bluuebunny/crossref_metadata_2025 huggingface dataset:
PRICING AND INVENTORY STRATEGIES FOR A TWO-STAGE DUAL-CHANNEL SUPPLY CHAIN
Authors: NIU RUN H. , ZHAO XUAN , CASTILLO IGNACIO , JORO TARJA
Published: March 2012

The Internet is becoming increasingly important as a sales channel. Thus, most large retail firms have adopted a multi-channel strategy that includes both web-based channels and pre-existing offline channels. In this paper, we consider joint pricing and inventory/production decision problems for members in a monopoly two-stage dual-channel retailer supply chain. For a dual-channel retailer, pricing in one channel will affect the demand in the other channel. This subsequently affects the retailer's replenishment (ordering) decisions, which have an impact on the producer's inventory/production plans and wholesale price decisions. It is clear then that pricing decisions and inventory/production decisions are interacting in each member of the supply chain and among the members in the chain as well. In this paper, we analyze joint pricing and inventory/production problems under three scenarios by incorporating intra-product line price interaction in the EOQ model. We show that a unique equilibrium exists under certain realistic conditions. We also provide numerical results that offer insights for pricing strategies for the dual-channel retailer supply chain and for product design for different channels.
INFORMATION SHARING ACROSS MULTIPLE BUYERS IN A SUPPLY CHAIN
Authors: WU JIANGHUA , IYER ANANTH , PRECKEL PAUL V. , ZHAI XIN
Published: March 2012

We model the impact of information visibility in a two-level supply chain consisting of independent retailers who share upstream supply. The manufacturer supplies similar products to the two retailers and each retailer serves its independent end market. Retailers face one period of demand and satisfy the demand by ordering in the first period or back-ordering some of the demand and satisfying it in the second period. The wholesale price in the second period is decreasing in the total order size across the two retailers in the first period. This decrease in wholesale price captures the market learning effect of aggregate orders that has been extensively documented in empirical literature. We use a game-theoretic framework to investigate the ex-ante incentives for retailers to share their private demand information. We show that: (1) retailers have no incentives to share information about their private values when equilibrium order quantities are interior, i.e., the order size is between zero and the demand; (2) partial information sharing may be the equilibrium strategy for retailers when equilibrium order quantities are binding on the demand. Finally, numerical examples are provided for illustration. This paper thus identifies conditions under which different levels of information sharing may be the equilibrium outcomes in a supply chain.
SCATTERING TIMES IN THE MODIFIED PÖSCHL–TELLER POTENTIAL WELL
Authors: PARK CHANG-SOO
Published: March 2012

We study the scattering of a Gaussian wave packet in the modified Pöschl–Teller potential well in time respect. Analytical expressions of average dwell time, phase time, and average traversal time due to Larmor-clock times are obtained, from which the average traversal time can be identified with the average dwell time. We observe that the average dwell time is appreciably longer than the phase time at low energies, but they tend to coincide in the limit of narrow momentum distribution, high energy, and large interaction region. We also find that both of them are longer than the classical scattering time in the potential. All of these times are, however, shorter than the free-particle time, demonstrating the acceleration effect of the potential in temporal aspect of the scattering.
MOLECULAR DYNAMICS SIMULATION STUDY OF ATOMIC SEGREGATION OF (PdPt)147 DURING THE HEATING PROCESS
Authors: XIAO X. Y. , CHENG Z. F. , XIA J. H.
Published: March 2012

Research on the influence of alloy concentration and distribution on bimetallic cluster plays a key role in exploring new structural material. This paper studies the melting process of icosahedral bimetallic cluster (PdPt)147 with different Pt concentrations and different atomic distributions by using molecular dynamics with an embedded atom method. The results indicate that the mixed Pd–Pt cluster shows an irregular phenomenon between 580 and 630 K, i.e. the atomic energy decreases with the increase of temperature. This is because the surface energy of Pd is lower than that of Pt; the decreased energy due to Pd atomic segregation is larger than the increased energy due to heating during the segregation process. In addition, the temperature of Pd atomic segregation is strongly related to Pt concentration. This leads to that Pd atoms prefer to remain on the surface even after the cluster melted.
THE THEORY OF AN ELECTRON ON A LOXODROME
Authors: TOURIGNY DAVID S.
Published: March 2012

Single-electron models are regularly used in molecular physics to obtain information on the quantum properties of many-atom systems. Examples include applications of a particle contained on a ring to benzene, and an electron on a helix to helical polymers. Here it is shown that the model of an electron on a spherical helix (a loxodrome) is also amenable to such investigation, and may be used to describe an emerging class of molecules known as "molecular apple peels". Moreover, the Schrödinger equation that arises during consideration of this model is solved exactly.
STABILITY OF CLOSED LOOP FRACTIONAL ORDER SYSTEMS AND DEFINITION OF DAMPING CONTOURS FOR THE DESIGN OF CONTROLLERS
Authors: LANUSSE PATRICK , OUSTALOUP ALAIN , POMMIER-BUDINGER VALERIE
Published: March 2012

Fractional complex order integrator has been used since 1991 for the design of robust control-systems. In the CRONE control methodology, it permits the parameterization of open loop transfer function which is optimized in a robustness context. Sets of fractional order integrators that lead to a given damping factor have also been used to build iso-damping contours on the Nichols plane. These iso-damping contours can also be used to optimize the third CRONE generation open loop transfer function. However, these contours have been built using nonband-limited integrators, even if such integrators reveal to lead to unstable closed loop systems. One objective of this paper is to show how the band-limitation modifies the left half-plane dominant poles of the closed loop system and removes the right half-plane ones. Also presented are how to obtain a fractional order open loop transfer function with a high phase slope and a useful frequency response, and how the damping contours can be used to design robust controllers, not only CRONE controllers but also PD and QFT controllers.
STABILITY-PRESERVING HIGH-ORDER METHODS FOR MULTITERM FRACTIONAL DIFFERENTIAL EQUATIONS
Authors: GARRAPPA ROBERTO
Published: March 2012

