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1.
Application of X-ray computed tomography for analyzing cleat spacing and cleat aperture in coal samples 总被引：2，自引：2，他引：2
S. Mazumder K.-H.A.A. Wolf K. Elewaut R. Ephraim 《International Journal of Coal Geology》2006,68(3-4):205-222
New techniques to determine distributions of cleat aperture, cleat orientation and cleat spacing from CT scans have been developed. For cleat orientation and spacing distributions, two different coal blocks were scanned. The CT scans have been analyzed for the three orthogonal directions. Histograms of the cleat orientations are bimodal, expressing the typical cleat texture of face and butt cleats and bedding perpendicular relaxation fractures. Deviations up to 20° from the peak values in the cleat orientation distributions were used as input for automated image analysis of cleat spacing. Distributions of the cleat spacing measurements are related to the face and butt cleat directions. The term “relevant cleat length” is introduced as a measure to extract the amount of cleat length involved with the cleat spacing measurements. The ratio ranges from 0.03 to 0.38 and expresses the difference in cleat texture in both samples. Cleat spacing versus relevant cleat length shows sample specific patterns for face cleat, butt cleat and bedding. To describe cleat aperture quantitatively, peak height and missing attenuation have been used. The image of a cleat was seen as a convolution of a rectangular fracture profile with a Gaussian point spread function. 相似文献
2.
Jere H. Jenkins Ephraim Fischbach John B. Buncher John T. Gruenwald Dennis E. Krause Joshua J. Mattes 《Astroparticle Physics》2009,32(1):42-46
Unexplained periodic fluctuations in the decay rates of 32Si and 226Ra have been reported by groups at Brookhaven National Laboratory (32Si), and at the Physikalisch–Technische–Bundesanstalt in Germany (226Ra). We show from an analysis of the raw data in these experiments that the observed fluctuations are strongly correlated in time, not only with each other, but also with the time of year. We discuss both the possibility that these correlations arise from seasonal influences on the detection system, as well as the suggestion of an annual modulation of the decay rates themselves which vary with Earth–Sun distance. 相似文献
3.
Recent analyses of nuclear decay data show evidence of variations suggestive of a solar influence. Analyses of datasets acquired at the Brookhaven National Laboratory (BNL) and at the Physikalisch-Technische Bundesanstalt (PTB) both show evidence of an annual periodicity and of periodicities with sidereal frequencies in the neighborhood of 12.25 year?1 (at a significance level that we have estimated to be 10?17). It is notable that this implied rotation rate is lower than that attributed to the solar radiative zone, suggestive of a slowly rotating solar core. This leads us to hypothesize that there may be an ??inner tachocline?? separating the core from the radiative zone, analogous to the ??outer tachocline?? that separates the radiative zone from the convection zone. The Rieger periodicity (which has a period of about 154 days, corresponding to a frequency of 2.37 year?1) may be attributed to an r-mode oscillation with spherical-harmonic indices l=3,m=1, located in the outer tachocline. This suggests that we may test the hypothesis of a solar influence on nuclear decay rates by searching BNL and PTB data for evidence of a ??Rieger-like?? r-mode oscillation, with l=3,m=1, in the inner tachocline. The appropriate search band for such an oscillation is estimated to be 2.00??C?2.28 year?1. We find, in both datasets, strong evidence of a periodicity at 2.11 year?1. We estimate that the probability of obtaining these results by chance is 10?12. 相似文献
4.
D. Javorsek II M. C. Brewer J. B. Buncher E. Fischbach J. T. Gruenwald J. Heim A. W. Hoft T. J. Horan J. L. Kerford M. Kohler J. J. Lau A. Longman J. J. Mattes T. Mohsinally J. R. Newport M. A. Petrelli C. A. Stewart J. H. Jenkins R. H. Lee B. Morreale D. B. Morris R. Mudry D. O’Keefe B. Terry M. A. Silver P. A. Sturrock 《Astrophysics and Space Science》2012,338(1):9-13
A new prediction technique based on logarithmic values is proposed to predict the maximum amplitude (R
m) of a solar cycle from the preceding minimum aa geomagnetic index (aa
min). The correlation between lnR
m and lnaa
min (r=0.92) is slightly stronger than that between R
m and aa
min (r=0.90). From this method, cycle 24 is predicted to have a peak size of R
m(24)=81.7(1±13.2%). If the suggested error in aa (3 nT) before 1957 is corrected, the correlation coefficient between R
m and aa
min (r=0.94) will be slightly higher, and the peak of cycle 24 is predicted much lower, R
m(24)=52.5±13.1. Therefore, the prediction of R
m based on the relationship between R
m and aa
min depends greatly on the accurate measurement of aa. 相似文献
5.
