196,262 research outputs found
Electromagnetic Characterization of Materials by using Transmission/Reflection (T/R) Devices
No full textAn overview of transmission/reflection-based methods for the electromagnetic characterisation of materials is presented. The paper initially describes the most popular approaches for the characterisation of bulk materials in terms of dielectric permittivity and magnetic permeability. Subsequently, the limitations and the methods aimed at removing the ambiguities deriving from the application of the classical Nicolson–Ross–Weir direct inversion are discussed. The second part of the paper is focused on the characterisation of partially conductive thin sheets in terms of surface impedance via waveguide setups. All the presented measurement techniques are applicable to conventional transmission reflection devices such as coaxial cables or waveguides
A CELL OF VARIABLE THICKNESS FOR OPTICAL STUDIES OF HIGHLY ABSORBING LIQUIDS
No full textA new design of a simple and inexpensive optical cell of variable thickness for absorption coefficient measurements in highly absorbing liquids is presented. The cell, which can be also used with highly corrosive samples and up to temperatures of 300 degrees C, is suitable for measurements from the near infrared up to near ultraviolet. As an example, the absorption spectrum of liquid iodine measured over six decades is reported
A high frequency integral equation (HFIE) method for the scattering from finite, gently undulated random surfaces
No full textA novel procedure to calculatte the induced current densit on large gently undulated surfaces has been presented. The method is based on the use of high-frequency derived basis functions, which also accounts for the undulation of the surface. By employing these basis functions in an integral equation procedure, electrically large problems can be handled in a computationally efficient and numerically rigorous manner, considering, at the same time, the random characteristics of the surface undulations
Iterative non-ambiguous estimation of dielectric permittivity from broadband transmission/reflection measurements
No full textA non-resonant technique to retrieve the dielectric permittivity of an unknown sample is presented. The method exploits the correlation among contiguous frequency points to remove ambiguities typical of classical Nicolson-Ross algorithm. The method does not need any initial guess
Permittivity Measurement of Thin Dielectrics by Using Metamaterial Absorbers Inside a Waveguide
No full textProton dynamics in supercritical water
No full textProton mean kinetic energy in supercritical water was determined using deep inelastic neutron scattering (DINS) technique to validate harmonic approximation and the hypothesis of decoupling among translational, rotational and vibrational degrees of freedom. Anisotropy of proton momentum distribution due to nonspherical molecular symmetry in water was also assessed. Proton mean kinetic energy was well described by a semi-classical harmonic model. The experimental results were found to be in good agreement with the theoretical predictions
Epiluminescence microscopy: Criteria of cutaneous melanoma progression
No full textBackground: Cutaneous melanoma develops through a series of evolutionary steps (intraepidermal, radial, and vertical growth phases) that are traceable in specific histologic features. Epiluminescence microscopy (ELM) is an in vivo technique that enables the visualization of morphologic structures in pigmented lesions correlated with specific histologic architectural characteristics. Many ELM criteria associated with cutaneous melanoma have been described, but their correlation with tumor progression has not yet been established. Objective: In this preliminary study our purpose was to explore the possibility of recognizing ELM criteria that allow the in vivo detection of the various phases of melanoma progression as well as tumor depth. Methods: Seventy-two cutaneous melanomas (41 ''thin'' melanomas [TnM], 0.75 mm thickness) were investigated with ELM for the presence of nine standard ELM criteria; their significance was determined by calculating the chi-square test of independence. Results: A significant association is found between the presence of pigment network and TnM and between the presence of gray-blue areas, vascular pattern, and TkM. Moreover, pigment network plus radial streaming is the most significant association of ELM criteria in TnM, whereas gray-blue areas plus vascular pattern is the greatest in TkM. Conclusion: This study shows a good correlation between certain ELM criteria and the histologic architecture of cutaneous melanoma for a preoperative evaluation of the tumor thickness. Further investigation is needed for verifying on a larger number of cases our pilot estimates of sensitivity and specificity of ELM criteria in thin and thick melanomas
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