A Closed Loop Delay Compensation Technique to Mitigate the Common Mode Conducted Emissions of Bipolar PWM Switched Circuits

This paper presents the design of a new closed loop technique that reduces the common mode conducted emission. This technique can be applied to all switching circuits in which couples of outputs are modulated by a bipolar PWM signal. It is based on the compensation of the delay between complementary output switching edges, using a simple sensing circuit and a low computational effort software algorithm, which is implemented in a microcontroller driving the switching circuit. One of the main advantages of the proposed technique is the reduction of the disturbance energy, without affecting the system efficiency. The technique is practical to implement, and the measurements performed on a power inverter prototype confirm the theoretical analysis outcomes about the reduction of the conducted emission in the lower-to-medium frequency range

Evaluation of the Common Mode and the Differential Mode Components from Conducted Emission Measurements

The design of the power supply electromagnetic interference filter needed to mitigate the conducted emission of electronic modules can be performed best if the magnitude of the common mode (CM) and that of the differential mode (DM) interference are known. In common test setups, the two terms can be obtained from the signals measured at the line impedance stabilization networks (LISNs) output ports using DM and CM rejection networks or through the postprocessing of the output signals in the time domain. Both these approaches rely on the perfect matching of the LISNs internal filters, which is not realistic. The LISNs mismatch allow the DM to be measured as CM and vice versa. In this work, the influence of the LISNs mismatch on the separation of CM and DM is investigated and a fast and accurate method to do that is proposed

La preparazione degli studenti di Ingegneria e Economia dopo gli esami di matematica di base

The study of mathematics is essential in many fields as it is the basic language shared by all quantitative disciplines. Therefore, it is interesting to ascertain at what extent the basic concepts may be lost over time. We carried out a survey on students attending third-year courses and over, in the Faculty of Engineering and in the Faculty of Economics, administering a test containing items pertaining to elementary concepts of Mathematics. The results showed that students in the Faculty of Engineering had a better grasp of the mathematical concepts than those in the Faculty of Economics. However, considering the differences between the two Faculties, the gap was actually narrower than what the test results would first lead us to believe. The structure of the model representing the influences of the explanatory variables on the outcome of the test (test score) was similar for both Faculties. In particular, the more predictive factors were high school scores and the number of Mathematics exams already passed at the University. The time elapsed since the last Mathematics exam did not show any particular influence on test scores. However, among the Engineering students, the time elapsed demonstrated a weak concurrent action with other variables, \uabincorporating\ubb its influence. The correlation between the time elapsed since the last Mathematics exam and the test score was always negative, as expected

Precise optical timing of PSR J1023+0038, the first millisecond pulsar detected with Aqueye+ in Asiago

We report the first detection of an optical millisecond pulsar with the fast photon counter Aqueye+ in Asiago. This is an independent confirmation of the detection of millisecond pulsations from PSR J1023+0038 obtained with SiFAP at the Telescopio Nazionale Galileo. We observed the transitional millisecond pulsar PSR J1023+0038 with Aqueye+ mounted at the Copernicus telescope in January 2018. Highly significant pulsations were detected. The rotational period is in agreement with the value extrapolated from the X-ray ephemeris, while the time of passage at the ascending node is shifted by $11.55 \pm 0.08$ s from the value predicted using the orbital period from the X-rays. An independent optical timing solution is derived over a baseline of a few days, that has an accuracy of $\sim 0.007$ in pulse phase ($\sim 12$ $\mu$s in time). This level of precision is needed to derive an accurate coherent timing solution for the pulsar and to search for possible phase shifts between the optical and X-ray pulses using future simultaneous X-ray and optical observations.Comment: 6 pages, 4 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Letter

Suitability of 2D modelling to evaluate flow properties in 3D porous media

AbstractThe employment of 2D models to investigate the properties of 3D flows in porous media is ubiquitous in the literature. The limitations of such approaches are often overlooked. Here, we assess to which extent 2D flows in porous media are suitable representations of 3D flows. To this purpose, we compare representative elementary volume (REV) scales obtained by 2D and 3D numerical simulations of flow in porous media. The stationarity of several quantities, namely porosity, permeability, mean and variance of velocity, is evaluated in terms of both classical and innovative statistics. The variance of velocity, strictly connected to the hydrodynamic dispersion, is included in the analysis in order to extend conclusions to transport phenomena. Pore scale flow is simulated by means of a Lattice Boltzmann model. The results from pore scale simulations point out that the 2D approach often leads to inconsistent results, due to the profound difference between 2D and 3D flows through porous media. We employ the error in the evaluation of REV as a quantitative measure for the reliability of a 2D approach. Moreover, we show that the acceptance threshold for a 2D representation to be valid strongly depends on which flow/transport quantity is sought

