Vietnam Academy of Science and Technology: Journals Online
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SYNTHESIS AND ANTIBACTERIAL ACTIVITY OF COMPOSITE BASED ON CHITOSAN-GRAFTED-(N-BUTYL ACRYLATE) AND SILVER NANOPARTICLES
Get PDFIt has been found for a long time that chitosan (CS) and silver nanoparticles (AgNPs) have outstanding antibacterial activities but there were some drawbacks restricting their wide utilization. In this research, CS modified is combined with AgNPs to expand applications and enhance the antibacterial activities. The colloid of CS and AgNPs (CS/Ag) was synthesized via chemical reduction while grafting copolymerization was carried out with monomer n-butyl acrylate (BA) and initiator tert-butyl hydroperoxide (TBHP) generating composite between CS-g-BA/Ag. The effects of parameters on synthesizing CS-g-BA/Ag composite were studied by determining the grafting percentage (G%) and grafting efficiency (E%)
ĐẶC ĐIỂM PHÂN BỐ TRẦM TÍCH VÀ TRIỂN VỌNG SA KHOÁNG VÙNG BIỂN VEN BỜ BÌNH ĐỊNH
Get PDFThis paper presents characteristics of distribution of sediment types in shallow coastal waters (0–50 m water) in Binh Dinh province. The results show that sediments of the surface layer of the studied area have a rather complicated distribution, reflecting many sedimentation periods, in which the sandy sediment type is predominant. They consist of eight types of sediment and are divided into five major zones of sediment from the shore to the corresponding depths: From shore to 5 m, 6–24 m, 31–33 m, 35–47 m, and from 47 m or more. The paper also outlines the heavy mineral prospects contained in the sediments, including: Ilmenite, rutile, zircon, anatase, monazite, magnetite. Heavy minerals are concentrated mainly in the grain size from 0.125–0.25 mm, among which ilmenite is predominant with content in the heavy range of 65.5–83.43% and is mainly distributed in the type of fine sand deposits at depths from 5 m to 24 m. Based on that, it is possible to delineate five prospective areas within the study area.Bài báo trình bày về đặc điểm phân bố các kiểu trầm tích trong vùng biển ven bờ (0–50 m nước) tỉnh Bình Định. Kết quả nghiên cứu cho thấy trầm tích đáy tầng mặt khu vực nghiên cứu có sự phân bố khá phức tạp thể hiện nhiều thời kỳ lắng đọng trầm tích, trong đó kiểu trầm tích cát là chủ yếu; bao gồm 8 kiểu trầm tích và phân chia được 5 đới phân bố trầm tích chính từ bờ ra theo các độ sâu tương ứng: từ bờ đến 5 m, 6–24 m, 31–33 m, 35–47 m và từ 47 m nước trở ra. Bài báo cũng đã trình bày triển vọng sa khoáng chứa trong trầm tích, bao gồm: Ilmenit, rutil, zircon, anatas, monazit, magnetit. Các khoáng vật nặng tập trung chủ yếu trong cấp hạt 0,125–0,25 mm, trong đó ilmenit chiếm ưu thế với hàm lượng trong phần nặng dao động khoảng 65,5–83,43% và phân bố tập trung chủ yếu trong kiểu trầm tích cát nhỏ ở độ sâu từ 5–24 m nước. Trên cơ sở đó, có thể khoanh định 5 vùng có triển vọng khoáng sản trong phạm vi vùng nghiên cứu
Passive Friction Compensation Using a Nonlinear Disturbance Observer for Flexible Joint Robots with Joint Torque Measurements
Get PDFThe friction and ripple effects from motor and drive cause a major problem for the robot position accuracy, especially for robots with high gear ratio and for high-speed applications. In this paper we introduce a simple, effective, and practical method to compensate for joint friction of flexible joint robots with joint torque sensing, which is based on a nonlinear disturbance observer. This friction observer can increase the performance of the controlled robot system both in terms of the position accuracy and the dynamic behavior. The friction observer needs no friction model and its output corresponds to the low-pass filtered friction torque. Due to the link torque feedback the friction observer can compensate for both friction moment and external moment effects acting on the link. So it can be used not only for position control but also for interaction control, e.g., torque control or impedance control which have low control bandwidth and therefore are sensitive to ripple effects from motor and drive. In addition, its parameter design and parameter optimization are independent of the controller design so that it can be used for friction compensation in conjunction with different controllers designed for flexible joint robots. Furthermore, a passivity analysis is done for this observer-based friction compensation in consideration of Coulomb, viscose and Stribeck friction effects, which is independent of the regulation controller. In combining this friction observer with the state feedback controller \cite{Albu-Schaeffer2}, global asymptotic stability of the controlled system can be shown by using Lyapunov based convergence analysis. Experimental results with robots of the German Aerospace Center (DLR) validate the practical efficiency of the approach
