An Evolutionary Approach to the Theory of Entrepreneurship

An economic model featuring entrepreneurial behaviour is built and tested using simulation techniques. The building blocks of our model are bounded-rational actors with specific sets of endowments: ""entrepreneurial spirit', human capital, and venture capital. The entrepreneurial behaviour to found a firm is triggered by the individuals' endowments, their social network, and the evaluation of the economic situation. Bandwagon effects occur when high growth rates in emerging markets increase firm entries and firm entries in return increase growth rates until competition unfolds its selective power. The firm's survivability is determined by its founders' endowments and its competitiveness. Whether actors are right or wrong in evaluating their economic situation and their consequent decisions is proven ex post . Thus, there will be winners and losers in this economic system.     

Self-imaging chirped holographic optical waveguides

To manipulate light propagation in optical waveguides, we have studied holographic, chirped structures within the waveguide's core. The holographic structures were embedded along the wave propagation direction and extended throughout the entire guide. Various self-imaging guides have been analyzed and realized to demonstrate the effect of different structures.     

Near-field effects in multilayer inductive metal meshes

The transmittance of inductive single-layer and multilayer cross-shaped metal meshes has been calculated with the Micro-Stripes software program. The effect of symmetric and asymmetric alignment of the crosses of one mesh with respect to another was studied and compared with transmission line theory, which presents the nonaligned case. Significant differences are found for small spacing at approximately 1/5 the periodicity constant, whereas the differences disappear for large spacing. A pair of coupled surface waves is used to represent the mode of a single mesh. The resulting modes corresponding to the transmittance of multilayer metal meshes are interpreted by modes composed of resonance modes of a single mesh coupled by Fabry-Perot modes depending on the separation.     

Z-transform theory and FDTD stability

In this paper we analyze the stability and the accuracy of finite-difference time-domain (FDTD) algorithms using Z-transform technique. Conventional time-staggered approximation of the time-derivative is replaced by a rational transfer function discrete-time filter. Then a generalized formulation of the FDTD time-stepping is presented. Finally, we show that it is possible significantly reduce the time-sampling error of FDTD algorithm by properly choosing the transfer function coefficients.     

Depositing graphene films on solid and perforated substrates

Graphene-a monolayer of graphite-has attracted vast interest recently owing to its perfect two-dimensional crystallographic nature and its potential use in a new generation of microelectronic devices. Yet, a deposition method, which results in a large coverage of monolayer thick graphite, is still lacking. By using a chemical mechanical polishing (CMP) method we were able to deposit stress-free graphene on solid and perforated substrates alike, achieving area coverage of hundreds of microns squared.     

Three-dimensional metallo-dielectric photonic crystals with cubic symmetry as stacks of two-dimensional screens

Metallo-dielectric photonic crystals with cubic symmetries have been studied here both experimentally and theoretically in the millimeter wavelength region (15-60 mm). In a direct analogy to linear systems, we considered the three-dimensional lattices as a stack of two-dimensional resonating screens. The overall three-dimensional structure was introduced in the calculation through a structural phase. Such an approach proved useful in understanding the related mode propagation and guided us in a study of the transition between cubic and centered body cubic symmetries.     

Electrical and optical properties of carbon nanotube/polypyrrole addressable intra-connects

Carbon nanotube (CNT) intra-connects (bridges spanning across in-plane electrodes) were electroplated with polypyrrole (PPy), an electrically conductive polymer (ECP). Sharp metal electrodes initiated the CNT growth at pre-selected locations. The CNT bridge was then used as an electrode for conductive polymer electro-deposition. The samples were characterized by Raman spectroscopy and current–voltage measurements. We found that current–gate voltage (I_ds–V_gs) characteristics changed dramatically for the electroplated structures when the polymer exceeded a threshold thickness, in the order of 80 nm. In addition, the CNT/PPy structures exhibited large sensitivity to UV radiation: the current substantially reduced upon irradiation with moderate UV intensity values.     

Inductive cross-shaped metal meshes and dielectrics

The Micro-Stripes program has been used to calculate resonance wavelengths and the bandwidth of inductive cross-shaped metal meshes in contact with dielectric layers. The shift of the resonance wavelength, depending on the thickness of the dielectric layers, has been studied for two refractive indices. The transmittance of two mesh filters with dielectric spacers or embedded in a dielectric has been calculated for specific alignment of the crosses of one mesh with respect to the other. Transmission line theory has been used to calculate the transmittance of two mesh filters with nonaligned crosses and dielectric layers. A coupled oscillator model has been used for interpretation of the interaction of resonance and Fabry-Perot modes.