Searching for improvement

Engineering design can be thought of as a search for the best solutions to engineering problems. To perform an effective search, one must distinguish between competing designs and establish a measure of design quality, or fitness. To compare different designs, their features must be adequately described in a well-defined framework, which can mean separating the creative and analytical parts of the design process. By this we mean that a distinction is drawn between coming up with novel design concepts, or architectures, and the process of detailing or refining existing design architecture. In the case of a given design architecture, one can consider the set of all possible designs that could be created by varying its features. If it were possible to measure the fitness of all designs in this set, then one could identify a fitness landscape and search for the best possible solution for this design architecture. In this Chapter, the significance of the interactions between design features in defining the metaphorical fitness landscape is described. This highlights that the efficiency of a search algorithm is inextricably linked to the problem structure (and hence the landscape). Two approaches, namely, Genetic Algorithms (GA) and Robust Engineering Design (RED) are considered in some detail with reference to a case study on improving the design of cardiovascular stents

Robust optimization of cardiovascular stents: A comparison of methods

This is the post-print version of the Article. The official published version can be accssed from the links below. Copyright @ 2004 Taylor & FrancisModern engineering design contains both creative and analytic components. This paper discusses the design process and illustrates links between design optimization and conceptual design through the re-design of a cardiovascular stent. A comparison is presented of two methods for design improvement: genetic algorithms (GA) and model-based robust engineering design (RED). Computational fluid dynamics (CFD) models are used to generate measurements of the quality of competing designs based on the concept of dissipated power. Alternative performance measures are also discussed. Environmental noise is introduced into the analysis and consideration is given to the treatment of discrete and continuous design parameters. Improved designs are identified using both methods and verified with further CFD analyses, and the benefits of each method are discussed

Bond graph based sensitivity and uncertainty analysis modelling for micro-scale multiphysics robust engineering design

Components within micro-scale engineering systems are often at the limits of commercial miniaturization and this can cause unexpected behavior and variation in performance. As such, modelling and analysis of system robustness plays an important role in product development. Here schematic bond graphs are used as a front end in a sensitivity analysis based strategy for modelling robustness in multiphysics micro-scale engineering systems. As an example, the analysis is applied to a behind-the-ear (BTE) hearing aid. By using bond graphs to model power flow through components within different physical domains of the hearing aid, a set of differential equations to describe the system dynamics is collated. Based on these equations, sensitivity analysis calculations are used to approximately model the nature and the sources of output uncertainty during system operation. These calculations represent a robustness evaluation of the current hearing aid design and offer a means of identifying potential for improved designs of multiphysics systems by way of key parameter identification

Experimental and bond graph based sensitivity calculations for micro-scale robust engineering design

Copyright @ 2005 IEEEBond graph modeling and sensitivity analysis are used to provide a platform for the robust design of a small mechatronic device, a behind-the-ear (BTE) hearing aid. Two key components of the device, namely the telecoil and the receiver, are considered. Experimental measurements, bond graph simulation models and analytic sensitivity analysis are used to investigate the interaction between these components in order to gain insight into the effect of component placement on the robustness of the final product

Sensitivity analysis modelling for microscale multiphysics robust engineering design

Sensitivity Analysis (SA) plays an important role in the development of any practical engineering model. It can help to reveal the sources and mechanisms of variability that provide the key to understanding system uncertainty. SA can also be used to calibrate simulation models for closer agreement with experimental results. Robust Engineering Design (RED) seeks to exploit such knowledge in the search for design solutions that are optimal in terms of performance in the face of variability. Microscale and multiphysics problems present challenges to modelling due to their complexity, which puts increased demands on computational methods. For example, in developing a model of a piezoelectric actuator, the process of calibration is prolonged by the number of parameters that are difficult to verify with the physical device. In the approach presented in this paper, normalised sensitivity coefficients are determined directly and accurately using the governing finite element model formulation, offering an efficient means of identifying parameters that affect the output of the model, leading to increased accuracy and knowledge of system performance in the face of variability

The extent that health professionals suspect and address addiction to medicines in primary care: Findings from a survey in Northwest England.

