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Việt Trì, Vietnam

Giang P.T.K.,Hung Vuong University | Thu D.X.,Hanoi National University of Education | Quy H.V.,Hanoi National University of Education
Asian Journal of Chemistry | Year: 2013

Arsenic and heavy metals present in wastewater were determined before and after treatment on the adsorbent column is significant science in Vietnam. In this study, we used the available natural materials, it is powdered and Fe(0) yellow sand, MnO2 powder under the granules used as adsorbent in the column. The survey materials were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM). These study showed that the material consists of magnetite Fe3O4 38.18 %, hematite Fe2O 3 12.73 %, wuestite FeO 16.36 % of the beneficial minerals for the adsorption of heavy metals. The results showed that the material can remove As and some heavy metals out of the environment, in particular: arsenic adsorption capacity (169.65 mg/kg) and some metals such as Mn, Fe, Cu, Pb, Cd, respectively: 6616.05, 6664.24, 426.07, 143.06 and 120.21 mg/kg and maintained for a period of 4 days. This shows good potential applications of sand and iron powder Fe(0) in the treatment of heavy metal pollution by column adsorption method.

Ngo T.L.,University of Gottingen | Ngo T.L.,Hung Vuong University | Holscher D.,University of Gottingen
Tropical Conservation Science | Year: 2014

Rare tropical tree species are endangered due to the disappearance of old-growth forests. Although some undisturbed oldgrowth and formerly logged forests are protected today, the extent to which rare tree species persist and regenerate in such logged forests is often unclear. In a forested area over limestone in northern Vietnam, we studied the fate of five rare tree species after decades of logging and subsequent nine years of full protection, in comparison with an un-logged forest. Three of the studied species are largely restricted to limestone hills (Excentrodendron tonkinense, Chukrasia tabularis and Garcinia fagraeoides), while two of the species have a wider distribution (Parashorea chinensis and Melientha suavis). The bigger trees of the study species had lower densities and/or differences in the diameter distributions between the two forest types, indicating that these species had formerly been cut. The regeneration stem density of the study species was much lower (46% in M. suavis to 80% in P. chinensis) in the logged than un-logged forest. In the un-logged forest, we found clear relationships between ecological factors and regeneration density in four of the five study species; e.g., the regeneration of E. tonkinense increased with increasing rock-outcrop cover (r = 0.6, p < 0.01). Such relationships were almost absent in the logged forest. The widely distributed generalist species Cleidion javanicum dominated in the tree regeneration of the logged forest. Our results suggest that the studied rare tree species still existed as adults after logging and there was regeneration but at low densities. We assume that the potential for recovery remains, which further justifies the full protection of this and other restoration areas. © The Long Ngo and Dirk Hölscher.

Vo N.-S.,Duy Tan University | Nguyen M.-H.,Hung Vuong University | Ha D.-B.,Duy Tan University | Huynh D.-T.,Ho Chi Minh City University of Transport
2013 International Conference on Computing, Management and Telecommunications, ComManTel 2013 | Year: 2013

In this paper, we propose a joint method of distortion aware opportunistic routing and transmission rate assignment to specifically support video streaming in wireless mesh networks (WMNs). Particularly, we introduce a reduction in reconstructed distortion slope (RDS) metric used for routing algorithm. Based on this metric, each node knows that which is the best successor in the forwarding set by assigning the best transmission rate. As a result, the best path between the sender and the receiver is found to maximize the end-to-end reduction in reconstructed distortion (RRD) for high quality playback. Simulation results are shown to demonstrate that the proposed method significantly improves the quality playback of received video streaming. © 2013 IEEE.

Huy N.T.,Hanoi University | Anh N.K.,Hung Vuong University | Thai N.P.,Vietnam National University, Hanoi
Proceedings - 2011 3rd International Conference on Knowledge and Systems Engineering, KSE 2011 | Year: 2011

Functional tags represent the role of syntactic constituents such as noun phrases and verb phrases in a tree. Functional-tag labeling has been studied for languages such as English and Chinese. In this paper, we present a new system for tagging Vietnamese sentences functionally. We used maximum entropy model for this task with six tree-based features. Besides, a new feature based on word cluster has also been made use of. Our experiments on Vietnamese tree bank showed that the system achieved a good performance and the word cluster feature brought a significant improvement. © 2011 IEEE.

Trieu H.-L.,Thai Nguyen University | Nguyen P.-T.,Vietnam National University, Hanoi | Nguyen K.-A.,Hung Vuong University
Advances in Intelligent Systems and Computing | Year: 2014

Sentence alignment plays an extremely important role in machine translation. Most of the hybrid approaches get either a bad recall or low precision. We tackle disadvantages of several novel sentence alignment approaches, which combine length-based and word correspondences. Word clustering is applied in our method in order to improve the quality of the sentence aligner, especially when dealing with the sparse data problem. Our approach overcomes the limits of previous hybrid methods and obtains both highly recall and reasonable precision rates. © Springer International Publishing Switzerland 2014.

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