Sharif Digital Repository

The MAXQ hierarchical reinforcement learning method is computationally expensive in applications with deep hierarchy. In this paper, we propose a new learning algorithm for MAXQ method to address the open problem of reducing its computational complexity. While the computational cost of the algorithm is considerably decreased, the required storage of new algorithm is less than two times as the original learning algorithm requires storage. Our experimental results in the simple Taxi Domain Problem show satisfactory behavior of the new algorithm  

So far several methods have been proposed for clustering the web. On the other hand, many algorithms have been developed for clustering the relational data, but their usage for the Web is to be investigated. One main category of such algorithms is density based methods providing high quality results. In this paper first, a new density based algorithm is introduced and then it is compared with other algorithms of this category. The proposed algorithm has some interesting properties and capabilities such as hierarchical clustering and sampling, making it suitable for clustering the web data. © Springer-Verlag Berlin Heidelberg 2007  

A study was conducted to select the best alternative for the development of construction panels as well as investment in its manufacturing in Iran. Three alternatives are considered, cement-bonded wood composite product, substituted products (such as concrete panel) sandwich panel and a mixture of them. We apply the analytic network process (ANP) to achieve this goal. A hierarchy is designed to prioritize benefits, opportunities, costs and risks (BOCR) by using the Analytic Hierarchy Process (AHP) ratings approach. To evaluate the "control criteria" of the system, a control hierarchy is also created and prioritized by applying the Analytic Network Process (ANP). A total of four major control... 

Recently query log mining is extensively used by web information systems. In this paper a new hierarchical co-clustering for queries and URLs of a search engine log is introduced. In this method, firstly we construct a bipartite graph for queries and visited URLs, and then to discover noiseless clusters, all queries and related URLs are projected in a reduced dimensional space by applying singular value decomposition. Finally, all queries and URLs are iteratively clustered for constructing hierarchical categorization. The method has been evaluated using a real world data set and shows promising results. © Springer-Verlag Berlin Heidelberg 2007  

In this paper, a new cache placement scheme is proposed to achieve higher hit ratios with respect to the two conventional schemes namely set-associative and direct mapping. Similar to set-associative, in this scheme, cache space is divided into sets of different sizes. Hence, the length of tag fields associated to each set is also variable and depends on the partition it is in. The proposed mapping function has been simulated with some standard trace files and statistics are gathered and analyzed for different cache configurations. The results reveal that the proposed scheme exhibits a higher hit ratio compared to the two well-known mapping schemes, namely set-associative and direct mapping,... 

We purposed a new Network on Chip (NoC) architecture called Hierarchical Graph. The most interesting feature of this novel architecture is its simple implementation process. Furthermore, the flexible structure of this topology makes it suitable for use in application specified chips. To benchmark the suggested architecture with existing ones, basic models of physical implementation have been extracted and simulated using NS-2. The results compared with the common used architecture Mesh show that HG has better performance, especially in local traffics and high loads. © IFIP International Federation for Information Processing 2005  

The existence of the important similarities between gelation and glass transition makes it hard to distinguish between the two types of nonergodic states experimentally. Here, we report on a stochastic analysis of the scattered light intensity through a colloidal particles suspension during the gel and glass formation. In this analysis, we exploit the methods developed for complex hierarchical systems, such as turbulence. Using the multiplicative log-normal cascade models, we provide a criterion to distinguish gels from glasses  

Financial performance evaluation is a very crucial process for industries in current highly competitive environment. Therefore, designing an accurate and appropriate performance evaluation framework is beneficial for insiders and also shareholders of a company. To evaluate financial performance, we need to consider some financial indicators that reflect the competitiveness of a company. There are many financial indicators and criteria that are vague and can be regarded as a fuzzy multiple criteria decision-making (MCDM) problem. In this paper, we developed a new financial performance evaluation framework to rank the companies in Iranian petrochemical industry based on fuzzy MCDM approach. To... 

We report on a stochastic analysis of Earth's vertical velocity time series by using methods originally developed for complex hierarchical systems and, in particular, for turbulent flows. Analysis of the fluctuations of the detrended increments of the series reveals a pronounced transition in their probability density function from Gaussian to non-Gaussian. The transition occurs 5-10 hours prior to a moderate or large earthquake, hence representing a new and reliable precursor for detecting such earthquakes. © 2009 The American Physical Society  

In this paper, a new approach is presented for optimal control of large-scale chemical processes. In this approach, the chemical process is decomposed into smaller sub-systems at the first level, and a coordinator at the second level, for which a two-level hierarchical control strategy is designed. For this purpose, each sub-system in the first level can be solved separately, by using any conventional optimization algorithm. In the second level, the solutions obtained from the first level are coordinated using a new gradient-type strategy, which is updated by the error of the coordination vector. The proposed algorithm is used to solve the optimal control problem of a complex nonlinear... 

