• Journal of Environmental Science International
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• v.31 no.1
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• pp.1-8
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• 2022

In this study, solid-liquid separation conditions for coagulation and sedimentation experiments using inorganic coagulant (aluminum sulfate and Poly-Aluminum Chloride (PAC)) were optimized with brine wastewater discharged by the epoxy-resin process. When the turbidity and suspended solid (SS) concentration in raw wastewater were 74 NTU and 4.1 mg/L, respectively, their values decreased the lowest in a coagulant dosage of 135.0 - 270.0 mg Al³⁺/L. The epoxy resin was re-dispersed in the upper part of wastewater treated above 405.0 mg Al³⁺/L. The removal efficiencies of turbidity and SS via dosing with aluminum sulfate and PAC were evaluated at initial turbidity and SS of 74 - 630 NTU and 4.1 - 38.5 mg/L, respectively. They increased most in the range from 135.0 - 270.0 mg Al³⁺/L. The solid-liquid separation condition was quantitatively compared to the correlation of SS removal efficiency between the coagulant dosage and SS concentration based on the concentration of aluminum ions. The empirical formula, R = be^aD, shows the relationship between SS removal efficiency (R) and coagulant dosage (D) at 38.5 mg/L; it produced high correlation coefficients (r²) of 0.9871 for aluminum sulfate and 0.9751 for PAC.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.103-108
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• 2022

This research work reports the development of a Ruthenium/2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)/nitrate catalyst system for the highly selective transformation of isosorbide (1,4:3,6-dianhydro-D-glucitol) to isosorbide-diketone (2,6-dioxabicyclo (3,3,0)octan-4,8-one). Isosorbide is a critical platform molecule for future manufacturing processes. TEMPO has been utilized to convert alcohols to carbonyl compounds for a long time. The optimal chemical reaction condition was found to be when using isosorbide (0.5 mmol) with supported Ru (10 mol%), TEMPO (5 mol%), and sodium nitrate (0.03 mmol) in the presence of acetic acid (3 ml) as a solvent at 50 ℃ and 1 atm oxygen pressure. This catalyst system demonstrated good selectivity (> 97%) and yield (87%) with respect to the desired product, in addition to a putative catalytic double oxidation mechanism.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.995-1002
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• 2022

Global Navigation Satellite System(GNSS) is a convenient system that acquires position and time information of a receiver if only satellite signals can be received anywhere in the world. However navigation signals include errors and a position error occurs according to the reception state of the signal. Also, a position error is affected by the geometric arrangement of the satellites. Therefore a receiver position performance varies by the number and status of visible satellites The condition of satellite signals is not good when the satellite rises or sets and the position change of receiver occurs when the signal is blocked by an obstacle such as a building in the urban area. In this paper, we proposed methods to improve the GNSS performance by using pseudorange correction method estimating the correction amount and the visible satellites selection method. By applying the proposed methods to an environment in which the number of visible satellites changes variously, the performance enhancement was verified.

• Ocean Systems Engineering
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• v.12 no.2
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• pp.225-245
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• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• Smart Structures and Systems
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• v.30 no.6
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• pp.613-626
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• 2022

Guaranteeing the quality and integrity of structural health monitoring (SHM) data is very important for an effective assessment of structural condition. However, sensory system may malfunction due to sensor fault or harsh operational environment, resulting in multiple types of data anomaly existing in the measured data. Efficiently and automatically identifying anomalies from the vast amounts of measured data is significant for assessing the structural conditions and early warning for structural failure in SHM. The major challenges of current automated data anomaly detection methods are the imbalance of dataset categories. In terms of the feature of actual anomalous data, this paper proposes a data anomaly detection method based on data-level and deep learning technique for SHM of civil engineering structures. The proposed method consists of a data balancing phase to prepare a comprehensive training dataset based on data-level technique, and an anomaly detection phase based on a sophisticatedly designed network. The advanced densely connected convolutional network (DenseNet) and Transformer encoder are embedded in the specific network to facilitate extraction of both detail and global features of response data, and to establish the mapping between the highest level of abstractive features and data anomaly class. Numerical studies on a steel frame model are conducted to evaluate the performance and noise immunity of using the proposed network for data anomaly detection. The applicability of the proposed method for data anomaly classification is validated with the measured data of a practical supertall structure. The proposed method presents a remarkable performance on data anomaly detection, which reaches a 95.7% overall accuracy with practical engineering structural monitoring data, which demonstrates the effectiveness of data balancing and the robust classification capability of the proposed network.

