Examine the Reliability of Econometrics Software: An Empirical Comparison of Time Series Modelling

Researchers must understand that naively relying on the reliability of statistical software packages may result in suboptimal, biased, or erroneous results, which affects applied economic theory and the conclusions and policy recommendations drawn from it. To create confidence in a result, several software packages should be applied to the same estimation problem. This study examines the results of three software packages (EViews, R, and Stata) in the analysis of time-series econometric data. The time-series data analysis which presents the determinants of macroeconomic growth of Sri Lanka from 1978 to 2020 has been used. The study focuses on testing for stationarity, cointegration, and significant relationships among the variables. The Augmented Dickey-Fuller and Phillips Perron tests were employed in this study to test for stationarity, while the Johansen cointegration test was utilized to test for cointegration. The study employs the vector error correction model to assess the short-run and long-term dynamics of the variables in an attempt to determine the relationship between them. Finally, the Granger Causality test is employed in order to examine the linear causation between the concerned variables. The study revealed that the results produced by three software packages for the same dataset and the same lag order vary significantly. This implies that time series econometrics results are sensitive to the software that is used by the researchers while providing different policy implications even for the same dataset. The present study highlights the necessity of further analysis to investigate the impact of software packages in time series analysis of economic scenarios.

Estimation of permafrost thermal behavior using Fourier series model

Permafrost,being an important component of the cryosphere,is sensitive to climate change.Therefore,it is necessary to investigate the change of temperature within permafrost.In this study,we proposed a Fourier series model derived from the conduction equation to simulate permafrost thermal behavior over a year.The boundary condition was represented by the Fourier series and the geothermal gradient.The initial condition was represented as a linear function relative to the geothermal gradient.A comparative study of the different models(sinusoidal model,Fourier series model,and the proposed model)was conducted.Data collected from the northern Da Xing’anling Mountains,Northeast China,were applied for parameterization and validation for these models.These models were compared with daily mean ground temperature from the shallow permafrost layer and annual mean ground temperature from the bottom permafrost layer,respectively.Model performance was assessed using three coefficients of accuracy,i.e.,the mean bias error,the root mean square error,and the coefficient of determination.The comparison results showed that the proposed model was accurate enough to simulate temperature variation in both the shallow and bottom permafrost layer as compared with the other two Fourier series models(sinusoidal model and Fourier model).The proposed model expanded on a previous Fourier series model for which the initial and bottom boundary conditions were restricted to being constant.

A Hybrid Neural Network and Box-Jenkins Models for Time Series Forecasting

Time series forecasting plays a significant role in numerous applications,including but not limited to,industrial planning,water consumption,medical domains,exchange rates and consumer price index.The main problem is insufficient forecasting accuracy.The present study proposes a hybrid forecastingmethods to address this need.The proposed method includes three models.The first model is based on the autoregressive integrated moving average(ARIMA)statistical model;the second model is a back propagation neural network(BPNN)with adaptive slope and momentum parameters;and the thirdmodel is a hybridization between ARIMA and BPNN(ARIMA/BPNN)and artificial neural networks and ARIMA(ARIMA/ANN)to gain the benefits of linear and nonlinearmodeling.The forecasting models proposed in this study are used to predict the indices of the consumer price index(CPI),and predict the expected number of cancer patients in the Ibb Province in Yemen.Statistical standard measures used to evaluate the proposed method include(i)mean square error,(ii)mean absolute error,(iii)root mean square error,and(iv)mean absolute percentage error.Based on the computational results,the improvement rate of forecasting the CPI dataset was 5%,71%,and 4%for ARIMA/BPNN model,ARIMA/ANN model,and BPNN model respectively;while the result for cancer patients’dataset was 7%,200%,and 19%for ARIMA/BPNNmodel,ARIMA/ANN model,and BPNNmodel respectively.Therefore,it is obvious that the proposed method reduced the randomness degree,and the alterations affected the time series with data non-linearity.The ARIMA/ANN model outperformed each of its components when it was applied separately in terms of increasing the accuracy of forecasting and decreasing the overall errors of forecasting.

INDUSTRIAL PRODUCTION IN GERMANY AND AUSTRIA:A CASE STUDY IN STRUCTURAL TIME SERIES MODELLING

Industrial production series are volatile and often cyclical. Time series models can be used toestablish certain stylized facts, such as trends and cycles, which may be present in these series. Incertain situations, it is also possible that common factors, which may have an interesting interpretation,can be detected in production series. Series from two neighboring countries with close economicrelationships, such as Germany and Austria, are especially likely to exhibit such joint stylized facts.

