A Robust Bi-objective Optimization Model for Resource Levelling Project Scheduling Problem with Discounted Cash Flows

Sayyid Ali Banihashemi,Mohammad Khalilzadeh 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.6

Due to limited financial resources and high costs of infrastructure projects, project stakeholders seek to gain maximum profits with optimal resource utilization as well as cost and time minimization. Therefore, this study presents a multi-mode resource-constrained project scheduling model considering the uncertain parameters of cost and time together with the goals of maximizing the net present value and minimizing resource usage fluctuation. Also, the assumptions related to the real-world projects regarding multi-mode activities, limitation of renewable resources, and the deadline of project are incorporated into the proposed model. Moreover, a robust scheduling method is presented to better deal with the inherent uncertainties of projects regarding cost and time. The model is solved with the exact method named lexicographic goal programming (LGP). Due to the NP-hardness of the problem, two metaheuristic algorithms named Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-Objective Particle Swarm Optimization (MOPSO) are applied to solve various medium and large size problems. The obtained results indicate the high efficiency of the two meta-heuristic algorithms in solving the problem and the better performance of the MOPSO algorithm compared with NSGA-II in terms of five indices. Furthermore, the model is implemented in an offshore equipment installation phase of a wellhead platform project. Finally, the sensitivity analysis of the proposed robust model is performed considering different conservation levels, and the results are evaluated by Monte Carlo simulation with three normal, uniform and triangular distributions. The findings demonstrate that the robustness of the model against the variations of uncertain parameters.

Fluid conveying piezoelectric nanosensor: Nonclassical effects on vibration stability analysis

Sayyid H. Hashemi Kachapi 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.5

In current study, surface/interface effects for pull-in voltage and viscous fluid velocity effects on dimensionless natural frequency (DNF) of fluid-conveying piezoelectric nanosensor (FCPENS) subjected to direct electrostatic voltage DC with nonlinear excitation, harmonic force and also viscoelastic foundation (visco-pasternak medium and structural damping) are investigated using Gurtin–Murdoch surface/interface (GMSIT) theory. For this analysis, Hamilton’s principles, the assumed mode method combined with Lagrange–Euler’s are used for the governing equations and boundary conditions. The effects of surface/interface parameters of FCPENS such as Lame’s constants (λI,S, μI,S), residual stress (τ0I,S), piezoelectric constants (e31psk,e32psk) and mass density (ρI,S) are considered for analysis of dimensionless natural frequency respect to viscous fluid velocity u̅f and pull-in voltage V̅DC.

Nonlinear and nonclassical vibration analysis of double walled piezoelectric cylindrical nanoshell

Kachapi, Sayyid H. Hashemi Techno-Press 2020 Advances in nano research Vol.9 No.4

In current paper, nonlocal (NLT), nonlocal strain gradient (NSGT) and Gurtin-Murdoch surface/interface (GMSIT) theories with classical theory (CT) are utilized to investigate vibration and stability analysis of Double Walled Piezoelectric Nanosensor (DWPENS) based on cylindrical nanoshell. DWPENS simultaneously subjected to direct electrostatic voltage DC and harmonic excitations, structural damping, two piezoelectric layers and also nonlinear van der Waals force. For this purpose, Hamilton's principle, Galerkin technique, complex averaging and with arc-length continuation methods are used to analyze nonlinear behavior of DWPENS. For this work, three nonclassical theories compared with classical theory CT to investigate Dimensionless Natural Frequency (DNF), pull-in voltage, nonlinear frequency response and stability analysis of the DWPENS considering the nonlocal, material length scale, surface/interface (S/I) effects, electrostatic and harmonic excitation.

