• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.2
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• pp.159-174
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• 2022

Flow prediction was carried out through observational survey and three dimensional multi-layered numerical diagnostic model experiment to clarify the time and spatial structure of tidal current and residual flow dominant in the sea exchange and material circulation of the waters around Geumo Islands in the southern waters of Korea. The horizontal variation of tidal current is so large that it causes asymmetric tidal mixing due to horizontal eddies and the topographical effect creating convergence and dispersion of flow direction and velocity. Due to strong tidal currents flowing northwest-southeast, counterclockwise and clockwise eddies are formed on the left and right sides of the south of Sori Island. These topographical eddies are created by horizontal turbulence and bottom friction causing nonlinear effects. Baroclinic density flows are less than 5 cm/s at coastal area in summer and the entire sea area in winter. The wind driven currents assuming summer and winter seasonal winds are also less than 5 cm/s and the current flow rate is high in winter. Density current in summer and wind driven current in winter have a relatively greater effect on the net residual flows (tidal residual current + density current + density driven current) around Geumo Islands Sea area.

• Smart Structures and Systems
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• v.33 no.2
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• pp.105-118
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• 2024

In order to realize tiny bridge crack discovery by UAV-based machine vision, a novel method combining deep learning and tensor voting is proposed. Firstly, the grid images of crack are detected and descripted based on SE-ResNet50 to generate feature points. Then, the probability significance map of crack image is calculated by tensor voting with feature points, which can define the direction and region of crack. Further, the crack detection anchor box is formed by non-maximum suppression from the probability significance map, which can improve the robustness of tiny crack detection. Finally, a case study is carried out to demonstrate the effectiveness of the proposed method in the Xiangjiang-River bridge inspection. Compared with the original tensor voting algorithm, the proposed method has higher accuracy in the situation of only 1-2 pixels width crack and the existence of edge blur, crack discontinuity, which is suitable for UAV-based bridge crack discovery.

• Journal of Wetlands Research
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• v.10 no.1
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• pp.21-30
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• 2008

Evapotranspiration is an important factor in the energy interaction process between the surface and the air. Over a vegetable canopy, evapotranspiration was investigated by measuring the sensible heat flux, the soil heat flux and the net radiation flux. Evapotranspiration based on routine AWS data is in good agreement with that estimated from the energy balance equation except for weak wind shear less than $1s^{-1}$ and a cloudy period. Soil heat flux can be approximately to 10% of net radiation flux at the lower layer. When the slope of the saturation vapor pressure versus temperature curve ($de_s/dT$) is approximated to 1.5, the evapotranspiration can be described in function of the net radiation energy flux over Goheung bay wetland covered with the vegetable canopy, reeds.

• Structural Engineering and Mechanics
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• v.74 no.4
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• pp.533-545
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• 2020

An optimal design method for a spoke double-layer cable-net structure (SDLC) is proposed in this study. Simplified calculation models of the SDLC are put forward to reveal the static responses under vertical loads and wind loads. Next, based on an energy principle, the relationship among the initial prestress level, cross-sectional areas of the components, rise height, sag height, overall displacement, and relative deformation is proposed. Moreover, a calculation model of the Foshan Center SDLC is built and optimized. Given the limited loading cases, material properties of the components, and variation ranges of the rise height and sag height, the self-weight and initial prestress level of the entire structure can be obtained. Because the self-weight of the cables decreases with increasing of the rise height and sag height, while the self-weight of the inner strut increases, the total weight of the entire structure successively exhibits a sharp reduction, a gradual decrease, a slow increase, and a sharp increase during the optimization process. For the simplified model, the optimal design corresponds to the combination of rise height and sag height that results in an appropriate prestress level of the entire structure with the minimum total weight.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.5
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• pp.407-428
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• 1991

