Search results for "Performance improvement"
showing 9 items of 19 documents
Improvement of DSSC performance by voltage stress application
2016
Dye-sensitized solar cells (DSSCs) are promising third generation photovoltaic devices given their potential low cost and high efficiency. Some factors still affect DSSCs performance, such structure of electrodes, electrolyte compositions, nature of the sensitizers, power conversion efficiency, long-term stability, etc. In this work we discuss the effect of electrical stresses, which allow to improve DSSC performance. We have investigated the outcomes of forward and reverse DC bias stress as a function of time, voltage, and illumination level in the DSSCs sensitized with the N719, Ruthenium complex based dye. We demonstrate that all the major solar cell parameters, i.e., open circuit voltag…
Quasi-nash equilibria for non-convex distributed power allocation games in cognitive radios
2013
In this paper, we consider a sensing-based spectrum sharing scenario in cognitive radio networks where the overall objective is to maximize the sum-rate of each cognitive radio user by optimizing jointly both the detection operation based on sensing and the power allocation, taking into account the influence of the sensing accuracy and the interference limitation to the primary users. The resulting optimization problem for each cognitive user is non-convex, thus leading to a non-convex game, which presents a new challenge when analyzing the equilibria of this game where each cognitive user represents a player. In order to deal with the non-convexity of the game, we use a new relaxed equilib…
Fuzzified Game Tree Search – Precision vs Speed
2012
Most game tree search algorithms consider finding the optimal move. That is, given an evaluation function they guarantee that selected move will be the best according to it. However, in practice most evaluation functions are themselves approximations and cannot be considered "optimal". Besides, we might be satisfied with nearly optimal solution if it gives us a considerable performance improvement. In this paper we present the approximation based implementations of the fuzzified game tree search algorithm. The paradigm of the algorithm allows us to efficiently find nearly optimal solutions so we can choose the "target quality" of the search with arbitrary precision --- either it is 100% (pr…
Performance improvement of a novel combined water turbine
2020
Abstract Nowadays, industrials and researchers are looking for renewable energy resources due to the increase of energy demand. Recently, the ability of combined turbines in harnessing energy from water current has increased their renewed interest. However, there still exist a big knowledge gap to select the optimal design of these turbines. In this paper, systematic studies of stand-alone helical Savonius and delta bladed Darrieus turbines were carried out using experimental methods as a precursor to analyze their roles in hybrid configuration. By varying the attachment angle, two hybrid configurations were tested experimentally. Using the optimal attachment angle, six hybrid configuration…
Test-Bed Evaluation of CA and CF via a Software Defined Radio
2019
In Chaps. 3 and 4, we presented the analytical models and simulation approaches to study the impact of CA and CF on traffic flows in the single-flow single-user and the single-flow multi-user systems. In this chapter, we investigate the impact of CA and CF in a test-bed. We employ a software defined radio (SDR) from National Instruments (NI) to evaluate the performance of a CR system with user datagram protocol (UDP) flows. The adopted SDR is based on LTE protocol stack with additional functionalities that can support CA and CF, and accommodating PUs. By conducting measurements based on the test-bed system, we will be able to confirm that performance improvement can indeed be obtained by ap…
A Dynamic Viewpoint to Design Performance Management Systems in Academic Institutions: Theory and Practice
2014
This article illustrates how to design and apply Performance Management systems in academic institutions by identifying and modeling those factors affecting academic performance through a dynamic performance management view. Particularly, combining performance management with System Dynamics modeling may allow academic decision-makers to better identify key performance drivers for pursuing a sustainable performance improvement in universities. In the second section of the article, a number of examples based on empirical findings from a field project aimed at designing a dynamic performance management model for the University of Palermo (Italy) are discussed.
Understanding short- and long-term implications of “myopic” fleet maintenance policies: a system dynamics application to a city bus company
2010
Financial losses recorded in city bus companies often force managers to implement restructuring strategies aimed at improving business results. However, such decisions may not produce the expected consequences for a number of reasons. Both the internal and external environment in which such companies operate can make the design and implementation of long-term sustainable policies quite difficult. In fact, the result may be that decision makers introduce "effective" policies in a company subsystem, while ignoring the medium- and long-term implications of such decisions in the performance of the whole company. With the aim to detect the main causes underlying "myopic" fleet maintenance polici…
Performance improvement of a Savonius water rotor with novel blade shapes
2021
Abstract Savonius water rotor is a prominent drag based turbine able to extract energy available in flowing water with low velocity like river streams, tidal currents or other man made water canals. However, in view of its low performance, an enhanced design of the rotor blades is necessary to better its efficiency. Therefore, the present study aims to improve the efficiency of Savonius rotor by changing the blade design. Different blade shapes were investigated numerically using computational fluid dynamics (CFD). Using conventional design, the peak power coefficient was found to be 0.166 at tip-speed ratio of 0.78. However, the peak power coefficient reaches 0.184 using the optimal blade …
Anomalous electrical parameters improvement in Ruthenium DSSC
2018
. In this work, we present a series of measurements carried out on Ruthenium-based Dye Sensitized Solar Cells (DSSCs) after the application of different external electrical field values. Such measurements have been performed both in the dark and by illuminating the sample with sunlight emitted by a solar simulator (AM1.5G spectrum with a power irradiance of 1000 W/m2). Our results demonstrate that the initial electrical bias field modifies in both cases the behavior of the cell in terms of an anomalous improvement of the main electrical parameters.