Statistical studies of various time-to-fail distributions

Three models are considered that have U-shaped hazard functions, and a fourth model is considered that has a linear hazard function. Several methods for estimating the parameters are given for each of these models. Also, various tests of hypotheses are considered in the case of the model with the linear hazard function. One of the models with a U-shaped hazard function has a location and a scale parameter, and it is proved in general that any other parameters in a distribution of this type are distributed independently of the location and scale parameters. A new method used to estimate the parameters in the preceding distributions is also employed to estimate the parameters in the Logistic distribution, and comparisons based on Monte Carlo methods are made between these estimators and the maximum likelihood estimators for n = 10, 20, 40, 80 and for complete samples and censoring from the right for r/n = .1, .3, .5 and .7….The means and variances of the estimators of reliability are given --Abstract, page ii

The functionalisation of wool by tris(hydroxymethyl)phosphine for metal ion recovery

Tris(hydroxymethyl)phosphine (THP) was prepared by the addition of a stoichiometric amount of base to tetrakis(hydroxymethyl)phosphonium chloride (THPC). Freshly prepared THP was successfully immobilised onto wool through a Mannich-type condensation reaction between a hydroxymethyl group and an amine on the wool surface, forming stable gt;P-CH2-Nlt; coupling links. The immobilisation of THP to wool stabilised the THP, which resulted in the decreased oxidation of THP to tris(hydroxymethyl)phosphine oxide (THPO). The presence of immobilised phosphine groups was determined colorimetrically by reaction with Ni2+ ions, which produced a bright orange nickel-phosphine complex, as well as quantitatively, by measuring nickel uptake using ICP-MS. Immobilised THP-wool showed proportional binding for varying concentrations of metal solution. Decreasing or increasing the concentration of the metal solution resulted in a corresponding proportional response of metal binding. Following immobilisation onto wool, oxidation of the system by 6% H2O2 resulted in a reduced binding of 24% for Cu, 25% for Co, 27% for Ni, and 93% for Cd relative to unoxidised THP immobilised onto wool. Additional modification of the THP-wool systems via reaction with amino acids and other related compounds overall did not appear to enhance the metal binding capacity relative to the unmodified THP-wool system. The only modified THP-wool system that showed either retention or an increase in metal binding capacity for all metals analysed was that of 2-aminopyridine, followed by oxidation with H₂O₂

Spaces of justice

Thesis: M. Arch., Massachusetts Institute of Technology, Department of Architecture, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 137-140).The US has the highest incarceration rate in the world by far. Premised on punishment and isolation, incarceration most heavily affects vulnerable neighborhoods and individuals and creates a system of disenfranchised citizens. Incarceration makes it difficult for these individuals to earn jobs and income, receive necessary healthcare, and maintain social ties. In a move towards reform, the Massachusetts state legislature is currently proposing bills for the implementation of restorative justice and justice reinvestment practices. Restorative justice offers an opportunity for the offender, victim, and other affected parties to engage in a mediated discussion to understand and agree on how the harm done can be repaired. It promotes a healing rather than punitive response to crime. Justice reinvestment reassesses how funds spent on incarceration can be diverted to help vulnerable individuals and neighborhoods, through beneficial programs such as youth crime prevention and education. This thesis, Spaces of Justice, adopts these strategies of reform to propose a new place of community corrections that offers vocational training and restorative justice practices for minor offenders and returning citizens. Community corrections is where convicted individuals serve their sentence in society, such as probation, rather than locked in a facility. However, a report in Massachusetts found that, because judges lack faith in current community corrections programs, they choose to incarcerate people 85% of the time, even when community corrections would be a more appropriate sentence. Indeed, in Boston, the current facility that provides services to probationers is located across from the city prison, in an inaccessible area near the highway. As an inhospitable place, it discourages use by both judges and probationers, and thus detracts from the potential that community corrections has in decreasing incarceration and lifting neighborhoods out of the incarceration cycle. This thesis proposes an alternative model that, first and foremost, is actually located within the community it serves. In doing so, it reduces isolation and stigma associated with those involved in the criminal justice system by creating new relationships among spaces of justice, public space, and the neighborhood.by James Addison and Olivia Huang.M. Arch

