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Creep deformation characteristics of microalloyed HP40Nb steel at 950℃
Van Hung Dao,송정수,김주용,윤기봉 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10
In the present work, several specimens were obtained from microalloyed HP40Nb reformer tubes with the different serviced period. The creep tests were conducted at a temperature of 950 °C and under stress levels in the range 25-55 MPa. Results indicated that the degradation of the creep life was due to the increase of the serviced period. The microstructural degradation and creep voids were observed at the grain boundary regions, attributed to the main reason leading to the premature creep failure. The creep exponent started decreasing after the servicing and approached a constant value after 7.2 years. The creep coefficient was obtained to be a function of time when the creep exponent was constant. Norton’s creep power law equation was used to derive an equation describing the relationship between the diametrical expansion and serviced period of the reformer tubes. Larson-Miller curves were obtained from creep test data. Amount of carbides from the different serviced period was also calculated.
Nguyen Van Hung,Bui Thi Minh Nguyet,Nguyen Huu Nghi,Nguyen Minh Luon,Nguyen Ngoc Bich,Le Van Thanh Son,Nguyen Trung Kien,Dao Ngoc Nhiem,Nguyen Thanh Tuoi,Dinh Quang Khieu 대한환경공학회 2024 Environmental Engineering Research Vol.29 No.4
In the present work, ZnO/g-C₃N₄/biochar was prepared, and it was used for visible-light driven photocatalytic degradation of some colorants (methylene blue, rhodamine B, methyl orange) and some antibiotics (doxycycline, ciprofloxacin, amoxicilline). Biochar was prepared by pyrolysing Phragmites australis biomass. The ZnO/g-C₃N₄/biochar composite was synthesized with the alkaline hydrolysis method. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transition electron microscopy, energy dispersive X-ray/elemental mapping, ultraviolet-visible-diffuse reflectance spectroscopy, photoluminescence spectroscopy, nitrogen adsorption/desorption isotherms and X-ray photoelectron spectroscopy. The results show that ZnO nanoparticles with a large surface area are highly dispersed on the g-C₃N₄ particle surface and biochar. The composite exhibits superior photocatalytic degradation ability toward doxycycline, a broad-spectrum antibiotic of the tetracycline compared with individual components (ZnO or g-C₃N₄) and satisfies stability after six treatment cycles. The kinetics and degradation mechanisms of doxycyline were also addressed. In addition, the present catalyst also exhibits the photocatalytic degradation of methylene blue, rhodamine B, methyl orange, ciprofloxacin and amoxicillin in visible-light regions.
Anti-inflammatory compounds from Ampelopsis cantoniensis.
Van Thu, Nguyen,Cuong, To Dao,Hung, Tran Manh,Van Luong, Hoang,Woo, Mi Hee,Choi, Jae Su,Lee, Jeong-Hyung,Kim, Jeong Ah,Min, Byung Sun Natural Product Communications 2015 Natural product communications Vol.10 No.3
<P>Many natural products have been shown to have an inhibitory effect on nitric oxide (NO), and are used as chemotherapy agents for inflammation disease. The current study was designed to evaluate the anti-inflammatory activity of chemical components from the leaves of Ampelopsis cantoniensis. Sixteen compounds (1-16) were isolated and identified. Phloretin (5) and 5,7,3',5'-tetrahydroxyflavanone (16) inhibited nitric oxide (NO) production with IC50 values of 5.2, and 18.5 μM, respectively. The inhibitory effect of compounds 5 and 16 were accompanied by dose-dependent decreases in LPS-induced nitric oxide synthase (iNOS) in RAW 264.7 cells, respectively. This study investigated the significant anti-inflammatory properties of isolated compounds from the leaves of A. cantoniensis for the first time. The findings demonstrate that A. cantoniensis could be used beneficially in the treatment of inflammation disease.</P>
Dao Hang Thi,Beattie George Andrew Charles,Watson Gillian W.,Mottern Jason,Evans Greg,Van Nguyen Liem,Nguyen Hoa Thi,Nguyen Viet Duc,Holford Paul 한국응용곤충학회 2020 Journal of Asia-Pacific Entomology Vol.23 No.2
The false coconut scale, Aspidiotus rigidus Reyne (Hemiptera: Diaspididae), is a serious pest of coconut in the Indonesian and Philippine archipelagos. Field surveys in Viêt Nam in 2015–2018 discovered A. rigidus (a new country record). Also found were three of its primary hymenopteran parasitoids: an unidentified ectoparasitic Aphytis species (Aphelinidae) and two endoparasitoids, Comperiella calauanica (Encyrtidae) and Pteroptrix parvipennis (Aphelinidae). Aphytis sp. was the commonest parasitoid; the average level of parasitism of A. rigidus found in six surveys was 46%, in immatures of both sexes and adult females. Comperiella calauanica was recorded in three surveys, with an average parasitism level of 54% in adult female A. rigidus. It was also found attacking Aspidiotus destructor Signoret. Pteroptrix parvipennis was recorded in 47% of second instar A. rigidus in one survey. In molecular phylogenies based on 28S and COI genes, Pteroptrix parvipennis grouped with species of Encarsia. Although A. rigidus occurs in the largest coconut-growing areas in Việt Nam, incidence of the scale is low, and no outbreaks have been recorded. Its parasitoids therefore have potential for use as biological control agents in areas where the scale is problematic. The low incidence of A. rigidus in Việt Nam and the presence of the three parasitoid species there suggests that the scale and these parasitoids originated in Indochina.
