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311.
I M Shirobokova N S Pechurkin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(7):1737-1741
A mathematical model was used to investigate the effect of cannibalism intensity on the net primary production and the dynamics of trophic links in an aquatic ecosystem characterized by cannibalism at the upper trophic level. A mathematical model of an aquatic ecosystem has been constructed, with the following principal trophic links: limiting nutrient concentration, producers (phytoplankton), nonpredatory and predatory zooplankton. The model takes into account the age structure of the predator and includes two age groups (the young and adults). The adult predators are cannibals feeding on both nonpredatory zooplankton and their own young, which consume phytoplankton. It has been found that when cannibalism intensity increases above a certain level, the concentrations of both adults and the young of the predators decrease. At the same time, the concentrations of the nonpredatory zooplankton and of nutrients increase, while the biomass of producers decreases. When the cannibalism intensity is low, the net primary production of the system increases to a certain level correlated with the increase in cannibalism intensity and drops sharply when the level of consumption of young is high. There is an optimal intensity of cannibalism, at which the productivity in the photosynthesis link is maximal. 相似文献
312.
Basic design guidelines are presented for a three-phase tubular linear alternator (LA). A numerical example for the design of a 25 kVA, 14.4 mls, 120/220 V, 60 Hz alternator is used to illustrate the procedure. 相似文献
313.
I I Gitelson A A Tikhomirov O V Parshina S A Ushakova G S Kalacheva 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(7):1781-1786
The effect of elevated temperatures of 35 and 45 degrees C (at the intensities of photosynthetically active radiation 322, 690 and 1104 micromoles m-2 s-1) on the photosynthesis, respiration, and qualitative and quantitative composition of the volatiles emitted by wheat (Triticum aestuvi L., cultivar 232) crops was investigated in growth chambers. Identification and quantification of more than 20 volatile compounds (terpenoids--alpha-pinene, delta 3 carene, limonene, benzene, alpha- and trans-caryophyllene, alpha- and gamma-terpinene, their derivatives, aromatic hydrocarbons, etc.) were conducted by gas chromatograph/mass spectrometry. Under light intensity of 1104 micromoles m-2 s-1 heat resistance of photosynthesis and respiration increased at 35 degrees C and decreased at 45 degrees C. The action of elevated temperatures brought about variations in the rate and direction of the synthesis of volatile metabolites. The emission of volatile compounds was the greatest under a reduced irradiation of 322 micromoles m-2 s-1 and the smallest under 1104 micromoles m-2 s-1 at 35 degrees C. During the repair period, the contents and proportions of volatile compounds were different from their initial values, too. The degree of disruption and the following recovery of the functional state depended on the light intensity during the exposure to elevated temperatures. The investigation of the atmosphere of the growth chamber without plants has revealed the substances that were definitely technogenic in origin: tetramethylurea, dimethylsulfide, dibutylsulfide, dibutylphthalate, and a number of components of furan and silane nature. 相似文献
314.
G. V. Kasatkin 《Cosmic Research》2005,43(6):395-403
The problem of studying a ring in the gravitational field of a center arose after the discovery of Saturn's rings by Galileo and subsequent discovery of the rings of other planets of the Solar System. Modern theoretical investigations of the existence and stability of planetary rings are mostly related to studies of plane differentially rotating discs [1]. As opposed to this line of research, this paper follows the approach established in classical works [2–4]. 相似文献
315.
V. A. Sadovnichiy A. M. Amelyushkin V. Angelopoulos V. V. Bengin V. V. Bogomolov G. K. Garipov E. S. Gorbovskoy B. Grossan P. A. Klimov B. A. Khrenov J. Lee V. M. Lipunov G. W. Na M. I. Panasyuk I. H. Park V. L. Petrov C. T. Russell S. I. Svertilov E. A. Sigaeva G. F. Smoot Yu. Shprits N. N. Vedenkin I. V. Yashin 《Cosmic Research》2013,51(6):427-433
At present, the Institute of Nuclear Physics of Moscow State University, in cooperation with other organizations, is preparing space experiments onboard the Lomonosov satellite. The main goal of this mission is to study extreme astrophysical phenomena such as cosmic gamma-ray bursts and ultra-high-energy cosmic rays. These phenomena are associated with the processes occurring in the early universe in very distant astrophysical objects, therefore, they can provide information on the first stages of the evolution of the universe. This paper considers the main characteristics of the scientific equipment aboard the Lomonosov satellite. 相似文献
316.
