Localization and tracking of parameterized objects in point clouds

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 43-46).This thesis focuses on object recognition and tracking from three dimensional point cloud renderings of dense range and bearing data. Sensors like laser range-finders and depth cameras have become increasingly popular in autonomous robotic applications. A common task is to locate and track specific objects of interest located somewhere in the point cloud. This often introduces a tedious network of heuristics to build objects from identified primitives or an intractable high dimensional search space. Through a parameterized object model and certain relaxation functions, a likelihood based view of the data can be used to accomplish these goals with increased performance and reliability. Improvements in mathematics and convergence properties have shown that this method can be realized in real time.by Robert Truax.S.M

Characterization of side-slip dynamics in Land Rover LR3 for improved high speed autonomous control

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references.In this thesis, the side slip control dynamics of the Land Rover LR3 platform are examined for autonomous control. As autonomy becomes implemented in high speed safety applications, the importance of an accurate model for the vehicle becomes crucial for obstacle avoidance and emergency maneuvers. Testing on public highways under normal operation shows a slip ratio drop to 70% of the no-slip model, indicating a need for model improvement. By defining the slip ratio as a function of velocity with a slope of -0.018 ± 0.002 seconds per meter and a y-intercept of 1.23 + .04, much of this error may be reduced. While a more complex relationship may exist between the slip ratio, vehicle velocity, and the steering command, the noise and inaccuracy of the sensor prevent a more precise analysis.by Robert D. Truax.S.B

Chemicals having estrogenic activity can be released from some bisphenol a-free, hard and clear, thermoplastic resins

Background: Chemicals that have estrogenic activity (EA) can potentially cause adverse health effects in mammals including humans, sometimes at low doses in fetal through juvenile stages with effects detected in adults. Polycarbonate (PC) thermoplastic resins made from bisphenol A (BPA), a chemical that has EA, are now often avoided in products used by babies. Other BPA-free thermoplastic resins, some hypothesized or advertised to be EA-free, are replacing PC resins used to make reusable hard and clear thermoplastic products such as baby bottles. Methods: We used two very sensitive and accurate in vitro assays (MCF-7 and BG1Luc human cell lines) to quantify the EA of chemicals leached into ethanol or water/saline extracts of fourteen unstressed or stressed (autoclaving, microwaving, UV radiation) thermoplastic resins. Estrogen receptor (ER)-dependent agonist responses were confirmed by their inhibition with the ER antagonist ICI 182,780. Results: Our data showed that some (4/14) unstressed and stressed BPA-free thermoplastic resins leached chemicals having significant levels of EA, including one polystyrene (PS), and three Tritan™ resins, the latter reportedly EA-free. Exposure to UV radiation in natural sunlight resulted in an increased release of EA from Tritan™ resins. Triphenyl-phosphate (TPP), an additive used to manufacture some thermoplastic resins such as Tritan™, exhibited EA in both MCF-7 and BG1Luc assays. Ten unstressed or stressed glycol-modified polyethylene terephthalate (PETG), cyclic olefin polymer (COP) or copolymer (COC) thermoplastic resins did not release chemicals with detectable EA under any test condition. Conclusions: This hazard survey study assessed the release of chemicals exhibiting EA as detected by two sensitive, widely used and accepted, human cell line in vitro assays. Four PC replacement resins (Tritan™ and PS) released chemicals having EA. However, ten other PC-replacement resins did not leach chemicals having EA (EA-free-resins). These results indicate that PC-replacement plastic products could be made from EA-free resins (if appropriate EA-free additives are chosen) that maintain advantages of re-usable plastic items (price, weight, shatter resistance) without releasing chemicals having EA that potentially produce adverse health effects on current or future generations.This work was supported by the following NIH/NIEHS grants: R44 ES011469, 01–03 (CZY); 1R43/44 ES014806, 01–03 (CZY); subcontract (CZY, PI) on an NIH Grant 01–03 43/44ES018083-01. This work was also supported by NIH grants to MSD (P42 ES004699), and DJK and SIY (1R43ES018083-01-03, NIEHS 1R44ES019442-01-03 and NIEHS 2R44ES016964-01-03).Neuroscienc

Jogging not running: A narrative approach to exploring ‘exercise as leisure’ after a life in elite football

As research has shown, former elite athletes often struggle to adapt to aspects of their post-sport lives. This can include the management of their identities, dealing with the uncertainty of their new roles, and negotiating the changes that occur to their bodies. In this paper we discuss an under-reported challenge facing retired athletes: how to manage their ongoing relationship with exercise. To address this issue we adopted a narrative approach, based on the first author’s experiences as a former football player, to provide a socio-cultural reading of the various challenges involved in the transition from exercise as a vocation to a leisure activity. We suggest that these stories demonstrate that in retirement, former athletes’ docility, while seemingly advantageous, can also be a significant obstacle to developing alternative meanings for exercise, including as a potential re-creative or leisure activity that can become meaningful and important in its own right

Graduate student supervision policies and procedures: A case study of issues and factors affecting graduate study

