30 resultados para 2-STATE MARKOV-PROCESSES

em Deakin Research Online - Australia


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The thesis is an explanation of the development of pre-school children's services (infant welfare, kindergartens and child care) at local government level in Victoria. The critical framework of analysis focuses on three dimensions of public policy: 1) the socio-historical environment; 2) the political processes involved in the development of the specific children's service; and 3) the major individuals and groups that exerted pressure for children's service, The argument is threefold. Firstly it is argued that the political environment of children's services has been dominated by the practice of separate spheres of public and private, in which the care of children is primarily the role of women. Secondly, it is argued that the political processes surrounding the development of local children's services have involved all levels of government in what is termed a local state. Thirdly, it is argued that the development of these children's services in local government has resulted mainly from the work of women both individually and collectively. Since the three services of infant welfare, kindergartens and child care all became a normal function of children's services at different times, the circumstances that surrounded each development exhibited different aspects of the three major arguments. The periodisation is broken into four phases: 1) the establishment of local government with no children's services in the nineteenth century; 2) the establishment of infant welfare services in local government in the early part of the twentieth century; 3) the incorporation of kindergartens into local government after the second world war; and 4) the incorporation of child care into local government in the 1970s and 1980s. The thesis concludes by arguing that the existence of children's services in local government in Victoria is testimony to the remarkable work of those women who have pursued the issue both individually and collectively. It has been the identification of children's services as a women's issue in Australian politics that has enabled women's groups at different times to influence the policy makers in diverse ways. However, while the establishment of children's services as a legitimate political concern brings the matter onto the public agenda, the separate spheres still remains a contested issue in the public policies of children's services.

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Purpose: There are inconsistent research findings regarding the impact of rurality on adolescent alcohol, tobacco, and illicit substance use. Therefore, the current study reports on the effect of rurality on alcohol, tobacco, and illicit
drug use among adolescents in 2 state representative samples in 2 countries, Washington State (WA) in the United States and Victoria (VIC) in Australia.
Participants: The International Youth Development Study (IYDS) recruited representative samples of students from Grade 7 (aged 12 to 13 years) and Grade 9 (aged 14 to 15) in both states. A total of 3,729 students responded to questions about alcohol, tobacco, cannabis, and other illicit substance use (nVIC = 1,852; nWA = 1,877). In each state, males and females were equally represented and ages ranged from 12 to 15 years.
Methods: Data were analyzed to compare lifetime and current (past 30 days) substance use for students located in census areas classified as urban, large or small town, and rural. Findings were adjusted for school clustering and
weighted to compare prevalence at median age 14 years.
Findings: Rates of lifetime and current alcohol, tobacco, and cannabis use were significantly higher in rural compared to urban students in both states (odds ratio for current substance use = 1.31).
Conclusions: In both Washington State and Victoria, early adolescent rural students use substances more frequently than their urban counterparts. Future studies should examine factors that place rural adolescents at risk for alcohol, tobacco, and illicit drug use.

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In this paper, we present a method for recognising an agent's behaviour in dynamic, noisy, uncertain domains, and across multiple levels of abstraction. We term this problem on-line plan recognition under uncertainty and view it generally as probabilistic inference on the stochastic process representing the execution of the agent's plan. Our contributions in this paper are twofold. In terms of probabilistic inference, we introduce the Abstract Hidden Markov Model (AHMM), a novel type of stochastic processes, provide its dynamic Bayesian network (DBN) structure and analyse the properties of this network. We then describe an application of the Rao-Blackwellised Particle Filter to the AHMM which allows us to construct an efficient, hybrid inference method for this model. In terms of plan recognition, we propose a novel plan recognition framework based on the AHMM as the plan execution model. The Rao-Blackwellised hybrid inference for AHMM can take advantage of the independence properties inherent in a model of plan execution, leading to an algorithm for online probabilistic plan recognition that scales well with the number of levels in the plan hierarchy. This illustrates that while stochastic models for plan execution can be complex, they exhibit special structures which, if exploited, can lead to efficient plan recognition algorithms. We demonstrate the usefulness of the AHMM framework via a behaviour recognition system in a complex spatial environment using distributed video surveillance data.

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Permutation modeling is challenging because of the combinatorial nature of the problem. However, such modeling is often required in many real-world applications, including activity recognition where subactivities are often permuted and partially ordered. This paper introduces a novel Hidden Permutation Model (HPM) that can learn the partial ordering constraints in permuted state sequences. The HPM is parameterized as an exponential family distribution and is flexible so that it can encode constraints via different feature functions. A chain-flipping Metropolis-Hastings Markov chain Monte Carlo (MCMC) is employed for inference to overcome the O(n!) complexity. Gradient-based maximum likelihood parameter learning is presented for two cases when the permutation is known and when it is hidden. The HPM is evaluated using both simulated and real data from a location-based activity recognition domain. Experimental results indicate that the HPM performs far better than other baseline models, including the naive Bayes classifier, the HMM classifier, and Kirshner's multinomial permutation model. Our presented HPM is generic and can potentially be utilized in any problem where the modeling of permuted states from noisy data is needed.

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Inspired by the hierarchical hidden Markov models (HHMM), we present the hierarchical semi-Markov conditional random field (HSCRF), a generalisation of embedded undirected Markov chains to model complex hierarchical, nested Markov processes. It is parameterised in a discriminative framework and has polynomial time algorithms for learning and inference. Importantly, we develop efficient algorithms for learning and constrained inference in a partially-supervised setting, which is important issue in practice where labels can only be obtained sparsely. We demonstrate the HSCRF in two applications: (i) recognising human activities of daily living (ADLs) from indoor surveillance cameras, and (ii) noun-phrase chunking. We show that the HSCRF is capable of learning rich hierarchical models with reasonable accuracy in both fully and partially observed data cases.

