In this study, evolution of intermetallic layer of the cold roll bonded bilayer of Aluminum-Steel sheets, during severe plastic deformation (SPD) followed by annealing has been investigated. The ...effect of such evolution on mechanical properties has been discussed. For this purpose, Constrained Groove Pressing (CGP) was used as a SPD process. Field emission scanning electron microscope equipped with energy dispersive spectroscopy and optical microscopy were used for examination of intermetallic compounds morphology and composition. Meanwhile, tensile properties of the bilayer sheets were evaluated. According to microstructural observations, continuous intermetallic layer was formed during rolling and annealing processes. This intermetallic layer was completely cracked into very fine particles after the first pass of CGP. Some of these intermetallic compounds were pushed into the base layers by the shear stress and some of them remained at the interface. Moreover, it was observed that during the CGP process, at the interface and between remaining intermetallic compounds and fresh surfaces of both Al and steel, new bonds were formed. After formation of such new bonds and during the second step of the CGP process, flattening process, mechanical interlocks were created. However, after the second CGP pass, no intermetallic compound was observed at the interface yet delamination was seen. Due to formation of intermetallic compounds at the bonding area and the vicinity of it, reinforced area, mechanical interlocks and higher dislocation density in that region, the ultimate tensile strength (UTS) increased after the first pass of CGP, but due to delamination, it decreased in second pass. The effect of evolution of bond structure on the tensile strength was measured by using bonding portion (BP) criterion defined as the difference in the UTS of the bonded versus non-bonded samples undergone similar deformation and annealing treatment. The BP values show similar trend to the UTS data, increased at the first pass and decreased at the second pass. In the following study, the CGPed samples have been annealed in order to recover the intermetallic layer. The CGPed samples were annealed at 350 °C, 400 °C and 450 °C for 30, 60 and 90 min. The optimum thickness of 2.6 μm was observed at the 450 °C in 30 min annealing treatment. The UTS, BP and elongation to break increased 7%, 32% and 60%, respectively, in comparison to those of the as-CGPed sample.
Spontaneous endogenous generators are key elements in immature systems. Theta activity (TA) and the coalescent slow waves (SW) occur from 25wGA and address the basic mechanisms of cross frequency ...interdependencies in oscillations that compose brain rhythms in premature.
To evaluate the interactions between the two oscillations using phase-amplitude coupling.
EEGs of 34 prematures (25–27wGA) were analyzed. Temporal relationships between TA and SW were assessed, using event-locked analysis. SW and TA were automatically detected. Artifact-free epochs time locked to the SW trough were extracted. Time-frequency representations (TFRs) were calculated. To quantify locking between the SW phase and the TA power, a synchronization index was computed. To investigate the temporal relationships between SW and TA, event histograms were created referenced to the SW trough and TA peak.
TFR analysis demonstrated that TA power was increased during the SW descending slope and around the SW trough and showed a lasting suppression during the SW peak. Event histogram analysis confirmed the consistent timing of TA during SW cycle. Maximum TA was reached before the SW trough.
This cross frequency coupling with a so precise intimate temporal relationship between rapid and slow oscillators constitutes an index of “ideal” mechanisms with unique functional and structural wiring in the auditory network, disruptions of which might be of dramatic neurodevelopmental consequences. Coupling between the phase of the slow oscillations and the amplitude of theta oscillations in this early neural biomarker might suggest developing network level dynamics in early prematurity.
A modified grain size-dependent model developed to capture the combined effects of solute and grain size on the work hardening behaviour of fine-grained Cu-Ni alloys is provided. This work builds on ...a recent model that attributes the grain size-dependent work hardening of fine-grained Cu to backstresses. In the case of Cu-Ni alloys, unlike commercially pure Cu, a grain size-dependent separation between the Kocks-Mecking curves develops, this being explained here based on an extra contribution from geometrically necessary dislocations in the solid solution alloy. This is corroborated by strain-rate sensitivity experiments.
