Regression analysis of spectroscopic process data using a combined architecture of linear and nonlinear artificial neural networks

Author(s):  
S.E. Lee ◽  
B.R. Holt
Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 18
Author(s):  
Rahel Jedamski ◽  
Jérémy Epp

Non-destructive determination of workpiece properties after heat treatment is of great interest in the context of quality control in production but also for prevention of damage in subsequent grinding process. Micromagnetic methods offer good possibilities, but must first be calibrated with reference analyses on known states. This work compares the accuracy and reliability of different calibration methods for non-destructive evaluation of carburizing depth and surface hardness of carburized steel. Linear regression analysis is used in comparison with new methods based on artificial neural networks. The comparison shows a slight advantage of neural network method and potential for further optimization of both approaches. The quality of the results can be influenced, among others, by the number of teaching steps for the neural network, whereas more teaching steps does not always lead to an improvement of accuracy for conditions not included in the initial calibration.


2010 ◽  
Vol 102-104 ◽  
pp. 846-850
Author(s):  
Wen Yu Pu ◽  
Yan Nian Rui ◽  
Lian Sheng Zhao ◽  
Chun Yan Zhang

Appropriate selecting of process parameters influences the machining quality greatly. For honing, the main factors are product precision, material components and productivity. In view of this situation, a intelligence selection model for honing parameter based on genetics and artificial neural networks was built by using excellent robustness, fault-tolerance of artificial neural networks optimization process and excellent self-optimum of genetic algorithm. It can simulate the decision making progress of experienced operators, abstract the relationship from process data and machining incidence, realize the purpose of intelligence selection honing parameter through copying, exchanging, aberrance, replacement strategy and neural networks training. Besides, experiment was performed and the results helped optimize the theories model. Both the theory and experiment show the updated level and feasibility of this system.


Author(s):  
Lucas M. Amorim ◽  
Elton da S. Leite ◽  
Deoclides R. de Souza ◽  
Liniker F. da Silva ◽  
Carlos R. de Mello ◽  
...  

ABSTRACT Modeling is an important tool to estimate forest production in planted areas. Although this issue has been studied worldwide, knowledge regarding volume measurement in specific locations such as Northeast Brazil is still scarce. The present study aimed to evaluated the effectiveness of artificial neural networks (ANNs) and regression analysis in estimating the timber volume of homogeneous stands of Anadantera macrocarpa, Genipa americana, and Mimosa casalpinifolia, in order to better predict the growth and production of these species. Both methods were suitable for estimating the individual volume in 7-year-old stands with different spacing. The Spurr regression model showed better statistical results and dispersion of unbiased errors for Anadantera macrocarpa and Genipa americana, whereas the Shumacher-Hall model provided more accurate volume estimates for Mimosa caesalpinifolia. The ANNs calibrated with two neurons in the middle layer exhibited the best fit for all three species. As such, artificial neural networks can be recommended to estimate the individual volumes of the species analyzed in the study area.


Author(s):  
S. V. Guzhov

Forecasting the demand for thermal energy by energy complexes of buildings and structures is an urgent task. To achieve the necessary accuracy of the calculation, it is customary to use various deterministic methods based on the available changing and slightly changing data about the object of study. At the same time, statistical data can also be used in analysis by stochastic methods. The purpose of this article is to analyze the question of the admissibility of combining deterministic and stochastic approaches in order to increase the accuracy of the calculation. Formulas for calculating the components of the expenditure part of the heat balance are shown on the example of a building for water sports. Based on the above formulas, a calculation with a monthly discretization in the period from January 2009 is carried out. until January 2019. An example is given of calculating the accuracy of the forecast of demand for thermal energy through multivariate regression analysis and the use of artificial neural networks. Based on the same data, an artificial neural network was trained on seven different factors: six independent and seventh — the idealized value of the building’s heat loss through the building envelope. An example of the analysis of a building for practicing water sports shows the inadmissibility of the described approach if the same initial data are used in the deterministic and stochastic method. Results: the accuracy of the forecast made using regression analysis increases with an increase in the number of factors. However, the use of an additional group of factors in the stochastic method, for example, which are numerically processed climate data that are already used as initial data, will lead to an unreasonable overestimation of the significance of the twice used factor. The presence in the predictive models using artificial neural networks of collinearity and multicollinearity of variables does not negatively affect the forecast. Conclusion: the combination of the deterministic and stochastic approaches in preparing the predicted heat balance by using only the same input data that is used in the stochastic approach in the deterministic approach is unacceptable.


2021 ◽  
Vol 10 (5) ◽  
pp. 293
Author(s):  
Blerina Vika ◽  
Ilir Vika

Albanian economic time series show irregular patterns since the 1990s that may affect economic analyses with linear methods. The purpose of this study is to assess the ability of nonlinear methods in producing forecasts that could improve upon univariate linear models. The latter are represented by the classic autoregressive (AR) technique, which is regularly used as a benchmark in forecasting. The nonlinear family is represented by two methods, i) the logistic smooth transition autoregressive (LSTAR) model as a special form of the time-varying parameter method, and ii) the nonparametric artificial neural networks (ANN) that mimic the brain’s problem solving process. Our analysis focuses on four basic economic indicators – the CPI prices, GDP, the T-bill interest rate and the lek exchange rate – that are commonly used in various macroeconomic models. Comparing the forecast ability of the models in 1, 4 and 8 quarters ahead, we find that nonlinear methods rank on the top for more than 75 percent of the out-of-sample forecasts, led by the feed-forward artificial neural networks. Although the loss differential between linear and nonlinear model forecasts is often found not statistically significant by the Diebold-Mariano test, our results suggest that it can be worth trying various alternatives beyond the linear estimation framework.   Received: 19 June 2021 / Accepted: 25 August 2021 / Published: 5 September 2021


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