35,642 research outputs found
Inverse form finding with h-adaptivity and an application to a notch stamping process
The aim is to determine the optimized semi-finished workpiece geometry to its given target geometry after a forming process. Hereby, a novel approach for inverse form finding, a type of a shape optimization, is applied to a notch stamping process. As a special feature, h-adaptive mesh refinement is considered within the iteratively performed forming simulation
A non-invasive node-based form finding approach with discretization-independent target configuration
Form finding is used to optimize the shape of a semi-finished product, i.e. the material configuration in a forming process. The geometry of the semi-finished product is adapted so that the computed spatial configuration corresponds to a prescribed target spatial configuration. Differences between these two configurations are iteratively minimized. The algorithm works non-invasively, thus there is a strict separation between the form update and the finite element (FE) forming simulation. This separation allows the use of arbitrary commercial FE-solvers. In particular, there is no need for a modification of the FE forming simulation, only the material configuration is iteratively updated. A new method is introduced to calculate the difference between the target and the computed spatial configuration. Thereby the target mesh is separated from the mesh for the FE forming simulation, which enables a more accurate and independent representation of the target configuration. In addition, the possibility of taking into account manufacturing constraints in the optimization process is presented. The procedure is illustrated for the example of the first stage of a novel two-stage sheet-bulk metal forming process
Memory formation in matter
Memory formation in matter is a theme of broad intellectual relevance; it
sits at the interdisciplinary crossroads of physics, biology, chemistry, and
computer science. Memory connotes the ability to encode, access, and erase
signatures of past history in the state of a system. Once the system has
completely relaxed to thermal equilibrium, it is no longer able to recall
aspects of its evolution. Memory of initial conditions or previous training
protocols will be lost. Thus many forms of memory are intrinsically tied to
far-from-equilibrium behavior and to transient response to a perturbation. This
general behavior arises in diverse contexts in condensed matter physics and
materials: phase change memory, shape memory, echoes, memory effects in
glasses, return-point memory in disordered magnets, as well as related contexts
in computer science. Yet, as opposed to the situation in biology, there is
currently no common categorization and description of the memory behavior that
appears to be prevalent throughout condensed-matter systems. Here we focus on
material memories. We will describe the basic phenomenology of a few of the
known behaviors that can be understood as constituting a memory. We hope that
this will be a guide towards developing the unifying conceptual underpinnings
for a broad understanding of memory effects that appear in materials
Photo-responsive polymeric structures based on spiropyran
Spiropyrans are one of the most popular classes of photochromic compounds that change their optical and structural properties in response to external inputs such as light, protons and metal ions, making them ideal molecules for the fabrication of multifunctional stimuli-responsive materials. Nowadays, the emphasis in polymeric materials incorporating spiropyran units, focuses on the effectiveness of their reversible response to external photonic stimuli. Photo-control of a range of key characteristics for flow systems, such as wettability, permeability, photo-modulation of flow by photo-actuation of valves, photonic control of uptake and release of guests using films and coatings, and colorimetric sensing of various species, are highlighted and discussed
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Synthesis of molybdenum oxide nanoparticles by nanosecond laser ablation
Phothermal therapy (PTT) is one of the most promising techniques to treat cancer. Finding the ideal PTT agent nanomaterial has remained a challenge and has brought the interest of several researchers. In this work, we report the synthesis of molybdenum oxide (MoOx) nanoparticles (NPs), which exhibit absorption in the biological optical window ~840 nm, by using the laser ablation of solids in liquids (LASL) technique with nanosecond (ns) pulses. A Nd:YAG laser was used to synthesize the NPs in deionized (DI) water, free of surfactants or additives, which were optically characterized by absorption spectroscopy and TEM-EDX microscopy. Semi spherical NPs with a suitable average size and shape for potential use as PTT agents were obtained by laser ablation and ablation + fragmentation. The calculated band gap is 3.1 eV, which corresponds to MoO3. Micro-Raman spectroscopy studies determined that these NPs are composed of amorphous molybdenum oxide hydrates (MoO3 · xH2O)
Nanofilament Scaffold For Tissue Regeneration
A scaffold for tissue regeneration is provided. In a preferred embodiment, the scaffold is implantable in a patient in need of nerve or other tissue regeneration and includes a structure which has a plurality of uniaxially oriented nanofibers made of at least one synthetic polymer. Preferably, at least 75% of the nanofibers are oriented within 20 degrees of the uniaxial orientation. The scaffold beneficially provides directional cues for cell and tissue regeneration, presumably by mimicking the natural strategy using filamentous structures during development and regeneration.Georgia Tech Research Corporatio
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