Addiction to medicines available over the counter or via prescription is of growing international concern. The authors of the current article ran an online survey of health professionals in general medical practice and community pharmacy settings in Northwest England to explore the frequency of suspecting and responding to addiction to medicines. Health professionals reported frequently identifying addiction to medicines among patients including those with long-term pain, mental health problems, sleep disorders, and other substance use disorders, but that these addictions often go unchallenged. This adds to the evidence indicating the under-diagnosis of addiction to medicines in the United Kingdom. Strategies to improve diagnosis and treatment should recognize the diversity of individuals with addiction to medicines

The Nurse Manager: An Ethnography of Hospital-Based First-Line Nurse Managers Practicing in an Expanded Role

The behaviors, beliefs and values that characterize everyday practice of first-line nurse managers role were analyzed. Ethnographic field research techniques were used including nine months of observation and in-depth interviews with practicing nurse managers. After reviewing historical events that shaped the role of the nurse manager, the role was then placed within the economic, social and health care context of the 1970\u27s and 80\u27s. Research and anecdotal descriptions of the manager role of the past twenty years were also explored. Research was conducted in two voluntary acute care, multi-service hospitals. One manager was observed intensively for two months to develop a semi structured open-ended interview guide. The guide was then used to conduct extensive ethnographic interviews with 16 inpatient managers. In addition, six nurse administrators were interviewed, institutional documents examined and a variety of techniques used to triangulate observations and theories that emerged and to examine issues of validity and reliability. Managers described their role as four processes: (1) social control, establishing, monitoring and maintaining standards; (2) resourcing, the provision of emotional support, goods and services; (3) translating/ interpreting/negotiating among unit-based or related constituencies; and, (4) facilitating change. Administrators concurred with the managers\u27 descriptions emphasizing social control. Managers described themselves as desiring control/power to make beneficial changes; being stimulated by a changing work environment and deriving satisfaction from staff development. They identified essential skills for role enactment as communication/interpersonal expertise, clinical knowledge, flexibility, a strong ego and political savvy. The study then examined how managers analyze the complexity of change, alter their management strategies accordingly and create a working culture that is maximally adaptable to an unstable health care environment. They identified ways to enhance success and avoid or respond to failure, using knowledge acquired primarily through experience. Finally, the study examined the common culture of nursing management within the context of its historical roots, particularly the necessity for a bicultural identity that incorporates beliefs and values of both manager/employee and professional clinician/nurse. Structured mentoring was explored as a bridging strategy to enhance enculturation and skill acquisition

A geometrical formulation of the μ-lower bound problem

A new problem formulation for the structured singular value μ in the case of purely real (possibly repeated) uncertainties is presented. The approach is based on a geometrical interpretation of the singularity constraint arising in the μ lower bound problem. An interesting feature of this problem formulation is that the resulting parametric search space is independent of the number of times any parameter is repeated in the structured uncertainty matrix. A corresponding lower bound algorithm combining randomisation and optimisation methods is developed, and some probabilistic performance guarantees are derived. The potential usefulness of the proposed approach is demonstrated on two high-order real μ analysis problems from the aerospace and systems biology literature

A04 The role of splicing factor SRSF6 in incomplete splicing of the HTT transcript

Background Huntington’s disease (HD) is caused by an expanded CAG repeat in exon 1 of the HTT gene. In models of HD, an expanded CAG repeat in HTT causes premature termination of HTT RNA during transcription; this occurs by a process called incomplete splicing. Incompletely spliced HTT (HTTexon1) includes exon 1 of the coding region of HTT, as well as a 5’ region of intron 1, which is non-coding. HTTexon1 encodes a truncated exon 1 HTT protein, which is implicated in HD pathogenesis. Although the precise RNA processing mechanism of Httexon1 is unknown, splicing factor SRSF6 has been shown to co-precipitate with transcripts containing Htt intron 1 in HD mice. Aim To elucidate the role of splicing factor SRSF6 in incomplete splicing of Htt in HD mice. Methods Heterozygous Srsf6 knock-out (KO) mice (Srsf6±) were generated by CRISPR/Cas9. Characterisation of Srsf6± mice was undertaken by quantitative RT-PCR and western blotting. Viability of homozygous Srsf6 KO (Srsf6-/-) mice was examined by inbreeding of Srsf6± mice. To assess the modulation of incomplete splicing by decreasing SRSF6, Srsf6± mice were bred to HD knock in mice (zQ175) and tissues were analysed. Levels of Httexon1 were measured by Quantigene, a gene expression assay. Results Srsf6-/- homozygotes were embryonic lethal, limiting us to the use of Srsf6± mice only. In Srsf6± heterozygotes, Srsf6 mRNA was decreased by 50% in brain and peripheral regions, and SRSF6 protein was decreased by 70% in brain compared to wild type mice. However, heterozygosity for Srsf6 knock out did not modulate the level on incomplete splicing in zQ175 mice. Conclusion Ablation of a single Srsf6 allele did not reduce levels of incomplete splicing in HD mice and therefore, further Srsf6 knock down may be required. Accordingly, mouse embryonic fibroblasts (MEFs) have been generated and will be used to measure Httexon1 levels after further Srsf6 knockdown by RNA interference. This work is supported by the CHDI foundation