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Wanno B.,Mahasarakham University | Tabtimsai C.,Rajabhat Maha Sarakham University
Superlattices and Microstructures | Year: 2014

Adsorptions of CO on pristine, Fe-, Ru-, Os-, Co-, Rh-, Ir-, Ni-, Pd-, and Pt-doped graphene were investigated, using density functional theory calculation at B3LYP/LanL2DZ theoretical level. This work revealed that the transition metal doped graphenes were more highly sensitive to CO adsorption than that of pristine graphene. The Os- and Fe-doped graphenes displayed the strongest interaction with C and O atoms of CO molecule, respectively. © 2014 Elsevier Ltd. All rights reserved.

Martin J.E.,Rajabhat Maha Sarakham University | Gross M.,Universalmuseum Joanneum
Neues Jahrbuch fur Geologie und Palaontologie - Abhandlungen | Year: 2011

A re-examination of the original type series of PRANGNER (1845) and HOFMANN (1887a) of the primitive alligatoroids from the middle Miocene of Styria, led to a reappraisal of the taxonomy of the following species of Diplocynodon: D. steineri and D. styriacus. Of unsettled affinities, Enneodon ungeri was also re-examined. It is here demonstrated that it belongs to the same taxon of the specimens described by HOFMANN (1887a). These taxa are in fact junior synonyms of the previously erected Enneodon ungeri. Moreover, comparison with other European alligatoroids reveals that the Austrian specimens described by PRANGNER (1845) and HOFMANN (1887a) belong to the same genus: Diplocynodon POMEL, 1847. According to the rules of the International Commission on Zoological Nomenclature (ICZN), Diplocynodon has priority over Enneodon. Under the principle of priority, it is therefore proposed to rename all the Miocene remains of alligatoroids from Styria as Diplocynodon ungeri PRANGNER, 1845. Comparison of almost complete skulls from various Miocene contemporaneous localities reveals that there is no reason to erect another taxon for the French specimens of D. "styriacus" described in GINSBURG & BULOT (1997). However, these specimens need to be redefined as D. ungeri as well. D. ungeri was coded and included in a character matrix to cladistically test its affinities with other alligatoroids. A total of six species of Diplocynodon were analysed including: D. ratelii, D. hantoniensis, D. tormis, D. muelleri, D. darwini and D. ungeri. The results are consistent with previous studies and favour a monophyletic diplocynodontid clade. D. ungeri is the first species of the genus to be recognized from distant coeval European deposits, namely the Paris and the Pannonian Basins. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung Stuttgart Germany.

Phonphuak N.,Chiang Mai University | Phonphuak N.,Rajabhat Maha Sarakham University | Thiansem S.,Chiang Mai University
Construction and Building Materials | Year: 2012

The clay composite and production process of fired clay bricks are essential for the sustainability of clay bricks. The aim of this study was to investigate the physical and mechanical properties of fired test briquettes due to the effects of charcoal addition and firing temperature. Their characteristics were carried out with the determination by TGA/SDTA, XRF, XRD and SEM. The study yielded findings, namely, test briquettes consisting of 2.5% of charcoal additive with sizes less than 0.5 mm mixed with Hang Dong clay specimen and fired at 950 °C achieved the most desirable mechanical and physical properties of fired test briquettes because fired test briquettes were more durable, porous and stronger when compared with current commercial brick specimens that were tested. Thus, charcoal could be used as a pore former in clay body. Conclusively, the results revealed that charcoal could be regarded as a potential addition to raw materials used in the manufacturing of lightweight fired clay bricks. © 2011 Elsevier Ltd. All rights reserved.

