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Search Results: 1 - 10 of 322 matches for " Abolfazl Kalanaki "
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Using Bees Algorithm to Solve the Resource Constrained Project Scheduling Problem in PSPLIB
Amir Sadeghi,Abolfazl Kalanaki,Azadeh Noktehdan,Azamdokht Safi Samghabadi
Advances in Mathematical and Computational Methods , 2012, DOI: 10.5729
Abstract: Today, trade globalization caused optimum use of resources to become a vital factor for surviving in the global arena. The same need led to the introduction of concepts such as project, project control and resource constrained project scheduling. In the field of operations research and project management, project scheduling with resource constraints is of great importance. Most of the contributions made to this field can be attributed to two main factors. First, based on different conditions for objective function, characteristics of activities, resources and priority rules, the form of the problem tends to vary too much. Second, this kind of problem is of Np-Hard nature for which researchers are always trying to find new solutions. In this paper, Bees Algorithm is proposed as an approach to solve this kind of problem. Results obtained from deploying this algorithm are compared to those of other algorithms, and it is shown that Bees algorithm is a suitable one to solve RCPSP.
A Fault-Tolerant Cooperative Spectrum Sensing Algorithm over Cognitive Radio Network Based on Wireless Sensor Network  [PDF]
Mohammad Akbari, Abolfazl Falahati
Wireless Sensor Network (WSN) , 2011, DOI: 10.4236/wsn.2011.33009
Abstract: A serious threat to cognitive radio networks that sense the spectrum in a cooperative manner is the transmission of false spectrum sensing data by malicious sensor nodes. SNR fluctuations due to wireless channel effects complicate handling such attackers even further. This enforces the system to acquire authentication. Actually, the decision maker needs to determine the reliability or trustworthiness of the shared data. In this paper, the evaluation process is considered as an estimation dilemma on a set of evidences obtained through sensor nodes that are coordinated in an underlying wireless sensor network. Then, a likelihood-based computational trust evaluation algorithm is proposed to determine the trustworthiness of each sensor node's data. The proposed procedure just uses the information which is obtained from the sensor nodes without any presumptions about node’s reliability. Numerical results confirm the effectiveness of the algorithm in eliminating malicious nodes or faulty nodes which are not necessarily conscious attackers.
Frequency Hopping Spread Spectrum Security Improvement with Encrypted Spreading Codes in a Partial Band Noise Jamming Environment  [PDF]
Amirhossein Ebrahimzadeh, Abolfazl Falahati
Journal of Information Security (JIS) , 2013, DOI: 10.4236/jis.2013.41001
Abstract:

Frequency Hopping Spread Spectrum (FHSS) system is often deployed to protect wireless communication from jamming or to preclude undesired reception of the signal. Such themes can only be achieved if the jammer or undesired receiver does not have the knowledge of the spreading code. For this reason, unencrypted M-sequences are a deficient choice for the spreading code when a high level of security is required. The primary objective of this paper is to analyze vulnerability of linear feedback shift register (LFSRs) codes. Then, a new method based on encryption algorithm applied over spreading codes, named hidden frequency hopping is proposed to improve the security of FHSS. The proposed encryption security algorithm is highly reliable, and can be applied to all existing data communication systems based on spread spectrum techniques. Since the multi-user detection is an inherent characteristic for FHSS, the multi-user interference must be studied carefully. Hence, a new method called optimum pair “key-input” selection is proposed which reduces interference below the desired constant threshold.

Transmission over Cognitive Radio Channel with Novel Secure LT Code  [PDF]
Elham Hosseini, Abolfazl Falahati
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53023
Abstract:

With the increasing of communication applications in recent years, the demand for radio spectral resources has increased significantly. Cognitive radio scenario was proposed to improve spectrum efficiency in wireless communication systems. In cognitive radio network, it is essential that control information is sent securely and reliably. Ensuring the trustworthiness of the transmitting of spectrum sensing information is important in the CR networks since spectrum sensing directly affects spectrum management and incumbent coexistence. In this paper, the first secondary link channel model is presented, then a secure LT Code is proposed to be compatible with presented channel model and acquires good QoS. As we may know, LT code overcomes packet loss when the channel of the SU is reclaimed by PU. In the new proposed combined encoding and ciphered block, a LT code matrix is used to generate a symmetric cryptographic key. Thus, less complexity observed in the processing computation. Besides, cryptographic key is not sent over the channel. As a result, an attacker has no way to eavesdrop the key unless he is prepared to consider all possible key combinations. This replaced block supplies secure controlling channel and increases spectrum efficiency too.

