bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrational Spectroscopic and Optical Absorption Studies on PVA Based Polymer Electrolytes
Authors: Jayaprakash Pavithra , Suriya S. , Gnana Prakash D. , Bhargav P.Balaji
Published: October 2012

The electrochemical methods of energy storage and conversion are of great interest for many practical applications. In the present investigations, PVA: MgSO4 based solid polymer electrolytes were prepared at different weight percent ratios using solution cast technique. FTIR spectroscopic studies were carried out to verify the complexation of the dopant with polymer. Force constant measurement was also carried out to ensure the interactions of polymer with salt. Optical absorption studies were carried out in the wave length range 200 to 600 nm. Absorption edge as well as bandgap values were evaluated. In order to ensure the ionic conduction of these electrolyte systems, transference number measurements were also carried out. The dominant conducting species were ions rather than electrons. These studies will help in verification or in investigating the feasibility of these electrolyte systems in polymer batteries, fuel cells, and other electrochemical systems.
Thermal and Structural Characterization of Furfuryl Palmitate Coated Fly Ash Reinforced Recycled Polypropylene Matrix Composites
Authors: Sengupta Shubhalakshmi , Ray Dipa , Mukhopadhyay Aniruddha
Published: October 2012

Abstract: The fly ash (FA) particles were coated with furfuryl palmitate (FP) in different weight % like 1, 2, 3 and 5. The FP coated fly ash particles were incorporated as filler in recycled polypropylene (RPP) matrix composites by melt mixing in 1:1 weight ratio. X-ray diffraction (XRD) analysis, Dynamic Mechanical Analysis, Differential scanning calorimetry (DSC), and Thermogravimetric analysis (TGA) of the composite samples were carried out. The presence of the coupling agent FP resulted in changes in the packing order and structural properties of the composites. It also influenced the alignment of RPP molecules with better filler –matrix interaction in 2 wt % FP coated composite as ascertained from the DSC and DMA analysis. Distinct shift in the glass transition temperature was also observed in 2 wt % FP coated composite samples. However significant improvement in the thermal stability was not observed. Thus, an unconventional, renewable, low cost coupling agent FP was found to influence the structural and thermal properties of the RPP/FA composites significantly.
Linear and Nonlinear Optical Properties of L- Histidinium Perchlorate (LHPCl) Single Crystal
Authors: Arulmozhi S. , Madhavan J.
Published: October 2012

L- Histidinium Perchlorate, a semi organic nonlinear optical material was grown by solution growth method. The absorption studies show minimum absorption in the entire visible region. The optical band gap (Eg) value of the grown crystal is obtained from the tauc’s plot of (αhν)2 vs hν which was determined by extrapolating the linear region of the curve to the hν axis where (αhν)2=0. Furthermore linear optical parameters such as Extinction coefficient, Reflectance, Refractive index, Complex dielectric constant and Optical conductivity are calculated and its variation with incident photon energy is analyzed. Second Harmonic Generating (SHG) efficiency of the candidate material was determined by Nd:YAG Q-switched laser Kurtz powder techinqe and its 3.19 times greater than KDP.
Dichroic Dye Induced Nonlinearity in Polymer Dispersed Liquid Crystal Materials for Display Devices
Authors: Deshmukh Rajendra , Malik Manoj , Parab Sanmesh
Published: October 2012

The electro-optical characteristics of dye-doped polymer dispersed liquid crystals (PDLCs) have been investigated for display applications. The PDLC samples were obtained by polymerization induced phase separation of the nematic liquid crystal (LC)-dye-prepolymer mixtures under UV illumination with a constant intensity. The optimum conditions for the scattering characteristics of the dye-doped PDLC films as function of the dye concentration have been examined. It was seen that the phase separation and segregation of LC droplets is dependent on the amount of dye used. LC droplets in dye-doped PDLC films exhibit various configurations at lower and higher applied electric field when observed in situ under polarizing optical microscope. The effects of morphology on the electro-optical properties were examined. Experimental results indicate that the driving voltage and contrast ratio were affected considerably by the amount of dye. UV-VIS spectroscopy results showed that the molecular orientation of dye in LC droplets can be controlled to induce nonlinearity in these materials. The results showed that the dye concentration can be optimized to obtain promising electronic materials with minimum threshold and high contrast for display applications.
Growth, Spectral, Optical and Thermal Studies of Sodium Chloride Admixtured L-Alanine (SCLA) Single Crystals
Authors: Lucia Rose A.S.J. , Selvarajan P. , Perumal S.
Published: October 2012

Sodium chloride admixtured L-alanine single crystals of appreciable size were grown by slow evaporation technique at room temperature. The grown crystals were colourless and transparent. The cell parameters of the crystals were estimated by X-ray diffraction studies. The functional groups have been identified by FTIR spectral analysis. UV-Visible transmittance studies were carried out for the grown samples. Powder SHG measurements have been done using Kurtz – Perry powder technique. Thermal studies were carried out to check the thermal stability of the crystals.
Synthesis, Growth and Characterisation of Nonlinear Optical Nb-Doped L-Prolinium Picrate Single Crystals
Authors: Gurumurthi T. , Murugakoothan P.
Published: October 2012

