1,721,130 research outputs found
Integral equation-based approach for the analysis of tapered transmission lines
No full textA method for analysing tapered lossy transmission lines is presented. The Telegrapher's equations are solved by using the closed-form Green's function of the corresponding uniform transmission line. The space-dependent characteristic impedance is handled as a forcing term of the Telegrapher's equations whose effect is incorporated into the Fredholm integral equation of the second kind describing the space voltage distribution. The method allows to avoid the segmentation technique which is prone to inaccuracies because of spurious reflections at the boundaries of each section. Several tests are carried out and excellent results are obtained confirming the superior accuracy of the proposed method with respect to the standard segmentation technique
Tentative criteria for the design and installation of electrical power systems subject to seismic hazard
No full textThe paper discusses the need to study the criteria for the design and installation of electrical power systems in buildings subject to seismic hazard. Nowadays, all the recommended seismic requirements according to: Uniform Building Code (UBC), Structural Engineers Association of California (SEAOC), and National Earthquake Hazards Reduction Program (NEHRP) do not specifically take into account the electrical or technological power systems. The paper analyses the problems an earthquake can cause with regard to the functional reliability and continuity of supply of electrical power systems. Therefore, it proposes design and installation requirements, to be graduated according to building occupancy categories. Basically, the criteria relative to the installation of the electrical equipment are an appropriate extension of those general static ones for nonstructural components. Their consideration is essential for the settlement of the design criteria, which, as far as the configuration and the size of the electrical power system are concerned, are aimed at limiting the same installation problems. Other general design criteria, aimed as a guarantee for the supply continuity and system reliability, have a particular use in these appliance
Implementing Criteria and Indicators for Sustainable Forest Management in a Decentralized Setting: Italy as a Case Study
No full textThe study explored the sub-national implementation of the Pan-European Criteria and Indicators (C&I) for Sustainable Forest Management in Italy, based on the statistical analysis of answers to a questionnaire provided by representatives of the Italian sub-national forest administrations. The questionnaire explored the implementation of C&I in five applications and through the analytical lenses of ‘suitability of C&I to sub-national contexts’ and ‘adaptability of administrations to C&I’. The analysis of suitability and adaptability made it possible to identify and compare challenges in, and successful experiences with, the implementation of C&I, which were then used to formulate recommendations aimed at encouraging implementation and promoting academic and policy debate. The study reveals that C&I were implemented to a moderate extent. This level of implementation was determined most of all by the suitability of C&I to the Italian sub-national contexts, and less by the adaptability of administrations. Recommendations to foster implementation of and dialogue on C&I include the need for Italian sub-national administrations to transpose the Pan-European C&I into sub-national sets tailored to local circumstances by, for example, modifying existing C&I or integrating these into new customized indicator sets
On the passivity of the quasi-static partial element equivalent circuit method
No full textThe partial element equivalent circuit (PEEC) electromagnetic method has attracted a lot of attention for its capability to give a circuit interpretation to Maxwell's equations. The PEEC equivalent circuits are usually connected with terminations such as drivers and receivers in a time-domain circuit simulator. Passivity is a fundamental property for the time-domain simulations of circuit models connected to terminations at their electrical ports. Stable, but nonpassive, models can produce unstable systems when connected to other stable, even passive, loads. The so-called quasi-static PEEC formulations leads to a descriptor state-space circuital representation of the electromagnetic phenomena. Multiple state-space representations are possible. In this paper, we study the passivity property of different quasi-static PEEC representations in detail. A novel analytical additive decomposition is proposed concerning the admittance formulation, which allows extracting the polynomial part of the transfer function that represents the behavior at infinity in the Laplace domain. This decomposition is discussed from a mathematical and a physical point of view. Such a detailed study for the passivity of quasi-static PEEC models and the novel analytical decomposition is not available in the literature. Numerical results support the theoretical analysis
Sparse polynomial chaos expansion for high-dimensional uncertainty quantification of braided shielded cables
No full textThis paper proposes the use of a sparse polynomial chaos expansion method, whose set of basis functions is sparsified using the hyperbolic truncation scheme. This allows the reduction of the computational cost needed to generate a polynomial chaos model that can predict statistical properties of a high-dimensional uncertainty quantification problem of crosstalk in braided shielded cables. By comparing the results of the sparse polynomial chaos expansion with those of a standard polynomial chaos expansion and a Monte Carlo method, we verify that sparse polynomial chaos expansion using the hyperbolic truncation scheme can effectively reduce the curse of dimensionality issues in high-dimensional uncertainty quantification problems for braided shielded cables
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Stochastic collocation for uncertainty quantification of systems described by neutral delayed differential equations
No full textA technique is presented for variability analysis of large circuits described by neutral delayed differential equations. It is based on a delayed formulation of the partial equivalent element method coupled with stochastic collocation schemes. Pertinent numerical results validate the proposed technique
Limpopo National Park (Mozambico): groundwater assessment as a tool for a sustainable management of the area
Full text linkThis paper deals with updated results coming from hydrogeological studies carried on the framework of the SECOSUD
Phase II, called “Conservation and equitable use of biological diversity in the SADC region (Southern African Development
Community), a project supported by the Italian Ministry of Foreign Afairs in the SADC, whose focus area includes South
Africa Development Countries. The main goal of the SECOSUD Phase II Project is the defnition and implementation of
scenarios for sustainable development, aimed at an equitable conservation of biodiversity resources and, as a consequence
of this target, the hydrogeological characterization, with the groundwater recharge assessment, of this area and its bufer
zone. Limpopo National Park is one of the jewels in the crown of Mozambique’s protected areas. As a matter of fact, sustaining the conservation of biodiversity, due to its complexity and multiple drivers, which stress it, is on frst a matter of water
environment assessment, as most ecosystems are highly dependent on the hydrological cycle and groundwater availability.
After gathering regional and local geological data, which let us set up a detailed geological map of the area under study,
pointing out the main outcropping geological units, with their main hydrogeological properties, the methodological approach
adopted has been to assess the potential infltration, applying the Inverse Hydrogeological Budget Technique, performed for
the focus area. Because of the lack of meteorological data referred to Limpopo National Park, it has been applied a spatial
distribution of precipitation measurements, collected in many gauge stations, located in the Kruger National Park during
the last 54 years, which represent an interesting rainfall historical series. The target of the study has been to assess a trend of
meteorological data with the aim of understanding how precipitations could afect groundwater recharge, and their infuence
on groundwater availability. The estimation of groundwater recharge is the tool for suggesting better water management in
the area, aimed to preserve as much biodiversity as people living in the bufer zone
Parameterized macromodels of multiconductor transmission lines
No full textWe introduce a novel parametrization scheme for lossy and dispersive multiconductor transmission lines (MTLs) having a cross-section depending on geometrical and physical parameters, that is suitable to interconnect modeling. The proposed approach is based on the dyadic Green's function method for the analysis of lossy and dispersive MTLs which is parameterized by using the Multivariate Orthonormal Vector Fitting (MOVF) technique to build parametric macromodels in a rational form. Design parameters, such as substrate or geometrical layout features, in addition to frequency, can be easily handled. The rational form of the multi-port macromodel describing the MTL is a direct consequence of the MOVF technique and is especially suited to generate state-space macromodels or to be synthesized into equivalent circuits, which can be easily embedded into conventional SPICE-like solvers. A numerical example is presented providing evidence of the accuracy of the proposed approach in both frequency and time-domain
- …
