A heater made from graphite composite material for potential deicing application

A surface heater was developed using a graphite fiber-epoxy composite as the heating element. This heater can be thin, highly electrically and thermally conductive, and can conform to an irregular surface. Therefore it may be used in an aircraft's thermal deicing system to quickly and uniformly heat the aircraft surface. One-ply of unidirectional graphite fiber-epoxy composite was laminated between two plies of fiber glass-epoxy composite, with nickel foil contacting the end portions of the composite and partly exposed beyond the composites for electrical contact. The model heater used brominated P-100 fibers from Amoco. The fiber's electrical resistivity, thermal conductivity and density were 50 micro ohms per centimeter, 270 W/m-K and 2.30 gm/cubic cm, respectively. The electricity was found to penetrate through the composite in the transverse direction to make an acceptably low foil-composite contact resistance. When conducting current, the heater temperature increase reached 50 percent of the steady state value within 20 sec. There was no overheating at the ends of the heater provided there was no water corrosion. If the foil-composite bonding failed during storage, liquid water exposure was found to oxidize the foil. Such bonding failure may be avoided if perforated nickel foil is used, so that the composite plies can bond to each other through the perforated holes and therefore lock the foil in place

Design and Fabrication of Components with Optimized Lattice Microstructures

The design and fabrication of components with optimized lattice microstructures is a new approach to creating lightweight high-performance objects. This paper introduces a unique and complete integration of design and fabrication leading to the creation of structural components with complex composite microstructures. Rather than a solid cast component with optimized outer shape this new approach leads to a component with an inner skeleton or microstructure maximizing one or more properties such as the stiffness-to-weight ratio. Three dimensional gradient materials are a natural outcome of this approach. An introduction to the design optimization and hybrid fabrication approach will be provided in addition to research progress and challenges through Spring 2004.Mechanical Engineerin

Comparison of primordial tensor power spectra from the deformed algebra and dressed metric approaches in loop quantum cosmology

Loop quantum cosmology tries to capture the main ideas of loop quantum gravity and to apply them to the Universe as a whole. Two main approaches within this framework have been considered to date for the study of cosmological perturbations: the dressed metric approach and the deformed algebra approach. They both have advantages and drawbacks. In this article, we accurately compare their predictions. In particular, we compute the associated primordial tensor power spectra. We show -- numerically and analytically -- that the large scale behavior is similar for both approaches and compatible with the usual prediction of general relativity. The small scale behavior is, the other way round, drastically different. Most importantly, we show that in a range of wavenumbers explicitly calculated, both approaches do agree on predictions that, in addition, differ from standard general relativity and do not depend on unknown parameters. These features of the power spectrum at intermediate scales might constitute a universal loop quantum cosmology prediction that can hopefully lead to observational tests and constraints. We also present a complete analytical study of the background evolution for the bouncing universe that can be used for other purposes.Comment: 15 pages, 7 figure

Service substitution : a behavioral approach based on Petri Nets

Service-Oriented Computing is an emerging computing paradigm that supports the modular design of (software) systems. Complex systems are designed by composing less complex systems, called services. Such a (complex) system is a distributed application often involving several cooperating enterprises. As a system usually changes over time, individual services will be substituted by other services. Substituting one service by another one should not affect the correctness of the overall system. Assuring correctness becomes particularly challenging, as the services rely on each other, and each of the involved enterprises only oversees a part of the overall system. In addition, services communicate asynchronously which makes the analysis even more difficult. For this reason, formal methods to support service substitution are indispensable. In this thesis, we study service substitution at the level of service models. Thereby we restrict ourselves to service behavior. As a formalism to model service behavior, we use Petri nets. The first contribution of this thesis is the definition of several substitutability criteria that are suitable in the context of Service-Oriented Computing. Substituting a service S by a service S0 should preserve some behavioral properties of the overall system. For each set of behavioral properties and a given service S, there exists a set of behaviorally compatible services for S. A substitutability criterion defines which of these behaviorally compatible services of S have to be preserved by S0. We relate our substitutability criteria to preorders and equivalences known from process theory. The second contribution of this thesis is to present, for each substitutability criterion, a procedure to decide whether a service S0 can substitute a service S. The decision requires the comparison of the in general infinite sets of behaviorally compatible services for the services S and S0. Hence, we extend existing work on an abstract representation of all behaviorally compatible services for a given service. For each notion of behavioral compatibility, we present an algorithmic solution to represent all behaviorally compatible services. Based on these representations, we can decide substitutability of a service S by a service S0. The third contribution of this thesis is a method to support the design of a service S0 that can substitute a service S according to a substitutability criterion. Our approach is to derive a service S0 from the service S by stepwise transformation. To this end, we present several transformation rules. Finally, we formalize and we extend the equivalence notion for services specified in the language WS-BPEL. That way, we demonstrate the applicability of our work

