• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.75-86
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• 2019

Recently, natural disasters due to abnormal climates are frequently outbreaking, and there is rapid increase of damage to aged agricultural infrastructure. As agricultural infrastructure facilities are in contact with water throughout the year and the number of them is significant, it is important to build a maintenance management system. Especially, the current maintenance management system of pumping and drainage stations among the agricultural facilities has the limit of lack of objectivity and management personnel. The purpose of this study is to develop a performance evaluation model using the factors related to performance degradation of pumping and drainage facilities and to predict the performance of the facilities in response to climate change. In this study, we focused on the pumping and drainage stations belonging to each climatic zone separated by the Korea geographical climatic classification system. The performance evaluation model was developed using three different statistical models of POLS, RE, and LASSO. As the result of analysis of statistical models, LASSO was selected for the performance evaluation model as it solved the multicollinearity problem between variables, and showed the smallest MSE. To predict the performance degradation due to climate change, the climate change response variables were classified into three categories: climate exposure, sensitivity, and adaptive capacity. The performance degradation prediction was performed at each facility using the developed performance evaluation model and the climate change response variables.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.55-65
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• 2019

Although crack on concrete exists from its early formation, crack requires attention as it affects stiffness of structure and can lead demolition of structure as it grows. Detecting cracks on concrete is needed to take action prior to performance degradation of structure, and deep learning can be utilized for it. In this study, transfer learning, one of the deep learning techniques, was used to detect the crack, as the amount of crack's image data was limited. Pre-trained Inception-v3 was applied as a base model for the transfer learning. Web scrapping was utilized to fetch images of concrete wall with or without crack from web. In the recognition of crack, image post-process including changing size or removing color were applied. In the visualization of crack, source images divided into 30px, 50px or 100px size were used as input data, and different numbers of input data per category were applied for each case. With the results of visualized crack image, false positive and false negative errors were examined. Highest accuracy for the recognizing crack was achieved when the source images were adjusted into 224px size under gray-scale. In visualization, the result using 50 data per category under 100px interval size showed the smallest error. With regard to the false positive error, the best result was obtained using 400 data per category, and regarding to the false negative error, the case using 50 data per category showed the best result.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.291-299
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• 2021

This paper presents the control logic for the momentum wheel and gimbals in the CMG system. First, the design of the control logic for the momentum wheel is described in consideration of the power consumption and stability. Second, the design of the control logic for the gimbals considering the resonance of the vibration absorber and stability is explained. Third, the measurement configuration for the force and torque generated by the CMG is described. Fourth, the results of the frequency and time response test of the momentum wheel and gimbals are shown. Last, the measurements of the force and the torque generated through the CMG are explained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.11
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• pp.861-871
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• 2020

Raising the speed of the momentum wheel in the CMG increases the unintended force and torque caused by mass imbalance. This unintended force and torque should be minimized to get the better quality of satellite SAR image because they lead to the vibration of the output image. This paper shows the works on compensating the static imbalance and couple mass imbalance in the CMG wheel. First, the force and torque at the center of mass generated by the mass imbalance were predicted through M&S analysis. Second, the force and torque were estimated similarly through the M&S analysis when the measurement point was moved from the rotation center. Third, the measurement configuration for the force and torque by the mass imbalance was described. Fourth, the change of the force and torque by adding the specified mass to the momentum wheel was observed after comparing the measurements with the results of the M&S. And finally, the effect of the compensation was analyzed by comparing the force and torque before and after the correction while 24Nm class CMG was running in the standby mode.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.35-43
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• 2010

Nutrient limitation and light limitation was examined for the Youngsan Lake by collecting chlorophyll $\alpha$ and other properties including light intensity, nutrient concentrations, pheopigment ratio monthly from March, 2003 to April, 2004 (except for November-January). Chlorophyll $\alpha$ was fractionated into net-(>$20\;{\mu}m$) and nano-size(<$20\;{\mu}$). Light and nutrient limitation index was calculated based on the equations incorporating the mechanisms of limitation of light and nutrients from the literature. Phytoplankton population (chlorophyll $\alpha$) was low during the wet season especially in August and increased in short-period during other seasons. Photoperiod was short during the wet season but long during the dry season. Nutrients such as phosphate and ammonium were rapidly increased in spring, 2004. Light limitation index was minimum (0.01) in August during the wet season and nutrient limitation index was relatively high (>0.4) except for May and September. Light limitation may affect phytoplankton growth rather than nutrient limitation considering that nutrient levels are high in the Youngsan Lake. Results of correlation analyses showed a negative correlation between light and nutrient limitation indices and net-pheopigment index, and a positive correlation between the indices and nano-pheopigment index. These results suggest that phytoplankton response to change of light and nutrient may be size-dependant.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.5
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• pp.608-615
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• 2017

The objective of this study was to evaluate the physicochemical, structural, and rheological properties of new domestic potato cultivars ('Goun', 'Sebong', and 'Jinsun') against the foreign potato cultivar 'Atlantic'. Based on the results obtained from scanning electron micrograph, X-ray, and Fourier transform infrared spectrum analyses, the structural properties of all potato flours were not considerably different. Rapid visco analyzer analyses showed that the setback viscosities of 'Goun', 'Sebong', and 'Jinsun' were significantly lower than that of 'Atlantic'. For steady shear rheological properties, potato flour dispersions showed shear-thinning behaviors (n=0.45~0.49) at $25^{\circ}C$. Apparent viscosity and consistency index of 'Atlantic' were similar to those of 'Sebong' and 'Jinsun'. For dynamic shear rheological properties, storage modulus (G′) and loss modulus increased, whereas complex viscosity (${\eta}^*$) was reduced with increasing frequency from 0.63 to 62.8 rad/s. G′ and ${\eta}^*$ values of 'Jinsun' were significantly higher than those of the other potato cultivars.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.817-820
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• 2008