A nonlinear optical material Niobium doped L-Prolinium Picrate was synthesized and grown as single crystals by slow evaporation method. The grown crystals were subjected to structural, elemental, thermal, optical and dielectric studies. The structural analysis reveals that Nb : LPP belongs to the monoclinic crystallographic system with space group P21. Optical transparency of the grown crystals was investigated by UV-vis-NIR spectrum. The thermal analyses reveal that Nb doped L-Prolinium Picrate is thermally stable up to 185 °C. The dielectric constant and dielectric loss of the crystal were studied as a function of frequency. The nonlinear optical property of the grown crystal was confirmed by the Kurtz-powder second harmonic generation test and the results are compared with pure LPP. Mechanical strength of the crystal was also carried out by Vicker’s micro hardness test.
Evolution of the Solidification Microstructure of Rheocast High Purity Aluminium
Authors: George Sarah , Knutsen Robert
Published: October 2012

High purity aluminium has been successfully rheocast using the CSIR-RCS system combined with high pressure die casting. Analysis of the as-cast microstructure by SEM and EBSD revealed the presence of in-grain substructures. These morphological features show that the overall growth mode of the globular grains during rheocasting is planar, but the presence of these features indicates that the solidification mode is cellular at some stages during the slurry production process. Cellular solidification is associated with unstable growth at the solid-liquid interface and is initiated and exacerbated by solute gradients between the melt and the newly formed solid. This high purity alloy exhibits the same cellular growth, indicating that even minor solute variations have an effect on the stability of the solid-liquid interface and, hence, the mode of solidification during semi-solid rheocasting.
Characterization of the Microstructure and Rheological Behavior of Al-4wt%Si-2.5wt%Cu Alloy Produced by Direct Chill Casting and Electromagnetic Stirring
Authors: Torres Luis Vanderlei , Zoqui Eugênio José
Published: October 2012

This work involved an evaluation of a Al-4wt%Si-2.5wtCu alloy to be used as raw materials in the thixoforming process. The alloy was produced by direct casting under electromagnetic stirring to obtain ingots of 250 mm length and 30 mm diameter. The alloy was analyzed to determine their morphology and rheological behavior in the semi-solid range. The tests included characterization of the microstructural evolution by subjecting them to re-heating treatment in two conditions of solid fractions, 45% and 60%, for 0, 30, 90 and 210 s. A compression testing device designed specifically to evaluate semi-solid materials was used to determine the rheological behavior, and the tests were performed at the same heating rate and hold times to determine the apparent viscosity. The use of electromagnetic stirring to produce the raw material was effective in producing alloy with very small grain/primary particle sizes (80 up to 120 µm). Based on the morphological evolution in the semi-solid state, the alloy showed only minor variations in grain/primary particle size and surface factor (SF) as a function of the different globularization heat treatment times, suggesting that all these alloys are suitable for production. The Al-4.0wt%Si-2.5wt%Cu alloy with 45% solid fraction presented apparent viscosity about 1.5 x106 Pa.s.
Fusion Welding of Rheocast Semi-Solid Metal (SSM) Processed Aluminium Alloy 7017
Authors: du Toit Madeleine , Letsoalo Patronica , Möller Heinrich
Published: October 2012

Near-net shape casting of wrought aluminium alloys has proven to be difficult due to a tendency towards hot tearing during cooling. Rheocasting, or semi-solid metal (SSM) processing followed by high pressure die casting (HPDC), has recently been shown to be an effective alternative to conventional die casting, yielding near-net shape wrought aluminium alloy castings with less risk of hot tearing. This casting process involves pouring the liquid metal into a processing cup, which is then transferred into a coil for induction stirring and simultaneous forced air cooling. When the metal reaches the semi-solid casting temperature, the resultant slurry is transferred to a high pressure die casting machine and cast to near-net shape. This modifies the as-cast microstructure, yielding a more globular primary phase and results in mechanical properties in the -T6 condition closely approaching those of wrought material in the same condition. Little information is currently available on the response of SSM-HPDC material to welding. This project investigated the influence of autogenous laser and gas tungsten arc welding on the microstructure and mechanical properties of aluminium 7017 after rheocasting. It is possible to successfully weld this material without solidification or liquation cracking. The effect of welding on the rheocast microstructure in the heat-affected zone and weld metal was shown, and the hardness and tensile properties of the resulting joints in the as-welded condition were tested and related to the microstructures achieved.
The Heat Treatment of Rheo-High Pressure Die Cast Al-Cu-Mg-Ag Alloy 2139
Authors: Möller Heinrich , Govender Gonasagren
Published: October 2012

High strength wrought Al-Cu-Mg-Ag alloy 2139 was successfully processed using the CSIR rheocasting system and cast into plates using high pressure die casting. Differential scanning calorimetry was used to determine suitable homogenization/solution treatment temperatures. A two-step homogenization/solution treatment of 490oC for 24 h, followed by 520oC for 2 h does not cause any incipient melting. Artificial aging of the R-HPDC 2139 plates at 160oC for 24 h results in tensile properties similar to those reported for thixoformed casting alloy 201-T6. The minimum military specifications for wrought 2139-T8 are exceeded in terms of strength, with slightly lower ductility being obtained. Artificial aging at 153oC for 20 h results in tensile properties that exceed all the minimum military specifications for wrought 2139-T8.
Globule-Globule Interactions during Deformation in Semi-Solid Al-Cu Using Time-Resolved X-Ray Tomography
Authors: Kareh Kristina Maria , Lee Peter D. , Gourlay Christopher M.
Published: October 2012

