• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.295-306
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• 2010

Contrary to an intact rock, the jointed rock mass shows strain-dependent deformation characteristics (elastic modulus and damping ratio). The maximum elastic modulus of a rock mass can be obtained from an elastic wave-based exploration in a small strain level and applied to seismic analyses. However, the assessment and application of the non-linear characteristics of rock masses in a small to medium strain level ($10^{-4}{\sim}0.5%$) have not been carried out yet. A non-linear dynamic analysis module is newly developed for FLAC3D to simulate strain-dependent shear modulus degradation and damping ratio amplification characteristics. The developed module is verified by analyzing the change of the Ricker wave propagation. Strain-dependent non-linear characteristics are obtained from disks of cored samples using a rock mass dynamic testing apparatus which can evaluate wave propagation characteristics in a jointed rock column. Using the experimental results and the developed non-linear dynamic module, seismic analyses are performed for the intersection of a shaft and an inclined tunnel. The numerical results show that vertical and horizontal displacements of non-linear analyses are larger than those of linear analyses. Also, non-linear analyses induce bigger bending compressive stresses acting on the lining. The bending compressive stress concentrates at the intersection part. The fundamental understanding of a strain-dependent jointed rock mass behavior is achieved in this study and the analytical procedure suggested can be effectively applied to field designs and analyses.

• Industry Promotion Research
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• v.9 no.2
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• pp.95-102
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• 2024

This study aims to compare the role of the public sector in the U.S. and Korean medical security systems and study response measures in the social risk situation of the COVID-19 virus. The COVID-19 pandemic was a typical case of a 'disaster' that spread across the world across borders in a short period of time and caused serious social welfare losses by increasing the annual number of deaths by approximately 4% in 2020. Threats to health security, such as changes in social order, unpredictable endings, prolonged control of daily life, and deepening inequality, affected the economy, politics, and environment as a whole, and people had to experience anxiety and confusion due to mental and physical stress. Furthermore, developed countries failed to provide help to low-income countries in the face of global disasters. In this situation, the country's disaster management capacity to minimize harm and secure resilience, especially disaster response capacity in the health and medical field, is inevitably very important. Therefore, this study compares how the health insurance system, which is a system to guarantee citizens' right to life, differs from the United States, a liberal health care country, and raises the need to strengthen the role of the public sector.

• Korean Journal of Acupuncture
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• v.41 no.2
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• pp.33-42
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• 2024

Objectives : The sigma-1 receptor is implicated in stress, depression, psychostimulant sensitization, and addiction vulnerability. Prior studies have indicated that ethanol exposure modulates sigma-1 receptor activity within the Ventral Tegmental Area (VTA). Here, we explore the sub-mechanisms underlying sigma-1 receptor activity induced by HT7 (Shinmun) stimulation in behavioral alterations following acute ethanol (ETOH) administration. Methods : Male Wistar rats were investigated for pro- and anti-inflammatory markers after injection of ETOH (1 g/kg) using cytokine enzyme-linked immunosorbent assay (ELISA)s. After confirming that HT7 stimulation changed the total distance traveled in the open field test (OFT), protein changes in the Ventral tegmental area (VTA) were measured by Western blotting. The expression level of inducible nitric oxide synthase (iNOS) after administration of a sigma-1 receptor antagonist (dihydrobromide 1047; BD1047, 10 mg/kg i.p.) and Shenmen (HT7) stimulation was compared. Results : As a result, acute ETOH administration increased proinflammatory marker levels (TNF-𝛼 and IL-6). HT7 stimulation restored the total distance response after acute ethanol administration. In addition, in the VTA, the levels of a microglial marker (iNOS), sigma-1 receptor and protein kinase C, which are predicted to be involved in up- and downregulation, were restored by HT7 stimulation. In particular, HT7 stimulation modulates iNOS expression through effects similar to BD treatment. This study suggests that the stimulatory effect of HT7 may be driven by microglial activation. Conclusions : Microglial activity is regulated by sigma-1 receptor, and sigma-1 receptor activity is regulated by HT7 stimulation. Significantly, we demonstrate that HT7 stimulation ameliorates behavioral alterations induced by acute ETOH administration through microglial activation within the VTA.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.9-18
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• 2023

