EFFECT OF BLASTING ON THE STABILITY OF LINING DURING EXCAVATION OF NEW TUNNEL NEAR THE EXISTING TUNNEL

In recent years, experimental and numerical researches on the effect of blasting pressure on the stability of existing tunnels was widely obtained. However, the effect of the blasting pressure during excavation a new tunnel or expansion old tunnels on an existing tunnel has disadvantages and still unclear. Some researches were carried out to study the relationship of the observed Peak Particle Velocity (PPV) on the lining areas along the existing tunnel direction, due to either the lack of in situ test data or the difficulty in conducting field tests, particularly for tunnels that are usually old and vulnerable after several decades of service. This paper introduces using numerical methods with the field data investigations on the effect of the blasting in a new tunnel on the surrounding rock mass and on the existing tunnel. The research results show that not only predicting the tunnel lining damage zone under the impact of blast loads but also determination peak maximum of explosion at the same time at the surface of tunnel working

CONDITIONS FOR GRAPHS ON n VERTICES WITH THE SUM OF DEGREES OF ANY TWO NONADJACENT VERTICES EQUAL TO n-2 TO BE A HAMILTONIAN GRAPH

Let G be an undirected simple graph on  $n \geq 3$ vertices with the degree sum of any two nonadjacent vertices in G equal to $n - 2$.  We determine the condition for G to be a Hamiltonian graph

AN INVESTIGATION INTO ASSESSMENT CRITERIA OF THE CONTENT CONTEXT AND FORMS OF EXTRACURRICULAR SPORTS ACTIVITIES FOR STUDENTS AT SECONDARY SCHOOLS IN TAY NINH PROVINCE, VIETNAM

After using the conventional scientific research methods, observing the steps of document synthesis, interviewing, and checking the reliability of the questionnaire through Cronbach's Alpha, the paper has come up with five quantitative assessment criteria and eight qualitative assessment questions of the content and forms of extracurricular sports activities for students at secondary schools in Tay Ninh province. This research has contributed to renewing the content and forms of extracurricular sports activities for students at secondary school.  Article visualizations

THE CONTENT AND METHODS OF CONDUCTING EXTRA-CURRICULAR SPORTS FOR LOWER SECONDARY SCHOOL STUDENTS IN TAY NINH PROVINCE, VIETNAM

The paper aims to provide a comprehensive, scientific and thorough description of the content and methods of how extra-curricular sports activities are conducted for lower secondary school students in Tay Ninh province. To investigate the dependable data, the research employed a range of trustworthy approaches including document synthesizing, interviewing the students and PE teachers in some lower secondary schools, and evaluating the gathered data. The results indicate that the most popular sports among the PE teachers and students are football, badminton, and volleyball which are mostly organized in group, class, and club practice, without an instructor. About the practice durations, it generally ranges from thirty minutes to two hours, equating to two or three sessions at school. Moreover, these activities usually take place in school, and it is mainly held in the afternoon or after theoretical learning.   Article visualizations

Impact of Frequency Shift on Nonlinear Compensation Using Optical Phase Conjugation for M-QAM Signals

Nonlinear compensation using optical phase conjugation (OPC) have been considered a promising technique to increase the reach of high-speed fiber-optic transmission systems. OPC-based nonlinear compensation employs an optical phase conjugation located at a middle of the fiber link to generate a complexed conjugated signal with respect the signal in the first half of the link for propagation in the second half. OPC technique assumes a symmetry for signal propagating in the first and second half to obtain a perfect nonlinear and chromatic dispersion. However, as most of practical OPC schemes are realized by nonlinear effects such as four-wave mixing or a combination of second-harmonic generation and difference frequency generation, the frequency shift induced by OPC affects the signal symmetrical requirement for nonlinear compensation because the chromatic dispersion is different for the first and second half transmissions. In this paper, we investigate the impact of frequency shift on the nonlinear compensation using OPC for high symbol rate, high level modulation format signals. This will be important to understand the tolerance of the OPC techniques against such a practical condition for actual system implementations

An adaptive hierarchical sliding mode controller for autonomous underwater vehicles

The paper addresses a problem of efficiently controlling an autonomous underwater vehicle (AUV), where its typical underactuated model is considered. Due to critical uncertainties and nonlinearities in the system caused by unavoidable external disturbances such as ocean currents when it operates, it is paramount to robustly maintain motions of the vehicle over time as expected. Therefore, it is proposed to employ the hierarchical sliding mode control technique to design the closed-loop control scheme for the device. However, exactly determining parameters of the AUV control system is impractical since its nonlinearities and external disturbances can vary those parameters over time. Thus, it is proposed to exploit neural networks to develop an adaptive learning mechanism that allows the system to learn its parameters adaptively. More importantly, stability of the AUV system controlled by the proposed approach is theoretically proved to be guaranteed by the use of the Lyapunov theory. Effectiveness of the proposed control scheme was verified by the experiments implemented in a synthetic environment, where the obtained results are highly promising. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Linh Nguyen" is provided in this record*