Multivariate Analysis of the Main Operational Variables Involved in Steel Producing on BOF Using Time Series Tools

Simultaneous fault detection and isolation based on multi-task long short-term memory neural networks

In the estimation of future investments in the offshore wind industry, the operation and maintenance (O&M) phase plays an important role. In the simulation of the O&M figures, the weather conditions should contain information about the waves’ main characteristics and the wind speed. As these parameters are correlated, they were simulated by using a multivariate approach, and thus by generating vectors of measurements. Four different stochastic weather time series generators were investigated: Markov chains (MC) of first and second order, vector autoregressive (VAR) models, and long short-term memory (LSTM) neural networks. The models were trained on a 40-year data set with 1 h resolution. Thereafter, the models simulated 25-year time series, which were analysed based on several time series metrics and criteria. The MC (especially the one of second order) and the VAR model were shown to be the ones capturing the characteristics of the original time series the best. The novelty of this paper lies in the application of LSTM models and multivariate higher-order MCs to generate offshore weather time series, and to compare their simulations to the ones of VAR models. Final recommendations for improving these models are provided as conclusion of this paper.

The vector auto-regressive (VAR) model is one of the most successful, flexible, and easy to use models for the analysis of multivariate time series. It is a natural extension of the univariate auto-regressive model to a dynamic multivariate time series.The VAR model has proven to be especially useful for describing the dynamic behavior of economic and financial time series and for forecasting. It often provides superior forecasts to those from univariate time series models. The data used are monthlyobservations from January 2006 to October 2016 of Nigeria Crude Oil price and Naira to the dollar exchange rate. The VAR model was employed for modelling the data. The unit root test reveals that all the series are non-stationary at the level and stationary at first difference. The co-integration relations among the series indices were identified by applying Johansen’s cointegration test. The result of Johansen’s test indicates no existence of co-integration relation between the variables. The final result shows that a vector autoregressive (VAR) model of lag three with no co-integration equations best fits the data.

Summary Accurate prediction of subsurface fluid production remains a significant challenge in geoenergy engineering. To address this challenge, we present an innovative framework that combines multivariate time-series (MTS) analysis with deep learning (DL) methods to predict production variables in waterflooding reservoirs. Our approach transforms injection and production data sets into artificial 3D feature images, enabling comprehensive MTS analysis. This transformation allows us to extract interaction patterns among multiple time-series features and identify dependencies between injector and producer wells, ultimately leading to more accurate production forecasting. We developed a novel residual 3D convolutional long short-term memory neural network (residual 3D-CNN LSTM) by incorporating deeper and residual bottleneck structures into a conventional CNN-LSTM architecture. To validate our model’s effectiveness, we compared its performance against a conventional deep LSTM model, using different input data formats: artificial 3D feature images for our residual 3D-CNN LSTM and numerical production/injection data for the conventional LSTM. Statistical analysis demonstrated that our proposed approach consistently outperformed traditional deep LSTM models across all performance indicators.

The prediction of land subsidence is a crucial step for early warning of urban infrastructure damage and timely remedy. However, the performance of most mathematical and empirical prediction models is often compromised by their large number of parameters, complex operational processes and sparsely measured values. Currently, the traditional neural network models are popular and effective, but they cannot accurately discover the characteristic changes of time series data. In this paper, a long short-term memory (LSTM) neural network was proposed to predict the land subsidence of time series Interferometric Synthetic Aperture Radar (InSAR). First, the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique was utilized to monitor the time series land subsidence at Beijing Capital International Airport (BCIA) from 2005 to 2010 based on ENVISAT ASAR images with a descending orbit. The results were compared with the existing results to verify the reliability and then used to analyse the temporal and spatial characteristics of the time series land subsidence of the BCIA. Based on the time series InSAR deformation data, the LSTM neural network was used to establish the prediction model of time series InSAR, and the results were compared with those of the Multi-Layer Perceptron (MLP) and Recurrent Neural Network (RNN). The comparison results showed that the LSTM neural network was more accurate than the MLP and RNN on the point scale (the root mean square error was 4.60 mm and the mean absolute error was 3.18 mm), the correlation coefficients between the prediction results of the LSTM neural network and the real InSAR measurement results in 2007 and 2008 were 0.93 mm and 0.96 mm, respectively, indicating that LSTM neural network had better prediction performance. Eventually, based on the land subsidence data of time series InSAR from 2006 to 2010, the LSTM neural network was applied to predict the BCIA time series land subsidence in 2011. The results predicted that cumulative subsidence in September 2011 would reach a maximum of 350 mm. Therefore, the LSTM neural network is a potentially effective prediction method, which can replace numerical or empirical models in the absence of detailed hydrogeological data. Moreover, its prediction results can be used to assist decision-making, early warning and hazard relief.

