bluuebunny/crossref_metadata_2025 huggingface dataset:
Lineare Positionsregelung nichtlinearer mechanischer Systeme
Authors: Müller P. C.
Published: March 2011

Für die Regelung nichtlinearer Systeme stehen auf der Basis sehr genauer Systembeschreibungen aufwendige nichtlineare Regelungsverfahren zur Verfügung, die eine Positionsregelung nichtlinearer mechanischer Systeme erlauben. Im allgemeinen sind diese Regelungen jedoch nicht robust gegenüber Parameterungenauigkeiten und nicht modellierten Effekten, die Robustheit muß durch zusätzliche Maßnahmen erreicht werden. Demgegenüber wird in diesem Beitrag die Methode der Nichtlinearitäten‐Schätzung und ‐Kompensation vorgestellt, die effiziente, robuste, lineare Regler zur Positionsregelung zur Verfügung stellt. Das vorgeschlagene Verfahren behandelt nichtlineare, ungenau bekannte oder nicht‐modellierte Effekte nach der Methode der Störgrößenschätzung und ‐aufschaltung. Das Verfahren zeichnet sich durch seine Einfachheit sowohl beim Entwurf als auch bei der Reglerimplementierung aus.
Gleichmäßige (Rundungs‐)Fehlerschranken für Gleitkommaalgorithmen über Datenbereichen
Authors: Krämer W.
Published: March 2011

Häufig stellt sich die Frage, wie weit ein auf einem Computer berechnetes Ergebnis vom exakten Ergebnis (berechnet am Körper der reellen Zahlen) entfernt ist. Die hier vorgestellten Sätze erlauben es, für die Gleitkommaauswertung eines vorgegebenen Ausdrucks eine worst‐case Fehlerschranke automatisch mit einem Computer zu berechnen. Die Bestimmung dieser relativen bzw. absoluten Fehlerschranke geschieht a priori. Sie ist gültig, solange die Daten (Parameter, unabhängige Variablen) des Ausdrucks innerhalb der Bereiche (diese können je nach Problemstellung recht groß sein) variieren, die bei der Fehlerabschätzung spezifiziert wurden. Alle Rundungsfehler sowie deren Fortpflanzung und Fehler, die sich aus der Nichtdarstellbarkeit von z. B. transzendenten Konstanten ergeben, werden sicher im Sinne einer worst‐case Fehleranalyse erfaßt.
Contact Laws for Rough Surfaces
Authors: Willner K.
Published: March 2011

Contact laws for rough surfaces are used to obtain e.g. contact stiffness or contact conductivity. Usually contact laws are derived on the basis of asperity deformation models in conjunction with a stochastic roughness model. As the stochastic parameters depend strongly on the measurement procedure, the obtained contact laws have to be used carefully. Fractal surface parameters can be obtained, which are independent of sampling interval or length, but the resulting contact laws are still dependent on these values.
Parameter Estimation in a Hyperbolic Partial Differential Equation with a Focused Source as Initial Value
Authors: Kowar R.
Published: March 2011

We study the problem of recovering the continuously varying wave speed in the one‐dimensional wave equation with a focused source as initial data. In this paper this inverse problem is transformed into a parameter estimation, problem, which can be solved efficiently. The wave speed can be recalculated by solving an ordinary differential equation of second order where the parameter of the transformed inverse problem enters as a coefficient. We present a regularized finite difference scheme inversion for the stable recovery of the solution of the transformed parameter estimation problem, which combined with the solution of the ordinary differential equation, gives an estimation for the sound speed.
A Linear Viscoelastic Two‐Phase Model for Soft Tissues.: Application to Articular Cartilage
Authors: Ehlers W. , Markert B.
Published: March 2011

Hydrated soft tissues such as articular cartilage can be considered as porous materials consisting of an organic solid matrix saturated by a pore‐fluid. These types of biological tissues exhibit significant viscoelastic behaviour because of flow‐dependent fluid‐solid interaction and flow‐independent viscoelastic skeleton properties. To describe this complex behaviour, a linear viscoelastic two‐phase model based on the macroscopic Theory of Porous Media is presented. The required linear viscoelastic constitutive law is given in differential form deduced from rheological considerations. Numerical examples within the finite element method show the applicability of the presented model. Furthermore, they reveal the influence of the flow‐independent viscoelasticity of the solid skeleton on the general behaviour of hydrated soft tissues, for example on articular cartilage.
Selfexcitation of a MDF‐System with Coulomb friction, varying normal forces and impacts
Authors: Engleder T.
Published: March 2011

The investigation is focused on nonlinear oscillations of a beam structure with unilateral contact to a sliding surface. Analytical solutions for each state (stack, slip, free oscillation, impact) are used to reduce the non‐smoothness of the system to an algebraic task. The numerical results are compared with experimental data.
Non‐Unique Periodic Stick‐Slip Motions of a Forced 2‐DOF‐Frictional Oscillator
Authors: Hartung A. , Vielsack P.
Published: March 2011

Investigated was the influence of different friction models onto periodicity and uniqueness of stationary motions of a mechanical system.
Extreme Value Response of a Structure Subjected to a Stochastic Moving Load
Authors: Biernat S. , Sniady P.
Published: March 2011

The paper presents random dynamic problem being converted into static one using the probability distribution of the extreme maxima of the stochastic process. Such an approach gives the possibility of time invariant analysis for time variant problem. The theory presented is a basis for numerical solution in the example presented.
Simulation nichtlinearer hydraulischer Steuersysteme
Authors: Borchsenius F. , Pfeiffer F.
Published: March 2011

