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1.
FOREST C.GARNER MARTIN A.STAPANIAN KIRK E.FITZGERALD Lockheed Engineering Sciences Co. E.Flamingo R Las Vegas NV U.S.A. 《地理学报(英文版)》1991,(3)
Multivariate outliers in environmental data sets are often caused by atypical measurement error in a singlevariable.From a quality assurance perspective it is important to identify these variables efficiently so thatcorrective actions may be performed.We demonstrate a procedure for using two multivariate tests toidentify which variable‘caused’each outlier.The procedure is tested with simulated data sets that havethe same correlation structure as selected water chemistry variables from a survey of lakes in the WesternUnited States.The success rates are evaluated for three of the variables for sample sizes of 50 and 100,significance levels of 0.01 and 0.05 and various amounts of mean shift.The procedure works best forhighly correlated variables. 相似文献
2.
Three series of 111.88 MHz observations of giant pulses of PSR B0531+21 have been carried out in 2005 and 2007. The scattering of pulses observed in various series varies by a factor of 1.7: 10.6±0.5 ms in November 2005, 18±1 ms in January 2007, and 16±0.8 ms in June 2007. The cumulative probability distribution for the peak intensities of the giant pulses for each of these series shows that the distribution is stable and is a power law with a single slope (n = 2.3). This testifies to stability of the mechanism generating the giant pulses. The distribution functions for the 2005 and 2007 data can be superposed after correcting the intensities with a coefficient equal to the ratio of the effective pulse widths. Consequently, in the range of 23MHz-9GHz the energy in the pulses is conserved; i.e., the increase in the pulse intensity is proportional to the decrease in the scattering. Refractive scintillations at low frequencies in measurements with large time separation lead to variations in the number of giant pulses exceeding a given amplitude, proportional to the ratio of the mean flux densities of the pulsar in the corresponding observational series. The maximum energy of the recorded giant pulses is 2.5 × 107 Jy µs. A comparison with the statistical properties of the giant pulses observed at other frequencies shows that the frequency dependence of the maximum energy of the giant pulses in the range of 23 MHz-9GHz is a power-law with index 2.2±0.2. The degree of linear polarization of the giant pulses at 112 MHz does not exceed 12%. 相似文献
3.
We report the results of new observations of three anomalous X-ray pulsars: 1E 2259+586, 4U 0142+61, and XTE J1810-197. The
observations were carried out on high-sensitivity radio telescopes of the Pushchino Radio Astronomy Observatory: the Large
Phased Array at 111MHz and the DKR-1000 at 62 MHz. New, digital, multi-channel receivers designed for pulsar observations
were used. Pulse profiles and dynamical spectra for the three pulsars are presented. The mean flux density for XTE J1810-197
is estimated to be ∼160 mJy at 62 MHz. An estimated spectral index for this pulsar is also presented. 相似文献
4.
A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan (天山). The sample site temperature of -9.6 ℃ indicates that the unique glaciochemical re-cord was well preserved and suitable for the reconstruction of air pollution levels in this previously un-explored region. Samples were analyzed for major ions (Na+, K+, Ca2+, Mg2+, NH4+, Cl-, SO42-, NO3-, HCOO-, and CH3COO-). NO3- and SO42- were characterized by significant high levels of pollution con-centration. Most air masses ... 相似文献
5.
A. D. Kuz’min B. Ya. Losovskii S. V. Logvinenko I. I. Litvinov 《Astronomy Reports》2008,52(11):910-916
Our measurements of the arrival-time delays of radio pulses from the Crab pulsar, PSR B0531+21, at low frequencies 111, 63, and 44 MHz revealed additional delays compared to the usual quadratic frequency relation, Δt(v) ∝ v ?2. These additional delays are 65 ms between 63 MHz and 111 MHz—i.e., a factor of two longer than the pulsar’s period, i.e., a factor of five longer than the pulsar period—and cannot be explained by the “twisting” of the magnetic-field lines by the rotation of the pulsar. We suggest the model in which a previously unknown high-density plasma layer with a high electron concentration is present along the line of sight in the Crab nebula, causing an additional frequency-dependent delay of the observed radio pulses at low frequencies due to the contribution of the n e 2 v ?4 term in the dispersion-delay formula. The parameters of this inferred layer have been derived: emission measure EM ? 4 × 106 pc/cm6, electron density n e ? 106 cm?3, depth along the line of sight d ? 4 × 10?6 pc, and electron temperature T e ≥ 2 × 106 K. 相似文献
6.
