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

Papers by Ha Duong

Resource ReserVation Protocol (RSVP) is a QoS signalling protocol developed by IETF for fixed net... more Resource ReserVation Protocol (RSVP) is a QoS signalling protocol developed by IETF for fixed networks. However, in mobile networks where mobile nodes are freely moving, the standard RSVP is inadequate. There is substantial number of published works aiming to support RSVP mobility. Our contribution in this paper is to explore further the proactive context transfer scheme [6] in the context of RSVP state reestablishment. As shown in the paper, the proactive scheme is well suited to RSVP state reestablishment. We also suggest the concept of deferred reestablishment to increase the probability of resource availability during the proactive reestablishment process. Finally, we analyse the cost and benefits of state reestablishment in terms of wasted resources (we express the resources as a product of bandwidth and time and call it bandwidth-time in the paper) to confirm the effectiveness of our scheme.

2006 IEEE 63rd Vehicular Technology Conference

ABSTRACT

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012

This paper proposes an algorithm to identify groups of users connected to a mobile ad hoc network... more This paper proposes an algorithm to identify groups of users connected to a mobile ad hoc network that remain stable over time. Several similar algorithms have been proposed to manage mobility either by predicting disconnections or by identifying groups of peers stable over time. They all rely on information such as GPS, signal strength or routes and result in message overhead. The algorithm proposed here uses information from the routing layer to detect groups that are stable over time. This algorithm is fully distributed and creates no message overhead as the result of using cross-layer information.

TENCON 2005 - 2005 IEEE Region 10 Conference, 2005

A well-known problem in wireless multi-hop communication is the significant degradation of throug... more A well-known problem in wireless multi-hop communication is the significant degradation of throughput when the number of hops increases. Previous research shows that in a chain topology, nodes using IEEE 802.11 can at best achieve 1/4, but in practice only 1/7, much smaller than the ideal 1/3 of the throughput of single-hop transmission. In order to improve performance in multi-hop cases, we introduce a rate balance scheme and tune the sensing range at physical layer and contention window at MAC layer. Our simulation results show that the throughput ratio close to 1/4 is achievable when the number of hops is as high as 12; better ratios of 1/3.4 and 1/3.6 are achieved when number of hops is 5 and 8, respectively.

Multimedia Systems and Applications Series, 2005

ABSTRACT

Water Research, 2003

The occurrence and the fate of trihalomethanes (THMs) in the water supply system of Hanoi City, V... more The occurrence and the fate of trihalomethanes (THMs) in the water supply system of Hanoi City, Vietnam was investigated from 1998 to 2001. The chlorination efficiency, THM speciation, and, THM formation potential (THMFP) was determined in the water works and in tap water. With regard to THM formation, three types of groundwater resources were identified: (I) high bromide, (II) low bromide, and (III) high bromide combined with high ammonia and high dissolved organic carbon (DOC) concentrations. Under typical treatment conditions (total chlorine residual 0.5-0.8 mg/L), the total THM formation was always below WHO, EU, and USEPA drinking water standards and decreased in the order type I>type II>type III, although the THMFP was >400 mg/L for type III water. The speciation showed >80% of bromo-THMs in type I water due to the noticeable high bromide level (p140 mg/L). In type II water, the bromo-THMs still accounted for some 40% although the bromide concentration is significantly lower (p30 mg/L). In contrast, only traces of bromo-THMs were formed (B5%) in type III water, despite bromide levels were high (p240 mg/L). This observation could be explained by competition kinetics of chlorine reacting with ammonia and bromide. Based on chlorine exposure (CT) estimations, it was concluded that the current chlorination practice for type I and II waters is sufficient for X2-log inactivation of Giardia lamblia cysts. However, in type III water the applied chlorine is masked as chloramine with a much lower disinfection efficiency. In addition to high levels of ammonia, type III groundwater is also contaminated by arsenic that is not satisfactory removed during treatment. Nnitrosodimethylamine, a potential carcinogen suspected to be formed during chloramination processes, was below the detection limit of 0.02 mg/L in type III water.

