81,882 research outputs found
QR code: The global making of an infrastructural gateway
This article traces the history of machine-readable data encoding standards and argues that the QR code has become an infrastructural gateway. Through the analysis of patents, corporate documents and advertising, ethnographic observations, and interviews with professionals, I describe the global making of the QR code and argue that the convergence of data encoding standards, mobile computing, machine vision algorithms, and platform ecosystems has led to the emergence of a new component of computational infrastructures which functions as a gateway between different actors, systems, and practices. The central section of the article covers seven decades of machine-readable data encoding history across different national and regional contexts: from the invention and popularization of the barcode in the United States, through the QR codeâs invention in Japan and its success in East Asia, to its platformization in China. By revisiting this history through concepts drawn from the field of infrastructure studies, I argue that QR codes have become infrastructural gateways and conclude that this concept is useful not only to understand the current role of QR codes but also to identify and follow the emergence and change of other gateways in infrastructures to come.publishedVersio
Reliable ABC model choice via random forests
Approximate Bayesian computation (ABC) methods provide an elaborate approach
to Bayesian inference on complex models, including model choice. Both
theoretical arguments and simulation experiments indicate, however, that model
posterior probabilities may be poorly evaluated by standard ABC techniques. We
propose a novel approach based on a machine learning tool named random forests
to conduct selection among the highly complex models covered by ABC algorithms.
We thus modify the way Bayesian model selection is both understood and
operated, in that we rephrase the inferential goal as a classification problem,
first predicting the model that best fits the data with random forests and
postponing the approximation of the posterior probability of the predicted MAP
for a second stage also relying on random forests. Compared with earlier
implementations of ABC model choice, the ABC random forest approach offers
several potential improvements: (i) it often has a larger discriminative power
among the competing models, (ii) it is more robust against the number and
choice of statistics summarizing the data, (iii) the computing effort is
drastically reduced (with a gain in computation efficiency of at least fifty),
and (iv) it includes an approximation of the posterior probability of the
selected model. The call to random forests will undoubtedly extend the range of
size of datasets and complexity of models that ABC can handle. We illustrate
the power of this novel methodology by analyzing controlled experiments as well
as genuine population genetics datasets. The proposed methodologies are
implemented in the R package abcrf available on the CRAN.Comment: 39 pages, 15 figures, 6 table
A Global Plate Model Including Lithospheric Deformation Along Major Rifts and Orogens Since the Triassic
Global deepâtime plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global MesozoicâCenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 Ă 106 km2 in the Late Jurassic (~160â155 Ma), driven by a vast network of rift systems. After a midâCretaceous drop in deformation, it reaches a high of 48 x 106 km2 in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plateâmantle system
The education and professional experience of demographers: results of an international survey
This paper presents findings relating to the education, disciplinary background and professional experience of 634 demographers responding to a mainly internet-based survey carried out in 1999-2000. Two thirds of the survey respondents have some training in demography, and virtually all have studied some other subject also. Academic backgrounds are quite varied, with sociology (broadly defined), economics, mathematics/statistics and geography being the most common. Findings presented relate to: the combinations of disciplines studied, current practise of discipline of origin, interdisciplinary activity, place of education, education abroad, current and past sectors of employment and time-use. Differentials by age, gender and region of residence or birth are considered
Intensification in pastoralist cereal use coincides with the expansion of trans-regional networks in the Eurasian Steppe
The pace of transmission of domesticated cereals, including millet from China as well as wheat and barley from southwest Asia, throughout the vast pastoralist landscapes of the Eurasian Steppe (ES) is unclear. The rich monumental record of the ES preserves abundant human remains that provide a temporally deep and spatially broad record of pastoralist dietary intake. Calibration of human ÎŽ13C and ÎŽ15N values against isotope ratios derived from co-occurring livestock distinguish pastoralist consumption of millet from the products of livestock and, in some regions, identify a considerable reliance by pastoralists on C3 crops. We suggest that the adoption of millet was initially sporadic and consumed at low intensities during the Bronze Age, with the low-level consumption of millet possibly taking place in the Minusinsk Basin perhaps as early as the late third millennium cal BC. Starting in the mid-second millennium cal BC, millet consumption intensified dramatically throughout the ES with the exception of both the Mongolian steppe where millet uptake was strongly delayed until the end of first millennium cal BC and the Trans-Urals where instead barley or wheat gained dietary prominence. The emergence of complex, trans-regional political networks likely facilitated the rapid transfer of cultivars across the steppe during the transition to the Iron Age
Crime and Social media
Purpose-The study complements the scant macroeconomic literature on the development outcomes of social media by examining the relationship between Facebook penetration and violent crime levels in a cross-section of 148 countries for the year 2012.
Design/methodology/approach-The empirical evidence is based on Ordinary Least Squares (OLS), Tobit and Quantile regressions. In order to respond to policy concerns on the limited evidence on the consequences of social media in developing countries, the dataset is disaggregated into regions and income levels. The decomposition by income levels included: low income, lower middle income, upper middle income and high income. The corresponding regions include: Europe and Central Asia, East Asia and the Pacific, Middle East and North Africa, Sub-Saharan Africa and Latin America.
Findings-From OLS and Tobit regressions, there is a negative relationship between Facebook penetration and crime. However, Quantile regressions reveal that the established negative relationship is noticeable exclusively in the 90th crime decile. Further, when the dataset is decomposed into regions and income levels, the negative relationship is evident in the Middle East and North Africa (MENA) while a positive relationship is confirmed for sub-Saharan Africa. Policy implications are discussed.
Originality/value- Studies on the development outcomes of social media are sparse because of a lack of reliable macroeconomic data on social media. This study primarily complemented three existing studies that have leveraged on a newly available dataset on Facebook
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Hyper-power and private monopoly: the unholy marriage of (neo) corporatism and the imperial surveillance state
American hyper-power world dominance by public and private agencies has replaced British Empire hyper-power world domination in the period 1815-1914. Snowdenâs revelations have given rise to several important papers examining the geographical and territorial limits on the Internet, comparing it to the imperial telegraph (Kurbalija 2013) and even to the Roman imperial road (Moglen 2013). This paper recalls earlier telegraphy research (Standage 1999, Hills 2007) and explains how the previous hyperpower
(Marsden 2004, describing a global super-power without effective opposition, from the French hyperpuissance)
was able to control communications in order to extend its extraterritorial application of domestic law. I
explain that the telegraph âcables that girdled the Earthâ (Clarke 1958) were sunk into the sea in Cornwall,
southwest England, and that todayâs Internet fibre cables are in the same places â with the result that the greatest
National Security Agency espionage-gathering operation is a joint US/UK operation from the small town of Bude,
Cornwall. Add to that espionage the invention of encryption/decryption computing, devices from Babbageâs
Difference Engine to Turing and Tommy Flowerâs Colossus Marks I and II that broke both Enigma and Lorenz1.
The recipe now exists for what the National Security Agency calls âTotal Information Awarenessâ and the
Orwellian nightmare of totally efficient surveillance and âwar is peaceâ according to the Ministry of Truth2. But it
existed before, and we should learn from the past
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