- Détails du magazine
- Format
- Magazine
- eISSN
- 1314-4081
- Première publication
- 13 Mar 2012
- Période de publication
- 4 fois par an
- Langues
- Anglais

#### Chercher

- Accès libre

Risk estimation and stochastic control of innovation processes

Pages: 3 - 10

#### Résumé

The innovation introduction, no matter whether a product, technology, a method, etc., is being implemented, is connected with considerable risk of investments loss and highly stochastic behaviour, depending on unpredictable factors. It is acknowledged that the innovation passes at least through 6 general stages: 1 - Prestart stage; 2 - Start stage; 3 - Initial expansion stage; 4 - Quick expansion stage; 5 - Stage of reaching liquidity of venture investments; 6 - Stage of project failure and its cancelling. Each state may be refined in details. It is important for the Decision Maker (DM) on one hand to be able to estimate the risk of transitions from a state to state and the probability also for profitable outcome of the initiative - for this purpose a network flow model is proposed; and on the other hand - it is useful if the DM may apply different actions at each stage so that to minimize the losses and maximize the final profit - for this purpose a Markov Decision Process is proposed, which is very closely related to the network flow model and both may be united in a Markov flow.

#### Mots clés

- Innovation process control
- network flows
- Markov Decision Process
- risk estimation

- Accès libre

Rqa based approach to detect and prevent ddos attacks in voip networks

Pages: 11 - 24

#### Résumé

Voice over Internet Protocol (VoIP) is a family of technologies for the transmission of voice over Internet. Voice is converted into digital signals and transmitted as data packets. The Session Initiation Protocol (SIP) is an IETF protocol for VoIP and other multimedia. SIP is an application layer protocol for creating, modifying and terminating sessions in VoIP communications. Since SIP is a more flexible and simple protocol, it is quite easy to add features to it.

Distributed Denial of Service Attack (DDoS) floods the server with numerous requests from various hosts. Hence, the legitimate clients will not be able to get their intended services. A major concern in VoIP and almost in all network domains is availability rather than data consistency. Most of the surviving techniques could prevent VoIP network only after collision. This paper proposes a Recurrence Quantification based approach to detect and prevent VoIP from a DDoS attack. This model detects the attack at an earlier stage and also helps to prevent from further attacks. In addition, this techniques enables the efficient utilization of resources. QUALNET has been used to simulate the operation of the proposed technology.

#### Mots clés

- VoIP
- SIP
- Distributed denial-of-service attacks
- Recurrence Quantification Analysis

- Accès libre

An optimized scheduling algorithm on a cloud workflow using a discrete particle swarm

Pages: 25 - 39

#### Résumé

In order to solve the problems of security threats on workflow scheduling in cloud computing environments, the security of tasks and virtual machine resources are quantified using a cloud model, and the users’ satisfaction degree with the security of tasks assigned to the virtual resources is measured through the similarity of the security cloud. On this basis, combined with security, completion time and cost constraints, an optimized cloud workflow scheduling algorithm is proposed using a discrete particle swarm. The particle in the particle swarm indicates a different cloud workflow scheduling scheme. The particle changes its velocity and position using the evolution equation of the standard particle swarm algorithm, which ensures that it is a feasible solution through the feasible solution adjustment strategies. The simulation experiment results show that the algorithm has better comprehensive performance with respect to the security utility, completion time, cost and load balance compared to other similar algorithms.

#### Mots clés

- Scheduling algorithm
- cloud workflow
- discrete particle swarm
- evolution equation

- Accès libre

Cooperation of agents in complex systems based on supervision

Pages: 40 - 51

#### Résumé

Complex systems consist of many cooperating devices. To have a transparent view on the system structure, as well as on the structural interconnections and cooperation of the subsystems, it is useful to synthesize the complex systems systematically in a prescribed order, even in analytical terms (if possible). The supervision of the subsystems seems to be a very suitable approach to accomplish these demands, and consequently it makes the complex systems diagnostics easier. The substantial agents (i.e., the agents of material nature − e.g., devices like particular production lines, robots, numerically controlled machines, etc.) can be coordinated and forced to cooperation by means of efficiently synthesized supervisors. The cooperation process has the character of DES (Discrete-Event Systems), because any system (including continuous systems), has minimally two discrete states - idle and working. DES control theory can be successfully utilized in supervisor synthesis. There are several approaches to modeling the agents and the process of supervisor synthesis. The Petri net-based approach is one of them. Place/Transition Petri Nets (P/T PN) are used here for modeling the behaviour of particular agents, as well as in the computational parocess used for the supervisor synthesis. Two main methods of the P/T PN-based supervision will be used, namely (i) the supervision based on the place invariants (P-invariants) of P/T PN, utilizing only the state vector during the supervisor synthesis, and (ii) the extended supervision utilizing not only the state vector, but also the control vector and Parikh’s vector. The efficiency of the proposed approach is illustrated in a case study.