Es wird eine neuartige Methode zur Simulation hydraulischer Steuersysteme vorgestellt. Bei herkömmlichen Methoden zur Simulation von hydraulischen Steuersystemen werden die Komponenten durch elastische Verbindungselemente miteinander gekoppelt. Damit erhalten die Bewegungsgleichungen eine einfache Struktur ‐ sie sind jedoch für kleine Baugrößen der Komponenten steif. Besser geeignet ist ein Modell mit starren Koppelelementen wobei die hydraulischen Komponenten durch Zwangsbedingungen gekoppelt sind. Elemente mit einseitiger Kraftübertragung, z.B. Rückschlagventile, werden durch Komplementaritätsbedingungen erfasst. Das Verfahren wird an einem einfachen Beispiel angewendet.
A Time Adaptiv Finite‐Element Procedure Applied to Creep and Relaxation Processes
Authors: Hartmann S.
Published: March 2011

In this paper we interpret the finite‐element method applied to constitutive models with internal variables as the solution of differential algebraic equations (DAE). With this interpretation we can utilize Diagonal Implicit Runge‐Kutta methods (DIRK) as well as a corresponding step‐size control and a special solution technique for block‐structured systems of equations. This proceeding doesn't affect already developed FE‐implementations which are based on the Backward Euler method. Furthermore, the meaning of the consistent tangent operator becomes more obvious. The paper ends with some examples in creep and relaxation tests, where step size control should always be used conditioned by the different time scales.
Numerical Integration of Viscoplastic Problems
Authors: Scherf O.
Published: March 2011

Viscoplastic deformation is characterized by a combined system of balance equations for the displacements and evolution equations for the internal variables. The paper presents a very efficient algorithm to solve the nonlinear system that arises from the application of the Finite Element Method in combination with an implicit time‐discretization.
Self‐excited vibration of a rotor supported on journal bearings with flexibly mounted bushes
Authors: Starczewski Z.
Published: March 2011

The paper is concerned with dynamics of a rigid rotor supported on journal bearings having flexibly mounted bushes. In the analysis equations of motion of the journal as well as the bush center have been derived. The system has been examined with respect to self‐excited vibration resulting from interactions between the journal and bush through the oil film layer. Effect of structural parameters of the system (bearing gap, stiffness of the elastic mounting, masses of the elements) on critical rotation speed at which self‐excitation appears has been discussed. Appropriate diagrams and concluding remarks have been included.
Zur Simulation von Toroidreibradgetrieben
Authors: Bork H. , Pfeiffer F.
Published: March 2011

Reibradgetriebe sind eine alternative zu stufenlosen Umschlingungsgetrieben und bieten sich vor allem für den Einsatz in hinterradgetriebenen PKW der höheren Leistungsklasse an. Durch die physikalische Modellierung der Komponenten eines Reibradgetriebes soll dessen dynamisches Verhalten nachgebildet werden. In diesem Beitrag wird das mechanische Ersatzmodell, die Kontaktpunktbestimmung und die Kraftübertragung im Kontakt vorgestellt.
Finite element modeling of orthotropic material behaviour in pneumatic membranes
Authors: Raible T. , Reese S. , Wriggers P.
Published: March 2011

A new material formulation to describe nonlinear hyperelastic orthotropic behaviour of composite membranes at finite strains is presented in this article. To provide numerically efficient calculations, a reduced integration scheme avoiding locking and hourglass instabilities is used. Restrictions concerning material parameters are discussed, and material parameters are adapted to experimental data. Numerical calculations are used to demonstrate the potential of the approach to inflated rubber matrix membranes applications.
Comments on objective rates of 2nd order, symmetric Eulerian tensors
Authors: Meyers A. T. M. , Chiesse P. S. , Xiao H. , Bruhns O. T.
Published: March 2011

It is shown that objective rates of objective and symmetric second order Eulerian tensors should be corotational when one restricts to a single Euclidean vector space. As a consequence, when we equalize the objective strain rate and the deformation rate, only the Hencky strain is a mathematically consistent strain measure; and only the logarithmic rate is an admissible strain rate.
Shakedown Analysis at Finite Elastoplastic Strains and Deformations
Authors: Schjeck B.
Published: March 2011

A finite element method for shakedown analysis of structures that undergo finite elastic ‐ plastic strains and rotations is proposed The idea is the simultaneous computation of all relevant load cases coupled by a common plastic strain field.
On the Calculation of Plastic Spin in a Model of Crystal Plasticity Based on Symmetric Tensors
Authors: Schmidt M. O. , Hackl K.
Published: March 2011

In a model of anisotropic plasticity based on symmetric tensors the plastic spin is not determined by the principle of maximum plastic dissipation. The spin can be derived by introducing additional kinematic relations and applying a generalized inverse based on a minimum principle. A procedure specialized for the case of crystal plasticity is shown.
Shortest Curves for Vehicles on Surfaces of Celestial Bodies
Authors: Bittner L.
Published: March 2011

The classical problem, to find the shortest line connecting two given points of a given surface, does not take account of 1) obstacles, i. e. forbidden regions (islands, icebergs, foreign territories a. s. o.) through which the curve must not run, 2) alterations of the shape of the surface in the course of time (tides, tectonic displacements a. s. o.), 3) the fact that the length of the curve, described by a vehicle moving on the surface, has eventually to be measured with respect to a primary inertial coordinate system emitting the control signals. The surface system may change its position relating to the primary system.
Optimal design of steel barrelled shells
Authors: Blachut J.
Published: March 2011

