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Search Results: 1 - 10 of 198158 matches for " N. Modler "
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Process Chain Modelling and Analysis for the High-Volume Production of Thermoplastic Composites with Embedded Piezoceramic Modules
W. Hufenbach,M. Gude,N. Modler,Th. Heber
Smart Materials Research , 2013, DOI: 10.1155/2013/201631
Development of novel piezoceramic actuator modules for the embedding in intelligent lightweight structures
W. Hufenbach,M. Gude,N. Modler,C. Kirvel
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: Piezoceramic actuators in lightweight structures enable a purposeful manipulation of the dynamic and vibroacoustic structural behaviour. Above it, further studies focus on the application of thin and flexible piezoceramic modules as power sources in morphing structures aiming at a shape adaptation.Design/methodology/approach: A specific example of novel morphing structures is introduced, which rely on multistable deformation phenomena of fibre-reinforced composites with an unsymmetric lay-up. For the large-scale capable utilisation of such active struc tural parts made of fibre-reinforced thermoplastic composites, novel piezoceramic modules, which are specifically tailored to the structural material, and required manufacturing methods are developed.Findings: The piezoceramic modules with the highly regarded compatibility to ther moplastic composites permit their substantially coherent and homogeneous integration in the fibre composite structure without intricate adhesive assembly effort. Furthermore, thermally induced residual compressive stresses during the manufacturing process serve for pur posefully prestressing the piezoceramic components to reduce the module’s sensitivity to tensile loading.Research limitations/implications: For the manufacture of those novel piezoceramic modules, a continuously operating fabrication method has been developed. By the process-related integration of a hot press, residual compression stresses are thermally induced into the modules that considerably contribute to the decrease of the piezoceramic module’s sensitivity to tension.Originality/value: The successful development of the novel TPM offers a significant advancement in the efficieny within the large scale production of novel intelligent lightweight structures.
Process Chain Modelling and Analysis for the High-Volume Production of Thermoplastic Composites with Embedded Piezoceramic Modules
W. Hufenbach,M. Gude,N. Modler,Th. Heber,A. Winkler,T. Weber
Smart Materials Research , 2013, DOI: 10.1155/2013/201631
Abstract: Active composite structures based on thermoplastic matrix systems are highly suited to applications in lightweight structures ready for series production. The integration of additional functional components such as material-embedded piezoceramic actuators and sensors and an electronic network facilitates the targeted control and manipulation of structural behaviour. The current delay in the widespread application of such adaptive structures is primarily attributable to a lack of appropriate manufacturing technologies. It is against this backdrop that this paper contributes to the development of a novel manufacturing process chain characterized by robustness and efficiency and based on hot-pressing techniques tailored to specific materials and actuators. Special consideration is given to detailed process chain modelling and analysis focusing on interactions between technical and technological aspects. The development of a continuous process chain by means of the analysis of parameter influences is described. In conclusion, the use of parameter manipulation to successfully realize a unique manufacturing line designed for the high-volume production of adaptive thermoplastic composite structures is demonstrated. 1. Introduction The increasing scarcity or resources around the world necessitates the development of high-tech products with a high level of sustainability. Function-integrative lightweight engineering in multimaterial design is a vital source of key technologies for various applications in this field. In recent years comfort and environmental criteria have become an increasingly important element of automotive, medical, and civil engineering applications. The superior specific mechanical properties, excellent design flexibility, and cost-efficient, reproducible manufacturing processes which characterize fibre-reinforced composites based on thermoplastic matrix systems enable them to fulfil these criteria. In particular, those characteristics make them highly suited to applications in lightweight structures ready for high-volume production. Moreover, the integration of additional functional components such as piezoceramic actuators or sensors into thermoplastic lightweight structures facilitates the manipulation of the dynamic and vibroacoustic behaviour of those structures [1–3]. In addition to quality monitoring, energy harvesting, and active vibration or noise control [4–8], a number of structural applications (e.g., in morphing structures and compliant mechanisms) are also possible [9–13]. State-of-the-art production of adaptive lightweight
Quantum rotational band model for the Heisenberg molecular magnet Mo72Fe30
J. Schnack,M. Luban,R. Modler
Physics , 2001, DOI: 10.1209/epl/i2001-00599-0
Abstract: We derive the low temperature properties of the molecular magnet Mo72Fe30, where 30 Fe(3+) paramagnetic ions occupy the sites of an icosidodecahedron and interact via isotropic nearest-neighbour antiferromagnetic Heisenberg exchange. The key idea of our model (J.S. & M.L.) is that the low-lying excitations form a sequence of rotational bands, i.e., for each such band the excitation energies depend quadratically on the total spin quantum number. For temperatures below 50 mK we predict that the magnetisation is described by a staircase with 75 equidistant steps as the magnetic field is increased up to a critical value and saturated for higher fields. For higher temperatures thermal broadening effects wash out the staircase and yield a linear ramp below the critical field, and this has been confirmed by our measurements (R.M.). We demonstrate that the lowest two rotational bands are separated by an energy gap of 0.7 meV, and this could be tested by EPR and inelastic neutron scattering measurements. We also predict the occurrence of resonances at temperatures below 0.1 K in the proton NMR spin-lattice relaxation rate associated with level crossings. As rotational bands characterize the spectra of many magnetic molecules our method opens a new road towards a description of their low-temperature behaviour which is not otherwise accessible.
