scholarly journals A New Aneurysm Occlusion Classification after the Impact of Flow Modification

2015 ◽  
Vol 37 (1) ◽  
pp. 19-24 ◽  
Author(s):  
H.S. Cekirge ◽  
I. Saatci
Keyword(s):  
Flow Modification ◽  
Aneurysm Occlusion ◽  
The Impact

Natural Convection Heat Transfer in a Partially Open Square Cavity With a Thin Fin Attached to the Hot Wall

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Abdullatif Ben-Nakhi ◽  
M. M. Eftekhari ◽  
D. I. Loveday
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rayleigh Number ◽  
Inclination Angle ◽  
Computational Study ◽  
Vertical Wall ◽  
Temperature Fields ◽  
Arbitrary Length ◽  
Flow Modification ◽  
The Impact

A computational study of steady, laminar, natural convective fluid flow in a partially open square enclosure with a highly conductive thin fin of arbitrary length attached to the hot wall at various levels is considered. The horizontal walls and the partially open vertical wall are adiabatic while the vertical wall facing the partial opening is isothermally hot. The current work investigates the flow modification due to the (a) attachment of a highly conductive thin fin of length equal to 20%, 35%, or 50% of the enclosure width, attached to the hot wall at different heights, and (b) variation of the size and height of the aperture located on the vertical wall facing the hot wall. Furthermore, the study examines the impact of Rayleigh number (104⩽Ra⩽107) and inclination of the enclosure. The problem is put into dimensionless formulation and solved numerically by means of the finite-volume method. The results show that the presence of the fin has counteracting effects on flow and temperature fields. These effects are dependent, in a complex way, on the fin level and length, aperture altitude and size, cavity inclination angle, and Rayleigh number. In general, Nusselt number is directly related to aperture altitude and size. However, after reaching a peak Nusselt number, Nusselt number may decrease slightly if the aperture’s size increases further. The impact of aperture altitude diminishes for large aperture sizes because the geometrical differences decrease. Furthermore, a longer fin causes higher rate of heat transfer to the fluid, although the equivalent finless cavity may have higher heat transfer rate. In general, the volumetric flow rate and the rate of heat loss from the hot surfaces are interrelated and are increasing functions of Rayleigh number. The relationship between Nusselt number and the inclination angle is nonlinear.

scholarly journals The Extratropical Transition of Tropical Cyclones. Part II: Interaction with the Midlatitude Flow, Downstream Impacts, and Implications for Predictability

2019 ◽  
Vol 147 (4) ◽  
pp. 1077-1106 ◽  
Author(s):  
Julia H. Keller ◽  
Christian M. Grams ◽  
Michael Riemer ◽  
Heather M. Archambault ◽  
Lance Bosart ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Wave Pattern ◽  
High Impact ◽  
Future Research ◽  
Extratropical Transition ◽  
Initial Flow ◽  
Flow Modification ◽  
High Impact Weather ◽  
Relationship Of ◽  
The Impact

Abstract The extratropical transition (ET) of tropical cyclones often has an important impact on the nature and predictability of the midlatitude flow. This review synthesizes the current understanding of the dynamical and physical processes that govern this impact and highlights the relationship of downstream development during ET to high-impact weather, with a focus on downstream regions. It updates a previous review from 2003 and identifies new and emerging challenges and future research needs. First, the mechanisms through which the transitioning cyclone impacts the midlatitude flow in its immediate vicinity are discussed. This “direct impact” manifests in the formation of a jet streak and the amplification of a ridge directly downstream of the cyclone. This initial flow modification triggers or amplifies a midlatitude Rossby wave packet, which disperses the impact of ET into downstream regions (downstream impact) and may contribute to the formation of high-impact weather. Details are provided concerning the impact of ET on forecast uncertainty in downstream regions and on the impact of observations on forecast skill. The sources and characteristics of the following key features and processes that may determine the manifestation of the impact of ET on the midlatitude flow are discussed: the upper-tropospheric divergent outflow, mainly associated with latent heat release in the troposphere below, and the phasing between the transitioning cyclone and the midlatitude wave pattern. Improving the representation of diabatic processes during ET in models and a climatological assessment of the ET’s impact on downstream high-impact weather are examples for future research directions.

