Rapid Assessment of the Bacteriological Quality of Milk by the Use of Adenosine Triphosphate Bioluminescence.

Raw milk samples (n = 246) and pasteurized milk samples (n = 104) were analyzed to determine adenosine triphosphate (ATP) and compared with the standard plate count (SPC). An ATP filtration method was used to filter milk samples prior to ATP determination, which was measured in relative light units (RLU). The ATP assay took approximately 7 minutes to complete and could allow rapid prediction of SPC which is a measure of raw milk quality. Linear regression analysis was performed on data from three raw milk treatments defined as; fresh milk samples, samples preliminarily incubated at 12.8 and 15.6\sp\circC for 18 hours. Linear regression coefficients were significantly different from zero (P $\u3c$ 0.01). The R\sp2 calculated using log\sb{10} transformed SPC (LSPC) and log\sb{10} RLU (LRLU) for fresh and preliminarily incubated samples at 12.8 and 15.6\sp\circC were 0.58, 0.78, and 0.80, respectively and R\sp2 for all milk samples combined was 0.78. Differences in regressions among treatments were tested using a multiple slope and intercept model. The R\sp2 for the multiple slope model was 0.83 and the treatment intercepts and slopes were significantly different (P $\u3c$ 0.01). Analysis of predicted values of LSPC and one standard deviation of a single prediction above and below the regression line indicated that SPC could be predicted with sufficient accuracy using ATP in raw milk samples. Pasteurized milk samples were subjected to two preliminary incubation temperatures: 12.8 and 15.6\sp\circC for 18 hours. All of the 104 fresh pasteurized milk samples had a SPC count below 10\sp4 cfu/ml. Regression analyses as described for raw milk samples revealed that preliminary incubation at 15.6\sp\circC for 18 hours did not result in a significant increase in the standard plate count of the same samples. The ATP method was not effective in predicting bacterial numbers of freshly pasteurized milk or PI-15.6\sp\circC milk samples using linear regression. However, the SPC and RLU values increased for PI-21\sp\circC pasteurized milk and the regression analyses revealed that there was a linear relationship between LSPC and LRLU for PI-21\sp\circC samples

Online network monitoring

An important problem in network analysis is the online detection of anomalous behaviour. In this paper, we introduce a network surveillance method bringing together network modelling and statistical process control. Our approach is to apply multivariate control charts based on exponential smoothing and cumulative sums in order to monitor networks generated by temporal exponential random graph models (TERGM). The latter allows us to account for temporal dependence while simultaneously reducing the number of parameters to be monitored. The performance of the considered charts is evaluated by calculating the average run length and the conditional expected delay for both simulated and real data. To justify the decision of using the TERGM to describe network data, some measures of goodness of fit are inspected. We demonstrate the effectiveness of the proposed approach by an empirical application, monitoring daily flights in the United States to detect anomalous patterns. © 2021, The Author(s)

Simulation and Control of Univariate and Multivariate Set-Up Dominant Process

This thesis explores the use of statistically valid process improvement tools in low-volume applications. Setting out the following research questions: How can the Six Sigma Measure and Analyse phases of a chronic quality problem be statistically validated in a low-volume process? How can a statistically valid approach for process control be implemented in a low-volume process? And how can this tool be extended to fit multivariate processes and can the calculation of control parameter adjustments be automated? In answer, the thesis presents an enhanced PROcess VAriation Diagnosis Tool (PROVADT) method, driving a Six Sigma improvement project through the Measure and Analyse phases. PROVADT provides a structured sampling plan to perform a Multi-Vari study, Isoplot, Gage R&R and Provisional Process Capability in as few as twenty samples and eighty measurements, making the technique suited to low-volume applications. The enhanced PROVADT method provides a Gage R&R without confounded variation sources, as was the case in the original method, and its practical application was demonstrated through two case studies. Process control tools for low-volume, high-variety manufacturing applications were developed. An adjustable traffic-light chart, with control limits linked to tolerance and simple decision rules, was used for monitoring univariate processes. This tool, the Set-Up Process Algorithm (SUPA), uses probability theory to provide 98% confidence that the process is operating at a pre-specified minimum level of Cp in as few as five samples. SUPA was extended to deal with high-complexity applications, resulting in multivariate SUPA (mSUPA). mSUPA maintains SUPA’s principles, but presents the information about multiple process features on one chart, rather than multiple univariate charts. To supplement the mSUPA tool, a theoretical method for calculating optimal process adjustment when a multivariate process is off-target was introduced, combining discrete-event simulation and numerical optimisation to calculate adjustments

