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We show that the mechanism called “near-field effect” [e.g., Petrova, E.V., Tishkovets, V.P., Jockers, K., 2007. Icarus 188, 233-245], which is used to explain wide-phase-angle negative polarization branch observed for planetary regoliths and cometary comas, is not realistic as it contradicts laboratory experiments and results of modeling with discrete dipole approximation calculations. 相似文献
2.
Zubko V. A. Sukhanov A. A. Fedyaev K. S. Koryanov V. V. Belyaev A. A. 《Astronomy Letters》2021,47(3):188-195
Astronomy Letters - We present the results of our analysis of the optimal flight to the trans-Neptunian object (90377) Sedna at the launch in 2029. Sedna is a distant space object with a perihelion... 相似文献
3.
We have developed an autonomous portable digital seismometer for measurements in the field, in engineering constructions,
and in hard-to-reach places. The seismometer is a monoblock including an SM-6 seismic receiver and digital seismic recorder.
The SM-6 seismic receiver is a highly effective device for field work on investigating a microseismic wave field and for use
in systems of seismological monitoring. Field tests of these seismic receivers in comparison with well-known SM-3 devices
were carried out. The basic part of the seismic recorder is an MSC1213Y5 system-on-chip representing a precision 24-bit ADC
coupled with an 8051 compatible microcontroller. Autonomy of the seismometer up to 30 days is provided with data recording
into a flash memory chip of 1 Gbyte capacity. Time synchronization of seismic data is provided with the PPS second mark received
from a GPS receiver. A preproduction model of the portable digital seismometer was manufactured and tested. As a result of
tests, the working capacity of this preproduction model has been confirmed and its basic technical characteristics have been
determined. 相似文献
4.
Eismont N. A. Nazirov R. R. Fedyaev K. S. Zubko V. A. Belyaev A. A. Zasova L. V. Gorinov D. A. Simonov A. V. 《Astronomy Letters》2021,47(5):316-330
Astronomy Letters - We consider the concept of applying gravity assist maneuvers near Venus using resonant orbits with a period equal to the Venusian one. We show that the proposed operations based... 相似文献
5.
The Umov effect manifests itself as an inverse correlation between the linear polarization maximum of an object’s scattered light Pmax and its geometric albedo A. This effect is observed for the Moon, Mercury and Mars, and there are data suggesting this effect is valid for asteroids. The Umov effect is due to the contribution of interparticle multiple scattering that increases albedo and decreases polarization. We here study if the Umov effect can be extended to the case of single irregularly shaped particles with sizes comparable with the wavelength. This, in particular, is important for cometary dust polarimetry. We show the Umov effect being valid for weakly absorbing irregular particles (Im(m) ? 0.02) almost through the entire range of size parameters x considered. Highly absorbing particles (Im(m) > 0.02) follow the Umov effect only if x exceeds 14. In the case of weakly absorbing particles, the inverse correlation is essentially non-linear, which is caused by the contribution of particles with small x. However, averaging over many different types of irregularly shaped particles could make it significantly more linear. The size averaging does not change qualitatively the diagram log(Pmax)-log(A) for weakly absorbing particles. For single irregular particles whose sizes are comparable with wavelength, there is no reliable correlation between the slope of the polarization curve h near the inversion phase angle and geometric albedo A. Using the extended Umov Law, we estimate the geometric albedo of dust particles forming cometary circumnuclear haloes A = 0.1 − 0.2, which is a few times larger than the average geometric albedo over the entire comae. Note that, using the obtained values for A of cometary particles, one can derive their number density in circumnuclear haloes from photometric observations. 相似文献
6.
