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In this study, we exploit the advantages of non-ergodic modelling of the ground motion to map the regional characteristics of source and propagation effects in Italy. In particular, we focused on the study of source and propagation effects obtained from the decomposition of the total residuals, i.e. the logarithmic difference of ITACAext observations and the model predictions, for active crustal earthquakes in Italy. The spatial trends, obtained from interpolating the residuals, clearly showed areas where the motion was significantly different from that predicted by the reference model, and in particular was underestimated. This is the case, for example, for many events with epicentres in northern Italy and the southern Ionian Sea. In addition, the study shows that paths across the Po Valley and the Adriatic coast are characterised by slower attenuation compared to that observed in the central Apennines. In addition, a marked difference between attenuation in the volcanic domain of Etna and the Hyblaean Mountains is clearly observed. [ABSTRACT FROM AUTHOR]

We theoretically investigate the spatial-non-homogeneous laser pulse propagation through the quantum well. It is shown that the odd-order and even-order harmonic generations can be found due to breaking the inversion symmetry of the system. Importantly, the spectral intensity of high-order harmonics can be enhanced by changing the propagation distances and spatial-non-homogeneity of incident laser field. Moreover, the quantum well's shape has an important influence on the peak intensities of high-order harmonic generations, which may provide a new way to improve the spectral intensity of high-order harmonic generations. [ABSTRACT FROM AUTHOR]

This paper concentrates on harmonic analysis in gaseous helium, including microscopic generation, selective filtration and macroscopic propagation. A coherent method is proposed, with time-dependent Schrödinger equation for harmonic generation and Maxwell's wave equation for harmonic propagation. By introducing the polarization source based on the microscopic single-atom response, the macroscopic nonlinear propagation can be efficiently solved by a set of linear equations at each harmonic frequency. Using the proposed method, we numerically investigate the propagation effects of selective harmonics in gaseous helium. Our results reveal that specific harmonics allow the synthesis of an isolated attosecond pulse, which presents a high beam quality and an excellent spatial profile with Gaussian-like distribution. Moreover, the generated pulse provides a promising potential on high power defense, quantum radar and communication.

Frequency offset transmit reference (FoTR)—a noncoherent spread spectrum technique—is considered in dense multipath fading environments, in the context of wideband communication. The interplay between system parameters and propagation effects is investigated. Analytical relations between key design parameters and the channel delay spread are derived, which provide a framework for determining reasonable system parameters that optimize the performance. An approximated closed-form expression for the outage probability is also obtained, which is shown to be fairly accurate for low outage probabilities. It is shown that FoTR suffers significantly from noise-enhancement, but, is nonetheless, robust against frequency-selective fading. A large value of frequency offset can significantly deteriorate the performance, particularly in environments with large channel delay spreads. This restricts the maximum data rate as well as the multiple-access capability of the scheme. Despite the limitations, FoTR can be a useful communication scheme for low data rate sensor networks deployed in dense multipath environments, particularly where the design demands a simple receiver and a low outage probability. [ABSTRACT FROM AUTHOR]

A three-dimensional non-adiabatic model in combination with a rate equation model is used to characterize high-intensity (>10 16 W/cm 2 ) femtosecond laser pulse propagation in atomic gas medium. In these conditions the atoms in the target gas will become multiply charged ions, while the laser pulse will propagate in a medium with high electron concentration created by itself. We obtain pulse characteristics in time, frequency and space domain for two representative cases: 800 nm and 267 nm (third harmonic) multi-cycle pulses which are both of practical importance. We show that the spatial-temporal variation of the refractive index in the macroscopic medium is the primary reason for pulse temporal/spectral and spatial shaping during propagation. [ABSTRACT FROM AUTHOR]

Propagation effects on the narrow bipolar pulses (NBPs) or the radiation fields generated by compact cloud discharges as they propagate over finitely conducting ground are presented. The results were obtained using a sample of NBPs recorded with high time resolution from close thunderstorms in Sri Lanka. The results show that the peak amplitude and the temporal features such as the full width at half maximum (FWHM), zero-crossing time, and the time derivative of NBPs can be significantly distorted by propagation effects. For this reason, the study of peak amplitudes and temporal features of NBPs and the remote sensing of current parameters of compact cloud discharges should be conducted using NBPs recorded under conditions where the propagation effects are minimal.

