Agro-photovoltaics (APV) could be the optimal means of sustainable development in agricultural areas once a few challenges are overcome, perhaps the greatest of which is the constant shading from AVP structures. This study examined how the growth and yield of rice, potato, sesame, and soybean crops could be optimized when grown underneath different APV systems. The solar radiation, shading levels, and temperatures during crop cultivation were measured. In addition, the photosynthetic efficiency was measured at different growth stages. Adjacent to the APV systems were the control plots with full sun. In these studies with potato crops grown under APV systems, most growth and yield parameters were similar to those grown in the control plot except for the plant height. On the other hand, sesame crops grown underneath the APV systems had a lower stem length, effective branching number, 1000 seed weight, and a reduced yield of 19% compared to the crops from the control plot. In two distant locations (Paju and Youngkwang), soybean crops grown underneath APV systems at both sites showed increased ungrained ratios per pod and a reduced yield of 18–20% compared to the control plot. Finally, rice crops cultivated underneath the APV systems had a lower panicle number per hill, spikelet number per panicle, 1000 seed weight, and yield reduction of 13–30% compared to the control plot. Overall, crops grown underneath the APV systems had a greater plant height and stem length. Moreover, the solar radiation and PAR underneath the APV systems were also lower than in the control plots. The photosynthetic efficacy in rice plants grown underneath the APV systems was lower than in the control plots. The photosynthetic efficacy may help lower the crop yield when cultivation is underneath an APV system.
This study examined the growth promotion effects of selected water extracts on Peucedanum japonicum. As secondary considerations, the mineral nutrition levels were measured in both the extracts and the test plant. In addition, the levels of chlorophyll and the photosynthetic efficiency in the test plant were analyzed after the treatment of selected plant extracts. Finally, the total phenol, flavonoid contents, and DPPH (2,2′-diphenyl-1-picrylhydrazyl) radical scavenging activity in Peucedanum japonicum leaves were determined after the extract treatments. The shoot fresh weight of Peucedanum japonicum increased in response to all the extracts used, and in some cases increased at rates of 16–49% after extract treatments. Compared to the control, the photosynthetic efficiency and chlorophyll content of the Peucedanum japonicum plants did not vary significantly. In measuring the macro and microelements in the extracts, those with the highest levels were not necessarily the most effective growth promotors of Peucedanum japonicum plants. However, nutrition levels increased significantly in Peucedanum japonicum leaves after extract treatments. The total phenol contents in the Peucedanum japonicum leaves increased significantly when treated with the soybean stem extracts at 3%, Chinese chive extract at 0.5–3%, onion extract at 0.5%, or tomato extract at 3%. The total flavonoid contents in the Peucedanum japonicum leaves treated with the soybean leaf extracts at 0.5 to 3% increased by 23–36% compared to the control, but there were no differences with other extracts. Thus, the plant extracts tested in this study showed improved growth promotion, mineral contents, total phenol, total flavonoid contents, and DPPH radical scavenging activity.
This study examined the effects of changes to application methods, application time, and combinations of different extracts on the growth and yield of cucumbers. Chlorophyll and photosynthetic efficiency levels in cucumber plants were also measured after receiving treatments of selected liquid fertilizers. Mineral nutrition levels in both extracts themselves and the test plants were measured. Crude protein, crude fat, ash, total phenol and flavonoid contents, and DPPH radical scavenging activity in cucumber were determined. Cucumber plant height and shoot fresh weight at 7 and 14 days after treatments generally increased significantly regardless of the extraction methods or extract materials. On the other hand, cucumber leaf number was similar regardless of the extracts used. The application frequency effects differed according to the extraction methods, extracts, and parameters investigated. In addition, the combinations of extracts did not produce significant increases in cucumber plant growth. Cucumber fruit weight was 17–81%, 10–61%, and 10–45% higher than the control or oil cake when the plants were treated with fermentation, boiled water, and water extracts, respectively. The chlorophyll content and photosynthetic efficiency of cucumber plants treated with various extracts did not vary significantly. Extracts with the highest mineral nutrients were not effective growth promotors of cucumber plants. This means that growth promotion may not be caused by high levels of one specific macro or micro element but by some specific combinations of various elements. Compared to the control, most elements in the cucumber leaves decreased significantly when treated with most of the extracts. Generally, crude protein, crude fat, and ash contents were not negatively affected by the extract treatments. Moreover, most of the extracts did not adversely affect total phenol and flavonoid contents and DPPH radical scavenging activity. Thus, these extracts may be used for growth promotion without negative effects to primary and secondary substances in organically cultivated crop fields.
A feasibility study on microstructure design has been carried out to improve creep rupture life in alumina-forming austenitic (AFA) Fe-14Cr-20Ni-2.3Al stainless steel with and without 2 wt% W addition. After creep tests under 780 ˚C/80 MPa conditions, it was observed that internal cracks initiated primarily from grain boundaries in the W-free steel while voids nucleating at primary coarse NbC carbides elongated into fractures in the Wadded steel. This result indicates that the W addition shifts the fracture mode from intergranular to transgranular. Based on this observation, the fine intragranular NbC carbides, which need to precipitate as much as possible during the initial stage of creep, can be a promising metallurgical factor for enhancing the creep resistance of both the AFA steels. Cold work at 5% strain prior to creep accelerated the heterogeneous precipitation of nano-sized intragranular NbC during the early stage of creep, which was responsible for the strong hardening effect by pinning the dislocations. The creep life was found to be 3 times longer as compared to the unpre-strained AFA steels. Applying 5% cold work induces the generation of dislocations in the matrix, which can lead to the nucleation of nano-scale NbC without recrystallization. The intragranular NbC carbide showed excellent resistance to coarsening during creep: their size was as small as around 30 nm after creep rupture. † (
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