Saraphirom P.,Rajabhat Maha Sarakham University | Saraphirom P.,Khon Kaen University | Reungsang A.,Khon Kaen University
International Journal of Hydrogen Energy | Year: 2010

This study employed statistically based experimental designs to optimize fermentation conditions for hydrogen production from sweet sorghum syrup by anaerobic mixed cultures. Initial screening of important factors influencing hydrogen production, i.e., total sugar, initial pH, nutrient solution, iron (II) sulphate (FeSO 4), peptone and sodium bicarbonate was conducted by the Plackett-Burman method. Results indicated that only FeSO 4 had statistically significant (P ≤ 0.005) influences on specific hydrogen production (P s) while total sugar and initial pH had an interdependent effect on P s. Optimal conditions for the maximal P s were 25 g/L total sugar, 4.75 initial pH and 1.45 g/L FeSO 4 in which P s of 6897 mL H 2/L was estimated. Estimated optimum conditions revealed only 0.04% difference from the actual P s of 6864 mL H 2/L which suggested that the optimal conditions obtained can be practically applied to produce hydrogen from sweet sorghum syrup with the least error. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

Saraphirom P.,Rajabhat Maha Sarakham University | Saraphirom P.,Khon Kaen University | Reungsang A.,Khon Kaen University
International Journal of Hydrogen Energy | Year: 2011

Continuous biological hydrogen production from sweet sorghum syrup by mixed cultures was investigated by using anaerobic sequencing batch reactor (ASBR). The ASBR was conducted based on the optimum condition obtained from batch experiment i.e. 25 g/L of total sugar concentration, 1.45 g/L of FeSO 4 and pH of 5.0. Feasibility of continuous hydrogen fermentation in ASBR operation at room temperature (30 ± 3 °C) with different hydraulic retention time (HRT) of 96, 48, 24 and 12 hr and cycle periods consisting of filling (20 min), settling (20 min), and decanting (20 min) phases was analyzed. Results showed that hydrogen content decreased with a reduction in HRT i.e. from 42.93% (96 hr HRT) to 21.06% (12 hr HRT). Decrease in HRT resulted in a decrease of solvents produced which was from 10.77 to 2.67 mg/L for acetone and 78.25 mg/L to zero for butanol at HRT of 96 hr-12 hr, respectively. HRT of 24 hr was the optimum condition for ASBR operation indicated by the maximum hydrogen yield of 0.68 mol H2/mol hexose. The microbial determination in DGGE analysis indicated that the well-known hydrogen producers Clostridia species were dominant in the reacting step. The presence of Sporolactobacillus sp. which could excrete the bacteriocins causing the adverse effect on hydrogen-producing bacteria might responsible for the low hydrogen content obtained. © 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Phonphuak N.,Rajabhat Maha Sarakham University | Kanyakam S.,Rajabhat Maha Sarakham University | Chindaprasirt P.,Khon Kaen University
Journal of Cleaner Production | Year: 2016

The aim of this study was to investigate the enhancement of physical-mechanical properties of fired clay brick by incorporating waste glass in order to reduce the firing temperature. The ground waste glass was incorporated to the clay body at the dosages of 0, 5 and 10% by weight. Three temperatures viz., 900, 950 and 1000 °C were used for firing. Compressive strength, water absorption, density, and porosity of the fired clay bricks were tested. The study showed that the incorporation of up to 10 wt.% of waste glass to clay bricks and fired at the temperatures of 900-1000 °C enhanced the properties of fired clay bricks. The SEM micrographs showed the increased glass phase and reduced porosity with waste glass addition. The use of 10 wt.% waste glass and firing at 900 °C yielded bricks with similar strength compared to that of normal clay brick fired at 1000 °C. This allowed the use of low firing temperature of 900 °C instead of the normally used 1000 °C. The study also revealed that in addition to the glass phase fused-bond with the clay brick bodies, the fusion of crystalline quartz in clay also played an important role in enhancing the properties of clay bricks. As a conclusion, waste glass can be utilized in making brick to enhance the physical-mechanical properties of the fired clay brick or to lower the firing temperature. © 2015 Elsevier Ltd. All rights reserved.