The Simulated Annealing, SA, technique is applied to maximize the magnitude of external hydrostatic pressure for bowed out shells for which, the shape of the meridian is sought. A global maximum offers a 40% increase in load carrying capacity over the mass equivalent cylindrical shell of the same mass whilst the SA heuristic proves to be computationally affordable.
Effiziente semi‐analytische Gradientenberechnung in der Strukturoptimierung
Authors: Hörnlein H. R. E. M.
Published: March 2011

Bei der Lösung von Strukturoptimierungsaufgaben werden fast immer Gradientenverfahren der Mathematischen Optimierung eingesetzt. Die Bereitstellung der ersten Ableitungen beansprucht den größten Teil der Gesamtrechenzeit. Der Erfolg der Optimierung hängt aber auch von der numerischen Genauigkeit der Ableitungen ab. Hier wird auf einen entscheidenden Nachteil der favorisierten semi‐analytischen Sensitivitätsanalyse aufmerksam gemacht, gleich‐zeitig wird aber gezeigt wie dieser Nachteil zu beheben ist.
Sufficient condition of basis stability of an interval linear programming problem
Authors: Koníckocá Jana
Published: March 2011

The contribution deals with basis stability of an interval linear programming (ILP) problem. We consider the coefficients of the matrix, right‐hand side values and cost vector values to vary independently in the given intervals. We present the new necessary and sufficient condition, and the sufficient condition of basis stability of ILP problem.
Optimization of Composite Laminates under Uniaxial Tension with Respect to the Free‐Edge Effect
Authors: Lindemann J. , Becker W.
Published: March 2011

High interlaminar stresses in the vicinity of free edges of composite laminates can result in laminate failure by free‐edge delamination. In the current work it is shown in which way the interlaminar normal stress component is reduced by means of structural optimization resulting in laminate configurations with a minor risk of delamination.
Optimal layouts of structural components considering fatigue strength
Authors: Rottler A. , Eschenauer H. A.
Published: March 2011

Designing complete systems or system components, it is of vital importance for the manufacturers nowadays to optimally fulfil the ever increasing demands pertaining to safety, durability, reduction of energy consumption, noise reduction, improvement of comfort, accuracy, etc. This, for instance, applies to all types of traffic and transportation systems like rail vehicles, automobiles, airplanes, and ships.
A nonoverlapping DDM for the nonstationary Navier‐Stokes problem
Authors: Müller Lars , Lube Gert
Published: March 2011

We consider the nonstationary incompressible Navier‐Stokes problem in a bounded domain. A semidiscretization in time followed by a linearization procedure lead to Oseen type problems. For an efficient solution we take advantage of a nonoverlapping domain decomposition method (DDM) with interface conditions of Robin type. Strong convergence of the DDM‐iterations to the Oseen solution can be proven. Furthermore we apply an a‐posteriori estimate which controls the error on the subdomains in terms of the jumps of the velocity across the interface. This may serve as a stopping criterion and gives some information how to choose a free parameter appearing in the interface condition. A stabilized FEM is used to derive a discrete version of the DDM and requires a modification of the method.
Implementing Global Masters into Parallel Condensation
Authors: Pelzer Andreas , Hofferek Birgit , Voss Heinrich
Published: March 2011

The dynamic analysis of structures leads to very large generalized eigenvalue problems. Their number of unknowns can be reduced to a manageable size by condensation methods which can be parallelized by combining it with substructuring. In this note we implement global masters into the parallel condensation process.
Splitting techniques for the Navier‐Stokes equations
Authors: Haschke H. , Heinrichs W.
Published: March 2011

A pseudo spectral approximation for the Navier‐Stokes equations is presented. After considering the unsteady Stokes equations we use the Uzawa algorithm to decouple the spectral system into Helmholtz equations for the velocity components and an equation with the Pseudo‐Laplacian for the pressure. In order to avoid spurious modes the pressure is approximated with polynomials of one degree lower than the velocity on staggered grids. For the time discretization a high order backward differentiation scheme for the intermediate velocity is combined with a high order extrapolant for the pressure.
Experimental and Numerical Investigation of the Oblique Shock Wave/Turbulent Boundary Layer Interaction at M=5
Authors: Fedorova N. N. , Fedorchenko I. A. , Schülein E.
Published: March 2011

The results of the joint experimental investigations and numerical simulations of hypersonic separated flows are presented. The computed and experimental results are compared with respect to surface pressure, skin friction and Stanton numbers distributions as well as the integral boundary layer parameters and the mean gas‐dynamic profiles.
Large Eddy Simulation of a Counterflow Configuration
Authors: Kempf A. , Forkel H. , Chen J.‐Y. , Sadiki A. , Janicka J.
Published: March 2011

The aim of the present work is to extend the possibilities of predicting turbulent activity and mixing in counterflow burners. Such burners are well suited for the calibration and validation of combustion models. Because of their geometry, they allow simulations to be performed in only one dimension of space. This safes much computation time, rendering for example the simulation of detailed chemistry possible. Here, a three dimensional LES is applied without considering chemical reactions. Sub‐grid fluctuations are modeled according to Smagorinsky. The model constant is determined dynamically by the well known Germano approach.
Simulation of Condensation Processes in Turbines including Impurity Effects
Authors: Winkler G. , Heiler M. , Schnerr G. H.
Published: March 2011

