bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytotoxicity study of novel water‐soluble chitosan derivatives applied as membrane material of alginate microcapsules
Authors: Sobol Marcin , Bartkowiak Artur , de Haan Bart , de Vos Paul 
Published: December 2012

AbstractThe majority of cell encapsulation systems applied so far are based on polyelectrolyte complexes of alginate and polyvalent metal cations. Although widely used, these systems suffer from the risk of disintegration. This can be partially solved by applying chitosan as additional outer membrane. However, chitosan can be dissolved in water only at a low pH, which limits its use in the field of bioencapsulation. In this study, novel primary and tertiary amine chitosan derivatives have been synthesized, which may be dissolved at pH 7.0, and retain the ability to effectively form additional membrane on the surface of alginate beads. As aqueous solutions tertiary amines dimethylamino‐1‐propyl‐chitosan and dimethylethylamine‐chitosan with linear hydrochloride aliphatic chains had the lowest toxicity, whereas dimethylpropylamine‐chitosan, diethylaminoethyl‐chitosan, and diisopropylaminoethyl‐chitosan with branched hydrochloride aliphatic were cytotoxic to the majority of tested cells. When applied as polyelectrolyte complexation agent on the surface of alginate beads, none of the derivates had any negative effect on the metabolic activity of encapsulated beta‐cells. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
Study of inferior turbinate reconstruction with Medpor for the treatment of empty nose syndrome
Authors: Jiang Chenyan , Shi Runjie , Sun Yiyuan 
Published: December 2012

Objectives/HypothesisPatients with empty nose syndrome experience considerable discomfort in their daily lives and treatment is difficult for their physicians. The purpose of this study was to evaluate the outcome of an empty nose syndrome treatment via reconstruction of the inferior turbinate with porous polyethylene (Medpor).Design and MethodA prospective self‐controlled study was conducted, and 19 patients suffering from empty nose syndrome underwent a surgical therapy through submucosal implantation of Medpor in order to reconstruct their inferior turbinate. The outcome was assessed by comparison of the preoperative and follow‐up symptoms, nasal endoscopy findings, CT scans, mucociliary clearance, acoustic rhinometry, and the Sino‐Nasal Outcome Test‐20 scores.ResultsIn a follow‐up period of 3 to 18 months, all patients reported subjective symptom improvements and a statistically significant improvement of the Sino‐Nasal Outcome Test scores was achieved (P < 0.05). Mucociliary clearance assessments showed improvements at 3, 6, and 12 months postoperatively, but without statistical significance. Acoustic rhinometry assessments showed postoperative improvements of nasal resistance, nasal volume, and minimum cross‐sectional area with a significant overall average score (P < 0.05).ConclusionThe reconstruction of inferior turbinate with Medpor is a new promising approach to treat patients with empty nose syndrome.Level of Evidence4.
Syntheses and Properties of Novel Copolymers of Poly(1,4‐dioxane‐2‐one) and Aliphatic Polycarbonate Based on Ketal‐Protected Dihydroxyacetone
Authors: Wang Lian‐Sheng , Cheng Si‐Xue , Zhuo Ren‐Xi 
Published: December 2012

AbstractNovel random copolymers of 1,4‐dioxane‐2‐one (DON) and 2,2‐ethylenedioxy‐1,3‐propanediol carbonate (EOPDC) are synthesized in bulk at 120 °C using Sn(Oct)2 as a catalyst. The effects of different molar feed ratios of EOPDC/DON on the yield and molecular weight of the copolymers are investigated. The copolymers are obtained with a yield of 55.4–98%. The number‐average molecular weight of the copolymer is 0.49–4.18 × 104 g mol−1 with a polydispersity of 1.52–1.68. The poly(DON‐co‐EOPDC)s obtained are characterized by FTIR, 1H NMR, and 13C NMR spectroscopy, gel‐permeation chromatography (GPC), and DSC. The hydrolytic degradation of the copolymer in phosphate buffered saline (PBS) is also investigated. The results show that both the hydrophilicity and the degradation rate of the copolymers increase with increasing copolymer DON content.
On the interrelation between dissipation and chemical energies in modeling shape memory alloys
Authors: Junker Philipp , Hackl Klaus 
Published: December 2012

AbstractWe use the principle of maximum dissipation for thermo‐mechanically coupled modeling of poly‐crystalline shape memory alloys (SMA). This modeling scheme demands approaches for both Helmholtz free energy and dissipation. For time‐independent processes, dissipation is usually modeled by the norm of the internal variable's rate times a factor. We show that for SMAs this factor is not an additional modeling parameter. In contrast, it can be calculated from the Helmholtz free energy. This reduces the number of model parameters and provides furthermore an interesting effect of the model which allows to display the material behavior in an even more realistic manner. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational Phase Field Modeling of Laminate Deformation Microstructure in Finite Gradient Crystal Plasticity
Authors: Hildebrand Felix , Miehe Christian 
Published: December 2012