Optimising semi-solid processing and accurately modelling semi-solid deformation requires a fundamental understanding of the globule-scale mechanisms that cause the macroscopic rheological response. In this work, apparatus and analysis techniques are being developed for the time-resolved, three-dimensional imaging of semi-solid alloy deformation. This paper overviews synchrotron X-ray tomography results on globular Al-15wt%Cu deformed at 0.7 solid fraction using extrusion. The globule-globule interactions in response to load were quantified in terms of the response of individual globules with respect to globule translation, rotation, and deformation. The potential of time-resolved X-ray tomography in the study of semi-solid alloy deformation is then discussed.
In Situ Study of the Altering Globule Packing-Density during Semisolid Alloy Deformation
Authors: Gourlay C.M. , Nagira T. , Uesugi Kentaro , Yasuda Hideyuki
Published: October 2012

Synchrotron radiography experiments are overviewed that directly image semi-solid deformation at the globule-scale. Globular Al-15Cu at 50-60% solid was deformed in direct-shear at 10-2 s-1. Deformation is shown to occur by globule rearrangement without discernible deformation of the individual globules. Globules were found to translate and rotate as quasi-discrete bodies in response to forces acting at globule-globule contacts, similar to liquid-saturated granular materials such as water-saturated sand. Rearrangement caused the globule packing-density (the solid fraction) to adjust by local compaction and local dilation of the globule assembly, and deformation is highly inhomogeneous. During shear, there was a net dilation and strain began to localize into a shear band of decreased solid fraction by the end of the experiments.
Effect of Recrystallization and Partial Melting Method on Microstructural Evolution of SKD61 Tool Steel in Semi-Solid State
Authors: Yi Meng , Sugiyama Sumio , Yanagimoto Jun
Published: October 2012

The microstructural evolution and basic refinement mechanism of the semi-solid-state SKD61 tool steel fabricated by recrystallization and partial melting (RAP) method were investigated experimentally. The effects of different parameters in RAP processing were systematically clarified to achieve the grain refinement of cast SKD61 steel in the semi-solid state. Results showed that, the microstructure of RAP processed specimen were finer and more globular than the microstructure of starting material. The distribution of finer solid particles in the RAP processed specimen was affected by the distribution of strain during predeformation. Uniform and spherical solid particles inclined to locate in the regions suffered from larger strain. The specimens subjected to a plastic predeformation at a lower temperature have a more uniform and spherical semi-solid microstructure than those specimens undergoing predeformation with the same reduction at higher temperatures. In addition, the grain refinement mechanism of SKD61 tool steel processed by RAP method was discussed.
Study on Microstructural Evolution of Deformed Magnesium Alloy during Partial Remelting
Authors: Chen Qiang , Zhao Gao Zhan , Shu Da Yu
Published: October 2012

Microstructural evolution of ZK60 Mg alloy during partial remelting was investigated in this paper. The results show that ZK60 Mg alloy semi-solid billets were successfully produced by recrystallisation and partial remelting (RAP) process. Following partial remelting in each case, grain coarsening had occurred in the semi-solid state with increasing holding time. Liquid was present, during partial remelting all four temperatures, in the form of isolated intragranular droplets. These liquid droplets were produced by intragranular eutectic phase and entrapped liquid. Intragranular liquid droplets migrated and merged into some large rounded liquid droplets. After the spheroidization was completed, coarsening and coalescence occurred. When temperature is relatively low (the thickness of liquid is relatively thin), grains contacted with each other, which produced irregular-shaped grains.
Applications of Semi-Solid Slurry Casting Using the Gas Induced Semi-Solid Technique
Authors: Wannasin Jessada
Published: October 2012

A rheocasting technique called the Gas Induced Semi-Solid (GISS) is being developed for commercial applications in Thailand. The process creates semi-solid metal slurries by applying the injection of fine inert gas bubbles through a graphite diffuser to induce localized convection and heat extraction. The slurries are then formed into parts using different casting processes such as die casting, squeeze casting, gravity casting, and semi-solid infiltration process. This paper reports some of the current applications of the GISS forming processes, including prosthetic adaptors, lapping plates, sacrificial anodes, and armor plates. Preparation of semi-solid slurries of the alloys used in these applications, which are aluminum 356, Sn-Sb, Al-Zn-In, and 7075 alloys, is also reported and discussed.
Numerical Simulation on the Filling Process of Rheological Die Casting and Forming Defects Analysis
Authors: Zhang Fan , Song Nan Nan , Zhang Jun , Kang Yong Lin , Zhu Qiang
Published: October 2012

