A simple and low-power optical limiter for multi-GHz pulse trains

We study the limiting-amplification capability of a saturated Semiconductor Optical Amplifier (SOA) followed by an optical band-pass filter. We experimentally demonstrate that this simple optical circuit can be effectively exploited to realize a low-power optical limiter for amplitudemodulated pulse trains at multi-GHz repetition rate. We report very large amplitude-modulation-reduction factors for the case of 20 and 40 GHz pulse trains that are super-imposed with modulating frequencies ranging from 100 kHz to several GHz

EU polluting emissions: an empirical analysis

We provide an empirical study of the evolution of emissions of some specific air pollutants on a panel of EU member states from 1990 to 2000, and we relate observed patterns to macroeconomic performance. The ratio pollution emission to GDP, so-called emission intensity, has decreased over the period considered in most EU member states. However, a non-parametric analysis reveals that the relative positions of different countries in terms of GDP growth and reduction of emissions have remained basically unchanged. More specifically, remarkable differences can be detected between the richest and the poorest EU members notwithstanding. Also, more dispersion in emissions levels can be found in those countries with lower per capita GDP

Pattern compensation in SOA-based gates

We propose a novel scheme employing complementary data inputs to overcome the patterning normally associated with semiconductor optical amplifier based gates and demonstrate the scheme experimentally at 42.6Gb/s. The scheme not only avoids introducing patterning during switching, but also compensates for much of the patterning present on theinput data. A novel gate was developed for the experiment to provide the complementary signals required for the scheme

Chirp management in silicon-graphene electro absorption modulators

We study the frequency chirp properties of graphene-on-silicon electro-absorption modulators (EAMs). By experimentally measuring the chirp of a 100 \ub5m long single layer graphene EAM, we show that the optoelectronic properties of graphene induce a large positive linear chirp on the optical signal generated by the modulator, giving rise to a maximum shift of the instantaneous frequency up to 1.8 GHz. We exploit this peculiar feature for chromatic-dispersion compensation in fiber optic transmission thanks to the pulse temporal lensing effect. In particular, we show dispersion compensation in a 10Gb/s transmission experiment on standard single mode fiber with temporal focusing distance (0-dB optical-signal-to-noise ratio penalty) of 60 km, and also demonstrate 100 km transmission with a bit error rate largely lower than the conventional Reed-Solomon forward error correction threshold of 10 123

A digital design process for shell structures

Over the last few decades, the design of freeform structures has undergone a radical change: powerful computational tools within parametric environment associated with digital fabrication techniques are pushing the boundaries of architecture towards bold solutions. The present work proposes a digital workflow for a shell in compression. The design process starts with the form-finding phase, which generates a hanging model. Through the interoperability of digital tools within parametric environment, optimization of the shape and structural analysis were carried out in order to investigate its behavior. The resulting surface is subject to tessellation, planarization of its cells that take into account fabrication constrains, and the 3D generation of panels composing the thickness of the structure. In order to accomplish an easier assembly process a hypothesis of a puzzle-like connection system was developed. The whole process provides a guidance for the design of freeform shell by the creation of a “customized” digital workflow implemented by digital fabrication techniques for the realization phase

Public division about climate change rooted in conflicting socio-political identities

Of the climate science papers that take a position on the issue, 97% agree that climate change is caused by humans1, but less than half of the US population shares this belief2. This misalignment between scientific and public views has been attributed to a range of factors, including political attitudes, socio-economic status, moral values, levels of scientific understanding, and failure of scientific communication. The public is divided between climate change 'believers' (whose views align with those of the scientific community) and 'sceptics' (whose views are in disagreement with those of the scientific community). We propose that this division is best explained as a socio-political conflict between these opposing groups. Here we demonstrate that US believers and sceptics have distinct social identities, beliefs and emotional reactions that systematically predict their support for action to advance their respective positions. The key implication is that the divisions between sceptics and believers are unlikely to be overcome solely through communication and education strategies, and that interventions that increase angry opposition to action on climate change are especially problematic. Thus, strategies for building support for mitigation policies should go beyond attempts to improve the public’s understanding of science, to include approaches that transform intergroup relations