bluuebunny/crossref_metadata_2025 huggingface dataset:
Overview of Extracellular Matrix
Authors: Mecham Robert P.
Published: December 2012

The extracellular matrix provides an environment for cells. It is produced, assembled, and modified by cells and in turn, it modifies the functions and behavior of the cells it encounters. The molecules that make up the matrix are diverse in both structure and function. This well‐illustrated unit provides an introduction to the structure and function of the major components of the extracellular matrix and serves as a background for the other units in the chapter, which include protocols for isolation and analysis of individual components. Curr. Protoc. Cell Biol. 57:10.1.1‐10.1.16. © 2012 by John Wiley & Sons, Inc.
Highly Conductive Porous Graphene/Ceramic Composites for Heat Transfer and Thermal Energy Storage
Authors: Zhou Mi , Lin Tianquan , Huang Fuqiang , Zhong Yajuan , Wang Zhou , Tang Yufeng , Bi Hui , Wan Dongyun , Lin Jianhua
Published: December 2012

A novel architecture of 3D graphene growth on porous Al2O3 ceramics is proposed for thermal management using ambient pressure chemical vapor deposition. The formation mechanism of graphene is attributed to the carbothermic reduction occurring at the Al2O3 surface to initialize the nucleation and growth of graphene. The graphene films are coated on insulating anodic aluminum oxide (AAO) templates and porous Al2O3 ceramic substrates. The graphene coated AAO possesses one‐dimensional isolated graphene tubes, which can act as the media for directional thermal transport. The graphene/Al2O3 composite (G‐Al2O3) contains an interconnected macroporous graphene framework with an extremely low sheet electrical resistance down to 0.11 Ω sq−1 and thermal conductivity with 8.28 W m−1 K−1. The G‐Al2O3 provides enormous conductive pathways for electronic and heat transfer, suitable for application as heat sinks. Such a porous composite is also attractive as a highly thermally conductive reservoir to hold phase change materials (stearic acid) for thermal energy storage. This work displays the great potential of CVD direct growth of graphene on dielectric porous substrates for thermal conduction and electronic applications.
Alkyl Chain Orientations in Dicyanomethylene‐Substituted 2,5‐Di(thiophen‐2‐yl)thieno‐[3,2‐b]thienoquinoid: Impact on Solid‐State and Thin‐Film Transistor Performance
Authors: Wu Qinghe , Ren Shendong , Wang Mao , Qiao Xiaolan , Li Hongxiang , Gao Xike , Yang Xiaodi , Zhu Daoben
Published: December 2012

A series of dicyanomethylene‐substituted 2,5‐di(thiophen‐2‐yl)thieno[3,2‐b]thieno‐quinoids, in which soluble alkyl chains (2‐decyltetradecyls) are substituted at different positions (namely, 2,2′‐positions (Compound 1); 3,3′‐ positions (Compound 2); 6,6′‐positions (Compound 3)), are strategically designed and successfully synthesized. The photophysical and electrochemical properties as well as molecular packing of these new compounds are thoroughly investigated. Thin film transistor measurements reveal that Compounds 1–3 display markedly different charge transport performance. The solution processed thin film transistors of Compound 2 exhibits the highest electron mobility of up to 0.22 cm2 V−1 s−1 under ambient conditions, one and three orders of magnitude higher than those of Compounds 3 and 1, respectively, demonstrating the strong impact of alkyl chain orientations on transistor performance.
Allogeneic hematopoietic stem cell transplantation versus hypomethylating agents in patients with myelodysplastic syndrome: A retrospective case–control study
Authors: Jabbour Elias , Mathisen Michael S. , Garcia‐Manero Guillermo , Champlin Richard , Popat Uday , Khouri Issa , Giralt Sergio , Kadia Tapan , Chen Julianne , Pierce Sherry , Koca Ebru , Daver Naval , Tanaka Maria , Rondon Gabriela , Oran Betul , Parmar Simrit , Kantarjian Hagop , de Lima Marcos
Published: December 2012

Allogeneic stem cell transplantation (allo‐SCT) is the only potentially curative treatment for myelodysplastic syndrome (MDS). Recently, hypomethylating agents (HMAs) have been shown to improve survival in patients with high‐risk MDS. We conducted a retrospective case–control study to compare survival with these treatment modalities in patients with untreated MDS. Controls were identified using a departmental database and transplant patients were matched in at least three of the following five criteria: year of diagnosis, age, blast percentage, International Prognostic Scoring System cytogenetic risk, and time from diagnosis to treatment. Median overall survival (OS) was 26 and 25 months for, respectively, allo‐SCT [(n = 53); range, 2–210 months] and HMA [(n = 40); range, 2–98 months] (P = 0.89). Four‐year survival rates were 24 and 23% for allo‐SCT patients and the nontransplant cohort, respectively. Patients undergoing allo‐SCT after 2000 had longer median OS compared with those transplanted before 2000 (41 versus 7 months, P=0.001). These results would suggest that prospective studies are needed to delineate the timing and efficacy of allo‐SCT in the HMA era. Am. J. Hematol. 88:198–200, 2013. © 2012 Wiley Periodicals, Inc.
Katalytische asymmetrische Desaromatisierungen
Authors: Zhuo Chun‐Xiang , Zhang Wei , You Shu‐Li
Published: December 2012

