WP1: Analysing multilevel water and biodiversity governance in their context. Analysis and synthesis of consultations

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Centralised and decentralised configurations for panels with piezoelectric actuators

This paper discusses configurations for controlling broadband noise using piezoelectrically excited panels. The configurations can be distinguished by the physical layout and by the control structure. The physical layout of the system has some influence on the complexity of the control algorithms. For particular actuator/sensor combinations and a particular control objective, the control architecture can be decentralized, using very simple feedback or feedforward controllers, at small performance loss when compared to a centralized architecture. For some applications that require a different control objective, an additional centralized or possibly distributed architecture could be beneficial. A hardware realization with an associated control framework that allows the implementation of such a combined centralized-decentralized architecture is shown. Examples that are given are an embedded central control unit with all electronics in a single module and a centralized-decentralized architecture with partly decentralized hardware that is integrated with structural parts

Electrical safety in spinal cord stimulation: current density analysis by computer modeling

The possibility of tissue damage in spinal cord stimulation was investigated in a computer modeling study. A decrease of the electrode area in monopolar stimulation resulted in an increase of the current density at the electrode surface. When comparing the modeling results with experimental data from literature, it was concluded that even with a small electrode area (0.7 mm2) tissue damage in spinal cord stimulation is improbabl

Combined MIMO adaptive and decentralized controllers for broadband active noise and vibration control

Recent implementations of multiple-input multiple-output adaptive controllers for reduction of broadband noise and vibrations provide considerably improved performance over traditional adaptive algorithms. The most significant performance improvements are in terms of speed of convergence, the \ud amount of reduction, and stability of the algorithm. Nevertheless, if the error in the model of the relevant transfer functions becomes too large then the system may become unstable or lose performance. On-line adaptation of the model is possible in principle but, for rapid changes in the model, necessitates \ud a large amount of additional noise to be injected in the system. It has been known for decades that a combination of high-authority control (HAC) and low-authority control (LAC) could lead to improvements with respect to parametric uncertainties and unmodeled dynamics. In this paper a full digital implementation of such a control system is presented in which the HAC (adaptive MIMO control) is implemented on a CPU and in which the LAC (decentralized control) is implemented on a high-speed Field Programmable Gate Array. Experimental results are given in which it is demonstrated that the HAC/LAC combination leads to performance advantages in terms of stabilization under parametric uncertainties and reduction of the error signal

Spinal cord stimulation: fiber diameters in the dorsal columns modeled from clinical data

Computer simulations of clinical data were performed to estimate the diameter distribution of A¿ß nerve fibers in the human dorsal columns, activated by spinal cord stimulation. Qualitatively, the calculated distribution was in accordance with experimental data. Due to mismatches in impedance and limited resolution of the CT scans more patient data is needed to reliably predict the quantitative diameter distributio

WP1: Analysing multilevel water and biodiversity governance in their context. Report

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A model of the electrical behaviour of myelinated sensory nerve fibres based on human data

Calculation of the response of human myelinated sensory nerve fibres to spinal cord stimulation initiated the development of a fibre model based on electro-physiological and morphometric data for human sensory nerve fibres. The model encompasses a mathematical description of the kinetics of the nodal membrane, and a non-linear fibre geometry. Fine tuning of only a few, not well-established parameters was performed by fitting the shape of a propagating action potential and its diameter-dependent propagation velocity. The quantitative behaviour of this model corresponds better to experimentally determined human fibre properties than other mammalian, non-human models do. Typical characteristics, such as the shape of the action potential, the propagation velocity and the strength-duration behaviour show a good fit with experimental data. The introduced diameter-dependent parameters did not result in a noticeable diameter dependency of action potential duration and refractory period. The presented model provides an improved tool to analyse the electrical behaviour of human myelinated sensory nerve fibres

Anticipating climate change: knowledge use in participatory flood management in the river Meuse

Given the latest knowledge on climate change, the Dutch government wants to anticipate the increased risk of flooding. For the river Meuse in The Netherlands, the design discharge is estimated to increase from 3800m3/s to 4600m3/s. With the existing policy of “Room for the River”, this increase is to be accommodated without raising the dikes. At the same time the floodplains are often claimed for other functions, e.g. new housing or industrial estates. In 2001 the Ministry of Transport, Public Works and Water Management started the study “Integrated assessment of the river Meuse (IVM)” with the objectives of making an inventory of the probable physical effects of a design flood, assuming climate change, on the river Meuse in 2050, investigating possible spatial and technical measures to mitigate these effects, and finally combining various measures to create an integral strategy for flood protection, while at the same time increasing spatial quality. This paper presents the results of research into the decision making process that took place in order to achieve these objectives. Special attention was given to the role of scientific and technical knowledge in the decision making process, e.g. by investigating the effect of the quality of input data on acceptance by stakeholders, and the interactive use of a decision support system to visualise hydraulic effects. Conclusions on successes and pitfalls are drawn from observation and interviews with participants. It demonstrates how it is possible to integrate the necessary, technically complex knowledge in a political debate with stakeholders on how to deal with flood risk. Furthermore, the experience indicates in what area improvements could be made

Analysis of current density and related parameters in spinal cord stimulation

A volume conductor model of the spinal cord and surrounding anatomical structures is used to calculate current (and current density) charge per pulse, and maximum charge density per pulse at the contact surface of the electrode in the dorsal epidural space, in the dorsal columns of the spinal cord and in the dorsal roots. The effects of various contact configurations (mono-, bi-, and tripole), contact area and spacing, pulsewidth and distance between contacts and spinal cord on these electrical parameters were investigated under conditions similar to those in clinical spinal cord stimulation. At the threshold stimulus of a large dorsal column fiber, current density and charge density per pulse at the contact surface were found to be highest (1.9·105 ¿A/cm2 and 39.1 ¿C/cm2 ·p, respectively) when the contact surface was only 0.7 mm 2. When stimulating with a pulse of 500 ¿s, highest charge per pulse (0.92 ¿C/p), and the largest charge density per pulse in the dorsal columns (1.59 ¿C/cm2·p) occurred. It is concluded that of all stimulation parameters that can be selected freely, only pulsewidth affects the charge and charge density per pulse in the nervous tissue, whereas both pulsewidth and contact area strongly affect these parameters in the nonnervous tissue neighboring the electrode contact

Effects of electrode configuration and geometry on fiber preference in spinal cord stimulation

In contrast to the widespread assumption that dorsal column fibers are the primary targets of spinal cord stimulation by a dorsal epidural electrode, it appears that dorsal root fibers are recruited as well, and even preferentially under various conditions. This will, however, limit the coverage of the painful body areas with paresthesia, a prerequisite for the management of chronic pain. In order to favor the preferential stimulation of dorsal column fibers, advantage was taken of the different positions and orientations of fibers in the dorsal columns and dorsal roots. Using an SCS computer model, electrode configurations have been designed for the selective stimulation of the human dorsal column