• Journal of Forest and Environmental Science
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• v.38 no.4
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• pp.229-238
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• 2022

Q. mongolica and Q. dentata are representative species of deciduous forest communities in Korea and are known to be relatively resistant to soil drying condition among Korean oaks. This study attempted to elucidate the degree of competition and ecological niche characteristics of the two species by comparing the ecological responses of the two species according to soil moisture. Competition between Q. mongolica and Q. dentata was shown to be more intense under the conditions where moisture content was low than under the conditions where moisture content was high. As for the ecological niche overlaps of the two species for soil moisture, the structural traits of plant such as stem diameter overlapped the most, the traits of biomass such as petiole weight overlapped the least, and photosynthetic organ-related traits such as leaf width and length overlapped intermediately. When looking at the competition for soil moisture between the two species, it can be seen that Q. mongolica won in nine traits (leaf width length, leaf lamina length, leaf lamina weight, leaf petiole weight, leaf area, leaves weight, shoot weight, root weight, and plant weight) and Q. dentata won in the remaining seven traits (leaf petiole length, leaves number, stem length, stem diameter, stem weight, shoot length, and root length). Competition between the two species for the moisture environment of the soil was shown to be intense under the conditions where moisture content was low. The degree of competition between Q. dentata and Q. mongolica for soil moisture is high under the conditions where soil moisture content is low, and it is judged that Q. mongolica is more competitive for soil moisture than Q. dentata.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.2
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• pp.55-67
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• 2022

Land use is a critical factor that affects the hydrological characteristics of watersheds, thereby determining the biological condition of streams. This study analyzes the effects of land uses in the watersheds on biological indicators of streams across the Han River basin using a linear model (LM) and generalized additive model (GAM). LULC and biological monitoring data of streams were obtained from the Korean Ministry of Environment. The proportions of urban, agricultural, and forest areas in the watersheds were regressed to the three biological indicators, including diatom, benthic macroinvertebrate, and fish of streams. The estimated LM and GAM models for the biological indicators were then compared, using regression determination R² and AIC values. The results revealed that GAM models performed better than the LM models in explaining the variances of biological indicators of streams, indicating the non-linear relationships between biological indicators and land uses in watersheds. Also, the results suggested that the indicator of macroinvertebrates was the most sensitive indicator to land uses in watersheds. Although non-linear relationships between watershed land uses and biological indicators of streams could vary among biological indicators, it was consistent that streams' biological integrity significantly deteriorated by a relatively low percentage of urban areas. Meanwhile, biological indicators of streams were negatively affected by the relatively high percentage of agricultural areas. The results of this study can be integrated into effective quantitative criteria for the watershed management and land use plans to enhance the biological integrity of streams. In specific, land uses management plans in watersheds may need more close attention to urban land use changes than agricultural land uses to sustain the biological integrity of streams.

