Home – Home – Jornals – Thermophysics and Aeromechanics 2008 number 1

The Mayanian (1100-850 Ma) is an all-Siberian stratigraphic subdivision of the Neoproterozoic distinguished on the basis of generalized geological and paleontological data for the Maya Group in the southeast of the Siberian craton and for its counterparts in other structure-facies areas (SFA). The Mayanian deposits in all principally different structures of every SFA, such as intracratonic depressions, pericratonic troughs, and marginal parts of blocks with oceanic crust, were incorporated into the craton in the Vendian. It is separated from the surrounding stratigraphic divisions, Baikalian and Aimchanian, by distinct tectonic boundaries coinciding in time with the formation and starting breakup of the supercontinent Rodinia, i.e., with global events. In the adjacent parts of the platform they were reflected in erosion and considerable gaps in sedimentation. These events are well-expressed where they occurred under intense contraction or, on the contrary, are veiled where extension was predominant.
The boundary between the Kerpylian and Lakhandinian, subdivisions of the Mayanian, is not bearing on important events and is hardly traceable throughout the region. Therefore, the base of the Kerpylian is preferable to be taken as the lower boundary of the Upper Riphean. There are attempts to establish this boundary, as it is made for the Phanerozoic, from paleontological data in compositionally similar deposits. These attempts, however, fail in matching this boundary with the base of the Lakhandinian. Distinctive transitions in communities of microfossils and stromatolites appear to be linked to the Mayanian-Baikalian and, undoubtedly, Middle Riphean-Aimchanian boundaries. In the Lakhandinian, on the contrary, the changes that appeared in the Kerpylian only tend to continue. Some taxa typical of the Lakhandinian appear as early as the Kerpylian. In the Lakhandinian their amount gradually increases upsection, until the top of this division. Thus, it is reasonable to start the Upper Riphean with the lower boundary of the Mayanian.
All the main subdivisions of the Siberian Neoproterozoic - Mayanian, Baikalian, and Vendian - are linked to the most important stages of development of this vast and structurally heterogeneous territory. Each of the above-mentioned stratons can be divided, according to historico-geological and paleontological data, into two or three independent interregional subdivisions. Thus, the stratigraphic scheme of the Neoproterozoic of Siberia seems to be promising for the general scale of this period of the Late Precambrian.

The western half of the Ordos Basin lies in the north of Central China, on the western margin of the North Chinese Platform. In the southwest and south it borders the Qilian and Qinling folded systems. Their frontal northeastern flank is thrust over the Paleozoic nappe of the Ordos Basin and consists of a series of large parallel linear folds separated by thrusts. The basement of the basin is made up of deformed metamorphic rocks of tentatively Late Proterozoic age. Carbonate and terrigenous intracratonic facies accumulated on the Ordos block from Early Cambrian through Middle Ordovician. From Middle Ordovician through Middle Carboniferous, the western edge of the block was uplifted as a land as a result of Caledonian tectonic movement and underwent denudation for about 150 Myr. In the Late Paleozoic, a series of coal-bearing formations was deposited. In the Triassic, the Ordos Basin became filled with fluviolacustrine delta facies. Thrusts and folds on the southwestern margin of the basin formed in the Mesozoic and were intensified by Himalayan tectonic movements.

Results of the activity of Quaternary glaciations in the western Baikal area are considered based on new factual material. Also, the problem of the formation of

Assuming orbital modulation of Pleistocene climate cycles, we have generated a new time scale for the Asian geochemical limnic record in the BDP-96-2 Baikal and the KDP-01 Hovsgol cores and updated the chronologies for the global marine δ¹⁸O and Vostok ice-gas records. The time scales were obtained by orbital tuning with the assumption of arbitrary but time invariable amplitudes and phase lags of the orbital parameters and responses.
The retuned chronologies highlighted the cycles of eccentricity (100 kyr), obliquity (41 kyr), and precession (23 and 19 kyr), but the combined 70- and 30-kyr cycles became less prominent in the continental (Baikal) record though persisted in the global data (Vostok δD). The residual 70- and 30-kyr harmonics more likely result from errors in the untuned chronology for the Baikal record but are rather due to nonlinearity in the climate response.
We investigated the leads and lags of orbital climate signals with a special focus on the 100-kyr cycle. The phases of precession, obliquity, and eccentricity cycles, compared among the records, showed the lead of the continent. The Baikal geochemical signal at the 100-kyr band led the global glacial and greenhouse CH₄ responses and was almost synchronous with the earliest responding polar temperature signal. The reported results characterize the continent as a system highly responsive to eccentricity variations but do not contradict alternative hypotheses for the origin of the 100-kyr cycle in the Earth's climate history.

