Context guided retrieval

This paper presents a hierarchical case representation that uses a context guided retrieval method The performance of this method is compared to that of a simple flat file representation using standard nearest neighbour retrieval. The data presented in this paper is more extensive than that presented in an earlier paper by the same authors. The estimation of the construction costs of light industrial warehouse buildings is used as the test domain. Each case in the system comprises approximately 400 features. These are structured into a hierarchical case representation that holds more general contextual features at its top and specific building elements at its leaves. A modified nearest neighbour retrieval algorithm is used that is guided by contextual similarity. Problems are decomposed into sub-problems and solutions recomposed into a final solution. The comparative results show that the context guided retrieval method using the hierarchical case representation is significantly more accurate than the simpler flat file representation and standard nearest neighbour retrieval

Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 3: Major component development

Analytical and experimental investigations, performed to establish the feasibility of reinforcing metal aircraft structures with advanced filamentary composites, are reported. Aluminum-boron-epoxy and titanium-boron-epoxy were used in the design and manufacture of three major structural components. The components were representative of subsonic aircraft fuselage and window belt panels and supersonic aircraft compression panels. Both unidirectional and multidirectional reinforcement concepts were employed. Blade penetration, axial compression, and inplane shear tests were conducted. Composite reinforced structural components designed to realistic airframe structural criteria demonstrated the potential for significant weight savings while maintaining strength, stability, and damage containment properties of all metal components designed to meet the same criteria

Fischer-Tropsch synthesis in microchannels

Different metallic supports (aluminum foams of 40ppi, honeycomb monolith and micromonolith of 350 and 1180cpsi, respectively) have been loaded with a 20%Co-0.5%Re/γ-Al2O3 catalyst by the washcoating method. Layers of different thicknesses have been deposited onto the metallic supports. The catalytic coatings were characterized measuring their textural properties, adhesion and morphology. These structured catalysts have been tested in the Fischer-Tropsch synthesis (FTS) and compared with a microchannel block presenting perpendicular channels for reaction and cooling. The selectivity depends on the type of support used and mainly on the thickness of the layer deposited. In general, the C5+ selectivity decreased at increasing CO conversion for all of the systems (powder, monoliths, foams and microchannels block). On the other hand, the selectivity to methane increased with the thickness of the catalytic layer due to the higher effective H2/CO ratio over the active sites resulting from the higher diffusivity of H2 compared with CO in the liquid products filling the pores. The C5+ selectivity of the microchannels reactor is higher than that of the structured supports and the powder catalyst.Ministerio de Ciencia e Innovación MAT2006-12386-C05, ENE2009-14522-C0

Development and fabrication of improved positive expulsion bladders Final progress report

Aluminum foil-Teflon laminates for positive explusion bladder material

Charpy impact toughness of conventional and advanced composite laminates for aircraft construction

A weight-based analysis was made of the translaminar Charpy impact toughness performance of conventional and advanced composite materials for aircraft fabrication. The materials were carbon-epoxy (C-Ep) and hybrid fiber-metal TiGr (Titanium-Graphite) laminates. 5 mm-thick three-point bend specimens were tested over a temperature range of -70 to 180 ºC to reproduce typical in-service conditions of supersonic jetliners. The energies required for the processes of damage initiation (Ei), damage propagation (Ep), and whole fracture (Et = Ei + Ep), were evaluated at two loading rates, namely, 2.25 and 5.52 m/s in an instrumented Charpy impact testing machine. C-Ep laminates with unidirectional fiber tapes arranged in cross-ply architecture consistently showed the best performance in terms of damage initiation toughness, whereas the hybrid fiber-metal laminate TiGr excelled in terms of propagation toughness. On the other hand, the overall performance of bi-directional fabric C-Ep laminates was very disappointing. The impact behavior of composite laminates was substantiated by a qualitative analysis of topographic aspects of fracture surfaces.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Case-Based Reasoning Systems: From Automation to Decision-Aiding and Stimulation

Over the past decade, case-based reasoning (CBR) has emerged as a major research area within the artificial intelligence research field due to both its widespread usage by humans and its appeal as a methodology for building intelligent systems. Conventional CBR systems have been largely designed as automated problem-solvers for producing a solution to a given problem by adapting the solution to a similar, previously solved problem. Such systems have had limited success in real-world applications. More recently, there has been a search for new paradigms and directions for increasing the utility of CBR systems for decision support. This paper focuses on the synergism between the research areas of CBR and decision support systems (DSSs). A conceptual framework for DSSs is presented and used to develop a taxonomy of three different types of CBR systems: 1) conventional, 2) decision-aiding, and 3) stimulative. The major characteristics of each type of CBR system are explained with a particular focus on decision-aiding and stimulative CBR systems. The research implications of the evolution in the design of CBR systems from automation toward decision-aiding and stimulation are also explored

Through-Thickness Reinforcement and Repair of Carbon Fiber Based Honeycomb Structures Under Flexure and Tension of Adhesively Bonded Joints

Repair and reinforcement of composite honeycomb structures is an area of concern as higher demands are being placed on high strength, lightweight structural materials, such as carbon fiber reinforced plastics and corresponding honeycomb structures. A common issue with these structures is when a delamination in the facesheet may form and spread, leading to a failure scenario. An investigation of adding a through thickness reinforcement (TTR) to these structures at the sample level that undergo four-point-bending, tension, and joining methods is conducted throughout this thesis. The embedding of pultruded carbon fiber rods is found to be an ideal addition to composite honeycomb structures, not only in terms of reinforcement but also for repair and damage isolation. Facesheet thickness is found to play and important role in the effectiveness of TTR in four-point-bending. Adhesively bonded joints are tested to failure and the addition of defects and TTR are used to further analyze the potential failures of double lap joints in composite structures and how TTR may help to minimize damage in those scenarios

Cross-laminated strand-veneer composite mass timber panels for building construction

Cross-laminated timber (CLT) is gaining popularity for use in building mid-rise buildings. The variations in grain patterns and growth rings in the wood laminates cause differential shrinking and swelling behavior in CLT, which could result in delamination at the glue line. Additionally, the shear stress acting on the radial-tangential plane perpendicular to grain or rolling shear stress often results in premature failure. Another challenge in mass timber construction using CLT is to protect it from exposure to a high moisture environment and ensure long-term durability. To mitigate these issues, this study proposes to utilize thermally modified wood strands in a commercial autoclave to manufacture cross-laminated strand veneer lumber (CLSVL) that is durable and dimensionally stable. In the first part of the study, wood strands were hydrothermally treated in a closed inert environment with nitrogen gas at various temperatures (165°C, 170°C, and 180°C) and pressures (0.8 MPa and 1.4 MPa) with a constant dwelling time of 120 minutes. It was found that the lower pressure of 0.8 MPa decreased the boiling point of water in a high-temperature environment, which helped to increase the rate of extraction of hemicellulose from the wood resulting in a 35% reduction in equilibrium moisture content (EMC). Similarly, a 38% reduction in thickness swelling at 165°C & 0.8 MPa was obtained for thermally modified (TM) veneers while maintaining mechanical properties, implying a significant improvement in dimensional stability.In the second part of the study, CLSVL manufactured from thermally modified strands (165°C and 0.8MPa for 120 minutes) were evaluated for mechanical and physical properties. No significant differences were observed for effective bending stiffness, shear stiffness, bending resistance, and shear resistance of control and thermally modified (TM) panels. The shear analogy model (SAM) showed good predictions of mechanical properties. Better dimensional stability with a 25% reduction in water absorption and a 59% reduction in thickness swell was observed for TM-CLSVL panels without rolling shear failure for both flexural and shear specimens