The present work was planned to investigate the microstructural evolution and mechanical properties of a metastable β-type titanium alloy composing of Ti–27.96Nb–11.97Ta–5.02Zr %wt (so-called TNTZ ...alloy), after applying a predetermined low-temperature thermomechanical processing (LTMP) cycle. The room temperature uniaxial tensile testing was utilized to evaluate the processed material flow behavior. To this end, the occurrence of any phase transformation and twinning-induced elasto-plasticity effects along with the work hardening behavior of the experimental TNTZ alloy were thoroughly studied. A double yielding phenomenon was realized in the specimens subjected to cold rolling and subsequent short time annealing. The XRD analysis confirmed an increase in volume fraction of α″ martensite as a result of deformation-induced martensite transformation in the microstructure. Electron backscatter diffraction (EBSD) analysis revealed that low angle boundaries would form within grains holding near (001) texture and might well act as a preferred nucleation site to develop deformation-induced martensite. The intersections of α″ martensite and the contribution of dynamic Hall-Petch effect could result in spectacular work hardening behavior in comparison to other β-type titanium alloys. The presence of sub-sized grains in the microstructure was related to the martensite reversion; this could further increase the strain hardening rate in the experimental alloy.
•Complex structural stresses of spot welds during tensile shear test were estimated.•For the first time stress-strain curve and work hardening rate were estimated.•Work hardening of TWIP steel joints ...showed plateau due to occurrence of TWIPing.
Proper assessment of mechanical properties for friction stir spot welds is controversial due to complex stress conditions within the weld nugget. Because of that, mechanical testing results are expressed in terms of load displacement curves; therefore, interpretation of the plastic behavior by stress-strain curve is theoretically impossible. In the present work, stress intensity factors and complex structural stresses of spot welds during tensile shear test were estimated through analytical simulation based on fracture mechanics methods for elastic and plastic regions. Subsequently, the stress-strain curve and the corresponding work hardening rate were estimated and interpreted with acceptable precision. The experiments were performed using a high manganese twinning induced plasticity steel which is one of the commonly used steel grades in automotive industry. The best combination of tensile-shear strength and extension was found for the joints welded at rotation speed of 1600 rpm where stress intensity factor of mode I contribution was the highest. The occurrence of twinning induced plasticity in a higher extent was the main reason for an increase in extension and work hardening of this sample.
Hot deformation behavior of the Ni-based superalloy IN-738LC was investigated by means of hot compression tests over the temperature range of 1000-1200 °C and strain rate range of 0.01-1 s
−1
. The ...obtained peak flow stresses were related to strain rate and temperature through the hyperbolic sine equation with activation energy of 950 kJ/mol. Dynamic material model was used to obtain the processing map of IN-738LC. Analysis of the microstructure was carried out in order to study each domain’s characteristic represented by the processing map. The results showed that dynamic recrystallization occurs in the temperature range of 1150-1200 °C and strain rate of 0.1 s
−1
with the maximum power dissipation efficiency of 35%. The unstable domain was exhibited in the temperature range of 1000-1200 °C and strain rate of 1 s
−1
on the occurrence of severe deformation bands and grain boundary cracking.
Two new polyclad species, from northern intertidal zone and shallow rocky shores of the Persian Gulf, Discocelispersica sp. nov. and Discocelis hollemani sp. nov., are described. D. persica possesses ...a thick and broadly oval body tapering somewhat posteriorly, without any obvious color pattern; with marginal eyes extended around the anterior margin of the body; cerebral eyes forming two clusters, each further subdivided into anterior and posterior groups, about 100 eyespots at the anterior group and 55 eyespots at the posterior groups; mouth at the posterior end of the pharynx; male atrium with three to four distinct lobes, with numerous prostatoid organs of two distinct sizes, without villus-like projections; and with a horseshoe-shaped Lang's vesicle. D. hollemani characterized by a thick and broadly oval body, not tapering antro-posteriorly, without any obvious color pattern; marginal eyes extended to the vicinity of the posterior end of pharynx; the cerebral eyes forming two clusters, each further subdivided into anterior and posterior groups in relation to the cerebral organ, about 50 eyespots at the anterior group and 20 eyespots at the posterior groups; mouth at the posterior end of the pharynx; the male atrium with two distinct lobes, with numerous prostatoids of two distinct sizes and different contents; villus-like projections absent, and with a horseshoe-shaped Lang's vesicle.
In this investigation, the amounts of organic matter, types of sediment and distribution of macrobenthic species in the Boojagh Marine National Park (BMNP) were studied. Sampling was conducted in six ...transects perpendicular to the beach using a Van Veen grab sampler using cross section of 20 cm with five replications. Samples were collected in five seasons (from summer 2015 to summer 2016). Each transect include three stations at various depths of 1, 5 and 10 meters. Samples were washed and fixed in formalin. Then, they were transferred to a laboratory for sorting and identification of different groups of macrobenthic taxons. The identified species were as follows; Cerastoderma glaucum, Mytilaster lineatus, Pyrgula grimmi, Anisus kolesnikovi, Stenogammarus carusui, Paraniphargoides motasi, Onisimus caspius, Pterocuma pectinatum, Pterocuma sowinskyi, Pseudocuma (Stenocuma) gracile, Naiss sp., Hypania invalida, Manayunkia caspica, Streblospio gynobranchiata, Hediste diversicolor and Amphibalanus improvisus. Evaluation of sediment composition indicated that the highest proportions belonged to sand with an average amount of 89/25%, whereas the lowest proportions belonged to clay with an average amount of 0/26%. with highly significant difference among sand identified with other particles (P<0/01). The average percentage of organic matter in the summer 2015 in the fourth transect at the depth of five meters was significantly lower than that of the others (P<0/01). The highest density of macrobenthos was at the depth of 10 meters. Macrobenthos density was the highest in the summer 2015 and was the lowest in the spring 2016 as compared to the other seasons.