Study on turbidity prediction method of reservoirs based on long short term memory neural network

Autoregressive Distributed Lag Model Based Cointegration Analysis for Batch Process Monitoring

Inflation is a situation where there is an increase in the general price level. Inflation for goods and services purchased by consumers is measured by changes in the Indeks Harga Konsumen (IHK). Determination of the amount, type and quality of commodities in the package of goods and services in the IHK is based on the Survey Biaya Hidup (SBH). In Central Java, there are only four cities covered in the implementation of SBH, namely Purwokerto, Solo, Semarang, and Tegal. It was the underlying researchers took the four cities. In this case, researchers taken for the period of 2009-2013. Inflation Purwokerto, Solo, Semarang, and Tegal is a multivariate time series that show activity for a certain period. One method to analyze multivariate time series is Vector Autoregressive (VAR). VAR method is one of the multivariate time series analysis of variables that can be used to predict and assess the relationship between variables. Inflation researchers predict that by 2014 the four cities using VAR (1). Chosen VAR (1) is based on the results of some tests. VAR (1) have the optimal lag value, there is no correlation between the residual lag, and the value Root Mean Square Error (RMSE) is smaller than the other models. Keywords: Inflation, IHK, SBH, Multivariate Time Series, Forecasting, Vector Autoregressive (VAR).

As an important marine environmental parameter, sound velocity greatly affects the sound propagation characteristics in the ocean. In marine surveying work, prompt and low-cost acquisition of accurate sound speed profiles (SSP) is of immense significance for improving the measurement and positioning accuracy of marine acoustic equipment and ensuring underwater wireless communication. To address the problem of not being able to glean the accurate SSP in real time, we propose a convolution long short-term memory neural network (Conv-LSTM) which combines the long short-term memory (LSTM) neural network and convolution operation to predict the complete sound speed profile based on historical data. Considering SSP is a typical time series and has strong spatial correlation, Conv-LSTM can grasp not only the temporal relevance of time series, but also the spatial characteristics. The Argo temperature and salinity grid data of the North Pacific from 2004 to 2019 is imported to establish the model’s SSP dataset, and the convolution of input data is performed before going through the neurons in this recurrent neural network to extract the spatial relevance of the data itself. In the meantime, in order to prove the advanced nature of this model, we compare it with the LSTM network under the same parameter settings. The experimental results show that predicting the SSP time series at a single coordinate position under the same parameter conditions, it is best to predict the future SSP next month through the historical data of 24 months, and the prediction effect of Conv-LSTM is much better than that of the LSTM network, and the relative error (RE) is 0.872 m/s, which is 1.817 m/s less than that of LSTM. Predictions in the selected area are also exceedingly accurate relative to the actual data; the prediction error of deep water is less than 0.3 m/s, while RE on the surface layer is larger, exceeding 1.6 m/s.

It is key index of air-jet texturing yarn quality such as air-jet texturing yarn strength and so on. It can well control air-jet texturing yarn quality by predicting yarn strength and so on. Generally, it is normal used to predict yarn strength such as Multiple Linear Regression (MLR), Support Vector Regression (SVR) and shallow Artificial Neural Network (ANN). Because the processing of air-jet texturing yarn production has time sequence, the paper proposes a new deep neural network, it is Long Short-Term Memory neural network (LSTM). It used 1800 sets of data to train LSTM, SVR and ANN. It tested LSTM, MLR, SVR and ANN with 200 sets of data. Experimental results show that LSTM neural network is the best accuracy among these four algorithms.

This study examines the relationship between public debt and inflation rates in Kenya from 2011 to 2021 using the Vector Autoregressive (VAR) model. Despite the models likeAutoregressive Integrated Moving Average (ARIMA), Seasonal Autoregressive Integrated Moving Average (SARIMA), and Generalized Autoregressive Conditional Heteroscedasticity (GARCH) gaining popularity in time series analysis, the Vector Autoregressive model, being multivariate, is relevant in analyzing two or more time series variables simultaneously, benefiting from the bi-directional causality and providing a better outlook into the flow of the dynamic interaction between inflation and public debt. The main objectives are modelling the Vector Autoregressive model and forecasting future trends to provide insights for policymakers. Additionally, the methodological approach comprises descriptive statistics, stationarity tests, normality tests, and the Vector Autoregressive model. Descriptive statistics reveal significant variations, with public debt increasing from 1.35 trillion KES to a peak of 8.2 trillion KES, and inflation rates ranging from 3.2% to 19.72% for the period from 2011 to 2021. The Augmented Dickey-Fuller (ADF) test confirmed that both time series were stationary at their levels. The Vector Autoregressive model, chosen for its ability to analyze dynamic interactions, indicated a significant relationship between the variables, with inflation showing strong self-persistence (coefficient of 0.8731, <i>p</i> < 2 × 10<sup>−16</sup>), though public debt did not significantly impact inflation in the model (<i>p</i> = 0.5592). The models R-squared values, 95.82% for public debt and 84.74% for inflation, highlight its strong explanatory power. Moreover, findings indicate that while public debt does not directly affect inflation within the model lag structure, inflation exhibits a strong self-persistence. The model R-squared values are 95.82% for public debt and 84.74% for inflation, demonstrating high explanatory power. Recommendations include the implementation of a robust debt management strategy, emphasizing sustainable borrowing and enhancing revenue generation to mitigate inflationary pressures. Further research is recommended to explore the broader macroeconomic impacts of public debt on economic growth and employment in Kenya.

