A Trust Management Framework for Vehicular Ad Hoc Networks

The inception of Vehicular Ad Hoc Networks (VANETs) provides an opportunity for road users and public infrastructure to share information that improves the operation of roads and the driver experience. However, such systems can be vulnerable to malicious external entities and legitimate users. Trust management is used to address attacks from legitimate users in accordance with a user’s trust score. Trust models evaluate messages to assign rewards or punishments. This can be used to influence a driver’s future behaviour or, in extremis, block the driver. With receiver-side schemes, various methods are used to evaluate trust including, reputation computation, neighbour recommendations, and storing historical information. However, they incur overhead and add a delay when deciding whether to accept or reject messages. In this thesis, we propose a novel Tamper-Proof Device (TPD) based trust framework for managing trust of multiple drivers at the sender side vehicle that updates trust, stores, and protects information from malicious tampering. The TPD also regulates, rewards, and punishes each specific driver, as required. Furthermore, the trust score determines the classes of message that a driver can access. Dissemination of feedback is only required when there is an attack (conflicting information). A Road-Side Unit (RSU) rules on a dispute, using either the sum of products of trust and feedback or official vehicle data if available. These “untrue attacks” are resolved by an RSU using collaboration, and then providing a fixed amount of reward and punishment, as appropriate. Repeated attacks are addressed by incremental punishments and potentially driver access-blocking when conditions are met. The lack of sophistication in this fixed RSU assessment scheme is then addressed by a novel fuzzy logic-based RSU approach. This determines a fairer level of reward and punishment based on the severity of incident, driver past behaviour, and RSU confidence. The fuzzy RSU controller assesses judgements in such a way as to encourage drivers to improve their behaviour. Although any driver can lie in any situation, we believe that trustworthy drivers are more likely to remain so, and vice versa. We capture this behaviour in a Markov chain model for the sender and reporter driver behaviours where a driver’s truthfulness is influenced by their trust score and trust state. For each trust state, the driver’s likelihood of lying or honesty is set by a probability distribution which is different for each state. This framework is analysed in Veins using various classes of vehicles under different traffic conditions. Results confirm that the framework operates effectively in the presence of untrue and inconsistent attacks. The correct functioning is confirmed with the system appropriately classifying incidents when clarifier vehicles send truthful feedback. The framework is also evaluated against a centralized reputation scheme and the results demonstrate that it outperforms the reputation approach in terms of reduced communication overhead and shorter response time. Next, we perform a set of experiments to evaluate the performance of the fuzzy assessment in Veins. The fuzzy and fixed RSU assessment schemes are compared, and the results show that the fuzzy scheme provides better overall driver behaviour. The Markov chain driver behaviour model is also examined when changing the initial trust score of all drivers

Response of PPR soils to changing groundwater and salinity: a microcosm study of greenhouse gas emissions

Non-Peer Reviewe

The impact of short rotation willow on soil nutrients in riparian zones of the prairie pothole region

Non-Peer Reviewe

Nuclear matrix elements calculation for 0νββ0\nu\beta\beta decay of 124^{124}Sn using nonclosure approach in nuclear shell model

In this study, we calculate the nuclear matrix elements (NMEs) for the light neutrino-exchange mechanism of neutrinoless double beta $0\nu\beta\beta$) decay of $^{124}$Sn within the framework of the interacting nuclear shell model using the effective shell model Hamiltonian GCN5082. A novel method based on a nonclosure approach is employed, wherein for the intermediate nucleus $^{124}$Sb, effects of energy of 100 states for each $J_{k}^{\pi}$=$0^{+}$ to $11^{+}$ and $2^{-}$ to $9^{-}$ ($\Delta J_{k}$=1) are explicitly included in the NMEs calculation. Other common effects such as the finite size of nucleons, higher-order effects of nucleon currents, and short-range correlations (SRC) of nucleons are also taken into account. The extracted optimal closure energy is 2.9 MeV for a total NME of $^{124}$Sn $0\nu\beta\beta$ decay, which is independent of different forms of SRC parametrizations. A comparison of NMEs and half-lives with some of the recent calculations is presented. Further, to gain a comprehensive understanding of the role of nuclear structure on the $0\nu\beta\beta$ decay, the dependence of NMEs on spin-parity of the intermediate states, coupled spin-parity of neutrons and protons, and the number of intermediate states, is explored. It is observed that the inclusion of the effects of excitation energies of the intermediate nucleus yields more reliable NMEs. The present findings provide valuable insights for experimental investigations of $0\nu\beta\beta$ decay of $^{124}$Sn in India and elsewhere.Comment: 12 pages, 6 figures, submitted in the journal Physical Review C. arXiv admin note: text overlap with arXiv:2308.0821

Effect of plasma sprayed flyash based composite coatings on corrosion resistance

With the aim of exploring the possibility of achieving a low-cost thermal spray coating to prevent wear, erosion and corrosion. In the current study, flyash-Al2O3 and flyash-SiC composite coatings were effectively created using the air plasma spray process on substrates of Al6061 alloy. NiCr material is used as the bond coat to improve the bond strength between the coat and the substrate. Taguchi's DoE method is applied to for spray process parameters optimization. In addition, the developed coating is subjected to microstructure analysis and long-term immersion corrosion testing (1 year) in an aqueous environment to assess corrosion properties.The results revealed that the over a certain test period, the developed flyash-SiC coating has greater corrosion resistance than the uncoated and flyash-Al2O3 coated Al6061. It is noticed that the corrosion resistance of the flyash-Al2O3 coating shifts to a negative value with respect to the uncoated substrate. The uncoated sample is extensively pitted and locally corroded, as shown by the SEM image of the corroded surface. Flyash-corroded Al2O3's surface exhibits extensive degradation in the form of peeling, breaking, and cracking of the splats. With flyash-SiC composite coating a very minor corrosion splat deterioration is seen

Developing a Transient Drive Cycle Representing Ship Acceleration with Test-bed Engine

The “generalised propeller law” is a terminology commonly used for defining engine load with respect to propeller rotational speed, where ship propulsive load is proportional to the cubic power of engine revolutions per minute (rpm) at ideal conditions. In real scenarios, the ship engine load is disrupted, and the propeller law breaks down to some extent especially when ships are manoeuvring in ports. To investigate engine responses in such operational conditions, a propeller law transient drive cycle is designed for a test-bed engine. Ship propulsion power is emulated and mapped under propeller law configuration transient scenarios. The diesel engine exhaust emission factors (EFs) are measured and compared with theoretical and on-board measured values. It is found that at low load, test bed EFs of NOx and CO2 are up to 20 and 10 times higher, respectively than that at higher loads.</p