Detection and Mapping of Specular Surfaces Using Multibounce Lidar Returns

We propose methods that use specular, multibounce lidar returns to detect and map specular surfaces that might be invisible to conventional lidar systems that rely on direct, single-scatter returns. We derive expressions that relate the time- and angle-of-arrival of these multibounce returns to scattering points on the specular surface, and then use these expressions to formulate techniques for retrieving specular surface geometry when the scene is scanned by a single beam or illuminated with a multi-beam flash. We also consider the special case of transparent specular surfaces, for which surface reflections can be mixed together with light that scatters off of objects lying behind the surface

Measurement of Snowpack Density, Grain Size, and Black Carbon Concentration Using Time-domain Diffuse Optics

Diffuse optical spectroscopy (DOS) techniques aim to characterize scattering media by examining their optical response to laser illumination. Time-domain DOS methods involve illuminating the medium with a laser pulse and using a fast photodetector to measure the time-dependent intensity of light that exits the medium after multiple scattering events. While DOS research traditionally focused on characterizing biological tissues, we demonstrate that time-domain diffuse optical measurements can also be used to characterize snow. We introduce a model that predicts the time-dependent reflectance of a snowpack as a function of its density, grain size, and black carbon content, and we develop an algorithm that retrieves these properties from measurements at two wavelengths. To validate our approach, we use a two-wavelength lidar system and measure the time-dependent reflectance of snow samples with varying properties. Rather than measuring direct surface returns, our system captures photons that enter and exit the snow at different points, separated by a small distance (4-10cm). We find strong, linear correlations between our retrievals of density and black carbon concentration, and ground truth measurements. Although the correlation is not as strong, we also find that our method is capable of distinguishing between small and large grains

Impact of resilience enhancing programs on youth surviving the Beslan school siege

The objective of this study was to evaluate a resilience-enhancing program for youth (mean age = 13.32 years) from Beslan, North Ossetia, in the Russian Federation. The program, offered in the summer of 2006, combined recreation, sport, and psychosocial rehabilitation activities for 94 participants, 46 of who were taken hostage in the 2004 school tragedy and experienced those events first hand. Self-reported resilience, as measured by the CD-RISC, was compared within subjects at the study baseline and at two follow-up assessments: immediately after the program and 6 months later. We also compared changes in resilience levels across groups that differed in their traumatic experiences. The results indicate a significant intra-participant mean increase in resilience at both follow-up assessments, and greater self-reported improvements in resilience processes for participants who experienced more trauma events

Social cohesion through football: a quasi-experimental mixed methods design to evaluate a complex health promotion program

Social isolation and disengagement fragments local communities. Evidence indicates that refugee families are highly vulnerable to social isolation in their countries of resettlement. Research to identify approaches to best address this is needed. Football United is a program that aims to foster social inclusion and cohesion in areas with high refugee settlement in New South Wales, Australia, through skills and leadership development, mentoring, and the creation of links with local community and corporate leaders and organisations. The Social Cohesion through Football study’s broad goal is to examine the implementation of a complex health promotion program, and to analyse the processes involved in program implementation. The study will consider program impact on individual health and wellbeing, social inclusion and cohesion, as well as analyse how the program by necessity interacts and adapts to context during implementation, a concept we refer to as plasticity. The proposed study will be the first prospective cohort impact study to our knowledge to assess the impact of a comprehensive integrated program using football as a vehicle for fostering social inclusion and cohesion in communities with high refugee settlement

“We wouldn’t of made friends if we didn’t come to Football United”: the impacts of a football program on young people’s peer, prosocial and cross-cultural relationships

Background Sport as a mechanism to build relationships across cultural boundaries and to build positive interactions among young people has often been promoted in the literature. However, robust evaluation of sport-for-development program impacts is limited. This study reports on an impact evaluation of a sport-for-development program in Australia, Football United®. Methods A quasi-experimental mixed methods design was employed using treatment partitioning (different groups compared had different levels of exposure to Football United). A survey was undertaken with 142 young people (average age of 14.7 years with 22.5% of the sample comprising girls) in four Australian schools. These schools included two Football United and two Comparison schools where Football United was not operating. The survey instrument was composed of previously validated measures, including emotional symptoms, peer problems and relationships, prosocial behaviour, other-group orientation, feelings of social inclusion and belonging and resilience. Face to face interviews were undertaken with a purposeful sample (n = 79) of those who completed the survey. The participants in the interviews were selected to provide a diversity of age, gender and cultural backgrounds. Results Young people who participated in Football United showed significantly higher levels of other-group orientation than a Comparison Group (who did not participate in the program). The Football United boys had significantly lower scores on the peer problem scale and significantly higher scores on the prosocial scale than boys in the Comparison Group. Treatment partitioning analyses showed positive, linear associations between other-group orientation and total participation in the Football United program. A lower score on peer problems and higher scores on prosocial behaviour in the survey were associated with regularity of attendance at Football United. These quantitative results are supported by qualitative data analysed from interviews. Conclusions The study provides evidence of the effects of Football United on key domains of peer and prosocial relationships for boys and other-group orientation for young people in the program sites studied. The effects on girls, and the impacts of the program on the broader school environment and at the community level, require further investigation

Non-line-of-sight imaging using multi-bounce light

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 91-93).Non-line-of-sight (NLOS) imaging techniques produce images from light that has travelled from the scene of interest to the observer via indirect paths which typically include multiple reflections. Such techniques can be particularly useful when the direct line of sight between the observer and the scene is blocked. In this thesis we will explore two NLOS imaging techniques. The first is an occlusion-assisted imaging technique, which constructs images of hidden scenes by interpreting the patterns that are imposed on multiply reflected light by occluding objects. We will provide a conceptual and theoretical introduction to our technique, which uses a focused, scannable illumination source and a single-pixel, lensless detector. We will then present the results from an experimental implementation of this technique in a challenging environment. This will be followed by an analysis of a number of challenges that are commonly encountered in active, occlusion-assisted imaging scenarios, including single-bounce light rejection, inter-reflections, and asymmetries in measurement geometry. Finally, we will introduce a new NLOS imaging technique which uses the time-of-flight information in multiply reflected light to produce an unobstructed, line-of-sight view of a hidden scene. We will provide a conceptual introduction to the technique as well as a derivation of the physical model that underlies it, and will also discuss methods for visualizing the technique's output.by Connor A. Henley.S.M.S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc

Winning big but feeling no better? The effect of lottery prizes on physical and mental health

We use British panel data to determine the exogenous impact of income on a number of individual health outcomes: general health status, mental health, physical health problems, and health behaviors (drinking and smoking). Lottery winnings allow us to make causal statements regarding the effect of income on health, as the amount won by winners is largely exogenous. Positive income shocks have no significant effect on self-assessed overall health, but a large positive effect on mental health. This result seems paradoxical on two levels. First, there is a well-known gradient in health status in cross-section data, and, second, general health should partly reflect mental health, so that we may expect both variables to move in the same direction. We propose a solution to the first apparent paradox by underlining the endogeneity of income. For the second, we show that lottery winnings are also associated with more smoking and social drinking. General health will reflect both mental health and the effect of these behaviors, and so may not improve following a positive income shock