4,297 research outputs found

    Application of a simplified probe feed impedance formula to the design of a dual frequency patch antenna

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    A simplified probe feed input impedance for a rectangular patch antenna based on the Green's function is used to design a dual frequency matched antenna. The predicted results at design frequencies of 1.9 and 2.4 GHz are in close agreement with experimental measurements

    Expansion wave diffraction around sharp convex corners

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    A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. Johannesburg, December 2017Much work has been previously invested towards the study of shock wave phenomena. However, little or no literature can be found involving studies of expansion waves undergoing similar effects. The study of expansion wave diffraction was rst considered by Mohamed and Skews [1]. The investigation focussed on studying expansion wave diffraction around a 90 corner by using both experimental and computational methods. While a good agreement between the results was found there were several features which were apparent in the experimental imaging but could not be resolved by a numerical model. This included the large-scale turbulent structures in the separation bubble, shear layer instability and vortex shedding as well as a large wake region which was noted downstream of the bubble. In the current work, expansion wave di raction is examined using Large Eddy Simulation in an attempt to provide a better description of the ow eld. To make the analysis more feasible the Embedded LES hybrid technique was employed. Several subgrid-scale LES models were tested and the Wall Modelled LES technique showed the most promising results. The LES solution showed much improvement to the RANS solutions from the previous work. Turbulence in the separation bubble was evident and shear-layer instability and vortex shedding was observed. Due to the very low velocity uctuations the LES model did not resolve the wake region although, in certain cases, evidence of a wake region beginning to form could be seen. Using these results a further analysis into the structure of the bubble through the depth of the ow was conducted. As an extension of previous work the current study also examined expansion wave diffraction around other convex corners. The study involved an experimental as well as RANS and LES computational methods. The wedge angles investigated were 45 , 15 and 5 . The effects of changing the initial diaphragm pressure ratio and the diaphragm distance from the di raction corner were analysed. The results showed a high resemblance to what was found previously for the 90 case. However, signifi cant differences were noted in the shape of the bubble due to the inclination angle of the ow along vertical wall and the much higher velocity gradients of the ow at the diffraction corner and surrounding the bubble.MT 201

    Methodologies and tools for OSS: current state of the practice

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    Over the years, the Open Source Software (OSS) development has matured and strengthened, building on some established methodologies and tools. An understanding of the current state of the practice, however, is still lacking. This paper presents the results of a survey of the OSS developer community with a view to gain insight of peer review, testing and release management practices, along with the current tool sets used for testing, debugging and, build and release management. Such an insight is important to appreciate the obstacles to overcome to introduce certification and more rigour into the development process. It is hoped that the results of this survey will initiate a useful discussion and allow the community to identify further process improvement opportunities for producing better quality software

    Water-pipe smoking and albuminuria: new dog with old tricks

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    Water-pipe (WP) smoking is on rise worldwide for the past few years, particularly among younger individuals. Growing evidence indicates that WP smoking is as harmful as cigarette smoking. To date, most of the research has focused on acute health effects of WP smoking, and evidence remains limited when it comes to chronic health effects in relation to long-term WP smoking. Therefore, the aim of this study was to examine the association between WP smoking and albuminuria in apparently healthy individuals. This analysis was conducted on data of a population-based cross-sectional study—the Urban Rural Chronic Diseases Study (URCDS). The study sample was recruited from three sites in Pakistan. Trained nurses carried out individual interviews and obtained the information on demographics, lifestyle factors, and past and current medical history. Measurements of complete blood count, lipid profile, fasting glucose level, and 24-hour albuminuria were also made by using blood and urine samples. Albumin excretion was classified into three categories using standard cut-offs: normal excretion, high-normal excretion and microalbuminuria. Multiple logistic regression models were used to examine the relationship between WP smoking and albuminuria. The final analysis included data from 1,626 health individuals, of which 829 (51.0%) were males and 797 (49.0%) females. Of 1,626 individuals, 267 (16.4%) were current WP smokers and 1,359 (83.6%) were non-WP smokers. WP smoking was significantly associated with high-normal albuminuria (OR = 2.33, 95% CI 1.68-3.22, p-value <0.001) and microalbuminuria (OR = 1.75, 95% CI 1.18-2.58, p-value 0.005) after adjustment for age, sex, BMI, social class, hypertension, and diabetes mellitus. WP smoking was significantly associated with high-normal albuminuria and microalbuminuria when analysis was stratified on hypertension and diabetes mellitus categories. WP smoking has a strong association with albuminuria in apparently healthy individuals. More research is warranted to evaluate the temporality of this association between WP smoking and albuminuria

    Expressed emotion and wellbeing in South Asian heritage families living in the UK

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    The primary aim of this paper was to understand expressed emotion (EE) and its relationship to wellbeing in South Asians (SAs) living in the UK. A total of 529 participants of South Asian heritage were recruited from the UK and completed an online survey consisting of the family questionnaire, the level of expressed emotion scale (LEE), warmth measure, the hospital anxiety and depression scale. Components of EE and wellbeing were investigated using network analysis. Overall, the participants were classified as low EE for criticism, but high for emotional overinvolvement. They scored relatively high on the warmth scale. LEE scores were in the middle range. The network analysis revealed unique associations between EE subscales and symptoms of depression and anxiety, and highlighted positive aspects of EE. The network analysis also highlighted differences in EE between parents and partner. The findings provide an overview of the interactions and influence of EE variables within this population. Future research should focus on the differences between SA ethnicities and religions; differentiating between intrusive and non-intrusive involvement may help further explain part of the variance between variables; exploring first and second-generation immigrants would help discover the impact of acculturation and intergenerational trauma on EE

    Metal transport in cells: cadmium uptake by rat hepatocytes and renal cortical epithelial cells.

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    The toxic metals appear to use the transport pathways that exist for biologically essential metals. In this regard interactions between the toxic and essential metals are possible. This report summarizes recent findings on the transport of cadmium in rat hepatocytes and renal cortical epithelial cells in the presence or absence of certain essential metals. The transport of cadmium in hepatocytes does not require energy and, therefore, is not an active process. It occurs primarily (80%) by temperature-sensitive processes, i.e., ion channels and carriers, that involve interaction with sulfhydryl groups. These processes apparently exist for the transport of essential metals like copper, zinc and calcium. The remaining 20% of the cadmium in hepatocytes is transported via a temperature-insensitive process, possibly by diffusion. In comparison with the hepatocytes, a smaller fraction (30%) of the cadmium transport through the basolateral membrane and none from the apical membrane of the renal cortical epithelial cells is temperature-sensitive. Total accumulation through the basolateral membrane is about twice that through the apical membrane. A majority of the cadmium transport in the renal cells is by diffusion. As in hepatocytes, copper, zinc and mercury antagonize cadmium transport through the apical membranes of the renal cells. The relative antagonism by copper is the same (25%); however, the antagonism by zinc (16%) and mercury (10%) is 4- to 6-fold lower than in hepatocytes. It appears that the relative contribution of various transport pathways available for cadmium uptake is different in each cell type and apparently depends on the morphological and functional differences between the cell membranes

    An Improved Algorithm to Solve Transportation Problems for Optimal Solution

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    In this paper, we have developed an algorithm to obtain initial basic feasible solution of transportation problems where the object is to minimize the transportation cost. The proposed method is compared with well-known existing methods including Least-Cost Method and North-West Corner Method and is found to yield better results. Feasible solution from the proposed method leads to solution closest to the optimal solution; and in some numerical examples same as the optimal solution. Key words: Transportation problem, Initial Basic Feasible Solution, Optimal Solutio
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