Laboratory Assessment of Water Permeability Loss of Geotextiles Due to Their Installation in Pervious Pavements

During the last decades, the importance of sustainable development in society has increased considerably. Sustainable Urban Drainage Systems (SUDS) are a group of techniques that aim to improve the management of rain and run-off water while reducing their pollution. Many of these systems incorporate geotextiles in their structures, which act as a layer separation and water filter. Some authors defend the idea that by simply being installed, geotextiles partially or totally lose their separation and filtering capacities. This study proposes a testing methodology that can reproduce this effect and obtain a reduction factor for the water permeability of the material after its installation, which is defined here as the ?new condition factor?. The procedure simulated the real installation conditions in the laboratory by causing the specimen to undergo both mechanical and hydraulic damage and subsequently measuring the loss of water permeability that it provoked on the geotextile. Two different nonwoven geotextiles were tested in order to validate the procedure and to obtain initial results that could confirm the need for the new condition factor in the design of pervious pavements with geotextiles. Analysis of variance (ANOVA) was used to determine the statistical significance of the test variableshis research was funded by the Spanish Ministry of Economy and Competitiveness, grant number BIA2012-32463, and by the Dirección de Investigación of the Universidad Católica de la Santísima Concepción, fund FAA 02/2018. The authors would like to thank the support and collaboration from the Construction Technology Research Group (Grupo de Investigación de Tecnología de la Construcción - GITECO), the Geosynthetics Laboratory of the University of Cantabria (LAGUC), Grupo de Caminos de Santander (GCS) and the Geotechnical Group of the University of Cantabria

A Coherent Small/Large Signal FET model Based on Neuronal Architectures 1

A modular neural network architecture for accurate small/large signal microwave MESFET/HEMT modeling is presented. This is achieved by means of an original neural architecture having two main modules. A network captures the nonlinear dynamic Pulsed I/V characteristic of the device, which is mainly responsible of the large signal behavior, while the second network estimates the high order derivatives at the operation point, which are responsible of the IMD behaviour, by means of a neural network and then it locally reconstructs the current function by means of a third order Taylor series around that point. Finally, in order to have a maximum of coherence, the two networks are combined into a global model by means of a simple fuzzy controller. Computer simulations and experimental measurements validate this flexible modeling technique

Optical Control of a GaAs Chip MMIC Amplifier at S Band

This paper shows the results of research on the optical control of a GaAs chip monolithic amplifier,and is an extension of previous work by our group in the field of optical-microwave interaction [1-3 ].The amplifier was originally designed for the transmitter stage of an indoor mobile communications system in the 2.4 GHz band.The possibilities of optical control of this amplifier are evidenced as follows:if the amplifier operates with the same biasing, the gain can be optically controlled from a condition of almost isolation,(small signal gain less than -5 dB),up to an active condition,(small signal gain greater than 10 dB), which gives a range of optical control of about 15 dB.At the same time,the optical control provides an improvement of the input and output matching in a range of 12dB and 6dB, respectively.This optical control suggests an interesting control of gain and matching for other microwave FET based active devices

A straightforward method for determining SiGe HBTs intrinsic elements of hibrid PI and TEE small-signal circuit models for multibias operation

A new method to simultaneously determine the complete Tee and hybrid Pi equivalent circuit parameters of the SiGe HBT including parasitic intrinsic base resistance, is presented. This approach employs analytically derived expressions and is based on the analysis of measured scattering parameters over an adequate frequency range. This paper shows that a one-to-one correspondence exists between Tee and Pi topologies and very good fit between measured and simulated scattering parameters in the frequency range between 0.05 to 50 GHz is obtained

New Large Signal Model of AlGaAs P-HEMT and GaAs MESFET Under Optical Illumination

As an extension of previous works in the optical-microwave interaction field, this paper shows the results of the research on large signal dynamic behaviour (Pulsed I/V curves) of AlGaAs P-HEMT (pseudomorphic high electron mobility transistor) devices, in the overall I/V plane, when the incident optical input power is changed. A complete bias and optical power dependence of the large signal model for a P-HEMT, is determined from experimental scattering parameters, DC and pulsed measurements. All derivatives of the model shown here are continuous for a realistic description of circuit distortion and intermodulation. The model is also valid for GaAs MESFET. experimental results show very good agreement with theoretical analysis

A realistic large-signal microwave PHEMT transistors model for SPICE

A comprehensive large-signal HEMT model that provides a realistic description of measured characteristics over all operating regions for different PHEMTs is presented. The model was previously tested in harmonic-balance based simulators [1] and for the first time it has been implemented inside the time domain SPICE simulator. In order to do that, a new set of routines and libraries has been developed. The procedure introduced here can be extended to properly simulate other kind of devices described in terms of equivalent circuits. DC and scattering simulation results show very good agreement with the experimental measurements