—
One approach to obtain a cryptographically strong encryption gamma is to use linear-feedback shift registers defined by primitive polynomials. The ability to quickly select the appropriate ...polynomial can provide the required degree of security of the stream cipher. Currently, primitive polynomials for sufficiently large degrees are known, but usually these are so-called sparse polynomials. To increase the correlational stability, it is necessary to be able to quickly generate new primitive polynomials of the given degrees, which is the focus of this study.
Abstract
Plane gravitational waves in the Riemann space of General Relativity is considered. The criterion of plane gravitational waves is used based on the analogy between plane gravitational and ...electromagnetic waves. The Theorem is proved that the action of the Lie derivative on the plane wave curvature 2-form in the direction of the vector generating the invariance group of this wave in the Riemann space is equal to zero. It is justified that the gravitational waves can be used to transmit information in the Riemann space.
The article is devoted to solving the problem of stabilization of hydrological regime and hydro-ecological conditions of the Tuzla group of lagoons located in the central part of the Danube-Dniester ...interfluve by ensuring and regulating their water exchange with the open sea through artificially created channels in the barrier beach that separates the water body from the sea.
The research presents the results of adaptation of the well-known modern numerical hydrodynamic model Delft3D Flow Flexible Mesh to the conditions of the Tuzla group of lagoons, as well as the results of its application to determine the effectiveness of various variants for ensuring water exchange with the sea based on the outcomes of scenario mathematical modeling.
In particular, the following variants of channels functioning were studied: (1) a relatively narrow connecting channel at the 2nd km of the barrier beach (near the Burnas Lagoon) together with a wide and deep outlet that existed before 2015 at the 24th km of the barrier beach (near the Shagany Lagoon); (2) a wide controllable connecting channel in the Shagany Lagoon placed on the outlet, alongside with the above-mentioned channel in the Burnas Lagoon; (3) an additional (third) narrow channel at the strip of the barrier beach near the Alibey Lagoon.
The characteristics of the annual cycle of water salinity spatio-temporal variability were used as indicators of the effectiveness of management decisions for ensuring the stability of the lagoons' hydro-ecological conditions.
Based on the analysis of the scenario modeling results it was concluded that the optimum solution of the problem related to stabilizing the hydro-ecological regime of the water body consists in ensuring the constant multidirectional water exchange with the sea through two artificial connecting channels in the barrier beach (both with bottom marks of minus 1.0 m (Baltic Height System) and 60 m and 15 m wide for the Shagany Lagoon and the Burnas Lagoon respectively) throughout the year. This will deny any salinization of the water body over the long term.
For the specified variant the time of complete water renewal with sea water for the main lagoons of the Tuzla group would constitute 8 and 12 months for the Shagany Lagoon and the Alibey/Burnas Lagoons respectively.
The Trautman problem determines the conditions under which GWs transfer the information contained in them in an invariant manner. According to the analogy between plane gravitational and ...electromagnetic waves, the metric tensor of a plane gravitational wave is invariant under the five-dimensional group
, which does not change the null hypersurface of the plane wave front. The theorems are proven on the equality to zero for the result of the action of the Lie derivative on the curvature 2-form of a plane GW in Riemann and Riemann–Cartan spaces in the direction determined by the vector generating the group
. Thus the curvature tensor of a plane gravitational wave can invariantly transfer the information encoded in the source of the GW.
This study examines the characteristics of distribution of large volumes of freshened and polluted transitional waters from the Dnipro-Bug estuary across the northwestern part of the Black Sea (NWBS) ...that was caused by destruction of the Kakhovka HPP dam in June 2023. From June 6, 2023 to June 12, 2023 14.4 km³ of water were discharged from the Kakhovka Reservoir into the Dnipro-Bug estuary and subsequently into the sea. This volume constitutes 27% of the total annual average natural runoff of the Dnipro River (53.5 km³). During the initial days following the dam destruction water flow through the breach amounted to 40-50 thousand m³/s. The water carried a variety of pollutants into the sea that were present in the water of the Kakhovka Reservoir, in its bottom sediments, and also washed off from the flooded territories of the lower Dnipro area (more than 2000 hectares).
