Bio-inspired mechanics of reversible adhesion: Orientation-dependent adhesion strength for non-slipping adhesive contact with transversely isotropic elastic materials

Geckos and many insects have evolved elastically anisotropic adhesive tissues with hierarchical structures that allow these animals not only to adhere robustly to rough surfaces but also to detach easily upon movement. In order to improve Our understanding of the role of elastic anisotropy in reversible adhesion, here we extend the classical JKR model of adhesive contact mechanics to anisotropic materials. In particular, we consider the plane strain problem of a rigid cylinder in non-slipping adhesive contact with a transversely isotropic elastic half space with the axis of symmetry oriented at an angle inclined to the surface. The cylinder is then subjected to an arbitrarily oriented pulling force. The critical force and contact width at pull-off are calculated as a function of the pulling angle. The analysis shows that elastic anisotropy leads to an orientation-dependent adhesion strength which can vary strongly with the direction of pulling. This study may suggest possible mechanisms by which reversible adhesion devices can be designed for engineering applications. (C) 2006 Elsevier Ltd. All rights reserved.

Non linear constitutive models for lattice materials

We use a computational homogenisation approach to derive a non linear constitutive model for lattice materials. A representative volume element (RVE) of the lattice is modelled by means of discrete structural elements, and macroscopic stress-strain relationships are numerically evaluated after applying appropriate periodic boundary conditions to the RVE. The influence of the choice of the RVE on the predictions of the model is discussed. The model has been used for the analysis of the hexagonal and the triangulated lattices subjected to large strains. The fidelity of the model has been demonstrated by analysing a plate with a central hole under prescribed in plane compressive and tensile loads, and then comparing the results from the discrete and the homogenised models. © 2013 Elsevier Ltd.

Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements

Based on thermodynamic principles, we derive expressions quantifying the non-harmonic vibrational behavior of materials, which are rigorous yet easily evaluated from experimentally available data for the thermal expansion coefficient and the phonon density of states. These experimentally- derived quantities are valuable to benchmark first-principles theoretical predictions of harmonic and non-harmonic thermal behaviors using perturbation theory, ab initio molecular-dynamics, or Monte-Carlo simulations. We illustrate this analysis by computing the harmonic, dilational, and anharmonic contributions to the entropy, internal energy, and free energy of elemental aluminum and the ordered compound FeSi over a wide range of temperature. Results agree well with previous data in the literature and provide an efficient approach to estimate anharmonic effects in materials.

Development of an in-situ, non-destructive ultrasonic monitoring technique for solder pastes

This paper concerns the use of a non-destructive ultrasonic technique for characterising the rheological properties of solder paste and specifically, the use of through-mode microsecond ultrasonic pulses for evaluation of viscoelastic properties of paste materials at the molecular level. Ultrasonic techniques are a widely used and a reliable form of non-destructive testing of materials. This is because techniques such as ultrasounds while used for testing or monitoring material properties, has offered immense benefits in applications where access to the sample is restricted or when handling the sample for testing could interfere with the monitoring or analysis process. Very often, this would mean that the measurements taken are not a true representation of the behaviour of the material (due to externally incorporated changes into the material's physical state during the removal or testing process). Ultrasonic based techniques are being increasingly used for quality control and production monitoring functions which requires evaluation of the changes in material properties over wide range of industrial applications such as cement paste quality, plastic/polymer extrusion process, dough, and even sugar content in beverage drinks. In addition, ultrasound techniques are of great interest for their capacity to take rapid measurements in systems which are optically opaque. The viscometer and rheometer are two of the most widely used rheological instruments used in industry for monitoring the quality of solder pastes, during the production and packaging stage. One of the potential limitations of viscometer and rheometer based measurements is that the collection and preparation of the solder paste samples can irreversibly alter the structure and flow behaviour of the sample. Hence the measurement may not represent the actual quality of the whole production batch. Secondly, rheological measurements and the interpretation of rheological data is a very technical and time consuming process, which requires professionally trained R&D personnel. It is for these reasons that materials suppliers (who formulate and produce solder pastes) and solder paste consumers (especially, contract electronics manufacturers) are keen to see the development of simple, easy to use and accurate techniques for the theological characterisation of solder pastes. The results from the work show that the technique can be used by R&D personnel involved in paste formulation and manufacture to monitor the batch-to-batch quality and consistency.

In-situ non-destructive ultrasonic rheology technique for monitoring different lead-free solder pastes for surface mount applications

This paper investigates the application of a non-destructive ultrasonic technique for characterising the rheological properties of solder paste through the use of through-mode microsecond ultrasonic pulses for evaluation of viscoelastic properties of lead-free solder paste containing different types of flux. Ultrasonic techniques offer a robust and reliable form of non-destructive testing of materials where access to the sample is restricted or when sample handling can interfere with the monitoring or analysis process due to externally incorporated changes to the material’s physical state or accidental contamination during the removal or testing process. Ultrasonic based techniques are increasingly used for quality control and production monitoring functions which requires evaluation of changes in material properties for a wide range of industrial applications such as cement paste quality, plastic/polymer extrusion process, dough and even sugar content in beverage drinks. In addition, ultrasound techniques are of great interest for their capability to take rapid measurements in systems which are optically opaque. The conventional industry approach for characterising the rheological properties of suspensions during processing/packaging stage is mainly through the use of viscometer and some through the use of rheometer. One of the potential limitations of viscometer and rheometer based measurements is that the collection and preparation of the solder paste samples can irreversibly alter the structure and flow behaviour of the sample. Hence the measurement may not represent the actual quality of the whole production batch. Secondly, rheological measurements and the interpretation of rheological data is a very technical and time consuming process, which requires professionally trained R&D personnel. The ultrasound technique being proposed provides simple, yet accurate and easy to use solution for the in-situ rheological characterisation of solder pastes which will benefit the materials suppliers (who formulate and produce solder pastes) and solder paste consumers (especially, contract electronics manufacturers). The results from the work show that the technique can be used by R&D personnel involved in paste formulation and manufacture to monitor the batch-to-batch quality and consistency.

