101 research outputs found
Damage behavior of glass fiber reinforced plastic laminate and bovine-derived hydroxyapatite under low-velocity impact loading / Sadjad Naderi
Get PDFModeling and simulation of mechanical behavior of biomaterials is a very important topic. Until now, there is no single simulation model valid for the wide range of biomaterial, which includes metal alloys, composite and porous materials. Therefore the objective of the present study is to develop a numerical model to cover evaluation of mechanical properties for two types of brittle biomaterials: hydroxyapatite (HA) as a porous material for hard tissue replacement and Glass Fiber Reinforced Plastic laminates (GFRPs) as a layered composite for dental applications. The plastic behavior of HA and the effect of porosity on the elastic-plastic behavior of HA have not been well studied and fully discovered. On the other hand, biomedical and industrial applications have focused to detect the effect of low-velocity impact on mechanical response of GFRP materials under fatigue loading.
Finite element simulation models have been developed using MSC. MARC® to study on mechanical response of these brittle materials under impact and nanoindentation. The FE-inverse technique and semi-empirical method was introduced to infer the most suitable elastoplastic material model for HA. In addition, an effective approach is proposed to design irregular porous media using MATLAB code for HA with controllable pore shapes and distributions, without requiring any prior microscopic information. The impact damage process and contact stiffness for GFRP samples were investigated incrementally until when the composites were perforated. A Fatigue Damage index (FD) was introduced to capture the unique GFRP composite characteristics. Nanoindentation on HA and low-velocity impact, tensile static and fatigue tests on GFRP were performed to verify the numerical methods.
The elastic-plastic material model has shown more reasonable mechanical behavior of HA. Proposed approach for generating irregular porous structures is easier and faster
than the other existing approaches and constructed model appears more natural and realistic. The influence of low-velocity impact should be reflected in the design of GFRP structures. Even by increasing laminate thickness, the effect of impact is higher than the effect of thickness on the fatigue behavior of glass/epoxy laminates
To Mars and beyond; interview with Dr. Firouz Naderi, the director solar system exploration at NASA JPL
No full textNASA’s Jet Propulsion Laboratory (JPL) is the leader of the planetary missions. Located in Pasadena, California, this laboratory is responsible for the operation of NASA’s planetary spacecraft and its deep space network. The Leonardo Times was able to have an interview with Dr. Firouz Naderi, who is the director of the solar system exploration program at JPL, to talk about the new exciting missions NASA has planned for futureAerospace Engineerin
Corrigendum to “Sulfoethylated nanofibrillated cellulose: Production and properties” [Carbohydr. Polym. 169 (2017) 515–523]
No full textThe author Ali Naderi regrets the wrong information given with regard to his affiliation. The author would like to apologise for any inconvenience caused.</p
Numerical Simulation of Hydrodynamic Forces on Bridge Decks
No full textHighway bridges along the coast and small river bridges in mountainous regions can be submerged during storm surges or strong rainfall events, respectively. Loss of serviceability during these conditions can dramatically hamper the evacuation plan and the capacity for emergency transportation, thus it is essential to ensure the stability of bridges in extreme hydrological events. Correct estimates of the hydrodynamic forces on a bridge allows bridge designers to evaluate the robustness of the bridge in a more sophisticated approach rather than relying on a constant force magnitude obtained from a small range of physical tests. This study presents numerical simulations performed to quantify the hydrodynamic forces on a bridge deck with a rectangular cross section. The results of the numerical model are validated against the results of physical experiments. More than 700 simulations were performed to thoroughly investigate the effect of certain parameters on the flow field and forces on the deck. The parameters considered include: the water level, the Froude number, the blockage ratio, the proximity of the deck to the channel floor, the inclination of the deck, and the aspect ratio of the deck. The lift force is found to be downward unless the deck is significantly submerged i.e., inundation ratio (h*) is greater than 3.5, and the upstream velocity is relatively small, Frd<0.6. For h*<3.5 the development of flow patterns on the upper side of the deck is constrained by the presence of the free surface which causes an asymmetric pressure distribution in the vertical direction and ultimately results in a downward force. Increase in flow velocity results in a higher downward force and hence increase the bridge stability (provided that the submergence of the bridge is not too high, h*<4). When considering the trend of changes in lift and drag forces simultaneously, it can be said that the combination of small velocities and inundation ratios higher than 2 results in the most critical situation for the vertical stability of the bridge deck. An increase in the blockage ratio results