• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.4
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• pp.11-20
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• 2022

Currently, the operation rule of agricultural reservoirs in case of drought events follows the drought forecast warning standard of agricultural water supply. However, it is difficult to preemptively manage drought in individual reservoirs because drought forecasting standards are set according to average reservoir storage ratio such as 70%, 60%, 50%, and 40%. The equal standards based on average water level across the country could not reflect the actual drought situation in the region. In this study, we proposed the improvement of drought operation rule for agricultural reservoirs based on the percentile approach using past water level of each reservoir. The percentile approach is applied to monitor drought conditions and determine drought criteria in the U.S. Drought Monitoring (USDM). We applied the drought operation rule to reservoir storage rate in extreme 2017 spring drought year, the one of the most climatologically driest spring seasons over the 1961-2021 period of record. We counted frequency of each drought criteria which are existing and developed operation rules to compare drought operation rule determining the actual drought conditions during 2016-2017. As a result of comparing the current standard and the percentile standard with SPI6, the percentile standard showed severe-level when SPI6 showed severe drought condition, but the current standard fell short of the results. Results can be used to improve the drought operation criteria of drought events that better reflects the actual drought conditions in agricultural reservoirs.

• Journal of Ginseng Research
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• v.46 no.2
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• pp.275-282
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• 2022

Background: Stroke is a neurological disorder characterized by brain tissue damage following a decrease in oxygen supply to brain due to blocked blood vessels. Reportedly, 80% of all stroke cases are classified as cerebral infarction, and the incidence rate of this condition increases with age. Herein, we compared the efficacies of Korean White ginseng (WG) and Korean Red Ginseng (RG) extracts (WGex and RGex, respectively) in an ischemic stroke mouse model and confirmed the underlying mechanisms of action. Methods: Mice were orally administered WGex or RGex 1 h before middle cerebral artery occlusion (MCAO), for 2 h; the size of the infarct area was measured 24 h after MCAO induction. Then, the neurological deficit score was evaluated and the efficacies of the two extracts were compared. Finally, their mechanisms of action were confirmed with tissue staining and protein quantification. Results: In the MCAO-induced ischemic stroke mouse model, WGex and RGex showed neuroprotective effects in the cortical region, with RGex demonstrating superior efficacy than WGex. Ginsenoside Rg1, a representative indicator substance, was not involved in mediating the effects of WGex and RGex. Conclusion: WGex and RGex could alleviate the brain injury caused by ischemia/reperfusion, with RGex showing a more potent effect. At 1,000 mg/kg body weight, only RGex reduced cerebral infarction and edema, and both anti-inflammatory and anti-apoptotic pathways were involved in mediating these effects.

• New & Renewable Energy
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• v.18 no.3
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• pp.1-9
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• 2022

This study analyzed the anticipated supply-and-demand of forest biomass energy (through wood pellets) until 2050, in South Korea. Comparing the utilization rates of forest resources of five countries (United Kingdom, Germany, Finland, Japan, and S. Korea), it was found that S. Korea does not nearly utilize its forest resources for energy purposes. The total demand for wood pellets in S. Korea (based on a power generation efficiency of 38%) was predicted to be 3,629 and 4,371 thousand tons in 2034 and 2050, respectively. The anticipated total wood pellet power generation ratio to target power consumption is 1.13% (5,745 GWh), 1.17% (6,336 GWh), and 1.25% (7,631 GWh) in 2020, 2030, and 2050, respectively. Low value-added forest residues left unattended in forests are called "Unused Forest Biomass" in S. Korea. From the analysis, the total annual potential amount of raw material, sustainably collectible amount, and available amount of wood pellet in 2050 were estimated to be 6,877, 4,814, and 3,370 thousand tons, respectively. The rate of contribution to Nationally Determined Contributions was up to 0.64%. Through this study, the authors found that forest biomass energy will contribute to a carbon neutral society in the near future at the national level.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.5
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• pp.9-16
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• 2022

Syngas, also known as synthesis gas, synthetic gas, or producer gas, is a combustible gas mixture generated when organic material (biomass) is heated in a gasifier with a limited airflow at a high temperature and elevated pressure. The present research was aimed at modifying the existing LPG engine generator for fully operated syngas. During this study, the designed gasifier-powered woodchip biomass was used for syngas production to generate power. A 6.0 kW LPG engine generator was modified and tested for operation on syngas. In the experiments, syngas and LPG fuels were tested as test fuels. For syngas production, 3 kg of dry woodchips were fed and burnt into the designed downdraft gasifier. The gasifier was connected to a blower coupled with a slider to help the air supply and control the ignition. The convection cooling system was connected to the syngas flow pipe for cooling the hot produce gas and filtering the impurities. For engine modification, a customized T-shaped flexible air/fuel mixture control device was designed for adjusting the correct stoichiometric air-fuel ratio ranging between 1:1.1 and 1.3 to match the combustion needs of the engine. The composition of produced syngas was analyzed using a gas analyzer and its composition was; 13~15 %, 10.2~13 %, 4.1~4.5 %, and 11.9~14.6 % for CO, H₂, CH₄, and CO₂ respectively with a heating value range of 4.12~5.01 MJ/Nm³. The maximum peak power output generated from syngas and LPG was recorded using a clamp-on power meter and found to be 3,689 watts and 5,001 watts, respectively. The results found from the experiment show that the LPG engine generator operated on syngas can be adopted with a de-ration rate of 73.78 % compared to its regular operating fuel.