The main objective of this work is to provide two zonations of Italy useful to incorporate regional source and path effects in empirical Ground Motion Models (GMMs). To this end, we revise existing zonations developed for seismic and tsunami hazard studies, based on the results of a residual analysis between the observations of the ITACAext dataset and the predictions of ITA18, a GMM recently developed for Italy. The analysis consists in the decomposition of the residuals into repeatable terms, according to the well-established approach used for the calibration of non-ergodic models. Based on the spatial trend of the interpolated residuals, and geological and seismological considerations, the zonations are proposed and discussed, in the perspective of supporting regionalization of a future generation of GMMs for Italy. • The goal is to provide the tools to regionalize seismic motion in Italy. • Zonation for source effects is based on spatial variability of the event residuals. • Zonation for propagation effects is based on spatial variability of random residuals. [ABSTRACT FROM AUTHOR]

The propagation of an initially chirped incident few-cycle pulse through an ensemble of quantum wells is numerically investigated. It is found that the distribution characteristic of the transmitted spectrum sensitively depends on the incident laser parameters, especially its positive or negative chirp property. As for the incident pulse with a positive initial chirp, beyond the obvious spectral blue-shift, the transmitted spectral distribution is discrete. In contrast, as for a negative initial chirp, the spectral distribution is continuous instead. In addition, the insensitivity of chirp-dependent spectral distribution to medium symmetry character is also tested and the intensity of high-frequency spectral components enhances obviously due to the nonlinear propagation effects. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Capital Institute of Physical Education is the property of Shoudu Tiyu Xueyuan and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effect of the rotor–stator axial-gap on tonal noise generated by an axial-flow fan employed for automotive cooling systems has been studied. A fan equipped with a 9 blade rotor and a 18 vane stator positioned at several axial-gaps has been tested in a hemi-anechoic chamber. The acoustic measurements have been performed during rotational speed ramps. To analyze the experimental data, the propagation function, obtained by means of the spectral decomposition, has been compared with the velocity-scaled SPL and the phase angle, evaluated at the 1st and 2nd blade passing frequency harmonics. Opposite to what is commonly observed, the SPL due to the rotor–stator aerodynamic interaction does not monotonically decrease with the axial-gap and at the shortest gaps it may not be scaled with a single power of the rotational speed. The listed quantities have been plotted versus frequency, rotational speed, and axial-gap. Their analysis provides a detailed picture of the investigated phenomena and supports the assumption that the observed behavior is due to acoustic effects and not to the aerodynamic noise generating mechanism. [ABSTRACT FROM AUTHOR]

Detecting visual relationships among construction resources plays a pivotal role in understanding complex construction scenes and performing vision-based site monitoring and digitalization. Despite extensive efforts, the propagation effects of different resource-to-resource interactions were overlooked and thus, it is still challenging to precisely detect entangled and intertwined visual relationships from actual construction images. To address the challenge, this study proposes a semantic graph neural network approach that structuralizes construction resources and their entangled interactions in the form of a graph, and simulates the propagation effects using a neural message passing mechanism. The experimental results showed that the proposed approach achieved 77.1% F-score—11.5% higher than the performance of the baseline model. This suggests the positive impacts of the propagation effects and the applicability of the proposed approach. These findings can help understand what are actually happening at construction sites automatically and provide valuable insights for future vision-based monitoring studies. • The approach detected object-to-object visual relationships with 77.1% F-score. • Propagations effects among different object-to-object interactions were modeled. • The performance was improved by 11.5% compared to the baseline model. • Feasibility of graph neural networks was demonstrated with quantitative results. [ABSTRACT FROM AUTHOR]

This paper presents an electromagnetic (EM) technique for the reconstruction of the physical and geometrical properties (permittivity and thickness) of stratified media. The key points of the approach, belonging to the so-called layer stripping algorithms, are the introduction of an equalization step that takes into account propagation effects, and the design of a procedure devoted to multiple reflections' removal. Furthermore, the proposed main processing block is an energy-based method able to accurately estimate amplitudes and time of delays of backscattered echoes in the time domain. A numerical analysis of the algorithm's potentialities will show that it can be successfully employed under different working conditions and in the presence of noisy data. [ABSTRACT FROM PUBLISHER]

