia , Velapatiño Billie
Published: May 2010

Few studies have examined the influence of individual-, household-, and community-scale risk factors on carriage of resistant commensal bacteria. We determined children's medical, agricultural, and environmental exposures by household, pharmacy, and health facility surveys and Escherichia coli cultures of children, mothers' hands, household animals, and market chickens in Peru. Among 522 children with a positive stool culture, by log-binomial regression, using “any antibiotic” and 1–14 (versus 0) sulfa doses in the past 3 months increased children's risk, respectively, for ampicillin- and sulfamethoxazole-resistant E. coli carriage (P = 0.01–0.02). Each household member taking “any antibiotic” increased children's risk for sulfamethoxazole- and multidrug-resistant E. coli carriage (P < 0.0001). Residence in a zone where a larger proportion of households served home-raised chicken (as contrasted with intensively antibiotic-raised market chicken) protected against carrying E. coli resistant to all drugs (P = 0.0004–0.04). Environmental contamination with drug-resistant bacteria appeared to significantly contribute to children's carriage of antibiotic-resistant E. coli.
Ecological Niche Modeling of Francisella tularensis Subspecies and Clades in the United States
Authors: Nakazawa Yoshinori , Williams Richard A. J. , Peterson A. Townsend , Mead Paul S. , Kugeler Kiersten J. , Petersen Jeannine M.
Published: May 2010

Two subspecies of Francisella tularensis are recognized: F. tularensis subsp. tularensis (type A) and F. tularensis subsp. holartica (type B). Type A has been subdivided further into A1a, A1b, and A2, which differ geographically and clinically. The aim of this work was to determine whether or not differences among subspecies and clades translate into distinct ecological niches. We used 223 isolates from humans and wildlife representing all six genotypes (type A, B, A1, A2, A1a, or A1b). Ecological-niche models were built independently for each genotype, using the genetic algorithm for rule-set prediction. The resulting models were compared using a non-parametric multivariate analysis-of-variance method. A1 and A2 are ecologically distinct, supporting the previously observed geographic division, whereas ecological niches for types A and B overlapped notably but A1a and A1b displayed no appreciable differences in their ecological niches.
Leishmania tropica in Rock Hyraxes (Procavia capensis) in a Focus of Human Cutaneous Leishmaniasis
Authors: Talmi-Frank Dalit , Jaffe Charles L. , Nasereddin Abedelmajeed , Warburg Alon , King Roni , Svobodova Milena , Peleg Ofer , Baneth Gad
Published: May 2010

Cutaneous leishmaniasis, caused by Leishmania tropica, has recently emerged in urban and rural foci of central and northern Israel, and constitutes a major public health concern. Rock hyraxes (Procavia capensis), the suspected natural reservoir, were trapped in the cutaneous leishmaniasis urban focus of Maale Adumim in central Israel and evaluated for L. tropica infection by real-time kinetoplast DNA (kDNA) polymerase chain reaction (PCR) and serology. Real-time PCR on blood and computerized western blot serology analysis was positive for L. tropica in 58% and 80%, respectively, of the hyraxes tested. Phylogenetic analysis of the ribosomal internal transcribed spacer 1 region indicated that similar genotypes were present in humans and hyraxes from the same habitat. The high rates of infection and exposure to L. tropica among hyraxes supports their involvement in the transmission cycle of this parasite, and their potential role as a reservoir for human disease.
Prevalence and Pathology of West Nile Virus in Naturally Infected House Sparrows, Western Nebraska, 2008
Authors: O'Brien Valerie A. , Meteyer Carol U. , Reisen William K. , Ip Hon S. , Brown Charles R.
Published: May 2010

Nestling birds are rarely sampled in the field for most arboviruses, yet they may be important in arbovirus amplification cycles. We sampled both nestling and adult house sparrows (Passer domesticus) in western Nebraska for West Nile virus (WNV) or WNV-specific antibodies throughout the summer of 2008 and describe pathology in naturally infected nestlings. Across the summer, 4% of nestling house sparrows were WNV-positive; for the month of August alone, 12.3% were positive. Two WNV-positive nestlings exhibited encephalitis, splenomegaly, hepatic necrosis, nephrosis, and myocarditis. One nestling sparrow had large mural thrombi in the atria and ventricle and immunohistochemical staining of WNV antigen in multiple organs including the wall of the aorta and pulmonary artery; cardiac insufficiency thus may have been a cause of death. Adult house sparrows showed an overall seroprevalence of 13.8% that did not change significantly across the summer months. The WNV-positive nestlings and the majority of seropositive adults were detected within separate spatial clusters. Nestling birds, especially those reared late in the summer when WNV activity is typically greatest, may be important in virus amplification.
A Comparative Analysis of Coprologic Diagnostic Methods for Detection of Toxoplama gondii in Cats
Authors: Salant Harold , Spira Dan T. , Hamburger Joseph
Published: May 2010

