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131.
Ice cores contain an abundance of information about the Earth''s climate in the past,and recovered from shallow drilling down to 300--350 m give sufficient information for reconstructing of the last climatic chan- ges and for monitoring of pollution from human being. Cable-suspended core auger drills use an armored cable with a winch to provide power to the down-hole motor system and to retrieve the down-hole unit. Because of their lightweight,convenient transportation and installation,high penetration rates and low power consumption, core auger drills are widely used for shallow drilling in ice. Nowadays at least 14 types of auger electromechani- cal drills were designed and tested in different foreign and national glaciological laboratories. However,auger options were usually determined by experience,and the main parameters (helix angle of the fights and rotational speed) are varied in a wide range from drill to drill. If parameters of auger are not chosen properly,poorly en- gineered drills had troubles with low efficiency of cuttings transportation,jam of ice cuttings,repeated fragmen- tation,cutters icing and stop penetration,abnormal power consumption,high rotation torques,and so on. Thus,this paper presents the method of optimization of ice cuttings transportation of cable-suspended core auger drill on the base of the theory of rotary auger. As the result,the optimal helix angle was determined correspond- ing to the rotational speed from the transportation efficiency point of view. 相似文献
132.
ANN application for prediction of atmospheric nitrogen deposition to aquatic ecosystems 总被引:1,自引:0,他引:1
The occurrences of increased atmospheric nitrogen deposition (ADN) in Southeast Asia during smoke haze episodes have undesired consequences on receiving aquatic ecosystems. A successful prediction of episodic ADN will allow a quantitative understanding of its possible impacts. In this study, an artificial neural network (ANN) model is used to estimate atmospheric deposition of total nitrogen (TN) and organic nitrogen (ON) concentrations to coastal aquatic ecosystems. The selected model input variables were nitrogen species from atmospheric deposition, Total Suspended Particulates, Pollutant Standards Index and meteorological parameters. ANN models predictions were also compared with multiple linear regression model having the same inputs and output. ANN model performance was found relatively more accurate in its predictions and adequate even for high-concentration events with acceptable minimum error. The developed ANN model can be used as a forecasting tool to complement the current TN and ON analysis within the atmospheric deposition-monitoring program in the region. 相似文献
133.
Relation between two common localisation methods for the EnKF 总被引:3,自引:0,他引:3
This study investigates the relation between two common localisation methods in ensemble Kalman filter (EnKF) systems: covariance
localisation and local analysis. Both methods are popular in large-scale applications with the EnKF. The case of local observations
with non-correlated errors is considered. Both methods are formulated in terms of tapering of ensemble anomalies, which provides
a framework for their comparison. Based on analytical considerations and experimental evidence, we conclude that in practice
the two methods should yield very similar results, so that the choice between them should be based on other criteria, such
as numerical effectiveness and scalability. 相似文献
134.
G. G. Matishov D. G. Matishov I. S. Usyagina N. E. Kasatkina E. V. Pavel’skaya 《Doklady Earth Sciences》2011,439(2):1190-1195
The annual balance of radionuclides inflow/outflow was assessed for 137Cs and 90Sr isotopes in the Barents Sea, taking into account the atmospheric precipitation, inflow from the Norwegian and the White
seas, as well as riverine discharge, liquid radioactive waste disposal (LRWD), and outflow to the adjacent seas. The original
and published data for the period of 1950–2009 were analyzed. According to the multiyear dynamics (1960–2009), the inflow
of 137Cs and 90Sr into the Barents Sea was significantly preconditioned by the Norwegian Sea currents; and precipitation played a major role
in the 1950s, 1960s, and in 1986. Currently, the trans-border redeposition of 90Sr prevails over 137Cs redeposition in the Barents Sea, and constitutes about 99% of inflow of each element. 相似文献
135.
We suggest a two-step mechanism for the generation of the parallel electric field at the Alfvén wave. At the first step, the coupling with the compressional mode due to the magnetic field non-uniformity and finite plasma pressure provides the parallel magnetic field of Alfvén wave. At the second step, the compressional mode acquires the parallel electric field due to coupling with the electrostatic mode as required by the quasi-neutrality condition in kinetics. The parallel electric field acquired by the Alfvén mode is considerably larger than that due to the single-step coupling between the Alfvén and electrostatic modes in kinetics. 相似文献
136.
Regina Rudawska Joe Zender Peter Jenniskens Jeremie Vaubaillon Pavel Koten Anastasios Margonis Juraj Tóth Jonathan McAuliffe Detlef Koschny 《Earth, Moon, and Planets》2014,112(1-4):45-57
Some past October Draconid shower meteoroids fell apart in a spray of fragments at the end of their trajectory before slowing down, from which it was concluded that these were among the most fragile meteoroids known. In those instances, the dust could not be reliably traced to a particular return of the parent comet 21P/Giaconini-Zinner. On October 8th, 2011, Earth was predicted to transverse the 1900 A.D. dust ejecta of the comet. In 1900, the comet’s perihelion distance first moved significantly inwards to the Sun and ejection conditions could have been unusual. An airborne observing campaign was organized, with several teams contributing imaging and spectrographic cameras to study the manner in which these meteoroids released the volatile element sodium during the ablation process in the Earth’s atmosphere. IMCCE, ESA, and the SETI Institute contributed spectrographic cameras based on low-light WATEC 902H2 Ultimate, low-light LCC1, and GenII XX1332 image intensified cameras. An outburst was observed, much as predicted. Despite a lack of bright meteors, a total of 15 Draconid spectra were recorded. All show evidence of an early release of sodium. The loss of sodium was observed to coincide with the formation of a distinct wake of fragments. The observations show that 21P/Giacobini-Zinner ejected fragile meteoroids during the return in 1900. Those grains may have lost some sodium even before impacting Earth. 相似文献
137.
Pavel Voráček 《Astrophysics and Space Science》1989,155(2):331-333
A reply is given to the critique that the introduction of the cosmic potential and gravitational force into the general relativity is, at least, redundant, if not wrong. The introduction is both motivated and necessary, in order to make Mach's principle and the general relativity compatible. 相似文献
138.
We study the merging of star clusters out of cluster aggregates similar to Knot S in the Antennae on orbits close to the one
of ω Cen by carrying out high resolution numerical N-body simulations. We want to constrain the parameter space which is able
to produce merger objects with similar properties as ω Cen.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
139.
Pavel Mayer Marek Wolf P. G. Niarchos K. D. Gazeas V. N. Manimanis Drahomír Chochol 《Astrophysics and Space Science》2006,304(1-4):39-41
New precise times of minimum light for several early-type eclipsing binaries were obtained at three observatories. The changes of period of the following measured binaries are discussed: V1182 Aql, LY Aur, SZ Cam, FZ CMa, QZ Car, LZ Cen, V606 Cen, AH Cep and TU~Mus. 相似文献
140.