Duong Nguyen - Academia.edu (original) (raw)

Papers by Duong Nguyen

Search for the standard model Higgs boson decaying to W + W − in the fully leptonic final state i... more Search for the standard model Higgs boson decaying to W + W − in the fully leptonic final state in pp collisions at √ s = 7 TeV

Journal of Thermophysics and Heat Transfer, 2000

Effects of heater orientation and confinement on liquid nitrogen pool boiling. Duong NT Nguyen, R... more Effects of heater orientation and confinement on liquid nitrogen pool boiling. Duong NT Nguyen, Ruey-Hung Chen, Louis C Chow, Chuanbao Gu Journal of Thermophysics and Heat Transfer 14:11, 109-111, 1/2000. The objective ...

Bi-lateral negotiations represent an important class of encounter in agent-based systems. To this... more Bi-lateral negotiations represent an important class of encounter in agent-based systems. To this end, this paper develops and evaluates a heuristic model that enables an agent to participate in multiple, concurrent bi-lateral encounters in competitive situations in which there is information uncertainty and deadlines. * This work is sponsored by BT. 1 A service is here viewed an abstract representation of the capability of an agent.

Results are presented from a search for a W boson using a dataset corresponding to 5.0 fb −1 of i... more Results are presented from a search for a W boson using a dataset corresponding to 5.0 fb −1 of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at √ s = 7 TeV. The W boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both lefthanded and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W → tb, leading to a final state signature with a single electron or muon, missing transverse energy, and jets, at least one of which is identified as a b-jet. A W boson that couples to the right-handed (left-handed) chiral projections of the fermions with the same coupling constants as the W is excluded for masses below 1.85 (1.51) TeV at the 95% confidence level. For the first time using LHC data, constraints on the W gauge couplings for a set of left-and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.

Journal of Tribology-transactions of The Asme, 1998

International Journal of Fracture, 1993

The effects of partial closure and frictional slip of three-dimensional cracks on the stress inte... more The effects of partial closure and frictional slip of three-dimensional cracks on the stress intensity factors are studied using the eigenstrain method. The formulation, based on the correct modelling of the boundary conditions on the crack faces, is presented separately for partial closure and frictional slip, and applied to two simpler cases: partial closure of a surface-breaking crack normal to the free surface and under a residual stress field; and frictional slip of a completely closed crack under normal and shear tractions. The evolution of crack closure with the increase of crack depth and its influence on the stress intensity factor are examined and compared with a simple model for the first problem. the effect of coefficient of friction between crack faces on the stress intensity factors is investigated for the second problem.

Computational Mechanics, 1997

This paper is concerned with a numerical simulation of growth of fatigue cracks in a three-dimens... more This paper is concerned with a numerical simulation of growth of fatigue cracks in a three-dimensional geometry. A continuous distribution of infinitesimal dislocation loops is employed to model the crack faces, so that the crack problem can be formulated as a set of singular integral equations. A numerical procedure based on an analytical treatment of the associated finite part integral is developed to solve the singular integral equations. The Paris law is then used to predict the rate of crack growth, so that the evolution of the crack shape under fatigue can be traced by a step-by-step algorithm. Various crack growth problems, e.g., the growth of a subsurface crack in a surface treated specimen, are analyzed using the technique, providing new data for several cracks of practical interest.

Automated negotiation by software agents is a key enabling technology for agent mediated e-commer... more Automated negotiation by software agents is a key enabling technology for agent mediated e-commerce. To this end, this paper considers an important class of such negotiationsnamely those in which an agent engages in multiple concurrent bilateral negotiations for a good or service. In particular, we consider the situation in which a buyer agent is looking for a single service provider from a number of available ones in its environment. By bargaining simultaneously with these providers and interleaving partial agreements that it makes with them, a buyer can reach good deals in an efficient manner. However, a key problem in such encounters is managing commitments since an agent may want to make intermediate deals (so that it has a definite agreement) with other agents before it gets to finalize a deal at the end of the encounter. To do this effectively, however, the agents need to have a flexible model of commitments that they can reason about in order to determine when to commit and to decommit. This paper provides and evaluates such a commitment manager and integrates it into the negotiation model. * The first author is a PhD student who is funded by British Telecom (BT). 1 This view is now widespread in a range of domains that we are targeting for our work, including the web, the grid, pervasive computing and e-business.

