• Journal of the Korean Institute of Navigation
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• v.6 no.2
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• pp.35-55
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• 1982

The attempt of this paper is to examine the basic theory on the analysis of the effect of a shading coil fitted to an electromagnetic contactor, and to compare experimentally the attracting force of an AC electromagnetic contactor with that of a DC electromagnetic contactor, with varying the airgap length. Equations are also proposed for calculating the AC and DC attracting force per unit consumption wattage by using the circuit constants measured from the experiment, and these calculated attracting forces are compared with those actulally measured, and then, the experimental contactor is examined in the view of its design. The calculated attracting forces are appeared to coincide well with the measured ones and the experimental contactor fitted with shading coil is revealed not so well designed for reducing the fluctuation of the attracting force.

• Journal of Korean Society of Forest Science
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• v.100 no.4
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• pp.598-608
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• 2011

The purpose of this study was to examine potential effects of shading and fertilizing treatment - two basic applicable factors in production of 1-year-old container seedling - on growth and seedling quality of Quercus myrsinaefolia, one of evergreen tree species in warm temperate zone of Korean. Every experimental process was conducted in a facility that consisted of compartments under the lighting control with full sunlight and shading (35%, 55% and 75% of full sunlight). Based on fertilizing treatment, this study made an experiment in 4 groups of container seedling: control (non-treated seedlings) and 1000, 2000, 3000 ppm group (3 groups with different concentrations of water-soluble fertilizer (N:P:K=19:19:19, v/v). Seedlings under 55% shading with 2000 ppm concentration showed the highest height (totaling 21.1 cm), and under 35% shading with 2000 ppm concentration showed the highest root collar diameter growth (totaling 3.96 mm) among others. All three fertilizing groups except control showed H/D ratio ranging from 4.27 to 5.26 regardless of fertilizer concentration under 35% and 55% shading where container seedlings showed a tendency toward excellent growth of height and root collar diameter. Overall, 2000 ppm group under 55% shading showed highest dry mass production of leaves (1,292 g) among others, while 2000 ppm group under 35% shading showed highest dry mass production of shoots and roots (0.592 g and 0.998 g, respectively) among others. Also, it was found that 2000 ppm group under 35% shading showed the highest dry mass production of whole seedling, which was followed by 2000 ppm group under 55% shading and 3000 ppm group under 35% shading, respectively. According to analysis on LWR of Quercus myrsinaefolia depending on shading and fertilizing treatment, it was found that 3000 ppm group under 75% shading showed highest LWR level among others, whereas every fertilized group showed lower RWR level than control without fertilizing regardless of shading levels. In general, all fertilized groups under 55% shading had relatively high quality index (QI), and 2000 ppm group under 35% shading had highest QI among others. Based on the findings of this study, it is concluded that shading level ranging from 35 to 55% and fertilizing concentration of 2,000 ppm are suitable for producing 1-year-old container seedlings of Quercus myrsinaefolia with excellent growth and high quality index.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.4
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• pp.98-106
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• 2003

In order to set up structural improvement strategy against meteorological disasters of the shading structures in ginseng fields, structural safety analyses as well as some case studies of structural damage patterns were carried out. According to the results of structural safety analysis, allowable safe snow depth for type B(wood frame with single span) was 25.9 cm, and those for type A(wood frame with multi span) and type C and D (steel frame with multi span) were 17.6 cm, 25.8 cm, and 20.0 cm respectively. So types of shading structures should be selected according to the regional design snow depth. An experiential example study on meteorological disasters indicated that a strong wind damage was experienced once every 20 years, and a heavy snow damage once every 9.5 years. The most serious disasters were caused by heavy snow and it was found that a half break and complete collapse of structures were experienced by about 70% of snow damage. In addition to maintenance, repair and reinforcement, it is also recommended that improved model of shading structures for ginseng cultivation should be developed as a long term countermeasures against meteorological disasters.