in an increase in the drag coefficient. On the other hand, a decrease in the blockage ratio shifts the drag coefficient towards the value of 1.56, which corresponds to the drag coefficient of a rectangular cylinder in an unbounded flow. Considering the common flow conditions of practical interest for bridge designers, the upper boundary of the drag coefficient for the box deck was found to be 2.8. Incipient failure analysis is performed to establish a hydrodynamic situation that can cause the failure of the deck. Regardless of the proximity ratio and the Froude number, the bridge deck collapsed when the inundation ratio was higher than 1.3. This indicates that the deck is more susceptible to high water levels than to flood velocity or to the distance to the channel floor. Moreover, no bridge failure occurred for inundation ratios lower than 1.3, indicating that the deck must be deeply submerged to fail. By extracting the starting point of failure for a wide range of inundation ratios, proximity ratios, and Froude numbers, contour lines of the threshold of failure are drawn. These contour lines representing the starting point of failure provide the basis for more accurate estimates of the failure of the bridge due to flood loadings and can be considered to be included in the bridge design codes and guidelines. In fact, this proposed method is more reliable than the traditional method which assumes a constant value for drag and lift. The traditional methods are still present in some guidelines such as the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications. Attaching wing-shaped structures on the sides of the deck was proposed as a countermeasure to avoid failure of the bridge decks. Although the projected area of the deck perpendicular to the direction of flow was kept constant, it was expected that CD, CL, and CM would change; since they are dependent on the geometry of the deck, and the flow pattern is altered significantly due to the presence of wings. Results of several simulations for six different shape of wings under different inundation ratio and Froude number indicated that a rational shape of the wings can significantly alter the flow pattern around the deck and postpone occurrence of failure during conditions of really high water levels (h*>2.5) and high flood velocity (Fr>0.65). The proposed countermeasure can be considered as a robust solution for the wide range of probable floods, because of the fact that firstly, occurrence of this extreme hydrological situation is rare, and secondly, the stability of the deck in that situation might not be the first priority, especially compared with the risk of flooding a large part of the upstream land.The Erasmus+: Erasmus Mundus MSc in Coastal and Marine Engineering and Management is an integrated programme including mobility organized by five European partner institutions, coordinated by Norwegian University of Science and Technology (NTNU).Coastal and Marine Engineering and Management (CoMEM
Melanargia grumi lorestanensis n. ssp. dans le sud-ouest de l'Iran (Lep., Nymphalidae)
No full textMelanargia grumi lorestanensis n. ssp. in S-W Iran (Lep., Nymphalidae). The new entity was discovered by the first author mid june 2000 in the mountain range of the western part of Lorestan. It is distinguished from the nominotypical ssp., on the upper side by a darker pattern, on the hind wings by a larger white postdiscal band and by its quite immaculate underside. This is the first record of M. grumi for Iran.Carbonell Frédéric, Naderi Ali-Reza. Melanargia grumi lorestanensis n. ssp. dans le sud-ouest de l'Iran (Lep., Nymphalidae). In: Bulletin de la Société entomologique de France, volume 112 (4), décembre 2007. p. 454
Melanargia grumi lorestanensis n. ssp. dans le sud-ouest de l'Iran (Lep., Nymphalidae)
No full textMelanargia grumi lorestanensis n. ssp. in S-W Iran (Lep., Nymphalidae). The new entity was discovered by the first author mid june 2000 in the mountain range of the western part of Lorestan. It is distinguished from the nominotypical ssp., on the upper side by a darker pattern, on the hind wings by a larger white postdiscal band and by its quite immaculate underside. This is the first record of M. grumi for Iran.Carbonell Frédéric, Naderi Ali-Reza. Melanargia grumi lorestanensis n. ssp. dans le sud-ouest de l'Iran (Lep., Nymphalidae). In: Bulletin de la Société entomologique de France, volume 112 (4), décembre 2007. p. 454
Caspian sea-level changes during the last millennium: Historical and geological evidence from the south Caspian Sea
Get PDFThis article is made available through the Brunel Open Access Publishing Fund. Copyright @ Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.Historical literature may constitute a valuable
source of information to reconstruct sea-level changes. Here,
historical documents and geological records have been combined
to reconstruct Caspian sea-level (CSL) changes during
the last millennium. In addition to a comprehensive literature
review, new data from two short sediment cores were
obtained from the south-eastern Caspian coast to identify
coastal change driven by water-level changes and to compare
the results with other geological and historical findings.
The overall results indicate a high-stand during the Little Ice
Age, up to −21m (and extra rises due to manmade river
avulsion), with a −28m low-stand during the Medieval Climate
Anomaly, while presently the CSL stands at −26.5 m.
