11,814 research outputs found
Tunnel lining studies II
In the CRREL tunnel (Fig. B1, B2), sublimation is extremely apparent, but because of the tunnels limited usage it poses no significant problems. However, in an operating mine with forced air ventilation and continuously operating machinery, the problems associated with sublimation may no longer be insignificant. The dust released by the evaporating ice poses not only the obvious respiratory threat, but an additional safety threat, as fine silt suspended in the air reduces visibility, and removal or suppression of the dust will be of importance.Sublimation control measures of the permafrost in the CRREL tunnel -- Introduction -- The sublimation process -- Sublimation control -- Test installations -- Conclusion -- References -- Appendix A: Summary of data -- Appendix B: Photographs
The Cuntz splice does not preserve -isomorphism of Leavitt path algebras over
We show that the Leavitt path algebras and
are not isomorphic as -algebras. There are two key
ingredients in the proof. One is a partial algebraic translation of Matsumoto
and Matui's result on diagonal preserving isomorphisms of Cuntz--Krieger
algebras. The other is a complete description of the projections in
for a finite graph. This description is based on a
generalization, due to Chris Smith, of the description of the unitaries in
given by Brownlowe and the second named author. The
techniques generalize to a slightly larger class of rings than just
.Comment: 17 pages. Since version 2 we extended the arguments from Z to more
general ring
Articulated multiple couch assembly Patent
Shock absorbing articulated multiple couch assembl
Protoplanetary Disk Turbulence Driven by the Streaming Instability: Non-Linear Saturation and Particle Concentration
We present simulations of the non-linear evolution of streaming instabilities
in protoplanetary disks. The two components of the disk, gas treated with grid
hydrodynamics and solids treated as superparticles, are mutually coupled by
drag forces. We find that the initially laminar equilibrium flow spontaneously
develops into turbulence in our unstratified local model. Marginally coupled
solids (that couple to the gas on a Keplerian time-scale) trigger an upward
cascade to large particle clumps with peak overdensities above 100. The clumps
evolve dynamically by losing material downstream to the radial drift flow while
receiving recycled material from upstream. Smaller, more tightly coupled solids
produce weaker turbulence with more transient overdensities on smaller length
scales. The net inward radial drift is decreased for marginally coupled
particles, whereas the tightly coupled particles migrate faster in the
saturated turbulent state. The turbulent diffusion of solid particles, measured
by their random walk, depends strongly on their stopping time and on the
solids-to-gas ratio of the background state, but diffusion is generally modest,
particularly for tightly coupled solids. Angular momentum transport is too weak
and of the wrong sign to influence stellar accretion. Self-gravity and
collisions will be needed to determine the relevance of particle overdensities
for planetesimal formation.Comment: Accepted for publication in ApJ (17 pages). Movies of the simulations
can be downloaded at http://www.mpia.de/~johansen/research_en.ph
Arsitektur Rumah Betang (Radakng) Kampung Sahapm
Arsitektur dari suatu bangsa, pada suatu masa sering berbeda-beda, baik dalam hal bentuk maupun konsep-konsep yang melandasinya. Hal ini tentu disebabkan adanya perbedaan kebudayaan dari suatu masyarakat dengan masyarakat lainnya. Setiap suku bangsa biasanya akan menunjukkan identitas budayanya melalui benda-benda budaya yang mereka buat. Demikian halnya masyarakat Dayak Kanayatn memiliki ciri tersendiri dalam bentuk arsitektur bangunan khususnya bangunan rumah tinggal. Bentuk arsitektur masyarakat Dayak Kanayat'n yang tinggal di Desa Sahapm tercermin dalam bentuk Rumah Betang atau Rumah Panjang dan hingga kini masih dijaga dan dihuni oleh masyarakat. Bentuk rumah Betang juga menunjukkan hidup kebersamaan bagi penghuninya. Dalam Rumah panjang atau Rumah Betang mereka berinteraksi antara bilik yang satu dengan bilik yang lainnya. Tujuan penulisan untuk mendeskripsikan bentuk arsitektur Rumah Betang dan keberadaannya pada saat ini, selain itu penelitian ini juga mendeskripsikan kehidupan masyarakat di Rumah Betang. Metode yang digunakan adalah metode deskriptif kualitatif dengan menggunakan tehnik pengamatan dan wawancara dalam menggali data di lapangan serta studi kepustakaan sebagai menggali bahan untuk menulis
Stock mechanics: predicting recession in S&P500, DJIA, and NASDAQ
An original method, assuming potential and kinetic energy for prices and
conservation of their sum is developed for forecasting exchanges. Connections
with power law are shown. Semiempirical applications on S&P500, DJIA, and
NASDAQ predict a coming recession in them. An emerging market, Istanbul Stock
Exchange index ISE-100 is found involving a potential to continue to rise.Comment: 14 pages, 4 figure
Terrestrial planets across space and time
The study of cosmology, galaxy formation and exoplanets has now advanced to a
stage where a cosmic inventory of terrestrial planets may be attempted. By
coupling semi-analytic models of galaxy formation to a recipe that relates the
occurrence of planets to the mass and metallicity of their host stars, we trace
the population of terrestrial planets around both solar-mass (FGK type) and
lower-mass (M dwarf) stars throughout all of cosmic history. We find that the
mean age of terrestrial planets in the local Universe is Gyr for FGK
hosts and Gyr for M dwarfs. We estimate that hot Jupiters have
depleted the population of terrestrial planets around FGK stars by no more than
, and that only of the terrestrial planets at the
current epoch are orbiting stars in a metallicity range for which such planets
have yet to be confirmed. The typical terrestrial planet in the local Universe
is located in a spheroid-dominated galaxy with a total stellar mass comparable
to that of the Milky Way. When looking at the inventory of planets throughout
the whole observable Universe, we argue for a total of and terrestrial planets around FGK and M
stars, respectively. Due to light travel time effects, the terrestrial planets
on our past light cone exhibit a mean age of just Gyr. These
results are discussed in the context of cosmic habitability, the Copernican
principle and searches for extraterrestrial intelligence at cosmological
distances.Comment: 11 pages, 8 figures. v.2: Accepted for publication in ApJ. Some
changes in quantitative results compared to v.1, mainly due to differences in
IMF assumption
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