According to semi-solid slurry rheological behavior, an apparent viscosity model of A356 alloy developed based on the Carreau model was established to simulate filling process of rheo-diecasting about automobile shock absorber parts and to compare with conventional liquid filling process. Numerical simulation results showed that the filling process of rheo-diecasting was smooth but difficult to splash, which reduced the tendency of the alloy oxidation and inclusion. Meanwhile, a certain percentage of the primary solid particles precipitated before filling and solidification shrinkage of semi-solid slurry were small. This benefited to reduce or eliminate shrinkage defects of the castings. Compared with conventional liquid die casting process, rheo-diecasting process had unique advantages in reducing the internal defects and improving mechanical properties of castings.
R-HPDC in South Africa
Authors: Curle Ulyate Andries , Möller Heinrich , Govender Gonasagren
Published: October 2012

The history of semi-solid metal forming and in particular rheo-high pressure die casting at the Council for Scientific and Industrial Research in South Africa is discussed. Processing flexibility is demonstrated on the Al-Si-Mg, Al-Mg-Si, Al-Cu-Mg and Al-Zn-Mg-Cu casting and wrought alloy systems as well as on high purity aluminium, unmodified Al-Si binary eutectic, metal matrix composites and magnesium alloys. Material properties are highlighted.
Friction Welding of Thixocast A356 Aluminium Alloy
Authors: Singh Shailesh K. , Chattopadhyay Kamanio , Dutta Pradip
Published: October 2012

In this paper, a numerical model for friction welding of thixo-cast materials is developed, which includes a coupling of thermal effect and plastic deformation using a finite element method (FEM). As the constitutive equations for flow behavior of materials for a thixo-cast material are expected to be different from those of conventionally cast material of the same alloy, the necessary material data are experimentally determined from isothermal hot compression tests of the A356 thixocast alloy. The Johnson-Cook model has been employed to represent the flow behavior of the thixocast A356 alloy. The purpose of this FEM analysis is to provide better understanding of the friction welding process of thixo-cast material, and to obtain optimized process parameters before an actual welding is carried out.
Flow Behaviour of M2 Steel Alloy during Semi Solid Isothermal Rapid Compression
Authors: Yekta Farzad Hosseini , Sadough S.A. , Pouyafar Vahid , Jabbari Amin
Published: October 2012

The key to all semisolid processes is spherical and non-dendritic particles suspended in a liquid matrix. This special kind of microstructure causes the semisolid material to behave like a non-Newtonian fluid dependent on time and shear rate. Semi solid metal processing gives less shrinkage and porosity, non-macro segregation, lower flow stress, good formability and increased die life compared with conventional production methods. Therefore, semi solid processing introduces a good option for massive forming of high temperature alloys. Here, by partial remelting of M2 tool steel alloy under rapid compression test, deformation mechanism of steel alloy and its correlation to rheological properties were investigated. Flow stress for M2 tool steel alloy corresponding to solid fraction above 55% derived at constant strain rate and holding time. In order to investigate the parameter involved in this process, in the second stage of experiments the ram speed and holding time are variable. The analysis of the derived curves shows that the semisolid slurries exhibit a pseudo plastic behavior dependent on stain rate and temperature. The classical power law model used to describe the rheological and thixotropic dependence.
The Rheological Behavior of HS6-5-2 Tool Steel for Non-Isothermal Processing
Authors: Yekta Farzad Hosseini , Sadough S.A. , Pouyafar Vahid , Jabbari Amin
Published: October 2012

The rheological behavior of semi-solid tool steel is investigated using a conventional rheometer under cooling rate and shear rate. The processing of steels in semi-solid state is still at development stage due to the high processing temperature involved. The candidate grades of steel for thixoforming are high speed, high carbon, stainless steel and ductile iron. TheHS6-5-2 tool steel has a wide semi-solid range of over 200 C and the required spheroidal microstructure achieved by partial re-melting from as supplied state without any mechanical agitation, indicated the potential of this grade to be investigated in semi-solid processing. For non-isothermal processing an increase of solid fraction related to solidification due to thermal exchanges is observed. In the first series of experiment after melting the feed stock in an alumina cup, the alloy is sheared continuously by a rotating rod with a constant shear rate under three different cooling rates to the 55% corresponding liquid fraction. In the second series of experiment three different shear rates were applied under a constant cooling rate. The apparent viscosity of the slurry as a function of cooling rate and solid fraction is calculated from the applied torque to the outer cylinder. The results show that the slurry viscosity decreases with increasing shear rate and increases with increasing cooling rate and solid fraction. Additionally for a given solid fraction, shear thinning behavior is observed.
Wall Slip Effect in Couette Rheometers
Authors: Harboe Siri , Modigell Michael , Pola Annalisa
Published: October 2012

Wall slip of suspensions in confined flow is caused by segregation of a thin layer of liquid phase adjacent to the walls. This causes the bulk phase to slide along the walls, which means that the fluid flow velocities respective to the walls are not zero. In rheometers this affects the evaluation of the rheological properties. Despite the importance of understanding and controlling segregation effects, little research has been done on this subject area. Indeed in industrial casting, the die filling behaviour, and therefore the product quality, may depend on the segregation phenomena. It is important to understand the wall slip phenomenon’s correlation with experimental parameters, as a step towards casting process optimization. Two issues are handled in the present work, the first is the evaluation of different methods to investigate the wall slip effect, the second is the investigation of the wall slip effect dependency on the suspension parameters particle size and solid fraction, respectively. The suspensions employed for the investigations were the aluminium alloy A356 in semi-solid form and a “synthetic suspension” built up of glass spheres in silicon oil. As a result of the above described investigations, influence of suspension parameters are found, and a validated method to avoid the wall slip effect is suggested.
A High-Precision Rotational Rheometer for Temperatures up to 1700 °C
Authors: Modigell Michael , Volkmann Torsten , Zang Christoph
Published: October 2012