Drag Reduction of Ground Vehicles Using Air-Injected Wheel Deflectors

2019 ◽  
Author(s):  
Kaloki L. Nabutola ◽  
Sandra K. S. Boetcher
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Drag Coefficient ◽  
Parametric Study ◽  
Ground Vehicles ◽  
Ground Vehicle ◽  
Flow Modification ◽  
Air Jets ◽  
Air Jet ◽  
The Impact

Abstract Numerical simulations of flow modification devices on a simplified ground vehicle are conducted. A parametric study on the size and distance upstream of conventional wheel deflectors is conducted on a simplified body at a Reynolds number of 1.6 × 105 to observe the impact on drag coefficient. Results show that wheel drag is decreased as the height of the conventional wheel deflector is increased. Additionally, the further the conventional wheel deflector is from the wheelhouse, the more sensitive the wheel is to changes in drag coefficient. The conventional wheel deflectors are then replaced by air-jets which are used to manipulate the flow field in and near the wheelhouse to reduce the wheel drag of the simplified body. The air-jet successfully decreases the wheel drag and it is observed that the closer the air-jet is to the wheelhouse the less impact it has on the single wheel drag, but the greater the impact on the overall drag of the simplified body.

Abstract WMP29: Single-Center Experience with The Pipeline Embolization Device: The Treatment of Smaller Secondary Aneurysms

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Ratul Raychaudhuri ◽  
Inam Kureshi ◽  
Martin Ollenschleger ◽  
Stephen Ohki ◽  
Gary Spiegel
Keyword(s):  
Single Case ◽  
Endovascular Coiling ◽  
Limited Information ◽  
Single Center ◽  
Pipeline Embolization Device ◽  
Single Center Experience ◽  
Aneurysm Occlusion ◽  
The Impact ◽  
Wide Neck

The Pipeline embolization device is a flow diverting stent that is now available as an FDA approved treatment for giant wide-neck cavernous and supraclinoid aneurysms. This revolutionary device has made it possible to safely treat large wide necked aneurysms with excellent results. There is limited information on the impact of Pipeline on smaller secondary aneurysms. We present single center data regarding Pipeline’s efficacy in the treatment of these aneurysms. Methods: Since August 2012, 24 patients have been electively treated utilizing the Pipeline Embolization Device (PED) (Covidien, Mansfield, MA) at Hartford Hospital. Of these patients, 17 patients have had follow up angiograms and 9 (52%) had smaller secondary aneurysms that was covered by the Pipeline stent. For each patient where angiographic follow-up was available, the degree of secondary aneurysm occlusion was assessed utilizing the Raymond criteria. Results: All procedures were successfully completed and a total of 41 PEDS were implanted. No intraprocedural complications were present. During the clinical follow-up period, no major complications resulted. One patient developed a partial CN III and IV neuropathy secondary to thrombosis of a large cavernous aneurysm 4 days following treatment. The results of 6 month follow-up angiography demonstrated that out of a total of 9 cases, 8 cases (89%) with smaller secondary aneurysms resolved and 1 case (11%) improved significantly. In all cases where the smaller secondary aneurysm was occluded, the larger primary aneurysm was also occluded. The single case of significant improvement demonstrated that the primary aneurysm had also significantly decreased in size. Conclusion: Smaller secondary aneurysms are adequately treated by Pipeline stenting. In all cases, the primary aneurysm either improved significantly or totally occluded along with the secondary aneurysms. This suggests that the Pipeline device, in addition to treating large wide-necked aneurysms, can effectively treat smaller associated aneurysms without the need for additional endovascular coiling. Key Words: Pipeline embolization device, giant wide-neck cavernous and supraclinoid aneurysm, secondary aneurysms

scholarly journals Impacts of loss of vegetation cover on biodiversity of Ikere-gorge, Oyo State Nigeria

