Showing 6 results for Sharafat
Ahmad. Reza Sharafat, M. H. Miran-Beigi, S. V. Shojaeddini,
Volume 7, Issue 0 (0-2007)
Abstract
One of the challenges in non-destructive testing schemes using the ultrasound pulse-echo technique is to identify those defects whose sizes are less than or equal to the detection resolution that is dependent on the width of the ultrasound pulse. Existing methods also require a reference specimen of the same defective material, which may not be available in some cases. We present a new method for detecting and identifying such defects. In the proposed approach, each layer of the test specimen is modeled as a linear time invariant (LTI) filter, and therefore, each defect is characterized by its corresponding impulse response. We use a combination of time gating and system identification techniques to detect and identify the defects, and as such, do not require a reference specimen. To demonstrate the performance of the proposed approach, we tested metallic blocks in which specific defects were impregnated. Results show that the proposed method can detect such defects, does not depend on the test set-up (including the ultrasound transducer), does not require a reference specimen, and is capable of detecting several defects situated in different depth on top of each other
Ahmad Sharafat, Mahdi Rasti,
Volume 7, Issue 0 (0-2007)
Abstract
High processing loads, need for complicated and frequent updating, and high false alarm are some of the challenges in designing anomaly detection and misuse detection systems. We propose a new network-based intrusion detection system (IDS) that resolves such shortcomings. Our scheme fuses anomaly detection and misuse detection systems, which has not been utilized so far in existing systems. In doing so, we have employed a mix of modified back-propagation (BP) and self-organizing map (SOM) neural networks that perform pattern recognition and classification in an effective and efficient manner. Results indicate that the performance of our proposed IDS is significantly improved as compared to the existing systems.
Ali Heydari Chaleshtori, Ahmad Reza Sharafat,
Volume 10, Issue 3 (10-2010)
Abstract
We compare performance of adaptive schemes which are based on radial-basis functions and Kalman filters for fast extraction of auditory evoked potentials. Moreover, we propose a new method based on evoked potential modeling in the Kalman filter framework, which can improve the accuracy compared to the existing methods. Simulation results show that adaptive schemes and the Kalman method are not significantly different in reducing the number of trials needed for accurate extract on of auditory evoked potentials, and that the proposed method significantly improves the extraction accuracy of the evoked potentials even when the number of trials is small.
Volume 14, Issue 4 (12-2014)
Abstract
Congestion pricing is one of the main strategies for demand management in urban areas. One of the main questions for decision makers, for implementing this strategy, is the effect of congestion pricing on users' mode split. For defining this, the willingness to pay of users should be estimated. In another word, we should know that how much users still will to pay for using their personal cars and how they intend to perform their mobility according to various prices. Previous studies had pay less attention to paratransit mode according to pricing. In this research, the effect of congestion pricing on users' mode choice has been investigated. The restricted traffic zone of Tehran has been selected for case study. Due to impossibility of direct observation, the stated preference method was applied for data gathering. Various pricing scenarios, based on experimental design concept, were defined and several types of questionnaires were designed. In these questionnaires, 3 types of data were asked from interviewees including trip chain of the users, socio economic characteristics and pricing scenarios. According to pricing scenarios, 4 choices including using personal car, public transportation, taxi and cancelling the trip were presented to users which they should choose only one option due to every pricing scenario. The reliability of questionnaires have been investigated with cronbach's alpha which results showed the proper reliability of questionnaires. More than 3500 interviews were performed and after preliminary validation, were entered in the database. Based on this data, more than 70 variables were defined which their correlation was estimated and proper variables were chosen. For modeling, due to discrete nature of data, multinomial logit model was applied and calibrated for every choice. In this regard, the feasibility of applying nested logit model was also tested which results showed the invalidity of this model. More than 200 models have been calibrated and finally best validated models have been chosen for describing the mode choice of every alternative.
Results of modeling showed that having more expansive cars will increase the utility of using personal cars and reduce the public transport utilization. Also the residence location of the users is effective in their mode choice. Living in restricted zone, increase the willingness of users to use transit and paratransit mode. Users' education is also important in their choice. People with higher education level have more willingness to pay. The sensitivity analysis showed that pricing can be a proper tool for managing personal vehicles demand. When entrance toll is equal to 3000 tomans, only 35 percents use their personal vehicles. In this condition, 30 percents of users choose transit mode. Results also showed that choosing transit and paratransit mode is similar. When the toll is more than 17000 tomans, the rate of using taxi have higher growth comparing to transit utilization. Also, results showed that the demand for entering to restricted zone can be assumed inelastic. In highest toll, only 10 percents of users cancelled their trip. Finally, the sensitivity analysis for every mode has been accomplished and multiple future researches have been proposed.
Keywords: Mode Split models, Congestion pricing, stated preference method
Volume 17, Issue 1 (Spring 2013)
Abstract
Where several persons cause damage, any of them will be responsible to compensate the victim. This responsibility may be common and dividable among them from the beginning (partial responsibility) or may be that each of them will have integral or solidary responsibility to the victim, and have to pay the whole damage. An important question that arises in this context is that the damage divided among several responsibles - whether at first, according to theory of partial liability, or after full payment of compensation by one of the responsibles - should be based on what criteria. Three criteria have been suggested in this regard by French lawyers: negligence criteria, equality criteria and degree of influence criteria. By studying Iranian and French law, this article tries to show that the third criterion, that is division of damage on the basis of the degree of influence in causing damage, is consistent with justice and enjoys the elements of civil responsibility particularly relation of causality between harmful act and the resulting damage.
Volume 17, Issue 4 (7-2015)
Abstract
The aim of this study was evaluation of phytochemical components, antioxidant activity, and antibacterial effects of basil (Ocimum basilicum L.) essential oil (BEO) in vitro. The lipid oxidation of the meat and antibacterial effects of BEO were also evaluated in beef burger product. In this empirical study, essential oil of the basil was isolated by hydrodistillation. Then, BEO was analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography/mass spectrometry (GC-MS). The effect of different concentrations of BEO (0.00, 0.062, 0.125, and 0.25%) at 4±1ºC temperature and storage time of up to 12 days was evaluated on lipid oxidation, anti Staphylococcus aureus activity, and organoleptic effects in beef burger. The main compounds in BEO were methyl chavicol (85.19%), 1,8 cineol (3.96%), trans-alpha bergamotene (1.18%) and linalool (1.03%). In the storage temperature (4±1ºC), the BEO decreased the growth rate of S. aureus in beef burger (P< 0.05). Also, overall acceptance rate in the beef burger containing 0.125% BEO created a better sense in the product (P< 0.05). No significant differences were observed after adding different concentrations of essential oil to decrease lipid oxidation in raw beef burger (P> 0.05). Therefore, this essential oil might be used as antibacterial agent and flavor enhancer in meat products such as beef burger.