The numerical approximation of linear multiterm fractional differential equations is investigated. Convolution quadratures based on Runge–Kutta methods together with formulas for the efficient inversion of the Laplace transform are considered to provide highly accurate numerical solutions. Implementation issues are discussed and good stability properties are shown. The effectiveness of the algorithm is analyzed by means of some numerical experiments.
ON IMPACT SCRIPTS WITH BOTH FRACTIONAL AND DRY FRICTION TYPE OF DISSIPATION
Authors: GRAHOVAC NENAD , ZIGIC MIODRAG , SPASIC DRAGAN
Published: March 2012

We study the dynamics of a mass, sliding on a dry surface and impacting against a rigid wall through a viscoelastic body, that we model as a straight rod of negligible mass. The problem comprises a constitutive model of the viscoelastic body with fractional derivatives of stress and strain, restrictions on the coefficients that follow from Clausius–Duhem inequality, and discontinuous inequality constraint conditions imposed by the Coulomb friction model. We show that the dynamics of the problem is governed by a single integro-differential inclusion. By use of the slack variable algorithm the problem was solved numerically. The predictions of the model concerning the duration of the impact, maximal values of the impacting force and deformation, as well as the restitution coefficient are determined for several values of system parameters. Depending on the dry friction coefficient three different impact scripts are identified: rebound after the impact, capture in the approaching phase, and capture in the rebound phase.
A NONSTANDARD FINITE DIFFERENCE SCHEME FOR TWO-SIDED SPACE-FRACTIONAL PARTIAL DIFFERENTIAL EQUATIONS
Authors: MOMANI SHAHER , RQAYIQ ABDULLAH ABU , BALEANU DUMITRU
Published: March 2012

In this paper, we apply the Mickens nonstandard discretization method to solve a class of initial-boundary value fractional partial differential equations with variable coefficients on a finite domain, and thereby increase the accuracy of the solutions. We examine the case when a left-handed and a right-handed fractional spatial derivative may be present in the partial differential equation. Two numerical examples using this method are presented and compared successfully with the exact analytical solutions.
MULTIFRACTIONAL PROPERTY ANALYSIS OF HUMAN SLEEP EEG SIGNALS
Authors: SHENG HU , CHEN YANGQUAN , QIU TIANSHUANG
Published: March 2012

Electroencephalogram (EEG), the measures and records of the electrical activity of the brain, exhibits evidently nonlinear, nonstationary, chaotic and complex dynamic properties. Based on these properties, many nonlinear dynamical analysis techniques have emerged, and much valuable information has been extracted from complex EEG signals using these nonlinear analysis techniques. Among these techniques, the Hurst exponent estimation was widely used to characterize the fractional or scaling property of the EEG signals. However, the constant Hurst exponent H cannot capture the detailed information of dynamic EEG signals. In this research, the multifractional property of the normal human sleep EEG signals is investigated and characterized using local Hölder exponent H(t). The comparison of the analysis results for human sleep EEG signals in different stages using constant Hurst exponent H and the local Hölder exponent H(t) are summarized with tables and figures in the paper. The results of the analysis show that local Hölder exponent provides a novel and valid tool for dynamic assessment of brain activities in different sleep stages.
ON STABILITY OF COMMENSURATE FRACTIONAL ORDER SYSTEMS
Authors: SABATIER JOCELYN , FARGES CHRISTOPHE
Published: March 2012

This paper proposes a new proof of the Matignon's stability theorem. This theorem is the starting point of numerous results in the field of fractional order systems. However, in the original work, its proof is limited to a fractional order ν such that 0 < ν < 1. Moreover, it relies on Caputo's definition for fractional differentiation and the study of system trajectories for non-null initial conditions which is now questionable in regard of recent works. The new proof proposed here is based on a closed loop realization and the application of the Nyquist theorem. It does not rely on a peculiar definition of fractional differentiation and is valid for orders ν such that 1 < ν < 2.
EXISTENCE RESULTS FOR FRACTIONAL BOUNDARY VALUE PROBLEM VIA CRITICAL POINT THEORY
Authors: JIAO FENG , ZHOU YONG
Published: March 2012

In this paper, by the critical point theory, the boundary value problem is discussed for a fractional differential equation containing the left and right fractional derivative operators, and various criteria on the existence of solutions are obtained. To the authors' knowledge, this is the first time, the existence of solutions to the fractional boundary value problem is dealt with by using critical point theory.
PATTERN FORMATION IN FRACTIONAL REACTION–DIFFUSION SYSTEMS WITH MULTIPLE HOMOGENEOUS STATES
Authors: DATSKO BOHDAN , LUCHKO YURY , GAFIYCHUK VASYL
Published: March 2012

This paper is devoted to the investigation of self-organization phenomena in time-fractional reaction–diffusion systems with multiple homogeneous states. It is shown that the fractional reaction–diffusion systems possess some new properties compared to the systems with derivatives of integer orders. In particular, some complex spatio-temporal solutions that cannot be found in the standard reaction–diffusion systems are identified. The simulation results are presented for the case of a incommensurate time-fractional reaction–diffusion system with a cubic nonlinearity.
ANALYTICAL DYNAMICS OF PERIOD-m FLOWS AND CHAOS IN NONLINEAR SYSTEMS
Authors: LUO ALBERT C. J. , HUANG JIANZHE
Published: March 2012

