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971.
972.
G. Thuillier G. Schmidtke C. Erhardt B. Nikutowski A. I. Shapiro C. Bolduc J. Lean N. Krivova P. Charbonneau G. Cessateur M. Haberreiter S. Melo V. Delouille B. Mampaey K. L. Yeo W. Schmutz 《Solar physics》2014,289(12):4433-4452
Onboard the International Space Station (ISS), two instruments are observing the solar spectral irradiance (SSI) at wavelengths from 16 to 2900 nm. Although the ISS platform orientation generally precludes pointing at the Sun more than 10?–?14 days per month, in November/December 2012 a continuous period of measurements was obtained by implementing an ISS ‘bridging’ maneuver. This enabled observations to be made of the solar spectral irradiance (SSI) during a complete solar rotation. We present these measurements, which quantify the impact of active regions on SSI, and compare them with data simultaneously gathered from other platforms, and with models of spectral irradiance variability. Our analysis demonstrates that the instruments onboard the ISS have the capability to measure SSI variations consistent with other instruments in space. A comparison among all available SSI measurements during November–December 2012 in absolute units with reconstructions using solar proxies and observed solar activity features is presented and discussed in terms of accuracy. 相似文献
973.
H. J. Peng Q. Gao Z. G. Wu W. X. Zhong 《Celestial Mechanics and Dynamical Astronomy》2011,110(4):319-342
In this paper, from a Hamiltonian point of view, the nonlinear optimal control problems are transformed into nonlinear two-point
boundary value problems, and a symplectic adaptive algorithm based on the dual variational principle is proposed for solving
the nonlinear two-point boundary value problem. The state and the costate variables within a time interval are approximated
by using the Lagrange polynomial and the costate variables at two ends of the time interval are taken as independent variables.
Then, based on the dual variational principle, the nonlinear two-point boundary value problems are replaced by a system of
nonlinear equations which can preserve the symplectic structure of the nonlinear optimal control problem. Furthermore, the
computational efficiency of the proposed symplectic algorithm is improved by using the adaptive multi-level iteration idea.
The performance of the proposed algorithm is tested by the problems of Astrodynamics, such as the optimal orbital rendezvous
problem and the optimal orbit transfer between halo orbits. 相似文献
974.
Machine-learning algorithms are applied to explore the relation between significant flares and their associated CMEs. The
NGDC flares catalogue and the SOHO/LASCO CME catalogue are processed to associate X and M-class flares with CMEs based on
timing information. Automated systems are created to process and associate years of flare and CME data, which are later arranged
in numerical-training vectors and fed to machine-learning algorithms to extract the embedded knowledge and provide learning
rules that can be used for the automated prediction of CMEs. Properties representing the intensity, flare duration, and duration
of decline and duration of growth are extracted from all the associated (A) and not-associated (NA) flares and converted to
a numerical format that is suitable for machine-learning use. The machine-learning algorithms Cascade Correlation Neural Networks
(CCNN) and Support Vector Machines (SVM) are used and compared in our work. The machine-learning systems predict, from the
input of a flare’s properties, if the flare is likely to initiate a CME. Intensive experiments using Jack-knife techniques
are carried out and the relationships between flare properties and CMEs are investigated using the results. The predictive
performance of SVM and CCNN is analysed and recommendations for enhancing the performance are provided. 相似文献
975.
976.
The loss rate of fast electrons (with an energy much higher than the energy of the plasma electron thermal motion), when they
leave a magnetic cavern during a disturbance of the magnetic field azimuthal symmetry, is studied. The cases of point and
volume sources of fast particles have been considered. The plasma density in the cavern is supposed to be low, so that collisions
of fast electrons with plasma particles can be neglected. The effect of the electric field on particle motion is neglected
because it is assumed that the electric charge particles outgoing from the cavern is compensated by the counter current of
plasma conductivity electrons. The dependence of the loss value on the harmonic number and the amplitude of the cavern boundary
radius disturbance has been obtained. 相似文献
977.
978.
