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Hai Le Xuan,Quoc-Dong Hoang,Soon Geul Lee,Dat Pham Xuan,Hoang Tran Viet,Minh Pham Van,Hung Pham Van,Hung Pham Viet,PHAM DUC TUAN,Duc Anh Nguyen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2
Ballbots, which have been studied for over ten years, are under-actuated mobile robots that operate using the inverted pendulum paradigm. Controlling a ballbot poses a number of challenges, including maintaining the stable upright posture from the ground in all directions and making sure it follows the desired trajectory. External factors such as a minor change in contact surface properties or fabrication errors can affect the system's stabilization and transfer capabilities. In this study, an adaptive hierarchical sliding mode control algorithm based on an artificial neural network is developed to make the ballbot robust to external factors. The use of the proposed controller ensures system stability despite uncertainties including friction, accidental centrifugal forces and gravity that occur when the ballbot follows the reference trajectory. The system stability is guaranteed on the basis of Lyapunov theory. Control efficiency and robot stability under system uncertainties are demonstrated by numerical simulation.
Hai Dinh Pham,Sunwook Kim,Viet Hung Pham,Eun-Suok Oh,정진석 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.1
A highly conductive polypyrrole (PPy)-reduced graphene oxide (RGO) composite with an electrical conductivity of 610 S m−1 was successfully synthesized by the in-situ photopolymerization of pyrrole in a graphene oxide suspension. Graphene oxide (GO) played the role of an electron acceptor and was reduced as it accepted electrons. The reduction of GO was confirmed by the increase in the C/O ratio of RGO with the UV irradiation time as well as the high electrical conductivity of PPy-RGO composite. Through the thermogravimetric analysis, it has been found that the PPy-RGO composite exhibited high thermal stability compared to the GO and PPy. This material was used as an electrode in a supercapacitor cell and showed excellent performance for electrical energy storage. The composite exhibited a specific capacitance of 376 F g−1 at a scan rate of 25 mV s−1.
Hung Hai Pham,임영일,NGOICHSON,방윤혁 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.73 No.-
A three-dimensional computationalfluid dynamics (CFD) model with new permeability and off-gasemission equations was developed in a four-zone low-temperature furnace (LTF) for carbonfibercarbonization. Four performance criteria (residence time, dead-volume ratio, tow temperature standarddeviation, and tar formation area) were proposed to identify the optimal ratio between the two N2 flowrates introduced into the front and rear of LTF. A higher N2 flow rate at the front rather than at the rear waspreferred to reduce tar formation. The tar formation area calculated from carbon activity provides usefulguideline for determining optimal LTF design and operating conditions.
Pham, Hung Hai,Lim, Young-il,Ngo, Son Ich,Bang, Yun-Hyuk Elsevier 2019 Journal of industrial and engineering chemistry Vol.73 No.-
<P><B>Abstract</B></P> <P>A three-dimensional computational fluid dynamics (CFD) model with new permeability and off-gas emission equations was developed in a four-zone low-temperature furnace (LTF) for carbon fiber carbonization. Four performance criteria (residence time, dead-volume ratio, tow temperature standard deviation, and tar formation area) were proposed to identify the optimal ratio between the two N<SUB>2</SUB> flow rates introduced into the front and rear of LTF. A higher N<SUB>2</SUB> flow rate at the front rather than at the rear was preferred to reduce tar formation. The tar formation area calculated from carbon activity provides useful guideline for determining optimal LTF design and operating conditions.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
LiFePO4 nanoparticle and graphene Loaded carbon nanofibers for use of Lithium-ion battery cathodes
박준서,( Hung Hai Pham ) 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
LiFePO4/Graphene/C nanofibers, in which LiFePO4 nanoparticles were encapsulated in graphene-containing carbon nanofiber matrix, were synthesized by electrospinning. Graphene was used in order to increase the conductivity of the composite. Polyimide (PI) fabricated by first electrospinning of the pre-polymer, poly(amid acid) ammonium salt (PAAS) then imidizing the electrospun nanofiber was used as the electrospinning media and the carbon source. The morphology and microstructure of LiFePO4/Graphene/C nanofiber were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical performance of LiFePO4/Graphene/ C nanofibers was evaluated in coin-type cells. Both graphene and PI contribute to improve electrochemical performance of lithium batteries cathode sesulting in the enhancement of capacity and cycling ability.