Investigating the accuracy achievable in reconstructing the angular sizes of stars through stellar intensity interferometry observations

Context: In recent years, stellar intensity interferometry has seen renewed interest from the astronomical community because it can be efficiently applied to Cherenkov telescope arrays. Aims: We have investigated the accuracy that can be achieved in reconstructing stellar sizes by fitting the visibility curve measured on the ground. The large number of expected available astronomical targets, the limited number of nights in a year, and the likely presence of multiple baselines will require careful planning of the observational strategy to maximise the scientific output. Methods: We studied the trend of the error on the estimated angular size, considering the uniform disk model, by varying several parameters related to the observations, such as the total number of measurements, the integration time, the signal-to-noise ratio, and different positions along the baseline. Results: We found that measuring the value of the zero-baseline correlation is essential to obtain the best possible results. Systems that can measure this value directly or for which it is known in advance will have better sensitivity. We also found that to minimise the integration time, it is sufficient to obtain a second measurement at a baseline half-way between 0 and that corresponding to the first zero of the visibility function. This function does not have to be measured at multiple positions. Finally, we obtained some analytical expressions that can be used under specific conditions to determine the accuracy that can be achieved in reconstructing the angular size of a star in advance. This is useful to optimise the observation schedule.Comment: Accepted for publication by Astronomy & Astrophysics (A&A

Electronically ordered ultrathin Cr2O3 on Pt(1 1 1) in presence of a multidomain graphene intralayer

In the last decade, reducing the dimensionality of materials to few atomic layers thickness has allowed exploring new physical properties and functionalities otherwise absent out of the two dimensional limit. In this regime, interfaces and interlayers play a crucial role. Here, we investigate their influence on the electronic properties and structural quality of ultrathin Cr2O3 on Pt(111), in presence of a multidomain graphene intralayer. Specifically, by combining Low-Energy Electron Diffraction, X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy, we confirm the growth of high-quality ultrathin Cr2O3 on bare Pt, with sharp surface reconstructions, proper stoichiometry and good electronic quality. Once a multidomain graphene intralayer is included at the metal/oxide interface, the Cr2O3 maintained its correct stoichiometry and a comparable electronic quality, even at the very first monolayers, despite the partially lost of the morphological long-range order. These results show how ultrathin Cr2O3 films are slightly affected by the interfacial epitaxial quality from the electronic point of view, making them potential candidates for graphene-integrated heterostructures

Spin-down rate of the transitional millisecond pulsar PSR J1023+0038 in the optical band with Aqueye+

We present a timing analysis of the transitional millisecond pulsar PSR J1023+0038 using observations taken between January 2018 and January 2020 with the high time resolution photon counter Aqueye+ mounted at the 1.82 m Copernicus telescope in Asiago. We report the first measurement of the timing solution and the frequency derivative of PSR J1023+0038 based entirely on optical data. The spin-down rate of the pulsar is $(-2.53 \pm 0.04) \times 10^{-15}$ Hz$^2$, which is $\sim$20% slower than that measured from the X-ray observations taken in 2013-2016 and $\sim$5% faster than that measured in the radio band during the rotation-powered state.Comment: 6 pages, 4 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Letter

Application of simulation modeling for wildfire exposure and transmission assessment in Sardinia, Italy

Abstract The development of comprehensive fire management and risk assessment strategies is of prominent concern in Southern Europe, due to the expanding scale of wildfire risk. In this work, we applied simulation modeling to analyze fine-scale (100-m resolution) wildfire exposure and risk transmission in the 24,000 km2 island of Sardinia (Italy). Sardinia contains a variety of ecological, cultural, anthropic and touristic resources that each summer are threatened by wildfires, and represents well the Mediterranean Basin environments and conditions. Wildfire simulations based on the minimum travel time algorithm were used to characterize wildfire exposure and risk transmission in terms of annual burn probability, flame length, structures exposed and type and amount of transmission. We focused on the historical conditions associated with large (>50 ha) and very large (>200 ha) wildfires that occurred in Sardinia in the period 1998–2016, and combined outputs from wildfire simulation modeling with land uses, building footprint locations, weather, and historical ignition data. The outputs were summarized for weather zones, main wind scenarios and land uses. Our study characterized spatial variations in wildfire spread, exposure and risk transmission among and within weather zones and the main winds associated with large events. This work provides a novel quantitative approach to inform wildfire risk management and planning in Mediterranean areas. The proposed methodology can serve as reference for wildfire risk assessment and can be replicated elsewhere. Findings can be used to better understand the spatial dynamics and patterns of wildfire risk and evaluate expected wildfire behavior or transmission potential in Sardinia and neighboring regions