The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
A L Collins - One of the best experts on this subject based on the ideXlab platform.
-
developing Demonstration Test catchments as a platform for transdisciplinary land management research in england and wales
Environmental Science: Processes & Impacts, 2014Co-Authors: Daniel F Mcgonigle, A L Collins, S Burke, Richard Gartner, M R Haft, R C Harris, P M Haygarth, Mark Hedges, Kevin M HiscockAbstract:Whilst a large body of plot and field-scale research exists on the sources, behaviour and mitigation of diffuse water pollution from agriculture, putting this evidence into a practical, context at large spatial scales to inform policy remains challenging. Understanding the behaviour of pollutants (nutrients, sediment, microbes and pesticides) and the effectiveness of mitigation strategies over whole catchments and long timeframes requires new, interdisciplinary approaches to organise and undertake research. This paper provides an introduction to the Demonstration Test catchments (DTC) programme, which was established in 2009 to gather empirical evidence on the cost-effectiveness of combinations of diffuse pollution mitigation measures at catchment scales. DTC firstly provides a physical platform of instrumented study catchments in which approaches for the mitigation of diffuse agricultural water pollution can be experimentally Tested and iteratively improved. Secondly, it has established national and local knowledge exchange networks between researchers and stakeholders through which research has been co-designed. These have provided a vehicle to disseminate emerging findings to inform policy and land management practice. The role of DTC is that of an outdoor laboratory to develop knowledge and approaches that can be applied in less well studied locations. The research platform approach developed through DTC has brought together disparate research groups from different disciplines and institutions through nationally coordinated activities. It offers a model that can be adopted to organise research on other complex, interdisciplinary problems to inform policy and operational decision-making.
-
contemporary fine grained bed sediment sources across the river wensum Demonstration Test catchment uk
Hydrological Processes, 2013Co-Authors: A L Collins, Y Zhang, R Hickinbotham, G Bailey, S Darlington, S E Grenfell, Robert Evans, M S A BlackwellAbstract:Because the sources of fine-grained sediment problems in river systems are diffuse, it is essential to assemble catchment scale information for informing management strategies. Sediment source-tracing procedures have increasingly been adopted in this respect. Accordingly, a recently refined composite tracing procedure was used to investigate contemporary sources of fine-grained channel bed sediment in 11 sub-catchments (364 km2) of the River Wensum Demonstration Test Catchment, in the eastern UK. The procedure incorporated a combination of statistical Tests for discriminating source end members, plus numerical mass balance modelling incorporating weightings for within-source tracer variations and tracer-specific discriminatory power, as well as a combination of local and genetic algorithm optimisation coupled with Monte Carlo uncertainty analysis. Replicate Monte Carlo runs demonstrated the convergence of the modelling outputs within ±1% of the average medians. Relative frequency-weighted average median source type contributions were estimated to range between 27%–69% (agricultural topsoils; predicted deviate median inputs 0%–98% and 9%–100%), 0%–38% (damaged road verges; predicted deviate median inputs 0%–58% and 0%–100%) and 21%–48% (channel banks/subsurface sources; predicted deviate median inputs 0%–50% and 4%–50%). The study provides further evidence of the importance of channel banks and damaged road verges as sediment sources and the need to include such areas in catchment sediment management strategies. Copyright © 2012 John Wiley & Sons, Ltd.
-
application of the farmscoper tool for assessing agricultural diffuse pollution mitigation methods across the hampshire avon Demonstration Test catchment uk
Environmental Science & Policy, 2012Co-Authors: Y Zhang, A L Collins, R GoodayAbstract:Abstract Agricultural diffuse pollution is a significant contributor to water and air quality in many catchments and the need to control harmful emissions remains paramount for government policy. In England, the Demonstration Test Catchments (DTCs) have been established to provide a basis for Testing on-farm mitigation measures using collaborative multi-partner research and some of this work is targeting the Hampshire Avon (∼1700 km2) catchment. To help provide integrated farm advice across England and Wales, a new Excel-based tool, FARM Scale Optimisation of Pollutant Emission Reductions (FARMSCOPER), has recently been developed for characterising diffuse agricultural pollutant emissions from representative farm types and quantifying the expected impacts of control options on those losses to the environment. Against this background, this paper describes the application of FARMSCOPER in the Hampshire Avon DTC in order to assess its utility at catchment scale and the potential benefits of relevant and practical mitigation options. Spatial datasets and the Agricultural Census returns for 2009 specific to the River Avon catchment were integrated to produce a collection of representative farm types which capture the characteristics of the local physical environment, land use patterns and farm management practices. FARMSCOPER was used to estimate the annual emissions of nitrate, phosphorus, sediment, nitrous oxide, methane and ammonia for each representative farm type. The scenarios investigated comprised baseline losses with no mitigation measures implemented, current emissions using information on the present implementation of options under existing schemes and initiatives and, the maximum potential reduction possible on the basis of implementing all available and relevant options. Model outputs suggested that reductions in pollutant loads in response to the existing uptake of mitigation methods are small (e.g. 10% for phosphorus, 7% for sediment, 4% for nitrate and 5% for nitrous oxide). FARMSCOPER suggested that technically feasible pollutant reductions on the basis of the implementation of more mitigation options could be of the order of 47% for phosphorus, 66% for sediment, 22% for nitrate and 16% for nitrous oxide. This work represents the first catchment scale application of the FARMSCOPER tool.
