• The Journal of Engineering Geology
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• 제29권2호
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• pp.113-122
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• 2019

In this study, the flow analysis to evaluate the extent of groundwater decline and the effect of the small valleys caused by the decrease of groundwater level in the construction of road tunnel, and the pollutant movement analysis to evaluate pollution of nearby water source by pollutant discharge during tunnel construction, respectively. The decrease of the groundwater during the 30 month tunnel excavation period was maximum 27 m and it was found to be the largest within 50 m from the tunnel center. The flow of groundwater is shown in the form of flowing into the tunnels and the effects of groundwater level decline were observed up to a tunnel radius of 200 m. As a result of the numerical modeling of the contaminant transport to examine the influence of the polluted water discharge from the tunnel, the range of the turbid water generated at the end of the tunnel is up to 120 m and it is estimated that the risk of contamination of the small river is not large.

• Journal of the Society of Disaster Information
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• 제15권1호
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• pp.28-38
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• 2019

Purpose: The purpose of this study is to contribute to improvement of measurement management level of construction structure and technology development of monitoring sensor by presenting the detailed causes and improvement plans of construction monitoring sensor's decline in durability. Method: The causes and improvement plans of the durability degradation of the construction monitoring sensor were divided into the construction field and the electric, electronic field. The detailed status was reviewed. Results: In the field of construction, approval and inspection, inspection and testing, verification and calibration, and minimization of loss and damage ratio were reviewed. In the field of electric and electronics, sensor package and sealing, disconnection of stress concentration area, damage caused by lightning and corrosion were reviewed. Conclusion: It is expected that the durability of monitoring sensors applied to the construction site will become longer than the present status based on the study that analyzed causes and improvement plans of construction monitoring sensor's decline in durability in the field of construction and electric, electronic devices.

• Fisheries and Aquatic Sciences
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• 제24권1호
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• pp.53-62
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• 2021

Gindai (Pristipomoides zonatus) is one of six snappers in a management complex called the Deep 7 of the Hawaiian Islands. Little is known about its life history and a preliminary analysis of otolith thin sections indicated the species may exhibit moderate growth with a lifespan approaching 40 years. Preliminary age estimates from the previous study were reinvestigated using the same otolith sections in an attempt to validate those ages with bomb radiocarbon (¹⁴C) dating. From the misalignment of birth years for the otolith ¹⁴C measurements with regional references - the post-peak bomb ¹⁴C decline period - it was concluded that previous ages were inflated from overcounting of the earliest growth zone structure in otolith sections. The oldest gindai was re-aged to 26 years once the age reading was adjusted for early overcounting, 13 years younger than the original estimate of 39 years for this fish. In general, the earliest otolith growth of gindai was massive and complicated by numerous subannual checks. The approach of lumping the early growth structures was supported by the alignment of ¹⁴C measurements from otolith core material (first year of growth). The result was greater consistency of calculated birthdates with the ¹⁴C decline reference, along with minor offsets that may indicate age estimation was imprecise by a few years for some individuals. The revised von Bertalanffy growth function applied to the validated age-at-length estimates revealed more rapid growth (k = 0.378 cf. 0.113) and a lifespan of approximately 30 years. The findings presented here are a case study of how the bomb ¹⁴C decline period can be used as a tool in the refinement of age reading protocols.

• Clinical and Experimental Reproductive Medicine
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• 제49권1호
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• pp.16-25
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• 2022

In mammalian species, females are born with a number of oocytes exceeding what they release via ovulation. In humans, an average girl is born with over a thousand times more oocytes than she will ovulate in her lifetime. The reason for having such an excessive number of oocytes in a neonatal female ovary is currently unknown. However, it is well established that the oocyte number decreases throughout the entire lifetime until the ovary loses them all. In this review, data published in the past 80 years were used to assess the current knowledge regarding the changing number of oocytes in humans and mice, as well as the reported factors that contribute to the decline of oocyte numbers. Briefly, a collective estimation indicates that an average girl is born with approximately 600,000 oocytes, which is 2,000 times more than the number of oocytes that she will ovulate in her lifetime. The oocyte number begins to decrease immediately after birth and is reduced to half of the initial number by puberty and almost zero by age 50 years. Multiple factors that are either intrinsic or extrinsic to the ovary contribute to the decline of the oocyte number. The inflammation caused by the ovulatory luteinizing hormone surge is discussed as a potential contributing factor to the decline of the oocyte pool during the reproductive lifespan.