Assessing the effectiveness of quarantine measures during the COVID-19 pandemic in Chile using Bayesian structural time series models

Background:With the emergence of the COVID-19 pandemic,all existing health protocols were tested under the worst health crisis humanity has experienced since the Black Death in the 14th century.Countries in Latin America have been the epicenter of the COVID-19 pandemic,with more than 1.5 million people killed.Worldwide health measures have included quarantines,border closures,social distancing,and mask use,among others.In particular,Chile implemented total or partial quarantine measures depending on the number of infections in each region of the country.Therefore,it is necessary to study the effectiveness of these quarantines in relation to the public health measures implemented by government entities at the national level.Objective:The main objective of this study is to analyze the effectiveness of national-and region-level quarantines in Chile during the pandemic based on information published by the Chilean Ministry of Health,and answers to the following question are sought:Were quarantine measures in Chile effective during the COVID-19 pandemic?Methods:The causal effect between the rates of COVID-19 infections and the population rates in Phase 1 and Phase 2 quarantines in the period from March 2020 to March 2021 in different regions of Chile were evaluated using intervention analyses obtained through Bayesian structural time series models.In addition,the Kendall correlation coefficient obtained through the copula approach was used to evaluate the comovement between these rates.Results:In 75%of the Chilean regions under study(12 regions out of a total of 16),an effective Phase 1 quarantine,which was implemented to control and reduce the number of cases of COVID-19 infection,was observed.The main regions that experienced a decrease in cases were those located in the north and center of Chile.Regarding Phase 2,the COVID-19 pandemic was effectively managed in 31%(5 out of 16)of the regions.In the southcentral and extreme southern regions of Chile,the effectiveness of these phases was null.Conclusion:The findings indicate that in the northern and central regions of Chile,the Phase 1 quarantine application period was an effective strategy to prevent an increase in COVID-19 infections.The same observation was made with respect to Phase 2,which was effective in five regions of northern Chile;in the rest of the regions,the effectiveness of these phases was weak or null.

TIME SERIES MODEL OF LONG-RANGE PREDICTION AND ITS APPLICATION

By generalizing the concept of mean in mathematical statistics to a mean generation function(MGF), the extended matrix of MGF is defined and then a new model of time series is presented.A calculatingseheme for modelling of monovariate time series is deduced cooperating with a normalization procedure of vector and a couple score criterion.An example of climatic prediction for ten-year scale is given in this paper,the tendency of variation for every year can be predicted skillfully with the model.

Emanation-Sedimentary Metallogenic Series and Models of the Proterozoic Rift in the Kangdian Axis

The Kangdian axis basement can be divided into two tectonic layers. The lower tectonic layer is the crystalline basement which is made up of the Archaean Dibadu Formation and early Proterozoic Dahongshan Group. The former is a kata-metamorphic basic volcano-sedimentary formation of the old geosyncline (old continental nucleus), and the latter is a medium-grade metamorphosed alkali-rich basic volcanic (emanation)-sedimentary formation of the Yuanjiang-Dahongshan marginal rift. They are in disconformable contact. The upper tectonic layer is the folded basement, and made up of the middle-late Proterozoic Kunyang Group. It is the result of Dongchuan-Yuanjiang intercontinental rifting with discordant contract with the underlying and overlying strata. Along with the evolution of Proterozoic from early to late, four types of emanation-sedimentary deposits in the Kangdian axis rift were formed in turn: emanation-sedimentary iron-copper-gold deposits related to basic volcanic rocks in the Yuanmou-Dahongshan marginal rift; emanation-sedimentary iron-copper deposits related to intermediate-basic volcanic rocks in the early stage of the Dongnchuan-Yuanjiang intercontinental rift; emanation-sedimentary copper deposits related to sedimentary rocks in the middle stage; copper deposits related to the late tectonic reworking. From early to late Proterozoic, with the evolution of the Kangdian axis rift and lowering volcanic basicity, the ore-forming elements also evolved from Fe, Cu and (Au) through Cu and Fe to Cu.

