Sharif Digital Repository

This paper presents design and analysis of a cabledriven mechanism for a spherical laparoscopy surgical robot manufactured at the Research Center for Science and Technology in Medicine. The design is featured by two types of 'idler pulleys', which allow change of cables' plane of motion in spherical workspace. This robot suffers from back-lash and high friction due to the usage of motor and gear-box in each joint. In order to find a precise and optimal design, the paper studies various designs of cable robots, considering pulleys and cable arrangements, as well as pre-tensioning methods. Final scheme introduces two series of pulleys for each DOF, which transmits power from motors located on... 

Design, implementation and experimental evaluation of a classic PID, and a modern Generalized Predictive Control (GPC) for an off-pump heart tracking system were carried out. Following the design and simulation analysis of the controllers, experimental evaluation was conducted on the slave robot of SINA tele-operational surgical system. Results revealed that considering the volatile high-frequency/speed pattern of heart motion, the agility of the controlled system is the most influential factor on its performance. With this in mind, unlike the Ziegler-Nichols-based tuned PID with emphasis on steady-state condition, the PID control with more transient behavior showed a superior performance.... 

Design, implementation and experimental evaluation of a classic PID, and a modern Generalized Predictive Control (GPC) for an off-pump heart tracking system were carried out. Following the design and simulation analysis of the controllers, experimental evaluation was conducted on the slave robot of SINA tele-operational surgical system. Results revealed that considering the volatile high-frequency/speed pattern of heart motion, the agility of the controlled system is the most influential factor on its performance. With this in mind, unlike the Ziegler-Nichols-based tuned PID with emphasis on steady-state condition, the PID control with more transient behavior showed a superior performance.... 

Network-on-Chip (NoC) is a precious approach to handle huge number of transistors by virtue of technology scaling to lower than 50nm. Virtual channels have been introduced in order to improve the performance according to a timing multiplexing concept in each physical channel. The incremental effect of virtual channels on power consumption has been shown in literatures. The issue of power saving has always been controversial to many designers. In this paper, we introduce a new technique which tries to adaptively mange the number of virtual channels in order to reduce the power consumption while not degrading the performance of the network without any reconfiguration. Our experimental results... 

The majority of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. In order to understand the mechanical behavior of this soil, a series of triaxial compression tests (CD, CU) were performed on uncemented and artificially cemented samples. Hydrated lime was used as the cementation agent for sample preparation to model the Tehran cemented deposit. The tests were performed on artificially cemented samples after an appropriate curing time. The effect of confining pressure, cement content and fine content is investigated in this research. The tests results show that peak shear strength is followed by strain softening for all cemented samples. Shear strength... 

In this paper, a novel multi-objective location model within multi-server queuing framework is proposed, in which facilities behave as M/M/m queues. In the developed model of the problem, the constraints of selecting the nearest-facility along with the service level restriction are considered to bring the model closer to reality. Three objective functions are also considered including minimizing (I) sum of the aggregate travel and waiting times, (II) maximum idle time of all facilities, and (III) the budget required to cover the costs of establishing the selected facilities plus server staffing costs. Since the developed model of the problem is of an NP-hard type and inexact solutions are... 

To what extent can a short-term decline in the output of a small open economy be explained by trade barriers? To answer this, we extend the Business Cycle Accounting method of Chari et al. (2007) to a small open economy model. We include an additional time-varying wedge to model financial trade frictions caused by barriers on imports. International sanctions on Iran provide an empirical opportunity to apply this method to data on Iran's recession in 2012-13. The results indicate that efficiency and investment wedges account for most of the fluctuations in aggregate variables during the sanctions, and trade barriers had little contemporaneous explanatory power. The effect of oil boycotts... 

To what extent can a short-term decline in the output of a small open economy be explained by trade barriers? To answer this, we extend the Business Cycle Accounting method of Chari et al. (2007) to a small open economy model. We include an additional time-varying wedge to model financial trade frictions caused by barriers on imports. International sanctions on Iran provide an empirical opportunity to apply this method to data on Iran's recession in 2012-13. The results indicate that efficiency and investment wedges account for most of the fluctuations in aggregate variables during the sanctions, and trade barriers had little contemporaneous explanatory power. The effect of oil boycotts... 

This paper presents a small open economy, dynamic general equilibrium model with cash-in advance constraint and a currency attack to explain the dynamic effects of changes in trade barriers in the short and long run. The model is calibrated using data on macroeconomic variables in Iran's economy from 1990 to 2013 to identify and analyze the effects of barriers imposed on trade. We analyze the effects of counterfactual fiscal, monetary and exchange rate policies in response to trade barriers and show how the economy would respond in different time horizons. We also evaluate the effects of eliminating each of the factors causing this stagflation. Our findings show that the short-term drop in... 

Studies have shown that balance and mobility in people with Parkinson's disease (PD) can improve through rehabilitation interventions. However, until now no quantitative method investigated how these patients improve their balance control. In this study, a single inverted pendulum model with PID controller was used to describe the improvement of forty PD patients after a 12-session therapy program, and to compare their balance with twenty healthy subjects. The Center of Pressure (COP) data were recorded in seven sensory conditions - on rigid and foam surface, each with eyes open and closed, and with visual disturbance; and stance on rigid surface with attached vibrator to the Achilles... 

