Nonlinear analysis of multilayer composite pipes

The use of composite materials has constantly increased in aerospace and offshore applications. One of -typical composite structures for offshore application is multilayer unbonded composite pipe. The composite pipe comprised of several layers such as helically wound steel layers and polymeric layers, among which the helically wound steel wires play essential roles in providing axial and flexural stiffnesses of the pipe. Because of the -geometric nonlinearity of each layer of the composite pipe and the flexibility in motion of individual layers against their adjacent layers, analyses of the composite pipe are highly nonlinear and computationally challenging. In this study, detailed three-dimensional Representative Volume Element models of the multilayer unbonded composite pipe are developed, and nonlinear analyses of the composite pipe are performed. The developed FE models effectively predict nonlinear responses of the pipe including slipping effects of steel layers under application of axial loading, bending, internal and external pressures. Based on the predicted results, a constitutive model of the pipe under various loadings is obtained which can be employed in the large scale analysis of the composite pipe to improve the accurate and computational efficiency of the global analysis

Progressive Failure Analysis of Double-Notched Composite Laminates

Ph.DDOCTOR OF PHILOSOPH

Composite riser design and development – a review

There is accelerating interest in composite risers for deepwater applications. Composite risers offer much higher strength to weight ratios over metallic risers but there is less experience of their behavior in deepwater environments. A general review on current developments specific to composite risers highlighting the remaining challenges and the applications, design evolution, state-of-the-art modeling and experimental techniques is lacking. This paper provides such a review on fiber-reinforced polymer composite risers. The major issues for composite risers are addressed including the complicated combination of loads under harsh deep sea environment, the lack of long-term material degradation database for assessing the reliability of these riser systems and the need of effective numerical models to fully account for complex realistic loading configurations. The paper also highlights current gaps for design and application of composite risers in off-shore technology and promising future research areas to help expand their utilization in deeper wate

USING EXPERIMENTAL PLANNING TO OPTIMIZE THE HYDROLYSIS OF SUGAR CANE BAGASSE INTO FERMENTABLE SUGARS FOR BIOETHANOL PRODUCTION BY FUNGAL ENZYME MIXTURE

In this study, the unpretreated sugar cane bagasse was milled to a particle size of 0.5 – 1 mm and be used as material for bioconversion into fermentable sugars by using an enzyme cocktail acted synergistically. Experimental planning was used to optimize the enzyme conversion through assessment and analysis of individual parameter. As the result, the optimal condition for enzymatic conversion of sugar cane bagasse into reducing sugar product are at pH = 5, 400C, and 48 h incubation in rate of enzyme (Cell/Xyl, AltFAE, XpoAE) and substrate (bagasse meal) is 3.1. From the above application, the mathematical model is found to describe equation of the bioconversion of bagasse into reducing sugars: = 206.946 + 29.954x1 + 5.501x2 + 7.323x3 + 2.288x2x3 – 7.011; and using flexible algorithm of nonlinear planning to identify optimal conditions of enzyme mixture of conversion into reducing sugars that the reaction reached max = 251.86 mg per gram bagasse with x1 = 1.215, x2 = 1.215, x3 = 1.215 or Cell/Xyl = 1 ml (100U), AltFAE = 0.5 ml (7.56U), XpoAE = 0.4 ml (10.8U) on the test range. Experimental verification has the same result in constant conditons and reached total reducing sugars of 260.2 mg per gram substrate.In this study, the unpretreated sugar cane bagasse was milled to a particle size of 0.5 – 1 mm and be used as material for bioconversion into fermentable sugars by using an enzyme cocktail acted synergistically. Experimental planning was used to optimize the enzyme conversion through assessment and analysis of individual parameter. As the result, the optimal condition for enzymatic conversion of sugar cane bagasse into reducing sugar product are at               pH = 5, 40 oC, and 48 h incubation in rate of enzyme (Cell/Xyl, AltFAE, XpoAE) and substrate (bagasse meal) is 3.1. From the above application, the mathematical model is found to describe equation of the bioconversion of bagasse into reducing sugars: = 206.946 + 29.954x1 + 5.501x2 + 7.323x3 + 2.288x2x3 – 7.011; and using flexible algorithm of nonlinear planning to identify optimal conditions of enzyme mixture of conversion into reducing sugars that the reaction reached max = 251.86 mg per gram bagasse with x1 = 1.215, x2 = 1.215, x3 = 1.215 or Cell/Xyl = 1 ml (100U), AltFAE = 0.5 ml (7.56U), XpoAE = 0.4 ml (10.8U) on the test range. Experimental verification has the same result in constant conditons and reached total reducing sugars of 260.2 mg per gram substrate