A comparison of the CSL curve with other lake systems and
proxy records suggests that the main sea-level oscillations
are essentially paced by solar irradiance. Although the major
controller of the long-term CSL changes is driven by climatological
factors, the seismicity of the basin creates local
changes in base level. These local base-level changes should be considered in any CSL reconstruction
Gammarus parthicus Stock, Mirzajani, Vonk, Naderi & Kiabi 1998
No full textGammarus parthicus Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998 Gammarus parthicus Stock, Mirzajani, Vonk, Naderi & Kiabi, 1998: 194 –201, Figs. 13–16. Locus typicus. Sarabe Abbasabad (33 ˚ 55 ʹN, 49 ˚ 30 ʹE), Shahzand, Markazi Province. Material examined. Holotype and 22 paratypes (ZMA Crust. Amph. 201373); new material: many specimens Dimeh, Esfahan (32 ˚ 30 ʹN, 50 ˚ 13 ʹE) (FAIC 111290); many specimens Sudejan, Esfahan (32 ˚ 32 ʹN, 50 ˚ 21 ʹE) (FAIC 111291); many specimens Guzdak, Meshkinshahr, Ardebil (FAIC 111293); many specimens, Aluch, Meshkinshahr, Ardebil (FAIC 111294). Distribution. First record (locus typicus) of this species was from the central Iranian basin, in northern Central Zagros, but recent sampling done by the first author revealed its presence also in the far eastern Alborz localities (Fig. 1). Ecological notes. Sample from Meshkinshahr was collected in a spring with water temperature of 13 ºC and pH of 7. Taxonomic remarks. The most conspicuous feature of this species – dense long setae on peduncles and flagellum of antenna 2 (much longer than what is drawn in the original description), makes it close to G. pretzmanni and G. komareki. However, presence of 1–2 tiny spines in postero-distal corner of basis in pereopod 7 (Stock et al. 1998, Fig. 15 c) makes it easy to distinguish G. parthicus from G. komareki (such spines are present also in G. p re t z - manni). In addition, anterior margins of carpal and meral segments of pereopods are bare in G. parthicus (ibid.), vs. having setae in G. komareki. Setae of both peduncles and flagellum on antenna 2 are highly curled in G. pretzmanni, while in G. parthicus they are slightly curved distally only on the flagellum (ibid., Fig. 13 e), such setation pattern can also be seen on pereopod 3 (ibid., Fig. 14 e). Moreover, dorsal side of antenna 2 peduncle is almost free of setae in G. parthicus (ibid., Fig. 13 e), while in G. pretzmanni the setae are present in dense groups also on the dorsal surface.Published as part of Zamanpoore, Mehrdad, Grabowski, Michal, Poeckl, Manfred & Schiemer, Friedrich, 2011, Taxonomic review of freshwater Gammarus (Crustacea: Amphipoda) from Iran, pp. 1-14 in Zootaxa 3140 on page 8, DOI: 10.5281/zenodo.20563
3D meso-scale modelling of tensile and compressive fracture behaviour of steel fibre reinforced concrete
Get PDFThis paper presents a novel meso-scale modelling framework to investigate the fracture process in steel fibre reinforced concrete (SFRC) under uniaxial tension and compression considering its 3D mesostructural characteristics, including different types of fibres, realistic shaped aggregates, mortar, interfacial transition zone and voids. Based on a hybrid damage model consisting of cohesive element method and damage plasticity method, a cost-effective finite element approach was proposed to simulate the fracture behaviour of SFRC in terms of stress-strain response, energy dissipation and crack morphology. The results indicated that under given conditions, the straight and hooked-end fibres improved the compressive damage tolerances of concrete over 11.5% while the spiral fibres had a negligible effect of 2.6%. The tensile macro-damage level index introduced was reduced over 15% by all fibres. Compared to straight fibres, the higher anchoring capacity of spiral fibres reduced the reinforcement performance while hooked-end fibres did not exhibit a significant influence
Plebeius callaghani n. sp. dans le nord de l'Iran (Lep., Lycaenidae)
No full textPlebeius callaghani n. sp. in N. Iran (Lep., Lycaenidae). The new entity was discovered by the second author in the beginning of June 2001 in the subalpine stage of the mountain range on the north of Karaj (prov. Tehràn), and rediscovered recently by Curtis Callaghan on the north of Qazvin (prov. Zanjan). The male of the new species is well characterized by a small size, a dark violet blue upperside showing a broad black suffusion margin, as Plebeius argus Linné, 1758, and, on the underside of the hindwings, by a greyish ground colour with well defined submarginal markings, somewhat P. ferganus (Staudinger, 1881), but without blue-green metallic spot and with a series of orange lunula almost complete. The female is unknown.Carbonell Frédéric, Naderi Ali-Reza. Plebeius callaghani n. sp. dans le nord de l'Iran (Lep., Lycaenidae). In: Bulletin de la Société entomologique de France, volume 112 (1), mars 2007. p. 126
- …
