• Weed & Turfgrass Science
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• v.5 no.4
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• pp.236-240
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• 2016

Weeding measures is an important issue for cereal crop because weed is superior to crops in early growth stage and there are not many herbicides applicable to cereal crop. Since the concern about well-being and eco-environmental products are increasing, cultivation with polyvinyl chloride (PVC) is needed. Five treatments included as weed-free, control (not remove weed) and covering with polyvinyl chloride removed 20, 30, 40 DAS (day after seeding). At removing PVC, plant height did not differ depending on the growth stage. However, weed-free plot by weed competition were somewhat short. And, removing PVC accelerated the earlier by 2-3 day than weed-free plot. Soil moisture which removed from the control was higher than 20, 30, 40 DAS and weed-free, and it was kept low by evaporation. The chlorophyll meter of weed-free plot was 34.3, 30 DAS was 40.6 at heading time. Weed-free showed that increased in weed population $300.8g\;m^{-2}$. Weed control value of 20 DAS, 30 DAS, 40 DAS were 86.5%, 84.0% and 74.8%, respectively. In 30 DAS, yield of foxtail millet according to treatment of removing PVC were $355kg\;10a^{-1}$. At weed competition early in 30 DAS, the removing PVC was good for control. Thus, 30 DAS was judged to be suitable.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.9-16
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• 2013

Recent years have witnessed a strong need for eco-friendly and energy-efficient systems owing to global environmental problems. A heat exchanger is a well-known mechanical rig that has long been used in many energy systems. The use of a heat exchanger in an airplane engine has been attempted. In this case, the heat exchanger should be redesigned to be compact, lightweight, and highly reliable, and the issue of mechanical integrity gains importance. Therefore, in this study, we proposed a method for evaluating the mechanical integrity of a tube-type heat exchanger. A U-shaped single tube was used as an example, and its behavior and stress distribution were studied using fluid-structure interaction (FSI) analysis.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.2
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• pp.151-155
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• 2007

The issue of acid precipitation and related environmental problems in East Asia have been emerging. To evaluate the acidity and chemical characteristics of rainwater in Korea, its chemical properties during crop cultivation season from April to October were investigated at Suwon, Korea. Also, to estimate the contribution of ions on its acidity, ion composition characteristics and neutralization effects by cation ions were determined. Ion balance and electrical conductivity balance between the measured and estimated values showed high correlation. Rainwater had distributed highly in the range of pH 4.5~5.6. The pH of rainwater was relatively high at June as compared with other monitoring periods. $Na^+$ was the main cation followed by $NH_4{^+}$, $Ca^{2+}$, $H^+$ > $K^+$ > $Mg^{2+}$. Among these, $Na^+$, $NH_4{^+}$, $Ca^{2+}$ and $H^+$ covered over 93% of total cations. About 86% of anion in rainwater was composed of $SO{_4}^{2-}$ and $NO_3{^-}$. In rainwater samples, $NH_4{^+}$ and $Ca^{2+}$ contributed greatly to neutralization of the rain acidity. Also, 88% of soluble sulfate in rainwater was nss-$SO{_4}^{2-}$(non-sea salt sulfate).

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.4
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• pp.317-330
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• 2021

