Lyapunov Analysis of Two Imbalanced Power System Areas

The transient stability is the capability of the system to preserve synchronism while being affected by large disturbances. It is a nonlinear problem that requires a simultaneous solution for many differential equations. Therefore, a thorough analysis is needed to resolve it. In this paper, we present the transient stability for multimachine under different fault cases and to analyze using the Lyapunov function. It serves as an analytical tool to determine the necessary condition to be stable. The system is stable as long as it is contained in the region of attraction. Meanwhile, the swing equation and reduced admittance matrix are used to model the system in three conditions, pre-fault, during the fault, and post-fault. The numerical simulations are conducted to verify that the synchronism can be preserved despite under faults on the transmission lines by achieving the critical clearing time.

Modeling Non-Cooperative Water Use in River Basins

Conventional water use and management models have mostly emulated purposefully designed water use systems where centralized governance and rule-based cooperation of agents are assumed. However, water use systems, whether actively governed or not, involve multiple, independent decision makers with diverse and often conflicting interests. In the absence of adequate water management institutions to effectively coordinate decision processes on water use, water users’ behaviors are rather likely to be non-cooperative, meaning that actions by individual users generate externalities and lead to sub-optimal water use efficiency. The objective of this review is to evaluate the advantages and disadvantages of recently proposed modeling systems dealing with non-cooperative water use regarding their ability to realistically represent the features of complex hydrological and socioeconomic processes and their tractability in terms of modeling tools and computational efficiency. For that purpose, we conducted a systematic review of 47 studies that address non-cooperative water use in decentralized modeling approaches. Even though such a decentralized approach should aim to model decisions by individual water users in non-cooperative water use, we find that most studies assumed the presence of a coordinating agency or market in their model. It also turns out that most of these models employed a solution procedure that sequentially solved independent economic decisions based on pre-defined conditions and heuristics, while only few modeling approaches offered simultaneous solution algorithms. We argue that this approach cannot adequately capture economic trade-offs in resource allocation, in contrast to models with simultaneous solution procedures.

Dynamic Modelling and Simulation of a Multistage Flash Desalination System

As the leading thermal desalination method, multistage flash (MSF) desalination plays an important role in obtaining freshwater. Its dynamic modeling and dynamic performance prediction are quite important for the optimal control, real-time optimal operation, maintenance, and fault diagnosis of MSF plants. In this study, a detailed mathematical model of the MSF system, based on the first principle and its treatment strategy, was established to obtain transient performance change quickly. Firstly, the whole MSF system was divided into four parts, which are brine heat exchanger, flashing stage room, mixed and split modulate, and physical parameter modulate. Secondly, based on mass, energy, and momentum conservation laws, the dynamic correlation equations were formulated and then put together for a simultaneous solution. Next, with the established model, the performance of a brine-recirculation (BR)-MSF plant with 16-stage flash chambers was simulated and compared for validation. Finally, with the validated model and the simultaneous solution method, dynamic simulation and analysis were carried out to respond to the dynamic change of feed seawater temperature, feed seawater concentration, recycle stream mass flow rate, and steam temperature. The dynamic response curves of TBT (top brine temperature), BBT (bottom brine temperature), the temperature of flashing brine at previous stages, and distillate mass flow rate at previous stages were obtained, which specifically reflect the dynamic characteristics of the system. The presented dynamic model and its treatment can provide better analysis for the real-time optimal operation and control of the MSF system to achieve lower operational cost and more stable freshwater quality.

Mathematical Modeling of Technological Modes of Operation of Liquid Stamping of Aluminum Alloy AK7

In this paper we examine a mathematical model of solidification of the melt in a two-phase zone during the formation of forgings through liquid stamping. From the simultaneous solution of the Fourier equations of thermal conductivity for the melt, the two-phase zone, and the solid crust, the solidification kinetics has been established and the effect of external pressure on the temperature fields and components of the solidification time of hollow thin-walled forgings has been thoroughly assessed.

Synchronization Method and Detection of Sequent Signals in the Ultra Wide Band Channel

The physical features of ultra-wideband signals are considered. The well-known technical solutions for synchronizing signals during their accumulation are analyzed. The necessity of randomizing the temporal parameters of the following pulse their accumulation is substantiated. The main steps of the technique are described that allow the simultaneous solution of the problem of detecting sequential signals by accumulating them on the receiving side and synchronizing them. An assessment of the computational complexity of the technique is presented and recommendations for its practical application are given.

About magnetoelectric effect in a two-layer system ferromagnetic-piezoelectric

The theory of the direct magnetoelectric (ME) effect in a two-layer ferromagnet-piezoelectric structure is presented, differing from [1-4] is accurate accounting the heterogeneity of electric field through the thickness of the layer. The simultaneous solution of the equations of motion for the piezoelectric and ferromagnetic media made it possible to calculate numeral analytically the dependence of the frequency of the system's own mechanical oscillations on its parameters and determine the frequency dependence of the coefficient ME effect, and the consideration of system dissipative properties made it possible to estimate the maximum value of the coefficient ME coupling. The influence of the ME layer length on the structure natural frequencies and the coefficient of ME coupling is analyzed.

The Cogeneration Installations with Injection of Steam in the Course of Utilization

The possibility of effective use of technology of microbiological degradation for recycling of a phytogenesis with receiving biogas and further development of electric and thermal energy on the basis of small-sized gas turbine installation with injection of steam with two-level utilization of warmth is investigated. Settlement indicators of efficiency of GTU with injection of steam and the utilization boiler are given. Lower temperature condition in UVK of condensation type will allow to use less expensive materials for production of the heat exchanger and to increase a work resource. It is shown that when using this technology production of biogas which it can be useful is carried out it is used for complex development of energy that promotes economical, rational optimum use of natural resources with the simultaneous solution of the current problems in the field of protection of the surrounding environment connected with utilization and neutralization of solid municipal waste of consumption and production.