1,672 research outputs found
Atmospheric inputs of nitrogen.
No full textThe requirement for estimates of the terrestrial inputs of fixed nitrogen for Europe with a spatial resolution of between 5 km x 5 km and 50 km x 50 km places great demands on the monitoring information available and our knowledge of processes. It also provides a clear focus for the monitoring and process based research to provide both the input and an estimate of the uncertainty in inputs and its spatial variability.
For the estimates of critical loads exceedance maps for nitrogen, maps of the total inputs are of course essential. In this brief review the focus is on what is known, and can be mapped, what is not known because insufficient monitoring is in place, and lastly what is not known because the processes are not understood or for which key parameters are uncertain. In addition, because the principal applications of mapped data are to estimate critical loads exceedance, the issue of the scale dependence of deposition estimates and the extent to which current approaches can be extended to provide fine scale or land use specific resolution is considered qualitatively and to a limited extent quantitatively
Segmenting Mechanomyography Measures of Muscle Activity Phases Using Inertial Data
No full textThis dataset contains the data used in our manuscript titled "Segmenting Mechanomyography Measures of Muscle Activity Phases Using Inertial Data". Data structure is explained in the README.txt file located at the top-level of the dataset. Manuscript title in the README.txt file and contained in the title of the zip file are of a previous working title. Please contact corresponding author Richard B. Woodward for any questions.</span
Critical loads for nutrient nitrogen for soil-vegetation systems
No full textMembers of the UK Critical Loads Advisory Group (CLAG) have calculated critical loads for nutrient nitrogen to produce maps for Great Britain. The results of three methods, based upon the conclusions from the Lokeberg workshop are described below. Two of these methods use the empirical approachand the other the steady state equation ("mass balance") for nitrogen saturation
Modification of the simple mass balance equation for calculation of critical loads of acidity.
No full textOver the last few years, the simple mass balance equation for the calculation of critical loads of acidity has been gradually modified as the underlying critical load concepts have developed and as problems with particular forms of the equation have been identified, through application in particular countries. The first major update of the equation took place following a workshop held in Vienna, Austria (Hojesky et al. 1993). The workshop was held to discuss problems which had been identified when the then current form of the equation was applied in countries with high rainfall. The problems had largely arisen because of simplifications and assumptions incorporated into the early formulation of the equation. The equation was reformulated to overcome the problems identified at the workshop. However, further problems were identified when the reformulated equation was applied in the UK in situations with a combination of high rainfall, large marine inputs and widespread occurrence of organic soils. A small workshop was, therefore held in Grange-over-Sands, UK in late 1993 to dicuss the problems and to further re-evaluate the equation. The problems had arisen in the UK because of simplifications and assumptions made in the formulation concerning, in particular, cation leaching and uptake. As a result, a more rigorous treatment of these variables was incorporated into the equation. The reformulation of the equation, as derived at the September 1993 workshop is described below
Critical loads of nitrogen and their exceedance in UK freshwaters
No full textIn June 1994 the United Kingdom government signed the European sulphur protocol which committed them to a 70% reduction in SO2 emissions by the year 2005 and 80% by 2010, based on 1980 levels. This was the first instance of international legislation being formulated using the critical load concept. Notwithstanding the anticipated benefits to the environment of such reductions it was also recognised that such improvements could be diminished unless a similar approach was used to address the problem of increasing nitrogen emissions.
The Freshwater Sub-group of the UK Critical Loads Advisory Group (CLAG) has responsibility for evaluating available techniques for calculating critical loads for nitrogen and for establishing a scientific programme to address key issues and gaps in our knowledge of nitrogen dynamics. This paper summarises the preliminary findings of the Freshwater Group with respect to the nitrogen status and critical loads of UK freshwater
Critical loads for nitrogen to avoid eutrophication: assessment of the mass balance approach using the Aber site, N. Wales
No full textThe nitrogen critical load to avoid eutrophication has been calculated for a 32 year old stand of Sitka spruce in N.Wales which has been intensively studied for 4 years. Default and measured values for the mass balance equation have been used to calculate a range of probable nitrogen critical load values which have then been compared to the range estimated from methods other than the mass balance approach
Exceedances of acidity and nutrient nitrogen critical loads
No full textA CLF for an ecosystem simply defines protection and exceedance for all ratios of sulphur and nitrogen deposition in relation to acidity and nutrient nitrogen critical loads. However, when the load is exceeded it is possible to relate exceedance to excess sulphur, nitrogen, or both, by examination of the relative deposition loads of sulphur and nitrogen. In this exercise we have defined a number of regions, described by the CLF parameters, which help indicate reduction strategies for sulphur and nitrogen deposition
Mixed-Mode Fatigue Disbond on Metallic Bonded Joints
No full textAerospace structures have been long dealing with the safety versus weight issue. Lighter airplanes are cheaper to operate, however, they may face a safety issue because of the reduced fatigue life. Consequently, a heavier/safer structure is designed. Adhesive bonding is a joining technique that offers potential for improvement in the fatigue behavior of a structure, resulting in reduced weight. However, predicting the fatigue behavior of a bonded joint for its use in a damage tolerance design philosophy still remains a problem with no satisfactory solution. Often, the joint is subjected to a combination of peeling and shearing stresses. Hence, one of the most important factors influencing the fatigue behavior of an adhesively bonded joint is the Mode Ratio. The objective of this investigation was to study of the Mode Ratio on the fatigue behavior of a bonded joint. First, the fatigue disbond mechanisms were investigated throughout the entire Mode Ratio range and compared to fatigue delamination mechanisms. After the mechanisms were identifed, a parameter related to the mechanisms was chosen as similitude in the Paris relation and the Mixed-Mode fatigue disbond model was developed. Later, the model was evaluated on a different adhesive and on a condition of variable Mode Ratio. The fatigue disbond mechanisms study identified the local principal stress as the driving force for the micro-crack formation and growth, and the Mode Ratio was identified as the controlling parameter for coalescence between the micro-cracks. Based on these findings, a parameter directly related to the principal stress was proposed as a similitude parameter. Additionally, a linear interpolation between Mode I and Mode II parameters of the Paris relation was proposed to predict the Mixed-Mode fatigue behavior. Thus, the model predicts the fatigue behavior for the entire Mode Ratio range using only pure Mode I and pure Mode II as inputs. The evaluation of this model revealed that it presents good predictions for Mode Ratios in the range of 0% to 50% and conservative predictions in the range of 50% to 100%. The model also seems to be valid in a variable Mode Ratio condition. The limitations and shortcomings of the model along with the limitations of using a damage tolerance philosophy on adhesive bonding were discussed. Despite these issues, the model is an improvement over the models available in the literature because it captures some of the phenomena involved in the Mixed-Mode fatigue disbond. Additionally, the model also reduces the amount of empirical data required for its implementation.Aerospace Structures and MaterialsAerospace Engineerin
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