bluuebunny/crossref_metadata_2025 huggingface dataset:
L’écriture de soi, et ses modalités de constitution en archives
Authors: Cohen Anouk
Published: May 2012

L’Instance équité et réconciliation (IER), créée au Maroc en 2006, vise à « établir la vérité sur plusieurs faits de l’histoire » (de la date de l’indépendance du Maroc, 1956, à la fin du règne de Hassan II, 1999). Devant l’absence d’archives officielles, l’IER a procédé à l’archivage des livres carcéraux récemment publiés au Maroc. Cela pose un certain nombre de questions : comment les récits carcéraux sont-ils passés du statut d’écrits littéraires à celui d’archives ? De quelles manières l’articulation des notions de « témoignages », de « récits » et d’« archives » est-elle conçue et opérée par les acteurs qui les mobilisent (IER, auteurs, éditeurs, lecteurs) et pourquoi leur attribuent-ils cette terminologie ? Autant d’interrogations qui seront au cœur de cette réflexion axée sur les procédés à l’origine de la mutation des livres carcéraux en archives.
Annotation et rature
Authors: Pohn-Weidinger Axel
Published: May 2012

Ce texte interroge les traces graphiques laissées sur un corpus de formulaires de demande de logement social telles qu’annotations, ratures, biffures et commentaires griffonnés. L’étude de ces traces, laissées en marge des catégories de l’imprimé administratif lors du remplissage, montre le recours au droit comme une opération problématique. Pour les administrés, il s’agit de décrire leur situation de vie de sorte à établir l’éligibilité à un droit, mais bien souvent il est impossible de traduire celle-ci dans les catégories préétablies du formulaire. Les annotations et commentaires laissés sur le formulaire tentent alors d’ouvrir la catégorisation juridique des situations à une prise en compte de la singularité des circonstances de vie du demandeur. Elles montrent le recours au droit comme un accomplissement réflexif, un travail à la fois sur sa propre perception de sa situation et sur celle que l’institution offre à travers le formulaire, et dont la négociation et la mise en œuvre sont au cœur de la production du dossier administratif.
Le corps numérique des données
Authors: Beltrame Tiziana Nicoletta
Published: May 2012

Le transfert des collections extra-européennes du musée de l’Homme au musée du quai Branly implique le déplacement des informations documentaires sur les objets. Des différentes fiches en papier (de collection ou d’inventaire, descriptive de l’objet, méthodique) créées et classées au sein des départements du musée de l’Homme, on passe à la fiche informatique « TMS objets » au musée du quai Branly. L’information ne change pas simplement de place et de matière, elle est reconfigurée dans de nouvelles articulations du savoir sur les collections. L’inventaire muséal est ici conçu comme le système qui matérialise un savoir structuré. Pour pouvoir analyser ce système, il faut mettre en relation les propriétés des documents et les modalités de leur classement dans un espace créé ad hoc. La matérialité des supports, les multiples possibilités de rangements et de création de liens (la mise en relations entre rubriques de la fiche informatique) agissent sur le contenu des données et ouvrent ainsi de nouvelles voies pour la construction du savoir.
L’archive comme enjeu de présentation de soi : la mémoire du syndicat des ouvriers des savonneries à Naplouse, Cisjordanie
Authors: Bontemps Véronique
Published: May 2012

Cet article part de la « quête d’archives » à laquelle je me suis livrée dans le cadre d’une enquête sur le syndicat des ouvriers des savonneries à Naplouse. Dans un premier temps, il interroge le caractère insaisissable de la mémoire de ce syndicat, qui a laissé peu de traces matérielles de son existence. Je me penche ensuite sur la manière dont les documents écrits étaient utilisés par deux anciens ouvriers des savonneries, dans la reconstruction de la mémoire syndicale. Je montre que ces ouvriers mobilisaient conjointement deux régimes de légitimation de leur parole qui, loin de s’opposer, devaient se renforcer mutuellement : la possession de « documents authentiques » ne devait pas tant ajouter foi au contenu de leur discours, que fournir de l’autorité à leur parole. L’article interroge, in fine, la puissance symbolique accordée à l’écrit, et plus largement la matérialité dans le régime de légitimation du discours, en particulier en situation d’entretien.
The Principles of Processing Siderite Ores with a High Magnesium Oxide Content
Authors: Klochkovskii S. , Smirnov A.
Published: May 2012

Due to the depletion of high-quality iron ore, it is becoming ever more urgent to involve the ores which, for some reason or other, could not be used in metallurgy, or were used in limited quantities. For example, the siderite ores of Bakalsk deposit (Chelyabinsk region, Russia, stocks of more than 1 billion tons) are of very limited use in the blast-furnace practice because of the relatively low iron content (29% on average) and high magnesium oxide content (11-15%). At present, the technology of obtaining calcined siderite concentrate (CSC) from the ores of Bakalsk deposit includes raw ore roasting (fractions 10 - 60 mm) in blast furnaces at temperatures above 10000С, and dry magnetic separation.
Fabrication and Properties of Sn-3.5Ag-XCu Solder by Ball Milling and Paste Mixing
Authors: Nadia Aemi , Haseeb A.S.M. Abdul
Published: May 2012

