bluuebunny/crossref_metadata_2025 huggingface dataset:
Differences of metal concentrations and morpho-anatomical adaptations between obligate and facultative serpentinophytes from Western Serbia
Authors: Dudic B. , Rakic Tamara , Sinzar-Sekulic Jasmina , Atanackovic Valentina , Stevanovic Branka
Published: March 2008

In the present study, some important macro- and micronutrients (Ca, Mg, Fe, Ni) and the trace element Cr are analyzed in the obligate serpentinophytes Fumana bonapartei and Stachys recta var. chrysophaea, Balkan endemic species, as well as in Seseli rigidum, a widespread facultative serpentinophyte. Differences of adaptive structural features between these plants relative to serpentine tolerance strategy are also presented. Our investigations were carried out on plant samples deriving from the serpentine area of Mt. Tara in Western Serbia.
Morpho-anatomical differentiation of the Balkan endemic species Teucrium arduini L. (Lamiaceae)
Authors: Lakusic Branislava , Lakusic D. , Slavkovska Violeta , Stevanovic V. , Stevanovic Branka
Published: March 2008

Teucrium arduini L. is an endemic of the Mediteranean to sub-Mediterranean part of the Western Balkans. The ecological plasticity, i.e., inter-population differentiation, of the species Teucrium arduini was analyzed on the basis of morpho-anatomical variability of six populations from different types of vegetation, i.e., of rocky crevices, rocky ground, and a thermophilous forest in the eu-Mediterranean, sub-Mediterranean, and transitional sub-Mediterranean-Central-European climate zones. Univariant statistic analysis included 22 quantitative characters related to leaf and stem anatomy and morphology. In order to establish the variability and significance of morpho-anatomical differentiation, principal component analyses (PCA), multivariant analyses of variances (MANOVA), and discriminant components analysis (DCA) were done. The analyses of plants from these spatially separated populations confirmed that the species T. arduini belongs to the category of xerophytes with malacophyllous leaves.
Prilog proucavanju fonetske prirode glasova u srpskom jeziku - lateralni glasovi
Authors: Guduric Snezana , Petrovic Dragoljub
Published: March 2008

(francuski) Ce texte porte sur la nature des sons lat?raux en langue serbe sur leurs points convergents et divergents, et en particulier sur leur distribution. En d?pit de leur mode de prononciation presque identique (passage lat?ral de l?air des deux cote de l?obstacle fait dans le r?sonateur buccal), les deux sons montrent des diff?rences importantes concernant tout autre caract?ristique. Le son dit palatal, par son image acoustique ressemble plus au son transitoire [j] ou au son nasal [n] qu?a sa paire lat?rale. C?est peut-?tre la raison pour laquelle on le substitue souvent par le [j] dans certains dialectes serbes. De m?me, nous montrons que la nature du [l] dit syllabique diff?re de celle de la sonante non-syllabique, tout en consid?rant les deux sons phonologiquement identiques.
Prefiksalno-predloski odnosi u tvorbenoj strukturi glagola - na primeru slovenackog jezika
Authors: Zele Andreja
Published: March 2008

(ruski) V stat'e na primere slovenskogo jazyka rassmatrivaetsja vzaimozavisimost' mezdu pristavocnymi derivacionnymi morfemami i predlogami v glagolah i glagol'nyh socetanijah. Suscestvujuscaja vzaimosvjaz' vyrazaetsja v raspredelenii kategorii vida, fazisnogo i obstojatel'stvennogo znacenija mezdu razlicnymi prefikasal'nymi i predloznymi glagol'nymi morfemami.
O jednom tipu redukovanog infinitiva u nekim zetsko-sjenickim govorima s osvrtom na stanje u bugarskom i makedonskom jeziku
Authors: Stijovic Rada
Published: March 2008

(ruski) V nastojascej rabote rec' idet ob infinitive bez infinitivnogo okoncanija -ti (radi, uze, peva, pomenu), casto upotrebljajuscegosja v govore Vasoevicej i Pastrovicej; on takze vstrecaetsja i po sej den' v nekotoryh konstrukcijah bolgarskogo i makedonskogo jazykov. V bolgarskom takoj infinitiv vstrecaetsja v konstrukcii s modal'njami glagolami (ne moga kaza) i v opredelennom tipe futura (sca napravi), a v bolgarskom i makedonskom - v inperativnyh konstrukcijah s otricatel'noj imperativnoj casticej nedej, t.e. nemoj (nedej plaka, nemoj nosi) stiga hodi, a takze v nekotoryh redkih vyraz enijah. .
O tekucoj lingvistickoj bibliografiji u Juznoslovenskom filologu
Authors: Golubovic Ana
Published: March 2008

(ruski) Nacinaja s 1921 goda so vtorogo vypuska zurnala, Juznoslovenski filolog, reguljarno publikuet svodnuju tekuscuju bibliografiju knig i statej po indoevropejskoj filologii i obscemu jazykoznaniju. Imenno ?tim on otlicaetsja ot ostal'nyh naucnyh zurnalov takogo tipa v Serbii. ?ta bibliografija daet materialja dlja izucenija ne tol'ko osnovnyh napravlenij razvitija otecestvennogo jazykoznanija, no i bibliograficeskoj naucno-issledovatel'skoj dejatel'nosti.
Antimicrobial activity of some isatin-3-thiosemicarbazone complexes
Authors: Konstantinovic Sandra , Radovanovic Blaga , Sovilj Sofija , Stanojevic Svetlana
Published: March 2008

