Analytical Study of Force-Displacement Behavior and Ductility of Self-centering Segmental Concrete Columns

Reza Hassanli,Osama Youssf,Julie Mills,Mostafa Fakharifar 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.3

In this study the behavior of unbonded post-tensioned segmental columns (UPTSCs) was investigated and expressions were proposed to estimate their ductility and neutral axis (NA) depth at ultimate strength. An analytical method was first employed to predict the lateral force-displacement, and its accuracy was verified against experimental results of eight columns. Two stages of parametric study were then performed to investigate the effect of different parameters on the behavior of such columns, including concrete compressive strength, axial stress ratio, diameter and height of the column, axial stress level, duct size, stress ratio of the PT bars, and thickness and ultimate tensile strain of fiber reinforced polymer wraps. It was found that the column’s aspect ratio and axial stress ratio were the most influential factors contributing to the ductility, and axial stress ratio and column diameter were the main factors contributing to the NA depth of self-centering columns. While at aspect ratios of less than ten, as the axial stress ratio increased, the ductility increased; at aspect ratios higher than ten, the ductility tended to decrease when the axial stress ratio increased. Using the results of parametric study, nonlinear multivariate regression analyses were performed and new expressions were developed to predict the ductility and NA depth of UPTSCs.

Eight Weeks Combination of Plyometric and Resistance Training on Agility, Speed and Explosive Power in Well-trained Male Taekwondo Players of Fars Province in Iran

( Hassan Estakhr ),( Gholam Reza Shahafv ) 국제태권도학회 2017 International Symposium for Taekwondo Studies Vol.2017 No.-

Purpose: The purpose of this study was to determine the effect of eight weeks plyometric and resistance training on agility, speed, and explosive power in well-trained male Taekwondo players. Methods: The present study is a semi-experimental and practical study. Thirty well-trained male Taekwondo athletes (aged 13-20 yr) participated in the study. They were assigned in training (n = 15) and control group (n = 15) randomly. The training group engaged in a combination of plyometric and resistance training for eight weeks (3 times/wk, 90 minutes/session). Results: The results showed a significant effect of a combination of plyometric and resistance training on agility, speed, and explosive power (p<0/05) in well-trained male Taekwondo athletes from the Fars Province in Iran. Conclusions: These findings indicate that well-trained male Taekwondo athletes will achieve a high level of agility, speed, and explosive power with a combination of plyometric and resistance training.

Zircon U-Pb geochronology, Hf isotopes and geochemistry of intrusive rocks in the Simorgh prospecting area, Lut Block, eastern Iran: petrogenesis and geological implications

Reza Borabadi,Seyed Ahmad Mazaheri,Mohammad Hassan Karimpour,Sebastien Meffre,Jay Thompson,Rosanna Clare Murphy,Azam Entezariharsini 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.5

The Simorgh prospecting area is located in the central part of the Lut Block in eastern Iran. The Lut Block, the eastern part of the Central Iranian Microcontinent (CIM), has a complex tectonic evolution and is characterized by extensive magmatic activities with a range of geochemical signatures. The Simorgh intrusions have features typical of calc-alkaline to high-K calc-alkaline rocks, metaluminous to slightly peraluminous and formed in a volcanic arc setting. Mineralization in the area is believed to be related to these intrusions. To better understand the petrogenesis of these intrusions, we report zircon U-Pb dating and Hf isotopes and whole rock geochemistry of two granites and one diorite. Age dating using Zircon U-Pb method on pyroxene diorite porphyry stock and two granite porphyry dikes revealed 24.85 ± 0.51 Ma, 25.37 ± 0.56 Ma and 25.94 ± 0.76 Ma ages respectively (late Oligocene, Chattian). Field observations and U-Pb dating indicate that there are at least two stages of emplacement: pre-mineralization intrusions (diorite porphyry) and syn-mineralization intrusions (granite porphyry, granodiorite porphyry and pyroxene diorite porphyry). Mantle-normalized, trace-element spider diagrams display enrichment in large ion lithophile elements (LILE) and light rare earth elements ((La/Yb)N = 9.26–14.48), and depletion in high field strength elements (HFSE) and heavy rare earth elements, as well as negative Eu anomalies (Eu/Eu* = 0.49–0.91). Zircon Hf isotope data from the Simorgh intrusive rocks show largely positive εHf(t) (average = 3.6 ± 2.0). Hf model ages are ranging from 720 to 1320 Ma, indicating its derivation from a relatively juvenile source. The presence of zircon xenocrysts may prove its contamination by older continental crust (Siderian).

