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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Modelos de previsão de tarifa de água, aplicados a autarquias municipais e empresas privadas, nas regiões Sul e Sudeste do Brasil /

Bezerra, Alberto Guilherme de Oliveira. January 2019 (has links)
Orientador: Marcelo Libânio / Resumo: O objetivo do presente trabalho é avaliar modelos de previsão de tarifa de água, aplicados a autarquias municipais e empresas privadas, nas regiões Sul e Sudeste do Brasil. Utilizando a metodologia de cálculo e posterior comparação dos erros obtidos para as previsões, verificando também a aplicabilidade das tarifas previstas para cada sistema de abastecimento. Utilizou-se dois modelos de previsão, o primeiro, fundamentado em técnicas de regressão linear múltipla e o segundo, baseado na aplicação de redes neurais artificiais. Avaliando, dessa forma, a capacidade de os dois modelos em questão preverem os valores tarifários a serem cobrados pelos prestadores de serviços de abastecimento de água e coleta de esgoto, a partir da análise das tarifas anteriormente praticadas. Os dados subsidiários para elaboração dos modelos foram obtidos por meio do sistema nacional de informações sobre saneamento (SNIS). Confirmada a consistência do banco de dados primário, procedeu-se com processamento destes dados, e definição das variáveis mais intervenientes para a definição da tarifa por meio da técnica de análise de correlação. Propôs-se a classificação dos sistemas de acordo com a classe jurídica do prestador de serviço, os cenários financeiros (superávit ou déficit) destes prestadores e o porte populacional dos municípios atendidos. Os resultados obtidos indicaram que os processos de previsão, em ambos os modelos utilizados, foram capazes de prever com elevada acurácia as tarifas, e garanti... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of the present work was evaluating forecasting models for water tariff applied to municipal and private companies in the South and Southeast regions of Brazil. Using the calculation methodology and subsequent comparison of the errors obtained for the forecasts, also verifying the applicability of the forecast tariffs for each supply system. Two prediction models are used, the first based on multiple linear regression techniques and the second based on the application of artificial neural networks. Evaluating, in this way, the ability of the two models in question to predict the tariff values to be charged by the water supply and wastewater collection service providers, based on the analysis of the tariffs previously practiced. The subsidiary data for the elaboration of the models were obtained through the national sanitation information system (SNIS). Confirming the consistency of the primary database, we proceeded with processing of these data and definition of the most intervening variables for the definition of the tariff through the correlation analysis technique. The classification of the systems according to the legal class of the service provider, the financial scenarios (surplus or deficit) of these providers and the population size of the municipalities served were proposed. The obtained results indicated that the forecasting processes, in both models used, were able to predict with high accuracy the tariffs, and guaranteed the maintenance of the surplu... (Complete abstract click electronic access below) / Mestre
272

Fusão de sensores para obtenção de dados de produtividade em colhedora de cana-de-açúcar / Fusion of sensors to obtain a yield data for sugarcane harvesters

