Numerical analysis of the interaction between rockbolts and rock mass for coal mine drifts in Vietnam

The thesis describes the application of anchors in mining and tunneling and gives an up-to-date overview about anchor types, design principles and the interaction mechanisms between anchors and rockmass. A constitutive model was developed, implemented and tested for the 2- and 3-dimensional numerical codes FLAC and FLAC3D to simulate non-linear anchor behaviour including unloading and reloading. The interaction between rockbolts and rockmass was studied in detail via numerical simulations for 5 Vietnamese coal mines. An extended version of the so-called c-Φ reduction method and a new introduced reinforcement factor were applied to quantify the effect of bolting. Mine specific and generalised relations were deduced to quantify the influence of anchor length and distance between anchors on the effect of bolting

SOME PROPERTIES OF EF-EXTENDING RINGS

In [16], Thuyet and Wisbauer considered the extending property for the class of (essentially) finitely generated submodules. A module M is called ef-extending if every closed submodule which contains essentially a finitely generated submodule is a direct summand of M. A ring R is called right ef-extending if RR is an ef-extending module. We show that a ring R is right ef-extending and the R-dual of every simple left R-module is simple if and only if R is semiperfect right continuous with Sl = Sl &#8804;e RR. We also prove that a ring R is a QF-ring if and only if R is left Kasch and RR(&#969;) is ef-extending if and only if R is right AGP-injective satisfying DCC on right (or left) annihilators and (R &#8853; R)R is ef-extending.</p

On a viscoelastic heat equation with logarithmic nonlinearity

This work deals with the following viscoelastic heat equations with logarithmic nonlinearity ut − ∆u + Z t 0 g(t − s)∆u(s)ds = |u| p−2u ln |u|. In this paper, we show the effects of the viscoelastic term and the logarithmic nonlinearity to the asymptotic behavior of weak solutions. Our results extend the results of Peng and Zhou [Appl. Anal. 100(2021), 2804–2824] and Messaoudi [Progr. Nonlinear Differential Equations Appl. 64(2005), 351–356.]

Social Justice Innatural Resources Explosion in Vietnam Currently Looked at the Aspect of Benefits

Social justice is always a lofty goal which humanity targets at. However, for the sake of dominance, the issue of social justice is causing a wide range of challenges. Therefore, in addition to generalizing some general theoretical issues about social justice, this article raises a number of issues of social justice of the natural resources exploitation in Vietnam and the meaning of studying this issue for Vietnam's socio-economic development now. Keywords: justice, equality, benefits, natural resources DOI: 10.7176/RHSS/9-12-03 Publication date:June 30th 201

CONNECTING MATHEMATICS AND PRACTICE: A CASE STUDY OF TEACHING EXPONENTIAL FUNCTIONS

There is a need for teaching exponential functions to show the necessity for a better match between the knowledge of exponential functions in high schools with the practical application of it in fields. In this research, a teaching process was built in association with teaching situations to show students the relationship between mathematics and real life. The research sample included 76 students in high schools in Vietnam. Additionally, two problems of compound interest and population growth were integrated and were the main research instruments. Data were collected, including student work, and they were analyzed qualitatively. The results showed that students had improved their problem-solving skills and saw the relationship between mathematics and practice. Furthermore, there were some recommendations suggested for textbook authors and teachers. Article visualizations

Optimization of Logistics Services in Vietnam Through LOGIVAN Application

Logistics is a type of service that plays an important role in promoting the country's economic growth. In addition, it is also of great significance to the transport sector in Vietnam in dealing with the challenges of traffic congestion in large cities. In Vietnam today, logistics services are growing. However, there is one major limitation that still exists, that is freight costs are still high. This does not meet the best requirements of customers. There are many reasons for this problem, one of the reasons is that trucks only carry one-way cargo, but there are no goods to ship backwards. The paper studies the application of LOGIVAN smart transport model in developing Logistics services in Vietnam today. Research results show that LOGIVAN transport model is the optimal model in solving the problem of empty cars in the transport of goods when they go back to the place of departure. This helps minimize Logistics costs for businesses, increases income for drivers and leads towards sustainable transport development. LOGIVAN develops two platform solutions for goods owners and vehicle owners. Accordingly, the author of the article confirms the quality of this model in developing Logistics services in Vietnam and guide the operation for users via applications on personal mobile devices at the same time. Keywords: Logistics; LOGIVAN; Vietnam. DOI: 10.7176/JESD/10-14-01 Publication date:July 31st 202

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