Lubienska Cristina L.J. Ribeiro

Evaluation of Optimization Algorithms to Adjust Efficiency Curves for Hydroelectric Generating Units

AbstractThe power generated by a hydroelectric plant depends on the penstock head loss, the turbine efficiency, and the generator efficiency among other factors. Initially, the functions related to these variables are provided by the equipment manufacturer; however, over time they change as the plant ages. This paper presents a methodology to adjust an efficiency function for each generating unit based on measured data. It is applied using two optimization methods: the generalized reduced gradient and the evolutionary algorithm. A case study with data from a large Brazilian hydroelectric plant demonstrates how the methodology can be employed and compares the performance of the optimization tools. A comparison metric is used to show that the optimal unit efficiency function significantly improves the performance of simulation models to reproduce observed data and better describe the actual operation of the hydroelectric plant.

Effects of Consumption of Cement in Mechanical Properties of Lightweight Concrete Containing Brazilian Expanded Clay

Concrete is one of the oldest building materials known to humankind. From 1824, with the advent of Portland cement, concrete assumed a prominent place among the construction materials, due to large amounts of strength, durability and versatility it offered compared to other products, allowing the molding of various forms architectural. Until the early 80s, the concrete remained only as a mixture of cement, aggregates and water, however, in recent decades, due to the development of new techniques and products, the concrete has been undergoing constant changes. The concrete with lightweight aggregates have been used since the beginning of the last century, with low values of density (< 2000 kg/m3), demonstrating the great potential of using this material in several areas of construction [. With the objective of analyzing the influence of the consumption of cement in conventional concrete and light, were molded, tested and compared body-of-evidence containing two different amounts of cement consumption: a) 350 kg/m3 and b) 450 kg / m3. The results were compared with those obtained by other researchers, as well as with [ and [.

Evaluation of the Behaviour of Mortar with the Addition of Rubber

This research studies the mechanical behaviour of mortars with the addition of increasing percentages of rubber from used tires. This type of mortaris usually destined to wall coating and components, in which case it should present the required properties. In this study natural sand has been partially substituted by fine aggregate from recycled rubber and the hard state properties have been evaluated. The results obtained indicate the technical viability of the substitution. With the use of recycled aggregate the quality of the mortars has been preserved, which shows the possibility to properly adequate the destination of discharged rubber aiming to minimize environmental impacts and to reduce natural sand extraction from non renewable sources.

Using genetic algorithm to define the governor parameters of a hydraulic turbine

There are several governor architectures, but in general, all of them are designed to maintain the controlled variable fluctuations within acceptable range. The Proportional, Integral and Derivative (PID) governor is one of the types used to regulate a hydraulic turbine, in which the deviation of the variable controlled is corrected through earnings proportional, integral and derivative. For a definition of the governor parameters and its stability analysis there are several methods that in general can be classified into a time domain and frequency domain. The frequency domain method, based on the control theory, have ease application, expeditious manner of obtaining the parameters, but the physical phenomena involved are linearized. However the time domain methods are more difficult to be applied, but have the advantage of being able to take into account the non-linearities presents in physical phenomena. Despite the time-domain method offers advantages, it does not provides a structured way to optimize the parameters of the governor, since the parameters are obtained through simulations with adopted values. This paper presents a methodology to obtain the turbine governor appropriate parameters through a hybrid model (simulation and optimization model), based on method of characteristic to the hydraulic simulation (time domain) and Genetic Algorithm (GA) to obtain appropriate values. Examples are presented showing the application of the proposed methodology.

Contribution from the Use of Alternative Materials in Concrete for Accessibility on Sidewalks

This study aims to address the question of accessibility on sidewalks in accordance with Rule 9050 of the Brazilian Association of Technical Standards (ABNT NBR 9050:2004) and analyze the feasibility of using alternative materials (steel fibers, construction waste and rubber) to produce Interlocking tactile concrete paver. It was performed an experimental dosage of concrete with 04 specimens: reference, with steel fiber, with rubber and with steel fiber and construction waste. The pavers molded with conventional concrete and with the addition of alternative materials were tested as for compression strength and water absorption and the results were satisfactory, meeting the specifications of the Brazilian standard.