Developing a 3D-FEM Model for Electromagnetic Analysis of an Axial Flux Permanent Magnet Machine  [PDF]
Seyyed Mehdi Mirimani, Abolfazl Vahedi
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2010, DOI: 10.4236/jemaa.2010.24032
Abstract: Recently, many optimal designs for axial flux permanent magnet (AFPM) motors were performed based on finite- element (FE) analysis. Most of the models are based on reduction of 3D problem to 2D problem which is not accurate for design aspects. This paper describes an accurate electromagnetic analysis of a surface mounted, 28 pole AFPM with concentrated stator winding. The AFPM is modeled with three-dimensional finite-element method. This model in-cludes all geometrical and physical characteristics of the machine components. Using this accurate modeling makes it possible to obtain demanded signals for a very high precision analysis. Magnetic flux density, back-EMF, magnetic axial force and cogging torque of the motor are simulated using FLUX-3D V10.3.2. Meanwhile, the model is paramet-ric and can be used for design process and sensitivity analysis.
Radar Signal Recognition by CWD Picture Features  [PDF]
Erfan Tahbaz Tavakoli, Abolfazl Falahati
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2012, DOI: 10.4236/ijcns.2012.54031
Abstract: In this paper a system for automatic recognition of radar waveform is introduced. This technique is used in many spectrum management, surveillance, and cognitive radio and radar applications. For instance the transmitted radar signal is coded into six codes based on pulse compression waveform such as linear frequency modulation (LFM), Frank code, P1, P2, P3 and P4 codes, the latter four are poly phase codes. The classification system is based on drawing Choi Willliams Distribution (CWD) picture and extracting features from it. In this study, various new types of features are extracted from CWD picture and then a pattern recognition method is used to recognize the spectrum. In fact, signals from CWD picture are defined using biometric techniques. We also employ false reject rate (FRR) and false accept rate (FAR) which are two types of fault measurement criteria that are deploy in biometric papers. Fairly good results are obtained for recognition of Signal to Noise Ratio (-11 dB).
Employing Power Allocation to Enhance Zero Forcing Scheme Advantages over Multi-Antenna Multiple Relay Networks  [PDF]
Abolfazl Falahati, Y. Attar Izi
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2012, DOI: 10.4236/ijcns.2012.511077
Abstract: A multi-antenna multiple relay (MAMR) network is considered and a variation of two-hop zero-forcing amplify-forward relaying method is proposed. Deploying ZF method together with application of diagonal power allocation matrices at the relays, it is shown that the overall MAMR network is simplified to M independent single antenna multiple relay (SAMR) networks, where M is the number of source and destination antennas. This enables to incorporate network beamforming proposed for SAMR networks. Accordingly, using the BER as the performance metric, we present simulation results to show the proposed approach outperforms the common ZF method addressed in the literature.
Proton-Coupled Electron-Transfer Mechanism for the Radical Scavenging Activity of Cardiovascular Drug Dipyridamole
Abolfazl Barzegar
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039660
Abstract: Dipyridamole (DIP) is a well-known pharmaceutical drug used as a coronary vasodilator and anti-platelet agent in clinics for treating several cardiovascular diseases. Primarily, the therapeutic effects of the drug are attributed to its antioxidant potency. In this research, we aim to declare the unknown antioxidant mechanism of DIP as well as its potent chain-breaking antioxidant activity in polar aqueous medium inside the cells, using different experimental methods and theoretical quantum calculations. Data demonstrated the higher antioxidant capacity of DIP against ROS and free radicals in polar cell's interior. DIP is capable of generating long living and noninvasive DIP? radicals in oxidant condition that leads to an effective “chain-breaking antioxidant” activity. Quantum computational data indicated that DIP antioxidant has more favorable ionization potential than trolox which means DIP has higher antioxidant activity. Also, data showed that the direct hydrogen-transfer is not a favorable process to construct DIP? because of high barrier energy, though electron-transfer process can more easily to produce DIP?+ with the lowest barrier energy. Altogether, the electron donating potency of DIP to reduce ferric ion, having the low anodic oxidation peak potential, producing long lived stable DIP? radicals and protecting myoblast cells from oxidation, proposed the excellent “chain-breaking antioxidant” potency via electron-transfer mechanism of this vasodilator DIP drug in polar aqueous medium.
Serum Thyroid Hormone Levels in Epileptic Children Receiving Anticonvulsive Drugs
Abolfazl MAHYAR
Iranian Journal of Child Neurology , 2011,
Abstract: ObjectiveThe aim of this study was to investigate serum thyroid hormone levels in epileptic children receiving anticonvulsive drugs.Materials & MethodsIn this case- control study, 30 epileptic children who were receiving anticonvulsive drugs (case group) were compared with 30 healthy children (control group). This study was carried out in the Qazvin Children's Hospital (Qazvin, Iran) from October to December 2007. Both groups were matched for age and sex. Thyroid hormone levels were measured using a radioimmunoassay and immunoradiometric assay. Data were analyzed using Chi-square and Student's t-tests.ResultsThe mean serum T3 and T4 levels in the case group were 2.36 ± 0.73 nmol/L and 95.96 ± 27.01 nmol/L, respectively, and the corresponding values in the control group were 1.88 ± 0.93 nmol/L and 147.46 ± 35.77 nmol/L, respectively. The mean serum thyroid-stimulating hormone (TSH) levels in the case and control groups were 2.73±0.73 mIU/mL and 2.49 ± 2.17mIU/mL, respectively.ConclusionThis study revealed that long-term consumption of anticonvulsive drugs resulted in a decline in serum T4 levels and an increase in serum T3 levels, but had no effect on TSH levels.
Effects of Uncertain Inflationary Conditions on an Inventory Model for Deteriorating Items with Shortages
Abolfazl Mirzazadeh
Journal of Applied Sciences , 2010,
Abstract: This study proposes an inventory model with stochastic internal and external inflation rates for deteriorating items and allowable shortages. The many economic, political, social and cultural variables affect the inflation rates. For instance, economic factors such as changes in the world inflation rate, demand level, labor cost, cost of raw materials, exchange rates, unemployment rate, productivity level, tax, liquidity, etc are effective in this direction. Therefore, the assumption of constant inflation rates is not valid, especially, when the time horizon is long. This model considers stochastic inflationary conditions. Numerical examples are used to illustrate the theoretical results, which are further clarified through a sensitivity analysis on the model parameters. It has been shown that the optimal solution is highly sensitive to considerable uncertainty of the inflation rates.
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