In this paper, the analytical solutions for period-m flows and chaos in nonlinear dynamical systems are presented through the generalized harmonic balance method. The nonlinear damping, periodically forced, Duffing oscillator was investigated as an example to demonstrate the analytical solutions of periodic motions and chaos. Through this investigation, the mechanism for a period-m motion jumping to another period-n motion in numerical computation is found. In this problem, the Hopf bifurcation of periodic motions is equivalent to the period-doubling bifurcation via Poincare mappings of dynamical systems. The stable and unstable period-m motions can be obtained analytically. Even more, the stable and unstable chaotic motions can be achieved analytically. The methodology presented in this paper can be applied to other nonlinear vibration systems, which is independent of small parameters.
MULTIPLE SOLUTIONS OF A GENERALIZED SINGULAR PERTURBED BRATU PROBLEM
Authors: BAKRI TAOUFIK , KUZNETSOV YURI A. , VERHULST FERDINAND , DOEDEL EUSEBIUS
Published: March 2012

Nonlinear two-point boundary value problems (BVPs) may have none or more than one solution. For the singularly perturbed two-point BVP εu″ + 2u′ + f(u) = 0, 0 < x < 1, u(0) = 0, u(1) = 0, a condition is given to have one and only one solution; also cases of more solutions have been analyzed. After attention to the form and validity of the corresponding asymptotic expansions, partially based on slow manifold theory, we reconsider the BVP within the framework of small and large values of the parameter. In the case of a special nonlinearity, numerical bifurcation patterns are studied that improve our understanding of the multivaluedness of the solutions.
STABLE HARMONIC MAPS BETWEEN FINSLER MANIFOLDS AND SSU MANIFOLDS
Authors: LI JINTANG
Published: March 2012

Using the properties of Cartan tensor, we rewrite the second variation formula for harmonic maps between Finsler manifolds, and we prove that there is no non-degenerate stable harmonic map from a compact SSU manifold to any Finsler manifold, which is obtained by Howard and Wei for the Riemannian case. We also include a proof of a theorem of Shen–Wei which states that there is no non-degenerate stable harmonic map from a compact Finsler manifold to any SSU manifold, by the same second variational formula (see Eq. (2.1) in [Y. B. Shen and S. W. Wei, The stability of harmonic maps on Finster manifolds, Houston J. Math. 34 (2008) 1049–1056]) and the same method [S. W. Wei, An extrinsic average variational method, in Recent Developments in Geometry, Contemporary Mathematics, Vol. 101 (American Mathematical Society, Providence, RI, 1989), pp. 55–78].
REGULARITY OF WEAK SOLUTIONS FOR THE NAVIER–STOKES EQUATIONS IN THE CLASS L∞(BMO-1)
Authors: WANG WENDONG , ZHANG ZHIFEI
Published: March 2012

We study the regularity of weak solution for the Navier–Stokes equations in the class L∞( BMO-1). It is proved that the weak solution in L∞( BMO-1) is regular if it satisfies a mild assumption on the vorticity direction, or it is axisymmetric. A removable singularity theorem in ∈ L∞( VMO-1) is also proved.
ON THE WELL-POSEDNESS OF THE FULL LOW MACH NUMBER LIMIT SYSTEM IN GENERAL CRITICAL BESOV SPACES
Authors: DANCHIN RAPHAËL , LIAO XIAN
Published: March 2012

This work is devoted to the well-posedness issue for the low Mach number limit system obtained from the full compressible Navier–Stokes system, in the whole space ℝd with d ≥ 2. In the case where the initial temperature (or density) is close to a positive constant, we establish the local existence and uniqueness of a solution in critical homogeneous Besov spaces of type [Formula: see text]. If, in addition, the initial velocity is small then we show that the solution exists for all positive time. In the fully nonhomogeneous case, we establish the local well-posedness in nonhomogeneous Besov spaces [Formula: see text] (still with critical regularity) for arbitrarily large data with positive initial temperature. Our analysis strongly relies on the use of a modified divergence-free velocity which allows to reduce the system to a nonlinear coupling between a parabolic equation and some evolutionary Stokes system. As in the recent work by Abidi and Paicu [Existence globale pour un fluide inhomogène, Ann. Inst. Fourier 57(3) (2007) 883–917]. Concerning the density-dependent incompressible Navier–Stokes equations, the Lebesgue exponents of the Besov spaces for the temperature and the (modified) velocity, need not be the same. This enables us to consider initial data in Besov spaces with a negative index of regularity.
A RELATIVE ISOPERIMETRIC INEQUALITY
Authors: BROCK FRIEDEMANN , WILLEM MICHEL
Published: March 2012

We prove that, if Ω is an open subset of ℝN with finite measure, there exists a hyperplane H through 0 such that the measure of Ω ∩ H is less than the measure of B ∩ H, where B is the open ball with center 0 having the same measure as Ω. An application is given to the optimal Poincaré inequality on BV(Ω).
Observation of Reverse Transformation of α-ε-γ in ultrafine - grainedFe-Ni-MnAge Hardenable Martensitic Steel
Authors: GHASEMI-NANESA H. , NILI AHMADABADI M. , SHIRAZI H. , HOSSEIN NEDJAD S.
Published: March 2012

Fe -10 Ni -7 Mn ( wt %) martensitic steel is a member of ultrahigh strength steels. This alloy is ductile in the solution annealed condition and shows good age hardenability but it suffers from severe embrittlement after aging. Discontinuous coarsening of grain boundary precipitates was found as the main source of embrittlement. In this paper the effect of cold rolling on the mechanical properties and phase stability of Fe -10 Ni -7 Mn steel was investigated. Cold rolling for 20%, 60%, and 90% were carried out on a solution annealed material with subsequent aging at 753 K. X- ray diffraction results and transmission electron microscopy (TEM) micrographs showed the presence of austenite in severely cold rolled samples. This austenite is likely formed as a result of deformation, and it seems to originate from a reverse transformation from bcc-martensite to hcp-martensite to austenite, stimulated by increasing the amount of deformation. This transformation improves the mechanical properties in this steel while in as annealed and aged condition it has premature fracture and zero ductility.
THE EFFECT OF VARIOUS PHYSICAL AND CHEMICAL ROUTES ON TEXTURAL AND STRUCTURAL CHARACTRISTICS OF SYNTHESIZED Ni(OH)2 NANOPARTICLES
Authors: ZAREI HOSEIN , YUZBASHI AMIR ALI
Published: March 2012

