703 research outputs found
Component and cladding wind loads for low-slope roofs on low-rise buildings
The component and cladding wind load provisions for low-sloped roofs on low-rise buildings in ASCE 7-10 were examined using measured pressure data from an aerodynamic database. It was found that both the design pressure coefficients and size of the roof zones in ASCE 7-10 are much smaller in magnitude than indicated by the data. The data indicate that building height is the most significant parameter affecting the size of the roof zones, while plan dimensions have a limited impact on this class of buildings. Recommendations for revised roof zones are developed, which include a modification to the shape of the corner zone, the addition of a new interior zone far from the roof edges, and a zone size definition that depends only on building height. However, even with increased roof zone sizes, the measured data indicate that the design pressure coefficients must also be increased in the corners and edges
The Uncertainty of Fluxes
In the ordinary quantum Maxwell theory of a free electromagnetic field,
formulated on a curved 3-manifold, we observe that magnetic and electric fluxes
cannot be simultaneously measured. This uncertainty principle reflects torsion:
fluxes modulo torsion can be simultaneously measured. We also develop the
Hamilton theory of self-dual fields, noting that they are quantized by
Pontrjagin self-dual cohomology theories and that the quantum Hilbert space is
Z/2-graded, so typically contains both bosonic and fermionic states.
Significantly, these ideas apply to the Ramond-Ramond field in string theory,
showing that its K-theory class cannot be measured.Comment: 33 pages; minor modifications for publication in Commun. Math. Phy
Optimization of photomixers and antennas for continuous-wave terahertz emission
We have studied terahertz emission from interdigitated
finger photomixers coupled to planar antenna structures.
Using both pulsed and continuous-wave excitation, polarization
measurements reveal that the antenna design dominates the properties
of the radiated output at frequencies below 0.6 THz, while
the efficiency at higher frequencies is additionally dependent on
the design of the photomixer fingers. We have produced terahertz
maps of the device, characterizing the photomixer by measuring
the generated power as a function of the excitation position. Together,
these measurements have allowed us to understand better
the distinct roles of the photomixer and antenna in emission at
different fre
Classical and Thermodynamic Stability of Black Branes
It is argued that many non-extremal black branes exhibit a classical
Gregory-Laflamme instability if, and only if, they are locally
thermodynamically unstable. For some black branes, the Gregory-Laflamme
instability must therefore disappear near extremality. For the black -branes
of the type II supergravity theories, the Gregory-Laflamme instability
disappears near extremality for but persists all the way down to
extremality for (the black D3-brane is not covered by the analysis of
this paper). This implies that the instability also vanishes for the
near-extremal black M2 and M5-brane solutions.Comment: 21 pages, LaTeX. v2: Various points clarified, typos corrected and
reference adde
Associations between tactile intimacy and sleep quality in healthy adults: a systematic review
Prior research suggests that different types of touch can affect sleep, but whether there is a consistent association between tactile intimacy and sleep quality is unclear. Here, we report a pre-registered systematic review (PROSPERO - CRD42020158683) of studies examining the association between tactile intimacy and sleep quality in healthy adults. The databases PsycINFO, PubMed, Web of Science, the Cochrane Central Register of Controlled Trials and EMBASE were searched on August 7th, 2020. 13 studies met the inclusion criteria and were synthesised qualitatively. Most commonly, articles researched sexual intimacy in relation to sleep quality, but some studies also investigated nonsexual affective touch and emotionally neutral touch. Some evidence for a connection between sexual function, sexual satisfaction and masturbation with sleep quality was found, however, no evidence for an association between sexual frequency or sexual positions and sleep was found. Interestingly, studies employing more subjective approaches were more likely to report an association between touch and sleep, potentially highlighting a discrepancy between self-reported and the objectively measurable association between touch and sleep
Path integral formulation of Hodge duality on the brane
In the warped compactification with a single Randall-Sundrum brane, a
puzzling claim has been made that scalar fields can be bound to the brane but
their Hodge dual higher-rank anti-symmetric tensors cannot. By explicitly
requiring the Hodge duality, a prescription to resolve this puzzle was recently
proposed by Duff and Liu. In this note, we implement the Hodge duality via path
integral formulation in the presence of the background gravity fields of warped
compactifications. It is shown that the prescription of Duff and Liu can be
naturally understood within this framework.Comment: 7 pages, LaTe
On the existence of a static black hole on a brane
We study a static black hole localized on a brane in the Randall-Sundrum (RS)
II braneworld scenario. To solve this problem numerically, we develop a code
having the almost 4th-order accuracy. This code derives the highly accurate
result for the case where the brane tension is zero, i.e., the spherically
symmetric case. However, a nonsystematic error is detected in the cases where
the brane tension is nonzero. This error is irremovable by any systematic
methods such as increasing the resolution, setting the outer boundary at more
distant location, or improving the convergence of the numerical relaxation. We
discuss the possible origins for the nonsystematic error, and conclude that our
result is naturally interpreted as the evidence for the nonexistence of
solutions to this setup, although an "approximate" solution exists for
sufficiently small brane tension. We discuss the possibility that the black
holes produced on a brane may be unstable and lead to two interesting
consequences: the event horizon pinch and the brane pinch.Comment: 26 pages, 9 figures, submitted to JHE
CFT driven cosmology and the DGP/CFT correspondence
We present a dual 5D braneworld picture of a recently suggested model for a
microcanonical description of a 4D cosmology driven by a conformal field theory
with a large number of quantum fields. The 5D side of the duality relation is
represented by a generalized brane induced gravity model in a Schwarzschild-de
Sitter bulk. The values of the bulk cosmological and the induced 4D
cosmological constants are determined by requiring the absence of conical
singularity at the de Sitter horizon of the Euclidean Schwarzschild-de Sitter
bulk. Those values belong to the vicinity of the upper bound of a range of
admissible values for the cosmological constant. This upper bound is enforced
by the 4D CFT and coincides with the natural gravitational cutoff in a theory
with many quantum species. The resulting DGP/CFT duality suggests the
possibility of a new type of {\em background independent} correspondence. A
mechanism for inverting the sign of the effective cosmological constant is
found, which might reconcile a negative value of the primordial cosmological
constant compatible with supersymmetry with the one required by inflationary
cosmology.Comment: LaTeX, 23 pages, 3 figure
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