Multi-factor high-order intuitionistic fuzzy timeseries forecasting model

Fuzzy sets theory cannot describe the neutrality degreeof data, which has largely limited the objectivity of fuzzy time seriesin uncertain data forecasting. With this regard, a multi-factor highorderintuitionistic fuzzy time series forecasting model is built. Inthe new model, a fuzzy clustering algorithm is used to get unequalintervals, and a more objective technique for ascertaining membershipand non-membership functions of the intuitionistic fuzzy setis proposed. On these bases, forecast rules based on multidimensionalintuitionistic fuzzy modus ponens inference are established.Finally, contrast experiments on the daily mean temperature ofBeijing are carried out, which show that the novel model has aclear advantage of improving the forecast accuracy.

Modelling of Indian Monsoon Rainfall Series by Univariate Box-Jenkins Type of Models

The time domain approach, i.e. Autoregressive (AR) processes, of time series analysis is applied to the monsoon rainfall series of India and its two major regions, viz. North-West India and Central India. Since the original time series shows no modelable structure due to the presence of high interannual variability, a 3-point running filter is applied before exploring and fitting appropriate stochastic models. Out of several parsimonious models fitted, AR(3) is found to be most suitable. The usefulness of this fitted model is validted on an independent datum of 18 years and some skill has been noted. These models therefore can be used for low skill higher lead time forecasts of monsoon. Further the forecasts produced through such models can be combined with other forecasts to increase the skill of monsoon forecasts.

Optimal Culture Capacity of White Shrimp (Litopenaeus vannamei) and Razor Clam (Sinonovacula constricta) in a New Series-Connection Culture Model

To construct an effective circular mix-culture model and investigate its culture capacity,we established one small and one large systems,with white shrimp(Litopenaeus vannamei)and razor clam(Sinonovacula constricta)cultured in separate ponds.The culture water from the L.vannamei was pumped to the S.constricta,and the culture water from the S.constricta overflowed back into the L.vannamei via gravity.In trial I,we tested four culture densities(groups 1–4),and monitored water quality,growth indices,and digestive and immune enzyme activities.From the results,the nitrogen and phosphorus levels generally increased then declined after 56 days,and were lower in groups 1 and 2.The specific growth rate of group 2 was the highest.After 56 days,activities of four digestive enzymes were increased in group 2,and lysozyme activity was significantly decreased in S.constricta in groups 1–4;Alkaline phosphatase activity of L.vannamei was increased in group 3,but decreased in S.constricta in groups 2–4;Acid phosphatase activity was significantly higher in groups 1–3(P<0.05),while SOD and CAT activities were significantly elevated in group 2(P<0.05).Thus,we applied group 2 density for trial II.In trial II,nitrogen and phosphorus concentrations declined significantly during the latter stages,and growth indices were higher than the control(P<0.05).The yields of L.vannamei and S.constricta were significantly higher than the control(P<0.05).The results revealed a good circular mix-culture system with the optimal culture capacity for L.vannamei(40 ind m^(−2))and S.constricta(300 ind m^(−2)),which provided a reference for the future culture of them.

Multimodality Prediction of Chaotic Time Series with Sparse Hard-Cut EM Learning of the Gaussian Process Mixture Model

The contribution of this work is twofold： （1） a multimodality prediction method of chaotic time series with the Gaussian process mixture （GPM） model is proposed, which employs a divide and conquer strategy. It automatically divides the chaotic time series into multiple modalities with different extrinsic patterns and intrinsic characteristics, and thus can more precisely fit the chaotic time series. （2） An effective sparse hard-cut expec- tation maximization （SHC-EM） learning algorithm for the GPM model is proposed to improve the prediction performance. SHO-EM replaces a large learning sample set with fewer pseudo inputs, accelerating model learning based on these pseudo inputs. Experiments on Lorenz and Chua time series demonstrate that the proposed method yields not only accurate multimodality prediction, but also the prediction confidence interval SHC-EM outperforms the traditional variational 1earning in terms of both prediction accuracy and speed. In addition, SHC-EM is more robust and insusceptible to noise than variational learning.

