A METHOD OF REAL-TIME NURBS INTERPOLATION WITH CONFINED CHORD ERROR FOR CNC SYSTEMS

This paper presents a method of real-time CNC interpolation for free-form NURBS curves. The interpolation algorithm is based on second order Taylor’s expansion with the principle part being a formula for updating the parametric value u after each sampling period. With the updated value of u, a new interpolated point is calculated based on the DeBoor’s algorithm. In this paper, an efficient method of limiting chord error introduced by the interpolation algorithm is also presented with the basic idea of reducing machining feedrate at positions with a radius of curvature smaller than a critical value

A hybrid heuristic optimization algorithm PSOGSA coupled with a hybrid objective function using ECOMAC and frequency in damage detection

Presence of damage leads to variation in modal properties of observed structures. The majority of studies use the changes in natural frequencies for damage detection. The reason is that the frequencies are often easily measurable with high accuracy by using reasonable sensors. However, frequencies are more sensitive to environmental effects, such as temperature, in comparison with mode shapes. Besides, defects in symmetric structures can cause the same changes in frequency. In contrast, mode shapes are more sensitive to local damage because they own local information and are independent of symmetric characteristics. These make mode shapes have dominant advantages in detecting nonlinear and multiple damage. ECOMAC is an index derived from mode shapes. It is a fact that these indices are not always possible to detect faults successfully in structures. Therefore, in this paper, a hybrid optimization algorithm, particle swarm optimization – gravitational search algorithm, namely PSOGSA, is used to improve the accuracy of infect detection using a hybrid objective function combined ECOMAC and frequency based on the inverse problem. Numerical studies of a two-span continuous beam, a simply supported truss, and a free-free beam, are utilized to verify the effectiveness and reliability of the proposal. From the obtained results, the proposed approach shows high potential in damage identification for different structures

A metal atmosphere corrosion in the industrial zones - Reliability and durability prediction models of steel structures

Currently, the steel structure has been popularly used in industrial zones due to cost advantage and fast construction time. However, the industrial zone is an area with complex corrosive agents in the environment such as sulfur dioxides and chlorides. This paper presents a reliability prediction model considering atmosphere corrosion at the industrial zones. The prediction model is a combination of metal atmosphere corrosion (MAC), finite element method (FEM), and Monte Carlo (MC) simulation. Thereafter, that predictive model is applied for reliability and durability assessment of the steel structures due to atmosphere corrosion in the industrial zones until a life-service of 100 years. The result reveals that the safe probability of the steel structure is reduced to approximately 90 and 80% after 50 years and 100 years, respectively. It implies that the time-varying structural degradation at the design step should be considered

A hybrid heuristic optimization algorithm PSOGSA coupled with a hybrid objective function using ECOMAC and frequency in damage detection

Presence of damage leads to variation in modal properties of observed structures. The majority of studies use the changes in natural frequencies for damage detection. The reason is that the frequencies are often easily measurable with high accuracy by using reasonable sensors. However, frequencies are more sensitive to environmental effects, such as temperature, in comparison with mode shapes. Besides, defects in symmetric structures can cause the same changes in frequency. In contrast, mode shapes are more sensitive to local damage because they own local information and are independent of symmetric characteristics. These make mode shapes have dominant advantages in detecting nonlinear and multiple damage. ECOMAC is an index derived from mode shapes. It is a fact that these indices are not always possible to detect faults successfully in structures. Therefore, in this paper, a hybrid optimization algorithm, particle swarm optimization – gravitational search algorithm, namely PSOGSA, is used to improve the accuracy of infect detection using a hybrid objective function combined ECOMAC and frequency based on the inverse problem. Numerical studies of a two-span continuous beam, a simply supported truss, and a free-free beam, are utilized to verify the effectiveness and reliability of the proposal. From the obtained results, the proposed approach shows high potential in damage identification for different structures

A metal atmosphere corrosion in the industrial zones - Reliability and durability prediction models of steel structures

