Microstructure–Property Correlations in Industrial Thermal Barrier Coatings

This paper describes the results from multidisciplinary characterization/scattering techniques used for the quantitative characterization of industrial thermal barrier coating (TBC) systems used in advanced gas turbines. While past requirements for TBCs primarily addressed the function of insulation/life extension of the metallic components, new demands necessitate a requirement for spallation resistance/strain tolerance, i.e., prime reliance, on the part of the TBC. In an extensive effort to incorporate these TBCs, a design-of-experiment approach was undertaken to develop tailored coating properties by processing under varied conditions. Efforts focusing on achieving durable/high-performance coatings led to dense vertically cracked (DVC) TBCs, exhibiting quasi-columnar microstructures approximating electron-beam physical-vapor-deposited (EB-PVD) coatings. Quantitative representation of the microstructural features in these vastly different coatings is obtained, in terms of porosity, opening dimensions, orientation, morphologies, and pore size distribution, by means of small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) studies. Such comprehensive characterization, coupled with elastic modulus and thermal conductivity measurements of the coatings, help establish relationships between microstructure and properties in a systematic manner.     

Hybrid Thermoelectric–Photovoltaic Generators in Wireless Electroencephalography Diadem and Electrocardiography Shirt

Hybrid wearable energy harvesters consisting of a thermoelectric generator (TEG) and photovoltaic (PV) cells are used in this work for powering two autonomous medical devices: an electroencephalography (EEG) system and an electrocardiography (ECG) system in a shirt. Two alternative solutions for powering the systems have been implemented. In the battery-free EEG diadem, PV cells cover the outer surface of radiators used in a TEG. In the ECG shirt, thermoelectric modules are the main power supply that constantly recharges a battery, while PV cells are used mainly to provide standby power, i.e., when the shirt is not worn. Both devices are maintenance free for their entire service life.     

Two-step biodiesel production from Jatropha curcas crude oil using SiO2·HF solid catalyst for FFA esterification step

A high quality biodiesel was produced from Mexican Jatropha curcas crude oil (JCCO) by a two step catalyzed process. The free fatty acids (FFA) were first esterified with methanol, catalyzed by a solid catalyst: SiO₂ pretreated with HF. The catalyst showed a high number of Lewis acid surface sites, and no CO₂ or H₂O adsorption activity. This catalyst showed a high FFA esterification activity and high stability. After 30 esterification runs, the catalyst activity remained unchanged. During the second step, the triglycerides present in the JCCO were transesterified with methanol catalyzed by NaOH. The chromatographic analysis of the biodiesel obtained, revealed that the process proposed in this investigation led to a very high quality biodiesel, meeting the international requirements for its utilization as a fuel. The combustion gas emissions of the JCCO biodiesel were studied by FTIR spectroscopy using a laboratory combustor. These preliminary results showed low amounts of aromatic and sulfur containing compounds. However, halogenated compounds and dicyclopentadiene were also detected at the combustor exhaust.     

Heat transport in structured packings with co-current downflow of gas and liquid

Improvements in catalyst activity make the heat transport in fixed bed reactors increasingly important. Structured packings operated in two-phase flow are expected to outperform randomly packed beds, but heat transfer data on structured packings is scarce. In this work structured packings such as OCFS (Open Cross Flow Structures), CCFS (Closed Cross Flow Structures), knitted wire, and foam were characterised with respect to the heat transfer performance. A dedicated set-up was designed and built which enabled us to measure the heat transfer rates in two-phase flow at ambient pressure in the absence of reaction. Benchmarking and set-up validation was carried out using glass beads. The structured packings—especially OCFS and CCFS—show heat transfer coefficients that are superior over those of glass beads, at lower energy dissipation.     

Organisations going virtual

This paper deals with the different meanings given to the concept of virtual organisation. A typology developed by Campbell, consisting of four forms of virtual organisation, is presented. We illustrate this categorisation with practical examples. We will explain why we use the term virtual organising rather than virtual organisation. Our conclusion is that organisations planning to go virtual have to make technological and organisational decisions that are intertwined at a strategic level, resulting in a specific sociotechnical configuration of virtual organising.     

