Semisolid Metal Processing Techniques for Nondendritic Feedstock Production

Semisolid metal (SSM) processing or thixoforming is widely known as a technology that involves the formation of metal alloys between solidus and liquidus temperatures. For the procedure to operate successfully, the microstructure of the starting material must consist of solid near-globular grains surrounded by a liquid matrix and a wide solidus-to-liquidus transition area. Currently, this process is industrially successful, generating a variety of products with high quality parts in various industrial sectors. Throughout the years since its inception, a number of technologies to produce the appropriate globular microstructure have been developed and applied worldwide. The main aim of this paper is to classify the presently available SSM technologies and present a comprehensive review of the potential mechanisms that lead to microstructural alterations during the preparation of feedstock materials for SSM processing

A Resistor-Network Model of Dickson Charge Pump Using Steady-State Analysis

This paper presents a new average behavioral model, named a resistor-network (RN) model, that accurately predicts the electrical characteristics of the Dickson charge pump (DCP) circuit in the slow-switching limit and the fast-switching limit regions based on steady-state analysis. The RN model describes the steady-state behavior of a single-stage DCP using a network of resistors, which can then be cascaded to model N-stage DCP, taking into account the top- and bottom-plate parasitic capacitances. The RN model provides a comprehensive insight into various design parameters of the DCP, including the input/output current, output voltage, load characteristics, losses caused by parasitics, and power efficiency. Simulation results show that the proposed RN model accurately predicts the output voltage and power efficiency of the DCP over a wide range of switching frequencies, from 0.1 Hz to 1 GHz, with an error of less than 2% at the maximum power efficiency. The RN model provides designers with a simple and effective model to design DCP quickly and efficiently for a broad spectrum of applications, including energy harvesting and flash memory applications

A Resistor-Network Model of Dickson Charge Pump Using Steady-State Analysis

This paper presents a new average behavioral model, named a resistor-network (RN) model, that accurately predicts the electrical characteristics of the Dickson charge pump (DCP) circuit in the slow-switching limit and the fast-switching limit regions based on steady-state analysis. The RN model describes the steady-state behavior of a single-stage DCP using a network of resistors, which can then be cascaded to model N-stage DCP, taking into account the top- and bottom-plate parasitic capacitances. The RN model provides a comprehensive insight into various design parameters of the DCP, including the input/output current, output voltage, load characteristics, losses caused by parasitics, and power efficiency. Simulation results show that the proposed RN model accurately predicts the output voltage and power efficiency of the DCP over a wide range of switching frequencies, from 0.1 Hz to 1 GHz, with an error of less than 2% at the maximum power efficiency. The RN model provides designers with a simple and effective model to design DCP quickly and efficiently for a broad spectrum of applications, including energy harvesting and flash memory applications

High resolution non-hydrostatic numerical simulations for wind energy assessment over Libya.

This research is aimed at understanding the national wind energy resource of Libya to examine the viability of obtaining wind-generated electricity in the country. High-resolution regional wind observations in Libya are not sufficient for wind resource assessments throughout the country. To overcome such a barrier, the wind conditions have been estimated utilising high-resolution 3-D nested numerical simulations by the Non-hydrostatic Mesoscale Model of the Weather Research and Forecasting system (WRF-NMM). Analysis 2007 data from the Global Forecast System (GFS) were used as initial conditions whereas the boundary conditions came from a combination of GFS analysis and forecast data, in all runs. The coarse domain had a horizontal resolution of 15 km and a temporal resolution of 30 seconds while the fine domain had a horizontal resolution of 5 km and a temporal resolution of 10 seconds. 365 successive nested simulations were performed to produce hourly wind velocity data at 10 m above the ground along with at model sigma levels for both domains for the entire year. A cubic spline interpolation was used to interpolate wind velocity data between sigma levels and 10-m winds. Thus, wind velocity data at each grid point at six fixed heights (25, 50, 75, 100, 125, and 150 m above the ground) were obtained. Hourly power density data were computed at the seven mentioned heights. Wind power outputs were also estimated based on the power curves of commercial wind turbines of different sizes and designs.Results have shown that Libya has a very good potential for wind power generation. Several areas have been identified to be promising for future wind farms. The eastern and western coastlines, the northwestern high-altitude regions, and the mountainous areas in the Sahara Desert, have great potentials of using wind-generated electricity. Summer experiences the highest wind power resource over most parts of Libya. Over most areas, vertical wind shear peaks in the atmospheric layer of 75-100m. The use of the standard value of wind shear exponent would underestimate the vertical wind speed and power changes on most parts of the nation, while it would overestimate them in a few areas

