Dynamics of fluid circulation in coupled free and heterogeneous porous domains

Fluid flow in coupled free and porous domain, particularly when the porous medium is heterogeneous, is encountered in many hydro-environmental conditions, e.g., leakage from underground pipe, combined groundwater lake-subsurface interactions. One of the most difficult problems in the study of coupled flow behaviour has been the development of a universally applicable modelling scheme for combining the flow regimes. This is because the free/porous interfacial properties (e.g., shear-stress; velocity slip) that govern the coupled flow behaviour are difficult to determine experimentally under hydro-environmental conditions. On the other hand, the implications of various forms of heterogeneity in the porous media properties can be very different on the fluid-flow behaviour. Difficulties may also arise in direct coupling of the model equations that govern the fluid flow in the individual regions (e.g., Navier-Stokes for free-flow region and the Darcy's equation for the porous flow region). Consequently, models of coupled free and porous flow for hydro-environmental conditions are not very well developed at the moment. While there are some indications that fluids in coupled free and porous domains may circulate (i.e., development of flow cells), there is a lack of appropriate 3D analysis on how heterogeneities in porous media may affect such flow patterns. In this paper, we aim to analyse how porous media heterogeneity affects the dynamics of flow circulation in the porous side of a coupled free and porous domain. For this purpose, we analyse flow patterns in several model domains made up of two porous layers with differing permeabilities. The governing model equations are discretised and solved using the standard finite volume method on a staggered cell-centred mesh. The temporal discretisation is done using the explicit method. An in-house graphical user interface (GUI) has been created specifically to aid in the visualisation of otherwise complex flow patterns. The GUI contains many post-processing options and provides a comprehensive tool for the analysis of hydrodynamics and contaminant motion (not discussed in this paper) in coupled free and porous flow domains. This GUI is described in this paper briefly. The effects of altering the aspect ratio (i.e., multi-scale) of the domain on the coupled flow pattern have also been discussed.     

Automatic and Efficient Human Pose Estimation for Sign Language Videos

We present a fully automatic arm and hand tracker that detects joint positions over continuous sign language video sequences of more than an hour in length. To achieve this, we make contributions in four areas: (i) we show that the overlaid signer can be separated from the background TV broadcast using co-segmentation over all frames with a layered model; (ii) we show that joint positions (shoulders, elbows, wrists) can be predicted per-frame using a random forest regressor given only this segmentation and a colour model; (iii) we show that the random forest can be trained from an existing semi-automatic, but computationally expensive, tracker; and, (iv) introduce an evaluator to assess whether the predicted joint positions are correct for each frame. The method is applied to 20 signing footage videos with changing background, challenging imaging conditions, and for different signers. Our framework outperforms the state-of-the-art long term tracker by Buehler et al. (International Journal of Computer Vision 95:180–197, 2011), does not require the manual annotation of that work, and, after automatic initialisation, performs tracking in real-time. We also achieve superior joint localisation results to those obtained using the pose estimation method of Yang and Ramanan  (Proceedings of the IEEE conference on computer vision and pattern recognition, 2011).     

Some mechanical properties of an epoxy resin system cured with multiple crosslinking agents

Arbitrary cure times and glass transition temperatures are reported for an epoxy resin cocrosslinked by various weight fractions of hexamethylenediamine (HMDA) and m-phenylenediamine (m-PLDA). The glass transition temperatures of the epoxy resin systems studied yielded an excellent fit to an empirical equation developed by Dyvik for copolymers. The cure time parameters were found to be a linear function of the weight fractions of each crosslinking agent present. The mechanical properties of the epoxy resins were measured by an in situ dynamic modulus technique which employed the use of a resin-coated metallic substrate.     

Chlorination of polystyrene

Chlorination of a low molecular weight polystyrene in the α position was studied by following changes in the infrared spectrum, glass transition temperature, and molecular weights of the polymer. The logarithm of the absorbance ratio at 2920 and 1500 cm^?1 as a function of mole per cent chlorination was linear. The glass transition temperatures, determined by use of a differential scanning calorimeter (DSC), were found to obey an equation developed by Dyvik for copolymers. The molecular weight of the chlorinated polystyrene decreased as a function of chlorination.     

Cure rates of some epoxy systems

The property changes of Epon 828 crosslinked by either diethylenetriamine or m-phenylenediamine at several temperatures have been studied by two in situ techniques. The mechanical property changes were followed by continuously monitoring the changes in the fundamental frequency of vibration during cure of a resin-coated substrate acting as a cantilever reed. The disappearance of the reactive epoxy group was followed in situ by continuously monitoring the absorbance of the infrared epoxide band at 915 cm.^?1. Correlation of the two techniques was accomplished by normalizing both the mechanical property and infrared data. The apparent energy of activation was calculated to be 10.4 and 11.4 kcal. /mole, respectively, for the m-phenylenediamine and diethylenetriamine systems by the mechanical technique, and 11.0 kcal./mole for the m-phenylenediamine crosslinked system by the infrared technique.     

