Development Of Microscopic Models Research Articles

A Study on Characteristics of Vehicular Lateral Position on Rural Highways

Many pieces of research have concentrated on traffic speed, time headway, space headway, and so on under non-lane-based heterogeneous traffic streams. In contrast, limited studies have been conducted for analyzing and modeling the vehicular lateral position. The lateral position of vehicles plays an equally vital role in the development of microscopic models. Moreover, the vehicle characteristics such as the lateral position and speed are considered independent in the traffic simulation modeling, ignoring their correlation. This study investigates the relationship between the lateral position of vehicles with traffic speed on rural highways. For this purpose, the traffic data related to different vehicles’ lateral positions and speed were collected using an infra-red sensor instrument from the National Highways in India. The relationship of vehicles’ lateral position with the traffic speeds under different ranges is analyzed to understand their dependence. The study results show that the relationship between vehicles’ lateral position is significantly associated with the traffic speed. The study findings help formulate a microscopic simulation model to reproduce accurate maneuvering in the traffic stream, which is useful for analyzing traffic characteristics.

A review of thixotropy and its rheological modeling

We review thixotropy, its attributes, and accompanying rheological phenomena, such as yielding, hysteresis in shear-rate ramps, the influence of rest time and viscosity bifurcation, and the prevalence and importance of thixotropy in common fluids. While older work is reviewed in brief, the major emphasis is on recent developments, including nonmonotonic responses of stress to changes in strain rate, viscosity bifurcation, shear banding, and kinematic hardening. The major categories of phenomenological constitutive models are reviewed; these can include viscoelasticity and aging, plasticity, kinematic hardening, and thixotropy; and distinctions between these phenomena and thixotropy are discussed. A few available microstructural models are also reviewed, including population balance models and mesoscopic simulations. We end by highlighting important future work that is needed, including further development of microscopic models and their connection to phenomenological constitutive equations, detailed measurements of microstructures and flow fields with bands, and the investigation of flows other than simple shear.

The importance of closed shell structures in the synthesis of super heavy elements

The importance of shell closures and gaps in the single-particle energies for protons and neutrons on the stability of elements beyond Z = 100 will be described. Following the development of microscopic models with shell corrections, microscopic-macroscopic models predicted large gaps in the single-particle energy levels for protons and neutrons at Z = 102, 108 and N = 152, 162 for the same deformed shapes. Shell gaps for spherical shapes for N = 184 and Z = 114, 120 or 126 were also predicted to form an "Island of Stability" with very long half lives for fission and alpha decay. Cold fusion reactions involving beams of Ca to Zn and targets of stable 208Pb and 209Bi were pioneered at GSI and used to synthesize new elements for Z = 107 to 112 and in Japan a new isotope of 113. Hot fusion reactions between radioactive actinide targets and neutron-rich 48Ca beams were pioneered in JINR leading to the synthesis of new elements with Z = 113 to 118. Data on two neutron separation energies, spontaneous fission half lives and total half lives of super heavy elements showing the importance of reinforcement of the Z = 102, N = 152 and Z = 108, N = 162 single particle level gaps at the same deformation and Z = 114-126, N = 184 shell gaps in the synthesis of super heavy elements 107 to 118 are presented along with the latest results on their synthesis.

A Cellular Automaton Model for Highway: Considering Multi-Lane Traffic Rules

Vehicular flow in highway is inherently complex and development of microscopic models of vehicular flow has been a daunting task for researchers. This paper presents the use of Cellular automata (CA) micro simulation for modeling multi-lane traffic characteristics in highway, as well as considering the average speed difference (ASD) and lane-changing rules (LCR) in the CA model. Firstly, on the base of the Symmetric Two-Lane Cellular Automata (STCA) model, we analyzed the impact on traffic characteristics, through adjusting the maximum speed and lane-changing rules. Secondly, by the micro simulation, the relationships between speed and density in traffic flow were given considering the ASD and the LCR. The simulation results showed that, (a) the more obvious of speed dispersion, the more serious about speed declining, (b) the speed of overall traffic flow slowed down by 163% under extreme conditions, (c) the more reckless of lane-changing rule drivers used, the higher speed of traffic flow can reach.

Breakdown of phonon glass paradigm in La- and Ce-filled Fe4Sb12 skutterudites

The material class of skutterudites is believed to have strong potential for thermoelectric application due to the very low thermal conductivity of the filled structures. It is generally assumed that the atoms filling the skutterudite cages act as 'rattlers' and essentially induce a disordered lattice dynamics referred to as 'phonon glass'. Here, we present neutron spectroscopy experiments and ab initio computational work on phonons in LaFe(4)Sb(12) and CeFe(4)Sb(12). Our results give unequivocal evidence of essentially temperature-independent lattice dynamics with well-defined phase relations between guest and host dynamics, indicative of a quasi-harmonic coupling between the guests and the host lattice. These conclusions are in disagreement with the 'phonon glass' paradigm based on individual 'rattling' of the guest atoms. These findings should have an essential impact on the design and improvement of thermoelectric materials and on the development of microscopic models needed for these efforts.

Landau theory revisited

Abstract The Landau free energy GL(T,Q) is an important concept in structural phase transitions because it is often the meeting point of experiment and the development of microscopic models. We review recent work on the real Q and T dependence of GL, the origin of non-classical non-critical exponents for T below Tc, the cross-over from soft mode to O/D behaviour, local bifurcation at T* and relation to ordering kinetics. Framework structures such as many silicates and the perovskite structure allow special geometrical Rigid Unit phonon Modes. The material is then likely to be near to the soft mode limit, resulting in classical behaviour of Q(T) over a very wide T range. Long range correlations result in a very small Ginzburg interval.

Remarks on the use of Boltzmann's equation for electrical conduction calculations in metal matrix and in situ composites

The Boltzmann equation and its solutions are cental to the development of microscopic models describing the longitudinal and transverse electrical conductivity of metal matrix and in situ composites. Such solutions are needed to describe electron and phonon scattering and transport phenomena in the matrix due to the presence of a second filamentary phase, and to describe electrical conductivity at cryogenic and higher temperatures. In this paper, we derive solutions to the Boltzmann equation in the relaxation time approximation in cylindrical coordinates. It is shown that one solution for the electric field parallel to the fibre direction leads to an expression for composite conductivity at cryogenic and higher temperatures. We also present a solution for the case in which the electric field is normal to the fibre direction.

Ferroelectrics in the para phase in a homogeneous, intense vhf field

Investigation of the behavior of ferroelectrics in an intense variable electric field has revealed a number of significant features. The choice of models explaining the observed effects requires that the interaction between the electric field and the acoustic vibrations of the crystal lattice of the material be taken into account, demonstrates the role of static charged defects, and reveals features of charge-carrier kinetics. The main interest centers on investigations in the vhf range, which is distinguished by high information content. Here, primarily, the small wavelength of the acoustic vibrations (∿ l μm) at frequencies of the intense excitation comparable with the film thickness and the crystallite size must be noted, together with the small duration of the vibration period, comparable with the charge-carrier relaxation time. The next problem is the creation of a model combining both the nonlinear effects and the charge-carrier kinetics determining the redistribution of the static internal field and the charge transfer. The development of such a model will have a decisive influence in improving the characteristics of ferroelectric devices. The development of microscopic models explaining the noted features of the ferroelectric properties is also very urgent. One of the interesting trends in this field is the use of the interband theory of ferroelectricity.