Preferred Language
Articles
/
jeasiq-1824
Applying some hybrid models for modeling bivariate time series assuming different distributions for random error with a practical application
...Show More Authors

Abstract

  Bivariate time series modeling and forecasting have become a promising field of applied studies in recent times. For this purpose, the Linear Autoregressive Moving Average with exogenous variable ARMAX model is the most widely used technique over the past few years in modeling and forecasting this type of data. The most important assumptions of this model are linearity and homogenous for random error variance of the appropriate model. In practice, these two assumptions are often violated, so the Generalized Autoregressive Conditional Heteroscedasticity (ARCH) and (GARCH) with exogenous variables (GARCHX) are applied to analyze and capture the volatility that occurs in the conditional variance of a linear model. Since time series observations rarely have linear or nonlinear components in nature or usually included together. Therefore, the main purpose of this paper is to employ the hybrid model technique according to Zhang methodology for hybrid models to combine the linear forecasts of the best linear model of ARMAX models and the nonlinear forecasts of the best nonlinear models of (ARCH, GARCH & GARCHX) models and thus increase the efficiency and accuracy of performance forecasting future values of the time series.

This paper is concerned with the modeling and building of the hybrid models (ARMAX-GARCH) and (ARMAX-GARCHX), assuming three different random error distributions: Gaussian distribution, Student-t distribution, as well as the general error distribution and the last two distributions were applied for the purpose of capturing the characteristics of heavy tail distributions which have a Leptokurtic characteristic compared to the normal distribution. This research adopted a modern methodology in estimating the parameters of the hybrid model namely the (two-step procedure) methodology. In the first stage, the parameters of the linear model were estimated using three different methods: The Ordinary Least Squares method (OLS), the Recursive Least Square Method with Exponential Forgetting Factor (RLS-EF), and the Recursive Prediction Error Method (RPM). In the second stage, the parameters of the nonlinear model were estimated using the MLE method and employing the numerical improvement algorithm (BHHH algorithm).

 

 

 

The hybrid models have been applied for modeling the relationship between the exogenous time series represented by the exchange rate and the endogenous time series represented by the unemployment rate in the USA for the period from (January 2000 to December 2017 i.e. 216 observations), and also the out-of-sample forecasts of unemployment rate in the last twelve values of (2018). The forecasting performance of the hybrid models and the competing individual model was also evaluated using the loss function accuracy measures (MAPE), (MAE), and the robust (Q-LIKE). Based on statistical measurements, the results showed the hybrid models improved the accuracy and efficiency of the single model. () hybrid model error whose conditional variance follows a GED distribution is the optimal model in modeling the bivariate time series data under study and more efficient in the forecasting process compared with the individual model and the hybrid model. This is due to having the lowest values for accuracy measures. Different software packages (MATLAB (2018a), SAS 9.1, R 3.5.2 and EViews 9) were used to analyze the data under consideration.

Crossref
View Publication Preview PDF
Quick Preview PDF
Publication Date
Thu Jul 11 2019
Journal Name
Journal Port Science Research
Evaluation Activity of Alanine Aminopeptidase (AAP) in Patients with Renal Dialysis, Purification and Isolation of Isoenzymes
...Show More Authors

Publication Date
Thu May 12 2016
Journal Name
Journal Of Biosciences
Dictyostelium discoideum RabS and Rab2 colocalize with the Golgi and contractile vacuole system and regulate osmoregulation
...Show More Authors

View Publication
Scopus (11)
Crossref (13)
Scopus Clarivate Crossref
Publication Date
Tue Aug 01 2017
Journal Name
Iosr Journal Of Dental And Medical Sciences (iosr-jdms)
Is deferasirox As Effective As Desferrioxamine in Treatment of Iron Overload In Patients With Thalassemia Major?
...Show More Authors

View Publication
Publication Date
Wed Dec 20 2023
Journal Name
Al-rafidain Journal Of Medical Sciences ( Issn 2789-3219 )
Systemic Melatonin Supplementation as an Adjunct to Non-Surgical Periodontal Treatment in Obese Patients with Periodontitis
...Show More Authors

