A Novel Model for Vehicular Delay Tolerant Networks using Deterministic Bundle Relaying Scheme

The traditional bundle relaying scheme rarely utilizes the impact of selfish nodes in Vehicular Delay Tolerant Networks (VDTNs) that may not be able to transmit messages to other nodes because of limited resources in the road transport system. Here the Railway Transport System (RTS) is used to transfer the data from one end to another end into the network. In RTS, the proposed approach utilizes stationary nodes deployed along the railway tracks (usually at railway stations) with a large memory size, known as Track Side Units (TSUs), and mobile nodes which are trains equipped with devices having large buffer capacity and message relaying capability. In this paper, the VDTN scenario is developed using RTS in which all nodes have high buffer capacity and power availability hence storage and transfer of message bundles will be done through all nodes. Further, this paper proposed a novel model for transmitting data in VDTN environment using an Efficient Deterministic Bundle Relaying Scheme with Bulk Bundle Release (DBRS-BBR). To validate this, a mathematical model of queuing processes, M/G/1: FIFO/&amp;#x221E;/&amp;#x221E;, is applied at the TSUs and mobile units, and a Deterministic Scheduling technique is applied for relaying the bundles. To evaluate the proposed DBRS-BBR scheme, different performance measures are used, including Mean Queueing Delay, Mean Transit Delay, and Mean End-To-End Delay. This proposed scheme has the potential to improve message bundle transmission in remote areas and it outperforms the existing Probabilistic Bundle Relaying Scheme with Bulk Bundle Release (PBRS-BBR) in terms of various performance measures.</p

Arctic ozone depletion in 2002–2003 measured by ASUR and comparison with POAM observations

We present ozone loss estimated from airborne measurements taken during January–February and March in the Arctic winter 2002/2003. The first half of the winter was characterized by unusually cold temperatures and the second half by a major stratospheric sudden warming around 15–18 January 2003. The potential vorticity maps show a vortex split in the lower stratosphere during the major warming (MW) in late January and during the minor warming in mid-February due to wave 1 amplification. However, the warming can be termed as a vortex displacement event as there was no vortex split during the MW period at 10 hPa. Very low temperatures, large areas of polar stratospheric clouds (PSCs), and high chlorine activation triggered significant ozone loss in the early winter, as the vortex moved to the midlatitude regions. The ozone depletion derived from the ASUR measurements sampled inside the vortex, in conjunction with the Mimosa-Chim model tracer, shows a maximum of 1.3 ± 0.2 ppmv at 450–500 K by late March. The partial column loss derived from the ASUR ozone profiles reaches up to 61 ± 4 DU in 400–550 K in the same period. The evolution of ozone and ozone loss assessed from the ASUR measurements is in very good agreement with POAM observations. The reduction in ozone estimated from the POAM measurements shows a similar maximum of 1.3 ± 0.2 ppmv at 400–500 K or 63 ± 4 DU in 400–550 K in late March. Our study reveals that the Arctic winter 2002/2003 was unique as it had three minor warmings and a MW, yet showed large loss in ozone. No such feature was observed in any other Arctic winter in the 1989–2010 period. In addition, an unusually large ozone loss in December, around 0.5 ± 0.2 ppmv at 450–500 K or 12 ± 1 DU in 400–550 K, was estimated for the first time in the Arctic. A careful and detailed diagnosis with all available published results for this winter exhibits an average ozone loss of 1.5 ± 0.3 ppmv at 450–500 K or 65 ± 5 DU in 400–550 K by the end of March, which exactly matches the ozone depletion derived from the ASUR, POAM and model data. The early ozone loss together with considerable loss afterwards put the warm Arctic winter 2002/2003 amongst the moderately cold winters in terms of the significance of the ozone loss