Vietnam Academy of Science and Technology: Journals Online
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Theoretical model of guided waves in a bone-mimicking plate coupled with soft-tissue layers
No full textQuantitative ultrasound has shown a significant promise in the assessment of bone characteristics in the recent reports. However, our understanding of wave interaction with bone tissues is still far from complete since the propagation of ultrasonic waves in bones is a very challenging topic due to their multilayer nature. The aim of the current study is to develop a theoretical model for guided waves in a bone-mimicking plate coupled with two soft-tissue layers. Here, the bone plate is modeled as an isotropic solid layer while the soft tissues are modeled as fluid layers. Based on the boundary conditions set for the three-layered structure, a characteristic equation is obtained which results in dispersion curves of the phase and group velocities. New expressions for free guided waves propagating in the trilayered plate are introduced. The amplitudes of wave modes generated by time-harmonic loads applied in the plate are theoretically computed by reciprocity consideration. As an example of calculation, the normalized amplitudes of the lowest wave modes are presented. The obtained results and equations discussed in this study could be, in general, useful for further applications in the area of bone quantitative ultrasound
The effect of the chilled water temperature on the performance of an experimental air-cooled chiller
No full textThis paper presents the study results on the effect of the chilled water temperature on the coefficient of performance (COP) of an experimental air-cooled chiller. The measuring sensors and instrument were calibrated, and the uncertainty of the measuring temperature and pressure were evaluated. The uncertainty of measured temperature and pressure at 95% confidence level is 0.12 °C and 1.4 kPa, respectively. The isentropic compression efficiency and the COP of the air-cooled chiller operating at a condensation temperature of 48.05 °C and evaporation temperature of 3.17 °C are 63% and 2.69, respectively. The chilled water temperature has a significant influence on evaporation pressure and the COP of the chiller. If the temperature of the air entering the condenser of the chiller is maintained at 35 °C, the COP of the chiller increases from 2.55 to 2.89 when the temperature of the chiller water increases only 4 K, from 8 °C to 12 °C
ENHANCEMENT OF SPECIFIC ABSORPTION RATE IN Co0.7Zn0.3Fe2O4 and Co0.5Zn0.5Fe2O4 COMPOSITE NANOPARTICLES
No full textWe report the advantage of the exchange coupling between a magnetically soft (MnFe2O4) and magnetically hard (Co0.7Zn0.3Fe2O4 and Co0.5Zn0.5Fe2O4) magnetic phase to increase the specific absorption rate (SAR) in magnetic inductive heating. All samples were synthesized by hydrothermal method. While the saturation magnetization (Ms) of two composite nanoparticles is approximately 1.1 times higher the Ms of single-component, the SAR is more 2 times than those values of single-component
Estimation of shear strength parameters of soil using Optimized Inference Intelligence System
No full textIn recent years, machine learning techniques have been developed and used to build intelligent information systems for solving problems in various fields. In this study, we have used Optimized Inference Intelligence System namely ANFIS-PSO which is a combination of Adaptive Neural-Fuzzy Inference System (ANFIS) and Particle Swarm Optimization (PSO) for the estimation of shear strength parameters of the soils (Cohesion “C” and angle of internal friction “φ”). These parameters are required for designing the foundation of civil engineering structures. Normally, shear parameters of soil are determined either in the field or in the laboratory which require time, expertise and equipments. Therefore, in this study, we have applied a hybrid model ANFIS-PSO for quick and cost-effective estimation of shear parameters of soil based on the other six physical parameters namely clay content, natural water content, specific gravity, void ratio, liquid limit and plastic limit. In the model study, we have used data of 1252 soft soil samples collected from the different highway project sites of Vietnam. The data was randomly divided into 70:30 ratios for the model training and testing, respectively. Standard statistical measures: Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Correlation Coefficient (R) were used for the performance evaluation of the model. Results of the model study indicated that performance of the ANFIS-PSO model is very good in predicting shear parameters of the soil: cohesion (RMSE = 0.075, MAE = 0.041, and R = 0.831) and angle of internal friction (RMSE = 0.08, MAE = 0.058, and R = 0.952)
THE PREPARATION OF ENZYME-RESISTANT PYRODEXTRIN FROM RICE STARCH BY PYROLYTIC REACTION WITH ACID CATALYSTS
No full textThe aim of this study was to obtain appropriate technological parameters of acid-catalytic pyrolysis to synthesize resistant dextrin from rice starch. Hydrochloric acid has the highest catalytic efficiency of the four tested acids (acetic, citric, lactic, and hydrochloric). With HCl catalyst, pyrodextrins have content of indigestible fraction (IDF), water solubility and whiteness reaching 70.82%, 96.73% and 64.27% respectively. An appropriate condition for pyrolysis of rice starch of IR50404 variety has been determined, including: 0.15% HCl catalyst in starch, pH 2.3 ÷ pH 2.5, pyrolysis temperature 170oC, duration less than 2 h (depends on starch pH and heating device) in order their whiteness to reach 60 ÷ 65%. The pyrolysis applied at a pilot-scale of 8 kg/batch with identified technological parameters showed no significant difference in pyrodextrin quality between production batches and gained about 94% compared with the small laboratory scale. The final product contained 66.56% IDF, 59.63% TDF (total dietary fiber), dextrose equivalent 4.87, and 98.14% water solubility
