The effect of acceleration versus displacement methods on steady-state boundary forces

This study describes the acceleration and displacement methods for use in the recovery of coupled system boundary forces. A simple two degree of freedom system has been used for illustration. The effect of the choice of method for use with indeterminate or over-constrained boundaries has been investigated. It has specifically looked at results from a simple two dimensional beam problem using both methods. Much work has been done on the effect of Craig-Bampton modal truncation system displacements and forces, however, little work has been done on system level modal truncation. The findings of this study indicate that the effect of this system level truncation is significant. This may be particularly true for the 35 Hz system cutoff frequency that is required by the space shuttle. From this study's findings, recommendations for areas of study with space shuttle payload systems are made

A numerical method for interface problems in elastodynamics

The numerical implementation of a formulation for a class of interface problems in elastodynamics is discussed. This formulation combines the use of the finite element and boundary integral methods to represent the interior and the exteriro regions, respectively. In particular, the response of a semicylindrical alluvial valley in a homogeneous halfspace to incident antiplane SH waves is considered to determine the accuracy and convergence of the numerical procedure. Numerical results are obtained from several combinations of the incidence angle, frequency of excitation, and relative stiffness between the inclusion and the surrounding halfspace. The results tend to confirm the theoretical estimates that the convergence is of the order H(2) for the piecewise linear elements used. It was also observed that the accuracy descreases as the frequency of excitation increases or as the relative stiffness of the inclusion decreases

The Vehicle Integrated Performance Analysis Experience: Reconnecting With Technical Integration

Very early in the Space Launch Initiative program, a small team of engineers at MSFC proposed a process for performing system-level assessments of a launch vehicle. Aimed primarily at providing insight and making NASA a smart buyer, the Vehicle Integrated Performance Analysis (VIPA) team was created. The difference between the VIPA effort and previous integration attempts is that VIPA a process using experienced people from various disciplines, which focuses them on a technically integrated assessment. The foundations of VIPA s process are described. The VIPA team also recognized the need to target early detailed analysis toward identifying significant systems issues. This process is driven by the T-model for technical integration. VIPA s approach to performing system-level technical integration is discussed in detail. The VIPA process significantly enhances the development and monitoring of realizable project requirements. VIPA s assessment validates the concept s stated performance, identifies significant issues either with the concept or the requirements, and then reintegrates these issues to determine impacts. This process is discussed along with a description of how it may be integrated into a program s insight and review process. The VIPA process has gained favor with both engineering and project organizations for being responsive and insightfu

The ASTRO-1 preliminary design review coupled load analysis

Results of the ASTRO-1 preliminary design review coupled loads analysis are presented. The M6.0Y Generic Shuttle mathematical models were used. Internal accelerations, interface forces, relative displacements, and net e.g., accelerations were recovered for two ASTRO-1 payloads in a tandem configuration. Twenty-seven load cases were computed and summarized. Load exceedences were found and recommendations made

A Strategy for Integrating a Large Finite Element Model Using MSC NASTRAN/PATRAN: X-33 Lessons Learned

The X-33 vehicle is an advanced technology demonstrator sponsored by NASA. For the past 3 years the Structural Dynamics and Loads Branch of NASA's Marshall Space Flight Center has had the task of integrating the X-33 vehicle structural finite element model. In that time, five versions of the integrated vehicle model have been produced and a strategy has evolved that would benefit anyone given the task of integrating structural finite element models that have been generated by various modelers and companies. The strategy that has been presented here consists of six decisions that need to be made: purpose of models, units, common materials list, model numbering, interface control, and archive format. This strategy has been proven and expanded from experience on the X-33 vehicle

Development of a Chinese version of the National Eye Institute Visual Function Questionnaire (CHI-VFQ-25) as a tool to study patients with eye diseases in Hong Kong

