42,184 research outputs found
Nimbus C first orbit flight evaluation report
Flight evaluation of power, control, thermal, and pulse code modulation signal subsystems during first orbit of Nimbus C satellit
Workpiece positioning vise
A pair of jaw assemblies simultaneously driven in opposed reciprocation by a single shaft has oppositely threaded sections to automatically center delicate or brittle workpieces such as lithium fluoride crystal beneath the blade of a crystal cleaving machine. Both jaw assemblies are suspended above the vise bed by a pair of parallel guide shafts attached to the vise bed. Linear rolling bearings, fitted around the guide shafts and firmly held by opposite ends of the jaw assemblies, provide rolling friction between the guide shafts and the jaw assemblies. A belleville washer at one end of the drive shaft and thrust bearings at both drive shaft ends hold the shaft in compression between the vise bed, thereby preventing wobble of the jaw assemblies due to wear between the shaft and vise bed
Some Applications of Detailed Wind Profile Data to Launch Vehicle Response Problems
The response of a launch vehicle to a number of detailed wind profiles has been determined. The wind profiles were measured by two techniques which are briefly described. One of these techniques uses an angle-of-attack sensor in conjunction with guidance data to measure the wind profile traversed by some particular launch vehicle. The other wind-measuring technique is a photographic triangulation method, whereby two cameras take simultaneous pictures of a vertical trail of smoke left by a launch vehicle or sounding rocket. The response of a vehicle flying these detailed profiles is compared with the response of the same vehicle flying through balloon-measured profiles. The response to the detailed wind profiles, relative t o the balloon-measured profiles, is characterized by the large excitation of the rigid pitch and elastic bending modes. This is found to cause higher loads on the launch vehicle structure. Established design criteria which utilize balloon measured wind profiles have arbitrarily accounted-for this increased load by adding a load due to some type of discrete gust
Automatically assembling a full census of an academic field
The composition of the scientific workforce shapes the direction of
scientific research, directly through the selection of questions to
investigate, and indirectly through its influence on the training of future
scientists. In most fields, however, complete census information is difficult
to obtain, complicating efforts to study workforce dynamics and the effects of
policy. This is particularly true in computer science, which lacks a single,
all-encompassing directory or professional organization. A full census of
computer science would serve many purposes, not the least of which is a better
understanding of the trends and causes of unequal representation in computing.
Previous academic census efforts have relied on narrow or biased samples, or on
professional society membership rolls. A full census can be constructed
directly from online departmental faculty directories, but doing so by hand is
prohibitively expensive and time-consuming. Here, we introduce a topical web
crawler for automating the collection of faculty information from web-based
department rosters, and demonstrate the resulting system on the 205
PhD-granting computer science departments in the U.S. and Canada. This method
constructs a complete census of the field within a few minutes, and achieves
over 99% precision and recall. We conclude by comparing the resulting 2017
census to a hand-curated 2011 census to quantify turnover and retention in
computer science, in general and for female faculty in particular,
demonstrating the types of analysis made possible by automated census
construction.Comment: 11 pages, 6 figures, 2 table
Remarks on the boundary set of spectral equipartitions
Given a bounded open set in (or a compact Riemannian
manifold with boundary), and a partition of by open sets
, we consider the quantity , where
is the ground state energy of the Dirichlet realization of
the Laplacian in . We denote by the infimum
of over all -partitions. A minimal -partition
is a partition which realizes the infimum. The purpose of this paper is to
revisit properties of nodal sets and to explore if they are also true for
minimal partitions, or more generally for spectral equipartitions. We focus on
the length of the boundary set of the partition in the 2-dimensional situation.Comment: Final version to appear in the Philosophical Transactions of the
Royal Society
Bone mechanical properties in healthy and diseased states
The mechanical properties of bone are fundamental to the ability of our skeletons to support movement and to provide protection to our vital organs. As such, deterioration in mechanical behavior with aging and/or diseases such as osteoporosis and diabetes can have profound consequences for individualsâ quality of life. This article reviews current knowledge of the basic mechanical behavior of bone at length scales ranging from hundreds of nanometers to tens of centimeters. We present the basic tenets of bone mechanics and connect them to some of the arcs of research that have brought the field to recent advances. We also discuss cortical bone, trabecular bone, and whole bones, as well as multiple aspects of material behavior, including elasticity, yield, fracture, fatigue, and damage. We describe the roles of bone quantity (e.g., density, porosity) and bone quality (e.g., cross-linking, protein composition), along with several avenues of future research.Author manuscrip
Investigation into the variations of moisture content of two buildings constructed with light earth walls
This paper briefly describes the background to light earth buildings and details a series of moisture measurements undertaken upon the clay and straw, (light earth) constructed walls of two UK based buildings. The methodology of measurement that was based upon previous studies undertaken on walls made from straw bales is described. A novel âin-wallâ wet heating system used in one of the two buildings allows the investigation of the effects of direct wall heating upon the distribution of moisture in the walls. The influence of exterior and interior temperature and humidity are described as are the variations in moisture migration introduced by the in-wall heating system. It was concluded that both buildings have exterior wall moisture content readings that indicate little risk of degradation due to interior wall moisture levels (although the Studio walls do exhibit higher and if suffered over long time periods, dangerous moisture readings for part of the measurement period)
A Special Homotopy Continuation Method For A Class of Polynomial Systems
A special homotopy continuation method, as a combination of the polyhedral
homotopy and the linear product homotopy, is proposed for computing all the
isolated solutions to a special class of polynomial systems. The root number
bound of this method is between the total degree bound and the mixed volume
bound and can be easily computed. The new algorithm has been implemented as a
program called LPH using C++. Our experiments show its efficiency compared to
the polyhedral or other homotopies on such systems. As an application, the
algorithm can be used to find witness points on each connected component of a
real variety
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