A detailed study is presented of the expected performance of the ATLAS detector. The reconstructi... more A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

Fuel and Energy Abstracts, 2011

A measurement of the cross-section for ϒ(1S) → µ + µ − production in proton-proton collisions at ... more A measurement of the cross-section for ϒ(1S) → µ + µ − production in proton-proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ϒ(1S) transverse momentum in two bins of rapidity, |y ϒ(1S) | < 1.2 and 1.2 < |y ϒ(1S) | < 2.4. The measurement requires that both muons have transverse momentum p µ T > 4 GeV and pseudorapidity |η µ | < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarization. The results are based on an integrated luminosity of 1.13 pb −1 , collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model including colour-singlet and colour-octet matrix elements as implemented in PYTHIA while it disagrees by up to a factor of ten with the next-to-leading order prediction based on the colour-singlet-model.

Arthroscopy-the Journal of Arthroscopic and Related Surgery, 2006

Purpose: Elbow contracture is a common and difficult problem to manage. The purpose of this study... more Purpose: Elbow contracture is a common and difficult problem to manage. The purpose of this study was to determine the functional outcomes of arthroscopic capsular release in the management of elbow contractures. Methods: A total of 22 patients (14 males, 8 females; mean age, 42 years) undergoing arthroscopic contracture release were retrospectively reviewed at a minimum follow-up of 1 year (mean, 25 months). In all, 20 patients had a capsulectomy, and 2 underwent capsulotomy. Patient-rated questionnaires (Disability of the Arm, Shoulder, and Hand questionnaire [DASH], American Shoulder and Elbow Surgeons Elbow Form [ASES-e], and Short Form-36 [SF-36]) and clinical, radiographic, and objective evaluations were used to assess outcomes. Motion and strength were measured by independent evaluators through standard goniometry and the LIDO Isokinetic System (Loredan Biomedical, West Sacramento, CA). Results: Mean flexion significantly improved from 122° ± 15° to 141° ± 12° (P < .001). Mean extension significantly improved from 38° ± 18° to 19° ± 13° (P < .001). Mean arc improvement was 38° ± 23° (P < .001). None of the patients had instability, and no major neurovascular complications were reported. All patients had improved elbow function with a mean ASES-e score of 31 out of 36. Most patients were satisfied with their surgery, experienced minimal pain, and exhibited minimal impairment on the DASH. Conclusions: Arthroscopic debridement and capsulectomy of the contracted elbow is effective. Results are comparable with those of other reports in the literature in which both arthroscopic and open methods were used. Level of Evidence: Level IV.

We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Ou... more We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Our focus is a collaborative search mission in an uncertain and/or hostile environment. The controllers are decision trees constructed from a set of low-level functions. Evolved decision trees are robust to changes in initial mission parameters and approach the optimal bound for time-to-completion. We compare results between steady-state and generational approaches, and examine the effects of two common selection operators.

We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Ou... more We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Our focus is a collaborative search mission in an uncertain and/or hostile environment. The controllers are decision trees constructed from a set of low-level functions. Evolved decision trees are robust to changes in initial mission parameters and approach the optimal bound for time-to-completion. We compare results between steady-state and generational approaches, and examine the effects of two common selection operators.

Bt Technology Journal, 2006

In our view, customers in the future are likely to obtain their services from coalitions of servi... more In our view, customers in the future are likely to obtain their services from coalitions of service providers. These coalitions can be described as virtual organisations (VOs); they are group of service providers that form relationships to service customers' demands on an ad-hoc basis. For a VO to be effective, it must be reliable and scalable, and realistically, it must be created and maintained in a dynamic, open and competitive environment. The CONOISE-G project has focused on resolving the technology challenges that emerged from these requirements. Specifically, CONOISE-G provides mechanisms to assure effective operation of VOs in the face of failure, unexpected events and changing requirements in dynamic, open and competitive environment. In this paper, we describe the CONOISE-G system; motivated by a scenario based on mobile service provision; outline its use in the context of VO formation and perturbation and review current efforts to progress the work to deal with unreliable information sources. 1

Search for the standard model Higgs boson decaying to W + W − in the fully leptonic final state i... more Search for the standard model Higgs boson decaying to W + W − in the fully leptonic final state in pp collisions at √ s = 7 TeV

Journal of Thermophysics and Heat Transfer, 2000

Effects of heater orientation and confinement on liquid nitrogen pool boiling. Duong NT Nguyen, R... more Effects of heater orientation and confinement on liquid nitrogen pool boiling. Duong NT Nguyen, Ruey-Hung Chen, Louis C Chow, Chuanbao Gu Journal of Thermophysics and Heat Transfer 14:11, 109-111, 1/2000. The objective ...

