Nanocrystalline Mg2Ni for hydrogen storage

This is an accepted manuscript of an article published byElsevier in Reference Module in Materials Science and Materials Engineering on 14/12/2020, available online: https://doi.org/10.1016/B978-0-12-815732-9.00061-9 The accepted version of the publication may differ from the final published versionHydrogen continues to receive increased attention as the most promising energy carrier enabling sustainable and eco-friendly energy systems. Despite the various advantages of hydrogen fuel, storing hydrogen in a light-weight and compact form is the barrier towards the commercialization of the hydrogen technologies. Thus, the availability of a reliable, inexpensive, safe and efficient hydrogen storage technology is crucial to support and foster the transition to a hydrogen-powered world. Among the possible hydrogen storage solutions, storing hydrogen in the solid-state, such as metal hydrides, is the safest and most attractive method for on-board hydrogen storage. The metal hydrides can release highly pure hydrogen, via a low-pressure endothermic process, suitable to be used directly in the hydrogen fuel cell devices. This article presents an overview of using Mg and Mg2Ni-based alloys for solid-state hydrogen storage. A review of the hydrogen storage technologies is presented first and then the most recent developments on Mg and Mg2Ni-based hydrogen storage materials are highlighted.Published versio

Event Scheduling Based On Combined Rollback Cost In Time Warp Parallel Simulation

An event scheduling policy for Time Warp parallel simulations based on combined rollback cost considerations is proposed. This policy takes into consideration a multitude of factors which affect the selection of the next event to be processed by any processor. These factors are: the event timestamp, the expected event execution time (granularity), the expected number of children events to be produced as a result of processing the candidate parent event and the particular event cancellation scheme used. Our scheduling policy is suitable for simulation models with event types having significantly different event granularity values and different numbers of children events. On any processor, it selects for scheduling from a set of candidate events the one having the smallest sum of granularity value and the expected cancellation cost for children events to be sent to other logical processes. This helps delay the execution of those candidate events which have high combined rollback costs as measured by the sum of granularity values and the expected cancellation cost of children events. Experimental results for a synthetic workload are reported. These results show that our scheduling policy can achieve a smaller simulation execution time and a fewer number of rollbacks than both LTF and grain-sensitive scheduling

Design of a lightweight authentication scheme for IEEE 802.11p vehicular networks

With the growing popularity of vehicle-based mobile devices, vehicular networks are becoming an essential part of wireless heterogeneous networks. Therefore, vehicular networks have been widely studied in recent years. Because of limited transmission range of wireless antennas, mobile vehicles should also switch their access points to maintain the connections as conventional mobile nodes. Considering the inherent characteristics of vehicular networks such as dynamic topology and high speed, the question of how to implement handoff protocol under real-time scenarios is very important. IEEE 802.11p protocol is designed for vehicular networks for the long distance transmission. To reduce handoff latency for 802.11p protocol, the authentication phase is waived during the handoff. However, security is also very important for wireless communications, and authentication can forbid access from malicious nodes and prevent wireless communications from potential attacks. Thus, in this paper, a lightweight authentication scheme is introduced to balance the security requirements and the handoff performance for 802.11p vehicular networks. In our scheme, the access points are divided into different trust groups, and the authentication process is completed in a group-based method. Once a vehicle is authenticated by an access point group, during the handoff within the same group, few extra authentication operations are needed. As a result, there is no extra overhead introduced to the authentication servers. Simulation results demonstrate that our authentication scheme only introduces small handoff latency and it is ideal for vehicular networks

A Simulation Study of a Shuttle-Bus Transportation System

The shuttle-bus transportation system in the annual Islamic pilgrimage, known as Hajj, relies on using dedicated two-way lanes between the holy sites of Arafat and Muzdalifah, in the first segment, and between Muzdalifah and Mina in the second segment. Shuttle buses have been used successfully for the past seven years to transport one group of pilgrims consisting of more than 160,000 pilgrims out of a total of more than two million pilgrims. The Saudi Ministry of Hajj would like to revise the current experience gained from this project and evaluate any constraints or shortcomings associated with it. In this paper, a description of the shuttle bus transportation system that existed in the 2002 Hajj season is given. Next, a simulation model is designed for this system and translated into a simulation program using the Arena simulation system. This simulation model is used to conduct a series of experiments designed with the goal of achieving a better understanding of the characteristics and limitations of the system

Multidisciplinary management approach to fulminant hepatic encephalopathy in the neurocritical care unit: A single-center experience

Objective: Measure and change mortality/morbidity in patients with Fulminant Hepatic encephalopathy (FHE) using aggressive multimodality monitoring and multidisciplinary approach. Background: Fulminant hepatic encephalopathy (FHE) with diffuse cerebral edema has dismal prognosis if transplantation is not performed. Novel therapeutic interventions may change this outcome. Design/Methods: We reviewed all cases with FHE admitted to our hospital since 2008. In 2010, we developed a multidisciplinary management protocol, mandating transfer of patients entering grade 3 from other ICUs to the Neurosciences-ICU (NICU) for intracranial pressure (ICP) management. Multiple interventions were utilized including coagulopathy reversal with Factor VII and prothrombin complex concentrate (PCC, Kcentra), ICP device placement, osmotherapy, aggressive ammonia lowering regimen with lactulose and rifaximin, early renal replacement therapy, mild hypothermia for refractory ICP, in conjunction with liver transplantation candidacy investigation. Results: Twenty-four patients (19 women, mean age of all patients 40 years) were admitted; seven were managed in the MICU/SICU and 17 in the NICU. The etiology of FHE was acetaminophen toxicity in 72% of patients. The Model for End-Stage Liver Disease (MELD) admission scores and liver enzymes between the MICU/SICU and the NICU were not different (Mann- Whitney test). Although the NICU admission ammonia level was higher than the MICU/SICU (168.75 vs 99.50, p = 0.00), the lowest achieved ammonia was lower in the NICU (41.31 vs 7978.13, p = 0.022, Mann-Whitney). Patients received ICP monitoring (all in the NICU plus 2 in the SICU) and the highest ICP recorded was 120 mm Hg. The pre- and post- coagulation reversal INR were 3.37 and 1.3, p=0.031, Wilcoxon test). Seven patients in the NICU received hypothermic treatment. Mortality in the MICU/SICU was 85.7% (6/7) and in the NICU 41.1% (7/17), p = 0.13 (chi square test). Conclusions: A multidisciplinary approach centered around anti-cerebral edema protocol-driven management based on novel interventions may improve the outcome of patients with FHE