Effects of disciplinary uncertainty on multi-objective optimization in aircraft conceptual design

The problem of aircraft sizing during conceptual design is characterized by limited knowledge and high uncertainty. Uncertainty is especially prevalent in the early-phase estimates of design characteristics from the aerodynamics, propulsion, and weights discipline areas. In order to develop effective conceptual designs that are robust and fare well in later program phases, trade space exploration and optimization should favor design choices that are both ??balanced?? in terms of the multiple performance objectives and resistant to system-level losses due to missed targets for disciplinary metrics. This paper presents a study of the effects of uncertainty in multi-objective optimization in aircraft conceptual design by demonstrating the changes in the Pareto frontiers due to variability in disciplinary metrics and differences in the formulation of the probabilistic optimization problem. By analyzing these frontiers, the decision maker can judge the tradeoff between expected performance and resistance to uncertainty and can identify regions of the design space where this tradeoff is either favorable or high risk, resulting in improved decision making. To enable this analysis, multi-objective optimization and visualization techniques are tailored to the problem by incorporating Monte Carlo methods and other mechanisms of quantitatively capturing the effects of uncertainty.     

Intuitive Expertise and Perceptual Templates

We provide the first demonstration of an artificial neural network encoding the perceptual templates that form an important component of the high level strategic understanding developed by experts. Experts have a highly refined sense of knowing where to look, what information is important and what information to ignore. The conclusions these experts reach are of a higher quality and typically made in a shorter amount of time than those of non-experts. Understanding the manifestation of such abilities in terms of both the psychology of expert performance and the underlying neural mechanisms constitutes one of the most challenging problems in the cognitive sciences. Using perceptual templates we show how the amount of contextual information can change significantly even within a given task, the relationship between local and non-local contexts and finally why there is very little correlation between measures of intelligence and level of expertise in many of the most complex tasks performed by humans.     

Interfacial Reaction Between Nb Foil and n-Type PbTe Thermoelectric Materials During Thermoelectric Contact Fabrication

PbTe is a high-conversion-efficiency thermoelectric (TE) material that is commonly used in space exploration applications. Integration of PbTe in TE devices has a significant impact on the conversion efficiency and reliability of TE devices. Hence, our effort focuses on developing novel approaches for bonding metallic contacts to PbTe to improve device performance and reliability. In this study, pure Nb foil was directly bonded to PbTe-based TE materials to fabricate the hot-side contacts of TE elements using a rapid hot-press. The materials were sintered at 700°C under pressure of 40 MPa for various holding times. We found that a reaction layer of needle-like Nb₃Te₄ mixed with Pb forms at the interface of the Nb/PbTe joints and that Pb is distributed in the gaps of the Nb₃Te₄ grains. We analyze the resulting microstructure and finally calculate the time exponent of the growth kinetics of the Nb₃Te₄ layer. Fracture surface analysis showed that the Nb/PbTe joint fractures at the interface between Nb and Nb₃Te₄ and within the PbTe matrix, indicating that the bonding between Nb and Nb₃Te₄ is weak.     

Solubility and formation of ternary Widmanstätten precipitates in PbTe in the pseudo-binary PbTe–Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> system

A unidirectional solidification experiment by Bridgman method has been performed for the Pb₁₄Bi_28.8Te_57.2 composition, which lies on the pseudo-binary PbTe–Bi₂Te₃ system, resulting in the formation of Widmanstätten precipitates of a ternary compound, most likely with the structure of PbBi₂Te₄ in the PbTe matrix. The formation of the precipitates is caused by the decrease of bismuth solubility in the PbTe phase with decreasing temperature. The PbTe-rich part of the PbTe–Bi₂Te₃ phase diagram was investigated from the compositional variations in the unidirectionally solidified sample and the diffusion couples. This proved that the solubility decreases with decreasing temperature: 15.6 ± 0.9 (583 °C) to \( 6. 2_{ - 1.7}^{ + 2.1} \) (450 °C) at.% Bi. The orientation relationship between the matrix and precipitates has been examined by electron backscatter diffraction technique; precipitation occurs on {111} habit planes in PbTe with orientation relationship (0001)_precipitate//{111}_PbTe and <11\( \overline{2} \)0>_precipitate//<110>_PbTe. The thermoelectric properties in PbTe with Widmanstätten precipitates as examined by the scanning Seebeck probe method is –46 ± 2 μVK^?1.     