#### Mots clés

- Agent
- complex systems
- cooperation
- supervision
- supervisor synthesis

- Accès libre

Privacy preservation in fuzzy association rules using rough computing and DSR

Pages: 52 - 71

#### Résumé

In the present age of Internet, data is accumulated at a dramatic pace. The accumulated huge data has no relevance, unless it provides certain useful information pertaining to the interest of the organization. But the real challenge lies in hiding sensitive information in order to provide privacy. Therefore, attribute reduction becomes an important aspect for handling such huge database by eliminating superfluous or redundant data to enable a sensitive rule hiding in an efficient manner before it is disclosed to the public. In this paper we propose a privacy preserving model to hide sensitive fuzzy association rules. In our model we use two processes, named a pre-process and post-process to mine fuzzified association rules and to hide sensitive rules. Experimental results demonstrate the viability of the proposed research.

#### Mots clés

- Almost indiscernibility
- fuzzy proximity relation
- fuzzy approximation space
- ordering rules

- Accès libre

Error reduction in promoted confidence factor of a rule using improved fuzzy rule promotion technique

Pages: 72 - 83

#### Résumé

A dynamic fuzzy rule promotion approach for the promotion of a confidence factor of a rule for every successful session in diagnosis of a disease in crops by using the specific rules, has already been proposed in literature. This technique has the limitation that an error in the initial estimation of weights reduces linearly after every session the rule is being used. In this paper an improved approach has been proposed using the square root of sum of squares of frequencies, which are spread around the mean true value to reduce the error around a mean value. A rule set for the diseases and their symptoms for the paddy plant has been provided to make comparison between the previous and the improved approach. It has been shown that the improved approach decreases the error in uncertainty of estimation of weight for rules after every successful session. It has also been proposed that the improved approach must be applied in agricultural information dissemination system.

#### Mots clés

- Improved rule promotion methodology
- rule promotion methodology
- Fuzzy Logic
- confidence in rule
- agricultural information System
- weight factor
- confidence factor

- Accès libre

Programming learning style diagnosis scheme using pso-based fuzzy knowledge fusion

Pages: 84 - 100

#### Résumé

Different students have different learning styles, which are corresponding to their performances and make them behave differently in the learning process. Discovering the learning style of the students can help the development of teaching plans the students would accept more likely. It is a pity that few people dedicate to programming the learning style diagnosis. In view of the learning style, which is always closely linked with the learning performance, the programming learning behavior is introduced to programme the learning style diagnosis. This paper identifies the learning style of programming students in the learning process through their behavior preferences. To make the diagnosis more accurate, Particle Swarm Optimization (PSO) algorithm is introduced. The experiments invite junior students, senior students, graduate students and teachers of the College of Computer Science and Technology in the authors’ university to fill out questionnaires as data. The experimental results show that PSO provides a great contribution.

#### Mots clés

- Learning style
- programming learning behavior
- particle swarm optimization
- fuzzy knowledge fusion

- Accès libre

Towards a design space exploration methodology for system-on-chip

Pages: 101 - 111

#### Résumé

This paper provides an overview of a design space exploration methodology for customizing or tuning a candidate OCI architecture, given a resources budget and independent of a particular application traffic pattern. Three main approaches are introduced. The first approach allows customizing the On- Chip Interconnect by adding strategic long-rang links, while the second consists in customizing the buffer sizes at each switch according to the traffic. The third approach uses a feedback control-based mechanism for dynamic congestion avoidance. Some results are presented to shed more light on the usefulness of these approaches for System-on-Chip design.

#### Mots clés

- System-on-Chip
- On-chip interconnect
- simulation
- performance evaluation
- design-space exploration

- Accès libre

Improved structure-adaptive anisotropic filter based on a nonlinear structure tensor

Pages: 112 - 127

#### Résumé

A variety of structure-adaptive filters are proposed to overcome the blurred effects of image structures caused by the classical Gaussian weighted mean filter. However, two major issues are needed to be dealt with carefully for structure-adaptive anisotropic filters. One is to properly construct the filter kernel and the other is to accurately estimate the orientation of the image structures. In this paper we propose to improve the structure-adaptive anisotropic filtering approach based on the nonlinear structure tensor (NLST) analysis technique. According to the anisotropism measurements of image structures, a new kernel construction method is designed to make the filter shape fine adapted to image features. Through the accurately estimated orientation of the image structures, the filter kernels are then properly aligned to perform the filtering process. Experimental results show that the proposed filter denoises the noisy images carefully and image features, such as corners and junctions are well preserved. Compared with some other known filters, the proposed filter obtains great improvements both in Mean Square Error (MSE) and visual quality.

