Sharif Digital Repository

We propose a nano-plasmonic thin-film solar cell (TFSC) as a receiver for the visible light communication (VLC). The presented design is a novel and optimized structure that can be used instead of photodetectors and power supplies in the VLC. The plasmonic TFSC that described in this work is capable of increasing the light absorption in comparison with the conventional thick Si solar cell without plasmonic nanostructures. However, plasmonic nanoparticles can improve the absorption of Si solar cell in a visible range of solar spectra. In this paper, different situations for inserting nanoparticles in an active layer are considered and the absorption is calculated as a function of particle... 

We can notice that security problems of inappropriate integration of native and web technologies in hybrid mobile applications (apps) have been covered in the related state-of-the-art research. However, analyzing hybrid mobile apps' unique behaviors has been seldom addressed. In this paper, we explore the influence of native and web technologies integration in hybrid mobile apps on the generated profile of mobile applications. Specifically, we analyze the type of Security Sensitive APIs (SS-APIs) exposed to web content and identify the corresponding usage patterns by systematically tracking function-call-graphs of a large number of hybrid and native mobile apps. Our investigations indicate... 

This paper aims to identify an optimum bone fracture stabilizer. For this purpose, three design variables including the ratio of the screw diameter to the plate width at three levels, the ratio of the plate thickness to the plate width at three levels, and the diameter of the bone at two levels were selected for analysis. Eighteen 3D verified finite element models were developed to examine the effects of these parameters on the weight, maximum displacement and maximum von Mises stress of the fixation structure. Considering the relations between the inputs and outputs using multivariate regression, a genetic algorithm was used to find the optimal choices. Results showed that the diameter of... 

Photonic crystal fibers (PCFs) are widely used in optical communications systems, nonlinear devices, gas sensors, high power transmission, and so on. Photonic crystal fiber with minimum values of confinement loss, nonlinear effects, and chromatic dispersion is used in optical communication. But in some applications, high nonlinear coefficient is required. This paper presents new design of index-guiding photonic crystal fiber (IGPCF) with characteristics appropriate for nonlinear applications. In the present design with a square-hexagonal nano-structure having air holes with unequal diameters, nearly zero dispersion at the wavelength range of 1540 to 1550 nm is achieved. The simulation... 

In this paper, a plasmonic absorber consisting of a metal-dielectric-metal stack with a top layer of Sierpinski nanocarpet is theoretically investigated. Such a compact absorber depicts broadband angle-independent behavior over a wide optical wavelength range (400 700 nm) and a broad range of incidence angles (0 80). Including several feature sizes, such a fractal-like structure shows average simulated extinction response of 0:85 for either transverse electric or magnetic polarization states under normal incidence. Underlying mechanisms of absorbance due to excited surface plasmon modes as well as electric/magnetic dipole resonances are well revealed by investigating electric field, magnetic... 

This paper presents two new space time block codes (STBCs) with quasi orthogonal structure for an open loop multi-input single-output (MISO) systems. These two codes have been designed to transmit from three or four antennas at the transmitter and be given to one antenna at the receiver. In this paper first, the proposed codes are introduced and their structures are investigated. This is followed by the demonstration of how the decoder decodes half of transmitted symbols independent of the other half. The last part of this paper discusses the simulation results, makes performance comparison against other popular approaches and concludes that the proposed solutions offer superiority  

Bone And Site Hold Tendon Inside (BASHTI) implant-less technique is proposed as an alternative to conventional tendon repair methods. This study aims to evaluate the strength of this technique under biceps loading conditions with different xation strategies. Twelve specimens with bovine tendons and Sawbones were constructed using two different insertion methods; in Group 1, 4 samples were prepared using a hand-hammer with a hitting frequency of 300 Beats Per Minute (BPM), while Group 2 included eight specimens with insertion using an auto-hammer applying a frequency of 3600 BPM. Both of the groups were tested under cyclic loading, followed by a pull-out until the failure. All the samples... 

The buckling behaviour of compression members is very important in structural engineering especially those that are made from high strength steel (HSS). This paper presents an investigation into the behaviour of four columns which were designed according to EN 1993-1-1 (2005) so that the buckling capacity of both HSS and mild steel column was equal. A finite element model was created which included imperfections due to residual stresses as well as local and global imperfections. It was found that the buckling capacity of the columns made from 460 MPa steel was lower than that for similar capacity mild steel columns with a yield strength of 275 MPa. Accordingly, a buckling curve for HSS is... 

In this paper, we design a dimming compatible visible light communication (VLC) system in a standard office room according to illumination standards under channel constraints. We use overlapping pulse position modulation (OPPM) to support dimming control by changing the code weights. The system parameters such as a valid interval for dimming together with an upper bound for bit rate according to the channel delay spread are investigated. Moreover, considering the dispersive VLC channel and using Monte Carlo (MC) simulations, a method is proposed to determine the minimum code length in different dimming levels in order to achieve a valid bit error rate (BER). Finally, trellis coded modulation... 

In this paper, we design a dimming compatible visible light communication (VLC) system with asynchronous and optimum indoor positioning method in a standard office room in combination with asynchronous and optimum indoor positioning method according to illumination standards under channel constraints. We use overlapping pulse position modulation (OPPM) to support dimming control by changing the code weights. The system parameters such as a valid interval for dimming together with an upper bound for bit rate according to the channel delay spread are investigated. Moreover, considering the dispersive VLC channel and using Monte Carlo (MC) simulations, a method is proposed to determine the... 