Condensation processes are important for many technical applications such as in transsonic low pressure steam turbines. Impurities like dust particles or chemical deposits significantly affect the condensation process. Depending on the expansion rate the condensate formation is controlled by homogeneous or heterogeneous nucleation. Technical steam for example, used in power processes, typically consists of several impurities, which change due to lower expansion rates the condensation behaviour, so that a large fraction of the condensate mass is formed heterogeneously. Numerical parameter variations in the nozzle BA‐1 were performed to study as how to the number of particles influences the condensation onset and the total amount of formed condensate mass. In comparison to the homogeneous case, a smaller supersaturation is reached if heterogeneous condensation dominates. The condensation occurs close to the equilibrium state and reduces losses caused by the pure non‐equilibrium process.
Gas/Liquid Two‐Phase Flow under Low Gravity Conditions
Authors: Wölk G. , Dreyer M. , Rath H. J.
Published: March 2011

A novel flow pattern map is developed based on five dimensionless parameters. The transition region from dispersed bubble to slug flow, from slug to frothy slug/annular flow and from frothy slug/annular to annular flow is presented and good agreement between theory and experimental data from the literature is obtained.
Modeling Rule-Based Item Generation
Authors: Geerlings Hanneke , Glas Cees A. W. , van der Linden Wim J.
Published: March 2011

An application of a hierarchical IRT model for items in families generated through the application of different combinations of design rules is discussed. Within the families, the items are assumed to differ only in surface features. The parameters of the model are estimated in a Bayesian framework, using a data-augmented Gibbs sampler. An obvious application of the model is computerized algorithmic item generation. Such algorithms have the potential to increase the cost-effectiveness of item generation as well as the flexibility of item administration. The model is applied to data from a non-verbal intelligence test created using design rules. In addition, results from a simulation study conducted to evaluate parameter recovery are presented.
Structural and functional changes linked to, and factors promoting, cytoplasmic maturation in mammalian oocytes
Authors: Yamada Masayasu , Isaji Yuuki
Published: March 2011

In most mammals, oocyte maturation is the final process of oogenesis, from the prophase of the first meiosis (germinal vesicle stage) to the metaphase of the second meiosis (MII), during which the oocyte acquires fertilizable competence as well as post‐fertilization development competence. The nuclear and cytoplasmic maturation processes occur in synchrony but independently. Cytoplasmic maturation entails biochemical and structural changes in the cytoplasm, which give rise to oocytes capable of being fertilized and developing into embryos. Herein we review the literature and results from our own experiments on the structural and molecular events regulating cytoplasmic maturation in oocytes, concentrating on (1) the appropriate reorganization of active mitochondria and the endoplasmic reticulum, a structural and functional feature of cytoplasmic maturation, and (2) factors involved in regulatory mechanisms such as cumulus cell–oocyte gap junctional signaling, cumulus cell–oocyte bidirectional paracrine signaling, and the complex interactions of these signaling processes and follicular fluid constituents in the follicle environment.
Displaced tick-parasite interactions at the host interface
Authors: Nuttall P. A.
Published: March 2011

Reciprocal interactions of parasites transmitted by blood-sucking arthropod vectors have been studied primarily at the parasite–host and parasite–vector interface. The third component of this parasite triangle, the vector–host interface, has been largely ignored. Now there is growing realization that reciprocal interactions between arthropod vectors and their vertebrate hosts play a pivotal role in the survival of arthropod-borne viruses, bacteria, and protozoa. The vector–host interface is the site where the haematophagous arthropod feeds. To obtain a blood meal, the vector must overcome the host's inflammatory, haemostatic, and immune responses. This problem is greatest for ixodid ticks which may imbibe as much as 15 ml blood whilst continuously attached to their host for 10 days or more. To feed successfully, the interface between tick and host becomes a battle between the host's mechanisms for combating the tick and the tick's armoury of bioactive proteins and other chemicals which it secretes, via saliva, into the feeding lesion formed in the host's skin. Parasites entering this battlefield encounter a privileged site in their vertebrate host that has been profoundly modified by the pharmacological activities of their vector's saliva. For example, ticks suppress natural killer cells and interferons, both of which have potent antiviral activities. Not surprisingly, vector-borne parasites exploit the immunomodulated feeding site to promote their transmission and infection. Certain tick-borne viruses are so successful at this that they are transmitted from one infected tick, through the vertebrate host to a co-feeding uninfected tick, without a detectable viraemia (virus circulating in the host's blood), and with no untoward effect on the host. When such viruses do have an adverse effect on the host, they may impede their vectors' feeding. Thus important interactions between ticks and tick-borne parasites are displaced to the interface with their vertebrate host - the skin site of blood-feeding and infection.
Niche restriction in parasites: proximate and ultimate causes
Authors: Rohde K.
Published: March 2011

