A response surface approach to noise optimization of engine structures

The work presented within this thesis concerns the optimization of finite element models of engine structures to reduce radiated noise. For many engineering problems, current methods of structural optimization provide an efficient means by which to identify an optimum design, subject to a set of imposed bounds and constraints. They do not, however, have the flexibility to carry out efficient investigation of a range of different constraint criteria, and this is often a requirement of a noise optimization study. In order to address this restriction, an alternative method of noise optimization is developed, which is based on the techniques of experimental design theory and response, surface methodology. The main feature of this approach is that values of the response functions of interest are calculated at a number of selected points Within the design variable space, from which an approximating mathematical model is generated. It is this analytical model of the original responses which is used as the basis of the optimization procedure. Experimental design theory is employed in order to ensure that a sufficiently accurate model can be generated With the minimum number of function evaluations. A number of competing experimental designs and mathematical models are considered, and numerical trials are carried out to evaluate their performance in representing the noise function. A quadratic model is found to perform well throughout the design region, and can be estimated efficiently using a particular class of economic second-order designs. A number of detailed noise optimization studies are presented, involving up to seven design variables, which illustrate the ways in which the requirements of the noise optimization problem can be met using the response surface approach

Effects of Anaesthesia with a High Oxygen Concentration on the Acid-Base State of Babies Delivered at Elective Caesarean Section

Babies delivered from mothers who had 60% oxygen administered during general anaesthesia at elective Caesarean section, had higher pH and lower pCO2 levels, and were clinically in better condition than babies delivered after a similar induction-delivery interval when a concentration of 30 - 33% oxygen was given to the mother. The clinical and acid-base states in both these groups of babies were not as good as in those delivered after induction- delivery times of less than 6 minutes

Key features of New Zealand business cycles

Within a modern business cycle framework, this paper utilises basic statistical techniques to reexamine stylised empirical facts associated with business cycles in New Zealand since the midl 960's. The approach is essentially a bivariate one, and uses Hodrick-Prescott methodology for trend computations. Point estimates and GMM standard errors are presented for the amplitude of each variable's deviations from trend, degree of contemporaneous cyclicality and phase shift. Many relationships change markedly over time and, at least with this methodology, it is not easy to establish many "regularities" with confidence. "Real variable regularity" in a broad sense is confirmed, but a number of our other stylised empirical facts and uncertainties are not consistent with outcomes usually associated with prominent theoretical business cycle models. In particular, domestic price fluctuations in New Zealand have been basically countercyclical, and the real net exports share of GDP does not seem to have moved countercyclically over the past decade. No systematic cyclical tendency has been discovered for fluctuations in government purchases, and the scale of changes affecting the monetary sector over the past decade continues to present difficulties for establishing "financial regularities"

Dating New Zealand Business Cycles

Dating the turning points and durations of business cycles has long been associated with NBER type reference cycle indexes. More recently, such work has become additionally important for evaluating modern theoretical business cycle models and for analysing the time varying characteristics of cycles. This paper applies the relatively simple and transparent Bry and Boschan business cycle dating procedure to four New Zealand real gdp series; compares the resulting turning points with those previously identified using NBER type cycle identification techniques, and with those obtained from three relatively mechanistic "deviations from trend" methods; provides some empirical benchmark turning point and cycle duration characteristics; and as a prelude to further theoretical and empirical work, compares these with results obtained from a number of potentially relevant AR and 1(1) statistical processes

Use of cumulative mortality data in patients with acute myocardial infarction for early detection of variation in clinical practice: observational study

OBJECTIVES: Use of cumulative mortality adjusted for case mix in patients with acute myocardial infarction for early detection of variation in clinical practice. DESIGN: Observational study. SETTING: 20 hospitals across the former Yorkshire region. PARTICIPANTS: All 2153 consecutive patients with confirmed acute myocardial infarction identified during three months. MAIN OUTCOME MEASURES: Variable life­adjusted displays showing cumulative differences between observed and expected mortality of patients; expected mortality calculated from risk model based on admission characteristics of age, heart rate, and systolic blood pressure. RESULTS: The performance of two individual hospitals over three months was examined as an example. One, the smallest district hospital in the region, had a series of 30 consecutive patients but had five more deaths than predicted. The variable life­adjusted display showed minimal variation from that predicted for the first 15 patients followed by a run of unexpectedly high mortality. The second example was the main tertiary referral centre for the region, which admitted 188 consecutive patients. The display showed a period of apparently poor performance followed by substantial improvement, where the plot rose steadily from a cumulative net lives saved of - 4 to 7. These variations in patient outcome are unlikely to have been revealed during conventional audit practice. CONCLUSIONS: Variable life­adjusted display has been integrated into surgical care as a graphical display of risk­adjusted survival for individual surgeons or centres. In combination with a simple risk model, it may have a role in monitoring performance and outcome in patients with acute myocardial infarction