Dieser Aufsatz fasst die bisherigen Entwicklungen auf dem Gebiet der katalytischen asymmetrischen Desaromatisierungen (CADAs) zusammen. Die hier diskutierten katalytischen asymmetrischen Desaromatisierungen umfassen oxidative Desaromatisierungen, Desaromatisierungen durch Diels‐Alder‐ und verwandte Reaktionen, alkylierende Desaromatisierungen elektronenreicher Arene, Übergangsmetall‐katalysierte Desaromatisierungen, Kaskadensequenzen mit asymmetrischer Desaromatisierung sowie nucleophile Desaromatisierungen von Pyridinium‐Derivaten. Zudem werden kurz asymmetrische Desaromatisierungen mithilfe chiraler Auxiliare sowie katalytische asymmetrische Reaktionen mit desaromatisierten Substraten eingeführt. Ziel dieses Aufsatzes ist es, ein Konzept für die asymmetrische Desaromatisierung zu liefern.
Identification and Expression Analysis of the Zebrafish Homologs of the ceramide synthase Gene Family
Authors: Brondolin Mirco , Berger Susanne , Reinke Michael , Tanaka Hideomi , Ohshima Toshio , Fuβ Bernhard , Hoch Michael
Published: December 2012

Background: Sphingolipids represent a major class of lipids which both serve as structural components of membranes and as bioactive molecules involved in lipid signaling. Ceramide synthases (cers) reside in the center of sphingolipid metabolism by producing ceramide through de novo synthesis or degradative pathways. While the six mammalian cers family members have been extensively studied in cell culture and in adult tissues, a systematic analysis of cers expression and function during embryogenesis is still lacking. Results: Using bioinformatic and phylogenetic analysis, we identified nine highly conserved homologs of the vertebrate cers gene family in the zebrafish genome. A systematic expression analysis throughout five developmental stages indicates that, whereas until 48 hours post fertilization most zebrafish cers homologs are expressed in distinct patterns, e.g., in the intermediate cell mass and the pronephric duct, they show a highly overlapping expression during later stages of embryonic development, mostprominently in the developing brain. Conclusions: In this study, the expression of the cers gene homologs is comprehensively analyzed for the first time during vertebrate embryogenesis. Our data indicate that each embryonic tissue has a unique profile of cers expression during zebrafish embryogenesis suggesting tissue‐specific profiles of ceramides and their derivatives. Developmental Dynamics 242:189–200, 2013. © 2012 Wiley Periodicals, Inc.
Origin of dyke swarms by mixing of metasomatized subcontinental lithospheric mantle‐derived and lower crustal magmas in the Guocheng fault belt, Jiaodong Peninsula, North China Craton
Authors: Tan Jun , Wei Jun‐Hao , Shi Wen‐Jie , Feng Bo , Li Yan‐Jun , Fu Le‐Bing
Published: December 2012

Cretaceous dyke swarms are widespread in the Guocheng fault belt, Jiaodong Peninsula, eastern North China Craton (NCC). Elemental analyses show that these dykes are classified as high‐K calc‐alkaline to shoshonitic series, and are characterized by high MgO (up to 10.33 wt%; Mg# < 69.8), Cr (<571 ppm) and Ni (<235 ppm) at low silica contents. They are enriched in LILEs (e.g. Sr, Ba, K and Pb) and LREEs, depleted in HFSEs (e.g. Nb–Ta, Zr–Hf, Ti and P), and possess relatively radiogenic Sr (initial 87Sr/86Sr = 0.7078 to 0.7116) and Nd [εNd(t) = −20.8 to −13.5] and much less radiogenic Pb (206Pb/204Pb = 17.13 to 17.56) isotope signatures. These data, combined with inversely zoned amphibole and pyroxene phenocrysts, suggest a hybrid origin for the Guocheng dykes. The inferred magma evolution is dominated by repeated injection of basic magma from metasomatized subcontinental lithospheric mantle (SCLM) into a lower crustal reservoir of intermediate‐felsic composition. This refertilized lithospheric mantle source, probably together with its overlying enriched lower crust, was formed by subduction‐related fluid metasomatism in the Palaeoproterozoic, which resulted from final cratonization of the NCC at ca. 1.8 Ga during assembly of Columbia supercontinent. Our observations also imply that similar mixed magma system with oxidized and sulphur‐rich signatures may be the key to the formation of hydrothermal polymetal deposits and the potential target for mineral exploration in some undiscovered areas. Copyright © 2012 John Wiley & Sons, Ltd.
Quality changes of Atlantic horse mackerel fillets (Trachurus trachurus) packed in a modified atmosphere at different storage temperatures
Authors: Alfaro Begoña , Hernández Igor , Baliño‐Zuazo Lander , Barranco Alejandro
Published: December 2012

Background

Atlantic horse mackerel (Trachurus trachurus) is an important commercial fish in Europe. Changes in microbial growth, sensory quality and chemical evolution of modified atmosphere packed (MAP) horse mackerel fillets (48% CO2/50% N2/2% O2) were monitored at different storage temperatures (2, 4, 6 and 10 °C).

