The History of the Perfect Aspect Ratio

Author(s):  
Mark Schubin
Keyword(s):  
1988 ◽  
Vol 110 (1) ◽  
pp. 26-31 ◽  
Author(s):  
R. S. Sayles ◽  
E. Ioannides

Predictions of fatigue life from debris indented roller bearings are calculated by the methods described by Webster, Ioannides, and Sayles [9] and presented as a comparison to the actual fatigue history of the bearings. Research is also presented on the influence of debris type and geometry in relation to the formation of dents within nonconforming contacts. In particular, the concept of elastic conformity around entrained debris is studied in detail and it is shown that a critical debris aspect ratio may well exist which defines a boundary between debris that can damage the contact surfaces, and that which cannot.


Author(s):  
David W. Fogg ◽  
Ching-Hsiang Cheng ◽  
Ken E. Goodson

The growth and departure of vapor bubbles governs pressure drop and thermal resistance of two-phase microchannel heat sinks. Little data is available for the growth, departure, and convection of bubbles in microchannels. The current study uses isothermal air injection to simulate the nucleation and growth of bubbles in high aspect microchannels with Dh≈48μm and aspect ratios from 20 to 40 with 1 < ReH < 10. Liquid pressure drop and flow rate are measured during bubble growth along with the time history of the bubble geometry obtained from a high speed video imaging system at rates up to 50,000 frames per second. Bubble departure is found to vary linearly with aspect ratio divided by inlet Reynolds number, while the convection velocity depends on the normalized bubble width and normalized liquid film thickness. A scaling analysis identifies the increase in axial pressure drop due to bubble confinement as the driving force for both bubble departure and convection.


2004 ◽  
Vol 17 (5) ◽  
pp. 1-5 ◽  
Author(s):  
Robert D. Ecker ◽  
L. Nelson Hopkins

Since the publication of the retrospective part of the International Study of Unruptured Intracranial Aneurysms (ISUIA) in 1998, there has been a significant focus in the neurosurgical literature on the natural history of these lesions. The prospective data from the second part of the ISUIA, which was published in 2003, provided further evidence that small, asymptomatic intracranial aneurysms may have a more benign course than previously believed. With the data from the ISUIA as a reference point, in this paper the authors strive to provide a source of practical clinical data to aid cerebrovascular physicians in the initial decision to treat or observe a patient with a small, asymptomatic intracranial aneurysm. The issues covered will include previous rupture, symptoms other than rupture, aneurysm size, site, and aspect ratio. It is the authors' goal to provide a useful practical framework on the relevant clinical issues as an aid to practitioners treating patients who present with intracranial aneurysms.


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