Objectives: By law, companies in Korea must periodically measure workers' exposure to harmful chemicals (the system is called the Work Environment Monitoring Program (WMP)[a]) and report the results to the government. The government also measures exposure to monitor the WMP's reliability (called Reliability Assessment (RA) for WMP[b]). The issue is that measured data from these two sources are so different that the objectivity of WMP needs to be confirmed by comparing the results using the European Centre for Ecotoxicology and Toxicology of Chemicals' Targeted Risk Assessment (ECETOC TRA). Methods: Step 1: Data collection from WMP reports submitted by companies (n=586) and RA for WMP written by the government (n=33). Step 2: Data Standardization by key information included. Step 3: Data conversion to input-variables required to run the ECETOC TRA model, and run the model with specific data (n=514) which meet the predetermined exposure scenario. Step 4: Statistical data analysis by process category (PROC) and ventilation type from each source ([A] and [B]). Step 5: Additional analysis of any unexpected results. Results: The process categories of the production and handling of Dichloromethane were classified into 12 PROCs, and ten of them were selected to run ECETOC TRA. Modeled values tended to be higher than measured values from both sources. For the measured values from WMP, RCR distribution by PROC was narrow (0.197-0.267, 95% CI) and did not have a relationship with ventilation type, which differs from the tendency of the modeling result. Meanwhile, the measured values from RA for WMP were relatively widely distributed (0.301-1.177, 95% CI) by PROC. In particular PROCs (13,19) were high enough to exceed 1. Also, they become low with better ventilation types and appear differently depending on the ventilation type, similar to the model result. Conclusions: This study revealed that ECETOC TRA might have the potential to serve as a screening tool for exposure assessment and to be used as assistive method for WMP to estimate exposure. Further empirical study is required to confirm its availability as a screening tool.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.662-673
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• 2019

This paper investigates the most recent status of multi-GNSS, including technical features, types of ranging signals provided, and satellite constellation. Furthermore, a series of multi-GNSS positioning experiments in SPP mode were carried out to assess the achievable accuracy and continuity with an application to various positioning scenarios. A week of GNSS measurements each in 2018 and 2019 was acquired from the national geographical information institute and processed. The results show that a single GNSS-based scenario often encounters positioning blockage in the harsh operational environment, while multi-constellation cases are able to remedy this situation. The accuracy of multi-GNSS with a combination of GPS and Galileo is superior to that of other GNSS compositions due to the larger SISRE (Signal In Space Ranging Errors) of GLONASS and Beidou. Due to the different characteristics of GNSS SISRE, an issue has been raised to optimally integrate satellite measurements to maximize accuracy of multi-GNSS positioning.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.839-850
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• 2018

The flood damage in urban areas due to torrential rain is increasing with urbanization. For this reason, accurate and rapid flooding forecasting and expected inundation maps are needed. Predicting the extent of flooding for certain rainfalls is a very important issue in preparing flood in advance. Recently, government agencies are trying to provide expected inundation maps to the public. However, there is a lack of quantifying the extent of inundation caused by a particular rainfall scenario and the real-time prediction method for flood extent within a short time. Therefore the real-time prediction of flood extent is needed based on rainfall-runoff-inundation analysis. One/two dimensional model are continued to analyize drainage network, manhole overflow and inundation propagation by rainfall condition. By applying the various rainfall scenarios considering rainfall duration/distribution and return periods, the inundation volume and depth can be estimated and stored on a database. The Rainfall-Duration-Flooding Quantity (RDF) relationship curve based on the hydraulic analysis results and the Self-Organizing Map (SOM) that conducts unsupervised learning are applied to predict flooded area with particular rainfall condition. The validity of the proposed methodology was examined by comparing the results of the expected flood map with the 2-dimensional hydraulic model. Based on the result of the study, it is judged that this methodology will be useful to provide an unknown flood map according to medium-sized rainfall or frequency scenario. Furthermore, it will be used as a fundamental data for flood forecast by establishing the RDF curve which the relationship of rainfall-outflow-flood is considered and the database of expected inundation maps.

• Journal of Korea Port Economic Association
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• v.35 no.2
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• pp.93-108
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• 2019

Recently, air pollution from the marine ports has become a serious issue all over the world. Because marine trade accounts for 99.7% of Korea's trade, efforts are required to recognize the level of port pollution and establish environmental policies. This study estimates air pollution emitted during the berthing process in the Gwangyang and Ulsan ports. Data on ship activity and characteristics are collected and reasonable methodologies and factors from EEA and EPA are adopted. The results show that 253.09 tons of CO, 1986.61 tons of NOx, 684.01 tons of SOx, 47.88 tons of $PM_{10}$, and 44.69 tons of $PM_{2.5}$ are emitted at the Gwangyang port. Further, the Ulsan port emitted 212.28 tons of CO, 1712.54 tons of NOx, 573.72 tons of SOx, 40.16 tons of $PM_{10}$, and 37.48 tons of $PM_{2.5}$. A stage-by-stage plan for installing AMP infrastructure is suggested as part of a green port policy. This research provides the current pollution status and contributes guidelines for the direction of future policy.