Rheometrical analysis of steel slurries in rotational rheometers requires a range of operating temperatures of about 1300 to 1600 °C, leading to a delicate device-related challenge with respect to the applied materials on the one hand and a suitable constructional set-up gaining unbiased measurements on the other hand. Accordingly, a new high-precision rotational rheometer for temperatures up to 1700 °C has been developed as an improvement on an existing rheometer previously developed at the Chair of Mechanical Process Engineering (AVT) of RWTH Aachen University. First measurements on the tool steel X210CrW12 in the mushy state with solid fractions of 20% to 40% demonstrate a remarkable improvement on the preciseness of torque gain which broadens the area of possible experimental operations on steel slurries in order to reliably characterize transient behavior of the material by e.g. creep, relaxation and oscillation experiments.
Microstructure of Al Alloy Semi-Solid Slurry Made in Metallic Vessel Using Vibrating Plate
Authors: Hirata Naoya , Zulaida Yeni Muriani , Itamura Masayuki , Anzai Koichi
Published: October 2012

Recently, semi-solid slurry making method using metallic vessels, called "Cup-method", have been studied by the authors. In this method, semi-solid slurry with globular and fine structure is obtained only by pouring molten metal at certain temperature into a metallic vessel which is designed for desired slurry volume and solid fraction of the slurry. The method provides us shorter slurry making time and finer microstructure of α grain with around 50 μm in its size. However, the cup-method requires precise control in the slurry making condition; therefore it is difficult to obtain the homogeneous microstructure in the slurry, especially for the larger slurry. In this study, mechanical vibration was introduced to enhance homogeneity and fine microstructure generation. As a result, mechanical vibration provides the fine and homogeneous distribution of microstructure for wider slurry making conditions. Fine and non-dendrite structure of the slurry could be obtained even by using higher superheated melt, while the conventional method without vibration showed coarse and dendritic microstructure in the similar conditions.
Forced Convection Rheomoulding Process for Semisolid Slurry Preparation and Microstructure Evolution of 7075 Aluminum Alloy
Authors: Zhou Bing , Kang Yong Lin , Zhang Jun , Gao Jun Zhen , Zhang Fan
Published: October 2012

A self-developed forced convection rheomoulding (FCR) machine for light alloy semisolid slurry preparation is introduced, which is high efficient, reliable and easy to maintain. Its core component contains a shearing system, a central temperature processing system and a discharge system. Flow characteristics and the parameter of FCR process affecting semisolid slurry organization are analysed. Taking 7075 aluminium alloy as experimental material, experimental results show that the FCR process could obtain semisolid microstructure with the small primary α-Al particles of nearly spherical and uniformly distributed. The melt of aluminium alloy involves complex convection mixing characteristics when flowing in FCR device. As the pouring temperature decreases, the primary particles become fine and homogeneous with the mean size diminished and the shape factor increased.
Effect of Ultrasounds during the Solidification Process of the A357 Aluminium Alloy
Authors: Forn Antonio , da Silva Manel , Baile Maite Teresa , Picas Josep A. , Fauria Antolí
Published: October 2012

It is known that ultrasonic waves promote nucleation and globulization of solid particles in aluminium alloys. However, the studies performed up to date have been conducted, in the laboratory, using small volumes of aluminium. This article aims to establish the application of ultrasound effect in the A357 aluminium-silicon alloy in amounts of about 2 kg of material. The experiments have been conducted with different parameters of ultrasonic treatment, evaluating the microstructure of the slurry quenched from the semi-solid state. The globulization effect of aluminium α phase by ultrasounds is very effective in the area close to the ultrasonic horn tip and the transmission system, but its effect highly reduces in the regions far away from the source of ultrasonic waves.
Application Research on Annular Electromagnetic Stirring Casting Process of Al-Zn-Mg-Cu Alloy
Authors: Xu Jun , Gao Zhi Hua , Zhang Zhi Feng , Tang Men Gou , Yu Wei Dong
Published: October 2012

Annular electromagnetic stirring (A-EMS) process is verified an advanced metal melt treatment technology. Application research was performed to investigate the solidification behavior of Al-Zn-Mg-Cu alloy in this study. The results indicated that uniformly fine microstructure, less composition macro-segregation and improved mechanical properties were achieved.
Some Approaches on Industrial Installation of Steel Thixoforged Processes
Authors: Bigot Régis , Becker Eric , Langlois Laurent
Published: October 2012

Based on several years of research, this paper presents some approaches on industrial installation on thixoforging steel with an important potential of an innovative technology. The possibility of Thixoforging industrialization makes it possible to consider new steel components production. From billet to final part with complex shape obtained in one step, several “keys” are developed as heating system, transfer system, part and die design.
Tooling Materials and Solutions for Thixoforming of Steel
Authors: Rassili Ahmed , Falzone Salvatore , Lecomte-Beckers Jacqueline
Published: October 2012

