Sharif Digital Repository

In the present work, the feasibility of friction stir welding (FSW) of poly(methyl methacrylate) sheets was studied experimentally and theoretically by employing thermomechanical simulations. The effect of processing parameters including tool plunge depth, tilt angle, tool rotational speed (w), and transverse velocity (v) was investigated to determine suitable conditions to attain sound and defect-free joints. It is shown that a low tool plunge depth of 0.2 mm and a tilt angle of 2° provide suitable material flow to gain sound joints. By controlling the heat input into stir zone by increasing the tool rotational speed and decreasing linear velocity, the formation of defects can be minimised.... 

The effects of various process parameters on caustic current efficiency (CCE) in a zero-gap oxygen-depolarized chlor-alkali cell employing a state-of-the-art silver plated nickel screen electrode (ESNS®) were studied. For doing a thorough research, we selected the process parameters from both cathodic and anodic compartments. Seven process parameters were studied including anolyte pH, temperature, flow rate and brine concentration from the anode side, oxygen temperature and flow rate from the cathode side and the applied current density. The effect of these parameters on CCE was determined quantitatively. A feed forward neural network model with the Levenberg-Marquardt (LM) back propagation... 

Abstract: A novel simple synthetic procedure for improving cell efficiency and reducing the production cost of TiO2 dye-sensitized solar cells (DSSCs) by modification and optimization of homemade formulated paste is reported. This is achieved in terms of morphological manipulation of deposited monolayer TiO2 films by controlling three processing parameters of paste formulation. These parameters are tailored to obtain a paste with proper viscosity suitable for spin-coating technique and to achieve uniform, homogeneous, and crack-free films with good connections between TiO2 grains and porous structure. Photovoltaic measurements show that TiO2... 

In this study, hot rolling behavior of a low alloy steel in the dual-phase region is studied. The effects of various process parameters such as initial temperature, soaking time, rolling speed and the cooling conditions are investigated. Then, mechanical testing and microstructural studies are performed and the effects of process parameters are studied and finally the optimum rolling program is determined based on the achieved results. The results show that rolling speed significantly alters the final microstructures and mechanical properties. Higher rolling speed results higher volume fraction of ferrite phase. In addition, the optimum dual-phase microstructure for this steel can be... 

We introduce a novel probabilistic framework to achieve robust non-fragile tuning methods in control of processes with parametric uncertainties. We consider probability distributions to model the process parameters' uncertainties. First, we propose the tuning framework in a general setting. Then, as an illustration, we apply it to PD control of IPD-modeled processes. It is noteworthy that the proposed tuning method is robust against the considered parametric uncertainties. Also, to empower the proposed robust tuning method in the viewpoint of non-fragility, we utilize a centroid approach. Selecting the form of the probabilistic framework, we empirically observe some of the popular tuning... 

Leakage power has already become the major contributor to the total on-chip power consumption, rendering its estimation a necessary step in the IC design flow. The problem is further exacerbated with the increasing uncertainty in the manufacturing process known as process variability. We develop a method to estimate the variation of leakage power in the presence of both intra-die and inter-die process variability. Various complicating issues of leakage prediction such as spatial correlation of process parameters, the effect of different input states of gates on the leakage, and DIBL and stack effects are taken into account while we model the simultaneous variability of the two most critical... 

Determining an optimum height is remarked as one of the most important issues in heap designing and this is obtained by calculating the number and the height of heap lifts. Although the increase of lift height has benefits in heap leaching method from economic point of view, it will reduce the stability and make process problems such as low permeability. The current paper analyzes the effect of sulphuric acid irrigation on the strength parameters of Miduk oxide copper ores. In addition, the result of the process experiments have evaluated with different irrigation rates as well as variable conditions of permeability. From process view, approximately 75% of copper is recovered at irrigation... 

Statistical Process Control (SPC) is an approach that uses statistical techniques to monitor the process. The techniques of quality control are widely used in controlling any kinds of processes. One of these processes is the short processes. In short run processes often do not have enough data in each run to produce good estimates of the process parameters. This will cause the reduction of the performance and efficiency of control charts. A common solution to this problem is considering a single machine or process to produce many different parts, or different products. In this paper a new method based on non-conformity degree and fuzzy membership functions has been developed for controlling... 

Stabilised titania sols were prepared using an additive free particulate sol-gel route, via electrostatic stabilisation mechanism, with various processing parameters. Peptisation temperature, 50°C and 70°C, and TiO2 concentration, 0.1, 0.2 and 0.4 molar, were chosen as processing parameters during sol preparation. Results from TiO2 particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter (13 nm) and the highest zeta potential (47.7 mV) were obtained for the sol produced at the lower peptisation temperature of 50°C and lower TiO 2 concentration of 0.1 M. On the other hand, between the sols prepared at 70°C, smaller titania particles (20 nm) and higher... 

