Investigation of airflow around buildings using Large-Eddy Simulations for Unmanned Aircraft Systems applications

The ever-increasing demand for Unmanned Aircraft Systems (UAS) has led to the desire for integrating them into spaces in close proximity of humans like dense urban spaces, a reality previously thought of as inconceivable. One of the main concerns to be addressed before its widespread adoption is safety, especially in areas of operation adjacent to structures like buildings. This work investigates the effect of building geometries on the flow field in a simplified urban setup consisting of an isolated building to predict their potential impacts on UAS operations. Unanticipated wind gusts or turbulent flow conditions prevalent around various structures constitute a significant challenge for UAS operations in urban environments. We use Large-Eddy Simulation to better understand the unsteady and highly coherent turbulent flow structures produced by buildings in neutral atmospheric boundary layer flow. Furthermore, we also demonstrate a non-intrusive machine learning methodology to predict flow fields to augment safe wind-aware navigation systems for Unmanned Aerial Vehicles as a first step towards safely integrating UAS into existing aerial infrastructure.Mechanical and Aerospace Engineerin

Determination of the Failure Susceptibility of a Flat Die used in Biomass Pelletizing Machines by means of FEA based Design Exploration

This paper focuses on a design analysis of a flat die used in an agricultural biomass pelletizing machine by considering its high pressure loading failure susceptibility. The pellet die is one of the key elements in a pelletizing machine, and the strength of the die plate has an important role on the pellet’s quality and producibility. In fact, higher compression ratio (CR - the ratio of effective length and the internal (press channel) diameter of a die orifice/hole) will provide denser pellets which is a desired phenomenon, however, if the compression pressure is too high or CR is not determined to compensate high pressures, the raw material may block the die and the die may experience deformation failure due to overloading. If the desire is to make high quality pellets with no die failure, optimum flat die hole/orifice design parameters should be used which can provide the best CR for a specific compression pressure. This is the core motivation of this research. In this study, Finite Element Analysis (FEA) based design exploration has been utilised for a sample single hole flat die with various die geometry parameters against various compression pressure values. Following the FEA design exploration undertaken, a response surface analysis (RSA) was carried out and then estimation models (empirical equations), which could be used to calculate parameters of the die hole/orifice against applied compression pressure and failure susceptibility based on structural stress and deformation, was described. The results gained from the RSA has indicated that the estimation models have high R2 values (higher than 98 %) which could be used for adequately predicting failure susceptibility indicators. In addition to this, FEM-based simulation print-outs have provided useful stress distribution visuals on the die against different compression pressure values. Most especially, the study has highlighted that a detailed structural optimisation study may be scheduled in order to obtain die geometry design parameters with a focus on the failure susceptibility

AMERICAN JOURNAL OF NEPHROLOGY

We encountered 9 cases of tuberculosis out of our 157 chronic HD patients in 36 months. Four pulmonary, 4 lymph nodal and one isolated dermal involvement were detected. Therapy was commenced without waiting for absolute cultural or pathologic diagnosis because of the high index of clinical suspicion. All cases except one recovered completely. Among associated conditions, peptic ulcer disease, anti-HCV positivity, and diabetes mellitus were noted, though the last two did not reach statistical significance. Prompt institution of the specific therapy and close supervision of the cases during treatment enabled us to obtain a cure in all cases except one and to discern adverse drug effects immediately and to make appropriate changes in the therapy. Thus, no morbidity due to the disease itself or drugs was observed. Copyright (C) 2001 S. Karger AG, Basel

NEPHRON CLINICAL PRACTICE

Background: The aim of this study is to investigate the relationship between the degree of malnutrition and inadequate volume control evidenced by echocardiography. Methods: In this study 72 chronic hemodialysis patients were investigated in a cross-sectional manner. The malnutrition score was calculated using Subjective Global Assessment. M-mode echocardiography was performed in all patients. Results: The highest malnutrition score (23.2 +/- 1.5 points) and lowest vena cava inferior collapse index (35 +/- 2%) were observed in the eccentric left ventricular hypertrophy group. The malnutrition index was found to be in positive relationship with the left atrium diameter and index, left ventricular mass and index, and left ventricular end-diastolic diameter. On the other hand, a negative correlation was detected with the vena cava inferior collapse index. When all parameters that were found to be related to malnutrition were assessed by multivariate analyses, a statistically significant relation was found between the left ventricular end-diastolic diameter and the malnutrition index. Conclusion: The results of our study show that the progressive worsening of the nutritional status follows a parallel course along with the deterioration in the echocardiographic parameters concerning hypervolemia. This in turn suggests that increasing degrees of malnutrition are associated with more profound derangements in the volume status. Volume excess might be a mechanism explaning the increased mortality and morbidity caused by malnutrition in hemodialysis patients. Owing to its cross-sectional design, this study cannot provide unequivocal evidence regarding the cause and effect relationship between volume overload and malnutrition in hemodialysis patients. Copyright (c) 2007 S. Karger AG, Basel

