Considering the risk of ignoring active factors in industrial experiments

This article draws attention to the importance of considering type II error in Design of Experiments contexts and shows, through two examples, an easy way to do that.Peer ReviewedPostprint (author's final draft

Contributions to industrial statistics

This thesis is about statistics' contributions to industry. It is an article compendium comprising four articles divided in two blocks: (i) two contributions for a water supply company, and (ii) significance of the effects in Design of Experiments. In the first block, great emphasis is placed on how the research design and statistics can be applied to various real problems that a water company raises and it aims to convince water management companies that statistics can be very useful to improve their services. The article "A methodology to model water demand based on the identification of homogeneous client segments. Application to the city of Barcelona", makes a comprehensive review of all the steps carried out for developing a mathematical model to forecast future water demand. It pays attention on how to know more about the influence of socioeconomic factors on customer's consumption in order to detect segments of customers with homogenous habits to objectively explain the behavior of the demand. The second article -related to water demand management, "An Approach to disaggregating total household water consumption into major end-uses" describes the procedure to assign water consumption to microcomponents (taps, showers, cisterns, washer machines and dishwashers) on the basis of the readings of water consumption of the water meter. The main idea to accomplish this is, to determine which of the devices has caused the consumption, to treat the consumption of each device as a stochastic process. In the second block of the thesis, a better way to judge the significance of effects in unreplicated factorial experiments is described. The article "Proposal of a Single Critical Value for the Lenth Method" analyzes the many analytical procedures that have been proposed for identifying significant effects in not replicated two level factorial designs. Many of them are based on the original "Lenth Method and explain and try to overcome the problems that it presents". The article proposes a new strategy to choose the critical values to better differentiate the inert from the active factors. The last article "Analysing DOE with Statistical Software Packages: Controversies and Proposals" review the most important and commonly used in industry statistical software with DOE capabilities: JMP, Minitab, SigmaXL, StatGraphics and Statistica and evaluates how well they resolve the problem of analyzing the significance of effects in unreplicated factorial design

Optimisation of the performance characteristics of Cu-Al-Mo thin film resistors

This thesis presents a novel approach to the manufacture of thin film resistors using a new low resistivity material of copper, aluminium and molybdenum, which under industrially achievable optimised process conditions, is shown to be capable of producing excellent temperature coefficient of resistance (TCR) and long term stability properties. Previous developments in the field of thin film resistors have mainly centred around the well established resistive materials such as nickel-chromium, tantalum-nitride and chromium-silicon-monoxide. However recent market demands for lower value resistors have been difficult to satisfy with these materials due to their inherent high resistivity properties. This work focuses on the development and processing of a thin film resistor material system having lower resistivity and equal performance characteristics to that of the well established materials. An in depth review of thin film resistor materials and manufacturing processes was undertaken before the electrical properties of a binary thin film system of copper and aluminium were assessed. These properties were further enhanced through the incorporation of a third doping element, molybdenum, which was used to reduce the TCR and improve the electrical stability of the film. Once the desired chemical composition was established, the performance of the film was then fine tuned through optimisation of critical manufacturing process stages such as sputter deposition, heat treatment and laser adjustment. The results of these investigations were then analysed and used to generate a set of optimum process conditions, suitable for repeatedly producing thin film resistors in the 1 to 10? resistance range, to tolerances of less than ±0.25% and TCR values better than ±15ppm/oC