Background: To develop a Chinese version of the National Eye Institute Visual Function Questionnaire (CHI-VFQ-25) and to test its reliability and validity in a group of patients with eye diseases in Hong Kong. Methods: The National Eye Institute Visual Function Questionnaire (NEI-VFQ) was translated into Chinese. Patients were recruited from Hong Kong, and their demographic data and visual acuity were documented. Psychometric properties of the CHI-VFQ-25, including internal consistency, test-retest reliability, item-scale correlations and construct validity were tested. Results: 250 patients were recruited. The mean age of the patients was 66.04 (SD 14.00). 46% of them were male. The non-response rate and the floor and ceiling numbers of the CHI-VFQ-25 were calculated. The internal consistency was high in most subscales (except the general health and driving subscales), with Cronbach α ranging from 0.72-0.90. The test-retest reliability was excellent (intraclass correlation coefficient >0.90). Patients with worse visual acuity had significantly lower scores on the CHI-VFQ-25 supporting construct validity. Conclusion: The CHI-VFQ-25 is a reliable and valid tool for assessing the visual functions of Chinese patients with eye diseases in Hong Kong. Some questions had high non-response rates and should be substituted by the available alternatives.published_or_final_versio

A study on health-related quality of life of patients with Colorectal Neoplasm and cost-effectiveness analysis of Colorectal Cancer Screening in Hong Kong

Conference Theme: Translating Health Research into Policy and Practice for Health of the PopulationPoster Presentation - Delivery of Health Services: abstract no. P41-Ab0005BACKGROUND: Colorectal cancer (CRC) is the most common cancer in Hong Kong. Health-related quality of life (HRQOL) is an important health outcome of CRC survivors. Screening for CRC has the potential of preventing CRC death but there was uncertainty on its impact on HRQOL and the cost-effectiveness of different screening strategies ...postprin

Long-term effects of the multidisciplinary risk assessment and management program for patients with diabetes mellitus (RAMP-DM): a population-based cohort study

Background: Studies on the long-term effectiveness of multidisciplinary risk-stratification based management in Chinese population were rare. This study aimed to evaluate the effectiveness of a multidisciplinary risk assessment and management program for patients with diabetes mellitus (RAMP-DM) in reducing the risks of cardiovascular complications and all-cause mortality. Methods: A prospective cohort study was conducted in 18,188 propensity score matched RAMP-DM participants and subjects with diabetes under usual primary care (9,094 subjects in each group). The study endpoints were the first occurrence of coronary heart disease (CHD), stroke, heart failure (HF), total cardiovascular disease (CVD) and all-cause mortality. We constructed multivariable Cox proportional hazard regressions to estimate the association between the RAMP-DM intervention and the first occurrence of study endpoints. Results: The median follow-up period was 36 months. Three hundred and ninety-nine CVD events occurred in the RAMP-DM group, as compared with 608 in the control group [adjusted hazard ratio, 0.629; 95 % confidence interval (CI) 0.554–0.715; P < 0.001]. The total number of all-cause deaths in RAMP-DM group was less than half that of control group (202 vs 552, adjusted hazard ratio, 0.363; 95 % CI, 0.308–0.428; P < 0.001). The adjusted hazard ratios of the RAMP-DM group for CHD, stroke, and HF were 0.570 (95 % CI, 0.470–0.691; P < 0.001), 0.652 (95 % CI, 0.546–0.780; P < 0.001), and 0.598 (95 %CI, 0.446–0.802; P = 0.001), respectively. Conclusions: The RAMP-DM intervention was associated with lower incidences of individual and total cardiovascular complications, as well as all-cause mortality over 3 years follow-up. The encouraging results provided evidence to support that the structured risk-stratification management leading by a multidisciplinary clinical team was an effective approach to reduce future cardiovascular complications in people with diabetes.published_or_final_versio

‘Ethnic group’, the state and the politics of representation

The assertion, even if only by implication, that ‘ethnic group’ categories represent ‘real’ tangible entities, indeed identities, is commonplace not only in the realms of political and policy discourse but also amongst contemporary social scientists. This paper, following Brubaker (2002), questions this position in a number of key respects: of these three issues will dominate the discussion that follows. First, there is an interrogation of the proposition that those to whom the categories/labels refer constitute sociologically meaningful ‘groups’ as distinct from (mere) human collectivities. Secondly, there is the question of how these categories emerge, i.e. exactly what series of events, negotiations and contestations lie behind their construction and social acceptance. Thirdly, and as a corollary to the latter point, we explore the process of reification that leads to these categories being seen to represent ‘real things in the world’ (ibid.)