Sharif Digital Repository

Fiber/matrix debonding at the free surface of unidirectional composites deteriorates their performance and ultimately reduces the working life of these materials. Identifying the source, controlling the propagation and elimination of the damages has been the subject of many research attempts. The results show that the singular radial thermal residual stress at the fiber/matrix interface on the free surface of composites is the main reason for initiation of the debonding. Also, it has been experimentally and numerically proven that a thin layer of matrix-like cover on the free surface could highly help in elimination and/or reduction of the damage. However, the results were limited to the... 

Control charts are useful tools of monitoring quality characteristics. One of the problems of employing a control chart is that the time it alarms is not synchronic with the time when assignable cause manifests itself in the process. This makes difficult to search and find assignable causes. Knowing the real time of manifestation of assignable cause (change point) helps to find assignable cause(s) sooner and eases corrective actions to be taken. In this paper, a probabilistic neural network (PNN)-based procedure was developed to estimate the variance change point of a normally distributed quality characteristic. The PNN was selected based on trial and error among different types of... 

A novel technique based on image processing inspired by the simple assumption for the first time to assess the roughness of nanofibrous mats based on grayscale variations is proposed. The height of a nanofibrous mat in different regions of the surface is simulated by grayscale variations in the image while the relation between grayscale and height is obtained as a linear function. The roughness is obtained by measuring height variations in the surface profile. Statistical roughness parameters of nanofibrous mats are also obtained from direct measurement with roughness profilometry and atomic force microscopy (AFM) for comparison of the roughness of nanofibrous mats between direct measurement... 

A novel technique based on image processing inspired by the simple assumption for the first time to assess the roughness of nanofibrous mats based on grayscale variations is proposed. The height of a nanofibrous mat in different regions of the surface is simulated by grayscale variations in the image while the relation between grayscale and height is obtained as a linear function. The roughness is obtained by measuring height variations in the surface profile. Statistical roughness parameters of nanofibrous mats are also obtained from direct measurement with roughness profilometry and atomic force microscopy (AFM) for comparison of the roughness of nanofibrous mats between direct measurement... 

We used two digital methods—rise time discrimination (RTD) and an artificial neural network (ANN)—to simultaneously discriminate alpha particles and gamma rays detected by a phoswich detector (50 μm BC-400 coupled to 3 mm CsI(Tl)). The results for 10,000 pulses discriminated by the RTD method showed that the rise time distribution of the pulses is rather vast (between 200 and 800 ns for gamma rays and less than 40 ns for alpha particles). The same result was also observed in the dual-parameter diagram (pulse rise time versus area under the pulse) for an 241Am source. Then, as another approach, three pulse features—rise time, pulse height ratio, and charge ratio—were extracted from 2000... 

Time reversal is a technique in which a signal is pre-filtered such that it focuses both in time and space. Spatial focusing reduces interference to other co-existing systems and temporal focusing concentrates the received power in a very short interval. Energy detector is a practical receiver for ultra-wideband (UWB) time reversed signals due to its low-complexity and low-cost implementation. However, selection of an optimum integration interval to minimize the bit error rate is a major problem. Weighted energy detection is an effective technique to overcome this problem and enhance the performance of energy detectors. However, this improvement is achieved at the expense of non-trivial... 

A novel technique based on image processing inspired by the simple assumption for the first time to assess the roughness of nanofibrous mats based on grayscale variations is proposed. The height of a nanofibrous mat in different regions of the surface is simulated by grayscale variations in the image while the relation between grayscale and height is obtained as a linear function. The roughness is obtained by measuring height variations in the surface profile. Statistical roughness parameters of nanofibrous mats are also obtained from direct measurement with roughness profilometry and atomic force microscopy (AFM) for comparison of the roughness of nanofibrous mats between direct measurement... 

Daily development in civil engineering arena and the importance of economical aspects in the design of structures have motivated the engineers to shift their approaches from designing upon strength to designing upon performance. This is of more importance regarding the forces induced by earthquakes which have unpredicted and random nature. However, it is not possible to design or assess exactly the structural performance against strong ground motion using analytical methods which are applied for static loads and therefore precise dynamic analysis methods are needed. Despite significant progress in the analytical methods and engineering software, using nonlinear time history analysis is very... 

Comparative studies between response surface methodology (RSM) and artificial neural network (ANN) methods to find the effects of electrospinning parameters on the porosity of nanofiber mats is described. The four important electrospinning parameters studied included solution concentration (wt.%), applied voltage (kV), spinning distance (cm) and volume flow rate (mL/h). It was found that the applied voltage and solution concentration are the two critical parameters affecting the porosity of the nanofiber mats. The two approaches were compared for their modeling and optimization capabilities with the modeling capability of RSM showing superiority over ANN, having comparatively lower values of... 

In this work, flow stress behavior, softening mechanisms and processing maps during deformation of aluminum-magnesium alloy i.e. AA5052, were investigated. Firstly, tensile tests were carried out in the range of room temperature up to 450 °C under different strain rates between 0.001 s-1 to 0.05 s-1. Then, neural network algorithms together with dynamic materials modeling were employed for determination of stain rate sensitivity parameter and processing maps under different working conditions. Moreover, the governing constitutive equations as well as the activation energies of dynamic strain aging and hot deformation were defined. Accordingly, the processing maps were developed for different... 

