Inference on Riemannian Manifolds: Regression and Stochastic Differential Equations

Statistical inference for manifolds attracts much attention because of its power of working with more general forms of data or geometric objects. We study regression and stochastic differential equations on manifolds from the intrinsic point of view. Firstly, we are able to provide alternative parametrizations for data that lie on Lie group in the problem of fitting a regression model, by mapping this space intrinsically onto its Lie algebra, while we explore the behaviour of fitted values when this base point is chosen differently. Due to the nature of our data in the application of soft tissue artefacts, we employ two correlation structures, namely Matern and quasi-periodic correlation functions when using the generalized least squares, and show that some patterns of the residuals are removed. Secondly, we construct a generalization of the Ornstein-Uhlenbeck process on the cone of covariance matrices SP(n) endowed with two popular Riemannian metrics, namely Log-Euclidean (LE) and Affine-Invariant (AI) metrics. We show that the Riemannian Brownian motion on SP(n) has infinite explosion time as on the Euclidean space and establish the calculation for the horizontal lifts of smooth curves. Moreover, we provide Bayesian inference for discretely observed diffusion processes of covariance matrices associated with either the LE or the AI metrics, and present a novel diffusion bridge sampling method using guided proposals when equipping SP(n) with the AI metric. The estimation algorithms are illustrated with an application in finance, together with a goodness-of-fit test comparing models associated with different metrics. Furthermore, we explore the multivariate volatility models via simulation study, in which covariance matrices in the models are assumed to be unobservable

Time-Frequency Nexus between Tourism Development, Economic Growth, Energy Consumption, and Ecological Footprint in Singapore

Singapore has been listed as one of the top-visited countries and has the highest ecological deficit. Despite the abundance of previous studies, the distinction between short, medium, and long term by decomposing tourism development, economic growth, energy consumption, and ecological footprint has been largely ignored. This study aims to investigate the lead-lag nexus structures between ecological footprint and Singapore's economic activities from 1978 to 2016. By adopting the wavelet analysis and scale-by-scale Granger causality test, the outcomes show that energy consumption positively impacts ecological footprint at high frequencies, while tourism and economic growth positively drive ecological footprint at high and medium frequencies. We also find that the positive impact of macroeconomic variables on ecological footprint has not been evident since 2003. Additionally, the wavelet-based Granger test confirms a bi-directional causal between economic growth and ecological footprint at all frequencies, whilst there is a bi-directional relationship between tourism, energy consumption, and ecological footprint at high frequency. Based on these findings, the research may further strengthen the belief of Singapore’s policy-makers on the promotion of tourism and suggests some helpful lessons for emerging countries

The lasting effects of innovation on firm profitability: Panel evidence from a transitional economy

This study is the first to study the lasting effects of innovation on firm profitability in Vietnam. Using a unique panel dataset for the period 2005-2015, our results show that innovators achieve higher profit in comparison with non-innovating firms. The positive effects of innovation on firm profitability are observed not only in the short term but also in the longer term. The benefits of innovation for firm profitability can be seen in higher export probability, better productivity, better access to formal credit, and the ability to secure government support, but only after innovation

COMMON ERRORS IN PRONOUNCING FINAL CONSONANTS OF ENGLISH-MAJORED SOPHOMORES AT TAY DO UNIVERSITY, VIETNAM

It is not deniable that pronunciation is considered one of the most crucial parts of learning English helping learners enhance their communication in both speaking and listening comprehension. To reach a level of a clear and precise pronunciation has never been an effortless task; however, it is a far more problematic one for English majored students regardless of their learning years. For this reason, the study entitled “Common Errors in Pronouncing Final Consonants of English-Majored Sophomores at Tay Do University” was implemented with the aim at investigating the errors that English-majored students encountered in pronouncing final consonants. 80 English-majored sophomores from course 13 at Tay Do University were selected to participate in the study. Questionnaires and recording tests were delivered to the participants for collecting data and getting more information. The collected data from the two instruments mentioned above were all analyzed afterward. The findings of the research revealed that sophomores of English major often mispronounced the final consonants, particularly /s/, /z/, /ʃ/, /f/ and /v/ in two main mistakes, including omission and substitution. The results of this study may also be useful for those who are interested in this field. Article visualizations

The lasting effects of innovation on firm profitability: panel evidence from a transitional economy

This study is the first to study the lasting effects of innovation on firm profitability in Vietnam. Using a unique panel dataset for the period 2005–2015, our results show that innovators achieve higher profit in comparison with non-innovating firms. The positive effects of innovation on firm profitability are observed not only in the short term but also in the longer term. The benefits of innovation for firm profitability can be seen in higher export probability, better productivity, better access to formal credit, and the ability to secure government support, but only after innovation

Research on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy when modified by La, Ce and thermo-mechanical treatment