An analysis is made of the oil pollution of the Ob river waters using a long-term (1993–2013) hydrochemical monitoring of oil fields in Khanty-Mansi Autonomous Okrug. Contents of oil hydrocarbons (OHC) were determined in 4277 samples from the main Ob channel, and in 7076 samples from its anabranches by using infrared spectrometry. An increase in MAC (0.05 mg/dm3) was observed in 28% of the samples from the main channel, and in 32% from the anabranches. The total percentage of samples with an extremely high (> 50 MAC) and high (30–50 MAC) pollution level made up 0.3% of the samples for the anabranches, and 0.1% for the main channel. Maximum pollution was revealed in the eastern part of Okrug, from its eastern boundary to the mouth of the Trom’egan river which is associated with a considerable number of accidents on the pipelines within the Nizhnevartovskii district. The upper and lower quantiles in the most polluted anabranches, Pasl and Bagras, are 0.03–01.7 and 0.032–0.16 mg/dm3, respectively, whereas in the main Ob channel they vary from 0.022 to 0.065 mg/dm3 (0.4–1.2 MAC). The methods of geoinformatics and mathematical statistics were used to assess a dependence of OHC on the number of pollution sources (well clusters, and the area of oil spills) in zones at different distances from the river channels. By calculating the Spearman correlation coefficients, it was shown that OHC contents are dependent mainly on the number of wells, and on the area of oil spills located at less than 2 km from the channels. 相似文献
979.
Philip M. Fearnside 《Climatic change》2000,46(1-2):115-158
Tropical forest conversion, shiftingcultivation and clearing of secondary vegetation makesignificant contributions to global emissions ofgreenhouse gases today, and have the potential forlarge additional emissions in future decades. Globally, an estimated 3.1×109 t of biomasscarbon of these types is exposed to burning annually,of which 1.1×109 t is emitted to the atmospherethrough combustion and 49×106 t is converted tocharcoal (including 26–31×106 t C of blackcarbon). The amount of biomass exposed to burningincludes aboveground remains that failed to burn ordecompose from clearing in previous years, andtherefore exceeds the 1.9×109 t of abovegroundbiomass carbon cleared on average each year. Above-and belowground carbon emitted annually throughdecomposition processes totals 2.1×109 t C. Atotal gross emission (including decomposition ofunburned aboveground biomass and of belowgroundbiomass) of 3.41×109 t C year-1 resultsfrom clearing primary (nonfallow) and secondary(fallow) vegetation in the tropics. Adjustment fortrace gas emissions using IPCC Second AssessmentReport 100-year integration global warming potentialsmakes this equivalent to 3.39×109 t ofCO2-equivalent carbon under a low trace gasscenario and 3.83×109 t under a high trace gasscenario. Of these totals, 1.06×109 t (31%)is the result of biomass burning under the low tracegas scenario and 1.50×109 t (39%) under thehigh trace gas scenario. The net emissions from allclearing of natural vegetation and of secondaryforests (including both biomass and soil fluxes) is2.0×109 t C, equivalent to 2.0–2.4×109 t of CO2-equivalent carbon. Adding emissions of0.4×109 t C from land-use category changesother than deforestation brings the total for land-usechange (not considering uptake of intact forest,recurrent burning of savannas or fires in intactforests) to 2.4×109 t C, equivalent to 2.4–2.9×109 t of CO2-equivalent carbon. The totalnet emission of carbon from the tropical land usesconsidered here (2.4×109 t C year-1)calculated for the 1981–1990 period is 50% higherthan the 1.6×109 t C year-1 value used by the Intergovernmental Panel on Climate Change. The inferred (= `missing') sink in the global carbonbudget is larger than previously thought. However,about half of the additional source suggested here maybe offset by a possible sink in uptake by Amazonianforests. Both alterations indicate that continueddeforestation would produce greater impact on globalcarbon emissions. The total net emission of carboncalculated here indicates a major global warmingimpact from tropical land uses, equivalent toapproximately 29% of the total anthropogenic emissionfrom fossil fuels and land-use change. 相似文献
980.
T. A. Shatilina G. Sh. Tsitsiashvili T. V. Radchenkova 《Russian Meteorology and Hydrology》2010,35(11):740-743
Peculiarities are investigated of the air temperature variation tendencies at some stations of the Far East in 1976–2005.
The estimate of linear trend equation coefficients is computed according to the air temperature observation data using the
least squares method. It is demonstrated that the air temperature trend in northern regions possesses a small probability
at small values of residual variability. In the southern regions, the trend significance increases for almost all seasons
at small values of residual variability. At midlatitude stations, the trend significance in January and February decreases
considerably due to the large values of residual variability. 相似文献