Min Xie - One of the best experts on this subject based on the ideXlab platform.
-
reliability Demonstration Test for load sharing systems with exponential and weibull components
PLOS ONE, 2017Co-Authors: Min XieAbstract:Conducting a Reliability Demonstration Test (RDT) is a crucial step in production. Products are Tested under certain schemes to demonstrate whether their reliability indices reach pre-specified thresholds. Test schemes for RDT have been studied in different situations, e.g., lifetime Testing, degradation Testing and accelerated Testing. Systems designed with several structures are also investigated in many RDT plans. Despite the availability of a range of Test plans for different systems, RDT planning for load-sharing systems hasn’t yet received the attention it deserves. In this paper, we propose a Demonstration method for two specific types of load-sharing systems with components subject to two distributions: exponential and Weibull. Based on the assumptions and interpretations made in several previous works on such load-sharing systems, we set the mean time to failure (MTTF) of the total system as the Demonstration target. We represent the MTTF as a summation of mean time between successive component failures. Next, we introduce generalized Test statistics for both the underlying distributions. Finally, RDT plans for the two types of systems are established on the basis of these Test statistics.
-
an approach for reliability Demonstration Test based on power law growth model
Quality and Reliability Engineering International, 2017Co-Authors: Min XieAbstract:Reliability Demonstration Test (RDT) is a critical and necessary step before the acceptance of an industrial system. Generally, a RDT focuses on designing a Test plan through which one can judge whether the system reliability indices meet specific requirements. There are many established RDT plans, but few have incorporated the reliability growth aspects of the corresponding products. In this paper, we examine a comprehensive Test plan that involves information concerning the reliability growth stage. An approach for RDT under the assumption of the power-law model is proposed. It combines data related to the growth stage with those pertaining to the Test stage of the product to reduce the cost of the Test. Through simulation studies and numerical examples, we illustrate the characteristics of the Test plan and significant reduction in Test costs through our approach. Copyright © 2017 John Wiley & Sons, Ltd.
-
bayes reliability Demonstration Test plan for series systems with binomial subsystem data
Reliability and Maintainability Symposium, 1998Co-Authors: Lin Mei Ten, Min XieAbstract:One reason that the Bayesian approach to reliability Demonstration has not gained popularity in industry is the difficulty in establishing the prior. The problem becomes more complicated when only subsystem data are available. It has received little attention in the existing literature and this paper makes an attempt to do that. A method is proposed to derive the Bayesian reliability Demonstration Test plan for series systems with binomial subsystem data. The method makes use of Mann's approximately optimum lower confidence bound model to derive the system prior based on binomial subsystem data. The system Bayesian reliability Demonstration Test plan can then be derived using existing methods for meeting posterior confidence requirements. The proposed method is easy to apply and no complicated computation is involved in deriving the system prior distribution. It uses objective subsystem Test data. No subjective judgement is required. This method is most beneficial for systems that already have substantial subsystem Test data before the reliability Demonstration.
A.e. Gera - One of the best experts on this subject based on the ideXlab platform.
-
A General Model for Start-Up Demonstration Tests
IEEE Transactions on Reliability, 2011Co-Authors: A.e. GeraAbstract:The commonly known consecutive successes total failures (CSTF) start-up Demonstration Test procedure is generalized to a total successes consecutive successes total failures consecutive failures (TSCSTFCF) procedure. Accordingly, a unit under Test is accepted when either a total number of successful Tests or a specified number of consecutive successes of Tests are observed before both a total number of failures and any run of specified length of failures; otherwise the unit is rejected. The waiting time until termination (the length of the set of Tests) of the general procedure is evaluated. A correct choice of parameters (e.g. the number of successes required for acceptance, or the length of a run of failures causing rejection) may yield a significantly shorter waiting time than that of the relevant CSTF procedure. Also, the new procedure is less sensitive to parameter changes, which is an obvious improvement in case the parameter values are miss-specified. We provide interval confidence bounds for the estimation of the reliability for the start-up Demonstration Test, which is based on maximum likelihood estimators. Then, we determine the minimum sample size needed in a Demonstration Test to achieve a certain precision of this reliability at a specified confidence level.
-
A New Start-Up Demonstration Test
IEEE Transactions on Reliability, 2010Co-Authors: A.e. GeraAbstract:The commonly known consecutive successes total failures (CSTF) start-up Demonstration Test procedure is improved to a total successes consecutive successes total failures (TSCSTF) procedure. Accordingly, a unit under Test is accepted when either a total number of successful Tests, or a specified number of consecutive successes of Tests are observed before a total number of failures; otherwise the unit is rejected. The waiting time until termination (the length of the set of Tests) of the new procedure is evaluated. A correct choice of parameters (e.g. the number of successes required for acceptance, the total number of failures causing rejection) using the new procedure may yield a shorter waiting time than that of the relevant CSTF procedure.
