Pre-dismantling THM modelling

FEBEX (Full-scale Engineered Barrier Experiment in Crystalline Host Rock) is a research and demonstration project that was initiated by ENRESA (Spain). The aim of the project is to study the behaviour of near-field components in a repository for high-level radioactive waste in granite formations. The main objectives of the project may be grouped in two areas: demonstration of the feasibility of constructing the engineered barrier system in a horizontal configuration according to the Spanish concept for deep geological storage (AGP-abbreviation in Spanish), and analysis of the technical problems to be solved for this type of disposal method to develop a better understanding of the thermo-hydro-mechanical (THM) and thermo-hydrogeochemical (THG) processes in the near-field, and development and validation of the modelling tools required for interpretation and prediction of the evolution of such processes. The project consists of two large-scale tests (see Fig. 1-1) – "in situ" and "mock-up" (the latter is managed by CIEMAT in Spain) –, a series of laboratory tests, and THM and THG modelling tasks. The full-scale heating test ("in-situ" test), to which this document refers, was performed at the Grimsel underground laboratory in Switzerland, also known as Grimsel Test Site (GTS) or Felslabor Grimsel (FLG in German). A complete description of the FEBEX project objectives and test program may be found in the "FEBEX Full-scale Engineered Barriers Experiment in Crystalline Host Rock

A third-order class-D amplifier with and without ripple compensation

We analyse the nonlinear behaviour of a third-order class-D amplifier, and demonstrate the remarkable effectiveness of the recently introduced ripple compensation (RC) technique in reducing the audio distortion of the device. The amplifier converts an input audio signal to a high-frequency train of rectangular pulses, whose widths are modulated according to the input signal (pulse-width modulation) and employs negative feedback. After determining the steady-state operating point for constant input and calculating its stability, we derive a small-signal model (SSM), which yields in closed form the transfer function relating (infinitesimal) input and output disturbances. This SSM shows how the RC technique is able to linearise the small-signal response of the device. We extend this SSM through a fully nonlinear perturbation calculation of the dynamics of the amplifier, based on the disparity in time scales between the pulse train and the audio signal. We obtain the nonlinear response of the amplifier to a general audio signal, avoiding the linearisation inherent in the SSM; we thereby more precisely quantify the reduction in distortion achieved through RC. Finally, simulations corroborate our theoretical predictions and illustrate the dramatic deterioration in performance that occurs when the amplifier is operated in an unstable regime. The perturbation calculation is rather general, and may be adapted to quantify the way in which other nonlinear negative-feedback pulse-modulated devices track a time-varying input signal that slowly modulates the system parameters

Assessment of nonlinear predictive control techniques for DC-DC converters

This article focuses on the application of two nonlinear predictive control strategies to fixed frequency switch-mode dc-dc converters. The first approach uses an averaged nonlinear model for predictions and provides an a priori robust stability guarantee for the resulting closed-loop system. The implementation of this scheme requires solving a single linear program on-line. The second approach employs a piecewise affine (PWA) approximation of the converter equations as prediction model and yields an explicit controller off-line, which allows for an a posteriori stability check. An assessment of the synthesis procedures and methodological characteristics is given and simulation results are shown to substantiate the effectiveness of the proposed approaches

Gardenia jasminoides Height Control Using a Photoselective Polyethylene Film

The use of chemical growth retardants is a standard practice for compact gardenia plant production. The aim of this study was to investigate the possibility of using a photoselective polyethylene greenhouse covering film as an alternative to chemical treatment for production of compact potted gardenia (Gardenia jasminoides Ellis) plants. Two types of experiments were carried out: 1) on gardenia cuttings rooted in rooting benches; and 2) on young potted plants grown under low tunnels. In both experiments, two types of cover materials were used: 1) a photoselective polyethylene (P-PE), filtering light within the wavelength range 600 to 750 nm; and 2) a common polyethylene film (CPE) routinely used in greenhouse practice. Values of photosynthetically active radiation (in a wavelength of 400 to 700 nm), cover materials' spectral properties (in a wavelength range of 400 to 1100 nm), air temperature, and relative humidity were recorded inside the rooting benches and under the low tunnels. Plant growth parameters (main shoot length and leaf area and lateral shoot number, leaf area, and fresh and dry weight) were determined along the growth cycle. Cuttings rooted under the P-PE film received light with high zeta(n) values (ratio of R(n) : 655 to 665 nm to far red FR(n) : 725 to 735 nm) and high blue (B: 400 to 500 nm) to red (R: 600 to 700 nm) ratio (B:R) and were 68.7% shorter and had 21% lower leaf area compared with cuttings rooted under the C-PE film. Similarly, plants that were rooted and then grown under the low tunnels covered with the P-PE film, compared with plants rooted and grown under C-PE film, were 59% shorter, had 85% lower leaf area, 89% lower fresh weight, and 86% lower dry weight, whereas they did not produce lateral shoots. However, plants rooted under the C-PE film and then grown under the P-PE-covered low tunnels were 26% shorter and developed fewer laterals than plants rooted and grown under tunnels covered with C-PE film. Finally, plants rooted under the P-PE film and then grown under tunnels covered with C-PE film developed into compact, well-shaped plants, because they had a drastic reduction of height (56%) without an effect on leaf area, shoot and leaf fresh and dry weight, and the number of lateral shoots

Effect of a red to far red light filtering plastic film on growth of gardenia (Gardenia jasminoides)

The aim of this study was to determine the influence of a light filtering plastic film (red to far red ratio modification) on gardenia (Gardenia jasminoides) growth and to investigate the possibility to use this film as a greenhouse cover material for compact gardenia pot plant production in a greenhouse. Experiments were carried out on gardenia cuttings and plants grown under low tunnels covered by a) a light filtering (light modification within the range of 600 to 750 nm) plastic film, b) a plastic film with low radiation transmission or c) a common plastic film. The energy flux entering the low tunnels, within the range of 400 to1100 nm, and the climate parameters, along with plant growth parameters (shoot length, leaf area, number of lateral shoots, number of nodes, leaf and root dry weight) were measured. Cuttings rooted under the light filtering plastic film, receiving light with high R/FR and B/R ratio, were found 68% shorter, and had 21% and 29% lower leaf area and dry weight, respectively, compared to cuttings grown under common plastic film. Developed plants grown under the light filtering plastic film were found 59% shorter, produced no lateral shoots, and had lower leaf area, dry weight and node number compared to plants grown under common covering material. So, light filtering plastic films with high R/FR and B/R ratio, could be promising for greenhouse covering, as an alternative method to chemical growth regulator use, for compact gardenia pot plant production. The effect on lateral branching though, may become a serious problem to the final compact plant formation. For this reason photoselective plastic films with different R/FR and B/R ratios must be tested

Assessment of nonlinear predictive control techniques for DC-DC converters

This article focuses on the application of two nonlinear predictive control strategies to fixed frequency switch-mode dc-dc converters. The first approach uses an averaged nonlinear model for predictions and provides an a priori robust stability guarantee for the resulting closed-loop system. The implementation of this scheme requires solving a single linear program on-line. The second approach employs a piecewise affine (PWA) approximation of the converter equations as prediction model and yields an explicit controller off-line, which allows for an a posteriori stability check. An assessment of the synthesis procedures and methodological characteristics is given and simulation results are shown to substantiate the effectiveness of the proposed approaches