Passive capillary wick samplers (PCAPs) are primarily used to sample water from the vadose zone. PCAPs use fiberglass wicks to form a hanging water column that exerts suction on the surrounding soil. Although PCAPs have been used to estimate soil water flux, the accuracy with which PCAPs can estimate flux comes into question due to over/undersampling caused by this applied flux. I used numerical models to explore the effects of a PCAP on flow through the vadose zone. Specifically, I used a two-dimensional axisymmetric flow model of a PCAP embedded in a medium based on HYDRUS. Both steady-state and transient conditions were simulated through the application of various precipitation rates and periods across several soil textures. In this study, I examine soil hydraulic properties, across the soil texture triangle, subject to a range of precipitation events. Results show that the PCAP does over/underestimate water flux. The degree of error is quantified by defining a capture efficiency, which is the ratio of the flux into the plate and the flux that would occur at the same depth with no PCAP present. Higher fluxes and longer time periods resulted in increased convergence of flux into the PCAP, while lower fluxes and shorter durations resulted in divergence of flux from the PCAP. The goal of the study is to understand the behavior of PCAPs under different conditions and to use that knowledge to interpret field measurements in the Jemez River Basin Critical Zone Observatory.

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Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-14T15:19:06Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado Gleidson Souza 2015.pdf: 4384688 bytes, checksum: 2b4f7a78258ef6b6b60955ac938994a0 (MD5) / Made available in DSpace on 2016-07-14T15:19:06Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Mestrado Gleidson Souza 2015.pdf: 4384688 bytes, checksum: 2b4f7a78258ef6b6b60955ac938994a0 (MD5) Previous issue date: 2015-05-15 / CAPEs / A probabilidade é um importante conteúdo e possui aplicações em outras áreas do conhecimento. Pesquisadores destacam a importância de conteúdos de probabilidade por possibilitar o desenvolvimento da criticidade e leitura de mundo pelos educandos, contudo realçam a escassez de estudos na área. Nesta pesquisa investigamos conhecimentos de estudantes do 9º ano do Ensino Fundamental sobre probabilidade com o uso da ferramenta Sampler do TinkerPlots 2.0. Buscou-se em específico, identificar conhecimentos prévios dos estudantes sobre probabilidade; descrever conhecimentos dos estudantes sobre probabilidade a partir de experimento aleatório não realizado e realizado no ambiente físico; e explorar a ferramenta Sampler do TinkerPlots para mobilizar conhecimentos dos estudantes sobre probabilidade. Quatro estudantes do 9º ano oriundos de uma escola pública do Recife participaram de quatro etapas de coleta de dados: 1) entrevista semi-estruturada com ênfase na investigação do perfil dos estudantes; 2) teste diagnóstico com questões sobre concepções e sobre experimento aleatório não realizado e realizado no ambiente físico. Nessas etapas iniciais os estudantes trabalharam individualmente. Em seguida, eles realizaram em duplas uma fase final do experimento realizado no ambiente físico; 3) na terceira etapa, subdividida em dois momentos, os estudantes em duplas, participaram de uma sessão de familiarização com o TinkerPlots para conhecer sua interface e ferramentas. Após esse contato inicial com o software eles participaram de uma sessão com o uso mais autônomo da ferramenta Sampler. Todo o processo ocorreu em dias alternados; 4) ao final da atividade de simulação com o Sampler, os estudantes realizaram novamente o teste diagnóstico administrado inicialmente, na segunda etapa, seguindo os mesmos procedimentos. Existem evidências de que as concepções iniciais dos estudantes estiveram mais voltadas para conhecimentos intuitivos sobre probabilidade. Ao longo das situações de pesquisa, mais particularmente no teste final, essas concepções foram ampliadas para incluir ideias de aleatoriedade, incerteza e chance. Seus conhecimentos sobre espaço amostral também foram se tornando mais explícitos a partir de suas reflexões sobre os experimentos aleatórios. O trabalho com a ferramenta Sampler do TinkerPlots permitiu que os estudantes realizassem simulações com tamanhos crescentes de amostras e verificassem as alterações nas representações gráficas produzidas. Esse processo foi realizado de forma dinâmica e mediado por diálogos e intervenções específicas do pesquisador. O TinkerPlots, por possibilitar a simulação de experimentos com tamanhos de amostras variadas pode ter contribuído para os estudantes refletirem melhor sobre a relação entre probabilidade teórica e probabilidade advinda da experimentação. Conclui-se que embora os estudantes não possuam conhecimentos formalizados sobre