Results

The observed sensory shelf life of MAP fish fillets was found to be approximately 7 days at 2 °C, 6 days at 4 °C, 5 at 6 °C and 3 days at 10 °C. A significant correlation was observed between all sensory attributes and two groups of bacteria [total viable count (TVC) and psychrotrophic bacteria], with sensorial rejection when the bacteria approached 106 CFU g−1 at 4, 6 and 10 °C. A level of 30–50 mg total volatile basic nitrogen 100 g−1 of mackerel muscle was well correlated with sensory shelf life determination at all temperatures, except for 2 °C. During the storage time, lipid oxidation did not increase at any temperature and could not be related to quality decay. The presence of acetaldehyde and butyraldehyde in the packing atmosphere was only found in fillets stored at the highest temperature studied (10 °C).

Conclusion

In this study, key quality parameters were established to monitor the spoilage and shelf life of MAP Trachurus trachurus stored at different temperatures. In addition, these results confirm the use of modified atmosphere packaging as a mild preservation method for fillets of Atlantic horse mackerel. © 2012 Society of Chemical Industry
Light‐Harvesting Organic Photoinitiators of Polymerization
Authors: Lalevée Jacques , Tehfe Mohamad‐Ali , Dumur Frédéric , Gigmes Didier , Graff Bernadette , Morlet‐Savary Fabrice , Fouassier Jean‐Pierre
Published: December 2012

Two new photoinitiators with unprecedented light absorption properties are proposed on the basis of a suitable truxene skeleton where several UV photoinitiators PI units such as benzophenone and thioxanthone are introduced at the periphery and whose molecular orbitals MO can be coupled with those of the PI units: a red‐shifted absorption and a strong increase of the molecular extinction coefficients (by a ≈ 20–1000 fold factor) are found. These compounds are highly efficient light‐harvesting photoinitiators. The scope and practicality of these photoinitiators of polymerization can be dramatically expanded, that is, both radical and cationic polymerization processes are accessible upon very soft irradiation conditions (halogen lamp, LED…︁) thanks to the unique light absorption properties of the new proposed structures.
Copolymerization of Ethylene with Vinyl Monomers using Heterogeneous Catalysts Consisting of α‐Diimine Ni(II) Complexes Immobilized into a Fluorotetrasilicic Mica Interlayer in the Presence of an Alkylaluminum Compound
Authors: Kurokawa Hideki , Nakazato Yoshiyuki , Tahara Shingo , Katakura Takahiro , Ishihama Yoshiyuki , Sakuragi Tsutomu , Miura Hiroshi
Published: December 2012

α‐Diimine nickel complexes immobilized into fluorotetrasilicic mica interlayers are prepared by the reaction of an α‐diimine ligand and nickel‐ion‐exchanged fluorotetrasilicic mica, and these are used for the copolymerization of ethylene with linear α‐olefins (1‐hexene, 1‐octene, and 1‐decene), cyclic olefins (norbornene and cyclopentene), or polar vinyl monomers (methyl acrylate and 5‐hexenenitrile). The copolymerization of ethylene with α‐olefins affords linear low‐density polyethylene including methyl and alkyl branches. The incorporation of cyclopentene into the main chain is proved by the 13C NMR spectrum of the ethylene/cyclopentene copolymer. No significant activity is observed during the copolymerization of ethylene with norbornene, methyl acrylate, or 5‐hexenenitrile.

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High‐order time integration methods in molecular dynamics
Authors: Niederhöfer Florian , Wackerfuß Jens
Published: December 2012

The mechanical behaviour of molecular structures can be described with stiff differential equations, which can not be solved analytically. Several numerical time integration schemes can be found in the literature. The aim of this paper is to present the class of partitioned Runge‐Kutta methods applied in molecular dynamics. This class of methods includes a wide range of explicit and implicit, single‐ and multi‐stage, symplectic and non‐symplectic, low‐ and high‐order time integration schemes. Also most of the classical methods like explicit and implicit Euler, explicit and implicit midpoint rule, Störmer‐Verlet and Newmark are also partitioned Runge‐Kutta methods.

The schemes are implemented in a finite element code which can serve as a numerical platform for molecular dynamics. This code is used to show the sensitivity of the simulations to the accuracy of the initial values. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of vehicles under nonstationary crosswind excitation
Authors: Zhang Xiaoyu , Proppe Carsten
Published: December 2012