Lima, Jeovano de Jesus Alves de 20 February 2019 (has links)
A cana-de-açúcar é uma importante cultura semi-perene em regiões tropicais do mundo como a principal fonte de açúcar e bioenergia e o Brasil é seu maior produtor. Como qualquer outra cultura, demanda um aperfeiçoamento prática constante, buscando uma cultura sustentável e com maiores rendimentos e menores custos. Uma das alternativas é a utilização de práticas de agricultura de precisão para explorar a variabilidade espacial dos rendimentos potenciais e para tanto, os mapas de produtividade são essenciais. Para obter os dados necessários para gerar um mapa confiável, é necessário um sistema com capacidade de ler e georreferenciar os dados do sensor e compará-los a uma calibração. No entanto, os resultados das pesquisas mais recentes associadas aos monitores de rendimento comercial, que utilizam apenas um tipo de sensor para determinar os mapas de produtividade, não retratam a exatidão exigida para a cana-de-açúcar. Este estudo teve como objetivo explorar o potencial do uso de dados provenientes de sensores instalados em diferentes partes da colhedora de cana-de-açúcar para determinação e aplicação em monitores de produtividade e determinação de falhas na lavoura. Para fins de comparação foi utilizado um transbordo instrumentado com células de carga para aferição da massa colhida. Foram utilizadas abordagens estatísticas convencionais e inteligência artificial para fusão dos dados e predição da produtividade da cana-de-açúcar, os métodos convencionais foram regressão linear simples e múltipla, e comparado com o método de redes neurais. Além da produtividade foi possível constatar que é possível identificar as falhas na lavoura através dos dados coletados e das falhas produzidas manualmente, todos os sensores medidos identificaram as falhas georeferenciadas. Com relação aos modelos implementados e utilizados, os baseados em regressão linear múltipla não apresentaram potencial na integração e predição da produtividade com os valores de erros definidos nas premissas do trabalho que é de menor que 2%. Além disso os mapas gerados com esses modelos tiveram algumas discrepâncias quanto ao aumento da produtividade em algumas áreas e extração das falhas existentes. Já o modelo de fusão utilizando redes neurais artificiais apresentou uma excelente alternativa para predição da produtividade. Uma vez que a rede é treinada, a mesma apresentou erros inferiores a 2% em todos os mapas gerados. De maneira geral todos os sensores quando avaliados individualmente apresentaram vantagens e desvantagens na determinação da produtividade. Porém, quando fundido os dados dos diversos sensores, as respostas encontradas apresentaram coeficiente de determinação R2 superiores a 95%, RMSE menor que 1kg e RE menor que 2%. / Sugarcane is an important semi-perennial crop in tropical regions of the world as the main source of sugar and bioenergy, and Brazil is its largest producer. Like any other culture, it demands constant improvement in practice, seeking a sustainable culture with higher yields and lower costs. One of the alternatives is the use of precision farming practices to explore the spatial variability of potential yields and for that, productivity maps are essential. To obtain the data needed to generate a reliable map, a system is required that is capable of reading and georeferencing the sensor data and comparing them to a calibration. However, the results of the most recent surveys associated with commercial yield monitors, which use only one type of sensor to determine productivity maps, do not depict the exactitude required for sugarcane. This study aimed to explore the potential of using data from sensors installed in different parts of the sugarcane harvester for determination and application in productivity monitors and determination of crop failure, for comparison purposes a transhipment was used instrumented with load cells to measure the mass harvested. We used conventional statistical approaches and artificial intelligence for data fusion and prediction of sugarcane productivity, conventional methods were simple and multiple linear regression, and compared with the neural network method. In addition to productivity, it was possible to verify that it is possible to identify crop failures through the data collected and the failures produced manually, all the measured sensors identified georeferenced faults. Regarding the implemented and used models, those based on multiple linear regression did not present potential in the integration and prediction of productivity with the values of errors defined in the assumptions of the work that is less than 2%. In addition, the maps generated with these models had some discrepancies regarding productivity increase in some areas and extraction of existing flaws. On the other hand, the model of fusion using artificial neural networks presented an excellent alternative for prediction of productivity; since the network is trained the same one presented in all the generated maps errors inferior to 2%. In a general way all the sensors when evaluated individually presented advantages and disadvantages in determining the productivity, but when fused the data of the various sensors the answers found of coefficient of determination R2 higher than 95%, RMSE less than 1kg and RE less than 2%.
273

Call-independent identification in birds

Fox, Elizabeth J. S. January 2008 (has links)
[Truncated abstract] The identification of individual animals based on acoustic parameters is a non-invasive method of identifying individuals with considerable advantages over physical marking procedures. One requirement for an effective and practical method of acoustic individual identification is that it is call-independent, i.e. determining identity does not require a comparison of the same call or song type. This means that an individuals identity over time can be determined regardless of any changes to its vocal repertoire, and different individuals can be compared regardless of whether they share calls. Although several methods of acoustic identification currently exist, for example discriminant function analysis or spectrographic cross-correlation, none are call-independent. Call-independent identification has been developed for human speaker recognition, and this thesis aimed to: 1) determine if call-independent identification was possible in birds, using similar methods to those used for human speaker recognition, 2) examine the impact of noise in a recording on the identification accuracy and determine methods of removing the noise and increasing accuracy, 3) provide a comparison of features and classifiers to determine the best method of call-independent identification in birds, and 4) determine the practical limitations of call-independent identification in birds, with respect to increasing population size, changing vocal characteristics over time, using different call categories, and using the method in an open population. ... For classification, Gaussian mixture models and probabilistic neural networks resulted in higher accuracy, and were simpler to use, than multilayer perceptrons. Using the best methods of feature extraction and classification resulted in 86-95.5% identification accuracy for two passerine species, with all individuals correctly identified. A study of the limitations of the technique, in terms of population size, the category of call used, accuracy over time, and the effects of having an open population, found that acoustic identification using perceptual linear prediction and probabilistic neural networks can be used to successfully identify individuals in a population of at least 40 individuals, can be used successfully on call categories other than song, and can be used in open populations in which a new recording may belong to a previously unknown individual. However, identity was only able to be determined with accuracy for less than three months, limiting the current technique to short-term field studies. This thesis demonstrates the application of speaker recognition technology to enable call-independent identification in birds. Call-independence is a pre-requisite for the successful application of acoustic individual identification in many species, especially passerines, but has so far received little attention in the scientific literature. This thesis demonstrates that call-independent identification is possible in birds, as well as testing and finding methods to overcome the practical limitations of the methods, enabling their future use in biological studies, particularly for the conservation of threatened species.
274