The analysis of the distribution characteristics was conducted using satellite images of the sea surface color and chlorophyll a concentrations, as well as the results of hydrodynamic modeling with application of the 3-D variant of a numerical hydrodynamic model Delft3D-Flow Flexible Mesh. It was established that the plume of freshened and polluted water initially spread across the Dnipro-Bug estuarine region of the NWBS and then moved towards the sea coast of Odesa reaching it on June 9-10, 2023. Subsequently, the plume began to spread along the western sea coast and reached the Tuzlivski Limans area on June 14, 2023. After this the narrow plume of dispersed water along the sea coast began to dilute when moving towards the open sea in the form of "tongues" that had formed over the sea bottom elevations. The modeling of dispersion of a conservative neutral buoyancy admixture serving as a marker of pollution spread with the transitional waters from the Dnipro-Bug estuary showed that reduction in pollution levels took place solely due to hydrodynamic dilution (up to 60% in Odesa District of the NWBS and up to 30% in the Danube-Dniester interfluve area of the river water pollution level observed in Kherson).
The identified characteristics were determined based on the water circulation process that formed in the Dnipro-Bug estuarine area under the influence of significant sea level gradients resulting from the inflow of large volumes of freshened transitional waters through the estuary and the Kinburn Strait during the first days, and then followed by the density currents formed at the hydrofront between the transformed river water and surrounding sea. The influence of wind conditions manifested itself in the form of spread across the NWBS of the plume of dispersed transitional water from the Dnipro-Bug estuary and the hydrofront's position and configuration. Though wind-induced currents were not dominant, they still influenced the water dynamics and distribution of concentrations of admixtures, for instance, chlorophyll a, within the freshened plume that was outlined by the hydrofront. They also promoted penetration along the coastal shallow area of transformed river water towards Odesa.
This paper highlights the results of adaptation and verification of the Delft3D Flexible Mesh numerical model under the conditions of the Sasyk reservoir. The objective of this work is to evaluate ...the expected spatio-temporal variability of water salinity in the Sasyk reservoir after completion of the Sasyk renaturalization project by means of establishing a constant water exchange with the sea through the artificial channel.
The Sasyk Lagoon was separated from the sea and transformed into a freshwater reservoir in the late 1970s. However, due to the poor water quality in the Sasyk reservoir in the modern period, the solution of the problem of transforming the reservoir to its original coastal conditions, i.e. the renaturalization, has acquired particular importance.
Model results, obtained under conditions of 2019, indicate the possibility of using a hydrodynamic model to evaluate the effectiveness and possible consequences of various scenario-based decisions to be implemented for the management of the hydrological regime of the reservoir under various options of its operation.
The model runs were used to evaluate the flushing time of the Sasyk Lagoon and the pattern of the salinity fluctuations in the reservoir after the restoration of the artificial channel in the sand bar with a width of 100 m and a depth of 1.5 m and the establishment of the constant “sea-lagoon” interconnection. Applying the hydrometeorological conditions of 2019, a scenario-based modelling for two consecutive years was performed. For the first year of the simulation, a variant of water management under the absence of freshwater inflow from the Danube and the presence of sea water inflow throughout the year was considered. The model results at the end of the first year of the simulation were set as the initial conditions for the second year, and the rest of the external forcing remained unchanged. Additionally, the variant considering the Danube discharge into the lagoon during May-July for the second year of simulation was investigated.
Based on the simulation results, it was found that in the case of a constant water exchange with the sea through the connecting “sea-lagoon” channel (with the abovementioned morphometric characteristics) and under the absence of the Danube freshwater inflow throughout the year: 1) the flushing time of the lagoon will be 1 year and 5 months; 2) stabilization of water salinity in the lagoon will not occur, i.e. the salinization of the lagoon water takes place in the long-term perspective; 3) the time period from the moment of initiating the water exchange with the sea, during which the lagoon reaches the water salinity limit of 7-8 ‰, that is critical for the existence of freshwater species of flora and fauna, is expected to amount to 4 months for the southern part and to 5.5 months for the northern part of the lagoon; after which the formation of the marine ecosystem of the reservoir will begin.