Isatin-3-thiosemicarbazone complexes with Co(II), Ni(II), Cu(II), Zn(II), Hg(II) and Pd(II) were synthesized and evaluated for their antimicrobial activity against 7 pathogenic bacteria and 4 fungi. The complexes have an en?hanced activity compared to the ligand due to transition metal involved in coor?dination. The anti-amoebic activity in vitro was evaluated against the HM1:IMSS strain of Entamoeba histolytica and the results were compared with the standard drug, metronidazole. The preliminary test results showed that the complexes had better anti-amoebic activity than their respective ligands. Moreover, the com?plexes showed better inhibition of the test organism.
On the dynamics of some small structural motifs in rRNA upon ligand binding
Authors: Rakic Aleksandra , Mitrasinovic Petar
Published: March 2008

The present study characterizes using molecular dynamics simulations the behavior of the GAA (1186-1188) hairpin triloops with their closing c-g base pairs in large ribonucleoligand complexes (PDB IDs: 1njn, 1nwy, 1jzx). The relative energies of the motifs in the complexes with respect to that in the reference structure (unbound form of rRNA; PDB ID: 1njp) display the trends that agree with those of the conformational parameters reported in a previous study1 utilizing the de novo pseudotorsional (?,?) approach. The RNA regions around the actual RNA-ligand contacts, which experience the most substantial conformational changes upon formation of the complexes were identified. The thermodynamic parameters, based on a two-state conformational model of RNA sequences containing 15, 21 and 27 nucleotides in the immediate vicinity of the particular binding sites, were evaluated. From a more structural standpoint, the strain of a triloop, being far from the specific contacts and interacting primarily with other parts of the ribosome, was established as a structural feature which conforms to the trend of the average values of the thermodynamic variables corresponding to the three motifs defined by the 15-, 21- and 27-nucleotide sequences. From a more functional standpoint, RNA-ligand recognition is suggested to be presumably dictated by the types of ligands in the complexes.
Vapor pressure, density, viscosity and refractive index of dimethyl sulfoxide + 1,4-dimethylbenzene system
Authors: Ciocirlan Oana , Iulian Olga
Published: March 2008

This paper reports the experimental results of isothermal vapor-liquid equilibrium data between 303.15 and 333.15 K, and densities, viscosities, refractive indices from 298.15 to 323.15 K of the dimethyl sulfoxide + 1,4-dime?thylbenzene system over the entire range of mixture composition. The obtained PTX data were correlated by the Wilson and NRTL models and estimated by the UNIFAC model. The excess Gibbs energy and activity coefficients were calculated and compared with others excess properties. Excess molar volumes, viscosity deviations and deviations in refractivity were calculated from the experimental data; all the computed quantities were fitted to the Redlich-Kister equation. The resulting excess functions were interpreted in terms of structure and interactions.
Potentiometric determination of ibuprofen, indomethacin and naproxen using an artificial neural network calibration
Authors: Aktaş Hakan , Ertokuş Pekcan
Published: March 2008

In this study, three anti-inflammatory agents, namely ibuprofen, indomethacin and naproxen, were titrated potentiometrically using tetrabutyl?ammonium hydroxide in acetonitrile solvent under a nitrogen atmosphere at 25?C. MATLAB 7.0 software was applied for data treatment as a multivariate calibration tool in the potentiometric titration procedure. An artificial neural network (ANN) was used as a multivariate calibration tool in the potentiometric titration to model the complex non-linear relationship between ibuprofen, indomethacin and naproxen concentrations and the millivolt (mV) of the solutions measured after the addition of different volumes of the titrant. The optimized network predicted the concentrations of agents in synthetic mixtures. The results showed that the employed ANN can precede the titration data with an average relative error of prediction of less than 2.30%.
Influence of cooling conditions and amount of retained austenite on the fracture of austempered ductile iron
Authors: Goryany Vyacheslav , Hofmann Eckart , Mauk Josef
Published: March 2008

SEM Analysis of fracture surfaces from tensile test specimens of thick-walled, austempered ductile irons (diameter 160 mm) shows different fracture behavior depending on the austenite retained in the matrix. The results show ductile fractures only in areas containing retained austenite sections. In section areas without or with a very low content of retained austenite, only brittle fracture without any plastic deformation occurs. The content of retained austenite determines the amount of ductile fracture in the microstructure.
Recombinant expression of monovalent and bivalent anti-TNT-antibodies: Evaluation of different expression systems
Authors: Simonovic Mladen , Zlatanovic-Milosevic Svetlana , Vrvic Miroslav , Simonovic Branislav
Published: March 2008