Strong crosswind gusts have great influence on the stability of railway and road vehicles. They may lead to accidents and also to a discomfort for the road vehicle driver. Risk assessment for overturning of railway and road vehicles is usually calculated based on the stationary situation or at least on wind‐tunnel experiments that are mostly carried out with a static vehicle model. Nonstationary excitation due to wind turbulence occurs if the vehicle accelerates or decelerates. Increasing vehicle speed relative to wind speed will move the energy content of the spectrum to a higher frequency range. It has been realized that nonstationary wind has a great influence on vehicle stability especially when the vehicle speed is high. Thus in order to assess the overturning risk in a more realistic way, a nonstationary wind model together with its interaction with the vehicle should be taken into consideration.This paper proposes a nonstationary wind turbulence model for the investigation of crosswind stability of ground vehicles. A wind model with nonstationary turbulence as well as the wind effects to the moving vehicle in a nonstationary situation (acceleration/deceleration) is described. Nonstationary aerodynamic forces are considered together with the interaction between the moving vehicle system and the wind turbulence. Failure probabilities are computed and reliability analyses are carried out. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and Quasi‐Static Trajectory Control of a Self‐Balancing Two‐Wheeled Vehicle
Authors: Kilian F. Johannes , Gattringer Hubert , Bremer Hartmut
Published: December 2012

This paper introduces the kinematical and dynamical model as well as a quasi‐static trajectory control of a self‐balancing two‐wheeled vehicle. The mobile robot is about 60cm tall, autonomous, unstable and driven by two wheels. Hence, it can be used for transport purposes. Due to the nonholonomic constraints only few modeling techniques are feasible. In this case, the modeling is based on the Projection Equation, followed by the derivation of various control strategies.

In order to allow a desired velocity and to stabilize the inclination angle of the robot a partial feedback linearization in combination with a LQR controller is applied. The quasi‐static trajectory controller, which is based on the kinematical model, uses a flatness based approach in order to remain on the desired path. Continuous curvature paths, composed by clothoids, enable good performance results in simulation and experiment. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of regenerative tissue for replacing the Bruch's membrane
Authors: Willenberg Wolfgang , Stoffel Marcus , Weichert Dieter , Thumann Gabriele
Published: December 2012

In the present study the anisotropic mechanical properties such as elasticity and diffusion of bovine Bruch's membrane (BM) and a collagen foils (CF) are compared with each other. For this reason, a constitutive material law is developed and implemented into a FEM software. Based on tensile tests, the material parameters of both materials are identified. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal control simulations of human arm motion
Authors: Maas Ramona , Leyendecker Sigrid
Published: December 2012

Using multibody systems to represent bones and joints is a common way to simulate human motion. Often, this is done with inverse or forward dynamics (solving initial value problems). However, many simulation tasks in biomechanics lead to boundary value problems, like performing a motion from a given start to a prescribed end position, which could be performed in various ways. In this context, we suppose that human motion is controlled in order to perform an optimal motion. Hence we formulate an optimal control problem (OCP) and compare the results when using different physiologically motivated cost functions. A direct transcription method called DMOCC (see [1]) is used to solve the OCP, whereby we benefit from it's structure preserving formulation, as the resulting optimal discrete trajectories are symplectic‐momentum preserving. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic Properties of Muscle Tissue: Comparison of an Inverse Finite Element Approach and Homogeneous Deformation
Authors: Kruse Roland , Weichert Christine , Böl Markus
Published: December 2012

Parameters of material models are commonly identified by fitting predicted stress‐stretch relations to experimentally derived ones, assuming homogeneous deformation. This approach has been compared with an inverse finite element strategy, where an FE model of the actual measurement set‐up is created to obtain stress‐stretch data. Compressive tests of skeletal muscle tissue have been conducted for different fiber orientations, with a stereo camera system capturing the geometry of the sample. The material exhibited an exponential increase in stiffness with increasing stretch, with large differences related to the fiber orientation; this behavior is described well by a model for arterial layers. Assuming homogeneous deformation led to significantly different stress‐stretch curves indicating that this assumption is unrealistic in this case. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibrations Action of the Trilling Machine MA750 on the Human Operator Hand
Authors: Arghir Mariana , Rus Mariana , Macovescu Sorin Constantin
Published: December 2012

The Work includes identifying and analyzing vibrations produced by a trilling machine MA750 within space work. To identify vibration is used a special method, which has not been used so far in identifying vibrations, with the action on the human body. For obtaining a very good identification of the human body vibrations has been used the Moiré projection method. General conditions were applied to human hand operator during working hours on a trilling machine, with different speeds of main shaft. In the paper are presented successively two methods of measuring the vibrations: the Moiré projection method and conventional method of measuring the vibrometer. The results in the booth situation (classical measurements and Moiré projection method) were in the same order of the unit scale, and the optical method named Moiré projection method can be considered a valid method for the human vibrations measurements without touch of the surface. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A network model for the EPS matrix of microbial biofilms
Authors: Ehret Alexander E. , Bolea Albero Antonio , Böl Markus
Published: December 2012

We present a constitutive model for microbial biofilms with application to biofilms of Pseudomonas aeruginosa whose EPS contain large amounts of alginate. The EPS matrix is modelled as a transient network of worm‐like chains with different types of junctions. The implementation as a nearly incompressible material allows large strain finite element calculations. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Creep damage modeling of a polycrystalline material
Authors: Ozhoga‐Maslovskaja Oksana , Altenbach Holm , Naumenko Konstantin , Prygorniev Oleksandr
Published: December 2012

