Sharif Digital Repository

Login section is one of the most important parts of each system. This section is usually achieved through a username-password entering method. Since in these methods, user's security relays on how strong the password is, accordingly it is important how the password is provided. There are lots of different approaches in this regard which can be categorized in two main subgroups: Static and Dynamic passwords. Dynamic passwords are taking the lead in password generation context, since static password approaches suffer from some disadvantages like their vulnerability to easily get cracked, high possibility of oblivion and etc. In this paper, we introduce a novel dynamic password providing idea,... 

Photovoltaic (PV) panel accurate modeling is essential for operational studies and generation estimation under actual conditions and power electronic control device designs in grid connected or isolated power systems. Inaccuracy in modeling parameters such as photon's current, diode's saturation current, series and parallel resistances and diodes ideality coefficients causes errors in modeling and simulating photovoltaic panel's operation. In this paper, photovoltaic panel's parameters are estimated according to characteristic curves obtained from experiments. Heuristic optimization methods are utilized to calculate parameters for both singlediode and double-diode models. Results indicate... 

In this paper, a restricted structure of PID controller is proposed for automobile gas turbine by considering a LQG cost function. So PID Controller coefficients are calculated by minimizing this cost function. One of the most important characteristics of this approach, its ability to design various structure PID controllers by solving optimization problem only for one time, moreover it can approximate main optimization problem by a repetitive Quadratic optimization Problem (QP). This approach is convex optimization and has an analytic solution; therefore its calculations are not complicated. In defined cost function, there are two weighting functions, control error and control action; they... 

Importance measures (IMs) are used for risk-informed decision making in system operations, safety, and maintenance. Traditionally, they are computed within fault tree (FT) analysis. Although FT analysis is a powerful tool to study the reliability and structural characteristics of systems, Bayesian networks (BNs) have shown explicit advantages in modeling and analytical capabilities. In this paper, the traditional definitions of IMs are extended to BNs in order to have more capability in terms of system risk modeling and analysis. Implementation results on a case study illustrate the capability of finding the most important components in a system. © 2018 World Scientific Publishing Company  

The major objective of this study is to provide an analytical tool to identify the role of investment on innovation in the process of new technologies development. To achieve this goal, a model of knowledge flow is developed and the effects of national and international knowledge spillovers are investigated. Results show that when knowledge spillovers are modelled in the Nordic countries, the required investment on domestic energy R&D decreases and the cumulative knowledge increases to 10.7 billion USD by 2030. This is a significant economic potential for technological innovation which can be considered for both energy researchers and energy planners. Finally, some important policy insights... 

We study the capacity region of the two-user binary fading (or erasure) interference channel, where the transmitters have no knowledge of the channel state information. We develop new inner bounds and outer bounds for this problem. We identify three regimes based on the channel parameters: weak, moderate, and strong interference regimes. Interestingly, this is similar to the generalized degrees of freedom of the two-user Gaussian interference channel, where transmitters have perfect channel knowledge. We show that for the weak interference regime, treating interference as erasure is optimal while for the strong interference regime, decoding interference is optimal. For the moderate... 

We introduce the blind index coding (BIC) problem, in which a single sender communicates distinct messages to multiple users over a shared channel. Each user has partial knowledge of each message as side information. However, unlike classical index coding, in BIC, the sender is uncertain of what side information is available to each user. In particular, the sender only knows the amount of bits in each user's side information but not its content. This problem can arise naturally in caching and wireless networks. In order to blindly exploit side information in the BIC problem, we develop a hybrid coding scheme that XORs uncoded bits of a subset of messages with random combinations of bits from... 

The debate over innovativeness of large firms and SMEs, which was bolded by Schumpeter, still continues under mixed empirical evidences. There are several implications for this debate including policy orientation in support of large firms or SMEs. But there is a scarce of studies in developing countries and no such study in Iran yet. The present study has explored the proportionality of increase of innovation activity versus firm size within 522 Iranian knowledge-based firms categorized in 9 industries. Innovation activity was measured by R&D expenditure while firm size stood for number of employees. Using log-log regression in the first phase, it was found that R&D expenditure confirms a... 

Software architecture patterns present solutions for software architecture problems and help to document architectural design decisions. Complexity and variability of patterns, and the required expertise for selecting an appropriate pattern, would cause some difficulties in utilizing architectural patterns. Using an ontology for registering architectural patterns is an efficient step in solving those problems. However, the mentioned difficulties make the process of constructing the architectural patterns ontology even more complicated. This paper proposes an approach that considers the construction of the architectural patterns ontology from four perspectives in order to overcome this... 