Header compression (HC) is a useful technique for reducing the load on bandwidth-scarce wireless ... more Header compression (HC) is a useful technique for reducing the load on bandwidth-scarce wireless links. HC normally depends on the establishment and synchronisation of context at the compressor and de-compressor. In Mobile IP networks, it is desirable to transfer this context between access routers to avoid the expensive process of context re- establishment. In this paper we propose a method for avoiding the need for context re-establishment when packets are lost during handovers, as well as means for efficiently transferring the context to new access routers (by piggybacking the context on Mobile IP signalling messages). The analysis of our scheme shows that it can reduce signalling load during handovers, which is beneficial in mobile networks with frequent handovers (e.g. wireless LAN hot spots).

Organisms Diversity & Evolution, 2014

Several important aspects of the evolution of the softshell turtle (family Trionychidae) have not... more Several important aspects of the evolution of the softshell turtle (family Trionychidae) have not been addressed thoroughly in previous studies, including the pattern and timing of diversification of major clades and species boundaries of the critically endangered Shanghai Softshell Turtle, Rafetus swinhoei. To address these issues, we analyzed data from two mitochondrial loci (cytochrome b and ND4) and one nuclear intron (R35) for all species of trionychid turtles, except Pelochelys signifera, and for all known populations of Rafetus swinhoei in Vietnam and one from China. Phylogenetic analyses using three methods (maximum parsimony, maximum likelihood, and Bayesian inference) produce a well resolved and strongly supported phylogeny. The results of our time-calibration and biogeographic optimization analyses show that trionychid dispersals out of Asia took place between 45 and 49 million years ago in the Eocene. Interestingly, the accelerated rates of diversification and dispersal within the family correspond surprisingly well to global warming periods between the mid Paleocene and the early Oligocene and from the end of the Oligocene to the mid Miocene. Our study also indicates that there is no significant genetic divergence among monophyletic populations of Rafetus swinhoei, and that previous taxonomic revision of this species is unwarranted.

ACM SIGMOBILE Mobile Computing and Communications Review, 2005

In recent years, many protocols have been developed to support user mobility in wireless networks... more In recent years, many protocols have been developed to support user mobility in wireless networks, e.g. Mobile IP suite of protocols designed to support IP routing to mobile nodes. However, support for truly seamless mobility requires more than just routing: every service associated with the mobile user needs to be transferred smoothly to the new access network. In this paper, we will concentrate on the problem of transferring service state (context) at both the link and the IP layers. We propose a method to estimate the best moment in time for transferring context information associated with the mobile user. As one of key issues in the proactive context transfer scheme is accuracy of handover prediction, we suggest and describe a new concept of Forced Handover that can provide very low handover latency. The simulation results and the following discussions show that our scheme is helpful in ensuring seamless mobility, while keeping the number of unnecessary handovers resulting from ...

Journal of the American Chemical Society, 2005

A mild and general route for preparing pyridines from nitriles and diynes is described. Ni/imidaz... more A mild and general route for preparing pyridines from nitriles and diynes is described. Ni/imidazolyidene complexes were used to mediate cyclization alkynes and both aryl and alkyl nitriles at ambient temperature. In addition, the efficacy of this protocol allows for the preparation of a fused seven-membered pyridone and for intermolecular cyclizations. When an asymmetrical diyne was employed, cyclization afforded a single pyridine regioisomer.

