Sharif Digital Repository

A classifier based on Support Vector Data Description (SVDD) is proposed for spoken digit recognition. We use the Mel Frequency Discrete Wavelet Coefficients (MFDWC) and the Mel Frequency cepstral Coefficients (MFCC) as the feature vectors. The proposed classifier is compared to the HMM and results are promising and we show the HMM and SVDD classifiers have equal accuracy rates. The performance of the proposed features and SVDD classifier with several kernel functions are evaluated and compared in clean and noisy speech. Because of multi resolution and localization of the Wavelet Transform (WT) and using SVDD, experiments on the spoken digit recognition systems based on MFDWC features and... 

This paper presents an analytical model to predict the residual stress distribution induced by Shot peening. The analytical approach is based on the work of Shen and Atluri (2006) [18] with some modifications. The modifications are related to the elasto-plastic unloading of shot impingements, friction coefficient effect and the fraction of kinetic energy transmitted to the treated material. In order to predict more realistic residual stresses, the elasto-plastic unloading phase of shot impacts is modeled using two nonlinear kinematic hardening models considering the Bauschinger effect. Moreover, the effect of the Coulomb friction between target surface and shots is evaluated. For this... 

The monolithic catalytic converter still is the main pollution control device for modern vehicles in order to reach the ever-increasing legislative demands for low emission standards. The catalytic converters require a large expansion from the exhaust pipe to the front face of the monolith. Unfortunately, packaging constraints often do not permit the use of long diffusers. Hence, flow separation within the diffuser leads to a non-uniform flow distribution across the monolith. A uniform flow distribution at the inlet monolith face is favorable for the conversion efficiency as well as the durability of the catalytic converter. Therefore the main problem is to optimize the flow distribution at... 

Nanocages (NCs) have emerged as a new class of drug-carriers, with a wide range of possibilities in multi-modality medical treatments and theranostics. Nanocages can overcome such limitations as high toxicity caused by anti-cancer chemotherapy or by the nanocarrier itself, due to their unique characteristics. These properties consist of: (1) a high loading-capacity (spacious interior); (2) a porous structure (analogous to openings between the bars of the cage); (3) enabling smart release (a key to unlock the cage); and (4) a low likelihood of unfavorable immune responses (the outside of the cage is safe). In this review, we cover different classes of NC structures such as virus-like... 

Dissimilar Al/Cu joints were produced through simple cold compression technique. The influence of different reductions (40, 53 and 66 %) on the joint strength was studied. Also, the effect of heat treatment on the joints’ mechanical characteristics was investigated using a modified miniature shear test. Microscopical examinations by means of optical and scanning electron microscopes were conducted and results confirmed that acceptable joints produced through 53 and 66 % deformations. According to the shear test results, it was revealed that post-weld heat treatment influenced the joint’s strength and caused strength enhancement in the samples which were not subjected to annealing prior to... 

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the COVID-19 pandemic that has been spreading around the world since December 2019. More than 10 million affected cases and more than half a million deaths have been reported so far, while no vaccine is yet available as a treatment. Considering the global healthcare urgency, several techniques, including whole genome sequencing and computed tomography imaging have been employed for diagnosing infected people. Considerable efforts are also directed at detecting and preventing different modes of community transmission. Among them is the rapid detection of virus presence on different surfaces with which people may come in... 

Resistance spot weldability of martensitic stainless steels is impaired by the formation of brittle martensite in the fusion zone (FZ). In this paper, in situ rapid tempering via applying a second pulse current after a first melting/solidification pulse during resistance spot welding of AISI 420 martensitic stainless steel sheets was used as a pathway to enhance the toughness of the FZ. By using proper second pulse conditions, the FZ with reduced hardness can be generated which is featured by a decomposed martensitic structure with nano-sized carbide precipitations. The improved toughness as a consequence of this modified microstructure resulted in remarkable enhancement of the peak load and... 

Understanding diffusion-induced isothermal solidification time during transient liquid phase bonding is vital in producing intermetallic-free robust joints. The isothermal solidification completion time is overestimated by the existing analytical models, even by the closest one to the real bonding conditions, known as the moving interface model. It was found that the boride formation in the diffusion affected zone of Ni-based superalloy upon using B-containing filler metals is one of the reasons behind the inability of the moving interface model to predict the isothermal solidification completion time accurately, which has received scant attention in the literature. Moreover, simplified... 

Aim: The aim of this study was to assess the relationship between microRNAs and viral and immunological markers in HIV-1 infection. Materials & methods: The expression level of miRNAs was evaluated in 60 HIV-1 patients and 20 healthy controls using real-time PCR assays. Results: The results showed that among all miRNAs, miR-29 and miR-150 were significantly downregulated in HIV-1 patients compared with healthy controls, while miR-155 and miR-223 were significantly upregulated compared with healthy controls (p < 0.001 for all comparisons). Conclusion: The mentioned miRNAs seem to influence the clinical progression of HIV-1 infection in naive patients. Moreover, determining the profiles of... 

Objective: This systematic review and meta-analysis was performed to determine the prevalence rate of influenza virus from different parts of Middle East region, and present an overall relative frequency (RF) for this region. Methods: The authors performed a systematic literature review from several reliable databases such as PubMed, ISI Web of Science and Scopus during 2000–2016. Furthermore, the keywords of this research were ‘Influenza’, ‘Subtype’, ‘Seroprevalence’, ‘Incidence’, ‘Seroepidemiology’, ‘H1N1’, ‘H3N2’, ‘H5N1’, ‘H9N2’, ‘Middle-East’ and ‘Meta-analysis’. The reported data were selected according to inclusion and exclusion criteria. Results: The authors selected 71 studies out of... 