probabilidade, eles foram capazes de aprofundar suas ideias iniciais sobre aspectos cruciais desse conceito como é o caso de espaço amostral e da relação sobre probabilidade teórica e frequencial. Novas pesquisas devem ser feitas para investigar outras possibilidades do uso do software TinkerPlots para mobilizarem conhecimentos sobre probabilidades. / The probability is an important discipline and has application in many branch of human knowledge. Researchers emphasize the importance of probability related disciplines for enhancement students critical thinking about the real world problems; however they also highlight the shortage of studies in the area. In this research we investigate students knowledge in 9th grade about probability with the support of the software tool Sampler do TinkerPlots 2.0. Specifically, we sought to identify prior knowledge of students about probability; describe students knowledge about probability based on experiments realized and not realized in physical environment; and to explore the Sampler tool of TinkerPlots in order to students enhance and apply their knowledge about probabilit. Four 9th grade students from a public school in Recife participated in the four data collection steps: 1) semi-structured interview with an emphasis on investigating the student profile; 2) diagnostic test with questions about concepts and random experiments realized both in physical environment and not physical environment. In these initial steps the students worked individually. Then they performed, in pairs, the final experiment phase in a physical environment; 3) in the third step, divided into two different moments, the pairs were introduced to the TinkerPlots interface and tools. After this initial contact with the software, they attended a session with more autonomous use of the Sampler tool. The whole process was performed on alternate days; 4) at the end of the activity involving simulation with the use of the Sampler, the students were submited again to the diagnostic test administered initially in the second step, following the same procedures. There is evidence that the initial conceptions of the students were more focused on intuitive knowledge of probability. Over the situations found during the research, particularly in the final test, these conceptions were broadened in order to include ideas of randomness, uncertainty and chance. Students knowledge about sample space became more explicit after their reflections on experiments about randomness. The work with the Sampler tool of TinkerPlots allowed students to process simulations with an increasing number of sample and observe the changes in the graphs produced and its visual effect. This process was dynamically conducted and mediated by the researcher with dialogues and interventions. The TinkerPlots software, by allowing simulation experiments with different sample sizes, may have contributed to students reflection on the relationship between theoretical probability and probability arising from experimentation. We can conclude that although students may not have a formal knowledge of probability, they were able to deepen their initial ideas about crucial aspects of these concept such as sample space and the relationship between theoretical and frequency probability. New researches should be done in order to investigate other possibilities for the use of the software TinkerPlots improve students knowledge about probabilities.

Master of Science / Department of Statistics / Paul I. Nelson / This research is devoted to studying statistical inference implemented using the Gibbs Sampler for a hierarchical Bayesian linear model with first order autoregressive structure. This model was applied to global-mean monthly temperatures from January 1880 to April 2008 and used to estimate a time trend coefficient and to test for the existence of global warming. The global temperature increase estimated by Gibbs Sampler was found to be between 0.0203℃ and 0.0284℃ per decade with 95% credibility. The difference between Gibbs Sampler estimate and ordinary least squares estimate for the time trend was insignificant. Further, a simulation study with data generated from this model was carried out. This study showed that the Gibbs Sampler estimators for the intercept and for the time trend were less biased than corresponding ordinary least squares estimators, while the reverse was true for the autoregressive parameter and error standard deviation. The difference in precision of the estimators found by the two approaches was insignificant except for the samples of small sizes. The Gibbs Sampler estimator of the time trend has significantly smaller mean square error than ordinary least squares estimator for the smaller sample sizes studied. This report also describes how the software package WinBUGS can be used to carry out the simulations required to implement a Gibbs Sampler.