Nano-sized nickel hydroxide powder has been synthesized by complexation-precipitation method through various decomposition routes in order to investigate its effect on textural and structural characteristics of the nickel hydroxide products. The products were then characterized by various analytical techniques such as XRD, SEM, ICP and FTIR. The results showed that the product with different size, shape and structure could be obtained by using different routes for decomposition of the complex.
DETERMINATION OF THE ADHESION PROPERTIES OF MICA VIA ATOMIC FORCE SPECTROSCOPY
Authors: Shadloo Tina , Firoozi Sadegh , Marashi Pirooz , Zolfaghari Hesari Alireza , Rezaee Masih , Jalilzadeh Somayeh
Published: March 2012

This paper addresses the Adhesion of mica surface employing Atomic Force Microscope (AFM) as a surface force apparatus. AFM is commonly used for atomic and nano-scale surface measurements. Based on the relations between cantilever responses and tip–sample interaction, methods for quantitative evaluation of a sample's mechanical parameters are described and issues concerning the use of AFM are discussed. The measurement of the Force-Distance curve was performed implementing Atomic Force Spectroscopy (AFS). During these measurements, the static deflection of the cantilever is monitored as a function of piezoelectric element displacement. The recorded plot is then used to quantitatively measure the mechanical properties like adhesion and elastic modulus. Forces were measured by multiplying the distance by force constant of the cantilever thorough Hook's law. It was necessary to calibrate the force constant of the cantilever to perform a precise force measurement. Force-Distance curves were obtained in three different points on the surface of mica and Distant Dependant Measurement (DDM) was conducted 10 times per each point by 1.5s interval. Adhesion force was then calculated in every single curve and the final data was the mean of thirty different curves.
THE EFFECT OF Mn ON α TO γ TRANSFORMATION IN THE NANOSTRUCTURED HIGH NITROGEN Fe-Cr-Mn STAINLESS STEEL PRODUCED BY MECHANICAL ALLOYING
Authors: TEHRANI FARIBA , ABBASI MOHAMMAD HASAN , GOLOZAR MOHAMMAD ALI , PANJEPOUR MASOUD
Published: March 2012

In this study, the effect of Mn on α to γ transformation in the nanostructured high nitrogen Fe -18 Cr - xMn stainless steel produced by mechanical alloying (MA) was investigated. MA was performed under nitrogen atmosphere using a high-energy planetary ball mill. X- ray diffraction (XRD) patterns of produced samples showed that α to γ transformation starts after 20 hours of milling and propagates by increasing the milling time. Completion of this phase transformation occurred in the Fe -18 Cr -8 Mn sample after 100 hours of milling. But, in the Fe -18 Cr -7 Mn sample, some α phase remained even after 150 hours of milling. Also, nitrogen analysis revealed that nitrogen solubility in the milled powders increased significantly by increasing the milling time, and ultimately reached 1wt%. This is believed to be due to the increase of the lattice defects and development of nanostructure through MA. Variations in grain size and internal lattice strain versus milling time in both cases showed that the critical ferrite grain size for austenite nucleation was lower than 10nm. Moreover, a lower transformation rate was found in samples containing lower Mn content.
WATER IONIC LIQUID-CROWN ETHER SYSTEM CONTROLLING MORPHOLOGIES AND SIZES OF SOLUBLE POLYPYRROLE NANOSTRUCTURES AND THEIR SELF-ASSEMBLY BEHAVIORS IN THE SYSTEM
Authors: YAVARI ISSA , KOWSARI ELAHEH
Published: March 2012

The present study reports a novel chemical route to synthesize different sizes of conducting polypyrrol (ppy) nanoparticles by hydrogen-bonding directionality in the presence of a crown ether, ionic liquid ([octmim] Br , octhyl-methyl imidazulim bromide) and ammonium persulfate in HCl solution. The morphology of the nanoparticle of PPy was confirmed by SEM images. The effects of reaction conditions on the morphology of the resultant ppy nanostructures were studied. The conductivity of the product varied with the mass ratio of aniline monomer to crown ether and IL. The chemical and electronic structures of the ppy nanoparticle were also studied by FT-IR and UV–Vis spectrometry, respectively.
FABRICATION OF BaCO3 NANO-RODS IN WATER/POLY VINYL ALCOHOL MIXED SOLVENTS
Authors: ASGARI MOTAHARE , ATAIE ABOLGHASEM , MOKHTABAD AMREI DIBA
Published: March 2012

Barium carbonate nano-particles have been synthesized by a simple PVA-assisted precipitation method using hydrated barium chloride and sodium carbonate as the starting materials. Crystal structure and morphology of the products were evaluated by XRD and SEM techniques, respectively. XRD results indicated that under the identical experimental conditions, single phase BaCO 3 was produced. SEM results showed that in the presence of PVA as guide reagent in the solution, nano-rods with regular (facet) surfaces were obtained. The results also showed that the concentration of PVA in the solution, reaction time and temperature have obvious influence on the agglomeration nature and mean particle size of the products. At high concentration of PVA less agglomerated nano size particles of BaCO 3 were synthesized. Increasing the synthesis time and temperature resulted in increasing the average diameter of BaCO 3 nano-rods. The performance of produced barium carbonate in the processing of barium hexaferrite ceramic magnet via conventional route has been approved.
SYNTHESIS OF ULTRAFINE NICKEL-IRON POWDER BY THE MAGNESIUM REDUCTION IN GAS PHASE
Authors: TABATABAEI SEYED YOUSEF , BATENI ALI , FIROOZI SADEGH
Published: March 2012

