• Sleep Medicine and Psychophysiology
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• v.27 no.1
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• pp.1-7
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• 2020

Mobile digital devices are very familiar and useful devices in the daily life of modern people, and are used for various tasks such as communication, reading, writing, and playing media. As the use of mobile digital devices has become more prevalent, user time has also been increasing. In particular, the number of people who use digital devices before sleep is growing. The light pollution associated with these devices is classified into four categories: urban sky glow, glare, light trespass, and clutter. The pattern in which modern people use digital devices corresponds to light pollution caused by light trespass and clutter from light exposure to artificial light at night. The light pollution caused by digital devices can cause melatonin secretion suppression, delayed sleep onset, reduction of sleepiness before bedtime, and periodic rhythm and cognitive function disturbances. In addition, a study of children and adolescents showed there may be disturbances in the sleep-wake cycle and circadian rhythm, deterioration of sleep quality, and daytime fatigue due to light pollution caused by artificial light at night from mobile digital devices. A multi-faceted research effort is also necessary to investigate the healthy use of mobile digital devices based on research evidence and insights with an accurate evaluation of the influence of mobile digital devices as a form of light pollution.

• Tuberculosis and Respiratory Diseases
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• v.78 no.4
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• pp.432-435
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• 2015

This is a report of the first South Korean case of a lung disease caused by Mycobacterium simiae. The patient was a previously healthy 52-year-old female. All serial isolates were identified as M. simiae by multi-locus sequencing analysis, based on hsp65, rpoB, 16S-23S rRNA internal transcribed spacer, and 16S rRNA fragments. A chest radiography revealed deterioration, and the follow-up sputum cultures were persistently positive, despite combination antibiotic treatment, including azithromycin, ethambutol, and rifampin. To the best of our knowledge, this is the first confirmed case of a lung disease caused by M. simiae in South Korea.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.17-23
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• 2013

In a subway vehicle, a lateral damper is used for compensating the lateral stiffness deterioration due to the air-spring as a secondary suspension. This lateral damper can reduce the lateral vibration of the carbody. When the damping force of the lateral damper is lowered, the running stability and ride quality of the subway vehicles worsens and the lateral motion of the carbody is increased. In this study, the lateral displacement variation of the carbody according to the damping force of the lateral damper was analyzed by multi-body dynamics to solve the abnormal impact problem during vehicle operation. Furthermore, the noise and vibration due to abnormal impact were considered. An adequate damping coefficient of the lateral damper for the subway vehicle treated in this paper was suggested for preventing abnormal impact.

• Journal of Korean Neurosurgical Society
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• v.38 no.6
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• pp.435-441
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• 2005

Objective : Expandable cage used for spinal reconstruction after corpectomy has several advantages over nonexpendable cages. Here we present our clinical experience with the use of this cage after anterior column corpectomy with an average of one year follow up. Methods : Ten patients underwent expandable cage reconstruction of the anterior column after single-level or multilevel corpectomy for various cervical spinal disorders. Anterior plating with or without additional posterior instrumentation were performed in all patients. Functional outcomes, complications, and radiographic outcomes were determined. Results : There was no cage-related complication. Functionally, neurological examination revealed improvement in 7 of 10 patients and no patient had neurological deterioration after the surgery. Immediate stability was achieved and maintained throughout the period of follow-up. There was minimal subsidence [<2mm] noticeable in three of the cases that underwent a two-level corpectomy. Subsidence was noted in osteoporotic patients and patients undergoing multi-level corpectomies. Average pre-operative kyphotic angle was 9 degrees. This was corrected to an average of 5.4 degrees in lordosis postoperatively. Conclusion : In conclusion, expandable cages are safe and effective devices for vertebral body replacement after cervical corpectomy when used in combination with anterior plating with or without additional posterior stabilization. The advantages of using expandable cages include its ability to easily accommodate itself into the corpectomy defect, its ability to tightly purchase into the end plates after expansion and thus minimizing the potential for migration, and finally, its ability to correct kyphosis deformity via its in vivo expansion properties.

• Structural Engineering and Mechanics
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• v.84 no.2
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• pp.143-154
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• 2022