This thesis investigates creative expression through needlework by wealthy or elite women in the eighteenth- and early nineteenth-century, focusing on women in the United States South. This inquiry begins in broad terms and proceeds to the close examination of one particular needlework sampler held in the collection of the Valentine Richmond History Center. The first chapter uses prescriptive literature popular in the eighteenth century to establish the restrictive, obedient, and subservient expectations for women’s behavior. The second chapter explores the reasons that the same books that prohibited many forms of pleasure promoted needlework as an acceptable activity for women. This chapter addresses the practical aspect of needlework, the presence and significance of textiles in the home, and the ways needlework expressed creativity. The final chapter analyzes a needlework sampler stitched in 1812, connecting it both with the themes introduced in the first two chapters and a wider range of issues.

Length-biased sampling method gives the samples from a weighted distribution. With the underlying distribution of the population, one can estimate the attributes of the population by converting the weighted samples. In this thesis, generalized gamma distribution is considered as the underlying distribution of the population and the inference of the weighted distribution is made. Both the models with known and unknown finite population size are considered. In the modes with known finite population size, maximum likelihood estimation and bootstrapping methods are attempted to derive the distributions of the parameters and population mean. For the sake of comparison, both the models with and without the selection bias are built. The computer simulation results show the model with selection bias gives better prediction for the population mean. In the model with unknown finite population size, the distributions of the population size as well as the sample complements are derived. Bayesian analysis is performed using numerical methods. Both the Gibbs sampler and random sampling method are employed to generate the parameters from their joint posterior distribution. The fitness of the size-biased samples are checked by utilizing conditional predictive ordinate.

The Waterloo Membrane Sampler (WMS) is a polydimethylsiloxane (PDMS)-based permeation passive sampler developed at the University of Waterloo. This sampler has found numerous applications in the sampling of volatile organic compounds (VOCs) from air and soil gas. In the presented thesis, studies were conducted to expand the WMS applicability to different environmental matrices. In the first part of this work, a modified version of the sampler, with a smaller area of the sampling surface, was calibrated towards seventeen VOCs listed as sources of concern in guidance documents for vapor intrusion. The calibration constant values obtained at different exposure periods demonstrated high reproducibility and independency of the exposure time. Furthermore, the application of the WMS for VOC sampling from groundwater was examined. This study involved seven VOCs considered as important groundwater pollutants. The performance of the sampler was examined at different concentration levels and for different exposure times. The effects of the sorbent type and bubble formation at the surface of the membrane on the sampling efficiency were evaluated in order to optimize the performance of the WMS. A hypothesis regarding the calibration constant values in water sampling compared to their values in air sampling was examined. The WMS demonstrated linear uptake of the targeted compounds over the studied periods of time and at different concentration levels. Very low detection limits were achieved for all studied compounds. The calibration constant values for the sampler towards the studied compounds were measured with a reasonable reproducibility. Nonetheless, the experimental values of the calibration constants in water sampling did not comply with the theory. Furthermore, a new method of bulk soil sampling was tested. In this approach, the soil sample is enclosed in a container along with the WMS placed in the headspace of the sample. The capability of the WMS to perform exhaustive extraction of volatile organic compounds trapped in the sample was tested in this case. Two compounds, TCE and PCE were used as model compounds to test the introduced method. The initial experiments involved sampling from spiked sand soil as the simplest scenario. The experimental setup was evaluated and modified accordingly to achieve the desired extraction. The effects of the exposure parameters on the extraction efficiency were examined through experimental design starting with extraction from sand followed by extraction from a soil with a high organic content. The three-factor factorial design used for this purpose included the three factors: temperature, water content, and exposure time. The results demonstrated high extraction efficiency achieved when sampling from sand and lower extraction efficiency when sampling from the soil with a high organic content. The recovery was enhanced to a large extent in the latter case at a higher temperature with very low detection limits. The results presented in this thesis indicate that the WMS can be a potential universal tool for sampling from all environmental matrices in vapor intrusion investigations.