ÁP DỤNG CHỈ SỐ MÔI TRƯỜNG W CỦA QUẦN XÃ TUYẾN TRÙNG SỐNG TỰ DO ĐỂ ĐÁNH GIÁ NHANH CHẤT LƯỢNG MÔI TRƯỜNG TRẦM TÍCH SÔNG SÀI GÒN
Get PDFThe W index of nematode communities was first applied to assess sedimentary environment quality at 12 stations in the Sai Gon river. The nematode samples were collected and examined during the dry and rainy seasons in 2014. The W results indicated considerable disturbance in the downstream stations of the Sai Gon river that is mainly disturbed by harbour activities. The nematode communities in these harbours such as the Bien Dong port, Lotus port and Navioil port areas have been seriously impacted in both seasons. In the rainy season, the sedimentary environment of the Tan Thuan Dong port, Sai Gon New port was disturbed significantly while that was lightly affected in Ben Nghe port, Vietnam International Container Terminals - VICT port and Ben Duoc - Cu Chi stations.Chỉ số môi trường W của quần xã tuyến trùng sống tự do được áp dụng để đánh giá nhanh chất lượng môi trường trầm tích tại 12 trạm trên sông Sài Gòn. Mẫu tuyến trùng được thu và phân tích trong mùa khô và mùa mưa năm 2014. Kết quả về chỉ số W cho thấy, các khu vực cảng phía hạ nguồn của sông đang bị xáo trộn môi trường trầm tích đáng kể. Nền đáy các khu vực cảng Biển Đông, cảng Bông Sen và cảng dầu thực vật bị xáo trộn nghiêm trọng trong suốt các đợt khảo sát. Vào mùa mưa, môi trường trầm tích các vị trí cảng Tân Đông Thuận, cảng Sài Gòn mới bị tác động lớn, trong khi có dấu hiệu xáo trộn nhẹ ở khu vực cảng Bến Nghé, cảng Công ty cổ phần Phát triển cảng hậu cần số 1 - VICT và điểm Bến Dược - Củ Chi
ACCELERATION IN STATE-OF-THE-ART ASR APPLIED TO A VIETNAMESE TRANSCRIPTION SYSTEM
No full textThis paper presents the adoption of state-of-the-art ASR techniques into Vietnamese. To better assess these techniques, speech corpora in the research community are assembled, and expanded, making a unified evaluation material under the name VN-Corpus. On this corpus, three ASR systems are built using the conventional HMM-GMM recipe, SGMM, and DNN respectively. Experimental results crown DNN with the overall WER of 12.1%. In the best case, DNN even cut down to 9.7% error rate
Wetting Control in the Layered Polymer-silver Thin Film via Femtosecond Laser Microstructuring
Get PDFWater wetting of a structured multi-layered thin film consisting of bottom silver and top polymer layers microstructured by femtosecond laser pulses was studied. The periodic trenches were ablatively produced on the top polymer layer of the film using 515-nm, 220-fs pulses of an ytterbium-doped fiber laser at different pulse energies and the repetition rate of 20 kHz. The topography of the structured film was observed by means of a JEOL 7001F scanning electron microscope and its water wetting angles were measured by side-view microscopic imaging. The wetting angle on the microstructured surface was 144°, comparing to 83° at the raw unstructured surface of the film
OPTIMIZATION OF MEDIUM COMPONENTS FOR THE PRODUCTION OF ECTOINE BY A HALOPHILIC BACTERIUM ISOLATED FROM CAN GIO MANGROVE
No full textThe effect of different carbon and nitrogen sources on growth of producer strain was investigated. Sucrose and glucose were found to be suitable carbon sources, and monosodium glutamate was favorable nitrogen source for bacterial cell growth. Optimum salt concentrations for bacterial growth was ranged from 4 to 6%, whereas, NaCl concentrations from 12 to 15% found to be good for ectoine accumulation. Two-step fed-batch fermentation was then designed, biomass and ectoine content were significant increased, maximum CDW of 25 g/l and ectoine content of 10.3% were obtained.