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Previous studies in speculative prefetching focus on building and evaluating access models for the purpose of access prediction. This paper investigates a complementary area which has been largely ignored, that of performance modelling. We use improvement in access time as the performance metric, for which we derive a formula in terms of resource parameters (time available and time required for prefetching) and speculative parameters (probabilities for next access). The performance maximization problem is expressed as a stretch knapsack problem. We develop an algorithm to maximize the improvement in access time by solving the stretch knapsack problem, using theoretically proven apparatus to reduce the search space. Integration between speculative prefetching and caching is also investigated, albeit under the assumption of equal item sizes.

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We present a distributed, surveillance system that works in large and complex indoor environments. To track and recognize behaviors of people, we propose the use of the Abstract Hidden Markov Model (AHMM), which can be considered as an extension of the Hidden Markov Model (HMM), where the single Markov chain in the HMM is replaced by a hierarchy of Markov policies. In this policy hierarchy, each behavior can be represented as a policy at the corresponding level of abstraction. The noisy observations are handled in the same way as an HMM and an efficient Rao-Blackwellised particle filter method is used to compute the probabilities of the current policy at different levels of the hierarchy The novelty of the paper lies in the implementation of a scalable framework in the context of both the scale of behaviors and the size of the environment, making it ideal for distributed surveillance. The results of the system demonstrate the ability to answer queries about people's behaviors at different levels of details using multiple cameras in a large and complex indoor environment.

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We present a novel technique for the recognition of complex human gestures for video annotation using accelerometers and the hidden Markov model. Our extension to the standard hidden Markov model allows us to consider gestures at different levels of abstraction through a hierarchy of hidden states. Accelerometers in the form of wrist bands are attached to humans performing intentional gestures, such as umpires in sports. Video annotation is then performed by populating the video with time stamps indicating significant events, where a particular gesture occurs. The novelty of the technique lies in the development of a probabilistic hierarchical framework for complex gesture recognition and the use of accelerometers to extract gestures and significant events for video annotation.

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This study is concerned with the delay-range-dependent stability analysis for neural networks with time-varying delay and Markovian jumping parameters. The time-varying delay is assumed to lie in an interval of lower and upper bounds. The Markovian jumping parameters are introduced in delayed neural networks, which are modeled in a continuous-time along with finite-state Markov chain. Moreover, the sufficient condition is derived in terms of linear matrix inequalities based on appropriate Lyapunov-Krasovskii functionals and stochastic stability theory, which guarantees the globally asymptotic stable condition in the mean square. Finally, a numerical example is provided to validate the effectiveness of the proposed conditions.

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The syntheses of cyclo-[R2Sn(OPPh2O)2SnR2](O3SCF3)2 (R = Me (1), t-Bu (2)) by the consecutive reaction of R2SnO (R = Me, t-Bu) with triflic acid and diphenylphosphinic acid are presented. In the solid state, 1 and 2 were investigated by 119Sn MAS and 31P MAS NMR spectroscopy as well as X-ray crystallography and appear to exist as ion pairs of cyclo-[R2Sn(OPPh2O)2SnR2]2+ dications and triflate anions. In solution, 1 and 2 are involved in extensive equilibria processes featuring cationic diorganotin(IV) species with Sn-O-P linkages, as evidenced by 119Sn and 31P NMR spectroscopy, electrospray mass spectrometry, and conductivity measurements.

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The synthesis of [R2Sn(H2O)2(OPPh3)2](O3SCF3)2 (R = Me (1), Bu (2)) by the consecutive reaction of R2SnO (R = Me, Bu) with triflic acid and Ph3PO is described. Compounds 1 and 2 feature dialkyltin(IV) dications [R2Sn(H2O)2(OPPh3)2]2+ apparently stabilized by the neutral ligands in the solid state. Compounds 1 and 2 readily dehydrate upon heating at 105 and 86 °C, respectively. The preparative dehydration of 1 afforded [Me2Sn(OPPh3)2(O3SCF3)](O3SCF3) (1a), which features both bidentate and non-coordinating triflate anions. In compounds 1 and 2 the ligands Ph3PO and H2O are kinetically labile in solution and undergo reversible ligand exchange reactions. Compounds 1, 1a and 2 were characterized by multinuclear solution and solid-state NMR spectroscopy, IR spectroscopy, electrospray mass spectrometry, conductivity measurements, thermogravimetry and X-ray crystallography.


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Structural investigations, i.e. solid-state (X-ray), solution (1H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(S)N(H)C6H4-4-Y: Y = H (1), NO2 (2), C(O)Me (3), Cl (4) have shown a general preference for the adoption of an E-conformation about the central C–N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded {H–N–C=S}2 synthon as the building block. In the cases of 1–3, additional C–H...O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the E-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y = C(O)OMe, (5), adopts a Z-conformation in the solid-state that facilitates the formation of N–H...O, C–H...O and C–H...S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules 1–5.

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Using mail survey data collected from primary and secondary school administrators in Washington State, United States, and in Victoria, Australia, this study compared aspects of the school drug policy environment in the 2 states. Documented substance-use policies were prevalent in Washington and Victoria but less prevalent in primary schools, especially in Victoria. Victorian school policy-setting processes were significantly more likely to involve teachers, parents, and students than processes in Washington schools. Consistent with expectations based on their respective national drug policy frameworks, school drug policies in Washington schools were more oriented toward total abstinence and more frequently enforced with harsh punishment (such as expulsion or calling law enforcement), whereas policies in Victorian schools were more reflective of harm-minimization principles. Within both states, however, schools more regularly used harsh punishment and remediation consequences for alcohol and illicit-drug violations compared to tobacco policy violations, which were treated more leniently. (J Sch Health. 2005;75(4):134-140)