3rd International conference on neglected and underutilized species (NUS): for a food-secure Africa. Accra, Ghana, 25-27 September 2013. Proceedings

The '3rd international conference on neglected and underutilized species: for a food-secure Africa' was held on 25-27 September in Accra, Ghana. These proceedings include 30 papers presented at the conference, organized under the themes: 1. Resilience of agricultural and livelihood systems -- with sub-themes on agronomy, conservation, climate change, health and nutrition; 2. Upgrading value chains on NUS; 3. Creating an enabling policy environment

Examining the links between parents' relationships with reading and shared reading with their pre-school children

While much is known about the benefits of shared reading activity for children, and the role of the home in cultivating shared reading practices far less is known about the factors that can influence parents’ shared reading practices with their children. Given that many young people leave school with poor relationships with reading, this study explores the links between parents’ own relationships with reading and the shared reading they practice with their own children in the home. Drawing on deep-level interview data, this paper presents data from six parents of pre-school children, who reported that they have had a poor personal relationship with reading. These parents all developed positive shared reading relationships with their children, however the importance of this study lies in understanding the interplay between these reading relationships. The data strongly suggested that the construct of ‘reading’ was very different from the ways in which reading had previously been defined for these participants. Reading, within a shared reading context, was seen as a very flexible construct which included activities such as talking and telling stories. In some cases, parents’ own relationships with reading seemed to improve. Implications for intervention with other families are discussed

Using set visualisation to find and explain patterns of missing values: a case study with NHS hospital episode statistics data

Objectives Missing data is the most common data quality issue in electronic health records (EHRs). Missing data checks implemented in common analytical software are typically limited to counting the number of missing values in individual fields, but researchers and organisations also need to understand multifield missing data patterns to better inform advanced missing data strategies for which counts or numerical summaries are poorly suited. This study shows how set-based visualisation enables multifield missing data patterns to be discovered and investigated. Design Development and evaluation of interactive set visualisation techniques to find patterns of missing data and generate actionable insights. The visualisations comprised easily interpretable bar charts for sets, heatmaps for set intersections and histograms for distributions of both sets and intersections. Setting and participants Anonymised admitted patient care health records for National Health Service (NHS) hospitals and independent sector providers in England. The visualisation and data mining software was run over 16 million records and 86 fields in the dataset. Results The dataset contained 960 million missing values. Set visualisation bar charts showed how those values were distributed across the fields, including several fields that, unexpectedly, were not complete. Set intersection heatmaps revealed unexpected gaps in diagnosis, operation and date fields because diagnosis and operation fields were not filled up sequentially and some operations did not have corresponding dates. Information gain ratio and entropy calculations allowed us to identify the origin of each unexpected pattern, in terms of the values of other fields. Conclusions Our findings show how set visualisation reveals important insights about multifield missing data patterns in large EHR datasets. The study revealed both rare and widespread data quality issues that were previously unknown, and allowed a particular part of a specific hospital to be pinpointed as the origin of rare issues that NHS Digital did not know exist

Confinement of matroid representations to subsets of partial fields

Let M be a matroid representable over a (partial) field P and B a matrix representable over a sub-partial field P' of P. We say that B confines M to P' if, whenever a P-representation matrix A of M has a submatrix B, A is a scaled P'-matrix. We show that, under some conditions on the partial fields, on M, and on B, verifying whether B confines M to P' amounts to a finite check. A corollary of this result is Whittle's Stabilizer Theorem. A combination of the Confinement Theorem and the Lift Theorem from arXiv:0804.3263 leads to a short proof of Whittle's characterization of the matroids representable over GF(3) and other fields. We also use a combination of the Confinement Theorem and the Lift Theorem to prove a characterization, in terms of representability over partial fields, of the 3-connected matroids that have k inequivalent representations over GF(5), for k = 1, ..., 6. Additionally we give, for a fixed matroid M, an algebraic construction of a partial field P_M and a representation A over P_M such that every representation of M over a partial field P is equal to f(A) for some homomorphism f:P_M->P. Using the Confinement Theorem we prove an algebraic analog of the theory of free expansions by Geelen et al.Comment: 45 page