Cavity induced vibration of flexible hydrofoils

The objective of this work is to investigate the influence of cavity-induced vibrations on the dynamic response and stability of a NACA66 hydrofoil at 8° angle of attack at Re=750 000 via combined experimental measurements and numerical simulations. The rectangular, cantilevered hydrofoil is assumed to be rigid in the chordwise direction, while the spanwise bending and twisting deformations are represented using a two-degrees-of-freedom structural model. The multiphase flow is modeled with an incompressible, unsteady Reynolds Averaged Navier–Stokes solver with the k–ω Shear Stress Transport (SST) turbulence closure model, while the phase evolutions are modeled with a mass-transport equation based cavitation model. The numerical predictions are compared with experimental measurements across a range of cavitation numbers for a rigid and a flexible hydrofoil with the same undeformed geometries. The results showed that foil flexibility can lead to: (1) focusing – locking – of the frequency content of the vibrations to the nearest sub-harmonics of the foil׳s wetted natural frequencies, and (2) broadening of the frequency content of the vibrations in the unstable cavitation regime, where amplifications are observed in the sub-harmonics of the foil natural frequencies. Cavitation was also observed to cause frequency modulation, as the fluid density, and hence fluid induced (inertial, damping, and disturbing) forces fluctuated with unsteady cavitation.The authors gratefully acknowledge Ms. Kelly Cooper (program manager) and the Office of Naval Research (ONR), for their financial support through Grant nos. N00014-11-1-0833 and N0014-12-C-0585, as well as ONR Global and Dr. Woei-Min Lin (program manager) through grant no. N62909-12-1-7076

Mesh termination schemes for the finite element method in electromagnetics

Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2007.The finite element method is a very efficient numerical tool to solve geometrically complex problems in electromagnetics. Traditionally the method is applied to bounded domain problems, but it can also be forged to solve unbounded domain problems using one of various mesh termination schemes. A scalar finite element solution to a typical unbounded two-dimensional problem is presented and the need for a proper mesh termination scheme is motivated. Different such schemes, specifically absorbing boundary conditions, the finite element boundary integral method and infinite elements, are formulated and implemented. These schemes are directly compared using different criteria, especially solution accuracy and computational efficiency. A vector finite element solution in three dimensions is also discussed and a new type of infinite element compatible with tetrahedral vector finite elements is presented. The performance of this infinite element is compared to that of a first order absorbing boundary condition

Better Bullets: How to Shoot Varmints Without Poisoning Scavengers

Recreational shooters kill millions of varmints each year. The carcasses can contain fragments of lead that scavengers can ingest. Less toxic bullets may alleviate the problem but their performance needs to be determined. In this study, ground squirrels were shot with .17 HMR, .22 LR, and .223 Rem rifles with expanding and non-expanding lead and nonlead bullets. We monitored whether the bullets instantly incapacitated ground squirrels and then estimated lead concentrations in each carcass using radiographs. We found lead in the majority of ground squirrel carcasses that were shot with five out of six lead bullets tested. Expanding ammunition in the .17 HMR and the .223 Rem calibers left the highest estimated concentrations of lead in ground squirrels, which had, on average, 23.6 and 91.2 mg/carcass, respectively. Within a caliber, expanding bullets did not contaminate ground squirrels more than non-expanding bullets. Non-lead bullets incapacitated ground squirrels as well as lead bullets. Recreational shooters and land managers may reduce the amount of lead available to scavengers by using non-lead bullets when shooting ground squirrels and other varmints

Near-Infrared Imaging Polarimetry of Young Stellar Objects in rho-Ophiuchi

The results of a near-infrared (J H K LP) imaging linear polarimetry survey of 20 young stellar objects (YSOs) in rho Ophiuchi are presented. The majority of the sources are unresolved, with K-band polarizations, P_K < 6 per cent. Several objects are associated with extended reflection nebulae. These objects have centrosymmetric vector patterns with polarization discs over their cores; maximum polarizations of P_K > 20 per cent are seen over their envelopes. Correlations are observed between the degree of core polarization and the evolutionary status inferred from the spectral energy distribution. K-band core polarizations >6 per cent are only observed in Class I YSOs. A 3D Monte Carlo model with oblate grains aligned with a magnetic field is used to investigate the flux distributions and polarization structures of three of the rho Oph YSOs with extended nebulae. A rho proportional to r^(-1.5) power law for the density is applied throughout the envelopes. The large-scale centrosymmetric polarization structures are due to scattering. However, the polarization structure in the bright core of the nebula appears to require dichroic extinction by aligned non-spherical dust grains. The position angle indicates a toroidal magnetic field in the inner part of the envelope. Since the measured polarizations attributed to dichroic extinction are usually <10 per cent, the grains must either be nearly spherical or very weakly aligned. The higher polarizations observed in the outer parts of the reflection nebulae require that the dust grains responsible for scattering have maximum grain sizes <=1.05 microns.Comment: 26 pages. Accepted by MNRAS. Available as online early versio

Magnetic signatures of plasma-depleted flux tubes in the Saturnian inner magnetosphere

