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Backstepping Sliding Mode-based Model-free Control of Electro-hydraulic Systems
Hoai Vu Anh Truong,TRINH HOAI AN,안경관 사단법인 유공압건설기계학회 2022 드라이브·컨트롤 Vol.19 No.1
This paper presents a model-free system based on a framework of a backstepping sliding mode control (BSMC) with a radial basis function neural network (RBFNN) and adaptive mechanism for electro-hydraulic systems (EHSs). First, an EHS mathematical model was dedicatedly derived to understand the system behavior. Based on the system structure, BSMC was employed to satisfy the output performance. Due to the highly nonlinear characteristics and the presence of parametric uncertainties, a model-free approximator based on an RBFNN was developed to compensate for the EHS dynamics, thus addressing the difficulty in the requirement of system information. Adaptive laws based on the actor-critic neural network (ACNN) were implemented to suppress the existing error in the approximation and satisfy system qualification. The stability of the closed-loop system was theoretically proven by the Lyapunov function. To evaluate the effectiveness of the proposed algorithm, proportional-integrated-derivative (PID) and improved PID with ACNN (ACPID), which are considered two complete model-free methods, and adaptive backstepping sliding mode control, considered an ideal model-based method with the same adaptive laws, were used as two benchmark control strategies in a comparative simulation. The simulated results validated the superiority of the proposed algorithm in achieving nearly the same performance as the ideal adaptive BSMC.
Hoai-An Trinh,Hoai Vu Anh Truong,Minh-Duc Pham,Tri Cuong Do,Hong-Hee Lee,Kyoung Kwan Ahn 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.2
Using renewable energy is becoming a new tendency for vehicular applications to reduce fossil fuel consumption and minimize greenhouse gas emissions. Well-known as an eco-friendly energy source, the proton exchange membrane fuel cell (PEMFC) is extensively used in hybrid power systems to achieve the objective of zero-emission and air protection. However, this type of fuel cell offers slow dynamics and cannot adapt to abrupt load variations when used as a primary energy source. To overcome this shortcoming, battery (BAT) and/or supercapacitor (SC) are supplemented as auxiliary sources. In this paper, an innovative energy management strategy (EMS) for a PEMFC/BAT/SC hybrid power source (HPS) is proposed to improve the accuracy of power distribution from energy sources to the load. In detail, according to different characteristics of energy sources, a frequency decoupling (FD) method is designed to determine the required currents for PEMFC, BAT, and SC based on the load power demand. Besides, an adaptive DC bus control loop is utilized to guarantee a stable DC output voltage by using the BAT. The proposed EMS is simulated in a MATLAB/Simulink environment and experimentally implemented with a real-time DSP TMS320F28379D controller board. Subsequently, a test bench of a 200 W PEMFC, 24 V–12 Ah battery, and 25 V–60 F supercapacitor is conducted for experimental validation. The obtained results show that the proposed EMS is effective to coordinate energy flows between the three used sources and enhance the fuel cell performance in a hybrid power system.
The Root Causes of Rural Tourism Development Intentions in Vietnam:A Local Government Perspective
Hoai Than Nguyen,Tan Thanh Nguyen,Thi Thanh Truc Nguyen,Tan Hai Nguyen 영남대학교 박정희새마을연구원 2023 새마을학연구 Vol.8 No.1
Rural tourism has gained popularity in Vietnam, attracting more tourists, particularly foreigners and urban visitors. Despite the attention it receives from the central government, rural tourism development faces challenges, including the perceptions of local civil servants. This study combines the theories of planned behavior and organizational support theory to propose a model predicting the intention of local civil servants to develop rural tourism. A quantitative approach was used, with a questionnaire survey distributed to 405 local civil servants participating in training programs. The findings indicate that factors from both theories positively and significantly influence the intention of rural tourism development. Notably, perceived leader support directly impacts intention and moderates the relationship between perceived government support and intention. Despite its limited practical performance, the study emphasizes the importance of attitude toward rural tourism development. The research provides implications for academics, government, and policymakers to enhance local civil servants' intention for future rural tourism development.