No-till practices play an important role in decreasing production costs, increasing soil organic matter content, improving soil structure and removing unwanted environmental impacts. However, due to ...a lack of access to proper machinery for direct seeding in unplowed lands, such practices have failed to produce successful results since they are incapable of providing sufficient contact between soil and seeds. Introducing a machine that can plant seeds and fertilizer at two different depths in hard (unplowed) soils covered with last season’s crop residues can be the first step towards pilot no-till initiatives. This step can finally lead to the promotion of this practice in the potential areas. In this study, different components of a disk furrow opener were optimally designed in Solid Works modelling software. ANSYS was used to analyze this furrow opener and its three main related components. Finally, the coulter’s stress was determined using the von Mises criterion. The result showed that the minimum coulter stress was 1985.5Pa throughout the plane and its maximum belonged to the holes inside the hub with 1.0819x107Pa. The safety factor of the initial coulter was 17.85, while that of the optimally designed coulter was 25.
Lifetime measurements of the 5
−
1, 4
−
1, and 3
−
2 levels in
144Nd, coupled with measurements of the
M1/
E2 mixing of the 4
−
1→3
−
1 and 3
−
2→3
−
1 transitions, show that the transition strengths ...from these levels are in good agreement with those expected for quadrupole–octupole coupled states. Admixtures of the
ν
2(
f
7/2
i
13/2) quasiparticle configuration are the most likely explanation for the relatively large
B(
M1:4
−→3
−) value measured in the current work and the previously measured
B(
E5:5
−→0
+) value.
The study of the anisotropy of the arrival directions is an essential tool to investigate the origin and propagation of cosmic rays primaries. A simple way of recording many cosmic rays is to record ...coincidences between a number of detectors. We have monitored multi-TeV cosmic rays by a small array of water cherenkov detectors in Tehran(35 43 N, 51 20 E, 1200m a.s.l). More than 1.1*10^6 extensive air shower events were recorded. In addition to the Compton- Getting effect due to the motion of the earth in the Galaxy, an anisotropy has been observed which is due to a unidirectional anisotropy of cosmic ray flow along the Galactic arms.
The portfolio selection is one of the most important and vital decisions that a real or legal person, who invests in stock market, should make. The main purpose of this article is the determination ...of the optimal portfolio with regard to relations among stock returns of companies which are active in Tehran's stock market. For achieving this goal, weekly statistics of company's stocks since Farvardin 1389 until Esfand 1390, has been used. For analyzing statistics and information and examination of stocks of companies which has change in returns, factors analysis approach and clustering analysis has been used (FC approach). With using multivariate analysis and with the aim of reducing the unsystematic risk, a financial portfoliois formed. At last but not least, results of choosing the optimal portfolio rather than randomly choosing a portfolio are given.
Today, reverse logistics (RL) is one of the main activities of supply chain management that covers all physical activities associated with return products (such as collection, recovery, recycling and ...destruction). In this regard, the designing and proper implementation of RL, in addition to increasing the level of customer satisfaction, reduces inventory and transportation costs. In this paper, in order to minimize the costs associated with fixed costs, material flow costs, and the costs of building potential centres, a complex integer linear programming model for an integrated direct logistics and RL network design is presented. Due to the outbreak of the ongoing global coronavirus pandemic (COVID-19) at the beginning of 2020 and the consequent increase in medical waste, the need for an inverse logistics system to manage waste is strongly felt. Also, due to the worldwide vaccination in the near future, this waste will increase even more and careful management must be done in this regard. For this purpose, the proposed RL model in the field of COVID-19 waste management and especially vaccine waste has been designed. The network consists of three parts – factory, consumers’ and recycling centres – each of which has different sub-parts. Finally, the proposed model is solved using the cuckoo optimization algorithm, which is one of the newest and most powerful meta-heuristic algorithms, and the computational results are presented along with its sensitivity analysis.
The parameter setting of meta-heuristic algorithms is one of the most effective issues in the performance of meta-heuristic algorithms and is usually done experimentally which is very time-consuming. ...In this research, a new hybrid method for selecting the optimal parameters of meta-heuristic algorithms is presented. The proposed method is a combination of data envelopment analysis method and response surface methodology, called DSM. In addition to optimizing parameters, it also simultaneously maximizes efficiency. In this research, the hybrid DSM method has been used to set the parameters of the cuckoo optimization algorithm to optimize the standard and experimental functions of Ackley and Rastrigin. In addition to standard functions, in order to evaluate the performance of the proposed method in real problems, the parameter of reverse logistics problem for COVID-19 waste management has been adjusted using the DSM method, and the results show better performance of the DSM method in terms of solution time, number of iterations, efficiency, and accuracy of the objective function compared to other.
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