Monoclonal 11B3 anti-TNT (trinitrotoluene) antibody was expressed as a monovalent and bivalent form using different prokaryotic and eukaryotic expression systems. Recombinant expression in Escherichia coli, mammalian cells and the methylotrophic yeast Pichia pastoris was performed to obtain disulfide-linked and glycosylated antibody forms. The generation of antibody and subsequent evaluation of the expression rates were performed using intracellular, excretory and periplasmatic expression techniques. All methods involved striving for native expressed antibody with maintenance of its functionality only.
Optimization of the production of biodiesel by a commercial immobilized lipase in a solvent-free system using a response surface methodology
Authors: Ognjanovic Nevena , Bezbradica Dejan , Knezevic Zorica
Published: March 2008

Response surface methodology was used for the evaluation of the effects of various factors on the synthesis of biodiesel catalyzed with immobilized lipase from Rhizomucor miehei in a solvent-free system. The production of biodiesel was optimized and model response equations were obtained, enabling the prediction of biodiesel production from the values of the four main factors. It would seem that the reaction temperature and the amount of water predominantly determined the conversion process while the methanol/oil molar ratio had no significant influence on the reaction rate. The temperature and amount of water showed negative interactive effects on the observed reaction rate per amount of enzyme. However, there were no significant interactions among the other variables according to the test of statistical significance. The highest yield of 10.15 mol kg-1 enzyme was observed at 45?C with a 6:1 methanol to oil molar ratio and with no added water in the system.
Mechanism and kinetics of the oxidation of synthetic α-NiS
Authors: Strbac Nada , Zivkovic Dragana , Mihajlovic Ivan , Boyanov Boyan , Zivkovic Zivan
Published: March 2008

The results of an investigation of the mechanism and kinetics of the oxidation process of synthetic ?-NiS are presented in this paper. The mechanism of ?-NiS oxidation was investigated based on the comparative analysis of DTA-TG-DTG and XRD results, as well as the constructed phase stability diagrams (PSD) for the Ni-S-O system. The kinetic investigations of the oxidation process were performed under isothermal conditions (temperature range 823-1073 K). The obtained degrees of desulfurization were used in the calculation process according to the Sharp model and the kinetic parameters, inclu?ding the activation energies and the rate constants of the characteristic reac?tions, for the oxidation of ?-NiS were determined. These results enabled the formulation of a kinetic equation for the desulfurization process: -ln (1 ? ?) = = k1? = 27.89 exp(-9860/T)?, with an activation energy of 82?4 kJ mol-1, for the first stage of the process and -ln (1 ? ?) = k2? = 1.177 exp(-4810/T)?, with an activation energy of 40?2 kJ mol-1, for the second stage.
Periodic current oscillations of zinc in nitric acid solutions
Authors: Crisan Florin , Salló Ervin
Published: March 2008

This paper presents current oscillations of a Zn anode in solutions of nitric acid and potassium dichromate. The effects of the nitric acid concentration were investigated. The system was analyzed using cyclic voltammetry, current-time plots and attractors. It was found that the concentration of nitric acid has a major effect on the behavior of the system and it is proposed that zinc hydroxide precipitation-dissolution processes are responsible for the current oscillations.
Determination of trace copper in water samples by flame atomic absorption spectrometry after preconcentration on a phosphoric acid functionalized cotton chelator
Authors: Gong Renmin , Zhang Demin , Zhong Keding , Feng Min , Liu Xingyan
Published: March 2008

This paper reports the preparation of a phosphorylated cotton chelator (PCC) by solid phase esterification of phosphoric acid (PA) onto defatted cotton fibres using urea as the catalyst. The synthesized PCC was employed for the preconcentration of copper from water samples prior to its determination by flame atomic absorption spectrometry (FAAS). The preconcentration of copper was studied under both batch and column techniques. The pH range for the quantitative preconcentration of copper was 4.0-7.0. The sorption time required for each sample was less than 30 min by the batch method. The copper sorption capacity of the PCC was found to be 15.3 mg/g at the optimum pH value. Elution with 1.0 mol dm-3 hydrochloric acid was found to be quantitative. Feasible flow rates of the copper solution for quantitative sorption onto the column packed with PCC were 0.5-4.0 ml min-1, whereas the optimum flow rate of the hydrochloric acid solution for desorption was less than 1.5 ml min-1. An 80-fold preconcentration factor could be achieved under the optimum column conditions. The tolerance limits for common metal ions on the preconcentration of copper and the number of times of column reuse were investigated. The proposed method was successfully applied for the preconcentration and determination of trace copper in natural and drinking water samples by FAAS.
Emergency exhaust system’s efficiency measurements for iodine removal at PARR-1
Authors: Israr Muhammad , Abdullah Muhammad , Bakhtyar Sabiha , Iqbal Masood , Pervez Showket
Published: March 2008

The emergency exhaust system of the Pakistan Research Reactor-1 (PARR-1) in corporates charcoal bed filters for the removal of radioiodine from exhaust gases in case of an emergency involving the release of radioiodine. The filters adsorb radioiodine. Testing of the filters is necessary so as to assess their iodine retention efficiency, if they are to meet regulatory requirements. The retention efficiency of our filters has been measured and found to be 99.1%. This value is higher than the value of the activated charcoal filter efficiency (99%) employed to determine the source term for release through emergency exhaust with filtration, for dose calculations. In this paper, the procedure for testing the efficiency of charcoal filters has been discussed and results obtained presented.
Multi-axis integrated Hall magnetic sensors
Authors: Popovic Radivoje , Kejik Pavel , Reymond Serge , Popovic Dragana , Blagojevic Marjan , Dimitrijevic Sasa
Published: March 2008