ASSESSMENT OF LONGITUDINAL VARIATION OF TROPHIC LEVELS OF THE RED RIVER WATER, THE SECTION FROM HANOI CITY TO BA LAT ESTUARY
No full textThe Red river system is a typical example of Southeast Asian rivers that is strongly impacted by human and climatic conditions, especially in the recent period. In this paper, we aim to investigate the longitudinal variation of the water quality of the Red river, in the section from Hanoi city to the Ba Lat estuary. The sampling campaigns were conducted in the dry seasons in 2017 and 2018. The monitoring results showed that the average concentrations of nutrients (NO2-, NO3-, NH4+, PO43-) were still lower than the allowed values of the Vietnamese standard limits for surface water quality (QCVN 08:2015/BTNMT, column A1) whereas the average concentrations of Cl- and TSS exceeded the allowed values of the QCVN 08:2015/BTNMT, column A1 4.6 and 2.3 times, respectively. NO3- and dissolved silica (DSi) concentrations showed a significant variation from the Hanoi site to the Ba Lat site (6.62 mg/l to 1.19 mg/l for NO3- and 5.21 mg/l to 2.14 mg/l for DSi) whereas SO42-, NO2- and Cl- increased markedly in this longitudinal section, especially from the point SH6 where the salinity started to increase. Based on the three different methods for classification of trophic levels and on the different variables observed during the dry seasons in 2017–2018, the nutrient concentrations of the Red river water tended to slightly increase from the site Hanoi (SH1) to the site SH5 at Nam Dinh, indicating the increase of nutrient external input along the river whereas it tended to decrease from the site SH6 (at mesotrophic/eutrophic level) to the last observed site SH9 (at oligotrophic/mesotrophic level) at the sea due to the dilution of seawater. Seawater in dry season could affect directly the river downstream about 35 km far from the sea. The results may be a guide for planning of water use including agricultural irrigation in the Red river estuary
Selection of suitable fragment from rbcL gene for DNA barcode analysis of family Halymeniaceae, Rhodophyta
Get PDFAmong the members of Halymeniaceae family, Grateloupia sensu lato occupies the largest composition in species. Classification based on morphological traits is difficult due to the highly variable terete to blade-like thalli among the members of this genus that usually leads to misidentification. Molecular systematics has been applied to classify Grateloupia sensu lato so that the taxonomists acquire a better understanding of the species diversity in general. The plastid gene encoding the large subunit of ribulose-1,5-bisphosphate-carboxylase-oxygenase (rbcL) was the focus of numerous marine algal studies concerning phylogeny and molecular evolution. However, using the full length of rbcL showed disadvantages such as cost and time consuming due to two times of sequencing and two times of PCR. In the present study, the shorter sequence, fragment 773 bp at 5’ end and fragment 579 bp at 3’ end of rbcL were applied and compared for the phylogenetic analysis of Halymeniaceae members. The results indicated there are no differences of topological phylogenetic trees, species resolution within genus and genus resolution within the family between fragment 773 bp at 5’ and the full length of rbcL. Therefore, we conclude that fragment 773 bp at 5’ should be used as DNA barcodes for the Halymeniaceae to reduce the cost and time during phylogenetic analysis. Two taxa Grateloupia newly collected in Vietnam were grouped to the known Phyllymenia, a new genus in Vietnam
The capability of organic matter decomposition and nutrient uptake in coastal waters of Ca Na bay, Ninh Thuan province
Get PDFThis paper focuses on the capability of organic matter decomposition and inorganic nutrient uptake in the coastal waters of Ca Na bay (Ninh Thuan province) in October, 2018 (the rainy season) and May, 2019 (the dry season). The results of laboratory experiments on organic decomposition, photosynthesis and nutrient uptake showed that the BODgh and the average values of k- decay rate in coastal waters of the surveyed area are higher in the rainy season compared with the dry season, with the average BODgh values of 5.474 mgO2/l and 4.768 mgO2/l respectively, and the corresponding k-values of 0.183 day-1 and 0.143 day-1. Howver, the half-life decay of organic matter is lower in the rainy season than in the dry season, with the corresponding values of 5.110 days and 5.571 days. In the studied area, the photosynthesis of phytoplankton strongly absorbs nitrate (NO3-), followed by ammonium (NH4+) and phosphate (PO43-). The capability of nutrient uptake for nitrogen and phosphorus components was 9.17 mgN/m3/hour and 0.92 mgP/m3/hour, respectively in the dry season; and 7.31 mgN/m3/hour and 0.63 mgP/m3/hour in the rainy season. The results of the study are favorable condition for calculating the environmental capacity in the coastal waters of Ca Na bay in the future