Cohen-Macaulay oriented graphs with large girth

We classify the Cohen-Macaulay weighted oriented graphs whose underlying graphs have girth at least $5$.Comment: We correct typos in Lemma 2.

Teachers’ Beliefs and Practices Regarding Assessment in English as a Foreign Language Classrooms in Vietnam

Task-based language teaching (TBLT) has generated worldwide popularity as a curriculum innovation, and extensive research has investigated various aspects of the approach. However, little is known about the implementation of classroom assessment in TBLT curricula. This study investigated high school English as a foreign language teachers’ beliefs and practices regarding assessment in a curriculum innovation context in Vietnam. Data comprised in-depth interviews with six teachers, as well as testing documents. The findings revealed a strong impact of the high-stakes exams on teachers’ testing beliefs in that they focused explicitly on linguistic items in the assessed content and forms of assessment. These beliefs were accurately reflected in their testing practices. However, both the teachers’ beliefs and practices were contradictory to teaching principles and the expectations of the intended curriculum. These findings suggest that in-service teacher professional development programs are necessary for innovations like TBLT to have a real change in the classroom

Students’ Attitudes Towards Education in Biology-Related Disciplines and the Need for Internationalization : A Survey at a Vietnamese University

This survey examined the attitudes of 538 undergraduate students enrolled at a Vietnamese university towards biology-related disciplines. Employing a structured questionnaire, the study explored several aspects, including students' interests in various biology-related fields, their motivations for pursuing these disciplines, their opinions on teaching methods, their aspirations for internationalization and study abroad experiences, the essential skills they believed were crucial for success, and the areas in teaching that required improvement. The survey results indicated that students acknowledged the significance of fields such as medicine and veterinary sciences, with their motivations largely influenced by job prospects and societal needs. Moreover, the results identified specific areas in teaching that students wanted to have improvement, such as laboratory work, practical skills development, fieldwork experiences, and exchange programs, and their attitude towards internationalization and study abroad opportunities, in relations to the factors such as age, gender, grade, and major. The insights gained from this survey can contribute to the enhancement of educational strategies and the creation of an engaging learning environment for students majoring in biology-related disciplines

ENERGY-ENVIRONMENT ISSUE IN TRANSPORT OF VIETNAM

Joint Research on Environmental Science and Technology for the Eart

Fuzzy gain scheduling control apply to an RC Hovercraft

The Fuzzy Gain Scheduling (FGS) methodology for tuning the Proportional – Integral – Derivative (PID) traditional controller parameters by scheduling controlled gains in different phases, is a simple and effective application both in industries and real-time complex models while assuring the high achievements over pass decades, is proposed in this article. The Fuzzy logic rules of the triangular membership functions are exploited on-line to verify the Gain Scheduling of the Proportional – Integral – Derivative controller gains in different stages because it can minimize the tracking control error and utilize the Integral of Time Absolute Error (ITAE) minima criterion of the controller design process. For that reason, the controller design could tune the system model in the whole operation time to display the efficiency in tracking error. It is then implemented in a novel Remote Controlled (RC) Hovercraft motion models to demonstrate better control performance in comparison with the PID conventional controller

High-Gain Observer–Based Sliding Mode Control of Multimotor Drive Systems

Multimotor drive systems have been widely used in many modern industries. It is a nonlinear, multi-input, multi-output (MIMO) and strong-coupling complicated system, including the effect of friction, elastic, and backlash. The control law for this drive system much depends on the determining of the tension. However, it is hard to obtain this tension in practice by using a load cell or a pressure meter due to the accuracy of sensors or external disturbance. In order to solve this problem, a high-gain observer is proposed to estimate the state variables in this drive system, such as speeds and tension. An emerging proposed technique in the control law is the use of high-gain observers together with adaptive sliding mode control scheme to obtain a separation principle for the stabilization of whole system. The theory analysis and simulation results point out the good effectiveness of the proposed output feedback for the drive system

Quantization Error Correction Schemes for Lattice-Reduction Aided MIMO Detectors

Lattice reduction aided (LRA) linear detectors have been known to achieve near optimal performance at low complexity. However, one weakness of LRA detector is that the quantization step in LRA detector is not optimal. Based on simulation results, we show that most of detection errors in LRA linear detectors are due to quantization errors. We then propose two methods to correct the quantization errors. In the first method, sphere detectors are introduced to correct quantization errors at low additional complexity. As a second approach, we propose a list quantization scheme which can generate a list of candidate symbols from the original LRA estimated symbols. From these listed symbols, decisions are made according to the minimum Euclidean distance between the received and estimated points. It is shown by simulations that both methods provide significant BER performance improvements with only a small additional complexity