The present work is focused on the preparation and the properties of Sn-Ag-nanoCu composite solder by two methods, i.e. ball milling and paste mixing. Copper nanoparticles were added at two different compositions, 0.7% and 3%, to Sn-3.5Ag solder powder and paste by ball milling and paste mixing, respectively. The composite solder was deposited on the Cu substrate and heated at 250°C for 60 seconds and allowed to cool at room temperature. The wetting ability was evaluated with the wetting angle of deposited composite solder on Cu substrate. The microstructure, morphology and hardness were examined for composite solder joints. It was found that the lowest melting point was achieved at 213.6°C for Sn-3.5Ag-3nanoCu produced by ball milling. The wetting angle deterioted as Cu nanoparticles were added into the Sn-3.5Ag solder paste by paste mixing. However, when Cu nanoparticles were added by 0.7% and 3.0% by ball milling, the wetting angle improved by 5% and 37%, respectively. The hardness of composite solder improved up to 32% when 3% Cu was added by ball milling.
Effect of TiC Particles Volume Fraction on the Mutual Diffusion of Al and Mg during Fabrication of Al-4.5wt%Mg/TiC via Mechanical Alloying Process
Authors: Ozhdelnia O. , Shokuhfar Ali
Published: May 2012

In this work the effects of volume fraction at different milling times and impact forces, defined as the ball-to-powder weight ratio (BPR), on the elemental diffusion during mechanical alloying process of Al-4.5wt%Mg/TiC composite were evaluated and compared with the TiC free samples (Al-4.5wt%Mg alloy). X-ray diffraction patterns of the monolithic and composite samples imply the fact that a higher level of mutual diffusion of constituents, Al and Mg, happened in the matrix in the presence of TiC particles. This effect of the reinforcing particles can be attributed to the increased densities of dislocation and vacancy caused by the presence of TiC particles within the matrix-giving rise to increasing the micro-strain, lattice parameter and decreasing the crystallite size. Scanning electron microscopy (SEM) was used not only to study the morphology of the powders but also to show the fact that the TiC powders were distributed during MA process. The TEM and HRTEM results showed that powder produced in this work has a nanosize.
Two-Phase Flow (Oil-Water) in Petroleum Reservoir with Irregular Geometry Including Water Injection: Effect of Porosity on the Oil Recovery Factor
Authors: Batista Francisco Alves , Gonçalves Coutinho B. , de Farias Neto Severino Rodrigues , de Lima Antônio Gilson Barbosa
Published: May 2012

The aim of this work is to study theoretically the effect of porosity of an oil reservoir with arbitrary geometry on the oil recovery factor. A two-dimensional mathematical modeling (Black-oil model) and numerical solution applied to two-phase flow (water-oil) into the reservoir with irregular geometry including water injection is presented. The conservation equations written in generalized coordinates are solved using the finite volume method, with a fully implicit technique. Results of the pressure and saturation distributions and oil recovery factor over time are presented and evaluated for different values of porosity of the reservoir.
Evaluation of Commercial Adsorbents for Removal of Biuret in Urea Solution for Automotive Applications
Authors: Estrela G.V. , Souza W.C. , Azevedo G.V. , Corrêa H.L. , Figueiredo M.A.G.
Published: May 2012

Currently, one of the major technological challenges refers to issues related to the emission of gaseous pollutants, particularly those based on SOx and NOx. Generated mainly by the burning of fossil fuels, their reduction can be achieved by changes in the conditions of refining processes, capable of adapting the legal specifications of fuel sulphur and nitrogen, or by treatment of gases exhausted. If on the one hand the industries represent an essential portion of such gases, on the other hand the automotive vehicles contribute resolutely to complement another fraction of the emissions. The growing number of diesel-powered cars in Brazil, together with the existing environmental constraints in the country, requires greater control of the indices of gaseous mixtures mentioned above, which can be decreased through reducing agents based on technologies Reducing Agents Automotive Liquids (RAAL). By injection of an aqueous solution of urea on vehicular exhaust, it is possible for example, to catalytically reduce NOx compounds to a mixture of N2 and H2O. Although this project is already in development, several challenges must be overcome, such as the catalyst deactivation by biuret (present in the solution of urea), more efficient engine design and development of fuels with lower levels of nitrogen. This work aims to study the removal of biuret by commercial adsorbents, as a way to adequate the RAAL to employment systems of diesel injection.
The Corrosion Resistance of the Mg-Al-Ca-Sr Sand Casting Magnesium Alloys
Authors: Kiełbus Andrzej , Rzychoń Tomasz , Michalska Joanna , Stopyra Michal
Published: May 2012

In this paper, the corrosion resistance of two sand-casting creep resistant magnesium alloys Mg-9Al-1.5Ca-0.3Sr and Mg-9Al-2.2Ca-0.8Sr in the salt environment has been investigated. Specimens of each alloy has been immersed in 3.5% NaCl solution at room temperature and successively taken out after 1, 2, 4, 5 and 9 days. After immersion test, the microstructure and the appearances of the corroded structure were examined. The corrosion rates of both investigated alloys increased lineally with increasing the exposure time in both solutions. Mg-9Al-1.5Ca-0.3Sr alloy exhibits the higher corrosion rate during the immersion test than Mg-9Al-2.2Ca-0.8Sr. The corrosion layer of both alloys consists of MgO, MgOH and phases containing Cl, Na, Al and Ca. The increase of Ca content in the Mg-9Al-2.2Ca-0.8Sr alloy improved the corrosion resistance due to the formation of the reticular (Mg,Al)2Ca phase, which acted as an effective barrier against corrosion.
Spatial Variation of Longitudinal Dispersion in LECA-Based Vegetated Beds
Authors: Albuquerque António
Published: May 2012