THE EFFECT OF MOISTURE CONTENT AND COMPOSITION ON THE COMPRESSIVE STRENGTH AND RIGIDITY OF COB MADE FROM SOIL OF THE BRECCIA MEASURES NEAR TEIGNMOUTH, DEVON

Earth has been used as a reliable building material for many thousands of years. Recently there has been a world wide renaissance in the use of earth as a building material due to its architectural versatility and environmental sustainability. However, in the United Kingdom it is regarded by the majority of building professionals as either obsolete or a novel historical material. The utilisation of earth as a modern building material and the repair of historic earth building structures is retarded by the uncertainty of the knowledge of the properties of the material. This thesis considers earth building materials as composite materials containing a cohesive, low compression modulus binder fraction, a high compression modulus aggregate fraction, and a fibre fraction. The compression properties of a building material without fibre content (cob matrix material) are described in terms of the interaction between the binder and aggregate fractions, and moisture and the binder fraction. The effect of the moisture content of the material upon the compression failure mechanisms is described. Values of compression modulus predicted by a rule of mixtures equation are compared to experimental results for this material. The following mechanisms are proposed to account for the apparent discrepancy between the predicted and experimental results: • the effect of pore size distribution and the proportions of binder and aggregate fractions upon strain magnification within the material • the effect of an efficiency factor, primarily dependent upon the proportion of binder and aggregate fractions, which determines the degree to which the potential modulus of the material is realised. Time Domain Reflectometry is employed for repeated, real time, non destructive measurement of the moisture content of an external cob wall. The results of these measurements are analysed and discussed. This thesis proposes that consideration of cob as a composite material has developed a paradigm which will enhance the level of understanding of all earth building materials, enabling the manipulation and accurate prediction of their structural properties. This will be an important contribution to the realisation of the significant sustainable qualities of earth building materials by the current construction industry

Predicting geogenic groundwater fluoride: Malawi as a case study

Geogenic fluoride contamination of groundwater causes the health condition fluorosis and is a global water degredation issue affecting an estimated 200 million people. It has been identified as a priority chemical contaminant of concern by the United Nations and will be a focus in many fluoride-vulnerable developing countries towards Sustainable Development Goal 6 (SDG 6) related to water quality. Predicting groundwater vulnerability to geogenic fluoride will be key to sustainably managing groundwater assets for SDG 6, however some developing nations may not have the resources or data available to develop a solution. Malawi has only sparse knowledge of issues with fluoride and fluorosis and it does not have access to comprehensive national groundwater fluoride data which is a hinderance to the development of a complex risk model. This thesis sought to fill the knowledge gap with a national data collation and a synthesis of geological, hydrogeological and hydro-geochemical analyses of fluoride occurrence, to develop an innovative prediction method to screen for groundwater fluoride contamination which can be applied nationally. National groundwater fluoride occurrence was documented for the first time in Malawi providing a master data set of groundwater fluoride spanning 50 years. Fluoride was found to occur from two distinct source types (lithological, hydrothermal), each of which was designated a fluoride risk factor using fluoride-lithology statistics from existing data and extrapolating where data were absent. The method was developed to be dynamic with prediction accuracy increasing as new data is acquired, and can be easily applied at any scale in any country for little expense. The prediction method developed will allow the Government of Malawi to manage its groundwater infrastructure assets for fluoride contamination in a targeted manner, boost their attainment potential for SDG 6, redefine their groundwater policy to include geogenic fluoride contamination and bring their groundwater fluoride standard in line with observed health risks.Geogenic fluoride contamination of groundwater causes the health condition fluorosis and is a global water degredation issue affecting an estimated 200 million people. It has been identified as a priority chemical contaminant of concern by the United Nations and will be a focus in many fluoride-vulnerable developing countries towards Sustainable Development Goal 6 (SDG 6) related to water quality. Predicting groundwater vulnerability to geogenic fluoride will be key to sustainably managing groundwater assets for SDG 6, however some developing nations may not have the resources or data available to develop a solution. Malawi has only sparse knowledge of issues with fluoride and fluorosis and it does not have access to comprehensive national groundwater fluoride data which is a hinderance to the development of a complex risk model. This thesis sought to fill the knowledge gap with a national data collation and a synthesis of geological, hydrogeological and hydro-geochemical analyses of fluoride occurrence, to develop an innovative prediction method to screen for groundwater fluoride contamination which can be applied nationally. National groundwater fluoride occurrence was documented for the first time in Malawi providing a master data set of groundwater fluoride spanning 50 years. Fluoride was found to occur from two distinct source types (lithological, hydrothermal), each of which was designated a fluoride risk factor using fluoride-lithology statistics from existing data and extrapolating where data were absent. The method was developed to be dynamic with prediction accuracy increasing as new data is acquired, and can be easily applied at any scale in any country for little expense. The prediction method developed will allow the Government of Malawi to manage its groundwater infrastructure assets for fluoride contamination in a targeted manner, boost their attainment potential for SDG 6, redefine their groundwater policy to include geogenic fluoride contamination and bring their groundwater fluoride standard in line with observed health risks