Corrosion of steel reinforcement is considered as the main cause of concrete structures deterioration, especially those under humid environmental conditions. Hence, fiber reinforced polymer (FRP) bars are being increasingly used as a replacement for conventional steel owing to their non-corrodible characteristics. However, predicting the shear strength of beams reinforced with FRP bars still challenging due to the lack of robust shear theory. Thus, this paper aims to develop an explicit data driven based model to predict the shear strength of FRP reinforced beams using multi-objective evolutionary polynomial regression analysis (MOGA-EPR) as data driven models learn the behavior from the input data without the need to employee a theory that aid the derivation, and thus they have an enhanced accuracy. This study also evaluates the accuracy of predictive models of shear strength of FRP reinforced concrete beams employed by different design codes by calculating and comparing the values of the mean absolute error (MAE), root mean square error (RMSE), mean (𝜇), standard deviation of the mean (𝜎), coefficient of determination (R²), and percentage of prediction within error range of ±20% (a20-index). Experimental database has been developed and employed in the model learning, validation, and accuracy examination. The statistical analysis illustrated the robustness of the developed model with MAE, RMSE, 𝜇, 𝜎, R², and a20-index of 14.6, 20.8, 1.05, 0.27, 0.85, and 0.61, respectively for training data and 10.4, 14.1, 0.98, 0.25, 0.94, and 0.60, respectively for validation data. Furthermore, the developed model achieved much better predictions than the standard predictive models as it scored lower MAE, RMSE, and 𝜎, and higher R² and a20-index. The new model can be used in future with confidence in optimized designs as its accuracy is higher than standard predictive models.

• Journal of Wetlands Research
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• v.18 no.4
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• pp.386-393
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• 2016

Agricultural ecosystem is recognized as a space for providing a variety of services, in addition to the food production that it originally encompassed, such as water purification, biological habitat, air purification, soil conservation, and landscape development. The construction of greenhouses in agricultural landscapes can cause deterioration of ecosystem services because of the increase of impermeable area and loss of biological habitats. This study aimed to compare insect diversity between different types of constructed greenhouses and paddy ecosystems. The target study area was selected by considering the distribution status of horticultural complexes and was classified as Single Vinyl Greenhouse, Multi Vinyl Greenhouse or Glass Greenhouse and they were compared with four paddies. The study locations were in Gu-Mi, Bu-Yeo, Ginje and Jin-Ju. A total of 2,333 individual insects belonging to 9 orders, 38 families, 76 genus, and 80 species were collected. The composition of orders was Hemiptera (22.37%), Coleoptera (18.42%), Hymenoptera (14.47%), Orthoptera (11.84%), and Diptera (10.53%). The average number of collected species were in the order Paddy (39.38 species) > Single Vinyl Greenhouse (35.50 species) > Multi Vinyl Greenhouse (22.50 species) > Glass Greenhouse (24.00 species). The Diversity Index (H') was Paddy (4.76) > Single Vinyl Greenhouse (4.57) > Multi Vinyl Greenhouse (4.12), and Glass Greenhouse (4.12). The Richness Index (RI) was Paddy (7.72) and Single Vinyl Greenhouse (7.03) > Multi Vinyl Greenhouse (4.99) and Glass Greenhouse (5.32). From our results, it can be seen that the biological diversity features of insects decreased when greenhouses are constructed.However, Single Vinyl Greenhouse is noted to promote insect diversity more than that by Multi Vinyl Greenhouse and Glass Greenhouse. Hence, when constructing greenhouses, it is necessary to consider insect habitat to conserve insect diversity.

• Journal of Korea Port Economic Association
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• v.25 no.3
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• pp.139-164
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• 2009

The purpose of this paper is to investigate the value chain efficiency of Korean port investment by using the newly developed multi-year and multi-stage value chain efficiency model of DEA(Data Envelopment Analysis). Inputs[port investment amount, cargo handling capacity, and berthing capacity], and outputs[cargo handling amount, number of ship calls, revenue, and score of customer service satisfaction] are used during 14 years(1994-2007) for 20 Korean seaports by using two kinds of DEA models. Empirical main results are as follows: First, Model 1 shows that the ranking order of multi-stage value chain efficiency is Stage 2, Stage 3-1, Stage 1, and Stage 3-2. And according to the value chain average efficiency scores, ranking order is stages 2, 1, 3-1, and 3-2. In Model 2, 3(Incheon, Mogpo, and Jeju) out of 9 ports show the ranking order of Stages 2, 3-2, 3-1, and 1. And value chain average efficiency scores rank in order of Stages 2, 3-2, 3-1, and 1. Second, the difference among the value chain efficiency scores of each stage comes from the efficiency deterioration of all ports except Stages 2 and 1 in Model 1. In Model 2, value chain efficiency scores among the Stages 3-1, 3-2 compared to Stage 1 were deteriorated. The main policy implication based on the findings of this study is that the manager of port investment and management of Ministry of Land, Transport and Maritime Affairs in Korea should introduce the multi-year, multi-stage value chain efficiency method for deciding the port investment amount and evaluating the effect of port investment after considering the empirical results of this paper carefully.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.397-409
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• 2014

