Collective Modes of Massive Dirac Fermions in Armchair Graphene Nanoribbons

We report the plasmon dispersion characteristics of intrinsic and extrinsic armchair graphene nanoribbons of atomic width N = 5 using a p_z-orbital tight binding model with third-nearest-neighbor (3nn) coupling. The coupling parameters are obtained by fitting the 3nn dispersions to that of an extended Huckel theory. The resultant massive Dirac Fermion system has a band gap E_g \approx 64 meV. The extrinsic plasmon dispersion relation is found to approach a common dispersion curve as the chemical potential $\mu$ increases, whereas the intrinsic plasmon dispersion relation is found to have both energy and momentum thresholds. We also report an analytical model for the extrinsic plasmon group velocity in the q \rightarrow 0 limit

A theoretical model for single molecule incoherent scanning tunneling spectroscopy

Single molecule scanning tunneling spectroscopy (STS), with dephasing due to elastic and inelastic scattering, is of some current interest. Motivated by this, we report an extended Huckel theory (EHT) based mean-field Non-equilibrium Green's function (NEGF) transport model with electron-phonon scattering treated within the self-consistent Born approximation (SCBA). Furthermore, a procedure based on EHT basis set modification is described. We use this model to study the effect of the temperature dependent dephasing, due to low lying modes in far-infrared range for which hw<<kT, on the resonant conduction through highest occupied molecular orbital (HOMO) level of a phenyl dithiol molecule sandwiched between two fcc-Au(111) contacts. Furthermore, we propose to include dephasing in room temperature molecular resonant conduction calculations.Comment: 12 pages, 5 figure

Exploring the effects of capital mobility on the saving–investment nexus: evidence from Icelandic historical data

We explore the effects of capital mobility on the relationship between saving and investment using historical data for Iceland. First, we analyse the saving–investment (S-I) correlation for the period of restricted capital mobility using data from 1960 and 1994. We then add a period of free capital mobility between 1994 and 2008 and estimate the correlation for the period 1960–2008. Finally, we extend our analysis to the 2008 to 2016 period, when capital controls were imposed in response to the crisis. Institutions matter: We find institutional changes, in particular, Iceland’s entry into the European Single Market in 1994, coincided with a fall in the long-run correlation between saving and investment. However, the correlation weakens further when we include the postcrisis regime of capital controls, suggesting a weaker relationship between savings and investment in this regime. We discuss the possible reasons for this pattern and also the implications of our findings for post-crisis policy in small open economies

Poverty and Its Determinants in Pakistan: Evidence from Pslm 2010-11

This study estimates the poverty in terms of head count ratio, poverty gap and squared poverty gap by using the fresh available PSLM data for the year 2010-11 in Pakistan. This study also finds its economic determinants by estimating multiple OLS regression.The results show that the headcount ratio, poverty gap and squared poverty gap are statistically significant 15.06 %, 2.29 % and 0.55 %, respectively in Pakistan. All of the poverty estimates arestatistically significant almost double in rural areas as compared to urban areas. The comparisons of the poverty estimates of this year with the previous ones of2007-08 at urban, rural and nationallevel show that poverty decreased statistically significantly. Among the provinces it is the highest in Baluchistan and the lowest in Sindh. The comparison of provincial poverty estimates of this year with the same ones of previous year (2007-08) depict that poverty decreased in all of the provinces, but it is statistically significant only in case of Baluchistan.Further the resultsshow that Poverty has statistically significantinverse relationship with education. Households having animals for transportation, owning residential buildings, shops and commercial buildings and living in urban areas have less poverty than those who do not. But it hasstatistically significant positive association with the household size and dependency ratio. The household size is greater in poor families than the rich ones. As far as household head’s employment status, occupation and industry is concerned, it is highest in sharecroppers,elementary occupations, and community, social services. At a policy level, it is suggested that Govt. should focus more on education and generationof employment opportunities. Further it should provide loansto lower income groups on reduced rates for housing facilities andto start their own businesses like shops.Family planning should be encouraged especially in poor families.All such policies should focus more on rural areas of especially Baluchistan and KPK in Pakistan. Keywords: Poverty; Education; Animal for transportation; Household size;  Dependency ratio; Family planning; Residential building;Shops; Pakistan

An atomistic quantum transport solver with dephasing for field-effect transistors

Extended Huckel theory (EHT) along with NEGF (Non-equilibrium Green's function formalism) has been used for modeling coherent transport through molecules. Incorporating dephasing has been proposed to theoretically reproduce experimental characteristics for such devices. These elastic and inelastic dephasing effects are expected to be important in quantum devices with the feature size around 10nm, and hence an efficient and versatile solver is needed. This model should have flexibility to be applied to a wide range of nano-scale devices, along with 3D electrostatics, for arbitrary shaped contacts and surface roughness. We report one such EHT-NEGF solver with dephasing by self-consistent Born approximation (SCBA). 3D electrostatics is included using a finite-element scheme. The model is applied to a single wall carbon nanotube (CNT) cross-bar structure with a C60 molecule as the active channel. Without dephasing, a negative differential resistance (NDR) peak appears when the C60 lowest unoccupied molecular orbital level crosses a van Hove singularity in the 1D density of states of the metallic CNTs acting as contacts. This NDR diminishes with increasing dephasing in the channel as expected.Comment: to appear in Journal of Computational Electronic

Deployment of drone-based small cells for public safety communication system

In the event of a natural disaster, communications infrastructure plays an important role in organizing effective rescue services. However, the infrastructure-based communications are often affected during severe disaster events such as earthquakes, landslides, floods, and storm surges. Addressing this issue, the article proposes a novel drone-based cellular infrastructure to revive necessary communications for out-of-coverage user equipment (UE) which is in the disaster area. In particular, a matching game algorithm is proposed using one-to-many approach wherein several drone small cells (DSCs) are deployed to match different UEs to reach a stable connection with optimal throughput. In addition, a medium access control framework is then developed to optimize emergency and high priority communications initiated from the rescue workers and vulnerable individuals. The simulation results show that the throughput for the out-of-coverage UEs are significantly improved when the DSCs are deployed in public safety network while the channel access delay is also notably reduced for emergency communications within the affected areas