Sharif Digital Repository

The currently available laparoscopic instruments are unable to manipulate and grasp the large intra-abdominal organs, such as spleen and kidney, with sufficient stability and safety. This paper describes a novel three-fingered endoscopic instrument, based on parallelogram mechanism, which can fully constrain the large organs and provide an effective grasping function. We first evaluated the efficacy of the design using a 3D model and finite element analysis. Then, a fully functional prototype was fabricated for experimental evaluations, including force propagation and pull force limitation characteristics. Finally, the instrument's capability for effective grasping was investigated on animal... 

Enlargement of ship size in recent decades and no change in the harbors and approach channels have resulted in global attention toward navigation in shallow and confined waters. A phenomenon which restricts ship navigation in shallow waters is reduction of under-keel clearance in terms of sinkage and dynamic trim, which is called squatting. Due to the complexity of flow around the ship hull, one of the best methods for predicting the ship squat is the experimental approach based on systematic model tests in the towing tank. In this study, model tests for tanker ship model and traditional Persian Gulf and Oman Sea vessel called dhow had been performed in the towing tank and the squat of the... 

Identifying clusters is an important aspect of analyzing large datasets. Clustering algorithms classically require access to the complete dataset. However, as huge amounts of data are increasingly originating from multiple, dispersed sources in distributed systems, alternative solutions are required. Furthermore, data and network dynamicity in a distributed setting demand adaptable clustering solutions that offer accurate clustering models at a reasonable pace. In this paper, we propose GoScan, a fully decentralized density-based clustering algorithm which is capable of clustering dynamic and distributed datasets without requiring central control or message flooding. We identify two major... 

The rapid development and growth of cellular mobile networks in recent years has made voice channels widely available almost everywhere. On the other hand, voice dedicated channels possess properties that make them ideal options for high priority real-time secure communications. Beside these realities, information embedding has gained remarkable attention in recent years due to its potential application in multimedia security. In this regard, this study aims to propose an efficient scheme for data hiding to show the feasibility of exploiting these channels for covert communications. To this end, the authors propose new suboptimal but practical schemes based on additive and multiplicative... 

Median filtering has received extensive attention from forensics analyzers, as a common content-preserving, smoothing, and denoising manipulation. We propose a detection scheme for median filtering of video sequences in compressed domain based on the singular value decomposition of the process matrix, which approximates the median filtering. Projection over some of the eigenspaces of the process matrix gives a set of features of small dimension, even as small as three, making the proposed scheme a fast and suitable detector for video median filtering. The experimental evaluations show that the proposed method outperforms the state-of-the-art detectors of median filtering, and its edge... 

Resolvers are widely used in the control of industrial inverter driven motors. Among different types of resolvers, disk-type wound-rotor resolvers have superior performance under mechanical faults. However, the rotary transformer's (RT's) presence in the inner side of the resolver's core leads to additional radial length. To overcome this problem, disk-type wound-rotor resolver without RT's core has been proposed. However, the optimization using time stepping finite-element method (TSFEM) is time consuming due to 3-D structure of this resolver. Accordingly, in this paper, an analytical model based on the magnetic equivalent circuit is proposed for the design and optimization process. The... 

The spread of influence in social networks is studied in two main categories: progressive models and non-progressive models (see, e.g., the seminal work of Kempe et al. [8]). While the progressive models are suitable for modeling the spread of influence in monopolistic settings, non-progressive models are more appropriate for non-monopolistic settings, e.g., modeling diffusion of two competing technologies over a social network. Despite the extensive work on progressive models, non-progressive models have not been considered as much. In this paper, we study the spread of influence in the non-progressive model under the strict majority threshold: given a graph G with a set of initially... 

Recently, data stream has become popular in many contexts of data mining. Due to the high amount of incoming data, traditional clustering algorithms are not suitable for this family of problems. Many data stream clustering algorithms proposed in recent years considered the scalability of data, but most of them did not attend the following issues: (1) The quality of clustering can be dramatically low over the time. (2) Some of the algorithms cannot handle arbitrary shapes of data stream and consequently the results are limited to specific regions. (3) Most of the algorithms have not been evaluated in multi-density environments. Identifying appropriate clusters for data stream by handling the... 

