Groundwater and River Interaction Parameter Estimation in Saigon River, Vietnam

The Saigon River system is one of the largest resources contributing water supply for domestic and industrial fields in the Ho Chi Minh City and Binh Duong Province where the drought issue are occurring at downstream area in recent years. To manage the water resources in Saigon Basin effectively, the groundwater and river interaction parameter needs to be assessed systematically. However, in the past researches, the parameters seem to be less described with full understandings. In this study, a groundwater modeling of the main stream of Saigon River was applied to analyze groundwater and river interaction parameter along the river. The interaction layer was defined as a combined layer by materials of riverbed and materials of aquitard or aquifer. The values of conductance, through groundwater model calibration by piezometric heads during 2000 to 2007 at three cross-sections in Saigon River, were used to estimate the interaction parameter (KiM-1) at correlative cross-section. A function of interaction parameter with ratio of wetted length (Rw) was developed to estimate interaction parameter at each cross-section along Saigon River. When river cross-sections has no penetration to the aquifer and the materials of interaction layer consists of materials of riverbed and aquitard, the value of interactions is equal to 0.0003 d-1. In the other hand, the value will be reach to 0.254 d-1 when river cross-section has fully penetration to the aquifer. The interaction parameter function developed was applied to investigate the flow in and out between river and aquifer in the study area. In the upper part of Saigon River, river gained water from inflow of groundwater through riverbed (river gain) and lost water to groundwater (river loss) by outflow through the riverbed in the lower part during 2000 to 2007 and the river recharge to the first aquifer supplies to the second aquifer to supplement the aquifer storage discharged from the pumping

On the Asymptotic Behavior of Solutions of Differential Systems

There are many studies on the asymptotic behavior of solutions of differential equations. In the present paper, we consider another aspect of this problem, namely, the rate of the asymptotic convergence of solutions.Асимптотичній поведінці розв'язків диференціальних рівнянь присвячено чимало досліджень. У даній роботі проблему розглянуто з іншого боку, а саме, з точки зору швидкості асимптотичної збіжності розв'язків

Parameter Estimation and Predictive Speed Control of Chopper-Fed Brushed DC Motors

This paper presents an effective speed control method for brushed DC motors fed by a DC chopper using the concept of Finite Control Set-Model Predictive Control (FCS-MPC). As this control algorithm requires the parameters of the controlled object, the estimation of motor parameters is first performed by using two types of data. The first data includes the output speed response corresponding to the step input voltage to obtain the transfer function in the no-load regime. The second data consists of the motor speed and armature current when a load torque is applied to the motor shaft. The discrete-time equation of the motor armature circuit is used to obtain the future values of the armature circuit current and the motor speed. A cost function is defined based on the difference between the reference and predicted motor speed. The optimal switching states of the DC chopper are selected corresponding to the maximum value of the cost function. The performance of the proposed speed control algorithm is validated on an experimental system. The simulation and experimental results obtained show that the MPC controller can outperform the conventional proportional-integral (PI) controller

Impact of Agency Costs on Firm Performance: Evidence from Vietnam

An assumption in agency costs theory is that agency costs can exert a negative impact on firm performance. In this study, we examine the impact of agency costs on firm performance of Vietnamese listed companies. Our sample includes 736 companies in Vietnam during the period om 2010 to 2015. We find that agency costs exert a negative impact on firm performance. Our results are robust to alternative econometric models, including an instrumental variables technique and a system generalized method of moment model. In addition, we show that a debt instrument can be a useful tool to reduce the negative impact of agency costs on firm performance

Simulation of proton-induced and iron-induced extensive air showers at extreme energies

The development of extensive air showers at extreme energies is studied using a simulation model much simpler and cruder, but also more transparent and flexible, than existing sophisticated codes. Evidence for its satisfactory performance is presented. As an illustration, shower elongation rates are evaluated in the $10^{18}$ to $10^{20}$ eV region and compared with recently published data. Lateral distribution functions of both muons and electrons/photons are also briefly discussed. Reliable results are obtained in the comparison between proton-induced and iron-induced showers.Comment: 22 pages, Preprint submitted to Astroparticle Physic

THE VIEWS OF SOME ECONOMIC THEORIES ON THE ECONOMIC CRISIS OF CAPITALISM AND SOME LESSONS FOR VIETNAM

After a brief analysis of the views presented in the economic theories of neo-liberalism, Keynes and Marx on the economic crisis of capitalism the authors of this article point out some methodological recommendations for the development of socialistic-oriented market economy in Vietnam. The experience of dealing with the crisis shows the importance of upholding the advantages of socialist regime: the leadership of the Communist Party in appropriate policyguidelines, the role of the Government in its consistent implementation of its policies, the role of the state's economic sector in sustaining the stability of the whole economy as well as in economic recovery, the contribution and support by the people for the common cause of development of Vietnam

Experiment-based Comparative Analysis of Nonlinear Speed Control Methods for Induction Motors

Field-oriented control (FOC) for induction motors is widely used in industrial applications. By using a fast and accurate torque controller based on a stator current controller it is possible to flexibly implement advanced speed control methods to achieve proper performance both in transient and steady-state states. In this study, a deadbeat controller was used for the current loop. The nonlinear methods used for the outer loop controller were backstepping, flatness-based control, and exact feedback linearization with state derivative. The dynamic responses of these three controls were compared through various experimental results. The advantages and disadvantages of the different control structures were analyzed and evaluated in detail. Based on this evaluation, an appropriate scheme can be specified when deployed in practice