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A theoretical study on propagation of guided waves in a fluid layer overlying a solid half-space
Get PDFUltrasonic guided waves propagating in a non-viscous fluid layer of uniform thickness bonded to an elastic solid half-space is theoretically investigated in this article. Based on the boundary conditions set for the joined configuration, a characteristic dispersion equation is found and new expressions for free guided waves are introduced. Closed-form solutions of guided waves generated by a time-harmonic load are derived by the use of elastodynamics reciprocity theorems. Through calculation examples, it is shown that the obtained computation of the lowest wave mode approaches the result of the Rayleigh wave in the solid half-space as the layer thickness approaches zero. The aim of the present work is to improve the understanding of wave motions in layered half-spaces for potential applications in the area of bone quantitative ultrasound
The impact of zerovalent cobalt nanoparticle on photosynthesis - related genes expression in soybean leaves Glycine max (L.) Merr. (Dt26)
Get PDFPhotosynthesis is an important physiological process in plants. It plays a crucial role in plant growth and development. In this study, we investigated the impact of zerovalent cobalt nanoparticles on the photosynthesis and expressing of gene involving in this process in leave of soybean Glycine max (L) Merr “DT26” at different growth stages. The results showed that treatment of zerovalent cobalt nanoparticles made in Vietnam and USA (with two doses of 0.17 and 16.67 mg/kg of soybean seed) enhanced the photosynthesis of soybean by increasing the content of chlorophyll a and the ratio of Fv/Fm compared with the control (without treatment of zerovalent cobalt nanoparticles). These values tended to increase and reached the maximum value at 40 days and then decreased in at 70 days. The expression level of photosynthesis-related genes of soybean leaves also changed depending on the soybean’s growth stage and concentration of zerovalent cobalt nanoparticles being treated. The genes psaA, Lhca, psaB, Cytb6f (belonging to photosystem I) and psbA, psbB, psbC, psbD, psbE (belonging to photosystem II) in the experimental fomulas were higher expressed than that in control group at 20 and 70 days. However, at 40 days, the expression levels of these genes were significantly different. Obtained results supplied the basis for understanding the active mechanism of the above genes to control/regulates photosynthetic activity of plants with and without the presence of zerovalent cobalt nanoparticles as well as under stress conditions.
Spatial distribution of hot days in north central region, Vietnam in the period of 1980-2013
No full textBased on the data of daily maximum temperature in 26 meteorological stations in the North Center Region, Vietnam over the period of 1980 to 2013, the authors conducted the research on the spatial distribution of the number of hot days. The initial result shows that in general, in the north of the study area, the large number of hot days occurred in the plain, and tended to decrease westward and eastward. In the south, this number tends to increase from the west to the east. Especially, the largest number occurred in two areas: The Ma and Ca River's valleys (Thanh Hoa and Nghe An provinces) and the coastal areas (Thua Thien Hue province), creating two heat centers in Tuong Duong district, Nghe An province and Nam Dong district, Thua Thien Hue province.ReferencesAdina-Eliza Croitoru, Adrian Piticar, Antoniu-Flavius Ciupertea, Cristina FlorinaRosca, 2016 Changes in heat wave indices in Romania over the period 1961-2015. Global and Plantary Change 146. Journal homepage: www. Elsevier.com/locate/gloplacha.Chu Thi Thu Huong et al., 2010. Variations and trends in hot event in Vietnam from 1961-2007, VNU Journal of Science and Technology, 26(3S).Climate Council, 2014a. Angry Summer 2013/2014. Accessed at http://www.climatecouncil.org.au/ angry-summer.Climate Council, 2014b. Angry Summer 2013/2014. Accessed at http://www.climatecouncil.org.au/ angry-summer.CSIRO and BoM, 2012. State of the