The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during steel thixoforming process in order to determine appropriate tool materials and solutions. This evaluation was realized thanks to experimental trials and to the finite elements simulations. The effect of these loadings on the tool’s failure modes are highlighted and compared to the ones observed in classical forming processes. Beyond this, the failure modes of different tool materials and solutions are presented. The tested materials are hot-working tool steels. Other possibilities and tool coating or surface treatments are discussed as well.
Semisolid Forging of Hypereutectic Al-Si Alloy for Automobile AC Compressor Components
Authors: Zhang Zhi Feng , Xu Jun , Bai Yue Long , Wang Ya Bao
Published: October 2012

Semisolid forging process, characterized by short process, near-net shape, low cost, and high performance, is increasingly playing an important role in lightweighting transportation systems for light metals. In this study, semisolid forging process for hypereutectic Al-Si alloy, as a substitute for nodular cast iron, was applied in producing automobile AC compressor components. The results showed that hypereutectic Al-Si alloy swash plate thixo-forged had higher strength than nodular cast iron one by optimizing forming process parameters.
Casting and Heat Treatment of Turbocharger Impellers Thixocast from Alloy 201
Authors: Zhu Qiang , Midson Stephen , Ming Chang Wei , Atkinson Helen V.
Published: October 2012

Commercial semi-solid cast impellers are produced from Al-Si-Cu alloys heat treated to the T6 temper. The study described in this paper involved the identification of casting and heat treatment parameters to produce semi-solid processed turbocharger impellers from a silicon-free, higher strength 201 alloy. Casting parameters were identified which minimized hot tearing in the alloy 201 impellers. A series of heat treatment studies were performed to determine optimum heat treatment parameters. The T71 temper was identified as the preferred heat treatment condition to produce high strength as well as superior elongation. The results from mechanical property measurements conducted on the T71 heat treated impellers are reported. Optical and scanning electron microscopy (SEM) were also used to characterize the microstructure of alloy 201 impellers before and after heat treatment, and representative microstructures are presented.
Semi-Solid Preparation and Performance of Magnesium Based Thermoelectric Materials
Authors: Song Ren Bo , Kang Yong Lin , Sun Jian Lin
Published: October 2012

Ternary Mg-based thermoelectric materials are prepared by Semi-Solid Processing (SSP) and Spark Plasma Sintering (SPS). DTA, XRD and SEM analysis are applied to explore the processing conditions of Mg2Si1-xSnx (x=0, 0.2, 0.4, 0.6, 0.8, 1). The results show that raw-materials should be put into the furnace at 773 K, and kept 60 min in 1123 K. Then stirring 5 min under semi-solid state and air cooled finally. At temperature of 1023 K, pressure of 30 MPa, the sample is sintered by SPS. The XRD shows that the peaks of sample are sharp and complete, and move left with increasing Sn. The thermoelectric properties of Mg2Si1-xSnx (x=0.4, 0.6) are analyzed between 373 K to 673 K. Results indicate that electrical conductivity (σ) increases continually, Seebeck coefficient (α) increases then decreases, and thermal conduction (κ) decreases and increases with increasing temperature. Except that, electrical conductivity and Seebeck of Mg2Si0.6Sn0.4 are better than Mg2Si0.4Sn0.6 made by the same method. The properties of Mg2Si0.4Sn0.6 sintered at 1023 K, is better than the one at 973 K. The maximum zT of Mg2Si0.4Sn0.6 is 0.086 at 573 K.
The Use of High Pressure Direct Squeeze Casting for Semi-Solid Processing of Aluminum Base Nano Composites
Authors: Weiss David , Black Michael
Published: October 2012

The production of nano-reinforced aluminium alloys in volume and quality suitable for subsequent shape casting has been problematic. Large specific surface area and high interfacial energy of the particles combined with high surface tension of the aluminium melt makes it difficult to add appreciable numbers of particles to the melt, even when later de-agglomerated by techniques such as ultrasonic cavitation. The objective of this work was to develop a technique to incorporate particles using pressure applied while the alloy was in a semi-solid state. The composites produced could be used as a master alloy to inoculate large batches of metal for subsequent casting using any suitable technique. The results show excellent distribution of 50 nm alumina particles in 2014 material. The procedure appears to have broad applicability to a full range of aluminium alloys and particle reinforcements.
Indicator mineral signatures of magmatic Ni-Cu deposits, Thompson Nickel Belt, Manitoba: Part 1 - bedrock data
Authors: McClenaghan M B , Kjarsgaard I M , Averill S A , Layton-Matthews D , Crabtree D , Matile G
Published: October 2012