We examined mercury distribution in soils and plants of the catchment area of Lake Bol'shoe Yarovoe with the Altaikhimprom chemical industrial complex situated on its shore. Data on mercury contents show a considerable mercury flow into the environment, though the industrial complex and its waste do not pose serious threat. The revealed pollution in the immediate vicinity of the industrial complex, including that due to atmospheric transport, as well as the elevated content of mercury in hydrochloric and alkaline extracts suggest its intense migration from the waste. Therefore, it is necessary to make up an inventory of the industrial-complex waste and perform a detailed study of the lake ecosystem as a model unit.

The effect of local stress on the interface response to dynamic loading in faulted crust has been studied through MCA (movable cell automata) simulation. Knowing the strain response of a fault block boundary to test impacts, one can estimate the proximity of the fault to critical stress that allows an unstable slip. The computing results are consistent with data of field experiments in fault fragments (vibration, water injection, explosions). The reported analysis makes the basis for a new approach to estimating stress and strain in active faults.

Electrical resistance measurements, thin-section, chemical, thermal differential, and thermal gravity analyses have been applied to study samples of chromite and the host serpentinite from the Podenny and Kurman deposits in the Alapaevsk ophiolite and from the Piany Bor and southern deposits in the Klyuchevskoi ophiolite. Samples from the four sites exhibit similar patterns of activation energy (E₀) vs. resistance coefficient (log R₀). The E₀-log R₀ points of samples collected away from ore fields align along a straight line corresponding to the log R ₀ = a - bE₀ relationship typical of nonmineralized rocks, with the a and b coefficients as in alpine ultramafics. The samples of mineralized rocks depart from the basic line, the departure increasing as they approach the orebody. Though having similar patterns, the E₀-log R₀ fields of the samples from different sites show no overlap. The revealed features may be useful as implicit diagnostic criteria for ophiolite-hosted chromite mineralization.

Various opinions on the position of the Middle/Upper Triassic boundary have been concisely reviewed. The lower boundary of the Carnian Stage is accepted at the base of the Trachyceras aon Zone. The recentmost data on biostratigraphy of boundary beds of the Ladinian and Carnian Stages of the Southern Alps, Himalayas, British Columbia, northeastern Asia, Svalbard, and Arctic Canada have been considered and critically analyzed. Using sections of British Columbia with mixed Boreal and Tethyan fauna of Ammonoidea, we compared biostratigraphic schemes of the Middle/Upper Triassic boundary interval of the Boreal and Tethyan regions. On the basis of correlations and paleontological data, the lower boundary of the Carnian Stage in Northeastern Asia is suggested to be drawn at the base of the ammonoid

The problem of processing mass-spectrum data in dope testing is considered. It is shown that this problem concerned with dope testing is characterized by a high level of a priori uncertainty. It is proposed to use a contrast method for detecting mass-spectrum peaks. The main point of the method is as follows. At first, a sample of observations without a useful signal is taken (i.e., there is no bioassay in the mass-spectrometer work chamber, in this case, the mass-spectrum depends only on the features of the measuring channel and remains of dirt in the work chamber). Then the work sample in which the useful signal has to be detected is taken. Optimal detection algorithms based on statistical principles of invariance and unbiasedness are obtained. Results of statistical tests of the algorithm and a full-scale experiment are presented.

Results of frequency stability of Nd:YAG lasers locked to resonances of high-Q Fabry

An alternative design of a frequency spectrum synthesizer for an optical time standard with a lower-level spectral density of noise FM at the synthesizer outputs is considered. This is achieved by using a transistor generator with frequency stabilization by a dielectric resonator and subsequent division of reference frequency by diode and trigger dividers, and by realization of a phase lock loop.

An automatic system for measuring the quantum efficiency of multielement photodetectors applied in atomic emission spectral analysis is created. Results of measuring the quantum efficiency of BLPP-369 photodiode lines with different dopants and coating layers, and also lines of CCDs (Sony ILX-526A) are presented. It is shown that the quantum efficiency of photodiode lines between 180 and 360 nm is 0.3

Results of measuring the voltage-current characteristics (VCCs) of diodes for IR detectors with the cutoff wavelength l_c= 11 mm are presented. The diodes are based on variband Hg_0,78Cd_0,22Te layers grown by molecular beam epitaxy on semi-insulating GaAs substrates. It is found that diffusion current and generation current in the depletion layer of the p

A set of conversion functions of a cluster single-coil eddy-current sensor as the sensor inductance dependences on the blade tip coordinate displacement is described. A simplified model of electromagnetic interaction between the sensitive elements and the object simulator, that is, a rectangular plate, is developed. The model ensures calculating the set of conversion functions in an analytical form. Results of calculating the set of conversion functions, which were obtained for the given geometrical parameters of the measurement object, sensor, and current directions of its sensitive elements, are illustrated.

