Search results for "Admittance"
showing 10 items of 33 documents
Analysis of the multipactor effect by means of the 3D BI-RME method
2017
Multipactor effect is a well-known phenomenon of RF breakdown in satellite pay-loads which degrades components, generates undesirable harmonics, contributes to power dissipation and increases noise in communications. Traditionally, multipactor has been investigated with the aim of obtaining the so-called multipactor threshold voltage, or to present different multipaction detection methods. Little effort has been devoted, in contrast, to study the problem from a full-wave point of view, thus allowing for the analysis of more complex structures. The main goal of this work is to analyze the interaction between a multipactor current and a realistic microwave cavity by means of a rigorous and ac…
Out-patient low-dose oral chemotherapy in hormone refractory prostate carcinoma (HRPC) patients unfit for hospital admittance.
2008
Objectives: Well tolerated out-patient regimens for HRPC chemotherapy in elderly patients with geographical difficulties and/or unwilling hospital admission are needed. The aim of the present study was to investigate the safety and efficacy of a low-dose oral combination of estramustine phosphate (EMP) and etoposide (VP16). Patients: Fifty-six HRPC patients, median age 75 years, were randomized between daily EMP (10mg/kg) – arm A, and low-dose EMP (3mg/kg) plus VP16 (25mg/mq) 2 weeks monthly – arm B. Randomization ratio was 2:3. Median PSA was 41.1 ng/ml. Baseline characteristics between the 2 groups were similar. LHRH therapy was maintained. Antiandrogen was stopped one month before entry.…
The Influence of Thermal Treatment on the Electronic Properties of a-Nb2O5
2009
The effect of thermal treatments for 1h at 250{degree sign}C in air or under vacuum on the electronic structure of thick amorphous anodic niobia was characterized by electrochemical impedance, differential admittance (DA) and photocurrent spectroscopy (PCS). The analysis of anodized niobia has revealed that it behaves as a pure dielectric. The thermal treatment in air increases the value of the differential capacitance of the niobia sample. The effect is stronger when the thermal treatment is carried out in vacuum and can be cancelled out by reanodizing the oxide to the initial formation potential. In the case of thermally vacuum-treated sample, a behavior typical of semiconducting amorphou…
Physicochemical Characterization of Passive Films and Corrosion Layers by Differential Admittance and Photocurrent Spectroscopy
2009
Two different electrochemical techniques, differential admittance and photocurrent spectroscopy, for the characterization of electronic and solid state properties of passive films and corrosion layers are described and critically evaluated. In order to get information on the electronic properties of passive film and corrosion layers as well as the necessary information to locate the characteristic energy levels of the passive film/electrolyte junction like: flat band potential (Ufb), conduction band edge (EC) or valence band edge (EV), a wide use of Mott-Schottky plots is usually reported in corrosion science and passivity studies. It has been shown, in several papers, that the use of simpl…
On the Rigorous Calculation of All Ohmic Losses in Rectangular Waveguide Multi-Port Junctions
2005
In this paper, all ohmic losses effects present in rectangular waveguide multi-port junctions are rigorous and efficiently computed. For this purpose, a new formulation based on the theory of cavities, which provides generalized admittance matrix representations for such junctions, is proposed. To validate this theory, we have successfully compared our results with numerical data of a lossy E-plane T-junction and of a hollow waveguide, as well as with experimental measurements of a real H-plane T-junction.
Accurate consideration of metal losses at waveguide junctions using admittance and impedance integral equation formulations
2005
[1] At higher frequencies, metal loss effects in passive waveguide components become more pronounced and hazardous. In this paper, we propose two integral equation techniques, based on the generalized admittance and impedance matrices, for the accurate consideration of losses in the metal walls of waveguide junctions. Both techniques have been evaluated in terms of accuracy and numerical efficiency, and conclusions are drawn regarding the best properties of the admittance parameter formulation. Finally, combining such technique with a classical perturbative method for considering propagation losses, we have successfully predicted all loss effects in two real waveguide filters used for comme…
Analysis of Inhomogeneously Dielectric Filled Cavities Coupled to Dielectric-Loaded Waveguides: Application to the Study of NRD-Guide Components
2004
In this paper, we present two contributions. First, we develop a computationally efficient technique for the full-wave characterization of inhomogeneously dielectric-filled cavities connected to inhomogeneously dielectric-loaded waveguides. This method is based on the expansion of the electromagnetic field within the cavity in terms of their solenoidal and irrotational modes. The presented formulation allows the treatment of hybrid modes in the waveguide ports, where the definition of a characteristic modal impedance or admittance is not possible. The multimode scattering matrix of the structure is computed throughout an efficient implementation of the orthonormal-basis method for the calcu…
Efficient and Accurate Consideration of Ohmic Losses in Waveguide Diplexers and Multiplexers
2006
The accurate consideration of all ohmic losses effects in waveguide manifold diplexers and multiplexers is rigorously studied in this paper. For such purposes, a full-wave CAD tool based exclusively on modal methods is originally proposed. Proceeding in this very efficient way, losses are precisely considered in all common components of such complex devices, i.e. planar junctions, uniform lines and multi-port circuits implemented in waveguide technology. For verification purposes, we have successfully compared our results for a magic-T junction and a manifold diplexer with experimental and numerical results.
Soil Water Content Diachronic Mapping: An FFT Frequency Analysis of a Temperature–Vegetation Index
2020
Among the indirect estimation approaches of soil water content in the upper layer of the soil, the &ldquo
Simplified thermal analysis of naturally ventilated dwellings
1991
Abstract A simplified comprehensive methodology for thermal comfort prediction in a naturally crossventilated room is described. The methodology mainly consists of the following three steps: • - analysis of the dynamic thermal behaviour of the given room, by means of the admittance procedure; • - evaluation of the air flows rates and their velocities in the room, by means of a new simplified method; • - thermal comfort prediction by means of the Fanger's theory. The results obtained appear satisfactory and the simplified methodology makes itself a useful tool for the identification of appropriate choices at the early stages of the design process, regarding naturally ventilated buildings. Th…