Preface

The development of technologies in the transportation sector covers a broad range of aspects, including reliability, safety, comfort, energy efficiency, economy, and environment. Moreover, the automobile business is tremendously peculiar due to several strict requirements regarding functional reliability, safety standards, comfort level, high-volume production, and environmental limits. In addition, the industry is experiencing a disruptive evolution of modern vehicle research and design: electrification, connectivity, and autonomous driving.

Clean and environmentally friendly transportation systems are urgently needed, due to the huge amounts of energy they currently use and the CO2 emissions they produce. Among potential secondary energy sources, hydrogen is considered very promising in terms of efficiency, cleanliness, and technological options for production, storage, and utilization. In transportation systems, it has been predicted that electricity and hydrogen will dominate the fuel supply for vehicles.

This book is organized into two sections. The first section deals with automotive engineering systems, while the second section discusses the potential of hydrogen as a clean and carbon-free energy source in the transportation sector.

The first section of the book provides a robust focus on automotive engineering, including new proposals and the latest trends about some road vehicle systems/ sub-systems. Each chapter in this section presents a rigorous analysis or a new solution; professional and academic readers will appreciate both the theory dissertation and the industrial application.

The first section "Automotive Engineering Systems" includes five chapters:

Chapter "Hybrid Steering Systems for Automotive Applications," presents a new type of small power hybrid steering system dedicated to some types of heavy mobile robots. It also includes research results on the static and dynamic performances of hybrid electrohydraulic servomechanisms. The new concept was generated by the needs of modern aerospace technology called "flight by wire." The new wave of autonomous driving generated many combinations of electric and hydraulic components and the authors focus on the accuracy of the hybrid steering system of an articulated tractor.

The chapter "New Robust Control Design of Brake-by-Wire Actuators" discusses the control design of three different brake-by-wire actuators. After modeling the actuators adopting the bond graphs method, a cascaded control architecture is used to control these active systems via the Youla parameterization technique. A one-wheel model is used to compare these brake-by-wire systems in terms of stopping distance and actuator efforts and energy usage. The chapter also introduces the design of disturbance rejections for each loop.

The chapter "Role of Bearings in New Generation Automotive Vehicles: Powertrain", explains the main activities to obtain high-performance bearings, such as correct

selection of materials, manufacturing technologies, design-optimized geometries, sealing, lubrication, and application. Bearings are essential to achieve some modern automobiles' performance targets (maximum vehicle uptime, utilization, and better total cost of ownership); furthermore, they have a crucial role in powertrain health monitoring.

The chapter "Generation and Relaxation of Residual Stresses in Automotive Cylinder Blocks", studies the relaxation of residual stresses and their correlation to aging temperature and aging time. Particularly, for I4 and V-6 engine blocks, there is refinement in microstructure due to the increase in solidification rate along the cylinder length. Solution heat treatment and freezing lead to the maximum amount of residual stress relaxation where 50 percent of the residual stresses are reduced after the solution heat treatment step. Relaxation of residual stresses depends on the geometry and size of the workpiece.

The chapter "Quality and Trends of Automotive Fuels", analyzes the combustion for the most used fuels: gas oil and gasoline. Due to different combustion requirements, the fundamental properties of both fuels are examined. In addition, with the advent of various renewable components in both fuels, new trends are emerging for both fuel quality assessments, as these are molecularly distinct from their crude oil counterparts.

The second section "Hydrogen in the Future Transportation System" focuses on several interesting and cutting-edge topics describing several issues in the following chapters:

The chapter "Light Weight Complex Metal Hydrides for Reversible Hydrogen Storage", investigates complex metal hydrides involving lightweight elements or compounds for reversible hydrogen storage. The complex hydrides are prepared via an inexpensive solid-state mechano-chemical process under a reactive atmosphere at ambient temperatures. The structural, microstructural, surface, and other physicochemical behaviors of these lightweight complex metal hydrides are analyzed and discussed.

The chapter "Hydrogen Storage: Materials, Kinetics and Thermodynamics", describes hydrogen storage and its impact on the envisaged green environment. Moreover, graphene and borohydrides hydrogen storage materials are also reviewed extensively along with the kinetic models thereof. Furthermore, the chapter discusses the reaction mechanism of graphene nanocomposites.

The chapter "Hydrogen Fuel Cell Implementation for the Transportation Sector", discusses the application of a fuel cell in the transportation sector. It reviews the status of projected fuel cell electric vehicles (FCEVs) and considers the factors influencing the commercialization of FCEVs, including the importance of fuel cells for electric vehicles. It also examines degradation diagnoses using accelerated stress test procedures, FCEV hybridization, and the contribution of an energy storage device for charging these vehicles. The chapter also includes case studies relating to material degradation occurring from driving behavior. Finally, the chapter describes the importance of energy storage to support the growth of electric vehicle technologies, especially the integration of vehicles and the grid.

The chapter "Quantum Calculations to Estimate the Heat of Hydrogenation Theoretically", deals with the calculation and analysis of standard enthalpies of hydrogenation of twenty-nine unsaturated hydrocarbon compounds in the gas phase by CCSD(T) theory. Geometries of reactants and products are optimized at the M06-2X/6-31g(d) level. The mean absolute deviations of the enthalpies of hydrogenation between the calculated and experimental results range from 8.8 to 3.4 kJ mol-1 based on the comparison between the calculation and experimental results. In addition, a very good linear correlation between experimental and calculated enthalpies of hydrogenation is obtained.

Our appreciation goes to all authors for their valuable contributions. The first editor would also like to thank his niece Maria Sofia for her motivating liveliness. The second editor would like to express his appreciation for his family, especially his wife and children.

> **Luigi Cocco, Ph.D.** Maserati S.p.A., Modena, Italy