Properties of SISO adaptive stabilization systems with different types of reference model for prescribing dynamic and static characteristics are discussed. The influence of the model structure that forms the input action on the control signal is considered.

A one-step sequential procedure using a special rule of observation accumulation is proposed for estimating the linear parameters of a stable random coefficient autoregressive process. The upper bound for rms precision of a sequential estimate which decreases inversely to the value of the procedure parameter that determines the time of observations is obtained. Asymptotic behavior of the mean time of the procedure is studied. Results of numerical simulations are presented.

An iterative approach to solving the inverse kinematic problem with optimized choice of the initial approximation is proposed. The investigation is important for acoustic, optical, and seismic tomography in the conditions of geometric optics approximation.

Amounts of calculations intended for implementing various algorithms of cone-beam 3D tomography reconstruction are analyzed. A technically simple way of spiral scanning meeting the requirement of completeness condition is considered. Methods for reducing the amount of calculations by considering only the necessary part of projection data for object reconstruction at a specific point and by eliminating calculation of the beam index in the reciprocal projection are proposed. A method for modeling the cone-beam tomography process is illustrated using the proposed algorithm.

An approach to constructing specialized Internet portals is considered. These portals have to ensure access to knowledge and information resources of a certain field of knowledge. The information basis for such portals is formed by ontologies, which allow heterogeneous data and knowledge to be presented in a unified manner and ensure their relatedness. For simpler customization of the portal to a chosen field of knowledge, its ontology is divided into the base ontologies (ontologies of research activities and knowledge) independent of the knowledge domain of the portal and the domain-related ontology, which describes a certain field of knowledge. Based on the portal ontology, internal storages of data are constructed; management of information content, navigation and search in the information space of the portal are organized.

A method for digital stroboscopic holographic interferometry of focused images for measuring points of displacements of a metal plate vibrating at a resonant frequency is considered. Unlike classical holographic interferometry, in this method, the measurement process does not include the process of interferogram obtaining, recording, and interpretation.

The problem of creating exact 3D models of complex real objects for virtual reality applications is considered. One of the systems reconstructing 3D coordinates of a scene from its 2D image by means of structured illumination is presented. Problems related with system operation and leading to reconstruction errors are described. A new method is proposed for improving performance of the system due to considering optical distortions and using several images for reconstructing the same scene area.

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Seed burial was determined in the soil of n

As a result of 17-year investigations, eight associations of weed vegetation in cereal-fallow rotation and unchangeable wheat in leached chernozems of the areas near the Ob River were singled out. Three of them are analyzed in the paper. The main effect on the formation of the weed community association was caused by long-term permanent agrocenosis factor.

The paper presents the results of unreduced egg-cell parthenogenetic development induction by intergeneric pollination in different ecotypes of  Fragaria vesca L. (2n = 2x = 14). Parthenogenetic seedlings had the same chromosome number as the mother plant did. We revealed various levels of tendency to pseudogamic diploid parthenogenesis among the specimens of F. vesca. Wild specimens less tend to the phenomenon of parthenogenesis than cultural ones (Alexandria variety) do. For F. vesca under the climatic conditions of West Siberia, diploid parthenogenesis is the facultative additive insuring mechanism of seed-forming which is realized in case of problems with pollination or fertilization.

Species composition of algae in the bed of the Elegest River and its tributaries was studied in winter. One hundred thirty eight species from 6 divisions: Cyanophyta

Possibilities of the production of ecologically pure provision products in the Buryat Republic are considered; the dependence of the quality of provision products on environmental pollution is shown; the territories unfavourable for the production of ecologically pure provision products are picked out.

The materials on the research of ecologo-biological particularities of  Caryopteris mongholica Bunge are considered. The modern conditions of coenopopulations are given. The data on the morphology of plant, anatomical structure of leaf and stem and water mode (transpiration intensity, water content), geographical distribution of this species in Russia (Transbaicalia) are reported. For the purpose of species conservation, it is recommended to establish botanical reservations.

