G. Borgioli

Wigner Approach to the Two-Band Kane Model for a Tunneling Diode

Abstract In this article we study a simple model for describing the electron behavior in a heterogeneous material characterized by two energy bands. The model, the so-called Kane system, is composed of two Schrödinger-like equations coupled by a k · P term which describes the interband tunneling. We give a physical justification of the Kane system and reformulate it in terms of Wigner functions. The well-posedness of the corresponding Wigner system is investigated in a suitable Hilbert space.

Respiratory rate assessments using a dual-accelerometer device.

Monitoring of respiration-related thoracic movements may be useful to assess respiratory rate (RR) objectively. RR was measured during spontaneous breathing, voluntarily modified breathing, and exercise hyperpnoea in normal subjects via visual inspection, spirometry and a pair of accelerometers positioned on the torso. Spirometric and accelerometric values of RR recorded during relaxed breathing were (mean±SD) 21.44±1.41bpm and 21.06±2.17bpm; during voluntarily augmented breathing, these values rose to 29.44±4.61bpm and 29.23±5.33bpm, respectively; spirometric and accelerometric RR values did not differ in any of the cases. RR assessment was unaffected by recumbence. During handgrip, spirometric (16.43±3.10bpm) and accelerometeric (16.22±2.76bpm) control RR values did not differ and increased to comparable levels (24.22±7.30 and 24.82±5.45bpm, respectively) by the end of exercise. At rest, visual (18.94±3.45bpm) and accelerometric (19.27±3.83bpm) RR values were compliant in normal subjects as well as in scoliotic and obese patients. Accelerometers are a reliable tool for monitoring RR, during both eupnoea and stressed breathing.

Semigroup properties of the streaming operator with multiplying boundary conditions

Abstract We study the one-dimensional streaming operator in a slab domain with boundary conditions of Maxwell type. By using techniques of the theory of semigroups of linear operators in a L1 space context, we prove that the streaming operator is the infinitesimal generator of a strongly continuos semigroup, even if the boundary is “particle multiplying”. This semigroup is positive, quasi-bounded and obviously not contractive.

Semigroup generation properties of the streaming operator in dependence of the boundary conditions

Abstract We study the one-dimensional free streaming operator in a slab domain with general boundary conditions described by a linear positive operator Λ. Under the assumptions that Λ−1 exists and is positive and the free streaming operator TΛ is resolvent positive, we prove that TΛ is the infinitesimal generator of a positive strongly continuous semigroup, which is contractive if ∥ Λ ∥ ≤ 1 and quasi-bounded if ∥ Λ > 1 and ∥ Λ−1 ≤ ∥ 1. We give also the mathematical definition of dissipative, conservative and multiplying boundary walls in terms of Λ, and we show how these properties of the boundary walls can affect the type of the semigroup generated by TΛ.

On the Initial-Value Problem to the Quantum Dual BBGKY Hierarchy

We develop a rigorous formalism for the description of the evolution of observables in quantum systems of particles. We construct a solution of the initial-value problem to the quantum dual BBGKY hierarchy of equations as an expansion over particle clusters whose evolution are governed by the corresponding-order dual cumulant (dual semi-invariant) of the evolution operators of finitely many particles. For initial data from the space of sequences of bounded operators the existence and uniqueness theorem is proved.

Acoustoseismic Method for Buried-Object Detection by Means of Surface-Acceleration Measurements and Audio Facilities

An experimental setup for acoustoseismic detection of shallow buried objects is presented. The seismic (Rayleigh) waves were generated by exciting an acoustic airborne source by a series of sine-wave bursts, which were designed to cover a frequency range (100-1000 Hz) large enough to distinguish the vibrational characteristics of buried compliant objects. The signals were recorded by means of contact-acceleration microelectromechanical-system sensors moved above different buried objects (compliant and rigid). Signal acquisitions on only sandy soil revealed the natural variability of the outdoor test bed. This variability of soil parameters pointed out the difficulties of buried-object detection based on the amplitude thresholding of the signal spectrum. For this aim, the signals were processed in both time and frequency domains. An audio-channel output was devised to avail of the human hearing apparatus in distinguishing the buried objects according to spatial variations of the acceleration signals obtained by scanning the soil surface.

Silicon micromachined accelerometers for the detection of compliant anti-personnel landmines

Acoustic methods have been recently investigated for the detection of shallow landmines. Some plastic landmines have a compliant case which can made to vibrate by an airborne excitation like a loudspeaker. Our study is based on the possibility to detect landmines by contact or non-contact sensors like accelerometers or phonometers. Phonometers can provide sufficient seismic sensitivity but their response is influenced by direct acoustic wave coupling from the driving source. On the contrary accelerometers are much less influenced by the direct acoustic wave coupling and they have high sensitivity to acquire soil surface vibrations. In our experiments we can measure typical accelerations in order of 2 m/s2 with sensitivity of 800 mV/g. The acceleration signal elaboration and visualization developed in this work demonstrates the suitability of these sensors for acoustic landmine detection study and allows a fast analysis to evaluate the presence of a buried landmine.

Theoretical and experimental analysis of an equivalent circuit model for the investigation of shallow landmines with acoustic methods

Acoustic methods have been recently investigated for the detection of shallow landmines. Some plastic landmines have a flexible case which can made to vibrate by an airborne excitation like a loudspeaker. The soil-mine system shows a resonant behavior which is used as a signature to discriminate from other rigid objects. The mechanical resonance can be detected at the soil surface by a remote sensing systems like a laser interferometer. An equivalent physical model of the mine-soil system has been investigated having the known physical characteristics of mine simulants. The authors designed and built a test-object with known mechanical characteristics (mass, elasticity, damping factor). The model has been characterized in laboratory and the results compared with the classic mass-spring loss oscillator described by Voigt. The vibrations at the soil surface have been measured in various positions with a micro machined accelerometer. The results of the simulations for the acceleration of the soil-mine system agree well with the experiment. The calibrated mine model is useful to investigate the variation of the resonance frequency for various buried depths and to compare the results for different soils in different environmental conditions.

A Single Display for RASCAN 5-frequency 2-polarisation Holographic Radar Scans

The RASCAN holographic radar system has been developed by the Remote Sensing Laboratory of Bauman Moscow Technical University. The present design uses flve frequencies and two polarisations to give 10 distinct images of scan from buried objects. Because of the sinusoidal phase variation of the interference signals, all displays show a complex picture of dark and light phases which vary in a complicated way between difierent frequencies and polarizations. This is a preliminary investigation into the optimal presentation of the 10 images as a single composite image. The objective is to display as much as possible of the information present in the original image. The solution presented here is to sum the absolute values of the background-corrected amplitude over both the flve frequencies and the two polarizations. The method is justifled using an experiment in which nine US pennies, and 9 metal washers, were buried in sand at increasing depths in the range 0 to 56mm. The method is illustrated by example images from the flelds of civil engineering and mine detection.

Criticality transport problems for spherical systems with specular type boundary conditions

The existence and simplicity are proved for the critical eigenvalue of aspherical system with specularly reflection boundary condi-tions, starting from the one-dimensional integral form of the prob...