Abstract: Eucalyptus globulus is widely planted in temperate regions of the world for pulpwood production and there are breeding programs in many countries. While breeding and deployment programs in Australia mainly use seedlings, in countries such as Chile, Portugal and Spain, a combination of seedlings and clones are used for genetic testing and plantation establishment. In the present study, we compared clones and seedlings produced from the same twenty open-pollinated families of the Jeeralang provenance of E. globulus, and randomised within the same field trial established in NW Tasmania. We specifically aimed to test whether mean performance, variance components, genetic parameters and breeding values estimated from the two propagule types were comparable. We studied the susceptibility of the juvenile foliage to leaf disease caused by Teratosphaeria nubilosa, the height at which the transition to the adult foliage occurred, as well as growth at selection and harvest ages. While the clones exhibited less disease damage, switched to the adult foliage at a slightly lower height and had less height and diameter growth than the seedlings, no significant differences in estimates of additive genetic variances and narrow-sense heritabilities between the two propagule types were detected. The additive genetic correlations estimated between the clonal and seedling populations did not differ significantly from one. The propagule type also had little effect on estimates of genetic correlations between traits. Thus, our results argue that while differences in trait means need to be taken into account, the propagation method is unlikely to affect the genetic architecture and predictions of breeding value in this species. [Copyright &y& Elsevier]

This paper considers weather radar measurements at linear depolarization ratio (LDR) mode, consisting of transmission of horizontal polarization and simultaneous reception of the copolar (horizontal) and cross-polar (vertical) components of the returned wave. Such a system yields the coherency matrix, with four degrees of freedom. After a theoretical analysis of its structure and symmetries, we focus on three cross-polarization variables: LDR, cross-polar correlation coefficient at horizontal transmit (ρxh) , and degree of polarization at horizontal transmit (pH). The different properties of these variables with respect to backscattering and propagation are analyzed, together with the bias induced by antenna cross-channel coupling. It is demonstrated that the degree of polarization at horizontal transmit possesses attractive properties in terms of robustness to propagation effects and antenna cross-channel coupling. [ABSTRACT FROM AUTHOR]

The effects of finitely conducting ground on the signature of lightning-generated magnetic fields at ground level were evaluated by numerical solution of Sommerfeld's integrals. Results are presented for distances between 10 m to 1 km from the lightning channel and for ground conductivities in the range of 0.01 and 0.0001 S/m. The results obtained from the exact theory are compared with the predictions of two frequently used analytical approximations to Sommerfeld's equations. Based on that comparison, the limits of validity of these approximate theories are obtained. [ABSTRACT FROM AUTHOR]

The effect of finitely conducting ground on the signature of lightning generated vertical electric fields at ground level was evaluated by numerical solution of Sommerfeld's integrals. Results are presented for distances between 10 m to 1 km from the lightning channel and for ground conductivities in the range of 0.01 and 0.001 S/m. The results obtained from the exact theory are compared with the predictions of several approximate theories available in the literature. Based on that comparison the limits of validity of these approximate theories are obtained. [ABSTRACT FROM PUBLISHER]

Abstract: As the electromagnetic fields propagate over finitely conducting ground, selective attenuation of the high frequencies takes place. As a result, the signatures of broad-band electromagnetic radiation fields generated by lightning flashes change as they propagate over such ground. In addition to being a function of the electrical parameters of the ground over which the electromagnetic fields propagate, these propagation effects depend on the height of their source above ground level. This makes the propagation effects on radiation fields from cloud flashes differ from those on the radiation fields generated by return strokes in ground flashes. In this paper the propagation effects on radiation field pulses of cloud flashes are illustrated and it is shown that these effects are not as severe as those of return strokes in ground flashes. [Copyright &y& Elsevier]

Abstract: The effects of propagation over finitely conducting ground on the features of radiation component of the electric field time derivatives are investigated. The results show that the peak, the half-width and the risetime of the electric field time derivative change significantly in propagating over finitely conducting ground. Furthermore, any correlation that may exist between various parameters could also change significantly due to propagation effects. Consequently, in return stroke model validations using experimentally measured fields, remote sensing of return stroke current time derivatives using measured electric field time derivatives and in the calculation of induced voltages generated by lightning flashes in electrical installations the distortions caused by propagation effects on the electric field time derivatives cannot be neglected. [Copyright &y& Elsevier]

Abstract: As the GPR pulse propagates in the geologic medium, it suffers attenuation as the result of absorption and dispersion, besides spherical divergence. High frequency components of the pulse suffer more pronounced effects of attenuation than low frequency components resulting in resolution loss in radargrams. The quality of the GPR images is then strongly dependent on an adequate correction of the attenuation effects. We present a practical approach to approximately correct the attenuation effects based on their influence on the amplitude and phase spectra of GPR signals. The key point of this approach is the fact that in low and moderate losses dielectric media the propagated signal suffers significant changes only in its amplitude spectrum; that is, the phase spectrum of the propagated signal remains practically unaltered for the usual travel time ranges. Based on this fact, we show using real data (both CMP and radargram) that the judicious application of the well known tools of time gain and spectral balancing can efficiently correct the attenuation effects, from the practical point of view. The proposed approach can be applied in heterogeneous media and it does not demand the precise knowledge of the attenuation parameters of the media. This approach should be understood as part of an interpretative data processing, which can be done by using the interpreter''s knowledge on the studied area and even during the fieldwork. As an additional benefit, the judicious application of spectral balancing promotes a partial deconvolution of the data without changing its phase. In this way, the spectral balancing acts in a similar way to a zero phase deconvolution. Usually, in GPR data, the resolution increase obtained with spectral balancing is greater than those obtained with spike and predictive deconvolutions. [Copyright &y& Elsevier]

