Gain Enhancement of a Wide Slot Antenna Using a Second-Order Bandpass Frequency Selective Surface

Gain enhancement of a wide slot antenna over a wide frequency band using a low profile, second order bandpass frequency selective surface (FSS) as a superstrate is presented in this paper. The proposed multilayered FSS with non-resonant unit cells in each layer allows in-phase transmission of waves radiated from the antenna over a 3dB bandwidth of about 50%. The design allows an enhancement of upto 4dBi in the antenna gain over the entire frequency band (5-8GHz) of operation. The FSS provides a very low insertion loss between the two transmission poles along with a linearly decreasing transmission phase over the band. The composite structure shows an impedance bandwidth (-10dB) of 65% with an average gain between 6-8dBi over the frequency band with a peak gain of 9dBi. Measurement results of the fabricated prototype matches well with the predicted values

Hot electron transport in metallic spin valve and graphene-silicon devices at the nanoscale

In het huidige tijdperk van nanotechnologie zijn individuele atomen, de lading en spin van enkele elektronen van groot belang voor de ontwikkeling van nieuwe devices voor de halfgeleider industrie. De alom erkende ‘wet van Moore’, die een maat is voor de ontwikkelingen binnen de halfgeleider industrie, voorspelt dat deze trend afneemt tegen het einde van 2013. Om de trend toch door te zetten heeft de International Technology Roadmap for Semiconductors (ITRS) haar pijlen gericht op nieuwe materialen met nieuwe of meerdere functionaliteiten en nieuwe methodes om de nanoschaal eigenschappen te onderzoeken. De spintronika op de nanoschaal biedt ons nieuwe mogelijkheden voor devices van de `Beyond Moore' technologie. Grafeen, een twee-dimensionaal materiaal gemaakt van één laag koolstofatomen, gerangschikt in een honingraat structuur, blijkt een veelbelovend materiaal voor spintronisch onderzoek. Spintronische, elektronische en optoelektronische devices brengen noodzakelijkerwijs het transport van hete elektronen met zich mee. Hete elektronen worden vaak gebruikt om verschillende aspecten te bestuderen van spin-afhankelijk transport en om de relevante transport parameters en verstrooiing mechanismes te karakteriseren in verschillende transitie-metaal ferromagneten en normale metalen in spintronika devices gebaseerd op halfgeleiders. Het onderzoek beschreven in dit proefschrift heeft als doel het doorgronden van heet elektron transport in metallische spin valves en grafeen-silicium devices op de nanoschaal. De gepresenteerde resultaten geven nieuwe inzichten in zowel spin-onafhankelijke en spin-afhankelijke verstrooiing van hete elektronen in diverse spintronische devices. Het Gr/Si grensvlak wordt als uniek beschouwd, met verscheidene nieuwe fenomenen die nog niet eerder zijn onderzocht. De techniek voor karakterisatie op nanoschaal, die in dit proefschrift gebruikt wordt, zal een belangrijke vereiste blijven voor het fabriceren en bestuderen van vaste stof devices

Government Expenditure and Economic Growth: A Demand-side Analysis

In a post-Keynesian growth model with positive saving propensity out of wages, in this paper we analyze the implication of different kinds of government expenditures on aggregate demand and economic growth. We distinguish government expenditure into consumption and investment expenditure. The basic idea is that certain kind of government investment expenditure influences labour productivity. In a formal model we incorporate this idea by assuming labour productivity as an increasing function of government investment expenditure. When the economy is in an exhilarationist regime, under the balanced budget assumption, we show that a shift in government expenditure from consumption to investment purposes leads to an unambiguous rise in both aggregate demand and economic growth. However the result is ambiguous in the stagnationist regime. Once the balanced budget assumption is dropped, while in a stagnationist regime a rise in government investment expenditure may decrease aggregate demand and growth, it unambiguously raises both aggregate demand and growth rate in an exhilarationist regime. On the other hand, in the absence of balanced budget assumption, a rise in government consumption expenditure has positive effect on both the regimes . We also show that allowing the government to run into deficit and incur in debt does not necessarily lead to the public debt to rise without bound

A Simple Macro-model of Covid-19 with Special Reference to India

Motivated by the prevailing severe situation in India, we extend the SIR(S) model of infectious diseases to incorporate demand dynamics and its interaction with Covid-19 spread. We argue that, on one hand, spread of Covid-19 creates panic among consumers and firms and negatively affects economic activity. On the other hand, economy activity intensifies the spread of the infection. Initially assuming that recovered individuals do not develop antibody and become susceptible again, we capture the interaction between economic activity and spread of the disease in a two-dimensional dynamical system. We show that a large fiscal expansion combined with measures to boost community health as well as improve health sector's capacity to provide critical care can at the same time improve the economy and control the spread of the disease. We also find a slightly counter-intuitive result that a fiscal contraction can, under certain conditions, increase output and reduce number of infected individuals. However, we show that such a policy also increases fragility in the system. Finally assuming that only a fraction of recovered individuals become susceptible to contracting the diseases again, we obtain richer dynamics in a three-dimensional dynamical system. The paper also highlights the important role of speed of adjustment in the goods market in stability properties of steady state including emergence of limit cycles