• Clean Technology
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• v.30 no.1
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• pp.47-54
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• 2024

Jatropha oil extracted from the seeds of Nepalese Jatropha curcas, a non-edible crop, was used as a raw material and converted to biodiesel through a two-step process consisting of an esterification reaction and a transesterification reaction. Amberlyst-15 catalyst was applied to the esterification reaction between the free fatty acids contained in the Jatropha oil and methanol. The acid value of the Jatropha oil could be lowered from 11.0 to 0.26 mgKOH/g through esterification. Biodiesel was synthesized through a transesterification reaction between Jatropha oil with an acid value of 0.26 mgKOH/g and methanol over NaOH/γ-Al₂O₃ catalysts. As the loading amount of NaOH increased from 3 to 25 wt%, the specific surface area decreased from 129 to 28 m²/g and the pore volume decreased from 0.249 to 0.129 cm³/g. The amount and intensity of base sites over the NaOH/γ-Al₂O₃ catalysts increased simultaneously with the NaOH loading amount. It was confirmed that the optimal NaOH loading amount for the NaOH/γ-Al₂O₃ catalyst was 12 wt%. The optimal temperature for the transesterification reaction of Jatropha oil using the NaOH/γ-Al₂O₃ catalyst was selected to be 65 ℃. In the transesterification reaction of Jatropha oil using the NaOH/γ-Al₂O₃ catalyst, the reaction rate was affected by external diffusion limitation when the stirring speed was below 150 RPM, however the external diffusion limitation was negligible at higher stirring speeds.

• Journal of Mushroom
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• v.17 no.4
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• pp.205-210
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• 2019

This study was conducted to elucidate the optimal nitrogen content for each variety of oyster mushroom (Pleurotus ostreatus) by investigating the change in the characteristics of fruiting body according to the nitrogen content of the sawdust media, and to use the results as the basic data for cultivation of high quality oyster mushroom. The nitrogen content was adjusted to 1.3%, 1.6%, 1.8% and 2.3%, and at each condition, mycelial growth was observed, which showed that the nitrogen content did not affect the rate of mycelial growth and density substantially. In the investigation of the characteristics of fruiting body, at the 1.8% nitrogen content, Chunchu No.2 showed the pileus diameter of 27 mm, and the stipe diameter and length of 11 mm and 61 mm, respectively, and the measurement of its color values revealed that the brightness of the pileus and the stipe was 31 and 80, respectively, offering the best commercial value, and yielding 25 valid stipes, which was the largest number. Likewise, at the 1.8% nitrogen content, Heuktari also showed the excellent growth characteristics including the pileus diameter of 29 mm and the stipe diameter and length of 10 mm and 68 mm, respectively, and the superb color values of the brightness of 37 at the pileus and 78 at the stipe. Moreover, the number of valid stipes was also found to be the highest with 19. In terms of morphological characteristics such as the pileus diameter and color, Soltari also produced the best mushrooms at the 1.8% nitrogen content and the number of valid stipes was high with 22. In summary, irrespective of varieties of oyster mushroom, high quality products could be cultivated at the nitrogen content of 1.8%.

• Korean Journal of Weed Science
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• v.16 no.2
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• pp.88-99
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• 1996

In recent years dry direct-seeding of rice has been encouraged by the government and increasingly practiced by farmers in Korea. This has been bringing up an increased occurrence of weedy rites. Some farmers in the southern region dare to sow the rice before winter after harvest, while most farmers wish to sow as early as possible in the spring to secure the growing period, and to disperse the intensive labor in early May. The purpose of this study was to determine the feasibility of moving the sowing of rice to an earlier date under dry direct-seeding, and to elucidate the nature of emergence of an old strain of rice, weedy rites, and barnyardgrasses tinder this farming practice and their adaptive competence over present cultivate. The presently recommended rice cultivar, Dongjinbyo and an old rice strain, Dadajo which prevailed in early 1900s, almost could not emerge from soil deeper than 6cm and could emerge to only 5.3% at best from 1cm deep loamy soil field when the seeds were sown on Nov. 28. However, two strains of weedy rites being weedy for over 200 years emerged by 17.0 to 63.0% from the loamy and sandy clay loam field 1 to 6cm deep. Emergence of the weedy rites was greater in the loamy soil and at a shallow depth, and negligible from the soil depth of 9cm. Barnyardgrasses sown on Nov. 28 emerged by 13.4 to 51 % from the 1 to 3cm deep loamy soil, and 8.6 to 46.7% from the 1cm deep sandy clay loam. Echinochloa crus-galli var. crus-galli emerged more than var. praticola, and var. oryzicola least. Most of the non-emerged barnyardgrasses seem to have entered secondary dormancy. Seeding rice a month earlier than the season lowered the emergence of Dongjinbyo by ca. 10, 18, and 26%, respectively at 1, 3, and 6cm soil depths, indicating that moving the seeding date a month earlier is impractical. The old strain, Dadajo sown in the soil at a depth of 6cm responded similarly. However, the strain has shown a significantly higher ability in emergence from 9cm deep soil. Weedy rices sown a month earlier A month earlier sown weedy rices have shown very similar emergence rates at various soil depths to those sown on May 1. Barnyardgrasses have also shown similar emergence rates when sown between April 3 and May 1. Like barnyardgrasses, the old strain and weedy rices apparantly posessed a greater adaptability to emerge under lower temperatures, and from deeper soil ; Dongjinbyo${\leq}$ Echinochloa species in that order. However, emergence- speed under lower temperature(sown on April 3) was faster in the order of weedy rice