Insights from Circular Economy Literature: A Review of Extant Definitions and Unravelling Paths to Future Research

The circular economy (CE) has become one of the prominent topics in both natural science and management literature over the last few decades. CE is a dual-loop regenerative system that focuses on the effective and efficient utilization of resources in the ecosystem, which is beneficial to environmental and economic performance optimization. Dual CE initiatives allow firms to increased resource eco-efficiency, as well as resource effectiveness. CE has profound consequences for economic and operational advantage. This reinforces the need for reflection on the definition that may provide guidelines to assess and advance the depth and diversity of the field. We aim to provide a definitional analysis of the CE and suggest future research streams to advance the existing literature. For this purpose, we employed a systematic literature review to collect related publications in the CE. As a result of this, a total of 91 papers were selected, studied, and analyzed. We proposed a sound definition of a circular economy that includes the main identified elements, organizational planning processes, customers and society, utilization of the ecosystem, and economic resource flows. Moreover, future direction agenda, in CE research, is suggested considering three research streams: (1) circular design as value creation and capture, (2) antecedents of key activities, and (3) consequences of key processes. There is limited empirical research conducted on CE, and much of the existing research focuses on theoretical, conceptual, and normative. A few empirical research studies are mainly cross-sectional in their focus and are confined to developing and emerging economies. We hope this study’s findings will extend the field of CE, in which some of the most influential information regarding CE literature is provided. This study suggests that the development of CE initiatives plays an important role in the growing digital transformation in the value chain. There have been limited research studies in the interface of circular economy and Industry 4.0. Future research studies may investigate the extent to which digital transformation can increase the implementation of CE, and their influence on digital performance management

Insights from circular economy literature: A review of extant definitions and unravelling paths to future research

The circular economy (CE) has become one of the prominent topics in both natural science and management literature over the last few decades. CE is a dual-loop regenerative system that focuses on the effective and efficient utilization of resources in the ecosystem, which is beneficial to environmental and economic performance optimization. Dual CE initiatives allow firms to increased resource eco-efficiency, as well as resource effectiveness. CE has profound consequences for economic and operational advantage. This reinforces the need for reflection on the definition that may provide guidelines to assess and advance the depth and diversity of the field. We aim to provide a definitional analysis of the CE and suggest future research streams to advance the existing literature. For this purpose, we employed a systematic literature review to collect related publications in the CE. As a result of this, a total of 91 papers were selected, studied, and analyzed. We proposed a sound definition of a circular economy that includes the main identified elements, organizational planning processes, customers and society, utilization of the ecosystem, and economic resource flows. Moreover, future direction agenda, in CE research, is suggested considering three research streams: (1) circular design as value creation and capture, (2) antecedents of key activities, and (3) consequences of key processes. There is limited empirical research conducted on CE, and much of the existing research focuses on theoretical, conceptual, and normative. A few empirical research studies are mainly cross-sectional in their focus and are confined to developing and emerging economies. We hope this study’s findings will extend the field of CE, in which some of the most influential information regarding CE literature is provided. This study suggests that the development of CE initiatives plays an important role in the growing digital transformation in the value chain. There have been limited research studies in the interface of circular economy and Industry 4.0. Future research studies may investigate the extent to which digital transformation can increase the implementation of CE, and their influence on digital performance management

