Design and experimental validation of the inlet guide vane system of a mini hydraulic bulb-turbine

The paper presents a fast design method for the inlet guide vanes of low-cost mini hydraulic bulb turbines. The guide vanes are positioned between two conical surfaces with a common vertex and have constant thickness distribution, except close to the leading and the trailing edges. The conical-walled inlet guide vane row is designed using a quasi-three-dimensional calculation method, by prescribing the angular-momentum distribution along the span at the outlet section of the guide vanes.The meridional through-flow is computed by a streamline curvature method and the blade-to-blade flow by a singularity surface method. The stagger angle and the vane camber are computed to fulfil the required design circulation and zero-incidence flow at the leading edge. The final vane shape is a single-curvature surface with straight leading and trailing edges. To validate the design method, a conical-walled inlet guide vane row nozzle-model with six fixed vanes was designed, manufactured and tested in an airflow rig. Traversing measurements along the circumferential and radial directions were made with a five-hole probe.The experimental results are compared with the prescribed design conditions and with numerical results from the three-dimensional inviscid and viscous flow computed with the FLUENT code.     

The use of recycled low-density polyethylene films from protective prepreg for the development of nanocomposites with bentonite clay

Prepreg is a pre-impregnated composite fiber where a thermoset polymer matrix material is present. Before being used, these materials are kept at low temperatures and have a low-density polyethylene (LDPE) film for your protection. The increase in the use of structural composites based on prepregs causes an increase in the amount of protective LDPE film. This material is usually discarded or incinerated and can cause great damage to the environment. Thus, the present work aimed to study the feasibility of recycling up to 100% of protective LDPE (rLDPE) to develop blends-based nanocomposites with rLDPE/virgin LDPE (60/40, 70/30, 80/20, 90/10 and 100/0) with the addition of 5 wt% of compatibilizer agent (maleic anhydride grafted LDPE, LDPE-g-MA), and 1 wt% of bentonite (BNT) using a co-rotational twin-screw extruder, followed by hot pressing in a hydropneumatic press and die-cutting. Water absorption test, thermal aging resistance, morphological characterization by scanning electron microscopy, mechanical properties by Izod impact strength and tensile tests, and differential scanning calorimetry were performed. By the results, it was possible to verify the viability of 100% of the recycling of rLDPE. The results showed a good distribution of 1 wt% of BNT in the matrix, better mechanical properties when compared with virgin LDPE. Furthermore, the thermal properties, water absorption test, and thermal aging resistance showed no statistical differences between the samples. These results confirm the effectiveness and the environmental gain in the use of the recycled material.     

Very Long SiC‐Based Coaxial Nanocables with Tunable Chemical Composition

We present a simple process for the fabrication of very long SiC‐based coaxial nanocables (NCs). The versatility of this technique is confirmed by the ability to change the chemical composition of the NC outer layers from silica to carbon and boron nitride. The NCs consist of a SiC core approximately 30 nm in diameter with lengths up to several hundred of nanometers. The thickness of the coating is in the range 2–10 nm. The morphology and structural characterization of the NCs is investigated by scanning electron microscopy (SEM) and high‐resolution transmission electron microscopy (HRTEM), respectively, and their chemical composition is probed by electron energy loss spectroscopy (EELS). A vapor–solid growth mechanism is proposed to explain the growth of SiC‐based NCs of various chemical compositions, depending on the chemical nature of the vapor phase. Because of the large quantity of very long and interlaced NCs produced during the synthesis, the macroscopic aspect of the as‐grown material is like a self‐supported felt.     

Simultaneous Flow over and under a Gate

This paper reports the results of an investigation carried out to establish the stage-discharge relationship for a flow simultaneously discharging over and under a sluice or a broad-crested gate. The stage-discharge relationship is deduced by a theoretical analysis, based on the application of the Π-theorem of the dimensional analysis and the incomplete self-similarity theory, coupled with an experimental investigation carried out by using a laboratory flume.     

Headache in intracerebral hematomas

OBJECTIVES: We sought to describe the frequency and location of headache in intracerebral hematoma (ICH) and to analyze its clinical and CT predictors by means of multivariate analysis. BACKGROUND: Headache is more common in intracerebral hemorrhage than in ischemic stroke, and its frequency varies with hematoma location, but the pathophysiologic mechanisms of headache associated with ICH are not fully known. METHODS: We examined a cohort of 289 patients with ICH during a 14-month period in a university hospital. Clinical, including the presence and location of headache, and CT features were collected by two neurologists. RESULTS: One hundred and sixty-five (57%) patients with ICH had a headache at the onset of their stroke. Headache was more common in cerebellar and lobar hemorrhages than in deep ones (thalamic, caudate, capsuloputaminal, brainstem). Headache was also more common in women, patients younger than 70 years, those who vomited, and those with meningeal signs, a Glasgow Coma Scale score < 10, a hematoma volume > 10 ml or CT evidence of intraventricular or subarachnoid bleeding, moderate to severe hydrocephalus, or transtentorial herniation or midline shift. In multiple logistic regression analysis, only meningeal signs (odds ratio [OR] = 2.3), cerebellar or lobar location (OR = 2.1), transtentorial herniation (OR = 1.8), and female gender (OR = 1.6) were significant predictors of headache at the onset of ICH. CONCLUSIONS: Hematoma location, meningeal signs, and gender are more predictive of headache than hematoma volume, suggesting that headache is more often related to the activation of an anatomically distributed system in susceptible individuals and to subarachnoid bleeding than to intracranial hypertension.     

A Vapor–Liquid–Solid Mechanism for Growing 3C‐SiC Single‐Domain Layers on 6H‐SiC(0001)

Growing device‐quality 3C‐SiC monocrystalline material is still an issue despite two decades of work dedicated to the subject. Using silicon as the substrate generates too many defects in the layers, owing to lattice mismatch, while it is very difficult to control the initial nucleation on an α‐SiC substrate so that 60° rotated domains are randomly formed. Herein, the elaboration of mono‐orientated 3C‐SiC layers on a 6H‐SiC(0001) on‐axis, Si face substrate using a vapor–liquid–solid mechanism is reported. This non‐conventional approach for growing monocrystalline layers involves feeding a Ge–Si melt by a propane flux at a temperature ranging from 1250 to 1550 °C. We show that, by using this technique, the 3C‐SiC material is almost always obtained on an hexagonal substrate, even if the crystal seed is oriented 8° off‐axis. Using on‐axis 6H‐SiC seeds and optimal growth conditions results in the reproducible deposition of single‐domain 3C‐SiC layers. A mechanism is proposed to clarify some aspects of this process.