Hutchinson's (1957) definition of an ecological niche as a multidimensional hypervolume determined by a number of physical and biotic variables is adopted. The number of niche dimensions is very great, but as a working hypothesis it is assumed that a few are sufficient to characterize the niche of a parasite species to a high degree of accuracy. They are host species, microhabitat(s), macrohabitat(s), geographical range, sex and age of host, season, food and hyperparasites. Methods to measure niche width, in particular specificity indices, are discussed, and some examples of niche restriction are described. Proximate and ultimate causes of niche restriction are discussed, mainly using marine parasites as examples. Among proximate causes of one niche dimension, host specificity, are ecological factors restricting exposure to infection to certain host species; host-specific chemical factors that induce hatching, direct infective stages to a host and bring about settlement of a parasite; factors that lead to mortality in or on the wrong host; morphological adaptations that guarantee survival in or on the ‘correct’ host; and availability of suitable hosts. Many factors are likely to be responsible for microhabitat specificity, but have been little studied, except for some physiological and morphological adaptations to particular microhabitats. Macrohabitats and geographical range may be determined by the distribution of intermediate hosts and certain food items, and by a variety of chemical and physical factors. Hosts of different sexes may differ in feeding habits and the composition of the skin, and thus acquire parasites differentially. Hosts of different age may be differentially infected due to accumulation of parasites with age, loss of parasites due to developing resistance (or immunity), and different size and feeding habits. Among ultimate causes of niche restriction and segregation are avoidance of competition, predation and hyperparasites; facilitation of mating; reinforcement of reproductive barriers; and adaptations to environmental complexity. Few studies permit a decision on which factor or factors are responsible in particular cases. Interspecific competition may play a greater role in helminth communities of some host groups than of others, but it seems that, overall, its role has been exaggerated at least for marine parasites. Some ‘classical’ examples of microhabitat segregation explained by interspecific competition can also be explained by reinforcement of reproductive barriers. There is evidence for the importance of facilitation of mating in microhabitat restriction, and the availability of many vacant niches indicates that competition, overall, is not of great importance.
Behavioural defense against parasites: interaction with parasite invasiveness
Authors: Hart B. L.
Published: March 2011

Behavioural patterns involved in avoiding, repelling, or removing parasites allow mammalian hosts to defend themselves from an array of parasites that threaten the host's fitness in the natural world. Some examples of behavioural defenses and the presumed target parasites are: grooming to remove ticks, grouping to reduce attack rate of biting flies, fly repelling movements to reduce parasitic flies, and selective grazing to reduce intake of faecal-borne parasites. These behavioural defenses are discussed with regard to effectiveness in controlling the target parasites. Parasites have sometimes evolved behavioural strategies of evading, penetrating or disabling these behavioural defenses. These parasite behavioural strategies, though less studied, are discussed. Also discussed is the possibility that host behavioural patterns that may defend against one parasite may be exploited by a different type of parasite to facilitate its own transmission. The interplay between host defensive strategies, the cost versus the effectiveness of such strategies, and a parasite's evasion or exploitation of such strategies, may be useful in understanding some aspects of host-parasite dynamics in nature.
Twisted Dickson–Mui invariants and the Steinberg module multiplicity
Authors: WAN JINKUI , WANG WEIQIANG
Published: March 2011

We determine the invariants, with arbitrary determinant twists, of the parabolic subgroups of the finite general linear group GLn(q) acting on the tensor product of the symmetric algebra S•(V) and the exterior algebra ∧•(V) of the natural GLn(q)-module V. In addition, we obtain the graded multiplicity of the Steinberg module of GLn(q) in S•(V) ⊗ ∧•(V), twisted by an arbitrary determinant power.
REDISCOVERY OF CROTON JOSEPHINUS (EUPHORBIACEAE) IN MINAS GERAIS, BRAZIL
Authors: Medeiros D. , Alves R. J. V. , De Senna-Valle L.
Published: March 2011

Croton josephinus Müll.Arg., a member of Croton sect. Medea (Klotzsch) Baill. (Euphorbiaceae), has not been recollected since 1824, nor mentioned in the literature since its original publication in 1873. This species has recently been rediscovered in a campo rupestre area at the ‘Pico 1430 m’ of the Serra de São José, Minas Gerais, after 20 years of field work in the area. In the protologue Croton josephinus was cited as having been collected from São Paulo State. This is likely to have been a simple misattribution of the area where it occurs. Based on the new material collected, a detailed description and an illustration of the species are provided. A lectotype and an isolectotype are designated.
Needs-oriented discharge planning for high utilisers of psychiatric services: multicentre randomised controlled trial
Authors: Puschner B. , Steffen S. , Völker K. A. , Spitzer C. , Gaebel W. , Janssen B. , Klein H. E. , Spiessl H. , Steinert T. , Grempler J. , Muche R. , Becker T.
Published: March 2011

Aims.

Attempts to reduce high utilisation of mental health inpatient care by targeting the critical time of hospital discharge are rare. In this study, we test the effect of a needs-oriented discharge planning intervention on number and duration of psychiatric inpatient treatment episodes (primary), as well as on outpatient service use, needs, psychopathology, depression and quality of life (secondary).

Methods.

Four hundred and ninety-one adults with a defined high utilisation of mental health care gave informed consent to participate in a multicentre RCT carried out at five psychiatric hospitals in Germany (Düsseldorf, Greifswald, Regensburg, Ravensburg and Günzburg). Subjects allocated to the intervention group were offered a manualised needs-led discharge planning and monitoring intervention with two intertwined sessions administered at hospital discharge and 3 months thereafter. Outcomes were assessed at four measurement points during a period of 18 months following discharge.

Results.

Intention-to-treat analyses showed no effect of the intervention on primary or secondary outcomes.

Conclusions.

