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Synthesis of Nanomaterials for Drug Delivery
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials II, 2021
Hemant K. S. Yadav, Shahnaz Usman, Karyman Ahmed Fawzy Ghanem, Rayisa Beevi
As an electron beam enters a solid material or polymeric film, it undergoes elastic scattering, leading to loss in energy. The electron scattering occurs either by elastic collisions or inelastic collisions. Energy is lost only during inelastic collisions, whereas elastic collisions only result in a direction change. Due to the scattering, the electrons spread out and penetrate into the solid. This will result in transversal or lateral flux which is normal for the incident beam direction, causing an exposure of resist at points remote from the point of electron incidence, leading to development of resist images wider than expected. The factors determining the magnitude with which electron scattering will take place are the atomic number, density of the substrate and resist, and also the velocity of electrons.[18]
Elementary Processes of Charged Species in Plasma
Published in Alexander Fridman, Lawrence A. Kennedy, Plasma Physics and Engineering, 2021
Alexander Fridman, Lawrence A. Kennedy
Ionization of atoms and molecules by electron impact, electron attachment to atoms or molecules, and ion-molecular reactions (see Figure 2.1a–c) are examples of elementary plasma-chemical processes, reactive collisions accompanied by the transformation of elementary plasma particles. These elementary reactive collisions, as well as others, for example, electron–ion and ion-ion recombination, excitation and dissociation of neutral species by electron impact, relaxation of excited species, electron detachment and destruction of negative ions, photochemical processes – altogether determine plasma behavior. Elementary processes can be divided into two classes – elastic and nonelastic processes. The elastic collisions are those in which the internal energies of colliding particles do not change, therefore the total kinetic energy is conserved as well. Hence, these processes result only in scattering. Alternately collisions are inelastic. All elementary processes listed in previous paragraphs are inelastic ones. Inelastic collisions result in the transfer of energy from the kinetic energy of colliding partners into internal energy. For example, processes of excitation, dissociation, and ionization of molecules by electron impact are inelastic collisions, including the transfer of high kinetic energy of plasma electrons into the internal degrees of freedom of the molecules.
Kinetics in Linear Motion
Published in Emeric Arus, Biomechanics of Human Motion, 2017
A collision in which the total kinetic energy of a system will remain the same after the collision is called elastic collision. To be more explicit, the bodies will deflect each other with no physical change of shape. An example is when two billiard balls collide.
Eulerian based population balance modeling of agglomeration in a bubbling fluidized bed combustor
Published in Particulate Science and Technology, 2023
Abdullah Tasleem, Syed Shah Jahan Gillani, Fazal e Rabbi, Syed Sheraz Daood, Fei Li, Atta Ullah
Different mitigation techniques are proposed to mitigate agglomeration phenomena in FBCs. The fuel of low ash content can be used to avoid agglomeration and consequently increased defluidization time. White wood can be considered as the best biomass fuel because it has low ash contents and didn’t undergo defluidization. Corrugated geometry can be another option so that dead zones are not formed in the system and U/Umf overcomes the adhesive forces between the particles of bed and ash. For the simulation of particle fluidization, the coefficient of restitution plays a significant role as it represents the nature of the colliding materials. A fully elastic collision is one in which the total amount of kinetic energy is not lost. The maximal coefficient of restitution for this kind of collision is e = 1. A perfectly inelastic collision is one in which kinetic energy is mostly wasted. They have a restitution coefficient of e = 0. Artificial agglomeration can be induced if the value of e is taken as zero. Most real-life collisions occur in the middle and the phenomena of agglomeration can be best studied in between 0 and 1.
Simulation study of the effect of the restitution coefficient on interphase heat transfer processes and flow characteristics in a fluidized bed
Published in Numerical Heat Transfer, Part A: Applications, 2019
Hamada Mohamed Abdelmotalib, Ik–Tae Im
The collision of solid particles has a great effect on the operation of a fluidized bed reactor. This effect can be characterized using the particle–particle restitution coefficient. The value of the coefficient of restitution can range from zero for a fully inelastic collision to 1 for a fully elastic collision. The present study investigated the effect of the collision elasticity represented by the restitution coefficient on particle–particle and gas–particle heat transfer processes, as well as the relevant bed hydrodynamics. A 2D and a two-phase model of a fluidized bed reactor were used in our simulations study. Two different materials, sand particles and steel beads, were used as bed materials fluidized by air. We investigated the heat transfer between the bed materials and the fluidized gas, as well as the heat transfer between the solid particles. Increasing the collision elasticity resulted in increasing the bed pressure drop and decreasing the granular temperature, solid velocity, and collision frequency. The interphase heat transfer process, including interparticle and gas–particle heat transfer processes, decreased with increasing collision elasticity (i.e., with increasing the particle–particle coefficient of restitution). Sand particles showed better fluidization and heat transfer rates than the steel beads. The simulations results indicated that both the particle–particle and the gas–solid heat transfer processes strongly depended on the bed flow hydrodynamics, especially the void fraction and solid particles velocity.
Experimental study on the rebound characteristics of oblique collision of ash particles and the influence of ammonium bisulfate
Published in Aerosol Science and Technology, 2022
Shihao Hu, Qi Yin, Yize Zhang, Kefa Cen, Hao Zhou
The process of ash particles depositing on the heat exchange surface can be simplified to the rebound process of the ash particles colliding with the target surface. When the particle is in contact with the impact plane, the forces on the particle include friction, thermophoresis, and surface forces. The surface forces are caused by adhesion and the van der Waals force (Abd-Elhady and Malayeri 2013). In collision dynamics, the restitution coefficient is a common parameter that reflects the energy consumption during impact. The definition of restitution coefficient e is the percentage of rebound velocity to incident velocity (Zhou et al. 2016): where and are the impact and rebound velocities of ash particles, respectively, is the kinetic energy of the incident particles (angular momentum is ignored), and is the energy dissipation during impact. According to Liu, Li, and Yao (2011), energy dissipation can be divided into two parts, first-contact energy loss and energy dissipation through damping effects (friction and adhesion) or plastic deformation. The first-contact energy loss is independent of the impact velocity. The energy loss caused by plastic deformation and damping effects is closely related to the impact velocity. When the collision is a perfect elastic collision, the coefficient of restitution is 1. When the ash particle dissipates all the kinetic energy and attaches to the target surface, the coefficient of restitution is 0.