The evaluation of the dispersion in vegetated beds may allow indentifying mechanisms that affect the transport and reaction of solutes, namely organic and nitrogen compounds. A set of non-reactive tracer experiments (slag injection) was performed in a vegetated bed (a mesocosm with a LECA-based substratum and colonized with Phragmites australis) used for the removal of organic and nitrogen pollutant loads. Loads of approximately 300 mg COD/L and 30 mg NH4-N/L and a hydraulic loading rate of 3.5 cm/d were used. The results showed a delay in all the residence time distribution (RTD) curves and a variation in the dimensionless residence time (μ(m,θ)) of the E(θ) curves, which means that the mass centre of the impulse was late relatively to the expected one. A strong dispersion and tracer retention (due to the presence of stagnated areas and internal recirculation) was observed, especially in the first 33 cm of the bed, which seems to have been related to the presence of complex clusters of roots, solid material, biofilm and LECA particles. An analytical solution of the Multiple-Tanks-in-Series (MTS) model well represents the RTD curves obtained in the tracer experiments. The detected dispersion and dead volume ratios (7% to 12%) did not affect the performance of the bed, which presented mean removal efficiencies of 85% and 60.4% for COD and NH4-N, respectively.
Structure and Properties of Gas Nitrided Layers on Nanoflex Stainless Steel
Authors: Kochmański Paweł , Baranowska Jolanta
Published: May 2012

The paper presents results of research on nitrided layers on Sandvik NanoflexTM precipitation hardened stainless steel. The influence of process parameters on nitriding kinetics and structure of the layers was investigated. The gas nitriding process was conducted in a mixture of ammonia 50% and products of its dissociation, as well as in 100% ammonia atmosphere at temperature range 400500°C and time between 2 and 8 h. The obtained diffusion layers were examined using the following methods: light and scanning electron microscopy, XRD phase analysis and EDS chemical analysis. Mechanical properties were tested with hardness measurements. It was found that kinetics depends on treatment temperature and nitrogen potential of the atmosphere. Moreover, treatment conditions affecting Sphase formation and expanded martensite in nitrided layers are discussed.
Enhancement of Heat Transfer over Spatial Stationary and Moving Sinusoidal Wavy Wall: A Numerical Analysis
Authors: Kumar Prashant , Topin Frédéric , Tadrist Lounes
Published: May 2012

Heat transfer phenomena are numerically studied with standing waves inside the tubes for stationary and moving sinusoidal wavy walls. Effects of spatial wavelengths (= 1/2, 2/3, 1 and 2 mm), Reynolds number (1-120), frequency (0-60 Hz) and amplitude (1%-20% of tube diameter, d) on heat transfer and pressure drop are studied. For stationary wall case, upon increasing the number of sine waves, the Nusselt number starts to decrease; the associated pressure drop and friction factor increases very rapidly at highest value of amplitude. Heat transfer enhancement characteristics on a moving sinusoidal wavy-walled tube with imposed frequency (0
Effect of Austenitising Temperature on Structural Changes in Modified High-Speed Steel of AISI M2 Type
Authors: Chaus Alexander S. , Beznák Matej , Bohačík M. , Porubský Ján , Úradník P.
Published: May 2012

The transformation of the solidification microstructure and the phase changes in AISI M2 grade high-speed steel modified with powder addition of TiB2 have been studied focusing on the effect of austenitising temperatures. In order to investigate kinetics of both the microstructure and phase transformations in eutectic carbides, primarily M2C carbide decomposition, upon heat treatments with respect to diffusion processes, different techniques of electron scanning microscopy, X-ray diffraction analysis and energy dispersive X-ray spectrometry have been used.
Investigations on Tensile Properties of Waste Fillers Reinforced Composites
Authors: Bodur Mehmet Safa , Gülmez Turgut , Durademir Ayhan
Published: May 2012

In this study, low density polyethylene (LDPE) matrix composites were manufactured with the ratios of 20%, 30% and 40%wt hazelnut and peanut reinforcements as the natural fibers. Composite plates were manufactured by using a single screw extruder. Various tests and measurements are performed to obtain mechanical properties such as density, tensile strength (TS), Youngs modulus (YM), failure strain (FS), impact strength (IS) etc. as well as the effect of maleic anhydride grafted resin as an additive with different ratios was investigated and the optimum composite content was obtained. This preliminary work showed that hazelnut and peanut fillers could be utilized with proper additives in order to produce the composite materials with good physical and mechanical properties.
The Increased Flow of a Railway Line by Repositioning of a Minimum Number of Axes Halts
Authors: Siguerdjidjene H. , Turbine I.V. , Saidi D.
Published: May 2012

The present work attempts to expose a method to increase the lines capacity. The problem to treat concerns the existing minimum number of halts ''Stops'' to reposition in order to obtain the optimum transport capacity. This applied method to a narrow way in the process of normalization allows to add to the gain capacity induces by normalization a surplus of flow.
The repositioning of the halts is a correction at lower cost having for objective to differ in time the heavy investments to modernize and standardize completely a narrow-gauge line. Throughout the text the term halt ''stop'' means any establishment or equipment ensuring the cantonment on one line.
Experimental Evaluation and Simulation of Al/Si Diffusion in Hot Dipped Fe-Si Steels
Authors: Danzo I. Infante , Malengier Benny , Miyar S. , Gomez E. , Verbeken Kim , Houbaert Yvan , Van Keer Roger , de Graeve Iris
Published: May 2012

