2,395 research outputs found
Photograph of Dorothy F. Steele in the surf in Myrtle Beach, S.C., August, 1972
No full textColor photograph of Dorothy F. Steele in the surf at Myrtle Beach, S.C. in August of 1972
Alternative approaches to multilevel modelling of survey non-contact and refusal
No full textWe review three alternative approaches to modelling survey non-contact and refusal: multinomial, sequential, and sample selection (bivariate probit) models. We then propose a multilevel extension of the sample selection model to allow for both interviewer effects and dependency between non-contact and refusal rates at the household and interviewer level. All methods are applied and compared in an analysis of household non-response in the United Kingdom, using a data set with unusually rich information on both respondents and non-respondents from six major surveys. After controlling for household characteristics, there is little evidence of residual correlation between the unobserved characteristics affecting non-contact and refusal propensities at either the household or the interviewer level. We also find that the estimated coefficients of the multinomial and sequential models are surprisingly similar, which further investigation via a simulation study suggests is due to non-contact and refusal having largely different predictor
Added mass energy recovery of octopus-inspired shape change
No full textDynamic shape change of the octopus mantle during fast jet escape manoeuvres results in added mass energy recovery to the energetic advantage of the octopus, giving escape thrust and speed additional to that due to jetting alone. We show through numerical simulations and experimental validation of overall wake behaviour, that the success of the energy recovery is highly dependent on shrinking speed and Reynolds number, with secondary dependence on shape considerations and shrinking amplitude. The added mass energy recovery ratio ?ma, which measures momentum recovery in relation to the maximum momentum recovery possible in an ideal flow, increases with increasing the non-dimensional shrinking parameter ??=a?max/URe0????, where a?max is the maximum shrinking speed, U is the characteristic flow velocity and Re0???? is the Reynolds number at the beginning of the shrinking motion. An estimated threshold ???10 determines whether or not enough energy is recovered to the body to produce net thrust. Since there is a region of high transition for 10<??<30 where the recovery performance varies widely and for ??>100 added mass energy is recovered at diminishing returns, we propose a design criterion for shrinking bodies to be in the range of 50<??<100, resulting in 61–82 % energy recovery
Alternative approaches to multilevel modelling of survey noncontact and refusal
No full textWe review three alternative approaches to modelling survey noncontact and refusal: multinomial, sequential and sample selection (bivariate probit) models. We then propose a multilevel extension of the sample selection model to allow for both interviewer effects and dependency between noncontact and refusal rates at the household and interviewer level. All methods are applied and compared in an analysis of household nonresponse in the UK, using a dataset with unusually rich information on both respondents and nonrespondents from six major surveys. After controlling for household characteristics, there is little evidence of residual correlation between the unobserved characteristics affecting noncontact and refusal propensities at either the household or the interviewer level. We also find that the estimated coefficients of the multinomial and sequential models are surprisingly similar, which further investigation via a simulation study suggests is due to there being little overlap between the predictors of noncontact and refusal
Natural Variation of the Circadian Clock in Neurospora
No full textMost living organisms on earth experience daily and expected changes from the rotation of the earth. For an organism, the ability to predict and prepare for incoming stresses or resources is a very important skill for survival. This cellular process of measuring daily time of the day is collectively called the circadian clock. Because of its fundamental role in survival in nature, there is a great interest in studying the natural variation of the circadian clock. However, characterizing the genetic and molecular mechanisms underlying natural variation of circadian clocks remains a challenging task. In this chapter, we will summarize the progress in studying natural variation of the circadian clock in the successful eukaryotic model Neurospora, which led to discovering many design principles of the molecular mechanisms of the eukaryotic circadian clock. Despite the success of the system in revealing the molecular mechanisms of the circadian clock, Neurospora has not been utilized to extensively study natural variation. We will review the challenges that hindered the natural variation studies in Neurospora, and how they were overcome. We will also review the advantages of Neurospora for natural variation studies. Since Neurospora is the model fungal species for circadian study, it represents over 5 million species of fungi on earth. These fungi play important roles in ecosystems on earth, and as such Neurospora could serve as an important model for understanding the ecological role of natural variation in fungal circadian clocks.Advances in Genetics, Vol. 99
Corrigendum to “A generic multi-level framework for microscopic traffic simulation with automated vehicles in mixed traffic” [Transport. Res. Part C: Emerg. Technol. 110 (2020) 291–311] (Transportation Research Part C (2020) 110 (291–311), (S0968090X19304322), (10.1016/j.trc.2019.11.019))
No full textThe authors regret that a contributing author was missing from the list of authors. The complete list of authors should be: “S.C. Calvert, B. van Arem, & J. W. C. van Lint”. All are with Delft University of Technology, Department of Transport & Planning, The Netherlands updated as above. The authors would like to apologise for any inconvenience caused.Transport and Plannin
OFR 07-07, Bedrock geology, topography, and karst feature inventory of Steele, Dodge, Olmsted and Winona Counties
No full textProject completed in 2004, not open-filed until 2007Final Project Report Regulating contaminant sources and addressing remediation of contaminated sites is difficult in sensitive
karst areas because of the unpredictable nature of groundwater movement in solution-weathered bedrock. In
this project, the Minnesota Departments of Health, Natural Resources and the Minnesota Pollution Control
Agency partnered with the Minnesota Geological Survey and the Department of Geology and Geophysics
– University of Minnesota, to develop better tools to understand and manage point and non-point sources on
contamination in karst terrains.