• Land and Housing Review
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• v.10 no.3
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• pp.33-41
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• 2019

This study examines the distributions of daylight illuminance in a small office space under clear and cloudy sky conditions. Three shading conditions using Venetian blinds were applied for the analysis of daylight illuminance. Computer simulations using the Lightscacpe were conducted for the daylight conditions applied to the office space. Results indicate that the illuminance differences between clear and cloudy sky for south-facing conditions were greater than those for north-facing conditions. The differences in December and June were the greatest and smallest, respectively. For the north-facing conditions, the daylight illuminance at 10:00, 12:00 and 14:00 in June and September under the cloudy sky was higher than those under the clear sky conditions. For all daylight conditions, the biggest amount of illuminance reduction occurred when the shading device conditions were changed from the no blind to the 45 degree blinds. As the distance from window increased, the shading effect that occurred when the shading device conditions were changed from the horizontal blind to the 45 degree blinds increased.

• Journal of the Korean Solar Energy Society
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• v.30 no.6
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• pp.102-107
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• 2010

a-Si solar cell has relatively dominant drift current when compared with crystalline solar cell due to the high internal electric field. Such drift current make an impact on the PV module in the local shading. In this paper, the a-Si PV module output characteristics of shading effects was approached in terms of process condition, because of the different deposition layer of thin film lead to rising the resistance. We suggested design condition to ensure the long-term durability of the module with regard to the degradation factors such as hot spot by analyzing the module specification. The result shows a remarkable difference on module uniformity for each shading position. In addition, the unbalanced power loss due to power mismatch of each module could intensify the degradation.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1489-1500
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• 2018

Partial shading analysis of large-scale photovoltaic (PV) arrays has recently become a theoretically and numerically challenging issue, and it is necessary for PV system designers. The main contributions of this study are the following: 1) A PSIM-based macro-model was employed because it is remarkably fast, has high precision, and has no convergence issues. 2) Three types of equivalent macro-models were developed for the transformation of a small PV sub-array with uniform irradiance to a new macro-model. 3) On the basis of the proposed new macro-model, a tearing method was established, which can divide a large-scale PV array into several small sub-arrays to significantly improve the efficiency improvement of a simulation. 4) Three platforms, namely, PSIM, PSpice, and MATLAB, were applied to evaluate the proposed tearing method. The proposed models and methods were validated, and the value of this research was highlighted using an actual large-scale PV array with 2420 PV modules. Numerical simulation demonstrated that the tearing method can remarkably improve the simulation efficiency by approximately thousands of times, and the method obtained a precision of nearly 6.5%. It can provide a useful tool to design the optimal configuration of a PV array with a given shading pattern as much as possible.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.222-223
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• 2007

Though there are many causes for the maximum output power reduction, the short-term problem is hot-spot effect by sun shading. To prevent this, normally PV maker uses bypass diode. In here, we tried to check the how bypass diodes works by varying sun shading portion on solar. In case of absence of bypass, the sun shading effect increases the series resistance and that promotes the reduction of maximum power and degradation of PV modules. Bypass diode worked normally when 60% of solar cell was shaded and the measured maximum output power was lower than that of theoretical one. The further analysis is needed.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.52-61
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• 2020