In today's competitive market, culture of excellence (CoE) and knowledge sharing (KS) are vital factors for organisations to thrive in the ever-expanding global market-economy. However, most previous studies have paid less attention to CoE especially in developing countries. In addition, they gave less attention to KS as a mediator in the CoE performance model. The purpose of this paper is to investigate the relationship among CoE, KS, and organisational performance (OP) in the sector of industrial companies in Iran, and to develop a conceptual framework based on extensive review of the literature. Based on a review of the literature, a link was established between CoE and OP. Furthermore,... 

Iran’s fifth Four Year Development Plan (2011-2015) and other high level acts in recent years have paid more attention to the topic of knowledge management. This in turn has encouraged the government agencies to pay special attention to this topic for the development of their regulations and future plans. The information technology field has not been an exception to this trend, and in September 2014 an Administrative and Technical Criteria Act (ATCA) was approved for the development of an agile and effective e-government in Iran. Under Article 40 of ATCA all executive bodies of government are required to design and implement a comprehensive knowledge management system within the next 2... 

In this paper, the topic model is adopted to learn traffic phases from video sequence. Phase detection is applied to determine where a video clip is in the traffic light sequence. Each video clip is labeled by a certain traffic phase, based on which, videos are segmented clip by clip. Using topic models, without any prior knowledge of the traffic rules, activities are detected as distributions over quantized optical flow vectors. Then, traffic phases are discovered as clusters over activities according to the traffic signals. We employ the Fully Sparse Topic Model (FSTM) as the topic model. The results show that our method can successfully discover both activities and traffic phases which... 

Multi-agent systems can be seen as an apparatus for testing the performance of real distributed systems. One problem encountered in multi-agent systems with the learning capability is credit assignment. This paper presents two methods for solving this problem. The first method assigns credit to the agents according to the history of the interaction while the second method assigns credit to the agents according to the knowledge of agents, and thus the shares of the agents are extracted from the feedback of the environment. The computer experiments show that critic learning has a positive impact in credit assignment problem  

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  

Visibility graph of a simple polygon in a plain is a graph in which the number of its vertices corresponds with the number of vertices in the polygon and each of its edges corresponds with a pair of visible vertices in the polygon. Visibility graph reconstruction of a polygon is one of the old and important problems in computational geometry for which no algorithm has been offered yet. Considering that the problem of visibility graph reconstruction of a pseudo-triangle has been solved, we present an O(n2)-time algorithm for pseudo-triangulation of a simple polygon, using the visibility graph corresponding with the polygon (n is number of vertices of the polygon). To do so, first we present a... 

With the advance and growth of knowledge management in the past two decades, currently knowledge is regarded as one of the most significant organizational assets. Today the success of businesses is dependent on the value that they give to knowledge and how they attempt to manage it. Hence, in such conditions, knowledge as a valuable asset of the organization must be well-protected. What is managed in knowledge management in organizations is actually not knowledge. What are managed are the knowledge-related processes thru which knowledge workers interact with each other. Hence, organizational knowledge protection does not mean protecting knowledge, but securing the management of knowledge and... 

Suggestion and application of a set of new features for on-line Partial Discharge (PD) monitoring, where there is no information about the type of PD is a challenging task for condition assessment of power equipments, such as a power transformer. This is looked for in this paper. So far, in past various techniques have been employed to develop a comprehensive PD monitoring system, however limited success has been achieved. One of the challenging issues in this field is the discovering of proper features capable of differentiating the involvement of possible types of PD sources. In order to examine the efficiency of the method established in this paper, which is based on application of a set... 

Every project is temporary and unique in nature. However, knowledge and lessons learned in projects may be used in other projects to improve the project management services. A learned lesson comes from past and current projects, captured through well-defined organizational processes. It aims to capture an essence of an experience which may be utilized to modify the project processes, or the situations for which that lesson applies. Although lessons learned is used in many industries and is an essential part of Project Management Body of Knowledge, no effective process has been defined to capture, validate, and reuse projects' lessons learned. A three stage system was developed and used to... 

The Putting human commonsense knowledge into computers has always been a long standing dream of artificial intelligence (AI). The cost of several tens of millions of dollars and time have been covered so that the computers could know about "objects falling, not rising.", "running is faster than walking". The large database was built, automated and semi-automated methods were introduced and volunteers' efforts were utilized to achieve this, but an automated, high-throughput and low-noise method for commonsense collection still remains as the holy grail of AI. The aim of this study was to build commonsense knowledge ontology using three approaches namely Hearst method, machine translation and... 

Knowledge architecture (KA) establishes the basic groundwork for the successful implementation of a short-term or long-term knowledge management (KM) program. An example of KA is the design of a prototype before a new vehicle is manufactured. Due to a transformation to large-scale organizations, the traditional architecture of organizations is undergoing fundamental changes. This paper explores the main strengths and weaknesses in the field of KA within large-scale organizations and provides a suitable methodology and supervising framework to overcome specific limitations. This objective was achieved by applying and updating the concepts from the Zachman information architectural framework...