Sharif Digital Repository

Given a terrain and a query point p on or above it, we want to count the number of triangles of terrain that are visible from p. We present an approximation algorithm to solve this problem. We implement the algorithm and then we run it on the real data sets. The experimental results show that our approximation solution is very close to the real solution and compare to the other similar works, the running time of our algorithm is better than their algorithm. The analysis of time complexity of algorithm is also presented. Also, we consider visibility testing problem, where the goal is to test whether p and a given triangle of train are visible or not. We propose an algorithm for this problem... 

The emergence of the globalization paradigm in manufacturing industry has changed the markets’ circumstances, and accordingly manufacturing systems need to be compatibilized with these situations. There are many solutions to assist manufacturing systems for this purpose. Computerized systems and their related solutions were being the most attractive ones for manufacturing systems in recent decade. Developing such systems and exploiting from the advantages of such solutions requires a consistent foundation. Computer Integrated Manufacturing (CIM) emerged as a philosophy to provide such foundation, and to assist the computerized manufacturing solutions. Despite of the high potentials of the... 

Existence of crosscutting concerns in software requirements often intensifies complexity of software development process. Modeling and analyzing of these concerns in the software architecture decrease possibility of finding tangled and complex components in the ultimate design. Aspect oriented ADLs have emerged to overcome this problem; however, imposing radical changes to existing architectural modeling methods is not easily acceptable by architects. In this paper, we present a method to enhance conventional software architecture description languages through utilization of aspect features with special focuses on non-functional requirements (NFRs). © 2007 IEEE  

Ambient Intelligence is the future of computing where devices predict what users need and help them carry out their everyday life activities easier. To make this prediction possible these environments should be aware of the context. Activity recognition is one of the most complex problems in context-aware environments. In this paper we propose a layered Dynamic Bayesian Network (DBN) to recognize activities in an oral presentation. The layered architecture gives us the opportunity to recognize complex activities using the classification results of sensory data in the first layer regardless of the physical environment. Our model is event-driven meaning the classification takes place only when... 

In this paper a novel approach to dynamic formulation of rovers has been presented. The complexity of these multi-body systems especially on rough terrain, challenged us to use the Kane's method which has been preferred to others in these cases. As an example, symbolic equations of a six-wheeled rover, named CEDRA Rescue Robot which uses a shrimp like mechanism, have been derived and a simulation of forward and inverse dynamics has been presented. Due to the clear form of equations, each term defines a physical meaning which represents the effect of each parameter, resulting in a frame-work for performance comparison of rovers. Although the method has been described for a 2-D non-slipping... 

Abstract Several researchers have worked on transmitting a given amount of flow through a network flow within fastest possible time, allowing flow to be transmitted through one or more paths. Extending this problem to the system reliability problem, the quickest path reliability problem has been introduced. The problem evaluates the probability of transmitting some given amount of flow from a source node to a sink node through a single minimal path in a stochastic-flow network within some specified units of time. Later, the problem has been extended to allow flow to be transmitted through two or more separate minimal paths (SMPs). Here, we consider the problem of sending flow through two... 

We present an efficient and provably-secure e-voting protocol, which is a variant of the JCJ e-votingprotocol (Juels et al., 2010). It decreases the total number of JCJ's operations from O(n2) to O(n), where n is the number of votes or voters (whichever is the maximum). Note that since the operations under consideration are time-consuming (e.g., public-key encryption), the improvement is quite substantial. As a rough comparison, consider a nation-wide election with around ten million voters/votes. Assuming each operation takes one microsecond, and no parallelization is used, one can see a huge difference: our protocol tallies the votes in 10 seconds, while the JCJ protocol requires over 3... 

Image completion is an active subject in image and video processing, which deals with recovering the missing or removed parts of a given 2-D or 3-D data. Here, we present a method to efficiently build the multiresolution pyramid for a partially-missing image, by which, multiresolution image completion can be efficiently initialized and performed. Using this approach, we improve our previous algorithm for multiresolution image completion, especially when the inputs suffer spread missing areas. In comparison with the overall process of image completion, the computational and space complexity of the proposed method for building multiresolution pyramid is eligible. The obtained results of our... 

Video transcoding comprises the necessary operations for the conversion of a compressed video stream from one syntax to another one for inter-network communications, without the need of any further decoding and re-encoding process. The two most recent and popular standard video coders are H.263 and H.264. In this paper, we present tools to enable low complexity intra transcoding from H.263 to H.264 using a novel fast intra prediction mode decision algorithm that does not require extra computation. It is shown that due to basic similarities of H.263 and H.264 it is possible to reuse predictor side information, so this side information is used to simplify the mode and direction decision for... 

In this paper, we propose a Jacobi-like Deflationary ICA algorithm, named JDICA. More particularly, while a projection-based deflation scheme inspired by Delfosse and Loubaton's ICA technique (DelLR) is used, a Jacobi-like optimization strategy is proposed in order to maximize a fourth order cumulant-based contrast built from whitened observations. Experimental results obtained from simulated epileptic EEG data mixed with a real muscular activity and from the comparison in terms of performance and numerical complexity with the FastICA, RobustICA and DelLR algorithms, show that the proposed algorithm offers the best trade-off between performance and numerical complexity when a low number (∼... 

