Physical Custody in Wisconsin Divorce Cases, 1980–1992

This report examines data from the court record of 9,500 Wisconsin divorce cases in twenty-one representative counties for a period of twelve years, from 1980 to 1992, in order to document how child custody is being handled in divorce. We find an increased involvement of fathers with their children after divorce, particularly through joint legal custody (81 percent in 1992), but also in shared physical custody (14 percent in 1992), and in an increase in specific and detailed physical placement awards. We find substantial differences in custody awards related to situations and actors in the divorce process, and wide variations in custody awards between counties. We also find major differences between families who have equal 50/50 time-share and those who have unequal shared-custody arrangements. These two kinds of shared-custody cases have been treated as one type in the research on custody to date, but appear in our data to characterize two quite different kinds of families.

An Analysis of Finite Difference and Galerkin Techniques Applied to the Simulation of Advection and Diffusion of Air Pollutants from a Line Source

A finite difference and a Galerkin type scheme are compared with reference to a very accurate solution describing time dependent advection and diffusion of air pollutants from a line source in an atmosphere vertically stratified and limited by an inversion layer. The accurate solution was achieved by applying the finite difference scheme on a very refined grid with a very small time step. Grid size and time step were defined according to stability and accuracy criteria discussed in the text. It is found that for the problem considered, the two methods can be considered equally accurate. However, the Galerkin method gives larger areas of small errors close to the source, This was assumed to be partly due to the different way the source term is taken into account by the two methods. An improvement of the accuracy of the finite difference scheme was achieved by approximating, at every step, the contribution of the source term by a Gaussian puff moving and diffusing with velocity and diffusivity of the source location, instead of utilizing a stepwise function for the numerical approximation of the delta function representing the source term

Real-Time Forecasting of Air Pollution Episodes in the Venetian Region. Part I: The Advection-Diffusion Model. Part II: The Kalman Predictor

The object of this overall research, which has an expected duration of two years is to set up a scheme for predicting ground-level pollutant concentrations for real-time control purposes (i.e. the action to be taken at the emission sources in the presence of forthcoming high pollutant events). The forecasting scheme is described, together with its application to sulphur dioxide pollution in the Venetian lagoon area. The scheme is based on a complex mathematical model to be run on a computer and receiving at the beginning of each interval of time all the information (about the meteorological and emission situation) required for the prediction. The type of control action which should be taken on the basis of such a forecast is the object of this part of the research

Mathematical Models for Planning and Controlling Air Quality; Proceedings of an IIASA Workshop, October 1979

Air-quality management problems fall into three main classes: it is difficult to obtain a reliable picture of all the physicochemical processes involved, comprehensive assessments of the costs and benefits of alternative control strategies are not easily made, and the technology for pollution abatement is not yet well established. Various mathematical or formal management models do exist but the overall impact of modeling on decision making has so far been relatively small. The first aim of the IIASA Workshop on which this volume is based was to bridge the gap between air-quality modeling and management. As described in the ten papers in Part One, Workshop participants examined the goals actually pursued by decision makers, the potential role of mathematical models in air-quality management, and the extent to which modeling has been used in real situations in a number of countries. The Workshop's second aim, reported in the eight papers in Part Two, was to consider the unusual strategy of real-time emission control. An extended description of the IIASA case study of the Venetian Lagoon area was presented, together with contributions on real-time forecast and control schemes in operation in Japan and Italy

Escape panels in trawls: does placement matter when every individual contacting the panel can escape?

Escape panels are one of the bycatch reduction devices most used in trawl fisheries but their efficiency rely on fish actively contacting the panel to escape. To investigate if contact behaviour changes at different panel placements, we tested a 300 mm square mesh panel placed in the upper panel of the codend at 3, 4 and 7 m from the codline. Seven competing models of contact probability were fitted to the empirical data. Based on the results, we inferred that panel placement significantly affects escape efficiency due to a change in type of contact behaviour. Cod (Gadus morhua) showed a contact increasing with length when the panel was closest to the codline, while contact probability decreased with length at the other placements. Similarly, contact probability for plaice (Pleuronectes platessa) was found to increase with length at 3 and 4 m, whereas a length-independent contact best represented the data at 7 m. Finally, Nephrops (Nephrops norvegicus) had in general low contact probability. The results provide new knowledge regarding species and placement-dependent panel escape