Conventional Hall magnetic sensors respond only to the magnetic field component perpendicular to the surface of the sensor die. Multi-axis sensing capability can be provided in the following two ways: (a) by integrating magnetic flux concentrators on the die, and (b) by using vertical Hall devices. Here we review the most important two-and three-axis integrated Hall magnetic sensors based on these concepts. Their applications include mapping of magnetic fields and sensing angular position.
A new way of obtaining analytic approximations of Chandrasekhar’s H function
Authors: Vukanic Jovan , Arsenovic Dusan , Davidovic Dragomir
Published: March 2008

Applying the mean value theorem for definite integrals in the non-linear integral equation for Chandrasekhar?s H function describing conservative isotropic scattering, we have derived a new, simple analytic approximation for it, with a maximal relative error below 2.5%. With this new function as a starting-point, after a single iteration in the corresponding integral equation, we have obtained a new, highly accurate analytic approximation for the H function. As its maximal relative error is below 0.07%, it significantly surpasses the accuracy of other analytic approximations.
Total number albedo and average cosine of the polar angle of low-energy photons reflected from water
Authors: Markovic Srpko , Ljubenov Vladan , Simovic Rodoljub
Published: March 2008

The total number albedo and average cosine of the polar angle for water and initial photon energy range from 20 keV to 100 keV are presented in this pa per. A water shield in the form of a thick, homogenous plate and per pendicular incidence of the monoenergetic photon beam are assumed. The results were obtained through Monte Carlo simulations of photon reflection by means of the MCNP computer code. Calculated values for the total number albedo were compared with data previously published and good agreement was confirmed. The dependence of the average cosine of the polar angle on energy is studied in detail. It has been found that the total average cosine of the polar angle has values in the narrow interval of 0.66-0.67, approximately corresponding to the reflection angle of 48?, and that it does not depend on the initial photon energy.
Genetically significant dose assessments of occupationally exposed individuals involved in industrial and medical radiographic procedures in certain establishments in Nigeria
Authors: Jibiri Nnamdi , Oguntade Grace
Published: March 2008

The main source of radiation doses received by humans from man-made sources of ionizing radiation in medicine and industry comes from X-rays. The genetic risks of ionizing radiation effects on an individual who is occupationally exposed largely depend on the magnitude of the radiation dose received period of practice, workload and radiological procedures involved. In this work, using the linear non-thresh old model, we have at tempted to assess the level of genetic risk of occupationally exposed individuals in two medical and industrial establishments in Nigeria by estimating their genetically significant dose values. The estimation was based on continuous personnel radiation dose monitoring data for the individuals in each of the establishments over a three year period (1998-2001). The estimated genetically significant dose values in the years considered were 12 mSv for the medical, and 29 mSv for the industrial personnel. Appropriate radiation protection precautions should be taken by the personnel to adhere to standard operational practices in order to minimize the genetically significant dose resulting from radio logical practices.
Quadratic level quasigroup equations with four variables I
Authors: Krapez Aleksandar
Published: March 2008

We consider a class of functional equations with one operational symbol which is assumed to be a quasigroup. Equations are quadratic, level and have four variables each. Therefore, they are of the form x1x2 ? x3x4 = x5x6 ? x7x8 with xi ? {x, y, u, v} (1 _< i _< 8) with each of the variables occurring exactly twice in the equation. There are 105 such equations. They separate into 19 equivalence classes defining 19 quasigroup varieties. The paper (partially) generalizes the results of some recent papers of F?rg-Rob and Krapez, and Polonijo.
Analytic equivalence of plane curve singularities yn +xαy +xβa(x) = 0
Authors: Stepanovic V. , Lipkovski A.
Published: March 2008

There are not many examples of complete analytical classification of specific families of singularities, even in the case of plane algebraic curves. In 1989, Kang and Kim published a paper on analytical classification of plane curve singularities yn+a(x)y+b(x) = 0, or, equivalently, yn+x?y+x?A(x) = 0 where A(x) is a unit in Ct{x}, ? and ? are integers, ? _ n ? 1 and ? _ n. The classification was not complete in the most difficult case ? n?1 = ? n. In the present paper, the classification is extended also in this case, the proofs are improved and some gaps are removed.
On the eigenvalues of some class of pseudo-linear transformations
Authors: Andjelic Milica
Published: March 2008

We develop a connection between the eigenvalues of a class of pseudo-linear transformation over a field K and the eigenvalues of a certain linear transformation. We give a new criterion for this class to be diagonalizable over algebraically closed field.
Normal form theorem for systems of sequents
Authors: Borisavljevic Mirjana
Published: March 2008

