Joint distribution of polarization-multiplexed UWB and WiMAX radio in PON

In this paper, the feasibility of the joint distribution of ultra-wideband (UWB) and WIMAX wireless using polarization multiplexing as a coexistence technique is proposed and experimentally demonstrated within the framework of passive optical networks (PON). Four single- and orthogonal-polarization multiplexing schemes are studied targeting to reduce the mutual interference when UWB and WiMAX are distributed jointly through standard single-mode fiber (SSMF) without transmission impairments compensation techniques and amplification. Experimental results indicate successful transmission up to 25 km, in SSMF exceeding the range in typical PON deployments. The radio link penalty introduced by optical transmission is also investigated in this paper

Stellar scattering and the origin of the planet around gamma-cephei-A

In the last years several exoplanets have been discovered that orbit one component of a compact binary system (separation < 50 astronomical units), the probably best-known case is gamma-Cephei. So far, all attempts to explain the in-situ formation of these planets has been unsuccessful, in part because of the strong gravitational perturbations of the secondary star on any initial planetesimal swarm. Here we test whether planetary bodies in compact binaries, in particular gamma-Cephei, could have originated from a close encounter with a passing star, assuming initial configurations for the stellar system suitable for planetary formation. In other words, we analyze whether the orbital configuration of the current binary system might have been generated after the formation of the planet, and as a consequence of a close encounter with a third star in hyperbolic orbit. We performed a series of time-reverse N-body simulations of stellar scattering events in which the present-day configuration of gamma-Cephei was used as the initial condition plus a hypothetical third star as an impactor. We analyzed which configurations and system parameters could have given birth to the current system. Depending on the maximum impact velocity allowed for accretional collisions, we find that between 1% and 5% of stellar encounters correspond to an "original" system in which planetary formation around the primary star is not inhibited by the secondary, but is acceptable within the classical core-accretion scenario. Thus, although not highly probable, it is plausible that stellar encounters may have played a significant role in shaping these types of exoplanetary systems.Comment: 9 pages, 6 figures, 3 table

Concrete Swelling in Existing Dams

Several chemical reactions are able to produce swelling of concrete for decades after its initial curing, a problem that affects a considerable number of concrete dams around the world. Principia has had several contracts to study this problem in recent years, which have required reviewing the state-of-the-art, adopting appropriate mathematical descriptions, programming them into user routines in Abaqus, determining model parameters on the basis of some parts of the dams’ monitored histories, ensuring reliability using some other parts, and finally predicting the future evolution of the dams and their safety margins. The paper describes some of the above experience, including the programming of sophisticated non-isotropic swelling models, that must be compatible with cracking and other nonlinearities involved in concrete behaviour. The applications concentrate on two specific cases, an archgravity dam and a double-curvature arch dam, both with a long history of concrete swelling and which, interestingly, entailed different degrees of success in the modelling effort

Integrated performance analysis of UWB wireless optical transmission in FTTH networks

The optical transmission of full standard ECMA_368 OFDM_UWB signals 400 Mbit/s per single user over 50 km SSMF, and the impact of optical transmission in the radio performance experimentally analyzed in this paper

Digital terrain models applied to the C/I ratio determination in frequency reduce design

A tool is developed to plan cellular systems based on the application of theoretical studies of propagation phenomena in urban areas to the real digital terrain models of a city. This permits the design of the cellular structure in an interactive way taking account of the real interference and ambiguity zones. Methods for the reduction of cochannel interference are considered.Peer ReviewedPostprint (published version

Ultra-wideband radio signals distribution in FTTH networks

The use of an ultra-wideband (UWB) radio technique is proposed as a viable solution for the distribution of high-definition audio/video content in fiber-to-the-home (FTTH) networks. The approach suitability is demonstrated by the transmission of standards-based UWB signals at 1.25 Gb/s along different FTTH fiber links with 25 km up to 60 km of standard single-mode fiber length in a laboratory experiment. Experimental results suggest that orthogonal frequency-division-multiplexed UWB signals exhibit better transmission performance in FFTH networks than impulse radio UWB signals

