[en] The reflection of electromagnetic plane waves incident obliquely upon a semibounded, maxwellian plasma is investigated based on the kinetic theory. The perturbed velocity distribution function is assumed to satisfy the boundary condition of a diffuse scattering at the surface of the plasma. The numerical results of the reflection coefficients are presented for both cases of incidence of TM and TE waves. It is shown that as the temperature of plasma increases, the reflected energy from the diffuse scattering boundary is significantly reduced, especially within the frequency range of usual total reflection. This phenomenon is discussed at some length and is brought out to be closely related to a collisionless energy absorption by the surface charges which couple resonantly to the incident wave. 12 references

No abstract available

[en] The decay instability of a high-frequency surface plasma wave and a low-frequency ion acoustic surface wave, which arises when an intense electromagnetic plane wave is incident perpendicularly on an unmagnetized semi-infinite plasma from a vacuum, is investigated on the basis of two-fluid hydrodynamics for warm electrons and cold ions. The growth rate for the instability and the threshold amplitude of the incident wave are determined. The growth rate is compared numerically with that for a similar decay instability of the corresponding volume-wave modes. In contrast to the ''volume'' decay instability, the present one gives an appreciable growth rate even if the frequency of the incident wave is lower than the electron plasma frequency

[en] The characteristics of an electromagnetic surface wave interacting with a semi-infinite single stream of a cold collisionless plasma are investigated by taking the plasma as a moving deformable polarized medium. The surface-wave dispersion equation shows the coupling of four waves, which are, approximately, the fast and slow space-charge waves in the plasma stream and the two waves in the free space whose phases progress in the same and opposite directions to the plasma stream. Compared to the analysis which has regarded the plasma stream as an equivalently stationary anisotropic plasma, the surface waves show drastically different characteristics. It is shown that there are no instabilities of the surface waves for any drift velocity of the plasma

[en] Turmeric finger as one of the most popular spices has been widely used for food manufacturing. However, it has also been a major cause of bacterial infestation of food materials especially in curry, ham and sausage manufacturing. In this study decontamination of bacteria in turmeric finger by electron beam irradiation was evaluated by comparing with several other decontamination methods: i.e., boiling, microwave irradiation, treatment by twin screw extruder and gamma-ray irradiation. By estimation of colony counting on nutrient agar plate, turmeric finger without any treatment gave total viable cell at 10⁸/g. Turmeric finger which was irradiated by electron beam at 10kGy dose dramatically reduced thermotolerant cell population below self restriction level (<1000/g), which has been required by food hygiene law. The same level of sterilization effect was obtained only by gamma-ray irradiation at 10kGy and 20kGy. On the other hand, although treatment through twin screw extruder slightly reduced bacterial numbers, neither boiling nor microwave irradiation gave sufficient decontamination effect on turmeric fingers

[en] The parametric decay instability of two high-frequency surface plasma waves, which arises when an intense electromagnetic plane wave is incident on a semi-infinite, unmagnetized plasma from a vacuum, is investigated on the basis of the hydrodynamic equations for warm electrons. It is shown that the instability occurs only if the incident wave is of the transverse magnetic type. The growth rate for the instability and the threshold amplitude of the incident wave are determined. In contrast to the usual ''two-plasmons decay instability'' in an infinite, unmagnetized plasma, the present ''surface-decay instability'' is possible even if the incident pump field is spatially homogeneous

[en] Two-dimensional radiation by a relativistic sheet electron beam propagating parallel to a reflection grating composed of a sinusoidally corrugated conducting surface is studied rigorously using the mode-matching method. Accurate dispersion curves are presented for the eigenmodes that govern the Smith-Purcell radiation and the instability of the electromagnetic surface wave. The dependences of the maximum leakage coefficient of radiation and the maximum growth rate of instability on the dimensions of the radiating structure are discussed

[en] Machine learning is a promising research topic that has recently achieved remarkable results, leading to the substitution of more traditional methods with automatically learned solutions. Some recent works have begun to highlight how a machine-learned model can be tricked by just applying small variations to the data, resulting in completely erroneous outcomes. Such behaviour can be traced to two elements: the lack of any metrological characterization of the inputs passed to the model, such as the uncertainty of the data, and the lack of an assessment of the reliability of the results. This paper tackles both these elements, considering the case of random forest model and proposing a method for assessing a confidence probability as an estimator for classification reliability. This considers the original classification structure, leaving it untouched, and the distribution of the training datasets. An overlaying structure statistically combines the two, and also includes in the process the propagation of feature uncertainties as a further element deriving from input measurements. The new classification outcome is a vector of probabilities that define how reliably a feature entry can be assigned, or not, to each of the considered classes, independently of others. In this new structure, an additional classification result naturally becomes available: the unclassifiable feature entry. (paper)

[en] This study reports the design and analysis of a plasmonic sensor based on a heavily doped silicon and metallic grating structure working in the mid-infrared region. The numerical results show that the reflection spectrum of the phosphorous-doped Si grating structure with a dopant concentration of 1  ×  20²⁰ has a sharp asymmetric Fano resonance dip, which is strongly dependent on the refractive index change in the surroundings. It yields a sensitivity of 8000 nm/RIU (refractive index unit) and 950 nm/RIU working in the air and water media, respectively, very high values compared with that of existing devices. Moreover, the Fano resonance caused by coupling of the Wood–Rayleigh anomaly and surface plasmon resonances is demonstrated by calculating the magnetic field and Poynting vector patterns. Further, a feasible and easy fabrication process of the sensor featuring high performance is represented. (paper)