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Jaikla W.,King Mongkuts University of Technology Thonburi | Noppakarn A.,Thonburi University | Lawanwisut S.,Thepsatri Rajabhat University
Radioengineering | Year: 2012

New first order allpass filter (APF) in current mode, constructed from 2 CCCCTAs and grounded capacitor, is presented. The current gain and phase shift can be electronically/orthogonally controlled. Low input and high output impedances are achieved which make the circuit to be easily cascaded to the current-mode circuit without additional current buffers. The operation of the proposed filter has been verified through simulation results which confirm the theoretical analysis. The application example as current-mode quadrature oscillator with noninteractive current control for both of oscillation condition and oscillation frequency is included to show the usability of the proposed filter. Source


Saripan A.F.,Thepsatri Rajabhat University | Reungsang A.,Khon Kaen University
International Journal of Hydrogen Energy | Year: 2013

Thermophilic hydrogen production from xylan by Thermoanaerobacterium thermosaccharolyticum KKU-ED1 isolated from elephant dung was investigated using batch fermentation. The optimum conditions for hydrogen production from xylan by the strain KKU-ED1 were an initial pH of 7.0, temperature of 55 °C and xylan concentration of 15 g/L. Under the optimum conditions, the hydrogen yield (HY), hydrogen production rate (HPR) and xylanase activity were 120.05 ± 15.07 mL H2/g xylan, 11.53 ± 0.19 mL H2/L h and 0.41 units/mL, respectively. The optimum conditions were then used to produce hydrogen from 62.5 g/L sugarcane bagasse (SCB) (equivalent to 15 g/L xylan) in which the HY and HPR of 1.39 ± 0.10 mL H2/g SCB (5.77 ± 0.41 mL H2/g xylan) and 0.66 ± 0.04 mL H2/L h, respectively, were achieved. In comparison to the other strains, the HY of the strain KKU-ED1 (120.05 ± 15.07 mL H2/g xylan) was close to that of Clostridium sp. strain X53 (125.40 mL H2/g xylan) and Clostridium butyricum CGS5 (90.70 mL H2/g xylan hydrolysate). Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source


Saripan A.F.,Thepsatri Rajabhat University | Reungsang A.,Khon Kaen University
International Journal of Green Energy | Year: 2015

Thermophilic bio-hydrogen production from xylan by anaerobic mixed cultures in elephant dung was conducted. The initial pH, temperature, and xylan concentration of 7.0, 55°C and 3.0 g/L, respectively, gave a respective maximum hydrogen yield (HY) and hydrogen production rate (HPR) of 12.16 mmol H2/g xylan and 61.30 mL H2/L.d. The optimum conditions were used to produce hydrogen from sugarcane bagasse (SCB) in which an HY of 2.60 mmol H2/g SCB and a HPR of 59.78 mL H2/L.d were obtained. The hydrogen producers present in both xylan and SCB fermentation broth were Thermoanaerobacterium thermosaccharolyticum and Clostridium sp. Copyright © 2015 Taylor & Francis Group, LLC. Source


Saripan A.F.,Thepsatri Rajabhat University | Reungsang A.,Khon Kaen University
Electronic Journal of Biotechnology | Year: 2013

Background: Biological hydrogen production by microorganisms can be divided into two main categories i.e. photosynthetic organisms that produce hydrogen using light as energy source and anaerobic bacteria that produce hydrogen via dark fermentation. Dark fermentative hydrogen production by anaerobic bacteria has the advantages of a higher HPR without illumination and of the capability to convert various kinds of substrate. Results: Thermophilic hydrogen producer was isolated from elephant dung and identified as Thermoanaerobacterium thermosaccharolyticum KKU-ED1 by 16S rRNA gene analysis, which was further used to produce hydrogen from mixed pentose sugar i.e., xylose/arabinose. The optimum conditions for hydrogen production from mixed xylose/arabinose by KKU-ED1 were a 1:1 xylose/arabinose mixture at the total concentration of 5 g/L, initial pH of 6.5 and temperature of 55°C. Under the optimum conditions, hydrogen from sugar derived from acid-hydrolyzed sugarcane bagasse at a reducing sugar concentration were achieved. Soluble metabolite product (SMP) was predominantly acetic acid indicating the acetate-type fermentation. Conclusions: The strain KKU-ED1 appeared to be a suitable candidate for thermophilic fermentative hydrogen production from hemicellulosic fraction of lignocellulosic materials due to its ability to use various types of carbon sources. © 2013 by Pontificia Universidad Católica de Valparaíso, Chile. Source


Saripan A.F.,Thepsatri Rajabhat University | Saripan A.F.,Khon Kaen University | Reungsang A.,Khon Kaen University
International Journal of Hydrogen Energy | Year: 2014

The objective of this study was to optimize the culture conditions for simultaneous saccharification and fermentation (SSF) of cellulose for bio-hydrogen production by anaerobic mixed cultures in elephant dung under thermophilic temperature. Carboxymethyl cellulose (CMC) was used as the model substrate. The investigated parameters included initial pH, temperature and substrate concentration. The experimental results showed that maximum hydrogen yield (HY) and hydrogen production rate (HPR) of 7.22 ± 0.62 mmol H 2/g CMCadded and 73.4 ± 3.8 mL H2/L h, respectively, were achieved at an initial pH of 7.0, temperature of 55 °C and CMC concentration of 0.25 g/L. The optimum conditions were then used to produce hydrogen from the cellulose fraction of sugarcane bagasse (SCB) at a concentration of 0.40 g/L (equivalent to 0.25 g/L cellulose) in which an HY of 7.10 ± 3.22 mmol H2/g celluloseadded. The pre-dominant hydrogen producers analyzed by polymerase chain reaction-denaturing gel gradient electrophoresis (PCR-DGGE) were Thermoanaerobacterium thermosaccharolyticum and Clostridium sp. The lower HY obtained when the cellulose fraction of SCB was used as the substrate might be due to the presence of lignin in the SCB as well as the presence of Lactobacillus parabuchneri and Lactobacillus rhamnosus in the hydrogen fermentation broth. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

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