Robert George Malcomson Papers, 1790s-2009 (non-inclusive)

Materials related to military and naval operations of the 1812 era, research of the late Robert Malcomson, Canadian author and historian. Materials include photocopies of materials relating to the War of 1812, photographs and detailed research notes Malcomson made regarding his approach to research (mainly found in Series VIII). Materials were originally arranged in binders relating to an area of research or a certain publication. Articles were removed from the binders and placed in folders using original titles from the binders as series or sub-series titles. Articles within the binders were separated by tabs indicating what the article related to in the publication or topic of interest. In order to avoid repetition, the writing on the tab was used for folder titles, as each folder would be a part of the Series under which it was grouped. The tab names could be authors, events, accounts etc. of the War. Series and sub-series titles were derived from the original titles on the binders. Original intellectual order was retained, grouping similar subjects into Series and Sub-series. Dates recorded were the publication dates of the articles; however, if no publication date was present the date of retrieval was used if from an academic database (ex. JSTOR). The black and white photos from various repositories are reproductions of paintings, microfilm etc. on photographic paper. The colour photographs from various repositories are actual photographs. All books donated by Malcomson were integrated into the University’s Special Collections book collection. These volumes are noted at the end of the finding aid under separated materials.

Dr. Stuart D. Scott Papers, 1837-2010 (non-inclusive)

Dr. Stuart D. Scott has written extensively in the fields of prehistory and history. As an archaeologist, he has traveled to some of the most significant sites in the world, including Pompeii, Stonehenge, the Valley of the Kings, Egypt’s pyramids and the Taj Mahal. He spent nine months excavating with the Tikal Project in Guatemala before returning to the University of Arizona where he received a Ph.D. in 1963. He excavated in New Zealand as a Fulbright scholar in 1963-1964. In the fall of 1964, Dr. Scott started a long career in the Anthropology Department of the State University of New York. He taught graduate and undergraduate archaeology courses and continued his archaeological and historical research. In 1979, Scott established the Old Fort Niagara Archaeology in Progress Project at Old Fort Niagara in Youngstown, New York. For many years, he became involved with historical archaeology in western New York. It was during this work that he became interested in the Upper Canada Rebellion of 1837-1838 and its aftermath. Dr. Scott and his wife, Patricia Kay Scott, would use Christmas breaks, summer vacations, and sabbatical years to travel. They were repeatedly lured back to the South Pacific, conducting research in New Zealand, Australia and many of the Micronesian and Polynesian islands. To tell the whole story of the Rebellion and the prison exiles, they traveled extensively in Canada, the United States, England and Tasmania to collect archival research and to experience the scenes of this remarkable narrative. In 2004, Dr. Scott published To the Outskirts of Habitable Creation: Americans and Canadians Transported to Tasmania in the 1840s, which told the story of the men captured, tried, convicted, and exiled as a result of the Rebellion, also called the Patriot War. Other contributions include: • A collaboration with Dr. Charles Cazeau on the book Exploring the Unknown, Great Mysteries Reexamined published by Plenum Press in 1979 • The Patriot Game: New Yorkers and the Canadian Rebellion of 1837-1838, which appeared in New York History, Vol. 68, No.3. 1987 • A Frontier Spirit: The Life of James Gemmell published in Australiasian Canadian Studies, Vol. 25, No. 2 2007 • To the Outskirts of Habitable Creation which appeared in the Friends of the National Archives, Vol. 20, No. 1 2009 • Numerous academic journal publications • Service on conference panels • Various research papers and proposals Before retiring in 1997 and while still a resident of Buffalo, N.Y., Dr. Scott spent considerable time with Brock University President Emeritus James A. Gibson and History Professor Colin Duquemin. The three shared a love of Rebellion history. It was largely because of this connection that Brock University was chosen as the recipient of Dr. Scott’s research materials.

Non-destructive evaluation of photovoltaic materials and solar cells using Photoluminescence

Photoluminescence (PL) spectroscopy is an optical technique that has emerged successful in the field of semiconductor material and device characterization. This technique is quite a powerful one which gives idea about the defect levels in a material, the band gap of the material, composition as well as material quality. Over the recent years it has received an elevation as a mainstream characterization technique. This thesis is an attempt to characterize each individual layer used in a thin film solar cell with special focus on the electrical properties. This will be highly beneficial from the lab as well as industrial point of view because electrical measurements generally are contact mode measurements which tend to damage the surface. As far as a thin film solar cell is concerned, the constituent layers are the transparent conducting oxide (TCO), absorber layer, buffer layer and top electrode contact. Each layer has a specific role to play and the performance of a solar cell is decided and limited by the quality of each individual layer. Various aspects of PL spectroscopy have been employed for studying compound semiconductor thin films [deposited using chemical spray pyrolysis (CSP)] proposed for solar cell application. This thesis has been structured in to seven chapters