Bi-lateral negotiations represent an important class of encounter in agent-based systems. To this... more Bi-lateral negotiations represent an important class of encounter in agent-based systems. To this end, this paper develops and evaluates a heuristic model that enables an agent to participate in multiple, concurrent bi-lateral encounters in competitive situations in which there is information uncertainty and deadlines. * This work is sponsored by BT. 1 A service is here viewed an abstract representation of the capability of an agent.

Results are presented from a search for a W boson using a dataset corresponding to 5.0 fb −1 of i... more Results are presented from a search for a W boson using a dataset corresponding to 5.0 fb −1 of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at √ s = 7 TeV. The W boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both lefthanded and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W → tb, leading to a final state signature with a single electron or muon, missing transverse energy, and jets, at least one of which is identified as a b-jet. A W boson that couples to the right-handed (left-handed) chiral projections of the fermions with the same coupling constants as the W is excluded for masses below 1.85 (1.51) TeV at the 95% confidence level. For the first time using LHC data, constraints on the W gauge couplings for a set of left-and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.

Journal of Tribology-transactions of The Asme, 1998

International Journal of Fracture, 1993

The effects of partial closure and frictional slip of three-dimensional cracks on the stress inte... more The effects of partial closure and frictional slip of three-dimensional cracks on the stress intensity factors are studied using the eigenstrain method. The formulation, based on the correct modelling of the boundary conditions on the crack faces, is presented separately for partial closure and frictional slip, and applied to two simpler cases: partial closure of a surface-breaking crack normal to the free surface and under a residual stress field; and frictional slip of a completely closed crack under normal and shear tractions. The evolution of crack closure with the increase of crack depth and its influence on the stress intensity factor are examined and compared with a simple model for the first problem. the effect of coefficient of friction between crack faces on the stress intensity factors is investigated for the second problem.

Computational Mechanics, 1997

This paper is concerned with a numerical simulation of growth of fatigue cracks in a three-dimens... more This paper is concerned with a numerical simulation of growth of fatigue cracks in a three-dimensional geometry. A continuous distribution of infinitesimal dislocation loops is employed to model the crack faces, so that the crack problem can be formulated as a set of singular integral equations. A numerical procedure based on an analytical treatment of the associated finite part integral is developed to solve the singular integral equations. The Paris law is then used to predict the rate of crack growth, so that the evolution of the crack shape under fatigue can be traced by a step-by-step algorithm. Various crack growth problems, e.g., the growth of a subsurface crack in a surface treated specimen, are analyzed using the technique, providing new data for several cracks of practical interest.

Automated negotiation by software agents is a key enabling technology for agent mediated e-commer... more Automated negotiation by software agents is a key enabling technology for agent mediated e-commerce. To this end, this paper considers an important class of such negotiationsnamely those in which an agent engages in multiple concurrent bilateral negotiations for a good or service. In particular, we consider the situation in which a buyer agent is looking for a single service provider from a number of available ones in its environment. By bargaining simultaneously with these providers and interleaving partial agreements that it makes with them, a buyer can reach good deals in an efficient manner. However, a key problem in such encounters is managing commitments since an agent may want to make intermediate deals (so that it has a definite agreement) with other agents before it gets to finalize a deal at the end of the encounter. To do this effectively, however, the agents need to have a flexible model of commitments that they can reason about in order to determine when to commit and to decommit. This paper provides and evaluates such a commitment manager and integrates it into the negotiation model. * The first author is a PhD student who is funded by British Telecom (BT). 1 This view is now widespread in a range of domains that we are targeting for our work, including the web, the grid, pervasive computing and e-business.

