• The KSFM Journal of Fluid Machinery
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• v.2 no.2 s.3
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• pp.27-31
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• 1999

This paper describes the shaft vibration phenomena measured on a pump-turbine of a pumped storage power plant. The pump-turbine runs at a rotational speed of 450 rpm (7.5 Hz). The power output (load) of the pump-turbine is varied from 100 to 300 MW in the generating mode. The magnitude of the shaft vibration highly depends on the power load. The vibration magnitude of the shaft is very high in the middle load zone from 170 to 210 MW, elsewhere the vibration is low. From nitration spectra, it is shown that the frequency of major nitration in that load zone is 2.5 Hz which is approximately $34\%$ of the shaft rotating speed in Hz. This frequency component does not occur below and above that load zone. This subsynchronous vibration is caused by the flow induced disturbance due to spiral vortex flow downstream of the pump-turbine runner. Furthermore, the shaft vibration is highly decreased due to an increased bearing preload.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.166-172
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• 1998

This paper describes the shaft vibration phenomena measured on a pump-turbine ofa pumped storage power plant. The pump-turbine runs at a rotational speed of 450 rpm (7.5 Hz). The power output (load) of the pump-turbine was varied from 100 to 300 MW in the generating mode. It was found that the magnitude of the shaft vibration was highly dependent upon the power load. The vibration magnitude of the shaft vibration is very high in the middle load zone from 170 to 210 MW, elsewhere the vibration low. From vibration spectra, it was found that the frequency of major vibration in that load zone was 2.5 Hz which is approximately $34\%$ of the shaft rotating speed in Hz. This frequency component disappeared below and above that load zone. This subsynchronous vibration is caused by the flow induced disturbance due to spiral vortex flow downstream of the pump-turbine runner. Furthermore, it was found that shaft vibration was highly decreased due to the increase of bearing preload.

• 전기의세계
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• v.13 no.3
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• pp.28-37
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• 1964

It is the intention of this thesis to discriminate and investigate the cause of the shaft vibration of the vertical type hydroelectric power generator with respect to electrical, mechanical and hydraulic aspects, and to analyze the vibration which will occure by the each cause investigated above. In order to test the shaft vibration of No.1 generator in Hwachon, Korea new measurement method and measuring equipments were designed. In practice the shaft vibration of the generator was measured by above equipments and analyzed by the discriminative method. Detailed explanation for the designed measurement method and instruments is presented, and the results which I had tested three times for the generator No.1 in Hwachon power plant are added. As a appendix the mechanism and causes of the thrust bearing's wear and remarks for the runner are written.

• Journal of agriculture & life science
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• v.45 no.4
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• pp.81-86
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• 2011

This study was conducted to evaluate the influence of crown diameter on plant growth after planting and fruit yield. All nursery plants were classified into three classes: A, > 9 mm; B, 8~9 mm; C, < 8 mm. The A-class nursery plant plot showed better root and plant growth after planting compared to the B-class and C-class nursery plants. The A-class nursery plant plot was 10 days faster in first flowering time then those of the B-class and the C-class. Also, the A-class nursery plant plot was 2~3 days faster in the mean flowering time. The accumulative yield of the A-class nursery plant plot was 481 g per plant, that of the B-class was 445 g, and the C 422 g, which the nursery plant plot of A-class yielded more 8.1% and 13.9% respectively than B-class plot and C-class plot per plant. In early yield of to February; A-class nursery plant plot showed 23.3% higher yield than B-class nursery plant plot, and 39.1% higher the C-class nursery plant.