Shewhart control charts in new perspective

The effects of estimating parameters and the violation of the assumption of normality when dealing with control charts are discussed. Corrections for estimating errors and extensions of the normal control chart to parametric and nonparametric charts are investigated. The underlying theory is extensively discussed, including the choice of a suitable parametric family containing the normal family. It turns out that classical contamination families like random or deterministic mixtures do not give a suitable solution here. The so called normal power family leads to an acceptable family as it is intimately connected to the problem at hand of modelling and estimating an extreme quantile. When the underlying distribution cannot be modelled sufficiently accurately by the normal power family, the nonparametric control chart comes into the picture. A data driven procedure makes the choice between the three different charts. When the nonparametric chart turns up, a large number of Phase I observations is needed. When such a large sample size is not available, it may be preferred to replace the individual chart by a grouped one. The new minimum chart is recommended in that case

A study on improving the performance of control charts under non-normal distributions

Master'sMASTER OF ENGINEERIN

Statistical Quality Control of a Production Process of Invisible Zippers

The present work exhibits the development and implementation of an innovative sta- tistical control plan applied to the production process of invisible zippers, within the context of a project developed by the NOVA School of Science and Technology for a zipper producer. The plan focused on two main axes: reevaluating currently applied sampling plans and iden- tifying critical characteristics in the various stages of the process, with the development of a proposal for control charts for each of the stages and implementation of the respective charts. An important part of the plan was the implementation of a design of experiments to optimize critical processes. Consequently, an integrated approach was implemented to define and solve the prob- lem. At first, a complete definition and description of the process was executed through a visual representation with flowcharts. Then, critical points of the process were identified, which led to a preliminary implementation of control charts, planification of a design of ex- periments, and execution of several hypothesis tests. Even though, as of the redaction of this study, no improvement on the process was achieved, several crucial conclusions were reached over its behavior following the implemen- tation of the statistical tools. Some important conclusions were the out-of-control state of the process on some important characteristics, and strong presence of internal variability in the process. As a result, a design of experiments was considered the best approach for improve- ment, and its full planification has been achieved, as it is currently being performed. As for the sampling plans, a necessity to reduce end-of-line inspections was identified and is expected to be enabled by the improvements arising from the design of experiments. On the other hand, the reception sampling plan was identified as insufficient, and is to be reviewed.O presente trabalho expõe o desenvolvimento e implementação de um plano de con- trolo estatístico inovador aplicado ao processo de produção de fechos invisíveis, no contexto de um projeto desenvolvido pela Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para um produtor de fechos de correr. O plano centrou-se em dois eixos principais: a reavaliação dos planos de amostragem atualmente aplicados e identificação de característi- cas críticas nas várias fases do processo, com o desenvolvimento de uma proposta de cartas de controlo para cada uma das fases e implementação das respetivas cartas. Uma parte im- portante do plano foi a implementação de um desenho de experiências para a otimização de processos críticos. Consequentemente, foi implementada uma abordagem integrada para definir e resolver o problema. No início, foi realizada uma definição e descrição completa do processo através de uma representação visual com fluxogramas. De seguida, foram identificados pontos críti- cos do processo, o que levou à implementação preliminar de cartas de controlo, planificação de um desenho de experiências e execução de vários testes de hipóteses. Apesar de, à data de redação deste estudo, não se ter alcançado uma melhoria do pro- cesso, alcançaram-se várias conclusões cruciais sobre o seu comportamento. Algumas conclu- sões importantes foram o estado fora de controlo do processo em certas características impor- tantes, e a forte presença de variabilidade interna no processo. Como resultado, o desenho de experiências foi considerado a melhor abordagem para a sua melhoria, e a sua planificação completa foi efetuada, sendo que as experiências se encontram de momento a decorrer. Quanto aos planos de amostragem, foi identificada a necessidade de reduzir as inspe- ções de fim de linha. Por outro lado, o plano de amostragem de receção foi identificado como insuficiente, e deverá ser revisto

