On the uniqueness of limit cycles for Li\'enard equation: the legacy of G. Sansone

We give an account of the results about limit cycle's uniqueness for Li\'enard equations, from Levinson-Smith's one to the most recent ones. We present a new uniqueness theorem in the line of Sansone-Massera's geometrical approach.Comment: 2 figure

Use of ground-truth measurements to monitor ERTS sensor calibration, volume 2

Application of ground-truth data to monitor sensor calibrations for Earth Resources Technology Satellites - Vol.

Limit cycle's uniqueness for a class of planar dynamical systems

A uniqueness theorem for limit cycles of a class of plane differential system is proved. The main result is applicable to secord order O.D.E.'s with dissipative term depending both on the position and the velocity

Filtering Strategies for Relative Navigation in Lunar Scenarios Using LCNS

This paper investigates the performance of the forthcoming lunar navigation satellite systems for estimating not only the position of an onboard receiver in a lunar inertial reference frame but also, and with a consistent accuracy, the relative position between two or more spacecraft in proximity. This could be the case of two spacecraft performing a rendezvous, of a lander released by an orbiter, or the case of the permanent relative navigation service for a formation of satellites around the Moon. The considered observables are the pseudorange and pseudorange-rate measurements provided by the upcoming lunar communication and navigation system (LCNS), expected to support lunar missions. A single-stage Kalman filter is implemented, and its performance is demonstrated through error statistics, which are then compared to what can be achieved with sequential filtering

Sustainable technologies for aircraft energy generation, storage, and distribution

It is estimated that the contribution of the aviation industry to global warming is currently 2-3%. The projected growth of the industry may increase this to 10-20% by 2050. As such, the aim of this research is to explore how proposed aircraft energy generation, storage, and distribution technologies can improve sustainability in the aviation industry. The primary research question addressed by this work is: What are the current technological trends in aircraft energy generation, storage, and distribution and how much will these technologies help reduce the aviation industries contribution to climate change? An explanatory case study methodology was utilised in this research. A number of research tools were used, specifically document analysis, trend analysis, and technology forecasting methods. The technological developments were identified with a preliminary document analysis. The trend analysis identified which technologies were of importance in terms of the historical development and technology effectiveness. A number of trends were identified in aircraft technologies for energy generation, storage and distribution to improve sustainability. The primary consideration identified was energy storage. That is, energy generation and distribution technologies are a significant facet of future more electric aircraft, and even all-electric aircraft. However, the key enabling technology is the storage of energy, specifically the energy densities in terms of either battery capacity, or hydrogen storage (for use with fuel cells). Aircraft energy generation, storage, and distribution technologies are a single facet of the airframe and avionic systems for greener aircraft; the contributions from other facets maybe more significant, specifically in terms of fuels and engines

A sustainable approach to airport design and operations: Case study of Munich airport

The aim of this research is to empirically examine the sustainable aspects of airport design and operations, in the context of Munich Airport, one of the world's major airports. The primary research question addressed by this work is: What aspects of airport design and operation in a major airport are critical to its sustainability and mitigating its contributions to climate change? An exploratory single site case study methodology was utilised and the research concentrated on Munich Airport, Germany's second busiest airport, located in Bavaria, in south east Germany. The primary business of the airport is commercial and general aviation services. Air cargo, catering and retail, and real estate are other important strategic market segments. Data was gathered from the Flughafen M nchen GmbH annual sustainability reports and company websites. Finally, the data was analysed using content analysis. All major aspects of airports infrastructure design and operations were explored, focussing on the environmental impacts. This included water usage and management, energy consumption, waste management, and other key aspects of pollution, including noise. In the case of Munich Airport, the most significant environmental impact factors identified were aircraft emissions and noise, waste, and water management. The significance of sustainable operations in the global aviation industry is, of course, relevant to airports. Since the commencement of operations in 1992, Munich Airport's strategic objectives have incorporated key sustainability focus areas. Indeed, the airport's strategy is essentially sustainability-driven. The airport has implemented systems and procedures to optimise its environmental footprint, and to ensure its compliance with all applicable statutory requirements

First ALMA Maps of Cosmic-Ray Ionization Rate in High-mass Star-forming Regions

Low-energy cosmic rays (<1 TeV) are a pivotal source of ionization of the interstellar medium, where they play a central role in determining the gas chemical composition and drastically influence the formation of stars and planets. Over the past few decades, H3 + absorption line observations in diffuse clouds have provided reliable estimates of the cosmic-ray ionization rate relative to H2 ( ζionH2 ζ H 2 i o n ). However, in denser clouds, where stars and planets form, this method is often inefficient due to the lack of H3 + rotational transitions. The ζionH2 ζ H 2 i o n estimates are, therefore, still provisional in this context and represent one of the least understood components when it comes to defining general models of star and planet formation. In this Letter, we present the first high-resolution maps of the ζionH2 ζ H 2 i o n in two high-mass clumps obtained with a new analytical approach recently proposed to estimate the ζionH2 ζ H 2 i o n in the densest regions of molecular clouds. We obtain ⟨ζionH2⟩ ⟨ ζ H 2 i o n ⟩ that span from 3 × 10-17 to 10-16 s-1, depending on the different distribution of the main ion carriers, in excellent agreement with the most recent cosmic-ray propagation models. The cores belonging to the same parental clump show comparable ζionH2 ζ H 2 i o n , suggesting that the ionization properties of prestellar regions are determined by global rather than local effects. These results provide important information for the chemical and physical modeling of star-forming regions

Unveiling the inner morphology and gas kinematics of NGC 5135 with ALMA

The local Seyfert 2 galaxy NGC5135, thanks to its almost face-on appearance, a bulge overdensity of stars, the presence of a large-scale bar, an AGN and a Supernova Remnant, is an excellent target to investigate the dynamics of inflows, outflows, star formation and AGN feedback. Here we present a reconstruction of the gas morphology and kinematics in the inner regions of this galaxy, based on the analysis of Atacama Large Millimeter Array (ALMA) archival data. To our purpose, we combine the available $\sim$100 pc resolution ALMA 1.3 and 0.45 mm observations of dust continuum emission, the spectroscopic maps of two transitions of the CO molecule (tracer of molecular mass in star forming and nuclear regions), and of the CS molecule (tracer of the dense star forming regions) with the outcome of the SED decomposition. By applying the $^{\rm 3D}$BAROLO software (3D-Based Analysis of Rotating Object via Line Observations), we have been able to fit the galaxy rotation curves reconstructing a 3D tilted-ring model of the disk. Most of the observed emitting features are described by our kinematic model. We also attempt an interpretation for the emission in few regions that the axisymmetric model fails to reproduce. The most relevant of these is a region at the northern edge of the inner bar, where multiple velocity components overlap, as a possible consequence of the expansion of a super-bubble.Comment: 15 pages, 13 figures, resubmitted to MNRAS after moderate revision