In a system of sequents for intuitionistic predicate logic a theorem, which corresponds to Prawitz?s Normal Form Theorem for natural deduction, are proved. In sequent derivations a special kind of cuts, maximum cuts, are defined. Maximum cuts from sequent derivations are connected with maximum segments from natural deduction derivations, i.e., sequent derivations without maximum cuts correspond to normal derivations in natural deduction. By that connection the theorem for the system of sequents (which correspond to Normal Form Theorem for natural deduction) will have the following form for each sequent derivation whose end sequent is ??A there is a sequent derivation without maximum cuts whose end sequent is ??A.
Intersection types for λGtz-calculus
Authors: Ghilezan Silvia , Ivetic Jelena
Published: March 2008

We introduce an intersection type assignment system for Espirito-Santo?s ?Gtz-calculus, a term calculus embodying the Curry-Howard correspondence for the intuitionistic sequent calculus. We investigate basic properties of this intersection type system. Our main result is Subject reduction property.
Analytic tableaux and interpolation
Authors: Kapetanovic Miodrag
Published: March 2008

A tableau system for the predicate logic with countable conjunctions and disjunctions is presented and the completeness of the set of rules proved. These tableaux are used to prove a slightly more general form of the Malitz interpolation theorem.
A theorem on anti-ordered factor-semigroups
Authors: Crvenkovic Sinisa , Romano Daniel
Published: March 2008

Let K be an anti-ideal of a semigroup (S,=, ?,?,?) with apartness. A construction of the anti-congruence Q(K) and the quasi-antiorder ?, generated by K, are presented. Besides, a construction of the anti-order relation ? on syntactic semigroup S/Q(K), generated by ?, is given in Bishop?s constructive mathematics.
Unsteady incompressible MHD boundary layer on porous aerofoil in high accelerating fluid flow
Authors: Ivanovic Decan
Published: March 2008

The fluid, flowing past the surface, is incompressible and its electro-conductivity is constant. The present magnetic field is homogenous and perpendicular to the surface and through the porous contour the fluid has been injected or ejected. In order to study this problem, a polyparametric method known as generalized similarity method has been established. The corresponding equations of unsteady boundary layer, by introducing the appropriate variable transformations, momentum and energy equations and three similarity parameters sets, being transformed into generalized form. The numerical integration of the generalized equation with boundary conditions has been performed by means of the difference schemes and by using Tridiagonal Algorithm Method with iterations in the four parametric and twice localized approximation. So obtained generalized solutions are used to calculate the shear stress distribution in laminar-turbulent transition of unsteady boundary layer on porous high accelerating aerofoil. It's shown that for both in confuser and in diffuser regions the ejection of fluid postpones the boundary layer separation, and vice versa the fluid injection favors the separation. For both injection and ejection of fluid, the magnetic field increases the friction and postpones the laminar-turbulent transition.
On an evaluation of the drag force of a growing vapor bubble at rectilinear accelerated ascension
Authors: Askovic Radomir
Published: March 2008

By applying the in viscid approximation, a simple relation for predicting the drag coefficient of a growing vapor bubble at rectilinear accelerated ascension in uniformly-superheated pure liquids was developed. The relation is valid in both regions: inertia controlled and heat diffusion controlled bubble growth, respectively. The drag coefficient decreases with time for all accelerations, as well as with augmentation of the bubble acceleration at each instant of time, independently of the internal vapor parameters.
Spin fluids and hyperfluids
Authors: Brocato Maurizio , Capriz Gianfranco
Published: March 2008

The general theory of continua with microstructure reviewed in [2] (and, in particular, the theory of gyrocontinua studied in [1]) is adapted to apply to perfect spin fluids and hyperuids [10]. Obvious changes are needed due to the prevailing interest for solids in [1] and to some extent in [2]; here, in addition, the conservative character of the continuum is exploited. Finally, the roles of metric, coframe, connection, torsion and curvature in fluids are explored. .
Homogenization methods and mechanics of generalized continua - part 2
Authors: Forest S.
Published: March 2008

The need for generalized continua arises in several areas of the mechanics of heterogeneous materials, especially in homogenization theory. A generalized homogeneous substitution medium is necessary at the global level when the structure made of a composite material is subjected to strong variations of the mean fields or when the intrinsic lengths of non-classical constituents are comparable to the wavelength of variation of the mean fields. In the present work, a systematic method based on polynomial expansions is used to replace a classical composite material by Cosserat and micromorphic equivalent ones. In a second part, a mixture of micromorphic constituents is homogenized using the multiscale asymptotic method. The resulting macroscopic medium is shown to be a Cauchy, Cosserat, microstrain or a full micromorphic continuum, depending on the hierarchy of the characteristic lengths of the problem. .
Spin axioms in relativistic continuum physics
Authors: Herrmann H.J. , Ruckner G. , Muschik W. , Borzeszkowski H.H.v.
Published: March 2008

The 24 components of the relativistic spin tensor consist of 3 + 3 basic spin fields and 9 + 9 constitutive fields. Empirically only 3 basic spin fields and 9 constitutive fields are known. This empirem can be expressed by two spin axioms, one of them identifying 3 spin fields, and the other one 9 constitutive fields to each other. This identification by the spin axioms is materialindependent and does not mix basic spin fields with constitutive properties. The approaches to the Weyssenhoff fluid and the Dirac-electron fluid found in literature are discussed with regard to these spin axioms. The conjecture is formulated, that another reduction from 6 to 3 basic spin fields which does not obey the spin axioms introduces special material properties by not allowed mixing of constitutive and basic fields. .
Configurational balance laws for dynamical fracture
Authors: Kalpakides V.K. , Agiasofitou E.K.
Published: March 2008

