Evaluating the use of particle-spring systems in the conceptual design of grid shell structures

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.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 (p. 63-64).This thesis evaluates particle-spring systems as conceptual design tools in an effort to create efficient grid shell structures. Currently many simulation tools are available to create representations of intricate geometries and forms. However, these forms can become highly complex and challenging upon their realization. A lack of understanding of these forms leads to structures that cannot support their corresponding loads due to their shape, boundary conditions or edge conditions. To create successful grid shells, designers must understand the design principles behind these forms. The goals of this research were achieved through a parametric study that involved manipulating the topology and topography of three global grid shell geometries. It was determined that the ability of particle-spring form finding methods to create good structures is highly dependent on both the mesh type used and the structure's global geometry. A list of implications has been developed and is presented in this work.by Trevor B. Bertin.M.Eng

Big Data, Social Physics, and Spatial Analysis: The Early Years

This paper examines one of the historical antecedents of Big Data, the social physics movement. Its origins are in the scientific revolution of the 17th century in Western Europe. But it is not named as such until the middle of the 19th century, and not formally institutionalized until another hundred years later when it is associated with work by George Zipf and John Stewart. Social physics is marked by the belief that large-scale statistical measurement of social variables reveals underlying relational patterns that can be explained by theories and laws found in natural science, and physics in particular. This larger epistemological position is known as monism, the idea that there is only one set of principles that applies to the explanation of both natural and social worlds. Social physics entered geography through the work of the mid-20th-century geographer William Warntz, who developed his own spatial version called ‘‘macrogeography.’’ It involved the computation of large data sets, made ever easier with the contemporaneous development of the computer, joined with the gravitational potential model. Our argument is that Warntz’s concerns with numeracy, large data sets, machine-based computing power, relatively simple mathematical formulas drawn from natural science, and an isomorphism between natural and social worlds became grounds on which Big Data later staked its claim to knowledge; it is a past that has not yet passed

Big data, little history

Abstract The paper makes the argument that what is forgotten in the celebration of big data is history. Big data is presented as if it were disconnected from the past, removed from issues or problems that went before. I argue in this short commentary that the past remains potent for big data and that proponents ignore it at their peril. Rather than being a brand new approach, big data brings a series of problematic assumptions and practices first criticised 40 years ago by opponents of geography's quantitative revolution. Those assumptions, practices and criticisms are reviewed in the paper

Synchronised displaying of three adult male Wilson’s Bird-of-Paradise Cicinnurus respublica on Batanta Island, West Papua, and an undescribed display posture

Wilson’s Bird-of-paradise Cicinnurus respublica is endemic to two islands of the Raja Ampat island group off the western tip of the Bird’s Head peninsula of the island of New Guinea. Due to its remote home, it is little known, and its courtship behaviour in the wild was not described until the 1990s. To attract females for mating, males create and maintain a clearing, known as a court, on the forest floor, where they display on perches. These displays are normally performed by solitary males, but in this paper we describe an instance of three adult males displaying simultaneously, with highly synchronised movements, in the presence of three female-plumaged birds. This cooperative display incorporated at least five postures, one of which has not been described to date, involving the bird ‘bowing’ to accentuate its yellow hind neck patch. Whilst cooperative displays have not been observed in the closest relatives of this species, the Magnificent and King Birds-of-paradise, they appear to occur regularly in the four species of parotias Parotia spp., albeit for much shorter periods of time

CNETML: Maximum likelihood inference of phylogeny from copy number profiles of spatio-temporal samples

Phylogenetic trees based on copy number alterations (CNAs) for multi-region samples of a single cancer patient are helpful to understand the spatio-temporal evolution of cancers, especially in tumours driven by chromosomal instability. Due to the high cost of deep sequencing data, low-coverage data are more accessible in practice, which only allow the calling of (relative) total copy numbers due to the lower resolution. However, methods to reconstruct sample phylogenies from CNAs often use allele-specific copy numbers and those using total copy number are mostly distance matrix or maximum parsimony methods which do not handle temporal data or estimate mutation rates. In this work, we developed a new maximum likelihood method based on a novel evolutionary model of CNAs, CNETML, to infer phylogenies from spatio-temporal samples taken within a single patient. CNETML is the first program to jointly infer the tree topology, node ages, and mutation rates from total copy numbers when samples were taken at different time points. Our extensive simulations suggest CNETML performed well even on relative copy numbers with subclonal whole genome doubling events and under slight violation of model assumptions. The application of CNETML to real data from Barrett’s esophagus patients also generated consistent results with previous discoveries and novel early CNAs for further investigations

CNETML: maximum likelihood inference of phylogeny from copy number profiles of multiple samples

Phylogenetic trees based on copy number profiles from multiple samples of a patient are helpful to understand cancer evolution. Here, we develop a new maximum likelihood method, CNETML, to infer phylogenies from such data. CNETML is the first program to jointly infer the tree topology, node ages, and mutation rates from total copy numbers of longitudinal samples. Our extensive simulations suggest CNETML performs well on copy numbers relative to ploidy and under slight violation of model assumptions. The application of CNETML to real data generates results consistent with previous discoveries and provides novel early copy number events for further investigation

"I DONT REALLY LIKE THE MILL; IN FACT, I HATE THE MILL": Changing Youth Vocationalism Under Fordism and Post-Fordism in Powell River, British Columbia