The product quality attributes, PQA (bulk density, color b index, and moisture content), of extrudates producedusing a twin-screw food extruder with two different screw configurations (A and B) were evaluated and analyzed as afunction of operating and process variables. Relationships were obtained using multiple linear regression methods.Results showed that PQA became less sensitive to changes in operating variables when using screw configuration B (tworeverse kneading paddles added to the shear section of the extruder). Models of on-line measured PQA (extrudatemoisture and color b index) could be used in the design of extrusion process control systems.

The vector autoregression (VAR) model is one of the most successful, flexible, and easy to use models for the analysis of multivariate time series. It is a natural extension of the univariate autoregressive model to dynamic multivariate time series. The VAR model has proven to be especially useful for describing the dynamic behavior of economic and financial time series and for forecasting. It often provides superior forecasts to those from univariate time series models and elaborate theory-based simultaneous equations models. Forecasts from VAR models are quite flexible because they can be made conditional on the potential future paths of specified variables in the model.

Vector autoregression is an important technique for modelling multivariate time series and has been widely used in a variety of applications. Owing to its fast growth of parameters with the dimension of the time series vector, dimension reduction is often desirable in multivariate time series analysis. The envelope model is a new approach to achieve dimension reduction and allows efficient estimation in multivariate analysis. In this paper, we provide the first work to explore the application and extension of envelope models to multivariate time series data. We present the envelope and partial envelope formulations for vector autoregression and elaborate model selection, parameter estimation and asymptotic results. Simulations and real data analysis demonstrate the efficiency gains of the envelope vector autoregression models compared with the standard models in terms of estimation. Meanwhile, the envelope models can excel in prediction improvement.

Since it is one of the world's most significant financial markets, the foreign exchange (Forex) market has attracted a large number of investors. Accurately anticipating the forex trend has remained a popular but difficult issue to aid Forex traders' trading decisions. It is always a question of how precise a Forex prediction can be because of the market's tremendous complexity. The fast advancement of machine learning in recent decades has allowed artificial neural networks to be effectively adapted to several areas, including the Forex market. As a result, a slew of research articles aimed at improving the accuracy of currency forecasting has been released. The Long Short-Term Memory (LSTM) neural network, which is a special kind of artificial neural network developed exclusively for time series data analysis, is frequently used. Due to its high learning capacity, the LSTM neural network is increasingly being utilized to predict advanced Forex trading based on previous data. This model, on the other hand, can be improved by stacking it. The goal of this study is to choose a dataset using the Hurst exponent, then use a two-layer stacked Long Short-Term Memory (TLS-LSTM) neural network to forecast the trend and conduct a correlation analysis. The Hurst exponent (h) was used to determine the predictability of the Australian Dollar and United States Dollar (AUD/USD) dataset. TLS-LSTM algorithm is presented to improve the accuracy of Forex trend prediction of Australian Dollar and United States Dollar (AUD/USD). A correlation study was performed between the AUD/USD, the Euro and the Australian Dollar (EUR/AUD), and the Australian Dollar and the Japanese Yen (AUD/JPY) to see how AUD/USD movement affects EUR/AUD and AUD/JPY. The model was compared with Single-Layer Long Short-Term (SL-LSTM), Multilayer Perceptron (MLP), and Complete Ensemble Empirical Mode Decomposition with Adaptive Noise–Improved Firefly Algorithm Long Short-Term Memory. Based on the evaluation metrics Mean Square Error (MSE), Root Mean Square Error, and Mean Absolute Error, the suggested TLS-LSTM, whose data selection is based on the Hurst exponent (h) value of 0.6026, outperforms SL-LSTM, MLP, and CEEMDAN-IFALSTM. The correlation analysis conducted shows both positive and negative relations between AUD/USD, EUR/AUD, and AUD/JPY which means that a change in AUD/USD will affect EUR/AUD and AUD/JPY as recorded depending on the magnitude of the correlation coefficient (r).