Climate 2012.CSIRO and Bureau of Meteorology, Melbourne.Accessed at http://www.csiro.au/Outcomes/ Climate/Understanding/State-of-the-Climate-2012.aspx.D'Ippoliti D., Michelozzi P., Marino C., De'Donato F., Menne B., Katsouyanni K., Kirchmayer U., Analitis A., Medina-Ramon M., Paldy A., Atkinson R., Kovats S., Bisanti L., Schneider A., Lefranc A., Iñiguez C., Perucci C., 2010. The impact of heat waves on mortality in 9 European cities: results from the EuroHEAT project. Environ. Health 9, 37. http://dx.doi.org/10.1186/1476-069X-9-37.Gerald A. Meehl, 1992. Effect of tropical topography on global climate, Ann. Rev. Earth Planet. Sci., 20, 85-112.Hayhoe K., Cayan D., Field C.B., Frumhoff P.C., Maurer E.P., Miller N.L., Moser S.C., Schneider S.H., Cahill K.N., Cleland E.E., Dale L., Drapek R., Hanemann R.M., lkstein L.S., Lenihan J., Lunch C.K., Neilson R.P., Sheridan S.C., Verville J.H., 2004. Emissions pathways, climate change, and impacts on California. PNAS, 101(34), 12422-12427.Ho Thi Minh Ha, Phan Van Tan, 2009. Trends and variations of extreme temperature in Vietnam in the period from 1961 to 2007, VNU Journal of Science and Technology, 25(3S).IPCC, 2007: Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri R.K and Reisinger A. (eds.)]. IPCC, Geneva, Switzerland, 104p.IPCC, 2014. Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151p.Liu G., Zhang L., He B., Jin X., Zhang Q., Razafindrabe B., You H., 2015. Temporal changes in extreme high temperature, heat waves and relevant disasters in Nanjing metropolitan region, China. Nat. Hazards, 76, 1415–1430. http://dx.doi.org/10.1007/s11069-014-1556-y.Manton M.J et al., 2001. Trends in extreme daily temperature in Southeast Asia Rainfall ad and the South Pacific, J. Climatol. 21.Nairn J.R., Fawcett R.J.B., 2015. Int. J. Environ. Res. Public Health 12, 227–253. http://dx.doi.org/10.3390/ijerph120100227.Nguyen Duc Ngu, 2009. Climate Change Challenges to development, Journal of Economy and Environment, No. 1.Perkins S.E., Alexander L.V., 2013. On the measurement of heat waves. J. Clim. 26, 4500–4517. http://dx.doi.org/10.1175/JCLI-D-12-00383.1.Peterson T.C., Heim Jr. R.R., Hirsch R., Kaiser D.P., Brooks H., Diffenbaugh N.S., Dole R.M., Giovannettone J.P., Guirguis K., Karl T.R., Katz R.W., Kunkel K., Lettenmaier D., McCabe G.J., Paciorek C.J., Ryberg K.R., Schubert S., Silva V.B.S., Stewart B.C., Vecchia A.V., Villarini G., Vose R.S., Walsh J., Wehner M., Wolock D., Wolter K., Woodhouse C.A., Wuebbles D., 2013. Monitoring and understanding changes in heat waves, cold waves, floods, and droughts in the United States: state of knowledge. Bull. Amer. Meteor. Soc., 94, 821–834.Pham Thi Ly, Hoang Luu Thu Thuy, 2015. Variation of heat waves in the North Central Region over the period of 1980-2013, Journal of natural resources and environment, 9, 81-89.Phan Van Tan et al., 2010. Study impact of global climate change on extreme weather phenomena and factors in Vietnam, prediction and adaptation strategies. Project final report, KC 08.29/06-10, Hanoi University of Science.Spinoni J., Lakatos M., Szentimrey T., Bihari Z., Szalai S., Vogt J., Antofie T., 2015. Heat and cold waves trends in Carpathian Region from 1961 to 2010. Int. J. Climatol, 35, 4197–4209. http://dx.doi.org/10.1002/joc.4279.Toreti A., Desiato F., 2008.Temperature trends over Italy from 1961 to 2004, Theor. Appl. Climatol 91.Tran Cong Minh, 2007. Principle of meteorology and climate, Book, Public House of Hanoi National University.Tran Quang Duc, Trinh Lan Phuong, 2013. Changes of Hot day and Fohn Activities at Ha Tinh- Central Vietnam, VNU Journal of Science, Science and Technology, 29(2S).Trewin B., Smalley R., 2013.Changes in extreme temperature in Australia, 1910 to 2011. In: 19th AMOS National Conference, Melbourne, 11-13.Unal Y.S., Tan E., Mentes S.S., 2013. Summer heat waves over western Turkey between 1965 and 2006.Theor. Appl. Climatol, 112, 339–350. http://dx.doi.org/10.1007/s00704-012-0704-0.Will Steffen, 2015. Quantifying the impact of climate change on extreme heat in Australia. Published by the Climate Council of Australia Limited. ISBN: 978-0-9942453-1-1 (print) 978-0-9942453-0-4 (web)
