Sharif Digital Repository

Biological parameters and life tables are the most appropriate criteria for measuring a population’s adaptation to environmental and dietary circumstances. The effects of temperatures 10, 14, 20, 25, 27, 30, 33, and 35℃ on biological and life table parameters of the carob moth Ectomyelois ceratoniae (Zeller) [a 10:14 hour (D: L cycle) and 65±5% RH] were experimentally studied. Based on the age-stage, two-sex life table theory, data were analyzed at different temperatures. The findings indicated that by increasing temperature, the mean incubation period of eggs, larvae, pupae, total immature development time, and adult longevity change significantly. The Adult Pre-Oviposition Periods (APOP)... 

The recrystallization behavior of an Al-Cu-Mg alloy is investigated in multi-directionally forged over-aged and solution treated alloys, during non-isothermal annealing. Deformation and non-isothermal annealing are performed with a Gleeble 3800 thermo-mechanical simulator. The hardness measurements show that there is a thermal stability in mechanical properties during non-isothermal annealing up to 250 °C with heating rate of 10 K·min− 1. Differential scanning calorimetry curves of deformed over-aged and solution treated alloys describe the related precipitation phenomena. EBSD maps demonstrate that partially recrystallized and fully recrystallized microstructures appear in deformed... 

Concurrent precipitation in an age hardenable aluminum alloy determines recrystallization behavior especially grains structure and recrystallization texture during continuous heating. In this study, to investigate the effect of concurrent precipitation on the recrystallization texture and grains structure, a solution treated Al-Cu-Mg alloy has been multi-directionally forged at room temperature and continuously heated with different heating rates (800, 1600 and 2500 K·min− 1) up to 450 °C using Gleeble 3800 thermo-mechanical simulator. At lower heating rates (800 K·min− 1), Goss texture component {110} 〈001〉 (Φ1 = 90°/0°, Φ = 90°/45°, Φ2 = 45°/90°) is developed during continuous heating and... 

Particle stimulated nucleation (PSN) is one of the important mechanisms of recrystallization which is investigated in this research during non-isothermal annealing of multi-directionally forged solution treated aluminum alloy 2024. Non-isothermal annealing is performed up to temperatures of 380 °C and 450 °C at heating rates of 10, 100 and 200 K·min− 1 using a Gleeble 3800 thermo-mechanical simulator. In order to investigate the microstructure, field emission gun scanning electron microscope (FEG-SEM) equipped with electron backscatter diffractometer (EBSD) and differential scanning calorimetry (DSC) are utilized. The results show that the heating rate has a significant effect on the PSN and... 

The effects of initial heat treatments, i.e. solution treating and over ageing, on deformation behavior of an age hardenable Al-Cu-Mg alloy, including mechanical properties and texture evolution, during multi-directional forging (MDF) are investigated. Hardness measurements, electron back scatter diffraction (EBSD) maps, and differential scanning calorimetry (DSC) are carried out. Mechanical behaviors of the alloy in terms of compressive stress and hardness test after MDF are investigated. In both solution treated and over-aged alloys, the compressive stress during MDF shows an increase up to the second pass, and by further straining the flow stress is decreased. However, shear and... 

Passive cooling systems such as wind towers or wind catchers can create thermal comfort for building residents in hot and dry regions. This paper introduces an experimental study of a modular design of wind tower called the modular wind tower with wetted surfaces. Air temperature, relative humidity (RH) and airflow velocity parameters were measured at different times and at points when the velocity of the ambient air was zero. The results show that the modular wind tower can decrease the air temperature by an average of 10 °C and increase the relative humidity of airflow in a building by approximately 36% on average. Additionally, the wind tower can create the airflow velocity entering the... 

The non-isothermal aging behaviour of a newly developed Al–Zn–Mg–Cu alloy containing 17 wt-% Zn was investigated. Hardness and shear punch tests demonstrated that during non-isothermal aging, the mechanical properties of the alloy first increased and then decreased. The best properties were obtained in a sample which was non-isothermally aged upto 250°C with heating rate of 20°C min−1, due to the presence of η′/η (MgZn2) phases. This was confirmed by differential scanning calorimetery. After homogenisation, residual eutectic phases remained at triple junctions or in a spherical form. During aging, these phases transformed into rodlike S (Al2CuMg)-phase at 400°C, with sizes ranging from 50 to... 

The non-isothermal aging behaviour of a newly developed Al–Zn–Mg–Cu alloy containing 17 wt-% Zn was investigated. Hardness and shear punch tests demonstrated that during non-isothermal aging, the mechanical properties of the alloy first increased and then decreased. The best properties were obtained in a sample which was non-isothermally aged upto 250°C with heating rate of 20°C min−1, due to the presence of η′/η (MgZn2) phases. This was confirmed by differential scanning calorimetery. After homogenisation, residual eutectic phases remained at triple junctions or in a spherical form. During aging, these phases transformed into rodlike S (Al2CuMg)-phase at 400°C, with sizes ranging from 50 to... 

This paper aims at investigating free vibrations and stability of double-walled carbon nanotube (DWCNT)-based spinning nanobearings. The so-called nanobearing consists of two coaxial carbon nanotubes (CNTs) where either of the two CNTs can be a rotor while the other takes the role of stator. Euler–Bernoulli beam model along with the Eringen’s nonlocal theory of elasticity are employed to obtain governing equations of transverse vibrations for the CNTs. The coupling of the two CNTs originates from the van-der-Waals (vdW) forcing present in the interface of the two CNTs. The coupling is taken into account as distributed spring foundation with an equivalent elastic stiffness. Based on the... 