A detailed study is presented of the expected performance of the ATLAS detector. The reconstructi... more A detailed study is presented of the expected performance of the ATLAS detector. The reconstruction of tracks, leptons, photons, missing energy and jets is investigated, together with the performance of b-tagging and the trigger. The physics potential for a variety of interesting physics processes, within the Standard Model and beyond, is examined. The study comprises a series of notes based on simulations of the detector and physics processes, with particular emphasis given to the data expected from the first years of operation of the LHC at CERN.

Fuel and Energy Abstracts, 2011

A measurement of the cross-section for ϒ(1S) → µ + µ − production in proton-proton collisions at ... more A measurement of the cross-section for ϒ(1S) → µ + µ − production in proton-proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ϒ(1S) transverse momentum in two bins of rapidity, |y ϒ(1S) | < 1.2 and 1.2 < |y ϒ(1S) | < 2.4. The measurement requires that both muons have transverse momentum p µ T > 4 GeV and pseudorapidity |η µ | < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarization. The results are based on an integrated luminosity of 1.13 pb −1 , collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model including colour-singlet and colour-octet matrix elements as implemented in PYTHIA while it disagrees by up to a factor of ten with the next-to-leading order prediction based on the colour-singlet-model.

Arthroscopy-the Journal of Arthroscopic and Related Surgery, 2006

Purpose: Elbow contracture is a common and difficult problem to manage. The purpose of this study... more Purpose: Elbow contracture is a common and difficult problem to manage. The purpose of this study was to determine the functional outcomes of arthroscopic capsular release in the management of elbow contractures. Methods: A total of 22 patients (14 males, 8 females; mean age, 42 years) undergoing arthroscopic contracture release were retrospectively reviewed at a minimum follow-up of 1 year (mean, 25 months). In all, 20 patients had a capsulectomy, and 2 underwent capsulotomy. Patient-rated questionnaires (Disability of the Arm, Shoulder, and Hand questionnaire [DASH], American Shoulder and Elbow Surgeons Elbow Form [ASES-e], and Short Form-36 [SF-36]) and clinical, radiographic, and objective evaluations were used to assess outcomes. Motion and strength were measured by independent evaluators through standard goniometry and the LIDO Isokinetic System (Loredan Biomedical, West Sacramento, CA). Results: Mean flexion significantly improved from 122° ± 15° to 141° ± 12° (P < .001). Mean extension significantly improved from 38° ± 18° to 19° ± 13° (P < .001). Mean arc improvement was 38° ± 23° (P < .001). None of the patients had instability, and no major neurovascular complications were reported. All patients had improved elbow function with a mean ASES-e score of 31 out of 36. Most patients were satisfied with their surgery, experienced minimal pain, and exhibited minimal impairment on the DASH. Conclusions: Arthroscopic debridement and capsulectomy of the contracted elbow is effective. Results are comparable with those of other reports in the literature in which both arthroscopic and open methods were used. Level of Evidence: Level IV.

We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Ou... more We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Our focus is a collaborative search mission in an uncertain and/or hostile environment. The controllers are decision trees constructed from a set of low-level functions. Evolved decision trees are robust to changes in initial mission parameters and approach the optimal bound for time-to-completion. We compare results between steady-state and generational approaches, and examine the effects of two common selection operators.

We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Ou... more We present a Genetic Programming approach to evolve cooperative controllers for teams of UAVs. Our focus is a collaborative search mission in an uncertain and/or hostile environment. The controllers are decision trees constructed from a set of low-level functions. Evolved decision trees are robust to changes in initial mission parameters and approach the optimal bound for time-to-completion. We compare results between steady-state and generational approaches, and examine the effects of two common selection operators.

Bt Technology Journal, 2006

In our view, customers in the future are likely to obtain their services from coalitions of servi... more In our view, customers in the future are likely to obtain their services from coalitions of service providers. These coalitions can be described as virtual organisations (VOs); they are group of service providers that form relationships to service customers' demands on an ad-hoc basis. For a VO to be effective, it must be reliable and scalable, and realistically, it must be created and maintained in a dynamic, open and competitive environment. The CONOISE-G project has focused on resolving the technology challenges that emerged from these requirements. Specifically, CONOISE-G provides mechanisms to assure effective operation of VOs in the face of failure, unexpected events and changing requirements in dynamic, open and competitive environment. In this paper, we describe the CONOISE-G system; motivated by a scenario based on mobile service provision; outline its use in the context of VO formation and perturbation and review current efforts to progress the work to deal with unreliable information sources. 1