160 research outputs found
Advanced Manufacturing from Macro- to Nanoscale: Impact and Shock Loading
No full textTrends and developments in advanced manufacturing from macro- to nanoscale, mainly associated with nanotechnology, precision/ultraprecision manufacturing and advanced materials under low/high speed impact and shock loading, with industrial applications to net-shape manufacturing, biomedical engineering, energy and transport, an outcome of the very extensive work over 40 years on these fields performed by the author and his research international team, are briefly outlined in the present Plenary Lecture of the 5th ESHP 2016 Symposium.</jats:p
Advanced Manufacturing under Shock
No full textSome recent trends and developments in advanced manufacturing of advanced materials from macro-to nanoscale subjected to shock loading, i.e. the up-to-date very important engineering area from industrial, research and academic points of view, with industrial applications to net-shape manufacturing, bioengineering, energy and safety, an outcome of the very extensive, over 40 years, work on this field performed by the author and his research international team, are briefly outlined.</jats:p
Motivations and Cognitive Structures of Consumers in their Purchasing of Functional Foods
No full textThe present study initially fulfils a two-fold aim: first, to identify the functional foods most frequently purchased by a homogeneous group of well-educated consumers; and second, to define the most important functional food attributes that affect consumers’ purchasing decisions when examined in two separate age groups (young adults and early-middle-aged). By employing the MEC analysis methodology, the study further fulfils two additional aims: third, to obtain insights into the functional food-related buying motives of consumers; and fourth, to design a MEC hierarchy of consumption-relevant cognitive structures per age group in order to explain their functional food-related purchasing behaviour. The results of the study highlight health enhancement and health risk prevention through appropriate dietary choices as the most important motives of functional food purchasing for the two age groups, respectively. A special interest in eating enjoyment that results from functional food consumption and in trust that must surround those foods also emerge from both age groups. Moreover, some differences among the two age groups are prominent, such as that the early-middle-aged consumers show a great interest in knowing the origin of the functional product; while the young adults emphasize on functional foods’ convenience and (low) price. These results lead to the conclusion that functional foods should deliver their health benefits above and beyond the standard (high) perceived quality required by consumers from any common food product
Peak power reduction algorithms in asymmetric digital subscriber line modems
No full textThesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (leaves 94-96).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.This thesis investigates peak-to-average ratio (PAR) reduction techniques for multicarrier modulation systems, such as discrete multitone (DMT) modems and orthogonal frequency-division multiplexed (OFDM) terrestrial broadcast transmitters. Through simulation and test implementation on a state-of-the-art programmable ADSL development platform, this thesis pursues a suitable solution for minimizing PAR given the resources of a programmable platform. This solution is integrated as a prototype implementation into a fully-functional ADSL modem and optimized for maximum PAR reduction performance within modem complexity constraints.by Athanasios Dimitri Dousis.M.Eng
Microstructural Magnetic Characterization of Annealed Non-Oriented Electrical Steel
No full textThe present paper investigates the utilization of the magnetic Barkhausen noise and magnetic permeability methods for the nondestructive characterization of annealed non-oriented electrical steel samples which were isothermally annealed in a wide range of temperatures (400°C – 950°C) and subsequently cooled in air. The resulting magnetic properties were compared with the microstructural changes occurring during annealing.</jats:p
Assessing the Distributional Impacts of Transferable Pollution Permits: The Case of Phosphorus Pollution Management at a River Basin Scale
No full textAlthough the initial allocation of pollution permits is neutral in terms of efficiency, it does have a significant impact on distributive equity. In this paper, we examine the two main categories of permit allocation rules, the distributive and the reductive, for controlling phosphorus pollution in a small catchment in South West England. Based on the premise that the regulatory choice compromises efficiency and equity, the main result of this paper is that an allocation of permits in proportion to the intensity of environmental preferences is a “win-win†choice. The reason is that it simultaneously achieves two goals. First, it is efficient (or cost-effective) since a permit system achieves a prespecified target at a minimum abatement cost, while second, it is the only allocation rule which reduces the income inequality of the baseline scenario.pollution permits, phosphorus, nutrient management, export coefficient model, water quality, distributive justice, income inequality, Atkinson Index, Environmental Economics and Policy,
Optical breakdown acoustics : transduction and sensing underwater
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 191-199).In the sea, infrastructures such as ships, pipelines, and wind turbines are exposed to harsh conditions that can wear down the structures through wave loading and corrosion. Because of these wear mechanisms, maritime structures require regular inspections to identify early signs of damage or fatigue. Currently, inspections are performed visually or with contact acoustic transducers, often by a human diver. However, these methods are slow and costly, and can be hindered by surface irregularities like biofouling. Therefore, new sensing techniques are needed to meet the rising demand for offshore infrastructure monitoring. In this thesis, I develop optical breakdown as an acoustic source for non-contact measurements of underwater structures. Optical breakdown occurs when a high-power laser is focused to a small spot, causing nonlinear interactions between the light and water. A compact plasma forms at the focus and expands explosively, radiating a loud, broadband pressure wave.Since this source is compact, laser-controlled and broadband, it provides unique sensing capabilities that overcome challenges faced by traditional transducers. First, I demonstrate how the breakdown source can be used to remotely measure the internal properties of submerged plates. The source is used to excite leaky Lamb waves in the plates, and broadband elastic dispersion spectra are measured using hydrophones in the water. The dispersion spectra are used to calculate the thicknesses and sound speeds in aluminum, steel, bronze and glass plates of varying thickness. Second, I characterize how the source can be controlled and scaled up by combining acoustic measurements with high-speed images of the breakdown plasma. In general, breakdown produces a loud (>100kPa at 10cm), ultra-broadband (5kHz-5MHz) source, whose characteristics depend on measurement orientation and laser properties.This transduction behavior is explained by modeling the breakdown plasma as an array of laser-driven explosions. When the laser is tightly focused, the plasma is compact, producing a loud and omnidirectional signal. However, for weak focusing and high energies, the plasma lengthens and becomes erratic, producing a weaker signal with less consistent behavior. These results reveal design challenges, tradeoffs and opportunities when adapting the breakdown source for dierent applications.by Athanasios G. Athanassiadis.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineerin
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