Bedrock and till sampling around the Ni-Cu deposits in the northern Thompson Nickel Belt, Manitoba, was conducted by the Geological Survey of Canada in collaboration with the Canadian Mining Industry Research Organization and the Manitoba Geological Survey to
document the types and compositions of minerals indicative of Ni-Cu mineralization in both mineralized bedrock and till. This report constitutes Part 1 of the reporting of indicator-mineral results from the study: bedrock samples. Bedrock samples used in this study were collected in 2005 and their
compositional data were compared to published data from previous Thompson Nickel Belt studies. Potential indicator minerals were identified and characterized in both polished thin section and heavy mineral concentrates prepared from crushed bedrock samples. Pentlandite, Ni-bearing pyrrhotite,
chalcopyrite, pyrite, and sperrylite are documented in the samples and are potential indicators of Ni-Cu mineralization, however these minerals are prone to physical abrasion and post-glacial weathering when eroded, transported, and deposited in till. Chalcopyrite and pentlandite are the most
abundant ore minerals in till and are most abundant in pan concentrates (25-250 ?m) and the 0.25-0.5 mm fractions.
The most physically robust indicator mineral documented in the bedrock samples is Zn-rich (>2 wt.% ZnO) chromite to Cr-magnetite. These minerals were expected to be Zn-rich due to the high grades of metamorphism found in many of the Ni-Cu deposits within the Thompson Nickel Belt.
Olivine, in association with mineralized rocks, has a restricted composition range >Fo78 and <3000 ppm Ni, making it another potential indicator mineral. Although abundant in till down ice of the Thompson Nickel Belt, Cr-diopside was not recovered from bedrock samples and its
bedrock source remains to be identified.
Influence of air quality model resolution on uncertainty associated with health impacts
Authors: Thompson T. M. , Selin N. E.
Published: October 2012

Abstract. We use regional air quality modeling to evaluate the impact of model resolution on uncertainty associated with the human health benefits resulting from proposed air quality regulations. Using a regional photochemical model (CAMx), we ran a modeling episode with meteorological inputs simulating conditions as they occurred during August through September 2006 (a period representative of conditions leading to high ozone), and two emissions inventories (a 2006 base case and a 2018 proposed control scenario, both for Houston, Texas) at 36, 12, 4 and 2 km resolution. The base case model performance was evaluated for each resolution against daily maximum 8-h averaged ozone measured at monitoring stations. Results from each resolution were more similar to each other than they were to measured values. Population-weighted ozone concentrations were calculated for each resolution and applied to concentration response functions (with 95% confidence intervals) to estimate the health impacts of modeled ozone reduction from the base case to the control scenario. We found that estimated avoided mortalities were not significantly different between the 2, 4 and 12 km resolution runs, but the 36 km resolution may over-predict some potential health impacts. Given the cost/benefit analysis requirements motivated by Executive Order 12866 as it applies to the Clean Air Act, the uncertainty associated with human health impacts and therefore the results reported in this study, we conclude that health impacts calculated from population weighted ozone concentrations obtained using regional photochemical models at 36 km resolution fall within the range of values obtained using fine (12 km or finer) resolution modeling. However, in some cases, 36 km resolution may not be fine enough to statistically replicate the results achieved using 2, 4 or 12 km resolution. On average, when modeling at 36 km resolution, an estimated 5 deaths per week during the May through September ozone season are avoided because of ozone reductions resulting from the proposed emissions reductions (95% confidence interval was 2–8). When modeling at 2, 4 or 12 km finer scale resolution, on average 4 deaths are avoided due to the same reductions (95% confidence interval was 1–7). Study results show that ozone modeling at a resolution finer than 12 km is unlikely to reduce uncertainty in benefits analysis for this specific region. We suggest that 12 km resolution may be appropriate for uncertainty analyses of health impacts due to ozone control scenarios, in areas with similar chemistry, meteorology and population density, but that resolution requirements should be assessed on a case-by-case basis and revised as confidence intervals for concentration-response functions are updated.
Quantitative comparison of the variability in observed and simulated shortwave reflectance
Authors: Roberts Y. L. , Pilewskie P. , Kindel B. C. , Feldman D. R. , Collins W. D.
Published: October 2012

Abstract. The Climate Absolute Radiance and Refractivity Observatory (CLARREO) is a climate observation system that has been designed to monitor the Earth's climate with unprecedented absolute radiometric accuracy and SI traceability. Climate Observation System Simulation Experiments (OSSEs) have been generated to simulate CLARREO hyperspectral shortwave imager measurements to help define the measurement characteristics needed for CLARREO to achieve its objectives. To evaluate how well the OSSE-simulated reflectance spectra reproduce the Earth's climate variability at the beginning of the 21st century, we compared the variability of the OSSE reflectance spectra to that of the reflectance spectra measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY). Principal component analysis (PCA) is a multivariate spectral decomposition technique used to represent and study the variability of hyperspectral radiation measurements. Using PCA, between 99.7% and 99.9% of the total variance the OSSE and SCIAMACHY data sets can be explained by subspaces defined by six principal components (PCs). To quantify how much information is shared between the simulated and observed data sets, we spectrally decomposed the intersection of the two data set subspaces. The results from four cases in 2004 showed that the two data sets share eight (January and October) and seven (April and July) dimensions, which correspond to about 99.9% of the total SCIAMACHY variance for each month. The spectral nature of these shared spaces, understood by examining the transformed eigenvectors calculated from the subspace intersections, exhibit similar physical characteristics to the original PCs calculated from each data set, such as water vapor absorption, vegetation reflectance, and cloud reflectance.
Timing and magnitude of equatorial Atlantic surface warming during the last glacial bipolar oscillation
Authors: Weldeab S.
Published: October 2012

