Self-centering passive base isolation system incorporating shape memory alloy wires for reduction in base drift

Muhammad Usman,Sania Dawood,Mati Ullah Shah,Muhammad Rizwan 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.31 No.5

Base isolation is one of the most widely implemented and well-known technique to reduce structural vibration and damages during an earthquake. However, while the base-isolated structure reduces storey drift significantly, it also increases the base drifts causing many practical problems. This study proposes the use of Shape Memory Alloys (SMA) wires for the reduction in base drift while controlling the overall structure vibrations. A multi-degree-of-freedom (MDOF) structure along with base isolators and Shape-Memory-Alloys (SMA) wires in diagonal is tested experimentally and analytically. The isolation bearing considered in this study consists of laminates of steel and silicon rubber. The performance of the proposed structure is evaluated and studied under different loadings including harmonic loading and seismic excitation. To assess the seismic performance of the proposed structure, shake table tests are conducted on base-isolated MDOF frame structure incorporating SMA wires, which is subjected to incremental harmonic and historic seismic loadings. Root mean square acceleration, displacement and drift are analyzed and discussed in detail for each story. To better understand the structure response, the percentage reduction of displacement is also determined for each story. The result shows that the reduction in the response of the proposed structure is much better than conventional base-isolated structure.

Photocatalytic systems as an advanced environmental remediation: Recent developments, limitations and new avenues for applications

Ahmad, Rizwan,Ahmad, Zaki,Khan, Asad Ullah,Mastoi, Naila Riaz,Aslam, Muhammad,Kim, Jeonghwan Elsevier 2016 Journal of environmental chemical engineering Vol.4 No.4

<P><B>Abstract</B></P> <P>Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photocatalytic systems for improved environmental remediation. </LI> <LI> Existing challenges and techniques to improve quantum efficiency for environmental remediation. </LI> <LI> Optimization of parameters governing capability of photocatalytic systems. </LI> <LI> Applications of photocatalytic systems in new avenues for environmental remediation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Dynamic Stability Enhancement Using Fuzzy PID Control Technology for Power System

Khaled Eltag,Muhammad Shamrooz Aslam,Rizwan Ullah 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.1

This article presents Fuzzy Particle Swarm Optimization of PID controller PSO-FPIDC used as a ConventionalPower System Stabilizer CPSS to improve the dynamic stability performance of generating unit duringlow frequency oscillations. Speed deviation Δw and acceleration Δw˙ of synchronous generator are taken as inputto the PSO-FPIDC controller connected to Single Machine Infinite Busbar SMIB system. This controller examinedunder different perturbation scenarios. The dynamic performance of the PSO-FPIDC is compared with theFuzzy Teacher Learner Based Optimization PID TLBO-FPIDC, PSO-PID, TLBO-PID and optimal parameters ofconvectional Power System Stabilizer CPSS. The results show that the performance of PSO-FPIDC has small overshoot/undershoot and damp out lower frequency oscillations very quickly as compared to other controllers.

Mediating Role of Liquidity Policy on the Corporate Governance-Performance Link: Evidence from Pakistan

TAHIR, Safdar Husain,SADIQUE, Muhammad Abu Bakar,SYED, Nausheen,REHMAN, Faiza,ULLAH, Muhammad Rizwan Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

Based on the theoretical underpinnings of the agency theory and liquidity theory, the purpose of this study is to show how managers who want to enhance the performance of Pakistan's non-financial sector can use liquidity policy in relation to corporate governance. Nowadays, Pakistan is facing a severe liquidity crisis; this study contributes by examining the mediating role of liquidity on the link of corporate governance-performance. We use data from 63 firms from 2010 to 2018, excluding 17 outliers. To analyze the data, we use the Seemingly Unrelated Regression (SURE) model and nlcom-Stata test. Our findings support the mediating role of liquidity on the link between corporate governance and performance. In addition, the results show that corporate governance improves performance. Furthermore, the study supports a significant positive association of liquidity and performance. For robustness, we use two performance variables - return on assets (ROA) and Tobin's q (TQ) - where ROA represents full mediation and TQ indicates partial mediation. This study helps to use liquidity policy to strengthen the inside and outside dimensions of corporate governance mechanisms that improve the performance of firms. Overall, these findings suggest better disclosure, transparency, and solutions to auditing issues that add value to the firms.

