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Impact of temperature on the pullout of reinforcing geotextiles from unsaturated silt
This study investigates the thermal soil-geosynthetic interaction mechanisms of reinforcing geotextiles confined in compacted silt that may be encountered when using mechanically-stabilized earth (MSE) walls as geothermal heat sinks. A thermo-mechanical geosynthetic pullout device was used that incorporates standard components for geosynthetic pullout or creep testing but also heating elements at the top and bottom of the soil box to apply boundary temperatures and dielectric sensors embedded in the soil layer to monitor distributions in temperature and volumetric water content. Two test series were performed: the first involves monotonic pullout of woven polypropylene geotextiles after reaching steady-state conditions under different boundary temperatures without a seating load, and the second involves monotonic pullout of woven polyethylene-terephthalate geotextiles after reaching steady-state conditions under different boundary temperatures with a seating pullout load. The results indicate that the pullout resistance of both geotextiles decreased with increasing temperature. Although heating led to drying of the unsaturated silt layers as expected, measurements from the second test series indicate accumulation of water at the silt-geotextile interface. An effective stress analysis considering thermal softening of soils indicates that the increase in effective saturation at the silt-geotextile interface was the cause of the decrease in pullout resistance with heating
Information Technology Externalities: Empirical Evidence from 42 U.S. Industries
Using interindustry transaction in input-output tables, we examine Information Technology (IT) externalities in U.S. private industries over the period 1984-2000. Our empirical results show that computerization of an industry's customer and supplier industries reduces both labor and material costs of the industry. Moreover, cost savings driven by supplier industries are larger than those driven by customer industries. We also find that industries in the services sector enjoy more benefits from IT spillovers than industries in other sectors because of their high IT capital intensity and composition of interindustry transaction. Decomposition of total factor productivity (TFP) suggests that IT externalities can explain considerable parts of TFP growth, although possible mismeasurement of output in services industries leads to exacerbated technical changes of services industries.INFORMATION TECHNOLOGY; NETWORK EXTERNALITY; INPUT-OUTPUT TABLE; TOTAL FACTOR PRODUCTIVITY
Diamagnetic response of Aharonov-Bohm rings: Impurity backward scatterings
We report a theoretical calculation on the persistent currents of disordered
normal-metal rings. It is shown that the diamagnetic responses of the rings in
the vicinity of the zero magnetic field are attributed to multiple backward
scatterings off the impurities. We observe the transition from the paramagnetic
response to the diamagnetic one as the strength of disorder grows using both
the analytic calculation and the numerical exact diagonalization.Comment: final versio
Phase diagram of CeVSb3 under pressure and its dependence on pressure conditions
We present temperature dependent resistivity and ac-calorimetry measurements
of CeVSb3 under pressure up to 8 GPa in a Bridgman anvil cell modified to use a
liquid medium and in a diamond anvil cell using argon as a pressure medium,
respectively. We observe an initial increase of the ferromagnetic transition
temperature Tc with pressures up to 4.5 GPa, followed by decrease of Tc on
further increase of pressure and finally its disappearance, in agreement with
the Doniach model. We infer a ferromagnetic quantum critical point around 7 GPa
under hydrostatic pressure conditions from the extrapolation to 0 K of Tc and
the maximum of the A coefficient from low temperature fits of the resistivity
\rho (T)=\rho_{0}+AT^{n}. No superconductivity under pressure was observed down
to 0.35 K for this compound. In addition, differences in the Tc(P) behavior
when a slight uniaxial component is present are noticed and discussed and
correlated to choice of pressure medium
Extent of Fermi-surface reconstruction in the high-temperature superconductor HgBaCuO
High magnetic fields have revealed a surprisingly small Fermi-surface in
underdoped cuprates, possibly resulting from Fermi-surface reconstruction due
to an order parameter that breaks translational symmetry of the crystal
lattice. A crucial issue concerns the doping extent of this state and its
relationship to the principal pseudogap and superconducting phases. We employ
pulsed magnetic field measurements on the cuprate HgBaCuO to
identify signatures of Fermi surface reconstruction from a sign change of the
Hall effect and a peak in the temperature-dependent planar resistivity. We
trace the termination of Fermi-surface reconstruction to two hole
concentrations where the superconducting upper critical fields are found to be
enhanced. One of these points is associated with the pseudogap end-point near
optimal doping. These results connect the Fermi-surface reconstruction to both
superconductivity and the pseudogap phenomena.Comment: 5 pages. 3 Figures. PNAS (2020
Hydrostatic pressure study of single-crystalline UNi0.5Sb2
We studied single-crystals of the antiferromagnetic compound UNi0.5Sb2 (TN ~
161 K) by means of measurements of magnetic susceptibility (chi), specific heat
(Cp), and electrical resistivity (rho) at ambient pressure, and resistivity
under hydrostatic pressures up to 20 kbar, in the temperature range from 1.9 to
300 K. The thermal coefficient of the electrical resistivity (drho/dT) changes
drastically from positive below TN to negative above, reflecting the loss of
spin-disorder scattering in the ordered phase. Two small features in the rho vs
T data centered near 40 and 85 K correlate well in temperature with features in
the magnetic susceptibility and are consistent with other data in the
literature. These features are quite hysteretic in temperature, i.e., the
difference between the warming and cooling cycles are about 10 and 6 K,
respectively. The effect of pressure is to raise TN at the approximate rate of
0.76 K/kbar, while progressively suppressing the amplitude of the small
features in rho vs T at lower temperatures and increasing the thermal
hysteresis.Comment: 9 pages, 3 figues, 2007-mmm conferenc
The Infrared Einstein Ring in the Gravitational Lens MG1131+0456 and the Death of the Dusty Lens Hypothesis
We have obtained and modeled new NICMOS images of the lens system
MG1131+0456, which show that its lens galaxy is an H=18.6 mag, transparent,
early-type galaxy at a redshift of about z_l = 0.85; it has a major axis
effective radius R_e=0.68+/-0.05 arcsec, projected axis ratio b/a=0.77+/-0.02,
and major axis PA=60+/-2 degrees. The lens is the brightest member of a group
of seven galaxies with similar R-I and I-H colors, and the two closest group
members produce sufficient tidal perturbations to explain the ring morphology.
The host galaxy of the MG1131+0456 source is a z_s > 2 ERO (``extremely red
object'') which is lensed into optical and infrared rings of dramatically
different morphologies. These differences imply a strongly wavelength-dependent
source morphology that could be explained by embedding the host in a larger,
dusty disk. At 1.6 micron (H), the ring is spectacularly luminous, with a total
observed flux of H=17.4 mag and a de-magnified flux of 19.3 mag, corresponding
to a 1-2L_* galaxy at the probable source redshift of z_s > 2. Thus, it is
primarily the stellar emission of the radio source host galaxy that produces
the overall colors of two of the reddest radio lenses, MG1131+0456 and
B~1938+666, aided by the suppression of optical AGN emission by dust in the
source galaxy. The dusty lens hypothesis -- that many massive early-type
galaxies with 0.2 < z_l < 1.0 have large, uniform dust opacities -- is ruled
out.Comment: 27 pages, 8 COLOR figures, submitted to ApJ. Black and white version
available at http://cfa-www.harvard.edu/castle
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