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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in fulfillment of the requirements for the degree Master of Science. Johannesburg, 2017. / Multicomponent gas mixtures are inherently challenging to produce in the laboratory because of matrix effects, boiling points and reactivity amongst other factors. Therefore, methods must be continuously developed to control these challenges. The purpose of this work was to study these complex gas mixtures to improve their measurements with emphasis on the reduction of uncertainty. There are three critical steps to be followed in gas metrology for primary reference gas mixtures of the highest metrological level; purity analysis of source gases, gravimetric preparation and verification/validation which includes stability testing. Purity analysis of select source gases was quantified using various techniques. This methodology incorporated the use of molar masses and their uncertainties in order to obtain purity values for the chemical composition of gas mixtures. While many preparation methods such as permeation and dynamic methods are available, a static gravimetric method was used to prepare the complex stack and automotive gas mixtures following International Standard Organisation: 6142-1. For the mole fraction range of interest, four components (carbon dioxide, carbon monoxide, sulphur dioxide and nitric oxide) excluding propane, were obtained from analysis by non-dispersive spectroscopy techniques calibrated by several standard gas mixtures of different mole fractions. Propane was analysed by a gas chromatograph coupled with flame ionisation detection. Multipoint calibration was used to evaluate the linearity or nonlinearity of the detector. The final results for the stack gas mixture components showed an achievement of 0.4% to 0.8% percentage relative expanded uncertainty and 0.4% to 1.3% for carbon dioxide depending on the matrix of the standard gas mixtures used, 0.5% to 1% for propane, 0.8% to 1.8% for nitric oxide, 2% to 6% for carbon monoxide and 0.3% to 2.3% for sulphur dioxide. One of the most important suppositions drawn was the incidence of synergistic effects associated with calibration by nonrepresentative standard gas mixtures when these were used for analysis for some of the components of stack mixtures. To evaluate improvements in measurement capability, the results of the current work were compared to the data of the laboratory in 2008-2011 and there was an improvement in the measurement of carbon dioxide, carbon monoxide, propane and nitric oxide. These improvements are attributed to rigorous purity analysis of starting materials, reduction of uncertainty and developments in measurement expertise. In this work, different measurement and calibration methods were used to analyse the components of the new stack gas mixtures. The stability of these components was evaluated by analysing them at different times and the statistical D-test was used to check for significant instability. An unknown stack sample was compared with the standard gas mixtures prepared for this work. In combination with same matrix and same concentrations, single point calibration was found suitable for stack gas measurement. To reiterate the concept of matrix effect, the results of carbon dioxide in a mixture containing carbon monoxide and oxygen as well in nitrogen, were used to show how differences in matrix often give erroneous results and same conclusions cannot be made for different mixtures. While the data of this measurement was unsatisfactory, an improved method developed for this type of emission multicomponent was very successful. Emission industries also require automotive primary reference gas mixtures. These are equally important and complex multicomponent mixtures measured and improved in this work. A very precise and repeatable single point method was developed for the analysis of the components of automotive mixtures. The repeatability of the gas chromatography method was 0.2% for oxygen, 0.1% for carbon monoxide, 0.5% for carbon dioxide and 0.3% for propane. The percentage relative expanded uncertainty was 0.4% for oxygen, 0.8% for carbon monoxide, 0.8% for carbon dioxide and 0.5% for propane. However, its limitation was the use of different calibration gases for each analysis. This led to inconsistencies in the calculated mole fractions, non-predictability and instability. A proficiency testing scheme was coordinated by the laboratory for automotive emission as part of this study. Given the complexity of the samples, the work aimed to check any improvements that could be made to the capability of measurement over the years. This new method using gas chromatography coupled with different detectors (residual gas analyser) was successful in verifying the gravimetric values very V accurately. Finally, the results of the stack gas mixtures were ≤1% relative except carbon monoxide and ≤1% for automotive mixtures. This work aimed to support the emission industry by providing it with representative and accurate reference gas mixtures, extend the accreditation scope of the laboratory and improve its calibration and measurement capability for multicomponent gas mixtures. / LG2018

Metrology and Tooling are considered as discrete disciplines within Manufacturing Engineering, however, assembly tooling often acts as a checking mechanism. Assembly tooling has the primary function of controlling part location during assembly; with a secondary requirement as a quality gate. In-tool checks are manual mechanical checks of the assembly, these gauging checks assume the tooling has the correct, nominal geometry. Tooling conformance is certified periodically; however these intervals can be up to three years. Further examination of the metrology requirements within the aerospace industry with respect to large scale assembly tooling identify a requirement to: reduce manual metrology checks, reduce tooling recertification time, and enable greater automation. Currently, there is a lack of integration between metrology and Wing-box assembly tooling. This research investigates how to increase manufacturing confidence with respect to tooling conformance; and, ultimately improve the manufacturing process for aero-structures, through the increased and enhanced use of metrology in the assembly tooling environment. The Metrology Enhanced Tooling for Aerospace (META) framework has been created to provide a robust framework for deploying metrology in the tooling environment. The major elements of the framework are subsequently detailed and demonstrated in three chapters: i) large volume metrology networks, for the measurement of tooling structures; testing instrument performance, quantifying and improving the uncertainty estimation, and ultimately, establishing a rapid measurement process for assembly tooling; ii) embedded metrology systems demonstrates how local measurement systems can be utilised to replace and improve on, traditional in-tool checks; and iii) metrology feedback presents an example of an automated tooling pick-up that manipulates the assembly to achieve the design intent. The contributions can be summarised as: firstly, the creation of the META framework for the deployment of metrology in assembly tooling environment, accommodating and facilitating a number of the future tooling and assembly requirements. Secondly, the establishment of a generic commissioning methodology and measurement strategy for the rapid measurement of assembly tooling to increase tooling confidence. The research output was demonstrated in a case study, through a combination of physical measurement and digital automation simulation to prove the process time was greatly decreased from current methods.

