Nonlinear analysis of 3D reinforced concrete frames: effect of section torsion on the global response

Valipour, Hamid R.,Foster, Stephen J. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.4

In this paper the formulation of an efficient frame element applicable for nonlinear analysis of 3D reinforced concrete (RC) frames is outlined. Interaction between axial force and bending moment is considered by using the fibre element approach. Further, section warping, effect of normal and tangential forces on the torsional stiffness of section and second order geometrical nonlinearities are included in the model. The developed computer code is employed for nonlinear static analysis of RC sub-assemblages and a simple approach for extending the formulation to dynamic cases is presented. Dynamic progressive collapse assessment of RC space frames based on the alternate path method is undertaken and dynamic load factor (DLF) is estimated. Further, it is concluded that the torsional behaviour of reinforced concrete elements satisfying minimum standard requirements is not significant for the framed structures studied.

A reinforced concrete frame element with shear effect

Valipour, Hamid R.,Foster, Stephen J. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.1

A novel flexibility-based 1D element that captures the material nonlinearity and second order P-$\Delta$ effects within a reinforced concrete frame member is developed. The formulation is developed for 2D planar frames in the modified fiber element framework but can readily be extended to 3D cases. The nonlinear behavior of concrete including cracking and crushing is taken into account through a modified hypo-elastic model. A parabolic and a constant shear stress distribution are used at section level to couple the normal and tangential tractions at material level. The lack of objectivity due to softening of concrete is addressed and objectivity of the response at the material level is attained by using a technique derived from the crack band approach. Finally the efficiency and accuracy of the formulation is compared with experimental results and is demonstrated by some numerical examples.

Effectiveness of phase- and morphology-controlled MnO₂ nanomaterials derived from flower-like δ-MnO₂ as alternative cathode catalyst in microbial fuel cells

Valipour, Alireza,Hamnabard, Nazanin,Meshkati, Seyed Mohammad Hadi,Pakan, Mahyar,Ahn, Young-Ho Royal Society of Chemistry 2019 Dalton Transactions Vol. No.

<P>Crystal phase and morphology variations obtained by simple high-temperature annealing offer promising strategies for employing nanostructured manganese oxide as a cathode catalyst for microbial fuel cells (MFCs). This study examines the effectiveness of simultaneous-phase and morphology-controlled manganese dioxide nanomaterials, designed by annealing a hydrothermally synthesized flower-like δ-manganese dioxide precursor at 300-800 °C, as cathode catalysts for MFCs. MFCs with the best-performing catalyst cathode (at a reasonable mass loading) were also analyzed through cyclic voltammetry and electrochemical impedance spectroscopy. Among MFCs with non-annealed and annealed manganese dioxide cathodes (0.5 mg cm<SUP>−2</SUP>), those with the catalyst annealed at 500 °C (148 ± 7 mW m<SUP>−2</SUP>, CE = 13 ± 1%) generated the most power (5-52%). MFCs with the catalyst annealed at 500 °C at a loading of 1 mg cm<SUP>−2</SUP> as the cathode delivered the highest maximum power density (213 ± 9 mW m<SUP>−2</SUP>, CE = 13 ± 1%), representing 44% of that obtained using Pt/C at 0.5 mg Pt per cm<SUP>2</SUP> (483 ± 11 mW m<SUP>−2</SUP>, CE = 18 ± 2%) and a comparatively low internal resistance (164 ± 2 Ω). Both cyclic voltammetry and electrochemical impedance spectroscopy results were consistent with empirical data. Compared with previously reported cathode materials, the annealed product from the precursor flower-like δ-manganese dioxide annealed at 500 °C (particularly at a loading of 1 mg cm<SUP>−2</SUP>) was a more reliable, efficient, and inexpensive sustainable cathode catalyst for scaled-up MFCs.</P>

Using Multi Criteria Decision Making for Selection the Telecom Operators' Strategy for OTT Services: A Case Study of Mobile Communications Company of Iran

Valipour, Omid,Hosseini, Mohammad Reza Korean Institute of Industrial Engineers 2017 Industrial Engineeering & Management Systems Vol.16 No.4