AbstractThe macroscopic mechanical behavior of many materials crucially depends on the formation and evolution of their microstructure. In this work, we consider the formation and evolution of laminate deformation microstructure in plasticity. Inspired by work on the variational modeling of phase transformation [5] and building on related work on multislip gradient crystal plasticity [9], we present a new finite strain model for the formation and evolution of laminate deformation microstructure in double slip gradient crystal plasticity. Basic ingredients of our model are a nonconvex hardening potential and two gradient terms accounting for geometrically necessary dislocations (GNDs) by use of the dislocation density tensor and regularizing the sharp interfaces between different kinematically coherent plastic slip states. The plastic evolution is described by means of a nonsmooth dissipation potential for which we propose a new regularization. We formulate a continuous gradient‐extended rate‐variational framework and discretize it in time to obtain an incremental‐variational formulation. Discretization in space yields a finite element formulation which is used to demonstrate the capability of our model to predict the formation and evolution of laminate deformation microstructure in f.c.c. Copper with two active slip systems in the same slip plane. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Perspectives on Constructive and Functional Optimizing of a Serial Robot with Four Degrees of Freedom Destined for Special Applications
Authors: Petrişor Silviu Mihai , Bârsan Ghiţă 
Published: December 2012

AbstractThis paper deals with aspects on the dynamic modulation of the robots mechanical structure, using Lagrangian formalism, choosing the adequate DC servomotors, translation modules constituting the TTRT robot, the constructive solution and modelling the three translation subassemblies of the studied robot, with the intention that, in the end, based on a dynamic‐organologic algorithm, a functional optimization of the robot be brought out within a workcell destined for special applications, so that the energetic consumption be as low as possible. This paper also presents the organological calculi and solutions for the efficient design of modules specific to mechanical structures of industrial serial‐modular robots. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Discrete Element Model for Degradation of Ballast Tracks
Authors: Ergenzinger Christian , Seifried Robert , Eberhard Peter 
Published: December 2012

AbstractA Discrete Element Model that is capable to describe degradation of ballast tracks in consideration of breakage of the ballast stones is presented. Strong rock is modelled as a granular solid by introduction of breakable bonds with suitable failure criteria between adjacent particles. Irregular angular stones are generated from the granular solid and their crushing strength is evaluated. The degradation process of a ballast bed is assessed and related to the damage occurring to the individual stones. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐excited vibrations of deformable multibody systems due to friction: Explanation with the help of two point masses and a belt
Authors: Maier Christian , Glocker Christoph , Meier David 
Published: December 2012

AbstractThe aim of this paper is to present the results of the investigations of the ability of self‐excited vibrations due to friction in a planar simplified mechanical model, with a constant coefficient of friction. The Hurwitz criteria is used for the stability analysis and the determination of the critical value of the coefficent of friction. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Hamiltonian conserving indirect optimal control method for multibody dynamics
Authors: Siebert Ralf , Betsch Peter 
Published: December 2012

AbstractIn the past, a lot of effort has gone into the development of structure‐preserving time‐stepping schemes for forward dynamic problems. This is due to the superior numerical stability of these integrators. Guided by previous developments in the design of energy‐momentum integrators for forward dynamic problems, a Hamiltonian conserving indirect optimal control method will be introduced. For the state equations, a consistent variant of the midpoint evaluation introduced in [1] will be applied. Based on this specific discretization of the state equations, a discretization of the costate equations will be introduced, which is based on the notion of a discrete derivative and which leads to the algorithmic conservation of the discrete Hamiltonian. The newly developed method will be compared with a direct transcription method. We will test the newly proposed method within two numerical examples, which are the optimal control of a particle in a gravitational field and a 3‐link manipulator. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Analysis of Multibody Systems in the Presence of Uncertainties
Authors: Walz Nico‐Philipp , Hanss Michael 
Published: December 2012

AbstractThis contribution introduces and illustrates the concept of fuzzy arithmetic as a modeling and analysis tool for the simulation of multibody systems subjected to uncertainties. The uncertainties are described by the use of fuzzy numbers and the simulation procedure is performed by employing the Transformation Method, which is a practical methodology for the implementation of fuzzy arithmetic. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid coordinate approach for the modelling and simulation of multibody systems
Authors: Becker Christian , Betsch Peter , Franke Marlon , Siebert Ralf 
Published: December 2012