Abstract. The timing and magnitude of millennial-scale thermal oscillation in the equatorial Atlantic during the last glacial and marine isotope stage 3 have been perceived as merely a response to meltwater-induced perturbations of the northern high latitude climate. The relatively asymmetric distribution of available temperature records has so far impeded testing whether this view is valid across the equatorial Atlantic. This study presents a centennially resolved record of Mg/Ca-derived sea surface temperature (SST) estimates from the eastern equatorial Atlantic (EEA) and a core top-based proxy validation. Multivariate analysis of the EEA core top data indicates that the Mg/Ca ratio varies by 8 ± 2% per unit SST (°C) and 1 ± 0.9% per unit salinity (psu) change, indicating that temperature is the most dominant factor controlling planktonic foraminiferal Mg/Ca variation. The EEA SST time series exhibits a close correlation between episodes of rapid equatorial surface water warming, the onset of massive meltwater inputs into the North Atlantic (Heinrich events H3–H6), and Antarctic climate changes, indicating that the EEA was very sensitive to millennial-scale bipolar oscillations. Rapid EEA SST rise between 0.8 °C and 2 °C, synchronous with the onset of Heinrich events, is consistent with the concept of tropical Atlantic warming in response to meltwater-induced perturbation of Atlantic meridional ocean circulation (AMOC). At variance with model results that suggest a basin-wide SST rise during and rapid surface cooling concomitant with the termination of Heinrich events, this study indicates persistently elevated EEA SST during and up to 2300 yr after the abrupt termination of Heinrich events. This study emphasizes that changes in wind-induced low-latitude zonal surface currents were crucial in shaping the spatial heterogeneity and duration of equatorial Atlantic surface water warmth.
Climate change, growing season water deficit and vegetation activity along the north–south transect of eastern China from 1982 through 2006
Authors: Sun P. , Yu Z. , Liu S. , Wei X. , Wang J. , Zegre N. , Liu N.
Published: October 2012

Abstract. Considerable work has been done to examine the relationship between environmental constraints and vegetation activities represented by the remote sensing-based normalized difference vegetation index (NDVI). However, the relationships along either environmental or vegetational gradients are rarely examined. The aim of this paper was to identify the vegetation types that are potentially susceptible to climate change through examining their interactions between vegetation activity and evaporative water deficit. We selected 12 major vegetation types along the north–south transect of eastern China (NSTEC), and tested their time trends in climate change, vegetation activity and water deficit during the period 1982–2006. The result showed significant warming trends accompanied by general precipitation decline in the majority of vegetation types. Despite that the whole transect increased atmospheric evaporative demand (ET0) during the study period, the actual evapotranspiration (ETa) showed divergent trends with ET0 in most vegetation types. Warming and water deficit exert counteracting controls on vegetation activity. Our study found insignificant greening trends in cold temperate coniferous forest (CTCF), temperate deciduous shrub (TDS), and three temperate herbaceous types including the meadow steppe (TMS), grass steppe (TGS) and grassland (TG), where warming exerted more effect on NDVI than offset by water deficit. The increasing growing season water deficit posed a limitation on the vegetation activity of temperate coniferous forest (TCF), mixed forest (TMF) and deciduous broad-leaved forest (TDBF). Differently, the growing season brownings in subtropical or tropical forests of coniferous (STCF), deciduous broad-leaved (SDBF), evergreen broad-leaved (SEBF) and subtropical grasslands (STG) were likely attributed to evaporative energy limitation. The growing season water deficit index (GWDI) has been formulated to assess ecohydrological equilibrium and thus indicating vegetation susceptibility to water deficit. The increasing GWDI trends in CTCF, TCF, TDS, TG, TGS and TMS indicated their rising susceptibility to future climate change.
Changing Concepts of Childhood: Children’s Folklore Scholarship since the Late Nineteenth Century
Authors: Tucker Elizabeth
Published: October 2012

This essay examines children’s folklore scholarship from the late nineteenth century to the present, tracing key concepts from the Gilded Age to the contemporary era. These concepts reflect significant social, cultural, political, and scientific changes. From the "savage child" to the "secret-keeping child," the "magic-making child," the "cerebral child," the "taboo-breaking child," the "monstrous child," and others, scholarly representations of young people have close connections to the eras in which they developed. Nineteenth-century children’s folklore scholarship relied on evolutionism; now evolutionary biology provides a basis for children’s folklore research, so we have re-entered familiar territory.
The Role of Vitamin K in Bone Remodeling and Osteoporosis
Authors: Giammanco Marco , Majo Danila Di , Leto Gaetano , Flandina Carla , Piazza Melania Di , Guardia Maurizio La
Published: October 2012

Vitamin K is an essential fat soluble vitamin involved in the regulation of normal coagulation. However, growing evidence highlights that this molecule appears to be also implicated in the regulation of other important biological functions such as bone mineralization, calcium homeostasis, apoptosis, cell growth and signal transduction. In particular, many studies have focused their attention on the protective effects of vitamin K on bone tissue in the outlook of its use in the prevention and treatment of osteoporosis in post-menopausal women. The objective of the present paper is to review data of the literature regarding the metabolic effects of Vitamin K in bone tissue and its clinical role in the prevention and treatment of osteoporosis.