#### Mots clés

- Structure-adaptive anisotropic filter
- non-linear structure tensor
- image denoising
- orientation estimation

- Accès libre

Discrete-time modeling and input-output linearization of current-fed induction motors for torque and stator flux decoupled control

Pages: 128 - 140

#### Résumé

In this paper an exact discrete-time model of the induction motor in a current-fed mode, including stator flux components is derived and validated. The equations of the motor are written in a frame aligned with the rotor electrical position, which results in a linear, time-invariant system. Based on the derived exact discrete-time representation of the motor dynamics, an input-output linearizing control law is designed for decoupled torque and stator flux control. The applied design technique led to a non-trivial, still useful, definition of the electromagnetic output of the motor. Simulation results are presented showing that the aimed performance is obtained, that is, no coupling exists between the outputs, and the initial design problem of controlling a nonlinear interacting TITO system is reduced to a problem of controlling two linear and decoupled SISO systems with simple dynamics.

#### Mots clés

- Input-output linearization
- induction motor
- discrete-time nonlinear control

- Accès libre

Nonlinear pd controllers with gravity compensation for robot manipulators

Pages: 141 - 150

#### Résumé

A Nonlinear Proportional-Derivative (NPD) controller with gravity compensation is proposed and applied to robot manipulators in this paper. The proportional and derivative gains are changed by the nonlinear function of errors in the NPD controller. The closed-loop system, composed of nonlinear robot dynamics and NPD controllers, is globally asymptotically stable in position control of robot manipulators. The comparison of the simulation experiments in the position control (the step response) of a robot manipulator with two degrees of freedom is also presented to illustrate that the NPD controller is superior to the conventional PD controller in a position control system. The experimental results show that the NPD controller can obtain a faster response velocity and higher position accuracy than the conventional PD controller in the position control of robot manipulators because the proportional and derivative gains of the NPD controller can be changed by the nonlinear function of errors. The NPD controller provides a novel approach for robot control systems.

#### Mots clés

- Nonlinear proportional-derivative controller
- proportional-derivative controller
- robot manipulator
- position control

- Accès libre

Intelligent methods for process control and diagnostics of a mill fan system

Pages: 151 - 160

#### Résumé

The intelligent methods for process control and diagnostics of the mill fan system is an established field of scientific and applied investigations. In the present paper several types of process control approaches with different structures are considered. In order to choose the most efficient one, comparative analysis is carried out. The mill fans are a basic element of the dust-preparing systems of steam generators with direct breathing of the coal dust in the furnace chamber. Such generators in Bulgaria are the ones in Maritsa East 2 Thermal Power Plant, in Maritsa East 3 Thermal Power Plant and also in Bobov Dol Thermal Power Plant. The subject of this research is a device from Maritsa East 2 Thermal Power Plant. This is the largest thermal power plant on the Balkan Peninsula. Standard statistical and probabilistic (Bayesian) approaches for diagnostics are inapplicable to estimate the mill fan technical state due to non-stationarity, non-ergodicity and the significant noise level. The possibility to predict eventual damages or wearing out without switching off the device is significant for providing faultless and reliable work, avoiding the losses caused by planned maintenance.

#### Mots clés

- Internal model control
- intelligent process control
- mill fan system
- intelligent methods for fault detection
- maintenance

- Accès libre

Evaluating the performance of various segmentation techniques in industrial radiographs

Pages: 161 - 171

#### Résumé

At present, image processing concepts are widely used in different fields, such as remote sensing, communication, medical imaging, forensics and industrial inspection. Image segmentation is one of the key processes in image processing key stages. Segmentation is a process of extracting various features of the image which can be merged or split to build the object of interest, on which image analysis and interpretation can be performed. Many researchers have proposed various segmentation algorithms to extract the region of interest from an image in various domains. Each segmentation algorithm has its own pros and cons based on the nature of the image and its quality. Especially, extracting a region of interest from a gray scale image is incredibly complex compared to colour images. This paper attempts to perform a study of various widely used segmentation techniques in gray scale images, mostly in industrial radiographic images that would help the process of defects detection in non-destructive testing.

#### Mots clés

- Segmentation techniques
- weld radio graphic images
- image analysis

- Accès libre

High precision computing of definite integrals with .net framework c# and x-mpir

Pages: 172 - 182

#### Résumé

This paper concerns high precision numerical computing of definite integrals in a specific environment, namely .NET Framework. The work is a part of a series, tracing the progress of creating tools for high precision computations in this environment and may be considered as a continuation, in this direction, of the beginning, described in [15], that includes special function calculations with arbitrary precision. Some of the methods used are described. The results are clearly illustrated with the help of an application, purposefully created, using the current state-of-the-art library being created for realization of functions and numerical methods of arbitrary precision in a given environment.

#### Mots clés

- High precision computation
- numerical quadrature
- definite integral computation
- computational mathematics
- .NET Framework