Sharif Digital Repository

Capsule endoscopy is a minimally invasive diagnostic technology for gastrointestinal diseases providing images from the human's digestion system. Developing a robust and real-time localization algorithm to determine the orientation and position of the endoscopic capsule is a crucial step toward medical diagnostics. In this paper, we propose a novel model-aided real-time localization approach to estimate the position and orientation of a magnetic endoscopic capsule swimming inside the stomach. In the proposed method, the governing equations of the motion of an ellipsoidal capsule inside the fluid, considering different hydrodynamics interactions, are derived. Then, based on the dynamic model,... 

Capsule endoscopy is a minimally invasive gastrointestinal diagnostic procedure. The active endoscopic capsule enables the physician to steer the device to any desired position and direction, resulting in a better diagnosis of the disease. Due to the model uncertainties and the existence of disturbances in the gastrointestinal system, traditional control methods cannot achieve robust performance and stability. To overcome this issue, in this paper, a robust sliding mode controller is proposed for 5 Degrees Of Freedom (DOF) control (3-DOF closed-loop control for position and 2-DOF open-loop control for orientation) of the capsule endoscope using an electromagnetic actuation system. The... 

In this paper, we report on the design and analysis of filters and lenses realized by an array of metallic posts integrated in a parallel-plate waveguide (PPWG). The design methodology of these components is inferred from the modal analysis of a spoof surface plasmonic waveguide composed of metallic posts arranged in a 1D periodic structure inside PPWG. Samples of the proposed devices are analyzed using a full-wave analysis method and their performance is assessed. We show that the mentioned structure can be used to realize all-metallic band-pass filters and lenses for mm-wave and terahertz applications  

Edit distance is one of the most fundamental problems in combinatorial optimization. Ulam distance is a special case of edit distance where no character is allowed to appear more than once in a string. Recent developments have been very fruitful for obtaining fast and parallel algorithms for both edit distance and Ulam distance. In this work, we present an almost optimal MPC algorithm for Ulam distance and improve MPC algorithms for edit distance. Our algorithm for Ulam distance is optimal in the sense that (1) the approximation factor of our algorithm is 1 + ϵ, (2) the round complexity of our algorithm is constant, (3) the total memory of our algorithm is almost linear (OH(n)), and (4)] the... 

The Haptic device is capable of interacting dynamically with the operator by the forces it can exert on human's hand. Controlling the haptic device and constraining it through the desired trajectory is the common task in the most of the training systems. Haptic interface application in virtual Persian handwriting learning system is investigated in this paper. Two different modes of learning is investigated: The full guidance mode, guides the user to follow a prerecorded trajectory by applying proper force to operator's hand; whereas in partial guidance, combination of haptics andvisual feedback guides the operator and prevents deviation from the desired trajectory. © 2009 IEEE  

One of the shortcomings of photoconductive (PC) antennas in terahertz (THz) generation is low effective radiated power in the desirable direction. In this paper, we propose a defective photonic crystal (DPC) substrate consisting of a customized 2D array of air holes drilled into a solid substrate in order to improve the radiation characteristics of THz PC antennas. The effect of the proposed structure on the performance of a conventional THz PC antenna has been examined from several aspects including radiation efficiency, directivity, and field distribution. By comparing the radiation performance of the THz antenna on the proposed DPC substrate to that of the conventional solid substrate, it... 

In this paper, arrays of two different terahertz (THz) antennas based on defective photonic crystal (DPC) substrates are proposed and their radiation characteristics are investigated by using full-wave simulation. We show that employing DPC substrates in THz photoconductive antenna (PCA) arrays reduces the amount of power coupled to the substrate surface waves and, as a result, decreases the mutual coupling between the elements of the antenna array and increases the directivity in the boresight direction. By studying 1 × 2 arrays of bowtie and four-leaf-clover-shaped antennas, we show that either the improvement of directivity in a broad bandwidth or the enhancement of photomixer antenna... 

Several lattice Boltzmann models for multi-phase flow have been developed, but few of them are capable of modeling fluid flows with high density ratio in the order of 1000. Therefore, an advanced chromodynamics, Rothmann-Keller (RK) type model is employed in current study, which can handle liquid-gas density ratio in the order of 1000 and viscosity ratio in the order of 100. Other distinctive characteristics of the proposed model are high stability, and capability of setting parameters such as surface tension independently. In spite of these benefits, the original RK model fails to model wetting tendency of the fluids. As a result, it is impossible to correctly simulate two-fluid phase flow... 

In this study, the kinetics of aging in AA6061 and AA6061 with 5% volume fraction SiCp were studied and compared. The composite was first produced and homogenized using stir casting technique followed by hot extrusion with the ratio of 18:1. Then, both AA6061 and the composite were aged at three different temperatures including room temperature, 170 °C and 240 °C, while mechanical properties during aging were evaluated employing hardness measurements and tensile testing. Moreover, in order to assess the effect of plastic deformation on the kinetics of aging, a series of samples were first deformed by equal-channel angular pressing immediately after solution treatment and then aged in the... 

Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well... 

Edit distance is one of the most fundamental problems in combinatorial optimization to measure the similarity between strings. Ulam distance is a special case of edit distance where no character is allowed to appear more than once in a string. Recent developments have been very fruitful for obtaining fast and parallel algorithms for both edit distance and Ulam distance. In this work, we present an almost optimal MPC (massively parallel computation) algorithm for Ulam distance and improve MPC algorithms for edit distance. Our algorithm for Ulam distance is almost optimal in the sense that (1) the approximation factor of our algorithm is $1+epsilon$1+ϵ, (2) the round complexity of our...