1,864 research outputs found

    On the use of the Peak Stress Method for the calculation of Residual Notch Stress Intensity Factors: a preliminary investigation

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    Residual stresses induced by welding processes significantly affect the engineering properties of structural components. If the toe region of a butt-welded joint is modeled as a sharp V-notch, the distribution of the residual stresses in that zone is asymptotic with a singularity degree which follows either the linear-elastic or the elastic-plastic solution, depending on aspects such as clamping conditions, welding parameters, material and dimension of plates. The intensity of the local residual stress fields is quantified by the Residual Notch Stress Intensity Factors (R-NSIFs), which can be used in principle to include the residual stress effect in the fatigue assessment of welded joints. Due to the need of extremely refined meshes and to the high computational resources required by non-linear transient analyses, the R-NSIFs have been calculated in literature only by means of 2D models. It is of interest to propose new coarse-mesh-based approaches which allow residual stresses to be calculated with less computational effort. This work is aimed to investigate the level of accuracy of the Peak Stress Method in the R-NSIFs evaluation

    Aggregation and breakup of acrylic latex particles inside millimetric scale reactors

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    Aggregation of acrylic latex is investigated inside tubular millireactors working under laminar hydrodynamic conditions. The size distribution and fractal dimension of aggregates are measured using light scattering. Results show that the equilibrium between rupture and aggregation is achieved quickly, allowing the study of cluster size distribution and shape at the aggregation/rupture steady state. Both laminar hydrodynamic conditions and high shear rate are suspected to promote the formation of aggregates with a high fractal dimension, which means that the particles are almost spherical, thereby offering an interesting alternative to conventional batch processes. These results can provide useful information for industries aiming at producing aggregates at specified size and quality

    Failure to Preserve β-Cell Function With Mycophenolate Mofetil and Daclizumab Combined Therapy in Patients With New- Onset Type 1 Diabetes

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    OBJECTIVE This trial tested whether mycophenolate mofetil (MMF) alone or with daclizumab (DZB) could arrest the loss of insulin-producing β-cells in subjects with new-onset type 1 diabetes. RESEARCH DESIGN AND METHODS A multi-center, randomized, placebo-controlled, double-masked trial was initiated by Type 1 Diabetes TrialNet at 13 sites in North America and Europe. Subjects diagnosed with type 1 diabetes and with sufficient C-peptide within 3 months of diagnosis were randomized to either MMF alone, MMF plus DZB, or placebo, and then followed for 2 years. The primary outcome was the geometric mean area under the curve (AUC) C-peptide from the 2-h mixed meal tolerance test. RESULTS One hundred and twenty-six subjects were randomized and treated during the trial. The geometric mean C-peptide AUC at 2 years was unaffected by MMF alone or MMF plus DZB versus placebo. Adverse events were more frequent in the active therapy groups relative to the control group, but not significantly. CONCLUSIONS Neither MMF alone nor MMF in combination with DZB had an effect on the loss of C-peptide in subjects with new-onset type 1 diabetes. Higher doses or more targeted immunotherapies may be needed to affect the autoimmune process

    Towards the design of an intensified coagulator

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    This study compares the hydrodynamics in three millimeter-scale continuous reactor geometries that can be easily used in laboratories and industries – a straight tube, a coiled tube and a Dean-Hex reactor – via numerical simulations and analyses the data in a way that is specifically relevant to coagulation processes, thereby offering insights for engineers to develop new coagulation reactors. A numerical approach based on Lagrangian particle tracking is presented to better understand the impact of the geometry and flow on properties that influence coagulation. The results show that the Dean-Hex meandering geometry provides narrower residence time and shear rate distributions, as well as higher mean average shear rates and Camp number distribution than the other geometries. This is attributed to the generation of transverse flows and radial mixing in the Dean-Hex reactor and suggests that a faster and more homogenous coagulation can be expected

