Sharif Digital Repository

Semantic web search engines are evolving and many prototype systems and some implementation have been developed. However, there are some different views on what a semantic search engine should do. In this paper, a categorization scheme for semantic web search engines are introduced and elaborated. For each category, its components are described according to a proposed general architecture and various approaches employed in these components are discussed. We also propose some factors to evaluate systems in each category. © 2006 IEEE  

The estimation of the wind resource at the hub height of a wind turbine is one of the primary goals of site assessment. Since in a majority of cities the wind speed is measured at lower heights, the power law model is applied to estimate the wind speed at higher heights. In this study, the wind data for 10 cities in Iran have been analyzed over a period of one year. The accuracy of the power law model to estimate the wind speed has been examined with variations of height and time during this year. The energy production of a wind turbine using the measured wind speeds and the speeds estimated by the power law model were compared. The measured data revealed that in some cities the wind speed... 

Modern search engines use link structure of the World Wide Web in order to gain better results for ranking the results of users' queries. One of the most popular ranking algorithms which is based on link analysis is HITS. It generates very accurate outputs but because of huge amount of online computations, this algorithm is relatively slow. In this paper we introduce PHITS, a parallelized version of the HITS algorithm that is suitable for working with huge web graphs in a reasonable time. For implementing this algorithm, we use WebGraph framework and we focus on parallelizing access to web graph as the main bottleneck in the HITS algorithm. © 2006 IEEE  

In content based image retrieval similarity measurement is one of the most important aspects in a large image database for efficient search and retrieval to find the best answer for a user query. Color and texture are among the more expressive of the visual features. Considerable work has been done in designing efficient descriptors for these features for applications such as similarity retrieval. The MPEG-7 specifies a standard set of descriptors for color, texture and shape. In the Human Vision System (HVS), visual information is not perceived equally; some information may be more important than other information. The purpose of this paper is to show how the MPEG-7 descriptor based on... 

Multimedia files including audio, music and movies are important part of resources available on the Internet. With the expansion of personal computers and other digital devices such as digital cameras, ordinary people are also creating different multimedia files. Hence, there are huge amount of multimedia files in the Internet. Considering the volume of files available, we need automatic methods for indexing, classification and retrieval of multimedia files. But, there are a number of problems in processing multimedia files. Two important issues are the large size of multimedia files and different lengths of different files. In this PhD project, we want to develop a solution for these two... 

We present an ontology based indexing method for unstructured P2P networks. We maintain limited size indexes at each node to identify number of documents accessible on each concept without loosing any indexing information. Out method supports complex queries, combined of conjunction and disjunction phrases. We simulate our search algorithm on an unstructured P2P network and show that our method significantly reduces the network traffic. © 2008 Springer-Verlag  

When performing segmentation using tree based representations it is evident that contiguous objects are often dispersed widely across the tree making controlled selection difficult. This paper demonstrates robust segmentation by the generation of Binary Partition Trees entirely within the wavelet domain. By using spatial frequency in conjunction with colour, a threshold free tree is produced which compels objects to reside inside single branches of the tree by constraining their merging development. Experimental results show the superior performance of the proposed algorithm compared to the existing colour based BPT algorithms. ©2008 IEEE  

Peer-to-peer networks (P2P) are beginning to form the infrastructure of future applications. One of the problems with unstructured P2P networks is their scalability limitation. This is also the problem in structured P2P networks that use broadcasting to find objects. These networks can't contain a large number of nodes because of the large amount of traffic that they have to handle. Local indexing is a method to reduce this traffic. But local indexes tend to become large with the growth of the network. Also limiting the size of these indexes causes loss of indexing information. In this paper we introduce a novel ontology based local index which limits the size of the local indexes without... 

The growth of process industries has escalated the probability of loss containment scenarios of hazardous materials that can be tackled via process safety schemes. For preliminary design stage, the inherent scheme is more promising to generate sustainable process designs. For this purpose, various process routes are typically compared to recognize the safer one via numerous indexing methods to eliminate routes with hazardous materials. However, these indices lack in accommodating the equipment characteristics and the underutilization of process and chemical characteristics. Specifically for chemical characteristics, the toxicity aspect has not been engaged for process route selection in... 

The duct inverse design in fluid flow problems usually involves finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this investigation, an iterative inverse design method for 2-D subsonic ducts is presented. In the proposed method, the duct walls shape is changed under a novel algorithm based on the deformation of a virtual flexible string in flow. The deformation of the string due to the local flow conditions resulting from changes in wall geometry is observed until the target shape satisfying the prescribed wall's pressure distribution is reached. The flow field at each step is analysed using Euler equations and the advection upstream splitting... 

Peer-to-peer (P2P) networks are beginning to form the infrastructure of future applications. Heavy network traffic limits the scalability of P2P networks. Indexing is a method to reduce this traffic. But indexes tend to become large with the growth of the network. Also, limiting the size of these indexes causes loss of indexing information. In this paper we introduce a novel ontology based index (OI) which limits the size of the indexes without sacrificing indexing information. We show that the method can be employed by many P2P networks. The OI sits on top of routing and maintenance modules of a P2P network and enhances it. The OI prunes branches of search trees which have no chance to... 

Massively multi-user virtual environments (MMVE) incorporate computer graphics, sound and haptics to simulate the experience of real-time interaction among multiple users in a shared three-dimensional virtual world. Such applications therefore deal with the distribution of updates among their users to provide them with a common sense of time and place while interacting in the virtual environment. As MMVEs grow larger in terms of size and numbers of users, they tend to rely on P2P architecture as a scalable way of exchanging the huge bulk of updates among their users without the need for the exponential increase in their central servers. While much work has been done on P2P architectures for...