Showing 8 results for Ashtari
Sedighe Ashtari, Qodratollah Sabahi, Khalil Talebi Jahromi,
Volume 7, Issue 4 (9-2018)
Abstract
The effects of four insecticides, abamectin (1500 and 750mgl-1), emamectin benzoate (1000 and 500mgl-1), acetamiprid (500 and 250mgl-1), and flubendiamide (500 and 250mgl-1), were studied on different preimaginal stages of T. brassicae and T. evanescens, the egg parasitoids of tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae). Parasitized eggs of the Angoumois grain moth Sitotroga cerealella (Lepidoptera: Gelechiidae) were treated by the dipping method at the larval, prepupal, and pupal stages of the parasitoid. For persistence evaluation, the insecticides were applied at the recommended concentration on tomato plants by a hand sprayer till runoff point. Plants were maintained under a transparent polyethylene rain cover in the field. Leaves of the treated tomato plants were sampled and transferred to the laboratory at time intervals of 3, 5, 16, and 31 days after application. Based on our study, abamectin was the most harmful insecticide for immature stages of both parasitoids T. brassicae and T. evanescence. Treatment by abamectin at the pupal stage had more adverse effects compared to prepupal or larval stages. Acetamiprid with 30.5% and 31.6% mortality in less than five days was classified as the short-lived insecticide for T. brassicae and T. evanescens, respectively. The same result was obtained in flubendiamide treatment which caused 27.2% and 26.1% mortality to the parasitoids, respectively. Abamectin with 16.1% and 13.8% mortality in less than 16 days was slightly persistent. However, emamectin benzoate with 13.3% and 15.5% mortality in less than 30 days was classified as moderately persistent for those two species, respectively. Therefore, flubendiamide and acetamiprid were non-harmful to both T. brassicae and T. evanescence wasps and are good candidates to be incorporated into IPM programs in combination with biological agents for the control of tomato leaf miner T. absoluta. By contrast, emamectin and abamectin should be used with greater care as a part of an IPM procedure.
Volume 14, Issue 6 (11-2012)
Abstract
Enzymatic acidolysis of canola oil through caprylic acid was investigated to produce certain medium chain Ttriacyliglycerol (TAG) structured lipids (SLs). Lipozyme TL IM, an sn-1,3 specific Thermomyces lanuginosa lipase, and Novozym 435, a non-specific Candida antarctica lipase, were utilized as the biocatalysts in a batch reactor. Reaction conditions were designed according to Taguchi’s approach, considering three levels of fatty acid to oil ratio (1:1, 2:1, and 3:1), three levels of enzyme load (4, 8 and 12%, w/w), three levels of temperature (45, 55, and 65°C) as well as three levels of reaction time (15, 30 and 45 hours). Results indicated that fatty acid composition of canola oil was modified by the above acidolysis reactions. The highest mole percent of caprylic acid incorporation (37.2 mole%) was obtained after 15 hours of incubation in the presence of Lipozyme TL IM at 55°C, fatty acid to oil ratio of 3:1 and at 12% of enzyme level. However, with Novozym 435 the highest level of incorporation (38.5 mole%) was obtained after 45 hours of reaction at 45°C, fatty acid to oil ratio of 3:1, and at 8% enzyme level. Novozym 435 was able to incorporate more caprylic acid in the oil than did Lipozyme TL IM. SLs prepared using either Lipozyme TL IM or Novozym 435 differed in terms of their TAG compositions. According to the obtained results, SLs produced by use of Lipozyme TL IM lipase contained higher levels of MLM-type (Medium-Long-Medium) triacylglycerols than those produced using Novozym 435 lipase (21.2 and 9.9%, respectively).
Volume 15, Issue 2 (3-2013)
Abstract
Spaghetti samples were prepared by replacing wheat flour with defatted soy flour (DSF) at 0, 10, and 20% levels (w/w). Each sample had 4% gluten. In addition, xanthan gum was added at three levels (0.0, 0.2, and 0.4%) to spaghetti dough containing 20% soy flour as a modifying agent. Samples were extruded at 35 or 50oC and dried at, respectively, 52oC for 21h or 72oC for 6 hours. The color, protein content, cooking loss, cooked weight, and firmness of all spaghetti samples were measured. A trained sensory group evaluated chewiness, firmness, stickiness, color, and flavor. The overall results showed that increasing protein level in spaghetti caused an increase in the firmness and cooking loss with a decrease in cooked weight and consumer acceptance. However, when xanthan gum was added to spaghetti dough containing 20% DSF, the positive properties of spaghetti, including cooked weight and consumer acceptances, were improved significantly and its negative aspects, including firmness and cooking loss, were reduced noticeably. When xanthan gum and DSF levels reached, respectively, 0.4 and 20%, and the spaghetti dough was extruded at 50oC followed by drying at average temperature of 72oC, the best spaghetti in terms of physico-chemical and organoleptic properties was obtained.