• The Plant Pathology Journal
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• 제38권6호
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• pp.551-571
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• 2022

Xylella fastidiosa is xylem-limited bacterium capable of infecting a wide range of host plants, resulting in Pierce's disease in grapevine, citrus variegated chlorosis, olive quick decline syndrome, peach phony disease, plum leaf scald, alfalfa dwarf, margin necrosis and leaf scorch affecting oleander, coffee, almond, pecan, mulberry, red maple, oak, and other types of cultivated and ornamental plants and forest trees. In the European Union, X. fastidiosa is listed as a quarantine organism. Since its first outbreak in the Apulia region of southern Italy in 2013 where it caused devastating disease on Olea europaea (called olive leaf scorch and quick decline), X. fastidiosa continued to spread and successfully established in some European countries (Corsica and PACA in France, Balearic Islands, Madrid and Comunitat Valenciana in Spain, and Porto in Portugal). The most recent data for Europe indicates that X. fastidiosa is present on 174 hosts, 25 of which were newly identified in 2021 (with further five hosts discovered in other parts of the world in the same year). From the six reported subspecies of X. fastidiosa worldwide, four have been recorded in European countries (fastidiosa, multiplex, pauca, and sandyi). Currently confirmed X. fastidiosa vector species are Philaenus spumarius, Neophilaenus campestris, and Philaenus italosignus, whereby only P. spumarius (which has been identified as the key vector in Apulia, Italy) is also present in Americas. X. fastidiosa control is currently based on pathogen-free propagation plant material, eradication, territory demarcation, and vector control, as well as use of resistant plant cultivars and bactericidal treatments.

• The Journal of the Convergence on Culture Technology
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• 제7권4호
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• pp.607-612
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• 2021

This study estimated the impact of the shock of housing price increase on the total fertility rate and the contribution of each variable to changes in the TFR. This study is differentiated by estimating the contribution rate of each variable to the fertility rate through the Shapley decomposition and the panel VAR's forecast error variance decomposition, which previous studies have not attempted. The main results of this study are as follows. First, the decline in the TFR in Korea has been strongly influenced by the recent decline in the total fertility rate, and this influence is expected to continue in the future. In the case of housing costs, in the past, housing sales prices had a relatively small contribution to changes in the total fertility rate compared to the jeonse prices, but their influence is expected to increase in the long term in the future. It has been demonstrated that private education expenses other than housing sale price and Jeonse price also acted as a major cause of the decline in the total fertility rate.

• Journal of Korean society of Dental Hygiene
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• 제22권5호
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• pp.333-340
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• 2022

Objectives: This study aimed to confirm the association between cognitive function and oral health status in the elderly. Methods: In this study, 5,794 respondents, aged 55 or older, who had participated in the 7th aging research panel survey were used. Statistical analyses were performed using a complex samples cross-tabulation analysis, complex samples general linear model, and a complex sample multinomial logistic regression analysis. Results: After analyzing the cognitive function of the elderly according to their oral health conditions, it was found that suspicions of dementia (19.6%) and cognitive function decline (25.9%) were more common for those who wore dentures than for those who did not wear dentures (p<0.001). Compared to those who did not wear dentures, those who wore dentures were linked to a 1.665 times higher suspicion of dementia (p<0.001). In comparison, cognitive decline was 0.964 times lower when the number of natural teeth increased by 1, and it was 0.941 times lower when the oral health evaluation index for the elderly increased by 1 point (p<0.001). Conclusions: As a result of this study, it was confirmed that cognitive function and oral health status are related in the elderly. Therefore, systematic measures for oral health management and oral health promotion should be prepared in tandem with awareness of possible cognitive decline in the elderly.