Variation of the foF2 parameter during fluctuating activity: Prediction with IRI-2012 compared to measured data from Ouagadougou inosonde station during solar cycles 21 and 22
No full textIn this paper, we review on diurnal variations of the foF2 ionospheric parameter predicted by the IRI-2012 model, and data from Ouagadougou ionosonde station located in the crest of the Equatorial Anomaly (Lat: 12.5°N; Long: 358.5°E, dip: 1.43°) during fluctuating geomagnetic activity conditions for the solar cycles 21 and 22. Our investigations are focused on the electrodynamic aspects, the influence of the ionospheric electric currents as well as the variations of the hourly values given by model and experimental measurements. A comparative study pointed out that the IRI-2012 model, through its URSI and CCIR subroutines, gives a good prediction of the critical frequency of the F2 layer between 0700 TL and 0000 TL. In addition, IRI -2012 tries to reproduce, as best as possible, the vertical drift E × B during minimum, decreasing phase, winter, and autumn. However, there is no effect of drift during the other seasons and solar cycle phases. A last, the model does not take into account the PRE phenomenon observed in autumn and the influence of the equatorial electrojet in this ionospheric zone.ReferencesAcharya R., Roy B., Sivaraman M.R., 2010. Dasgupta A. An empirical relation of daytime equatorial total electron content with equatorial electrojet in the Indian zone. J Atmos Terr Phys, 72(10), 774–780.Acharya R., Roy B., Sivaraman M.R.; Dasgupta A., 2011. On conformity of the EEJ based Ionospheric model to the Fountain effect and resulting improvements. J Atmos Terr Phys, 73, 779-784.Adeniyi J.O., Oladipo O.A., Radicella S.M., 2005. Variability of fof2 and comparison with iri model for an equatorial station. The Abdus Salam International Centre for Theoretical Physics, IC/2005/085, http://www.ictp.it/~pub_off.Adeniyi1 J.O., Oladjipo O.A., Radicella S.M., 2005. Variability of foF2 and comparison with IRI model for an equatorial station. The Abdus Salam International Centre for Theoretical Physics, IC/2005/085.Bilitza D., et al., 2014. The International Reference Ionosphere 2012-a model of international collaborationI. J. Space Weather Space Clim, 4, A07.Bilitza D., Reinisch B.W., 2008. International Reference Ionosphere 2007: Improvements and new parameters. Adv. Space Res, 42, 599–609.Farley D.T., Bonell E., Fejer B.G., Larsen M.F., 1986. The Prereversal Enhancement of the Zonal Electric Field in the Equatorial Ionosphere. J Geophys Res, 91(A12), 13,723–13,728.Faynot J.M., Villa P., 1979. F region at the magnetic equator. Ann Geophys, 35, 1–9.Fejer B.G., 1981. The equatorial ionospheric electric fields: A review. J Atmos Terr Phys, 43, 377.Fejer B.G., Farley D.T., Woodman R.F., Calderon C., 1979. Dependence of equatorial F region vertical drifts on season and solar cycle. J Geophys Res, 84, 5792.Legrand J.P., Simon P.A., 1989. Solar cycle and geomagnetic activity: A review for geophysicists. Part I. The contributions to geomagnetic activity of shock waves and of the solar wind. Ann. Geophys, 7, 565–578.Obrou K.O., 2008. Contribution à l’amélioration du modèle "International Reference Ionosphere" (IRI) pour l’ionosphère équatoriale. Thèse de doctorat Université de Cocody, Abidjan, Côte d’Ivoire.Ouattara F., 2009. Contribution à l’étude des relations entre les deux composantes du champ magnétique solaire et l’Ionosphère Equatoriale. Thèse de Doctorat d’Etat ès Sciences, Université Cheikh Anta Diop, Dakar, Sénégal.Ouattara F., 2013. IRI-2007 foF2 Predictions at Ouagadougou Station during Quiet Time Periods from 1985 to 1995. Archives of Physics Research, 4, 12–18.Ouattara F., Amory-Mazaudier C., 2009. Solar–geomagnetic activity and Aa indices toward a Standard. J. Atmos. Terr. Phys, 71, 1736–1748.Ouattra F., Nanéma, 2014. Quiet Time foF2 Variation at Ouagadougou Station and Comparison with TIEGCM and IRI-2012 Predictions for 1985 and 1990. Physical Science International Journal, 4(6), 892–902.Oyekola O.S., Fagundes P.R., 2012. Equatorial F2-layer variations: Comparison between F2 peak parameters at Ouagadougou with the IRI-2007 model. Earth, Planets Space, 64, 