Hopf bifurcation index for large scale power systems

In this paper, we propose a novel index for the prediction of the Hopf bifurcation (HB) in power systems. The proposed index has strictly less processing load and less computation time in comparison to former HB indices. It also uses modern control properties of the power system such as system matrix and critical eigenvalue. Therefore, stochastic subspace system identification (SSSI) is used as a tool for estimation and prediction of the proposed HB index. Combining beneficial properties of SSSI methods and the processing advantages of the proposed index, we project a new algorithm for power system monitoring. The algorithm is easy and straight-forward. We conduct several test conditions for the proposed materials using 2-area 4-machine system, New England 10-Machine and IEEE 50-machine system. Simulation outcome expresses good performance of proposed index in comparison to former HB indices. The proposed index has fairly linear behavior, without discontinuities with respect to increases of system load. It also has less computation load.     

Design and Numerical Simulation of a Symbiotic Thermoelectric Power Generation System Fed by a Low-Grade Heat Source

All liquid heating systems, including solar thermal collectors and fossil-fueled heaters, are designed to convert low-temperature liquid to high-temperature liquid. In the presence of low- and high-temperature fluids, temperature differences can be created across thermoelectric devices to produce electricity so that the heat dissipated from the hot side of a thermoelectric device will be absorbed by the cold liquid and this preheated liquid enters the heating cycle and increases the efficiency of the heater. Consequently, because of the avoidance of waste heat on the thermoelectric hot side, the efficiency of heat-to-electricity conversion with this configuration is better than that of conventional thermoelectric power generation systems. This research aims to design and analyze a thermoelectric power generation system based on the concept described above and using a low-grade heat source. This system may be used to generate electricity either in direct conjunction with any renewable energy source which produces hot water (solar thermal collectors) or using waste hot water from industry. The concept of this system is designated “ELEGANT,” an acronym from “Efficient Liquid-based Electricity Generation Apparatus iNside Thermoelectrics.” The first design of ELEGANT comprised three rectangular aluminum channels, used to conduct warm and cold fluids over the surfaces of several commercially available thermoelectric generator (TEG) modules sandwiched between the channels. In this study, an ELEGANT with 24 TEG modules, referred to as ELEGANT-24, has been designed. Twenty-four modules was the best match to the specific geometry of the proposed ELEGANT. The thermoelectric modules in ELEGANT-24 were electrically connected in series, and the maximum output power was modeled. A numerical model has been developed, which provides steady-state forecasts of the electrical output of ELEGANT-24 for different inlet fluid temperatures.     

Electric Power Generation from Thermoelectric Cells Using a Solar Dish Concentrator

In this paper, design details, theoretical analysis, and outcomes of a preliminary experimental investigation on a concentrator thermoelectric generator (CTEG) utilizing solar thermal energy are presented. The designed CTEG system consisted of a parabolic dish collector with an aperture diameter of 1.8 m used to concentrate sunlight onto a copper receiver plate with 260 mm diameter. Four BiTe-based thermoelectric cells (TEC) installed on the receiver plate were used to convert the concentrated solar thermal energy directly into electric energy. A microchannel heat sink was used to remove waste heat from the TEC cold side, and a two-axis tracking system was used to track the sun continuously. Experimental tests were conducted on individual cells and on the overall CTEG system under different heating rates. Under maximum heat flux, a single TEC generator was able to produce 4.9 W for a temperature difference of 109°C, corresponding to 2.9% electrical efficiency. The overall CTEG system was able to produce electric power of up to 5.9 W for a 35°C temperature difference with a hot-side temperature of 68°C. The results of the investigation help to estimate the potential of the CTEG system and show concentrated thermoelectric generation to be one of the potential options for production of electric power from renewable energy sources.     

Bed moisture estimation by monitoring of air stream temperature rise in packed-bed solid-state fermentation

We develop a method for predicting the moisture content of the fermenting solids in an intermittently mixed packed-bed bioreactor on the basis of measurements of the inlet and outlet gas stream temperatures and the assumption that both the gas streams are saturated with water vapor. This method can be used to estimate when an intermittently mixed packed bed should be mixed and how much water should be added during the mixing event. The predictions were experimentally verified for the growth of Aspergillus niger on wheat bran in a thin packed bed. We show that the application of a controller based on our estimation method would have led to adequate moisture control, with significant errors in moisture content prediction only occurring after the last mixing and water-addition event. Our method therefore represents a simple and practical method that can be incorporated into control schemes for intermittently mixed solid-state fermentation bioreactors with forced aeration.     

