Phuong Nguyen

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A high quality hierarchical organization of the concepts in a dataset at different levels of granularity has many valuable applications such as search, summarization, and content browsing. In this paper we propose an algorithm for recursively constructing a hierarchy of topics from a collection of content-representative documents. We characterize each topic(More)
We define a new NP search problem, the “local improvement” principle, about labellings of an acyclic, bounded-degree graph. We show that, provably in PV, it characterizes the ∀Σb1 consequences of V 1 2 and that natural restrictions of it characterize the ∀Σb1 consequences of U 1 2 and of the bounded arithmetic hierarchy. We also show that over V 0 it(More)
We consider an agent interacting with an environment in a single stream of actions, observations, and rewards, with no reset. This process is not assumed to be a Markov Decision Process (MDP). Rather, the agent has several representations (mapping histories of past interactions to a discrete state space) of the environment with unknown dynamics, only some(More)
MapReduce is promising for developing both scalable business and scientific data intensive applications. However, there are few existing scientific workflow systems which can benefit from the MapReduce programming model. We propose a workflow system for integrating structure, and orchestrating MapReduce jobs for scientific data intensive workflows. The(More)
In this study an attempt is made to estimate nitrogen and phosphorus discharged to the environment from the striped catfish (Pangasianodon hypophthalmus) farming sector in the Mekong Delta (8 degrees 33'-10 degrees 55' N, 104 degrees 30'-106 degrees 50' E), South Vietnam. The sector accounted for 687,000 t production in 2007 and 1,094,879 t in 2008, with(More)
A rapid and specific method for the detection of pathogenic Leptospira spp. in bovine semen using the polymerase chain reaction (PCR) is described. The primers used were derived from an EcoR1/BamH1 fragment that hybridized strongly to chromosomal DNA from the hardjobovis serovar. Three different extraction methods were evaluated in this study:(More)
As consumer electronic devices become more powerful and networked, users are required to understand more and more `complex' device functionalities just to carry out simplest tasks. Users are experiencing more and more inconvenience and frustration as the number and complexity of home devices rise and the amount of content/data stored in the home increases.(More)
BACKGROUND Tobacco smoking is one of the leading public health problems in the world. It is also possible to prevent and/or reduce the harm from tobacco use through the use of cost-effective tobacco control measures. However, most of this evidence comes from developed countries and little research has been conducted on this issue in developing countries. (More)
We consider a reinforcement learning setting where the learner also has to deal with the problem of finding a suitable staterepresentation function from a given set of models. This has to be done while interacting with the environment in an online fashion (no resets), and the goal is to have small regret with respect to any Markov model in the set. For this(More)
Trichlorfon (TRC) is the most common organophosphorous insecticide used in aquaculture practices in Southeast Asian countries. Indiscriminate use of TRC can either damage or alter the enzymatic and hormonal activities in the living organisms. In this present study, therefore, toxicogenomic analyses using real time PCR was used to characterize expression(More)