Procurement of optimum available transfer capability (ATC) in the restructured electricity industry is a crucial challenge with regards to open access to transmission network. This paper presents an approach to determine the optimum location and optimum capacity of TCSC in order to improve ATC as well as voltage profile. Real genetic algorithm (RGA) associated with analytical hierarchy process (AHP) and fuzzy sets are implemented as a hybrid heuristic technique in this paper to optimize such a complicated problem. The effectiveness of the proposed methodology is examined through different case studies. © 2007 Elsevier B.V. All rights reserved  

In this paper, we use the regular distribution method to design a perfect load balancing algorithm for an n-star with a maximum error of 1 and a time complexity of 3n(n+1). This algorithm is based on the novel notion of leader trees. A second algorithm proposed in this paper as an enhancement to our first algorithm and uses an arbitrary spanning tree as the leader tree and has a worst time complexity of 2.25n 2-3n+0.75. We also discuss the issue of dynamically selecting the leader tree and hybrid load balancing algorithms in general. Furthermore, we present a hybrid algorithm for load balancing on the star interconnection network which benefits from a diffusion load balancing preprocessing... 

One of the main properties of fragile watermarking schemes is to indicate the location of changes made to the image, i.e. tamper localization, In addition to detection of watermarked image modifications. In this paper, the localization property Is added to the SVD(Singular Value Decomposition) based fragile watermarking scheme proposed by Byun et al. To do this, a hierarchical watermarking structure is used, where the Image is partitioned into blocks In a multilevel hierarchy, and then the SVD-based algorithm Is employed at each level to Insert authenticating data In sub-blocks. In the verification process, blocks at the lowest hierarchical level can detect modifications made to the... 

Analytic Hierarchy Process (AHP) is a multiple criteria decision making approach which is widely used in different engineering domains. The hierarchical structure of AHP makes it a very suitable approach for behavior design in artificial life-based games. But the details of an AHP is always designed by a series of interviews with experts of the domain, and this is not possible for problems in which an expert does not exist such as computer simulations. In such cases, the behavioral engineering of agents is a very complicated task because the designer may not be able to see all different aspects of agents' life. To overcome this problem, this paper has used an artificial life algorithm to... 

Hierarchical stochastic activity networks (HSANs) are a newly introduced extension of stochastic activity networks (SANs). HSAN models encapsulate hierarchies and a key benefit of these models is the possibility of automatic employment of composition techniques by their modelling tools. For modelling and evaluation with HSANs, we have developed a software tool called SANBuilder. This tool has an integrated development environment (IDE) for construction, animation, simulation and analytic solution of SAN-based models. We have implemented in this tool some state-of-the-art methods for the simulation and analytic solution of SAN and HSAN models. In addition to an introduction to HSANs, this... 

In hierarchical service networks, facilities at different levels provide different types of service. For example, in health care systems, general centers provide low-level services, such as primary health care, while specialized hospitals provide high-level services. Because of the demand congestion at service networks, the location of servers and their allocation of demand nodes can have a strong impact on the length of the queue at each server, as well as on the response time to service calls. This study attempts to develop hierarchical location-allocation models for congested systems by employing a queueing theory in a fuzzy framework. The parameters of each model are approximately... 

Global economic expansion and increasing concentration of people in the large cities, especially in developing countries leads to some environmental issues such as air pollution. Relocation of the firms as a great air pollutant can be an appropriate alternative for diminishing these pollutions. Yet, there is a lack of research about factors precluding firm relocation with respect to decision making factors when determining whether or not to relocate. Thus, the purpose of this case study is to examine firm relocation decision-making factors and to apprehend the role of environment issues in making them using a combination of SWOT matrix and Analytic Hierarchy Process (AHP). The combination... 

Crash data availability is a significant requirement for identifying hazardous roads. However, for roads with poor data sets or no crash record, a method is needed to find and rank road segments independent of the crash records. In this paper, an auditing based methodology is proposed to determine the hazardous locations. A Rural road is investigated by decomposing it first into six elements, and then into safety factors corresponding to each element. The elements are: straight segments, horizontal and vertical curves, bridges, tunnels, merges and intersections, and side road land use. The relative contribution of the elements to the safety of a road segment is determined using the... 

Security is one of the important issues in developing and implementing software systems especially in highly critical applications. Quantification and measurement of security is one of the approaches adopted to achieve the desired degree of security. In this paper, Stochastic Activity Networks (SANs) are used to formally model the attacks on the system under investigation. To this end, the semi-Markov attack model is sketched. Having the semi-Markov model, Probability of Attack Success (PAS), Mean Time to First Breach (MTFB), and System Misuse Proportion (SMP) are measured according to the appropriate transformation of the model to a SAN model. As a case study, we have studied a high-level... 

This research investigates a three dimensional parametric risk assessment model considering the 3rd factor to be the impact on business. In order to represent the 3rd order risk assessment matrix monitoring the impact of safety reports on the continuous economical performance of the airline, the other two factors, probability of safety and severity are redefined. Introducing two quantitative and qualitative assessment methodologies, the overall risk of the organization can be studied by means of Analytical Hierarchy Process (AHP). providing an adequate background to define the safety goals of the organization