Vietnam Academy of Science and Technology: Journals Online
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Comparison of lipid compositions of soft coral Sinularia brassica collected in different coastal regions of Vietnam
Get PDFFive soft coral samples belonging to the same specimen Sinularia brassica were collected in the coastal area of Ha Long Quang Ninh, Nhat Le beach, Quang Binh, Hon Vang - Thanh Hoa and Nha Trang areas (2014–2016), these samples were examined and analyzed by total lipid content, content and composition of lipid and fatty acids. Highest total lipid content was found in the sample SHM 09 collected in Nha Trang bay (1.11%), and the lowest total lipid content was in HL-SHM 07 collected in Ha Long, Quang Ninh (0.68%).The lipid composition of samples contained basic classes such as polar lipids, sterols, free fatty acids, triacylglycerols, monoankyldiacylglycerols, hydrocarbons and waxes. In studied soft corals, there are the appearance of all fatty acids from C12 to C24. There are differences in composition and content of lipids and fatty acids in samples collected in different locations: Samples collected at Nha Trang bay contain more polyunsaturated fatty acids than the other samples collected in Ha Long, Thanh Hoa, Quang Binh. Another two samples, collected in Hon Vang (Thanh Hoa) have similar composition and content of lipid classes, the composition and content of fatty acids in total lipids. The obtained results also show the significant impact of habitat and time of acquisition on the studied subject
CFD results on hydrodynamic performances of a marine propeller
Get PDFIn this work, the commercial Computational Fluid Dynamics (CFD), ANSYS-Fluent V.14.5 has been used to illustrate the effects of rudder and blade pitch on hydrodynamic performances of a propeller. At first, the characteristic curves of a container ship propeller are computed. Then, effects of rudder on hydrodynamic performances of the propeller in the both cases of the propeller with and without rudder have been investigated. The relationships between the blade pitch angle and the hydrodynamic performances of the selected referent propeller in this work having designed conditions as diameter of 3.65 m; speed of 200 rpm; average pitch of 2.459 m and the boss ratio of 0.1730. Using CFD, the characteristic curves of the marine propeller, pressure distribution, velocity distribution around propeller and the efficiency of the propeller have been shown. From the obtained results, the effects of rudder and blade pitch angle on hydrodynamic performances of the propeller have been evaluated
Institute of Marine Geology and Geophysics - 30 years for studying geology and geophysics in the marine zones of Vietnam and Eastern Sea
Get PDFGeological and geophysical investigation and study in the marine zones of Vietnam and Eastern Sea, its application in the mineral exploration, for natural disaster and hazard prevention, environment and resource protection, for sea and island management, marine economic development, sea defence and security is the important, main and long-term tasks of the Institute of Marine Geology and Geophysics. For last 30 years, the institute has a leading role for conducting a numerous projects of national and international programs of marine research and investigation in the marine zones of Vietnam and Eastern Sea. The obtained results and achievements include big, abundant, up to date databases, newest and detailed schemes and maps, valuable published papers, books, and contributions on characteristics of geophysical fields, deep crustal structure, seabed sediment and environment, geological structure and tectonic evolution, seismotectonics and earthquake, tsunami hazard assessment, mineral potential and perspective evaluation. Results of study on geophysical fields, deep crustal structure, seabed topography and geomorphology have been used for determination of outer limits of continental shelf of Vietnam in the Eastern Sea. Big part of the results was gained from research and investigation projects conducted in the Truong Sa and Hoang Sa areas. On the basis of the obtained achievements, some special tasks are proposed to continue conducting the geological and geophysical research and investigation in the sea of Vietnam and adjacent areas
Two Electro-weak Phases in the Model
No full textOur analysis shows that SM-like electroweak phase transition (EWPT) in the (2-2-1) model is a first-order phase transition at the GeV scale, enough for baryogenesis. This first order EWPT is described by a non-smooth correlation length function. The second VEV is larger than 1.1 TeV in a two-stage EWPT senarino
Applying Fiber Bragg Grating for Acoustic Sensor