Volume 18, Issue 2 (7-2014)
Abstract
Abstract Nanotechnology policy making in different countries is performed using various programs. Each country according to its own characteristics and uses of various actors is endeavored critical to the development of this critical field of application. In Iran a special committee of nanotechnology as the key responsible to policy making in this area was formed in 2003 and two years later, Nanotechnology Development Plan has been formulated. This research using Network Analysis Approach is aimed to focus on Nanotechnology Strategic Plan in order to find that to which extent decision making in this area is based on optimal and efficient networking between involved programs and actors in the field. Research findings are showed that there is a relatively significant distribution and balance of power among actors and programs and also an network of communications and co-operations have been formed. Finally, in some of sections, there are centers of power in the network that these arose from the circumstances and needs of the country and have been formed based on purposeful policy making.
Volume 19, Issue 2 (7-2019)
Abstract
The purpose of this study is to develop the previous proposed analytical model by the first and second authors for short links, so it can be used for all kinds of links including short, intermediate, and long links. Eccentrically braced frames (EBF) offer high lateral stiffness because of their braced configuration while also providing high ductility and energy dissipation. They are widely used as a lateral-force resisting system for multi-story buildings located in seismic areas. The key components of the EBF system include columns, collector beams, braces and active links. The active links are designed to provide ductility and energy dissipation through yielding under design basis earthquakes, while all other structural members are designed to be stronger than the links and stay in elastic range. The link is defined by a horizontal eccentricity between the intersection points of the two brace centerlines with the beam centerline. Sufficient analytical model which can accurately predict the inelastic performance of the links is needed to perform reliable nonlinear analyses of EBFs. Analytical models that are used to study the inelastic seismic response of the EBFs usually reflect the anticipated behavior of the different frame elements. Links are modeled as inelastic elements with concentrated end flexural and shear hinges. Beams outside of the link, braces, and columns are typically modeled as elastic beam-column elements, because no inelastic behavior is anticipated in design. Ricles and Popov proposed an analytical model for short links. Ramadan and Ghobarah replaced the sub-hinges with translational and rotational springs and proposed a new model. Both models had incorrect shear stiffness so that the shear stiffness of model was half the link shear stiffness. Richards and Uang corrected the shear stiffness of the model proposed by Ramadan and Ghobarah, and proposed a new analytical model for short links. Koboevic et al. proposed an analytical model based on the results of experimental test performed by Okazaki and Engelhardt, regardless of the fact that the actual measured dimensions of sections were different from the standard dimensions of sections. To account for this issue, despite of what is said in their paper, the strain-hardening ratio was set to 0.0045. For this reason, the shear stiffness of their proposed model was incorrect and the predicted shear forces are 15 to 24 percent more than the experimental shear forces. Ashtari and Erfani showed that available analytical models do not predict very well the maximum shear forces and deformations too, and proposed an analytical model which can accurately predict both maximum and intermediary values of shear force and deformation of short links. To the authors’ knowledge, currently there are only suitable analytical models for short links. In this study an analytical model which can accurately predict both maximum and intermediary values of forces and deformations for short, intermediate, and long links, is proposed. The parameters of model are established based on test results from several experiments on links and EBFs. Comparison of available test results with the hysteresis curves obtained using the proposed analytical model established the accuracy of the model. The proposed model is recommended to be used to perform inelastic analyses of EBFs.
Volume 19, Issue 3 (9-2015)
Abstract
The aim of this research is exploring and analyzing the informational interactions among the actors of Iran’s nanotechnology domain by the quantitative exploring of their relations using Network Analysis approach. Recognition and delineation of the informational networks resulted in identification of powerful and influential actors and the weaknesses and strengths of status and relations among the actors. The results can be used by policy analysts and policy-makers as policy tools. The results in the individual level of actors revealed that Iran’s Nanotechnology Initiative Council with the highest amount of centrality is the most powerful actor of network. In the current conditions which Iran’s nanotechnology has not been entered to commercialization phase sufficiently, established institutions by the government to develop this technology have the highest amount of centrality in network. Also Nano Products Production Companies Group and Policy-Maker Institutions Group are the most powerful groups in the information network, respectively. On the other hand, Policy-maker institutions have the least informational interactions with media, non-governmental associations, and promotional institutions.