AbstractThe main goal of the present work is to provide an add‐on scheme for the formulation of multibody dynamics, based on natural coordinates, in regard to ideally balanced rigid bodies with high rotational spin, e.g. gyroscopes. The underlying aim of this approach is to achieve higher numerical accuracy whenever the preferred axis of rotation coincides with the balanced main axis of the body. This will be achieved by seperating the spin of the balanced rigid body along the denoted axis as an additional angular coordinate, whereas the other rotations will be covered by a carried frame, parameterized via natural coordinates. At the same time the carried frame provides a link to the existing modelling framework in terms of natural coordinates, enabling a straightforward implementation into existing multibody systems (e.g. rotary crane [2]). (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Natural co‐ordinates for control applications
Authors: Sänger Nicolas , Betsch Peter 
Published: December 2012

AbstractNatural coordinates have emerged to be well‐suited for both rigid and flexible multibody dynamics. Especially the combination of structural elements and energy‐momentum consistent time stepping schemes leads to superior numerical stability as well as an automatable assembly, resulting in both excellent run‐time behaviour as well as moderate modelling effort (see [1]). Incorporation of modern methods for finite‐element simulations, such as mortar methods for contact or domain decomposition both for structural elements as well as continuum elements is straightforward ([2]).Augmentation techniques allow a systematic integration of both mechanical and non‐mechanical quantities for simulation (see [3] and [4]), which makes this approach suitable especially for emulation and simulation of mechatronic systems. We will present an approach for evaluating forward control strategies with flexible multibody systems. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topology Optimization of Members of Elastic Multibody Systems
Authors: Held Alexander , Seifried Robert 
Published: December 2012

AbstractLightweight techniques are applied increasingly often for modern machine designs in order to reduce the moving masses and therewith the energy consumption. However, as a result the stiffness of the system decreases causing undesired elastic deformations and therewith end‐effector deviations. In this work a topology optimization procedure for elastic multibody systems based on the solid isotropic material with penalization approach is presented to lower end‐effector tracking errors. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Maxwell‐Contact
Authors: Grundl Kilian , Cebulla Thomas , Schindler Thorsten , Ulbrich Heinz 
Published: December 2012

AbstractIn multibody systems, two alternative approaches exist to compute contact forces between bodies. The unilateral constraint contact and the unilateral regularized contact do not take into account the influence of the deformation due to other contacts on a body using rigid body dynamics. In this paper, a third alternative, i.e. the Maxwell‐Contact, is derived coupling the deformations of different contacts on one body quasi‐statically. An academic example validates the fundamental properties of the contact model and the application in a simulation of a pushbelt CVT shows improved results. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recursive Methods in Modeling and Control of Modular Robotic Systems
Authors: Oberhuber Bernhard , Gattringer Hubert , Bremer Hartmut , Fellhauer Bruno 
Published: December 2012

AbstractThis paper addresses the dynamical modeling and control of reconfigurable modular robots. The modular actuators (brushless DC motors with Harmonic Drive gears) for the robots under consideration are connected by rigid links. This way the robot can be assembled in different configurations by rearranging these components. For dynamical modeling the Projection Equation in Subsystem representation is used, taking advantage of its modular structure. Due to the lack of position sensors at the gearbox output shaft, deflections caused by the elasticities in the gears can not be compensated by the PD motor joint controller. Therefore, a correction of the motor trajectory is needed, which can be calculated as part of a flatness based feed‐forward control using the exact model of the robot. With the recursive approach proposed in this paper the concept of reconfigurability is retained. For validation a redundant articulated robot arm with seven joints is regarded and results are presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A modular and efficient approach to computational modeling and sensitivity analysis of robot and human motion dynamics
Authors: Friedmann Martin , Wojtusch Janis , von Stryk Oskar 
Published: December 2012

AbstractIn this paper a new class library for the computation of the forward multi‐body‐system (MBS) dynamics of robots and biomechanical models of human motion is presented. By the developed modular modeling approach the library can be flexibly extended by specific modeling elements like joints with specific geometry or different muscle models and thus can be applied efficiently for a number of dynamic simulation and optimization problems. The library not only provides several methods for solving the forward dynamics problem (like articulated body or composite rigid body algorithms) which can transparently be exchanged. Moreover, the numerical solution of optimal control problems, like in the forward dynamics optimization of human motion, is significantly facilitated by the computation of the sensitivity matrix with respect to the control variables. Examples are given to demonstrate the efficiency of the approach. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical and experimental investigation of cartilage replacement material for medical applications
Authors: Zhou B. , Stoffel M. , Weichert D. , Rath B. 
Published: December 2012

AbstractSoft tissues are commonly applied in surgery to replace the injured articular cartilage. Many biological researches were carried out through mechanical and histological experiments. They focus on the function, degeneration and regeneration of the articular cartilage and fibrocartilage. The aim of the presented work is to develop a method to characterize the mechanical properties of different kinds of soft tissues and to trace the evolution of elastic properties in implants during the remodeling process. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and simulation of injecting acrylic bone cement into osteoporotic vertebral bones within percutaneous vertebroplasty
Authors: Kolmeder Sebastian , Lion Alexander , Landgraf Ralf , Ihlemann Jörn , Lebsack Helena , Kober Cornelia , Blattert Thomas R. 
Published: December 2012