Polymer Analyses for an Adapted Process Design of the Pipe-Extrusion of Polyetherimide  [PDF]
Michael Stegelmann, Michael Müller, Anja Winkler, Alexander Liebsch, Niels Modler
Materials Sciences and Applications (MSA) , 2018, DOI: 10.4236/msa.2018.97044
Abstract: Over the last years, the use of high performance thermoplastic materials increased significantly especially in aviation applications. Thus, the processing of these high temperature polymers became more and more interesting. Especially, the groups of polymers like polyphenylene sulfide (PPS), polyether ether ketone (PEEK) or polyetherimide (PEI) are in the focus of recent developments and investigations. These materials show excellent thermal, mechanical and chemical properties while processing remains still challenging. Especially the influence of processing temperatures, temperature depending viscosities, the specific heat capacities and the thermal expansion show a high impact to the quality of the produced parts, e.g. degradation and dimensionally stability. Thus, this paper shows experimental characterizations in regard to the processing of PEI by pipe extrusion processes. In this context, a suitable methodology for the determination of appropriate process parameters is shown, which includes the comprehensive determination of temperature dependent thermal, thermomechanical and degradation properties of specific PEI extrusion materials.
Scorpion sting in southern Africa: diagnosis and management
GJ Müller, H Modler, CA Wium, DJH Veale
Continuing Medical Education , 2012,
Abstract: CME October 2012 Vol. 30 No. 10
Analysis of the Concrete Developed With Recycled Coarse Aggregate
Luís Eduardo Azevedo Modler,Cristina Eliza Pozzobon
Revista Teoria e Prática na Engenharia Civil , 2008,
Abstract: The aim of this study is to analyze concretes developed by partial and total substitution of coarse aggregate, obtained by the recycled concrete. The study begins with the characterization of the materials: coarse aggregate obtained by grinding of the concrete samples, coarse aggregate obtained by grinding of the natural rock, natural fine aggregate and Portland cement. The next step is to find the mixture composition, through a mix-design method, to produce concretes having compressive strength of 15-40 MPa, and with 0%-75% of substitution of the natural aggregate for the recycled aggregate. After that, the mixtures are tested to analyze theirs properties in the fresh state and in the mature state. In possession of these results it makes possible to compose some tendency graphs that can correlate the studied variable. Then it is possible to evaluate some aspects of technical viability of the substitution of the natural aggregate for the recycled aggregate.
Snake bite in southern Africa: diagnosis and management
GJ Müller, H Modler, CA Wium, DJH Veale, CJ Marks
Continuing Medical Education , 2012,
Abstract: CME October 2012 Vol. 30 No. 10
Observation of field-dependent magnetic parameters in the magnetic molecule {Ni4Mo12}
J. Schnack,M. Brueger,M. Luban,P. Koegerler,E. Morosan,R. Fuchs,R. Modler,Hiroyuki Nojiri,Ram C. Rai,Jinbo Cao,J. L. Musfeldt,Xing Wei
Physics , 2005, DOI: 10.1103/PhysRevB.73.094401
Abstract: We investigate the bulk magnetic, electron paramagnetic resonance, and magneto-optical properties of {Ni4Mo12}, a magnetic molecule with antiferromagnetically coupled tetrahedral {Ni4Mo12} in a diamagnetic molybdenum matrix. The low-temperature magnetization exhibits steps at irregular field intervals, a result that cannot be explained using a Heisenberg model even if it is augmented by magnetic anisotropy and biquadratic terms. Allowing the exchange and anisotropy parameters to depend on the magnetic field provides the best fit to our data, suggesting that the molecular structure (and thus the interactions between spins) may be changing with applied magnetic field.
Implementation of a Higher Quality dc Power Converter  [PDF]
N. N. Barsoum
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.22012
Abstract: Many single and three-phase converters are well developed, and covered up in most of electric markets. It is used in many applications in power systems and machine drives. However, an exact definite output signal from the dc side still not recognized. The waveforms of output voltage and current demonstrate an imperfect dc signal and constitute losses, harmonic distortion, low power factor, and observed some ripples. An approximately perfect rectifier bridge is the aim of this research. Perhaps it gives the ability to identify the parameters of the converter to obtain, as much as possible, a perfect dc signal with less ripple, high power factor and high efficiency. Design is implemented by simulation on Power Simulator PSIM, and practically, a series regulator LM723 is applied to provide regulating output voltage. Comparisons of both simulation and hardware results are made to observe differences and similarities.
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