Get PDFIn this work, we interested to utilize Fiber Bragg Grating (FBG) for monitoring sound intensity level. Acoustic disturbance could induce strain and changing the refractive index of FBG. Therefore, light will interfere for the trough of transmission at one specific wavelength satisfied Bragg’s condition. In our demonstrations, FBG sensor was perturbed with sound intensity levels of 60, 80 and 100 dB , the measuring Bragg wavelength were recorded at 1552 nm, 1553 nm and 1555 nm, respectively. It was found that the Bragg wavelength shift has a quite linear variation with sound intensity level. In addition, the sensitivity for sensor was 0.0566 nm/dB. The obtained results are promising for developing acoustic and vibration sensors
Light Absorption and Photoluminescence Quenching Properties of Bulk Heterojunction Materials Based on the Blend of Poly(n-vinylcarbazole)/poly(n-hexylthiophen)
Get PDFThe enhancement of light absorption and photoluminescence quenching properties of the bulk heterojunction systems which were fabricated using poly(N-vinylcarbazole) (PVK); poly(N-hexylthiophene)(P3HT) and fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6] C61 (PCBM) were investigated. The optimized material showed a broad absorption in the region from ultra violet to near infra-red and the luminescence quenching higher than 90%. The obtained results provide further insight into photophysics of the heterojunction system and device performance improvement by using this system as an active layer
Hydrodynamic Simulations of Circumstellar Envelopes under the Gravitational Influence of a Wide Binary Companion: Comparison Between Circular and Elliptical Orbits
Get PDFShapes of circumstellar envelopes around mass losing stars contain information of the very inner region of the envelope where mass loss process takes place. It’s well known that the presence of a binary companion leads to strong influence on the structure of the envelope through orbital motion of the mass losing star and the gravitational interaction of the companion with the stellar wind. To investigate this effect and structures of envelopes, we have performed high resolution hydrodynamic simulations of a wide binary system in a number of orbital configurations. Our simulations clearly show the importance of the equation of state of the gas because in isothermal case the width of the spiral arm is significantly broadened with respect to the ideal gas case, therefore resulting in unrealistic spiral patterns. As the orbital geometry changes from circular to elliptical, our simulation results show that the spiral becomes bifurcated and increasingly asymmetric as indicated in previously published results. In the polar direction, the prominent alternating arcs associated with circular orbital configuration morph into almost continuous circular rings. The physical condition of the gas in the envelope is shown to vary strongly between the spiral arm and inter-arm regions. Our hydrodynamic simulations will be useful to interpret high angular resolution observations of circumstellar envelopes
Determination of drainage corridor in the downstream Vu Gia - Han river, Da Nang city
No full textFlood is one of the most well-known phenomena in the Central Vietnam where Da Nang city is located. As the most area in the central coastal part, this city frequently suffers to flood without any prevented structure like sea dike or river levee. The only thing that can help to the response for flood is emergency plans. Therefore, flooding still causes great damages to the economic development and social stability in this region. For ensuring the sustainable development of Da Nang city under the impacts of climate change and sea level rising, it requests a change in direction of the solution, from the flood control to the adaptation and living with floods through spatial planning to make a good condition for optimal drainage corridors. This paper suggests a design flood drainage corridors for Da Nang city that was developed by combining of mathematical model, GIS, hydro-meteorological documents of Vu Gia - Thu Bon basin from 2009 to present. These proposal solutions include (i) widening of the riverbed and providing a river corridor protection along both river banks; (ii) creating of drainage channels for the land between the rivers and (iii) creating of space for floodwater in an appropriate time. The result was so good and it helps to reduce the flood in Da Nang from 5% to 10%. Therefore this would be a scientific basis for identifying the flood drainage corridors of other river basins in the central coastal region without typical dike cover.ReferencesBruun et al., 2013 On the Frontiers of Climate and Environmental Change: Vulnerabilities and Adaptation in Central Vietnam, Springer Verlag, Berlin, Germany.CCFSC (Central Committee for Flood and Storm Control), 2005. “National Report on Disasters