Vietnam Academy of Science and Technology: Journals Online
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The risk of typhoon and storm surge along the coast of Vietnam
Get PDFThe history (1951–2016) and the risk of typhoon and storm surge in coastal areas of Vietnam are analyzed and evaluated based on the observation data, results of statistical and numerical models. The Monte Carlo method was used to construct a bogus typhoon. A coupled numerical model of Surge, Wave and Tide (called SuWAT) was used for simulation of storm surge. The results show that in the period of 1951–2016 there were many typhoons which landed and induced high storm surge on the coast of the North and the North of Center of Vietnam. During one thousand years, there have been 4,678 typhoons entering the coastal zone from Quang Ninh to Ca Mau. In particular, the most severe typhoon in coastal area from Quang Ninh to Thanh Hoa is at level 16 (Beaufort scale), Nghe An - Quang Tri at level 16, Quang Binh - Phu Yen at level 17, Binh Dinh - Ninh Thuan at level 15 and Binh Thuan - Ca Mau at level 13. The coastal areas with highly vulnerable storm surge are provinces from Quang Ninh to Hai Phong (4.5 m), Thanh Hoa to Nghe An (4.0 m), Quang Tri (5.0 m). The results of this study are the basis for the preparation to cope with strong/super typhoon in the coast of Vietnam
Resonant and antiresonant frequencies of multiple cracked bar
Get PDFThe natural frequencies or related resonant frequencies have been widely used for crack detection in structures by the vibration-based technique. However, antiresonant frequencies, the zeros of frequency response function, are less involved to use for the problem because they have not been thoroughly studied. The present paper addresses analysis of antiresonant frequencies of multiple cracked bar in comparison with the resonant ones. First, exact characteristic equations for the resonant and antiresonant frequencies of bar with arbitrary number of cracks are conducted in a new form that is explicitly expressed in term of crack severities. Then, the conducted equations are employed for analysis of variation of resonant and antiresonant frequencies versus crack position and depth. Numerical results show that antiresonant frequencies are indeed useful indicators for crack detection in bar mutually with the resonant ones
Study on total lipid content, lipid class composition of some fire and soft corals collected in Nha Trang, Vietnam
Get PDFFor the first time, the total lipid content and lipid class composition of the Vietnamese soft corals (Sinularia brassica, Sinularia flexibilis) and fire corals (Millepora dichotoma, Millepora platyphylla) were investigated. The results indicated that the total lipid content of the investigated species was significantly different. Compositions of the lipid classes were analyzed using TLC and image analysis program Sorbfil TLC Videodensitometer DV and the results showed that phospholipids (PL, 10.91–16.02%), monoalkyldiacylglycerols (MADAG, 20.69-39.92%) and hydrocarbon wax (HW, 29.83-37.17%) were the main lipid classes of the total lipid in soft coral species. Meanwhile, PL (24.11-33.23%), TG (14.27–34.92%), ST (10.10–14.50%) and HW (12.08–19.95%) were predominant in fire coral species. ST, TG and FFA contents in soft and fire corals were at low level. DG was only present in the Sinularia flexibilis but not in other studied corals
ANTIBACTERIAL AND PHOTOCATALYTIC ABILITY OF THE Ag/TiO2 COATING ON THE GLASS SURFACE.