• Animal Bioscience
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• v.35 no.3
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• pp.434-443
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• 2022

Objective: The study was conducted to investigate the impact of boron supplementation on nutrient digestibility, inflammatory responses, blood metabolites and diarrhea index, and their relevance to growth performance in weaned pigs housed in good and poor sanitary environments for 14 days after weaning. Methods: A total of 108 male pigs (Duroc×[Yorkshire×Landrace]) weaned at 21 days of age were used in a randomized complete block design with 2×3 factorial arrangement. Pigs were assigned to three boron treatments (0, 5, and 10 mg/kg) under two environments (good and poor sanitary) to give six replicates per treatment (3 pigs per replicate). On 0, 7, and 14 days, one pig per replicate was euthanized to collect, ileum tissue samples, and rectal fecal samples. Results: Boron supplementation quadratically influenced (p<0.001) feed intake and weight gain in pigs housed in good sanitary conditions from 1 to 14 days post-weaning where pigs offered 5 mg/kg boron optimized weight gain and feed intake. There is a quadratic interaction (p = 0.019) on feed intake for 1 to 14 days post-weaning where 5 mg/kg boron increased feed intake in good sanitary conditions. Pigs housed in the poor sanitary environment decreased (p<0.001) villus height and crypt depth in ileum at days 7 and 14. On day 7 and 14, crude protein digestibility was quadratically influenced (p<0.05) by boron supplementation. Boron supplementation linearly increased (p<0.05) plasma calcium and cholesterol levels whilst linearly (p = 0.005) reducing plasma triglyceride concentrations. Diarrhea index was quadratically influenced (p<0.05) by boron supplementations regardless of sanitary conditions where 5 mg/kg boron inclusion achieved the lowest diarrhea index. Conclusion: Pigs offered 5 mg/kg of boron increased weight gain which may be deduced by improved dry matter, crude protein, and energy digestibility regardless of the sanitary conditions.

• Research in Community and Public Health Nursing
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• v.33 no.3
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• pp.269-278
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• 2022

Purpose: This study analyzed the retention factors of Korean community health practitioners who sustained over 20 years based on a multi-dimensional framework. This study suggests global implications for nurses working in rural or remote areas, even during a worldwide pandemic. Methods: The participants were 16 Korean community health practitioners who worked in rural or remote locations for over 20 years. This study identified nurses' key retention factors contributing to long service in rural and remote areas. This is a qualitative study based on the narrative method and analysis was conducted using grounded theory. A semi-structured questionnaire was conducted based on the following: the life flow of the participants' first experience, episodes during the work experience, and reflections on the past 20 years. Results: First, personal 'financial needs' and 'callings' were motivation-related causal conditions. The adaptation of environment-work-community was the contextual condition leading to intervening conditions, building coping strategies by encountering a lifetime crisis. The consequences of 'transition' and 'maturation' naturally occurred with chronological changes. The unique factors were related to the 'external changes' in the Korean primary health system, which improved the participants' social status and welfare. Conclusion: Considering multi-dimensional retention factors was critical, including chronological (i.e., historical changes) and external factors (i.e., healthcare systems), to be supportive synchronously for rural nurses. Without this, the individuals working in the rural areas could be victimized by insecurity and self-commitment. Furthermore, considering the global pandemic, the retention of nurses is crucial to prevent the severity of isolation in rural and remote areas.

• Tribology and Lubricants
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• v.38 no.6
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• pp.255-260
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• 2022

This research presents tetrahedral amorphous (ta-C) coating on the artificial tooth for improving the durability and functionality (esthtics, foreign body of tooth) by filtered cathodic vacuum arc (FCVA). A differentiated coating method is required for a ta-C coating on polymer owing to the low melting point of the polymer, inter-facial adhesion, low friction, and non-conductivity. Herein, ta-C coating is applied below 50℃, and the potential difference of the carbon plasma drawn to the substrate was controlled by applying a positive duct bias voltage without using a substrate bias voltage. Consequently, the ta-C coating with a thickness of 70nm using the duct bias condition of 20V with the highest plasma intensity satisfies the esthetics of the artificial tooth and had a 5B level of inter-facial adhesion. In addition, the composite hardness of ta-C/polymer is 380 MPa, and correlations with esthetics, sp³ bonding, and mechanical properties. The friction coefficient (CoF) of the ta-C coating in a water-lubricated environment is 0.07, showing a six-fold reduction in CoF compared with that of a polymer.