Athletic Success and Donation Intentions: Does Sense of Community Mediate?

As Division-I FBS expenditures continue to rise, it is of paramount importance for universities to better understand the benefits received as a result of athletic success. Specifically, previous research has identified a strengthened campus sense of community and increased donation levels as potential beneficial outcomes of football success. However, it is not clear how football success, sense of community, and donation intention operate cumulatively. Therefore, this study sought to explain the effect of football success on donation intentions, with the mediating effect of campus sense of community. FBS students (N = 253) reported their perceptions of football success, campus sense of community, and intentions to donate to their universities’ annual funds, as well as the athletic departments. Two separate mediation analyses indicated partial mediation for both annual fund donation intentions and athletic department donation intentions. Team identification was also found to be a positive, significant predictor of sense of community, (p < .05). These results suggest university administrators may anticipate institution-wide benefits from football success, but they may be contingent upon students’ identification levels with the football team

Athletic Success and Donation Intentions: Does Sense of Community Mediate?

As Division-I FBS expenditures continue to rise, it is of paramount importance for universities to better understand the benefits received as a result of athletic success. Specifically, previous research has identified a strengthened campus sense of community and increased donation levels as potential beneficial outcomes of football success. However, it is not clear how football success, sense of community, and donation intention operate cumulatively. Therefore, this study sought to explain the effect of football success on donation intentions, with the mediating effect of campus sense of community. FBS students (N = 253) reported their perceptions of football success, campus sense of community, and intentions to donate to their universities’ annual funds, as well as the athletic departments. Two separate mediation analyses indicated partial mediation for both annual fund donation intentions and athletic department donation intentions. Team identification was also found to be a positive, significant predictor of sense of community, (p < .05). These results suggest university administrators may anticipate institution-wide benefits from football success, but they may be contingent upon students’ identification levels with the football team

Information Criterion for Nonparametric Model-Assisted Survey Estimators

Nonparametric model-assisted estimators have been proposed to improve estimates of finite population parameters. More efficient estimators are obtained when the parametric model is misspecified due to the flexibility of nonparametric models. In this dissertation, we derive information criteria to select appropriate auxiliary variables to use in an additive model-assisted method. By removing irrelevant auxiliary variables, our method reduces model complexity and decreases estimator variance. Our proposed Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) account for the sampling design using the first order inclusion probabilities of each element. We approximate the additive nonparametric components using polynomial splines. We establish that the proposed BIC is asymptotically consistent to select the important explanatory variables in a finite population. This result is confirmed by our numerical study under a range of superpopulation models. Our numerical study shows that the AIC tends to overfit and does not show an increase in performance as the sample size increases. Using the BIC, our proposed method is easier to implement and theoretically justified compared with a previously proposed method