Currently, the steel structure has been popularly used in industrial zones due to cost advantage and fast construction time. However, the industrial zone is an area with complex corrosive agents in the environment such as sulfur dioxides and chlorides. This paper presents a reliability prediction model considering atmosphere corrosion at the industrial zones. The prediction model is a combination of metal atmosphere corrosion (MAC), finite element method (FEM), and Monte Carlo (MC) simulation. Thereafter, that predictive model is applied for reliability and durability assessment of the steel structures due to atmosphere corrosion in the industrial zones until a life-service of 100 years. The result reveals that the safe probability of the steel structure is reduced to approximately 90 and 80% after 50 years and 100 years, respectively. It implies that the time-varying structural degradation at the design step should be considered

An experimental study and a proposed theoretical solution for the prediction of the ductile/brittle failure modes of reinforced concrete beams strengthened with external steel plates

An experimental study and a proposed theoretical solution are conducted in the present study to investigate the ductile/brittle failure mode of reinforced concrete beams strengthened with an external steel plate. The present experimental study has fabricated and tested six steel plate-strengthened RC beams and one non-strengthened RC beam under 4-point bending loads. The proposed theoretical model is then developed based on the observed experimental results to analyze the crack formation, to determine the distance between vertical cracks and to quantitatively predict the ductile/brittle failure mode of plate-strengthened RC beams. The experimental study shows that the failure mode is based on the sliding of concrete along with the external plate. This slip is limited between two vertical cracks, from which the maximum stress in the external steel is determined. Based on comparisons conducted in the present study, excellent agreements of the stresses/strains in soffit steel plates, crack distances, and system failure modes between the current theoretical solution and the previous and present experimental results are observed.&nbsp

The Role of Cultural and Institutional Distances in International Trade

Despite the effectiveness of the observed barriers such as taxes and quotas to adjust bilateral trade, they are still not well supported by governments in general and the World Trade Organization in particular. Therefore, in recent years, unobserved barriers have been critical tools to modify the trade flows between nations worldwide. China’s exports account for a massive proportion of global trade. However, the role of cultural and institutional distance in China’s trade flow has not been much explored. This study analyzes the impact of cultural and institutional differences on China's exports between 2006-2017 by adopting a system-GMM estimator. The main findings are, first, that cultural and institutional differences between China and its trading partners reduce China's exports. Second, cultural and institutional distances have the strongest influence on China's exports to high-income countries, followed by low-income countries, and finally middle-income countries. Third, manufactured products are the most sensitive to cultural and institutional distances. Based on these findings, several policies for China, as well as for emerging economies in general, are suggested for reducing cultural and institutional distances and boosting their exports. Doi: 10.28991/ESJ-2023-07-02-015 Full Text: PD

Factors affecting learner’s satisfaction towards online learning during COVID-19 pandemic: A case study of Vietnam

Online learning is being considered a new model of knowledge exchange in modern education. In parallel with the incredible impacts of the global pandemic, this is considered an opportunity to promote the development of online learning globally. Therefore, this study proposed a research framework including four factors affecting learner satisfaction towards online learning during the COVID-19 pandemic at a university, which are system quality, service quality, transformational leadership, and self-efficacy. A questionnaire was conducted online to assess which 131 respondents were representative students from two large private universities in Da Nang: FPT University and Duy Tan University. The results from the regression analysis show that three factors have a positive impact on learner satisfaction during COVID-19. This study concludes that students at private universities in Da Nang prioritize system quality as the most significant factor in their satisfaction with the online learning system, followed by transformational leadership and the last one is self-efficacy. Therefore, it can be more strategic for private organizations, developers, software designers, or even transformation-trained trainers to be emphasized to build a system of processes for implementing online learning for students effectively

Do Technical Barriers to Trade Measures Affect Vietnam’s Tea Exports? Evidence from the Gravity Model

This paper explores how technical barriers to trade (TBT) affect Vietnam’s tea exports to 55 importing countries from 2001 to 2019. We use the gravity model with different estimation methods: ordinary least square (OLS), fixed-effect (FE), and random effect (RE) to estimate the impact of TBT on Vietnam’s tea exports. The results show that although GDP, population, distance, tariff, and participation in World Trade Organization (WTO) are crucial factors, the TBT measures imposed by these importing countries have significantly negative impacts on Vietnam’s tea exports. Our findings reveal that while a 1% increase in the cumulative TBT measures imposed by developing countries decreases Vietnam's tea export by 0.341%, the figure for developed countries is 1.308%