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Pourak T.,King Mongkuts University of Technology Thonburi | Suwanjan P.,King Mongkuts University of Technology Thonburi | Jaikla W.,King Mongkuts University of Technology Thonburi | Maneewan S.,Buriram Rajabhat University
2012 IEEE International Conference on Electron Devices and Solid State Circuit, EDSSC 2012

The voltage-mode quadrature sinusoidal oscillator using single voltage differencing tranconductance amplifier (VDTA) and grounded elements is presented. The proposed oscillator can provide 2 sinusoidal output voltages with 90° phase difference. The condition of oscillation (CO) and frequency of oscillation can be electronically/orthogonally controlled by adjusting the bias current of the VDTA. The use of only grounded elements is ideal for integration. The PSpice simulation results are depicted. The given results agree well with the theoretical anticipation. © 2012 IEEE. Source

Uthitsunthorn D.,Suranaree University of Technology | Uthitsunthorn D.,Buriram Rajabhat University | Kulworawanichpong T.,Suranaree University of Technology
International Review of Electrical Engineering

This paper presents optimal coordination of over-current relays by using improved harmony search method (IHS). The objective function of the relay coordination problem is to minimize the operation time of associated relays for given fault conditions in the protection system. The control variables used in this paper are the pickup current and the time dial setting of the relays. The proposed method was tested with 5-bus, WSCC 9-bus and standard IEEE 14-bus test systems. For benchmarking, sequential quadratic programming (SQP) and genetic algorithm (GA) were employed to solve this optimal relay coordination problem. The results showed that the IHS is capable to minimize the operation time of relays in the entire system. As a result, all search algorithms can solve optimal coordination relay which the improved harmony search method gives the best solutions for optimal coordination relay setting. © 2012 Praise Worthy Prize S.r.l. - All rights reserved. Source

Maneewan S.,Buriram Rajabhat University | Udorn N.,Nakhon Phanom University | Duangmalai D.,Nakhon Phanom University | Silapan P.,Uttaradit Rajabhat University | Jaikla W.,King Mongkuts University of Technology Thonburi
Advances in Electrical and Electronic Engineering

This article presents a new voltage-mode first order allpass filter (APF) employing voltage differencing transconductance amplifier (VDTA). The advantages of the circuit are that: the circuit description is very compact, consists of merely a VDTA and a capacitor: the phase shift can be electronically adjusted by current bias: it provides the lower THD of the output signal. Without any component matching conditions, the proposed circuit is very appropriate to further develop into an integrated circuit. Moreover, the proposed APF can provide the output current with high output impedance without modification of the circuit topology. The PSpice simulation results are depicted. The given results agree well with the theoretical anticipation. The maximum power consumption is 400μ W at ±1.25V power supplies. © 2014 Advances in electrical and electronic engineering. Source

Seemakram W.,Khon Kaen University | Boonrung S.,Buriram Rajabhat University | Katekaew S.,Khon Kaen University | Aimi T.,Tottori University | Boonlue S.,Khon Kaen University

A low molecular weight alkaline xylanase from Neosartorya tatenoi KKU-CLB-3-2-4-1 was purified to homogeneity by ammonium sulfate precipitation, Sephadex G-100 and DEAE-cellulose column chromatography. The xylanase was purified 32.09 fold, with the specific activity of 16.07 U mg-1 protein and a recovery yield of 2.67%. The purified xylanase was estimated by SDS-PAGE with a molecular weight of 20 kDa. The purified xylanase was active at pH 10.0 and retained over 75% of the original activity in pH range 7.0-11.0 after incubation at 4 °C for 24 h. The optimum temperature of the purified xylanase was 45 °C. As for thermo-stability, more than 80% of original xylanase activity was retained after heating at 45 °C for 120 min. Xylanase activity was stimulated by Ag+ and inhibited by Hg2+. The purified xylanase was specific to beechwood xylan, birchwood xylan and oat spelt xylan. The Km and Vmax values for beechwood xylan were 10.34 mg/mL and 45.66 μmol/min/mg, respectively. In addition, the xylanase hydrolyzed beechwood xylan yielded mainly xylotriose and xylotetraose as end products, suggesting it was an endo-xylanase. Thus, its properties may make it attractive for application in the pulp and paper industry. © 2016 The Mycological Society of Japan. Source

Uthitsunthorn D.,Buriram Rajabhat University | Kulworawanichpong T.,Suranaree University of Technology
Asia-Pacific Power and Energy Engineering Conference, APPEEC

This paper presents a conceptual design of multi-agent for adaptive over-current relay coordination. In some temporary circumstances e.g. line outage, connecting a new or existing generator, etc., may lead to mal-operation of pre-coordinated protective devices in power systems. The set of protective relays must be enhanced with ability of adaptation in such a way that their parameter setting is adjusted. The multi-agent system proposed here is to develop optimal relay coordination adaptively according to environment changes. In this paper, Java Agent Development (JADE) software package was used for implementing the proposed multi-agent system. The communication process and data transfer can be simulated and monitored by using the sniffer agent GUI that helps us to confirm the use of multi-agent systems for an application of adaptive relay coordination. The 6-bus test power system was used for test. The results showed that the use of the multi-agent system is very useful in adaptive over-current relay coordination. © 2012 IEEE. Source

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