Van Noi Nguyen,Thi Dieu Cam Nguyen,Thanh Phuong Dao,Hung Thuan Tran,Dinh Bang Nguyen,안대희 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.2
Organoclays were synthesized by exchanging inorganic cations between layers in Thanh Hoa bentonite using organic cations including benzylhexadecyldimethylammonium (BHDDM+), dimethyldioctadecylammonium (DMDOD+) and benzylstearyldimethylammonium (BSDM+). Inserting organic cations increases material interlayer distance significantly (from 15 A˚ to 40 A˚ ) and simultaneously enhances affinity of materials toward organic pollutants. The results show that adsorption capacity of organics on organoclays strongly depends on affinity between organic substances and ammonium cations rather than on interlayer distance of organoclays. This means that the sorption of organoclays for organic contaminants was significantly influenced by the nature of the surfactants added to the clay.
Hang T. Dao,George A.C. Beattie,Gillian W. Watson,Van Lam Pham,Van Liem Nguyen,Duc Khanh Le,Thi Hoa Nguyen,Viet Nguyen,Paul Holford 한국응용곤충학회 2018 Journal of Asia-Pacific Entomology Vol.21 No.1
Armoured scales (Hemiptera: Diaspididae) belong to the largest scale insect family and are among the mostinvasive insects in the world. Accurate identification of armoured scales is essential for systematic and phylogeneticstudies; biogeography; trade and plant quarantine; and pest management, particularly biological control. Several species are serious pests of citrus. Records of past field surveys conducted in Viet Nam between 1967 and2010 indicated the presence of 28 species on citrus there. Discrepancies in these records, and the retention ofspecimens of only five species in collections, led us to undertake surveys throughout the citrus-growing regionsof the country in 2013 and 2014 to verify previous records and conserve voucher specimens. The presence of 21diaspidid species was confirmed based on morphological and molecular data. The species observed werecommon but rarely abundant. Populations in commercial orchards may have been influenced by use of pesticides,but most species were recorded also in gardens and orchards where pesticide use was uncommon. Naturalenemies were abundant, but were not thoroughly documented for all the diaspidids we observed. An identificationkey to the species collected is provided. Differences between our findings and previous records from VietNam, from Yunnan and Guangxi in China, and from Indochinese countries neighbouring Viet Nam, indicate theneed for extensive surveys to fully document the diaspidid fauna on citrus in the region.
Dao, Anh Tuan,Phan, Thi Kieu Loan,Nguyen, Van Hieu,Le, Vu Tuan Hung Institute of Korean Electrical and Electronics Eng 2013 전기전자학회논문지 Vol.17 No.2
Using a ceramic target ZnO:In with In doping concentration of 2%, hetero-junctions of n-ZnO:In/p-Si and p-ZnO:(In, N)/n-Si were fabricated by depositing Indium doped n - type ZnO (ZnO:In or IZO) and Indium-nitrogen co-doped p - type ZnO (ZnO:(In, N)) films on wafers of p-Si (100) and n-Si (100) by DC magnetron sputtering, respectively. These films with the best electrical and optical properties were then obtained. The micro-structural, optical and electrical properties of the n-type and p-type semiconductor thinfilms were characterized by X-ray diffraction (XRD), RBS, UV-vis; four-point probe resistance and room-temperature Hall effect measurements, respectively. Typical rectifying behaviors of p-n junction were observed by the current-voltage (I-V) measurement. It shows fairly good rectifying behavior with the fact that the ideality factor and the saturation current of diode are n=11.5, Is=1.5108.10-7 (A) for n-ZnO:In/p-Si hetero-jucntion; n=10.14, Is=3.2689.10-5 (A) for p-ZnO:(In, N)/n-Si, respectively. These results demonstrated the formation of a diode between n-type thin film and p-Si, as well as between p-type thin film and n-Si..