A polycrystalline material is investigated under creep conditions within the framework of continuum micromechanics. Geometrical 3D model of a polycrystalline microstructure is represented as a unit cell with grains of random crystallographical orientation and shape. Thickness of the plains, separating neighboring grains in the unit cell, can have non‐zero value. Obtained geometry assigns a special zone in the vicinity of grain boundaries, possessing unordered crystalline structure. A mechanical behavior of this zone should allow sliding of the adjacent grains. Within the grain interior crystalline structure is ordered, what prescribes cubic symmetry of a material. The anisotropic material model with the orthotropic symmetry is implemented in ABAQUS and used to assign elastic and creep behavior of both the grain interior and grain boundary material. Appropriate parameters set allows transition from the orthotropy to the cubic symmetry for the grain interior. Material parameters for the grain interior are identified from creep tests for single crystal copper. Model parameters for the grain boundary are set from the physical considerations and numerical model validation according to the experimental data of the grain boundary sliding in a polycrystalline copper [2]. As the result of analysis representative number of grains and grain boundary thickness in the unit cell are recommended. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of gradient‐enhanced damage evolution in viscoplastic plates under propagating disturbance
Authors: Nguyen A.D. , Stoffel M. , Weichert D.
Published: December 2012

This work investigates gradient‐enhanced damage evolution by performing a parameter study for the authors's finite element shell model [1], in which the free energy function is enhanced phenomenologically in terms of a non‐local damage variable and its gradient on the mid‐surface of shell structures. This enhancement gives rise to an introduction of gradient parameters in terms of a substructure‐related intrisic length‐scale and a relationship between non‐local and local damage variable. Based on the global displacement‐force curves obtained from shock‐tube tests on aluminium plate specimens, the gradient parameters are determined to validate the proposed shell model. The influence of spatial gradient of loading on the material behaviour within a macroscopic continuum element will be discussed through several examples. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Calving Events in Antarctic Ice Shelves Using Configurational Forces
Authors: Plate Carolin , Gross Dietmar , Humbert Angelika , Müller Ralf
Published: December 2012

Previous studies on the sensitivity of cracks in ice shelves with different boundary conditions, stress states and density profiles revealed the need for further analyses. As the transfer of boundary conditions from dynamic ice flow simulations to the linear elastic fracture analyses proved to be a critical point in previous studies, a new approach to relate viscous and elastic material behaviour is proposed. The numerical simulations are conducted using Finite Elements utilizing the concept of configurational forces. To show the applicability of the approach, a 2‐dimensional plane stress geometry with volume loads due to the ice shelf flow is analyzed. The resulting crack path is compared to available crack paths from satellite images. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A BEM for transient thermoelastic analysis of a functionally graded layer on a homogeneous substrate under thermal shock
Authors: Ekhlakov Alexander , Khay Oksana , Zhang Chuanzeng
Published: December 2012

Transient thermoelastic analysis of isotropic and linear thermoelastic bimaterials, which are constituted by a functionally graded (FG) layer attached to a homogeneous substrate, subjected to thermal shock is presented in this paper. For this purpose, a boundary element method for transient linear coupled thermoelasticity is developed. The material properties of the FG layer are assumed to be continuous functions of the spatial coordinates. The boundary‐domain integral equations are derived by using the fundamental solutions of linear coupled thermoelasticity for the corresponding isotropic, homogeneous and linear thermoelastic solids in the Laplace‐transformed domain. For the numerical solution, a collocation method with piecewise quadratic approximation is implemented. Numerical results for the dynamic stress intensity factors are presented and discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative Study of Experimental and Simulated Buckled Shapes of Alternately‐Loaded Plates
Authors: Todres Russell , Stoffel Marcus , Weichert Dieter
Published: December 2012

A circular plate is inelastically deformed by uniform pressure, unloaded and then alternately reloaded to the same peak level. For each iteration, snap‐through occurs at an increased pressure relative to the previous one, leading to additional plastic deformation. By repeating this process, the plate either fails or a limit state of deformation is reached under peak pressure without snap‐through. For the case of a limit state, the results of [1] are extended to numerically determine the pressure above the peak level causing the plate to snap‐through again. This is compared to the snap‐through pressure of an initially unloaded spherical cap whose radius corresponds to the maximum displacement achieved in the limit case. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the lamination stack influence on the stiffness of stator active component
Authors: Luchscheider Vera , Willner Kai
Published: December 2012

For electric motors light weight construction is becoming increasingly important. Therefore the mechanical behavior of the lamination stack is necessary to be known for the simulation. The stacking of a lot of sheets has a relevant influence onto the behavior of the whole motor, because of the significant contact characteristics between the sheets. Quasi‐static tests are performed to identify this. In these tests an axial load, representing the packaging process, is applied onto the stacked sheets and thereafter a cyclic load is superposed. With these quasi‐static tests elastic and plastic effects and a hysteretic behavior are detected. For modeling this stiffness behavior nonlinear springs and frictional elements, containing the Coulomb's law, are assembled. The nonlinearities and the hysteresis are dependent on the sheet's roughness. Moreover the behavior of the stack is influenced by the coreplate varnish viscoelasticity. With modeling these effects, the measured values can be well simulated. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of nano‐particle interactions on the mechanical behavior of colloidal structures in polymeric solutions
Authors: Dargazany Roozbeh , Khiêm Vu Ngoc , Itskov Mikhail
Published: December 2012