553–566.Rishbeth H., 1971. The F-layer dynamo. Planet, Space Sci, 19, 263.Vassal J.A., 1982. The variation of the magnetic field and its relationship with the equatorial electrojet in Senegal Oriental. Annals of Geophysics, Tome French, 38.Zerbo J.L., Amory-Mazaudier C. Ouattara F., Richardson J., 2012. Solar Wind and Geomagnetism, toward a Standard Classification 1868-2009. Ann Geophys, 30, 421–426. http://dx.doi.org/10.5194/angeo-30-421-2012.Zerbo J.L., Amory-Mazaudier C., Ouattara F., 2013. Geomagnetism during solar cycle 23: Characteristics. J. Adv. Res, 4(3), 265–274. Doi:10.1016/j.jare.2013.08.010.Zerbo J.L., Ouattara F., Zoundi C., Gyébré A., 2011. Solar cycle 23 and geomagnetic activity since 1868. Revue CAMES serie A, 12(2), 255–262
Influence of Mn Doping on Structural Phase Transformation and Optical Property of TiO:Mn Nanoparticles
Get PDFTitanium dioxide (TiO2) nanoparticles with various Mn2+-doping concentration (from 0 to 12 mol%) were successfully synthesized by the sol–gel method using titanium tetrachloride (TiCl4), and manganese II chloride tetrahydrate (MnCl2.4H2O) as precursors. The phase and crystallinity of the synthesized materials were investigated by powder X-ray diffraction pattern and Raman spectroscopy. Diffuse reflection and photoluminescence spectra were taken to investigate the absorption and emission characteristics of the synthesized samples. The results show that the anatase and rutile phases existed simultaneously in all the doping TiO2 nanoparticles and the Mn2+ doping enhances anatase-rutile transformation. The Mn2+ contents did not affect the lattice of TiO2 host, but affected positions of its Raman modes. The optical band gap of the TiO2:Mn2+ decreases with the increase of doping concentration. Photoluminescence spectra of the TiO2:Mn2+ nanopaticles showed the transitions between the bands, the transitions related to defect states and the Mn2+ ion doping leads to quenching the photoluminescence
VLSP SHARED TASK: SENTIMENT ANALYSIS
Get PDFSentiment analysis is a natural language processing (NLP) task of identifying orextracting the sentiment content of a text unit. This task has become an active research topic since the early 2000s. During the two last editions of the VLSP workshop series, the shared task on Sentiment Analysis (SA) for Vietnamese has been organized in order to provide an objective evaluation measurement about the performance (quality) of sentiment analysis tools, and encouragethe development of Vietnamese sentiment analysis systems, as well as to provide benchmark datasets for this task. The rst campaign in 2016 only focused on the sentiment polarity classication, with a dataset containing reviews of electronic products. The second campaign in 2018 addressed the problem of Aspect Based Sentiment Analysis (ABSA) for Vietnamese, by providing two datasets containing reviews in restaurant and hotel domains. These data are accessible for research purpose via the VLSP website vlsp.org.vn/resources. This paper describes the built datasets as well as the evaluation results of the systems participating to these campaigns
The Bioclimatic map of Southern Vietnam for tourism development
No full textAlthough research and evaluation of climate conditions for tourism development are a pressing issue, in Vietnam in general and in the Southern region in particular, these studies are still limited. Based on climatological parameters (T-annual temperature, R-rainfall and N-rainy days) with their levels of classification representing the bioclimatic impact on tourism, the bioclimatic classification map of Southern Vietnam is built at the scale of 1:250,000. Base on the calculated data from 20 meteorological stations of Southern Vietnam in many years (1981-2015, 12 suitable bioclimatic units are established. It is a necessary scientific background to organize territory for tourism in Southern Vietnam. With plentiful bioclimatic resources, one can organize many types of tourism in Southern Vietnam. The result of classification and bioclimatic map for tourism is an important and necessary sciential basis which help the orientation of development and tourism territory organization of the governments.