Algal problem in drinking water treatment is being gradually increased by causing deterioration of water supplies therefore, especially taste and odor compounds such as geosmin and 2-MIB occur mainly aesthetic problem by its unpleasant effects resulting in the subsequent onset of complaints from drinking water consumer. Recently, geosmin and 2-MIB are detected frequently at abnormally high concentration level. However, conventional water treatment without advanced water treatment processes such as adsorption and oxidation process, cannot remove these two compounds efficiently. Moreover, it is known that the advanced treatment processes i.e. adsorption and oxidation have also several limits to the removal of geosmin and 2-MIB. Therefore, the purpose of this study was not only to evaluate full scale nanofiltration membrane system with $300m^3/day$ of permeate capacity and 90% of recovery on the removal of geosmin and 2-MIB in spiked natural raw water sources at high feed concentration with a range of approximately 500 to 2,500 ng/L, but also to observe rejection property of the compounds within multi stage NF membrane system. Rejection rate of geosmin and 2-MIB by NF membrane process was 96% that is 4% of passage regardless of the feed water concentration which indicates NF membrane system with an operational values suggested in this research can be employed in drinking water treatment plant to control geosmin and 2-MIB of high concentration. But, according to results of regression analysis in this study it is recommended that feed water concentration of geosmin and 2-MIB would not exceed 220 and 300 ng/L respectively which is not to be perceived in drinking tap water. Also it suggests that the removal rate might be depended on an operating conditions such as feed water characteristics and membrane flux. When each stage of NF membrane system was evaluated relatively higher removal rate was observed at the conditions that is lower flux, higher DOC and TDS, i.e., $2^{nd}$ stage NF membrane systems, possibly due to an interaction mechanisms between compounds and cake layer on the membrane surfaces.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.3
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• pp.1-17
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• 2004

The focus of this study is the promotion of green area volumes and their naturalness, water circulation system, decline of entropy, creation of biological habitats and linkage of separated urban green space. Re-presentative urban biotope survey sites were categorized as urban biotope, semi-natural biotope, and natural forest. In the urban biotope, a residential biotope was constructed near the Han river and in mountain areas. The green-area ratio at the housing complex was about 25%. GVZ(Grunvolumenzahl) was 0.35m$^3$/m$^2$ at the 5∼10-story housing complex, and 1.53m$^3$/m$^2$ over the 11-story. As for the green-area structure of the housing complex, canopy layer, understory layer, and shrub layer were not differentiated and the green-area volume was not high enough. The green-area ratio of school areas as a public area biotope was 5∼20%. GVZ was 1.12m$^3$/m$^2$ at Myungduk High School, and 1.78m$^3$/m$^2$ at Jeonggok Elementary School. In order to convert the urban biotope into an ecological area, green areas around the buildings should be connected to urban buffer green areas, and multi-layer structures should be established with natural plant species. In the semi-natural biotope, neighbor parks were created park in the vicinity of the natural forests. GVZ was 0.28m$^3$/m$^2$, and plantation was established with single layer structure and was definitely insufficient for the area. The urban buffer green areas have been established in strip corridors with the width of 20∼123m. In those areas, GVZ was 0.16∼0.27m$^3$/m$^2$ and had a deficient canopy layer, understory layer, and shrub layer. Soil conditions were not favorable for tree growth. In the natural biotope, GVZ of the plantation was 1.03∼1.5m$^3$/m$^2$ but the high crown closure of this area reduces the chance of species change and succession. GVZ of natural forest was 2.53∼2.57m$^3$/m$^2$. It is desirable to plant diverse plants and the natural forest should be succeeded by broad-leaf deciduous tree species. To improve the value of biotope at Kangseo-Gu, building height needs to be limited to reduce the environmental deterioration in the city. In order to maintain the water circulation system, water-permeable material is recommened when the urban surface areas are paved. The establishment of a water circulation system will improve ground water levels, soil moisture, water quality, and habitats. In order to improve biological diversity, it is desirable to have multi-layer structures in urban green areas with native species.

• Korean Journal of Social Welfare Studies
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• v.44 no.2
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• pp.327-358
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• 2013

This study aimed to analyze the trajectories of cognitive function and functional disability, and to identify the impacts of socio-demographic factors on the two variables. Based on the assumption that there are differences according to the progress of cognitive impairment, it focused on examining the differences in trajectories of cognitive function and functional disability between two groups: dementia conversion group and dementia non-conversion group among cognitively normal older adults. This study was conducted based on the data from a 3-wave panel study of a sample of 966 Yeoncheon elderly cohort aged 65 and over between 1997 and 2003. Latent growth curve model and multi-group structural equation modeling were used to examine the hypothesis. Results revealed that dementia conversion group exhibited faster rate of cognitive decline as well as lower initial cognitive level. Difference between two groups was not significant in the initial level of functional disability, yet dementia conversion group showed greater degree of deterioration in the functional disability over time than dementia non-conversion group did. In terms of the influence of socio-demographic factors on cognitive function and functional disability, the cognitive decline was more drastic in the female group, whereas functional decline was more apparent for the male group. The level of education in early life had a strong impact on the cognitive function in later life. Based on these findings, practical implication for high risk groups in cognitive function and functional disability were discussed.