Effects of floating wave barriers on wave-induced forces exerted to offshore-jacket structure

Arash Dalili Osgouei,Ramin Vafaei Poursorkhabi,Hamed Hosseini,Diyar N. Qader,Ahmad Maleki,Hamid Ahmadi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.1

The main objective of the present research was investigating the effects of a floating wave barrier installed in front of an offshore jacket structure on the wave height, base shear, and overturning moment. A jacket model with the height of 4.55 m was fabricated and tested in the 402 m-long wave flume of NIMALA marine laboratory. The jacket was tested at the water depth of 4 m subjected to the random waves with a JONSWAP energy spectrum. Three input wave heights were chosen for the tests: 20 cm, 23 cm, and 28 cm. Two different cross sections with the same area were selected for the wave barrier: square and rhombus. Results showed that the average decrease in the jacket’s base shear due to the presence of a floating wave barrier with square and rhombus cross section was 24.67% and 34.29%, respectively. The use of wave barriers with square and rhombus cross sections also resulted in 19.78% and 33.11% decrease in the jacket’s overturning moment, respectively. Hence, it can be concluded that a floating wave barrier can significantly reduce the base shear and overturning moment in an offshore jacket structure; and a rhombus cross section is more effective than an equivalent square section.

Effects of near-fault records characteristics on seismic performance of eccentrically braced frames

Reyhaneh Eskandari,Davoud Vafaei 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.5

In this paper the effects of fling-step and forward-directivity on the seismic performance of steel eccentrically braced frames (EBFs) are addressed. Four EBFs with various numbers of stories (4-, 8-, 12- and 15-story) were designed for an area with high seismic hazard. Fourteen near-fault ground motions including seven with forward-directivity and seven with fling-step effects are selected to carry out nonlinear time history (NTH) analyses of the frames. Furthermore, seven more far-field records were selected for comparison. Findings from the study reveal that the median maximum links rotation of the frames subjected to three set of ground motions are in acceptable range and the links completely satisfy the requirement stated in FEMA 356 for LS performance level. The arrival of the velocity pulse in a near-fault record causes few significant plastic deformations, while many reversed inelastic cycles result in low-cycle fatigue damage in far-fault records. Near-fault records in some cases are more destructive and the results of these records are so dispersed, especially the records having fling-step effects.

Application of copper sulfide nanoparticles loaded activated carbon for simultaneous adsorption of ternary dyes: Response surface methodology

Fatemeh Momtazan,Azam Vafaei,Mehrorang Ghaedi,Abdol Mohammad Ghaedi,Daryoush Emadzadeh,Woei Jye Lau,Mohammad Mehdi Baneshi 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.5

Copper sulfide nanoparticles were synthesized and loaded on activated carbon (CuS-NPs-AC) for ternary dye removal. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) were used to characterize the synthesized materials. The performance of the materials was subsequently evaluated for simultaneous ultrasound assisted adsorption of Disulphine Blue (DB), Eosin Yellow (EY) and Safranin O (SO) dyes in ternary solution under different conditions that include variation in solution pH, initial concentrations of dyes, sonication time and adsorbent dosage. Response surface methodology (RSM) using central composite design (CCD) was employed to obtain the optimum experimental conditions. The maximum removal efficacies (88.39%, 68.49% and 55.69% for DB, EY and SO, respectively) were found at the optimum conditions: 3.63 min of sonication time, 0.02 g of CuS-NPs-AC, 7.76mg L1 of DB, 8.89mg L1 of EY, 9.87mg L1 of SO and pH 6.5. Very high adsorbent capacities of 198.12, 165.0, 139.58mg g1 for DB, EY and SO, respectively, were yielded from Langmuir isotherm as best fitted model. Kinetic study indicated that the pseudo-second-order kinetic model was well fitted to the experimental data of ternary adsorption process. The results of the study display very good adsorption efficiency of the synthesized adsorbent for dye removal with high adsorption capacity under optimum conditions.

Application of (G'/G)-expansion method for systems of nonlinear evolution equations

H. Kheiri,V. Vafaei,M.R. Moghaddam 장전수학회 2011 Advanced Studies in Contemporary Mathematics Vol.21 No.1

In this paper, the [수식]-expansion method is used to seek more general exact solutions of the (2 + 1)-dimensional coupled nonlinear extension of the reaction-diffusion (CNLERD) equation and the Jaulent-Miodek (JM) equation. As a result, hyperbolic function solutions, trigonometric function solutions and rational function solutions with free parameters are obtained. When the parameters are taken as special values the solitary wave solutions are also derived from the travelling wave solutions. It is shown that the proposed method is more powerful and more general.

Experimental Investigation of Steel Frames Braced with Symmetrical Pairs of y-shaped Concentric Bracings

Sohail Majid Zamani,Abolhassan Vafaei,A. A. Aghakouchak,Chandrakant Desai 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.2

Concentric bracings composed of three members arranged in y shaped geometry have been traditionally used to provide openings in braced bays. However, simultanous occurance of compression in three braces leads to instability and out of plane buckling of braces accompanied by low hysteretic energy absorption. In order to study the behavior of y-braced frames, a research program including experimental tests was conducted at BHRC† structural engineering laboratory. Quasi-static cyclic loading was applied to specimens including four full-scale two-bay frames with y-bracings of different cross sections and connection types.The bays are braced symmetrically to have a combination of tensile and compressive braces at all loading stages. The results show that out-of-plane buckling with single curvature in braces can be substituted by in plane, double curvature buckling through appropriate detailing of cross sections and connections.Thus, hysteretic energy dissipation of ybracing is remarkably improved due to spreading of plastic strains in braces. In this paper, seismic performance of y-braced frame specimens and a reference X-braced frame are also assessed by capacity spectrum method.

