Vietnam Academy of Science and Technology: Journals Online
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ASSESSING CONSUMER BEHAVIOR TOWARDS FISH SAUCE PRODUCTS BY USING FOOD CHOICE QUESTIONNAIRE
Get PDFThis study aims to assess Vietnamese consumer behavior towards fish sauce product. It consists of two experiments. In the first experiment, consumer concept was explored using word association method. It was performed on 300 Vietnamese consumers with the prompt word as “fish sauce”. The data were analyzed by a triangulation method. The results evoke six factors associated with fish sauce as Sensory Appeal, Health, Price, Convenience, Traditional Value, Quality and Safety. These findings were the starting point for a modification of food choice questionnaire (FCQ) adapted to fish sauce product. In the second experiment, the modified FCQ with 18 items was used to assess the consumer behavior. The survey was performed on 300 Vietnamese consumers. The data were analyzed by using Exploratory Factor Analysis and Confirmatory Factor Analysis. The obtained model with five factors was adapted to fish sauce for Vietnamese consumers ( = 1.67, GFI = 0.93, CFI = 0.92, RSME = 0.47). In this, Sensory Appeal is the most important factor which might affect consumer food choice motivations. We expect that these results will be useful for the local manufacturers who want to develop traditional food products and/or enlarge national market
Characteristics on distribution of chemical composition in groundwater along the Mekong and Bassac (Hậu) river, Vietnam
No full textAlong the Mekong River (MR), arsenic contamination in the groundwater has been recognized since the 2000s. Due to arsenic contamination in shallow aquifers, the drinking water has been prevented from being contaminated with arsenic by installing wells, 200 m to 400 m deep. However, it has been known that groundwater was contaminated by not only arsenic but also other trace elements. The need to reveal characteristics on the distribution of chemical composition by horizontally and vertically is increasing for purposes of appropriate development and management of groundwater. This study summarized the results of surveys for arsenic since 2008 and surveys for dissolved ions and trace elements since 2015, and described characteristics on distribution for chemical composition at the regional areas along the MR and Bassac (Hậu) River (BR). Groundwater samples were collected from existing wells in 8 provinces and 1 city. The authors used Piper and Stiff diagram that reflect the chemical composition of groundwater to respond to varying horizontal and vertical distributions. The Principal Component Analysis (PCA) was also carried out to reveal the correspondences of dissolved ions and trace elements. Variety concentrations and distributions of ions and trace elements show the obvious distinction between upper (200 m deep) and lower (200 m deep) aquifers broadly divided by geologic age. A wide variety of ion compositions and trace elements was found in the upper aquifer, and concentration of some trace elements in groundwater was high and exceed the World Health Organization (WHO) drinking water guideline value. On the other hand, groundwater in the lower aquifer is simple and rarely contaminated by trace elements. However, the arsenic concentration ranging from 0.01–0.065 mg/L slightly exceeding the WHO guideline value was found at the lower aquifer in the downstream areas of the Mekong River Delta. These results on the distribution analysis provide the insight that deep groundwater is not necessarily safe by over-pumping from deep aquifer and drilling new wells in the downstream areas
A new record of congrid eel, Bathycongrus bleekeri (Congridae) from Vietnam
Get PDFThree specimens of Bathycongrus bleekeri were collected during the survey in 2015 and 2017. The newly recorded species is described herein, a small, moderately elongate species of Bathycongrus with head and body compressed; vertical fins without black mark; tail slender, attenuated, but not filiform; trunk length 1.2 times greater than head length; teeth small, conical, in about three-four rows on jaws, in a small triangular patch on vomer; 28–29 preanal vertebrae, total of 111–113 vertebrae; 26–28 preanal lateral-line pores. Additional data on the morphology and distribution of the species increases the total number of known species in the family Congridae in Vietnamese waters to twelve
Exotic States Emerged By Spin-Orbit Coupling, Lattice Modulation and Magnetic Field in Lieb Nano-ribbons
Get PDFThe Lieb nano-ribons with the spin-orbit coupling, the lattice modulation and the magnetic field are exactly studied. They are constructed from the Lieb lattice with two open boundaries in a direction. The interplay between the spin-orbit coupling, the lattice modulation and the magnetic field emerges various exotic ground states. With certain conditions of the spin-orbit coupling, the lattice modulation, the magnetic field and filling the ground state becomes half metallic or half topological. In the half metallic ground state, one spin component is metallic, while the other spin component is insulating. In the half topological ground state, one spin component is topological, while the other spin component is topological trivial. The model exhibits very rich phase diagram
Taylor expansion for matrix functions of vector variable using the Kronecker product
