Inference of dominant modes for linear stochastic processes

For dynamical systems that can be modelled as asymptotically stable linear systems forced by Gaussian noise, this paper develops methods to infer (estimate) their dominant modes from observations in real time. The modes can be real or complex. For a real mode (monotone decay), the goal is to infer its damping rate and mode shape. For a complex mode (oscillatory decay), the goal is to infer its frequency, damping rate and (complex) mode shape. Their amplitudes and correlations are encoded in a mode covariance matrix that is also to be inferred. The work is motivated and illustrated by the problem of detection of oscillations in power flow in AC electrical networks. Suggestions of some other applications are given.

Joint optimization of production and maintenance for multi-machines subject to degradation and subcontracting constraints

PurposeThe purpose of this paper is to consider various possible constraints of the problem of production and maintenance planning control for a multi-machine under subcontracting constraint, in order to bring the manufacturer industry closer to real mode. In this paper, we present an efficient and feasible optimal solution, by comparing optimization procedures.Design/methodology/approachOur manufacturing system is composed of parallel machines producing a single product, to satisfy a random demand under a given service level. In fact, the demand is greater than the total capacity of the set of machines; hence there rises a necessity of subcontracting to complete the missing demand. In addition, we consider that the unit cost of subcontracting is a variable depending on the quantity subcontracted. As a result, we have developed a stochastic optimal control model. Then, to solve the problem we compared three optimization methods: (exact/approximate), the genetic algorithm (GA), the Pattern Search (PS) and finally fmincon. Thus, we validate our approach via a numerical example and a sensitivity analysis.FindingsThis paper defines an internal production plan, a subcontracting plan and an optimal maintenance strategy. The optimal solution presented in this paper significantly improves the ability of the decision maker to consider larger instances of the integrated model. In addition, the decision maker can answer the following question: Which is the most optimal subcontractor to choose?Practical implicationsThe approach developed deals with the case of the real-mode manufacturing industry, taking into consideration different constraints and determining decision variables which allow it to expand the profits of the manufacturing industry in different domains such as automotive, aeronautics, textile and pharmacies.Originality/valueThis paper is one of the few documents dealing with the integrated maintenance in subcontracting constraint production which considers the complex aspect of the multi-machine manufacturing industry. We also dealt with the stochastic aspect of demand and failures. Then, we covered the impact of the unit cost variation of subcontracting on the total cost. Finally, we shed light on a comparison between three optimization methods in order to arrive at the most optimal solution.

Surface profiling of the underground infrastructure in the technology of IT platforms - Part II

The article is devoted to one of main elements of the technology of IT PLATFORMS, i.e. VIRTUAL PROFILING of the underground infrastructure. Implementing of this technology to the wide scale can very much change investment and administrative processes. This section presents information on the technology of SURFACE UNDERGROUND INFRASTRUCTURE using VIRTUAL REALITY 3D. This technology is extremely useful for interactive support of investment processes. It can be useful for effective engineering work associated with interactive remote visualization in real mode. Keywords: IT platform; Virtual profiling; Underground infrastructure

A Modal Perturbation Method for Eigenvalue Problem of Non-Proportionally Damped System

The non-proportionally damped system is very common in practical engineering structures. The dynamic equations for these systems, in which the damping matrices are coupled, are very time consuming to solve. In this paper, a modal perturbation method is proposed, which only requires the first few lower real mode shapes of a corresponding undamped system to obtain the complex mode shapes of non-proportionally damped system. In this method, an equivalent proportionally damped system is constructed by taking the real mode shapes of a corresponding undamped system and then transforming the characteristic equation of state space into a set of nonlinear algebraic equations by using the vibration modes of an equivalent proportionally damped system. Two numerical examples are used to illustrate the validity and accuracy of the proposed modal perturbation method. The numerical results show that: (1) with the increase of vibration modes of the corresponding undamped system, the eigenvalues and eigenvectors monotonically converge to exact solutions; (2) the accuracy of the proposed method is significantly higher than the first-order perturbation method and proportional damping method. The calculation time of the proposed method is shorter than the state space method; (3) the method is particularly suitable for finding a few individual orders of frequency and mode of a system with highly non-proportional damping.

Analysis and forecast spatiotemporal distribution of thunderstorms and hail the territory of Belarus

The article is devoted to the study of the problem of ensuring the safety of aircraft during take-off and landing. Thunderstorm and hail is one of the most dangerous meteorological phenomena in aviation. To prevent accidents associated with these phenomena, it is necessary to clearly understand the patterns of their occurrence and spatial distribution. In connection with the rapid growth of passenger and cargo traffic, it is necessary to be able to receive and provide actual meteorological information in real mode, as well as to be able to receive high-quality and timely weather forecast. To study the spatial-temporal patterns of the distribution of thunderstorms and hail, Belgidromet’s meteorological instrumental data for 1989–2016 was processed, synoptic maps were analyzed in comparison with calculated forecasts, including WRF, and maps were made using ArcGIS.