Medical images include human body picture and it is used in diagnosis purpose [1]. Lossless compression of medical image is an application of medical imaging. During lossless compression task, transformation algorithm can be used to increase compression ratio. In Real time applications such as telemedicine and online diagnosis, hardware implementation accelerates the process. Hence, for such purposes medical compression is better to be simple. Lossless JPEG and JPEG2000 are some compression method. JPEG2000 gives better compression ratio. However, it is complex. In this paper an efficient method of lossless image transformation has been introduced by improving prediction model. Simulation... 

Efficiency in cloud servers’ power consumption is of paramount importance. Power efficiency makes the reduction in greenhouse gases establishing the concept of green computing. One of the beneficial ways is to apply power-aware methods to decide where to allocate virtual machines (VMs) in data center physical resources. Virtualization is utilized as a promising technology for power-aware VM allocation methods. Since the VM allocation is an NP-complete problem, we use of evolutionary algorithms to solve it. This paper presents an effective micro-genetic algorithm in order to choose suitable destinations between physical hosts for VMs. Our evaluations in simulation environment show that... 

We construct an efficient statistical zero-knowledge authentication protocol for smart cards based on general assumptions. We show how it can be instantiated using lattice-based primitives, which are conjectured to be secure against quantum attacks. We illustrate the practicality of our protocol on smart cards in terms of storage, computation, communication, and round complexities. Furthermore, we compare it to other lattice-based authentication protocols, which are either zero-knowledge or have a similar structure. The comparison shows that our protocol improves the best previous protocol in several aspects  

Long Term Evolution (LTE) supports peak data rates in excess of 300 Mb/s. A good approach to achieve such rates is by parallelizing the required processing in turbo decoders. An interleaver is an important part of a turbo decoder. LTE uses the Quadratic Permutation Polynomial (QPP) interleaver, which makes it suitable for parallel decoding. In this paper, we propose an efficient architecture for the QPP interleaver, called the Add-Compare-Select (ACS) permuting network. A unique feature of the proposed architecture is that it can be used both as the interleaver and deinterleaver leading to a high-speed low-complexity hardware interleaver/deinterleaver for turbo decoding. The proposed design... 

Cyclic voltammetry, j-t transients and transient time measurements have been used to characterize the Au-Ni alloy deposition and to obtain the nucleation and growth mechanism. The electrodeposition of gold, nickel and gold-nickel alloys was studied in cyanide-citrate electrolytes. The analysis of the voltammograms and j-t transients clearly shows that deposition of the Au and hence, of Au-Ni alloys, is affected by adsorbed cyanide ligands mainly at low overpotentials and a direct reduction occurs at high overpotentials. In this case, the Au deposition is kinetically favored, while the Ni deposition is controlled by the cyanide-citrate adsorbed adlayer. In an alloy electrolyte, the Au and Ni... 

An integrated approach is presented for predicting granule particle size using Partial Correlation (PC) analysis and Artificial Neural Networks (ANNs). In this approach, the proposed model is an abstract form from the ANN model, which intends to reduce model complexity via reducing the dimension of the input set and consequently improving the generalization capability of the model. This study involves comparing the capability of the proposed model in predicting granule particle size with those obtained from ANN and Multi Linear Regression models, with respect to some indicators. The numerical results confirm the superiority of the proposed model over the others in the prediction of granule... 

In the past few years, the study of complex networks has attracted the attention of researchers. Many real networks, ranging from technological networks such as the Internet to biological networks, have been considered as special types of complex networks. Through application of the network science, important structural properties of such networks have been analyzed and the mechanisms that form such characteristics have been introduced. In this paper, we address the structural characteristics of a technological network called Vehicular Ad hoc Networks (VANETs). Recent studies reveal that the communication graph of VANETs has some interesting characteristics including: the Gaussian degree... 

The quickest path reliability problem evaluates the probability of transmitting some given units of flow from a source node to a sink node through a single minimal path in a stochastic-flow network within some specified units of time. This problem has been recently extended to the case of transmitting flow through q separate minimal paths (SMPs) simultaneously within a budget constraint. Here, we propose a new algorithm to solve such problems. The algorithm finds all the minimal vectors for which a given demand level d units of flow can be transmitted through q SMPs from a source node to a sink node satisfying some given time and budget limits. In our proposed algorithm, a special... 

Oxone® (2KHSO5·KHSO4·K 2SO4) in the presence of mer-tris[(2-oxazolinyl)phenolato] manganese(III), Mn(phox)3, as catalyst under biphasic reaction conditions (CH2Cl2/H2O) and tetra-n-butylammonium bromide as phase transfer agent efficiently oxidises alcohols to their corresponding aldehydes and ketones at room temperature with very short reaction times (5 min) and good to quantitative yields. © 2003 Elsevier Ltd. All rights reserved  

Motivated by the statistical correspondence between phases of the transmitted and received vectors, we present a fast decoding method for quasi-orthogonal space-time block codes (QOSTBCs) in this paper. The proposed decoder selects proper candidates from precomputed and sorted sets by focusing on the phase of a specific entry of the combined and decoupled vector. The ML metric of the most probable candidates is first evaluated, and then, the remaining candidates are assessed based on the similarity between the phases. The new algorithm can work with any type of constellation such as QAM and PSK and supports generalized block-diagonal QOSTBCs. Theoretical results backed by simulation tests...