Sharif Digital Repository

Recently, moment dual approach of sums of squares relaxations developed for polynomial optimization problems was successfully extended to optimization problems with polynomial matrix inequality constraints. In this paper, we first derive an efficient polynomial formulization for matrix rank minimization problem which does not add any slack variable or additional equality or inequality constraint. Using the aforementioned theory, then we propose a hierarchy of convex LMI relaxations to provide a sequence of increasingly tight lower bounds on the global minimum rank of an arbitrary matrix under linear and polynomial matrix inequality constraints. Surprisingly enough, these lower bounds are... 

In this paper, the intra-cell link adaptation problem is formulated as a constrained nonconvex nondifferentiable optimization problem to maximize the average link throughput while guaranteeing the best possible coverage reliability. We proceed to solve the resulted nonsmooth optimization problem using proximal point bundle method known in nondifferentiable optimization context. For this purpose, we first exploit the problem structure and reduce the original large scale optimization problem to a sequence of one-dimensional problems coordinated by a master program using direct primal decomposition technique. Proximal bundle method with aggregation policy is then adopted in master program to... 

We consider the problem of minimizing rank of a matrix under linear and nonlinear matrix inequality constraints. This problem arises in diverse applications such as estimation, control and signal processing and it is known to be computationally NP-hard even when constraints are linear. In this paper, we first formulize the RMP as an optimization problem with linear objective and simple nonlinear semialgebraic constraints. We then proceed to solve the problem with augmented Lagrangian method known in nonlinear optimization. Despite of other heuristic and approximate methods in the subject, this method guarantees to find the global optimum in the sense that it does not depends on the choice of... 

Monitoring the oxygen in the fume and controlling its amount at high temperatures is an efficient way to regulate combustion efficiency. Zirconia can be an attractive candidate for use in oxygen sensors due to its good physical and chemical properties. The crystal structure of pure zirconia nanopowder due to the lack of cubic phase cannot be used for the fabrication of gas sensor electrodes. Moreover, the change of temperature during ceramic processing and application can promote structural and phase stresses. In this work, to achieve a pure cubic phase, yttria was successfully added to zirconia by a large-scale and effective method called Pechini. The yttria-stabilized zirconia nanopowders... 

TiO2/ZnO and ZnO/TiO2 nanolayer thin films were synthesized using sol-gel method. Optical analysis revealed high transmittance of the films in the visible range with almost the same bandgap energy for the both systems. XPS technique shows stoichiometric formation of TiO2 and ZnO on the surface of TiO2/ZnO and ZnO/TiO2 layers, respectively. According to AFM observations and its data analysis, the TiO2/ZnO films exhibited a higher surface roughness and more effective interfaces with electrolyte during redox reactions. Based on photoelectrochemical measurements, TiO2/ZnO nanolayer photoanode possesses a lower charge transfer resistance and higher transient time for charge carriers (e- and h+)... 

In this study, the effects of TiO2 addition on the physical and photoelectrochemical properties of ZnO thin films have been investigated. The (TiO2)x-(ZnO)1-x nanocomposite thin films were dip-coated on both glass and indium tin oxide (ITO)-coated conducting glass substrates with various values of x, specifically 0, 0.05, 0.1, 0.25 and 0.5. Optical properties of the samples were studied by UV-vis spectrophotometry in the range of 300-1100 nm. The optical spectra of the nanocomposite thin films showed high transparency in the visible region. The optical bandgap energy of the (TiO2)x-(ZnO)1-x films increased slightly with increasing values of x. The crystalline structure of the nanocomposite... 

The approximation power of general feedforward neural networks with piecewise linear activation functions is investigated. First, lower bounds on the size of a network are established in terms of the approximation error and network depth and width. These bounds improve upon state- of-the-art bounds for certain classes of functions, such as strongly convex functions. Second, an upper bound is established on the difference of two neural networks with identical weights but different activation functions. © The Author(s) 2018  

Deep excavation in urban areas can cause instability problems due to significant settlement at the ground surface and large movements at the excavation facing walls. One of the most popular methods used to stabilise these excavations is utilising soil-nailing method. This method has also been widely used to stabilise natural slopes and earth retaining structures. Because of the complexity involved in the mechanism of this stabilising system due to interacting effects of the soil, nails, grout and shotcrete, numerical modelling with high accuracy should be used to analyse the behaviour of the soil-nailed walls. Considering all aspects of soil-structure interaction in the present research, a... 

Deep excavation in urban areas can cause instability problems due to significant settlement at the ground surface and large movements at the excavation facing walls. One of the most popular methods used to stabilise these excavations is utilising soil-nailing method. This method has also been widely used to stabilise natural slopes and earth retaining structures. Because of the complexity involved in the mechanism of this stabilising system due to interacting effects of the soil, nails, grout and shotcrete, numerical modelling with high accuracy should be used to analyse the behaviour of the soil-nailed walls. Considering all aspects of soil-structure interaction in the present research, a... 

In the present study, the effect of using magnetorheological elastomer materials and a magnetic field on the dynamic stability of a sandwich beam under a follower force has been investigated for various boundary conditions. The considered sandwich beam consists of a magnetorheological elastomer core constrained by elastic layers. The structural governing equations are derived using Hamilton’s principle and solved by the finite element method. The validity of the result is examined by comparison with those in the literature. The effects of variation in the parameters such as magnetic field intensity and the thickness of the layers on the stability of the sandwich beam are studied. Finally,... 

