Urban Sensibility of Landscape Structures in Italy General Characteristics and Local Details

Recently the conservation policies in Europe are considering the problem of the urban increasing in terms of soil destroyed and ecosystem fragmentation effects. In Italy this phenomena are becoming particularly important if we consider it at national level, but also at regional level. The paper has the goal to show some data relative to the distribution and the impact of urban surfaces on the large landscape national units, comparing the values among the units kind. Moreover will be implemented the data relative to some regional situation (Lazio, Marche, Umbria) of the Italian peninsula for having the indication about different environmental conditions as, for example, coastal areas, mountain areas or hill areas or also flat areas and different morphological structures. These data will be compare with other territorial characteristics, as the protected areas distribution and the biopermeability areas distribution. The knowledge of these information is very important for the planning action because it is possible to obtain, by means particular GIS models, indications about the urban sensibility of the different land parts in the future.

Time-domain analysis of RF and microwave autonomous circuits by vector fitting-based approach

This work presents a new method for the analysis of RF and microwave autonomous circuits directly in the time-domain, which is the most effective approach at simulation level to evaluate nonlinear phenomena. For RF and microwave autonomous circuits, time-domain simulations usually experiment convergence problems or numerical inaccuracies due to the presence of distributed elements, preventing de-facto their use. The proposed solution is based on the Vector Fitting algorithm applied directly at circuit level. A case study relative to a RF hybrid oscillator is presented for practical demonstration and evaluation of performance reliability of the proposed method

On the Flux Linkage between Pancake Coils in Resonance-Type Wireless Power Transfer Systems

This work presents a series representation for the mutual inductance of two coaxial pancake coils which remains accurate in non-quasi-static regime under the hypothesis that the current in the source coil is uniformly distributed. Making use of Gegenbauer's addition theorem and a term-by-term analytical integration, the mutual inductance between two generic turns belonging to distinct coils is expressed as a sum of spherical Hankel functions with algebraic coefficients. The accuracy and efficiency of the resulting expression is proved through pertinent numerical examples

The Partial Elements Equivalent Circuit Method: The State Of The Art

This year marks about half a century since the birth of the technique known as the partial element equivalent circuit modeling approach. This method was initially conceived to model the behavior of interconnect-type problems for computer-integrated circuits. An important industrial requirement was the computation of general inductances in integrated circuits and packages. Since then, the advances in methods and applications made it suitable for modeling a large class of electromagnetic problems, especially in the electromagnetic compatibility (EMC)/signal and power integrity (SI/PI) areas. The purpose of this article is to present an overview of all aspects of the method, from its beginning to the present day, with special attention to the developments that have made it suitable for EMC/SI/PI problems

Effective time-domain approach for the assessment of the stability characteristics and other non-linear effects of RF and microwave circuits

This study describes a systematic approach for the stability analysis of RF and microwave non-linear circuits in the time-domain and that can be useful also for the verification of other non-linearities, like intermodulation. The time-domain analysis is the most reliable approach for the evaluation of complex non-linear phenomena but, in general, the transient behaviour of non-linear circuits is difficult to verify at high frequencies, where distributed elements are common. The solution here addressed overcomes this limitation and it may be applied, without restrictions, also to monolithic microwave integrated circuits and EM-based designs. Examples of application to hybrid prototypes are provided, and the comparison between simulations and measurements illustrates the accuracy and reliability of the proposed approach

Thermodynamic assessment of liquid metal–steam USC binary plants to break 50% efficiency in pulverized coal plants

Nowadays the state-of-the-art technology to convert coal energy of combustion into electricity is to adopt a pulverized coal boiler coupled with an Ultra Super Critical (USC) steam cycle. The total installed capacity of this well-proven configuration is of hundreds of GW worldwide with an increasing share respect to both supercritical and subcritical cycles. Typical coal USC cycles have maximum pressures of around 270 bar and maximum temperatures of 600-620°C for the high pressure and the mid pressure steam respectively. Maximum attainable efficiency is close to 45% in favorable locations and is mainly penalized by two irreversible processes: coal combustion (about 30%) and heat introduction (about 10%) that is characterized by large temperature differences between the hot flue gases and the steam. The main strategy to reduce the second loss is focused on the development of new super alloys able to withstand higher temperatures, higher pressures and water corrosion and so bring efficiencies close to 49% in the so called Advanced USC plants (AUSC). However, the increasing of maximum cycle pressure and temperature results in a relatively small increase of cycle efficiency due to the large increase of specific heat around the critical point but, on the other hand, it involves a considerably increase of equipment’s cost. Another option to increase cycle efficiency is represented by the introduction of a high temperature and low pressure power cycle between the flue gases and the steam cycle. In this case, the topping power cycle could be (i) an external combustion gas cycle, (ii) an open gas cycle fueled by syngas produced by coal gasification or (iii) a Rankine cycle that uses a proper working fluid with a very high critical temperature. This study aims to define a number of optimized binary plant configurations with saturated Rankine potassium cycle as top cycle and a conventional USC plant as bottom cycle. Top cycle receives heat from the flue gases within the coal-fired boiler while bottom cycle recovers heat from the top cycle fluid condensation and the flue gases cooling before the Ljunström air preheater. Potassium thermodynamic properties are computed with a proper equation of state calibrated on experimental data from reference [2] and able to predict accurately both the volumetric and the thermodynamic behavior of potassium in liquid, vapor and two-phase conditions. Different liquid metal cycles have been designed and the trends of the main quantities (heat of condensation, turbine isentropic enthalpy drop and plant efficiency) have been correlated to both evaporation and condensation temperatures. This information is implemented in the USC scheme, calculated with an in-house process simulation code GS developed at the Department of Energy at Politecnico di Milano [3], which has been validated and used on hundreds of publications and projects. Analysis is completed by the evaluation of the potassium turbine design in terms of number of stages, need of cross-over and optimal rotational speed. A double condensation level configuration is also considered for the top cycle in order to further reduce the temperature difference between the top cycle condensation and evaporation process in the bottom cycle, which further increases the efficiency. The thermal input of coal to the burner is fixed for all the simulations to 1.66 GW, five plant configurations have been selected as the most promising ones and fairly compared with a conventional USC coal-fired power plant having a calculated efficiency equal to 44.72%. Limiting the maximum potassium temperature at 800°C, which corresponds to an evaporation pressure of 1.5 bar, it is possible to reach electric efficiencies close to 51% with a single condensation level top cycle and value close to 52% with a double condensation level top cycle. Power produced by the metal cycle ranges between 25 and 30% of the net system power output. As general conclusion the adoption of binary cycles with a top Rankine liquid metal cycle is demonstrated to be an attractive option from a thermodynamic point of view leading to an electric efficiency larger than in AUSC plants. However, these binary metal-steam cycles still need to face a number of technical and safety issues mainly related to the use of liquid metals. Technical issues are related to the high temperature of heat exchange surface of the boiler, to the very high vacuum at condenser, the need of limiting air leakages and the design of a turbine expanding a fluid with an increasing liquid fraction. Safety issues are due to working fluid reactivity with water that requires the need of expensive solution to limit fire hazard. [1] World Energy Council, 2016. World Energy Resources: Coal. [2] Reynolds, W.C. Thermodynamic properties in SI - graphs, tables and computational equations for 40 substances. Department of Mechanical Engineering, Stanford Univ., 1979 [3] GECOS, GS software. www.gecos.polimi.it/software/gs.ph