Journal of the American Chemical Society, 2004

Pyridine derivatives R 0380 Nickel-Catalyzed Cycloaddition of Alkynes and Isocyanates.-An efficie... more Pyridine derivatives R 0380 Nickel-Catalyzed Cycloaddition of Alkynes and Isocyanates.-An efficient route for the synthesis of 2-pyridones from isocyanates and diynes is described. Both intramolecular and intermolecular reactions are catalyzed by a combination of a Ni(0) precursor and a N-heterocyclic carbene under mild conditions. First time, a seven-membered ring is formed by cycloaddition of an isocyanate with a diyne. Application of the present new method also allows a three component cyclization.-(DUONG,

Conservation Genetics, 2014

ABSTRACT Distribution and taxonomic status of the Roosevelt’s Barking Deer (Muntiacus rooseveltor... more ABSTRACT Distribution and taxonomic status of the Roosevelt’s Barking Deer (Muntiacus rooseveltorum) have remained poorly understood after more than 80 years since its description. All records of this species so far have been reported only from Lao PDR. During recent surveys in central Vietnam, we found several specimens from local hunting trophies morphologically resembling this species. Our molecular data, including both mitochondrial and nuclear genes, based on collected materials confirm for the first time that M. rooseveltorum is distributed in Vietnam. In addition, the phylogenetic analyses demonstrate that the Roosevelt’s Barking Deer represents a distinct evolutionary lineage closely related to the Truong Son Muntjac, in central Vietnam, and the Leaf Muntjac in Myanmar. Given the rarity of this species and the escalating hunting and habitat loss in the region, it is important to conduct field research to assess its population status. Such information is critically needed to design a conservation plan for this highly elusive and threatened taxon.

Chemical Communications, 2004

Spectroscopic analysis, thermogravimetric analysis, and crossover experiments performed on a seri... more Spectroscopic analysis, thermogravimetric analysis, and crossover experiments performed on a series of imidazolium carboxylates revealed carboxylation was reversible with N-aryl substituted adducts.

Angewandte Chemie International Edition, 2010

Copper(II)-Catalyzed meta-Selective Direct Arylation of a-Aryl Carbonyl Compounds** Scheme 1. The... more Copper(II)-Catalyzed meta-Selective Direct Arylation of a-Aryl Carbonyl Compounds** Scheme 1. The utility of the a-aryl carbonyl framework.

Resource ReserVation Protocol (RSVP) is a QoS signalling protocol developed by IETF for fixed net... more Resource ReserVation Protocol (RSVP) is a QoS signalling protocol developed by IETF for fixed networks. However, in mobile networks where mobile nodes are freely moving, the standard RSVP is inadequate. There is substantial number of published works aiming to support RSVP mobility. Our contribution in this paper is to explore further the proactive context transfer scheme [6] in the context of RSVP state reestablishment. As shown in the paper, the proactive scheme is well suited to RSVP state reestablishment. We also suggest the concept of deferred reestablishment to increase the probability of resource availability during the proactive reestablishment process. Finally, we analyse the cost and benefits of state reestablishment in terms of wasted resources (we express the resources as a product of bandwidth and time and call it bandwidth-time in the paper) to confirm the effectiveness of our scheme.

2006 IEEE 63rd Vehicular Technology Conference

ABSTRACT

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012

This paper proposes an algorithm to identify groups of users connected to a mobile ad hoc network... more This paper proposes an algorithm to identify groups of users connected to a mobile ad hoc network that remain stable over time. Several similar algorithms have been proposed to manage mobility either by predicting disconnections or by identifying groups of peers stable over time. They all rely on information such as GPS, signal strength or routes and result in message overhead. The algorithm proposed here uses information from the routing layer to detect groups that are stable over time. This algorithm is fully distributed and creates no message overhead as the result of using cross-layer information.

TENCON 2005 - 2005 IEEE Region 10 Conference, 2005

A well-known problem in wireless multi-hop communication is the significant degradation of throug... more A well-known problem in wireless multi-hop communication is the significant degradation of throughput when the number of hops increases. Previous research shows that in a chain topology, nodes using IEEE 802.11 can at best achieve 1/4, but in practice only 1/7, much smaller than the ideal 1/3 of the throughput of single-hop transmission. In order to improve performance in multi-hop cases, we introduce a rate balance scheme and tune the sensing range at physical layer and contention window at MAC layer. Our simulation results show that the throughput ratio close to 1/4 is achievable when the number of hops is as high as 12; better ratios of 1/3.4 and 1/3.6 are achieved when number of hops is 5 and 8, respectively.