Ultra fine metallic powders have an increasing application in magnetic materials, catalysts and chemical and metallic industries. In this research, magnesium-thermic reduction in gas phase was used to synthesize an ultra-fine nickel-iron intermetallic compound. Synthesis of nickel-iron submicron powder by metal chlorides and magnesium vapors was studied. Evaporation rate of the chlorides and magnesium in the range of 800 to 920 degrees Celsius was measured in order to control the composition of the resulting compound. The simultaneous reduction of the chlorides was done in a tubular furnace under argon atmosphere at 920 degrees Celsius. Chemical analysis of the resulting compound and the X ray diffraction analysis identified the formation of Ni 3 Fe compound. The particle size of the compound was measured 60 to 230 nano-meters by scanning electron microscopy. In addition, the particles were spherical and homogeneous. The product may be used for production of magnetic and catalytic applications.
MECHANOCHEMICAL REDUCTION OF MoO3 POWDER BY Al AND Si TO SYNTHESIZE NANOCRYSTALLINE MoSi2
Authors: RAMEZANALIZADEH H. , HESHMATI-MANESH S.
Published: March 2012

In this study, mechanical alloying was used to produce MoSi 2 powder directly from molybdenum trioxide. Mixture of MoO 3, Si and Al powders were exposed to high mechanical activation in a planetary ball mill. The ball to powder mass ratio was constant at 33:1 and the rotation speed (cup speed) was 290 rpm during the milling operations. Phase compositions and structural evolutions during milling were investigated by X-ray diffraction analysis. The morphology of the mechanically alloyed powders was evaluated with scanning electron microscope (SEM). From XRD results, it was observed that within 3 hours of milling, MoO 3 was completely reduced and a MoSi 2- Al 2 O 3 composite powder was produced. Further milling resulted in transformation of β- MoSi 2 phase to α- MoSi 2. Mean crystallite sizes in product phases in the sample milled for 30 hours calculated by Scherer method using XRD patterns were found to be less than 100 nm.
SYNTHESIS OF MAGNETITE NANO-PARTICLES BY REVERSE CO-PRECIPITATION
Authors: KAZEMZADEH HAMID , ATAIE ABOLGHASEM , RASHCHI FERESHTEH
Published: March 2012

Magnetite nano-particles have been synthesized by reverse co -precipitation method using iron salts in alkaline medium in the presence of diethylene glycol (DEG). Effect of DEG on the nano-particle characteristics was investigated by XRD, FE-SEM, FTIR and VSM techniques. From XRD results it was concluded that in the presence of DEG the composition of magnetite did not change, however the mean crystallite size reduced from 10 to 5 nm. SEM micrograph showed that DEG decreased the size of spherical magnetite nano-particles from 50 to 20 nm. Fourier transform infrared spectra (FTIR) indicated that the DEG molecules chemisorbed on the magnetite nano-particles. Under the given experimental conditions, the rate of crystallization and growth reduced, which is probably due to the capping of DEG to the magnetite nano-particles. The agglomeration was also decreased which is attributed to the coating of magnetite nano-particles by DEG which prevents the formation of hydrogen bonding between magnetite and water molecules.
Platinum nano particles dispersed in alumina
Authors: Gholidoust Abedeh , Naderifar Abbas , Rahmani Mohammad , Sahebdelfar Saeed
Published: March 2012

We report the propane dehydrogenation behavior of catalysts prepared using wet impregnation method that immobilize Pt nano cluster on the alumina surface. The immobilization of the metal particles and their nano size dimensions were demonstrated by transmission electron microscopy. Selectivity to propylene for these catalysts is comparable to those obtained over industrial Pt catalysts, yet the resistance to deactivation by carbon poisoning is much greater for our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts on γ-alumina than of catalysts supported onθ-alumina.
EFFECT OF KINETIC PARAMETERS ON GROWTH OF ONE-DIMENSIONAL TIN OXIDE NANOSTRUCTURES
Authors: SALEHI M. , SADRNEZHAAD S.K.
Published: March 2012

One-dimensional tin oxide nanostructures were synthesized by carbothermal reduction process. Results showed that using Au as catalyst on Si wafer and shorter distance from source materials lead to higher nucleation and growth rate. It was understood that SnO 2 to carbon mixing ratio of 1:4 is appropriate. SnO 2 nanostructures were grown by VLS mechanism.
CRYSTAL ANALYSIS OF MULTI PHASE CALCIUM PHOSPHATE NANOPARTICLES CONTAINING DIFFERENT AMOUNT OF MAGNESIUM
Authors: GOZALIAN AFSANEH , BEHNAMGHADER ALI ASGHAR , MOSHKFOROUSH ARASH
Published: March 2012