Analytical Framework for the Choice of Dispute Resolution Methods in International Construction Projects Based on Risk Factors

International construction projects provide opportunities for developing countries to advance in the global economy and for international construction and design firms to increase their profit and market share. Despite the attractive opportunities that international construction offers, international contractors are faced with many challenges and difficulties when moving into international markets. Many risks are associated with international construction, whether external or project-specific risks. Those risks affect how contract clauses are written, including the dispute resolution clause. This paper discusses the different dispute resolution methods employed in international construction contracts and develops an analytical framework (DRM-Risk matrix) suggesting the use of specific dispute resolution methods depending on the risks expected in the project. The matrix may eventually help international contractors in the selection of the appropriate dispute resolution method during contract formation depending on the risks involved in a project.     

Model for Faculty, Student, and Practitioner Development in Sustainability Engineering through an Integrated Design Experience

Sustainable development and the green building movement have been adopted faster than any recent movement in the engineering field. With over 40% of the total U.S. energy usage servicing the operation of commercial and residential buildings, this trend is well founded. Recent surveys of the industry indicate that within 4 to 5?years, a vast majority of engineering firms expect their business will be significantly dedicated to green building designs. In contrast, current academic institutions are not well positioned to prepare young engineers for this challenge, and current faculty are not well trained in the tenets of sustainability or the roles of engineers in this movement. Change must occur if the engineering and design professions are to remain relevant and responsive to societal needs. To accommodate this challenge, the writers have designed and implemented the Integrated Design Experience (IDeX), a capstone course in which undergraduate and graduate students interact with faculty and practitioners on real projects with challenging needs in sustainability. The course is designed to provide an actual and virtual space for the multitude of disciplines to interact on real designs to foster both improved research and outreach efforts. Expected outcomes from the course include both student and faculty learning on the methods and value of sustainable design as well as the development of an interdisciplinary network of faculty and practitioners involved in sustainable design. Learning is being evaluated using a continuous authentic assessment of design products. First-year results indicate that students learned interdisciplinary teamwork and communication skills, and they see substantial value in the authentic design experience. In future years, the development of the interdisciplinary network will be tracked by using social networking tools and by assessing faculty attitudes toward involvement in IDeX. Both metrics will be investigated using the diffusions of innovation framework. The combined evaluation will lead to an in-depth understanding of how the IDeX model can be scaled and replicated at other institutions.     

The effects of using ALD-grown ZnO buffer layers on the properties of indium tin oxide grown by chemical solution deposition

In comparison to ITO films prepared by chemical solution deposition on bare substrates, the use of a ZnO buffer layer and Al2O3 barrier layer has been shown to have a significant effect on morphology, measured sheet resistance and therefore resistivity. In the case of quartz substrates, ITO resistivity decreased from 9.6 x 10(-3) ohms cm to 4.3 x 10(-3) ohms cm on incorporation of a ZnO buffer layer and Al2O3 barrier layer, both grown by ALD. A change in surface morphology was observed, due to the presence of the buffer layer, however, the ZnO buffer layer was not found to influence the XRD pattern of the ITO films.     

Development and evaluation of a processing sector model for butter manufacture using a mass balance technique at two dairy processing sites

The butter manufacturing process at two different commercial dairy processing sites in Ireland was evaluated using a mass balance approach to develop, evaluate and validate a processing sector model of the flow of milk fat from intake to final product. The mass balance was represented as a function of fat intake = fat in products + fat losses + recycled fat. Representative samples of all products, namely whole milk, cream, skim milk, butter, buttermilk and cleaning‐in‐place streams (cream silo flush, butter churn residue and sludge), were collected from two different sites. Milk fat levels and product quantities were measured to obtain the fat outputs. Total fat losses at the end of butter production ranged between 1.90% and 2.25% of the total fat input for both sites. Three different scenarios were examined to evaluate the model: S1 (Animal Breed) high genetic merit (Elite) and national average (NA) Holstein Friesian (HF) cows were evaluated, for their effect on the net value of milk; S2 (Product Portfolio) a mixed product portfolio of cheese, butter and skim milk powder (SMP) was compared to a product portfolio comprised of butter alone; and S3 (Process Efficiency) the impact of varying process losses on net values of milk and the quantities of products produced was simulated. The value per 1000 L of milk for S1 was €410.69 and €393.20 for Elite and NA cow’s milk, respectively. For S2, the butter‐only product portfolio returned €355.10, whereas the mixed‐products portfolio returned €369.60. Lastly, S3 corresponding returns for 1%, 2.2% and 5% losses was €365.90, €361.47 and €351.12, respectively.