KPI Science News

Paradoxical properties of the line of pursuit in the problem of intercepting a fugitive on a horizontal plane

2025-01-29T20:58:16+02:00

Background. A new approach to the construction, integration and analysis of the differential equation of the pursuit curve in the classical problem of intercepting a fugitive on the plane is considered. In the proposed wording, it is new and relevant from a practical point of view in such areas as transport, logistics, military affairs, sports events, etc.

Objective. The purpose of the work is to determine the optimal angle of inclination of the straight line along which the fugitive should move in order to get as close as possible to the "life" line before being caught by the pursuer.

Methods. To achieve the goal, classical methods of integrating differential equations in parametric form were used, as well as graphic and numerical tools provided by the MathCad software package.

Results. The differential equation of the pursuit curve is formulated and its solution in closed parametric form is established. Its numerical analysis was carried out and the influence of the parameters (ratio of speeds of the pursuer and the fugitive) and on the behaviour of the pursuit curve was investigated. The dependence of the change in the distance along the horizontal axis at the moment of apprehension of the fugitive, depending on the magnitude of the angular coefficient of the straight line of his movement at a fixed coefficient , was analysed.

Conclusions. As a result of the research, it was found that if the coefficient (that is, the speed of the pursuer significantly exceeds the speed of the fugitive), then the distance at which the latter will be detained goes to zero. On the other hand, if (that is, the speeds of the boats are equal), then the specified distance goes to infinity, that is, the fugitive will not be apprehended. The dependence of the change of the distance along the horizontal axis on the coefficient has a well-defined local maximum under the condition , which indicates that there is a certain non-zero angle of inclination of the direct flight, which enables the fugitive to achieve the maximum movement towards the border between the two countries. Thus, we observe a paradoxical phenomenon: for a successful escape, the strategy of choosing an angle of inclination of a straight line equal to zero (that is, moving along the shortest segment connecting two parallel lines) is not correct.

TIME-UNIT SHIFTING IN 3-PERSON GAMES IN FINITE AND UNCOUNTABLY INFINITE STAIRCASE-FUNCTION SPACES SOLVED IN PURE STRATEGIES

2025-01-28T23:23:21+02:00

Background. Games played with staircase-function pure strategies can model discrete-time dynamics of rationalizing the distribution of some limited resources among players. Along with 2-person games, 3-person games are the most applicable models of rationalization in economics, ecology, social sciences, politics, government, and sports. There is a known method of finding an equilibrium in a 3-person game played in staircase-function pure strategy spaces. The time interval on which the game is defined consists of an integer number of time units. The equilibrium is stacked from time-unit equilibria. An open problem is a multiplicity of equilibria (on some time units) leading to a multiplicity of equilibrium stacks. Another open question is how to deal with a 3-person game in which the time interval can be changed or shifted by an integer number of time units.

Objective. The purpose of the paper is to expand and develop the tractable method of solving 3-person games played within players’ finite sets of staircase functions for the case when the length of the time interval on which the 3-person game is defined is varied by an integer number of time units.

Methods. To achieve the said objective, a 3-person game, in which the players’ strategies are staircase functions of time, is formalized. In such a game, the set of the player’s pure strategies is a continuum of staircase functions. The time can be thought of as it is discrete due to the time interval is comprised of time units (subintervals). Then the set of possible values of the player’s pure strategy is discretized so that the player possesses a finite set of staircase functions.

Results. The known method is expanded to build a single pure-strategy equilibrium stack in a discrete-time staircase-function 3-person game. The criterion for selecting a single equilibrium solution is to maximize the players’ payoff sum. In the case of a time-unit shifting, this criterion allows extracting the respective best staircase-function equilibrium pure strategy of the player in any “narrower” subgame from the player’s best staircase-function equilibrium pure strategy in the “wider” game.

Conclusions. A tractable and efficient method of finding the best pure-strategy equilibrium in a 3-person game played in finite or uncountably infinite staircase-function spaces is to solve a succession of time-unit 3-person games, whereupon their best equilibria are stacked into the best pure-strategy equilibrium. To deal with the case when not every time-unit 3-person game is solved in pure strategies, an effective way is to put a staircase-function game on hold-up on those time units which do not have pure-strategy equilibria. The result of putting the staircase-function game on hold-ups is that the player will obtain one’s best staircase-function equilibrium pure strategy with gaps, whichever the time interval and time-unit shifting are.