Colloidal structures inside solutions are usually considered as rigid bodies or linear springs. However, recent experimental results show a strongly nonlinear mechanical response of large clusters. In this contribution, the nonlinear elastic behavior of the colloidal structures inside polymeric solutions is studied. So far, the influences of initial length and fractal dimension on the elastic response of colloidal structures have mostly been considered by scaling theory. Here, we additionally take into account a deformation induced evolution of the aggregate structure which is mainly influenced by inter‐particle interactions. To this end, central and lateral (non‐central) inter‐particle forces are considered separately. Next, the directional stiffness of the colloidal structure is evaluated by using the concept of a backbone chain. The backbone chain is a unique path between two ends of the colloidal structure that carries the main portion of load. The mechanical response of the backbone chain depends on aggregate geometry, deformation history and moreover, on the nature and the strength of the inter‐particle interactions. The aggregate geometry is described by means of the angular averaging concept. The so‐obtained model can further be generalized for all types of colloidal structures with central and lateral inter‐particle forces. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of heat treatment on the phase transformation in powder metallurgical multi‐functional coating
Authors: Kebriaei Reza , Vladimirov Ivaylo , Frischkorn Jan , Reese Stefanie
Published: December 2012

Heat treatment is an important part of the manufacturing of metallic products, especially in powder coating processes. It provides an efficient way to improve the properties of the metal as e.g. hardness by controlling the rate of diffusion and the rate of cooling within the microstructure. The process‐integrated powder coating by radial axial rolling of rings is a new hybrid production technique which is introduced in [1]. The applied temperatures in hot rolling are within the range of austenitizing temperatures for the investigated steels [2]. Therefore, reasonably controlling the temperature is an important task [3]. The paper is concerned with the integration of heat treatment of the rolled ring into the subsequent cooling process. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A rheological model for arbitrary symmetric distortion of the yield surface
Authors: Shutov A. V. , Ihlemann J.
Published: December 2012

A phenomenological model of metal viscoplasticity, which takes combined isotropic, kinematic, and distortional hardening into account, is motivated by a new rheological model. The distinctive advantage of the material model is that any smooth convex saturated form of the yield surface which is symmetric with respect to the recent loading direction can be captured. In particular, an arbitrary sharpening of the saturated yield locus in the loading direction combined with a flattening on the opposite side can be covered. Moreover, the yield locus evolves smoothly and its convexity is guaranteed at each hardening stage. The underlying two‐dimensional rheological analogy can be used to provide insight into the main constitutive assumptions. This rheological model is utilized as a guideline for the construction of phenomenological constitutive relations. The distortion of the yield surface is described with the help of a so‐called distortional backstress. Thus, 2nd rank tensors are utilized only. The resulting material model is thermodynamically consistent. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Accelerating constitutive modeling by automatic tangent generation
Authors: Rothe Steffen , Hartmann Stefan
Published: December 2012

Within the framework of finite elements the linearization within a Newton‐like method requires the computation of the so‐called consistent tangent operator. There are several possibilities to get these derivatives. Three methods, namely analytical, numerical and automatic differentiation, for tangent generation will be analyzed concerning the simulation time and applicability for three different constitutive models. These models are a finite strain hyperelasticity model, finite strain viscoplasticity model for metal powders and a small strain thermoviscoplasticity model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the connection of dissipation and deviatoric stress in the continuum theory of defects
Authors: Schnepp Johannes
Published: December 2012

In a material space‐time manifold an expression for the entropy production is developed. It is based on a Lagrangian formulation for a hyperelastic solid. The material structure and heat transfer are represented by a tetrad field. The derivatives of the Lagrangian with respect to the time‐like vector of the tetrad yields entropy density and current. An identity for the divergence of this four‐current follows from the invariance of the Lagrangian and yields the entropy production due to heat transfer and defect movement. The latter part only depends on a kind of deviatoric stress if the conservation of mass is considered. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bituminous asphalt concrete: Aspects on scale‐bridging
Authors: Schüler Thorsten , Jänicke Ralf , Steeb Holger
Published: December 2012

This paper will give a short overview about a multi‐scale modelling approach for bituminous asphalt concrete. The goal is to describe the micro‐heterogeneous medium by a homogeneous surrogate medium, which has similar effective mechanical properties. Starting from the varying constitutive behaviour on the micro‐scale, our up‐scaling procedure is realised via volume averaging techniques. By use of a Finite‐Element model, the results for different types of boundary conditions (BCs) and their influence on the properties of the compund are investigated on the effective scale. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture toughness investigations of ferroelectric materials considering effects on macro‐ and micro‐scale
Authors: Gellmann Roman , Ricoeur Andreas
Published: December 2012

