Collection and analysis of pre-evacuation time data collected from evacuation trials conducted in library facilities in Brazil

Two evacuation trials were conducted within Brazilian library facilities by FSEG staff in January 2005. These trials represent one of the first such trials conducted in Brazil. The purpose of these evacuation trials was to collect pre-evacuation time data from a population with a cultural background different to that found in western Europe. In total some 34 pre-evacuation times were collected from the experiments and these ranged from 5 to 98 seconds with a mean pre-evacuation time of 46.7 seconds

Fracture mechanics analysis of cracks in solder joint intermetallic compounds

The trend towards miniaturization of electronic products leads to the need for very small sized solder joints. Therefore, there is a higher reliability risk that too large a fraction of solder joints will transform into Intermetallic Compounds (IMCs) at the solder interface. In this paper, fracture mechanics study of the IMC layer for SnPb and Pb-free solder joints was carried out using finite element numerical computer modelling method. It is assumed that only one crack is present in the IMC layer. Linear Elastic Fracture Mechanics (LEFM) approach is used for parametric study of the Stress Intensity Factors (SIF, KI and KII), at the predefined crack in the IMC layer of solder butt joint tensile sample. Contrary to intuition, it is revealed that a thicker IMC layer in fact increases the reliability of solder joint for a cracked IMC. Value of KI and KII are found to decrease with the location of the crack further away from the solder interfaces while other parameters are constant. Solder thickness and strain rate were also found to have a significant influence on the SIF values. It has been found that soft solder matrix generates non-uniform plastic deformation across the solder-IMC interface near the crack tip that is responsible to obtain higher KI and KII.

Uncertainty analysis to minimise risk in designing micro-electronics manufacturing processes

A design methodology based on numerical modelling, integrated with optimisation techniques and statistical methods, to aid the process control of micro and nano-electronics based manufacturing processes is presented in this paper. The design methodology is demonstrated for a micro-machining process called Focused Ion Beam (FIB). This process has been modelled to help understand how a pre-defined geometry of micro- and nano- structures can be achieved using this technology. The process performance is characterised on the basis of developed Reduced Order Models (ROM) and are generated using results from a mathematical model of the Focused Ion Beam and Design of Experiment (DoE) methods. Two ion beam sources, Argon and Gallium ions, have been used to compare and quantify the process variable uncertainties that can be observed during the milling process. The evaluations of the process performance takes into account the uncertainties and variations of the process variables and are used to identify their impact on the reliability and quality of the fabricated structure. An optimisation based design task is to identify the optimal process conditions, by varying the process variables, so that certain quality objectives and requirements are achieved and imposed constraints are satisfied. The software tools used and developed to demonstrate the design methodology are also presented.

Predictive reliability and prognostics for electronic components: current capabilities and future challenges

Future analysis tools that predict the behavior of electronic components, both during qualification testing and in-service lifetime assessment, will be very important in predicting product reliability and identifying when to undertake maintenance. This paper will discuss some of these techniques and illustrate these with examples. The paper will also discuss future challenges for these techniques.

The UK WTC 9/11 evacuation study: an overview of the methodologies employed and some analysis relating to fatigue, stair travel speeds and occupant response times

This paper briefly describes the methodologies employed in the collection and storage of first-hand accounts of evacuation experiences derived from face-to-face interviews with evacuees from the World Trade Center (WTC) Twin Towers complex on 11 September 2001 and the development of the High-rise Evacuation Evaluation Database (HEED). The main focus of the paper is to present an overview of preliminary analysis of data derived from the evacuation of the North Tower.

A case study of the effectiveness of the electronic survey as a research tool for measuring students' experience of e-learning

This paper uses a case study approach to consider the effectiveness of the electronic survey as a research tool to measure the learner voice about experiences of e-learning in a particular institutional case. Two large scale electronic surveys were carried out for the Student Experience of e-Learning (SEEL) project at the University of Greenwich in 2007 and 2008, funded by the UK Higher Education Academy (HEA). The paper considers this case to argue that, although the electronic web-based survey is a convenient method of quantitative and qualitative data collection, enabling higher education institutions swiftly to capture multiple views of large numbers of students regarding experiences of e-learning, for more robust analysis, electronic survey research is best combined with other methods of in-depth qualitative data collection. The advantages and disadvantages of the electronic survey as a research method to capture student experiences of e-learning are the focus of analysis in this short paper, which reports an overview of large-scale data collection (1,000+ responses) from two electronic surveys administered to students using surveymonkey as a web-based survey tool as part of the SEEL research project. Advantages of web-based electronic survey design include flexibility, ease of design, high degree of designer control, convenience, low costs, data security, ease of access and guarantee of confidentiality combined with researcher ability to identify users through email addresses. Disadvantages of electronic survey design include the self-selecting nature of web-enabled respondent participation, which tends to skew data collection towards students who respond effectively to email invitations. The relative inadequacy of electronic surveys to capture in-depth qualitative views of students is discussed with regard to prior recommendations from the JISC-funded Learners' Experiences of e-Learning (LEX) project, in consideration of the results from SEEL in-depth interviews with students. The paper considers the literature on web-based and email electronic survey design, summing up the relative advantages and disadvantages of electronic surveys as a tool for student experience of e-learning research. The paper concludes with a range of recommendations for designing future electronic surveys to capture the learner voice on e-learning, contributing to evidence-based learning technology research development in higher education.

Stability analysis of the amplifier with negative impedance compensation

A novel amplifier design technique based on negative impedance compensation has been proposed in our recent paper. In this paper, we investigate the stability of this amplifier system. The parameter space approach has been used to determine system parameters in the negative impedance circuit such that the stability of the amplifier system can be guaranteed in a certain region represented by those parameters. The simulation results have demonstrated that stable circuit behavior for the amplifier can be achieved