FEATURES OF THE INFLUENCE OF THE STRESS STATE ON THE THERMAL STABILITY OF THE NiSi PHASE IN Ni(Pt)/Si FILMS

2025-01-31T19:49:01+02:00

Background. It is possible to increase the speed, the degree of integration of microcircuits and their reliable operation due to the use of thermostable nanoscale films of transition metal silicides as functional elements. Stress in nanostructures is a general problem of microelectronics, which must be taken into account at all stages of production, storage and operation of both discrete devices and integrated circuits

Objective. Study of the effect of stress state and Pt alloying element on the phase composition and thermal stability of NiSi nickel monosilicide in nanoscale [(Ni+1 at.% Pt)30 nm] and [(Ni+8 at.% Pt)30 nm] films on single crystalline Si(001) substrates during vacuum annealing in the temperature range of 400-1000 °С.

Methods. Nanoscale films were deposited by magnetron sputtering on Si(001) substrates at room temperature. The samples were annealed in a vacuum of ~1.3∙10^-3 Pa in the temperature range of 400-1000 °C. The influence of Pt on the change in stress state and the thermal stability of the NiSi phase in Ni(Pt) films on a single crystalline Si(001) substrate was investigated using the methods of X-ray structural phase analysis, mass spectrometry of secondary neutrals, and resistometry (four-probe method).

Results. The influence of internal mechanical stresses and the content of the Pt alloying element in the film on the sequence, temperature of silicide phases formation, and thermal stability of NiSi nickel monosilicide during vacuum annealing was determined.

Conclusions. It was established that the addition of Pt to the Ni film leads to an increase in the nickel monosilicide formation temperature compared to the Ni(30 nm) film.

Nickel monosilicide NiSi begins to form in films with 1 at.% Pt and 8 at.% Pt during annealing at temperatures of 500 °C and 450 °C, respectively. An increase in the thermal stability of NiSi is associated with a significant decrease in the driving force of the NiSi into NiSi₂ phase transition due to the formation of a Ni_xPt_1-xSi solid solution, which has a lower free energy, due to the positive contribution of the .

Fleet management algorithm for enhancing environmental friendliness of maritime delivery

2024-10-09T11:49:26+03:00

Background. Maritime cargo delivery accumulates over 80% of international transport operations, providing a cost-effective method for global trade, particularly vital for developing countries. However, maritime transportation is heavily dependent on fossil fuels, which results in significant emissions of carbon dioxide (CO₂) and creates environmental problems for water resources. To address these issues, this study proposes a solution to optimize maritime delivery route planning projects, and reduce fuel consumption and CO₂ emissions.

Objective. The objective is to develop an algorithm for planning delivery routes at optimal vessel speed, consisting of a genetic algorithm and a speed optimization step, to reduce fuel consumption and CO₂ emissions during maritime transportation. In addition, the results will be validated and the efficiency of the developed algorithm will be compared with a standard genetic algorithm without a speed optimization step.

Methods. This article proposes an implementation of an additional step of vessel speed optimization into the algorithm for calculating delivery routes, which can significantly reduce fuel consumption and CO₂ emissions without increasing the complexity of the algorithm itself. The route is computed by solving the vehicle routing problem.

Results. The study demonstrates that the application of the speed optimization step in the algorithm for planning delivery routes significantly reduces the volumes of fuel consumption and CO₂ emissions. Comparison of the experimental results showed that the genetic algorithm with a speed optimization step outperforms the standard genetic algorithm in terms of the volumes of fuel used and CO₂ emissions. Detailed analysis of various combinations of fleet composition emphasizes the need to balance the capacity of vessels to achieve maximum efficiency of cargo delivery. While adding more feeders initially reduces overall fuel consumption, overloading the fleet with underutilized vessels can lead to inefficiencies and increased operational costs. The study also considers alternative approaches such as increasing capacity and reallocating vessels among routes, highlighting their impact on fuel consumption and CO₂emissions.

Conclusions. The study proposes an improved algorithm for constructing maritime cargo delivery routes using a genetic algorithm with a speed optimization step. Such an algorithm ensures effective management of maritime delivery route planning projects, while significantly reducing fuel consumption and CO₂ emissions into the environment. Also, optimal control of the fleet composition ensures the reduction of CO₂ emissions due to the efficient use of each vessel.

