Performance of some new Liu parameters for the linear regression model

Abstract

This article introduces some Liu parameters in the linear regression model based on the work of Shukur, Månsson, and Sjölander. These methods of estimating the Liu parameter d increase the efficiency of Liu estimator. The comparison of proposed Liu parameters and available methods has done using Monte Carlo simulation and a real data set where the mean squared error, mean absolute error and interval estimation are considered as performance criterions. The simulation study shows that under certain conditions the proposed Liu parameters perform quite well as compared to the ordinary least squares estimator and other existing Liu parameters.     

Poverty in the Kingdom of Saudi Arabia: An Exploratory Study of Poverty and Female‐headed Households in Jeddah City

This article reports an exploratory study in Jeddah City, Saudi Arabia, which assembled data and information from government and non‐governmental organizations about poverty and poverty alleviation policies. A list of poor families which were receiving benefits from the Social Security Department and charitable associations in Jeddah City was constructed, from which female‐headed households were identified and classified depending on the circumstances of the female head. The article describes the social, cultural and demographic characteristics of poor female‐headed households in Jeddah. The article also uses the results of interviews with 13 poor female heads of households to analyse aspects of their everyday lives. This evidence is used to discuss the ability of the Saudi state's income support system to address poverty as the country undergoes economic and social modernization.     

Ideological or religious? Contending visions on the future of Alevi identity

Establishing a coherent collective identity within the modern urban context among people who have different ideological, social and religious orientations, and social and economic backgrounds, is an ongoing struggle within the Alevi community in Turkey. This study tries to understand how alternative positions on Alevi identity dynamically construct the boundaries, moral contents and the new shape of Alevi identity in modern urban contexts through use of various discursive resources. At least two main contending ‘positions’ on Alevi identity try to institutionalise Alevi identity in modern urban contexts, which are ‘Ideological Position’ and ‘Religious Position’. Those discourse positions constitute different visions about the past and the future of the Alevi community as well as the cultural and the political boundaries of Alevi identity. More importantly, those positions resonate in ordinary citizens’ life stories as well as group narratives. This study utilises the analytical frame of ‘positioning theory’ to shed light on the complexities of identity negotiation.     

Thermal,viscoelastic and mechanical properties' optimization of polyphenylene sulfide via optimal processing parameters using the Taguchi method

Thermal, viscoelastic and mechanical properties of polyphenylene sulfide (PPS) were optimized as a function of extrusion and injection molding parameters. For this purpose, design of experiments approach utilizing Taguchi's L₂₇ (3⁷) orthogonal arrays was used. Effect of the parameters on desired properties was determined using the analysis of variance. Differential scanning calorimeter (DSC) tests were performed for the analysis of thermal properties such as melting temperature (T_m) and melting enthalpy (ΔH_M). Dynamic mechanical analysis (DMA) tests were performed for the analysis of viscoelastic properties such as damping factor (tan?δ) and glass transition temperature (T_g). Tensile tests were performed for the analysis of mechanical properties such as tensile strength and modulus. With optimized process parameters, verification DSC, DMA and tensile tests were performed for thermal, viscoelastic and mechanical properties, respectively. The Taguchi method showed that ‘barrel temperature’ and its level of ‘340°C’ were seen to be the most effective parameter and its level; respectively. It was suggested that PPS can be reinforced for further improvement after optimized thermal, viscoelastic and mechanical properties.