利用類神經網路估算國內電子股投資風險值績效

高世儒 Unknown Date (has links)
本研究首次提出以未來臨界報酬率為輸出變數,利用兩種類神經網路(Artificial Neural Network)估算國內電子股代表樣本報酬率的風險值(Value at Risk , VaR)。在研究設計上考慮到使用不同期長來計算自變項所帶來的影響而產生兩種預測方法。本研究並以回顧檢定(Backtesting )檢討藉由臨界值報酬率作為類神經估計法與一般以變異數/共變數法或蒙地卡羅模擬法所估算出VaR的差異。 綜合本研究,在學術及實務上的貢獻有下列四點: 1. 設計臨界報酬率作為估算VaR的方式,可以避免以往計算VaR時,報酬率分配主觀給定的問題。 2. 相關研究過去並未同時涉及類神經網路與VaR,而本研究首次應用類神經網路估算VaR。 3. 本文亦提出以多種不同的基本變數衡量期長來估算VaR,或可幫助界定差異的研究設計。 4. 本研究使用類神經網路可能的一項限制是報酬率臨界值 的設計方式;而類神經網路可能勝出其它預測工具的理由可能是 (1)學習到隱性因子的特性 (2)預測方式為非線性 (3)毋須依賴常態或特定分配之假設。以往類神經網路研究在賽馬決定各工具優劣時,較少探究類神經勝出或落敗的理由,而這卻是本研究設計的焦點。
275

應用神經網路於解決線性規劃問題之探討 / The Artificial Neural Networks for Linear Programming Problems

程至方, Cheng Chin-Fang Unknown Date (has links)
在此論文中,我們提出一個用來解釋線性規劃問題的類神經網路系統。這 個系統,我們取名為 LP-ANN 系統,它引用了能量函數(Energy Function)的概念及懲罰(Penalty)的方法。從這兩個概念,我們提出了一 個處理非負限制式的新想法。基本上,這個 LP-ANN 系統是以數位電腦來 做模擬,而不以類比式的電子電路來做模擬。這個系統可以判斷所給的線 性規劃問題是否有最佳解。如果有的話,再進一步找出一個符合可接受準 確度範圍內的最佳解。最後,以1200個任意產生的線性規劃問題來測試系 統的模擬結果也在本篇論文中詳述。
276

台股指數交易之研究 – EEMD與ANN方法 / Taiwan weighted stock index trading research-EEMD And ANN method

蔡橙檥 Unknown Date (has links)
在台灣證券市場中,有許多的技術分析方法或指標,市場參與者或財 務學者會利用歷史資料來做回溯測試,找出可運用的方法或指標,以此來 推測出台股加權指數未來的趨勢,也有學者利用類神經網路(Artificial Neural Network, ANN)考慮經濟景氣、技術分析指標等作為輸入變數來預測 台股加權指數,而本文則利用 EEMD(Ensemble Empirical Mode Decomposition)拆解出來的結果作為 ANN 的輸入變數,並將 ANN 預測出 的值轉換成 FK (Forward-calculated %K) 值,再搭配不同的交易方式,來 補捉台股加權指數的走勢,並比較各種交易方式的績效,找出一個能夠穩 定獲利的交易模型。
277

Embedded Intelligence In Structural Health Monitoring Using Artificial Neural Networks