• Economic Analysis
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• 제27권2호
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• pp.1-40
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• 2021

Using an unobserved components model that features trend growth as a random walk, we find that GDP trend growth rates had gradually declined from the late 1980s to early 2010s in Korea. To uncover the underlying features of the slowdown, we use trend growth accounting. A major feature appears to be a significant decline in the growth rate of labor productivity. To be specific, the first gradual decline in trend growth, which started in 1988 and continued to 1998, is associated with a drop in TFP measured in labor-augmenting units. This finding is inconsistent with the hypothesis that the slowdown in GDP trend growth can be attributed to the 1997-1998 Korean financial crisis. Sluggish investment growth is behind the second period of the gradual slowdown, from 2002 to 2012.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제59권4호
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• pp.315-327
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• 2023

In the last five decades, there has been a consistent decline in the total catch of fisheries in the Korean jurisdiction since the peak in 1986. The decline in catch slowed and slightly rebounded in the 2000s, but changed back to a decline in the 2010s. As indicators that can identify changes in the marine ecosystem, trophic level (TL), biodiversity index (H'), and the ratio between pelagic fish and demersal fish (P/D) were analyzed by each local marine ecosystem. There were some different changes in each local marine ecosystem, but the mean TL and H' decreased and P/D increased in general in Korean waters. Demersal fish, which were dominant in the 1970s and 1980s, declined, and small pelagic fish and cephalopods have dominantly changed since the 1990s. However, these changes are not simple, and they are fluctuating in complex ways relating to each marine ecosystem and the timing. It is believed that changes in marine ecosystems in Korean waters are likely caused by a combination of fisheries and climate change. The ecosystem indicators reflected a change in the total catch, a sharp drop in catch of demersal fish, and increasing catch of pelagic fish since the mid-1980s.

• Management & Information Systems Review
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• 제35권4호
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• pp.99-122
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• 2016

The social networking services (SNSs) have become popular among smartphone users, and one of the most popular services. In order to explain users' motivations toward SNS, this study considers uses and gratification theory which can explain individuals' motivations to select certain media channels. The purposes of this study is to investigate the relationships between motivations and addiction of SNS, and between addiction of SNS and decline in the subjective wellbeing. We examine moderating effects of social tie based on the social capital theory in the relationships between SNS addiction and decline in the subjective wellbeing. The motivations of SNS are subdivided into emotional motive (entertainment and fantasy) and cognitive motive (information share burden and challenge burden) based on the use and gratifications theory. The addiction of SNS is subdivided into time tolerance, withdrawal symptoms, interruption, and barrier of living. The data used in this study were collected from 286 SNS users through surveys. The data analysis in this study was performed using AMOS 17.0, and we used SEM(Structural Equation Modeling) methods in order to test the research model. The result shows that the emotional motive(entertainment and fantasy) and cognitive motive(information share burden and challenge burden) have an effect on the addiction of SNS. Especially emotional motive such as entertainment and users' fantasy toward SNS is an important factor that can cause SNS addiction. The addiction of SNS such as time tolerance, withdrawal symptoms, interruption, and barrier of living has an effect on the decline in the subjective wellbeing. Our result show that social tie partially moderates the relationship SNS addiction and decline in the subjective wellbeing. In addition, social tie between interruption of SNS and decline in the subjective wellbeing is an important moderating factor. The results focuses on the understanding toward relationship between SNS addiction based on the online and decline in the subjective wellbeing in the real world. The findings of this study also provides theoretical as well as practical implications which reflect the major features of SNS, and moderating effects of social tie based on the social capital.