317.
A. I. Efimov L. A. Lukanina V. K. Rudash L. N. Samoznaev I. V. Chashei M. K. Bird M. Pätzold 《Cosmic Research》2013,51(1):13-22
We have performed spectral processing of the data of experiments on radio sounding of circumsolar plasma by coherent S- and X-band signals from the spacecraft Ulysses, Mars Express, Rosetta, and Venus Express carried out from 1991 to 2009. The experiments were realized in the mode of coherent response, when a signal stabilized by the hydrogen standard is transmitted from the ground station to a spacecraft, received by the onboard systems, and retransmitted to the Earth with conserved coherence. Thus, the signal sounding the coronal plasma passes twice through the medium: on the propagation path ground station — spacecraft and on the same path in the opposite direction. The spectra of frequency fluctuations in both the bands are obtained and, using them, the radial dependences of fluctuation intensities are found, which can be approximated by a power law. It is shown that the ratio of intensities of frequency fluctuations in the S- and X-bands is comparable with the theoretical value and characterizes the degree of correlation of irregularities of the electron density along the propagation path ground station — spacecraft and back. Analysis of the correlation of frequency fluctuations on the two paths allows one to get a lower estimate of the outer scale of the circumsolar plasma turbulence. For heliocentric distances R = 10 solar radii (R S ) the outer scale is larger than 0.25R S . 相似文献
318.
Dynamics of a satellite-stabilizer system is studied. It is supposed that there is a viscous friction in a hinge connecting
two bodies, but there is no elasticity. The attitude motion in a plane of circular orbit is considered, and parameters are
determined, at which natural oscillations near a stable equilibrium position in the orbital coordinate system are damped out
most rapidly. The rate of transient processes is estimated by a value of the degree of stability of linearized equations of
motion. The optimization of the degree of stability is sequentially performed in dimensionless damping coefficient (the first
stage) and in inertial system parameters (the second stage). The result of the first stage is the partition of system parameter
space into the regions, in each of which the maximum of the degree of stability is reached on a particular configuration of
roots of the characteristic equation. It is shown at the second stage that the global maximum is reached at two points of
parameter space, where one of system bodies degenerates into a plate, and the characteristic equation has four equal real
roots. 相似文献
319.
A review is given of the present state of the problem of upper atmospheric emission, in relation to the processes which take
place in that region.
Translated by the Express Translation Service, Wimbledon, London, W-2. 相似文献
320.
We investigate the behavior of mean values of the solar wind’s and interplanetary magnetic field’s (IMF) parameters and their
absolute and relative variations during the magnetic storms generated by various types of the solar wind. In this paper, which
is a continuation of paper [1], we, on the basis of the OMNI data archive for the period of 1976–2000, have analyzed 798 geomagnetic
storms with D
st
≤ −50 nT and their interplanetary sources: corotating interaction regions CIR, compression regions Sheath before the interplanetary
CMEs; magnetic clouds MC; “Pistons” Ejecta, and an uncertain type of a source. For the analysis the double superposed epoch
analysis method was used, in which the instants of the magnetic storm onset and the minimum of the D
st
index were taken as reference times. It is shown that the set of interplanetary sources of magnetic storms can be sub-divided
into two basic groups according to their slowly and fast varying characteristics: (1) ICME (MC and Ejecta) and (2) CIR and
Sheath. The mean values, the absolute and relative variations in MC and Ejecta for all parameters appeared to be either mean
or lower than the mean value (the mean values of the electric field E
y
and of the B
z
component of IMF are higher in absolute value), while in CIR and Sheath they are higher than the mean value. High values
of the relative density variation sN/〈N〉 are observed in MC. At the same time, the high values for relative variations of the velocity, B
z
component, and IMF magnitude are observed in Sheath and CIR. No noticeable distinctions in the relationships between considered
parameters for moderate and strong magnetic storms were observed. 相似文献