Reconstructing historical forest fire risk in the non-satellite era using the improved forest fire danger index and long short-term memory deep learning-a case study in Sichuan Province,southwestern China

Historical forest fire risk databases are vital for evaluating the effectiveness of past forest management approaches,enhancing forest fire warnings and emergency response capabilities,and accurately budgeting potential carbon emissions resulting from fires.However,due to the unavailability of spatial information technology,such databases are extremely difficult to build reliably and completely in the non-satellite era.This study presented an improved forest fire risk reconstruction framework that integrates a deep learning-based time series prediction model and spatial interpolation to address the challenge in Sichuan Province,southwestern China.First,the forest fire danger index(FFDI)was improved by supplementing slope and aspect information.We compared the performances of three time series models,namely,the autoregressive integrated moving average(ARIMA),Prophet and long short-term memory(LSTM)in predicting the modified forest fire danger index(MFFDI).The bestperforming model was used to retrace the MFFDI of individual stations from 1941 to 1970.Following this,the Anusplin spatial interpolation method was used to map the distributions of the MFFDI at five-year intervals,which were then subjected to weighted overlay with the distance-to-river layer to generate forest fire risk maps for reconstructing the forest fire danger database.The results revealed LSTM as the most accurate in fitting and predicting the historical MFFDI,with a fitting determination coefficient(R^2)of 0.709,mean square error(MSE)of0.047,and validation R^2 and MSE of 0.508 and 0.11,respectively.Independent validation of the predicted forest fire risk maps indicated that 5 out of 7 historical forest fire events were located in forest fire-prone areas,which is higher than the results determined from the original FFDI(2 out of 7).This proves the effectiveness of the improved MFFDI and indicates a high level of reliability of the historical forest fire risk reconstruction method proposed in this study.

Comparison of performance of statistical models in forecasting monthly streamflow of Kizil River,China

This paper presents the application of autoregressive integrated moving average （ARIMA）, seasonal ARIMA （SARIMA）, and Jordan-Elman artificial neural networks （ANN） models in forecasting the monthly streamflow of the Kizil River in Xinjiang, China. Two different types of monthly streamflow data （original and deseasonalized data） were used to develop time series and Jordan-Elman ANN models using previous flow conditions as predictors. The one-month-ahead forecasting performances of all models for the testing period （1998-2005） were compared using the average monthly flow data from the Kalabeili gaging station on the Kizil River. The Jordan-Elman ANN models, using previous flow conditions as inputs, resulted in no significant improvement over time series models in one-month-ahead forecasting. The results suggest that the simple time series models （ARIMA and SARIMA） can be used in one-month-ahead streamflow forecasting at the study site with a simple and explicit model structure and a model performance similar to the Jordan-Elman ANN models.

On Mixed Model for Improvement in Stock Price Forecasting

Stock market trading is an activity in which investors need fast and accurate information to make effective decisions.But the fact is that forecasting stock prices by using various models has been suffering from low accuracy,slow convergence,and complex parameters.This study aims to employ a mixed model to improve the accuracy of stock price prediction.We present how to use a random walk based on jump-diffusion,to obtain stock predictions with a good-fitting degree by adjusting different parameters.Aimed at getting better parameters and then using the time series model to predict the data,we employed the time series model to smooth the sequence utilizing logarithm and difference,which successfully resulted in drawing the auto-correlation figure and partial the auto-correlation figure.According to the comparative analysis,which focuses on checking the mean absolute error,including root mean square error and R square evaluation index,we have drawn a clear conclusion that our mixed model prediction effect is relatively good.In the context of Chinese stocks,the hybrid random walk model is very suitable for predicting stocks.It can“interpret”the randomness of stocks very well,and it also has an unparalleled prediction effect compared with other models.Based on the time series model’s application in this paper,the abovementioned series is more suitable for predicting trends.

Analysis of seasonal position variation for selected GNSS sites in Poland using loading modelling and GRACE data

In this study we compared weekly GNSS position time series with modelled values of crustal deformations on the basis of Gravity Recovery and Climate Experiment （GRACE） data. The Global Navigation Satellite Systems （GNSS） time series were taken from homogeneously reprocessed global network solutions within the International GNSS Service （IGS） Reprucessing 1 project and from regional solutions performed by Warsaw University of Technology （WUT） European Permanent Network （EPN） Local Analysis Center （LAC） within the EPN reprocessing project. Eight GNSS sites from the territory of Poland with observation timespans between 2.5 and 13 years were selected for this study. The Total Water Equivalent （TWE） estimation from GRACE data was used to compute deformations using the Green＇s function formalism. High frequency components were removed from GRACE data to avoid aliasing problems. Since GRACE observes mainly the mass transport in continental storage of water, we also compared GRACE deformations and the GNSS position time series, with the deformations computed on the basis of a hydrosphere model. We used the output of Water GAP Hydrology Model （WGHM） to compute deformations in the same manner as for the GRACE data. The WGHM gave slightly larger amplitudes than GNSS and GRACE. The atmospheric non-tidal loading effect was removed from GNSS position time series before comparing them with modelled deformations. The results confirmed that the major part of observed seasonal variations for GNSS vertical components can be attributed to the hy- drosphere loading. The results for these components agree very well both in the amplitude and phase. The decrease in standard deviation of the residual GNSS position time series for vertical components corrected for the hydrosphere loading reached maximally 36% and occurred for all but one stations for both global and regional solutions. For horizontal components the amplitudes are about three times smaller than for vertical components therefore the comparison is much more complicated and the conclusions are ambiguous.