Volume 20, Issue 5 (11-2020)
Abstract
Structures designed to resist moderate and frequently occurring earthquakes must have sufficient stiffness and strength to control deflection and prevent any collapse. Since stiffness and ductility are generally two opposing properties; it is desirable to devise a structural system that combines these properties in the most effective manner without an excessive increase in the cost. Steel structural systems including moment resisting and concentrically braced frames have been widely used to resist earthquake loads. Concentrically Braced Frames (CBFs) have high stiffness, and due to the probable buckling of their diagonal members, are not ductile enough. Versus, Moment-Resisting Frames (MRFs) have adequate ductility as their beam sections can undergo inelastic deformations. However, due to the low stiffness of moment frames, the construction costs will be increased. In recent decades, steel shear panels are utilized as one of the lateral resistant systems, in Steel Plate Shear Walls (SPSWs), and the link beam of steel frames with eccentric bracing to achieve the aim of shear performance and keep the adjacent members in the elastic range. The Tubular frame is one of the common lateral resistant systems in which the columns are placed in close spaces and connected through deep MRF beams around the building perimeters. Based on the new design codes, the minimum limit of span-to-depth ratio (7 for moderate moment-resisting frames and 5 for special moment-resisting frames) is not satisfied at tubular system. So the idea of Shear Resisting Frames (SRFs) with non-prismatic beams connected by a shear fuse in the middle of the span was proposed as one of the alternatives. Using SRFs remove these limitations and increase the energy dissipation capability. In this new concept, the shear force in the beam is considered as the displacement-controlled component of the system. Similar to eccentrically braced frames (EBFs), the link is tuned as a sacrificial component so that the seismic energy is dissipated by shear yielding in a small segment in the middle of the beam. According to the stiffeners layout, lateral loading capacity in SRFs usually is achieved through buckling strengths or post- buckling capacity resulted from tension field action or load carrying capacity from the yielding of the web plates. So stiffeners play a crucial role in the lateral loading capacity of shear resisting frames and have a significant effect on the energy dissipation capability. Following this issue, the effect of transverse stiffeners with different layouts and placements (various spaces and two or one-sided arrangement) on the seismic performance parameters (response modification factor, overstrength factor and rotation capacity of link beam) of steel shear frames with different link length ratios where all of them are controlled with shear behavior, are evaluated by finite element cyclic and pushover analysis. At the end, an optimum space is proposed for different link length ratios and the response modification factors and overstrength factor of multi-story shear resisting frames including 3, 5, 7, 9, 10, 15, and 20-story for a specific link length ratio are presented. Also for facilitating the modeling process of multi-story SRFs in SAP2000 software, modeling parameters and acceptance criteria were extracted from cyclic and monotonic curves. Finally, pushover curves from SAP2000 were compared to ABAQUS to validate these parameters. At the end, a 25-story building with two different lateral resisting systems including tubular frame and SRFs were compared.
Volume 21, Issue 3 (5-2021)
Abstract
Nowadays, building structures encounter with challenges such as construction speed and cost, especially in high seismicity zones. To accomplish this, steel structures was developed to accelerate the construction process and other economic issues. According to high strength ductility and energy dissipation, steel structure systems have been used widely in active seismic regions. The idea of application of shear panels has been using from many years ago as systems with high energy dissipation capability in EBFs as link beams and steel shear walls. The purpose of the EBFs design is the yielding of link beam and remaining the adjacent member at elastic region. According to the available criteria in design codes, shear in beams is a force-controlled action that exceeding the specified value as nominal strength is not permissible and the capacity design theory should be considered. Increasing the web thickness is the main effective factor achieving the needed shear strength and leads to the enhancement of plastic flexural capacity. The result of this action is more seismic demands in other structural members to keep in desirable operational level. So the shear plastic hinges is introduced instead of flexural plastic hinges at both ends. At this case because of uniform shear yielding through the web, energy dissipation capability is much better than the flexural yielding which begins from the outer face of the beam located on flanges. The web panels of built-up sections restrained by top and bottom flanges and two-sided transverse stiffeners have the ability to carry further loading beyond the web buckling load. The small lateral web displacements produced by excessive loading are not substantial because of available components to supply more resistance. Using adequate stiff transverse to resist against the out-of-plane deformation resulted from post-buckling; tension field actions are developed in shear panels before reaching the maximum shear strength by forming a truss with tension diagonals and compression verticals fixed by stiffeners.
The concept of shear resisting frames with non-prismatic beams were presented with the scope of reduction in link beam rotation, elimination of architectural limitations, restrictions on the ratio of span free length to beam total depth and high energy dissipation capacity. Shear yielding and out of plane deformations caused by tension action field mainly control the frame behavior and energy dissipation. The proposed system is made up two strong side columns connected to the link element with weaker section in the middle of the frame as shear fuse with non-prismatic beams. Tendency to use haunched beams makes it feasible to achieve any link length ratio especially less than 1.0. This paper presents the introducing, design and performance of 1-story-shear resisting frames with different link length ratios (ranges from 0.5 to 1.6 with 0.1 variations) and shear-controlled behavior. The goal is achieved by implementing pushover and cyclic analyses numerically with ABAQUS software. But at first a verification analysis is done to validate the modeling procedure and reach a good conformity between numerical and experimental results. The outputs are presented in the form of response modification factor, displacement ductility and overstrength factor for pushover analyses and hysteresis behavior, backbone curve, energy dissipation capability and overstrength factor for cyclic analysis. Also at the end, 3, 5 and 7-story-frames were studied through pushover analysis and values of response modification factor and overstrength factor of the total frames presented. The results indicate desirable behavior of 1-story-shear resisting frames from the point of stiffness and strength degradation with high values of response modification factor equal to 9.18.