Just -in -time selling: Relation to market orientation, organizational structure and organizational performance

The purpose of this dissertation is to answer the following research questions related to the efficacy of a Just-in-Time (JIT) selling strategy: (1) What is the nature of the relationships among market orientation, JIT selling, organizational structure, and organizational performance constructs? (2) Does JIT selling mediate and/or moderate the relationships among market orientation and organizational structure and organizational performance? The market orientation model theorized by Kohli and Jaworski (1990) and the JIT selling model theorized and tested by Germain, Dröge and Daugherty (1994) and Claycomb, Dröge and Germain (1999) are combined to facilitate investigation of the link between market orientation and JIT selling. Generally, the combined model incorporates market orientation as an antecedent to JIT selling and organizational structure and performance as consequences. Data relating to all constructs were collected from 177 marketing oriented representatives from manufacturing firms using a combined Internet survey and traditional mailing methodology. A multiple regression and structural equation modeling approach returned results indicating that market orientation and JIT selling are positively linked, that market orientation and JIT selling are positively associated with organizational performance and with the integration, formalization and specialization components of organizational structure but not with the decentralization component. JIT selling partially mediates the relationship between market orientation and organizational performance but neither mediates nor moderates the relations among market orientation and integration, formalization and specialization. Managers implementing a JIT selling strategy within the context of an organization exhibiting a high market orientation may expect improvements in organizational performance. A JIT selling strategy requires development of long-term, single-source relationships with buyers and efforts by the organization\u27s sales representatives to build value during the selling process based on established organizational abilities to deliver zero-defect products precisely on-time and in the precise quantities desired by customers while minimizing total waste and total cost throughout the supply chain

Optimization of Properties of Injectable Bone Cement for Vertebral Augmentation Procedures: Application of Response Surface Methodology

The literature on the interaction effects of explanatory variables on properties of injectable bone cements used in the vertebral augmentation procedures of vertebroplasty and ballon kyphoplasty is sparse. In the present work, response surface methodology was used to investigate the direct and interaction effects of variables on three properties of a poly (methyl methacrylate) bone cement (maximum exotherm temperature, residual monomer content (RMC), and degradability) and three properites of a calcium phosphate cement (CPC) (injectability, final setting time (F), and compressive strength). Some main findings were 1) interaction effects were statistically significant for some properties, such as F, but not for others, such as RMC; and 2) values of variables that led to optimum or minimum cement properties; for example, optimum injectability of a CPC (98%) could be attained using a cement with a poly(ethylene glycol) content of 20 wt/wt% and prepared using a powder-to-liquid ratio of 2.0 g mL-1

Online network monitoring

An important problem in network analysis is the online detection of anomalous behaviour. In this paper, we introduce a network surveillance method bringing together network modelling and statistical process control. Our approach is to apply multivariate control charts based on exponential smoothing and cumulative sums in order to monitor networks generated by temporal exponential random graph models (TERGM). The latter allows us to account for temporal dependence while simultaneously reducing the number of parameters to be monitored. The performance of the considered charts is evaluated by calculating the average run length and the conditional expected delay for both simulated and real data. To justify the decision of using the TERGM to describe network data, some measures of goodness of fit are inspected. We demonstrate the effectiveness of the proposed approach by an empirical application, monitoring daily flights in the United States to detect anomalous patterns