A novel method for combining bigram model and Probabilistic Latent Semantic Analysis (PLSA) is introduced for language modeling. The motivation behind this idea is the relaxation of the bag of words assumption fundamentally present in latent topic models including the PLSA model. An EM-based parameter estimation technique for the proposed model is presented in this paper. Previous attempts to incorporate word order in the PLSA model are surveyed and compared with our new proposed model both in theory and by experimental evaluation. Perplexity measure is employed to compare the effectiveness of recently introduced models with the new proposed model. Furthermore, experiments are designed and... 

In this article, the cyclic performance of an innovative precast beam-to-column connection is evaluated experimentally and numerically. Two full-scale beam-column cross-shape interior connection specimens named PF-1 and PF-2 are tested. By adding extra nuts to the connecting bolts, specimen PF-2 behaves in a more shear-dominant pattern and shows less pinching. Comparison of performance of these specimens with the numerical monolithic model in terms of stiffness, strength, ductility and energy dissipation capacity indicates the proposed system can provide conditions close to the monolithic connection. However, to reduce the pinching drawback, a minor modification was made leading to... 

This paper presents the experimental investigation of an innovative energy dissipation system in steel moment resisting frames. In the proposed system, a replaceable beam with a smaller cross-section than that of the main beam is placed at the mid span of the beam designed to act as a shear fuse. This shifts the location of the plastic hinging from the end of the beam to the middle since the shear fuse yields in shear prior to the flexural yielding of the main beam. This system eliminates the need to comply with the rigorous limitation on the beam span-To-depth ratio that is proposed by seismic design codes to ensure the formation of plastic hinges at the two ends of the beam. Moreover, this... 

Cells can sense and respond to changes in the topographical, chemical, and mechanical information in their environment. Engineered substrates are increasingly being developed that exploit these physical attributes to direct cell responses (most notably mesenchymal stem cells) and therefore control cell behavior toward desired applications. However, there are very few methods available for robust and accurate modeling that can predict cell behavior prior to experimental evaluations, and this typically means that many cell test iterations are needed to identify best material features. Here, we developed a unifying computational framework to create a multicomponent cell model, called the... 

In this paper, an experimental evaluation on the viscosity of water-based manganese ferrite nanofluid with and without magnetic field with 100, 200, 300, and 400 G intensities has been conducted. The Brookfield DV-I PRIME viscometer is implemented to measure the MnFe2O4/water nanofluid viscosity and to evaluate the influence of different volume concentrations (from 0.25% to 3%) and various temperatures (from 20 to 60 °C) on the viscosity. According to the measurements, viscosity incrementally increases with the augmentation of nanoparticles concentration while it remarkably decreases at higher temperatures under absence and attendance of magnetic field. The maximum viscosity ratio of 1.14 is... 

A precise and compact tubular ultrasonic motor driven by a single-phase source is proposed and tested in this study. The motor is designed by modeling a motor stator in FEM software. The motor fabricated according to the design is tested experimentally and its working characteristics including speed and torque are measured and presented. The maximum speed and torque of the motor are 59 rpm and 0.28 mN m at 80 Vpp of applied voltage. The proposed motor possesses advantages such as a simple and compact structure with application in the fields of robotics, space, medical devices and high-resolution stages, among others. The proposed motor is a good candidate for applications where accurate... 

Field-Programmable Gate Arrays (FPGAs) employ a significant amount of SRAM cells in order to provide a flexible routing architecture. While this flexibility allows for a rather easy realization of arbitrary functionality, the respectively required cells significantly increase the area and power consumption of the FPGA. At the same time, it can be observed that full routing flexibility is frequently not needed in order to efficiently realize the desired functionality. In this work, we are proposing an FPGA realization which focuses on what is needed and realizes only a subset of the possible routing options using what we call Turn-Restricted Switch-Boxes. While this may yield a slight... 

Discrete-time Markov Chains (MCs) and Markov Decision Processes (MDPs) are two standard formalisms in system analysis. Their main associated quantitative objectives are hitting probabilities, discounted sum, and mean payoff. Although there are many techniques for computing these objectives in general MCs/MDPs, they have not been thoroughly studied in terms of parameterized algorithms, particularly when treewidth is used as the parameter. This is in sharp contrast to qualitative objectives for MCs, MDPs and graph games, for which treewidth-based algorithms yield significant complexity improvements. In this work, we show that treewidth can also be used to obtain faster algorithms for the...