Isolation and identification of indole acetic acid producing bacteria from the coasts of Ben Tre and Tra Vinh Provinces
Get PDFBeneficial plant-growth-promoting bacteria (PGPB) have been reasonably applied to rescue crucial issue for agriculture by salinity soil. Observed most of PGPB was found in endophyte, rhizosphere and soil. Indole acetic acid (IAA)-producing bacteria could naturally stimulate and facilitate plant growth. The knowledge of IAA production and content of bacteria resident in the marine environment has been typically insufficient and limited to date. In recent years, unwarrantable intrusions of sea water have been enlarged in the Mekong River Delta of Vietnam, threatening productive rice fields, local fruits, and cash crops. Therefore, finding PGPB in the coastal regions in the Mekong River Delta as a creative resource for sustainable agriculture is necessary and is a prompt challenge. In this study, IAA-producing bacteria from coastal regions of Ben Tre and Tra Vinh Provinces were isolated and adequately identified. Out of 202 bacterial isolates, 10 isolates showed the possible ability to produce IAA from L-tryptophan. These 10 isolates were objectively evaluated the capacity to produce IAA under 5% (w/v) NaCl in King B and marine broths. The results revealed that IAA production decreased in 5% NaCl, even though bacterial growth increased. These 10 IAA-producing bacteria were classified at the species level, Marinobacter hydrocarbonoclasticus, M. pelagius, M. daepoensis, and Mameliella phaeodactyli by 16S rRNA gene analysis. The most IAA producer in King’s B broth, the isolate C7, was investigated in more detail. The isolate C7 produced the maximum IAA amount (192.2 ± 1.14 µg/ml) under the presence of 20 g/l yeast extract, 2 g/l of L-tryptophan and 1% NaCl. The isolate C7 was able to grow at 1–17% (w/v) NaCl (optimum, 4%), but not in the absence of NaCl, indicating it is a moderate halophilic bacteria. This study highlighted the considerable ability to produce IAA of marine bacteria, which could be thoughtfully considered to use naturally as biofertilizers to promote plant growth in saline intrusion lands.
EFFECTS OF PROCESS PARAMETERS ON THE EXTRACTION EFFICIENCY AND CHEMICAL CHARACTERISTICS OF TEA SEED OIL FROM “TRUNGDU” TEA VARIETY
No full textThis research was aimed at investigating the effects of some extraction process parameters on the extraction efficiency and some chemical characteristics of tea seed oil from “Trungdu” tea variety, one of the high-quality vegetable oils, similar to olive oil with high portion of unsaturated fatty acids, especially essential linoleic acid and low content of saturated fat. This work reports for the first time the effects of process parameters using solvent extraction method on the efficiency and chemical characteristics of “Trungdu” tea seed oil. The study parameters were particle size (0.25-2.00 mm), material/solvent ratio (1/12-1/6), temperature (25-55oC), time (5-11 h), speed of solvent movement (0-250 r/m) and extraction cycle (1-3 times). The responses such as extraction efficiency, chemical characteristics (acid, peroxide, iodine and saponification values) were determined. The results indicated that the extraction efficiency was affected by all designed parameters. In addition, the temperature, particle size and extraction time had the most significant effect on the iodine value and acid value. The extraction temperature and the speed of solvent movement had pronounced effects on all the acid value, peroxide value, iodine value and saponification value of tea seed oil. However, ratio of material/solvent and extraction cycle did not appreciably effect on chemical characteristics of tea seed oil. Furthermore, the optimal extraction efficiency related to higher quality properties had been achieved in the range of 35 to 45oC, 7 to 9 hours, with a particle size of 0.5 mm, material/content ratio 1/8 to 1/12, movement speed of solvent 200 to 250 r/m and extraction cycle 1 or 2 times. Therefore, the results from this work will be useful for developing an optimal procedure for obtaining tea seed oil. In addition, tea seed oil with the main acid component is oleic acid and linoleic acid, is considered a high quality oil
Study the appropriate conditions to obtain germinated brown rice with high biological activity
Get PDFABSTRACT – QMFS 2019Germinated brown rice strains contain more bioactive substances than germinated regular rice ones, however germination conditions play an important role in the activity and the content of those substances. The proper germination process provides the optimized active ingredients from rice that can be used for the production of nutritious beverages. In this study, we investigated the effects of pH, temperature and incubation time in microaerobic culture condition on the change of bioactive substances in AnhDao brown rice. The optimal germination condition with pH at 3, temperature of 35 0C and time for 36h release 109.11U/g of the α-amylase activity, 17.22(U/g) of the enzyme glutamate decacboxylase (GAD), 1.38(U/g) of protease, 231.76mg/100g of GABA content and 21.9 (mgGAE/100g) of polyphenol from germinated AnhDao brown rice. In nutrient evaluation, germinated AnhDao brown rice contains 65.53% of starch, 2.49% of lipid, 9.13%of protein, 2.04% of reducing sugar, and 1.26% of ash.Key words: Germinated brown rice, bioactive substances, α-amylase, protease, glutamate decacboxylase (GAD), Gamma aminobutyric acid (GABA)