28 resultados para Process control -- Statistical methods


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Changing social trends indicate that more young Australians are electing to live at home longer. Residing in the parental home is the most common mode of living for those aged in their 20s, with recent data indicating more than 30 per cent decisively remain in this arrangement with their parents.

While there are obviously still those who decide to move out, this housing arrangement seems to be proving unsustainable; many young adults are returning home to reside with their parents after time spent on their own in a trend increasingly referred to as the ‘boomerang’ effect.

This paper reviews the available literature on young adults’ living arrangements, identifying those factors implicated both in the leaving home process and the likelihood a young adult will return home after previously moving out. In highlighting how much of this earlier research has relied on the use of statistical methods, the paper aims to justify the need for the proposed study- a contemporary exploration of generation Y Australians’ experiences of home returning.

The study, guided by an ecological theoretical perspective, will utilise a qualitative methodology to investigate the reasons why young adults are experiencing difficulty sustaining their move to independent living. In-depth interviews will be conducted in Melbourne with young adults aged between 20 and 30 years who currently reside in the parental home after living independently for four months or more. It is anticipated the study sample will include both males and females who are currently engaged in, or have previously completed, tertiary study.

These interviews will be analysed and through the emergent themes, will provide a clearer insight into the ‘boomerang’ generation- a group of young adults who will become increasingly more common in light of the current uncertainty surrounding finances, employment and housing markets. The implications of this research will therefore be significant for those concerned with the future housing decisions of Australian society.

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Determination of the optimal operating condition for moulding process has been of special interest for many researchers. To determine the optimal setting, one has to derive the model of injection moulding process first which is able to map the relationship between the input process control factors and output responses. One of most popular modeling techniques is the linear least square regression due to its effectiveness and completeness. However, the least square regression was found to be very sensitive to the outliers and failed to provide a reliable model if the control variables are highly related with each other. To address this problem, a new modeling method based on principal component regression was proposed in this paper. The distinguished feature of our proposed method is it does not only consider the variance of covariance matrix of control variables but also consider the correlation coefficient between control variables and target variables to be optimised. Such a modelling method has been implemented into a commercial optimisation software and field test results demonstrated the performance of the proposed modelling method.

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The impact of salmon farming on the environment has been widely studied; there is, however, no consensus on the magnitude and quality of these effects and little information on their extent over large salmon farming areas. Forty-three salmon farm sites of which 29 are in full operation and grouped in nine locations in southern Chile were evaluated. Using statistical methods (two-way anova), no effects were found on water column variables such as nitrate, ammonia, orthophosphate and chlorophyll, whereas they were significant on sediment variables such as nitrogen (N), phosphorus (P) and organic carbon (OC), among others. Natural variability evaluation of some parameters revealed that P in sediments had the lowest coefficient of variation (23.2%) when compared with N (65.2%), particulate organic matter (POM) (139%) and OC (39%), and showed more marked salmon farming effects with no locality effects. Four of the nine locations showed stronger effects on sediments, with average P values ranging from 150 to 230 mmol that were six to nine times higher than in control sites (25 mmol). Nitrogen and carbon in sediments, while showing significant effects on salmon farming, also showed locality effects that revealed other biogenic processes influencing sediment composition. Thus, P in sediments was proposed as a promising indicator of impact on salmon farming, although the relationship with fauna in sediments was not linear and somewhat variable; more research is therefore needed to understand such connections. Considering entire geographical locations, no relationship was found between sediment conditions under salmon cages and the condition of the water column at a farm. This may indicate the possibility of high dilution rates and recycling processes, which so far preclude the detection of more global impacts beyond the cages shadow.

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Emergency department access block is an urgent problem faced by many public hospitals today. When access block occurs, patients in need of acute care cannot access inpatient wards within an optimal time frame. A widely held belief is that access block is the end product of a long causal chain, which involves poor discharge planning, insufficient bed capacity, and inadequate admission intensity to the wards. This paper studies the last link of the causal chain-the effect of admission intensity on access block, using data from a metropolitan hospital in Australia. We applied several modern statistical methods to analyze the data. First, we modeled the admission events as a nonhomogeneous Poisson process and estimated time-varying admission intensity with penalized regression splines. Next, we established a functional linear model to investigate the effect of the time-varying admission intensity on emergency department access block. Finally, we used functional principal component analysis to explore the variation in the daily time-varying admission intensities. The analyses suggest that improving admission practice during off-peak hours may have most impact on reducing the number of ED access blocks.