In the spirit of modern continuum mechanics, global balance laws for momentum, angular momentum, energy and pseudomomentum are formulated for an elastic body in the presence of a moving crack. Upon localization, the corresponding balance equations in the bulk and at the crack tip are simultaneously obtained. The proposed framework is convenient for the derivation of the well-known formula, which relates the crack propagation velocity, the global material force and the energy release rate. .
Correlation between mechanical and conductive properties of porous/microcracked metals
Authors: Sevostianov Igor
Published: March 2008

Difierent physical properties of anisotropic porous/microcracked materials - the elastic and the conductive ones, in particular - can be explicitly related to one another. The practical usefulness of such relations lies in the fact that one physical property (say, electric conductivity) may be easier to measure than the other (say, full set of anisotropic elastic constants). Man-made microstructures designed for the optimal combined elastic/conductive performance constitute yet another application. These relations, derived from the micromechanical considerations, are confirmed by experiments on several heterogeneous materials. It is also shown that the anisotropic yield surface for a porous ductile material can be constructed from measurements of the efiective electric conductivities. The derived cross-property correlations are sensitive to pore aspect ratios and Poisson's ratio of the virgin material. .
An O(n) invariant rank 1 convex function that is not polyconvex
Authors: Silhavy M.
Published: March 2008

An O(n) invariant nonnegative rank 1 convex function of linear growth is given that is not polyconvex. This answers a recent question [8, p. 182] and [5]. The polyconvex hull of the function is calculated explicitly if n = 2: .
The Green's and the Eshelby's identities in generalised continua and in dielectrics
Authors: Trimarco Carmine
Published: March 2008

In 1973, A. E. Green pointed out several interesting formulae, which hold true in finite elasticity [1]. One of them (formula (2.10), p.75) is repeatedly quoted in the literature as the Green identity. This remarkable identity has been successfully employed in several contexte. We only mention here its central role in theorems on uniqueness in elastostatics [2,3]. A deeper insight to the Green identity shows in evidence an intimate link of this formula with the Eshelby tensor and with the material balance law of equilibrium [4,5]. In homogeneous hyperelastic materials, this law turns out to an identity, the Eshelby identity, and one can easily prove that the Green identity stems straightforwardly from the Eshelby identity. These identities possibly extend to generalized continua, such as continua with microstructure and elastic dielectrics. Hereafter, the validity of the Eshelby identity is discussed for these materials. Basing on the novel extended Eshelby-like identity, the corresponding extended Green-like identity can be also established, under specifie assumptions. In the case of dielectrics, two equivalent forms for the Eshelby tensor emerge from the treatment, both satisfying the Eshelby identity. One of them is more appropriate for deriving the desired Green-like identity. The second one, which is a reduced form of the first one, represents the physical Eshelby tensor in dielectrics [4-5].
Numerical simulation of complex 3D compressible viscous flows through rotating blade passage
Authors: Despotovic M. , Babic Milun , Milovanovic D. , Sustersic Vanja
Published: March 2008

This paper describes a three-dimensional compressible Navier-Stokes code, which has been developed for analysis of turbocompressor blade rows and other internal flows. Despite numerous numerical techniques and statement that Computational Fluid Dynamics has reached state of the art, issues related to successful simulations represent valuable database of how particular tech?nique behave for a specifie problem. This paper deals with rapid numerical method accurate enough to be used as a design tool. The mathematical model is based on System of Favre averaged Navier-Stokes equations that are written in relative frame of reference, which rotates with constant angular velocity around axis of rotation. The governing equations are solved using finite vol?ume method applied on structured grids. The numerical procedure is based on the explicit multistage Runge-Kutta scheme that is coupled with modem numerical procedures for convergence acceleration. To demonstrate the accuracy of the described numer?ical method developed software is applied to numerical analysis of flow through impeller of axial turbocompressor, and obtained results are compared with available experimental data.
Plane symmetric cosmological micro model in modified theory of Einstein’s general relativity
Authors: Panigrahi U.K. , Sahu R.C.
Published: March 2008

In this paper, we have investigated an anisotropic homogeneous plane symmetric cosmological micro-model in the presence of massless scalar field in modified theory of Einstein's general relativity. Some interesting physical and geometrical aspects of the model together with singularity in the model are discussed. Further, it is shown that this theory is valid and leads to Ein?stein's theory as the coupling parameter ? ?>? 0 in micro (i.e. quantum) level in general.
Properties of the first eigenfunctions of the clamped column equation
Authors: Karaa Samir
Published: March 2008

We show that the clamped column equation may not possess a positive first eigenfunction. This result discovers the anomalies of some papers in determining the shape of the strongest clamped-clamped column.
Heat and mass transfer effects on moving vertical plate in the presence of thermal radiation
Authors: Muthucumaraswamy R. , Senthil Kumar
Published: March 2008