While mobile operators are competing closely, new players of OTT (Over-The-Top) services such as Skype, What-sApp, Instagram providing communication and media services in the context of mobile communications have created a new space in the ecosystem of mobile services. These companies make use of the internet capacity of mobile operators instead of creating a dedicated network. However, on the one hand, mobile operators are in need of huge investment in order to take advantage of extensive telecommunication networks, and their income, on the other hand, has been significantly reduced. Therefore the success of mobile operators need to adopt a right strategy against OTT services. In this paper, strategies using Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis were developed by evaluating the external and internal environment factors of Mobile Telecommunication Company of Iran (MCI) as well as using library and field studies into company experts. Then, the strategies were prioritized using Analytical Network Process (ANP) as an efficient techniques of Multi Criteria Decision Making (MCDM) which deals with dependencies between criteria. MCI should be focus on the strategy of "cooperation and partnership with OTT companies" and then toward the strategy of "creation of innovative service and penetration into new markets."

Application of graphene-based nanomaterials as novel cathode catalysts for improving power generation in single chamber microbial fuel cells

Valipour, A.,Ayyaru, S.,Ahn, Y. Elsevier Sequoia 2016 Journal of Power Sources Vol.327 No.-

The low catalytic activity, limited resources, complexity and costs, and non-environmentally friendly nature are key factors limiting the application of non-precious metals and their composites at the cathode in microbial fuel cells (MFCs). This study evaluated the feasibility of graphene-based nanomaterials (RGO<SUB>HI-AcOH</SUB> vs. RGO/Ni nanoparticle composite) as novel cathode catalysts in single chamber air-cathode MFCs. A series of MFCs with different catalyst loadings were produced. The electrochemical behavior of the MFCs were evaluated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). As a result, the MFCs with the RGO<SUB>HI-AcOH</SUB> cathodes showed greater maximum power densities (>37%) than those with the RGO/Ni nanoparticle cathodes. In the MFCs, the highest maximum power density of 1683 +/- 23 mW/m<SUP>2</SUP> (CE = 72 +/- 3%), which covers 77% of that estimated for Pt/C (2201 +/- 45 mW/m<SUP>2</SUP>, CE = 81 +/- 4%), was obtained from the double loading RGO<SUB>HI-AcOH</SUB> cathodes. Among the MFCs with the RGO/Ni nanoparticle composite cathodes, those loaded with a double catalyst (1015 +/- 28 mW/m<SUP>2</SUP>, CE = 70 +/- 2%) showed better power performance than the others. Both CV and EIS showed good agreement with the MFC results. This study suggests that the RGO<SUB>HI-AcOH</SUB> cathode, particularly with a double catalyst loading, is promising for sustainable low-cost green materials, stable power generation and the long-term operation of MFCs.

Determination of maternal risk factors of preterm delivery: adjusted for sparse data bias; results from a population-based case-control study in Iran

( Mehrdad Valipour ),( Erfan Ayubi ),( Narges Shiravand ),( Yousef Moradi ),( Abolfazl Abbaszadeh ),( Firooz Amrai ),( Shahin Mokhtari ),( Kaveh Bahmanpour ),( Kamyar Mansori ) 대한산부인과학회 2020 Obstetrics & Gynecology Science Vol.63 No.2

Objective To determine the maternal risk factors associated with preterm delivery in Iran. Methods A population-based case-control study was conducted including 48 women having preterm delivery (case group) and 100 women having term delivery (control group) between March 2007 and March 2012 in the maternity hospitals of the Selseleh County, Lorestan province, Iran. Information regarding maternal risk factors was collected by structured interview and reviewing the medical records. The maternal risk factors associated with preterm delivery were identified using univariate and multivariable logistic regression analysis after adjusting the sparse data bias. The area under the receiver operating characteristic (ROC) curves was estimated to evaluate the discrimination power of the statistical models. Results Multivariable analysis demonstrated that multiparty (odds ratio [OR], 14.23; 95% confidence interval [CI], 1.60-127.05), history of gestational diabetes (OR, 0.10; 95% CI, 0.01-0.99), thyroid dysfunction (OR, 97.32; 95% CI, 5.78-1,637.80), urinary tract infection (OR, 16.60; 95% CI, 3.20-85.92), and taking care during pregnancy (OR, 0.12; 95% CI, 0.03-0.50) had significant impact on preterm delivery after adjusting the potential confounders. The area under the ROC curve for the aforementioned maternal risk factors was 0.86 (95% CI, 0.80-0.92). Conclusion Our study provides evidence for the associations between multiparty, history of gestational diabetes, thyroid dysfunction, urinary tract infection, as well as taking care during pregnancy, and preterm delivery.