Hot dipping is a coating technique used in industry for galvanizing machine elements and steel profiles for construction or automotive applications. However, an alternative use of this process might be to improve specific properties. For instance, in order to improve the magnetic properties of electrical steels, it may be desirable to increase the Si and/or Al content. A possible and alternative route to realize this is by the application of an Al-Si-rich coating on the steel substrate using a hot dipping process, followed by a diffusion annealing treatment in order to distribute the Al/Si more evenly in the steel. The obtained distribution depends on the annealing parameters and can be both beneficial and detrimental for the magnetic properties.
In the present work, Fe-Si substrates were hot dipped in different Al-Si baths. Subsequently, the samples were annealed at 1100°C during 20 minutes and concentration profiles were measured with scanning electron microscope energy dispersive spectroscopy line scans. The experimental results were analyzed using a specifically designed simulation model in order to determine the Al and Si diffusion coefficients. This model uses an inverse algorithm to determine interdiffusion coefficients that arise in a macro ternary diffusion system.
Fluoride Influence on the Properties of Oxide Layer Produced by Plasma Electrolytic Oxidation
Authors: Kazanski Barbara , Kossenko Alexei , Lugovskoy Alex , Zinigrad Michael
Published: May 2012

Plasma Electrolytic Oxidation (PEO) is a powerful technique allowing hardening and corrosion protection of valve metals due to formation of an oxide layer on the metal surface. The addition of fluoride ions to the alkaline electrolyte for the PEO processing of aluminum and magnesium alloys produces significant changes in the structure and properties of the coating [1-, however the mechanism of these changes is not clear. A study of the influence of the fluoride concentration on the composition, structure and morphology of thin (to 20 µm) PEO layers was performed. The oxide layer thickness on aluminum is significantly smaller than that on magnesium. Fluorine is detected as an amorphous phase in the vicinity of the base metal.
Modifying the Sorption Capacity of Biopolymers by the Mechanochemical Activation
Authors: Lugovskoy Svetlana , Zinigrad Michael , Eliaszade Moshe
Published: May 2012

Mechanochemical activation (MCA) of electrode lignin was performed and the activated lignin was studied by IR-spectroscopy for different activation times. The activated lignin was tested for the ability of binding Cr2O72-, Cu2+, Ni2+ ions. It was established that structure deformation, which does not distort the stronger hydrogen bond lattice, but leads to the formation of highly developed surface with active functional groups, occurs in the course of MCA. Weaker inter-layer bonds are broken in the activation process and quickly recovered after the load release.
The comparison of the sorption capacity of Cr2O72-, Cu2+, Ni2+ ions by the MCA treated vs. inactivated lignin for different activation times was performed.
Application of Simplified Inverse Solution to Estimate the Thermo-Physical Parameters of Granular Porous Materials Bonded by Different Resins
Authors: Ignaszak Zenon , Popielarski Paweł
Published: May 2012

The paper presents the complexity of the thermo-mechanical phenomena in multi-component porous material during thermal shock and heat transfer, including identification of its behavior by Hot Distortion Plus® test, elastic/plastic interpretation and modelling using Comsol system on the example of granular material (quartz sand bonded by selected resins used for mould production in foundry industry).
Problem of Acceptability of Internal Porosity in Semi-Finished Cast Product as New Trend "Tolerance of Damage" Present in Modern Design Office
Authors: Ignaszak Zenon , Popielarski Paweł , Hajkowski Jakub , Prunier J.B.
Published: May 2012

Discontinuities in cast products, obtained from a liquid state of an alloy, are the result of phenomena occurring during multiphase system crystallization. On the one hand, compacted defects as a shrinkage pipe are relatively easy to eliminate. On the other hand, it is known that presence of fine shrinkage and gas porosity is unavoidable. Detectability of these dispersed discontinuities depends on type of inspection method applied. Structure, including intensity and location of porosity zones, is dependent on the type of the alloy, casting configuration and conception of technological solution, related with control of velocity of the heat extraction to the mould. Thus, mechanical properties in the volume of a casting are not homogenous and are strongly reduced only in the zones of porosity. However, in strength calculations of cast products, this obvious fact is not taken into consideration. The rule of material homogeneity is applied instead, along with drastic increase of factor of safety. The paper indicates benefits of precise determination of limits of porosity zones located in the casting, using the NTD methods (for example, Phased Array ultrasonic tomography). Coordinates of porosity zones in 3D, introduced into CAD geometry and assigned with different properties allow to estimate the actual state of stress and strain of real object using FEM methods (systems like Ansys, Comsol). Load justified by operating conditions and application of tolerance of damage rule, with simultaneous reference to the limited state of stress according to LOV (Loss of Volume) and LEFM (Linear Elastic Fracture Mechanics) methods should find their place in design procedures of cast products, which will allow for better use of material and reduction of weight of the casting. This approach, named Tolerance of damage concerning the castings is the motto of this paper.
Characterising the Differences between the Adsorption and Desorption Processes in a Desiccant Layer by Detailed Numerical Modelling
Authors: Ruivo C.R. , Costa J.J. , Figueiredo A.R.
Published: May 2012

In this paper, the performance of a channel element of a hygroscopic matrix is evaluated by detailed numerical modeling. The adopted physical model takes into account the gas-side and solid-side resistances to heat and mass transfer, as well as the simultaneous heat and mass transfer occurring simultaneously with the water adsorption/desorption process in the desiccant porous channel wall domain. The desiccant medium is silica gel RD, the equilibrium being characterized by sorption isotherms. Appropriate convective transfer coefficients are taken into account for the calculation of the heat and mass transfer phenomena between the airflow and the channel wall. The response of the channel element to a step change in the airflow states is simulated, the results enabling the investigation of some differences between the adsorption and desorption processes.
Oxygen Diffusion in Ti-20Mo Alloys, Used as Biomaterial, Measured by Mechanical Spectroscopy
Authors: Nogueira Renata Abdallah , Grandini Carlos Roberto
Published: May 2012

