A social approach can be exploited for the Internet of Things (IoT) to manage a large number of connected objects. These objects operate as autonomous agents to request and provide information and services to users. Establishing trustworthy relationships among the objects greatly improves the effectiveness of node interaction in the social IoT and helps nodes overcome perceptions of uncertainty and risk. However, there are limitations in the existing trust models. In this paper, a comprehensive model of trust is proposed that is tailored to the social IoT. The model includes ingredients such as trustor, trustee, goal, trustworthiness evaluation, decision, action, result, and context. Building on this trust model, we clarify the concept of trust in the social IoT in five aspects such as (1) mutuality of trustor and trustee, (2) inferential transfer of trust, (3) transitivity of trust, (4) trustworthiness update, and (5) trustworthiness affected by dynamic environment. With network connectivities that are from real-world social networks, a series of simulations are conducted to evaluate the performance of the social IoT operated with the proposed trust model. An experimental IoT network is used to further validate the proposed trust model.Comment: 14 pages, 16 figures. Submitted to IEEE Transactions on Knowledge and Data Engineerin

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The influence of fullerene additives on the combustion behaviour of cyclotrimethylene trinitramine/ammonium perchlorate composite modified double-base (RDX/AP-CMDB) propellants are investigated by thermogravimetricdifferential thermogravimetric (TG-DTG) analysis, burning rate tests, and scanning electron microscopy observations. The difference between lead salicylate (F-Pb) and bismuth citrate acid (CP-Bi) as combustion modifiers has also been examined. TG-DTG investigations show that the addition of all additives advanced and accelerated the evaporation of nitroglycerin (NG). The addition of Extracted Fullerene Soot (EFS), C 60 and carbon black (CB) additives obviously accelerated the liquid phase decomposition of NG. Also, the solid phase decomposition of nitrocellulose (NC) and the liquid phase decomposition of RDX were accelerated by 0.5 per cent Fullerene Soot (FS)/2.5 per cent CP-Bi/0.5 per cent copper adipic acid (J-Cu) composite catalyst. The addition of all composite catalysts promoted the decomposition of ammonium perchlorate (AP) except 0.5 per cent EFS/2.5 per cent CP-Bi/0.5 per cent J-Cu composite catalysts. It is well known that there exists dark zone in the flame structure of RDX-CMDB propellant, but in our observation, the dark zone vanished with the addition of 10 per cent AP to the forenamed propellant. The burning rates were increased at low pressure but reduced at high pressure by all catalysts except 0.5 per cent EFS/2.5 per cent CP-Bi/0.5 per cent J-Cu and 0.5 per cent C 60 /2.5 per cent CP-Bi/0.5 per cent J-Cu which reduced the burning rates at every tested pressure. The pressure exponents of tested propellants were reduced by 0.5 per cent FS/2.5 per cent CP-Bi/0.5 per cent J-Cu with a factor of 17 per cent . The quenched surface observations significantly differed with the additions of diverse composite catalysts, which were consistent with the burning rate results.

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