2021 ◽  
Vol 48 (4) ◽  
pp. 14-23
Author(s):  
S. O. Ajagbe ◽  
O. O. Oyewole ◽  
T. A. Adebisi-Fagbohungbe ◽  
M. T. Ojubolamo ◽  
O. O. Ajayi ◽  
...  
Keyword(s):  
Climate Change ◽  
Vegetation Cover ◽  
Natural Phenomenon ◽  
Management Decision ◽  
Freshwater Ecosystem ◽  
Changement Climatique ◽  
Remote Sensing Technique ◽  
Flow Modification ◽  
La Modification ◽  
The Impact

Climate change is inevitable as it is caused by natural phenomenon but most often by human induced activities; the impacts of which can be devastating. Ikere-gorge is a freshwater ecosystem. The impact of climate change on Ikere-gorge is examined in this study. Remote sensing technique is employed and land use/cover classification was adopted. The processing of satellite data involved the manipulation and interpretation of images. The results showed that there was loss of vegetation cover around Ikere-groge. But, flow modification was governed by management decision, vegetation cover and climate change. The resultant effect of this was the observed dryness of some parts and changes in the shape of Ikere-gorge. The implication of this is that the biodiversity of Ikere-gorge is vulnerable to these changes. This led to change, modification and/or destruction of ecosystem. The ready- to-spawn fish lost their eggs and they were even becoming prey easily. The most affected fish were the newly spawned or recruited fish (billions of fish eggs, fry, fingerlings and juveniles) that could not swim swiftly to escape into the deeper parts of the gorge. Therefore, management of Ikere-gorge should be holistic incorporating all necessary stakeholders for the survival of the gorge and sustainability of the biodiversity it supports.     Le changement climatique est inévitable car il est causé par des phénomènes naturels mais le plus souvent par des activités anthropiques; dont les effets peuvent être dévastateurs. Ikere- gorge est un écosystème d'eau douce. L'impact du changement climatique sur la gorge d'Ikere est examiné dans cette étude. Une technique de télédétection est employée et une classification de l'utilisation / couverture des terres a été adoptée. Le traitement des données satellitaires impliquait la manipulation et l'interprétation d'images. Les résultats ont montré qu'il y avait une perte de couverture végétale autour d'Ikere-groge. Mais la modification du débit était régie par la décision de gestion, la couverture végétale et le changement climatique. Cela a eu pour effet la sécheresse observée de certaines parties et des changements dans la forme de la gorge d'Ikere. L'implication de ceci est que la biodiversité d'Ikere-gorge est vulnérable à ces changements. Cela a conduit au changement, à la modification et / ou à la destruction de l'écosystème. Les poissons prêts à frayer perdaient leurs œufs et devenaient même facilement des proies. Les poissons les plus touchés étaient les poissons nouvellement pondus ou recrutés (milliards d'œufs de poissons, alevins, alevins et juvéniles) qui ne pouvaient pas nager rapidement pour s'échapper dans les parties les plus profondes de la gorge. Par conséquent, la gestion d'Ikere-gorge doit être holistique et intégrer toutes les parties prenantes nécessaires à la survie de la gorge et à la durabilité de la biodiversité qu'elle soutient.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Organic Syntheses During the Impact of a Comet with a Gaseous Planet

1997 ◽  
Vol 161 ◽  
pp. 189-195
Author(s):  
Cesare Guaita ◽  
Roberto Crippa ◽  
Federico Manzini
Keyword(s):  
Polymeric Material ◽  
Molecular Form ◽  
Parent Compound ◽  
Blue Filter ◽  
Organic Syntheses ◽  
The Impact

AbstractA large amount of CO has been detected above many SL9/Jupiter impacts. This gas was never detected before the collision. So, in our opinion, CO was released from a parent compound during the collision. We identify this compound as POM (polyoxymethylene), a formaldehyde (HCHO) polymer that, when suddenly heated, reformes monomeric HCHO. At temperatures higher than 1200°K HCHO cannot exist in molecular form and the most probable result of its decomposition is the formation of CO. At lower temperatures, HCHO can react with NH3 and/or HCN to form high UV-absorbing polymeric material. In our opinion, this kind of material has also to be taken in to account to explain the complex evolution of some SL9 impacts that we observed in CCD images taken with a blue filter.

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