    Optimal Sample Size Planning for the Wilcoxon-Mann-Whitney-Test

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    There are many different proposed procedures for sample size planning for the Wilcoxon-Mann-Whitney test at given type-I and type-II error rates α\alpha and β\beta, respectively. Most methods assume very specific models or types of data in order to simplify calculations (for example, ordered categorical or metric data, location shift alternatives, etc.). We present a unified approach that covers metric data with and without ties, count data, ordered categorical data, and even dichotomous data. For that, we calculate the unknown theoretical quantities such as the variances under the null and relevant alternative hypothesis by considering the following `synthetic data' approach. We evaluate data whose empirical distribution functions match with the theoretical distribution functions involved in the computations of the unknown theoretical quantities. Then well-known relations for the ranks of the data are used for the calculations. In addition to computing the necessary sample size NN for a fixed allocation proportion t=n1/Nt = n_1/N, where n1n_1 is the sample size in the first group and N=n1+n2N = n_1 + n_2 is the total sample size, we provide an interval for the optimal allocation rate tt which minimizes the total sample size NN. It turns out that for certain distributions, a balanced design is optimal. We give a characterization of these distributions. Furthermore we show that the optimal choice of tt depends on the ratio of the two variances which determine the variance of the Wilcoxon-Mann-Whitney statistic under the alternative. This is different from an optimal sample size allocation in case of the normal distribution model

    Towards the design of an intensified coagulator

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    This study compares the hydrodynamics in three millimeter-scale continuous reactor geometries that can be easily used in laboratories and industries – a straight tube, a coiled tube and a Dean-Hex reactor – via numerical simulations and analyses the data in a way that is specifically relevant to coagulation processes, thereby offering insights for engineers to develop new coagulation reactors. A numerical approach based on Lagrangian particle tracking is presented to better understand the impact of the geometry and flow on properties that influence coagulation. The results show that the Dean-Hex meandering geometry provides narrower residence time and shear rate distributions, as well as higher mean average shear rates and Camp number distribution than the other geometries. This is attributed to the generation of transverse flows and radial mixing in the Dean-Hex reactor and suggests that a faster and more homogenous coagulation can be expected

    Scenario Planning for Future Development of Rural Areas in Iran: Case of Rural Areas Around the City of Varzegan

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    Development in rural areas is affected by internal and external factors. These factors are making the structure of the system within which decisions are made. Since the policies and decisions adopted in rural plans affect the process of development in the rural areas, the role of them has been considered in the future of rural areas in Iran. Different scenarios and options have been suggested with the use of GIS to clarify the future outcome of these decisions. This study selected three rural areas around the city of Varzegan to consider the effect of both internal and external factors in the future of these areas. Internal factors directly influenced by the independent variable (Population Growth Rate suggested in rural plans), while external factor is beyond the control of it and affects it. Scenario sets shows that the rural area’s sustainability is affected by the population growth rate (actor of the structure), the damages in agricultural lands and employment composition. This fact is not considered in rural plans of Iran because of the need for residential areas due to reverse migration

    Strengthening and stretching for rheumatoid arthritis of the hand (SARAH). A randomised controlled trial and economic evaluation

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    Study registration: Current Controlled Trials ISRCTN 89936343.Background - The effectiveness of exercise for improving hand and wrist function in people with rheumatoid arthritis (RA) is uncertain. Objectives - The study aims were (1) to estimate the clinical effectiveness and cost-effectiveness of adding an optimised exercise programme for hands and upper limbs to standard care for patients with RA; and (2) to qualitatively describe the experience of participants in the trial with a particular emphasis on acceptability of the intervention, exercise behaviours and reasons for adherence/non-adherence.This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 19, No. 19. See the NIHR Journals Library website for further project information. This report has been developed in association with the NIHR Collaboration for Leadership in Applied Health Research and Care Oxford and the NIHR Biomedical Research Unit Funding Scheme. This project benefited from facilities funded through Birmingham Science City Translational Medicine Clinical Research and Infrastructure Trials Platform, with support from Advantage West Midlands
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