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Two New C-Glucosyl Benzoic Acids and Flavonoids from Mallotus nanus and Their Antioxidant Activity
Phan Van Kiem,Nguyen Thi Mai,Chau Van Minh,Nguyen Huu Khoi,Nguyen Hai Dang,Nguyen Phuong Thao,Nguyen Xuan Cuong,Nguyen Hoai Nam,Nguyen Xuan Nhiem,Yvan Vander Heyden,Joëlle Quetin-Leclercq,김교남,장해동,김영호 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.2
Two new 2-C-β-D-glucopyranosyl benzoic acid derivatives named mallonanosides A (1) and B (2) were isolated from the methanolic extract of the leaves of Mallotus nanus along with five known flavonoids, kaempferin (3), juglanin (4), quercitrin (5), myricitrin (6), and rhoifolin (7). Their structures were established on the basis of spectral and chemical evidence. Their antioxidant activities were shown to depend on the number of hydroxyl groups, and the location and species of sugar moiety.
New Technique for the Synthesis of Carbon Nanotubes
Phan Ngoc Minh,Phan Hong Khoi,Nguyen Van Chuc,Phan Ngoc Hong,Ngo Thi Thanh Tam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
Carbon nanotubes (CNTs) are considered as a promising material for various applications. However, due to their limited availability and high purchasing costs, at the present time, only a few of these applications have been realized. The realization of CNT-based devices and CNT-based materials depends on success in material synthesis and on the possibility of controlling the nanotube's chirality, diameter and purity. This paper describes new simple techniques for (i) synthesis of vertically-aligned carbon nanotubes (VA-CNTs), (ii) mass and low-cost production of multiwall carbon nanotubes (MWCNTs) and (iii) growth of individual CNTs on tungsten tips.
Synthesis of Carbon Nanotubes on Steel Foils
Nguyen Van Chuc,Nguyen Duc Dung,Phan Ngoc Hong,Le Dinh Quang,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost. Carbon nanotubes (CNTs) were synthesized by using a thermal chemical vapor deposition (CVD) at 800 ℃ in a mixture of C₂H₂, H₂ and N₂ gases with steel foils as both catalysts and substrates. More than 2 grams of CNTs were grown on approximately 7 grams of steel foil with a 0.5 cm² surface area after 30 minutes of growth. The effects of CVD parameters, such as the growth temperature and the deposition time, on the size and the morphology of the CNTs were studied using scanning electron microscopy (SEM). We found that the optimized temperature and growth time for having high quality CNTs were 800 ℃ and 30 minutes, respectively. The purity of the CNTs was evaluated by using thermogravimetric analysis (TGA) and the result showed that the carbon content was approximately 93 wt.%. The graphite crystallinity of the CNTs was analyzed by using Raman spectroscopy. The steel foil was found to maintain its catalytic behavior after several growths. The technique holds great promise for use in mass production (approximately 120 grams CNTs per day) with signicantly reduced cost.
Hedge-Algebras-Based Controller for Mechanisms of Relative Manipulation
Phan Bui Khoi,NGUYEN VAN TOAN 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.3
Mechanisms of relative manipulation (MRM robot) has become an interesting topic in recent years which aims to enhance the flexibility and the accuracy in mechanical manufacturing processes. However, the identification of exactly dynamical equations of MRM robot is tough and time-consuming; and the modeling error is inevitable. It is difficult to control MRM robot via vector algorithms since these methods require exactly dynamical equations of control systems. To this end, advanced controllers based on the inference mechanism of fuzzy logic are presented to overcome above problems. Unfortunately, the order relationships between the linguistic terms must be utilized by human experts when building the fuzzy-rule-base of fuzzy controller because there is no formalized liaison of the fuzzy sets with the natural linguistic term semantics. This paper proposes an alternative solution for controlling MRM robot that based on a bilinear-hedge-algebra approach. To our best knowledge, a controller based on such algebraic approach is firstly considered for application in robotics. The proposed method discovers order-based semantic relationships of terms and term-domains. Besides, the normalization, denormalization and composition operators of the fuzzy logic are eliminated. The proposed controller is evaluated by conducting a welding task using a two-component mechanism.
Nguyen Van Toan,Phan Bui Khoi 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11
In recent years, a great deal of research is conducted to improve the accuracy of manipulator kinematic calibration of which the product of exponential formula (PoE) is used to represent the manipulator kinematics, whose purpose is to solve the singularity problem of the Denavit-Hartenberg (D-H) parameters. However, the noise sensibility is still an open problem since a matrix inverse calculation of Jacobian matrix is inevitable during the process of solving the kinematic-linearized-equations to obtain the calibrated parameters. This problem may causes non-convergence, or low-accurate solution of calibration algorithm if the environmental noises and the error of endeffector’s actual frame measurement techniques are considerable. This paper presents a kinematic calibration method using singular value decomposition least square algorithm based on the product of exponentials formula (SVD-PoE-least-squares algorithm) to improve the accuracy of calibrated parameters. The proposed algorithm is evaluated in simulation level using a 6-DOF puma 560-type manipulator. The obtained results have shown that SVD-PoE-least-square algorithm is insignificantly affected by environmental noises, and, the proposed method can complete the robot calibration with respect to the work frame directly.
Bui Hung Thang,Pham Van Trinh,Le Dinh Quang,Nguyen Thi Huong,Phan Hong Khoi,Phan Ngoc Minh 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.3
Carbon nanotubes (CNTs) are some of the most valuable materials with high thermal conductivity. The thermal conductivity of individual multiwalled carbon nanotubes (MWCNTs) grown byusing chemical vapor deposition is 600 ± 100 Wm−1K−1 compared with the thermal conductivity419 Wm−1K−1 of Ag. Carbon-nanotube-based liquids – a new class of nanomaterials, have shownmany interesting properties and distinctive features offering potential in heat dissipation applicationsfor electronic devices, such as computer microprocessor, high power LED, etc. In this work,a multiwalled carbon-nanotube-based liquid was made of well-dispersed hydroxyl-functional multiwalledcarbon nanotubes (MWCNT-OH) in ethylene glycol (EG)/distilled water (DW) solutionsby using Tween-80 surfactant and an ultrasonication method. The concentration of MWCNT-OHin EG/DW solutions ranged from 0.1 to 1.2 gram/liter. The dispersion of the MWCNT-OH-basedEG/DW solutions was evaluated by using a Zeta-Sizer analyzer. The MWCNT-OH-based EG/DWsolutions were used as coolants in the liquid cooling system for the Intel Core i5 processor. Thethermal dissipation efficiency and the thermal response of the system were evaluated by directlymeasuring the temperature of the micro-processor using the Core Temp software and the temperaturesensors built inside the micro-processor. The results confirmed the advantages of CNTs inthermal dissipation systems for computer processors and other high-power electronic devices.