5,628 research outputs found
Enhanced thermoelectric properties by Ir doping of PtSb2 with pyrite structure
The effects of Ir doping on the thermoelectric properties of Pt1-xIrxSb2 (x =
0, 0.01, 0.03, and 0.1) with pyrite structure were studied. Measurements of
electrical resistivity rho, Seebeck coefficient S, and thermal conductivity
kappa were conducted. The results showed an abrupt change from semiconducting
behavior without Ir (x = 0) to metallic behavior at x = 0.01. The sample with x
= 0.01 exhibited large S and low rho, resulting in a maximum power factor
(S^2/rho) of 43 muW/cmK^2 at 400 K. The peculiar "pudding mold"-type electronic
band dispersion could explain the enhanced thermoelectric properties in the
metallic state.Comment: 3 pages, 2 figure
Using Statistical Process Control Methods to Classify Pilot Mental Workload
The problem of classifying pilot mental workload is important to the United States Air Force. Pilots are more subject to errors and G-induced loss of consciousness during periods of mental overload and task saturation. Often the result is the loss of aircraft, and in extreme cases, the loss of the pilot\u27s life. Current research efforts use different psychophysiological features to classify pilot mental workload. These include cardiac, ocular, respiratory, and brain activity measures. The focus of this effort is to apply statistical process control methodology on different psychophysiological features in an attempt to classify pilot mental workload. The control charts track these features throughout the flight, and classify a segment as high workload if the measurements of these feature, are greater than predefined control limits. We find that using certain control charts prove to be effective workload classifiers and maintain high classification accuracies when applied to other flight data
Single-crystal growth and dependences on the hole concentration and magnetic field of the magnetic ground state in the edge-sharing CuO chain system CaYCuO
We have succeeded in growing large-size single-crystals of
CaYCuO with and measured the
magnetic susceptibility, specific heat and magnetization curve, in order to
study the magnetic ground state in the edge-sharing CuO chain as a function
of hole concentration and magnetic field. In , it has been
found that an antiferromagnetically ordered phase with the magnetic easy axis
along the b-axis is stabilized and that a spin-flop transition occurs by the
application of magnetic fields parallel to the b-axis. The antiferromagnetic
transition temperature decreases with increasing and disappears around 1.4. Alternatively, a spin-glass phase appears around . At where the hole concentration is 1/3 per Cu, it appears that a
spin-gap state is formed owing to the formation of spin-singlet pairs. No sign
of the coexistence of an antiferromagnetically ordered state and a spin-gap one
suggested in CaCuO has been found in
CaYCuO.Comment: 13 pages, 12 figures, 1 tabl
Magnetic-field effects on the in-plane electrical resistivity in the single-crystal LaBaCuO and LaNdSrCuO around : Relating to the field-induced stripe order
Temperature dependence of the in-plane electrical resistivity, , in various magnetic fields has been measured in the single-crystal
LaBaCuO with , 0.10, 0.11 and
LaNdSrCuO with . It has been found that the
superconducting transition curve shows a so-called fan-shape broadening in
magnetic fields for , while it shifts toward the low-temperature side
in parallel with increasing field for and 0.12 where the charge-spin
stripe order is formed at low temperatures. As for , the broadening is
observed in low fields and it changes to the parallel shift in high fields
above 9 T. Moreover, the normal-state value of at low
temperatures markedly increases with increasing field up to 15 T. It is
possible that these pronounced features of are understood in terms of
the magnetic-field-induced stabilization of the stripe order suggested from the
neutron-scattering measurements in the La-214 system. The in
the normal state at low temperatures has been found to be proportional to
ln(1/) for , 0.11 and 0.12. The ln(1/) dependence of is robust even in the stripe-ordered state.Comment: 6 pages, 4 figures, ver. 2 has been accepted for publication in Phys.
Rev.
Dynamic Strength of Gravelly Soils and Its Relation to the Penetration Resistance
Undrained cyclic triaxial tests have been conducted on specimens of dense diluvial gravelly soils taken from four sites by an in-situ freeze sampling method. The test results and previous test results obtained by other researchers suggest that the dynamic strength of gravelly soils can be evaluated based on both the modified blow count of the penetration tests and on the effective confining pressure. A method for the evaluation by utilizing the large penetration test (LPT) blow counts is proposed in this paper by considering the effect of the effective confining pressure on the dynamic strength
Thermal Conductivity of the Quasi One-Dimensional Spin System Sr_2_V_3_O_9_
We have measured the thermal conductivity along the [101] direction,
kappa_[101]_, along the [10-1] direction, kappa_[10-1]_, and along the b-axis,
kappa_b_, of the quasi one-dimensional S=1/2 spin system Sr_2_V_3_O_9_ in
magnetic fields up to 14 T, in order to find the thermal conductivity due to
spinons and to clarify whether the spin-chains run along the [101] or [10-1]
direction. It has been found that both kappa_[101]_, kappa_[10-1]_ and kappa_b_
show one peak around 10 K in zero field and that the magnitude of kappa_[10-1]_
is larger than those of kappa_[101]_ and kappa_b_. By the application of
magnetic field along the heat current, the peak of kappa_[10-1]_ is markedly
suppressed, while the peaks of kappa_[101]_ and kappa_b_ little change. These
results indicate that there is a large contribution of spinons to kappa_[10-1]_
and suggest that the spin-chains run along the [10-1] direction.Comment: 3 pages, 4 figure
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