Assessment of flood damages and benefits of remedial actions: "What are the weak links?"; with application to the Loire

Flood damage models are used to determine the impact of measures to reduce damage due to river flooding. Such models are characterized by uncertainty. This uncertainty may affect the decisions made on the basis of the model outcomes. To reduce uncertainty effectively, the most important sources of uncertainty must be found. Uncertainty analysis serves this purpose.\ud \ud By way of a questionnaire experts were asked about their judgment of the significance of uncertainty sources in flood damage assessment. The results of this questionnaire are compared to an uncertainty analysis by Monte Carlo Simulation, which Torterotot (1993) applied to the French model CIFLUPEDE.\ud \ud The paper concludes that the role of uncertainty in flood damage assessment is highly significant and cannot be neglected. Both the experts and the analysis on the flood damage assessment model indicate the hydrologic relations ‘frequence of occurrence — river discharge — river water level’ and the damage estimates as the most important uncertainty sources. For embanked rivers dike breach is the most significant uncertainty source.\ud \ud A question which appears is, taking into account these uncertainties, to what level of precision can flood damage assessment models predict the expected annual flood damage and the costs and revenues of flood alleviation measures? It is of importance to explore the boundaries of flood damage modeling and to try to find ways to move these boundaries. The uncertainty analysis presented in this paper can be seen as one more step on the way to this goal

Fast evaluation of the Rayleigh integral and applications to inverse acoustics

In this paper we present a fast evaluation of the Rayleigh integral, which leads to fast and robust solutions in inverse acoustics. The method commonly used to reconstruct acoustic sources on a plane in space is Planar Nearfield Acoustic Holography (PNAH). Some of the most important recent improvements in PNAH address the alleviation of spatial windowing effects that arise due to the application of a Fast Fourier Transform to a finite spatial measurement grid. Although these improvements have led to an increase in the accuracy of the method, errors such as leakage and edge degradation can not be removed completely. Such errors do not occur when numerical models such as the Boundary Element Method (BEM) are used.Moreover, the forward models involved converge to the exact solution as the number of elements tends to infinity. However, the time and computer memory needed to solve these problems up to an acceptable accuracy is large. We present a fast (O(n log n) per iteration) and memory efficient (O(n)) solution to the planar acoustic problem by exploiting the fact that the transfer matrix associated with a numerical implementation of the Rayleigh integral is Toeplitz. In this paper we will address both the fundamentals of the method and its application in inverse acoustics. Special attention will be paid to comparison between experimental results from PNAH, IBEM and the proposed method

Near Source Acoustical Particle Velocity Measurements with Ambient Noise

An acoustical measurement very near a structure can be a cheap alternative to other contactless vibration measurement techniques such as laser vibrometry. However, measurements of the acoustical pressure suffer greatly from ambient noise, making these measurements unsuitable for many industrial applications. De Bree and Druyvesteyn suggested that a measurement of the acoustical particle velocity does not have this drawback and provided theory and qualitative measurement results [1]. We present quantitative measurement results of the relative noise contribution in pressure and particle velocity measurements. The ratio of these quantities receives special attention. The model used in previous research is a lumped model, in which some important aspects are neglected. We present results of a numerical model of the vibrating structure and the air. The numerical model and the measurements indicate the same trends but the lumped model does not describe the trends well. Nevertheless, this study also suggests that the sensitivity to background noise is generally considerably greater in pressure measurement than in a particle velocity measurement

Distributed multilevel optimization for complex structures

Optimization problems concerning complex structures with many design variables may entail an unacceptable computational cost. This problem can be reduced considerably with a multilevel approach: A structure consisting of several components is optimized as a whole (global) as well as on the component level. In this paper, an optimization method is discussed with applications in the assessment of the impact of new design considerations in the development of a structure. A strategy based on fully stressed design is applied for optimization problems in linear statics. A global model is used to calculate the interactions (e.g., loads) for each of the components. These components are then optimized using the prescribed interactions, followed by a new global calculation to update the interactions. Mixed discrete and continuous design variables as well as different design configurations are possible. An application of this strategy is presented in the form of the full optimization of a vertical tail plane center box of a generic large passenger aircraft. In linear dynamics, the parametrization of the component interactions is problematic due to the frequency dependence. Hence, a modified method is presented in which the speed of component mode synthesis is used to avoid this parametrization. This method is applied to a simple test case that originates from noise control. \u

Employment Protection, Technology Choice, and Worker Allocation

Using a country-industry panel dataset (EUKLEMS) we uncover a robust empirical regularity, namely that high-risk innovative sectors are relatively smaller in countries with strict employment protection legislation (EPL). To understand the mechanism, we develop a two-sector matching model where firms endogenously choose between a safe technology with known productivity and a risky technology with productivity subject to sizeable shocks. Strict EPL makes the risky technology relatively less attractive because it is more costly to shed workers upon receiving a low productivity draw. We calibrate the model using a variety of aggregate, industry and micro-level data sources. We then simulate the model to reflect both the observed differences across countries in EPL and the observed increase since the mid-1990s in the variance of firm performance associated with the adoption of information and communication technology. The simulations produce a differential response to the arrival of risky technology between low- and high-EPL countries that coincides with the findings in the data. The described mechanism can explain a considerable portion of the slowdown in productivity in the EU relative to the US since 1995.employment protection legislation, exit costs, information and communications technology, heterogeneous productivity, sectoral allocation

Source localization using acoustic vector sensors: a music approach

Traditionally, a large array of microphones is used to localize multiple far field sources in acoustics. We present a sound source localization technique that requires far less channels and measurement locations (affecting data channels, setup times and cabling issues). This is achieved by using an acoustic vector sensor (AVS) in air that consists of four collocated sensors: three orthogonally placed acoustic particle velocity sensors and an omnidirectional sound pressure transducer. Experimental evidence is presented demonstrating that a single 4 channel AVS based approach accurately localizes two uncorrelated sources. The method is extended to multiple AVS, increasing the number of sources that can be identified. Theory and measurement results are presented. Attention is paid to the theoretical possibilities and limitations of this approach, as well as the signal processing techniques based on the MUSIC method

Effects of Environmentally Relevant Concentrations of 4-methyl-1- cyclohexanemethanol (MCHM) on General Esterase and Glutathione-S-Transferase Activity in Fathead Minnows (Pimephales promela)

Abstract In 2014, several thousand gallons of coal-processing chemicals, which included 4-methyl-1- cyclohexanemethanol (MCHM), spilled into the Elk River in West Virginia. The location of this spill in West Virginia’s chemical valley is historically significant in defining the exploitations of people residing in this area. The concentration of crude MCHM in the river was approximated at 0.15 µg/L. Although some initial studies did consider the effects of MCHM exposure on humans, little attention has been given to aquatic wildlife. In this project, I will expose fathead minnows, Pimephales promelas, an environmentally relevant species, to concentrations of MCHM between zero and fifty ppm for 72 hours. General Esterase and Glutathione-S-Transferase enzyme activities will be measured using whole body protein extracts, and compared to the control groups. I expect to see a significant increase in the activity of both systems. Increased activity could indicate that the fish have exhibited a detoxification response, which has potential implications for the endogenous functions of these enzyme systems