Characterizations of Precipitated Zinc Powder Produced by Selective Leaching Method

F.F. Sayyid,Marwa F. Abd,Sami I. Jafar Al-rubaiey 한국부식방식학회 2024 Corrosion Science and Technology Vol.23 No.1

This work investigated the influence of concentration and applied potential on the characteristics of zinc powder (purity, apparent density, morphology, particle size distribution, and particle zeta potential) produced by the electrochemical process from waste brass. High-purity zinc powder is obtained using selective leaching of industrial brass waste in acidic, neutral, and alkaline solutions. The free immersion method with and without voltage using linear polarization technique is used. In the electrochemical process, hydrochloric acid HCl in three different concentrations (0.1, 0.2, and 0.3) M is used. The time and the distance between the electrodes are set to be 30 min and 3 cm, respectively. It has been found that the percentage purity is 98%, 96%, and 94% for the acidic, neutral, and alkaline solutions, respectively. In addition, the morphology of zinc powder analyzed by SEM was dendritic and mossy. It has been recorded that the purity of zinc increases with the increase of the concentration and applied potential. The highest value of purity for zinc powder was %98.58 in 1000 mV and 0.3M concentration for graphite cathode.

Potential role for metformin in urologic oncology

Rashid Khalid Sayyid,Neil Eric Fleshner 대한비뇨의학회 2016 Investigative and Clinical Urology Vol.57 No.3

Metformin is one of the most commonly used drugs worldwide. It is currently considered first-line pharmacological agent for management of diabetes mellitus type 2. Recent studies have suggested that metformin may have further benefits, especially in the field of urologic oncology. Use of metformin has been shown to be associated with decreased incidence and improved outcomes of prostate, bladder, and kidney cancer. These studies suggest that metformin does have a future role in the prevention and management of urologic malignancies. In this review, we will discuss the latest findings in this field and its implications on the management of urologic oncology patients.

Triggering of Herding Instincts due to COVID-19 Pandemic in Pakistan Stock Exchange

Shaista JABEEN,Sayyid Salman RIZAVI,Adeel NASIR 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.10

The present research intends to examine the herding aspect during the COVID-19 outbreak. The study is conducted to achieve specific objectives, so the underlying sampling technique is purposive sampling. The considered data source is the Pakistan Stock Exchange (PSX). Daily stock prices of 528 listed companies in PSX have been taken from the official website of PSX from 1998 to 2021. The current study envisions investigating the herding aspects for pre-pandemic and the time covering the pandemic period. The study has also targeted ten sectors of PSX. The present study’s motive is to investigate investors’ herding prospects before and during the pandemic in the Pakistan Stock Exchange (PSX) and its selected sectors. Daily closing stock prices of listed companies have been collected from the official website of PSX to calculate the stock returns. The Cross-Sectional Absolute Deviation (CSAD) has been used as a herding measure. Findings revealed that herding has not been observed in PSX during both time spans and even not during the bullish and bearish trends. However, robust sectoral evidence has been observed during the pandemic. It implies that investors in PSX tend to follow the crowd irrespective of making their own decisions to avoid further losses.

Modeling and optimization of dynamic viscosity of oil-based nanofluids containing alumina particles and carbon nanotubes by response surface methodology (RSM)

Mohammad Hemmat Esfe,Sayyid Majid Motallebi,Davood Toghraie 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.10

The dynamic viscosity of MWCNT-Al2O3 (40 : 60)/SAE50 nanofluid (NF) is investigated. NF viscosity modeling is also performed using the response surface methodology (RSM). Several different models are proposed, including modified and unmodified cubic, quartic and fifth models, and the best modeling is selected using the parameters R2, Adjusted R2, Predicted R2 and Square root of the residual mean square (Std. Dev.). The results show that the fifth-order model has values of 0.9997, 0.9997, 0.9996 and 2.39 for R2, Adjusted R2, Predicted R2 and Std. Dev. parameters, respectively, which indicates high accuracy of modeling. Using the perturbation diagram, it was found that among the parameters of temperature, solid volume fraction () and shear rate (), the temperature parameter has the greatest effect on the dynamic viscosity of NF. The trend of changes in viscosity also shows that  and  have little effect on viscosity. Due to the importance of low viscosity in fluid flow and pumping, the optimal values of NF viscosity are presented, including dynamic viscosity equal to 108.092 cP in  =0.063 and T=49.998 oC and  =7,866.7786 s1.

