| 1. |
- Helms, Sandra, et al.
(author)
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Classification of Methods for the Indication of Change Propagation - a Literature Review
- 2014
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In: Proceedings of International Design Conference - Design 2014.
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Conference paper (peer-reviewed)abstract
- In today’s globalized and competitive world, product development processes need to be innovative, effective and efficient. Engineering changes (EC) are an unavoidable part of product development and are both source of innovation and costs. Every innovation derives from a change, but at the same time unnecessary and late changes can be the reason for sky-rocketing costs [Fricke 2000]. Therefore, companies have to find a balance between having too many changes which are costly and time-consuming, and having too few which might lead to missed opportunities with regards to improving quality and being innovative. One particular aspect of changes in engineering design is their risk of propagating further through the product. Engineering change propagation (ECP) can occur wherever there are dependencies within the product and thus a change to one part of the system will trigger subsequent changes in other parts [Yang 2011]. To tackle the problem of unwanted ECP, various methods that aim at supporting designers with the assessment of alternative change options have been developed in recent years. These methods, however, often apply to different scopes and intend at answering different questions. There are academic papers that include a listing and discussion of the various methods that are out in literature such as the one from Jaratt et al. (2011). Moreover, authors that introduce their own method in their paper often refer to other already existing methods. However, most of these papers not exclusively consider the methods that are able to deal with ECP but rather consider the broader field of EC. Also, there is no classified overview in literature that provides deeper insights into what aspects of the various methods differ or are similar. Having such a classified overview at hand with methods that can handle ECP a quicker comparison and assessment of those methods can take place and can therefore save precious time. Hence, this work’s objective is to find methods that can indicate change propagation and to analyse how these differ to each. Therefore, the research questions to be answered are; (RQ 1) what methods in literature to EC propagation do already exist and (RQ 2) based on the findings from RQ 1, how do the so found methods differ to each other?Based on the definitions from Jarratt et al. [Jarratt 2011] and Conrat [Conrat 1998], ECs are in this work defined as modifications in forms, fits, materials, dimensions, functions, drawings or software of a product or component that has already been released during the production design process. ECs include the connected process changes and can be of any size or type, can involve any people, and can take any length of time. EC propagation, based on Tang et al.’s [Tang 2008] and Koh et al.’s [Koh 2012] definition, originates from the relationships or dependencies between items, such as between components, parameters, functions, etc., and describes the process by which a change to one part or element of an existing system configuration or design results in one or more additional changes to the system, when those changes would not have otherwise been required.
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| 2. |
- Helms, Sandra, et al.
(author)
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Procedure Model for the Indication of Change Propagation
- 2014
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In: Proceedings of International Design Conference - Design 2014.
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Conference paper (peer-reviewed)abstract
- Engineering changes (EC) occur within the product development and account for up to 50% of its capacities [Lindemann 1998]. Despite the fact that ECs are necessary to improve a product’s quality and that they often are the source for innovation [Fricke 2000], ECs are also costly and bear the risk of propagating further through the product. Propagation occur when a change to one part of the system will trigger subsequent changes in other parts [Yang 2011]. In recent years, many methods on change propagation have been developed which aim at supporting designers assessing alternative change options. These methods, however, often apply to different scopes and intend at answering different questions, which makes it difficult to know which one to choose for one’s own specific situation. For instance, some methods aim at indicating potential change propagation paths so that product designers can see what other components are to be affected in the course of the initiated change, others, on the contrary, aim at calculating the risk for a change to propagate. Some methods are delimited to certain stages during product development such as the conceptual design phase, whereas others can be applied throughout all product development stages. Some methods map physical components, whereas others are able to map functional or parameter linkages in a product, etc. Hence, the methods developed in recent years differ to each other with regards to various aspects such as purpose or expected outcome. This means that, depending on the situation and intention of the product developer, not all methods are equally suitable. Thus, product developers who find themselves in a situation where alternative ways of implementing a change in order to meet the new requirement or to correct faults are available might question themselves what methods are out there that can support them and which of them is the most suitable. Therefore, this work’s objective is to develop a procedure model for product developers that can be used as a guide to decide what method for EC propagation fits best to their specific application environment and shall therefore be chosen.This paper’s definition of ECs is based on the definitions from Jarratt et al. [Jarratt 2011] and Conrat [Conrat 1998]: ECs are modifications in forms, fits, materials, dimensions, functions, drawings or software of a product or component that has already been released during the production design process. ECs include the connected process changes and can be of any size or type, can involve any people, and can take any length of time. This paper’s definition of EC propagation is based on Tang et al.’s [Tang 2008] and Koh et al.’s [Koh 2012] definition: EC propagation originates from the relationships or dependencies between items, such as between components, parameters, functions, etc., and describes the process by which a change to one part or element of an existing system configuration or design results in one or more additional changes to the system, when those changes would not have otherwise been required.
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| 3. |
- Wickel, Eric E, et al.
(author)
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Do children take the same number of steps every day?
- 2007
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In: American journal of human biology : the official journal of the Human Biology Council. - : Wiley. - 1042-0533. ; 19:4, s. 537-43
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Journal article (peer-reviewed)abstract
- The purpose of this study was to examine the day-to-day variability in pedometer-assessed physical activity (steps/day). A total of 1,443 children aged 6-12 years from the United States (195 boys, 254 girls), Sweden (257 boys, 252 girls), and Australia (229 boys, 256 girls) wore a pedometer for 4 consecutive weekdays. Repeated measures analysis of variance was used to examine daily differences in steps/day and the coefficient of variation (CV) was calculated for each individual to describe the day-to-day variability. Overall, mean steps/day were higher among boys (14,698 +/- 3,373 steps/day) than girls (12,086 +/- 2,929 steps/day). Significant differences were found between the 4 monitoring days for the entire sample; however, the absolute mean differences were small (55-958 steps) with an overall effect size of 0.01. This trend was apparent regardless of age, gender, and country. Individual CVs ranged from approximately 2 to 88% and the overall mean CV approximated 22%. An age-related increase in the mean CV was observed between 6- and 12-year-old children. The age x gender x country interaction was not significant (P > 0.05). These findings have implications toward the proper design, analysis, and interpretation of studies regarding physical activity among children. Beyond this aspect, our results lend insight into potential age-related biological mechanisms that may also influence daily levels and patterns of physical activity.
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