In the present work we study toughness variation of ferroelectric materials (PZT‐5H) considering different scales for different poling and loading conditions. On the macro‐scale we apply an extended theory of stresses at interfaces in dielectric solids. Further, on the micro‐scale, nonlinear effects are introduced by applying the small scale switching approximation. The analysis is done considering the full anisotropy and electromechanical coupling of the material. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluid‐Structure‐Interaction‐Analysis concerning Damping Features of Viscous Fluids
Authors: Fuchs Vilmar , Wünsch Olaf
Published: December 2012

This work deals with Fluid‐Structure‐Interaction (FSI) concerning damping characteristics of viscous liquids, which are investigated to make the offshore structures more secure and efficient. On that account, we modeled a damping element prototype consisting essentially of an elastic cover that is attached to the cylindrical mono pile foundation at the height of waves. Within the framework of FSI, the impact of breaking waves on a three‐dimensional model of a damping element prototype corresponding to [1] is simulated. In order to measure the influence of different liquid properties on the damping of the impact, the calculations are set up using newtonian and non‐newtonian fluids with varying viscosity. For the non‐newtonian investigation verification is carried out with a CFD model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational homogenization of materials with small deformation to determine configurational forces
Authors: Khalaquzzaman Md. , Xu Baixiang , Müller Ralf
Published: December 2012

In this work the mechanical boundary condition for the micro problem in a two‐scaled homogenization using a FE2 approach is discussed. The strain tensor is often used in the literature for small deformation problem to determine the boundary conditions for the boundary value problem on the micro level. This strain tensor based boundary condition gives consistent homogenized mechanical quantities, e.g. stress tensor and elasticity tensor, but the present work points out that it leads to unphysical homogenized configurational forces. Instead, we propose a displacement gradient based boundary condition for the micro problem. Results show that the displacement gradient based boundary condition can give not only the consistent homogenized mechanical quantities but also the appropriate homogenized configurational forces. The interpretation of the displacement gradient based boundary condition is discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscoelastic effects and shrinkage as accompanying phenomena of the curing of polymers. Single‐ and multiscale effects
Authors: Klinge Sandra , Bartels Alexander , Hackl Klaus , Steinmann Paul
Published: December 2012

The contribution deals with the modeling of two phenomena that are characteristic of the curing of polymers, namely the increasing viscosity and the volume decrease known as autogeneous shrinkage. Both of these processes are caused by the crosslinking of polymer chains during polymerization. In order to model the viscoelastic effects, the free energy consisting of an equilibrium and a non‐equilibrium part is proposed. The former is related to the elastic processes and depends on total deformations. The latter is caused by the viscoelastic effects and only depends on the elastic part of deformations. In order to avoid volume locking effects typical of isochoric materials, both parts of the free energy density are furthermore split into a volumetric and a deviatoric part. A multifield description depending on the displacements, volume change and hydrostatic pressure is introduced as well. Different from the viscous process, the modeling of shrinkage effects does not require a new assumption for the free energy but a split of the total deformation gradient into a shrinkage and a mechanical part. The model suitable for simulating both of the mentioned phenomena is implemented in the single‐ and multiscale FE program. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite element simulation of deformation behaviour of cellular rubber components
Authors: Raghunath R. , Juhre D.
Published: December 2012

This paper presents a new prospect of investigating the mechanical behaviour of cellular rubber using porous hyperelastic material model. There are number of hyperelastic material models to describe the behaviour of homogeneous elastomer, but very few to characterise the complex properties of cellular rubber. The analysis of dependence of material behaviour on pore density using the new material model is supported with experiments to characterise the actual material behaviour. The new material model which is based on Danielsson et al [1] decouples the influence of porosity from the mechanical properties of the solid material by introducing volume fraction of the pores as an explicit scalar variable. The finite element simulations are then followed by experiments on complex model to validate the material model. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two Kinds of Monoclinic‐I Martensite and some Insight into the Microstructures they Form
Authors: Chenchiah Isaac , Schlömerkemper Anja
Published: December 2012

By analysing the facet structure of the convex polytope generated by the twelve transformation strains of cubic to monoclinic‐I martensite, we show that there are two different kinds of monoclinic‐I martensite. These two kinds differ in the sign of a material parameter. While the symmetry properties of both kinds are the same, the geometrical structure of the set of recoverable strains is different. A key idea is to consider the convex polytope formed by the transformation strains and to study its facets. Another insight is to use invariant theory to exploit the fact that compatible cones are algebraic surfaces. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a reduced mixed s‐v least‐squares finite element formulation for the incompressible Navier‐Stokes equations
Authors: Schwarz Alexander , Schröder Jörg
Published: December 2012

In the present work a mixed finite element based on a least‐squares approach (LSFEM) is proposed. We consider a formulation for Newtonian fluid flow, which is described by the incompressible Navier‐Stokes equations. The starting point is a div‐grad three‐field first‐order system with stresses, velocities, and pressure as unknowns. Following the idea in CAI et al. [1], this three‐field formulation can be transformed into a reduced stress‐velocity (s‐v) two‐field formulation, which is the basis for the associated minimization problem. In order to show the applicability of the considered approach a numerical example is presented at the end of the paper. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental investigation of the electrokinetic flow in microchannels with internal electrodes
Authors: Gizewski Carsten , Ehrhard Peter
Published: December 2012