Geocasting is a variation of traditional multicasting in which the goal is to deliver a packet to all nodes within a geographical area often referred to as a geocast region. Several protocols have ...been designed for geocasting in mobile ad hoc networks (MANETs) which focus on how to route packets to the geocast region efficiently, while packet delivery within the geocast region is usually achieved by flooding. Given the known limitations of simple flooding on a network, it is beneficial to look for solutions that improve the packet delivery mechanism within a geocast region. In this paper, a protocol is proposed that extends existing geocast protocols by supporting a novel packet delivery mechanism through the use of efficient flooding. The solution employs coverage information and partitioning the geocast region into grids. Using coverage information, only nodes that can reach the new portion of the region, which has not been covered by a transmission, will rebroadcast the packet. The paper shows that this solution is superior to simple flooding since it reduces the number of redundant retransmissions within the geocast region considerably.
In this investigation, the amounts of organic matter, types of sediment and distribution of macrobenthic species in the Boojagh Marine National Park (BMNP) were studied. Sampling was conducted in six ...transects perpendicular to the beach using a Van Veen grab sampler using cross section of 20 cm with five replications. Samples were collected in five seasons (from summer 2015 to summer 2016). Each transect include three stations at various depths of 1, 5 and 10 meters. Samples were washed and fixed in formalin. Then, they were transferred to a laboratory for sorting and identification of different groups of macrobenthic taxons. The identified species were as follows; Cerastoderma glaucum, Mytilaster lineatus, Pyrgula grimmi, Anisus kolesnikovi, Stenogammarus carusui, Paraniphargoides motasi, Onisimus caspius, Pterocuma pectinatum, Pterocuma sowinskyi, Pseudocuma (Stenocuma) gracile, Naiss sp., Hypania invalida, Manayunkia caspica, Streblospio gynobranchiata, Hediste diversicolor and Amphibalanus improvisus. Evaluation of sediment composition indicated that the highest proportions belonged to sand with an average amount of 89/25%, whereas the lowest proportions belonged to clay with an average amount of 0/26%. with highly significant difference among sand identified with other particles (p<0/01). The average percentage of organic matter in the summer 2015 in the fourth transect at the depth of five meters was significantly lower than that of the others (p<0/01). The highest density of macrobenthos was at the depth of 10 meters. Macrobenthos density was the highest in the summer 2015 and was the lowest in the spring 2016 as compared to the other seasons.
Neuro Fuzzy Model Predictive Control of AQM Networks Supporting TCP Flows Maghsoudlou, A.R.; Barzamini, R.; Soleimanpour, S. ...
2008 Ninth ACIS International Conference on Software Engineering, Artificial Intelligence, Networking, and Parallel/Distributed Computing,
2008-Aug.
Conference Proceeding
One of the challenges in designing computer networks is "queue management and congestion avoidance". There are several studies for congestion reduction and controlling such as random early detection ...(RED) and its variants. More recent works on developing congestion avoidance methods include modeling a TCP flow in an active queue management (AQM) of a bottlenecked network link. Rather than classical control theories, that are applied to improve performance and stability of network flows, some studies are developed based on new control tools such as neural networks. In this article a neuro-fuzzy controller for active queue management is proposed. In this model, the number of neurons are determined according to complexity of the model and instead of using random values for initializing networkpsilas weights, near to optional values are used. The proposed method decreases the network training time and ensures convergence with higher probability. The results of this method show superior performance over other previous controllers such as classical and neural networks methods.
A number of congenital and acquired disorders require esophageal tissue replacement.Various surgical techniques,such as gastric and colonic interposition,are standards of treatment,but frequently ...complicated by stenosis and other problems.Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function.We review the literature of esophageal tissue engineering,discuss its implications,compare the methodologies that have been employed and suggest possible directions for the future.Medline,Embase,the Cochrane Library,National Research Register and ClinicalTrials.gov databases were searched with the following search terms：stem cell and esophagus,esophageal replacement,esophageal tissue engineering,esophageal substitution.Reference lists of papers identified were also examined and experts in this field contacted for further information.All full-text articles in English of all potentially relevant abstracts were reviewed.Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation.When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality.Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration,whilst omental wrapping to induce vascularization of the construct has an uncertain benefit.Decellularized matrices have been recently suggested as the optimal choice for scaffolds,but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution.Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement.Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus.Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease,important barriers remain that need to be addressed.
Juvenile angelfish (Pterophyllum scalare) was exposed to six different concentrations of Naphthalene, Anthracene, Phenanthrene and Pyrene for a period of 132 h. Mortalities were recorded each 12 h ...and an average of total mortalities for three replicates of each PAHs was designated as the endpoint of toxicity for angelfishes. This parameter correlated with geometric descriptors (length, width, thickness, length/breadth ratio, molecular volume and molecular surface area), physiochemical descriptors (molar volume, molecular weight, octanol-water partition coefficient and boiling point) and an electronic descriptor (resonance energy). The regression equations showed the significant correlation for three dimensional geometric descriptors, physiochemical descriptors and resonance energy versus mortality. These results indicate that at the range of log Kow<=5.2, raising three dimensional geometric descriptors values will result in more mortality.
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