Results of a lake model intercomparison study conducted within the framework of Lake Model Intercomparison Project are presented. The investigated lake was Groser Kossenblatter See (Germany) as a ...representative of shallow, (2 m mean depth) turbid midlatitude lakes. Meteorological measurements, including turbulent fluxes and water temperature, were carried out by the Lindenberg Meteorological Observatory of the German Meteorological Service (Deutscher Wetterdienst, DWD). Eight lake models of different complexity were run, forced by identical meteorological variables and model parameters unified as far as possible given different formulations of processes. All models generally captured diurnal and seasonal variability of lake surface temperature reasonably well. However, some models were incapable of realistically reproducing temperature stratification in summer. Total heat turbulent fluxes, computed by the surface flux schemes of the compared lake models, deviated on average from those measured by eddy covariance by 17-28 W m super(-2). There are a number of possible reasons for these deviations, and the conclusion is drawn that underestimation of real fluxes by the eddy covariance technique is the most probable reason. It is supported by the fact that the eddy covariance fluxes do not allow to close the heat balance of the water column, the residual for the whole period considered being approximately -28 W m super(-2). The effect of heat flux to bottom sediments can become significant for bottom temperatures. It also has profound influence on the surface temperatures in autumn due to convective mixing but not in summer when the lake stratification is stable. Thus, neglecting sediments shifts the summer-autumn temperature difference in models lacking explicit treatment of sediments considerably. As a practical recommendation based on results of the present study, we also infer that in order to realistically represent lakes in numerical weather prediction and climate models, it is advisable to use depth-resolving turbulence models (or equivalent) in favor of models with a completely mixed temperature profile.
Abstract
Experimental simulation of the inhomogeneity of the incident flow localized in time and space on a bluff tear-drop airfoil is carried out. It is shown that in the region outside the ...aerodynamic wake of the tear-drop airfoil, the presence of inhomogeneity leads to an increase in the amplitudes of velocity fluctuations in a wide frequency range. In the region inside the wake, the presence of inhomogeneity leads to the suppression of velocity fluctuations at the frequency of vortex shedding by a factor of 2–3 in amplitude. The intensification of fluctuations at frequencies above the main one was also noted, and there was no effect on fluctuations at lower frequencies.
Issues related to the study of wear resistance, strength, and other material characteristics of parts of tillage machinery are addressed. The importance of improving the heavy-duty tool of domestic ...tillage machines is evaluated. Chemical compositions and mechanical properties of steels for tools of agricultural machines of leading European manufacturers are given. New grades of steel for high-strength rolled products have been developed.
Comparative results of laboratory bench tests for wear resistance of commercial and prototype domestic and foreign grades of rolled steel and powder hard-alloy coatings are presented. An effective technology for hard-facing of wearable parts of tillage machinery is substantiated and analyzed. Verification comparison performance and life-cycle tests of tools manufactured using new materials and facing technology were carried out. The life of the prototype tools was increased by a factor of 2.8 to 3.8. The market potential of using new materials science and technology developments in Russian agricultural production is assessed.
The task of improving the effectiveness of activities aimed at prompt receipt of information by students of Reshetnev Siberian State University of Science and Technology is solved by using the ...developed mobile application «Schedule of classes». Due to the heavy load on the University's unified server, there are temporary delays in accessing the main site, which makes it inconvenient to use it. In this regard, there is a need to solve this problem by bringing the described process to partial autonomy. This approach will allow you to combine high performance due to the speed of the mobile operating system and expanding the functionality of both the application itself and the means of sending information from the management of the Institute to students. The purpose of this work is to study and analyze existing mobile applications of other universities, their advantages and disadvantages. Based on the research, develop a mobile application, agreeing with the Directorate of the Institute of Informatics and telecommunications tasks. This article presents the main aspects of the design and software solution. The software solution is implemented in the Android Studio integrated development environment in the Dart programming language, using the Flutter SDK.
Vacuum Chamber of the MEPhIST-1 Tokamak Vorobyov, G. M.; Krat, S. A.; Mironov, V. D. ...
Physics of atomic nuclei,
12/2020, Letnik:
83, Številka:
12
Journal Article
Recenzirano
One of the most important structural elements of a tokamak is a vacuum discharge chamber, which satisfies specific requirements concerning the induction method of plasma generation and, accordingly, ...the presence of alternating magnetic fields additionally acting on the chamber. Moreover, the chamber should not only be able to create and confine a current plasma but also be able to diagnose its parameters through appropriate pipes. The small spherical tokamak being created at MEPhI for both educational and research purposes has an extensive program of such studies; therefore, the discharge chamber should not only allow fast evacuation and withstand alternating magnetic fields but also be convenient for measuring its parameters, using various diagnostics, as well as allow quick replacement of internal elements and introduction of additional power into the chamber. The paper describes the design of the vacuum chamber of the MEPhIST-1 tokamak, which meets these requirements, and presents calculations to justify the choice of material and the thickness of the characteristic elements of the chamber, and also presents the test results of the finished chamber.
The paper describes the results of studying the influence of a freestream disturbance localized in time and space on the structure of the wake of a symmetric teardrop-shaped airfoil in the range of ...angles of attack from −20° to +20°. It is demonstrated that the existence of such a disturbance leads to the suppression of vortex formation at certain angles of attack. Ranges of angles of attack in which the wake structure remains unchanged are found.
Abstract
An integral part of maintaining a favorable environmental situation on our planet is the observation of its individual objects, including special attention is paid to water bodies. This is ...due not only to the natural human need for its consumption, but also to other aspects of the anthropogenic factor, which includes unintentional pollution of the environment with industrial and other waste. The task of increasing the effectiveness of measures aimed at the effective performance of work on the collection of water and soil samples from individual reservoirs, as well as the collection, accumulation and processing of data on reservoirs through the introduction of a system of environmental monitoring of water bodies is being solved. Such a system will speed up the work of environmental organizations, and also contributes to the formation of a brief set of recommendations for restoration measures and will give an overall assessment of the ecological state of the reservoir. The purpose of this work is to automate the process of accounting and processing information about the results of laboratory studies of various types of samples and tests on the basis of the performed cycle of calculations to form estimates and recommendations on the ecological state of the reservoir and to make final reports.
We define cut-and-join operators in Hurwitz theory for merging two branch points of an arbitrary type. These operators have two alternative descriptions
: (1)
the GL characters are their ...eigenfunctions and the symmetric group characters are their eigenvalues
; (2)
they can be represented as W-type differential operators
(
in particular, acting on the time variables in the Hurwitz-Kontsevich τ-function
).
The operators have the simplest form when expressed in terms of the Miwa variables. They form an important commutative associative algebra, a universal Hurwitz algebra, generalizing all group algebra centers of particular symmetric groups used to describe the universal Hurwitz numbers of particular orders. This algebra expresses arbitrary Hurwitz numbers as values of a distinguished linear form on the linear space of Young diagrams evaluated on the product of all diagrams characterizing particular ramification points of the branched covering
.
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