E. Fischbach K. J. Chen R. E. Gold J. O. Goldsten D. J. Lawrence R. J. McNutt E. A. Rhodes J. H. Jenkins J. Longuski 《Astrophysics and Space Science》2012,337(1):39-45
We have analyzed 137Cs decay data, obtained from a small sample onboard the MESSENGER spacecraft en route to Mercury, with the aim of setting
limits on a possible correlation between nuclear decay rates and solar activity. Such a correlation has been suggested recently
on the basis of data from 54Mn decay during the solar flare of 13 December 2006, and by indications of an annual and other periodic variations in the
decay rates of 32Si, 36Cl, and 226Ra. Data from five measurements of the 137Cs count rate over a period of approximately 5.4 years have been fit to a formula which accounts for the usual exponential
decrease in count rate over time, along with the addition of a theoretical solar contribution varying with MESSENGER-Sun separation.
The indication of solar influence is then characterized by a non-zero value of the calculated parameter ξ, and we find ξ=(2.8±8.1)×10−3 for 137Cs. A simulation of the increased data that can hypothetically be expected following Mercury orbit insertion on 18 March 2011
suggests that the anticipated improvement in the determination of ξ could reveal a non-zero value of ξ if present at a level consistent with other data. 相似文献
6.
Recently, correlations have been reported between fluctuations in nuclear decay rates and Earth–Sun distance, which suggest that nuclear decay rates may be affected by solar activity. In this paper, we report the detection of a significant decrease in the decay of 54Mn during the solar flare of 2006 December 13, whose X-rays were first recorded at 02:37 UT (21:37 EST on 2006 December 12). Our detector was a 1 μCi sample of 54Mn, whose decay rate exhibited a dip coincident in time with spikes in both the X-ray and subsequent charged particle fluxes recorded by the Geostationary Operational Environmental Satellites (GOES). A secondary peak in the X-ray and proton fluxes on December 17 at 12:40 EST was also accompanied by a coincident dip in the 54Mn decay rate. These observations support the claim by Jenkins et al. that nuclear decay rates may vary with Earth–Sun distance. 相似文献
7.
8.
P. A. Sturrock J. B. Buncher E. Fischbach J. T. Gruenwald D. JavorsekII J. H. Jenkins R. H. Lee J. J. Mattes J. R. Newport 《Solar physics》2010,267(2):251-265
Evidence for an anomalous annual periodicity in certain nuclear-decay data has led to speculation on a possible solar influence
on nuclear processes. We have recently analyzed data concerning the decay rates of 36Cl and 32Si, acquired at the Brookhaven National Laboratory (BNL), to search for evidence that might be indicative of a process involving
solar rotation. Smoothing of the power spectrum by weighted-running-mean analysis leads to a significant peak at frequency
11.18 year−1, which is lower than the equatorial synodic rotation rates of the convection and radiative zones. This article concerns measurements
of the decay rates of 226Ra acquired at the Physikalisch-Technische Bundesanstalt (PTB) in Germany. We find that a similar (but not identical) analysis
yields a significant peak in the PTB dataset at frequency 11.21 year−1, and a peak in the BNL dataset at 11.25 year−1. The change in the BNL result is not significant, since the uncertainties in the BNL and PTB analyses are estimated to be
0.13 year−1 and 0.07 year−1, respectively. Combining the two running means by forming the joint power statistic leads to a highly significant peak at
frequency 11.23 year−1. We will briefly comment on the possible implications of these results for solar physics and for particle physics. 相似文献
9.
10.
An experiment carried out at the Brookhaven National Laboratory over a period of almost 8 years acquired 364 measurements of the beta-decay rates of a sample of \({}^{32}\mbox{Si}\) and, for comparison, of a sample of \({}^{36}\mbox{Cl}\). The experimenters reported finding “small periodic annual deviations of the data points from an exponential decay?…?of uncertain origin”. We find that power-spectrum and spectrogram analyses of these datasets show evidence not only of the annual oscillations, but also of transient oscillations with frequencies near 11 year?1 and 12.5 year?1. Similar analyses of 358 measurements of the solar neutrino flux acquired by the Super-Kamiokande neutrino observatory over a period of about 5 years yield evidence of an oscillation near 12.5 year?1 and another near 9.5 year?1. An oscillation near 12.5 year?1 is compatible with the influence of rotation of the radiative zone. We suggest that an oscillation near 9.5 year?1 may be indicative of rotation of the solar core, and that an oscillation near 11 year?1 may have its origin in a tachocline between the core and the radiative zone. Modulation of the solar neutrino flux may be attributed to an influence of the Sun’s internal magnetic field by the Resonant Spin Flavor Precession (RSFP) mechanism, suggesting that neutrinos and neutrino-induced beta decays can provide information about the deep solar interior. 相似文献