• Journal of Bio-Environment Control
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• v.29 no.4
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• pp.337-343
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• 2020

This study was carried out to evaluate the yield of cuttings according to the planting and runner releasing times of mother plants in order to raise the cutting seedlings of raising seedling period 75 days or more needed for forcing culture of strawberries to be transplanted into the field around the 15^th of September. Three domestic cultivars of 'Maehyang', 'Jukhyang', and 'Kuemsil' were tested. For experiment 1 to determine the yield of cuttings with the change of transplanting time, the mother plant were planted on February 28, March 20, and April 9 in 20 days intervals, and the cuttings were collected two to three times from June 4 to July 1. Experiment 2 was conducted to investigate the yield of cuttings depending on the runner releasing time, the runners were released in three intervals of 20 days, 40 days, and 60 days after planting the mother plant on March 5, and the cutting were collected once to three times from May 29 to June 26. From the comparisons of cutting yield according to the transplanting time of mother plants, February 28 treatment was more 9~25% and 114~165% for each cultivar than March 20 and April 9, respectively (Experiment 1). The yield of cuttings with releasing time 20 days after planting the mother plants had higher by 60~77% and 104~176% for each cultivar than 40 days and 60 days, respectively (Experiment 2). From these results, in case of propagating the seedlings from cuttings needed for field planting around September 15, early planting around in the latter part of February is the best for cuttings yield. In addition, releasing after the removal of the runners produced from mother plants by 20 days after planting gives an advantage over higher yield of cuttings. Consequently, this study suggest to apply an efficient raising seedling system for labor saving and quality improvement in raising seedlings of three strawberry cultivars in Korea.

• Horticultural Science & Technology
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• v.31 no.2
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• pp.224-230
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• 2013

The objective of this study was to identify the content of phenolic and volatile organic compounds in edible and non-edible parts of 'Seolhyang' strawberry plants. We performed a comparative chemical analysis of the compounds found in roots, leaves, petioles, runners, and unripe and ripe fruits during vegetative propagation and reproductive growth. The contents of ellagic and gallic acids in the leaves of runner plants during vegetative propagation were $7.36{\pm}1.10$ and $5.07{\pm}3.66mg{\cdot}g^{-1}$ FW, respectively, and were higher than those in the other parts. The main volatile organic compound was identified as 3-hexen-1-ol, and it was mostly detected in leaves. The content of ellagic acid in leaves during reproductive growth was $12.96{\pm}2.30mg{\cdot}g^{-1}$ FW, while that in the other parts was below $6.00mg{\cdot}g^{-1}$ FW. The content of gallic acid in unripe fruits was $2.75{\pm}0.48mg{\cdot}g^{-1}$ FW and was higher than that in the other parts. Ripe fruits contained the lowest contents of ellagic and gallic acids but contained the most diverse volatile organic compounds, including sesquiterpenes, among the tested plant parts. The results indicate that non-edible parts (e.g., leaves and unripe fruits) of strawberry plants can be used as a raw material for antioxidant and anti-inflammatory agents, and edible parts (i.e., ripe fruits) can be available for making an essential oil.

• Korean Journal Plant Pathology
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• v.10 no.2
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• pp.112-118
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• 1994

Forth microbial isolates out of 167 isolates from the soil of controlled cultivation areas inhibited mycelial growth of Rhizoctonia solani AG2-1 causing the strawberry bud rot in vitro. Among the isolates, Kr013 and Kr020 showed suppressive effect to R. solani AG2-1 on seedlings of chinese cabbage treated by root immersion, charcoal carrier granule and drenching on 1.0% infested soil in pot. Furthemore, the corresponding effect was also revealed when the charcoal carrier granule of the isolates were treated on the seedling of strawberry that were planted on the planting hole in pot. To examine the effects of biological control in green house, it had been tested the infection rates by using two different treatments. First, the strawberry runner were planted on the nursery soil mixed with 20% charcoal carrier granule of Kr013 and Kr020 isolate respectively, and grown for 20 days before transplanting. Then the young plants form the mother plant were separated and transplanted on the 1.0% infested soil. Another method was that the charcoal carrier of Kr013 and Kr020 isolates applied to planting hole of 1.0% infested soil just before transplanting. Then the young plants were grown for 20 days on the sterilized nursery soil before transplanting. From the results, the effects of biological control was significantly higher on former treatment (e.g. the infection rates were 7.3 and 5.7%, respectively) than on the latter treatment (e.g. the corresponding value were 16.7 and 15.7%, respectively). The antagonistic isolates of Kr013 and Kr020 were respectively identified as Pseudomonas cepacia with the similarity of 55.0% and 60.0% by using the Biolog GN Microplate system.