Thermal radiation effects on moving infinite vertical plate in the presence variable temperature and mass diffusion is considered. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The plate temperature and the concentration level near the plate are raised linearly with time. The dimensionless governing equations are solved using the Laplace-transform technique. The velocity and skin-friction are studied for different parameters like thermal Grashof number, mass Grashof number, time and radiation parameter. It is observed that the velocity slightly decreases with increasing value of the radiation parameter.
Ionized gas boundary layer on a porous wall of the body within the electroconductive fluid
Authors: Obrovic Branko , Savic Slobodan
Published: March 2008

This paper investigates the ionized gas flow in the boundary layer, when the contour of the body within the fluid is porous. Ionized gas is exposed to the influence of the outer magnetic field induction Bm = Bm(x), which is perpendicular to the contour of the body within the fluid. It is presumed that the electroconductivity of the ionized gas is a function only of the longitudinal coordinate, i.e. ? = ?(x). By means of adequate transformations, the governing boundary layer equations are brought to a generalized form. The obtained generalized equations are solved in a four-parameter localized approximation. Based on the obtained numerical solutions, diagrams of important physical values and characteristics of the boundary layer have been made. Conclusions have also been drawn.
On the heat transfer to an accelerated translating droplet
Authors: Hanchi S. , Oualli H. , Askovic R.
Published: March 2008

An analysis is made for the transient response behavior of the both, outer and inner, thermal boundary layers of a fluid sphere moving at constant acceleration with internal circulation in an other viscous fluid of large extent initially at rest under the condition of large Reynolds and Peclet numbers. The disturbance is initiated by a step change in temperature of either the continuous or disperse region fluids. The approximate solutions of the governing energy equations are found by using the inviscid approximations for the flow fields.
Some practical issues in the computational design of airfoils for the helicopter main rotor blades
Authors: Kostic Ivan
Published: March 2008

Very important requirement for the helicopter rotor airfoils is zero, or nearly zero moment coefficient about the aerodynamic center. Unlike the old technologies used for metal blades, modern production involving application of plastic composites has imposed the necessity of adding a flat tab extension to the blade trailing edge, thus changing the original airfoil shape. Using computer program TRANPRO, the author has developed and verified an algorithm for numerical analysis in this design stage, applied it on asymmetrical reflex camber airfoils, determined the influence of angular tab positioning on the moment coefficient value and redesigned some existing airfoils to include properly positioned tabs that satisfy very low moment coefficient requirement. .
On the instability of equilibrium of a mechanical system with nonconservative forces
Authors: Veskovic Miroslav , Covic Vukman
Published: March 2008

In this paper the stability of equilibrium of nonholonomic systems, on which dissipative and nonconservative positional forces act, is considered. We have proved the theorems on the instability of equilibrium under the assumptions that: the kinetic energy, the Rayleigh?s dissipation function and the positional forces are infinitely differentiable functions; the projection of the positional force component which represents the first nontrivial form of Maclaurin?s series of that positional force to the plane, which is normal to the vectors of nonholonomic constraints in the equilibrium position, is central and repulsive (with its centre of action in the equilibrium position). The suggested theorems are generalization of the results from [V.V. Kozlov, Prikl. Math. Mekh. (PMM), T58, V5, (1994), 31-36] and [M.M. Veskovic, Theoretical and Applied Mechanics, 24, (1998), 139-154]. The result obtained is analogous to the result from [D.R. Merkin, Introduction to theory of the stability of motion, Nauka, Moscow (1987)], which refers to the impossibility of equilibrium stabilization in a holonomic conservative system by dissipative and nonconservative positional forces in case when the potential energy in the equilibrium position has the maximum. The proving technique will be similar to that used in the paper [V.V. Kozlov, Prikl. Math. Mekh. (PMM), T58, V5, (1994), 31-36]. .
Boundary layer of the dissociated gas flow over a porous wall under the conditions of equilibrium dissociation
Authors: Obrovic Branko , Nikodijevic Dragisa , Savic Slobodan
Published: March 2008

This paper studies the ideally dissociated air flow in the boundary layer when the contour of the body within the fluid is porous. By means of adequate transformations, the governing boundary layer equations of the problem are brought to a general form. The obtained equations are numerically solved in a three-parametric localized approximation. Based on the obtained solutions, very important conclusions about behavior of certain boundary layer physical values and characteristics have been drawn.
Elastic-plastic analysis of crack on bimaterial interface
Authors: Nikolic Ruzica , Veljkovic Jelena
Published: March 2008

In this paper are presented solutions for the stress and dis?placement fields for a crack that lies along the interface of an elastic and elastic - plastic material and for a crack between two different elastic - plastic materials. These solutions are obtained using the J2-deformation theory with the power - law strain hardening. In this paper results are described for a small scale yielding at the crack tip. The near tip fields do not have a separable singular form, of the HRR type fields, as in homogeneous media, they do, however bare interesting similarities to certain mixed -mode HRR fields. Under the small scale yielding the elastic fields are specified by a complex stress intensity factor and phase angle loading, while plastic field is characterized by a new phase angle. The size of plastic zone in plane strain and plane stress and displacement fields at the crack tip for the new phase angle are obtained. The crack tip opens smoothly and the crack opening displacement is scaled by the J-integral. The whole analysis is performed by application of the Mathematica symbolic programming routine.
Mobility of the compliant joints and compliant mechanisms
Authors: Pavlovic Nenad , Pavlovic Nenad
Published: March 2008