An analysis of monitoring observations for the pulsar PSR B0655+64, which is located in a binary system, at 111 MHz during 2002–2015 are presented. The Keplerian parameters of the pulsar have been refived: the longitude of periastron ω = 276.°5785 ± 0.°0005 and the orbital semi-major axis is ap sin i = 4.124976± 0.000003 s. The parameters of the perturbed motion have been determined: the motion of periastron ω = 0.°315 ± 0.°005/ year, and the derivative of the period of the binary system ? = (-1.66 ± 0.11) × 10-14 s/s = (-0.524 ± 0.038) µs/year. The estimated time scale for the decay of the PSR 0655+64 system is (1.7 ± 0.1) × 1011 yrs. 相似文献
7.
A. D. Kuz’min Ya. N. Istomin B. Ya. Losovskiȝ S. V. Logvinenko D. V. Dumskiȝ 《Astronomy Reports》2010,54(5):433-436
The frequency dependence of scattering of the radio emission from the Crab pulsar at the low frequencies 111, 63, and 44 MHz
has been measured and analyzed during sporadic enhancements of scattering and dispersion measure in October–December 2006
and December 2008. The frequency dependence of the scattering differs from the generally accepted dependence, τ
sc
(ν) ∝ ν
γ
, where γ = −4.0 for Gaussian and γ = −4.4 for power-law Kolmogorov distributions of inhomogeneities of the scattering medium. In intervals of enhancement, the
exponent of the frequency dependence γ decreased to −3.2(0.2) at the above frequencies. A model is proposed in which this is due to the presence of a dense plasma
structure in the nebula in the line of sight toward the pulsar, in which scattering of the radio emission on turbulence differs
from scattering in the interstellar medium. It is shown that the frequency dependence of scattering of the radio emission
can be weaker in a dense plasma than in the rarefied interstellar medium. 相似文献
8.
S. V. Logvinenko A. P. Venger G. N. Il’in V. K. Dubrovich A. S. Morozov 《Astrophysical Bulletin》2008,63(2):193-200
The spectral measuring facility with a new Fourier analyzer for use with the radio telescope RATAN-600 is described and its experimental data are reported. 相似文献
9.
A. D. Kuz’min Yu. A. Belyatsky D. V. Dumsky V. A. Izvekova K. A. Lapaev S. V. Logvinenko B. Ya. Losovsky V. D. Pugachev 《Astronomy Reports》2011,55(5):416-424
Results of long-term (2002–2010) monitoring of giant radio pulses of the pulsar PSR B0531+21 in the Crab Nebula at ν = 44, 63, and 111 MHz are reported. The observations were conducted on the LPA and DKR-1000 radio telescopes of the Lebedev
Physical Institute. The giant pulses were analyzed using specialized software for calculating the magnitude of the scattering
τ
sc
, signal-to-noise ratio, and other required parameters by modeling the propagation of a pulse in the scattering interstellar
medium. Three pronounced sharp increases in the scattering were recorded in 2002–2010. Analysis of the dependence between
the variations of the scattering and dispersion measure (data of Jodrell Bank Observatory) shows a strong correlation at all
frequencies, ≈0.9. During periods of anomalous increase in scattering and the dispersion measure, the index γ in the frequency dependence of the scattering in the Crab Nebula, τ
sc
(ν) ∝ ν
−γ
, was smaller than the generally accepted values γ = 4.0 for a Gaussian and γ = 4.4 for a Kolmogorov distribution. This difference in combination with the piece-wise power-law spectrum may be due to
the presence of a dense plasma structure with developed Langmuir turbulence in the nebula, along the pulsar’s line of sight.
The magnetic field in the Crab Nebula estimated from measurements of the rotation measure toward the pulsar is 100 μG. 相似文献
10.
Samodurov V. A. Tyul’bashev S. A. Toropov M. O. Logvinenko S. V. 《Astronomy Reports》2022,66(4):341-347
Astronomy Reports - A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data... 相似文献