Optical distribution of OFDM and impulse-radio UWB in FTTH networks

Proposal, experimental demonstration and performance comparison of impulse-radio UWB and OFDM UWB distribution in FTTH networks for high-definition audio/video broadcasting is presented. OFDM-UWB exhibits better performance compared with its impulse-radio counterpart with better spectral efficiency

Post-cracking Behabiour of a Wind Turbine Concrete Tower

The paper deals with the dynamic performance of a simply reinforced concrete tower built using prefabricated elements. The main uncertainty of this strategy stems from the possible cracking of the concrete and its implications on the stiffness, natural frequency and dynamic amplification of the tower. In 2006 an 80 m high prototype was built, supporting a 1.5 MW wind generator, carefully instrumented and test loaded to 80% of its design capacity. The prototype and installed instrumentation remained in operation for 3 years. Detailed calculations were carried out of the cracking induced in the concrete and its effects on the natural frequency of the tower, as a function of wind speed and orientation; the results were compared with the monitoring data. It is concluded that numerical modelling with Abaqus allowed good predictions and interpretations of the observed response of the tower. Also, simply reinforced concrete is shown to be a good option for high towers; if the structure is well designed, the natural frequency will not migrate to a point where its proximity to the forcing frequency will lead to unacceptable levels of the dynamic amplification

Integral Bridge for High-Speed Railway

The structural continuity of fully integral bridges entails many advantages and some drawbacks. Among the latter, the cyclic expansions and contractions of the deck caused by seasonal thermal variations impose alternating displacements at the piers and abutments, with effects that may be difficult to establish reliably. The advantages include easier construction and cheaper maintenance but, especially, horizontal loads can be transmitted to the ground in a much better way than in conventional bridges. This paper first presents a methodology for dealing with the problems that the cyclic displacements imposed raise at the abutments and at the bridge piers. At the former, large pressures may develop, possibly accompanied by undesirable surface settlements. At the latter, the degree of cracking and the ability to carry the specified loads may be in question. Having quantified the drawbacks, simplified but realistic analyses are conducted of the response of an integral bridge to braking and seismic loads. It is shown that integral bridges constitute an excellent alternative in the context of the requirements posed by new high-speed railway lines

Changes in UCP mRNA expression levels in brown adipose tissue and skeletal muscle after feeding a high-energy diet and relationships with leptin, glucose and PPARgamma

Brown adipose tissue and skeletal muscle are known to be important sites for nonshivering thermogenesis. In this context, it is accepted that uncoupling proteins (UCPs) are involved in such process, but little is known about the physiological regulation of these proteins as affected by the intake of a high-energy (cafeteria) diet inducing fat deposition. In this study, the UCP messenger RNA (mRNA) expression in interscapular brown adipose tissue (iBAT) and skeletal muscle was assessed to evaluate the influence of a dietary manipulation on energy homeostasis regulation. We report a statistically significant increase in mRNA levels of iBAT UCP1 and UCP3 and a statistical marginal rise in skeletal muscle UCP3 mRNA expression after feeding a high-energy diet, whereas no changes in UCP2 expression were found in either tissue. Furthermore, significant positive associations between iBAT UCP1 and UCP3 mRNA levels with serum leptin were found. Although the expression of the b3 adrenoceptor (b3AR) was about 50% in the lean controls compared with the obese group in iBAT, no statistically significant changes were observed concerning peroxisome proliferator-activated receptor g2 (PPARg2) mRNA levels in muscle or iBAT. We conclude that feeding a diet inducing weight and fat gain produces different outcomes on iBAT and skeletal muscle UCP mRNA expression, revealing a tissue-dependent response for the three UCPs. Results suggest that the regulation of UCP expression in both tissues under these specific dietary conditions may be related to leptin circulating levels