Contaminant Management in the Karst Region
Contract with MGS, also includes summary
information for 319 Karst Demonstration ProjectTipping, R.G.; Mossler, J.H.; Alexander, E. Calvin, Jr.; Gao, Y.; Green, Jeffrey A.; Alexander, S.C.. (2007). OFR 07-07, Bedrock geology, topography, and karst feature inventory of Steele, Dodge, Olmsted and Winona Counties. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/123367
Towards the Holy Grail: combining system dynamics and discrete-event simulation in healthcare
No full textThe idea of combining discrete-event simulation and system dynamics has been a topic of debate in theoperations research community for over a decade. Many authors have considered the potential benefits ofsuch an approach from a methodological or practical standpoint. However, despite numerous examples ofmodels with both discrete and continuous parameters in the computer science and engineering literature,nobody in the OR field has yet succeeded in developing a genuinely hybrid approach which truly integratesthe philosophical approach and technical merits of both DES and SD in a single model. In this paperwe consider some of the reasons for this and describe two practical healthcare examples of combinedDES/SD models, which nevertheless fall short of the “holy grail” which has been so widely discussed inthe literature over the past decade
Flooding observations in Rotterdam: mapping of flood-prone locations, flood vulnerability and risk analysis
No full textThis thesis focuses on identifying flood-prone locations, flood vulnerability and analyzing risk for the Municipality of Rotterdam. Municipal call center data of flooding complaints from 2012-2016 are investigated to identify the most flood-prone locations, which are called hot spots. This is performed by creating heat maps of the flooding record locations. The most dominant hot spots for multiple analyses are all situated in the sub districts of ‘Rotterdam Centrum’, ‘Delfshaven’ and ‘Noord’. Most flooding records are related to gully pots (≈55%), followed by sewer related problems (≈20%). Flood vulnerability is investigated by analyzing the influence of amount of inhabitants and degree of imperviousness on the hot spot locations. Both factors are involved in the origin of the hot spots. Investigating the influence of rainfall on flooding incidents pointed out an exponential relationship. From comparing differences in resulting flooding records for heavy/extreme rainfall events and cloudbursts, it can be concluded that Rotterdam’s drainage system is better capable at handling short heavy bursts of rainfall than consecutive hours of rainfall. The influence of seasonality on flooding incidents has also been investigated. There do appear to be seasonal patterns, which can be linked to blockages of gully pots by leave fall. In the risk & asset management analysis, asset maps related to infrastructure are created. They are used to calculate risk levels, based on the company values matrix of the Water Management department of Municipality of Rotterdam. The lower elevation of Rotterdam’s city center and surrounding downward slopes, which have been identified from the created elevation map, might contribute to the increased flood vulnerability and hot spots in the city center area.Civil Engineering and GeosciencesWater ManagementWater Resource Managemen
Investigating the MetOp ASCAT vegetation parameters
No full textIn this study, an unsupervised classification approach is used to investigate and characterize the spatial and temporal variability of MetOp-A ASCAT backscatter (σ◦) and the TUW SMR vegetation parameters across mainland France between 2007 and 2017. Currently, soil moisture data is retrieved from ASCAT backscatter measurements using the TU Wien Soil Moisture Retrieval (TUW SMR) approach. To correct for the influence of vegetation on soil moisture, two so-called ’vegetation parameters’ are also estimated from the backscatter measurements. These vegetation parameters are the slope (σ′) and curvature (σ′′) of a second-order Taylor polynomial which describes the incidence angle dependence of backscatter. Recently, Steele-Dunne et al. (2019) showed that the slope and curvature contain significant information about vegetation phenology and vegetation water dynamics across the North-American grasslands, suggesting that the vegetation parameters are a potentially valuable source of information on vegetation dynamics. This study further investigates the value of the vegetation parameters as a source of information about vegetation dynamics for land cover types present in France. 3492 ASCAT grid points were clustered using agglomerative hierarchical clustering based on σ′ and subsequently analysed. The results show that clusters based on σ′ are contiguous and can resemble distinct land cover features; areas like Paris and the Alps are clearly visible in cluster maps. While the clusters differ in terms of σ′ – which follows from a clustering based on σ′ – the results show that the clusters generally also have distinct σ◦ and σ′′ characteristics. This suggests that the clusters represent ’scattering surfaces’ that differ in terms of their seasonal scattering characteristics. It was found that grid points with a heterogeneous land cover footprint tend to have noisy seasonal backscatter signatures, while homogeneous land cover footprints have more recognizable seasonal behavior. Additionally, certain backscatter signatures tend to correspond to certain land cover footprints; in particular the agricultural area around Paris produced clear σ◦ , σ′, and σ′′ signatures corresponding to specific growth stages of wheat and the rapid land cover change during the agricultural season. In general, the results are consistent with the existing assumptions that σ′ is a measure for vegetation density and σ′′ is a measure for the relative dominance of ground-bounce and direct scattering from vertical vegetation constituents. Finally, clustering was performed on ten years of dynamically estimated σ′ and a measure for robustness was introduced to quantify the clustering certainty for each grid point. Robust grid points are found in areas that have relatively stable land cover like the Alps or Paris, suggesting that these areas exhibit predictable seasonal backscatter behavior with low interannual variability. Poor robustness scores are mainly found in north-west France, where land cover is heterogeneous and seasonal backscatter behavior is highly variable. This study confirms that the TUW SMR vegetation parameters contain valuable information about vegetation phenology across different land cover footprints. Furthermore, it was shown that unsupervised classification methods based on the vegetation parameters are able to identify areas with similar scattering characteristics, and are able to show how these areas change over time.Water Managemen
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