Microgrids (MGs) have a special role in developing several consumers' energy infrastructure and supply in more economical, safer, and sustainable ways. The interaction and mutual relationship between each energy carrier on the reliable performance of other carriers and the high growth of tri-generation technologies in the MG face the optimal performance of such networks with many challenges. Combined cooling, heating, and power (CCHP)-based MGs are a new generation of MGs that simultaneously provide electrical, thermal, and cooling loads. However, the interaction between these carriers is very influential in CCHP-based MG's operation, which is rarely analyzed. Hence, this paper focuses on... 

A computational tool is developed to capture the interaction of solid object with two-phase flow. The full two-dimensional Navier–Stokes equations are solved on a regular structured grid to resolve the flow field. The level set and the immersed boundary methods are used to capture the free surface of a fluid and a solid object, respectively. A two-step projection method along with Multi-Processing (OpenMP) is employed to solve the flow equations. The computational tool is verified based on numerical and experimental data with three scenarios: a cylinder falling into a rectangular domain due to gravity, transient vertical oscillation of a cylinder by releasing above its equilibrium position,... 

Shot peening is one of the most effective surface strengthening treatment technologies in which compressive residual stresses are induced beneath the specimen surface. Effects of various factors on the distribution of residual stress profile induced by shot peening have been investigated by many researchers. However, initial residual stresses are one of the important factors which affect the shot peening residual stress.This study is aimed to present comprehensive numerical and experimental study on the effect of initial residual stresses on the shot peened specimen. Initial residual stresses were induced using a four-point bending rig and grinding. Incremental center hole drilling (ICHD)... 

In this paper, the effect of morphology, size and volume fraction of the most important microstructural constituents of cast A356 aluminum alloy on its main mechanical properties has been studied. The investigated variables consist of Dendrite Arm Spacing (DAS) of α aluminum phases, spheroicity of silicon particles in eutectic areas and 2-D micro porosity areas. The variations of Quality Index (Qi) with DAS and spheroicity of eutectic silicon particles follow a linear relationship. For the micro-porosity area of a polished section of the studied samples, two linear relationships were found, one for values less than 1.25% and another for higher values. As the basis for a quantitative analysis... 

Background: Breast cancer is currently the most common neoplasm diagnosed in women globally. There is a growing body of evidence to suggest that human papillomavirus (HPV) infection may play a key role in invasiveness of breast cancer. The aim of this study was to determine the presence of HPV in patients with breast cancer and its possible association with cancer progression. Methods: Breast specimens were collected from 72 patients with breast cancer and 31 healthy controls. The presence of HPV was investigated by polymerase chain reaction (PCR) and genotyping was performed for positive cases. We also evaluated the viral factors such as E6, E2, and E7 in HPV positive cases. Enzyme-linked... 

Introduction: It is 23 years since carbon allotrope known as carbon nanotubes (CNT) was discovered by Iijima, who described them as "rolled graphite sheets inserted into each other". Since then, CNTs have been studied in nanoelectronic devices. However, CNTs also possess the versatility to act as drug- and gene-delivery vehicles.Areas covered: This review covers the synthesis, purification and functionalization of CNTs. Arc discharge, laser ablation and chemical vapor deposition are the principle synthesis methods. Non-covalent functionalization relies on attachment of biomolecules by coating the CNT with surfactants, synthetic polymers and biopolymers. Covalent functionalization often... 

Introduction: Carbon nanotubes (CNT) have recently been studied as novel and versatile drug and gene delivery vehicles. When CNT are suitably functionalized, they can interact with various cell types and are taken up by endocytosis.Areas covered: Anti-cancer drugs cisplatin and doxorubicin have been delivered by CNT, as well as methotrexate, taxol and gemcitabine. The delivery of the antifungal compound amphotericin B and the oral administration of erythropoietin have both been assisted using CNT. Frequently, targeting moieties such as folic acid, epidermal growth factor or various antibodies are attached to the CNT-drug nanovehicle. Different kinds of functionalization (e.g., polycations)... 

Smart drug delivery systems (DDSs) have attracted the attention of many scientists, as carriers that can be stimulated by changes in environmental parameters such as temperature, pH, light, electromagnetic fields, mechanical forces, etc. These smart nanocarriers can release their cargo on demand when their target is reached and the stimulus is applied. Using the techniques of nanotechnology, these nanocarriers can be tailored to be target-specific, and exhibit delayed or controlled release of drugs. Temperature-responsive nanocarriers are one of most important groups of smart nanoparticles (NPs) that have been investigated during the past decades. Temperature can either act as an external... 

New achievements in the realm of nanoscience and innovative techniques of nanomedicine have moved micro/nanoparticles (MNPs) to the point of becoming actually useful for practical applications in the near future. Various differences between the extracellular and intracellular environments of cancerous and normal cells and the particular characteristics of tumors such as physicochemical properties, neovasculature, elasticity, surface electrical charge, and pH have motivated the design and fabrication of inventive "smart" MNPs for stimulus-responsive controlled drug release. These novel MNPs can be tailored to be responsive to pH variations, redox potential, enzymatic activation, thermal... 

Isothermal solidification stage during transient liquid phase bonding is the key to preclude intermetallic phase formation during solidification of the liquid phase. The rate of isothermal solidification is controlled by solid-state diffusion. Therefore, the bonding time required to complete isothermal solidification is generally long. This paper reports a very short isothermal solidification time for transient liquid phase bonding of IN617 solid solution nickel-based superalloy using a boron-containing filler metal. A eutectic-free bond with limited grain growth in the base material with high shear strength is achievable by utilizing a short (i.e., 5 minutes) thermal bonding strategy. The...