Modelling the unsteady melt flow under a pulsed magnetic field

A numerical model for the unsteady flow under a pulsed magnetic field of a solenoid is developed, in which magnetohydrodynamic flow equations decouple into a transient magnetic diffusion equation and unsteady Navier–Stokes equations in conjunction with two equations of the k–ε turbulent model. A Fourier series method is used to implement the boundary condition of magnetic flux density under multiple periods of a pulsed magnetic field （PMF）. The numerical results are compared with the theoretical or experimental results to validate the model under a time-harmonic magnetic field; it is found that the toroidal vortex pair is the dominating structure within the melt flow under a PMF. The velocity field of a molten melt is in a quasi-steady state after several periods; changing the direction of the electromagnetic force causes the vibration of the melt surface under a PMF.

Sensitivity Test and Data Analysis for Storage Reliability Assessment of Explosive Initiator

The explosive initiator is one kind of sensitivity products with long life and high reliability.In order to improve the storage reliability assessment,the method of storage reliability assessment for explosive initiator was proposed based on time series model using the sensitivity test data.In the method,the up and down test was used to estimate the distribution parameters of threshold.And an approach to design the up and down test was present to draw better estimations.Furthermore,the method of shrinkage estimation was introduced to get a better estimation of scale parameter by combining the sample information with prior information.The simulation result shows that the shrinkage estimation is better than traditional estimation under certain conditions.With the distribution parameters estimations,the time series models were used to describe the changing trends of distribution parameters along with storage time.Then for a fixed storage time,the distribution parameters were predicted based on the models.Finally,the confidence interval of storage reliability was obtained by fiducial inference.The illustrative example shows that the method is available for storage reliability assessment of the explosive initiator with high reliability.

Resting Study of Tracer Experiment on Catalytic Wet Oxidation Reactor under Micro-gravity and Earth Gravity Conditions

The International Space Station（ISS） employs catalytic wet oxidation carried out in a Volatile Reactor Assembly （VRA） for water recycling. Previous earth gravity experiments show that the VRA is very effective at removing polar, low molecular weight organics. To compare the reactor performance under micro-gravity and Earth gravity conditions, a tracer study was performed on a space shuttle in 1999 by using 0.2% potassium carbonate as the chemical tracer. In this paper, the experimental data were analyzed and it is indicated that the reactor can be considered as a plug flow one under both micro-gravity and earth gravity experimental conditions. It has also been proved that dispersion is not important in the VRA reactor under the experimental conditions. Tracer retardation was observed in the experiments and it is most likely caused by catalyst adsorption. It is concluded that the following reasons may also have influence on the retardation of mean residence time ： （1） the liquid can be held by appurtenances, which will retard the mean residence time; （2） the pores can hold the tracer, which can also retard the mean residence time.

Trading Strategies for All Stock Programs

Market traders buy and sell volatile assets frequently,with a goal to maximize their total return.There is usually a commission for each purchase and sale.Two such assets are gold and bitcoin.In order to solve the existing issues of purchases between gold and bitcoin,given that we have 1,000 USD,what strategies should we take to maximize our profits?In this article,the authors established seven models to predict the value of gold and bitcoins and how you should buy them,as the trends of value fluctuate,our models must be accurate enough to avoid being influenced.Targeted at that,the content is divided into three parts.For part 1:The authors selected several indicators that feature how the stock runs.For instance,price of gold and profit of gold to build first two models,which are the risk of investment model and the judgment on bull-or-bear market model.Then we use these models to evaluate whether it is safe to invest.The models are as follows:bear-bull market judgment model,risk of investment evaluation model,prediction model,trade model.For part 2:Based on the data concerned,the authors established the time series model to predict the way the market fluctuates.Meanwhile,the result of this model can be applied in correcting the results of former two models so as to make it more accurate.For part 3:The authors combined models above to give the best trading strategy.In addition,we improved the models by adding more indicators to make it more precise.We hope that by applying our models and strategies,you can successfully maximize your profit.