METHOD OF SELECTING THE WORKING BODY FOR OCR CYCLES OF FLUE GAS HEAT RECOVERY

2025-01-29T23:05:42+02:00

Background. The choice of the optimal working fluid for condensing heat exchangers operating based on the organic Rankine cycle on gas-fired power and water boilers with waste gas heat recovery arises due to the growing need for energy-efficient technologies and the need to ensure maximum efficiency of generation systems at minimal costs. This requires studying the properties of various working fluids and their optimal use, taking into account specific operating conditions, and addressing the lack of research for specific equipment conditions.

Objective. The purpose of the paper is to justify the choice of the working fluid for the heat recovery system with a condensing heat exchanger and a turbine operating on the organic Rankine cycle based on the E-480-560-140 GM power boiler.

Methods. The scientific approach in this study is based on the comparative method. This approach involves comparing different options for organic working fluids through a literature review and modelling their operation for existing conditions. During the literature review, approaches that have already been used in other studies and practices were analyzed. Modelling the operation of working fluids made it possible to assess their efficiency and suitability for a specific system, considering its parameters and limitations.

Results. A list of effective organic bodies is presented based on a literature review and the results of technical, economic and mathematical analysis. The algorithm for selecting a working body is based on the obtained research results and takes into account the criteria of energy efficiency, compatibility with system parameters, resistance to corrosion and wear, as well as the availability and cost of working substances. Taking these criteria and research conclusions into account, the following working fluids are suitable for the given system: R717, R245FA, R123, R141B.

Conclusions. For the conditions of the given project, ammonia (R717) is the most optimal working medium. This decision can be applied to similar conditions of projects on heat utilization of flue gas products of natural gas combustion using ORC cycles

A method for protecting digital assets from permanent loss in the event of private key loss

2024-08-06T15:48:04+03:00

Background. Cryptocurrencies have introduced a decentralized and secure way to transfer value, with private keys playing a crucial role in authorizing transactions and verifying ownership. However, the loss or destruction of private keys leads to permanent asset loss, presenting a significant risk to users and hindering broader adoption.

Objective. This paper proposes a smart contract-based mechanism to mitigate the risk of losing digital assets in the event of permanent private key loss, providing an automated recovery procedure without compromising the security of digital assets.

Methods. The proposed solution leverages smart contract technology to create an automated recovery process. Key components include a protected address (Address A), a predefined recovery address (Address B), and a time interval (Period T). If no outgoing transactions are registered during Period T, the smart contract transfers assets from Address A to Address B.

Results. The proposed algorithm ensures that in the event of private key loss, assets are automatically transferred to a backup address after Period T. This process ensures users maintain full control over their assets, allowing adjustments to Period T and Address B as needed.

Conclusions. The smart contract-based recovery mechanism provides a reliable and user-friendly solution to address the consequences of possible permanent private key loss. It complements existing solutions, offering an additional layer of security and enhancing user confidence in decentralized financial systems. Future research might focus on improving the security and reliability of the backup address.

DETERMINATION OF PARAMETERS OF STEALTHY CYBER ATTACKS ON CONTROL SYSTEMS OF CRITICAL INFRASTRUCTURE OBJECTS

2025-02-13T19:57:49+02:00

Background. The integration of industrial control systems with modern network technologies has led to a significant increase in cyber attacks targeting critical infrastructure. Detection and mitigation methods for such attacks remain underdeveloped, necessitating the advancement of mathematical frameworks capable of identifying attack parameters in such systems.

Objective. The objective of this study is to develop and investigate the parameters of a stealthy attack on a critical infrastructure control system. The attack serves as a testing tool for cybersecurity systems by evading standard fault detection mechanisms.

Methods. The industrial control system model is represented as a differential equation. Parameters of an additive attack on the control system are introduced. A fault detection criterion is defined. The problem of determining attack parameters is addressed using optimal state control methods, employing the Lagrangе functional and the gradient descent method.

Results. A new method and corresponding algorithm for identifying malicious control distortions using variational optimization and the fast gradient descent method are proposed. A computational experiment confirms the effectiveness of the proposed algorithm.

Conclusions. A stealthy attack aimed at modifying control signals in critical infrastructure management systems, capable of bypassing standard fault detectors, is examined. The proposed method and algorithm can be utilized in penetration testing to assess the security of automated control systems in industrial critical infrastructure. The algorithm’s functionality has been validated through computational experiments.