• Current Optics and Photonics
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• v.6 no.2
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• pp.202-211
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• 2022

In the pasteurization of escalator handrails using ultraviolet (UV) sterilizers, a combination of light distribution and escalator speed has priority over other important factors. Furthermore, since part of the escalator handrail has a curved structure, proper design is needed to improve the sterilization rate on the surfaces touched by users. In this paper, two types of sterilizers satisfying these conditions are manufactured with 275-nm UV-C LEDs, after modeling the three-dimensional (3D) structure of an escalator handrail and simulating optical distributions of UV-C irradiation on the handrail's surface according to light-emitting diode (LED) positions and reflector variations in the sterilizers. Pasteurization experiments with the UV-C LED sterilizers are conducted on six types of gram-positive and gram-negative bacteria, with exposure times of 0.2, 5, and 15 s at an actual installation distance of 20 mm. The sterilization rates for the gram-positive bacteria are 10.63% to 27.94% at 0.2 s, 89.44% to 96.30% at 5 s, and 99.64% to 99.88% at 15 s. Those for the gram-negative bacteria are 57.70% to 77.63% at 0.2 s, 98.90% to 99.49% at 5 s, and 99.88% to 99.99% at 15 s. The power consumption of the UV-C LED sterilizer is about 8 W, which can be supplied by a self-generation module instead of an external power supply.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.4
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• pp.55-64
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• 2022

The objectives of this study were to assess physical habitat suitability of fish species for different life cycle stages and to suggest appropriate ecological stream flows in a Bokha downstream reach. A dominant species of Zacco platypus was selected as the study fish of which three stages of spawning, juvenile and adult in life cycle were considered into assessment. The stream hydraulic environment was calibrated with HEC-RAS before the PHABSIM simulation. The hydraulics of flow velocity and depth were used to estimate Weighted Usable Area (WUA) by multiplying respective habitat suitability indices with stream area. Overall the WUAs tend to be great in gentle slopes with relatively shallow water depth regions. Maximum WUAs, ie, candidate for ecological flow rates were 1 m³/s, 7 m³/s and 8 m³/s for the respective spawning, juvenile and adult stages of Zacco platypus. Since the ecological flow rates for juvenile and adult stages appeared to be is greater than the abundant flow rate (3.67 m³/s) for the study reach, additional water supply may be needed but should be cautious to avoid the spawning period of Apr through May from the stream water management perspective.

• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.845-855
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• 2022

The purpose of this study is to develop a self-propelled underground crop harvester and its performance was evaluated by measuring the load during actual potato harvesting operations. This study was conducted at a constant working speed of 1 km·h^-1. A load measurement system was installed to measure the actual load and the required working power was analyzed. A hydraulic pressure sensor was also installed to measure the hydraulic pressure. The required hydraulic power was calculated using the hydraulic pressure and flow rate. The results showed that the engine speed, torque, and power during harvesting operation were in the range of 845 - 1,423 rpm, 95 - 228 Nm, and 9 - 31 kW, respectively. Traction power, excluding the hydraulic pump of the tractor and power take-off (PTO) output, was in the range of 9 - 28 kW, and it was confirmed that it occupies a ratio of 16.2 to 50% of the engine rated output. The engine can supply the minimum required traction power to move the vehicle. This means that the engine used in this study could be down-sized to be suitable for an underground crop harvester. In this study, the gear stages of the tractor were not considered. This research thus shows the possibility of developing a self-propelled underground crop harvester.

• Korean Journal of Veterinary Service
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• v.45 no.4
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• pp.263-268
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• 2022

The current study examined the impact of fermented barley sprout extract prepared using lactic acid bacteria (Lactobacillus sp.) in decreasing odor and increasing livestock productivity and measured the difference in the polyphenol and flavonoid contents of the extract after fermentation. Furthermore, the effectiveness of fermented barley sprout extract was evaluated through order level and production index of livestock by supplying it to a broiler house. The results showed that with fermented barley sprout extract, the polyphenol and flavonoid contents were increased significantly by 174% and 562%, respectively. When the extract was applied as an additive to drinking water in the test farm, the productivity improved by about 10%, the mortality rate was reduced by about 66%, and there was a significant decrease in odor by about 80%. Compared with the control group, the production index increased by about 21%, the feed requirement decreased by about 8%, the odor showed a decrease in the NH₃ level, and no other gas was detected. It was observed that lactic acid bacteria settle in the intestine, suppress the proliferation of bacteria that cause diarrhea and enteritis, and help digestion. The lactic acid bacteria effectively remove bad odor gases such as NH₃, Amines, H₂S and CH₄S. Such odor reduction improves productivity. Our findings provide valuable information for quality water supply, production optimization and livestock management.

• Journal of the Korean Association of Geographic Information Studies
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• v.26 no.2
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• pp.20-41
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• 2023

Recently, urban shrinkage due to low birth rate and aging population and the decline of local cities are causing a new urban problem of empty houses. This study examines the distribution of vacant homes using spatial panel data collected from 2015 to 2019 at local administraitve districts and estimates the factors of vacant house occurrence using a spatial panel model considering spatio-temporal dependency. As a result, the spatio-temporal dependence of vacant houses was identified and it was estimated using spatial panel model not OLS model. Based on the spatial panel model, it was found that the most influential factor in the occurrence of vacant houses was the housing-related factor. This result shows that policy considerations for housing supply are necessary for the management of vacant housing as well as population movement and poor infrastructure.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.4
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• pp.71-81
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• 2010

The purpose of this study is to examine the moderating effects of the Leader-member exchange(LMX) on relationship between the interpersonal conflict and turnover intention. Since effective management of IS personnel is important issue for the IS related researchers and practitioners since their turnover rate has been known to be high and skilled personnel have been in short supply. We develop the hypotheses from the prior studies and empirically testing them in the context of IS personnels from various companies located in vicinity of capital city of Korea. This empirical study show interesting results. Good leader-member exchange has the moderating effect on the management of interpersonal conflict level and drastic reduction of the turnover behavior. Based on the analyzed results, we discussed the theoretical implications and limitations.