Process evaluation pending, the intervention cannot be recommended for implementation in routine care. Other approaches, e.g. team-based community care, might be more beneficial for people with persistent and severe mental illness.
Magnetic anisotropy in (Ga,Mn)As grown on vicinal GaAs: Effects of the orientation of microwave magnetic field
Authors: Dziatkowski K. , Liu X. , Furdyna J. K. , Twardowski A.
Published: March 2011

Ferromagnetic resonance (FMR) study of the magnetic anisotropy in epitaxial (Ga,Mn)As grown on vicinal GaAs is presented. The data collected in the growth plane reveal very limited dependence on the miscut angle η, with a negligible effect of η on the in-plane uniaxial anisotropy. In the out-of-plane configuration, the substrate misorientation has a pronounced influence on FMR, which features are partially explained with a phenomenological treatment of the atomic step-induced anisotropy. This simple model, however, does not account for the miscut-induced dependence of FMR on the orientation of microwave magnetic field, that is observed with the static field applied invariably along the growth direction.
Tunable microwave multiband filters based on a waveguide with antiferromagnetic and dielectric sandwiches
Authors: Zhang J. S. , Zhang R. L. , Hu Qing , Fan R. H. , Peng R. W.
Published: March 2011

We theoretically study the propagation of hybrid electromagnetic-spin waves in a multiple-band-stop microwave waveguide, which is constructed as an antiferromagnetic (AFM1)/dielectric/antiferromagnetic (AFM2) sandwiched structure. Band stops, which are characterized by multiple attenuation peaks, have been found in the system. The frequencies of multiple band stops and the intensities of attenuation peaks can be manipulated by external magnetic field. However, by tuning the thickness of the dielectric layer or the thickness of AFM layers, the frequencies of the band stop are almost invariable, while the intensities of the attenuation peaks change significantly. This feature originates from the coupling between the microwave and spin wave associated with the collective excitations of spin motions. Our investigation may potentially be applied to the design of high-frequency microwave band-stop filters.
First-principles investigations of Zn (Cd) doping effects on the electronic structure and magnetic properties of CoFe2O4
Authors: Hou Y. H. , Zhao Y. J. , Liu Z. W. , Yu H. Y. , Zhong X. C. , Qiu W. Q. , Zeng D. C. , Wen L. S.
Published: March 2011

The electronic structures and magnetic properties of spinel Co1-x Zn (Cd)xFe2O4 (x = 0.0, 0.25, 0.5, 0.75, and 1.0) have been studied systematically by the first-principles calculation. The optimized structures show that with increasing Zn (Cd) content the crystal lattice parameter increases by 1.47% (5.13%) when the Co ions are completely replaced by Zn (Cd) ions. The results also indicate that the magnetic moment of Co/Fe ion increases and the total spin magnetic moment linearly increases with the Zn (Cd) doping from 3.00 μB for x = 0.0 up to 10.00 μB for x = 1.0 per formula unit. The electronic distribution in the Co spin-down subband is highly localized for the crystal field splitting between t2g and eg levels in the Zn (Cd) doped CoFe2O4 compounds and the energy band moves downwards while doped with Zn (Cd). Meanwhile, the bandgap decreases with the increase of Zn (Cd) except where x = 1 and the spinel structure is half-metal at some degree of doping.
Magnetostriction, elasticity, and D03 phase stability in Fe–Ga and Fe–Ga–Ge alloys
Authors: Petculescu G. , Ledet K. L. , Huang M. , Lograsso T. A. , Zhang Y. N. , Wu R. Q. , Wun-Fogle M. , Restorff J. B. , Clark A. E. , Hathaway K. B.
Published: March 2011

The contrast between the saturation tetragonal magnetostriction, λγ,2 = (3/2)λ100, of Fe1−xGax and Fe1−yGey, at compositions where both alloys exhibit D03 cubic symmetry (second peak region), was investigated. This region corresponds to x = 28 at. % Ga and y = 18 at. % Ge or, in terms of e/a = 2 x + 3 y + 1, to an e/a value of ∼1.55 for each of the alloys. Single crystal, slow-cooled, ternary Fe1−x−y GaxGey alloys with e/a ∼1.55 and gradually increasing y/x were investigated experimentally (magnetostriction, elasticity, powder XRD) and theoretically (density functional calculations). It was found that a small amount of Ge (y = 1.3) replacing Ga in the Fe–Ga alloy has a profound effect on the measured λγ,2. As y increases, the drop in λγ,2 is considerable, reaching negative values at y/x = 0.47. The two shear elastic constants c′ = (c11− c12)/2 and c44 measured for four compositions with 0.06 ≤ y/x ≤ 0.45 at 7 K range from 16 to 21 GPa and from 133 to 138 GPa, respectively. Large temperature dependence was observed for c′ but not for c44, a trend seen in other high-solute Fe alloys. The XRD analysis shows that the metastable D03 structure, observed previously in slow-cooled Fe–Ga at e/a = 1.55, is replaced with two phases, fcc L12 and hexagonal D019, at just 1.6 at. % Ge. The two are the stable phases of the assessed Fe–Ga phase diagram at x ∼ 28. Notably, at y = 7.8, only the D03 phase (the equilibrium phase of Fe–Ge at e/a = 1.54) was found in the ternary alloy. The theory also shows that the D03 instability is removed for compositions with y ≥ 3.9, when D03 becomes the structure’s ground-state phase. Thus, the high, positive λγ,2 value for Fe–Ga at x = 28 could be the result of the high sensitivity of its metastable D03 structure.
Universal Barkhausen critical scaling behavior observed in NixFe1−x (x = 0−0.5) films
Authors: Lee Hun-Sung , Ryu Kwang-Su , Kang Im-Seok , Shin Sung-Chul
Published: March 2011

