Fabrication and characterisation of novel Ge MOSFETs

As high-k dielectrics are introduced into commercial Si CMOS (Complimentary Metal Oxide Semiconductor) microelectronics, the 40 year channel/dielectric partnership of Si/SiO2 is ended and the door opened for silicon to be replaced as the active channel material in MOSFETs (Metal Oxide Semiconductor Field Effect Transistor). Germanium is a good candidate as it has higher bulk carrier mobilities than silicon. In addition, Si and Ge form a thermodynamically stable SiGe alloy of any composition, allowing Ge to be implemented as a thin layer on the surface of a standard Si substrate. This thesis is a practical investigation on several aspects of Ge CMOS technology. High-k dielectric Ge p-MOSFETs are electrically characterised. A large variation in interface state densities is demonstrated to be responsible for a threshold voltage shift and this is proportional to reciprocal peak mobility due to the Coulomb scattering of carriers by charged states. A theoretical mobility is fitted to that measured at 4.2 K and confirms that interface states are the main source of interface charged impurities. The model demonstrates a reduction in the interface charged impurity density in p-MOSFETs that underwent a PMA (Post Metallisation Anneal) in hydrogen atmosphere and that the anneal also reduces the RMS (Root Mean Square) dielectric/semiconductor interface roughness, from an average of 0.60 nm to 0.48 nm. High-k strained Ge p-MOSFETs are electrically characterised and have peak mobilities at 300 K (470 cm2 V-1 s-1) and 4.2 K (1780 cm2 V-1 s-1) far in excess of those measured for the unstrained Ge p-MOSFETs (285 cm2 V-1 s-1,785 cm2 V-1 s-1 respectively). Strained Ge n-MOSFETs perform significantly worse than standard Si P, - MOSFETs primarily due to a high source/drain resistance. A 10 nm thick SiGe-01 (On Insulator) layer with a Ge composition of 58% is obtained from a 55 nm Si0_88Ge1o2. initial layer on 100 nm Si-Ol substrate via the germanium condensation technique. For the first time, germanium is demonstrated to diffuse through the BOX (Buried OXide) during Ge-condensation and into the underlying Si substrate. An order of magnitude increase in the calculated ITOX (Internal Thermal OXidation) rate of the BOX in the final stages of Ge-condensation is hypothesised to be responsible for stopping this diffusion

Dynamic modelling and emulation of a high temperature proton exchange membrane fuel cell (HT PEMFC)

Includes bibliographical references (p. 152-157).Fuel cells (FC) are power sources that convert chemical energy into electrical and thermal energy in a clean and efficient manner. In the 21st century, fuel cells appear poised to meet the power demands of a variety of applications, ranging from portable electronics to utility power plants. Compared to systems utilizing fossil fuels, fuel cells offer greater efficiency and superior reliability. In particular, proton exchange membrane FCs (PEMFCs) presents a good alternative energy source for distributed generation (DG) systems. FCs however, have had limited commercial success despite their performance, durability and low environmental impact in comparison to other energy conversion and power generation devices. This lack of success has led to low commercial production levels resulting in high costs. Therefore, an increase in research and development is being conducted with the aim of producing cost effective, more efficient and reliable fuel cells for portable transportation and stationary applications. This dissertation aims to produce an emulator design for a HT PEM FC system. A model is developed that takes into account the steady state and the dynamic characteristics of the fuel cell. The emulator hardware is developed from first principles and tested to evaluate performance under dynamic operating conditions. Phenomena such as polarization curve hysteresis and fuel starvation is investigated, simulated and reproduced with the emulator system. The experimental results are compared with that of an actual HT PEM FC stack and evaluated. It was shown that the final system is able to deliver accurate steady state and transient state outputs when compared with the fuel cell stack. The final design can be used for hardware in the loop applications, specifically for fuel cell power conditioning system development

Reduction of tablet weight variability by optimizing paddle speed in the forced feeder of a high-speed rotary tablet press

Context: Tableting is a complex process due to the large number of process parameters that can be varied. Knowledge and understanding of the influence of these parameters on the final product quality is of great importance for the industry, allowing economic efficiency and parametric release. Objective: The aim of this study was to investigate the influence of paddle speeds and fill depth at different tableting speeds on the weight and weight variability of tablets. Materials and methods: Two excipients possessing different flow behavior, microcrystalline cellulose (MCC) and dibasic calcium phosphate dihydrate (DCP), were selected as model powders. Tablets were manufactured via a high-speed rotary tablet press using design of experiments (DoE). During each experiment also the volume of powder in the forced feeder was measured. Results and discussion: Analysis of the DoE revealed that paddle speeds are of minor importance for tablet weight but significantly affect volume of powder inside the feeder in case of powders with excellent flowability (DCP). The opposite effect of paddle speed was observed for fairly flowing powders (MCC). Tableting speed played a role in weight and weight variability, whereas changing fill depth exclusively influenced tablet weight. Conclusion: The DoE approach allowed predicting the optimum combination of process parameters leading to minimum tablet weight variability. Monte Carlo simulations allowed assessing the probability to exceed the acceptable response limits if factor settings were varied around their optimum. This multi-dimensional combination and interaction of input variables leading to response criteria with acceptable probability reflected the design space