The immense space of composition-processing parameters leads to numerous trial-and-error experimental works for engineering of novel bulk metallic glasses (BMGs). To tackle this challenging problem, it is required to consider specific guidelines which are able to restrict the productive alloying compositions. In this work, a correlation-based neural network (CBNN) approach was developed, based on a dataset of 7950 alloying compositions, to design potential new MGs through prediction of casting ability, reduced glass transition (Trg) and critical thickness (Dmax). This approach involves individual and mutual characteristics of contributory factors to improve the prediction accuracy. To... 

Motion blur is one of the most common blurs that degrades images. Restoration of such images are highly dependent to estimation of motion blur parameters. Many researchers have developed algorithms to estimate linear motion blur parameters. These algorithms are different in their performance, time complexity, precision and their robustness in noisy environments. In this paper we have presented a novel algorithm to estimate linear motion blur parameters such as direction and extend by using Radon transform to find direction and fuzzy set concepts to find its extend. The most benefit of this algorithm is its robustness and precision in noisy images. Our method was tested on a wide range of... 

This paper introduces an analytical method for approximating the performance of a soft real-time system modeled by a single-server queue. The service discipline in the queue is earliest-deadline-first (EDF), which is an optimal scheduling policy. Real-time jobs with exponentially distributed deadlines arrive according to a Poisson process. All jobs have deadlines until the end of service and are served non-preemptively. Occurrences of transient faults in the server are also taken into account. The important performance measure to calculate is the loss probability due to deadline misses and/or transient faults. The system is approximated by a Markovian model in the long run. A key parameter,... 

A new composite adaptive control strategy is developed for both of the reduction of cancer tumor volume and the online identification of tumor parameters during the drug delivery process in chemotherapy. This control strategy is developed for three different nonlinear mathematical cell-kill models of the cancer tumor including the log-kill hypothesis, Norton-Simon hypothesis and Emax hypothesis. All of these models are considered to have fully parametric uncertainties. The stability, tracking convergence and parameters identification convergence during the chemotherapy process are proved using the Lyapunov method. For the first time, the parameters identification of the uncertain... 

Indium tin oxide (ITO) thin films have been deposited using RF sputtering technique at different pressures, RF powers, and substrate temperatures. Variations in surface morphology, optical properties, and film resistances were measured and analyzed. It is shown that a very low value of sheet resistance (1.96 ω/sq.) can be achieved with suitable arrangement of the deposition experiments. First, at constant RF power, deposition at different pressure values is done, and the condition for achieving minimum sheet resistance (26.43 ω/sq.) is found. In the next step, different values of RF powers are tried, while keeping the pressure fixed on the previously found minimum point (1-2 Pa). Finally,... 

In this work, a three-dimensional model has been proposed to predict temperature distribution and weld-pool shape during dissimilar arc welding of low-carbon steel (CK4) and ferritic stainless steel (AISI 409). The model has been developed using the finite-element software ANSYS, while in the analysis, the effects of process parameters, as well as dilution, in the weld pool have been considered. To verify the predictions, welding experiments were conducted under different welding conditions, and the model results were then compared with the measured weld-pool geometry; a reasonable consistency was observed  

In this study organically modified nanoclay were prepared by exchanging of the cetyltrimethylammonium (CTAB), with inorganic/metal ions/cations in montmorillonite structure. To investigate the influence of the amount of modifier on basal spacing and subsequent removal efficiency of hydrocarbon, different amount of modifier was used. The modified and unmodified nanoclays characterized by XRD, CHN and FTIR techniques. The X-ray diffraction results showed that the interlayer spacing of CTAB-modified clays increased from 12 to 22Å. The effectiveness of the sorbent materials for sorption of a range of products was investigated using crude oil, kerosene, gasoline and toluene. The process... 

In this work, an optimum multilayer perceptron neural network is developed to model the correlation between hot working parameters (temperature, strain rate and strain) and flow stress of IN625 alloy. Three variations of standard back propagation algorithm (Broyden, Fletcher, Goldfarb and Shanno quasi-Newton, Levenberg-Marquardt and Bayesian) are applied to train the model. The results show that, in this case, the best performance, minimum error and shortest converging time are achieved by the Levenberg-Marquardt training algorithm. Comparing the predicted values and the experimental values reveals that a well trained network is capable of accurately calculating the flow stress of the alloy...