This paper deals with a mobility of the single compliant joints and entire compliant mechanisms. The compliance of the joints and the mobility of the compliant mechanism can be increased by variations of geometry as well as material type of the joints. Therefore the mobility of three kinds of compliant joints with different geometrical shapes (beam joints, film joints and notch joints) will be researched. The mobility of the compliant joints made of different material types (plastic joints, silicone joints) will be also researched. The mobility of compliant mechanisms will be analyzed by using of the Roberts-Tchebicheff mechanism which coupler point can be guided on an approximately rectilinear path.
Temperature boundary layer on a rotating surface - the problem of the constant temperature wall
Authors: Pavlovic Milos
Published: March 2008

Introducing the group of Loitskanskii [1] form-parameters and transformations of Saljnikov [2], the set of governing equations of the in compressible laminar temperature boundary layer was transformed in the universal form, with Prandtl number as parameter, for the case of the constant wall temperature. Using the universal results for air (Pr=0.72) the procedure for calculation of the Nusselt number (dimensionless heat transfer coefficient) on the particular contour (airfoil NACA 0010-34) was developed. The dimensionless temperature profiles within the boundary layer were presented also. The parameter of rotation ?0, as well as Eckert number, was varied, and their influences on the heat transfer from the surface to the working fluid were presented and analyzed. .
The influence of variation of electroconductivity on ionized gas flow in the boundary layer along a porous wall
Authors: Savic Slobodan , Obrovic Branko
Published: March 2008

This paper investigates ionized gas flow in the boundary layer when its electroconductivity is varied. The flow is planar and the contour is porous. At first, it is assumed that the ionized gas electroconductivity ? depends only on the longitudinal variable. Then we adopt that it is a function of the ratio of the longitudinal velocity and the velocity at the outer edge of the boundary layer. For both electroconductivity variation laws, by application of the general similarity method, the governing boundary layer equations are brought to a generalized form and numerically solved in a four-parametric three times localized approximation. Based on many tabular solutions, we have shown diagrams of the most important nondimensional values and characteristic boundary layer functions for both of the assumed laws. Finally, some conclusions about influence of certain physical values on ionized gas flow in the boundary layer have been drawn. .
A note on the damped vibrating systems
Authors: Bulatovic Ranislav
Published: March 2008

The presence of pure imaginary eigenvalues of the partially damped vibrating systems is treated. The number of such eigenvalues is determined using the rank of a matrix which is directly related to the system matrices.
On the effects of geometry on guided electromagnetic waves
Authors: Tucker Robin
Published: March 2008

The method of moving (Cartan) coframes is used to analyze the influence of geometry on the behavior of electromagnetic fields in confining guides and the effect of such fields on their ultra-relativistic sources. Such issues are of relevance to a number of topical problems in accelerator science where the need to control the motion of high current-density micro-meter size bunches of relativistic radiating charge remains a technical and theoretical challenge. By dimensionally reducing the exterior equations for the sources and fields on spacetime using symmetries exhibited by the confining guides one achieves a unifying view that offers natural perturbative approaches for dealing with smooth non-uniform and curved guides. The issue of the back-reaction of radiation fields on the sources is approached in terms of a simple charged relativistic fluid model. .
A multiscale description of growth and transport in biological tissues
Authors: Grillo A. , Zingali G.Y. , Borrello D.Y. , Federico S.Z. , Herzog W.Z. , Giaquinta G.
Published: March 2008

We study a growing biological tissue as an open biphasic mixture with mass exchange between phases. The solid phase is identified with the matrix of a porous medium, while the fluid phase is comprised of water, together with all the dissolved chemical substances coexisting in the pore space. We assume that chemical substances evolve according to transport mechanisms determined by kinematical and constitutive relations, and we propose to consider growth as a process able to influence transport by continuously varying the thermo-mechanic state of the tissue. By focusing on the case of anisotropic growth, we show that such an influence occurs through a continuous rearrangement of the tissue material symmetries. In order to illustrate this interaction, we restrict ourselves to diffusion-dominated transport, and we assume that the time-scales associated with growth and the transport process of interest are largely separated. This allows for performing an asymptotic analysis of the "field equations" of the system. In this framework, we provide a formal solution of the transport equation in terms of its associated Green's function, and we show how the macroscopic concentration of a given chemical substance is "modulated" by anisotropic growth. .
Bifurcation of the roots of the characteristic polynomial and the destabilization paradox in friction induced oscillations
Authors: Kirillov O.N.
Published: March 2008

Paradoxical effect of small dissipative and gyroscopic forces on the stability of a linear non-conservative system, which manifests itself through the unpredictable at first sight behavior of the critical non-conservative load, is studied. By means of the analysis of bifurcation of multiple roots of the characteristic polynomial of the non-conservative system, the analytical description of this phenomenon is obtained. As mechanical examples two systems possessing friction induced oscillations are considered: a mass sliding over a conveyor belt and a model of a disc brake describing the onset of squeal during the braking of a vehicle.