1994 ASEM Conference Information and Registration Form

Abstract:

Complex investment decisions by corporate executives often require the comparison of dissimilar attributes and competing technologies. A technique to evaluate qualitative input from experts using a multi-criteria decision making (MCDM) method is described to select a new reactor technology for a merchant nuclear generator. The capital cost, risks from design, licensing and construction, reactor safety, and security considerations are some of the diverse considerations when choosing a reactor design. The uncertainty inherent in experts' opinions for the attribute weighting in the MCDM is modeled through the use of probabilistic inversion. After creating a distribution, random samples from the distribution are used to analyze the “strength” of the results. The decision results for the pool of experts identified the U.S. EPR as their optimal choice.     

Parametric simulation and performance analysis of a solar gas turbine power plant from thermodynamic and exergy perspectives

Using solar energy in gas turbine cycles is a new method that can improves the efficiency of gas turbines. Placing a solar receiver before a combustion chamber can raise the temperature of the air coming into the chamber and reduce the consumption of fuel in the chamber. The system that combines a solar energy receiver with a gas turbine cycle is technically called a “solar gas turbine”. The goal of this paper is the parametric simulation and performance analysis of a gas turbine cycle equipped with a solar receiver from thermodynamic and exergy aspects of view. The selected parameters in this study, include the pressure ratio of compressor, the temperature of gases at the turbine inlet and the direct normal irradiance. The obtained results indicate that the fuel consumption of this combined system is reduced by using a solar receiver and the temperature of gases entering the combustion chamber increased. The reduction of consumed fuel, in turn, reduces the rate of exergy destruction in the combustion chamber. Another important point is that the solar receiver itself has the least amount of exergy destruction. The net power generated by a solar gas turbine cycle is 10 % higher than that produced by a simple gas turbine cycle. Also, the studies show that the electrical efficiency of a solar gas turbine cycle is about 41 % higher than the simple gas turbine cycle.

     

Adaptive predictive control of a differential drive robot tuned with reinforcement learning

One of the most important steps in designing a model predictive control strategy is selecting appropriate parameters for the relative weights of the objective function. Typically, these are selected through trial and error to meet the desired performance. In this paper, a reinforcement learning technique called learning automata is used to select appropriate parameters for the controller of a differential drive robot through a simulation process. Results of the simulation show that the parameters always converge, although to different values. A controller chosen by the learning process is then ported to a real platform. The selected controller is shown to control the robot better than a standard model predictive control.     

A visible-light-active BiFeO<Subscript>3</Subscript>/ZnS nanocomposite for photocatalytic conversion of greenhouse gases

Given the changes in environmental conditions in the world, photocatalytic conversion of greenhouse gases is of great interest today. Our aim was to increase the photocatalytic efficiency of BiFeO₃/ZnS (p-n heterojunction photocatalyst) by varying the molar ratio of ZnS to perovskite structure of BiFeO₃ using hydrothermal synthesis. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), FT-IR spectroscopy showed the small crystal size and suitable distribution of ZnS particles on the BiFeO₃ structure. The results of UV-visible, and photoluminescence (PL) spectroscopy analyses showed the good behavior of p-n heterostructure in absorption of visible light and lowering electron-hole recombination. The best visible light photocatalytic efficiency of CO₂ reduction, 24.8%, was obtained by an equimolar ratio of BiFeO₃/ZnS.     

All-Grounded Passive Elements Voltage-Mode DVCC-Based Universal Filters

In this paper two new voltage-mode (VM) universal filters employing three plus-type differential voltage current conveyors (DVCC+s) and grounded passive elements are presented. The first proposed filter is a single-input five-output (SIFO) circuit which can realize simultaneously all of the standard responses, i.e. low-pass (LP), band-pass (BP), high-pass (HP), all-pass (AP) and notch (NH) from the same configuration. The second proposed circuit is a three-input single-output (TISO) universal filter for realizing standard responses depending on the selection of the input signal from the same topology. Both of the proposed filters have the advantage of a high input impedance, which enables easy cascading to obtain higher order filters. The proposed filters are simulated using the SPICE program to verify the theoretical analysis.     

Energy saving potential of an indirect evaporative cooler as a pre-cooling unit for mechanical cooling systems in Iran

The performance of indirect evaporative cooling system (IEC) to pre-cool air for a conventional mechanical cooling system has been investigated for four cities of Iran. For this purpose, a combined experimental setup consisting of an IEC unit followed by a packaged unit air conditioner (PUA) was designed, constructed and tested. Two air simulators were designed and used to simulate indoor heating load and outdoor design conditions. Using of experimental data and an appropriate analytical method, the performance and energy reduction capability of combined system has been evaluated through the cooling season. The results indicate IEC can reduce cooling load up to 75% during cooling seasons. Also, 55% reduction in electrical energy consumption of PUA can be obtained.     

Vibration control of structures using adjustable slippage elements

A new method for passive control of structural vibrations is introduced and investigated. The method is based on providing nonlinearity to the stiffness of a structure by installing elements with adjustable slippage in the proper locations. An adjustable slippage element (ASE) is a mechanical link with a two-branch elastic force–displacement response. The slippage threshold, which is the transition point between the two branches, can be adjusted within a relatively broad range, and can thus control the shape of the force–displacement curve of the element. An ASE can be used to rearrange the elastic restoring forces in the structure protected, and can be used separately or in combination with other passive control systems such as conventional damping devices. A structure equipped with such elements may gain enhanced dynamic performance, because the ASE redistributes elastic and plastic deformations, decreases force transmissibility, and improves resonance escape properties. These effects are achieved by separating the characteristic displacement within the ASE device among four prestressed elastic springs. The relative deformation between these elastic springs is controlled by their designed stiffness and also by the level of prestressing. The latter also controls the value of the slippage threshold of the device. The present study investigates the behavior and effectiveness of the proposed elements by considering a single-degree-of-freedom (SDOF) system equipped with an ASE and subjected to harmonic loading and earthquake base excitation.     

Topological aspects of meshless methods and nodal ordering for meshless discretizations

The meshless element‐free Galerkin method (EFGM) is considered and compared to the finite‐element method (FEM). In particular, topological aspects of meshless methods as the nodal connectivity and invertibility of matrices are studied and compared to those of the FE method. We define four associated graphs for meshless discretizations of EFGM and investigate their connectivity. The ways that the associated graphs for coupled FE‐EFG models might be defined are recommended. The associated graphs are used for nodal ordering of meshless models in order to reduce the bandwidth, profile, maximum frontwidth, and root‐mean‐square wavefront of the corresponding matrices. Finally, the associated graphs are numerically compared. Copyright © 2001 John Wiley & Sons, Ltd.