We perform spectrally resolved degenerate four wave mixing (DFWM) measurements by resonantly exciting 1s heavy hole excitons in 8 and 17.5 nm wide GaAs multiple quantum wells (MQW) with subpicosecond laser pulses. The signal is detected in a self-diffraction mode in backward geometry. The DFWM spectra reveal a multiple peak structure, evolving into a double peak for positive delays. This may be related to the propagation effects in MQWs due to strong photon–exciton coupling. The different peaks in the DFWM spectra show a dissimilar dependence on pulse excitation intensity, delay and polarization. [Copyright &y& Elsevier]

The electric fields generated by lightning flashes striking the North sea were measured, with a time resolution better than a few tens of nanoseconds, at Fanö island in Denmark. The measuring station was located a few tens of meters away from the high water mark at the west coast of the island. This particular location made it possible to capture, with minimal propagation effects, the electromagnetic fields from lightning flashes striking the North Sea. The waveforms were recorded by a measuring system that could provide a time resolution of about 10 ns. The data recorded had the following features. The initial rising part of the positive return-stroke fields contains a slow front followed by a fast transition. The duration of the slow front of the positive return-stroke fields had an average of 8.3 μs and its amplitude, measured as a fraction of the initial peak, had an average of 0.61. The 10%-90% rise time of the fast rising portion of the positive return-stroke fields was about 0.26 μs, on average. The average peak value of the measured radiation fields normalized to 100 km was 15.7 V/m. The mean of the peak value of the time derivative of the radiation fields was 25 V/m/μs. The full width at half maximum of the radiation field derivative had a mean of 170 ns. [ABSTRACT FROM AUTHOR]

The move to provide direct to home (DTH) multi-media services from satellites requires a number of new insights to be gleaned from the propagation effects that occur along satellite-to-ground paths. Annual statistics will not be sufficient to describe the likely performance of the link, nor will they provide information on the likely customer acceptance of the DTH service. What are required are the likely number of outages due to rain attenuation in a given period, their duration, the time between the outages, and the diurnal characteristics of rain attenuation along the link. This paper presents results obtained in three, two-year, Ku-band experiments in tropical Africa on diurnal attenuation effects, as well as on rain and attenuation event duration and inter-event duration. The implications of the results are discussed. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A strong pump-power dependence of the four-wave mixing (FWM) signal for an aqueous solution of Malachite green is reported. The characteristics of the pump-power dependence of the nonlinear signal are reproduced by a theoretical model based on the coupling between pump-probe, considering signal fields and propagation effects. The effect of the intramolecular coupling on the nonlinear intensity of the FWM signal is studied using a model molecule consisting of two-coupled harmonic curves of electronic energies with minima displaced in energy and nuclear positions. Two-vibrational states are considered while including non-adiabatic effects for the two-state model. Moreover, the coupling among the field components, as well as the propagation effects, are studied by considering a constant pump-intensity. Our calculation scheme, considering both the intramolecular coupling effects in the description of the molecular structure and the effects produced by the propagation of the FWM signal along the optical length, allows the exponential dependence of the latter, as the intensity of the pumping beam increases. Our treatments do not require the inclusion of other non-resonant processes outside the RWA approximation, due to the consideration of an adiabatic basis. [ABSTRACT FROM AUTHOR]

• Compensation of the propagation effects for enhancement of the EUV harmonics yield. • Role of the band structure on the harmonics spectrum control. • Various control schemes of HHG spectra in MgO, sapphire, and quartz. • Optimization of anisotropic HHG for yield enhancement by an order of magnitude. High harmonic generation (HHG) from solids offers a convenient means of producing coherent extreme ultraviolet (EUV) radiation. However, the achievable harmonic yield is greatly affected by propagation effects that the driving laser pulse experiences with spatiotemporal distortion when passing through solids. Here, we intend to optimize EUV harmonics generated from crystals by pre-shaping the driving laser pulse via spectral phase modulation through a genetic algorithm. Our experimental results obtained from MgO, sapphire and quartz crystals demonstrate EUV yield improvements, without increasing the incident laser fluence, up to an order of magnitude along with cut-off extension and selective harmonic enhancement. As a practical tool of compensating laser propagation effects, our method is expected to facilitate solid-based HHG applications such as high-energy photon spectroscopy and multi-petahertz signal processing. [ABSTRACT FROM AUTHOR]