AbstractPercutaneous vertebroplasty is a common clinical procedure to treat vertebral compression fractures and osteoporotic vertebral bodies. However, this operation technique is accompanied by different complications due to lack of knowledge about the complicated behaviour of bone cement within the human body. To contribute to a better understanding of the processes that take place inside the body during a vertebroplasty, a detailed model of the thermomechanical behaviour of acrylic bone cement has been developed. All important effects are covered, that influence the behaviour of acrylic bone cement during the injection in a human vertebral body. Implemented in the opensource CFD‐code OpenFOAM®, first results show that this comprehensive simulation of the minimal invasive injection is capable to accurately predict the cement distribution and temperature field of acrylic bone cement inside the vertebral body. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling 3D and 1D Skeletal Muscle Models
Authors: Sprenger Michael , Schmitt Syn , Röhrle Oliver 
Published: December 2012

AbstractThis work introduces a modelling framework towards a forward dynamics simulation of skeletal muscle mechanics that couples three‐dimensional (3D) continuum‐mechanical‐based Finite Element (FE) simulations to rigid body simulations. In this regard, this is a methodological approach, which incorporates different methods to realise simulations of the musculoskeletal system. Such simulations are at present computationally not feasible.To set up such a modelling framework the upper limp is selected. Here, the upper limb consists of an antagonistic muscle pair, the elbow (a simple hinge joint) and an external load. The skeletal muscles are represented by a 3D continuum‐mechanical model. The tendons are, for now, assumed to be rigid. The results demonstrate the ability of the system to converge to a physiological realistic position. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Study of Psychoacoustic Effects of Noise Emitted by the Machine Tools Structure
Authors: Ţepeş‐Bobescu Alina‐Sabina , Ţepeç‐Bobescu Florin , Gligor Anamaria , Arghir Mariana 
Published: December 2012

AbstractThe main sources of noise at work, in industrial environments, are machine tools: namely, mechanical transmission structure composed of gears, bearings, electric motors drive and the cutting process. Generated vibrations are transmitted through structures, carcasses or directly to environment, developing a complex acoustic field around machine tools. In terms of occupational medicine, the noise is generated by a combination of vibrations producing sounds with different characteristics and that are produced in the workplace [2]. It is important to identify the dominant noise source, the cause of exceeding the admissible limits (87dB) and noise transmission mode to make an objective correlation with effects on humans [1]. Hearing loss can occur immediately at extreme sound levels, but, in general, the problem is noise exposure over time. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Remodelling Processes in Bones: A Biphasic Porous Media Model
Authors: Krause Robert , Schittler Daniella , Waldherr Steffen , Allgöwer Frank , Markert Bernd , Ehlers Wolfgang 
Published: December 2012

AbstractIn the context of the Theory of Porous Media (TPM), a continuum‐mechanical model is introduced to describe the complex fluid‐structure interaction in bone tissue on the macro‐scale. The tissue is treated as an aggregate of two immiscible constituents, where the cells and the bone matrix are summarised to the solid phase, and the fluid phase summarises the extracellular fluids and their components. The remodelling process is described on the macro‐scale by a distinct mass exchange that also causes a change of the constituents' material properties. In addition to the mechanical description, systems‐biological control mechanisms are included into the model by evaluating a systems‐biological cell interaction model at every integration point of the spatially discretised domain.Here, an integrative solution strategy is presented for this combined mechanical and systems‐biological problem. Therein, the mechanical problem is treated using the Finite‐Element Method (FEM), where the systems‐biological problem is solved locally on integration point level in the sense of a collocation method. To reveal the whole capability of this approach, a 3‐dimensional numerical example of the remodelling process in the upper human femur under physiological loading conditions is presented. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic crack analysis in 2D elastic solids with the singular edge‐based smoothed finite element method
Authors: Bui Tinh Q. , Zhang Chuanzeng 
Published: December 2012

AbstractThe singular edge‐based smoothed finite element method (sES‐FEM) is developed for stationary dynamic crack analysis in two‐dimensional (2D) elastic solids. The paper aims at providing a better understanding of the dynamic fracture behaviors in linear elastic solids by means of the strain smoothing technique. The strains are smoothed and the system stiffness matrix is performed using the strain smoothing over the smoothing domains associated with the element edges. A two‐layer singular five‐node crack‐tip element is employed while the standard implicit time integration scheme is used for solving the discrete sES‐FEM equation system. Dynamic stress intensity factors (DSIFs) are extracted using the domain‐form of interaction integrals in terms of the smoothing technique. The normalized DSIFs are compared with reference solutions showing a high accuracy of the sES‐FEM. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)