Process monitoring and visualization solutions for hot-melt extrusion : a review

Objectives: Hot-melt extrusion (HME) is applied as a continuous pharmaceutical manufacturing process for the production of a variety of dosage forms and formulations. To ensure the continuity of this process, the quality of the extrudates must be assessed continuously during manufacturing. The objective of this review is to provide an overview and evaluation of the available process analytical techniques which can be applied in hot-melt extrusion. Key Findings: Pharmaceutical extruders are equipped with traditional (univariate) process monitoring tools, observing barrel and die temperatures, throughput, screw speed, torque, drive amperage, melt pressure and melt temperature. The relevance of several spectroscopic process analytical techniques for monitoring and control of pharmaceutical HME has been explored recently. Nevertheless, many other sensors visualizing HME and measuring diverse critical product and process parameters with potential use in pharmaceutical extrusion are available, and were thoroughly studied in polymer extrusion. The implementation of process analytical tools in HME serves two purposes: (1) improving process understanding by monitoring and visualizing the material behaviour and (2) monitoring and analysing critical product and process parameters for process control, allowing to maintain a desired process state and guaranteeing the quality of the end product. Summary: This review is the first to provide an evaluation of the process analytical tools applied for pharmaceutical HME monitoring and control, and discusses techniques that have been used in polymer extrusion having potential for monitoring and control of pharmaceutical HME

Disseminating Broadcast Archives: Exposing WGBH Materials for Scholarly Use

4th International Conference on Open RepositoriesThis presentation was part of the session : Fedora User Group PresentationsDate: 2009-05-21 08:30 AM – 10:00 AMThe WGBH Media Library and Archives is currently prototyping an online archive of moving image content. Funded by The Andrew W. Mellon Foundation, the project seeks to serve scholars in their efforts to incorporate media into their research and communications activities. WGBH Boston is the single greatest producer of programming for PBS. Our archive holds the master copies of television and radio programs dating back to the 1950s. Not only do we hold final programs, we also hold all of the numerous interviews, stock footage, music, producer's notes, and images that went into the making of the films. As these materials are used and re-used, the relationships between assets become increasingly complex. These relationships, however, are vital information necessary for a researcher to interpret and understand our archive. In addition to the complexity of our collection, our project must consider the needs of traditional, text-oriented scholars and the rising generation of "digital natives" for whom content format is not a boundary. To that end, we are incorporating annotation, citation and other workflow tools to facilitate the use of moving images in scholarly work. We are currently prototyping a Fedora-backed online archive incorporating search, browse, data visualization, and web services. We will present the open source infrastructure behind our web project which includes Fedora, Solr and a PHP front end. Our Fedora content model addresses the specific needs of a moving image archive, allowing for the expression of complex relationships between conceptual and instantiated assets. In addition, it allows us to express the myriad permutations and oddities occurring within broadcast asset relationships. We will share lessons learned and new challenges regarding the representation of archival moving image collections online, the unique cataloging and metadata needs of the online researcher, and barriers to the use of online archives by scholarly researchers. Finally, we will cover technical challenges involving storage and delivery of long form video content, rights management, and user authentication and sustainable business models.The Andrew W. Mellon Foundatio

Open Innovation and Knowledge Appropriation in African Micro and Small Enterprises (MSEs)

This article seeks enhanced understanding of the dynamics of open innovation and knowledge appropriation in African settings. More specifically, the authors focus on innovation and appropriation dynamics in African micro and small enterprises (MSEs), which are key engines of productivity on the continent. The authors begin by providing an expansion of an emergent conceptual framework for understanding intersections between innovation, openness and knowledge appropriation in African small-enterprise settings. Then, based on this framework, they review evidence generated by five recent case studies looking at knowledge development, sharing and appropriation among groups of small-scale African innovators. The innovators considered in the five studies were found to favour inclusive, collaborative approaches to development of their innovations; to rely on socially-grounded information networks when deploying and sharing their innovations; and to appropriate their innovative knowledge via informal (and, to a lesser extent, semi-formal) appropriation tools