The river environments of many streams in korea have been deteriorate through the rapid industrialization and urbanization since the 1960s. In korea, on the other hand, much efforts on the research and project have been made for the restoration of the deteriorated streams to close-to-nature. in order to restore the deteriorated streams, therefore, it is necessary to investigate such advanced technologies and materials. In view of this requirement, various research paths are being taken focusing on coarse aggregates to make multi-functional porous concrete having continuous voids so as to improve water and air permeability, acoustic absorption, water purification and applicability to vegetation. The Purpose of this study is to investigate the method for recovery of the environment in the streams area using porous concrete retaining wall block. the multi-P.O.C block applies for test in the Jangduri-cheon have been monitored planting, stability etc. after 6 months, plant grows flourishing and reconstructed in state such as nature rivers.

• Korean Journal of Food Science and Technology
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• v.49 no.4
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• pp.360-368
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• 2017

The objective of this research was to elucidate the physicochemical, structural, pasting and rheological properties of potato starch isolated from a foreign potato cultivar ('Atlantic') and new domestic potato cultivars ('Goun', 'Sebong', and 'Jinsun'). Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and one-dimensional nuclear magnetic resonance (1D NMR) showed that the structural properties of potato starch did not vary significantly with cultivars. RVA analysis demonstrated that the 'Atlantic' starch had the highest breakdown viscosity among all potato starches. In steady shear rheological analysis, all potato starch dispersions showed shear-thinning behaviors (n =0.63-0.72) at $25^{\circ}C$. The highest apparent viscosity (${\eta}_{a,5}$), consistency index (K), and yield stress (${\sigma}_{oc}$) were observed in the 'Goun' starch dispersion. In dynamic shear rheological analysis, storage modulus (G') and loss modulus (G") values of new domestic potato starch dispersions were higher than those of the 'Atlantic' starch dispersion.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.5
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• pp.19-32
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• 2023

The fragmentation of habitats resulting from human activities leads to the isolation of wildlife and it also causes wildlife-vehicle collisions (i.e. Road-kill). In that sense, it is important to predict potential habitats of specific wildlife that causes wildlife-vehicle collisions by considering geographic, environmental and transportation variables. Road-kill, especially by large mammals, threatens human safety as well as financial losses. Therefore, we conducted this study on roe deer (Capreolus pygargus tianschanicus), a large mammal that causes frequently Road-kill in Jeju Island. So, to predict potential wildlife habitats by considering geographic, environmental, and transportation variables for a specific species this study was conducted to identify high-priority restoration sites with both characteristics of potential habitats and road-kill hotspot. we identified high-priority restoration sites that is likely to be potential habitats, and also identified the known location of a Road-kill records. For this purpose, first, we defined the environmental variables and collect the occurrence records of roe deer. After that, the potential habitat map was generated by using Random Forest model. Second, to analyze roadkill hotspots, a kernel density estimation was used to generate a hotspot map. Third, to define high-priority restoration sites, each map was normalized and overlaid. As a result, three northern regions roads and two southern regions roads of Jeju Island were defined as high-priority restoration sites. Regarding Random Forest modeling, in the case of environmental variables, The importace was found to be a lot in the order of distance from the Oreum, elevation, distance from forest edge(outside) and distance from waterbody. The AUC(Area under the curve) value, which means discrimination capacity, was found to be 0.973 and support the statistical accuracy of prediction result. As a result of predicting the habitat of C. pygargus, it was found to be mainly distributed in forests, agricultural lands, and grasslands, indicating that it supported the results of previous studies.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.2
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• pp.192-198
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• 2006

Treatment effects of grape fruit stem extracts (GFSE) containing trans-resveratrol on the storage property of fresh jujube (Zizyphus jujube) were investigated. Fresh jujubes were packed in different storage containers [polyethylene terephthalate (PET) and polyethylene (PE)], and treated with GFSE containing trans-resveratrol of 10, 30 and 50 ppm, respectively. The storage vessels filled with $N_2$ gas, and stored in refrigerator $(0{\pm}1^{\circ}C)$ during 18 weeks, and then quality characteristics during storage period were analysed. Ethylene gas increased until 8 weeks and decreased afterward. Decaying of jujube started at $6\~8$ weeks in control, but it did at 14 week storage for the fruits at $50\%$ maturity treated with 10 ppm of GFSE and packed in PE vessel. Soluble solid (Brix degree) and total acidity of fresh jujube slightly increased in all the treatments during storage period. Hardness slightly increased until 4 weeks and decreased afterward. Vitamin C content was at the highest content of $86.8\~273.4$ mg/100g for most of treatments at 2 weeks and decreased afterward. Storage stability was higher for $50\%$ maturity fruits than for the $70\%$ maturity, and higher for PE vessels than PET containers. Storage period of fresh jujube in this experiment ranges in $10\~12$ weeks for $50\%$ maturity fruits treated with 10 ppm of GFSE and packed in PE vessel.