Vietnam Academy of Science and Technology: Journals Online
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Structural parameter identification of a bolted connection embedded with a piezoelectric interface
Get PDFAs the impedance-based technique has been commonly accepted as an innovative structural health monitoring tool, structural identification of a piezoelectric-driven system is of significant interest for damage identification and quantification. This study presents a predictive modelling strategy, which combines the finite element (FE) method with a model-updating approach, for estimating the structural parameters of a piezoelectric interface-bolted connection system. Firstly, the basic operating principle of the piezoelectric-based smart interface is introduced. Secondly, a bolted connection is selected as a host structure to conduct real impedance measurement via the smart interface. Thirdly, a numerical FE model corresponding to the experimental model is established by using a FE program, COMSOL Multiphysics. A sensitivity-based model updating algorithm is adopted to fine-tune the FE model. Finally, structural parameters of the FE model are determined as the numerical impedance signatures match with the measured ones at the same high-frequency band with identical patterns. This study is expected to open an alternative approach for determining unknown structural parameters of the piezoelectric interface-bolted joint system in practice
Experimental and numerical investigations of full-field strain measurement and fracture parameter of lead-free solder using DIC technique
No full textIn this study, rupture of notched SENT specimens fabricated from a novel lead-free solder alloy is investigated. The lead-free solder alloy, focused on in this study, is particularly used as interconnect material in power modules of electric vehicles. Its commercial denomination is InnoLot and it can be used in harsh environments thanks to its improved reliability. Up to now, studies on their resistance to rupture remain relatively limited. Yet the comprehension of fracture behavior is essential for the correct design of the electronic packages which must be robust against fatigue and vibrations loads. The tests are performed with the help of a micro-tensile testing machine equipped with an optical system for full-field measurements with Digital Image Correlation. The images are taken at successive steps of deformation and the displacement field is measured in a region of interest which is the singularity dominated zone surrounding the plastic zone at the crack tip. The procedure consists then in comparing the measured field with the theoretical field given by the Williams' solution. The stress intensity factor is calculated by fitting the analytical fields to the experimental data. The effects of the size and shape of the zone of data collection, as well as that of the number of terms considered in the Williams's expansion series, are examined in the study. A method is also proposed for the automatic crack tip detection. From these finding, it is easy to predict the crack propagation and failure mechanism of solder joint. In addition, the theoretical solution of displacement, given by the Williams series, is compared with measurements to identify the coefficients of these series, including the stress intensity factor. Finally, a 5-order truncation of the Williams series seems sufficient to obtain a correct estimate of the stress intensity factor
SOUND TRANSMISSION LOSS ACROSS A FINITE CLAMPED DOUBLE-LAMINATED COMPOSITE PLATE WITH POROELASTIC MATERIAL
Get PDFA theoretical study of sound transmission loss across a clamped double-laminated composite plate filled with poroelastic material is formulated. Biot’s theory is employed to describe wave propagation in elastic porous media. The two face composite plates are modeled as classical thin plates. By using the modal superposition theory, a double series solution for the sound transmission loss of the structure is obtained with the help of the Galerkin method. The analytical model is validated against previous experimental results of a single sound wave under normal incidence. The numerical results suggest that the density of poroelastic material, the type of composite materials and the composite plies arrangement have significant effects on the sound transmission loss of considered structure
ĐẶC TRƯNG NGUỒN LỢI CÁ TRONG CÁC HỆ SINH THÁI Ở KHU DỰ TRỮ SINH QUYỂN THẾ GIỚI CÙ LAO CHÀM - HỘI AN
Get PDFAssessments of fish fauna in the World Biosphere Reserve of Cu Lao Cham - Hoi An were based on analyses of data of visual censuses and samples collected at 5 sites of nipa palm, 9 sites of seagrass beds and 15 sites of coral reefs in June 2016, 200 samples from 25 fishing gears in wet and dry seasons (November 2015 and June 2016), and species composition gathered from previous (1994, 2004 and 2008) and recent studies (2017). A total of 356 species of 186 genera and 81 families of fishes were found in the waters of the Biosphere, in which some families were the most common including wrasses (Labridae: 42 species), damselfishes (Pomacentridae: 35), butterflyfishes (Chaetodontidae: 24), jack and travellies (Carangidae: 17), groupers (Serranidae: 14), surgeonfishes (Acanthuridae) and gobies (Gobiidae) with 11 species for each family, snappers (Lutjanidae: 10). The number of species in Cu Lao Cham waters (253 species) was 2.8 times higher than that in the Thu Bon estuary (91 species) and 4.2 times higher than that in transitional waters between the Thu Bon estuary and Cu Lao Cham (60 species). The coral reefs contributed 249 species and this was 8.6 times higher than that in the nipa palm (29 species), 6.5 times higher than in the seagrass beds (38 species) and 3.5 times higher than in the soft bottoms (71 species), however there were no significant differences between the nipa palm and the seagrass beds in the Thu Bon estuary. Among them, there were 10 valuable species of fishes found both in the Thu Bon estuary and Cu Lao Cham islands, and this indicates a high potential connectivity of these species among marine habitats in the two locations mentioned above.