Free axial vibration of cracked axially functionally graded nanoscale rods incorporating surface effect

Reza Nazemnezhad,Hassan Shokrollahi 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.3

This work aims to study effects of the crack and the surface energy on the free longitudinal vibration of axially functionally graded nanorods. The surface energy parameters considered are the surface stress, the surface density, and the surface Lamé constants. The cracked nanorod is modelled by dividing it into two parts connected by a linear spring in which its stiffness is related to the crack severity. The surface and bulk material properties are considered to vary in the length direction according to the power law distribution. Hamilton's principle is implemented to derive the governing equation of motion and boundary conditions. Considering the surface stress causes that the derived governing equation of motion becomes non-homogeneous while this was not the case in works that only the surface density and the surface Lamé constants were considered. To extract the frequencies of nanorod, firstly the non-homogeneous governing equation is converted to a homogeneous one using an appropriate change of variable, and then for clamped-clamped and clamped-free boundary conditions the governing equation is solved using the harmonic differential quadrature method. Since the present work considers effects of all the surface energy parameters, it can be claimed that this is a comprehensive work in this regard.

Nucleotide Sequence, Structural Investigation and Homology Modeling Studies of a Ca2+-independent α-amylase with Acidic pH-profile

( Reza Hassan Sajedi ),( Majid Taghdir ),( Hossein Naderi Manesh ),( Khosro Khajeh ),( Bijan Ranjbar ) 생화학분자생물학회 2007 BMB Reports Vol.40 No.3

Liver Dysfunction and Oxidative Stress in Streptozotocin-Induced Diabetic Rats: Protective Role of Artemisia Turanica

Hassan Bgheri Yazdi,Vida Hojati,Abdolhossein Shiravi,Sara Hosseinian,Gholamhassan Vaezi,Mousa-Al-Reza Hadjzadeh 대한약침학회 2019 Journal of pharmacopuncture Vol.22 No.2

Objectives: Oxidative stress plays a central role in diabetes-induced complications. In the present study, the protevtive effect of Artemisia turanica (A. turanica) was evaluated against diabetes-induced liver oxidative stress and dysfunction. Methods: Fifty male Wistar rats were randomly divided into five groups: control, diabetic, diabetic + metformin, diabetic + A. turanica extract, and diabetic + A. turanica extract + metformin. Experimental diabetes was induced by a single-dose (55 mg/kg, intraperitoneally (ip)) injection of streptozotocin (STZ). Metformin (300 mg/kg) and A. turanica extract (70 mg/kg) were orally administrated three days after STZ injection for four weeks. The levels of malondialdehyde (MDA), total thiol content and superoxide dismutase (SOD) and catalase activities were measured in the liver tissue. Serum glucose concentration, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were also determined. Results: In the diabetic group, serum glucose concentration, serum AST and ALT activities and liver MDA level were significantly higher while tissue total thiol content as well as catalase and SOD activities were lower, compared to the control group. Serum glucose in diabetic rats treated with metformin + A. turanica extract showed a significant decrease compared with the diabetic group. In all the A. turanica extract and metformin treated groups, serum ALT, tissue MDA level, total thiol content and SOD activity significantly improved compared with the diabetic rats. However, treatment of the diabetic rats only with metformin could not significantly change the activities of catalase and AST compared with the diabetic group. Conclusion: These findings suggested that A. turanica extract had a therapeutic effect on liver dysfuncyion and oxidative stress induced by diabetes, that may be probably due to its antioxidant and antiinflammatory effects.