Interlocking Tactile Concrete Paver with Addition of Steel Fibers

This work deals with the investigation of the performance of concrete with addition of steel fibers for production of interlocking paver. Was accomplished an experimental dosage of concrete and the addition fibers contents were 40Kg/m3, the molded pavers with conventional concrete and with addition of steel fibers and were accomplished tests of compression strength and water absorption, through the preliminary results, we verified that are satisfactory and achieve the specifications of Brazilian standard (ABNT NBR 9781:2013) and some international (ASTM-C936:1996 e CSA A231.2:1995).

Management of Gypsum in Construction Site - Case Study

The waste generated by the construction sector have increased significantly, becoming an increasing problem, since most of this waste is deposited irregularly, not giving its proper disposal. Such waste, if not disposed properly contribute to environmental degradation, affecting not only the environment, but also, the quality of life. The gypsum products are among the wastes of this activity. Gypsum is a material that has many applications in the construction and generates significant volume of waste that most often is not reused, and usually has its final destination in landfills or dumps. The objective of this research was check on a construction site what kinds of alternatives are used for the management of waste gypsum in the building. The plaster can be recycled easily, being used in the production of cement. For the realization of recycling, theres the ATT - Transshipment Areas and Screening, in which they receive the plaster and other residues to prepare them for their industrial reuse. This way you can properly allocate the waste gypsum, without causing environmental damage and promoting better management of the construction site. Keywords: recycling of gypsum, management of construction site.

PSO Applied to Reduce the Cost of Energy in Water Supply Networks

The growth of urban population and subsequent expansion of the cities impose difficulties of gather a reliable water supply systems that attend the fluctuations of demand throughout the day, and their operation with appropriate hydraulic and operational parameters. The search of better routines for water pumping stations with both starting and stopping of pumps or use of variable speed devices has become increasingly common, and the motivation of this search is found in the need for energy saving. But the task is arduous and becomes fertile field for the application of modern techniques and robust optimization. Noteworthy are currently those that seek their inspiration in nature systems, such as Particle Swarm Optimization, which is based on intelligence of groups, such as schools of fish or swarms of bee. By this way, the present work aims to contribute to the topic, developing a hybrid algorithm (simulator-optimizer) for determination of optimized routines for pumping station i.e., routines that seek the best operational routine for an extended period of 24 hours.

Implementation of Environmental Management on a Construction Site

The Construction sector in Brazil has increased significantly, and the waste from these activities are becoming an increasing problem, thus receiving special attention, especially in recent decades, since a lot of them are deposited irregularly without proper disposal. Such waste, if not disposed properly, help environmental degradation, affecting not only the environment, but also, the quality of life. The objective of this research was to evaluate procedures that contribute to the development of sustainable management of construction waste, aiming to reduce, reuse and recycling of materials. Deploying a methodology for sorting waste more suitable for the work and for the monitoring and control suitable for final disposal, able to meet the legislation.

Mechanical Evaluation of Concrete Containing Lightweight Aggregates

Since the invention of modern concrete, in the mid-nineteenth century until the early 80s, the concrete remained a mixture of aggregate, cement and water, with no major innovations that significantly alter the performance of its properties. But in recent decades, concrete technology has undergone tremendous development that has occurred due to the development of techniques and equipment for the study of the concrete and the use of new materials.The concrete with lightweight aggregate have been used, mainly due to the low values of density, thus demonstrating the great potential of using this material in several areas of construction [.With the objective of analyzing the influence of the consumption of cement in conventional concrete and light, were molded, tested and compared body-of-evidence containing two different values of cement consumption. The values were compared with those obtained by other researchers, as well as with the ABNT NBR 6118:2003 [ and ACI 213R-03:2003 [.