Initial Cassini observations have revealed evidence for interchanging magnetic flux tubes in the inner Saturnian magnetosphere. Some of the reported flux tubes differ remarkably by their magnetic signatures, having a depressed or enhanced magnetic pressure relative to their surroundings. The ones with stronger fields have been interpreted previously as either outward moving mass-loaded or inward moving plasma-depleted flux tubes based on magnetometer observations only. We use detailed multi-instrumental observations of small and large density depletions in the inner Saturnian magnetosphere from Cassini Rev. A orbit that enable us to discriminate amongst the two previous and opposite interpretations. Our analysis undoubtedly confirms the similar nature of both types of reported interchanging magnetic flux tubes, which are plasma-depleted, whatever their magnetic signatures are. Their different magnetic signature is clearly an effect associated with latitude. These Saturnian plasma-depleted flux tubes ultimately may play a similar role as the Jovian ones

The HK2 Dependent "Warburg Effect" and Mitochondrial Oxidative Phosphorylation in Cancer:Targets for Effective Therapy with 3-Bromopyruvate

This review summarizes the current state of knowledge about the metabolism of cancer cells, especially with respect to the “Warburg” and “Crabtree” effects. This work also summarizes two key discoveries, one of which relates to hexokinase-2 (HK2), a major player in both the “Warburg effect” and cancer cell immortalization. The second discovery relates to the finding that cancer cells, unlike normal cells, derive as much as 60% of their ATP from glycolysis via the “Warburg effect”, and the remaining 40% is derived from mitochondrial oxidative phosphorylation. Also described are selected anticancer agents which generally act as strong energy blockers inside cancer cells. Among them, much attention has focused on 3-bromopyruvate (3BP). This small alkylating compound targets both the “Warburg effect”, i.e., elevated glycolysis even in the presence oxygen, as well as mitochondrial oxidative phosphorylation in cancer cells. Normal cells remain unharmed. 3BP rapidly kills cancer cells growing in tissue culture, eradicates tumors in animals, and prevents metastasis. In addition, properly formulated 3BP shows promise also as an effective anti-liver cancer agent in humans and is effective also toward cancers known as “multiple myeloma”. Finally, 3BP has been shown to significantly extend the life of a human patient for which no other options were available. Thus, it can be stated that 3BP is a very promising new anti-cancer agent in the process of undergoing clinical development

Preliminary interpretation of Titan plasma interaction as observed by the Cassini Plasma Spectrometer: Comparisons with Voyager 1

The Cassini Plasma Spectrometer (CAPS) instrument observed the plasma environment at Titan during the Cassini orbiter's TA encounter on October 26, 2004. Titan was in Saturn's magnetosphere during the Voyager 1 flyby and also during the TA encounter. CAPS measurements from this encounter are compared with measurements made by the Voyager 1 Plasma Science Instrument (PLS). The comparisons focus on the composition and nature of ambient and pickup ions. They lead to: A) the major ion components of Saturn's magnetosphere in the vicinity of Titan are H+, H-2(+) and O+/CH4+ ions; B) finite gyroradius effects are apparent in ambient O+ ions as the result of their absorption by Titan's extended atmosphere; C) the principal pickup ions are composed of H+, H-2(+), N+/CH2+, CH4+, and N-2(+); D) the pickup ions are in narrow energy ranges; and E) there is clear evidence of the slowing down of background ions due to pickup ion mass loading

HYPOGLYCEMIC, ANTI-INFLAMMATORY EFFECT OF PORANG (AMORPHOPHALLUS ONCHOPYLLUS) ON ALLOXAN-INDUCED DIABETIC RATS

Introduction: Iles-iles / Porang is a tuber-producing plant that is commonly found in Indonesia. One of the most sought after content from Porang is Glucomannan. One of Porang’s health benefit is related to the effect of lowering blood glucose levels because it can prevent glucose absorption. These benefit is interesting to study because there has been no research linking the use of Porang to reduce inflammatory process in hyperglycmic conditions. Purpose: This study aims to analyze the anti-inflammatory, anti-oxidant and hypoglycemis effects of Glucomannan from Porang (Amorphophallus onchophyllus) extract in experimental animals. Method: The research design was a true experimental post-test only control group with random sampling to determine 5 white rats into the normal group, positive control group, negative control group and treatment 1, 2 and 3. The positive control group received Acarbose therapy thile the negative control group received carboxy-methyl-cellulose (CMC) therapy. This study used Porang extract (Amorphophallus onchophyllus) with concentrations of 200, 400 and 800 mg/Kg in hyperglycemic white rats that had been induced by Aloxan. The study was conducte for 50 days and then blood and serum samples were taken to assess the effect of hypoglycemia, anti-inflammatory and anti-oxidant using blood glucose, Malondialdehyde and C-reactiveprotein (CRP) measurement. Result and Discussion: The results showed no significant difference between the groups of rats receiving Porang extract and the positive and negative control groups. However, the MDA levels after 50 days of intervention between the negative control group and the therapy with doses of 200, 400 and 800 mg/Kg showed significant differences. Similarly found for blood glucose levels after intervention between negative control group and the 200 and 400 mg/Kg therapy group. This results may be caused by the type of Porang used, the form of the Porang and the concentration level of the Porang extract. Conclusion: Porang with the type of Amorphophallus onchophyllus can’t be used directly, but requires further processing to obtain the active substance Glucomannan