Optical Phonon Modes and Electron-optical Phonon Interaction in Core-shell Semiconductor Quantum Wires

Within the framework of the macroscopic dielectric continuum model the longitudinal optical (LO) phonon modes are derived for a cylindrical semiconductor quantum wire made of semiconductor 1 (well material) embedded in another finite semiconductor 2 (barrier material).  The phonon states of modes are given by solving the generalized Born-Huang equation. It is shown that there may exist four types of longitudinal optical phonon modes according to the concrete materials forming the wire. The dispersion equations for phonon frequencies with wave-vector components parallel to the wire are obtained. After having quantized the phonon field we derive the Fröhlich Hamiltonian describing the electron--LO-phonon interaction. The influence of the thickness of the barrier layer as well as the thin metallic shell on the phonon frequencies and their interaction with electrons is studied

Hematological parameters of red tilapia (Oreochromis sp.) fed lemongrass essential oil (Cymbopogon citratus) after challenge with Streptococcus agalactiae

The study involved feeding lemongrass essential oil (LEO) supplements to red tilapia (Oreochromis sp.) at concentrations including Control - 0 mg, T1 – 200 mg, T2 – 300 mg, and T3 – 400 mg per kg of feed. The research investigated changes in hematological (HCT, Hb, RBC, WBC & thrombocytes) and erythrocyte’s morphological (major/minor axis; perimeter, and area of erythrocyte) parameters before infection, 5- and 10-days post-infection (DPI). According to analytical findings, a diet containing LEO enhanced the synthesis of both erythrocytes and leukocytes in the peripheral blood of red tilapia after 20 days of being used. Therefore, the indicators of this group of fish showed better performance than those that did not use LEO supplement five days after bacterial infection. Fish fed 200 mg/kg of LEO after being challenged with S. agalactiae for ten days showed an improved effect on red blood cell production. White blood cells decreased at all concentrations because of citral’s immunomodulatory properties

Development of PSO for tracking Maximum Power Point of Photovoltaic Systems

For a photovoltaic system, the relationship of the output voltage and power is usually non-linear, so it is essential to equip a MPPT controller in PV systems. Furthermore, the hotspot problem is a common phenomenon, resulting from the PV system operating under PSC. Partial shading not only damages the PV cells, but also makes it difficult to find the global MPP in the characteristic curves of P-V. The paper proposes a novel version of PSO, namely PPSO in order to detect the global peak among the multiple peaks, known as the true maximum energy from PV panel. For this, the PPSO algorithm makes the velocity of each particle be perturbed once the particles are struck into a local minima state in order to find the best optimum solution in the MPPT problem. The perturbation in the velocity vector of each particle not only helps them tracking the MPP accurately under the changing environmental conditions, such as large fluctuations of insolation and temperature like PSC; but also removes the steady-state oscillation. The proposed approach has been tested on a MPPT system, which controls a dc-dc boost converter connected in series with a resistive load. Moreover, the obtained results are compared to those obtained without any MPPT controller to prove the efficiency of the suggested method. In addition, this novel version gives the highest accuracy of tracking the optimum power in the least iteration number as compared to the conventional PSO

Effects of perceived corporate social responsibility practices on customers’ satisfaction and perceived value – A study in the food industry in Vietnam

The main purpose of this study is to investigate the effects of perceived Corporate Social Responsibility (CSR) practices on customers’ satisfaction and perceived value. According to the result of the literature review, the studied CSR practices include environmental protection, customer protection, community, HR policies, price, product quality, relationship selling, empathy, and fulfill expectations. To address the research objective, the present study proposed two following research questions: (1) What are factors of CSR practices impacting customers’ satisfaction?; and (2) How do these factors influence customer satisfaction and perceived value? The study approached 236 customers of the food industry to conduct a survey empirically and tested the proposed hypotheses using structural equation modeling. The research findings show that (1), in Vietnamese customers perceptions, Perceived price, Perceived quality and Empathy are three components of CSR practices; (2) these components have positive impacts on Customer satisfaction; and (3) Customer satisfaction has a positive relationship with customers’ perceived value. These findings help to enrich the CSR literature in developing countries like Vietnam, and to confirm the findings of previous studies. Moreover, from the research findings, the present study suggested some managerial implications for firms in the food industry relating to price, product quality and empathy