in Vietnam.”, the World Conference on Disaster Reduction, January 18–22, Kobe-Hyogo, Japan.Da Nang Statistical Office, 2016. Statistical Yearbook, Statistical publishing house, Hanoi.Da Nang University of Science and Technology, 2014. Project of Da Nang Hydrology and Urban Development Simulation Model supported by Rockefeller, Stored report of the Climate Change Coordination Office, Da Nang.Da Nang City Steering Board for Storm and Flood Prevention and Search and Rescue, Resume of the Flood Prevention and Search and Rescue works from 2000 to 2016, Stored report of the Office of People’s Committee of Da Nang city.Dang Thi Kim Nhung, 2016. Review of flood prevention planning in the central provinces from Quang Binh to Binh Thuan. Proceedings of the 55th anniversary of InstituteofWater Resources Planning, Hanoi.Decision No. 2357/QD-TTG dated 04 December 2013 approving the adjustment of general planning of Da Nang city by 2030 with a vision toward 2050.Decree No. 43/2015/ND-CP dated on 6 May 2015. Hanoi establishment and management of water source protection corridors.DHI Dan Mach, 2011. MIKE 11(RR+HD) - A Modelling system for rivers and channels, User guide.DHI Dan Mach, 2011. MIKE 21- Flow Model FM, User guide.Dinh Phung Bao, 2013. The study using GIS for flood prevention mapping system in Vu Gia-Thu Bon river basin, Stored report of the Mid-Central regional hydrometeorological center, Da Nang.FEMA, 1995. Managing Floodplain Development in Approximate Zone A Areas - A Guide for Obtaining and Developing Base Flood (100-year) Flood Elevations - FEMA 265.Floodway: https://www.fema.gov/floodplain-management/floodway#0.Hoang Ngoc Tuan, 2016. Comprehensive assessment of resistance of surface water resource to the climate change of the city, Stored report of Climate Change Coordination Office, Da Nang.Hoang Thai Binh, 2017. Determination of flood drainage corridor in the downstream area of Vu Gia - Thu Bon river (in Da Nang city) when the hydropower system in the upper in operation in the context of climate change. Final report of project’s code VAST-NĐP.12/15-16, Hanoi.JICA, 2009. Report Project for Building Disaster Resilient Societies in Central Regions of Vietnam.LUCCI, 2015. Study on the land use and climate change interactions in Central Vietnam, http://www.lucci-vietnam.info/vn/.Ministry of natural resources and environment, 2016. Climate change, sea level rise scenarios for Vietnam.NRWA Waterways Section And BGE Pty LTD, 2006. Floodway Design Guide, Government of Western Australia.Nguyen Kim Loi, 2016. The support system for Flood warning (case study in Vu Gia - Thu Bon river basin, Quang Nam province), Agricultural Publishing House, Hanoi.SRV (Socialist Republic of Vietnam), 2007. National Strategy for Natural Disaster Prevention, Response and Mitigation to 2020. November 16. Hanoi, VietnamTran Tuan, Bui Dung, 2012. The.Natural Disasters in Vietnam A SYNTHESIS FROM A SOCIOECONOMIC PERSPECTIVE, 179-198.Vu Thi Thu Lan, 2011. Field survey and hydraulic modeling of Thu Bon river basin, Quang Nam province, Stored report of Steering Board for Storm and Flood Prevention of Quang Nam.Vu Thi Thu Lan, 2013. Flood prevention mapping of Vu Gia-Thu Bon river and Thach Han-Ben Hai river in scale 1/10.000. Stored report of Office for Water Resources Projects, Ministry of Agriculture Rural Development, Hanoi.Vu Thi Thu Lan, 2013. The study of natural disasters variation (floods and droughts) in Quang Nam in the context of climate change, J. Sci. of the Earth, Hanoi, 35(1), 66-74.World Bank, 2012. Fiscal Impact of Natural Disasters in Vietnam, http://www.worldbank.org/fpd/drfip
Effect of enriching live feeds with HUFA on growth and survival of clownfish Amphiprion ocellaris (Cuvier, 1830) larvae
Get PDFThe aims of this study was to evaluate the effect of HUFA-enriched live feed in rearing Nemo fish larvae (Amphiprion ocellaris), 5 treatments were set up (each treatment was repeated in triplicate) with 5 concentrations of HUFA (Super Selco) (0, 50, 100, 150 and 200 ppm). After 45 days of culture with HUFA-enriched live feeds of different concentrations, the total length-TL as well as the specific growth rate (SGRL) in body length and survival rate of Nemo fish larvae in the treatments had significant differences (p 0.05). In the enriched live prey diet of 100 ppm Selco, TL, SGRL and the survival rate of Nemo fish larvae were the highest (10.01 ± 0.150 mm, 7.20 ± 0.099%/day and 82.67 ± 0.881%, respectively). Lowest TL, SGRL and survival rate were obtained in larvae fed with the control diet (8.65 ± 0.051 mm, 6.23 ± 0.041%/day and 68.70 ± 0.881%, respectively). The results of this experiment suggest that the optimal Selco concentration used to enrich live feeds for Nemo fish larvae is 100 ppm, which can improve the production efficiency of Nemo stock