• Horticultural Science & Technology
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• v.30 no.4
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• pp.357-362
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• 2012

Proper light intensity, shading tolerance, potting media, and fertilization level were investigated to develop Orostachys iwarenge for. magnus (Korean name, Ullungyeonwhabawisol) as a potted ornamental plant. The plants were grown under different light intensity (52, 82, 90, and 97% shading). The best growth was shown at 52% shading, which indicated that the proper light intensity for O. iwarenge for. magnus is less than 52% of shading. Plant growth decreased severely at 82% shading and leaf color became lighter as the shading rate increased, which indicated that O. iwarenge for. magnus has no tolerance against low light intensity. To select a proper potting media, decomposed granite (DG), fertilizer-amended media (FAM), river sand (RS) were used as potting medium with different ratio of 60:20:20 (DG:FAM:RS, v/v/v), 80:20 (DG:FAM, v/v), 60:40 (DG:FAM, v/v), and 20:80 (FAM:RS, v/v). DG:FAM:RS (60:20:20) showed the highest values in shoot fresh weight, plant width, and number of runner in potted O. iwarenge for. magnus. Fresh weight of shoot part was 16 g in DG:FAM:RS (60:20:20), which was about 2 folds of those at the other medium. At the experiment for selection of proper fertilization level, plants showed a better growth as the concentration of hyponex solution and application frequency increased. Once drenching 1 week interval of hyponex solution diluted by 1,000 folds brought the highest results in fresh weight, plant width, and runner number. Particularly, fresh weight of shoot part was 35 g at once drenching per week of 1,000 folds solution, indicating 84% improvement comparing with non treatment (19 g).

• Journal of Bio-Environment Control
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• v.20 no.4
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• pp.357-364
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• 2011

Proper light intensity, potting media, fertilization level, and shade tolerance were investigated to develop Orostachys (Korean name, Nungyu bawisol) as a potted ornamental plant. The best plant growth was shown at 52% shading. Although plant growth decreased at 82% shading, ornamental value maintained at that shading rate, which indicate that O. 'Nungyu bawisol' has high shading tolerance. At over 90% shading, some of the plants died and showed decolorization and standing erect in leaves, resulting in a big decrease in ornamental value. Potting medium of decomposed granite (DG) : fertilizer-amended media (FAM) : river sand (RS) (6 : 2 : 2, v/v/v) showed the best growth in potted O. 'Nungyu bawisol'. Fresh weight of shoot part was 16 g in DG : FAM : RS (6 : 2 : 2, v/v/v), which was over 2 folds of those at the other medium. Drenching of Hyponex solution diluted by 1,000~2,000 folds 1 time per week brought the highest results in fresh weight, plant width, and runner number. Particularly, fresh weight of shoot part was 13 g higher than that of control (16 g). Leaf color tended to be darkened as concentration of Hyponex solution increased.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.169-182
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• 2015

When simulating the dynamic behaviour of a hydro power plant, it is essential to have a good representation of the turbine behaviour. The pressure transients in the system occurs because the flow changes, which the turbine defines. The flow through the turbine is a function of the pressure, the speed of rotation and the wicket gate opening and is, most often described in a performance diagram or Hill diagram. In the Hill diagram, the efficiency is drawn like contour lines, hence the name. A turbines Hill diagram is obtained by performance tests on scaled model in a laboratory. However, system dynamic simulations have to be performed in the early stage of a project, before the turbine manufacturer has been chosen and the Hill diagram is known. Therefore one have to rely on diagrams for a turbine with similar speed number. The Hill diagram is drawn through measured points, so for using the diagram in a simulation program, one have to iterate in the diagram based on curve fitting of the measured points. This paper describes an alternative method. By means of the Euler turbine equation, it is possible to set up two differential equations which represents the turbine performance with good enough accuracy for the dynamic simulations. The only input is the turbine's main geometry, the runner blade in- and outlet angle and the guide vane angle at best efficiency point of operation (BEP). In the paper, simulated turbine characteristics for a high head Francis turbine, and for a reversible pump turbine are compared with laboratory measured characteristics.