This study was designed to identify salient issues in supervision across disciplines at a Canadian research university with a history of decentralized administration of graduate programs. Three sets of issues guided the inquiry: (a) the definition of supervision, (b) policies and procedures for supervision, and (c) the resources available for supervision. Although most departments reported having some form of policies and procedures, they did not tend to be explicitly stated or communicated. According to program directors, the two most important factors in the graduate supervision process were the supervisor's knowledge of the research field and his or her availability. There was considerable variability across faculties in the existence of policies and in the importance attached to different factors. Resources also varied greatly across disciplines. One conclusion of the study is that since the process of supervision is complex and occurs within a disciplinary context, much of the effort involved in enhancing the quality of graduate student supervision must be made at the department level. However, a comprehensive definition of graduate student supervision is needed to ensure that, where possible, there is common ground for graduate student supervision policy and practice.Cette étude a été conçue de manière à identifier des questions importantes de supervision dans diverses disciplines, dans une université de recherche canadienne ayant des antécédents en matière de décentralisation administrative de programmes d'études supérieures. Trois ensembles de questions ont guidé l'étude: (a) la définition du terme supervision, (b) les politiques et procédures régissant la supervision, et (c) les ressources affectées à la supervision. Si la plupart des départements ont dit disposer de quelconques politiques et procédures, plus rares étaient ceux qui les avaient formulées ou communiquées explicitement. La connaissance du domaine de recherche et la disponibilité du superviseur étaient les deux facteurs les plus importants du processus de supervision. On a constaté des différences considérables entre les facultés pour ce qui a trait à l'existence de politiques et à l'importance attachée à divers facteurs. Le niveau de ressources variait en outre grandement d'une discipline à une autre. L'étude conclut notamment que, le processus de supervision étant complexe et s'inscrivant dans le contexte d'une discipline, une grande partie des efforts déployés afin de relever la qualité de la supervision des étudiants aux niveaux supérieurs doit se faire dans les départements. Toutefois, il y aurait lieu de formuler une définition globale de ce qu 'on entend par supervision des étudiants aux niveaux supérieurs afin de s'assurer que la politique et la pratique en matière de supervision des étudiants à ces niveaux reposent dans la mesure du possible sur une base commune

Distributed leadership, trust and online communities

This paper analyses the role of distributed leadership and trust in online communities. The team-based informal ethos of online collaboration requires a different kind of leadership from that in formal positional hierarchies. Such leadership may be more flexible and sophisticated, capable of encompassing ambiguity and rapid change. Online leaders need to be partially invisible, delegating power and distributing tasks. Yet, simultaneously, online communities are facilitated by the high visibility and subtle control of expert leaders. This paradox: that leaders need to be both highly visible and invisible as appropriate, was derived from prior research and tested in the analysis of online community discussions using a pattern-matching process. It is argued that both leader visibility and invisibility are important for the facilitation of trusting collaboration via distributed leadership. Advanced leadership responses to complex situations in online communities foster positive group interaction and decision-making, facilitated through active distribution of specific tasks

Electron correlations, spontaneous magnetization and momentum density in quantum dots

The magnetization of quantum dots is discussed in terms of a relatively simple but exactly solvable model Hamiltonian. The model predicts oscillations in spin polarization as a function of dot radius for a fixed electron density. These oscillations in magnetization are shown to yield distinct signature in the momentum density of the electron gas, suggesting the usefulness of momentum resolved spectroscopies for investigating the magnetization of dot systems. We also present variational quantum Monte Carlo calculations on a square dot containing 12 electrons in order to gain insight into correlation effects on the interactions between like and unlike spins in a quantum dot.Comment: 6 pages, 4 figure

Method AHP to Flood Risk Map Approach

The phenomenon of flooding is a natural event, given by the extravasation of water to the river bed. The main objective of this study was the analysis of susceptibility to flooding of the basin of Uraim River in the municipality of Paragominas Pará state based on the physical characteristics and morphometric basin. It used the Analysis method Hierarchical method for generating gas order susceptibility map of the basin. The AHP technique used to determine map algebra contributed to the analysis of the susceptibility to floods and was effective because it reduces and simplifies the proposed problem, which minimizes the errors of judgment during the process

A Variable Metric Probabilistic k-Nearest-Neighbours Classifier

Copyright © 2004 Springer Verlag. The final publication is available at link.springer.com5th International Conference, Exeter, UK. August 25-27, 2004. ProceedingsBook title: Intelligent Data Engineering and Automated Learning – IDEAL 2004k-nearest neighbour (k-nn) model is a simple, popular classifier. Probabilistic k-nn is a more powerful variant in which the model is cast in a Bayesian framework using (reversible jump) Markov chain Monte Carlo methods to average out the uncertainy over the model parameters.The k-nn classifier depends crucially on the metric used to determine distances between data points. However, scalings between features, and indeed whether some subset of features is redundant, are seldom known a priori. Here we introduce a variable metric extension to the probabilistic k-nn classifier, which permits averaging over all rotations and scalings of the data. In addition, the method permits automatic rejection of irrelevant features. Examples are provided on synthetic data, illustrating how the method can deform feature space and select salient features, and also on real-world data