It is shown that the stabilization of water salinity in the lagoon in the second year of the simulation can be achieved under conditions of ensuring the Danubian freshwater discharge in the period of significantly higher water level in the Danube River, compared to the lagoon water level (May-July 2019).
In 2014 Ukraine lost the Ukrainian National Automated System of Marine Forecasting for the Black Sea that was created and operated at the premises of Marine Hydrophysical Institute of the National ...Academy of Sciences of Ukraine located in the Crimea. Within the framework of research works aimed at establishing a new marine forecasting system a possibility of employing the internationally acclaimed set of coupled numerical models Delft3D-FLOW + SWAN (the Simulating WAves Nearshore) for operational forecasting of the short-term (5 to 10 days) spatio-temporal variability of oceanographic features in the Ukrainian part of the Sea of Azov and the Black Sea Basin is considered. To ensure operation of the models set in the forecasting mode it was suggested to use a prediction of variability of meteorological characteristics at the air-sea interface obtained with the help of the numerical weather forecast model GFS (Global Forecast System). This paper presents the results of verification of Delft3D-FLOW and SWAN numerical models which were adapted to the conditions of the North-Western part of the Black Sea and its Odesa area in the version of meteorological data (fields of wind speed and direction, atmospheric pressure) assimilation from the GFS forecast archive. A technique of telescoping the spatial curvilinear computational grids with different resolution capacity was used in the process of models set adaptation to the conditions of the prognostic area. The models were verified by comparing modelling results with observational data on sea level variability in the ports of Odesa area of the North-Western part of the Black Sea (Chornomorsk, Odesa, Yuzhnyi), as well as with data on wind speed and direction, drift currents and characteristics of wind-induced waves recorded over the studied periods by the gauges of stationary hydrometeorological buoy which was mounted in the Bay of Odessa. Based on the analysis of the results of verification of coupled numerical models Delft3D-FLOW + SWAN set it was concluded that the set of coupled models has good prospects of being used in the system of operational forecasting of the variability of oceanographic parameters of the sea environment in the Ukrainian part of the Sea of Azov and the Black Sea Basin in the version of assimilation of meteorological information obtained from the GFS global forecast model.
In order to solve the problems of diagnosis and forecast of spatial-temporal variability of hydrological characteristics of the Kuyalnik Liman (water level, salinity and temperature) which cause ...chemical and biological processes occurring therein, and, therefore, affect the properties of brine and therapeutic mud, a non-stationary 3D numerical hydrothermodynamic model Delft3D-FLOW was applied.
The model can be applied for research of the features and forecasting of spatial-temporal variability of hydrological characteristics of the Kuyalnik Liman under the influence of natural and anthropogenic factors forming its hydrological regime. Such opportunity is also indicated by the results of adaptation of the model to the Kuyalnik Liman conditions and its validation that are specified in this work.
The important role of accounting of small streams flowing into the liman and accurate setting of intensity of storm rainfall during modelling is also shown. It is found that at the time of storm winds with longitudinal directions in relation to the liman’s water surface, the difference of watermarks in its northern and southern parts may reach 0.35-0.4 m.
The potentialities of averting a further salinization of the Tyligulskyi Liman lagoon were identified on the basis of the results of the hydrodynamic modelling, using the numerical model ...Delft3D-FLOW. The means to prevent the salinization in the lagoon include a reconstruction of the “lagoon-sea” interconnecting channel and the changing of its operational schedule, as well as the increasing of the river inflow considering the climatic conditions of the first half of the XXI century. The results of the verification of the hydrodynamic model are given. It is shown that for stabilizing water levels and reducing the rate of the water salinity in the lagoon the most effective option is the year-round operation of the deepened “lagoon-sea” connecting channel. This will be facilitated by a multi-directional exchange of water through the channel caused by wind-induced water level oscillations in the lagoon and in the sea. However, while maintaining the current level of the water management activity in the catchment area of the lagoon, a long-term trend of increasing water salinity in the lagoon still remains. Only the restoration of natural river discharge into the lagoon could reduce the tendency of growing water salinity to a minimum.
PDF
