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Numerical study of mechanical behaviour of tubular structures under dynamic compression
Amir Partovi,M. M. Shahzamanian,P. D. Wu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.3
This paper presents a novel point of view for the performance investigation and optimization of energy absorber devices, which is numerically introduced using the finite element method employing corrugated tubes. The numerical results show that structural or material softening leads to an optimal configuration at which the corrugated or circular tube achieves its peak performance. The performance and optimization parameters used in this study are absorbed crash energy and specific energy absorption. The force-displacement (f-d) diagram of the energy absorbers is divided into three parts for numerical investigation. The optimum point of each corrugated tube is observed when the values of energy absorption (EA) at different stages of the stroke (i.e., in the first, middle, and last portions of deformation) are almost equal or close to one another. Furthermore, the effect of material softening is discussed. The effects of cladding a ductile layer on f-d diagram, EA and deformation of thin-walled circular tubes are numerically investigated. Adding soft material layers oriented at 30° to 70° to the model can increase the performance of energy absorbers by approximately 10 % compared with the model that uses only the core material.
Nasim Partovi Mehr,Faramarz Khoshnoudian,Hamed Tajammolian 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.20 No.6
The effects of vertical component of earthquakes on torsional amplification due to mass eccentricity in seismic responses of base-isolated structures subjected to near-field ground motions are studied in this paper. 3-, 6- and 9-story superstructures and aspect ratios of 1, 2 and 3 have been modeled as steel special moment frames mounted on Triple Concave Friction Pendulum (TCFP) bearings considering different period and damping ratios. Three-dimensional linear superstructures resting on nonlinear isolators are subjected to both 2 and 3 component near-field ground motions. Effects of mass eccentricity and vertical component of 25 near-field earthquakes on the seismic responses including maximum isolator displacement and base shear as well as peak superstructure acceleration are studied. The results indicate that the effect of vertical component on the responses of asymmetric structures, especially on the base shear is significant. Therefore, it can be claimed that in the absence of the vertical component, mass eccentricity has a little effect on the base shear increase. Additionally, the impact of this component on acceleration is remarkable so the roof acceleration of a nine-story structure has been increased 1.67 times, compared to the case that the structure is subjected to only horizontal components of earthquakes.
Composite locomotive frontend analysis and optimization using genetic algorithm
Rohani, S.M.,Vafaeesefat, A.,Esmkhani, M.,Partovi, M.,Molladavoudi, H.R. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5
This paper addresses the structural design of the front end of Siemens ER24 locomotive body. The steel structure of the frontend is replaced with composite. Optimization of the composite lay-up is performed using Genetic Algorithms. Initially an optimized single design for the entire structure is presented. Then a more refined optimum is developed by considering the separate optimization of 7 separate regions of the structure. Significant savings in the weight of the structure are achieved.
Hoefling, Alexander,Nguyen, Dan Thien,Partovi-Azar, Pouya,Sebastiani, Daniel,Theato, Patrick,Song, Seung-Wan,Lee, Young Joo American Chemical Society 2018 Chemistry of materials Vol.30 No.9
<P>Rechargeable lithium-sulfur (Li-S) batteries have drawn significant attention as next-generation energy storage systems. Sulfur-copolymers are promising alternative cathode materials to elemental sulfur in Li-S batteries as they provide high reversible capacity. However, the redox mechanisms of these materials are not well understood owing to the difficulty in characterizing amorphous structures and identifying individual ionic species. Here, we use solid-state NMR techniques together with electrochemistry experiments and quantum calculations to investigate the structural evolution of the prototype S-copolymer cathodes, sulfur-diisopropenylbenzene copolymers (poly(S-co-DIB)), during cycling. We demonstrate that polysulfides with different chain lengths can be distinguished by <SUP>13</SUP>C and <SUP>7</SUP>Li NMR spectroscopy, revealing that the structure of the copolymers can be tuned in terms of polysulfide chain lengths and resulting reaction pathways during electrochemical cycling. Our results show that the improved cyclability of these cathodes originates from the role of organic moieties acting as anchors that fixate polysulfides to the polymeric network during cycling, thus preventing their diffusion into the electrolyte. We provide a new methodological concept for the mechanistic studies to track the intermediate species and phase transition in Li-S batteries.</P> [FIG OMISSION]</BR>
Composite locomotive frontend analysis and optimization using genetic algorithm
S.M. Rohani,A. Vafaeesefat,M. Esmkhani,M. Partovi,H.R. Molladavoudi 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.5
This paper addresses the structural design of the front end of Siemens ER24 locomotive body. The steel structure of the frontend is replaced with composite. Optimization of the composite lay-up is performed using Genetic Algorithms. Initially an optimized single design for the entire structure is presented. Then a more refined optimum is developed by considering the separate optimization of 7 separate regions of the structure. Significant savings in the weight of the structure are achieved.
Estimating Completeness of Cancer Registration in Iran with Capture-Recapture Methods
Mohammadi, Gohar,Akbari, Mohammad Esmaeil,Mehrabi, Yadolah,Motlagh, Ali Ghanbari,Pour, Elham Partovi,Roshandel, Gholamreza,Khosravi, Ardasheir Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.no.sup3
Completeness is an important indicator of data quality in cancer registry programs. This study aimed to estimate the completeness of registered cases in a population based cancer registry program implemented in five provinces of Iran. Capture-recapture methods were used to estimate the number of cases that may have been missed and to estimate rates of completeness for different categories of age, year, and sex. The data used for this study were obtained from three sources: 1) National Pathology Database; 2) National Hospital Discharge Database; and 3) National Death Registry Database. The three sources were linked and duplicates were identified based on first name, last name, father's names, and date of birth, ICD code, and case's residency address using Microsoft Excel. Removing duplicates, the three sources reported a total of 35,643 cases from March 2008 to March 2011. Running many different multivariate models of capture-recapture and controlling for source dependencies revealed an overall under-reporting of 49% in all five registries combined. The estimated completeness differed based on age, sex, and year. The overall completeness was higher for males than females (71.2% for males and 59.9% for females). Younger age had lower rates of completeness compared to older age (38.1% for <40 years, 55.4% for 40-60 years, and 76.7 for >60 years). The results of this study indicated a moderate to severe (depending on the age, sex and year) degree of completeness in the population based cancer registration of Iran.
Multiparametric ultrasound for upper extremity dialysis access evaluation
Vasileios Michas,Mehdi Taghipour,Angeliki Papachristodoulou,Maria Sidiropoulou,Sasan Partovi,Demosthenes Cokkinos,Vasileios Rafailidis,Sameer Gadani,Amanjit Gill,Hans Michell,Panos Prassopoulos 대한초음파의학회 2023 ULTRASONOGRAPHY Vol.42 No.4
The evolution of ultrasound (US) techniques has greatly improved the evaluation of many parameters in dialysis vascular access, which is typically achieved through an arteriovenous fistula (AVF) or graft (AVG). These techniques include grayscale B-mode, color Doppler, power Doppler, spectral Doppler, non-Doppler US flow imaging techniques, contrast-enhanced US, and elastography. In conjunction with a patient’s medical history and physical examination, US provides crucial information about the native vascular bed prior to the surgical creation of an arteriovenous anastomosis. It also tracks the maturation progress of the newly created AVF or AVG and aids in diagnosing potential complications of the vascular access. These complications include thrombosis, steal syndrome, aneurysms, pseudoaneurysms, hematomas, infection, ischemic neuropathy, exacerbation of preexisting congestive heart failure, and stenosis.