Titanium alloys are favorable implant materials for orthopedic applications, due to their desirable properties such as good corrosion resistance, low elasticity modulus, and excellent biocompatibility. The research on titanium alloys is concentrated in the β type, as the Ti-20Mo alloys and the addition of interstitial elements in these metals cause changes in their mechanical properties. The mechanical spectroscopy measurements have been frequently used in order to verify the behavior of these interstitials atoms in metallic alloys. This paper presents the study of oxygen diffusion in Ti-20Mo alloys using mechanical spectroscopy measurements. A thermally activated relaxation structure was observed in the sample after oxygen doping. It was associated with the interstitial diffusion of oxygen atoms in a solid solution in the alloy. The diffusion coefficient for the oxygen diffusion in the alloy was obtained by the frequency dependence of the peak temperature and by using a simple mathematical treatment of the relaxation structure and the Arrhenius law.
Diffusion of Interstitial Solutes in Nb-46wt% Ti Alloys Measured by Mechanical Spectroscopy
Authors: Grandini Carlos Roberto , Florêncio Odila , Filho Walter José Botta
Published: May 2012

The mechanical properties of metals with a body-centered cubic (bcc) structure, such as Nb, Ta, V, and their alloys, are modified with the introduction of interstitial impurities, such as O, N, C, or H. These metals can dissolve great amounts of O and N, for example, to form solid solutions. The interstitial solute atoms (ISA) in metals with a bcc structure occupy octahedral sites and cause local distortion with tetragonal symmetry. So ISA in these metals forms an elastic dipole that can align along one of the three cubic axis of the crystal. In the present paper, the torsion pendulum technique was employed for the investigation of various interactions among the metallic matrix and different interstitial solutes in the Nb-46wt%Ti alloy. From the relaxation spectra, we obtained the diffusion coefficients, pre-exponential factors, and activation energies for nitrogen in the Nb-46wt%Ti alloy.
New Developments in NdFeB-Based Permanent Magnets
Authors: Liu Zhong Wu
Published: May 2012

NdFeB based alloys have been used as permanent magnets for almost thirty years. The recent researches aim at optimizing the composition, microstructure and properties, reducing cost, and developing new processes. The demand for sintered magnet is increasing. Efforts are directed towards improving properties by controlling grain boundary diffusion, minimizing the rare earth (RE) content and also improving production yield. As for bonded magnets, to enhance remanence and energy product, nanocrystalline powders are employed. High thermal stability has been realized by mixing NdFeB with hard ferrite powders. For nanocrystalline and nanocomposite NdFeB based alloys, both compositional modification and microstructural optimization have been carried out. New approaches have also been proposed to prepare NdFeB magnets with idea structure. Surfactant assisted ball milling is a good top-down method to obtain nanosized hard magnetic particles and anisotropic nanoflakes. Synthesis of NdFeB nanoparticles and NdFeB/Fe (Co) nanocomposite powders by bottom-up techniques, such as chemical reduction process and co-precipitation, has been successful very recently. To assemble nanocrystalline NdFeB powders or nanoparticles into bulk magnets, various novel consolidation processes including spark plasma sintering and high velocity press have been employed. Hot deformation can be selected as the process to achieve anisotropy in nanocrystalline magnets.
Martensitic Transformation and Microstructural Characteristics in Copper Based Shape Memory Alloys
Authors: Adiguzel Osman
Published: May 2012

Martensitic transformations are first order solid state phase transitions and occur in the materials on cooling from high temperature. Shape memory effect is an unusual property exhibited by certain alloy systems, and based on martensitic transformation. The shape memory property is characterized by the recoverability of previously defined shape or dimension when they are subjected to variation of temperature. The shape memory effect is facilitated by martensitic transformation, and shape memory properties are intimately related to the microstructures of the materials. Martensitic transformations occur as martensite variant with the cooperative movement of atoms on {110}β - type plane of austenite matrix. Martensitic transformations have diffusionless character, and the atomic movement is confined to interatomic lengths in the materials. The basic factors which govern the martensitic transformation are Bain distortion and homogeneous shears. Copper based alloys exhibit this property in metastable β-phase field.
Effect of Ageing on Mechanical and Shape Memory Properties of Ti-5Cr-4Ag Alloy
Authors: Wadood Abdul , Inamura Tomonari , Hosoda Hideki , Miyazaki Shuichi
Published: May 2012

The effect of ageing on mechanical, shape memory and pseudoelastic properties of our recently developed Ti-5Cr-4Ag alloy was investigated for biomedical and engineering applications. The results are summarized as follows. (A) Solution-treated alloy exhibited ductile behavior (13% fracture strain), shape memory properties (57% shape recovery) and pseudoelastic response. (B) Ageing at 573K and 973K for 3.6ks has resulted into improvements of UTS and yield stress. However the fracture strain, shape recovery ratio and pseudoelastic response were decreased due to precipitation of α (hcp) phase and stabilization of remaining β (bcc) phase. (C) Ag addition suppressed ω (hexagonal) phase precipitation as ω phase could not be detected for solution-treated and aged conditions. It is concluded that Ti-5Cr-4Ag in solution-treated and 973K aged conditions has potential for biomedical and engineering applications due to good strength-ductility correspondence, shape memory and pseudoelastic properties and suppression of ω phase precipitation.
Liner Material's Output Characteristics of Explosively Formed Projectiles (EFPs)
Authors: Hussain G. , Hameed A. , Barton P. , Malik A.Q. , Khan Mohammad Bilal , Hussain A.
Published: May 2012

