Abstract

We introduce a tool for simulation and optimization of gas pipeline networks coupled to power grids by gas-to-power plants. The model under consideration consists of the isentropic Euler equations to describe the gas flow coupled to the AC powerflow equations. A compressor station is installed to control the gas pressure such that certain bounds are satisfied. A numerical case study is presented that showcases effects of fast changes in power demand on gas pipelines and necessary operator actions. Document type: Part of book or chapter of book

Abstract

In this chapter the impact of realistic communication channels and uncertain location information on formation control of multi-agent systems aiming to achieve a common task is highlighted. First, the work is motivated by elucidating the need to incorporate realistic communication models as well as the need to model the agents’ location uncertainty. Second, it is discussed how control can be utilised to reduce the agents positioning error in cooperative systems to achieve a higher level goal, such as steering a group of agents towards a destination. Third, the impact of location uncertainty on channel gain prediction is addressed for formation control. Finally, conclusions and an outlook on future directions for controlled multi-agent systems are provided. Document type: Part of book or chapter of book

Abstract

The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) provides continuous full-disk observations of solar oscillations. We develop a data-analysis pipeline based on the time-distance helioseismology method to measure acoustic travel times using HMI Doppler-shift observations, and infer solar interior properties by inverting these measurements. The pipeline is used for routine production of near-real-time full-disk maps of subsurface wave-speed perturbations and horizontal flow velocities for depths ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic maps for the subsurface properties are made from these full-disk maps. The pipeline can also be used for selected target areas and time periods. We explain details of the pipeline organization and procedures, including processing of the HMI Doppler observations, measurements of the travel times, inversions, and constructions of the full-disk and synoptic maps. Some initial results from the pipeline, including full-disk flow maps, sunspot subsurface flow fields, and the interior rotation and meridional flow speeds, are presented. Document type: Part of book or chapter of book

Abstract

This paper explores the inter-connectedness of the evolution of transportation networks and land use through the application of a Markov Chain mode. The model investigates how individual cells, with both land use and transportation network attributes, change over time. While this paper does not consider land use density directly, it does not consider land use type, and as cells change, it can be concluded that some form of development is likely to be occurring. The next section of the paper outlines the Markov Chain model and a discussion of the Twin Cities data used in the study follows. The subsequent section develops the transition probability matrices used by the Markov Chain. Those matrices are analyzed in order to understand the empirical regularities that appear in the data. They are then applied to both assess the predictive ability of the Markov Chain model (comparing what the model would predict with what actually happened), and then applying the mode to forecast future changes the Twin Cities area. The paper concludes with some suggestions for future research. Document type: Part of book or chapter of book

Abstract

Network design models have wide applications in telecommunications and transportation planning; see, for example, the survey articles by Magnanti and Wong (1984), Minoux (1989), Chapter 16 of the book by Ahuja, Magnanti and Orlin (1993), Section 13 of Ahuja et al. (1995). In particular, Gavish (1991) and Balakrishnan et al. (1991) present reviews of important applications in telecommunications. In many of these applications, it is required to send flows (which may be fractional) to satisfy demands given arcs with existing capacities, or to install, in discrete amounts, additional facilities with fixed capacities. In doing so, one pays a price not only for routing flows, but also for using an arc or installing additional facilities. The objective is then to determine the optimal amounts of flows to be routed and the facilities to be installed. Document type: Part of book or chapter of book

Abstract

Stochastic hybrid systems arise in numerous applications of systems with multiple models; e.g., air traffc management, flexible manufacturing systems, fault tolerant control systems etc. In a typical hybrid system, the state space is hybrid in the sense that some components take values in a Euclidean space, while some other components are discrete. In this paper we propose two stochastic hybrid models, both of which permit diffusion and hybrid jump. Such models are essential for studying air traffic management in a stochastic framework. Document type: Part of book or chapter of book

Abstract

We are interested in the simulation and optimization of gas transport in networks. Different regions of the network may be modelled by different equations. There are three models based on the Euler equations that describe the gas flow in pipelines qualitatively different: a nonlinear model, a semilinear model and a stationary also called algebraic model. For the whole network, adequate initial and boundary values as well as coupling conditions at the junctions are needed. Using adjoint techniques, one can specify model error estimators for the simplified models. A strategy to adaptively apply the different models in different regions of the network while maintaining the accuracy of the solution is presented. Document type: Part of book or chapter of book

Abstract

One of the key issues in mobile communication system is how to predict the number of calls per each cell. It is an important parameter and usually assumed as random Poisson value. For effective management of cellular network, the average number of calls should be traced and the changes in the numbers need to be promptly detected. In this paper we propose an algorithm detecting the changes in the behavior of the users using the technique proposed for point-of-change problem based only on the number of call arrivals. Computer simulation reveals that the proposed method can effectively detect the discord, and the developed model is very accurate as showing mostly less than 1% differences. Document type: Part of book or chapter of book