This paper introduces a new supergraph, called the k-Semi-Yao graph (k-SYG), of the k-nearest neighbor graph (k-NNG) of a set P of points in Rd. We provide a kinetic data structure (KDS) to maintain the k-SYG on moving points, where the trajectory of each point is a polynomial function whose degree is bounded by some constant. Our technique gives the first KDS for the theta graph (i.e., 1-SYG) in Rd. It generalizes and improves on previous work on maintaining the theta graph in R2. As an application, we use the kinetic k-SYG to provide the first KDS for maintenance of all the k-nearest neighbors in Rd, for any k≥1. Previous works considered the k=1 case only. Our KDS for all the 1-nearest... 

Let (Formula presented.) be a graph of order (Formula presented.) and size (Formula presented.). Suppose that (Formula presented.) is a function such that (Formula presented.). In this paper we provide a criterion for (Formula presented.)-choosability of (Formula presented.). Using this criterion, it is shown that the choice number of the complete (Formula presented.)-partite graph (Formula presented.) is (Formula presented.), which is a well-known result due to Erdös, Rubin and Taylor. Among other results we study the (Formula presented.)-choosability of the complete (Formula presented.)-partite graphs with part sizes at most (Formula presented.), when (Formula presented.), for every vertex... 

Modern SoC architectures use NoCs for high-speed inter-IP communication. For NoC architectures, high-performance efficient routing algorithms with low power consumption are essential for real-time applications. NoCs with mesh and torus interconnection topologies are now popular due to their simple structures. A torus NoC is very similar to the mesh NoC, but has rather smaller diameter. For a routing algorithm to be deadlock-free in a torus, at least two virtual channels per physical channel must be used to avoid cyclic channel dependencies due to the warp-around links; however, in a mesh network deadlock freedom can be insured using only one virtual channel. The employed number of virtual... 

Modern SoC architectures use NoCs for high-speed inter-IP communication. For NoC architectures, high-performance efficient routing algorithms with low power consumption are essential for real-time applications. NoCs with mesh and torus interconnection topologies are now popular due to their simple structures. A torus NoC is very similar to the mesh NoC, but has rather smaller diameter. For a routing algorithm to be deadlock-free in a torus, at least two virtual channels per physical channel must be used to avoid cyclic channel dependencies due to the warp-around links; however, in a mesh network deadlock freedom can be insured using only one virtual channel. The employed number of virtual... 

Network-on-Chip (NoC) has been proposed as an attractive alternative to traditional dedicated wires to achieve high performance and modularity. Power efficiency is one of the most important concerns in NoC architecture design. The choice of network topology is important in designing a low-power and high-performance NoC. In this paper, we propose the use of the WK-recursive networks to be used as the underlying topology in NoC. We have implemented VHDL hardware model of mesh and WK-recursive topologies and measured the latency results using simulation with these implementation. We also propose a novel approach in high level power modeling based on latency for these topologies and show that... 

Reaction of the zwitterions generated from isoquinoline or pyridine and dialkyl acetylenedicarboxylate with tetronic acid leads to 1,2- dihydroisoquinoline or 1,2-dihydropyridine tetronic acid derivatives without using any catalyst or activation at room temperature  

For a set of n points in the plane, this paper presents simple kinetic data structures (KDSs) for solutions to some fundamental proximity problems, namely, the all nearest neighbors problem, the closest pair problem, and the Euclidean minimum spanning tree (EMST) problem. Also, the paper introduces KDSs for maintenance of two well-studied sparse proximity graphs, the Yao graph and the Semi-Yao graph. We use sparse graph representations, the Pie Delaunay graph and the Equilateral Delaunay graph, to provide new solutions for the proximity problems. Then we design KDSs that efficiently maintain these sparse graphs on a set of n moving points, where the trajectory of each point is assumed to be... 

Background: Impaired postural control in Parkinson's disease (PD) seriously compromises life quality. Although balance training improves mobility and postural stability, lack of quantitative studies on the neurophysiological mechanisms of balance training in PD impedes the development of patient-specific therapies. We evaluated the effects of a balance-training program using functional balance and mobility tests, posturography, and a postural control model. Methods: Center-of-pressure (COP) data of 40 PD patients before and after a 12-session balance-training program, and 20 healthy control subjects were recorded in four conditions with two tasks on a rigid surface (R-tasks) and two on foam.... 

Background: Balance training improves postural control in Parkinson's disease (PD). However, a systematic approach for the development of individualized, optimal training programs is still lacking, as the learning dynamics of the postural control in PD, over a training program, are poorly understood. Objectives: We investigated the learning dynamics of the postural control in PD, during a balance-training program, in terms of the clinical, posturographic, and novel model-based measures. Methods: Twenty patients with PD participated in a balance-training program, 3 days a week, for 6 weeks. Clinical tests assessed functional balance and mobility pre-training, mid-training, and post-training.... 

Process variation has already emerged as a major concern in design of multi-processor system on chips (MPSoC). In recent years, there have been several attempts to bring variability awareness into the task scheduling process of embedded MPSoCs to improve performance yield. This study attempts to provide a comparative study of the current variation-aware design-time task and communication scheduling techniques that target embedded MPSoCs. To this end, the authors first use a sign-off variability modelling framework to accurately estimate the frequency distribution of MPSoC components. The task scheduling methods are then compared in terms of both the quality of the final solution and the...