Forest towns in British Columbia  are  in  the  throes   of.  a profound  restructuring  (Hayter  2000). The  most  recent  turn  of  the screw,  the  US  imposition   of  a  27%  import  tax   on   softwood  lumber    (May  2002),  is  only  the  latest  twist  in  a  twenty-year history scarred by volatility and industrial  downsizing.  Persistent  job  losses due  to  technological  change,  corporate   rationalization,   increased international  competition,  trade  conflicts,  and   resource   depletion have  progressively  undone   the  fabric   of  BC   forest   communities, especially on the  coast. But while  a plethora  of policies, schemes,  and programs  have  been  initiated  to  help  those  worst  affected,  little attention  has been paid to high  school youth who  have  yet to enter the job market  (Hay  1993 ; Barnes  and Hayter  1992,1995a,  and  1995b; Barnes, Hayter,  and Hay  1999; Hayter  2000, 288-320; Egan and  Klausen  1998). Historically, high  school students\u27job  expectations  were  directly  tied to  a  buoyant  resource  economy,  which,  in  turn,  helped  to  define the  culture  of  the  resource  town  itself  But  in  this  era  of economic  downsizing   and  industrial  restructuring,   those   expectations    are increasingly  frustrated. The  purpose  of this  paper  is  to  examine how  the  new  economic  reality  of  forest   towns   has   influenced  not only the  expectations  of high  school students  but  also  the  content and  philosophy  of  high  school  programs

Superheavy Elements in Kilonovae

As LIGO-Virgo-KAGRA enters its fourth observing run, a new opportunity to search for electromagnetic counterparts of compact object mergers will also begin. The light curves and spectra from the first "kilonova" associated with a binary neutron star binary (NSM) suggests that these sites are hosts of the rapid neutron capture ("$r$") process. However, it is unknown just how robust elemental production can be in mergers. Identifying signposts of the production of particular nuclei is critical for fully understanding merger-driven heavy-element synthesis. In this study, we investigate the properties of very neutron rich nuclei for which superheavy elements ($Z\geq 104$) can be produced in NSMs and whether they can similarly imprint a unique signature on kilonova light-curve evolution. A superheavy-element signature in kilonovae represents a route to establishing a lower limit on heavy-element production in NSMs as well as possibly being the first evidence of superheavy element synthesis in nature. Favorable NSMs conditions yield a mass fraction of superheavy elements is $X_{Z\geq 104}\approx 3\times 10^{-2}$ at 7.5 hours post-merger. With this mass fraction of superheavy elements, we find that kilonova light curves may appear similar to those arising from lanthanide-poor ejecta. Therefore, photometric characterizations of superheavy-element rich kilonova may possibly misidentify them as lanthanide-poor events.Comment: 9 pages, 5 figure

Abnormal structure of frontostriatal brain systems is associated with aspects of impulsivity and compulsivity in cocaine dependence

A growing body of preclinical evidence indicates that addiction to cocaine is associated with neuroadaptive changes in frontostriatal brain systems. Human studies in cocaine-dependent individuals have shown alterations in brain structure, but it is less clear how these changes may be related to the clinical phenotype of cocaine dependence characterized by impulsive behaviours and compulsive drug-taking. Here we compared self-report, behavioural and structural magnetic resonance imaging data on a relatively large sample of cocaine-dependent individuals (n = 60) with data on healthy volunteers (n = 60); and we investigated the relationships between grey matter volume variation, duration of cocaine use, and measures of impulsivity and compulsivity in the cocaine-dependent group. Cocaine dependence was associated with an extensive system of abnormally decreased grey matter volume in orbitofrontal, cingulate, insular, temporoparietal and cerebellar cortex, and with a more localized increase in grey matter volume in the basal ganglia. Greater duration of cocaine dependence was correlated with greater grey matter volume reduction in orbitofrontal, cingulate and insular cortex. Greater impairment of attentional control was associated with reduced volume in insular cortex and increased volume of caudate nucleus. Greater compulsivity of drug use was associated with reduced volume in orbitofrontal cortex. Cocaine-dependent individuals had abnormal structure of corticostriatal systems, and variability in the extent of anatomical changes in orbitofrontal, insular and striatal structures was related to individual differences in duration of dependence, inattention and compulsivity of cocaine consumption

The Great Debate in Mid-Twentieth-Century American Geography: Fred K. Schaefer vs. Richard Hartshorne

The mid-twentieth-century debate around whether geography should be ideographic, and descriptively study the unique, or nomothetic, and seek law-like explanatory generalizations, was sparked in 1953 by Fred K. Schaefer. Schaefer was a political refugee from Nazi Germany and not trained as a geographer. Nonetheless, he was a professor in the Geography Department at the University of Iowa, when he penned the paper that attacked America‘s most famous and powerful geographer, Richard Hartshorne. Hartshorne‘s celebrated book, The Nature of Geography (1939) defined, justified and genealogically fixed geography as an ideographic science, that is, “concerned with the description and interpretation of unique cases. …" (Hartshorne 1939, 449). Schaefer‘s paper excoriated all of Hartshorne‘s claims, both historical and philosophical. His alternative was the philosophy of logical positivism originating in Austria during the 1920s with a group of philosophers, scientists and mathematicians collectively known as the Vienna Circle. Logical positivism said that for any knowledge to be taken seriously as knowledge it must be expressible as a law-like generalization. When Hartshorne read Schaefer‘s critique, he was apoplectic. He wrote two virulent replies denying all of Schaefer‘s charges. Schaefer, though, was already dead so couldn‘t reply. But others did. Over the next decade some form of logical positivism took hold in the discipline and geography was never the same again