SST: Integrated Fluorocarbon Microsensor System Using Catalytic Modification

Selective, sensitive, and reliable sensors are urgently needed to detect air-borne halogenated volatile organic compounds (VOCs). This broad class of compounds includes chlorine, fluorine, bromine, and iodine containing hydrocarbons used as solvents, refrigerants, herbicides, and more recently as chemical warfare agents (CWAs). It is important to be able to detect very low concentrations of halocarbon solvents and insecticides because of their acute health effects even in very low concentrations. For instance, the nerve agent sarin (isopropyl methylphosphonofluoridate), first developed as an insecticide by German chemists in 1938, is so toxic that a ten minute exposure at an airborne concentration of only 65 parts per billion (ppb) can be fatal. Sarin became a household term when religious cult members on Tokyo subway trains poisoned over 5,500 people, killing 12. Sarin and other CWAs remain a significant threat to the health and safety of the general public. The goal of this project is to design a sensor system to detect and identify the composition and concentration of fluorinated VOCs. The system should be small, robust, compatible with metal oxide semiconductor (MOS) technology, cheap, if produced in large scale, and has the potential to be versatile in terms of low power consumption, detection of other gases, and integration in a portable system. The proposed VOC sensor system has three major elements that will be integrated into a microreactor flow cell: a temperature-programmable microhotplate array/reactor system which serves as the basic sensor platform; an innovative acoustic wave sensor, which detects material removal (instead of deposition) to verify and quantify the presence of fluorine; and an intelligent method, support vector machines, that will analyze the complex and high dimensional data furnished by the sensor system. The superior and complementary aspects of the three elements will be carefully integrated to create a system which is more sensitive and selective than other CWA detection systems that are commercially available or described in the research literature. While our sensor system will be developed to detect fluorinated VOCs, it can be adapted for other applications in which a target analyte can be catalytically converted for selective detection. Therefore, this investigation will examine the relationships between individual sensor element performance and joint sensor platform performance, integrated with state-of-the-art data analysis techniques. During development of the sensor system, the investigators will consider traditional reactor design concepts such as mass transfer and residence time effects, and will apply them to the emerging field of microsystems. The proposed research will provide the fundamental basis and understanding for examining multifunctional sensor platforms designed to provide extreme selectivity to targeted molecules. The project will involve interdisciplinary researchers and students and will connect to K-12 and RET programs for underrepresented students from rural areas

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

The use of stereolithography and related technologies to produce short run tooling

ThesisWhere material properties are critical to a polymer part, rapid prototype (RP) models are inappropriate for evaluation purposes and actual parts moulded in a range of materials are required for evaluation. Conventional tool making processes have extremely long lead times considering that numerous iterations may be required. The aim of this project was to generate polymer parts, utilising various approaches to Rapid Tooling (RT) , including Stereolithography or related technologies, as part of the process. The objective was to establish decision-making criteria for deciding on the appropriateness of various processes and the risks involved to assist prospective users of these technologies. The first phase of the project focused on the process validation of utilising Stereolithography as a direct means to generate injection mould tooling inserts, which were fitted into an injection mould designed for the trial purposes. The objective was to obtain process information with regard to insert generation for Stereolithography. A three dimensional model of the part was generated with CAD and the associated mould was generated around the part. The insert halves were processed and solid epoxy inserts were generated with the 3D Systems SLA500 Stereolithography machine. These inserts were post-finished and fitted to the injection mould . Additional features were added to the inserts to test cooling and gating and wear resistance of the cavity material. The author attended the basic injection tool setting course of the Plastics Federation to enable him to contribute more directly to this process. This also highlighted some of the design issues to facilitate ease of production . Initial difficulties were experienced in finding optimal process parameters. A total of 70 parts were produced, with measurable insert degradation. During the author's training at 3D Systems in the USA, he obtained additional insight in current methods of insert modelling and insert generation. If these process problems could be overcome, it would be possible to produce in excess of a 100 parts with one set of inserts, assuming a tolerance specification of 0.2mm. The cost of producing the inserts was approximately 50% that of conventional tooling fabrication . The time lapse between growing of the inserts and production of parts was one week compared to 6 to 8 weeks tool manufacture time with conventional methods. The second phase of the project focused on methods to enhance the cavity surface. Electroplating of inserts and inserts generated from Aluminium filled epoxy were tested , to investigate the effects that plating has on tool life, dimensional accuracy, temperature distribution, and the cost implications for these subsequent process steps. Stereolithography inserts were generated, taking into account the design considerations. Aluminium filled epoxy inserts were subsequently cast from silicone moulds drawn off the Stereolithography master patterns. Two sets of Stereolithography inserts were plated with 20 ~m of electrolytic nickel plating. One set of aluminium filled epoxy inserts were plated with electrolytic copper followed by electroless nickel. The mould sets were subjected to the same injection moulding trials using Polypropylene. The third phase of the project evaluated the use of Stereolithography investment casting masters to produce tool steel inserts, through the QuickCast process. Porosity was evident, with substantial machining required to fit the inserts. Not all the detail was retained during the casting process. Thin rib features on the part were thus lost. Due to the porosity the cooling was changed to copper tubes fitted into the rear of the tool and back-filled with aluminium epoxy. As the Stereolithography patterns were not polished the metal inserts had to be hand finished. This was a time consuming process and skill is required to obtain a good finish. A cost comparison indicated that machining aluminium inserts would be more cost effective. The tool manufacture time and eventual cost is not significantly less than conventional machining . In fact, trials with aluminium High speed CNC machining proved to be more time, finish and cost effective. This is discussed as part of the trial examples. Wax injection into AIM tooling was investigated on behalf of a client, with good results . As ceramic and polymer injection are very similar, apart from the ceramic being far more abrasive, it is the author's opinion that AIM tooling would be applicable, taking into account that fewer parts may be achieved. The KelTool process was also investigated during the author's USA visit. The licensing fees and additional equipment are extremely costly due to the Rand IDollar exchange rate. Issues related to this process are documented in this report. Clearly the deciding factors remain the quantity of parts required and the complexity of form. Each manufacturing process has a certain level of risk involved. Accumulative risk not only sets manufactured parts at risk but could jeopardise project time scales and iterations of a process have significant impact on a project budget