Conceptual Model for Collaborative Planning in Iran with Emphasis on the Role of Urban Planners： A Case Study of Anzali＇s Development Strategy

Nowadays, public participation is one of the most important factors to improve the feasibility, legitimacy and quality of urban plans. In Iran, due to lack of comprehensive understanding about the participation notion and its necessary socio-economic and political infrastructures, participatory decision-making has faced with some serious challenges in both processes of preparing and implementing. The present paper focuses on providing practical strategies for preparing collaborative urban plans in Iran＇s conditions. Also it seeks to answer this question： What is the role of planners to prepare a real collaborative plan？ It is assumed that a conceptual model for collaborative planning can be fitted with Iran＇s conditions by means of integrating the fundamental philosophic ideas of participatory planning such as theories of Paul Michel Foucault and Jürgen Habermas, given the fact that the present situation of collaborative planning in Iran needs a supportive theory which is compatible with power structures of Iranian urban planning system. In this regard, the Habermas＇ theory of “communicative action” and the Foucault＇s theory of “power structures” are reviewed by a comparative analysis methodology to present an integrated conceptual model for collaborative planning in Iran＇s condition. At the end, the CDS （City Development Strategy）---making process of Anzali City of Iran is analysed to examine this claim in the practice. The results yield that enabling urban planners to act as communication facilitators during planning can direct the collaborative planning in Iran from theory to a real practice by means of integrating the positive aspects of communication and power.     

Design and analysis of a split reaction water turbine

This paper explores the performance characteristics of a split reaction water turbine. The governing equations are derived by using the principles of conservation of mass, momentum and energy for a practical case, which includes consideration of frictional losses. The optimum diameter for a simple reaction turbine is defined and an equation for the optimum diameter is derived. Design and building procedures for a split reaction turbine are described. Using the equation for optimum diameter and assuming a loss factor (k-factor) of 0.05, optimum rotor diameters for different operating heads and rotational speeds are plotted and discussed. Measured performance of a 122 mm diameter split reaction water turbine rotor is presented. The relationship between k-factor and relative velocity for a split reaction turbine model is discussed with reference to experimental data.     

Fuzzy Bayesian system reliability assessment based on prior two‐parameter exponential distribution under different loss functions

The fuzzy Bayesian system reliability assessment based on prior two‐parameter exponential distribution under squared error symmetric loss function and precautionary asymmetric loss function is proposed in this paper. In order to apply the Bayesian approach, the fuzzy parameters are assumed as fuzzy random variables with fuzzy prior distributions. Because the goal of the paper is to obtain fuzzy Bayes point estimators of system reliability assessment, prior distributions of location‐scale family has been changed to scale family with change variable. On the other hand, also the computational procedures to evaluate the membership degree of any given Bayes point estimate of system reliability have been provided. In order to achieve this purpose, we transform the original problem into a non‐linear programming problem. This non‐linear programming problem is then divided into four sub‐problems for the purpose of simplifying computation. Finally, the sub‐problems can be solved by using any commercial optimizers, e.g. GAMS or LINGO. Copyright © 2010 John Wiley & Sons, Ltd.     

Intelligent power management strategy of hybrid distributed generation system

This paper describes a novel control strategy for active power flow in a hybrid fuel cell/battery distributed generation system. The method introduces an on-line power management by a hierarchical hybrid controller between dual energy sources that consist of a battery bank and a solid oxide fuel cell (SOFC). The proposed method includes an advance supervisory controller in the first layer which captures all of the possible operation modes. This layer has been developed by Stateflow toolbox and prepares a proper supervisory environment for this complex structure. In the second layer, an advanced fuzzy controller has been developed for power splitting between battery and fuel cell. With regards to the operation modes, the upper layer makes decision to choose the switching chain rules and corresponding controller in the second layer. Finally in the third layer, there are local controllers to regulate the set points of each subsystems to reach the best performance and acceptable operation indexes. Simulation results of a test system illustrate improvement in the operation efficiency of the hybrid system and the battery state of charge has been maintained at a reasonable level.     

Enumeration Order Equivalence in Rational Numbers

The enumeration of elements of c.e. sets in the theory of computability and computational complexity has already been investigated. However, the order of this enumeration has received less attention. The enumeration orders of elements of c.e. sets by means of Turing machines on natural numbers are investigated. In this paper, we consider the enumeration orders of elements of c.e. sets on rational numbers. We present enumeration order reducibility and enumeration order equivalence on rational numbers and propose some lemmas and theorems on these concepts. Also, we show that the theories here hold for Rc and we could repeat the same theories in this domain, in a same way.     

Application of artificial neural networks and genetic programming in vapor–liquid equilibrium of C1 to C7 alkane binary mixtures

In this study, the capacity of artificial neural networks (ANNs) and genetic programming (GP) in making possible, fast and reliable predictions of equilibrium compositions of alkane binary mixtures is investigated. A data set comprising 847 data points was gathered and used in both training the proposed ANN and generating the closed-form expressions of the GP procedure. The results obtained demonstrate the relative precision of the proposed ANN, while, on the other hand, exhibit that the GP model, although less precise, affords high CPU time efficiency and simplicity. Concisely, the proposed models can serve the purpose of being close first estimates for more thermodynamically rigorous vapor–liquid equilibrium calculation procedures and do obviate the necessity for the availability of a large set of experimental binary interaction coefficients. Mean absolute errors of 0.0100 and 0.0404 for liquid compositions and of 0.0054 and 0.0254 for vapor-phase mole fractions, for the proposed ANN and GP models, respectively, are a testament to the reliability of the proposed models.