Geometric corrections for sonar images
Hoai-Nam Ho,이종재,박철,조병완 한국구조물진단유지관리학회 2012 한국구조물진단학회 학술발표회논문집 Vol.2012 No.1
This study introduces an algorithm for geometric distortion corrections in sonar images. The proposed algorithm mainly consists of two stages. At the first stage, the raw images are processed with median filter and Frost filter for noise reduction and intensity enhancement. In the last stage, the geometric distortion correction is conducted using angular information given by a gyro sensor. The algorithm was successfully applied on raw sonar data collected on a pier survey.
Solvent Extraction of Tungsten(VI) from Moderate Hydrochloric Acid Solutions with LIX 63
Hoai Thanh Truong,김용환,이만승 대한금속·재료학회 2017 대한금속·재료학회지 Vol.55 No.6
The solvent extraction of tungsten(VI) from hydrochloric acid solutions using 5,8-diethyl- 7-hydroxydodecan-6-one oxime (LIX 63) was analyzed in solutions having an initial pH range from 2 to 5, by varying the concentration of metal and extractant. In our experimental range, the cationic exchange reaction as well as the solvation reaction occurred simultaneously. The cation exchange reaction was identified by applying a slope analysis method to the extraction data. The existence of cationic tungsten(VI) species was confirmed by ion exchange experiments with Diphonix resin at pH 3. Further study is needed to identify the nature of this tungsten cationic species.
Hoai Bac Nguyen,이신영,박수현,이무열,장인호,명순철 대한비뇨의학회 2013 Investigative and Clinical Urology Vol.54 No.5
Purpose: The location of acetylcholinesterase-containing nerve fibers suggests a role for acetylcholine in both contractility and secretion in the prostate gland. The colocalization of nitrergic nerves with cholinergic nerves, and the cotransmission of nitric oxide with acetylcholine in cholinergic nerves, has been demonstrated in the prostate glands of various species. Thus, we investigated the effects of acetylcholine on phenylephrine-induced contraction and the correlation between cholinergic transmission and nitric oxide synthase by using isolated prostate strips of rabbits. Materials and Methods: Isolated prostate strips were contracted with phenylephrine and then treated with cumulative concentrations of acetylcholine. Changes in acetylcholine-induced relaxation after preincubation with NG-nitroarginine methyl ester,7-nitroindazole, and aminoguanidine were measured. The effects of selective muscarinic receptor antagonists were also evaluated. Results: In the longitudinal phenylephrine-contracted strip, the cumulative application of acetylcholine (10-9 to 10-4 M) elicited a concentration-dependent relaxation effect. Acetylcholine-induced relaxation was inhibited not only by nitric oxide synthase inhibitors (10 μM L-NAME or 10 μM 7-nitroindazole) but also by 10 μM atropine and some selective muscarinic receptor antagonists (10-6 M 11-([2-[(diethylamino)methyl]-1-piperdinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one and 10-6M 4-diphenylacetoxy-N-methyl-piperidine). In contrast, relaxation was significantly increased by pretreatment of the strips with 10 mM L-arginine. Conclusions: Acetylcholine relaxed phenylephrine-induced contractions of isolated rabbit prostate strips. This relaxation may be mediated via both cholinergic and constitutive nitric oxide synthase with both the M2 and M3 receptors possibly playing key roles.
Hoai Nam NGUYEN,김회수,Yoonjeong JO,Kevin 한국교육공학회 2015 Educational Technology International Vol.16 No.1
The purpose of this research is to propose a novel social LMS developed for group collaborative learning with a think-aloud tool integrated for sharing cognitive processes in order to improve group collaborative learning performance. In this developmental research, the system was designed with three critical elements: the think-aloud element supports learners through shared cognition, the social network element improves the quality of collaborative learning by forming a structured social environment, and the learning management element provides a understructure for collaborative learning for student groups. Moreover, the three critical elements were combined in an educational context and applied in three directions.