Adaptive Physically Based Models in Computer Graphics

One of the major challenges in physically based modelling is making simulations efficient. Adaptive models provide an essential solution to these efficiency goals. These models are able to self‐adapt in space and time, attempting to provide the best possible compromise between accuracy and speed. This survey reviews the adaptive solutions proposed so far in computer graphics. Models are classified according to the strategy they use for adaptation, from time‐stepping and freezing techniques to geometric adaptivity in the form of structured grids, meshes and particles. Applications range from fluids, through deformable bodies, to articulated solids.     

Texturing fluids

We present a novel technique for synthesizing textures over dynamically changing fluid surfaces. We use both image textures as well as bump maps as example inputs. Image textures can enhance the rendering of the fluid by either imparting realistic appearance to it or by stylizing it, whereas bump maps enable the generation of complex micro-structures on the surface of the fluid that may be very difficult to synthesize using simulation. To generate temporally coherent textures over a fluid sequence, we transport texture information, i.e. color and local orientation, between free surfaces of the fluid from one time step to the next. This is accomplished by extending the texture information from the first fluid surface to the 3D fluid domain, advecting this information within the fluid domain along the fluid velocity field for one time step, and interpolating it back onto the second surface -- this operation, in part, uses a novel vector advection technique for transporting orientation vectors. We then refine the transported texture by performing texture synthesis over the second surface using our "surface texture optimization" algorithm, which keeps the synthesized texture visually similar to the input texture and temporally coherent with the transported one. We demonstrate our novel algorithm for texture synthesis on dynamically evolving fluid surfaces in several challenging scenarios.     

Effect of cross-linker length on the thermal and volumetric properties of cross-linked epoxy networks: A molecular simulation study

Volumetric and thermal properties of cross-linked epoxy systems consisting of diglycidyl ether of bisphenol A (DGEBA) and poly(oxypropylene) (POP) diamines of four different lengths ranging from 3 to 68 units were investigated by molecular dynamics (MD) simulations. The cross-linked structures were built by using the simulated annealing polymerization approach. The density, coefficients of volume thermal expansion and glass transition temperature (T_g) of each of the four cross-linked epoxy systems were obtained from their volume–temperature behavior. The density obtained in the simulations agreed well with the experimental value, whereas the coefficients of volume thermal expansion were at least 30% lower than their corresponding experimental results. The predicted T_g values were higher than the experimental values due to the considerably faster cooling rates that are used in the simulations. It was observed that an increase in the chain length of the cross-linker POP-diamines led to a larger difference between the predicted and experimental values of T_g. Three different approaches were used to estimate the expected shift in the experimental T_g to higher values had these measurements been made at cooling rates comparable to those used in MD simulations. It is shown that, in general, the T_g values obtained in MD simulations are consistent with such shifted T_g values that account for the difference in the cooling rates, although no one particular shift approach worked well for all four epoxy systems studied.     

Effects of chondrogenic and osteogenic regulatory factors on composite constructs grown using human mesenchymal stem cells, silk scaffolds and bioreactors.

Human mesenchymal stem cells (hMSCs) isolated from bone marrow aspirates were cultured on silk scaffolds in rotating bioreactors for three weeks with either chondrogenic or osteogenic medium supplements to engineer cartilage- or bone-like tissue constructs. Osteochondral composites formed from these cartilage and bone constructs were cultured for an additional three weeks in culture medium that was supplemented with chondrogenic factors, supplemented with osteogenic factors or unsupplemented. Progression of cartilage and bone formation and the integration between the two regions were assessed by medical imaging (magnetic resonance imaging and micro-computerized tomography imaging), and by biochemical, histological and mechanical assays. During composite culture (three to six weeks), bone-like tissue formation progressed in all three media to a markedly larger extent than cartilage-like tissue formation. The integration of the constructs was most enhanced in composites cultured in chondrogenic medium. The results suggest that tissue composites with well-mineralized regions and substantially less developed cartilage regions can be generated in vitro by culturing hMSCs on silk scaffolds in bioreactors, that hMSCs have markedly higher capacity for producing engineered bone than engineered cartilage, and that chondrogenic factors play major roles at early stages of bone formation by hMSCs and in the integration of the two tissue constructs into a tissue composite.     

An adaptive neuro-fuzzy and NSGA-II-based hybrid approach for modelling and multi-objective optimization of WEDM quality characteristics during machining titanium alloy

Neural Computing and Applications - In this paper, an intelligent approach of adaptive neuro-fuzzy inference system (ANFIS) and non-dominated sorting genetic algorithm-II (NSGA-II) was delineated...     

Investigation of flow boiling in horizontal tubes: Part I—A new diabatic two-phase flow pattern map

Several important modifications to the flow pattern map of Kattan-Thome-Favrat [J. Heat Transfer 120(1) (1998) 140-147] made, resulting in a significantly new version of the map. Based on the dynamic void fraction measurements described in [Int. J. Multiphase Flow 30 (2004) 125-137], the stratified-wavy region has been subdivided into three subzones: slug, slug/stratified-wavy and stratified-wavy. Furthermore, annular-to-dryout and dryout-to-mist flow transition curves have been added and integrated into the new flow pattern map, identified by distinct trends of the heat transfer coefficient as a function of vapor quality and by flow pattern observations to determine (and then predict) the inception and completion of dryout in horizontal tubes.     

Synthesis of hydrophilic to superhydrophobic SU8 surfaces

In published literature, it is widely reported that the plasma treatment and funtionalization with Octadecyltrichlorosilane (OTS) self‐assembled monolayer (SAM) can individually alter the wetting properties of SU8 surface. A combination of the two approaches gives better results and the synergism of the two approaches produces a superhydrophobic SU8 surface, which is presented in this work. We have investigated various composition of plasma for treatment of SU8 surfaces and permuted the treated SU8 surfaces with deposition of OTS SAM. In all such synergized experiments, we obtained water contact angle higher than 150°, which is much higher than the one that can be obtained with individual application of the two approaches. The combined approach presented in this work is suitable for bulk production of superhydrophobic surface, and is a mask‐less process, which makes it cost effective. The surface topography, wetting, and chemical properties of SU8 surfaces were characterized using the contact angle goniometry, atomic force microscopy, FTIR, Raman, and XPS spectra. The superhydrophobic SU8 surfaces were observed to be stable even after five months. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41934.     

Quantitative phase imaging of nanoscale electrostatic and magnetic fields using off-axis electron holography

Off-axis electron holography in the transmission electron microscope is a powerful interferometric technique that enables electrostatic and magnetic fields to be imaged and quantified with spatial resolution often approaching the nanometer scale. Here, we demonstrate the capabilities of the technique for phase quantification at the nanoscale by briefly reviewing some of our recent studies of nanostructured materials. Examples that are described include determination of the electrostatic potential profiles associated with doped Si- and GaAs-based semiconductor devices, measurement of hole accumulation in Ge quantum dots, mapping of polarization fields in III-nitride heterostructures, and observation of the remanent states and reversal mechanisms of lithographically patterned magnetic nanorings. Some issues associated with sample preparation for doped semiconductor heterostructures are also briefly discussed.     

Quantum information processing in localized modes of light within a photonic band-gap material

Abstract

The single photon occupation of a localized field mode within an engineered network of defects in a photonic band-gap (PBG) material is proposed as a unit of quantum information (qubit). Qubit operations are mediated by optically-excited atoms interacting with these localized states of light as the atoms traverse the connected void network of the PBG structure. We describe conditions under which this system can have independent qubits with controllable interactions and very low decoherence, as required for quantum computation.