The output considerations: velocity, pressure, density, internal energy, temperature and L/D ratio of explosively formed projectiles (EFPs) were investigated. The internal energy of the EFPs was inversely proportional to the density of the liner material. The shock pressure generated and its fluctuations were highest for Fe and Ta liner materials respectively. The least pressure variations were observed for Cu along its axial direction with highest length to diameter (L/D) ratio to supports deeper penetration. The maximum difference between numerical simulation and experiment was 9.7 % for Cu EFP.
Recent Advances in Fatigue Crack Growth
Authors: McEvily A.J.
Published: May 2012

Many of the recent advances in the understanding of the fatigue crack growth process have resulted from an improved realization of the importance of fatigue crack closure in the crack growth process. Two basic crack closure processes have been identified. One of which is known as plasticity-induced fatigue crack closure (PIFCC), and the other is roughness-induced fatigue crack closure (RIFCC). Both forms occur in all alloys, but PIFCC is a surface-related process which is dominant in aluminum alloys such as 2024-T3, whereas RIFCC is dominant in most steels and titanium alloys.
A proposed basic equation governing fatigue crack growth is
(1)
where where Kmax is the maximum stress intensity factor in a loading cycle and Kop is the stress intensity factor at the crack opening level. is the range of the stress intensity factor at the threshold level which is taken to correspond to a crack growth rate of 10-11 m/cycle. The material constant A has units of (MPa)-2, and therefore Eq. 1 is dimensionally correct. Eq.1 has been successfully used in the analysis of both long and short cracks, but in the latter case modification is needed to account for elastic-plastic behavior, the development of crack closure, and the Kitagawa effect which shows that the fatigue strength rather than the threshold level is the controlling factor determining the rate of fatigue crack growth in the very short fatigue crack growth range.
Eq. 1 is used to show that
The non-propagating cracks observed by Frost and Dugdale resulted from crack closure.
The behavior of cracks as short as 10 microns in length can be predicted.
Fatigue notch sensitivity is related to crack closure.
Very high cycle fatigue (VHCF) behavior is also associated with fatigue crack closure.
Effect of Sintering Temperature on Structural, Electrical and Dielectric Parameters of Mn-Zn Nano Ferrites
Authors: Anwar Humaira , Maqsood Ashari
Published: May 2012

Mn-Zn ferrite powders (Mn0.5Zn0.5Fe2O4) were prepared by the chemical co-precipitation method. The effect of sintering temperature on the crystalline phase formation and dielectric properties were investigated by X-ray diffraction and impedance analyzer respectively. The TGA/DTA analysis was carried out to know decomposition mechanism. Ferrites decomposed to Fe3O4 above 873 K sintering temperature. Crystallite size increased with increasing sintering temperature between 7-13 nm. The resistivity decreased with increase in temperature showing semiconducting like behaviour. Activation energy was in the range of 0.70 to 0.77eV for these samples. Dielectric constant decreased with increasing frequency. Relaxation peak occurred for loss tangent versus frequency curves. The ac conductivity explained using small polaron tunnelling (SPT) model.
Optoelectronic Properties of Cadmium Sulfide Thin Films Deposited by Thermal Evaporation Technique
Authors: Ali N. , Iqbal M.A. , Hussain S.T. , Waris M. , Munair S.A.
Published: May 2012

The substrate temperature in depositions of thin films plays a vital role in the characteristics of deposited films. We studied few characteristics of cadmium sulphide thin film deposited at different temperature (150°C-300°C) on corning 7059 glass substrate. We measured transmittance, absorbance, band gap and reflectance via UV spectroscopy. It was found that the transmittance for 300nm to 1100nm was greater than 80%. The resistivity and mobility was calculated by Vander Pauw method which were 10-80 cm and 2-60 cm2V-1S-1 respectively. The thermoelectric properties of the film were measured by hot and cold probe method which shows the N-type nature of the film.
Synthesis, Characterization and Hall Effect Measurements of Nanocrystalline ZnO Thin Films
Authors: Maqsood Ashari , Islam M. , Ikram M. , Salam S. , Ameer S.
Published: May 2012

ZnO thin films were prepared by sol-gel method. Prepared thin films were then characterized by SEM, XRD, EDX and Hall effect measurements. SEM confirmed the morphological studies of ZnO thin films. Crystallite size is calculated using the Scherrer formula. Crystallite and grain sizes are obtained through XRD and SEM. EDS analysis confirms mass percentage of ZnO deposited. Decreasing trend of magneto resistance with temperature is observed. The optical transmission spectra of the solgel deposited ZnO thin films showed high transmittance (>70%) in the visible region and indicates that the transmittance of ZnO films gradually decreased as the thickness increased. Decreasing trend of resistivity and sheet resistance with thickness are also observed. The IV characterization of ZnO thin films under influence of UV and dark conditions are reported. The dc electrical resistivity data follow the hoping model.
Electrical and Dielectric Spectroscopic Characterization of Polycrystalline Dy2Si2O7
Authors: Ameer Shahid , Maqsood Asghari
Published: May 2012