Background: Obesity is considered an important risk factor for periodontal disease. It has been reported that reactive oxygen species linking both diseases, systemic melatonin supplementation as antioxidant therapy, was addressed as an adjuvant to scaling and root surface debridement (SRP) to enhance the treatment of periodontitis. Objective: To investigate the efficacy of systemic melatonin administration in periodontitis-obese patients as an adjuvant to scaling and root surface debridement (SRP). Methods: A randomized clinical trial was conducted at a dental-specialized center. Eighty subjects were included and allocated into group-I: twenty periodontium-healthy, normal-weight people; group-II: 30 obese patients with stage-III tre

... Show More
View Publication
Scopus Crossref
Publication Date
Tue Nov 01 2022
Journal Name
Chemical Methodologies
Study of Optical and Structural Properties of CdTe Quantum Dots Capped with 3MPA Using Hydrothermal Method
...Show More Authors

Quantum dots (QDs) can be defined as nanoparticles (NPs) in which the movement of charge carriers is restricted in all directions. CdTe QDs are one of the most important semiconducting crystals among other various types where it has a direct energy gap of about 1.53 eV. The aim of this study is to exaine the optical and structural properties of the 3MPA capped CdTe QDs. The preparation method was based on the work of Ncapayi et al. for preparing 3MPA CdTe QDs, and hen, the same way was treated as by Ahmed et al. via hydrothermal method by using an autoclave at the same temperature but at a different reaction time. The direct optical energy gap of CdTe QDs is between 2.29 eV and 2.50 eV. The FTIR results confirmed the covalent bonding betwee

... Show More
View Publication Preview PDF
Scopus (6)
Scopus
Publication Date
Fri Dec 01 2023
Journal Name
Russian Journal Of General Chemistry
Preparation, Characterization, and Biological Activity of Mixed Schiff Base Ligand Complexes with Amino Acid L-Proline
...Show More Authors

View Publication
Scopus (10)
Crossref (10)
Scopus Clarivate Crossref
Publication Date
Tue Mar 01 2011
Journal Name
Journal Of Kufa For Chemical Science
systhesis,spectral and kinetic of N2O2macrocycle ligand with divalent metal ions ( Co , Ni and Cu ) complexes
...Show More Authors

Publication Date
Thu Jun 15 2017
Journal Name
Journal Of Baghdad College Of Dentistry
Dental caries and treatment needs in relation to nutritional status among children with congenital heart disease
...Show More Authors

Background: Congenital heart disease is one of the most common developmental anomalies in children. These patients commonly have poor oral health that increase caries risk. Dental management of children with congenital heart disease requires special attention, because of their heightened susceptibility to infectious endocarditis. The aims of this study were to assess the severity of dental caries of primary and permanent teeth and treatment needs in relation to nutritional indicator (Body Mass Index) among children with congenital heart disease. Materials and Methods: In this case-control study, case group consisted of 399 patients aged between 6-12 years old with congenital heart disease were examined for dental status in Ibn Al-Bitar spec

... Show More
View Publication Preview PDF
Crossref (2)
Crossref
Publication Date
Sun May 01 2022
Journal Name
Optical Fiber Technology
Optical fiber sensor network integrating SAC-OCDMA and cladding modified optical fiber sensors coated with nanomaterial
...Show More Authors

View Publication
Scopus (12)
Crossref (13)
Scopus Clarivate Crossref
Publication Date
Wed Jul 07 2010
Journal Name
Al-mustansiriya J. Sci
Synthesis and Spectroscopic Studies of New Heterocyclic Azo Dye and Their Complexes with Selected Metal Ion
...Show More Authors

Coupling reaction of 4-aminoantipyrene with 8-hydroxyqunoline gave the new bidentate azo ligand 5-(4-antipyrene azo)-8-hydroxyqunoline. Treatment of this ligand with the following metals ions (MnII, CoII, NiII, CuII and ZnII) in aqueous ethanol with a 1:2 M:L ratio yielded a series of neutral complexes of the general formula [M(L)2Cl2]. The prepared complexes were characterized using flame atomic absorption, FT.IR, UV-Vis spectroscopic as well as magnetic susceptibility and conductivity measurements. Chloride ion content were also evaluated by (Mohr Method). From above data, the proposed molecular structure for these complexes as octahedral geometry.