Study of Rheological Behavior, Economic Performance and Development of a Model for MWCNT-ZnO (30:70)/10W40 Hybrid Nanofluid Using Response Surface Methodology

Hemmat Esfe Mohammad,Motallebi Sayyid Majid,Esfandeh Saeed,Toghraie Davood 한국화학공학회 2024 Korean Journal of Chemical Engineering Vol.41 No.3

The aim of this article is an empirical investigation of the MWCNT and ZnO (30:70)/10W40 HNF against SR, SVF, and T. In this study, the nanoparticles (NPs) are examined with SVF = 0.05%-1% and T = 5–55 °C. After adding NPs to 10W40 engine oil, non-Newtonian behavior is observed. Optimizing the viscosity behavior of NF is another goal of this study, which has been achieved with the special combination of NPs and adding them to the base fl uid. The present introduced NF has given a more controlled viscosity and a cheaper price in competition with the other three reviewed NFs available in the literature. To predict the viscosity, RSM is used, which is based on the experimental results. The margin of deviation (MOD) is less than ±5%. Also, the sensitivity analysis in diff erent SVFs and temperatures is analyzed separately.

Corrosion Protection Effectiveness and Adsorption Performance of Schiff Base-Quinazoline on Mild Steel in HCl Environment

Ahmed A. Alamiery,Firas F. Sayyid,Ali M. Mustafa,Mahdi M. Hanoon,Lina M. Shaker 한국부식방식학회 2022 Corrosion Science and Technology Vol.21 No.2

Schiff base quinazoline derivative viz., 3-((2-hydroxy-3-methoxybenzylidene)amino)-2-methylquinazolin-4(3H)-one (SB-Q), was synthesized in this study. Its corrosion protection impact on mild steel (MS) in 1 Mhydrochloric acid solution was examined by performing weight loss measurements. The protective efficacyof SB-Q on MS in 1 M HCl was investigated based on its concentrations, immersion period, and immersion temperature. SB-Q was found to be an efficient inhibitor for the corrosion of MS. Its inhibitionefficiency was improved by increasing the concentration of SB-Q to an optimal concentration of 500 ppm. Its inhibition efficacy was 96.3% at 303K. Experimental findings revealed that its inhibition efficiency was increased with increasing immersion time, but decreased with an increase in temperature. The adsorption of SB-Q molecules was followed the Langmuir adsorption isotherm model. The adsorption of the examined inhibitor molecules on the surface of mild steel was studied by density functional theory (DFT). DFT investigation confirmed weight loss findings.

Gravimetric Measurements and Theoretical Calculations of 4-Aminoantipyrine Derivatives as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid Solution: Comparative Studies

A. A. Al-Amiery,Firas F. Sayyid,Ali M. Mustafa,Slafa I. Ibrahim,Mustafa K. Mohsin,Mahdi M. Hanoon,Mohammed H. H. Al-Kaabi,A. A. H. Kadhum,Wan Nor Roslam Wan Isahak 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.2

Due to continuous promotion of green alternatives to toxic petrochemicals by government policies,research efforts towards the development of green corrosion inhibitors have intensified recently. The objectiveof the current work was to develop novel green and sustainable corrosion inhibitors derived from 4-aminoantipyrine to effectively prevent corrosion of mild steel in corrosive environments. Gravimetricmethods were used to investigate corrosion inhibition of 4-((furan-2-ylmethylene)amino)antipyrine (FAP)and 4-((pyridin-2-ylmethylene)amino)antipyrine (PAP) for mild steel in 1 M HCl. FAP and PAP were subjectedto quantum chemical calculations using density functional theory (DFT). DFT was used to determinethe mechanism of mild steel corrosion inhibition using inhibitors tested in HCl. Results demonstratedthat these tested inhibitors could effectively inhibit mild steel corrosion in 1.0 M HCl. At 0.0005 M, theseinhibitors’ efficiencies for FAP and PAP were 93.3% and 96.5%, respectively. The Langmuir adsorptionisotherm was obeyed by these inhibitors on the mild steel surface. Values of adsorption free energies,, revealed that FAP followed chemical and physical adsorptions.