Enhanced Flame Retardancy, Thermal and Mechanical Properties of Hybrid Magnesium Hydroxide/Montmorillonite Reinforced Polyamide 6/Polypropylene Nanocomposites

Reza Arjmandi,Harintharavimal Balakrishnan,Azman Hassan,Mohammad Jawaid,Alothman Y. Othman 한국섬유공학회 2018 Fibers and polymers Vol.19 No.4

In this study, the effects of hybrid magnesium hydroxide/montmorillonite (MH/MMT) on the flame retardancy, thermal, mechanical, morphological and thermo-mechanical properties of polyamide 6/polypropylene (PA6/PP) nanocomposites prepared by melt blending technique were investigated. The partial replacement of MH with MMT (2 and 4 wt%) was done at total filler content of 30 wt% and maleated polypropylene was used as compatibilizer. Mass loss calorimeter analysis revealed that the peak heat release rate and total heat evolved values reduced in the presence of MMT due to the formation of the protective surface and insulation layer by MMT within the MgO layer formed on the surface upon combustion. The char residue also strengthened by migration of MMT layers to the surface of char. The thermal stability and flame retardancy of PA6/PP/MH/MMT nanocomposites improved with increasing MMT content. The MMT layers were well dispersed in the nanocomposites. The stiffness and toughness of PA6/PP/MH nanocomposites increased while the strength maintained with incorporation of MMT. The degree of crystallinity of both PA6 and PP increased with the addition of MMT while the melting point remained unaltered. The synergistic combination of MH and MMT has indeed maintained the mechanical properties of nanocomposites while further improving the flame retardancy.

Probabilistic models for curvature ductility and moment redistribution of RC beams

Hassan Baji,Hamid Reza Ronagh 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.2

It is generally accepted that, in the interest of safety, it is essential to provide a minimum level of flexural ductility, which will allow energy dissipation and moment redistribution as required. If one wishes to be uniformly conservative across all of the design variables, curvature ductility and moment redistribution factor should be calculated using a probabilistic method, as is the case for other design parameters in reinforced concrete mechanics. In this study, simple expressions are derived for the evaluation of curvature ductility and moment redistribution factor, based on the concept of demand and capacity rotation. Probabilistic models are then derived for both the curvature ductility and the moment redistribution factor, by means of central limit theorem and through taking advantage of the specific behaviour of moment redistribution factor as a function of curvature ductility and plastic hinge length. The Monte Carlo Simulation (MCS) method is used to check and verify the results of the proposed method. Although some minor simplifications are made in the proposed method, there is a very good agreement between the MCS and the proposed method. The proposed method could be used in any future probabilistic evaluation of curvature ductility and moment redistribution factors.

A Highly Selective and Sensitive Calcium(II)-Selective PVC Membrane Based on Dimethyl 1-(4-Nitrobenzoyl)-8-oxo-2,8-dihydro-1H-pyrazolo[5,1-a]isoindole-2,3-dicarboxylate as a Novel Ionophore

Hassan Ali Zamani*,Javad Abedini-Torghabeh,Mohammad Reza Ganjali 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.6

Anti-proliferative and Apoptotic Effects of the Derivatives from 4- aryl-4H-chromene Family on Human Leukemia K562 Cells

Hassan Aryapour,Majid Mahdavi,Seyed Reza Mohebbi,Mohammad Reza Zali,Alireza Foroumadi 대한약학회 2012 Archives of Pharmacal Research Vol.35 No.9

Previous studies suggest that 4-aryl-4H-chromenes are potent apoptosis-inducing agents in various cancer cell lines. In this study, anti-proliferative and apoptotic effects of the derivatives from 4-aryl-4H-chromene family were investigated in the human leukemia K562 cells using [3-(4,5)-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide (MTT) growth inhibition assay. 3-NC was more active among these compounds with IC50 of 65 nM and was selected for further studies. Apoptosis, as the mechanism of cell death, was investigated morphologically by Hoechst 33258 staining, cell surface expression assay of phosphatidylserine by Annexin V/PI technique,caspase-3 activation assay, as well as the formation of DNA ladder. The K562 cells underwent apoptosis upon a single dose (at IC50 value) of the compound, and also increased caspase-3 activity by more than 2.3-fold, following a 72 h treatment. Caspase-9 was also activated which could be detected 48 hours post-treatment. Furthermore, Western blot analysis revealed that the treatment with the compound down-regulated the expression of certain IAP protein, including survivin. These data further suggest that these derivatives from 4-aryl-4H-chromene may provide a novel therapeutic approach for the treatment of leukemia.