The compound Dy2Si2O7 exists in two polymorphs, the low temperature triclinic phase (type B) and a high temperature orthorhombic phase (type E).The dc and ac electrical conductivities of E-Dy2Si2O7 are measured in the temperature range 290-510 K and frequency range 1 kHz to 1 MHz . The dc electrical transport data are analyzed according to Motts variable-range hopping model. The disorder parameter (To) and density of states at fermi level are obtained. The ac conductivity σac (ω) is obtained through the dielectric parameters. The ac conductivity can be expressed as σac (ω) =B ω s , where s is slope and it decreases with increase in temperature. The conduction mechanism in the compound is discussed in low and high temperature regions in the light of theoretical models.
Failure of the Pressure Bulkhead of a Passenger Aircraft - A Case Study
Authors: Salam Iftichar Us , Nusair Khan Aamer , Farooque M.
Published: May 2012

The pressure bulkhead of a passenger aircraft ruptured when the aircraft was cruising at a height of 28,000 ft. Because of the sudden rupture, the rear toilets disintegrated and things like toilet rolls, tissue papers, towels, were sucked into the stabilizer compartment, where the entire tail control system was located. The debris damaged the green hydraulic system, ruptured fuel line and jammed the control cables. The damage resulted in the aircraft going into pitch-up mode (take-off position) and almost approached stalling position. The failed part was located near the toilets. Water from the toilets reached in this region due to leakage and penetrated inside the sheets and corrosion started in the presence of stagnant water. This was supplemented by the stresses present on the structure during flight. Stress corrosion started from inner sheet and led to initiation of fatigue. The combined effect of stress corrosion cracking and fatigue resulted in the failure of this sheet. No third stage (catastrophic) failure was observed in the fracture. The absence of catastrophic failure mode in the fractured sheet showed that it stood up to last stage.
Investigation of Source of N-Type Conductivity in Bulk ZnO
Authors: Asghar M. , Mahmood Khalid , Hasan M.A.
Published: May 2012

In this study, we have investigated the source of the n-type conductivity in bulk ZnO. Four samples with Zn concentrations 52%, 53%, 54% and 55 % were prepared by molecular beam epitaxy (MBE). ZnO layers exhibited reamarkable increase in carrier concentration (5.0×1016 cm-3 to 2.2×1019 cm-3) and decrease in resistivity (14.4 Ω cm to 0.009 Ω cm) as a function of Zn contents (52% to 55%) in the layers, respectively. We observed that with increasing thickness, the microstructure of films was improved. The thick films have less Zn-interstitials defects and consequently have lower carrier concentration and higher resistivity. The shifting of Raman E2high mode of ZnO towards higher frequency with increasing Zn contents in the samples also confirmed the presence of excessive Zn-interstitials in the layer.
Study of Corrosion-Electrochemical Behavior of Aluminum-Beryllium Alloys Alloyed with Yttrium, Lanthanum and Cerium
Authors: Safarov A.S. , Dzhuraev T.D. , Halimova M.I. , Karieva Z.M.
Published: May 2012

Advantage of alloys on the basis of system Al-Be,Al-Be-REM is raised technological, physical, chemical and corrosion resistance properties in damp and excessively aggressive atmospheres [. According to literary reviews, this alloys basically are foundry-hypoeuthectic and hypereuthectic, and the technology of moulding of these alloys very difficult and demands application of operations modifying. Difficultly deleted impurity basically (Fe), specifically influence phase structure, naturally influencing on physical and chemical properties industrial silumines with the maintenance not less than 0.4-0.5 %. Many additives as Fe, Mg, Ti, Be, especially in hypoeuthectic silumines increasing strength and foundry properties, can reduce them corrosion-resistance. In connection with the above-stated is of interest researches of influence of impurity such elements as, Be and REM on corrosion resistance industrial alumines. Studies corrosion-resistance spent samples potentiostatic a method on device " Potentiostate P-50" with a registering recorder in the environment of the muriatic solutions in a mode "Potential". he analysis of experimental data have shown, that addition Be, positively modifying structure of foundry alloys, reduces influences containing in it Fe, increases strength and corrosion resistance, which calculations testify experimental data of electrochemical indicators [2,3].
Effect of Zirconium Addition on the Grain Size and Mechanical Behavior of Aluminum Grain Refined by Titanium Plus Boron (Ti+B) in the as Cast and Cold Extruded Conditions
Authors: Zaid A.I.O. , Al-Qawabah S.M.A.
Published: May 2012

Aluminum and its alloys are the second most commonly used metal for a variety of industrial applications. They normally solidify in coarse grain columnar structure which tends to reduce their mechanical behavior and surface quality. It was found that this large grain size structure can be refined by using titanium, Ti, or titanium plus boron, Ti+B, and using the latter resulted in reducing the amount of Ti to fifth its values although boron itself is not a grain refiner. This is why it is becoming customary in the aluminum foundry to add Ti or Ti+B to their melt before solidification. The available literature reveals that most of the work is directed towards the metallurgical aspects and little was directed on the mechanical aspects. To the best of the authors knowledge, no work was directed on the aspects of grain refiners on the formability of metals. In this paper, the effect of addition of Zr on the mechanical properties of commercially pure aluminum grain refined by Ti+B in the as cast and extruded conditions is investigated. Comparison between the addition of Zr alone or Zr+Ti+B is also investigated. It was found that addition of Ti+B either alone or in the presence of Zr resulted in grain refinement of aluminum both in the as cast and in the cold extruded conditions. The maximum reduction in grain size was 53.22% and 76.92%, respectively. Similarly, it was found that addition of Ti+B either alone or in the presence of Zr to Al resulted in improvement of its Vickers's hardness, However addition of Zr alone to Al resulted in decrease of its hardness in the as cast conditions but increase in the extruded condition .The maximum increase was in the case of adding both of them in the extruded condition being 94.59 %, (from Hv 37 to Hv72). Similarly the ultimate tensile strength, UTS, was improved at all additions except when Ti+B or Zr is added alone. On the whole it may be concluded that addition of Zr to Al grain refined by Ti+B resulted in enhancement of its grain size and improvement of its hardness, mechanical strength and ductility in the cold extruded conditions and resulted in slight decrease of its ductility when added in the as cast condition.
Preparation and Characterization of Carbon Supported Nano-Nickel and its Sorption Behavior for Zinc from Aqueous Solutions
Authors: Asim Tayyaba , Ahmed R. , Ansari M.S.
Published: May 2012

