Model for the magnetoresistance and Hall coefficient of inhomogeneous graphene

We show that when bulk graphene breaks into n-type and p-type puddles, the in-plane resistivity becomes strongly field dependent in the presence of a perpendicular magnetic field, even if homoge- neous graphene has a field-independent resistivity. We calculate the longitudinal resistivity \rho_{xx} and Hall resistivity \rho_{xy} as a function of field for this system, using the effective-medium approximation. The conductivity tensors of the individual puddles are calculated using a Boltzmann approach suit- able for the band structure of graphene near the Dirac points. The resulting resistivity agrees well with experiment, provided that the relaxation time is weakly field-dependent. The calculated Hall resistivity has the sign of the majority carrier and vanishes when there are equal number of n and p type puddles.Comment: 5 pages, 4 figure

Numerical Study of Energy Loss by a Nanomechanical Oscillator Coupled to a Cooper Pair Box

We calculate the dynamics of a nanomechanical oscillator (NMO) coupled capacitively to a Cooper pair box (CPB), by solving a stochastic Schrodinger equation with two Lindblad operators. Both the NMO and the CPB are assumed dissipative, and the coupling is treated within the rotating wave approximation. We show numerically that, if the CPB decay time is smaller than the NMO decay time, the coupled NMO will lose energy faster, and the coupled CPB more slowly, than do the uncoupled NMO and CPB. The results show that the efficiency of energy loss by an NMO can be substantially increased if the NMO is coupled to a CPB.Comment: 10 pages, 3 figure

Measuring Institutional Relatedness

Firms in most emerging economies are engaged in seemingly un-related activities. This is particularly observed in the case of business groups which dominate the landscape of these economies. Initially, diversification in emerging economies that was not based on product or technological considerations was considered value reducing. However, according to the new emerging consensus unrelated diversification is a strategic response to the institutional voids that exist in such economies. Despite major breakthroughs in conceptualizing this institutional relatedness, the empirical support for this concept has come only through case studies and hence is not generalizable. Creating an appropriate measure of institutional relatedness is a challenge because it has to take into account the .unique and invisible. nature of institutional relatedness. An appropriate measure should capture the myriad reasons used by firms to combine various businesses in emerging economies as a response to various institutional voids, without giving undue importance to any specific rationale. Besides, the measure should not be a fixed value; it should be allowed to change to help gauge the impact of institutional transitions on relatedness. Finally, it should provide for the uniqueness of each firm when it ventures into areas not tried by other firms. In this paper we purport to address this lacuna in research by proposing an empirically implementable measure for institutional relatedness having the features described above. We also show that the empirical estimates for India of our measure of relatedness are in consonance with the tendencies observed by studies using the case-study method and seem to be linked with the institutional transitions that have been observed in recent years.

Empirical Assessment of Coherence in Information Technology Firms

Coherence is the ability to discover new – potentially profitable – combinations of various types of knowledge assets where complementarity is the basis for relevant combinations. Assets are considered complementary if doing (more of) any one of them increases the returns to doing (more of) others. Despite its strategic importance, few studies have addressed the issue of coherence in the Information Technology (IT) industry. This paper develops a novel methodology assess the extent of complementarity and coherence in the IT firms grounded in ‘sensemaking’, evolutionary economics, and strategic management. This paper uses managerial perspective for defining businesses. Managers and IT experts identify a typical IT firm based on the dimensions of applications (verticals) and specializations (service lines). Another feature of this paper is the use of survivor principle for assessing complementarity. The results on complementarity suggest that in case of applications, the boundaries between Transport & Ports and Airlines & Railways are getting blurred and these could become a generic combination. Similarly, in case of specializations Software maintenance migration and RDBMS, Datawarehousing & Datamining could become a generic combination. The results also suggest that there is substantial scope for improvement in coherence in both applications and specializations. Analysis of coherence also indicates greater fungibility of knowledge in applications than knowledge in specializations. Another finding is that the IT firms retain coherence with large number of applications but not with large number of specializations. Finally, as the number of applications and specializations reach a critical limit, the average coherence shows a definite decline.

Tunable Band Gap in Graphene with a Non-Centrosymmetric Superlattice Potential

We show that, if graphene is subjected to the potential from an external superlattice, a band gap develops at the Dirac point provided the superlattice potential has broken inversion symmetry. As a numerical example, we calculate the band structure of graphene in the presence of an external potential due to periodically patterned gates arranged in a triangular graphene superlattice (TGS) with broken inversion symmetry, and find that a band gap is created at both the original and "second generation" Dirac point. The gap can be controlled, in principle, by changing the external potential and the lattice constant of the TGS.Comment: 6 figures, Phys. Rev. B 79, 20543

Stability and Equilibrium Analysis of Laneless Traffic with Local Control Laws

In this paper, a new model for traffic on roads with multiple lanes is developed, where the vehicles do not adhere to a lane discipline. Assuming identical vehicles, the dynamics is split along two independent directions: the Y-axis representing the direction of motion and the X-axis representing the lateral or the direction perpendicular to the direction of motion. Different influence graphs are used to model the interaction between the vehicles in these two directions. The instantaneous accelerations of each car, in both X and Y directions, are functions of the measurements from the neighbouring cars according to these influence graphs. The stability and equilibrium spacings of the car formation is analyzed for usual traffic situations such as steady flow, obstacles, lane changing and rogue drivers arbitrarily changing positions inside the formation. Conditions are derived under which the formation maintains stability and the desired intercar spacing for each of these traffic events. Simulations for some of these scenarios are included.Comment: 8 page

Analysis of air flow and heat dissipation from a high performance passenger car front brake rotor

The increasing demand from the consumer for higher levels of refinement from their passenger vehicles has put considerable pressure on the automotive industry to produce ever quieter cars. In order to prevent the occurrence of many forms of brake noise, especially judder and drone, excessive heating of the brake disc must be avoided, whilst minimising temperature variations across the rotor. In order for this to be achieved the brake rotor must be designed such that it ensures sufficient uniform heat dissipation and thermal capacity. In high demand braking applications vented discs consisting of two rubbing surfaces separated by straight radial vanes are normally employed as they utilise a greater surface area to dissipate heat. Within this paper the convective heat dissipation from a high performance passenger car front brake disc has been investigated using computational fluid dynamics (CFD). The results obtained have been validated by those obtained in preliminary vehicle testing at Millbrook test facility. The computational model shows adequate correlation to the test results; overpredicting the average heat transfer coefficient by 18%. The CFD analysis enabled a detailed insight into the air flow and heat transfer distributions, that was not possible during the vehicle test regim

Shape sensitivity analysis of flutter response of a laminated wing

A method is presented for calculating the shape sensitivity of a wing aeroelastic response with respect to changes in geometric shape. Yates' modified strip method is used in conjunction with Giles' equivalent plate analysis to predict the flutter speed, frequency, and reduced frequency of the wing. Three methods are used to calculate the sensitivity of the eigenvalue. The first method is purely a finite difference calculation of the eigenvalue derivative directly from the solution of the flutter problem corresponding to the two different values of the shape parameters. The second method uses an analytic expression for the eigenvalue sensitivities of a general complex matrix, where the derivatives of the aerodynamic, mass, and stiffness matrices are computed using a finite difference approximation. The third method also uses an analytic expression for the eigenvalue sensitivities, but the aerodynamic matrix is computed analytically. All three methods are found to be in good agreement with each other. The sensitivities of the eigenvalues were used to predict the flutter speed, frequency, and reduced frequency. These approximations were found to be in good agreement with those obtained using a complete reanalysis