The eastern coastal area having variability of climate is located within Taebaek mountain range and the east coast of Korea. It is therefore ease to cause the wind damages in paddy field during rice growing season. The wind damages to rice plant in this area were mainly caused by the Fohn wind (dry and hot wind) blowing over the Taebaek mountain range and the cold humid wind from the coast. The dry wind cause such as the white head, broken leaves, cut-leaves, dried leaves, shattering of grain, glume discolouration and lodging, On the other hand the cold humid wind derived from Ootsuku air mass in summer cause such symptom as the poor rice growth, degeneration of rachis brenches and poor ripening. To minimize the wind damages and utilize as a preparatory data for wind injury of rice in future, several experiments such as the selection of wind resistant variety to wind damage, determination of optimum transplanting date, improvement of fertilizer application methods, improvement of soils and effect of wind break net were carried out for 8 years from 1982 to 1989 in the eastern coastal area. The results obtained are summarized as follows. 1. According to available statisical data from Korean meteorological services (1954-1989) it is apperent that cold humid winds frequently cause damage to rice fields from August 10th to September 10th, it is therefore advisable to plan rice cultivation in such a way that the heading date should not be later than August 10th. 2. During the rice production season, two winds cause severe damage to the rice fields in eastern coastal area of Korea. One is the Fohn winds blowing over the Taebaek mountain range and the other is the cold humid wind form the coast. The frequency of occurrence of each wind was 25%. 3. To avoid damage caused by typhoon winds three different varieties of rice were planted at various areas. 4. In the eastern coastal area of Korea, the optimum ripening temperature for rice was about 22.2$^{\circ}C$ and the optimum heading date wad August 10th. The optimum transplanting time for the earily maturity variety was June 10th., medium maturity variety was May 20th and that of late maturity was May 10th by means of growing days degree (GDD) from transplanting date to heading date. 5.38% of this coastal area is sandy loamy soil while 28% is high humus soil. These soil types are very poor for rice cultivation. In this coastal area, the water table is high, the drainage is poor and the water temperature is low. The low water temperature makes it difficult for urea to dissolve, as a result rice growth was delayed, and the rice plant became sterile. But over application of urea resulted in blast disease in rice plants. It is therefore advise that Ammonium sulphate is used in this area instead of urea. 6. The low temperature of the soil inhibits activities of microorganism for phosphorus utilization so the rice plant could not easily absorb the phosphorus in the soil. Therefore phosphorus should be applied in splits from transplanting to panicle initiation rather than based application. 7. Wind damage was severe in the sandy loamy soil as compared to clay soils. With the application of silicate. compost and soil from mointain area. the sand loamy soil was improved for rice grain colour and ripening. 8. The use of wind break nets created a mocro-climate such as increased air. soil and water temperature as well as the reduction of wind velocity by 30%. This hastened rice growth, reduced white head and glume discolouration. improved rice quality and increased yield. 9. Two meter high wind break net was used around the rice experimental fields and the top of it. The material was polyethylene sheets. The optimum spacing was 0.5Cm x 0.5Cm. and that of setting up the wind break net was before panicle initiation. With this set up, the field was avoided off th cold humid wind and the Fohn. The yield in the treatment was 20% higher than the control. 10. After typhoon, paddy field was irrigated deeply and water was sprayed to reduce white head, glume discolouration, so rice yield was increased because of increasing ripening ratio and 1, 000 grain weight.

• Korean Journal of Ichthyology
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• v.26 no.3
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• pp.222-229
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• 2014

As a study for offshore wind farm, we investigated the fish fauna of the Wi-do, Younggwang-gun, Chollabuk-do, Korea. From the four times collection of fish species from October 2013 to June 2014, we collected 46 species of 26 families including 9 orders. Among them, the fish of family Gobiidae includes the most number of six species (13.6%). The dominant species was the Argyrosomus argentatus with 53.10%. Total of 17 fish species, including the Cynoglossus joyneri were collected from all of four collecting sites. On the other hand, 13 species including Inimicus japonicus were collected from only one site. Being the wind farm under construction, fish will temporary decrease in this area. But in the long term, we think that Oplegnathus fasciatus, Sebastes shlegelli and others will increase with good inhabited environment provided by the wind farm structures.

• Nuclear Engineering and Technology
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• v.46 no.4
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• pp.557-568
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• 2014

This paper presents the results of an analysis of wind characteristics and atmosphere dispersion modeling that are based on computational simulation and part of a preliminary study evaluating environmental radiation monitoring system (ERMS) positions within the Barakah nuclear power plant (BNPP). The return period of extreme wind speed was estimated using the Weibull distribution over the life time of the BNPP. In the annual meteorological modeling, the winds from the north and west accounted for more than 90 % of the wind directions. Seasonal effects were not represented. However, a discrepancy in the tendency between daytime and nighttime was observed. Six variations of cesium-137 ($^{137}Cs$) dispersion test were simulated under severe accident condition. The $^{137}Cs$ dispersion was strongly influenced by the direction and speed of the main wind. A virtual receptor was set and calculated for observation of the $^{137}Cs$ movement and accumulation. The results of the surface roughness effect demonstrated that the deposition of $^{137}Cs$ was affected by surface condition. The results of these studies offer useful information for developing environmental radiation monitoring systems (ERMSs) for the BNPP and can be used to assess the environmental effects of new nuclear power plant.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.591-603
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• 2022

This study was conducted to identify changes of insect compositions and diversity after construction of an onshore wind farm. We investigated insect fauna and compositions between a grassland deforested by the construction and a forest located at Yeongdeok and Yeongyang, Gyeongsangbuk-do, Korea. Insects were collected using a sweeping net and light trap. A total of 11 orders, 50 families, and 246 species, and 1,076 individuals were collected at study sites. By taxonomic group, Lepidoptera species were the most frequently found with 141 species, 417 individuals (38.8%), followed by Hymenoptera (20.6%), Hemiptera (16.2%), and Orthoptera (12.3%). There were also significant differences in insect species and community compositions between sites. Creating open-field deforested forests are beneficial for some insect groups such as Hymenoptera and Orthoptera. Our results suggest that deforesting by the construction of an onshore wind farm might affect the composition and diversity of insects. Results of this study provide basic data for research on onshore wind farms.

• Wind and Structures
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• v.16 no.1
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• pp.93-115
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• 2013

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

• Journal of Bio-Environment Control
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• v.29 no.4
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• pp.448-455
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• 2020

This study was carried out to investigate reduction of the frost damage using the mesh net used for the purpose of non-bagged cultivation. A device measuring the weight of frost was developed and installed in both the control and the experimental, and the effect of frost reduction was evaluated with their weights. As a result, weight of frost in the control was reduced from 37% to 59% with mesh net on the day the frost was observed. In addition, the device for automatically observing the amount of frost was developed and the height of the windbreak of the frost measuring device was determined to be 30 cm through wind tunnel experiment. The results of this study are expected to reduce frost damage during the flowering season of fruit trees by installing mesh net and it is expected to be used as basic data for agricultural use of mesh net.