In this study, Mg doped hydroxyapatite [( Ca , Mg )10( PO4)6( OH )2] and β-tricalcium phosphate nanoparticles were synthesized via sol gel method. Triethyl phosphite, calcium nitrate tetrahydrate and magnesium nitrate hexahydrate were used as P , Ca and Mg precursors. The ratio of ( Ca + Mg )/ P and the amount of magnesium ( x ) were kept constant at 1.67 and ranging x = 0 up to 3 in molecular formula of Ca10- xMgx( PO4)6( OH )2, respectively. Phase composition and chemical structure were performed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Phase percentages, crystallite size, degree of crystallinity and lattice parameters were investigated. The presence of magnesium led to form the Mg doped tricalcium phosphate (β-TCMP) and Mg doped hydroxyapatite ( Mg - HA ). Based on the results of this study, lattice parameters, degree of crystallinity and crystallite size decreased with magnesium content. In addition, with increasing magnesium content, the amount of CaO phase decreased whereas the amount of MgO phase increased significantly. Obtained results can be used for new biomaterials design.
SYNTHESIS AND CHARACTERIZATION OF TiB2 NANOCRYSTALLINE POWDER BY MECHANICAL ALLOYING
Authors: MOALLEM MAHBOOBEH , ABBASI MOHAMMAD HASAN , ZADEH FATHOLLAH KARIM
Published: March 2012

In this investigation, TiB 2 nanocrystalline powder was synthesized by mechanical alloying of the elemental mixture of Ti and B powders in argon atmosphere. In order to study the structural evolution of the powder during ball milling, X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used. Adiabatic temperature calculations were performed for characterization of TiB 2 powder. Also, the effects of heat treatment on the structural evolution and thermal stability of mechanically alloyed powders were investigated. It was found from the XRD patterns that TiB 2 was formed via combustion mechanism. By increasing milling time, the grain size decreased while the lattice strain increased. SEM micrographs showed that TiB 2 particles were spherical. The grain size and lattice strain reached 24 nm and 1.8% respectively, after 60 hours ball milling.
Synthesis of Oxide Nanoparticles in Hybrid Nanocomposite Coatings as Nanoreservoirs of Corrosion Inhibitors
Authors: PIRHADY TAVANDASHTI NAHID , SANJABI SOHRAB
Published: March 2012

Nanostructured hybrid silica/epoxy films containing boehmite nanoparticles were investigated in the present work as pretreatments for AA2024 alloy. To produce the nanocomposite sol-gel films, boehmite nanoparticles prepared from hydrolysis/condensation of aluminum isopropoxide ( AlI ) were doped into another hybrid organosiloxane sol. The produced oxide nanoparticles have the capability to act as nanoreservoirs of corrosion inhibitors, releasing them controllably to protect the metallic substrate from corrosion. For this purpose the corrosion inhibitor, cerium nitrate, was introduced into the sol-gel system via loading the nanoparticles. The morphology and the structure of the hybrid sol-gel films were studied by Scanning Electron Microscopy (SEM). The corrosion protection properties of the films were investigated by Potentiodynamic Scanning (PDS) and Electrochemical Impedance Spectroscopy (EIS). The results show that the presence of boehmite nanoparticles highly improved the corrosion protection performance of the silica/epoxy coatings. Moreover, they can act as nanoreservoirs of corrosion inhibitors and provide prolonged release of cerium ions, offering a self-healing property to the film.
INVESTIGATION OF LIGANDS AND TEMPRATURE EFFECTS ON THE SIZE OF AQUEOUS PHASE SYNTHESIZED CDTE NANOCRYSTALS
Authors: POURJAFARI S. , SAIEVARE-IRANIZAD E. , MOLAEI M.
Published: March 2012

The synthesis and properties of high luminescent thio-stabilized nanocrystals (NCs) in aqueous media was discussed in this paper. The sharp peaks of photoluminescence ( PL ) and full width at half-maximum (fwhm), were observed in the range of 50 to 70nm. The PH was 9 and the molar ratio of Cd to thiol (1:2.4) was constant during the experiment. The stabilized NCs through thioglycolic acid ( TGA ) show great luminosity in which the spectral of PL emission is variable with controlling the size of NCs. The size ranges of thioglycerol( TG ) stabilized NCs and the spectral range of PL emission are more limited than TGA in the same condition. The concentration of thio-ligands and heating time are two factors that that will discuss in this paper to control the size of NCs.
Synthesis of TiO2/SnO2 core shell nanocomposite via sol-gel method
Authors: KHOBY-SHENDY SORAIA , VAEZI MOHAMMAD REZA , EBADZADEH TORAJ
Published: March 2012

The particles of TiO 2 core/ SnO 2 shell nanocomposite were prepared by hydrolysis of SnCl 4.5 H 2 O in the presence of titania nanoparticle after drying and calcinations treatments. TiO 2 particle were produced from titanium isopropoxide sol by hydrothermal processing. X-ray diffraction (XRD), Fourier transformed infrared (FTIR), and transmission electron microscopy (TEM) were used to characterize the TiO 2/ SnO 2 core shell nanocomposites. The obtained results from XRD show that the SnO 2 nanoparticles coated on TiO 2 yields diffraction peaks correspond to the crystalline SnO 2 phase. Also, TEM results show that the nanocomposite particles have a spherical morphology and a narrow size distribution. The thickness of SnO 2 shell on the surface of TiO 2 particles were about 8 nm. Moreover, the results obtained from EDX analysis show that the core-shell structured nanocomposites have crystalline structure.
EFFECT OF GELATIN AMOUNT ON PROPERTIES OF NANO-BCP/GEL SCAFFOLDS
Authors: BAKHTIARI LEILA , HOSSAINALIPOUR SEYED MOHAMAD , REZAIE HAMID REZA
Published: March 2012

Biodegradable polymers and bioactive ceramics are being combined in a variety of composite materials for tissue engineering scaffolds. Porous nano-biphasic calcium phosphate/gelatin structure was prepared by freeze-drying method. Pre-pores were created by using naphthalene with different particle sizes. Stabilization of gelatin network matrix carried out by EDC ( N -(3-dimethyl aminopropyl)- N ′-ethyl carbodiimide hydrochloride) with cross-linking method. Three different amount of gelatin (2, 6 and 10 mg/ml) solution were used to study the effect of gelatin amount on properties of the scaffold. Microstructural properties of scaffolds were characterized by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical composition of scaffold. Also the morphology and bending strength were investigated.
SYNTHESIS OF NANOSIZE SILICON CARBIDE POWDER BY CARBOTHERMAL REDUCTION OF SiO2
Authors: DEHGHANZADEH M. , ATAIE A. , HESHMATI-MANESH S.
Published: March 2012

A mixture of silicon carbide nano-particles and nano-whiskers has been synthesized through solid state reduction of silica by graphite employing high energy planetary ball milling for 25 h and subsequent heat treatment at 1300-1700°C in dynamic argon atmosphere. Effects of process conditions on the thermal behavior, phase composition and morphology of the samples were investigated using DTA/TGA, XRD and SEM, technique, respectively.

