The transient mode of a two-phase queuing system with a Poisson input flow, exponential distribution of service time in each phase, and a limitation on the total buffer size of the two phases is considered. Nonstationary probabilities of system states are found using the Laplace transform. A numerical calculation and analysis of the system performance characteristics in transient mode with parameters corresponding to new-generation optical networks were carried out.
Models with selective convexity are an important class of data envelopment analysis (DEA) models. This type of model allows managers to consider variables such as ratios, averages, percentages, etc. The paper proposes algorithms for constructing input and output isoquants using volume variables in models with selective convexity. These algorithms help investigate the relationship between any volume variables in the model. Computational experiments confirm the reliability and efficiency of the proposed methods.
This paper considers a linear continuous- or discrete-time dynamic object in the absence of its mathematical model. As is demonstrated below, a control law that suboptimally damps initial and (or) exogenous disturbances of such objects can be implemented based on experimental and a priori data. The approach involves the methods of robust control design and duality theory as well as the technique of linear matrix inequalities.
The problem of finding the optimal sequence of performing a set of tasks in a time-limited test is considered. That is, a task group is allocated for mandatory initial execution in the test, the remaining tasks are performed during the remaining time until the end of the test. For each correctly completed task of the test, the subject is awarded a certain number of points. The proposed criterion is the probability that the total number of points scored for the test exceeds a certain level, which is a fixed parameter, while simultaneously fulfilling the time limit of the test. Random parameters are the user’s response time to each test task. The correctness of the user’s answer to the task is modeled by a random variable with a Bernoulli distribution. The resulting stochastic bilinear programming problem boils down to a deterministic integer problem of mathematical programming.
The analysis of the known approach (Kirshtein, B.K. and Litvinov, G.L., Autom. Remote Control, 2014, vol. 75, no. 10, pp. 1802–1813.) in which tropical geometry over complex multifields of active power balances is used to estimate the region of existence of the electric power system mode. Its limitations are shown and a new approach is proposed, a criterion is also represented for determining the boundary that precedes the violation of the stability of the energy system due to the restructuring of the tropical set of solutions. The developed approach allows to determine the approach of the power system mode to the limit by the known parameters of the lines and the dynamics of changes of the nodes voltage modules and the nodes load.
Space debris is an urgent problem of our time. This paper considers the idea of reducing near-Earth space debris by releasing the spent additional fuel tank (AFT) and the booster’s central block (CB) into the Earth’s atmosphere. The spacecraft transfer from a reference circular orbit of an artificial Earth satellite to a target elliptical orbit is optimized. The transition maneuvers are carried out using a booster with a high limited-thrust engine and the AFT. The second zonal harmonic of the Earth’s gravitational field is taken into account. The optimal control problem is solved based on Pontryagin’s maximum principle. Bulky derivatives are calculated using a specially developed numerical-analytical differentiation technique. The Pontryagin extremals obtained below are the next step in implementing the problem hierarchy methodology.
This paper considers the problem of stabilizing the output variables of a Lurie-type nonlinear system in a given set at any time instant. A special output transformation is used to reduce the original constrained problem to that of analyzing the input-to-state stability of a new extended system without constraints. For this system, nonlinear control laws are obtained using the technique of linear matrix inequalities. Examples are given to illustrate the effectiveness of the method proposed and confirm the theoretical conclusions.
The problem considered includes the development and modeling of an adaptive control algorithm for unstable vertical plasma positioning in a vertically elongated tokamak. At each iteration, a new PID controller is automatically synthesized for the evolving plasma model identified using the least squares method. The parameters of the feedback controller were computed based on the desired placement of the poles of the closed-loop control system in the left half-plane of the complex plane. The initial control system model utilized was a robust system synthesized using Quantitative Feedback Theory (QFT). The system was simulated on a real-time digital test bed (https://www.ipu.ru/plasma/about).
The influence of the arrangement of amino acid residues in a pentapeptide on its stability is being studied. A forecast of pentapeptide stability is made using the gradient boosting method, which allows one to evaluate the influence of each feature on the stability of the pentapeptide. Combinations of amino acid arrangements in the pentapeptide have been identified that make a significant contribution to its stability. It has been shown that the use of such combinations reduces the amount of data required to obtain a reliable prediction of pentapeptide stability.
This paper considers the problem of motivating the reduction of project duration. The duration cuts of project works and the corresponding costs are given. A group incentive scheme is used to compensate for the costs. In this scheme, all works are partitioned into groups and a unified incentive scheme is applied for each group. Two types of unified incentive schemes are studied for groups, namely, linear and jump ones. The problem is to partition all project works into groups and choose an appropriate incentive scheme for each group by minimizing the total incentive fund. Solution algorithms are proposed based on determining the shortest path in the network. Special cases are also analyzed (partition with the minimum number of groups and partition with the maximum number of groups).
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