INVESTIGATION OF ARSENIC RELEASE FROM SEDIMENT MINERALS TO WATER PHASES -MOTIVATION FOR ARSENIC MITIGATION TECHNOLOGY

Joint Research on Environmental Science and Technology for the Eart

Teaching English vocabulary to young learners through total physical response method

This study attempts to investigate the effect of the Total Physical Response (TPR) Method on vocabulary retention and explore the young learners’ attitudes toward it. It involved sixty two English young learners (YLs) aging from 10 to 11. All of them were attending English classes at Viet Uc English Language Center (henceforth called VUC) in Bien Hoa City where the current study was conducted. Both quantitative and qualitative data was obtained through the three instruments, namely pre- and post-test and interview. Descriptive statistics was employed for data analysis. The results revealed that TPR had effect on the YLs’ vocabulary knowledge through an increase in their vocabulary retention after they underwent the treatment. Similarly, the findings of the study also revealed that the YLs had positive attitudes toward the use TPR in vocabulary teaching and learning. This study is expected to shed light to the implementation of teaching vocabulary methods in the VUC context and other similar contexts

Liquid pumping and mixing by PZT synthetic jet

In this paper, a PZT synthetic jet that can function as both an efficient pumping and mixing device is developed. Compare with the conventional design where the practice of controlling the internal flow is undertaken by microvalves structure, this approach promotes the durability and allows the device to work with different liquids at high Reynold number without losing of backflow from the diffuser, therefore provides efficient mixing. The pumping performance is applicable for commercialized counterparts while the homogeneous medium was obtained at downstream in the experiments, which was further confirmed by simulation. Notably, the chaotic mixing feature of the device is also applicable for immiscible liquids with the micro-droplet formation result at the outlet

AN INVESTIGATION INTO THE USE OF COLLOCATIONS IN ACADEMIC ESSAYS OF ENGLISH-MAJORED STUDENTS OF THE HIGH-QUALITY PROGRAM AT CAN THO UNIVERSITY, VIETNAM

One of the main goals of language learners is to master all four skills of listening, speaking, reading and writing when it comes to their acquisition of the target language. However, during the process of learning English, learners inevitably face a variety of challenges related to their writing including grammatical errors, word choice, organization, idea development, and most importantly their difficulties in using collocations (Duong & Nguyen, 2021). Therefore, this study has been conducted to investigate the students’ use of English collocations in their academic essays associated with their difficulties so that appropriate pedagogical approaches and practices would be taken into consideration in order to help students improve their English collocational competences in academic writing. This descriptive study was carried out with 103 English-majored students of the High-quality program of the School of Foreign Languages at Can Tho University, Vietnam. A 5-point Likert scale survey with 18 questionnaire items was employed to examine the frequency of students' exposure to as well as their usage of English collocations, and their difficulties in using English collocations. The results of this study have shown that the most commonly used collocations in the students’ academic essays were ‘verb + noun’, and ‘adjective + noun’ lexical collocations. Additionally, the research outcomes have revealed that the types of English collocations that the students were more likely to make the most mistakes belonged to ‘verb + adverb’, and ‘adjective + noun’ lexical collocations.  Article visualizations

Feasibility of wearable monitors to detect heart rate variability in children with hand, foot and mouth disease

Hand foot and mouth disease (HFMD) is caused by a variety of enteroviruses, and occurs in large outbreaks in which a small proportion of children deteriorate rapidly with cardiopulmonary failure. Determining which children are likely to deteriorate is difficult and health systems may become overloaded during outbreaks as many children require hospitalization for monitoring. Heart rate variability (HRV) may help distinguish those with more severe diseases but requires simple scalable methods to collect ECG data.We carried out a prospective observational study to examine the feasibility of using wearable devices to measure HRV in 142 children admitted with HFMD at a children's hospital in Vietnam. ECG data were collected in all children. HRV indices calculated were lower in those with enterovirus A71 associated HFMD compared to those with other viral pathogens.HRV analysis collected from wearable devices is feasible in a low and middle income country (LMIC) and may help classify disease severity in HFMD