WAVE FIELD GENERATED BY FINITE-SPAN HYDROFOILS OPERATING BENEATH A FREE SURFACE

The present paper focuses on the numerical investigation of the flow around the fully submerged 2D and 3D hydrofoils operating close to a free surface. Iterative boundary element method is implemented to predict the flow field. This study aims to investigate the aspect ratio effect on the free surface interactions and hydrodynamic performance of the hydrofoils under a free surface by using potential flow theory. Three different submergence depths and aspect ratios are studied in the wide range of Froude Numbers. In 3D cases, spanwise width of the numerical wave tank model is selected both equal and wider to the foil span, to observe the sidewall effects. Wave field seems to be two dimensional at low Froude numbers. On the other hand, signs of three dimensionalities are observed on the free surface structure for higher Fn, even the predicted wave elevations are very close to 2D calculations in the midsection. Increment in the Fn give a rise to the amplitude of the generated waves first, however a further increase in Fn has a lowering effect with the beginning of waves spill in the spanwise direction in the form of Kelvin waves. Free surface proximity and resultant wave field are also seeming to be linked with the lift force on the hydrofoil. As aspect ratio of the foil increase, 3D lift values are getting closer to those of 2D calculations. However, it is seen that, 3D BEM predictions of a hydrofoil under free surface effect cannot be considered two-dimensional even the aspect ratio is equal to 8

FREE SURFACE FLOW SIMULATION AROUND AN APPENDED SHIP HULL

This study brings forward the results of previously published work of free surface flow simulation around a fast ship model. Experimental measurements and numerical simulations of a fast bare-hull ship model form are now extended to the same ship form with appendices for a wide range of Froude numbers. The governing equations are discretized by means of an unstructured finite volume mesh. The standard k-ε turbulence model and Volume of Fluid Method to capture the two phase media are used. The total resistance, due to wave and wake fields of the ship model with appendages and the resistance of the appendages alone are calculated numerically, and compared with the experiments. The experiments and computations were performed for 11 different Froude numbers between 0.103 and 0.322. For Froude numbers up to 0.25, numerical simulations found to be quite in agreement with the experiments. It has been found that appendages increase the total drag mainly by increasing the pressure resistance, and the effect of the appendages becomes more important as the flow speed gets higher

A new generation, promising engineering material: Cubic boron nitride c-BN

In order to meet the design requirements and expanding demands in various engineering fields, it is essential to incorporate new technological improvements in material sciences into existing processes and applications. This involves engineering new material systems and improving existing ones towards higher strength, toughness and wear resistance. In this context, cubic boron nitride c-BN , which is a special polymorph of boron nitride, seems to be a high-potential candidate for engineering solutions due to its great mechanical and chemical properties. In this article, advantages and disadvantages of c-BN material system are presented with respect to our ongoing research efforts. The preliminary results about the characterization study of thin film c-BN coatings with Raman spectroscopy are also presente

Baseline aortic pre-ejection interval predicts reverse remodeling and clinical improvement after cardiac resynchronization therapy

Background: Cardiac resynchronization therapy (CRT) has been shown to reduce heart failure-related morbidity and mortality. However, approximately one in three patients do not respond to CRT. The aim of the current study was to determine the parameter(s) which predict reverse remodeling and clinical improvement after CRT. Methods: A total of 54 patients (43 male, 11 female; mean age 61.9 ± 10.5 years) with heart failure and New York Heart Association (NYHA) class III–IV symptoms and in whom left ventricular ejection fraction (LVEF) was £ 35% and QRS duration was ≥ 120 ms, despite optimal medical therapy, were enrolled. An echocardiographic examination was performed before, and six months after, CRT. An echocardiographic response was defined as a reduction of end-systolic volume ≥ 10% after six months, and a clinical response was defined as a reduction ≥ 1 in the NYHA functional class score. Results: An echocardiographic response was observed in 38 (70.4%) of the patients and a clinical response occurred in 41 (75.9%) of the patients. Of the dyssynchrony parameters, only the aortic pre-ejection interval (APEI) was observed to significantly predict the clinical response (p = 0.048) and echocardiographic response (p = 0.037). A 180.5 ms cut-off value for the APEI predicted the clinical response with a sensitivity of 92.3% and a specificity of 39%, and the echocardiographic response with a sensitivity of 93.0% and a specificity of 42%. Conclusions: APEI derived from pulsed-wave Doppler, which is available in every echocardiography machine, is a simple and practical method that could be used to select patients for CRT. (Cardiol J 2011; 18, 6: 639–647

Total white blood cell count is associated with the presence, severity and extent of coronary atherosclerosis detected by dual-source multislice computed tomographic coronary angiography

Background: Total white blood cell (WBC) count has been consistently shown to be an independent risk factor and predictor for future cardiovascular outcomes, regardless of disease status in coronary artery disease (CAD). The purpose of this study is to evaluate the relationship between total WBC count and the presence, severity and extent of coronary atherosclerosis detected in subjects undergoing multislice computed tomographic (MSCT) coronary angiography for suspected CAD. Methods: A total of 817 patients were enrolled in this cross-sectional study. Non-significant coronary plaque was defined as lesions causing &#163; 50% luminal narrowing, and significant coronary plaque was defined as lesions causing > 50% luminal narrowing. For each segment, coronary atherosclerotic lesions were categorized as none, calcified, non-calcified and mixed. All images were interpreted immediately after scanning by an experienced radiologist. Results: An association between hypertension, diabetes mellitus, age, gender, hyperlipidemia, smoking, total WBC counts and coronary atherosclerosis was found when patients were grouped into two categories according to the presence of coronary atherosclerosis (p < 0.05). Although plaque morphology was not associated with total WBC counts, the extent of coronary atherosclerosis was increased with higher total WBC quartiles (p = 0.006). Patients with critical luminal stenosis had higher levels of total WBC counts when compared to patients with non-critical luminal narrowing (7,982 &#177; 2,287 vs 7,184 &#177; 1,944, p < 0.05). Conclusions: Our study demonstrated that total WBC counts play an important role in inflammation and are associated with the presence, severity and extent of coronary atherosclerosis detected by MSCT. Further studies are needed to assess the true impact of WBC counts on coronary atherosclerosis, and to promote its use in predicting CAD. (Cardiol J 2011; 18, 4: 371&#8211;377