In this thesis, new metrology hardware is designed, fabricated, and tested to provide improvements over current MEMS metrology. The metrology system is a micromachined scanning interferometer having a sub-nm resolution in a compact design. The proposed microinterferometer forms a phase sensitive diffraction grating with interferometric sensitivity, while adding the capability of better lateral resolution by focusing the laser to a smaller spot size. A detailed diffraction model of the microinterferometer was developed to simulate the device performance and to suggest the location of photo detectors for integrated optoelectronics. A particular device is fabricated on a fused silica substrate using aluminum to form the deformable diffraction grating fingers and AZ P4620 photo resist (PR) for the microlens. The details of the fabrication processes are presented. The structure also enables optoelectronics to be integrated so that the interferometer with photo detectors can fit in an area that is 1mm x 1mm. The scanning results using a fixed grating micromachined scanning interferometer demonstrated that it could measure vibration profile as well as static vertical(less than a half wave length) and lateral dimension of MEMS. The SI, which is integrated with photo diodes, demonstrated its operation by scanning a cMUT. The PID control has been tested and resulted in improvement in scanned images. The integrated micromachined scanning interferometer demonstrated that the deformable grating could be used to tune the measurement keep the interferometer in quadrature for highest sensitivity.

Thesis (M.S.)--Kent State University, 2008. / Title from PDF t.p. (viewed Jan. 21, 2010). Advisor: Austin Melton. Keywords: Software metrics; comparison; classical measurement. Includes bibliographical references (p. 89-93).

Virtual Metrology (VM) predicts end-of-batch properties (metrology data) from measurable input data composed of pre-process metrology and fault detection and classi cation (FDC) system outputs. This dissertation aims at moving a step closer to the realization of VM in semiconductor manufacturing by providing solutions to the challenges that present VM technology faces. First, various VM methods are introduced and compared in terms of prediction accuracy using four industrial datasets collected from a plasma etch system at Texas Instruments, Inc.. Kalman lter estimation is employed in a novel way to serve as a VM model for predicting outputs of a static process. Recursive PLS regression (R-PLSR) and Kalman filter show the best prediction results as they update the model whenever new measurements are available. Next, two PLS variants (PLS with EWMA mean update and recursive PLS) are proposed as robust VM algorithms that can predict process outputs fairly accurately in the presence of unexpected process drifts and noise. The obtained results reinforce VM technology by suggesting appropriate prediction methods when unexpected process changes occur. For a successful implementation of VM, the data entering the VM model needs to be free from faults. Fault-free (reconstructed) data are obtained by performing fault detection, fault identi cation, and fault reconstruction. A novel fault detection method based on statistics pattern analysis (SPA) is presented. The SPA method provides better fault detection performance for diff erent types of faults as compared to the MPCA-based methods. Next, three well-known fault identi cation methods present in literature are implemented. An equation that relates the RBC with the SVI is derived. The contribution plot method identi es a smaller number of faults correctly as compared to the RBC and the SVI methods. Fairly good estimates of the fault magnitude are obtained when the faults are identi ed correctly. An approach that combines physical measurements with the VM estimates to develop a more robust approach than using VM alone is presented. EWMA-R2R control is implemented using three well-known sampling methods in order to demonstrate the superior performance of two novel control schemes: B-EWMA R2R control and VM-assisted EWMA-R2R control. A new reliance index, which is attractive from a mathematical and practical point of view, is proposed. The VM-assisted EWMA-R2R control yields the best control results among the control schemes employed in this study. The simulation results demonstrate that VM has the potential to reduce measurement costs signi cantly while promising better process control. / text

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This thesis suggests that prior to Ptolemaic and Roman times, ancient Egypt had two distinct and parallel linear systems: the royal system limited to official architectural projects and land measurements, and a great (aA) system used for everyday measurements. A key 1/3 ratio explains ancient Egyptian linear measurements and their agricultural origin. Emmer is 1/3 lighter than barley, consequently, for an equal weight, a container filled with emmer will be 1/3 greater than a container filled with barley. The lengths derived from both containers share the same 1/3 ratio. The second chapter, Previous Studies, lists the work of scholars involved directly or indirectly with ancient Egyptian metrology. The third chapter, The Royal Cubit as a Converter and the Scribe’s Palette as a Measuring Device, capitalizes on the colour scheme (black and white on the reproduction of Appendix A) appearing on the Amenemope cubit artifact to show the presence of two cubits and two systems: the black (royal system) and the white (great [aA] system) materialized by the scribe's palette of 30, 40, and 50 cm. The royal cubit artifacts provide a conversion bridge between the royal and the great systems. The information derived from the visual clues on the Amememope cubit artifact are tested against a database of artifacts scattered in museums around the world. The fourth chapter, The Origin and Evolution of Ancient Egyptian Cubits, historically relates the ancient Egyptian linear systems to the closed metrological systems they belong to. A closed metrological system is a system in which units of length, volume, and weight are related to each other. The conclusion is that the ancient Egyptian metrological system is backward compatible as it is possible - using a hin as a closing volumetric unit and emmer, barley, wheat (triticum durum) and water as commodities - to re-construct the linear metrological systems of all ancient Egyptian periods.