Optimisation of surface coverage paths used by a non-contact robot painting system

This thesis proposes an efficient path planning technique for a non-contact optical “painting” system that produces surface images by moving a robot mounted laser across objects covered in photographic emulsion. In comparison to traditional 3D planning approaches (e.g. laminar slicing) the proposed algorithm dramatically reduces the overall path length by optimizing (i.e. minimizing) the amounts of movement between robot configurations required to position and orientate the laser. To do this the pixels of the image (i.e. points on the surface of the object) are sequenced using configuration space rather than Cartesian space. This technique extracts data from a CAD model and then calculates the configuration that the five degrees of freedom system needs to assume to expose individual pixels on the surface. The system then uses a closest point analysis on all the major joints to sequence the points and create an efficient path plan for the component. The implementation and testing of the algorithm demonstrates that sequencing points using a configuration based method tends to produce significantly shorter paths than other approaches to the sequencing problem. The path planner was tested with components ranging from simple to complex and the paths generated demonstrated both the versatility and feasibility of the approach

Finite-Volume Filtering in Large-Eddy Simulations Using a Minimum-Dissipation Model

Large-eddy simulation (LES) seeks to predict the dynamics of the larger eddies in turbulent flow by applying a spatial filter to the Navier-Stokes equations and by modeling the unclosed terms resulting from the convective non-linearity. Thus the (explicit) calculation of all small-scale turbulence can be avoided. This paper is about LES-models that truncate the small scales of motion for which numerical resolution is not available by making sure that they do not get energy from the larger, resolved, eddies. To identify the resolved eddies, we apply Schumann’s filter to the (incompressible) Navier-Stokes equations, that is the turbulent velocity field is filtered as in a finite-volume method. The spatial discretization effectively act as a filter; hence we define the resolved eddies for a finite-volume discretization. The interpolation rule for approximating the convective flux through the faces of the finite volumes determines the smallest resolved length scale δ. The resolved length δ is twice as large as the grid spacing h for an usual interpolation rule. Thus, the resolved scales are defined with the help of box filter having diameter δ= 2 h. The closure model is to be chosen such that the solution of the resulting LES-equations is confined to length scales that have at least the size δ. This condition is worked out with the help of Poincarés inequality to determine the amount of dissipation that is to be generated by the closure model in order to counterbalance the nonlinear production of too small, unresolved scales. The procedure is applied to an eddy-viscosity model using a uniform mesh

Tailoring the etchability of aluminium foil by laser interference metallurgy : control of pit initiation sites for high-voltage aluminium capacitor applications