Đánh giá khu hệ cá trong vùng nước KSQ Cù Lao Chàm-Hội An được thực hiện thông qua việc phân tích nguồn số liệu khảo sát trực tiếp và thu mẫu tại 5 trạm rừng dừa nước, 9 trạm thảm cỏ biển và 15 trạm rạn san hô vào tháng 6/2016, phân tích 80 mẫu nguồn lợi thu thập từ 25 loại nghề khai thác vào 2 đợt mùa mưa (tháng 11/2015) và mùa khô (tháng 6/2016) và tư liệu thành phần loài tập hợp từ những đợt khảo sát vào năm 1994, 2004, 2008 và 2017. Kết quả nghiên cứu đã ghi nhận được 356 loài thuộc 186 giống và 81 họ cá với các họ phổ biến gồm họ cá Bàng chài (42 loài), họ cá Thia (35 loài), họ cá Bướm (24 loài), họ cá Khế (17 loài), họ cá Mú (14 loài), họ cá Đuôi gai và họ cá Bống trắng mỗi họ có 11 loài, họ cá Hồng (10 loài). Khu vực Cù Lao Chàm có mức độ đa dạng loài (253 loài) cao gấp 2,8 lần so với vùng hạ lưu sông Thu Bồn (91 loài) và 4,2 lần so với vùng chuyển tiếp (60 loài), trong khi đó rạn san hô có số loài (249 loài) cao gấp 8,6 lần so với rừng dừa nước (29 loài), gấp 6,5 lần so với thảm cỏ biển (38 loài) và gấp 3,5 lần so với vùng đáy mềm (71 loài), tuy nhiên không có sự khác biệt giữa thảm cỏ biển và rừng ngập trong khu vực cửa sông Thu Bồn. Trong số đó, có 10 loài có giá trị phân bố ở cả khu vực hạ lưu sông Thu Bồn và Cù Lao Chàm và điều này cho thấy có thể có sự liên kết về mặt nguồn lợi giữa các hệ sinh thái trong 2 khu vực nói trên
Research on wave regimes at the Cua Dai estuary, Quang Nam
Get PDFIn coastal area of the Cua Dai estuary - Quang Nam province, the processes of erosion-accretion strongly occur. Over this area, the ocean wave is a dynamical factor that directly affects the coastal areas causing erosion-accretion processes. This paper presents an evaluation of the ocean wave regime impacting the areas of Cua Dai estuary by using the model of MIKE21SW. The purpose of this study is to fully interprete the role of dynamical factor, ocean wave in erosion-accretion processes. The results showed a convergence of ocean waves at the estuary of Cua Dai although it is obstructed by the Cu Lao Cham island in front of the Cua Dai estuary. The northeast and north-northeast waves are mainly prevailing with the frequency of more than 60% in the year
Numerical model for simulation of waves in surfzone and nearshore areas based on Boussinesq equations: results for plane beaches
Get PDFA numerical model based on the 2D Boussinesq equations has been developed using the Finite Volume Method. The model was verified against experimental data for the case of wave breaking on a sloping beach. Simulated results by the model showed that the model has good capability of simulation of waves in the nearshore area. Numerical simulation was also carried out for the problem of waves on a plane beach with a breakwater and submerged dunes. Simulated results were compared with those computed by MIKE 21. The comparison showed that good agreements were obtained and confirmed the applicability of the Boussinesq model to the simulation of physical phenomena of waves in the nearshore areas, especially, suitable for the simulation of wave-induced current including rip currents
THE INTERACTION BETWEEN [Pt(µ-Cl)(Safrole-1H)]2 AND 1,3-DIISOPROPYLBENZIMIDAZOLIUM BROMIDE IN THE PRESENCE OF Ag2O
No full textThe interaction of the dimeric complex [Pt(µ-Cl)(Saf)]2 (1) (Saf: deprotonated safrole) with the salt iPr2-bimy·HBr in the presence of Ag2O in acetone solvent was studied. The obtained products were mixed complexes of [PtCl(Saf)(iPr2-bimy)] (2) and [PtBr(Saf)(iPr2-bimy)] (3) with different molar ratio (PI, PII, PIII) depended on the used molar ratio of 1:salt:Ag2O. In the case of this ratio being 1:2:1.1, the mixture PI with 75% for the complex 2 was obtained. When concentration of the salt was increased, the product was PII with the molar ratio of 2 : 3 of 1 : 3. However, when both the salt and Ag2O were increased at the same time, 2 and 3 in PIII had equal molar proportions. The two main factors affecting the 2 : 3 molar ratio are the different solubility of AgCl and AgBr and the different coordinating ability of Cl- and Br- ligands. The structure of 2 and 3 was determined by 1H NMR spectra and single crystal X-ray diffraction. The results reveal that Saf in 2 and 3 coordinates with Pt(II) via C=Colefinic and C5 of benzene ring. Meanwhile, iPr2-bimy coordinates with Pt(II) through CNCN and is in trans-position compared with the C=Colefinic bond
Process of extraction and isolation of canthaxanthin from saline bacteria biomass Paracoccus carotinifaciens VTP20181 isolated in Vietnam
No full textCanthaxanthin is a natural carotenoid, which can be biosynthesized from several different bacterial strains and exhibits a wide range of biological benefits such as antioxidant, immune booster, and vascular stabilization. Canthaxanthin is widely used in the food and pharmaceutical industries as a natural colourant, and its production from natural sources has been the topic of growing interest. In this study, we established the process of extracting, enriching and isolating canthaxanthin from the post-fermentation biomass of the saline bacteria Paracoccus carotinifaciens VTP20181 isolated in Vietnam at laboratory scale. This process consists of 5 steps: Dry biomass generation, dry biomass extraction, removal of saturated fat, fast column chromatography and slow column chromatography, canthaxanthin purification. Canthaxanthin compound is obtained with 98% purity. Canthaxanthin extraction and purification efficiency of the whole process reached 55.5%