Get PDFThe coating on the glass surface was made by heating the mixture of resinate Ag and tetra-n-butyl orthotitanate (TBO) at 570 oC for 1 hour. The characteristics and structure of the mixture Ag/TiO2 with the content of Ag : TiO2 from 0 – 8 (% mol) were studied by the methods such as XRD, FTIR, UV-viz, SEM, EDS. The research results of antibacterial ability and the degradation of blue methylene (MB) were shown that this coating can be used for antibacterial and photocatalytic abilit
HYDROGEN-PLASMA-TREATED NANO TIO2 FOR PHOTOCATALYTIC OXIDATION OF VOCS IN AIR STREAM
Get PDFUnlike water treatment processes, the photocatalytic oxidation of VOCs in air stream exhibits many challenges. This study will develop the hydrogen-plasma-treated TiO2 with improvement in photocatalytic activity. The hydrogen-plasma-treatment was carried out in the non-thermal atmospheric pressure reactor at room temperature or above. The catalysts were prepared and analyzed by advanced techniques such as X-ray diffraction (XRD), scanning electro-microscopy (SEM) and transmission electro-microscopy (TEM). The photocatalytic activity of the catalyst has been investigated under UV light with various reaction conditions such as different initial toluene/formaldehyde concentrations and water content. Significantly, the conversion of toluene by a plasma-treated sample was 1.5 times higher than the bare TiO2 in a similar reaction condition
SOUND TRANSMISSION ACROSS A FINITE SIMPLY SUPPORTED DOUBLE-LAMINATED COMPOSITE PLATE WITH ENCLOSED AIR CAVITY
Get PDFABSTRACTSound transmission across a finite orthotropic laminated double-composite plate with enclosed air cavity on an infinite acoustic rigid baffle is investigated analytically. Sound velocity potential method combined with simply supported boundary conditions is used instead of traditional methods, has good scalability and is important for studies of acoustic vibration of structures. The sound transmission loss is calculated from the ratio of incident to transmitted acoustic powers. Specifically, the focus is placed on the effects of several key system parameters on sound transmission including the plate dimensions, the laminate configurations, the boundary conditions, and the composite materials are systematically examined
Occurrence features of Rip current at Ha My (Dien Ban district) and Tam Thanh (Tam Ky city) beaches, Quang Nam province
No full textRip current is a relatively strong, narrow current flowing outward from the beach through the surf zone and presenting a hazard to swimmers. This paper presents some occurrence features of Rip current at main swimming beaches in Quang Nam province, Central Vietnam. Study results show that most of swimming beaches along Quang Nam province coast are directly opposed to open sea and strongly affected by swell. Therefore, Rip current system can occur at any time in the year with large dimension and intensity. During Northeast monsoon (November to March) beach morphology is considerably changed by strong wave action, thus the strongest rip current is formed. However, in this period careful swimmers can easily identify where that rip current occurs along the beach. During the transition period from Northeast monsoon to Southwest monsoon (April to May) wave energy is reduced, thus Rip current intensity is also decreased. During Southwest monsoon (June to August) wave energy is not strong and beach is accreted, therefore some Rip currents remain at reasonable morphology places along the beach. During the transition period from Southwest monsoon to Northeast monsoon (September to October) Rip current can occur at deep places along the beach with characteristics of narrow dimension, thus causing more danger to swimmer. Especially, dangerous rip current is caused by swell which comes from active region of tropical cyclone in open sea. In this period wave field in the nearshore region is not rough, thus most of swimmers are not cautious when swimming at dangerous rip current places
Some methods to stain cartilage and bone of vertebrates and application on small fish in museum of oceanography
Get PDFIn a natural scientific museum as Museum of Oceanography, a specimen should be not only awesome but also scientific in order to attract visitors and introduce knowledge to them. One of the methods satisfying those requirements is “Method of staining cartilages and bones for small vertebrates”. This method was applied to handle small fish: Anchovies (Encrasicholina devisi (Whitley, 1940)), amphiprions (Amphiprion ocellaris (Cuvier 1830)) and ponyfish (Leiognathus sp.), which is highly efficient, not only used in studying fish bones and cartilages but also attractive to visitors. This paper also gives details on experiences during handling process of this method
Holographic Wilson Loops in the Confining Backgrounds at Zero Temperature
Get PDFWe study Wilson loops in the exact renormalization group ow at zero tempera- ture via the 5d holographic model that reproduces the behavior of the QCD running coupling. Calculating the time-like rectangular Wilson loop we show that the model includes a conning phase at T = 0 in the IR region