63,183 research outputs found
Saturation in ânonmagneticâ stainless steel
Scientific equipment often uses ânonmagneticâ stainless steel, relying on the steelâs nonmagnetic behavior to leave external magnetic fields unaltered. However, stainless steelâs permeability can rise significantly when it is welded or machined, possibly perturbing an external field. Such perturbations will diminish well above the stainless steelâs saturation point. The authors measured the permeability of both welded and machined 304 stainless steel as a function of an external magnetic field, and found that both saturate at fields of approximately 0.25 T
Equation of State in 2+1 Flavor QCD at High Temperatures
We calculate the Equation of State at high temperatures in 2+1 flavor QCD
using the highly improved staggered quark action. We study the lattice spacing
dependence of the pressure at high temperatures using lattices with temporal
extent and and perform continuum extrapolations. We
also give a continuum estimate for the Equation of State up to temperatures
GeV, which are then compared with results of the weak-coupling
calculations. We find a reasonably good agreement with the weak-coupling
calculations at the highest temperatures.Comment: RevTeX, 16 pages, 16 figures, published versio
Dependence of the thermoluminescent high-temperature ratio (HTR) of LiF:Mg,Ti detectors on proton energy and dose
The high-temperature ratio (HTR) is a parameter quantifying changes of the
shape of the high-temperature part of the LiF:Mg,Ti glow-curve after exposure
to densely ionizing radiation. It was introduced in order to estimate the
effective LET of an unknown radiation field and to correct the decreased
relative TL efficiency for high Linear Energy Transfer (LET) radiation. In the
present work the dependence of HTR on proton energy (14.5 to 58 MeV) and dose
(0.5 to 30 Gy) was investigated. All measured HTR values were at the level of
1.2 or higher, therefore significantly different from the respective value for
gamma rays (HTR is equal to 1), but HTR was found to be insensitive to changes
of proton energy above 20 MeV. As a result the relationship between HTR and
relative TL efficiency is not unequivocal. The HTR was found to be dependent on
absorbed dose even for the lowest studied doses.Comment: Manuscript has been presented at the 17th International Conference on
Solid State Dosimetry, Recife, Brasil, September 22-27,201
Analysis of aggregated tick returns: evidence for anomalous diffusion
In order to investigate the origin of large price fluctuations, we analyze
stock price changes of ten frequently traded NASDAQ stocks in the year 2002.
Though the influence of the trading frequency on the aggregate return in a
certain time interval is important, it cannot alone explain the heavy tailed
distribution of stock price changes. For this reason, we analyze intervals with
a fixed number of trades in order to eliminate the influence of the trading
frequency and investigate the relevance of other factors for the aggregate
return. We show that in tick time the price follows a discrete diffusion
process with a variable step width while the difference between the number of
steps in positive and negative direction in an interval is Gaussian
distributed. The step width is given by the return due to a single trade and is
long-term correlated in tick time. Hence, its mean value can well characterize
an interval of many trades and turns out to be an important determinant for
large aggregate returns. We also present a statistical model reproducing the
cumulative distribution of aggregate returns. For an accurate agreement with
the empirical distribution, we also take into account asymmetries of the step
widths in different directions together with crosscorrelations between these
asymmetries and the mean step width as well as the signs of the steps.Comment: 9 pages, 10 figures, typos correcte
Lunar Surface Gravimeter Experiment
The lunar surface gravimeter which was emplaced on the moon by the Apollo 17 flight is described and a schematic diagram of the sensor is provided. The objective of the lunar surface gravimeter is to use the moon as an instrumented antenna to detect gravitational waves. Another objective is to measure tidal deformation of the moon. Samples of signals received during lunar sunrise activity and during quiet periods are presented in graph form based on power spectrum analysi
Solid state crystal physics at very low temperatures
The properties of nearly perfect crystals was studied at cryogenic temperatures. A large Helium 3 and Helium 4 dilution refrigerator has been assembled, and is described. A cryostat suitable for cooling a 35 liter volume to .020 Kelvin was designed and constructed, together with instrumentation to observe the properties of nearly perfect crystals
Aerodynamic influence coefficient method using singularity splines
A numerical lifting surface formulation, including computed results for planar wing cases is presented. This formulation, referred to as the vortex spline scheme, combines the adaptability to complex shapes offered by paneling schemes with the smoothness and accuracy of loading function methods. The formulation employes a continuous distribution of singularity strength over a set of panels on a paneled wing. The basic distributions are independent, and each satisfied all the continuity conditions required of the final solution. These distributions are overlapped both spanwise and chordwise. Boundary conditions are satisfied in a least square error sense over the surface using a finite summing technique to approximate the integral. The current formulation uses the elementary horseshoe vortex as the basic singularity and is therefore restricted to linearized potential flow. As part of the study, a non planar development was considered, but the numerical evaluation of the lifting surface concept was restricted to planar configurations. Also, a second order sideslip analysis based on an asymptotic expansion was investigated using the singularity spline formulation
The 'gated-diode' configuration in MOSFET's, a sensitive tool for characterizing hot-carrier degradation
This paper describes a new measurement technique, the forward gated-diode current characterized at low drain voltages to be applied in MOSFET's for investigating hot-carrier stress-induced defects at high spatial resolution. The generation/recombination current in the drain-to-substrate diode as a function of gate voltage, combined with two-dimensional numerical simulation, provides a sensitive tool for detecting the spatial distribution and density of interface defects. In the case of strong accumulation, additional information is obtained from interband tunneling processes occurring via interface defects. The various mechanisms for generating interface defects and fixed charges at variable stress conditions are discussed, showing that information complementary to that available from other methods is obtaine
Properties of large nearly perfect crystals at very low temperatures
A liquid helium cryostat of a size and construction unavailable commercially, was built for use in measuring the Q of several materials at milli-Kelvin temperatures. The design and testing of the cryostat is described as well as the design of the experiment vacuum chamber and adaptor for the dilution refrigerator insert. Theory, design, and testing are also discussed for the magnetic coils built to levitate the materials so as to isolate them and increase the measured Q. A four point suspension with capacitor end plates as the transducer was used to obtain preliminary Q measurements of 6061 aluminum alloy and single crystal silicon. Results are tabulated
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