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This bibliography begins with this introduction followed by a general overview of meta-analysis and research synthesis methods in education. The third section cites references to illustrate how the concept of statistical integration of research findings dates back to early 20th century. Citations in the fourth section highlight early calls from educational researchers to recognize the process of synthesizing research as a scholarly endeavor in its own right. As evident from the citations in the fifth section, it was in the 1980s when monographs exclusively devoted to research synthesis methods started to be published. Since then, a number of books have been published on research synthesis methods. The sixth section cites some of the most comprehensive books on research synthesis methods and includes contributions from key players of meta-analysis current at the time. The citations in the seventh section illustrate how meta-analysis has become very popular over time. Several large organizations have been set up and software developed to support systematic reviews of research. These are cited in the eighth section. Citations in the ninth section illustrate critiques of systematic reviews. As qualitative research is becoming popular in education, sophisticated discussions of issues associated with synthesizing qualitative research have also been published, some of which are cited in the tenth section. The eleventh section presents a methodologically inclusive account of current developments in research synthesis methods. The final section cites examples of journals exclusively devoted to publishing research reviews and exemplary research synthesis with different methodologies. Individual methods of research synthesis are discussed chronologically as they became popular in educational research. Accordingly, this bibliography starts with a discussion of statistical methods of integrating research that parallels the dominance of quantitative research in education until the 1970s. As the popularity and diversity of qualitative research methods have been increasing in educational research, more methodologically inclusive discussions of research synthesis methods are becoming popular as described in the later sections of this bibliography.

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The impact of regular additions of a surfactant (ethylene bis-stearamide; EBS) at different time intervals was investigated on the powder characteristics of a biomedical Ti-10Nb-3Mo alloy (wt.%). Ball milling was performed for 10 h on the elemental powders in four series of experiments at two rotation speeds (200 and 300 rpm). The addition of 2 wt.% total EBS at different time intervals during ball milling resulted in noticeable changes in particle size and morphology of the powders. The surfactant addition at shorter time intervals led to the formation of finer particles, a more homogenous powder distribution, a higher powder yield, and a lower contamination content in the final materials. Thermal analysis of the powders after ball milling suggested that differing decomposition rates of the surfactant were responsible for the measured powder particle changes and contamination contents. The results also indicated that the addition of surfactant during ball milling at 200 rpm caused a delay in the alloy formation, whereas ball milling at 300 rpm favored the formation of the titanium alloy.Crown Copyright © 2014 Published by Elsevier B.V. All rights reserved.

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Abstract: Background Inequalities in eating behaviours are often linked to the types of food retailers accessible in neighbourhood environments. Numerous studies have aimed to identify if access to healthy and unhealthy food retailers is socioeconomically patterned across neighbourhoods, and thus a potential risk factor for dietary inequalities. Existing reviews have examined differences between methodologies, particularly focussing on neighbourhood and food outlet access measure definitions. However, no review has informatively discussed the suitability of the statistical methodologies employed; a key issue determining the validity of study findings. Our aim was to examine the suitability of statistical approaches adopted in these analyses.
Methods: Searches were conducted for articles published from 2000–2014. Eligible studies included objective measures of the neighbourhood food environment and neighbourhood-level socio-economic status, with a statistical analysis of the association between food outlet access and socio-economic status.
Results Fifty four papers were included. Outlet accessibility was typically defined as the distance to the nearest outlet from the neighbourhood centroid, or as the numberof food outlets within a neighbourhood (or buffer). To assess if these measures were linked to neighbourhood disadvantage, common statistical methods included ANOVA, correlation, and Poisson or negative binomial regression. Although all studies involved spatial data, few considered spatial analysis techniques or spatial autocorrelation.
Conclusions: With advances in GIS software, sophisticated measures of neighbourhood outlet accessibility can be considered. However, approaches to statistical analysis often appear less sophisticated. Care should be taken to consider assumptions underlying the analysis and the possibility of spatially correlated residuals which could affect the results.