In the present work, a simple, green, rapid, and catalyst-free procedure for the synthesis of benzamide derivatives by ring opening of azlactones with diamines such as ethylene diamine and 1,3-propylenediamine is described. The present method offers several advantages such as short reaction times, easy work-up, and mild reaction conditions in the absence of catalyst and any toxic solvent and material. In addition, the structure obtained by X-ray crystallography was compared with the theoretical results obtained by density functional theory using the B3LYP functional and cc-pVDZ basis sets  

Overlay networks have been an active area of research for the past few years. The control overhead and the recovery from failure are the two important issues in the topology aware embedded overlay networks. In this research, we have introduced an enhanced version of the NICE protocol, called resilient NICE (R-NICE) that reduces the control overhead significantly. Furthermore, by saving the join path for an end host, the time and overhead of rejoining for isolated nodes have also been reduced. This will cause the clusters and consequently the overall network to become more stable and the effect of a node failure become localized. Our experimental results have confirmed the superior... 

Nonlinear numerical modeling of masonry-infilled frames is one of the most complicated problems in structural engineering field. This complexity is attributed to the existence of joints as the major source of weakness and material nonlinearities as well as the infill-frame interaction which cannot be properly modeled using the traditional finite element methods. Although there are many numerical studies available on solid masonry-infilled steel frames' behavior, however, few researches have been conducted on infilled frames with openings. In this paper a two-dimensional numerical model using the specialized discrete element method (DEM) software UDEC (2004) is developed for the nonlinear... 

Background: Current development of sequencing technologies is towards generating longer and noisier reads. Evidently, accurate alignment of these reads play an important role in any downstream analysis. Similarly, reducing the overall cost of sequencing is related to the time consumption of the aligner. The tradeoff between accuracy and speed is the main challenge in designing long read aligners. Results: We propose Meta-aligner which aligns long and very long reads to the reference genome very efficiently and accurately. Meta-aligner incorporates available short/long aligners as subcomponents and uses statistics from the reference genome to increase the performance. Meta-aligner estimates... 

Permeability as a fundamental reservoir property plays a key role in reserve estimation, numerical reservoir simulation, reservoir engineering calculations, drilling planning, and mapping reservoir quality. In heterogeneous reservoir, due to complexity, natural heterogeneity, non-uniformity, and non-linearity in parameters, prediction of permeability is not straightforward. To ease this problem, a novel mathematical robust model has been proposed to predict the permeability in heterogeneous carbonate reservoirs. To this end, a fairly new soft computing method, namely least square support vector machine (LSSVM) modeling optimized with coupled simulated annealing (CSA) optimization technique... 

Background: Human papillomavirus (HPV)-associated malignancy remain a main cause of cancer in men and women. Cancer immunotherapy has represented great potential as a new promising cancer therapeutic approach. Here, we report Mesenchymal stem cells (MSCs) as a carrier for the delivery of oncolytic Newcastle disease virus (NDV) for the treatment of HPV-associated tumor. Methods: For this purpose, MSCs obtained from the bone marrow of C57BL mice, then cultured and characterized subsequently by the flow cytometry analysis for the presence of cell surface markers. In this study, we sought out to determine the impacts of MSCs loaded with oncolytic NDV on splenic T cell and cytokine immune... 

The effects of applied magnetic and electric fields on electrospinning were investigated to produce more efficient nanofibers. Considering the previous extensive studies, polyamide nanofibers were prepared by a conventional approach and under auxiliary electric and magnetic fields. The first sorbent was synthesized by electrospinning of a solution of 18% polyamide in formic acid. The second and third types of polyamide were prepared similarly while the electrospinning processes were assisted by an electric and a magnetic field. The third type of polyamide contained a magnetic ionic liquid (MIL) to induce sufficient magnetic susceptibility in the polymeric solution. The SEM images revealed... 

An on-line extraction/determination set up was designed for micro solid-phase extraction of clodinafop propargyl from water, soil and wheat samples using electrospun polyamide nanofiber mats. The prepared mats were packed in a stainless steel tube which conveniently acted as a high-performance liquid chromatography injection loop. Influential parameters affecting the extraction efficiency were optimized using a distilled water sample fortified with 25 μg L-1 of clodinafop propargyl. An enrichment factor of 440 was achieved for clodinafop propargyl indicating the ability of the whole procedure. Under the optimum conditions, the linearity for the analyte was in the range of 6-700 μg L-1, while... 

Simulation optimization is an endeavor to determine the best combination of inputs that result in the best system performance criterion without evaluating all possible combinations. Since simulation optimization applies to many problems, it is extensively studied in the literature with different methods. However, most of these methods ignore the uncertainty of the systems’ parameters, which may lead to a solution that is not robustly optimal in reality. Motivated by this uncertainty, we propose a robust simulation optimization algorithm that follows the well-known Taguchi standpoint but replaces its statistical technique with a minimax method based on the kriging (Gaussian process)... 

Simulation optimization is an endeavor to determine the best combination of inputs that result in the best system performance criterion without evaluating all possible combinations. Since simulation optimization applies to many problems, it is extensively studied in the literature with different methods. However, most of these methods ignore the uncertainty of the systems’ parameters, which may lead to a solution that is not robustly optimal in reality. Motivated by this uncertainty, we propose a robust simulation optimization algorithm that follows the well-known Taguchi standpoint but replaces its statistical technique with a minimax method based on the kriging (Gaussian process)...