We have investigated the Barkhausen critical scaling behavior of NixFe1−x (x = 0−0.5) films using a magneto-optical microscope, capable of time-resolved domain observation. Real-time direct observations of the domain evolutions in these films revealed that magnetization reversal occurred with a sequence of random Barkhausen jumps. From more than 1000 repeated experiments with each sample, it was found that the distribution of the Barkhausen jump size followed a power-law distribution. The scaling exponent of the power-law distribution was found to have the same value of 1.1, independent of the film composition, revealing a universal critical scaling behavior in these alloy films.
Magnetic frustration in α-NaMnO2 and CuMnO2
Authors: Jia Ting , Zhang Guoren , Zhang Xiaoli , Guo Ying , Zeng Zhi , Lin H. Q.
Published: March 2011

The magnetic and electronic properties of α-NaMnO2 and delafossite CuMnO2 are investigated using a full-potential linearized augmented plane wave method. For the monoclinic structure at room temperature, CuMnO2 behaves like a frustrated spin-lattice. For the triclinic structure at low temperature, the obtained magnetic configurations of the lowest energy for both α-NaMnO2 and CuMnO2 are consistent with experiments. However, the exchange constants are all positive. This reveals that the magnetic frustration is only partially relieved at low temperature. It is also found that the Mn3+ ions are in a high-spin state. Taking into account the on-site Coulomb correlations, our results show that α-NaMnO2 and CuMnO2 are charge-transfer insulators.
The study of interaction between graphene and metals by Raman spectroscopy
Authors: Wang W. X. , Liang S. H. , Yu T. , Li D. H. , Li Y. B. , Han X. F.
Published: March 2011

Different metal films (Co, Ni, Au, and Ag) were deposited on graphene and the interactions between these metals and graphene were studied by Raman spectroscopy. The Raman peaks were shifted after the deposition of metal films. The electron doping of graphene with cobalt contacts and the hole doping with the nickel contacts are the main reasons for Raman peak shift. However, for gold contacts and silver contacts with graphene, strain effect dominates Raman peak shift instead of charge transfer.
Incorporation of iron on the clean and gallium-bilayer GaN(0001) surface
Authors: González-Hernández Rafael , López P. William , Moreno-Armenta María G. , Arbey Rodríguez Jairo
Published: March 2011

First-principles calculations of the energetic and magnetic properties of Fe incorporation in various sites on clean and Ga-bilayer GaN(0001) surfaces are presented. Employing a thermodynamic approach, the calculated formation energies demonstrate characteristic features in the structural stability and magnetism of Fe incorporated surfaces depending on the growth condition. It is found that the N-rich conditions produce greater magnetization compared to the Ga-rich condition. N-rich magnetization is attributed to the interface formation of FeN layers on the GaN(0001) surface. In addition, calculations for Fe incorporation in Ga-bilayer terminated surface suggest that it is possible to form a FeGax ferromagnetic alloy by performing the growth under extreme Ga-rich conditions.
L1-ordered FePtAg–C granular thin film for thermally assisted magnetic recording media (invited)
Authors: Zhang L. , Takahashi Y. K. , Hono K. , Stipe B. C. , Juang J.-Y. , Grobis M.
Published: March 2011

We studied highly L10-ordered FePtAg–C nanogranular film as a potential high-density storage medium in thermally assisted magnetic recording (TAR). A 6.4-nm-thick FePtAg–C film with a perpendicular coercivity of 37 kOe and an average grain size of 6.1±1.8 nm was fabricated on oxidized silicon substrate with a 10 nm MgO interlayer at 450 °C. The time-dependence measurement of remnant coercivity showed the energy barrier of Eb = 7.6 eV ∼300 kBT at room temperature, meaning the excellent thermal stability for long-term data storage. Static tester experiments on this film using a TAR head demonstrate the feasibility of recording at an areal density of ∼450 Gbits/in.2.
Domain wall velocity in submicron amorphous wires
Authors: Óvári Tibor-Adrian , Corodeanu Sorin , Chiriac Horia
Published: March 2011

Results on the study of the domain wall propagation in rapidly quenched submicron amorphous wires with positive and nearly zero magnetostriction are reported. Samples with metallic nucleus diameters between 350 and 950 nm have been analyzed. A correlation between the magnitude of the uniaxial anisotropy and the domain wall velocity has been found. The largest wall velocity value was 1600 m/s, close to the largest values reported in typical microwires with the same composition. Wall mobility increases as the metallic nucleus diameter decreases due to the crucial role played by shape anisotropy in such ultrathin wires. Magnetoelastic anisotropy still has an important contribution in positive magnetostrictive samples. The maximum velocity values are obtained in nearly zero magnetostrictive wires at much smaller fields compared to positive magnetostrictive ones.
Coupled periodic magnetic nanostructures (invited)
Authors: Adeyeye A. O. , Jain S.
Published: March 2011