The data of perennial algofloristic investigation of the Shulgan-Tash cave are reported. Taxonomic an

Results of the investigation of lichens of the forest ecosystems of the eastern coast of Lake Baikal during the years 2001

An experimental study of different control methods for hypersonic air inlets aimed at ensuring reliable starting of these apparatuses and improving their operating characteristics in the range of Mach numbers 2 to 8 is reported. Conditions for boundary-layer separation and possibilities for preventing this separation by using modified diffuser configurations and/or perforation bleedage are examined. An air-inlet model was tested for operation in an intermittent wind tunnel and in a blow-down wind tunnel respectively in the Mach-number ranges 2 to 6 and 5 to 8. Distributions of static and total air pressures on the walls of the model and in several cross sections were measured, together with air flow coefficients and total-pressure recovery coefficients. Perforation bleedage is shown to offer an efficient means to facilitate air-inlet starting. Perforation bleed has enabled a more than two-fold increase in the air flow coefficient on the model with sidewalls. A perforation-bleed panel installed closer to the air-inlet throat proved to be more efficient. The possibility of sudden starting of the air-inlet apparatus was checked in the intermittent wind tunnel; it was shown that, here, sudden starting could be realized. The data obtained in the intermittent wind tunnel proved to be consistent with data obtained in the blow-down wind tunnel with up to 150-ms blowdown time.

The effect of local periodic forcing in the form of blowing/suction through sequentially located annular slots on the features of the turbulent boundary layer formed on an axisymmetric body of revolution in an incompressible flow is studied experimentally. The Reynolds number based on the momentum thickness of the boundary layer ahead of the annular slot is 1362. The dimensionless amplitude of the forcing signal A₀ is set to be 0.4. The frequency of the forcing signal in the law-of-the-wall units is f⁺

The results are presented for experimental investigation of the peculiarities of the development of three-dimensional turbulent separated flows on a flat surface for the Mach number

Experimental data concerning the influence of initial conditions at the nozzle exit on the structure and development characteristics of round jets are reported. Features in the development of laminar and turbulent round jets emanating from variously elongated nozzles at identical Reynolds numbers are revealed. Smoke visualization pictures obtained for jets formed under different initial conditions (with different distributions of mean and pulsating flow velocities at the nozzle exit) are discussed. It is shown possible to make the zone of laminar flow in the jet stream more extended, and to delay the jet turbulization process in space, by making the flow-velocity profile more parabolic at the exit of elongated nozzle. Features in the development of vortical structures in a jet under an acoustic action are identified. It is shown that, for a turbulent round jet to be produced right at the nozzle exit, the nozzle length must be increased in excess of a certain value so that to provide for spatial growth of turbulent boundary layer thickness, finally ending in the formation of a fully turbulent flow velocity profile across the channel.

We consider the influence of the solar ultraviolet emission on the photoionization of the working body of drainage systems and microthruster units of a space vehicle, which leads to an increase in the decay of radio-waves of its radio systems. It is necessary to choose the working body of the microthruster units of the space vehicle orienting towards the substances with a low photoionization section (hydrazine, methyl alcohol, etc.). When choosing the working frequencies of radio systems it is necessary to orient oneself towards higher frequencies (hundreds and thousands of megahertz).

The field of application for the systems of high-altitude aerodynamics and typical problems solved are presented. The main requirements for these systems are formulated. Some methods for implementation of these requirements are shown by the example of RuSat system.

A single cell of the gas-liquid slug flow was studied. The flow around an immobile gas slug in a downflow of liquid and under its bottom was measured. The values of the wall shear stress and its pulsations were measured by the electrodiffusion method depending on a distance from the slug nose. It is shown that in a liquid film around a slug, turbulent pulsations are damped in comparison with a single-phase liquid flow. In the bottom part of a slug, where vortices are detached, turbulent pulsations exceed significantly the single-phase ones.

Results of numerical investigation of the boundary layer thickness on turbulent separation and heat transfer in a tube with an abrupt expansion are shown. The Menter turbulence model of shear stress transfer implemented in Fluent package was used for calculations. The range of Reynolds numbers was from 5× 10³ to 10⁵. The air was used as the working fluid. A degree of tube expansion was (D₂/D₁)² = 1.78. A significant effect of thickness of the separated boundary layer both on dynamic and thermal characteristics of the flow is shown. In particular, it was found that with an increase in the boundary layer thickness the recirculation zone increases, and the maximum heat transfer coefficient decreases.