This paper provides estimates of the frequency of occurrence, duration and probability of satellite EHF communication outages due to attenuation by rain. These can be used to determine optimum frequencies, power levels and the need for space diversity of terminals or other alternatives to maintain reliable communications. Ten years of 1 min rain rates at each of 12 U.S. cities were used in conjunction with an attenuation model to quantify communication outages at locations representing a variety of climatic regimes. Analyses of the 1 min rain rates and outage estimates at 10, 30 and 45 GHz for elevation angles of 10°, 30°, 50° and 70° are presented. [ABSTRACT FROM AUTHOR]

A method for the evaluation of seismic hazard in a given zone, taking into account both the spreading of macroseismic effects and seismic catalogue information, is applied. A data-bank of some 500 digitized isoseisms of earthquakes having occurred in Italy between 1542 and 1986 is used. The isoseismical maps are digitized considering for each degree of intensity the length of 24 spreading rays starting from the macroseismic epicenter or barycentre of the megaseismic area. These rays are separated from each other by the same angle, i.e. every isoseism is divided into 24 equal circular sectors. The year 1542 is taken as the beginning of the time span, since this is when the first seismic event occurred for which reliable isoseismal maps are available. The epicentral intensities considered lie between the VI and XI degrees of the Mercalli-Cancani-Sieberg scale (MCS). This digitized data-bank is analyzed to achieve, for each homogeneous seismogenetic zone that has been recognized, the mean azimuthal spreadings of effects for each degree of intensity as a function of the epicentral intensity. Once a mean propagation model is obtained for each zone, this is applied to seismic events of the same zone, the isoseismal maps of which are not available. A geographic grid is defined to cover the analyzed area, and for each cell of this grid it is then possible to count the number of felt events and their degree. These effects have been evaluated either on the basis of the isoseismal maps (when available) or on the basis of the mean propagations of the zone in which the single event occurred. Moreover, an index summarizing the seismic information was computed for each cell of the previous grid. All the events producing effects and their provenance are stored on files, allowing the main seismogenic zones influencing this cell to be identified. This methodology has been applied to central and southern Italy in an area between the latitudes 40.6 and 43.3 N. In particular, attention is focussed on the sample areas of Rome (given the historical and political importance of the city) and of the Sannio-Matese and Irpinia zone (in which some of the strongest earthquakes of the Apennine chain have occurred). Finally, in order to evaluate the maximum expected magnitude, extreme value statistics (Gumbel III-type) are applied to the Colli Albani area, which represents the seismogenic zone nearest to Rome. For the Sannio-Matese and Irpinia area, considering the more dangerous zone as a 'unicum', the Weibull distribution has been hypothesized to determine the mean return time for events with an intensity greater than or equal to IX. [ABSTRACT FROM AUTHOR]

The spatial and temporal dependence of population dynamics caused by ultrafast π laser pulses are studied by Maxwell-Bloch equations in terahertz quantum cascade lasers with and without propagation effects. It is shown that the presence of propagation effects could decrease the flopping of population inversion and affect the oscillation intensity in recovery process. Due to the modification of total macroscopic nonlinear polarization and many-body items, local field varies not only with electron doping concentration but also with period position, which also reflected in the evolution of population dynamics. • The Maxwell-Bloch approach is proposed to research the ultrafast population dynamics in terahertz quantum cascade lasers. • With the varying of doping concentration, population dynamics shows strong temporal-spatial dependence. • The causation of the behavior is analyzed by the evolution of the electric field. [ABSTRACT FROM AUTHOR]

Propagation effects on the narrow bipolar pulses (NBPs) or the radiation fields generated by compact cloud discharges as they propagate over finitely conducting ground are presented. The results were obtained using a sample of NBPs recorded with high time resolution from close thunderstorms in Sri Lanka. The results show that the peak amplitude and the temporal features such as the full width at half maximum (FWHM), zero-crossing time, and the time derivative of NBPs can be significantly distorted by propagation effects. For this reason, the study of peak amplitudes and temporal features of NBPs and the remote sensing of current parameters of compact cloud discharges should be conducted using NBPs recorded under conditions where the propagation effects are minimal. [ABSTRACT FROM AUTHOR]