Scientia Iranica
Volume:17 Issue: 2, 2010

Graph partitioning is a well-known problem in the literature. In this paper, path partitioning of trees in which the given tree is partitioned into edge-disjoint paths is considered. A linear time algorithm is given for computing a path partitioning of minimum height.

Fuzzy linear programming problems can be used to model a wide variety of practical applications in which all or some decision parameters are stated in an imprecise fashion. These problems have been investigated and expanded by many researchers from various points of view. In this paper, we study a class of in nite-dimensional linear programming problems, so-called separated continuous linear programs with a fuzzy valued objective function. For this class of problem, we develop a strong duality result and present an approximation algorithm. The basic idea is to use the discretization technique to establish a relationship between the problem and an ordinary fuzzy linear programming problem.

So far, most of the evidential distance and similarity measures proposed in the Dempster- Shafer theory literature have been based on the basic belief assignment function, so as the belief and plausibility functions as two main results of the theory are not directly used in this regard. In this paper, a new evidential distance measure is proposed based on these functions according to nearest neighborhood concept. After assigning basic belief values to propositions and constructing the belief and plausibility functions or the belief interval, this evidential distance measure compares the similarity between the unknown pattern and class belief intervals. For this purpose, we rst acquire the belief and plausibility functions or the belief intervals and then the distance between the belief intervals of uncertain pattern feature vectors and samples are calculated. We applied this novel distance measure to the bacillus colonies recognition and coronary heart disease patients classi cation problems to examine the proposed measure capability in contrast to other evidential measures. Our experiment illustrates that the belief interval distance measure yields the accuracy rates of 91.66 and 92.45 percent for unknown bacillus patterns recognition and coronary heart disease patients classi cation, respectively, which in contrast to other evidential measures shows superior performance.

In this paper we introduce the notion of a detection framework to facilitate the reasoning and cooperation process of detection and response systems. The presented framework de nes four dimensions as requirements to be satis ed: \What to detect «, \Where to inspect», \How to decide «, and \How to alert». The rst dimension tries to unify the understanding of the problem between systems. The second will introduce detection features and parameters. The third dimension exactly states how intelligent systems or expert knowledge should be deployed, while the task of the fourth is to unify the alert and message exchange format. To address the \What to detect«aspect of our framework, we have considered a network denial of service and have presented an ontology which relates three taxonomies of DoS attacks, each from a di erent point of view: Attack Consequence, Attack Location and Attack Scenario. For scenario based taxonomy, we present a decision tree-like structure, which can be used as a base for attack detection. All these taxonomies are then related to each other in an ontology. An implementation of this ontology using Web Ontology Language (OWL) might help IETF''s IDMEF to construct a base for a more accurate alert correlation.

The multidisciplinary eld of Microwave-Photonics is at the convergence of photonic and microwave or even wireless technologies. In this context, the processing, conversion and transmission of microwaves, as well as high data rate digital and wireless signals, today use broadband optical techniques with many applications. However, the frequency band available is frequently changing with up-to-date commercial standards, and it is necessary to up- or down- convert the frequency of the electrical signals using a suitable optical approach for mixing. This paper intends to give an overview on the optical techniques used for frequency conversion, i.e. mixing, and gives the advantages and drawbacks of all techniques presented.

In a Static Synchronous Series Compensator (SSSC), a controllable AC voltage is generated by a voltage-source converter. There are two control channels for controlling the magnitude and phase of the voltage. When this device is used for damping inter-area oscillations in multi-machine power systems, a damping stabilizer can be included in both channels. In this paper, a method for the simultaneous coordinated design of a Power System Stabilizer (PSS) and a SSSC-based stabilizer is presented using quadratic mathematical programming. In this method, the gain and phase of a leadlag stabilizer can be simultaneously calculated. By this method the e ect of the SSSC-based stabilizer in both control channels on damping inter-area oscillations has been assessed. Obtained results including eigenvalue analysis and non-linear simulations, on two multi-machine power systems under di erent operating conditions, show that the usage of a SSSC stabilizer in a suitable control channel can signi cantly reduce the control cost of the stabilizer.

An algorithm for guiding a launch vehicle carrying a small satellite to a sun synchronous LEO is presented. Before the launch, a nominal path and the corresponding nominal control law for the entire journey are computed. For each sampling instant during the guided ight, a linear equation approximately relating the di erences between the actual and nominal values is considered, and a Least- Squares formula using data from on-line state measurements is applied to compute the actual control. The coecient matrices of the Least-Squares formula can be determined by o -line computations. The method enjoys simplicity of implementation by onboard computers, as well as robust accuracy against strong winds and uncertainties in thrust magnitude.

In this essay, an optical arrangement for the measurement of dynamic weight, by means of conducting a thin ray of light through it, is designed in order to enhance the measuring accuracy in the weight-estimation device. In this arrangement, CCD is responsible for producing raw data for processing. An arti cial neural network type, RBF, is also used to improve the quality and speed of the measurement. While the scale of the weight-estimation device is oscillating, by applying the weight on the scale, the neural network by sampling the proportionate wave-shape yields the weight of object with high accuracy and high speed.

In this paper, the Active Constellation Extension (ACE) technique is applied to Space Frequency Block Coded (SFBC) OFDM systems to reduce the Peak to Average Power Ratio (PAPR). For the extension of this technique to SFBC systems, it will be shown that the space frequency coded signals are the combination of several subframes and that the ACE method may be applied to these subframes. Using this model, an iterative ACE method, based on Projection Onto Convex Sets (POCS), is introduced. At each iteration, the time domain samples of the subframes are clipped based on their e ect on the samples of all antennas. Then, the clipped subframes are ltered and the signals of the antennas are constructed from the modi ed subframes. The simulation results show that the performance of the proposed method is very close to the performance of the ACE method in the single antenna OFDM system.