Dataset of Vietnamese students’ intention in respect of study abroad before and during COVID-19 pandemic

The Covid-19 Pandemic had completely disrupted the worldwide educational system. Many schools chose the online delivery mode for students in case learning losses incurred during social distance decree. However, as to these students who are currently in the study abroad planning stages, reached an intention crossroads, whether standing for certain unchanging decisions in study abroad destinations or changing swiftly due to the unexpected policies in quarantine. This case opened to interpretation, which was based on our e-survey since 3 May to 13 May 2020 with 397 responses covering a range of Vietnamese students. In this dataset, we focused on (i) Students’ Demographics; (ii) The previous intention of students to study abroad before and during the Covid-19 ravaged and (iii) Their intention afterwards

Medical reverse engineering applications and methods

Understanding, controlling and manipulation of patient data as well as shape, geometry and structure of the biomedical objects are important for developing Biomedical Engineering (BME) applications. Medical Reverse Engineering (MRE) is aimed to use the Reverse Engineering (RE) technology to reconstruct 3D models of the anatomical structures and biomedical objects for design and manufacturing of medical products as well as BME research and development. This paper presents the state of the art applications and methods about MRE. Different concepts and methodologies are provided to understand fundamentally the MRE processes and workflow. The key MRE applications are presented, including personalised implants for bone reconstruction, dental implants and simulations, surgical tools, medical training, vision science and optometry, orthopedics, ergonomics, orthosis, prosthesis, and tissue engineering. The current challenges as well as the hardware and software for MRE application development and research are discussed

Survey on Vietnamese teachers’ perspectives and perceived support during COVID-19

The COVID-19 pandemic has caused unprecedented damage to the educational system worldwide. Besides the measurable economic impacts in the short-term and long-term, there is intangible destruction within educational institutions. In particular, teachers – the most critical intellectual resources of any schools – have to face various types of financial, physical, and mental struggles due to COVID-19. To capture the current context of more than one million Vietnamese teachers during COVID-19, we distributed an e- survey to more than 2,500 randomly selected teachers from two major teacher communities on Facebook from 6th to 11th April 2020. From over 373 responses, we excluded the observations which violated our cross-check questions and retained 294 observations for further analysis. This dataset includes: (i) Demographics of participants; (ii) Teachers' perspectives regarding the operation of teaching activities during the pandemic; (iii) Teachers' received support from their schools, government bodies, other stakeholders such as teacher unions, and parents' associations; and (iv) teachers' evaluation of school readiness toward digital transformation. Further, the dataset was supplemented with an additional question on the teachers' primary source of professional development activities during the pandemic

Antibiotic Resistance Profile and Methicillin-Resistant Encoding Genes of Staphylococcus aureus Strains Isolated from Bloodstream Infection Patients in Northern Vietnam

Background:  Evaluating the antibiotic susceptibility and resistance genes is essential in the clinical management of bloodstream infections (BSIs). Nevertheless, there are still limited studies in Northern Vietnam. AIM: This study aimed to determine the antibiotic resistance profile and methicillin-resistant encoding genes of Staphylococcus aureus (S. aureus) causing BSIs in Northern Vietnam. METHODS: The cross-sectional study was done from December 2012 to June 2014 in two tertiary hospitals in Northern Vietnam. Tests performed at the lab of the hospital. RESULTS:  In 43 S. aureus strains isolating, 53.5 % were MRSA. Distribution of gene for overall, MRSA, and MSSA strains were following: mecA gene (58.1 %; 95.7%, and 15%), femA gene (48.8%, 47.8%, and 50%), femB gene (88.4%, 82.6%, and 95%). Antibiotic resistance was highest in penicillin (100%), followed by erythromycin (65.1%) and clindamycin (60.5%). Several antibiotics were susceptible (100%), including vancomycin, tigecycline, linezolid, quinupristin/dalfopristin. Quinolone group was highly sensitive, include ciprofloxacin (83.7%), levofloxacin (86%) and moxifloxacin (86%). CONCLUSION:  In S. aureus causing BSIs, antibiotic resistance was higher in penicillin, erythromycin, and clindamycin. All strains were utterly susceptible to vancomycin, tigecycline, linezolid, quinupristin/dalfopristin