The relative role of transmission of Toxoplasma gondii infection from cats to humans appears to have recently increased in certain areas. Large-scale screening of oocyst shedding in cats cannot rely on microscopy because oocyst identification lacks sensitivity and specificity, or on bioassays, which require test animals and weeks before examination. We compared a sensitive and species-specific coprologic–polymerase chain reaction (copro-PCR) for detection of T. gondii infected cats with microscopy and a bioassay. In experimentally infected cats followed over time, microscopy was positive occasionally, and positive copro-PCR and bioassay results were obtained continuously from days 2 to 24 post-infection. The copro-PCR is at least as sensitive and specific as the bioassay and is capable of detecting infective oocysts during cat infection. Therefore, this procedure can be used as the new gold standard for determining potential cat infectivity. Its technologic advantages over the bioassay make it superior for large-scale screening of cats.
Identification of Adenoviruses in Fecal Specimens from Wild Chimpanzees (Pan trogylodytes schweinfurthii) in Western Tanzania
Authors: Tong Suxiang , Singh Jatinder , Ruone Susan , Humphrey Charles , Yip Cyril C. Y. , Lau Susanna K. P. , Anderson Larry J. , Kaur Taranjit
Published: May 2010

DNA of two distinctive adenoviruses was detected in wild chimpanzees in western Tanzania that showed clinical signs of acute, upper respiratory disease, notably coughing. The amplified sequences from part of the capsid hexon gene suggests that one virus is a novel adenovirus serotype candidate and the other virus is a species C adenovirus most closely related to recent isolates from captive chimpanzees in the United States, Simian AdV 37 with 86% nucleic acid identity and Simian AdV 40 with 95% nucleic acid identity, respectively. The species C adenovirus sequences suggest possible recombination with a human adenovirus. The source of these viruses and disease association is not known.
A Bayesian approach to estimating copepod development times from stage frequency data
Authors: Kimmerer Wim , Gould Alison
Published: May 2010

We developed Bayesian hierarchical models to estimate life stage durations of copepods from data on life stage frequencies over time in laboratory cohorts. This approach can determine stage duration or development rate, as well as other parameters of the development process, with probability distributions for each parameter. Uncertainty arising from sources such as experimental replication and the variability inherent in count data can easily be incorporated. Prior probability distributions can be uninformative, or they can apply constraints (e.g., stage durations > 0), general knowledge of development, or results of previous experiments. The approach is flexible, with the capability to model any number of life stages from experiments using replicated or unreplicated designs. We verified the model by accurately recovering the life stage distributions used to produce data in a simulation. We then applied the method to laboratory data on the development of two calanoid copepods and one cyclopoid copepod from the San Francisco Estuary. With replication (3 or 4 replicates), the method can determine stage durations with ~30 copepods per sample, although the uncertainty around estimates of stage duration increases as the number of copepods per sample decreases or the sampling interval increases.
Controls on open water evaporation
Authors: Granger R. J. , Hedstrom N.
Published: May 2010

Abstract. The paper presents the initial results of a field study of boundary layer behaviour and open water evaporation carried out on two small- to medium-sized lakes in Western and Northern Canada. Meteorological and boundary layer measurements were made over the water surfaces and over the upwind land surface, allowing for an examination of the effect of lake-land contrasts of temperature on the wind speed over the open water and on the evaporation rates. Lake evaporation was measured directly using eddy covariance equipment. The study showed that, for time periods shorter than daily, the open water evaporation bears no relationship to the net radiation. The wind speed is the most significant factor governing the evaporation rates, followed by the land-water temperature contrast and the land-water vapour pressure contrast. The effect of the stability on the wind field is demonstrated; stability over the water and adjacent land surfaces are, for the most part, out of phase. The derived relationships will be used to develop a model for estimating the hourly evaporation rates from open water. Examination of the seasonal trends shows that the open water period can be separated into two distinct evaporative regimes: the warming period in the Spring, when the land temperature is greater than the water temperature, the turbulent fluxes over water are suppressed; and the cooling period, when the water temperature is greater than the air temperature, and the turbulent fluxes over water are enhanced.
Enhanced‐Light‐Harvesting Amphiphilic Ruthenium Dye for Efficient Solid‐State Dye‐Sensitized Solar Cells
Authors: Wang Mingkui , Moon Soo‐Jin , Zhou Difei , Le Formal Florian , Cevey‐Ha Ngoc‐Lê , Humphry‐Baker Robin , Grätzel Carole , Wang Peng , Zakeeruddin Shaik M. , Grätzel Michael
Published: May 2010

A ruthenium sensitizer (coded C101, NaRu (4,4′‐bis(5‐hexylthiophen‐2‐yl)‐2,2′‐bipyridine) (4‐carboxylic acid‐4′‐caboxylate‐2,2′‐bipyridine) (NCS)2) containing a hexylthiophene‐conjugated bipyridyl group as an ancillary ligand is presented for use in solid‐state dye‐sensitized solar cells (SSDSCs). The high molar‐extinction coefficient of this dye is advantageous compared to the widely used Z907 dye, (NaRu (4‐carboxylic acid‐4′‐carboxylate) (4,4′‐dinonyl‐2,2′‐bipyridine) (NCS)2). In combination with an organic hole‐transporting material (spiro‐MeOTAD, 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine) 9, 9′‐spirobifluorene), the C101 sensitizer exhibits an excellent power‐conversion efficiency of 4.5% under AM 1.5 solar (100 mW cm−2) irradiation in a SSDSC. From electronic‐absorption, transient‐photovoltage‐decay, and impedance measurements it is inferred that extending the π‐conjugation of spectator ligands induces an enhanced light harvesting and retards the charge recombination, thus favoring the photovoltaic performance of a SSDSC.