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1,065 results on '"Timofeeva G"'

3. Measured and modelled source water δ18O based on tree-ring cellulose of larch and pine trees from the permafrost zone

Author

Churakova-Sidorova OV, Lienert S, Timofeeva G, Siegwolf R, Roden J, Joos F, and Saurer M

Subjects
conifers, climate, drought, permafrost thaw depth, siberia, δ18o of source water, Forestry, SD1-669.5
Abstract

To identify source water for trees growing on permafrost in Siberia, we applied mechanistic models that quantify physical and biochemical fractionation processes, leading to oxygen isotope variation (δ18O) in plant organic matter. These models allowed us to investigate the influence of a variety of climatic factors on tree-ring cellulose from two dominant species: Larix cajanderi Mayr. from northeastern Yakutia (69° 22′ N, 148° 25′ E, ~ 250 m a.s.l.) and Pinus sylvestris L. from Central Yakutia (62°14′ N, 129°37′ E, ~ 220 m a.s.l.). The climate of the region is highly continental with short growing seasons, low amount of precipitation and these forest ecosystems are growing on permafrost, which in turn impact the water cycle and climate variation in the δ18O of source water. We compared outputs of the Land surface Processes and eXchanges (LPX-Bern v. 1.3), and Roden-Lin-Ehleringer (RLE) models for the common period from 1945 to 2004. Based on our findings, trees from northeastern and central Yakutia may have access to additional thawed permafrost water during dry summer periods. Owing to differences in the soil structure, active thaw soil depth and root systems of trees at two Siberian sites, Larix cajanderi Mayr. trees can access water not more than from 50 cm depth, in contrast to Pinus sylvestris L. in Central Yakutia which can acquire water from up to 80 cm soil depth. The results enhance our understanding of the growth and survival of the trees in this extreme environment.

Published
2020
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8. Application of the model of choice of transport mode based on the generalized trip cost.

Author

Timofeeva, G. and Hazimullin, A.

Subjects
*TRAVEL time (Traffic engineering), *UNITS of time, *PRICES, *STATISTICS, *COST, *PASSENGER traffic, *CHOICE of transportation
Abstract

The problem of predicting the distribution of passenger traffic on duplicate routes depending on the price and travel time is studies. The possibilities of using the previously offered model are analyzed, where the choice of an individual (randomly selected) passenger is modeled as a solution to an optimization problem with a random parameter that reflects the value of the time unit of this passenger. The features of the application of the model are considered, statistical data and regularities that shall be considered in the calculations are analyzed. [ABSTRACT FROM AUTHOR]

Published
2023
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23. Hierarchical game with random second player and its application.

Author

Timofeeva, G.

Subjects
*PRICES, *GAMES, *NEW product development
Abstract

A hierarchical game with a random second player is considered, optimal strategies are defined on the base of Stackelberg equilibrium. The random second player is understood as a randomly selected person from a homogeneous set of decision-makers. The proposed model can be used in various problems. First of all, it is may be used for optimal price choosing for a new product. In the article the model is applied to the problem of setting the optimal fare to a new route. A carrier acts as a first player, a randomly selected passenger acts as a second player. It is assumed that the function of passenger's preferences depends on a random parameter. The price for the hierarchical game is an optimal payoff of the first player, this price is compared with the price of a game in which the strategies of both players depend on a random parameter. A model example is considered. [ABSTRACT FROM AUTHOR]

Published
2022
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24. Calculation of the optimal timeout of executing a SQL query for multi-master replication system.

Author

Babaylov, V. and Timofeeva, G.

Subjects
*SQL, *PROBLEM solving
Abstract

Many multi-master replication systems are based on a two-phase commit mechanism. One of its problems is waiting for a response from the database servers by the coordinator, which may not come due to problems on the network or on the database server itself, which leads to delays in the activity of the multi-master replication system. Usually, such problems are solved by introducing a timeout, but if its value is too large, the problem may not be noticed in a timely manner, and too small a timeout will be processed for SQL queries, which will cause an increase in the load on the network due to additional service messages. The paper analyzes the execution time of a SQL query on several servers in order to calculate the optimal timeout for a multi-master replication operation. Based on the results obtained, a module for calculating the optimal query execution timeout for multi-master replication systems has been developed. [ABSTRACT FROM AUTHOR]

Published
2022
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