In this Letter, we realize the concept of analog computing using an engineered gradient dielectric meta-reflect-array. The proposed configuration consists of individual subwavelength silicon nanobricks, in combination with a fused silica spacer and silver ground plane, realizing a reflection beam with full phase coverage of 2π degrees, as well as an amplitude range of 0 to 1. Spectrally overlapping electric and magnetic dipole resonances, such high-index dielectric metasurfaces can locally and independently manipulate the amplitude and phase of the incident electromagnetic wave. This practically feasible structure overcomes substantial limitations imposed by plasmonic metasurfaces such as... 

Purpose: Core Bone Plug Fixation (CBPF) technique is an implant-less methodology for ACL reconstruction. This study investigates the effect of bone density on CBPF stability to identify the bone quality that is likely to benefit from this technique. Methods: Artificial blocks with 160 (Group 1), 240 (Group 2), and 320 (Group 3) kg/m3 densities were used to simulate human bone with diverse qualities. These groups are representative of the elderly, middle age and young people, respectively. A tunnel was made in each test sample using a cannulated drill bit which enabled harvesting the core bone plug intact. Fresh animal tendon grafts were prepared and passed through the tunnel, so the core... 

The goal of this study is to investigate the effects of tendon and cannulated drill bit diameter on the strength of the bone and site hold tendon inside (BASHTI) fixation technique for an anterior cruciate ligament (ACL) reconstruction. Bovine digital tendons and Sawbones blocks were used to mimic the ACL reconstruction. Mechanical strength of the specimens was measured using a cyclic loading continued by a single cycle pullout load until failure to simulate the real postsurgical loading conditions. Finally, failure modes of specimens and ultimate failure load were recorded. The maximum possible tendon surface strain (i.e., tendon compression [TC]) for tendon diameters of 6, 7, 8, and 9 mm... 

The goal of this study is to investigate the effects of tendon and cannulated drill bit diameter on the strength of the bone and site hold tendon inside (BASHTI) fixation technique for an anterior cruciate ligament (ACL) reconstruction. Bovine digital tendons and Sawbones blocks were used to mimic the ACL reconstruction. Mechanical strength of the specimens was measured using a cyclic loading continued by a single cycle pullout load until failure to simulate the real postsurgical loading conditions. Finally, failure modes of specimens and ultimate failure load were recorded. The maximum possible tendon surface strain (i.e., tendon compression [TC]) for tendon diameters of 6, 7, 8, and 9 mm... 

Background: BASHTI is an implant-less anterior cruciate ligament (ACL) reconstruction technique, which resolves the problems caused by implants such as interference screws. This study aims to investigate the effect of the drill bit and tendon’s diameter on the Core Bone Engaged Length (CBEL) and the fixation strength. CBEL is the length of core bone which has a full engagement with both tunnel and graft at the same time. Methods: 60 in-vitro tests were conducted for 6, 7, 8, and 9 mm tendon sizes with a 10 mm bone tunnel. In this study bovine tendons and dummy bone blocks were used to model the fixation. Drill bits were used to extract the core bone for securing the auto-graft. A three-stage... 

This research is aiming to investigate the mechanical behaviour of the temporomandibular joint (TMJ), in response to kinematics/cyclical loading caused through actions of speech and mastication. A set of in-vitro experimental tests has been performed in three different groups on a fresh sheep jaw bone to examine the hypothesis of the study. No failure was monitored during the cyclical test. The study was concluded that the amount of loading is effective on the displacement of the TMJ  

Bone and Site Hold Tendon Inside (BASHTI) technique is an implant-less surgical methodology used for anterior cruciate ligament (ACL) reconstruction. It has some clinical advantages, such as speeding up the healing process. Since the force required to insert the core bone inside the tunnel may damage the core bone and affect the fixation process, the study aims to investigate the strength of fixation of BASHTI technique using proposed sheathed core bones. Experimental tests were performed to evaluate the biomechanical strength of the fixation. Synthetic bone combined with bovine tendons as a graft was used. Polymers were used to create the sheath for mechanical testing. The results showed... 

Optical signal propagation through underwater channels is affected by three main degrading phenomena, namely, absorption, scattering, and fading. In this paper, we experimentally study the statistical distribution of intensity fluctuations in underwater wireless optical channels with random temperature and salinity variations, as well as the presence of air bubbles. In particular, we define different scenarios to produce random fluctuations on the water refractive index across the propagation path and, then, examine the accuracy of various statistical distributions in terms of their goodness of fit to the experimental data. We also obtain the channel coherence time to address the average... 

Endoscopic endonasal surgery is a minimal invasive surgery that has been used to dissect pituitary gland tumour via curettes with the help of endoscope. However, this type of surgery has a high risk of failure because curettes may cause damages to blood vessels and optical nerves that lead to more complication for the patient. The aim of this study is to develop a new technique to dissect the tumour by using liquid jet. A series of experimental tests have been performed on animal tissue to study the effect of liquid pressure and nozzle diameter on dissecting and cutting the tissue. Continuous/pulsed liquid jet used with variable nozzle diameters, distances, pressures and angles. The study...