2,723 research outputs found
Experimental results on gravity driven fully condensing flows in vertical tubes, their agreement with theory, and their differences with shear driven flows\u27 boundary-condition sensitivities
This doctoral thesis presents the experimental results along with a suitable synthesis with computational/theoretical results towards development of a reliable heat transfer correlation for a specific annular condensation flow regime inside a vertical tube. For fully condensing flows of pure vapor (FC-72) inside a vertical cylindrical tube of 6.6 mm diameter and 0.7 m length, the experimental measurements are shown to yield values of average heat transfer co-efficient, and approximate length of full condensation.
The experimental conditions cover: mass flux G over a range of 2.9 kg/m2-s ≤ G ≤ 87.7 kg/m2-s, temperature difference ∆T (saturation temperature at the inlet pressure minus the mean condensing surface temperature) of 5 ºC to 45 ºC, and cases for which the length of full condensation xFC is in the range of 0 \u3c xFC \u3c 0.7 m.
The range of flow conditions over which there is good agreement (within 15%) with the theory and its modeling assumptions has been identified. Additionally, the ranges of flow conditions for which there are significant discrepancies (between 15 -30% and greater than 30%) with theory have also been identified.
The paper also refers to a brief set of key experimental results with regard to sensitivity of the flow to time-varying or quasi-steady (i.e. steady in the mean) impositions of pressure at both the inlet and the outlet. The experimental results support the updated theoretical/computational results that gravity dominated condensing flows do not allow such elliptic impositions
Thermodynamics of Squashed Kaluza-Klein Black Holes and Black Strings -- A Comparison of Reference Backgrounds --
We investigate thermodynamics constructed on different background reference
spacetimes for squashed Kaluza-Klein (SqKK) black hole and electrically charged
black string in five-dimensional Einstein-Maxwell system. Two spacetimes are
possible to be reference spacetimes giving finite gravitational classical
actions: one is four-dimensional Minkowski times a circle and the other is the
KK monopole. The boundary of the SqKK black hole can not be matched perfectly
to that of the former reference spacetime because of the difference in
topology. However, the resultant classical action coincides with that
calculated by the counterterm subtraction scheme. The boundary of the KK
monopole has the same topology with that of the SqKK black hole and can be
matched to the boundary of the black hole perfectly. The resultant action takes
different value from the result given by using the former reference spacetime.
After a brief review of thermodynamic quantities of the black hole solutions,
we calculate thermodynamic potentials relevant for several thermodynamic
environments. The most stable state is different for each environment: For
example, the KK monopole is the most stable state in isothermal environment
with fixed gravitational tension. On the other hand, when the size of the
extra-dimension is fixed, the Minkowski times a circle is the most stable. It
is shown that these two spacetimes can be reference spacetimes of the
five-dimensional black string.Comment: 28 pages; references added, typo corrected;version accepted for
publication in Class. Quantum Gra
Fermi surface and superconductivity in low-density high-mobility {\delta}-doped SrTiO3
The electronic structure of low-density n-type SrTiO3 delta-doped
heterostructures is investigated by angular dependent Shubnikov-de Haas
oscillations. In addition to a controllable crossover from a three- to
two-dimensional Fermi surface, clear beating patterns for decreasing dopant
layer thicknesses are found. These indicate the lifting of the degeneracy of
the conduction band due to subband quantization in the two-dimensional limit.
Analysis of the temperature-dependent oscillations shows that similar effective
masses are found for all components, associated with the splitting of the light
electron pocket. The dimensionality crossover in the superconducting state is
found to be distinct from the normal state, resulting in a rich phase diagram
as a function of dopant layer thickness.Comment: 4 pages, 5 figures, submitted for publicatio
"Spin-Flop" Transition and Anisotropic Magnetoresistance in Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4}: Unexpectedly Strong Spin-Charge Coupling in Electron-Doped Cuprates
We use transport and neutron-scattering measurements to show that a
magnetic-field-induced transition from noncollinear to collinear spin
arrangement in adjacent CuO_{2} planes of lightly electron-doped
Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4} (x=0.01) crystals affects significantly both
the in-plane and out-of-plane resistivity. In the high-field collinear state,
the magnetoresistance (MR) does not saturate, but exhibits an intriguing
four-fold-symmetric angular dependence, oscillating from being positive at
B//[100] to being negative at B//[110]. The observed MR of more than 30% at low
temperatures induced by a modest modification of the spin structure indicates
an unexpectedly strong spin-charge coupling in electron-doped cuprates.Comment: 4 pages, 5 figures, accepted for publication in Phys. Rev. Let
Thermodynamics of four-dimensional black objects in the warped compactification
We reinvestigate the thermodynamics of black objects (holes and strings) in
four-dimensional braneworld models that are originally constructed by Emparan,
Horowitz and Myers based on the anti-de Sitter (AdS) C-metric. After proving
the uniqueness of slicing the AdS C-metric, we derive thermodynamic quantities
of the black objects by means of the Euclidean formulation and find that we
have no necessity of requiring any regularization to calculate their classical
action. We show that there exist the Bekenstein-Hawking law and the
thermodynamic first law. The thermodynamic mass of the localized black hole on
a flat brane is negative, and it differs from the one previously derived. We
discuss the thermodynamic stabilities and show that the BTZ black string is
more stable than the localized black holes in a canonical ensemble, except for
an extreme case. We also find a braneworld analogue of the Hawking-Page
transition between the BTZ black string and thermal AdS branes. The localized
black holes on a de Sitter brane is discussed by considering Nariai instanton,
comparing the study of "black cigar" in the five-dimensional braneworld model.Comment: 15 pages, 4 figures, RevTex4, typos fixed, minor correction
Intraoperative Tissue Staining of Invaded Oral Carcinoma
PATHOLOGY & ONCOLOGY RESEARCH. 14(4):461-465 (2008)journal articl
Comparison of imaging follow-up between joints with arthroscopic surgery (Lysis and lavage) and those with nonsurgical treatment
ArticleJournal of Oral and Maxillofacial Surgery. 65(7):1309-1314 (2007)journal articl
Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2 and SrNi2P2
We have performed low-temperature specific heat and thermal conductivity
measurements on the Ni-pnictide superconductors BaNiAs
(=0.7 K and SrNiP (=1.4 K). The temperature
dependences and of the two compounds are similar to the
results of a number of s-wave superconductors. Furthermore, the concave field
responses of the residual for BaNiAs rules out the presence of
nodes on the Fermi surfaces. We postulate that fully gapped superconductivity
could be universal for Ni-pnictide superconductors. Specific heat data on
BaLaNiAs shows a mild suppression of and
relative to BaNiAs.Comment: 5 pages, 3 figures, to be published in J. Phys.: Conf. Se
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