Predicting Audit Reports Using Meta-Heuristic Algorithms

Hashem Valipour,Fatemeh Salehi,Mostafa Bahrami 한국유통과학회 2013 유통과학연구 Vol.11 No.6

Purpose - This study aims to predict the audit reports of listed companies on the Tehran Stock Exchange by using meta-heuristic algorithms. Research design, data, methodology - This applied research aims to predict auditors reports’ using meta-heuristic methods (i.e., neural networks,the ANFIS, and a genetic algorithm). The sample includes all firms listed on the Tehran Stock Exchange. The research covers the seven years between 2005 and 2011. Results - The results show that the ANFIS model using fuzzy clustering and a least-squares back propagation algorithm has the best performance among the tested models, with an error rate of 4% for incorrect predictions and 96% for correct predictions. Conclusion - A decision tree was used with ten independent variables and one dependent variable the less important variables were removed,leaving only those variables with the greatest effect on auditor opinion (i.e., net-profit-to-sales ratio, current ratio, quick ratio, inventory turnover, collection period, and debt coverage ratio).

Using Multi Criteria Decision Making for Selection the Telecom Operators` Strategy for OTT Services

Omid Valipour,Mohammad Reza Hosseini 대한산업공학회 2017 Industrial Engineeering & Management Systems Vol.16 No.4

While mobile operators are competing closely, new players of OTT (Over-The-Top) services such as Skype, WhatsApp, Instagram providing communication and media services in the context of mobile communications have created a new space in the ecosystem of mobile services. These companies make use of the internet capacity of mobile operators instead of creating a dedicated network. However, on the one hand, mobile operators are in need of huge investment in order to take advantage of extensive telecommunication networks, and their income, on the other hand, has been significantly reduced. Therefore the success of mobile operators need to adopt a right strategy against OTT services. In this paper, strategies using Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis were developed by evaluating the external and internal environment factors of Mobile Telecommunication Company of Iran(MCI) as well as using library and field studies into company experts. Then, the strategies were prioritized using Analytical Network Process (ANP) as an efficient techniques of Multi Criteria Decision Making (MCDM) which deals with dependencies between criteria. MCI should be focus on the strategy of “cooperation and partnership with OTT companies” and then toward the strategy of “creation of innovative service and penetration into new markets.”

Nonlinear analysis of 3D reinforced concrete frames: effect of section torsion on the global response

Hamid R. Valipour,Stephen J. Foster 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.4

In this paper the formulation of an efficient frame element applicable for nonlinear analysis of 3D reinforced concrete (RC) frames is outlined. Interaction between axial force and bending moment is considered by using the fibre element approach. Further, section warping, effect of normal and tangential forces on the torsional stiffness of section and second order geometrical nonlinearities are included in the model. The developed computer code is employed for nonlinear static analysis of RC sub-assemblages and a simple approach for extending the formulation to dynamic cases is presented. Dynamic progressive collapse assessment of RC space frames based on the alternate path method is undertaken and dynamic load factor (DLF) is estimated. Further, it is concluded that the torsional behaviour of reinforced concrete elements satisfying minimum standard requirements is not significant for the framed structures studied.

Analysis of RC beams subjected to shock loading using a modified fibre element formulation

Hamid R. Valipour,Luan Huynh,Stephen J. Foster 사단법인 한국계산역학회 2009 Computers and Concrete, An International Journal Vol.6 No.5

In this paper an improved one-dimensional frame element for modelling of reinforced concrete beams and columns subjected to impact is presented. The model is developed in the framework of a flexibility fibre element formulation that ignores the shear effect at material level. However, a simple shear cap is introduced at section level to take account of possible shear failure. The effect of strain rate at the fibre level is taken into account by using the dynamic increase factor (DIF) concept for steel and concrete. The capability of the formulation for estimating the element response history is demonstrated by some numerical examples and it is shown that the developed 1D element has the potential to be used for dynamic analysis of large framed structures subjected to impact of air blast and rigid objects.