We investigate the electrokinetic flow in microchannels with internal electrodes. Experiments and numerical simulations are performed. The micro–particle–image velocimetry method is used to measure two–dimesional, two–component velocity fields over the complete height of the microchannel. Based on this measurements, the third velocity component, which cannot be measured directly, is calculated by an integration of the continuity equation. Due to the fact that microparticles, used for the μPIV are electrically non‐neutral leads to the problem that these particles experience electrophoretic forces. That means that the particle movement appears to be a superposition of electroosmotic and electrophorectic effects. To verify the influence of electrophoretic effects on the microparticles, additional numerical calculations are made. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of structure and non‐gradient turbulent transfer in swirling flows
Authors: Čantrak Đorde , Gabi Martin , Janković Novica , Čantrak Svetislav
Published: December 2012

Turbulence structure of swirling flows is being investigated in this paper, on the basis of experimental, self conducted measurements, and theoretical and numerical results. Turbulent swirling flows are extremely inhomogeneous, three dimensional and anisotropic. The aim of this paper is to investigate significant influence of swirl onto statistical parameters and non‐gradient turbulent transfer. Contemporary optical measuring techniques two component laser Doppler anemometry (LDA) and stereo particle image velocimetry (SPIV) have been applied. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parametrization of the homogeneous ice nucleation rate for the numerical simulation of multiphase flow
Authors: Nemec Tomás , Eisenschmidt Kathrin , Rauschenberger Philipp , Weigand Bernhard
Published: December 2012

Homogeneous ice nucleation in supercooled water is studied with the classical nucleation theory (CNT). The nucleated ice particles are assumed to possess physical properties of metastable cubic ice. The comparison with literature data on homogeneous ice nucleation rates shows a good agreement between CNT predictions and experimental nucleation rates. The CNT predicted nucleation rate, critical cluster radius, and critical nucleation work are parametrized for use in numerical simulations of the freezing process of supercooled water droplets. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase‐Averaged Vortex Train Flow Generated by Plasma DBD Actuator
Authors: Procházka Pavel , Uruba Václav
Published: December 2012

It will be shown how plasma actuator can generate wall‐jet‐like flow or train of periodical vortices depending on the generator setting. For generation the high‐frequency high‐voltage AC is used. Low‐frequency modulation of the supply voltage is required to generate vortices. Data acquisition will be performed using time‐resolved PIV technique. Phase‐averaging will be studied from two different perspectives. Firstly, sampling of phases will be ensured using trigger that is contained in the PIV software and, secondly, phase‐averaged flow will be computed from two main modes of POD analysis. The generated flow patterns are to be applied for control of a boundary layer. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the modeling of slender heat sources
Authors: Cibis Thomas Martin , Marheineke Nicole , Wegener Raimund
Published: December 2012

Studying the heat exchange of small, slender objects in a surrounding flow, we approximate the impact of extended heat sources by Dirac‐distributions (point sources) with appropriate amplitudes in the context of slender‐body theory. The proposed model for the source strength functions is deduced from analytical considerations (Green's functions) of the stationary two‐dimensional heat equation. Numerical simulations show the L2‐approximation quality of the strategy. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Delamination in visco‐elastic materials with thermal effects
Authors: Thomas Marita , Rossi Riccarda
Published: December 2012

This contribution reports on a model describing the evolution of brittle delamination between two visco‐elastic bodies Ω+ and Ω−, bonded along a prescribed contact surface ΓC, over a fixed time interval (0, T); a detailed discussion and a rigorous mathematical analysis can be found in [1]. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical model for deformable roll coating with nip feed
Authors: Willinger Bettina , Epple Philipp , Delgado Antonio
Published: December 2012

The presented work deals with an analytical solution for a roll coater with deformable rolls, as commenly used in industry. The focus is on the calculation of the nip feed system in a forward coating mode. The calculation is done with thin film theory and includes Hook's law for elasticity for modelling the elasticity behaviour of the deformable roll. The new model has been validated by experimental data from literature. The agreement is sufficiently good. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Smooth 3D Model for Fiber Lay‐Down Processes
Authors: Maringer Johannes , Klar Axel , Stilgenbauer Patrik , Wegener Raimund
Published: December 2012

We present an improved three‐dimensional stochastic model concerning the fiber lay‐down in the production process of nonwoven materials. The model describes the position of the deposited fibers on a conveyor belt, which is determined by a system of stochastic differential equations. Here we remove a drawback of a previous 3D model, that is the non‐smoothness of the fiber paths. Besides the derivation of the smooth 3D model we show its connection to the non‐smooth model in a white noise limit. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Avoiding complex arithmetic in the low‐rank ADI method efficiently
Authors: Benner Peter , Kürschner Patrick , Saak Jens
Published: December 2012

We present a new reformulation of the low‐rank ADI method for solving large‐scale Lyapunov equations which uses only real arithmetic operation and storage in the presence of complex shift parameters. This makes the method applicable on computing environments where complex computations and storage are not supported or not efficiently available. For generalized Lyapunov equations it is significantly more efficient than the older completely real formulation of the low‐rank ADI as confirmed by numerical examples. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)