A Study of Macrophages in the Aging Liver and in the Host Response to Engineered Lung Scaffolds

Macrophages are innate immune cells that contribute to tissue remodeling and homeostasis, respond to foreign antigens, and regulate the recruitment and activation of auxiliary immune cells. In chronic disease or a foreign body reaction, macrophages drive inflammation, leading to tissue damage and fibrosis. As such, understanding the developmental and phenotypic diversity of macrophages is of interest in both the pathobiology of disease as well as the design of novel therapeutics and materials. This dissertation examines macrophage biology in two contexts: the aging liver and the host response to engineered lung scaffolds. The liver contains two subsets of macrophages: a stable population of embryonically-derived Kupffer cells and a transient population of monocyte-derived macrophages. The dynamics of hepatic macrophages during the process of aging is unknown and may influence the development of chronic liver disease. Studies presented here demonstrate an increase in hepatic macrophages from naturally aged (19-months-old) mice compared to young counterparts (3-months-old). Macrophages from aged livers express significantly greater amounts of CD11b surface antigen and upregulate arginase strongly after exposure to interleukin-4, suggesting monocytic origins and a predisposition towards an alternatively activated phenotype. Aged livers also exhibit increased triglycerides and pro-inflammatory signals, including monocyte chemoattractant protein (MCP-1). Inhibiting MCP-1 signaling reduced lipids and inflammation but did not significantly alter the macrophage population. Additional methods to modulate hepatic macrophages remain to be studied in the context of age-associated pathologies. Following implantation of biomaterials, macrophages are recruited and polarize to a classical or alternatively activated phenotype, which can influence the outcome of the foreign body response. A positive outcome is associated with reduced inflammation and is crucial for the success of animal-derived organs to be used for xenotransplantation. Studies presented herein demonstrate that the removal of the foreign Gal-epitope from decellularized porcine lung scaffolds improves the host response in non-human primates, in part by reducing CD86 expression on macrophages and preventing substantial adaptive immune recognition upon reimplantation. Taken together, these studies further the understanding of macrophage biology in the aging liver and in the host response to Gal-epitopes and demonstrate novel strategies to reduce inflammation in chronic disease and tissue engineering contexts

Teaching Ethical Reflexivity in Information Systems: How to Equip Students to Deal With Moral and Ethical Issues of Emerging Information and Communication Technologies

Teaching ethics to students of information systems (IS) raises a number of conceptual and content-related issues. The present paper starts out by developing a conceptual framework of moral and ethical issues that distinguishes between moral intuition, explicit morality, ethical theory and meta-ethical reflection. This conceptual framework demonstrates the complexity of the field and can be used to categorize different concerns and discourses. The paper then proceeds to discuss ethical issues that can be expected to arise from novel developments in information and communication technologies. These give rise to a set of recommendations, which are aimed at policy makers as well as ICT industry and professionals. The paper concludes by suggesting that the task of IS education is to develop ethical reflexivity in students. Such reflexivity will be required to provide the conceptual complexity and intellectual openness that will be needed to react appropriately to novel challenges