The static and dynamic properties of coupled one-dimensional (1D) and two-dimensional (2D) periodic Ni80Fe20 structures fabricated using deep ultraviolet lithography were systematically studied using broadband ferromagnetic resonance spectroscopy, magneto-optical Kerr effects measurements, and magnetic force microscopy. We have probed the influence of dipolar coupling on the spin configurations and magnetization reversal mechanisms in three different types of magnonic crystals, namely, a 1D chain of coupled ellipsoids arranged in two basic configurations (elements coupled along the major or minor axis) and a 2D noncollinear array of rectangular elements. We observed that the “collective” modes present in the spin wave spectrums for the array are significantly dependent on the geometrical parameters of the magnetic elements, as well as on their arrangement. For instance, the eigenmodes corresponding to the linear chain of ellipsoidal elements are considerably shifted when compared to a continuous film due to the varying demagnetizing field. However, for 2D periodic magnetic structures in which the elements are arranged in a “C” cell configuration with each unit cell comprising of three rectangular elements, we observed the presence of two distinct eigenmodes that vary with the magnitude and orientation of the applied field.
Stability of magnetization oscillations driven by spin-polarized currents
Authors: Bonin R. , d’Aquino M. , Bertotti G. , Serpico C. , Mayergoyz I. D.
Published: March 2011

The stability of spin-transfer-driven magnetization precession with respect to spatial nonuniform perturbations is discussed. Quantitative predictions are made for the critical currents and fields at which the precession becomes unstable as well as for the spatially nonuniform magnetization patterns that appear at instability. These predictions are compared with the results of computer simulations of the complete spin-transfer-driven magnetization dynamics.
Ground state of the magnetic molecule {V6} determined by broadband electron spin resonance at low frequency
Authors: Corti M. , Cattaneo L. , Mozzati M. C. , Borsa F. , Jang Z. H. , Fang X.
Published: March 2011

We utilize a nonconventional (i.e., without resonance cavity) broadband electron spin resonance (ESR) spectrometer operating continuously in the frequency range 0.3–9 GHz to investigate the ground state of the magnetic molecule {V6} at low temperature. There exist two different varieties of {V6} molecules with small differences in the organic part and in the crystal packing. We find differences in the width and hyperfine structure of the ESR line in the two compounds. However, the central frequency of the broad ESR line measured vs H down to 0.3 GHz shows a linear behavior in both compounds indicating a g value close to 2 and a zero field gap no larger than 30 × 10−3 K. The result is in contrast with a level scheme for the ground state previously reported for one of the two varieties of {V6}. We propose an alternative scenario for the structure of the magnetic ground state.
A study of the specific contact resistance and channel resistivity of amorphous IZO thin film transistors with IZO source–drain metallization
Authors: Lee Sunghwan , Park Hongsik , Paine David C.
Published: March 2011

We report on the specific contact resistance of interfaces between thin amorphous semiconducting IZO channel layers and IZO source/drain metallization in amorphous oxide thin film transistors (TFTs). As-deposited, low carrier density amorphous IZO layers are difficult to produce and consequently very thin (10–30 nm) channel layers are required for IZO TFT device applications in order to achieve adequately low off-state current. In this article, the transmission line model (TLM) and structures that also serve as IZO gate-down TFTs were used to examine IZO/IZO homojunctions with thin (10 nm) and thick (100 nm) channel layers. Thin, 10 nm, IZO channel devices with IZO source/drain contacts show a threshold voltage of −3.9 V and a very high specific contact resistance (ρC) that varies with gate voltage (VG) in the range 0–10 V from 460 to 130 Ω cm2. Annealing in air at 200  °C resulted in a tenfold improvement in ρC (34 Ω cm2) and corresponds to an increase in carrier density in the channel. Thicker IZO films (100 nm) were too conducting to function as TFTs, but, at zero bias, effective specific contact resistance measured using TLM was 17 Ω cm2 in the as-deposited state and 0.13 Ω cm2 in the annealed state. Corresponding channel resistivity obtained from TLM at VG = 0 V decreased after annealing from 8.2 Ω cm (as-deposited) to 0.3 Ω cm (annealed). The effect of both annealing and positive gate bias is shown to be an increase in carrier density and a corresponding decrease in specific contact resistance.
Biparametric equilibria bifurcations of the Pierce diode: A one-dimensional plasma-filled device
Authors: Terra Maisa O.
Published: March 2011

The equilibria bifurcations of the biparametric version of the classical Pierce diode, a one-dimensional plasma-filled device, are analyzed in detail. Our investigation reveals that this spatiotemporal model is not structurally stable in relation to a second control parameter, the ratio of the plasma ion density to the injected electron beam density. For the first time, we relate the existence of one-fluid chaotic regions with specific biparametric equilibria bifurcations, identifying the restricted regions in the parametric plane where they occur. We show that the system presents several biparametric scenarios involving codimension-two transcritical bifurcations. Finally, we provide the spatial profile of the stable and unstable one-fluid equilibria in order to describe their metamorphoses.
Magnetoresistance in single crystalline chromium sulfides
Authors: Lee K. D. , Won C. J. , Song K. M. , Hur N.
Published: March 2011

We studied the anisotropic magnetic and magnetotransport properties of Cr2S3 single crystals grown by using the vapor transport method. Large magnetoresistance of ∼ 46% was observed in 9 T magnetic field applied perpendicular to the c axis near the Néel temperature TN ≈ 118 K. Comparison of electric and magnetic properties of Cr2S3 crystals with different sulfur deficiencies suggested that the electron doping by the sulfur deficiency does not contribute to weak ferromagnetism. The correlation between the field-dependent magnetization and resistivity was analyzed by the polaron hopping model of magnetotransport in Cr2S3.