The Tapered Element Oscillating Microbalance (TEOM) sampler is an EPA approved Federal Equivalent Method Sampler for measuring PM10 concentrations. The Center for Agricultural Air Quality Engineering and Science (CAAQES) owns two Rupprecht and Patashnick (R&P) Series1400a monitors. The R&P Series 1400a monitor uses the TEOM method to measure particulate matter (PM) concentrations and was approved by EPA in 1990 as an automated equivalent method PM10 sampler. Since its approval, many state air pollution regulatory agencies (SAPRAs) have located R&P Series 1400a monitors at community-oriented monitoring sites. Some SAPRAs have even located TEOM samplers at the property line of major sources to determine if the source is meeting its permit requirements for PMc emissions. This thesis presents the results of PM10 and TSP concentrations measured with TEOM and low-volume gravimetric samplers at two Texas cattle feedlots. The purpose of this research was to compare the performance of the R&P Series 1400a monitor to the low-volume gravimetric sampler when sampling PM from a feedlot. Furthermore, this research was conducted to avoid the inappropriate regulation of cattle feedlots that may occur in the future as a consequence of the TEOM sampler being used to measure PMc emissions. The results of this research demonstrate that relationship between the R&P Series 1400a monitor and the low-volume gravimetric sampler is linear. In general, it was observed that the TEOM sampler measured higher PM10 and TSP concentrations than the low-volume gravimetric sampler when sampling downwind from a cattle feedlot. The opposite results were observed when sampling was conducted upwind from the feedlot. The collected data demonstrates that the concentration difference between the two sampling methods is linearly dependent with the concentration intensity for the upwind sampling locations. This trend was shown to be statistically significant. Another linear relationship was observed between the concentration difference and the particle size (mass median diameter and geometric standard deviation) of the sampled dust. Although this trend was not statistically significant, it is believed that additional downwind concentration measurements would validate this relationship.

Previous studies have demonstrated that EPA approved federal reference method (FRM) samplers can substantially misrepresent the fractions of particles being emitted from agricultural operations due to the relationship between the performance characteristics of these samplers and existing ambient conditions. Controlled testing in a wind tunnel is needed to obtain a clearer understanding and quantification of the performance shifts of these samplers under varying aerosol concentrations, wind speeds and dust types. In this study, sampler performance was tested in a controlled environment wind tunnel meeting EPA requirements for particulate matter (PM) sampler evaluation. The samplers evaluated included two low-volume PM10 and Total Suspended Particulate (TSP) pre-separators. The masses and particle size distributions (PSDs) obtained from the filters of tested samplers were compared to those of a collocated isokinetic sampler. Sampler performance was documented using two parameters: cut-point (d_50) and slope. The cut-point is the particle diameter corresponding to 50% collection efficiency of the pre-separator while the slope is the ratio of particle sizes corresponding to cumulative collection efficiencies of 84.1% and 50% (d_84.1/d_50) or 50% and 15.9% (d_50/d_15.9) or the square root of 84.1% and 15.9% (d_84.1/d_ 15.9). The test variables included three levels of wind speeds (2-, 8-, and 24-km/h), five aerosol concentrations varying from 150 to 1,500 mu g/m3 and three aerosols with different PSDs (ultrafine Arizona Road Dust (ARD), fine ARD and cornstarch). No differences were detected between the performance of the flat and louvered FRM PM10 samplers (a = 0.05). The mean cut-point of both the PM10 samplers was 12.23 mu m while the mean slope was 2.46. The mean cut-point and slope values were statistically different from the upper limit of EPA-specified performance criteria of 10.5 mu m for the cut-point and 1.6 for the slope. The PM10 samplers over-sampled cornstarch but under-sampled ultrafine and fine ARD. The performance of the dome-top TSP sampler was close to the isokinetic sampler, and thus it can be used as a reference sampler in field sampling campaigns to determine true PM concentrations. There were large variations in the performance of the cone-top TSP samplers as compared to the isokinetic sampler. Dust type and wind speed along with their interaction had an impact on sampler performance. Cut-points of PM10 samplers were found to increase with increasing wind speeds. Aerosol concentration did not impact the cut-points and slopes of the tested samplers even though their interaction with dust types and wind speeds had an impact on sampler performance.

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