5,113 research outputs found
Bayesian Inference for High-dimensional Time Series with a Directed Acyclic Graphical Structure
No full textIn multivariate time series analysis, understanding the underlying causal relationships among variables is often of interest for various applications. Directed acyclic graphs (DAGs) provide a powerful framework for representing causal dependencies. This paper proposes a novel Bayesian approach for modeling multivariate time series where conditional independencies and causal structure are encoded by a DAG. The proposed model allows structural properties such as stationarity to be easily accommodated, and further does not assume any pre-specified parent-child ordering. Given the application, we further extend the model for matrix-variate time series. We take a Bayesian approach to inference, and a “projection-posterior” based efficient computational algorithm is developed. The posterior convergence properties of the proposed method are established along with two identifiability results for the unrestricted structural equation models. The utility of the proposed method is demonstrated through simulation studies and real data analysis.The authors would like to thank the National Science Foundation for the Collaborative Research Grants DMS-2210280 (for Subhashis Ghosal), DMS-2210281 (for Anindya Roy), and DMS-2210282
(for Arkaprava Roy).https://arxiv.org/html/2503.23563v
Bayesian Inference for High-dimensional Time Series by Latent Process Modeling
No full textTime series data arising in many applications nowadays are high-dimensional. A large number of parameters describe features of these time series. We propose a novel approach to modeling a high-dimensional time series through several independent univariate time series, which are then orthogonally rotated and sparsely linearly transformed. With this approach, any specified intrinsic relations among component time series given by a graphical structure can be maintained at all time snapshots. We call the resulting process an Orthogonally-rotated Univariate Time series (OUT). Key structural properties of time series such as stationarity and causality can be easily accommodated in the OUT model. For Bayesian inference, we put suitable prior distributions on the spectral densities of the independent latent times series, the orthogonal rotation matrix, and the common precision matrix of the component times series at every time point. A likelihood is constructed using the Whittle approximation for univariate latent time series. An efficient Markov Chain Monte Carlo (MCMC) algorithm is developed for posterior computation. We study the convergence of the pseudo-posterior distribution based on the Whittle likelihood for the model's parameters upon developing a new general posterior convergence theorem for pseudo-posteriors. We find that the posterior contraction rate for independent observations essentially prevails in the OUT model under very mild conditions on the temporal dependence described in terms of the smoothness of the corresponding spectral densities. Through a simulation study, we compare the accuracy of estimating the parameters and identifying the graphical structure with other approaches. We apply the proposed methodology to analyze a dataset on different industrial components of the US gross domestic product between 2010 and 2019 and predict future observations.The authors would like to thank the National Science Foundation collaboative research grants DMS-2210280 (Subhashis Ghosal) / 2210281 (Anindya Roy) / 2210282 (Arkaprava Roy).http://arxiv.org/abs/2403.0491
United They Fall: Why the International Community Should Not Promote Military Integration after Civil War
No full textThe single strongest predictor of civil war is a nation having had one in the past, and preventing the recurrence of civil war has thus become the critical problem for both scholarship and policy. The conventional wisdom urges the creation of capable, legitimate, and inclusive postwar states to reduce the risk of relapse into civil war, and international peacebuilders have often encouraged the formation of a new national army including members of the war’s opposing sides. However, military integration has received little theoretical or empirical attention. Filling that gap, we argue that both the theoretical logics and the empirical record identifying military integration as a significant contributor to durable post-civil war peace are weak. Our analysis of eleven cases finds little evidence that military integration played a substantial causal role in preventing the return to civil war and little support for the likely causal mechanisms. Military integration does not usually send a costly signal of the parties’ commitment to peace, provide communal security, employ many possible spoilers, or act as a powerful symbol of a unified nation. We conclude that it is both unwise and unethical for the international community to press military integration on reluctant local forces.Based in part on a larger collective project: Roy Licklider (Ed.). (2014). New Armies from Old: Merging Competing Military Forces after Civil Wars. Washington, D.C.: Georgetown University Press; see http://press.georgetown.edu/book/georgetown/new-armies-old
Ekla Chalo Re: a tribute to Ms. Mary Roy
No full text
This is a tribute to activist Mary Roy, who passed away in 2022. The author traces the life of Mary Roy, highlighting the ways in which she challenged gendered norms and expectations. She was the applicant in a landmark case which brought equal property rights for Syrian Christian women in India. The author reminds readers that women's rights are human rights and change begins with us. 
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Yunnan (China), men with the cow caravan
No full textA cow caravan.Image is part of research conducted by Roy Chapman Andrews for the article: Traveling in China's Southland
Author(s): Roy Chapman Andrews
Source: Geographical Review, Vol. 6, No. 2 (Aug., 1918), pp. 133-146
Published by: American Geographical Society
Stable URL: http://www.jstor.org/stable/207476http://www.jstor.org/stable/207476Grayscal
Yunnan (China), cow loaded with grass and carrying a bell
No full textA cow loaded with grass and carrying a bell.Image is part of research conducted by Roy Chapman Andrews for the article: Traveling in China's Southland
Author(s): Roy Chapman Andrews
Source: Geographical Review, Vol. 6, No. 2 (Aug., 1918), pp. 133-146
Published by: American Geographical Society
Stable URL: http://www.jstor.org/stable/207476http://www.jstor.org/stable/207476Grayscal
Yunnan (China), women carrying salt from one of the large wells
No full textWomen carrying salt from one of the large wells.Image is part of research conducted by Roy Chapman Andrews for the article: Zoological Explorations in Yunnan Province, China
Author(s): Roy Chapman Andrews
Source: Geographical Review, Vol. 6, No. 1 (Jul., 1918), pp. 1-18
Published by: American Geographical Society
Stable URL: http://www.jstor.org/stable/207446http://www.jstor.org/stable/207446Grayscal
Immobile History: An Interview with Emmanuel Le Roy Ladurie
No full textThe author spoke with renowned French historian Emmanuel Le Roy Ladurie about Computers, Geography and History. Le Roy Ladurie was the "standard bearer" of the third generation of the French Annales school, a group of French intellectuals that combined different disciplines such as history, geography, anthropology, and more to delve into social history
Regional integration fifty years after the treaty of Rome. The EU, Asia, Africa and the Americas.
No full textThe European Union has been the pioneer and undisputed
leader of regional integration processes. Since its inception in
the 1950s, following the Schuman Declaration that set in motion
Jean Monnet’s innovative idea to join together European coal
and steel industries, Europe has offered a useful model for
regional integration. Strengthened by the 1957 Treaty of Rome
(exactly half a century ago), this bold entity was later transformed
into the European Union by the Maastricht Treaty.
Having successfully accomplished its primary goal (“to make
war unthinkable and materially impossible”), the EU is currently
facing challenges associated with its expansion and the deepening
of its pooled sovereignty. On the other hand, the effects
of the EU in international relations are of paramount relevance.
While the forceful transposition of national and regional structures
into other regions is a historical error, the essence of the
EU as a model to be adapted by other regions is a viable
approach to enhance stability and welfare. In this regard, this
volume examines the current challenges of the EU and the perspectives
of regional integration in Africa, Asia and Latin
America
Correspondence regarding Horace Kephart collection
No full textThis 1973 correspondence, between Congressman Roy A. Taylor, Ronald Walker, Lawrence C. Hadley, discusses the transfer of Horace Kephart collection from the library of Great Smoky Mountains National Park to Western Carolina University. Horace Kephart (1862-1931) was a noted naturalist, woodsman, journalist, and author and promoter of the Great Smoky Mountains National Park
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