Deep excavation in urban areas can cause instability problems due to significant settlement at the ground surface and large movements at the excavation facing walls. One of the most popular methods used to stabilise these excavations is utilising soil-nailing method. This method has also been widely used to stabilise natural slopes and earth retaining structures. Because of the complexity involved in the mechanism of this stabilising system due to interacting effects of the soil, nails, grout and shotcrete, numerical modelling with high accuracy should be used to analyse the behaviour of the soil-nailed walls. Considering all aspects of soil-structure interaction in the present research, a... 

Background: Once aligned, long-reads can be a useful source of information to identify the type and position of structural variations. However, due to the high sequencing error of long reads, long-read structural variation detection methods are far from precise in low-coverage cases. To be accurate, they need to use high-coverage data, which in turn, results in an extremely time-consuming pipeline, especially in the alignment phase. Therefore, it is of utmost importance to have a structural variation calling pipeline which is both fast and precise for low-coverage data. Results: In this paper, we present SVNN, a fast yet accurate, structural variation calling pipeline for PacBio long-reads... 

Background: Once aligned, long-reads can be a useful source of information to identify the type and position of structural variations. However, due to the high sequencing error of long reads, long-read structural variation detection methods are far from precise in low-coverage cases. To be accurate, they need to use high-coverage data, which in turn, results in an extremely time-consuming pipeline, especially in the alignment phase. Therefore, it is of utmost importance to have a structural variation calling pipeline which is both fast and precise for low-coverage data. Results: In this paper, we present SVNN, a fast yet accurate, structural variation calling pipeline for PacBio long-reads... 

Anchored wall system is one of the common methods used for deep excavation stabilization adjacent to sensitive structures in urban areas. A key aspect of the stability analysis of deep excavations is the amount of deformations occurring on the facing wall and the adjacent structures. In this research, a large number of parametric studies considering all aspects of soil-structure interaction is carried out for different excavation geometries to find the optimal design, and the outcome is shown in the form of design tables and charts. Also, by a GA-PSO algorithm and using the large database obtained from the numerical simulations, a simple equation is developed that can predict the deflections... 

Respiratory drug delivery has been under the research spotlight for the past few decades, mainly due to the high incidence of pulmonary diseases and the fact that this type of delivery offers the highest efficiency for treatment. Despite its invaluable benefits, there are some major drawbacks to respiratory drug delivery, the most important of which being poor delivery efficiency and relatively high drug deposition in undesirable regions, such as the mouth cavity. One way to improve the efficiency of respiratory drug delivery with metered-dose inhalers is placing a respiratory spacer between the inhaler exit and the mouth. It is argued that high drug deposition in the immediate airways of... 

A new method for forecasting the trend of time series, based on mixture of MLP experts, is presented. In this paper, three neural network combining methods and an Adaptive Network-Based Fuzzy Inference System (ANFIS) are applied to trend forecasting in the Tehran stock exchange. There are two experiments in this study. In experiment I, the time series data are the Kharg petrochemical company's daily closing prices on the Tehran stock exchange. In this case study, which considers different schemes for forecasting the trend of the time series, the recognition rates are 75.97%, 77.13% and 81.64% for stacked generalization, modified stacked generalization and ANFIS, respectively. Using the... 

The physical and photoelectrochemical properties of the anodized ZnO-TiO2 thin films were investigated in this study. Impedance spectroscopy revealed a decrease in charge transfer resistance and Tafel plots determined enhancement of about 200 times in the exchange current (i 0) after anodization at high positive potential. It was found from XPS analysis that after applying the potential of 5 V to the ZnO-TiO2 photoelectrode, the lattice oxygen (O2-) in the thin film is oxidized to molecular oxygen and then, cations such as Zn2+ can be solved in the basic electrolyte and passed to the solution. Moreover, according to AFM analysis it was observed that the surface of the samples has been... 

This study considers the aeroelastic instability of a partially treated magneto-rheological fluid sandwich panel in supersonic airflow. The linear first-order piston theory is used for modeling the aerodynamic pressure. Using classical Hamilton’s principle along with the finite element method, the equations of motion are derived. The critical value of the non-dimensional aerodynamic pressure is obtained by traditional p-method scheme. The validity of the finite element formulation is examined through comparison with those obtained from the assumed mode formulation and the available results in the literature. Various parametric studies including the effects of applied magnetic field, core and... 

This study considers the aeroelastic instability of a partially treated magneto-rheological fluid sandwich panel in supersonic airflow. The linear first-order piston theory is used for modeling the aerodynamic pressure. Using classical Hamilton’s principle along with the finite element method, the equations of motion are derived. The critical value of the non-dimensional aerodynamic pressure is obtained by traditional p-method scheme. The validity of the finite element formulation is examined through comparison with those obtained from the assumed mode formulation and the available results in the literature. Various parametric studies including the effects of applied magnetic field, core and... 

The present study reports synthesis of BaFe12O19 nanoparticles by sol gel technique followed by its characterization using Energy dispersive X-ray spectroscopy (EDS), X-Ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) analysis, and Fourier-transform infrared spectroscopy (FTIR). The BaFe12O19 nanoparticles have been applied to construct a modified graphite screen-printed electrode (GSPE). BaFe12O19/GSPE has been applied as a working electrode in the analysis of tramadol and acetaminophen by voltammetric techniques. The BaFe12O19/GSPE showed a good selectiveness for analysis of tramadol in the presence of acetaminophen with the...