248 research outputs found
Solar panel fabrication Patent
Method and apparatus for fabricating solar cell panel
Electrically induced tunable cohesion in granular systems
Experimental observations of confined granular materials in the presence of
an electric field that induces cohesive forces are reported. The angle of
repose is found to increase with the cohesive force. A theoretical model for
the stability of a granular heap, including both the effect of the sidewalls
and cohesion is proposed. A good agreement between this model and the
experimental results is found. The steady-state flow angle is practically
unaffected by the electric field except for high field strengths and low flow
rates.Comment: accepted for publication in "Journal of Statistical Mechanics: Theory
and Experiment
Wall effects on granular heap stability
We investigate the effects of lateral walls on the angle of movement and on
the angle of repose of a granular pile. Our experimental results for beads
immersed in water are similar to previous results obtained in air and to recent
numerical simulations. All of these results, showing an increase of pile angles
with a decreasing gap width, are explained by a model based on the redirection
of stresses through the granular media. Two regimes are observed depending on
the bead diameter. For large beads, the range of wall effects corresponds to a
constant number of beads whereas it corresponds to a constant characteristic
length for small beads as they aggregate via van der Waals forces
Maximum Angle of Stability of a Wet Granular Pile
Anyone who has built a sandcastle recognizes that the addition of liquid to
granular materials increases their stability. However, measurements of this
increased stability often conflict with theory and with each other [1-7]. A
friction-based Mohr-Coulomb model has been developed [3,8]. However, it
distinguishes between granular friction and inter-particle friction, and uses
the former without providing a physical mechanism. Albert, {\em et al.} [2]
analyzed the geometric stability of grains on a pile's surface. The
frictionless model for dry particles is in excellent agreement with experiment.
But, their model for wet grains overestimates stability and predicts no
dependence on system size. Using the frictionless model and performing
stability analysis within the pile, we reproduce the dependence of the
stability angle on system size, particle size, and surface tension observed in
our experiments. Additionally, we account for past discrepancies in
experimental reports by showing that sidewalls can significantly increase the
stability of granular material.Comment: 4 pages, 4 figure
Granular Avalanches in Fluids
Three regimes of granular avalanches in fluids are put in light depending on
the Stokes number St which prescribes the relative importance of grain inertia
and fluid viscous effects, and on the grain/fluid density ratio r. In gas (r >>
1 and St > 1, e.g., the dry case), the amplitude and time duration of
avalanches do not depend on any fluid effect. In liquids (r ~ 1), for
decreasing St, the amplitude decreases and the time duration increases,
exploring an inertial regime and a viscous regime. These regimes are described
by the analysis of the elementary motion of one grain
Complementary classifications of aeolian dunes based on morphology, dynamics, and fluid mechanics
Dunes form where winds blow over a bed of mobile sediment grains – conditions that are common in our solar system. On Earth, dunes abound in arid continental interiors and along sandy coastlines. Dune fields have also been recognized on Venus, Mars, Saturn's moon Titan, and Pluto. In response to the different boundary conditions and other environmental forcings, dunes adopt a rich diversity of shapes, sizes, and behaviors. Thus, people around the globe and over centuries have developed a rich vocabulary to describe dunes and their complexity. As a result, existing dune nomenclature often includes redundant terms with differing definitions across scientific communities. Previous studies have endeavored to link dune shape to environmental forcing, usually by means of correlation. Although instructive, correlation-based classifications can be misleading if not based on an underlying mechanics and if dune morphogenetic classes are not uniquely defined. Here, we synthesize existing dune terminology and use the last two decades of research on dune morphodynamics to propose three complementary dune classification schemes based on: (1) descriptive dune gemorphology, (2) morphodynamic processes, and (3) fluid mechanics and physics of sediment transport. The first classification relates dune types to geomorphic setting, presence or absence of vegetation or obstacles, and dune shape (including planform shape, and cross-sectional symmetry or asymmetry). Dune classes can be further subdivided where the direction of sand transport is known independently. The second classification relates dune types and shapes to bed properties (sand-covered vs partially starved bed) and wind forcing (directional variability or the relative strengths and directions of wind modes) that together influence dune dynamics (growth, migration, elongation) and select the dominant processes by which dunes are shaped and oriented relative to the resultant transport direction. The third classification relates, for different planetary environments, the range of possible dune sizes, from minimum to maximum wavelength, to flow regime (rough or smooth) and response of sediment transport, which influence the coupling between sand bed topography, fluid flow, and sediment transport. These characteristic lengths are useful scales for comparative geomorphology. The three classification schemes provide complementary information. Together, they form a unified framework for geomorphologists, sedimentologists, geographers, physicists, and others to describe windblown sand dunes on Earth and beyond through their shape, dynamics, and size as a response to winds and boundary conditions
Thymomectomy plus total thymectomy versus simple thymomectomy for early-stage thymoma without myasthenia gravis: A European Society of Thoracic Surgeons Thymic Working Group Study
OBJECTIVES: Resection of thymic tumours including the removal of both the tumour and the thymus gland (thymothymectomy; TT) is the procedure of choice and is recommended in most relevant articles in the literature. Nevertheless, in recent years, some authors have suggested that resection of the tumour (simple thymomectomy; ST) may suffice from an oncological standpoint in patients with early-stage thymoma who do not have myasthenia gravis (MG) (non-MG). The goal of our study was to compare the short-and long-term outcomes of ST versus TT in non-MG early-stage thymomas using the European Society of Thoracic Surgeons thymic database. METHODS: A total of 498 non-MG patients with pathological stage I thymoma were included in the study. TT was performed in 466 (93.6%) of 498 patients who had surgery with curative intent; ST was done in 32 (6.4%). The completeness of resection, the rate of complications, the 30-day mortality, the overall recurrence and the freedom from recurrence were compared. We performed crude and propensity score-adjusted comparisons by surgical approach (ST vs TT). RESULTS: TT showed the same rate of postoperative complications, 30-day mortality and postoperative length of stay as ST. The 5-year overall survival rate was 89% in the TT group and 55% in the ST group. The 5-year freedom from recurrence was 96% in the TT group and 79% in the ST group. CONCLUSION: Patients with early-stage thymoma without MG who have a TT show significantly better freedom from recurrence than those who have an ST, without an increase in postoperative morbidity rate
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