• Resources Recycling
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• v.28 no.3
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• pp.15-20
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• 2019

The recovery of struvite using nitrogen and phosphorus in wastewaters is useful for prevention of eutrophication and use as fertilizer, but there are theoretical and technical issues to be resolved. Through the detailed literature review, this study discusses the possible reasonable prediction of struvite formation reaction by setting a feasible reaction equation with some theoretical considerations. In a technical aspect, the purity of struvite in solid precipitates can be promoted by excluding Ca in an effective way. As for the struvite reaction prediction issue, selection of proper equilibrium reaction as well as its reaction equilibrium coefficient is significant in the neutral and basic pH regions. The equilibrium reaction agrees well with the experimental batch test results. Considering the charge balance of the ions, the pH drop along struvite formation in a diluted solution can be predicted. Also, improvement of struvite purity through elimination of Ca can be expected by providing a highly concentrated ${NH_4}^+-N$ relative to ${HPO_4}^{2-}-P$ because ${NH_4}^+$ can enhance the thermodynamic driving force toward favorable struvite formation. Even though the phosphate reacts rapidly with Ca to form a solid precipitate, the thermodynamic driving force due to the high ${NH_4}^+$ activity can dissociate the phosphate-calcium precipitates and produce struvite.

• Journal of Korea Foundry Society
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• v.41 no.1
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• pp.16-25
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• 2021

The development of technology to prevent environmental pollutants and reduce energy consumption has already become a very significant issue not only for the foundry industry but also for society as a whole. In this paper, we introduce a new dust collector developed for low energy consumption and high performance compared to a roof top dust collector. The roof top dust collector which is using widely in the domestic foundry plant has a low performance about the dust suction ability in spite of high energy consumption because it is installed in a high place to collect the whole dust from all processes in foundry. A dust collector away from dust sources inevitably has low energy efficiency. The development of an efficient collector for foundry is very difficult because the position of the dust source continues to change from the melting process to the pouring process. New dust collector is installed on the ladle transfer equipment such as cranes, hoists, and monorails to effectively respond to moving dust sources. The movable device, attached close to the source of dust, provides high performance even with low energy consumption. The new dust collector is expected to be an environment-friendly device that can be applied to the foundry.

• Environmental and Resource Economics Review
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• v.30 no.1
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• pp.79-105
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• 2021

In the circumstance of standing out the climate change issue, the purpose of this study is to compare the efficiency of offshore and coastal fisheries according to whether or not greenhouse gas (GHG) emissions are considered, and then to present policy alternatives based on the analysis results. For analysis, the traditional data envelopment analysis (DEA), the slacks-based measure (SBM) and the SBM-undesirable models were used, and robust analysis of variance (ANOVA) and Wilcoxon Signed-rank tests were performed. As a result, the study showed that the average efficiency of fisheries decreased as the traditional DEA extended to the SBM model considering the slack and the SBM-undesirable model including the GHG emissions. Specifically, the average efficiency of the traditional DEA model, SBM model, and SBM-undesirable model was analyzed as 0.7350, 0.5820 and 0.4976 respectively. In addition, the results of the robust ANOVA and Wilcoxon Signed-rank tests all showed that there are statistically significant differences in efficiency between offshore and coastal fisheries as well as among traditional DEA, SBM and SBM-undesirable models. As a policy alternative to the analysis, it was suggested that to improve the efficiency of coastal and offshore fisheries, it is necessary to actively implement the new fishing vessel project and develop smart and electric hybrid fishing vessels.