Kesavan, Ajay, not supplied January 2007 (has links)
The use of composite structures in engineering applications has proliferated over the past few decades due to its distinct advantages namely: high structural performance, corrosion resistance, and high strength/weight ratio. However, they also come with a set of disadvantages, i.e. they are prone to fibre breakage, matrix cracking and delaminations. These types of damage are often invisible and if undetected, could lead to catastrophic failures of structures. Although there are systems to detect such damage, the criticality assessment and prognosis of the damage is often much more difficult to achieve. The research study conducted here resulted in the development of a Structural Health Monitoring (SHM) system for a 2D polymeric composite T-joint, used in maritime structures. The SHM system was found to be capable of not only detecting the presence of multiple delaminations in a composite structure, but also capable of determining the location and extent of all t he delaminations present in the T-joint structure, regardless of the load (angle and magnitude) acting on the structure. The system developed relies on the examination of the strain distribution of the structure under operational loading. This SHM system necessitated the development of a novel pre-processing algorithm - Damage Relativity Assessment Technique (DRAT) along with a pattern recognition tool, Artificial Neural Network (ANN), to predict and estimate the damage. Another program developed - the Global Neural network Algorithm for Sequential Processing of Internal sub Networks (GNAISPIN) uses multiple ANNs to render the SHM system independent to variations in structural loading and capable of estimating multiple delaminations in composite T-joint structures. Upto 82% improvement in detection accuracy was observed when GNAISPIN was invoked. The Finite Element Analysis (FEA) was also conducted by placing delaminations of different sizes at various locations in two structures, a composite beam and a T-joint. Glass Fibre Reinforced Polymer T-joints were then manufactured and tested, thereby verifying the accuracy of the FEA results experimentally. The resulting strain distribution from the FEA was pre-processed by the DRAT and used to trai n the ANN to predict and estimate damage in the structures. Finally, on testing the SHM system developed with strain signatures of composite T-joint structures, subjected to variable loading, embedded with all possible damage configurations (including multiple damage scenarios), an overall damage (location & extent) prediction accuracy of 94.1% was achieved. These results are presented and discussed in detail in this study.
278

Design and implementation of controller for robotic manipulators using Artificial Neural Networks

Chamanirad, Mohsen January 2009 (has links)
<p>In this thesis a novel method for controlling a manipulator with arbitrary number of Degrees of freedom is proposed, the proposed method has the main advantages of two common controllers, the simplicity of PID controller and the robustness and accuracy of adaptive controller. The controller architecture is based on an Artificial Neural Network (ANN) and a PID controller.</p><p>The controller has the ability of solving inverse dynamics and inverse kinematics of robot with two separate Artificial Neural Networks. Since the ANN is learning the system parameters by itself the structure of controller can easily be changed to</p><p>improve the performance of robot.</p><p>The proposed controller can be implemented on a FPGA board to control the robot in real-time or the response of the ANN can be calculated offline and be reconstructed by controller using a lookup table. Error between the desired trajectory path and the path of the robot converges to zero rapidly and as the robot performs its tasks the controller learns the robot parameters and generates better control signal. The performance of controller is tested in simulation and on a real manipulator with satisfactory results.</p>
279

Image Based Visualization Methods for Meteorological Data

Olsson, Björn January 2004 (has links)
<p>Visualization is the process of constructing methods, which are able to synthesize interesting and informative images from data sets, to simplify the process of interpreting the data. In this thesis a new approach to construct meteorological visualization methods using neural network technology is described. The methods are trained with examples instead of explicitely designing the appearance of the visualization.</p><p>This approach is exemplified using two applications. In the fist the problem to compute an image of the sky for dynamic weather, that is taking account of the current weather state, is addressed. It is a complicated problem to tie the appearance of the sky to a weather state. The method is trained with weather data sets and images of the sky to be able to synthesize a sky image for arbitrary weather conditions. The method has been trained with various kinds of weather and images data. The results show that this is a possible method to construct weather visaualizations, but more work remains in characterizing the weather state and further refinement is required before the full potential of the method can be explored. This approach would make it possible to synthesize sky images of dynamic weather using a fast and efficient empirical method.</p><p>In the second application the problem of computing synthetic satellite images form numerical forecast data sets is addressed. In this case a mode is trained with preclassified satellite images and forecast data sets to be able to synthesize a satellite image representing arbitrary conditions. The resulting method makes it possible to visualize data sets from numerical weather simulations using synthetic satellite images, but could also be the basis for algorithms based on a preliminary cloud classification.</p> / Report code: LiU-Tek-Lic-2004:66.
280

Feature based conceptual design modeling and optimization of variational mechanisms

Wubneh, Abiy 06 1900 (has links)
This research investigates and proposes methods to be used for the automation of the conceptual design phases of variational mechanisms. It employs the concept of feature-based modeling approaches. A method is proposed for integrating the dimensional synthesis, mechanical design and CAD generation phases with minimal designer intervention. Extended feature definitions are used in this research to create a smooth data transfer platform between different engineering tools and applications. This paper also introduces another method by which a set of dimensional data collected from a family of existing products is used to predict possible solutions for a new design. This method, based on artificial neural networks for training and solution generation, is used with optimization algorithms for the dimensional synthesis of mechanisms. An excavator arm mechanism is used as a case study to demonstrate these methods. The design of this mechanism is carried out based on its digging mode configurations. / Engineering Design

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