DTA/TGA analysis shows that silicon carbide starts to form at ~ 1250°C. Analysis of the XRD patterns indicates that the phase composition of the sample heat treated at 1300°C for 2 h mainly consists of SiO 2 together with small amount of β- SiC . Nano-crystalline silicon carbide phase with a mean crystallite size of 38 nm was found to be dominate phase on heat treatment temperature at ~ 1500°C. Substantial SiO 2 was still remained in the above sample. SEM studies reveal that the sample heat treated at 1500°C for 2 h contains nano-particles and nano-whisker of β- SiC with a mean diameter of almost ~ 85 nm. The results obtained were also showed that the characteristics of the synthesized SiC particles strongly depend on the mechanical activation and heat treatment conditions.
MICROSTRUCTURAL EVOLUTION OF AZ31 MAGNESIUM ALLOY PROCESSED BY A NEW NOBLE SEVERE PLASTIC DEFORMATION METHOD
Authors: FATEMI-VARZANEH S.M. , ZAREI-HANZAKI A. , VAGHAR R.
Published: March 2012

A new noble severe plastic deformation method, called accumulative back extrusion (ABE), was developed to assist generating ultra fine grain materials. In the present work the ABE process was successfully applied on AZ 31 magnesium alloy up to three passes without any danger of cracks. The results showed that a large shear deformation may introduce through step one, where extensive shear banding and twinning are present in the microstructure. As the second step proceeds via constrained compressive deformation, more deformation inhomogenieties, which may act as preferred nucleation sites for new grains, were introduced in the microstructure. By increasing the number of passes to 3, more homogeneous microstructure with no significant smaller grain size was formed. The strain induced twinning and strain localization, which were led to occurrence of dynamic recrystallization (DRX), were found to be the main reasons of grain refinement during ABE process.
COMPARING THE BAKE HARDENING OF NANO-GRAIN AA6056 WITH ITS COARSE-GRAIN STRUCTURE
Authors: DEHGHANI KAMRAN
Published: March 2012

In preset work, the bake hardening behavior of 6056 aluminum alloy with nanostructured layer, produced by surface severe plastic deformation (SSPD), was compared with that of AA6056 with conventional coarse grain structure. Wire brushing process was employed in order to produce surface layers with nanograins. After formation of nanostructured surface layer, the structure was characterized using X-ray Diffraction (XRD) and scanning electron microscopy (SEM) techniques. According to the microhardness measurements, the depth of nanostructured layer, with the grains of 50-110 nm, was about 40-50 μm on each side of specimens. The bake hardenability of the produced nanostructured AA6056 was then studied. The results indicate an increase of about 40% in the bake hardening of nanograin AA6056 comparing to the bake hardening of coarse-grain AA6956. The maximum microhardness of nanograin layer was about 250 HV, whereas it was 65 HV for coarse-grain AA6056.
MICROSTRUCTURAL STUDY OF THE MULTIPHASE BAINITIC STEEL THROUGH HEAVY COMPRESSION
Authors: HAJI-AKBARI F. , NILI-AHMADABADI M. , PISHBIN H. , POORGANJI B. , FURUHARA T.
Published: March 2012

High Si bainitic steel has received much interest because of combined ultra high strength, good ductility along with high wear resistance. In this study, the microstructural evolution of dual phase bainitic ferrite-austenite steel after heavy compression was investigated. Compression tests were conducted at temperature of 298K on the rectangular billets at the strain rate of 0.001s-1. The samples were deformed to 40% and 70% of their original thickness. The EBSD results show formation of nano grains with high angle grain boundaries through 70% compression, which confirms grain refinement. Additionally, 40% deformation resulted in enhancement of the dislocation density and formation of subgrains at ferrite unites. Also, it was found during 70% compression of the steel, the austenite transforms to the martensite, which is in agreement with thermodynamic calculations.
PROCESSING OF NANO/SUBMICRON GRAINED STAINLESS STEEL 304L BY AN ADVANCED THERMOMECHANICAL PROCESS
Authors: FOROUZAN F. , KERMANPUR A. , NAJAFIZADEH A. , HEDAYATI A.
Published: March 2012

Nano/Submicron crystalline grains of about 250 nm were obtained in a metastable austenitic stainless steel AISI304L by an advanced thermomechanical process consisting of heavy conventional cold rolling and annealing. Effects of cold thickness reduction and temperature and time of the reversion treatment on microstructure and mechanical properties of the steel were investigated. The nano-structured austenitic steel exhibited not only high strength (above 1 GPa) but also good elongation (above 50%).
BULK NANOSTRUCTURED MATERIALS OBTAINED BY SHOCK WAVES COMPACTION OF ULTRAFINE TITANIUM AND ALUMINUM
Authors: CHIKHRADZE NIKOLOZ M. , POLITIS CONSTANTIN , CHIKHRADZE MIKHEIL , ONIASHVILI GEORGE
Published: March 2012