Adsorption of a cationic dye from aqueous solution using Turkish lignite: Kinetic, isotherm, thermodynamic studies and neural network modeling

A. Hassani,F. Vafaei,S. Karaca,A. R. KHATAEE 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4

The adsorption ability of Turkish lignite as a cheap and abundant material for removal of methylene blue was investigated. The depending of adsorption capacity on contact time, initial dye concentration, amount of adsorbent, mixing rate, pH and temperature was studied. An artificial neural network was used to model the adsorption process. BET, SEM and FT-IR analysis before and after adsorption were performed. The adsorption kinetic, thermodynamic and isotherm were also investigated. The rate of adsorption was shown the best fit with the pseudo-second order model. The values of thermodynamic parameters indicated that the dye adsorption on the lignite was endothermic.

Modeling Deformation Flow Curves and Dynamic Recrystallization of BA-160 Steel During Hot Compression

Babak Shahriari,Reza Vafaei,Ehsan Mohammad Sharifi,Khosro Farmanesh 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.5

The hot deformation behavior of a high strength low carbon steel was investigated using hot compression test at the temperaturerange of 850–1100 °C and under strain rates varying from 0.001 to 1 s −1 . It was found that the fl ow curves of the steelwere typical of dynamic recrystallization at the temperature of 950 °C and above; at tested strain rates lower than 1 s −1 . Avery good correlation between the fl ow stress and Zener–Hollomon parameter was obtained using a hyperbolic sine function. The activation energy of deformation was found to be around 390 kJ mol −1 . The kinetics of dynamic recrystallization of thesteel was studied by comparing it with a hypothetical dynamic recovery curve, and the dynamically fraction recrystallizedwas modeled by the Kolmogorov–Johnson–Mehl–Avrami relation. The Avrami exponent was approximately constant around1.8, which suggested that the type of nucleation was one of site saturation on grain boundaries and edges.

Mini-Review: Role of Drugs Affecting Renin-Angiotensin System (RAS) in Traumatic Brain Injury (TBI): What We Know and What We Should Know

Mohammad Kazem Sarpolaki,Ali Vafaei,Mohammad Reza Fattahi,Arad Iranmehr 대한신경손상학회 2023 Korean Journal of Neurotrauma Vol.19 No.2

Traumatic brain injuries (TBIs) are among the most important clinical and research areas in neurosurgery, owing to their devastating effects and high prevalence. Over the last few decades, there has been increasing research on the complex pathophysiology of TBI and secondary injuries following TBI. A growing body of evidence has shown that the renin-angiotensin system (RAS), a well-known cardiovascular regulatory pathway, plays a role in TBI pathophysiology. Acknowledging these complex and poorly understood pathways and their role in TBI could help design new clinical trials involving drugs that alter the RAS network, most notably angiotensin receptor blockers and angiotensin-converting enzyme inhibitors. This study aimed to briefly review the molecular, animal, and human studies on these drugs in TBI and provide a clear vision for researchers to fill knowledge gaps in the future.

Effects of a floating wave barrier with square cross section on the wave-induced forces exerted to an offshore jacket structure

Osgouei, Arash Dalili,Poursorkhabi, Ramin Vafaei,Maleki, Ahmad,Ahmadi, Hamid Techno-Press 2021 Ocean systems engineering Vol.11 No.3

The main objective of the present research was investigating the effects of a floating wave barrier with square cross section installed in front of an offshore jacket structure on the wave height, base shear, and overturning moment. A jacket model with the height of 4.55 m was fabricated and tested in the 402 m-long wave flume of NIMALA marine laboratory. The jacket was tested at the water depth of 4m subjected to the random waves with a JONSWAP energy spectrum. Three input wave heights were chosen for the tests: 20 cm, 23 cm, and 28 cm. Results showed that the average decrease in the jacket's base shear due to the presence of a floating wave barrier with square cross section was 18.97%. The use of wave barriers with square cross section also resulted in 19.78% decrease in the jacket's overturning moment. Hence, it can be concluded that a floating wave barrier can significantly reduce the base shear and overturning moment in an offshore jacket structure.

Comparative removal of two textile dyes from aqueous solution by adsorption onto marine-source waste shell : Kinetic and isotherm studies

Mehdi Shirzad-Siboni,Alireza Khataee,주상우,Fatemeh Vafaei 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.8

Scallop shell was used as a low-cost adsorbent for removal of two anionic textile dyes, Reactive Blue 19(RB19) and Acid Cyanine 5 R (AC5R), from aqueous solutions. The adsorbent was characterized using inductivelycoupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FT-IR) and scanning electron microscopy (SEM). The dye removal efficiency of scallop shell was determinedas function of contact time, solution pH, initial dye concentration and adsorbent dosage. With increasing dye concentration,the adsorption of both dyes decreased, while it increased with increasing adsorbent dosage. Optimum removalof RB19 and AC5R was achieved at pH=6. Adsorption equilibrium data were well described by the Freundlich model. The maximum dye adsorption capacity of scallop shell as estimated from the Langmuir isotherm was 12.36 and 12.47mg/g for RB19 and AC5R, respectively. The adsorption kinetic data showed excellent correlation with the pseudosecond-order model. It was concluded that scallop shell has a remarkable potential for the sorption of RB19 and AC5Rand can be used for treatment of the dye contaminated wastewater.