Study on Thixojoining Process Using Partial Remelting Method

Cold-work tool steel is considered to be a nonweldable metal due to its high percentage content of carbon and alloy elements. The application of a new process of the semisolid joining of two dissimilar metals is proposed. AISI D2 cold-work tool steel was thixojoined to 304 stainless steel by using a partial remelting method. After thixojoining, microstructural examination including metallographic analysis, energy dispersive spectroscopy (EDS), and Vickers hardness tests was performed. From the results, metallographic analyses along the joint interface between semisolid AISI D2 and stainless steel showed a smooth transition from one to another and neither oxides nor microcracking was observed. Hardness values obtained from the points in the diffusion zone were much higher than those in the 304 stainless steel but lower than those in the AISI D2 tool steel. The study revealed that a new type of nonequilibrium diffusion interfacial structure was constructed at the interface of the two different types of steel. The current work successfully confirmed that avoidance of a dendritic microstructure in the semisolid joined zone and high bonding quality components can be achieved without the need for force or complex equipment when compared to conventional welding processes

Trend and Development of Semisolid Metal Joining Processing

The semisolid metal joining (SSMJ) process or thixojoining process has recently been developed based on the principles of SSM processing, which is a technology that involves the formation of metal alloys between solidus and liquidus temperatures. Thixojoining has many potential benefits, which has encouraged researchers to carry out feasibility studies on various materials that could be utilized in this process and which could transform the production of metal components. This paper reviews the findings in the literature to date in this evolving field, specifically, the experimental details, technology considerations for industrialization, and advantages and disadvantages of the various types of SSMJ methods that have been proposed. It also presents details of the range of materials that have been joined by using the SSMJ process. Furthermore, it highlights the huge potential of this process and future directions for further research

Level of Depression and Anxiety on Quality of Life Among Patients Undergoing Hemodialysis

Sameeha Alshelleh,1 Hussein Alhawari,1 Abdullah Alhouri,2 Bilal Abu-Hussein,3 Ashraf Oweis4 1Division of Nephrology, Department of Medicine, The University of Jordan, Amman, Jordan; 2Department of Medicine, Division of Gastroenterology, Royal Berkshire Hospital, Reading, UK; 3Department of Medicine, The University of Jordan, Amman, Jordan; 4Division of Nephrology, Department of Medicine, Jordan University of Science and Technology, Amman, JordanCorrespondence: Abdullah Alhouri, Department of Medicine, Division of Gastroenterology, Royal Berkshire Hospital, London Road, Reading, RG1 5AN, UK, Email [email protected]: Despite the growing concern worldwide regarding the quality of life (QoL) and mental well-being among chronic kidney disease (CKD), a few research has been done to address this issue. The study aims to measure depression, anxiety, and QoL prevalence among Jordanian patients with End Stage Renal Disease (ESRD) on hemodialysis and how all of these variables are correlated.Methods: This is a cross-sectional, interview-based study on patients at the Jordan University Hospital (JUH) dialysis unit. Sociodemographic factors were collected, and the prevalence of depression, anxiety disorder, and QOL was assessed using the Patient Health Questionnaire 9 (PHQ9), the Generalized Anxiety Disorder 7-item (GAD7), and the WHOQOL-BREF, respectively.Results: In a study of 66 patients, 92.4% had depression, and 83.3% had generalised anxiety disorder. Females had significantly higher depression scores than males (mean = 6.2 ± 3.77 vs 2.9 ± 2.8, p < 0.001), and single patients had significantly higher anxiety scores than married patients (mean = 6.1 ± 6 vs 2.9 ± 3.5, p = 0.03). Age was positively correlated with depression scores (rs= 0.269, p = 0.03), and QOL domains showed an indirect correlation with GAD7 and PHQ9 scores. Males had higher physical functioning scores than females (mean = 64.82 vs 58.87, p = 0.016), and patients who studied in universities had higher physical functioning scores than those with only school education (mean of College/University = 78.81 vs mean of School Education = 66.46, p = 0.046). Patients taking < 5 medications had higher scores in the environmental domain (p = 0.025).Conclusion: The high prevalence of depression, GAD, and low QOL in ESRD patients on dialysis highlights the need for caregivers to provide psychological support and counselling for these patients and their families. This can promote psychological health and prevent the onset of psychological disorders.Keywords: chronic kidney disease, end stage kidney disease, hemodialysis, quality of life, depression, generalized anxiety disorde