Pasanai K.,Rajabhat Maha Sarakham University
Journal of Magnetism and Magnetic Materials | Year: 2015

The tunneling conductance spectra of a magnetic tunnel junction between ferromagnet/superconductor/ferromagnet material interfaces were theoretically studied using the scattering approach in a two dimensional system. As the main area of interest, the interfacial scattering at the two interfaces was modeled by Dirac delta potentials and set to be unequal in their values to verify which potential was more sensitive to the conductance spectra of the junctions. It was found that the conductance spectra in the region where the energy was less than the energy gap of the superconductor were sensitive to the potential strength at the first interface that is the incident side of an electron. When the electron was injected from different sides of the junctions, the conductance spectra of these two incident processes were different in magnitude in the case of asymmetric scattering potential. Particularly, the greater the different values of the two potential strengths, the larger the difference in the conductance spectra. This result can be used to identify the quality of a magnetic tunnel junction that is composed of a superconductor material. Moreover, the effect of the exchange energy and the superconducting thickness on the transport properties was analyzed. © 2015 Elsevier B.V. All rights reserved.

Pasanai K.,Rajabhat Maha Sarakham University
Journal of Magnetism and Magnetic Materials | Year: 2014

The electronic density of states (DOS) of ferromagnetic materials are theoretically studied within a two-band approach in one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) systems. In the two-band approximation, s-band and d-band coupling were considered. It has been found that if the coupling vanishes, the two bands can cross at some points in the energy spectra. When the coupling between bands is present, a gap is opened up at the corresponding point, thereby avoiding crossovers. The size of the gap depends on the size of the coupling strength. For any dimensionality, the DOS with no coupling behaves like a one-band model. When presenting the coupling strength, there is a change in the slope in the DOS, corresponding to those crossing points. In particular, this change is most prominent when the coupling strength is small and it almost disappears when the coupling strength is strong. With a large coupling strength, the energy band is extended. Finally, the measurable tunneling conductance spectra of a metal/ferromagnet junction within this approximation were clearly analyzed. © 2014 Elsevier B.V.

Pasanai K.,Rajabhat Maha Sarakham University
Journal of Magnetism and Magnetic Materials | Year: 2016

The tunneling conductance spectra of a ferromagnet/ferromagnet junction was theoretically studied under a scattering approach using two models of the interface: delta potential and finite width model in a one dimensional system. In the first model, the interface between the materials was characterized by the delta potential that has infinite height but no width. For the other model, the interface was modeled by an insulator with a finite thickness and potential barrier height. As a result, it was found that the potential strength under the delta potential model suppressed the conductance spectra as expected. In the finite width model, the insulating layer can give rise to an oscillation behavior when the layer is thick. This oscillation occurs in the region of the energy that is larger than the potential barrier. Moreover, the conductance spectra was suppressed by varying the insulating thickness, also depending on how high the potential barrier was. When the results from the two models were compared, they gave rise to the same result when the insulating layer was thin and the potential barrier was slightly larger than the energy of the bottom of the minority band of the ferromagnet. © 2015 Elsevier B.V. All rights reserved.

Pasanai K.,Rajabhat Maha Sarakham University
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2016

The tunneling conductance spectra of a ferromagnetic semimetal/metal junction, where there were electrons and holes with the same spin directions as the essential conducting particle, was theoretically studied based on a scattering approach in a ballistic regime. The main area of interest was to perform a high spin polarization by considering the effect of the interfacial scattering at the interface that was composed of normal and spin-flip scattering, the particle effective mass mismatch on the reflection and transmission probabilities, and spin polarization of conductance. It was found that the spin polarization of conductance decreased with increasing spin-flip scattering. Interestingly, the normal scattering can cause the spin polarization of the conductance to reach a maximum value in the presence of both kinds of scattering. When the particle effective mass mismatch was considered, the spin polarization of conductance was large when the electron effective mass in the valence band was smaller than that in the conduction band. However, in this calculation, the results of a ferromagnetic semimetal/metal junction behaved similarly to those of a ferromagnetic metal/metal junction. © 2015 Elsevier B.V.

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