Multimedia Systems and Applications Series, 2005

ABSTRACT

Water Research, 2003

The occurrence and the fate of trihalomethanes (THMs) in the water supply system of Hanoi City, V... more The occurrence and the fate of trihalomethanes (THMs) in the water supply system of Hanoi City, Vietnam was investigated from 1998 to 2001. The chlorination efficiency, THM speciation, and, THM formation potential (THMFP) was determined in the water works and in tap water. With regard to THM formation, three types of groundwater resources were identified: (I) high bromide, (II) low bromide, and (III) high bromide combined with high ammonia and high dissolved organic carbon (DOC) concentrations. Under typical treatment conditions (total chlorine residual 0.5-0.8 mg/L), the total THM formation was always below WHO, EU, and USEPA drinking water standards and decreased in the order type I>type II>type III, although the THMFP was >400 mg/L for type III water. The speciation showed >80% of bromo-THMs in type I water due to the noticeable high bromide level (p140 mg/L). In type II water, the bromo-THMs still accounted for some 40% although the bromide concentration is significantly lower (p30 mg/L). In contrast, only traces of bromo-THMs were formed (B5%) in type III water, despite bromide levels were high (p240 mg/L). This observation could be explained by competition kinetics of chlorine reacting with ammonia and bromide. Based on chlorine exposure (CT) estimations, it was concluded that the current chlorination practice for type I and II waters is sufficient for X2-log inactivation of Giardia lamblia cysts. However, in type III water the applied chlorine is masked as chloramine with a much lower disinfection efficiency. In addition to high levels of ammonia, type III groundwater is also contaminated by arsenic that is not satisfactory removed during treatment. Nnitrosodimethylamine, a potential carcinogen suspected to be formed during chloramination processes, was below the detection limit of 0.02 mg/L in type III water.

Header compression (HC) is a useful technique for reducing the load on bandwidth-scarce wireless ... more Header compression (HC) is a useful technique for reducing the load on bandwidth-scarce wireless links. HC normally depends on the establishment and synchronisation of context at the compressor and de-compressor. In Mobile IP networks, it is desirable to transfer this context between access routers to avoid the expensive process of context re- establishment. In this paper we propose a method for avoiding the need for context re-establishment when packets are lost during handovers, as well as means for efficiently transferring the context to new access routers (by piggybacking the context on Mobile IP signalling messages). The analysis of our scheme shows that it can reduce signalling load during handovers, which is beneficial in mobile networks with frequent handovers (e.g. wireless LAN hot spots).

Organisms Diversity & Evolution, 2014

Several important aspects of the evolution of the softshell turtle (family Trionychidae) have not... more Several important aspects of the evolution of the softshell turtle (family Trionychidae) have not been addressed thoroughly in previous studies, including the pattern and timing of diversification of major clades and species boundaries of the critically endangered Shanghai Softshell Turtle, Rafetus swinhoei. To address these issues, we analyzed data from two mitochondrial loci (cytochrome b and ND4) and one nuclear intron (R35) for all species of trionychid turtles, except Pelochelys signifera, and for all known populations of Rafetus swinhoei in Vietnam and one from China. Phylogenetic analyses using three methods (maximum parsimony, maximum likelihood, and Bayesian inference) produce a well resolved and strongly supported phylogeny. The results of our time-calibration and biogeographic optimization analyses show that trionychid dispersals out of Asia took place between 45 and 49 million years ago in the Eocene. Interestingly, the accelerated rates of diversification and dispersal within the family correspond surprisingly well to global warming periods between the mid Paleocene and the early Oligocene and from the end of the Oligocene to the mid Miocene. Our study also indicates that there is no significant genetic divergence among monophyletic populations of Rafetus swinhoei, and that previous taxonomic revision of this species is unwarranted.