Nickel deposited on carbon has been used as adsorbent to recover Zn (II) from aqueous system. The adsorbent was synthesized by depositing nickel nitrate on carbon under inert conditions and decomposing it to nickel by raising the temperature, washing and vacuum drying. Various techniques including XRD, FTIR, and SEM were employed for its characterization. FTIR showed that the nickel deposition enhanced the carbon functionalization due to presence of OH, C=O and C-O groups.Average crystallite size ofabout 9 nm was determined from XRD. Nickel deposition resulted in further division particles as indicated from the morphological study. Zn (II) was subjected to adsorptionon the synthesized adsorbent. It was observed that the rate of adsorption increased significantly on the nickel deposited carbon than the carbon alone. Morris-Weber, Lagergren and Reichenberg models were applied to find out the type and rate of adsorption employingfirst and second order rate equations.The adsorption data were applied toLangmuir, Freundlich and D-R isotherms and values of isotherm constants were calculated and were higher for Ni/C than carbon alone. The mean free energy of zinc sorption on carbon and Ni/C are 16.67 and 18.26 kJmol-1 which shows chemisorption. Thermodynamic studies were done to find out the effect of temperature on sorption. Positive values of ΔH and negative values of ΔG show endothermic and spontaneous type of sorption.
Effect of Cork Loading on Mechanical and Thermal Properties of Silica-Ethylene-Propylene-Diene Monomer Composite
Authors: Gul J. , Mirza S.
Published: May 2012

Ethylene-propylene diene ter-monomer (EPDM) filled with asbestos are widely used as thermal insulation in space vehicles because of its low specific gravity, low temperature flexibility, high ozone and oxygen resistant, superior thermal and ablation characteristics. However, asbestos has been banned worldwide because of its carcinogenic nature. This study was aimed to replace asbestos by environmental friendly and low specific gravity filler, cork in thermal insulation for space vehicles. Various batches of cork filled EPDM were obtained by compounding 0, 10, 20, 40, 50, 60, 70 and 100Phr (parts per hundred parts of rubber) of cork powder with EPDM in Two-roll-mill in presence of other necessary compounding ingredients. The resulted vulcanizates were characterized for mechanical, thermal and ablation performances. It was observed that cork loadings significantly enhanced tensile strength and hardness of EPDM. However, elongation at break of EPDM decreased with the increase of cork concentration. Moreover, no significant reduction in density of EPDM was obtained instead of compounding with lower specific gravity cork powder. Temperatures cures in Thermo-gravimetric analysis shifted to lower temperature with increasing of cork percentage in the formulation. Furthermore, char formation of the EPDM composites decreased with the increase of cork Phr in the composition which was the indication of degrading thermal stability of EPDM by cork powders. It can be concluded that on the basis of mechanical properties asbestos can be replaced by cork powder however, cork filled EPDM exhibited inferior thermal properties as compared to asbestos filled EPDM.
An Electrochemical Impedance Spectroscopy Study of Al-Zn and Al-Zn-Sn Alloys in Tropical Seawater
Authors: Isa M.C. , Daud Abdul Razak , Ahmad M.Y. , Daud M. , Shamsudin S.R. , Hassanuddin N. , Din Yati M.S. , Muhammad M.M.
Published: May 2012

In this paper, a study on the electrochemical behaviour and electrical properties of Al-Zn and Al-Zn-Sn alloys in tropical seawater using open circuit potential (OCP) measurement and electrochemical impedance spectroscopy (EIS) are reported. The results from both the OCP and EIS tests show that surface activation was observed in the Al-Zn alloy with the addition of 1.34 wt.% Sn which can be manifested by the shift of OCP values towards more electronegative direction. The EIS spectra of Al-Zn alloy exhibits a semicircle loop, while the EIS spectra for the Al-Zn-Sn alloy exhibits a semicircle with a semicircle inductive loop. The change in EIS spectra for Al-Zn-Sn alloy is correlated to the increase of surface activation resulting in a less stable passive layer. Equivalent circuits models were proposed to fit the impedance spectra and the corresponding electrical parameters with optimum values were deduced. The modulus impedance in the low frequency region or polarization resistance, Rpol obtained for the Al-Zn-Sn alloy, Rpol = 2.76 kΩ cm2) is slightly decreased compared to the corresponding value of the Al-Zn alloy, Rpol = 3.97 kΩ cm2), indicating a considerable reduction in the protective capability of the oxide layer on the Al-Zn-Sn alloy. It appears that the heterogeneous oxide film and pores formed on the Al-Zn-Sn alloy play a key role in reducing total resistance to the flow of electron at the alloy-electrolyte interface.