339 research outputs found
Collapse of composite tubes under end moments
Cylindrical tubes of moderate wall thickness such as those proposed for the original space station truss, may fail due to the gradual collapse of the tube cross section as it distorts under load. Sometimes referred to as the Brazier instability, it is a nonlinear phenomenon. This paper presents an extension of an approximate closed form solution of the collapse of isotropic tubes subject to end moments developed by Reissner in 1959 to include specially orthotropic material. The closed form solution was verified by an extensive nonlinear finite element analysis of the collapse of long tubes under applied end moments for radius to thickness ratios and composite layups in the range proposed for recent space station truss framework designs. The finite element analysis validated the assumption of inextensional deformation of the cylindrical cross section and the approximation of the material as specially orthotropic
Термінові одночасні гастро-ренальні ефекти води Нафтуся та їх вегето-гуморальний аккомпанемент. Повідомлення 2: Кластеризація на основі квалітативних варіантів ефектів на рН шлункового соку
Выделено 7 кластеров-вариантов качественных срочных эффектов биоактивной воды Нафтуся на базальный рН желудочного сока: переход нормоацидности в субацидностъ (4% больных); снижение кислотности в пределах нормоацидности (13%); повышение кислотности в пределах нормоацидности (25%); переход нормоаиидности в гиперацидность (16%); трансформация анацидности в субацидностъ (22%) или в нормоацидность (8%) при отсутствии существенных изменений щелочных значений рН у 10% обследованных. Прослежены сопутствующие изменения других параметров желудочной секреции, а также диуреза и салуреза, электролитемии, вегетативной нервной и гастроэнтеро-панкреатической эндокринной систем. Продемонстрирована возможность 'прогнозирования перечисленных эффектов по совокупности 14 базальных параметров, отобранных методом дискриминантного анализа.It is established 7 clusters-variantes of qualitativ immediate effects of water Naftussya on basal pH of gastric juice. By using method of discriminant analysis it is detected 14 basal parameters of gastroentero-pancreatic endocrine and vegetativ nervous systems, plasma electrolithes, secretory and evacuatory functions of stomach and diuretic and saluretic functions of kidney thouse conditionizes definite variant of effects
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Advanced Characterization of Fractured Reservoirs in Carbonate Rocks: The Michigan Basin
The main objective of this project is for a university-industry consortium to develop a comprehensive model for fracture carbonate reservoirs based on the ''data cube'' concept using the Michigan Basin as a prototype. This project combined traditional historical data with 2D and 3D seismic data as well as data from modern logging tools in a novel way to produce a new methodology for characterizing fractured reservoirs in carbonate rocks. Advanced visualization software was used to fuse the data and to image it on a variety of scales, ranging from basin-scale to well-scales
Accuracy and Limitations of Fitting and Stereoscopic Methods to Determine the Direction of Coronal Mass Ejections from Heliospheric Imagers Observations
Using data from the Heliospheric Imagers (HIs) onboard STEREO, it is possible
to derive the direction of propagation of coronal mass ejections (CMEs) in
addition to their speed with a variety of methods. For CMEs observed by both
STEREO spacecraft, it is possible to derive their direction using simultaneous
observations from the twin spacecraft and also, using observations from only
one spacecraft with fitting methods. This makes it possible to test and compare
different analyses techniques. In this article, we propose a new fitting method
based on observations from one spacecraft, which we compare to the commonly
used fitting method of Sheeley et al. (1999). We also compare the results from
these two fitting methods with those from two stereoscopic methods, focusing on
12 CMEs observed simultaneously by the two STEREO spacecraft in 2008 and 2009.
We find evidence that the fitting method of Sheeley et al. (1999) can result in
significant errors in the determination of the CME direction when the CME
propagates outside of 60deg \pm 20 deg from the Sun-spacecraft line. We expect
our new fitting method to be better adapted to the analysis of halo or limb
CMEs with respect to the observing spacecraft. We also find some evidence that
direct triangulation in the HI fields-of-view should only be applied to CMEs
propagating approximatively towards Earth (\pm 20deg from the Sun-Earth line).
Last, we address one of the possible sources of errors of fitting methods: the
assumption of radial propagation. Using stereoscopic methods, we find that at
least seven of the 12 studied CMEs had an heliospheric deflection of less than
20deg as they propagated in the HI fields-of-view, which, we believe, validates
this approximation.Comment: 17 pages, 6 figures, 2 tables, accepted to Solar Physic
Possible origins of macroscopic left-right asymmetry in organisms
I consider the microscopic mechanisms by which a particular left-right (L/R)
asymmetry is generated at the organism level from the microscopic handedness of
cytoskeletal molecules. In light of a fundamental symmetry principle, the
typical pattern-formation mechanisms of diffusion plus regulation cannot
implement the "right-hand rule"; at the microscopic level, the cell's
cytoskeleton of chiral filaments seems always to be involved, usually in
collective states driven by polymerization forces or molecular motors. It seems
particularly easy for handedness to emerge in a shear or rotation in the
background of an effectively two-dimensional system, such as the cell membrane
or a layer of cells, as this requires no pre-existing axis apart from the layer
normal. I detail a scenario involving actin/myosin layers in snails and in C.
elegans, and also one about the microtubule layer in plant cells. I also survey
the other examples that I am aware of, such as the emergence of handedness such
as the emergence of handedness in neurons, in eukaryote cell motility, and in
non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue.
Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in
Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec
A non-parametric structural hybrid modeling approach for electricity prices
We develop a stochastic model of zonal/regional electricity prices, designed to reflect information in fuel forward curves and aggregated capacity and load as well as zonal or regional price spreads. We use a nonparametric model of the supply stack that captures heat rates and fuel prices for all generators in the market operator territory, combined with an adjustment term to approximate congestion and other zone-specific behavior. The approach requires minimal calibration effort, is readily adaptable to changing market conditions and regulations, and retains sufficient tractability for the purpose of forward price calibration. The model is illustrated for the spot and forward electricity prices of the PS zone in the PJM market, and the set of time-dependent risk premiums are inferred and analyzed
Explorations, Vol. 6, No. 1
Cover: Panthera pardus, Chui in Kiswatuli, was photographed by Dr. Linda Karbonit ar Dr. James A. Sherburne in Serengeti National Park, Tanzania. Karbonit was accompanying Sherburne who was working on the design and development of the University of Maine, U.S. Fish and Wildlife Service, assistance program in wildlife training and conservation education to Tanzania’s National Parks. Sherburne, who has worked in Tanzania for several years, was there most recently in 1988 and 1989 working on the parks project. He serves as the Director of International Natural Resources and Agricultural Programs at the University of Maine.
Articles include:
Research and Economic Development: from the U.S. Senate Statement, December 22, 1989, by Sen. George J. Mitchell
Politics and Research: Providing a Key for Economic Development, by Sen. William S. Cohen.
Publisher’s Perspective, by Gregory N. Brown, Vice President, Research and Public Service
What’s EPSCoR? Editorial Reflections, by Carole J. Bombard
Past and Present: Marine Geologists Explore the Old and Teach the Young, by Daniel Belknap and Joseph Kelley
High Biological Productivity: Salt Marshes, by Mark E. Wood
Barrier Beaches, by William Duffy
Sediment Budgets & Bluff Slump, by Rebecca Smith
Coastal Environments and Change, by Andrew Walsh
Mapping What You Can\u27t See, by Donald Robbins
Casco Bay: Sea Level and the Shoreline, by Bradley W.B. Hay
Christmas at Sea, by Molly Horvath
A Short Course and the Local Economy, by Richard Hale and James Philp
Dr. Bernard Lown: Alumnus Receives Golden Door Award
The Sky is Falling . . . well, maybe, by Carole J. Bombard
A Growing Interest in Timberland, by Robert A. Strong and Bret P. Vicar
How Many CMEs Have Flux Ropes? Deciphering the Signatures of Shocks, Flux Ropes, and Prominences in Coronagraph Observations of CMEs
We intend to provide a comprehensive answer to the question on whether all
Coronal Mass Ejections (CMEs) have flux rope structure. To achieve this, we
present a synthesis of the LASCO CME observations over the last sixteen years,
assisted by 3D MHD simulations of the breakout model, EUV and coronagraphic
observations from STEREO and SDO, and statistics from a revised LASCO CME
database. We argue that the bright loop often seen as the CME leading edge is
the result of pileup at the boundary of the erupting flux rope irrespective of
whether a cavity or, more generally, a 3-part CME can be identified. Based on
our previous work on white light shock detection and supported by the MHD
simulations, we identify a new type of morphology, the `two-front' morphology.
It consists of a faint front followed by diffuse emission and the bright
loop-like CME leading edge. We show that the faint front is caused by density
compression at a wave (or possibly shock) front driven by the CME. We also
present high-detailed multi-wavelength EUV observations that clarify the
relative positioning of the prominence at the bottom of a coronal cavity with
clear flux rope structure. Finally, we visually check the full LASCO CME
database for flux rope structures. In the process, we classify the events into
two clear flux rope classes (`3-part', `Loop'), jets and outflows (no clear
structure). We find that at least 40% of the observed CMEs have clear flux rope
structures. We propose a new definition for flux rope CMEs (FR-CMEs) as a
coherent magnetic, twist-carrying coronal structure with angular width of at
least 40 deg and able to reach beyond 10 Rsun which erupts on a time scale of a
few minutes to several hours. We conclude that flux ropes are a common
occurrence in CMEs and pose a challenge for future studies to identify CMEs
that are clearly not FR-CMEs.Comment: 26 pages, 9 figs, to be published in Solar Physics Topical Issue
"Flux Rope Structure of CMEs
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