JOURNAL OF NEPHROLOGY

Background: Nocturnal hypertension (NH) is an unsolved problem in hemodialysis (HD) patients. The effect of ultrafiltration (UF) on NH and myocardial performance has not been systematically investigated in HD patients. Methods: Seventeen reverse-dipper (RD) HD patients were subjected to intensified UF. Before and after UF, echocardiographic and blood pressure (BP) measurements were taken. Results: Excluding daytime diastolic BP, all BP parameters (mmHg), namely daytime systolic BP (138.1 +/- 15.1; 131.1 +/- 12.5), night-time systolic BP (150.4 +/- 17.6; 125.3 +/- 16.5), night-time diastolic BP (87.3 +/- 10.3; 76.5 +/- 11.6), daytime pulse pressure (56.1 +/- 7.6; 50.5 +/- 5), night-time pulse pressure (63.3 +/- 9.4; 48.7 +/- 7), significantly decreased (p<0.001 for all comparisons). Thirteen patients converted to non-dipper and two patients converted to dippers, whereas two patients remained on RD. Unit for measurement of diameters was mm. Ejection fractions (EF) increased (51.23 +/- 9.01; 64.05 +/- 7.23, p<0.001), left atrial diameters (LAD) decreased (35 +/- 8.29; 32.05 +/- 7.12, p<0.001), the vena cava inferior collapse index increased (VCICI) [24.82 +/- 8.20 (%); 51.76 +/- 9.65 (%), p<0.001], left ventricular end-systolic (LVES) and diastolic diameters (LVED) decreased (3.19 +/- 0.60; 2.77 +/- 0.51, p<0.001; 4.39 +/- 0.65; 4.18 +/- 0.56, p=0.002, respectively). Percentage reduction in night-time diastolic BP correlated with the percentage reduction in LA-D (p=0.038). Percentage reduction in night-time pulse pressure correlated with the percentage increase in EF (p<0.013). Similarly, percentage reductions in night-time systolic BP, night-time diastolic BP and night-time mean BP correlated with the percentage reduction in LVESD (p=0.014, p<0.001 and p=0.001, respectively). Conclusions: NH in HD patients is a volume dependent phenomenon. Improved night-time BP parameters have a more profound effect on myocardial function than daytime BP parameters

SCANDINAVIAN JOURNAL OF UROLOGY AND NEPHROLOGY

Objective. The relationship between malnutrition, echocardiographic parameters, 24 h ambulatory blood pressure (ABP) parameters and decreased insulin sensitivity index (ISI-S) in chronic haemodialysis patients was investigated. Material and methods. ISI-S and inflammatory indicators were measured. The nutritional state was assessed by malnutrition score. Echocardiography and 24 h ABP were performed 1 day before the second haemodialysis session of the week. Results. ISI-S was inversely correlated with the night-time mean blood pressure (BP)/day-time mean BP ratio (p = 0.021) and malnutrition score (p < 0.01). High-sensitivity C-reactive protein, night-time mean BP/day-time mean BP and vena cava collapse index were independent risk factors affecting ISI-S (p < 0.001; beta = 0.412, p= 0.025; beta = -0.204, p < 0.001; beta = -0.465). Conclusions. The decrease in ISI-S along with the hypervolaemia suggests that volume overload is a contributory factor in the pathogenesis of insulin resistance in patients with chronic renal failure. This study indicates that, in addition to the traditional cardiovascular risk factors in these patients, insulin resistance can be regarded as a risk factor, but not an independent one, mainly a reflection of the underlying culprit, hypervolaemia

CLINICAL NEPHROLOGY

Aim: Increased blood pressure variability (BPV) in end-stage renal disease (ESRD) patients is proved to be a risk factor for cardiovascular disease [Tozawa et al. 1999]. The effect of ultrafiltration (UF) on BPV in hemodialysis (HD) patients has not been reported in the literature. This study was undertaken to define the effect of a single UF on BPV in HD patients. Methods: Prior and after HD with UF, 24-hour ambulatory BP monitoring (ABPM) was applied to each patient and then diurnal and nocturnal BP and BPV parameters (both before and after UF) were compared and correlated with UF values. Results: Increase in BPV after single UF in all groups was statistically significant (p < 0.05). Only the daytime systolic (DS) BPV increase (median 42.4%) was in positive correlation with &UDelta; body weight (body wt) (median 3.07%) or UF amount (r = 0.649, p < 0.01). Conclusions: Large volume depletions and sympathetic hyperreactivity could explain the increase in BPV. Increased interdialytic weight gain requires more UF and subsequently BPV, morbidity and mortality also increase. Thus, considerable efforts must be made to prevent great interdialytic weight gain in HD patients