During the last decades, different surface patterning techniques have been developed to produce structures in the nano/submicron scale, Laser Interference Metallurgy (LIMET) being one of them. LIMET allows the production of direct periodic arrays over large areas by using the interference of several laser beams. This technique is an attractive tool to improve the etching process of anode aluminium during the manufacturing of high-voltage aluminium capacitors, where aluminium foils are etched so as to develop a high surface area thereby achieving the maximum possible capacitance. The aim of this work was to develop a method for controlling the pit-site distribution during the etching process of aluminium foil. For this purpose, the mechanism that governs the surface patterning of metals and the physical/chemical changes induced by LIMET were investigated. It was demonstrated that the main forces producing the periodic structures on metallic surfaces are surface-tension-driven flow and recoil pressure. Moreover, the impact on aluminium etchability of ordered local oxidation and incorporation of small quantities of Pb and Cu was studied. It was found that periodic surface activation and/or passivation improve the pit distribution of the exposed aluminium. In all systems studied, the etching process followed the ordered array generated by laser interference. Finally, 3D quantitative characterisation of etched structures was performed using FIB tomography.In den letzten Jahren wurden verschiedene Oberflächenbehandlungstechniken entwickelt, um Strukturen im Nano/Submikrometer-Bereich zu erzeugen, zu denen auch die Laser Interferenz Metallurgie (LIMET) zählt. LIMET ermöglicht die direkte Erzeugung von periodischen, großflächigen Strukturen durch die Interferenz einzelner Laserstrahlen. Diese Technik stellt ein vielversprechendes Werkzeug dar, um den Ätzprozess der Aluminiumanode für Hochspannungskondensatoren zu verbessern. Bei der Herstellung von Aluminium-Elektrolytkondensatoren werden Aluminiumfolien geätzt, um eine Vergrößerung der Oberfläche herbeizuführen und damit eine deutlich höhe Kapazität zu erzielen. Das Ziel dieser Arbeit ist die Entwicklung eines Verfahrens zur Kontrolle der örtlichen Verteilung der beim Aluminiumätzprozess entstehenden Gruben. Es wurde demonstriert, dass die wichtigsten Effekte bei der Herstellung periodischer Strukturen sowohl der Oberflächenspannungsgradient als auch der Rückstoßdruck sind. Des Weiteren wurden die Auswirkungen von lokaler Oxidation und Einbau geringer Mengen von Pb und Cu auf die Ätzbarkeit von Aluminium untersucht. Es hat sich gezeigt, dass periodische Aktivierung und/oder Passivierung der Oberfläche die Grubenverteilung bei exponiertem Aluminium verbessert. In allen Fällen folgte der Ätzvorgang den durch Laserinterferenz vorgegebenen geordneten Mustern. Schließlich wurden die geätzten Strukturen mittels einer quantitativen 3D FIB-Tomographie charakterisiert

Proceedings of 2006 Kentucky Water Resources Annual Symposium

This symposium was funded in part by the U.S. Environmental Protection Agency, with Clean Water Act, Section 319(h) grant money through the Kentucky Division of Water and the Kentucky Waterways Alliance, #C9994861-00. Planning for this conference was conducted as part of the state water resources research annual program with the support and collaboration of the Department of Interior, U.S. Geological Survey and the University of Kentucky Research Foundation, under Grant Agreement No. 01HQGR0133. The views and conclusions contained in this document are those of the abstract authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government or other symposium organizers and sponsors

The evolution of morphology and fabric of a sand during shearing

Over the past 50 years, experimental studies have repeatedly demonstrated that the mechanical behaviour of sand is sensitive to the material fabric, i.e., the arrangement of the grains. Up until now there have been relatively few attempts to describe quantitatively the fabric of sands. In fact, most of our understanding of the link between the particle movements and interactions and the macro-scale response of granular materials, including sand, comes from discrete element modelling (DEM) and experiments on “analogue” sands with simple, idealized shapes. The aim of this study had been to describe quantitatively the particle morphology and fabric of reals and and their evolution under loading. The material investigated was Reigate sand (from Southeast England), a geologically old sand which, in its intact state, exhibits significant grain interlocking and nobonding. To explore the effects of fabric on the mechanical response of the soil, intact and reconstituted specimens both having similar densities were tested under triaxia lcompression. The specimens were impregnated with an epoxy resin at three different stages of shear deformation and small cores from each specimen were scanned using X-ray micro-tomography. Different systems and scanning parameters were explored in order to obtain three-dimensional high-resolution images with a voxel size of 5μm(0.018d50) and a quality level required for the identification of the individual particles and the surface defining each particle-particle contact.The quantification of particle size and shape has shown that breakage of fractured grains, along existing fissures, occurs both during reconstitution and shearing ofthe intact soil, a phenomenon that cannot be observed using invasive techniques such as sieve analysis. Statistical analyses of the distribution of fabric directional data in terms of particle orientations, contact normals, branch vectors and void orientations were carried out at each loading stage. It has been shown that the initial particle orientation fabric that develops during the deposition of the material tendsto persist during shearing, while the contact normals seem to be reorientated along the direction of the major principal stress in the post-peak regime. Different patterns were observed within the shear band as both the particles and the contact normals appeared to rotate towards the direction of the shear plane. The measurements from the tomographic data were complemented with a qualitative description of the morphology and fabric using SEM and optical microscope images of thin sections