Search results for "LOCI"
showing 10 items of 1277 documents
Optimization and analysis of processes with moving materials subjected to fatigue fracture and instability
2013
We study systems of traveling continuum modeling the web as a thin elastic plate of brittle material, traveling between a system of supports at a constant velocity, and subjected to bending, in-plane tension and small initial cracks. We study crack growth under cyclic in-plane tension and transverse buckling of the web analytically. We seek optimal in-plane tension that maximizes a performance vector function consisting of the number of cycles before fracture, the critical velocity and process effectiveness. The present way of applying optimization in the studies of fracture and stability is new and affords an analytical tool for process analysis. peerReviewed
Geometric Analysis of Type B Aortic Dissections Shows Aortic Remodeling After Intervention Using Multilayer Stents
2020
Recently, multilayer stents for type B aortic dissections (TBAD) have been proposed to decrease false lumen flow, increase and streamline true lumen flow, and retain branch vessel patency. We aimed to provide a protocol with standardized techniques to investigate aortic remodeling of TBAD by multilayer flow modulators (MFM) in static geometric and hemodynamic analyses. Combining existing literature and new insights, a standardized protocol was designed. Using pre- and postoperative CT scans, geometric models were constructed, lumen dimensions were calculated, computational fluid dynamics (CFD) models were composed, and velocity and pressures were calculated. Sixteen TBAD cases treated with …
Simultaneous recording of skin blood pulsations at different vascular depths by multiwavelength photoplethysmography.
2007
A new technique for parallel recording of reflection photoplethysmography (PPG) signals in a broad spectral band (violet to near-infrared) has been developed, and its potential for assessment of blood microcirculation at various depths from the skin surface is discussed. PPG signals have been simultaneously detected at cw laser wavelength sets comprising 405, 532, 645, 807, and 1064 nm. Various signal baseline responses to breath holding and different shapes of the PPG pulses originated from the same heartbeat but recorded at different wavelengths have been observed, indicating a depth variety of the skin blood pulsation dynamics.
The effects of linearly increasing flip angles on 3D inflow MR angiography
1994
As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP s…
The chemical composition of extremely metal-poor and carbon-rich star HD 112869
2005
The preliminary results of abundance analysis are presented for extremely metal-poor carbon star HD 112869 = TT CVn = CGCS 3319. The radial velocity was found to be −137.7 km s −1 . Our LTE abundance analysis supports an extremely low metallicity for TT CVn, [Fe/H] = −3.2, and a significant overabundance of carbon and neutron-capture elements. The 12 C/ 13 C ratio in the atmosphere of HD 112869 is high.
Application of Positron Annihilation Spectroscopy to Studies of Subsurface Zones Induced by Wear in Magnesium and Its Alloy AZ31
2011
Interaction of sliding bodies is an important aspect of numerous applications and subject of many studies (Solecki, 1989). Generally, when two surfaces are loaded together the true contact area is much smaller than the apparent one. The true contact is only at high points or asperities of the surfaces where the interactions in the atomic scale take place. Relative movement between the surfaces leads to friction and wear processes. The rate of wear is controlled by the load, the relative velocity and the behaviour of the material near asperities. The region of asperities can be plastically deformed and the stress is transported to the deeper laying region that becomes elastically deformed (F…
FSW of AA2139-T8 Butt joints for aeronautical applications
2011
The effect of process parameters on mechanical and microstructural properties of AA 2139 T8 joints produced by friction stir welding (FSW) was analysed by means of statistical tools. Three different parameters were taken into account: angular speed ( ω), welding speed ( va), and plunging depth ( p); each of them was varied on three levels. Forces and temperatures achieved during the welding were monitored and analysed for all joints. An accurate microstructural analysis was performed: the occurrence of some remarkable defects, typical of FSW, such as tunnel or lack of penetration, was related to actual process parameters adopted. The extension of each FSW characteristic zone was measured a…
Regional blood flow in deep structures of the brain measured in acute cat experiments by means of a new beta-sensitive semiconductor needle detector.
1967
Regional cerebral blood flow was measured by means of isotope clearance with a new type of solid state beta-sensitive needle detector (diameter 0.9 mm) introduced into the brain tissue in acute cat experiments. The flow values obtained within the cortex were compared with values recorded above the same cortical region with the same needle detector, or with a small GM-tube. The insertion of the needle detector into the brain tissue gave rise to injury (checked histologically) which deformed the clearance curves in a manner suggesting that the normal circulation had been destroyed within the tissue from which the measurements were made.
Shear characterization of CaCO3-filled linear low density polyethylene
1988
Shear properties of CaCO3-filled linear low density polyethylene have been determined over a wide range of filler loading. The viscosity rises with the filler loading especially at low shear rates and a yield value appears for CaCO3-contents larger than 5%. The decrease of the die-swell ratios of the filled samples indicates a reduction of the melt elasticity.
Grafted polymer layers under shear: A Monte Carlo simulation
1993
Endgrafted polymers at surfaces exposed to a shear flow are modeled by a nonequilibrium Monte Carlo method where the jump rate of effective monomers to neighboring lattice sites against the flow direction is smaller than in the flow direction, assuming that this difference in jump rates is proportional to the local velocity of the flowing fluid. In the dilute case of isolated chains, the velocity profile is assumed linearly increasing with the distance from the surface, while for the case of polymer brushes the screening of the velocity field is calculated using a parabolic density profile for the brush whose height is determined self‐consistently. Linear dimensions of isolated chains are o…