STRUCTURAL CHARACTERISTICS AND BIOLOGICAL ACTIVITY OF SULFATED POLYSACCHARIDE FROM RED ALGAE BETAPHYCUS GELATINUS
No full textIn this paper, sulfated polysaccharides were extracted from red algae Betaphycus gelatinus species collected at Ninh Thuan sea by using several extraction methods. The structural characteristics of sulfated polysaccharides was investigated by IR and NMR methods. The results indicated that polysaccharide from Betaphycus gelatinus identified as hybrid carrageenan, mainly composed of β-carrageenan, κ-carrageenan and g-carrageenan. Biological activity evaluation showed that the sulfated polysaccharides possessed antioxidant activity with different levels
MICROWAVE-ASSISTED THE CLAISEN-SCHMIDT CONDENSATION BETWEEN ARYLMETHYL KETONES AND ARYL ALDEHYDES CATALYZED BY CU(OTF)2 UNDER SOLVENT-FREE CONDITIONS. SYNTHESIS OF CHALCONES
No full textAn environmentally friendly and high yield method for the Claisen-Schmidt condensation has been investigated. A Mixture of an arylmethyl ketone and an aldehyde was irradiated in a microwave reactor for 20 minute using Cu(OTf)2 as catalyst in solvent-free conditions. 12 chalcones were synthesized in moderate to excellent yields (67-91%). This is the first time the Claisen-Schmidt condensation with Cu(OTf)2 under microwave irradiation was reported
ESSENTIAL OILS OBTAINED FROM EUCALYPTUS AND CYMBOPOGON LEAVES BY STEAM DISTILLATION FOR MAKING NATURAL MIXTURE HAVING EFFECT AS A MOSQUITO REPELLENT
No full textAbstract-HCTN7. Natural essential oils of plant have been applied over the world becausef these biosafety natural compounds. Applicant levels from the steaming pot among the common people to the raw essential oils or pure extract essence from original natural sources for making special products. Eucalyptus essential oil obtains from Eucalyptus leaves contain 998 mg/L α-eucalyptol, Cymbopogon essential oil obtains from lemon grasses contain 64,8% citral. These essential oils have been paid attention because of there were abundant raw materials in the Mekong Delta area. Therefore, the study was conducted to aim of extracting essential oils from Eucalyptus and Cymbopogon leaves as well as examminate their effect on mosquito repellent. The factors affecting the amount of extracted oils are the time to withered materials (0 h; 2.5 h; 5 h), how the way to preliminary treatment of the materials (crushing or without crushing), the distilled water aidding (400 mL, 500 mL, 600 mL)/300g materials, the distillation time (2 h; 2.5 h; 3 h). The data was evaluated by statistical program. Mixing ratio of Cymbopogon oil: Eucalyptus oil: coconut oil, one of the important criteria to be investigated for evaluating the ability to repel mosquitoes is in turn (40:10:50), (35:15:50), (30:20:50). Experimental results reveal that crushing (Cymbopogon), without crushing (Eucalyptus) of fresh materials, 500 mL of distilled water aidding, 3 h of distillation time were the best during the oil extraction process. The contents of mixing formula of the Cymbopogon essiential oil: Eucalyptus essiential oil: coconut oil (40: 10: 50) is the most effective with the ability to falling mosquitoes only after 5 minutes and killing 84.67% mosquitoes after 24 hours. The natural mixture of Cymbopogon oil, Eucalyptus oil, and coconut oil, safety for human health and more friendly to the environment.Keywords: Coconut oil, Eucalyptus essential oil, Eucalyptus leaves, Cymbopogon essential oil, Cymbopogon leaves, mosquito repellent, steam distillation.Classification numbers:1.4.6
Transcription expression of gene encoding cathelicidin CATHL4 in Vietnam indigenous yellow cattle
No full textCathelicidins, a family of host-defence peptides, are present in a diverse range of species, including fish, amphibians, birds, reptiles, and mammals. The evidence for the role of these cationic antimicrobial peptides in innate host defenses is convincing from the data of animal model and transgenic animal experiments as well as wildlife or domestic animals, indicating that the peptides protect against inflammatory and immune system after induction by bacterial infection. In this study, we present the assessment of transcription expression of CATHL4 gene which encodes indolicidin, a cathelicidin from indigenous yellow cattle of Vietnam. The research focused on RNA samples extracted from lung tissues and lymph node collected from diseased cattle which died of infectious respiratory symptoms and the healthy cattle which were slaughtered for food purposes. By quantitative real-time PCR, the relative expression of transcripts was determined and analyzed using the expression of YWHAZ gene as reference. The results showed that this gene was abundantly expressed at a higher level in tissues of the diseased cattle than in those of the healthy ones. In both infection and healthy states, the expression of CATHL4 in lymph nodes were higher than in lung tissues. This indicated that CATHL4 (indolicidin) may participate in functions against infectious pathogens.
Interaction Between Two Jackiw-Rebbi States in Interfaced Binary Waveguide Arrays with Cubic-quintic Nonlinearity
No full textWe study the coupling and switching effects of two discrete relativistic quantum Jackiw-Rebbi states in interfaced binary waveguide arrays with cubic-quintic nonlinearity. Like in the case with Kerr nonlinearity, two Jackiw-Rebbi states can couple efficiently to each other in the low-power regime, show the switching effect in the intermediate-power regime, and possess the trapping effect in the high-power regime. However, in the case with cubic-quintic nonlinearity, if the input Jackiw-Rebbi state power is increased further, one can observe the quasi-linear coupling effect between two Jackiw-Rebbi states which has not been found between two Jackiw-Rebbi states in interfaced binary waveguide arrays with Kerr nonlinearity