Post-uniform deformation energy of materials is defined as absorbed energy per unit area after necking. The energy is constant for a material type and its experienced specific processing history and also depends on its mechanical parameters as workhardening exponent, strain rate sensitivity, post-necking extension and inhomogeneity factor. Different methods such as single and multiple tensile testing had been proposed in the literature to calculate tearing energy, but the effect of post-necking extension had not been expressed explicitly. A new model by implementing uniform and failure elongations with the combination of Unwin theory is introduced. Based on the model, it was shown that... 

Plasma-catalytic conversion of formaldehyde, as a representative volatile organic compound, in a dielectric barrier discharge reactor over a NiOx/α-Al2O3 catalyst was studied. Effects of plasma treatment on the physicochemical properties of the catalyst were studied and XPS analysis showed that plasma treatment increased the surface contribution of more active sites (i.e. Ni2+ and adsorbed O). However, the physical properties of the catalyst, including BET surface area and porosity, did not significantly change after plasma exposure. Presence of oxygen in the plasma-catalytic process improved conversion efficiency. Individual roles of plasma and catalyst in the selective conversion of... 

Representing nonlinear systems by linear models along with structured or unstructured uncertainties and applying robust control strategies could reduce the computational complexity in comparison with implementing the nonlinear model predictive controllers. In this paper design of robust model predictive controllers which are based on special classes of nonlinear systems representations called Wiener and Hammerstein are presented. The proposed algorithms approximate the nonlinear systems by uncertain linear models and reduce online the computational demands in the control implementation. The advantages of the proposed approaches are illustrated by two examples  

Abstract This paper proposes a bumpless transfer method to overcome the problem of switching jumps in a scheduled robust model predictive control approach. A scheduled robust model predictive controller implements a set of local robust model predictive controllers based on an on-line switching strategy. This method could enlarge the domain of attraction efficiently but the transient response might be hampered by spikes appearing at the moment of switching between adjacent local controllers. The proposed algorithm could enhance the transient response by implementing some intermediate controllers augmented to the main control scheme to solve the problem without needing more computation. The... 

This paper proposes a tracking control strategy for nonlinear systems without needing a prior knowledge of the reference trajectory. The proposed method consists of a set of local controllers with appropriate overlaps in their stability regions and an on-line switching strategy which implements these controllers and uses some augmented intermediate controllers to ensure steering the system states to the desired set points without needing to redesign the controller for each value of set point changes. The proposed approach provides smooth transient responses despite switching among the local controllers. It should be mentioned that the stability regions of the proposed controllers could be... 

Industrial processes are inherently nonlinear with input, state, and output constraints. A proper control system should handle these challenging control problems over a large operating region. The robust model predictive controller (RMPC) could be an linear matrix inequality (LMI)-based method that estimates stability region of the closed-loop system as an ellipsoid. This presentation, however, restricts confident application of the controller on systems with large operating regions. In this paper, a dual-mode control strategy is employed to enlarge the stability region in first place and then, trajectory reversing method (TRM) is employed to approximate the stability region more accurately.... 

Wind towers or wind catchers, as passive cooling systems, can provide natural ventilation in buildings located in hot, arid regions. These natural cooling systems can provide thermal comfort for the building inhabitants throughout the warm months. In this paper, a modular design of a wind tower is introduced. The design, called a modular wind tower with wetted surfaces, was investigated experimentally and analytically. To determine the performance of the wind tower, air temperature, relative humidity (RH) and air velocity were measured at different points. Measurements were carried out when the wind speed was zero. The experimental results were compared with the analytical ones. The results... 

A model has been proposed to capture the complex strain rate effect on dynamic precipitation of GP zones in an age-hardenable aluminum alloy. The contributions of vacancies and dislocations to dynamically formed GP zones have been specified in the model. It has been demonstrated that the proposed model is capable for predicting the contribution of each dynamic precipitation mechanisms, accurately, which are acting during deformation. Furthermore, the vacancy and dislocation evolutions during deformation have been considered in this modeling. The effect of strain rate by considering different mechanisms of dynamic precipitation of GP zones has been studied and confirmed by experimental data... 

Microstructure and mechanical properties of AA2024 after severe plastic deformation (SPD) and non-isothermal annealing were investigated. The non-isothermal treatment was carried out on the severely deformed AA2024, and the interaction between restoration and precipitation phenomena was investigated. Differential scanning calorimetry, hardness and shear punch tests illustrate that static recovery and dissolution of GPB zones/Cu–Mg co-clusters occur concurrently through non-isothermal annealing. Scanning electron microscope and electron backscatter diffraction illustrate that non-isothermal annealing of deformed AA2024 up to 250 °C promotes the particle-free regions and also particle... 

Considering that about 90% of international trade is transported via sea and ship ventilation systems consume between 3.5% and 5.5% of the ship’s rated power, ship energy consumption is of particular interest and modelling and enhancing ventilation systems are vital to reducing and optimising energy consumption. Using Computational Fluid Dynamics (CFD) simulation, modelling heat transfer and airflow patterns helped us improve the ventilation system and temperature distribution, provide thermal comfort for staff and equipment, and increase energy efficiency. We discussed the radiation effect in CFD analysis; it affected wall temperatures significantly and temperature contours to some extent;... 

Prostate Cancer has become one of the deadliest cancers among males in many nations. Pathologists use various approaches for the detection and the staging of prostate cancer. Microscopic inspection of biopsy tissues is the most accurate approach among them. The Gleason grading system is used to evaluate the stage of Prostate Cancer using prostate biopsy samples. The task of assigning a grade to each region in a tissue is a time-consuming task. Furthermore, this task often has several challenges since it has considerable inter-observer variability even among expert pathologists. In this paper, we propose an automatic method for this task using a deep learningbased approach. For this purpose,...