Optimal Hidden Markov Models

In contrast with training algorithms such as Baum-Welch, which produce solutions that are a local optimum of the objective function, this thesis describes the attempt to develop a training algorithm which delivers the global optimum Discrete ICdden Markov Model for a given training sequence. A total of four different methods of attack upon the problem are presented. First, after building the necessary analytical tools, the thesis presents a direct, calculus-based assault featuring Matrix Derivatives. Next, the dual analytic approach known as Geometric Programming is examined and then adapted to the task. After that, a hill-climbing formula is developed and applied. These first three methods reveal a number of interesting and useful insights into the problem. However, it is the fourth method which produces an algorithm that is then used for direct comparison vAth the Baum-Welch algorithm: examples of global optima are collected, examined for common features and patterns, and then a rule is induced. The resulting rule is implemented in *C' and tested against a battery of Baum-Welch based programs. In the limited range of tests carried out to date, the models produced by the new algorithm yield optima which have not been surpassed by (and are typically much better than) the Baum-Welch models. However, far more analysis and testing is required and in its current form the algorithm is not fast enough for realistic application

Cloud identification using genetic algorithms and massively parallel computation

As a Guest Computational Investigator under the NASA administered component of the High Performance Computing and Communication Program, we implemented a massively parallel genetic algorithm on the MasPar SIMD computer. Experiments were conducted using Earth Science data in the domains of meteorology and oceanography. Results obtained in these domains are competitive with, and in most cases better than, similar problems solved using other methods. In the meteorological domain, we chose to identify clouds using AVHRR spectral data. Four cloud speciations were used although most researchers settle for three. Results were remarkedly consistent across all tests (91% accuracy). Refinements of this method may lead to more timely and complete information for Global Circulation Models (GCMS) that are prevalent in weather forecasting and global environment studies. In the oceanographic domain, we chose to identify ocean currents from a spectrometer having similar characteristics to AVHRR. Here the results were mixed (60% to 80% accuracy). Given that one is willing to run the experiment several times (say 10), then it is acceptable to claim the higher accuracy rating. This problem has never been successfully automated. Therefore, these results are encouraging even though less impressive than the cloud experiment. Successful conclusion of an automated ocean current detection system would impact coastal fishing, naval tactics, and the study of micro-climates. Finally we contributed to the basic knowledge of GA (genetic algorithm) behavior in parallel environments. We developed better knowledge of the use of subpopulations in the context of shared breeding pools and the migration of individuals. Rigorous experiments were conducted based on quantifiable performance criteria. While much of the work confirmed current wisdom, for the first time we were able to submit conclusive evidence. The software developed under this grant was placed in the public domain. An extensive user's manual was written and distributed nationwide to scientists whose work might benefit from its availability. Several papers, including two journal articles, were produced

An acoustic emission study of plastic deformation in polycrystalline aluminium

Acoustic emission experiments were performed on polycrystalline and single crystal 99.99% aluminium while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single dislocation slip events. The rate of decline in acoustic emission activity as grain size is increased beyond the peak value suggests that grain boundary associated dislocation sources are giving rise to the bulk of the detected acoustic emissions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44677/1/10853_2004_Article_BF01028325.pd

Revisiting Egyptian Foreign Policy towards Israel under Mubarak: From Cold Peace to Strategic Peace

This article is the first academic study of Egyptian foreign policy towards Israel under Hosni Mubarak (1981–2011). It challenges a deeply entrenched conventional wisdom that Egypt pursued a cold-peace foreign policy towards Israel throughout this period. We demonstrate that Egyptian foreign policy towards Israel was dynamic – comprising cold peace (1981–91), a hybrid foreign policy of cold peace and strategic peace (1991–2003), and a pure strategic peace posture (2003–11). We also use the case of Egyptian foreign policy towards Israel as a heuristic to develop a conception of a new type of peace, strategic peace, as an intermediary analytical category between cold and stable peace

How landscapes remember

This paper considers the possibility that as subject or agent, the landscape might have the potential to contain, store or transmit memories of their past, which are engaged experientially as uncanny. In a simple sense it asks why there are some landscapes – or landscape features – that are regarded as spiritually animated by different social groups, at different times. The paper focuses on the Neolithic temple site of Borġ-in-Nadur, in Southern Malta, which as well as having been a site of prehistoric ritual activity has more recently been the site of a significant devotion to the Virgin Mary, who graced the site with regular apparitions, and a focus for national and transnational Goddess pilgrimage. The paper suggests that sites such as Borġ-in-Nadur can be seen as palimpsest landscapes, in which memory is layered such that experiential engagements with them draw the past in to the present, and forwards into the future. The paper examines the intertwining of prehistoric, Catholic and Neo-pagan engagements with Borġ-in-Nadur, extending Pierre Nora’s concept of lieux de memoire (sites of memory) to encompass the milieux de memoire, or memorial environments, which are themselves also context of, and for, the uncanny

A Two-Step Theory and Test of Democratic Waves *

Abstract Scholars, observing clustering in transitions to democracy, argue that democratization diffuses across borders as citizens in autocracies demand the same reforms they witness in neighboring states. We disagree. The present paper asserts that the diffusion of democracy literature rests on weak theoretical foundations and does not properly test for diffusion. We advance an alternative two-step argument to explain clustering of democratization: (1) economic shocks, which are clustered spatially and temporally, induce the breakdown of authoritarian regimes; then (2) democratic diffusion, in turn, influences whether a fallen dictatorship will be replaced by a democracy or a new autocracy. Diffusion, despite playing an important role, is insufficient to explain the clustering of transitions, notably because it cannot account for the timing of the waves. Using data on 125 autocracies from 1875 to 2004, we show that economic crises trigger authoritarian breakdowns, while diffusion determines whether the new regime is democratic or authoritarian. * Thanks t

National trends in total cholesterol obscure heterogeneous changes in HDL and non-HDL cholesterol and total-to-HDL cholesterol ratio : a pooled analysis of 458 population-based studies in Asian and Western countries

Background: Although high-density lipoprotein (HDL) and non-HDL cholesterol have opposite associations with coronary heart disease, multi-country reports of lipid trends only use total cholesterol (TC). Our aim was to compare trends in total, HDL and nonHDL cholesterol and the total-to-HDL cholesterol ratio in Asian and Western countries. Methods: We pooled 458 population-based studies with 82.1 million participants in 23 Asian and Western countries. We estimated changes in mean total, HDL and non-HDL cholesterol and mean total-to-HDL cholesterol ratio by country, sex and age group. Results: Since similar to 1980, mean TC increased in Asian countries. In Japan and South Korea, the TC rise was due to rising HDL cholesterol, which increased by up to 0.17 mmol/L per decade in Japanese women; in China, it was due to rising non-HDL cholesterol. TC declined in Western countries, except in Polish men. The decline was largest in Finland and Norway, at similar to 0.4 mmol/L per decade. The decline in TC in most Western countries was the net effect of an increase in HDL cholesterol and a decline in non-HDL cholesterol, with the HDL cholesterol increase largest in New Zealand and Switzerland. Mean total-to-HDL cholesterol ratio declined in Japan, South Korea and most Western countries, by as much as similar to 0.7 per decade in Swiss men (equivalent to similar to 26% decline in coronary heart disease risk per decade). The ratio increased in China. Conclusions: HDL cholesterol has risen and the total-to-HDL cholesterol ratio has declined in many Western countries, Japan and South Korea, with only a weak correlation with changes in TC or non-HDL cholesterol.Peer reviewe

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements