Comparison of ARIMA, ANN and Hybrid ARIMA-ANN Models for Time Series Forecasting

This paper aims to compare between Auto Regressive Integrated Moving Average (ARIMA) model, Artificial Neural Networks (ANN) and hybrid models for time series forecasting. The dataset used on this study is based on the monthly gold prices during Nov-1989 to Dec-2019. This dataset was used to train and test the predictive models. The performances were evaluated based on three metrics Mean Square Error (MSE), Mean Absolute Error (MAE) and Mean Absolute Percentage Error (MAPE) to determine the more appropriate model and evaluate models’ performance. The most important finding was that applying hybrid models can improve the forecasting accuracy over the ARIMA and ANN models. This may suggest that neither ARIMA nor ANN model captures all of patterns in the data

Slow nucleation rates in Chain Inflation with QCD Axions or Monodromy

The previous proposal (by two of us) of chain inflation with the QCD axion is shown to fail. The proposal involved a series of fast tunneling events, yet here it is shown that tunneling is too slow. We calculate the bubble nucleation rates for phase transitions in the thick wall limit, approximating the barrier by a triangle. A similar problem arises in realization of chain inflation in the string landscape that uses series of minima along the monodromy staircase around the conifold point. The basic problem is that the minima of the potential are too far apart to allow rapid enough tunneling in these two models. We entertain the possibility of overcoming this problem by modifying the gravity sector to a Brans-Dicke theory. However, one would need extremely small values for the Brans-Dicke parameter. Many successful alternatives exist, including other "axions" (with mass scales not set by QCD) or potentials with comparable heights and widths that do not suffer from the problem of slow tunneling and provide successful candidates for chain inflation.Comment: 6 pages, 1 figur

Online Service Quality and Brand Equity: The Mediational Roles of Perceived Value and Customer Satisfaction

© 2015, Taylor & Francis Group, LLC. This research examines mediational roles of perceived customer value and customer satisfaction on the relationship between online service quality dimensions and brand equity dimensions. A theoretical model was developed based on a review of the existing literature on the topics, and a survey was developed to test the model using a sample of 576 participants with active online banking accounts in UAE. The structural findings showed that system efficiency, fulfillment and responsiveness have positive effects on brand awareness and brand image, whereas system reliability and security showed negative relationships. Moreover, the findings support the mediational roles of perceived customer value and customer satisfaction on the relationship between brand awareness, brand image, and brand loyalty

Building Mobile Brand Equity: The Mediating Roles of Perceived Values

© 2016, Copyright © Taylor & Francis Group, LLC. This research tests the mediational roles of hedonic and utilitarian values consumers receive from using mobile data services (MDS) on the relationship between mobile commerce experience and mobile provider brand equity. A theoretical model was developed based on a review of the existing literature, and a survey was developed to test the model using a sample of 371 students in major universities in Jordan. The structural findings showed that MDS experience positively influence MDS provider image, which positively influenced both utilitarian and hedonic values, the effect being stronger for the utilitarian value. Moreover, both types of perceived values from using the MDS fully mediate the effect of MDS provider image on mobile equity

Nutritional evaluation of yoghurt prepared by different starter cultures and their physiochemical analysis during storage

Yoghurt was prepared with two different types of starter cultures; Lactobacillus bulgaricus and Lactobacillus acidophilus. The preparation was made by 3, 4 and 5% concentrations. It was stored at 4°C for 12 days. To analyze the effect of the two different cultures and their concentrations on the properties of yoghurt, different physio-chemical tests were performed. These two starter culture slightly enhanced the quality of yoghurt. The results showed that the protein, lactose, ash, fat, acidity and total solid mass were slightly increased while pH and moisture values gradually decreased during the storage period of 12 days. The comparative study of starter cultures showed that L. acidophilus produced good quality yoghurt as compared to L. bulgaricus