Understanding the formative stage of technological innovation system development: The case of natural gas as an automotive fuel

This study contributes to insights into mechanisms that influence the successes and failures of emerging energy technologies. It is assumed that for an emerging technology to fruitfully develop, it should be fostered by a Technological Innovation System (TIS), which is the network of actors, institutions and technologies in which it is embedded. For an emerging technology a TIS has yet to be built up. This research focuses on the dynamics of this build-up process by mapping the development of seven key activities: so-called system functions. The main contribution revolves around the notion of cumulative causation, or the phenomenon that the build-up of a TIS accelerates due to system functions reinforcing each other over time. As an empirical basis, an analysis is provided of the historical development of the TIS around automotive natural gas technology in the Netherlands (1970–2007). The results show that this TIS undergoes a gradual build-up in the 1970s, followed by a breakdown in the 1980s and, again, a build-up from 2000 to 2007. It is shown that underlying these trends are different forms of cumulative causation, here called motors of innovation. The study provides strategic insights for practitioners that aspire to support such motors of innovation.     

Posture-based motion planning: Applications to grasping.

This article describes a model of motion planning instantiated for grasping. According to the model, one of the most important aspects of motion planning is establishing a constraint hierarchy—a set of prioritized requirements defining the task to be performed. For grasping, constraints include avoiding collisions with to-be-grasped objects and minimizing movement-related effort. These and other constraints are combined with instance retrieval (recall of stored postures) and instance generation (generation of new postures and movements to them) to simulate flexible prehension. Dynamic deadline setting is used to regulate termination of instance generation, and performance of more than one movement at a time with a single effector is used to permit obstacle avoidance. Old and new data are accounted for with the model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biometric perils and patches

Biometrics authentication offers many advantages over conventional authentication systems that rely on possessions or special knowledge. With conventional technology, often the mere possession of an employee ID card is proof of ID, while a password potentially can be used by large groups of colleagues for long times without change. The fact that biometrics authentication is non-repudiable (hard to refute) and, yet, convenient, is among its most important advantages. Biometrics systems, however, suffer from some inherent biometrics-specific security threats. These threats are mainly related to the use of digital signals and the need for additional input devices, though we also discuss brute-force attacks of biometrics systems. There are also problems common to any pattern recognition system. These include “wolves” and “lambs”, and a new group we call “chameleons”. An additional issue with the use of biometrics is the invasion of privacy because the user has to enroll with an image of a body part. We discuss these issues and suggest some methods for mitigating their impact.     

Generating cancelable fingerprint templates

Biometrics-based authentication systems offer obvious usability advantages over traditional password and token-based authentication schemes. However, biometrics raises several privacy concerns. A biometric is permanently associated with a user and cannot be changed. Hence, if a biometric identifier is compromised, it is lost forever and possibly for every application where the biometric is used. Moreover, if the same biometric is used in multiple applications, a user can potentially be tracked from one application to the next by cross-matching biometric databases. In this paper, we demonstrate several methods to generate multiple cancelable identifiers from fingerprint images to overcome these problems. In essence, a user can be given as many biometric identifiers as needed by issuing a new transformation "key". The identifiers can be cancelled and replaced when compromised. We empirically compare the performance of several algorithms such as Cartesian, polar, and surface folding transformations of the minutiae positions. It is demonstrated through multiple experiments that we can achieve revocability and prevent cross-matching of biometric databases. It is also shown that the transforms are noninvertible by demonstrating that it is computationally as hard to recover the original biometric identifier from a transformed version as by randomly guessing. Based on these empirical results and a theoretical analysis we conclude that feature-level cancelable biometric construction is practicable in large biometric deployments     

Positive Affect as Implicit Motivator: On the Nonconscious Operation of Behavioral Goals.

Recent research has revealed that nonconscious activation of desired behavioral states--or behavioral goals--promotes motivational activity to accomplish these states. Six studies demonstrate that this nonconscious operation of behavioral goals emerges if mental representations of specific behavioral states are associated with positive affect. In an evaluative-conditioning paradigm, unobtrusive linking of behavioral states to positive, as compared with neutral or negative, affect increased participants' wanting to accomplish these states. Furthermore, participants worked harder on tasks that were instrumental in attaining behavioral states when these states were implicitly linked to positive affect, thereby mimicking the effects on motivational behavior of preexisting individual wanting and explicit goal instructions to attain the states. Together, these results suggest that positive affect plays a key role in nonconscious goal pursuit. Implications for behavior-priming research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)