Preparation of nano-sized silicon carbide powder using thermal plasma

Nano-sized silicon carbide (SiC) powder was prepared by thermal plasma process using silicon tetrachloride (SiCl₄) and methane (CH₄). The synthesized powder was characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and particle size analyzer. The powder was dominated by β-SiC including some of α-SiC and free carbon species. The quality of the powder was varied with process conditions such as the molar ratio of H/Si and C/Si, and collecting positions. It was known that the conversion to SiC was mainly affected by the addition of hydrogen gas because it promoted the decomposition and reduction of SiCL. CH₄ was easily decomposed to carbon species for the formation of SiC as well as removal of impure oxygen, but excessive carbon suppressed the formation of crystalline SiC and resulted in the solid carbon contamination. The optimum ratio of H/Si was approx. 26 and that of C/Si was 1.1. For collecting positions, the powder collected at the vessel and filter was preferable to that at the reaction tube. The average size of the powder synthesized was estimated to be below 100 nm and uniform in distribution.     

The hitchhiker’s guide to ubicomp: using techniques from literary and critical theory to reframe scientific agendas

Literary criticism places fictional work in historical, social and psychological contexts to offer insights about the way that texts are produced and consumed. Critical theory offers a range of strategies for analysing what a text says and just as importantly, what it leaves unsaid. Literary analyses of scientific writing can also produce insights about how research agendas are framed and addressed. This paper provides three readings of a seminal ubiquitous computing scenario by Marc Weiser. Three approaches from literary and critical theory are demonstrated in deconstructive, psychoanalytic and feminist readings of the scenario. The deconstructive reading suggests that alongside the vision of convenient and efficient ubiquitous computing is a complex set of fears and anxieties that the text cannot quite subdue. A psychoanalytic reading considers what the scenario is asking us to desire and identifies the dream of surveillance without intrusion. A final feminist reading discusses gender and collapsing distinctions between public and private, office and home, family and work life. None of the readings are suggested as the final truth of what Weiser was “really” saying. Rather they articulate a set of issues and concerns that might frame design agendas differently. The scenario is then re-written in two pastiches that draw on source material with very different visions of ubiquitous computing. The Sal scenario is first rewritten in the style of Douglas Adams’ Hitchhiker’s Guide to the Galaxy. In this world, technology is broken, design is poor and users are flawed, fallible and vulnerable. The second rewrites the scenarios in the style of Philip K Dick’s novel Ubik. This scenario serves to highlight what is absent in Weiser’s scenario and indeed most design scenarios: money. The three readings and two pastiches underline the social conflict and struggle more often elided or ignored in the stories told in ubicomp literature. It is argued that literary forms of reading and writing can be useful in both questioning and reframing scientific writing and design agendas.     

Damage Mechanisms and the Mechanical Properties of a Laminated 0/90 Ceramic/Matrix Composite

The tensile properties of a 0/90 laminated CAS matrix composite reinforced with Nicalon fibers have been measured. Some effects of notches have also been explored. Changes in modulus and permanent strain caused by matrix cracking have been measured and compared with available models. For this comparison, independent measurements have been made of the constituent properties and the residual stress. The ultimate tensile strength has also been measured and compared with a global load-sharing model. It is concluded that lower-bound matrix cracking models provide good predictability of the stresses at which various matrix cracking mechanisms first operate. Also, the ultimate tensile strength is found to be consistent with a global load-sharing model, based on the in situ strength properties of the fibers. Conversely, the evolution of matrix cracks at stresses above the lower bound has yet to be adequately modeled. In addition, a need is identified for improved models relating elastic properties and permanent strains to matrix crack spacing.     

Model for the effects of water on the cationic UV-curing of cyclohexyl epoxides

The effect of relative humidity on the photoin-duced curing kinetics of cyclohexyl epoxide and epoxide/polyol coating formulations was investigated in real-time using FTIR spectroscopy. In total, five formulations were used in this study, including a cyclohexyl epoxide without polyol, and four with polyols. The polyol formulations were varied with respect to ratio of epoxide to polyol, and molar functionality of the hydroxyl group. The formulations were exposed to a maximum of seven different relative humidities (6, 16, 20, 30, 51, 62, 75 RH). The curing speed and overall conversion of the epoxy group passed through a maxima for all the formulations. The polyol had an effect on the hydrophilicity of the overall formulation. It was also found that water and polyols had a synergistic effect on the UV-curing kinetics, in effect lowering the relative humidity to achieve a maxima. A model for UV-curing mechanisms at low, medium, and high relative humidity was proposed for both systems with and without the polyols. Part of this work was done at the Polymers and Coatings Dept., North Dakota State University, Fargo, ND 58105. Presented at the 80th Annual Meeting of the Federation of Societies for Coatings Technology, Oct. 30–Nov. 1, 2002, in New Orelans, LA. Dept. of Polymer Engineering, Akron, OH 44325-0301.     

Neutral sterols of sawflies (symphyta): Their relationship to other hymenoptera

To investigate sterol utilization in sawflies, the neutral sterols of four species of sawflies were determined by gas-liquid chromatography and mass spectrometry, and compared to the respective dietary plant material. Cholesterol was the predominant (55–76%) sterol in all species and stages of sawflies examined. Host plants, however, contained primarily sitosterol (50–88%), along with other 24-alkylsterols and only 0.5–5.9% cholesterol, indicating that the sawflies examined are capable of dealkylating the C₂₈ and C₂₉ phytosterols in their diet to cholesterol. Comparative sterol metabolism in Hymenoptera is discussed.