Measurement of parallel blade–vortex interaction at low Reynolds numbers

In this study parallel blade–vortex interaction for a Schmidt-propeller configuration has been examined using particle image velocimetry (PIV). This tandem configuration consists of a leading airfoil (forefoil), used to generate a vortical wake of leading-edge vortices (LEVs) and trailing-edge vortices (TEVs) through a pitching or plunging motion, and a trailing airfoil (hindfoil), held fixed with a specified angle of attack and vertical spacing in its wake. The hindfoil incidence (loading) and not the vertical spacing to the incoming vortical wake has been found to dictate the nature of the interaction (inviscid vs. viscous). For cases where the vortex–blade offset is small and the hindfoil is loaded, vortex distortion and vortex-induced separations are observed. By tracking the circulation of the LEV and TEV, it has been found that the vortices are strengthened for the tandem arrangement and in certain cases dissipate quicker in the wake when interacting with the hindfoil. Time-averaged forces obtained using a standard control-volume analysis are then obtained and used to evaluate these vortex-interaction cases. A subsequent analysis of the varying pressure distribution over the suction side of the hindfoil is performed by integrating the Navier–Stokes equations through the velocity field. This allows for a direct comparison of the vortex-induced loading for the various configurations.     

Study on the Use of Motion Compensation Techniques to Determine Heat Sources. Application to Large Deformations on Cracked Rubber Specimens

This paper deals with the determination of the thermal response of elastomeric materials subjected to cyclic loading. In this case, the material undergoes large deformations, so a suitable motion compensation technique has been developed to track the material points and their temperature during the test. Special attention is paid to the Narcissus effect and to the detector matrix of the infrared camera used in the study. Heat sources are then derived from the temperature maps. The thermoelastic inversion phenomenon has been experimentally evidenced during a cyclic test performed on an elastomeric notched specimen. The heat source distribution close to the crack tip has also been deduced from the temperature maps, thus highlighting the relevance of the approach.     

Myocardial proton spin-lattice relaxation times in vitro: Effect of elapsed time after excision

An assumption made in using excised tissue for in vitro nuclear magnetic resonance (NMR) studies is that variables of interest, such as spin-lattice (T₁) relaxation times, remain stable for periods of time after excision sufficient to perform NMR spectroscopy. In this study, we evaluated the changes in T₁ of rat myocardium, measured at two NMR field strengths, at serial time intervals up to 72 hours postmortem. Left ventricular myocardium from six male Sprague-Dawley rats was excised and stored at room temperature in sealed NMR sample tubes. Spin-lattice relaxation times were determined with a modified inversion-recovery pulse sequence immediately postmortem and at intervals up to 72 hours post-excision; NMR studies were performed using 90 MHz and 360 MHz spectrometers. A gradual decrease in T₁ was noted with increasing time post-excision; T₁ was not significantly shorter than baseline until 72 hours postmortem at either field strength. The rate of change of T₁ was similar at the two field strengths. At any given time post-excision, T₁ was significantly higher (p < 0.001) at 360 MHz than at 90 MHz. We conclude that, with proper tissue handling and storage techniques, rat myocardial T₁ is stable postmortem sufficiently long to permit meaningful NMR studies of excised tissue.     

Development of an extremely wide-band planar frequency doubler from Q-band to W-band

A very broadband Q- to W-band MIC frequency doubler with a 28-GHZ band-width, employing a unique planar balanced circuit configuration, has been developed with good performance. Using two beamlead Schottky barrier diodes as varistors, the doubler exhibits an output power of 7±1 dbm and conversion loss of 13±1 db over the 66 to 94 GHZ output frequency range. The development demonstrates a unique concept in realizing wideband planar millimeter wave solid-state sources.     

Study of new resonances at high excitation energy by the 120Sn(p,t)118Sn reaction at 35 MeV

The ¹²⁰Sn(p,t)¹¹⁸Sn reaction was investigated at 35 MeV incident energy. The ¹¹⁸Sn excitation energy spectrum was reconstructed up to about 16 MeV. Preliminary results show the presence of a broad resonance at high excitation energy, compatible with the predicted population of the Giant Pairing Vibration (GPV).     

On the evolution of the viscoelastic properties and its microstructural/chemical origin in filled NBR subjected to coupled thermal and mechanical loads

This study deals with the effect of coupled thermal and cyclic mechanical loadings on the viscoelastic response of carbon black filled nitrile rubber. For this purpose, cyclic loading tests were performed at different temperatures by means of Dynamic Mechanical and Thermal Analysis (DMTA). The type and level of the thermomechanical loadings applied were chosen in order to determine the relative contribution of each of the mechanical and thermal loadings (and their coupling) to the viscoelastic response during the cyclic tests. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transformed Infrared spectroscopy (FTIR) analyses were also carried out to track the change in the chemical structure corresponding to the evolution in the viscoelastic response. First, results obtained show that due to the crosslink increase, the storage modulus increases with the number of cycles. It is also observed that temperature amplifies this phenomenon. Second, the cyclic mechanical loading is found to significantly amplify the effect of temperature.     

Reaction mechanism of CO methanation on nickel catalysts,as studied by isotopic and nonstationary methods

Kinetic isotope effects were measured upon the replacement of hydrogen by deuterium in the reaction of carbon monoxide methanation on nickel catalysts supported on TiO₂ and γ-Al₂O₃. Data on the mechanism of the process were obtained with the use of a nonstationary method. A step-scheme was proposed, in which the interaction of oxygen-containing compounds with hydrogen is a slow step of the process.