No full textTaylor expansion is one of the many mathematical tools that is applied in Mechanics and Engineering. In this paper, using the partial derivative of a matrix with respect to a vector and the Kronecker product, the formulae of Taylor series of vector variable for scalar functions, vector functions and matrix functions are built and demonstrated. An example regarding the linearization of the differential equations of an elastic manipulator is presented using Taylor expansion
VOLATILE COMPOSITION, ANTIOXIDANT PROPERTY AND ANTIMICROBIAL ACTIVITIES AGAINST FOOD-BORNE BACTERIA OF VIETNAMESE THYME (Thymus vulgaris L.) ESSENTIAL OIL
Get PDFThe essential oil (EO) obtained from the leaves of the thyme (Thymus vulgaris L.) grown in Vietnam was found to contain thymol (39.79%), cymene (17.33%), and γ-terpinene (13.45%) as the main volatile components. The antimicrobial activities of this oil were screened against several food-borne bacteria and fungi species. Significant growth inhibition effects against food-borne bacteria Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Salmonella Typhimurium were observed using the standard disc diffusion method. Thyme EO showed the antibacterial effect against all the test pathogenic strains with the inhibition zones were 23.3 ± 0.4 mm, 24.7 ± 0.4 mm, 29.0 ± 0.7 mm, 32 ± 0.7 mm in diameter against B. subtilis, E. coli, S. Typhimurium and S. aureus, respectively. The minimum inhibitory concentration (MIC) determined by micro-dilution method in MHB liquid medium was 1.56 µl/ml. The bactericidal concentrations (MBC) was 3.13 µl/ml for three isolates from B. subtilis, E. coli, and S. aureus, while the MBC tested for S. typhi was 1.56 µl/ml. The antifungal properties of the thyme EO were also determined in this study against three important pathogenic fungi such as Candida albicans, Rhizoctonia solani and Fusarium oxysporum with the inhibition zones ranging approximately from 23.20 ± 0.06 to 44.10 ± 0.03 mm. On the other hands, the results also showed the antioxidant activity of Vietnamese thyme EO and suggested that thyme EO can be applied in food industries as natural flavoring preservatives/additives to control food spoilage and food born bacteria and fungi
TEMPERATURE-DEPENDENT PHOTOLUMINESCENCE STUDY OF POROUS GAP
Get PDFThis paper reports on the temperature-dependent photoluminescence of porous GaP under the 532-nm excitation. Porous GaP formed by electrochemical anodization of (111)-oriented bulk material exhibits green emission at 550 nm (2.25 eV) and red emission at 770 nm (1.65 eV) at room temperature. In the temperature range from 25 K to 275 K intensity from the green emission gradually decreases when the temperature increases. Additionally, peak position of the green luminescence band shifts to lower energy with increasing temperature and the same the GaP band gap narrowing with temperature. This means a contribution of lattice vibrations
The Microstructural Revolution of Ti-6Al-4V Specimens Fabricated by Selective Laser Sintering of Pre-alloyed Powders
Get PDFSelective laser sintering (SLS) is known as a cutting-edge technique to manufacture complex geometry products. Among various kinds of materials, Ti-6Al-4V is one of the most popular materials for the SLS process. The as-built Ti-6Al-4V products were widely applied in many applications such as aerospace, automobile, and especially in medical and implant parts. The purpose of this research is to investigate the microstructure and other properties of Ti6Al4V pre-alloyed powders produced by selective laser sintering technique. Through this research, the direct fabrication of Ti6Al4V metal object by SLS machine has been carried out using MetalSys250 machine. Different parameters of the SLS process were used to produce 1cm x1cmx1cm cubic samples and then microstructure, as well as mechanical properties of the as-built samples were investigated. Powder particles are fully dense, possess a spherical shape and are composed of acicular α phase. The as-build sample shows the oriented acicular martensitic phase with the defined columnar grain structures
DISTORTION-BASED HEURISTIC METHOD FOR SENSITIVE ASSOCIATION RULE HIDING
Get PDFIn the past few years, privacy issues in data mining have received considerable attention in the data mining literature. However, the problem of data security cannot simply be solved by restricting data collection or against unauthorized access, it should be dealt with by providing solutions that not only protect sensitive information, but also not affect to the accuracy of the results in data mining and not violate the sensitive knowledge related with individual privacy or competitive advantage in businesses. Sensitive association rule hiding is an important issue in privacy preserving data mining. The aim of association rule hiding is to minimize the side effects on the sanitized database, which means to reduce the number of missing non-sensitive rules and the number of generated ghost rules. Current methods for hiding sensitive rules cause side effects and data loss. In this paper, we introduce a new distortion-based method to hide sensitive rules. This method proposes the determination of critical transactions based on the number of non-sensitive maximal frequent itemsets that contain at least one item to the consequent of the sensitive rule, they can be directly affected by the modified transactions. Using this set, the number of non-sensitive itemsets that need to be considered is reduced dramatically. We compute the smallest number of transactions for modification in advance to minimize the damage to the database. Comparative experimental results on real datasets showed that the proposed method can achieve better results than other methods with fewer side effects and data loss