Theoretical and experimental Investigations of shock wave consolidation processes of Ti - Al nano sized and ultra-disperse powder compositions are discussed. For theoretical calculations of the shock wave loaded materials were used the hydrodynamic theory and experimental adiabatic of Ti and Al . The normal and tangential stresses in the cylindrical steel tube (containers of Ti - Al reaction mixtures) were estimated using the partial solutions of elasticity theory. The mixtures of ultra-disperse Ti and nano sized (≤ 50nm) Al powder compositions were consolidated to full or near-full density by explosive-compaction technology. The ammonium nitride based industrial explosives were used for generation of shock waves. To form ultra-fine grained bulk TiAl intermetallics with different compositions, ultra-disperse Ti particles were mixed with nano-crystalline Al . Each reaction mixture was placed in a sealed container and explosively compacted using a normal and cylindrical detonation set-up. Explosive compaction experiments were performed in range of pressure impulse (5-20) GPa. X-ray diffraction (XRD), structural investigations (SEM) and micro-hardness measurements were used to characterize the intermetallics phase composition and mechanical properties. The results of analysis revealing the effects of the compacting conditions and precursor particles sizes, affecting the consolidation and the properties of this new ultra high performance alloys are discussed.
The Comparison between Continuous Confined Strip Shearing (C2S2) and ECAP Conform in Regard to Equivalent Plastic Strain Distribution for Al 1100
Authors: Shahab A. R. , Akbari Mousavi S. A. A. , Ranjbar Bahadori Sh. , Ebrahimi S. M.
Published: March 2012

During the last years lots of efforts have been done to industrialize equal channel angular pressing (ECAP) technique. Both Continuous Confined Strip Shearing (C2S2) and ECAP-Conform methods are rather recent techniques, making a continuous process from ECAP method. In present study both mentioned processes were simulated with ABAQUS Finite Element software for commercially pure aluminum. During C2S2 process the sample gradually experienced equivalent plastic strain (PEEQ) of 0.13 at initial stages of bending, while during ECAP-Conform the sample underwent rather sudden magnitude of strain of about 0.52 at primary stages, and it remained constant during the rest of the process. The final magnitude of the PEEQ differed significantly between two processes, as it was 0.86 and 1.36 in C2S2 and ECAP-Conform, respectively. Therefore, in the same processing condition employing the ECAP-Conform method led to a finer microstructure in comparison with C2S2 technique.
TENSILE PROPERTIES OF NANO AL2O3 PARTICULATE-REINFORCED ALUMINUM MATRIX COMPOSITES BY MECHANICAL ALLOYING AND HOT EXTRUSION
Authors: Mehdinia M. , Jenabali Jahromi S.A.
Published: March 2012

The powder of the micro Al and variant volume fractions of nano Al 2 O 3 were milled by a high energy planetary ball-mill. By milling, a homogenous distribution of nano Al 2 O 3 particles in the metal matrix were developed. Then the milled powder was cold compressed and sintered at 545°C for one hr. The mold and the sintered sample hold in a furnace until the temperature reached 545°C. Then the hot 27mm diameter sample was extruded to 6mm diameter. From the extruded specimens, tensile, hardness and microstructure of the prepared specimens were determined. By these tests the effect of milling time, the percent of nano-particles and the microstructure were evaluated. The hardness and tensile behaviors of aluminum matrix composites reinforced with nano Al 2 O 3 particulate have been found to increase remarkably with the volume fraction of the reinforcement.
SOLID STATE REDUCTION OF MoO3 WITH CARBON VIA MECHANICAL ALLOYING TO SYNTHESIZE NANO-CRYSTALINE MoO2
Authors: SAGHAFI M. , ATAIE A. , HESHMATI-MANESH S.
Published: March 2012

In this research, effect of milling time on solid state reduction of MoO 3 with carbon has been investigated. It was found that mechanical activation of a mixture of MoO 3 and carbon at ambient temperature by high energy ball milling was not able to reduce MoO 3 to metallic molybdenum. MoO 3 was converted to MoO 2 at the first stage of reduction and peaks of the latter phase in X-ray diffraction patterns were detected when the milling time exceeded from 50 hours. The main effect of increased milling time at this stage was decreasing of MoO 3 peak intensities and significant peak broadening due to decrease in size of crystallites. After prolonged milling, MoO 3 was fully reduced to nano-crystalline MoO 2 and its mean crystallite size was calculated using Williamson–Hall technique and found to be 17.5 nm.

Thermodynamic investigations also confirm the possibility of reduction of MoO 3 to MoO 2 during the milling operation at room temperature. But, further reduction to metallic molybdenum requires thermal activation at higher temperature near 1100 K.

XRD and SEM techniques were employed to evaluate the powder particles characteristics.
MICROSTRUCTURES AND ELECTROCHEMICAL PROPERTIES OF NANO-STRUCTURED Mg2Ni-BASED COMPOUND CONTAINING Nb ADDITIVES
Authors: MOHRI MARYAM , KASHANI-BOZORG S. F.
Published: March 2012

In the present work, high energy ball milling of binary ( Mg 2 Ni ) and ternary powder mixtures ( Mg 1.75 Nb 0.25 Ni and Mg 2 Ni 0.75 Nb 0.25, i.e., substitution of Nb for Mg and Ni , respectively) was carried out. The effects of milling process parameters on the microstructure of binary and ternary milled products were studied. Also, electrochemical properties of the nano-structured electrodes made from the milled products were measured. It was found that Nb substitution for Mg ( Mg 1.75 Nb 0.25 Ni ) has beneficial effect on the formation kinetic of Mg 2 Ni -based nano-crystallites. Electrode made from the 20h milled product using initial composition of Mg 1.75 Nb 0.25 Ni exhibited a high discharge capacity of ~600mAhg-1 and relatively longer discharge life. Such electrode showed a microstructure consisting of an amorphous core surrounded by nano-crystallites.