6,018 research outputs found
Social, Economic and Geographical Differences in Mid-Nineteenth-Century Homes: The Evidence from Inventories
This article was first published in Regional Furniture (2013)
Bayesian Learning and Predictability in a Stochastic Nonlinear Dynamical Model
Bayesian inference methods are applied within a Bayesian hierarchical
modelling framework to the problems of joint state and parameter estimation,
and of state forecasting. We explore and demonstrate the ideas in the context
of a simple nonlinear marine biogeochemical model. A novel approach is proposed
to the formulation of the stochastic process model, in which ecophysiological
properties of plankton communities are represented by autoregressive stochastic
processes. This approach captures the effects of changes in plankton
communities over time, and it allows the incorporation of literature metadata
on individual species into prior distributions for process model parameters.
The approach is applied to a case study at Ocean Station Papa, using Particle
Markov chain Monte Carlo computational techniques. The results suggest that, by
drawing on objective prior information, it is possible to extract useful
information about model state and a subset of parameters, and even to make
useful long-term forecasts, based on sparse and noisy observations
Localism, Self-Interest, and the Tyranny of the Favored Quarter: Addressing the Barriers to New Regionalism
This article argues that our nation\u27s ideological commitment to decentralized local governance has helped to create the phenomenon of the favored quarter. Localism, or the ideological commitment to local governance, has helped to produce fragmented metropolitan regions stratified by race and income. This fragmentation produces a collective action problem or regional prisoner\u27s dilemma that is well-known in the local governance literature
Models of Transportation and Land Use Change: A Guide to the Territory
Modern urban regions are highly complex entities. Despite the difficulty of modeling every relevant aspect of an urban region, researchers have produced a rich variety models dealing with inter-related processes of urban change. The most popular types of models have been those dealing with the relationship between transportation network growth and changes in land use and the location of economic activity, embodied in the concept of accessibility. This paper reviews some of the more common frameworks for modeling transportation and land use change, illustrating each with some examples of operational models that have been applied to real-world settings.Transport, land use, models, review network growth, induced demand, induced supply
Second-Order Occlusion-Aware Volumetric Radiance Caching
We present a second-order gradient analysis of light transport in
participating media and use this to develop an improved radiance caching
algorithm for volumetric light transport. We adaptively sample and interpolate
radiance from sparse points in the medium using a second-order Hessian-based
error metric to determine when interpolation is appropriate. We derive our
metric from each point's incoming light field, computed by using a proxy
triangulation-based representation of the radiance reflected by the surrounding
medium and geometry. We use this representation to efficiently compute the
first- and second-order derivatives of the radiance at the cache points while
accounting for occlusion changes.
We also propose a self-contained two-dimensional model for light transport in
media and use it to validate and analyze our approach, demonstrating that our
method outperforms previous radiance caching algorithms both in terms of
accurate derivative estimates and final radiance extrapolation. We generalize
these findings to practical three-dimensional scenarios, where we show improved
results while reducing computation time by up to 30\% compared to previous
work
The circumstellar disk of HH 30. Searching for signs of disk evolution with multi-wavelength modeling
Circumstellar disks are characteristic for star formation and vanish during
the first few Myr of stellar evolution. During this time planets are believed
to form in the dense midplane by growth, sedimentation and aggregation of dust.
Indicators of disk evolution, such as holes and gaps, can be traced in the
spectral energy distribution (SED) and spatially resolved images.
We aim to construct a self-consistent model of HH 30 by fitting all available
continuum observations simultaneously. New data sets not available in previous
studies, such as high-resolution interferometric imaging with the Plateau de
Bure Interferometer (PdBI) at lambda = 1.3 mm and SED measured with IRS on the
Spitzer Space Telescope in the mid-infrared, put strong constraints on
predictions and are likely to provide new insights into the evolutionary state
of this object.
A parameter study based on simulated annealing was performed to find unbiased
best-fit models for independent observations made in the wavelength domain
lambda ~ 1 micron ... 4 mm. The method essentially creates a Markov chain
through parameter space by comparing predictions generated by our
self-consistent continuum radiation transfer code MC3D with observations.
We present models of the edge-on circumstellar disk of HH 30 based on
observations from the near-infrared to mm-wavelengths that suggest the presence
of an inner depletion zone with about 45 AU radius and a steep decline of mm
opacity beyond 140 AU. Our modeling indicates that several modes of dust
evolution such as growth, settling, and radial migration are taking place in
this object.
High-resolution observations of HH 30 at different wavelengths with
next-generation observatories such as ALMA and JWST will enable the modeling of
inhomogeneous dust properties and significantly expand our understanding of
circumstellar disk evolution.Comment: Accepted for publication in Astronomy and Astrophysic
Shanghai rising in a globalizing world
In a globalizing world, cities at or near the apex of the international urban hierarchy are among the favored few--New York, London, and Tokyo--that have acquired large economic, cultural, and symbolic roles. Among a handful of regions that aspire to such a role--such as Hong Kong, Miami, and Sao Paulo--Shanghai has reasonable long-term prospects. If the Chinese economy can sustain its growth rate, it will rival the United States in a few decades. And if Shanghai can sustain its preeminence in China, it is the Asian city most likely to become a global center. The authors explore the makings of a world city, identify ingredients essential for that status, indicate national and municipal policies that may set Shanghai on the path to being a global city, and show how such policies are being implemented. As urbanization continues, the authors say, and as information technology and finance-related service activities take on even more importance, the number of regional and global centers could increase, but only if they satisfy some exacting requirements. Shanghai's chances, for example, depend on the extent to which China opens up and on a host of municipal policies--policies that emphasize Shanghai's industrial strength, substantially enlarge its base of information technology and producer services, ensure an adequate supply of skills, expand available housing and infrastructure enough to meet demand, and improve the quality of life.Decentralization,Banks&Banking Reform,Municipal Financial Management,Payment Systems&Infrastructure,Environmental Economics&Policies,Environmental Economics&Policies,ICT Policy and Strategies,Public Sector Economics&Finance,Banks&Banking Reform,Municipal Financial Management
Establishing a Sustainable Development Goal for Oceans and Coasts to Face the Challenges of our Future Ocean
Oceans regulate our climate, provide us with natural resources such as food, materials, substances, and energy and are essential for international trade, recreational, and cultural activities. Free access to and availability of ocean resources and services, together with human development, have put strong pressures on marine ecosystems, ranging from overfishing and reckless resource extraction to various channels of careless pollution. International cooperation and negotiations are required to protect the marine environment and use marine resources in a way that the needs of future generations will be met. For that purpose, developing and agreeing on a Sustainable Development Goal (SDG) Oceans and Coasts could be an essential element for sustainable ocean management. The SDGs will build upon the Millennium Development Goals (MDG) and replace them by 2015. Even though ensuring environmental sustainability is one of the eight MDG goals, the ocean is not explicitly included. Furthermore, the creation of a comprehensive underlying set of oceanic sustainability indicators would help assessing the current status of marine systems, diagnose on-going trends, and provide information for forward-locking and sustainable ocean governance
- …