Influence of rare-earth (La, Ce) and thermo-mechanical treatment on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy are presented in this article. After casting, the alloy which was modified by La, Ce, the grain size of samples obtained around 40–50 µm compared to that of without about 65 µm; and after homogeneous, the grain sizes is about 30 µm. After the cold deformation process, the distance between plates is 10 µm. By EDS after casting, the samples have tended to more La, Ce elements at the grain boundary, after homogeneous, the uniformation distribution of rare-earths was presented by mapping of EDS’s results. In addition, after rolling and heat treatment, the elements were found on the grain boundary and matrix. After recrystallization annealing, the grain size is around 10 µm with the modification sample. The grain size was reduced by two processes of modification as well as thermal-mechanical treatment is a condition for increasing the ductility of the studied alloy. Further, as a result of ability deformation from the tensile test, these results demonstrate that the tensile test obtained 140 % when adding La, Ce contents into the alloy combine with thermal-mechanical treatment. The combined used of La, Ce and thermal-mechanical treatment have increased the ductility of Al-Zn-Mg-Cu allo

The experience of using e-commerce platforms affects the online purchase intention of customers in the FMCG (Fast moving consumer goods) sector in Hanoi city

In recent times, the Vietnamese e-commerce market is in a period of strong development, in addition, to the sharp increase in people’s demands to join e-commerce platforms after the epidemic. The research group started with an overview study, then research hypotheses and models were proposed. After conducting preliminary qualitative and quantitative research to adjust the appropriate scales, the research group created a questionnaire and collected data in online forms with a sample size of 350. Next, the data was entered into the software for SEM analysis. The results of the study indicate that the quality of the e-commerce platform has an indirect impact on the purchase intention through the positive impact on the trust and the negative impact on the perceived risk. Attitudes towards information, trust, perceived risk, and perceived usefulness have direct influences on purchase intention. Attitude towards information, trust, and perceived usefulness have positive effects on purchase intention, while perceived risk harms purchase intention. In addition, purchase intention is relatively strongly influenced by trust and perceived usefulness. Perceived risk and attitude towards information have little influence on purchase intention. Finally, the research team proposes some solutions for businesses to increase the purchase intention of consumers through e-commerce platforms. &nbsp

Determinants of electronic word of mouth in the restaurant industry: An evidence from Vietnam

The food and beverage industry in Vietnam has developed dramatically, resulting in a highly competitive market. To win the competition, the restaurant managers not only strive to increase customer satisfaction but also create customers’ positive electronic Word-Of-Mouth (eWOM). This study aims to investigate the relationship between customer satisfaction, customer trust, customer loyalty, and eWOM. The quantitative method was implemented to examine the hypotheses in the research model. Data were collected from Ho Chi Minh City respondents using a convenient sampling method. Self-administrated questionnaires were delivered via the Internet for data collection. After data screening, 299 responses were qualified for analysis. Partial Least Squares Structural Equation Modeling (PLS-SEM) analysis was employed by SmartPLS software version 3.0. The measurement model test showed that one item of customer trust has a factor loading of less than 0.7 as a result, this item was removed from the research model. The structural model evaluation revealed the highly predictive accuracy of the model as all dependent variables have R2 values above 0.5. A bootstrapping test with 5,000 subsamples also showed that customer loyalty significantly influences eWOM, but customer trust does not. Customer satisfaction directly and significantly impacts customer trust and loyalty but has little influence on eWOM. However, the relationship between customer satisfaction and eWOM is significant without the presence of customer loyalty and trust. The indirect effect test also determines the full mediation role of customer loyalty in the relationship between customer satisfaction and eWOM

Factors Affecting Cooperation in the International Supply Chain of Seafood Enterprises: the Case of Vietnamese

Purpose: The purpose of this research is to analyze and evaluate factors affecting cooperation in the international supply chain of Vietnamese seafood enterprises.   Theoretical framework: Operations in international business context are associated with high risks, so cooperation in supply chain helps to improve management flexibility. On the other hand, acccording to the theory of resource dependency, resource sharing and information sharing strategies can affect the quality and the level of cooperation among supply chain partners.   Design/methodology/approach: To achieve the aim of this study, a literature survey related to supply chain and supply chain cooperation is carried out, and empirical analysis is conducted among 327 partners in seafood industry with the results analyzed using Cronbach’s Alpha analysis, exploratory factor analysis (EFA), and linear regression analysis (RA).   Findings: Research results have confirmed that there are six main factors directly affecting the international supply chain cooperation of Vietnamese seafood enterprises including: (1) Trust; (2) Power; (3) Distance; (4) Government policy; (5) Cooperation strategies and (6) Information sharing.   Research/Practical & Social implication: The encouraging policies and simplified export regulations are to be implemented by the government, VASEP and enterprises so the knowledge about international supply chain cooperation will be promoted with the help of comprehensive future research directions.   Originality/value: This is literally one of the first research works in Vietnam to incorporate the information sharing component into the model of affecting factors for international supply chain cooperation. Regardless of business uncertainties, the study shed new light on supply chain cooperation and promote firms to gain an edge in the global marketplace