Showing 3 results for Badiei
Volume 4, Issue 1 (9-2004)
Abstract
The current Internet inherently has a degree of survivability due to the connection less IP Protocol. Dynamic routing Protocols are designed to react to faults by changing routes when routers learn about topology changes via routing information updates (e.g., link status advertisements). Loss of Quality of service (QoS) has not been an issue because current Internet traffic is the best-effort. On the contrary, the multi protocol label switching (MPLS) approach is connection-oriented, which implies greater potential vulnerability to faults. At the same time, MPLS will support integrated services, which are more sensitive to loss of service. Reliability is becoming more important as more users depend on the internet for critical communication services and expect a higher level of performance. Usually, fault recovery is attempted first at the lowest layer, and escalated to the next layer if recovery was unsuccessful or impossible. Fault recovery capabilities in the MPLS layer are needed as well to decouple MPLS from dependence on physical layer fault recovery mechanisms which may differ between networks. This paper proposes an enhanced-scheme for fast rerouting to pre-assigned label-switched paths (LSPs) in case of LSP or link failures. In order to minimize backup resources, it allows possibility of splitting traffic of faulty LSP onto available alternative LSPs for fault recovery. We use Pre-assigned backup LSPs for restoration, when fault occurs. Total traffic throughput and resource utilization can be maximized if the traffic of faulty LSP is split over multiple pre-assigned LSPs. In this paper a new approach to providing fault tolerance in MPLS networks using case-based reasoning (CBR) as a method to find out the amount of traffic forwarded on each pre-assigned LSP based on past experiences of loading process is presented. The pre-assigned LSPs and the percentage of traffic splitting are calculated off-line based on desired QoS and capacity constraints. Also we evaluate the operation of successful decomposition of traffic based on the two mentioned constraints by using CBR, when the number of backup LSPs as a complexity factor increase. In another point of view, in cases when there is no possibility of using the experiences successfully, there would be no other way than using the erroneous unsuccessful experiences. We thus solved our recovery problem by using, first incorrect databases in our experiments, to moving later towards decreasing the error rate in a gradual manner.
M.h. Sadr, D. Badiei, Sh. Shams,
Volume 19, Issue 10 (October 2019)
Abstract
In precision of the aerodynamic coefficients, modification and development of the Boeing-Vertol model are the main goal of the presented paper in which unsteady wake effects are considered. Hence, this paper uses based on Wagner function to consider the unsteady wake effects and to introduce an effective angle of airfoil degrees of freedom and their derivatives for both bending and pitching oscillations. The aerodynamic lift coefficient of the Boeing- model is improved by using the introduced effective angle of attack and flow apparent mass effects. Also, a new pitching moment coefficient is introduced and is replaced in the model. The introduced aerodynamic coefficients are validated and verified by experimental data and also compared with the original model. The obtained results represent correction of the lift coefficient of the Boeing Vertol model in of the static lift curve and improvement of maximum lift coefficient and of . Also, the results show that the proposed formulation enhances the Boeing Vertol model to predict moment coefficient in dynamic condition. In addition, a parametric study is conducted to investigate the effects of reduced frequency on effective angle of attack and it is shown that while reduced frequency increases to 0.36, unsteady wake effects on effective angle of attack of an airfoil reach to its maximum value. Moreover, for reduced frequencies upper than 0.1, pitch axis location changes the characteristics of the effective angle of attack of the airfoil.
Mohammadjavad Bouloorchi Tabalvandani, Majid Badieirostami,
Volume 24, Issue 7 (July 2024)
Abstract
The emergence of microfluidic devices for various applications has created a demand for enhancing the efficiency of the mixing. In this article, an electroosmotic micromixer based on G-shaped electrodes that are excited by AC waveform was designed. The proposed micromixer was simulated using COMSOL Multiphysics and the effects of various parameters including voltage, frequency, distance between electrodes, and the number of electrodes on the mixing efficiency have been characterized. By compiling the obtained results, the performance of the optimized model with four electrodes each having a 6.5 µm distance between their opposite polarities, excited with voltage of 1 V and frequency of 16 Hz was evaluated. The results demonstrated that the proposed micromixer was able to achieve a mixing efficiency of over 99.7% with a response time of 220 ms. Furthermore, the proposed device was designed regarding practical consideration, enabling the micromixer to be fabricated without the need of sophisticated instruments.