FLEXSELECT: counter-herding device to reduce bycatch in crustacean trawl fisheries

FLEXSELECT is a simple counter-herding device which aims at reducing the bycatch of fish by scaring them away from the trawl path without affecting the catches of the target species. FLEXSELECT was tested in the Norway lobster (Nephrops norvegicus) directed trawl fishery, as this includes bycatch of both roundfish and flatfish. Length-based data were collected for Nephrops, four roundfish species (cod, haddock, whiting and hake) and two flatfish species (plaice and lemon sole) and length-based catch comparisons performed. No significant effect on the target species, Nephrops, was detected, whereas a reduction of 39% (CI: 29-46 %) was obtained for the overall number of fish. Catches of all the six fish species examined were significantly reduced by FLEXSELECT, with the efficiency varying considerably among species and over length classes. No significant diel differences were found for either roundfish or flatfish species. FLEXSELECT prevents bycatch species from interacting with the trawl, thus most likely enhancing their survival and fitness. Moreover, its fast attachment system makes FLEXSELECT a flexible tool, adaptable to different fisheries and catch goals.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The capability of square-meshes and fixed-shape meshes to control codend size selection

Trawl codends are commonly made of diamond-mesh netting. However, diamond-mesh codends vary in mesh geometry along its length and during fishing due to catch build up. This introduces variability in the size selection process. This phenomenon compromises the rationality of regulating exploitation patterns in trawl fisheries through adjustments in codend mesh size. One technical solution often applied to achieve more welldefined size selection is turning the codend netting 45 degrees (square-mesh). However, there is a lack of evidence that square-mesh codends result in more constant size selectivity. Therefore, we aimed at quantifying the variability in size selection in square-mesh codends. We tested the size selectivity of three codends; a standard square-mesh codend, and two rigid codends where mesh geometries were fixed in diamond shape with an opening angle of 60◦ and square shape, respectively. The two rigid codends were used to establish baselines with limited variability in size selection. The size selectivity of these codends was compared to results - previously obtained for a standard diamond-mesh codend. Using Atlantic cod (Gadus morhua) as a case study, we demonstrated that the standard square-mesh codend had significantly larger variability in size selection compared to the fixed diamond-mesh codend. Moreover, we found no evidence that the standard square-mesh codend had lower variability in size selection than a standard diamond-mesh codend with same mesh size. These results demonstrate that the use of standard square-mesh codends is not sufficient to reduce variability in codend size selection. Additionally, we demonstrate that the sizes of fish retained is strongly dependent on mesh shape and openness. We conclude that a profound re-thinking over codend designs is required in order to achieve better control of size selection in trawl fisheries

Real-Time Control of Sulphur Dioxide Emissions from an Industrial Area

Real-time emission control is an air quality policy which is alternative to permanent emission reduction. In general terms, it consists of controlling emission only when a forthcoming episode is forecast. Thus, control costs are lower than costs due to permanent abatement. The natural application is a case characterized by a limited number of polluting sources. In more specific terms, a real-time emission control scheme consists of the following operations at the beginning of each time interval (hour,say): (i) Collect current concentration and meteorological measures by a monitoring network. (ii) Forecast future values of relevant local meteorological variables. (iii) On the basis of information about current concentration values, forecast meteorology and scheduled emissions predict future concentrations. (iv) If future concentrations exceed some reference level, reduce the scheduled emissions. The paper describes a case study [application of scheme (i)-(iv)] to sulphur dioxide pollution from the industrial area in the Venetian lagoon region. The general characteristics are the following: The meteorological predictors [step (ii)] are simple stochastic mathematical predictors. The concentration predictor [step (iii)] is based on a complex forecast algorithm (Kalman predictor). It is derived from the "stochastic version" of the numerical solution of the advection- diffusion partial differential equation. The control policy [step(iv)] is assumed to consist of mixing with cleaner fuel under the constraint of maintaining the production scheduled by each polluting plant. The results of the case study are supplied as cost-effectiveness curves (cost versus effectiveness of the control action)