An attack resistant method for indirect trust computation (based on recommendation) for pervasive computing environment is proposed. The method extends a mechanism to detect outliers in dataset presented in [19] and apply it to filter out malicious recommendations in indirect trust computation. The method is based on a dissimilarity metric based on the statistical distribution of the recommendations grouped into recommendation classes. The proposed model has been evaluated in different attack scenarios (bad mouthing, ballot stuffing and random attack). The model has also been compared with other existing evolutionary recommendation models in this field, and it is shown that the proposed approach can effectively filter out dishonest recommendations provided that the number of dishonest recommendations is less than the number of honest recommendations.
Cloud definition says "everything is available everywhere at any time". As cloud computing evolves to accommodate future technologies, inter-cloud ecosystem is started to be required as a necessary architecture. Although there are some proposals presented to manage the inter-cloud but no one guarantee a lock-free, interoperable and federated ecosystem. Conducted research is biased and cloud provider's need base, pushing cloud market towards the interests of commercial dominators. To fill this gap, after surveying the maturity of open technologies and current state of adoption of the openness from cloud providers, this paper presents ICCM: Inter-Cloud Concern Model, a reference architecture to model the concerns of interoperable cloud ecosystem. The aim of this research is to formally describe the aspects to be considered to design a people-centric IT solution that put computing providers in a hard competition to fulfill client needs.
Ejectors have the prime function of thrust augmentation by mixing secondary flow with primary flow to impart greater momentum change. The original flow is referred to as the primary flow while the additional flow is referred to as the secondary flow. This paper explores usage of ejectors as drag reducing devices using numerical techniques. 2D axisymmetric and 3D half body symmetric CFD analysis have been carried out on different ejector configurations at two Mach Nos (0.4 & 0.6) . The results have been compared with the original body consisting of blunt and streamlined rear exhaust. Results show significant drag reduction along with thrust augmentation, giving greater net propulsive force at both Mach number. Further experimental validation is recommended to validate the findings of this paper.
This research focuses on supersonic combustion using Shock wave application theory, utilizing shock induced combustion with commercially available Ansys ® Fluent. The dominant mode employed with the design of scram jets is non-premixed fuel induction that entails complex geometries such as flame holders, cantilevered injectors etc. A premixed mode paired with shocked induced combustion, on the other hand, can be achieved with simpler geometries than other configurations. In current research work combustion as induced by a normal and oblique shock waves is investigated. Hydrogen gas at stoichiometric ratio and equivalence value was used as fuel. Normal shock induced combustion was investigated for flows accelerated in diverging test section at sea level conditions. Initially a non-reacting flow was studied. Subsequently, a case for reacting flow and supersonic combustion with normal-shock-induced ignition was investigated. For H2 combustion with NOx, a twenty-one (21) species variant was explored. The hydrogen combustion sub-mechanism was taken from Li et al. and comprises 21 elementary chemical steps. NOx sub-mechanism is based on the Glarborg group's research available with Fluent. A reaction zone was observed at Mach Line as well as radical formation zones were observed at two points beyond the Mach line. Hydrogen gas and Oxygen mass fraction was reduced across reaction zone whereas water formation was observed in the chamber. In the second case, the model is chosen from the experiment of Tan et al to model oblique shock induced combustion. A premixed air-hydrogen gas mixture at stoichiometric ratio is incident at Mach 5, hits a dual ramp configuration at varying incident angles. A global reaction mechanism is chosen for hydrogen gas combustion reaction along with FR/ED model for TCI in Ansys ® Fluent. Oblique shocks are created, and close coupling between the reaction zone and the shockwave occurs as a shock induced combustion, where burnt gases at elevated static pressure, density and temperature are observed post shock wave. The flow analysis for reacting flow shows a positive correlation between Mach numbers, flow turning angle and the heat of reaction. Whereas, there is a negative correlation between altitude and heat of reaction. Combustion is also modelled with Eddy Dissipation Concept (EDC) and it predicts a greater pressure ratio jump at shock wave formation. It also predicts more product formation compared to FR/EDM.
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