Comparative activity of carbapenem testing (the COMPACT study) in Turkey

<p>Abstract</p> <p>Background</p> <p>Recent evidence indicates that Gram-negative bacterial pathogens, the most common of which are <it>Pseudomonas </it>spp., <it>Enterobacteriaceae</it>, and <it>Acinetobacter baumannii</it>, are frequent causes of hospital-acquired infections. This study aims to evaluate the in vitro activity of doripenem and comparator carbapenem antibiotics against Gram-negative clinical isolates collected from COMParative Activity of Carbapenem Testing (COMPACT) study centres in Turkey.</p> <p>Methods</p> <p>Ten centres in Turkey were invited to submit <it>Pseudomonas aeruginosa</it>, <it>Enterobacteriaceae</it>, and other Gram-negative isolates from intensive care unit (ICU)/non-ICU patients with complicated intra-abdominal infections, bloodstream infections, or nosocomial pneumonia, including ventilator-associated pneumonia, between May and October 2008. Susceptibility was determined by each centre using E-test. A central laboratory performed species confirmation as well as limited susceptibility and quality-control testing.</p> <p>Results</p> <p>Five hundred and ninety six isolates were collected. MIC₉₀values for doripenem, meropenem, and imipenem, respectively, were 32, ≥ 64, and ≥ 64 mg/L against <it>Pseudomonas </it>spp.; 0.12, 0.12, and 0.5 mg/L against <it>Enterobacteriaceae</it>; and ≥ 64 mg/L for each against other Gram-negative isolates. In determining the susceptibility of hospital isolates of selected Gram-negative pathogens to doripenem, imipenem, and meropenem, we found that against all pathogens combined, the MIC₉₀for ICU compared with non-ICU isolates was higher.</p> <p>Conclusions</p> <p>Doripenem showed similar or slightly better activity than meropenem and better activity than imipenem against the Gram-negative pathogens collected in Turkey.</p

Factors Affecting the Outcome in Traumatic Subarachnoid Hemorrhage

Objective: To define risk factors affecting the outcome in traumatic subarachnoid hemorrhage.Material and Methods: Forty-four patients with traumatic subarachnoid hemorrhage were evaluated retrospectively. They were divided into three groups according to their age: elderly (≥65 years), adult (16- 64 years), and children (<16 years). The clinical picture on admission was evaluated using the Glasgow Coma Scale. The patients were also divided into three groups according to their coma grading on admission: mild injury (Glasgow Coma Scale score 13-15), moderate injury (8-12), and severe injury (3-7). The amount of subarachnoid blood shown in computerized tomography was evaluated according to the Fisher index, and additional tomography findings were recorded. At last follow-up, presence of headache and neurological deficits as well as return to work or school were investigated, and the last clinical picture was evaluated with the Glasgow Outcome Scale.Results: There were 11 children, 23 adults and 10 elderly patients. Twelve patients died between 1-49 days after trauma; the others were followed for a mean of 14.6 months (from 10 to 30 months). In the children group, Glasgow Coma Scale score was significantly higher (p=0.004), subarachnoid blood amount was significantly lesser, and Glasgow Outcome Scale score was significantly better compared to the other groups. For all groups, higher trauma severity on admission was associated with higher Fisher index (p=0.016). Most important factors affecting clinical results were severity of head injury on admission (p=0.0001), Fisher index (p=0.003), and presence of additional findings on computerized tomography (p=0.0001).Conclusion: Traumatic subarachnoid hemorrhage usually has a good clinical outcome in children; however, in elderly patients, the outcome is worse, and there are usually additional intracranial traumatic lesions. Most important factors affecting outcome are blood amount on first computerized tomography, head trauma severity, and presence of additional intracranial traumatic lesions

Influence of lead and zinc oxides on the radiation shielding properties of tellurite glass systems

The radiation shielding properties of xPbO-(100-x)TeO2, x = 10, 20, and 30 mol% binary glasses and y[ZnO]-(100-y)[70(TeO2)-30(PbO)] y = 15, 20, and 25 mol% ternary glasses were investigated using Geant4 simulations and the newly developed Phy-X/PSD program. The glasses’ gamma shielding abilities were assessed using their mass attenuation coefficient (μ/ρ), mean free path (MFP), effective atomic number (Zeff), and half value layer (HVL) values. The neutron shielding ability was evaluated by determining the removal cross-section (RCS) values, which were 0.097, 0.101, and 0.103 cm-1 for binary PbO-TeO2 (PT) glasses and 0.118, 0.116, and 0.114 cm-1 for ternary ZnO-PbO-TeO2 (PTZ) glasses. The gamma and neutron shielding features of the glasses were compared with those of various ordinary concretes and Pb-free, Pb-based, and commercial glasses. The addition of PbO changed the gamma and neutron properties of the PT glasses, while the addition of ZnO demonstrated a different trend in the gamma properties of the PTZ glass system