At small phase angles the light scattered by the Moon reveals a negative polarization branch whose average amplitude is 1%. We present results of polarimetric mappings of the Moon in Pmin at a phase angle near 11°. The observations were carried out with the Kharkov 50-cm telescope at the Maidanak Observatory (Middle Asia) using a polarizing filter. A thorough calibration of the camera array allows for the reliable detection of significant variations of |Pmin| over the lunar surface, from 0.2 to 1.6%, at a wavelength of 0.52 μm. The smallest |Pmin| are characteristic of young bright craters, while the |Pmin| are the highest for the lunar highland and bright mare areas. The horse-shoe shape of the correlation dependence Pmin (albedo) is treated with data of our laboratory measurements of powdered surfaces and computer modeling of light scattering by small particles with the DDA (discrete dipole approximation) technique. 相似文献
7.
The extinction curves of single clouds, seen towards the stars HD 147165, 179406 and 202904, have been modelled using various mixtures containing both the bare and inhomogeneous (composite and/or multilayer) grains. It has been shown that the models composed of the bare graphite and silicate grains together with the multilayer grains containing silicates, organic refractory and water ice, are more useful in explaining extinction under the reduced cosmic abundances. The models based on Mathis' composite grains or on Greenberg & Li's core-mantle grains can also provide quite good fits of the extinction and the measured scattering parameters, but still require an excessive amount of carbon which results in too large a C/O ratio. The inhomogeneous grains essentially contribute to the extinction in practically the whole wavelength range of our extinction curves. As a rule, such grains have quite wide size distributions, centred at around 100 nm, although graphite grains are mainly of small sizes. 相似文献
8.
The existence of condensed carbon in the form of liquid droplets and graphite grains is found in white dwarf atmospheres with parametersg=108 cm s–2, H/He10–3, andT
eff6000 K on the basis of model atmospheres techniques. It is shown that the condensation layers are dynamically stable and, consequently, that white dwarfs cannot supply the condensed particles to the interstellar medium. Possible observable effects are considered. 相似文献
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Requirements for the seismic resistance of nuclear power plants (NPPs) considerably differ from those for of other industrial facilities due to the necessity of protecting not only the NPP itself, but also the environment from radiation hazard. According to special regulations, even if an NPP construction site is located in a region with low seismicity, the NPP design should be based on the maximum design earthquake and peak acceleration typical of the region. Note that seismic warning systems for NPPs differ fundamentally in design and operation principles from conventional seismic monitoring systems. Seismic warning systems are required to reliably detect seismic events threatening the operability of nuclear power plants, to promptly inform operators, and to prevent false alarms and unauthorized access to the system. Atomseismoizyskaniya LLC has developed a seismic warming system (SSZ-1M) and put it into trial operation at the reactor units of the Smolensk NPP in 2014–2015. The system comprises six seismic groups: two groups per each reactor unit. Each group consists of three independent seismic recording channels, the sensors of which are distributed around the reactor unit at a distance of up to 500 m from the latter. Each channel records three components of seismic signals; the acceleration vector is calculated and compared with a preset threshold. Signals exceeding the threshold are fed to a coincidence circuit that generates an alarm if two of the three signals exceed the threshold. This scheme excludes false alarms. The components of the system are characterized by high reliability and stability. The performance of the system channels has been officially certified. The system automatically performs continuous fault diagnosis. The programs responsible for system function and diagnostics are independent; the system units have individual equipment. To exclude the possibility of external impacts, the SSZ-1M warning system has no Internet connection. Special seismic signal simulators were developed to test the operability of the system when deployed. 相似文献
10.
The results of registration of the catastrophic earthquake of March 11, 2011, that occurred near Honshu Island (Japan) with
the broadband bottom seismograph of the Oceanology Institute, Russian Academy of Sciences on a test bed of the Experimental
Design Bureau of Oceanologic Equipment (EDBOE), Russian Academy of Sciences (Moscow) are considered. The specification of
the equipment and conditions of the experiment are presented. The records of the earthquake made in EDBOE and those made with
a seismograph at the University of Portland (Oregon, United States) are compared, since these registration points are located
at identical distances from the epicenter, but the distributions of seismic waves are essentially different. The possible
directions of the development of methods and equipment for forecasting strong sea earthquakes and tsunami are examined. 相似文献
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