Effect of extraction methods on structural, physiochemical and functional properties of dietary fiber from defatted walnut flour

Gul Mali Khan,Nasir Mehmood Khan,Zia Ullah Khan,Farman Ali,Abdul Khaliq Jan,Nawshad Muhammad,Rizwan Elahi 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.4

The effect of different extraction methods i.e. extraction with alkali (AEDF), enzyme (EEDF) and enzyme plus shear emulsifying hydrolysis (SEDF) on structure, physiochemical as well as the functional characteristics of dietary fiber (DF) from defatted walnut flour were studied. AEDF process showed significantly higher (P\0.05) amount of water retention capacity (WRC; 5.39 g/g), water swelling capacity (WSC; 3.16 g/mL), and particle size; while, shown lower value of oil adsorption capacity (OAC; 29 g/g) amongst all. Compared to AEDF, no major differences were observed in network except the matrix in EEDF and SEDF was more porous and honey comb like. DF extracted through AEDF, EEDF and SEDF showed good viscosity and emulsifying activity however, less stability indices. The results from this study suggest that AEDF and EEDF and SEDF had specific effects on the structure-functional properties of DF from defatted walnut flour, which has great potential in food applications.

Incidence of Active HCV infection amongst Blood Donors of Mardan District, Pakistan

Karim, Fawad,Nasar, Abu,Alam, Ibrar,Alam, Iftikhar,Hassan, Said,Gul, Rahmat,Ullah, Sana,Rizwan, Muhammad Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.1

Hepatitis C is an ailment of liver caused by hepatitis C virus (HCV) infection. About 3% of the world population is infected by this virus. HCV infection is a leading reason for liver cirrhosis and therefore a major source of hepatocellular carcinoma. The study focused on the incidence of active HCV infection in blood donors of Mardan district of KPK, Pakistan. A total of 5318 blood donors were inspected for the presence of anti-HCV antibodies and HCV-RNA using ICT (immune-chromatographic test), ELISA and RT-PCR at Mardan Medical Complex (MMC), Mardan. Out of these, 157 (2.95%) were positive by ICT, 60 (1.12%) by ELISA and 56 (1.05%) for HCV-RNA. The frequency of active HCV infectivity amongst the blood donors from district Mardan, KPK Pakistan was 1.05 %. Application of strict measures during blood donor selection and use of proper screening assays such as ELISA in place of ICT devices can give a more accurate picture so that the incidence of this viral infection in HCV negative blood recipients can be reduced.

Entrenchment Effect and Audit Quality in Family Business of Pakistan

TAHIR, Safdar Husain,AKRAM, Sadaf,PERVEEN, Shahida,AHMAD, Gulzar,ULLAH, Muhammad Rizwan Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.8

The purpose of this study is to test both the alignment theory and entertainment theory on family firms listed on the Pakistan Stock Exchange. To achieve these goals, we collected secondary data from 164 non-financial family firms in various sectors during 2014-18. These family firms are classified into two categories: family control firms and family owned firms. We take the audit fee and the audit quality as dependent variables while family control firms, family-owned firms, and family CEOs as independent variables. In addition, the study uses leverage, profit and export as control variables. To test the effect of the explanatory variables on the output variables, we use two econometric models, Ordinary Least Square and the Probit regression model. In addition, Huber Sandwich test is used to check the non-normality and heteroscedasticity of panel data. Contrary to the alignment effect, the study supports the entrenchment effect and advocates that family-controlled firms as well as family-owned firms are not conscientious regarding the selection of external auditors during their contracts with audit firms. They are less likely to pay high audit fees for good quality audit in Pakistan. Furthermore, the study shows a statistically significant and positive relationship between audit quality and audit fees.

Stock Market Response to Terrorist Attacks: An Event Study Approach

TAHIR, Safdar Husain,TAHIR, Furqan,SYED, Nausheen,AHMAD, Gulzar,ULLAH, Muhammad Rizwan Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.9

The purpose of this research study is to examine the stock market's response to terrorist attacks. The study uses data of terrorist attacks in different parts of the country (Pakistan) from June 1, 2014 to May 31, 2017. The event window procedure applies to a 16-day window in which 5 days before and 10 days after the attack. In addition, several event windows have been built to test the response of the Pakistan Stock Exchange. KSE-100 index is taken as proxy of response. The total terrorist attacks are classified into four categories: attacks on law enforcement agencies, attacks on civilians, attacks on special places and attacks on politicians, government employees and bureaucrats. The standard market model is used to estimate the abnormal return of the Pakistan Stock Exchange, which takes 252 business days each year. Furthermore, BMP test is used to check statistical significance of cumulative abnormal rate of return (CAAR). The results of this study reveal that total number of terrorist attacks and attacks on law enforcement agencies show long-term effects on Pakistan stock exchange. However, attacks on civilians, attacks on special places and attacks on politicians, government employees and bureaucrats have little effect on the Pakistan Stock Exchange.