Y Zhang - One of the best experts on this subject based on the ideXlab platform.
-
contemporary fine grained bed sediment sources across the river wensum Demonstration Test catchment uk
Hydrological Processes, 2013Co-Authors: A L Collins, Y Zhang, R Hickinbotham, G Bailey, S Darlington, S E Grenfell, Robert Evans, M S A BlackwellAbstract:Because the sources of fine-grained sediment problems in river systems are diffuse, it is essential to assemble catchment scale information for informing management strategies. Sediment source-tracing procedures have increasingly been adopted in this respect. Accordingly, a recently refined composite tracing procedure was used to investigate contemporary sources of fine-grained channel bed sediment in 11 sub-catchments (364 km2) of the River Wensum Demonstration Test Catchment, in the eastern UK. The procedure incorporated a combination of statistical Tests for discriminating source end members, plus numerical mass balance modelling incorporating weightings for within-source tracer variations and tracer-specific discriminatory power, as well as a combination of local and genetic algorithm optimisation coupled with Monte Carlo uncertainty analysis. Replicate Monte Carlo runs demonstrated the convergence of the modelling outputs within ±1% of the average medians. Relative frequency-weighted average median source type contributions were estimated to range between 27%–69% (agricultural topsoils; predicted deviate median inputs 0%–98% and 9%–100%), 0%–38% (damaged road verges; predicted deviate median inputs 0%–58% and 0%–100%) and 21%–48% (channel banks/subsurface sources; predicted deviate median inputs 0%–50% and 4%–50%). The study provides further evidence of the importance of channel banks and damaged road verges as sediment sources and the need to include such areas in catchment sediment management strategies. Copyright © 2012 John Wiley & Sons, Ltd.
-
application of the farmscoper tool for assessing agricultural diffuse pollution mitigation methods across the hampshire avon Demonstration Test catchment uk
Environmental Science & Policy, 2012Co-Authors: Y Zhang, A L Collins, R GoodayAbstract:Abstract Agricultural diffuse pollution is a significant contributor to water and air quality in many catchments and the need to control harmful emissions remains paramount for government policy. In England, the Demonstration Test Catchments (DTCs) have been established to provide a basis for Testing on-farm mitigation measures using collaborative multi-partner research and some of this work is targeting the Hampshire Avon (∼1700 km2) catchment. To help provide integrated farm advice across England and Wales, a new Excel-based tool, FARM Scale Optimisation of Pollutant Emission Reductions (FARMSCOPER), has recently been developed for characterising diffuse agricultural pollutant emissions from representative farm types and quantifying the expected impacts of control options on those losses to the environment. Against this background, this paper describes the application of FARMSCOPER in the Hampshire Avon DTC in order to assess its utility at catchment scale and the potential benefits of relevant and practical mitigation options. Spatial datasets and the Agricultural Census returns for 2009 specific to the River Avon catchment were integrated to produce a collection of representative farm types which capture the characteristics of the local physical environment, land use patterns and farm management practices. FARMSCOPER was used to estimate the annual emissions of nitrate, phosphorus, sediment, nitrous oxide, methane and ammonia for each representative farm type. The scenarios investigated comprised baseline losses with no mitigation measures implemented, current emissions using information on the present implementation of options under existing schemes and initiatives and, the maximum potential reduction possible on the basis of implementing all available and relevant options. Model outputs suggested that reductions in pollutant loads in response to the existing uptake of mitigation methods are small (e.g. 10% for phosphorus, 7% for sediment, 4% for nitrate and 5% for nitrous oxide). FARMSCOPER suggested that technically feasible pollutant reductions on the basis of the implementation of more mitigation options could be of the order of 47% for phosphorus, 66% for sediment, 22% for nitrate and 16% for nitrous oxide. This work represents the first catchment scale application of the FARMSCOPER tool.
Serkan Eryilmaz - One of the best experts on this subject based on the ideXlab platform.
-
Start-Up Demonstration Test Based on Total Successes and Total Failures With Dependent Start-Ups
IEEE Transactions on Reliability, 2012Co-Authors: Femin Yalcin, Serkan EryilmazAbstract:Start-up Demonstration Testing is an effective method for illustrating the reliability of a unit before purchasing it. The Test consists of starting-up the unit, and observing the outcomes, either success or failure. According to the total successes total failures (TSTF) Test procedure, a unit under Test is accepted when a specified number of successes is observed before a specified number of failures; otherwise, the unit is rejected. We study the TSTF procedure for dependent start-ups where the outcome of the present start-up depends on the total number of successful start-ups so far. The main characteristics of the TSTF Test are obtained under this previous-sum dependent model, and numerical illustrations are presented.