The natural change of winter night temperature from 00:00 to 04:30 O'clock with the different height of thermal screen in a venlo type glasshouse (W59×L68×H5.9 m) was studied using computational fluid dynamics (CFD). At the early stage of CFD analysis, the room temperature decrease of glasshouse with the 5.9 m height of thermal screen were faster than it with the 4.1m height of thermal screen, but at 2 hr after analysis it was slower than in it with the 4,1m, the temperature difference was 0.6℃ after 4 hr. If we consider that turn on the heater when the temperature were decrease below 13℃ at 1hr after CFD analysis, it is good for energy saving in the glasshouse with the 4.1 m height of thermal screen rather than in it with the 5.9 m height, because of the temperature decrease were slow during 2 hrs after analysis. The airflow at the height of 2 m which were grown tomato were fast and wide in the glasshouse with the 5.9 m height thermal screen rather than in it with the 4.1 m, the speed difference was 0.034m·s^-1 at 1hr after CFD analysis. The effect of temperature decrease in summer season were compared with the different height of shading screen from 12:00 to 14:30 O'clock. The height of shading screen were 5.7, 3.9 m, the gap of it were 30%. The air-inflow quantity by the fan with duct at lower part of venlo glasshouse was 0.67 ㎥·s^-1 until 1hr and to increase 3 times of it from 1hr after analysis. The roof window were open 100%. Until 1hr of CFD analysis, the temperature in the 30% open of shading screen was 0.9℃ higher than in the none shading screen. From 13:00 O'clock when the air-inlet quantity to increase 3 times, the temperature in case 30% gap of shading screen were decreased compare with the none shading screen, the temperature difference was 0.5℃ at 14:30 O'clock. The temperature on the floor surface in case 30% gap of shading screen were lower with it's height increase, the temperature difference was 8℃ compare with none shading screen. The relative humidity difference were insignificant by the height and gap of shading screen.

• KIEAE Journal
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• v.6 no.2
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• pp.35-42
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• 2006

This study is to investigate the possibility of a quantitative analysis on sunshine right in apartment houses with a new evaluation index of shading area ratio(SAR) which represents seasonal average value of shaded portion of a window during definite period. SAR values of each apartment houses in a prototype building was calculated depending on apartment building arrangement types and orientations. Since the new method proposed in this research is able to measure the sunshine possibility of the each house in detail, which is more precise and descriptive than the existing method of sunshine judgment standard based on the sunshine hours only at winter solstice, it can be appropriately utilized as a highly qualified sunshine right judgment measures in apartment buildings.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.2
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• pp.146-154
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• 2021

This study was conducted to determine the degree of reduction in the yield of sweetpotato subjected to different shading treatments according to the growing season of the typical viscous sweetpotato 'Hogammi' and the powdery sweetpotato 'Jinyulmi'. Shading was provided using commercially available shading nets (55% and 75% shading level), and the treatments were applied at the following stages of storage root growth: SFS: the storage root formation stage (planting-50^th day), SSS: the storage root swelling stage (50-90^th day), and SAS: the storage root actively swelling Stage (90-120^th day). The growth characteristics according to shading treatments during each growth period, the number of tubers obtained at harvest, and sugar contents were investigated. For both assessed cultivars, there was no significant difference between the control group and the 55% shading treated group with respect to the maximum quantum yield (Fv/Fm) of photosystem II under different shading treatments, whereas the 75% shading group showed slightly higher values than the control group. In both cultivars, the contents of chlorophyll a and b tended to increase in plants subjected to shading treatments compared with the control plants, particularly that of chlorophyll b. Compared with the control group, the chlorophyll b content of 'Hogammi' subjected to 55% and 75% shading increased by 47% and 41%, respectively, whereas that of 'Jinyulmi' increased by 39% and 34%, respectively. We also detected reductions in the dry weights of the above- and belowground parts of the two varieties in response to shading compared with the control, with the reduction in the dry weight of belowground parts being significant. Furthermore, in both varieties, the T/R rate tended to increase in response to shading treatment. Owing to the lack of sunlight, both cultivars tended to suppress the formation and enlargement of tuber roots. Consequently, post-harvest yield analysis revealed that under shading treatments, both cultivars were characterized by poor tuber root growth according to growing season, with the yield of 'Hogammi' showing a greater reduction compared with that of 'Jinyulmi'. In addition, we found that the higher shading level also significantly reduced yields. Compared with the storage root formation and storage root actively swelling stages, shading treatments during the storage root swelling stage significantly affected yield reduction in both varieties.