1,244 research outputs found
Modeling and Estimation for Self-Exciting Spatio-Temporal Models of Terrorist Activity
Spatio-temporal hierarchical modeling is an extremely attractive way to model
the spread of crime or terrorism data over a given region, especially when the
observations are counts and must be modeled discretely. The spatio-temporal
diffusion is placed, as a matter of convenience, in the process model allowing
for straightforward estimation of the diffusion parameters through Bayesian
techniques. However, this method of modeling does not allow for the existence
of self-excitation, or a temporal data model dependency, that has been shown to
exist in criminal and terrorism data. In this manuscript we will use existing
theories on how violence spreads to create models that allow for both
spatio-temporal diffusion in the process model as well as temporal diffusion,
or self-excitation, in the data model. We will further demonstrate how Laplace
approximations similar to their use in Integrated Nested Laplace Approximation
can be used to quickly and accurately conduct inference of self-exciting
spatio-temporal models allowing practitioners a new way of fitting and
comparing multiple process models. We will illustrate this approach by fitting
a self-exciting spatio-temporal model to terrorism data in Iraq and demonstrate
how choice of process model leads to differing conclusions on the existence of
self-excitation in the data and differing conclusions on how violence is
spreading spatio-temporally
An Extended Laplace Approximation Method for Bayesian Inference of Self-Exciting Spatial-Temporal Models of Count Data
Self-Exciting models are statistical models of count data where the
probability of an event occurring is influenced by the history of the process.
In particular, self-exciting spatio-temporal models allow for spatial
dependence as well as temporal self-excitation. For large spatial or temporal
regions, however, the model leads to an intractable likelihood. An increasingly
common method for dealing with large spatio-temporal models is by using Laplace
approximations (LA). This method is convenient as it can easily be applied and
is quickly implemented. However, as we will demonstrate in this manuscript,
when applied to self-exciting Poisson spatial-temporal models, Laplace
Approximations result in a significant bias in estimating some parameters. Due
to this bias, we propose using up to sixth-order corrections to the LA for
fitting these models. We will demonstrate how to do this in a Bayesian setting
for Self-Exciting Spatio-Temporal models. We will further show there is a
limited parameter space where the extended LA method still has bias. In these
uncommon instances we will demonstrate how a more computationally intensive
fully Bayesian approach using the Stan software program is possible in those
rare instances. The performance of the extended LA method is illustrated with
both simulation and real-world data
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The Church of England and the Legislative Reforms of 1828-32: Revolution or Adjustment?
Since the 1950s, historians of the eighteenth- and nineteenth-century Church of England have generally maintained thatĀ the Sacramental Test Act (1828), the Roman Catholic Relief Act (1829) and the Reform Act (1832) amounted to a āconstitutional revolutionā, in which Anglican political hegemony was decisively displaced. This theory remains the dominant framework for understanding the effect of legislation on the relationship between church and state in pre-Victorian England. This article probes the validity of the theory. It is argued that the legislative reforms of 1828ā32 did not drastically alter the religious composition of parliament, which was already multi-denominational, and that they incorporated clauses which preserved the political dominance of the Church of England. Additionally, it is suggested that Anglican apprehensions concerning the reforming measures of those years were derived from an unfounded belief that these reforms would ultimately result in changes to the Church of Englandās formularies or in disestablishment, rather than from the actual laws enacted. Accordingly, the post-1832 British parliamentary system did not in the short term militate against Anglican interests. In light of this reappraisal, these legislative reforms may be better understood as an exercise in āconstitutional adjustmentā as opposed to a āconstitutional revolutionā.Pembroke College, Cambridg
The Morality of Intimate Faculty-Student Relationships
Presented September 19, 1996 for the Center for the Study of Ethics in Societ
Truth was his defense: The libel trial of John Peter Zenger
John Peter Zenger spent nearly eight months in jail starting in 1734 but still printed The New York Weekly Journal with the help of his wife while he was on trial for seditious libel. In those days, libel was anything that was against the government. It didnāt matter if the information was true or false. Controversy plagued Zengerās trial from the beginning as William Cosby, the governor of New York, did everything he could to sabotage Zenger as Cosby was the centerpiece of most of Zengerās editorials. Zenger was one of the first journalists to emphasize the importance of the media being the fourth estate and being a watchdog of the government
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Queen Adelaide and the Extension of Anglicanism in Malta
On a visit to Malta in 1838, Queen Adelaide expressed severe disappointment that the British colony did not possess a purpose-built Anglican place of worship. She determined to fund the building of one at her personal expense and within six years the grandiose neoclassical church of St Paul's, Valletta, was completed. This imposing structure occupied an ambiguous position in a colony where the British government was pledged to maintain Roman Catholicism. St Paul's was ostensibly intended for the existing Anglican population in Malta. However, the church was perceived by both evangelicals and Roman Catholics as a potential instrument of propagating Protestantism. In examining the basis for these perceptions, this article suggests that St Paul's was part of a larger effort, driven by high church clergy connected with the Society for Promoting Christian Knowledge (SPCK), to influence the Maltese towards greater sympathy with the Anglican tradition, while avoiding overt proselytizing. The concomitant establishment of the diocese of Gibraltar in 1842 was, it is argued, key to this enterprise. The analysis advanced here has important implications for our understanding of Anglicanism in an imperial context, the contribution of royal patronage to this process and the conflict between religious and governmental imperatives.</jats:p
Time-Varying Input and State Delay Compensation for Uncertain Nonlinear Systems
A robust controller is developed for uncertain, second-order nonlinear
systems subject to simultaneous unknown, time-varying state delays and known,
time-varying input delays in addition to additive, sufficiently smooth
disturbances. An integral term composed of previous control values facilitates
a delay-free open-loop error system and the development of the feedback control
structure. A stability analysis based on Lyapunov-Krasovskii (LK) functionals
guarantees uniformly ultimately bounded tracking under the assumption that the
delays are bounded and slowly varying
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