ACM SIGMOBILE Mobile Computing and Communications Review, 2005

In recent years, many protocols have been developed to support user mobility in wireless networks... more In recent years, many protocols have been developed to support user mobility in wireless networks, e.g. Mobile IP suite of protocols designed to support IP routing to mobile nodes. However, support for truly seamless mobility requires more than just routing: every service associated with the mobile user needs to be transferred smoothly to the new access network. In this paper, we will concentrate on the problem of transferring service state (context) at both the link and the IP layers. We propose a method to estimate the best moment in time for transferring context information associated with the mobile user. As one of key issues in the proactive context transfer scheme is accuracy of handover prediction, we suggest and describe a new concept of Forced Handover that can provide very low handover latency. The simulation results and the following discussions show that our scheme is helpful in ensuring seamless mobility, while keeping the number of unnecessary handovers resulting from ...

Journal of the American Chemical Society, 2005

A mild and general route for preparing pyridines from nitriles and diynes is described. Ni/imidaz... more A mild and general route for preparing pyridines from nitriles and diynes is described. Ni/imidazolyidene complexes were used to mediate cyclization alkynes and both aryl and alkyl nitriles at ambient temperature. In addition, the efficacy of this protocol allows for the preparation of a fused seven-membered pyridone and for intermolecular cyclizations. When an asymmetrical diyne was employed, cyclization afforded a single pyridine regioisomer.

Journal of the American Chemical Society, 2004

Pyridine derivatives R 0380 Nickel-Catalyzed Cycloaddition of Alkynes and Isocyanates.-An efficie... more Pyridine derivatives R 0380 Nickel-Catalyzed Cycloaddition of Alkynes and Isocyanates.-An efficient route for the synthesis of 2-pyridones from isocyanates and diynes is described. Both intramolecular and intermolecular reactions are catalyzed by a combination of a Ni(0) precursor and a N-heterocyclic carbene under mild conditions. First time, a seven-membered ring is formed by cycloaddition of an isocyanate with a diyne. Application of the present new method also allows a three component cyclization.-(DUONG,

Conservation Genetics, 2014

ABSTRACT Distribution and taxonomic status of the Roosevelt’s Barking Deer (Muntiacus rooseveltor... more ABSTRACT Distribution and taxonomic status of the Roosevelt’s Barking Deer (Muntiacus rooseveltorum) have remained poorly understood after more than 80 years since its description. All records of this species so far have been reported only from Lao PDR. During recent surveys in central Vietnam, we found several specimens from local hunting trophies morphologically resembling this species. Our molecular data, including both mitochondrial and nuclear genes, based on collected materials confirm for the first time that M. rooseveltorum is distributed in Vietnam. In addition, the phylogenetic analyses demonstrate that the Roosevelt’s Barking Deer represents a distinct evolutionary lineage closely related to the Truong Son Muntjac, in central Vietnam, and the Leaf Muntjac in Myanmar. Given the rarity of this species and the escalating hunting and habitat loss in the region, it is important to conduct field research to assess its population status. Such information is critically needed to design a conservation plan for this highly elusive and threatened taxon.

Chemical Communications, 2004

Spectroscopic analysis, thermogravimetric analysis, and crossover experiments performed on a seri... more Spectroscopic analysis, thermogravimetric analysis, and crossover experiments performed on a series of imidazolium carboxylates revealed carboxylation was reversible with N-aryl substituted adducts.

Angewandte Chemie International Edition, 2010

Copper(II)-Catalyzed meta-Selective Direct Arylation of a-Aryl Carbonyl Compounds** Scheme 1. The... more Copper(II)-Catalyzed meta-Selective Direct Arylation of a-Aryl Carbonyl Compounds** Scheme 1. The utility of the a-aryl carbonyl framework.