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The Internet has provided an ever increasingly popular platform for individuals to voice their thoughts, and like-minded people to share stories. This unintentionally leaves characteristics of individuals and communities, which are often difficult to be collected in traditional studies. Individuals with autism are such a case, in which the Internet could facilitate even more communication given its social-spatial distance being a characteristic preference for individuals with autism. Previous studies examined the traces left in the posts of online autism communities (Autism) in comparison with other online communities (Control). This work further investigates these online populations through the contents of not only their posts but also their comments. We first compare the Autism and Control blogs based on three features: topics, language styles and affective information. The autism groups are then further examined, based on the same three features, by looking at their personal (Personal) and community (Community) blogs separately. Machine learning and statistical methods are used to discriminate blog contents in both cases. All three features are found to be significantly different between Autism and Control, and between autism Personal and Community. These features also show good indicative power in prediction of autism blogs in both personal and community settings.

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Canarium indicum nuts are dried and consumed widely across the Pacific Region. Traditional methods of drying offer little process control resulting in highly variable product quality and loss. A more reliable and effective drying technology is required but the technology must suit local conditions. This paper describes a low profile solar tunnel dryer designed for batch drying of small quantities of the nuts. Prototypes have been tested. Experimental results indicate that drying temperatures are within the range to achieve good kernel quality and that the desired final moisture content for safe storage could be achieved after 30 hours of exposure.

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Thermal stabilization process of polyacrylonitrile (PAN) is the slowest and the most energy-consuming step in carbon fiber production. As such, in industrial production of carbonfiber, this step is considered as amajor bottleneck in the whole process. Stabilization process parameters are usually many in number and highly constrained, leading to high uncertainty. The goal of this paper is to study and analyze the carbon fiber thermal stabilization process through presenting several effective dynamic models for the prediction of the process. The key point with using dynamic models is that using an evolutionary search technique, the heat of reaction can be optimized. The employed components of the study are Levenberg–Marquardt algorithm (LMA)-neural network (LMA-NN), Gauss–Newton (GN)-curve fitting, Taylor polynomial method, and a genetic algorithm. The results show that the procedure can effectively optimize a given PAN fiber heat of reaction based on determining the proper values of heating rampand temperature

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This article considers a comparison study between different non-normal process capability estimation methods and utilizing themin the leukocyte filtering process in blood service sectors. Since the amount of leukocyte in a unit of the blood is a critical issue inthe blood transfusion process and patient safety, estimating and monitoring the capability of the leukocyte filtering process to meetthe target window is very important for blood service sectors. However, observed data from the leukocyte filtering process showthat the leukocyte levels after filtering demonstrate a right skewed distribution and applying conventional methods with a normalityassumption fails to provide trustful results. Hence, we first conduct a simulation study to compare different methods in estimating theprocess capability index of non-normal processes and then we apply these techniques to obtain the process capability of the leukocytefiltering process. The study reveals that the Box-Cox transformation method provides reliable estimation of the process capability ofthe leukocyte filtering process.

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There are many variations within sheet metal forming, some of which are manifest in the final geometry of the formed component. It is important that this geometric variation be quantified and measured for use in a process or quality control system. The contribution of this paper is to propose a novel way of measuring the geometric difference between the desired shape and an actual formed "U" channel. The metric is based upon measuring errors in terms of the significant manufacturing variations. The metric accords with the manually measured errors of the channel set. The shape error metric is then extended to develop a simple empirical, whole-component, springback error measure. The springback error measure combines into one value all the angle springback and side wall curl geometric errors for a single channel. Two trends were observed: combined springback decreases when the blank holder force is increased; and the combined springback marginally decreases when the die radii is increased.

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This research is concerned with the mechanical and physical properties of hemp fibre reinforced concrete (HFRC). An experimental program was developed based on the statistical method of fractional factors design. The variables for the experimental study were: (1) mixing method; (2) fibre content by weight; (3) aggregate size; and (4) fibre length. Their effects on the compressive and flexural performance of HFRC composites were investigated. The specific gravity and water absorption ratio of HFRC were also studied. The results indicate that the compressive and flexural properties can be modelled using a simple empirical linear expression based on statistical analysis and regression, and that hemp fibre content (by weight) is the critical factor affecting the compressive and flexural properties of HFRC.