Climate change affects the safety of river revetments, especially those associated with external flooding. Research on slope reinforcement has been actively conducted to enhance revetment safety. Recently, technologies for producing embankment blocks using recycled materials have been developed. However, it is essential to analyze the impact of block shapes on the flow characteristics of exclusion zones for revetment safety. Therefore, this study investigates the influence of revetment block shapes on the hydraulic characteristics of revetment surfaces through 3D numerical simulations. Three block shapes were proposed, and numerical analyses were performed by installing the blocks in an idealized river channel. FLOW-3D was used for the 3D numerical simulations, and the variations in maximum flow velocity, bed velocity beneath the revetment, and maximum shear stress were analyzed based on the shapes of the revetment blocks. The results indicate that for irregularly sized and spaced revetment blocks, such as the natural stone-type vegetation block (Block A), when connected to the revetment in an irregular manner, the changes in flow velocity in the revetment installation zone are more significant than those for Blocks B and C. It is anticipated that considering the topographical characteristics of rivers in the future will enable the design of revetment blocks with practical applicability in the field.

• Information Systems Review
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• v.19 no.4
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• pp.63-85
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• 2017

Recent information technology achieves remarkable progress in almost all areas where it can be applied. However, this technology also causes technostress, such as fear and pressure to individuals, due to events, such as the threat of job loss. This technostress is becoming an important factor that can affect user performance and productivity in future society where information technology will be the focus. This kind of stress should be studied considerably in academic and practical applications. The effects of technostress on individual performance remain ambiguous. Therefore, academic research is needed to prove these effects. This study aimed to clarify the direct and indirect effects of technostress on information technology end-users. We developed a research model that integrates innovation resistance and technostress theory through previous studies and analyzed the questionnaire of 317 people. The PLS structural equation model and the study results of Baron and Kenny (1986) indicated that rapid change, connectivity, reliability, and complexity are crucial factors affecting the technostress of information technology. Technostress was analyzed indirectly only through innovation resistance, which affected the performance of end-users. This study will provide new implications for the relationship between technostress and performance or productivity in the IS field.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.442-448
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• 2023

This study aimed to develop an optimal greenhouse model for strawberry seedling during the summer high-temperature period based on the results of field surveys. We conducted a survey on the structure types of 46 strawberry seedling farms nationwide, including width, ridge height, eaves height, ventilation method, seedling bed width, and spacing. Based on the survey results, we derived the optimal greenhouse model by considering various factors. The greenhouse width was set at 14 meters to maximize the efficiency of seedling beds and overall space. The height was determined at 2 meters, taking into account ventilation during the summer season. To reduce stress on the supporting structure due to snow loads, we established a reinforcement installation angle of 50 degrees. We analyzed two different models that use support beams with dimensions of φ48.1×2.1t and φ59.9×3.2t, respectively, to ensure structural safety against meteorological disasters, considering regional design wind speeds and snow accumulation. We utilized these developed greenhouse model to conduct strawberry seedling experiments, resulting in a high survival rate of average 93.2%. These findings confirm the usefulness of the strawberry seedling greenhouse in improving the seedling environment and enhancing overall efficiency.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.466-474
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• 2023

In recent years, the government has strongly promoted multi-purpose utilization of paddy field. However, poor drainage causes waterlogging stress in upland crops, requiring subsurface drainage technology, resulting in high installation and management costs. To address this issue, a low-cost and high-efficiency technique was developed that utilizes wasted coir substrates which have characteristics of high porosity and good drainage, for upland crop cultivation in paddy fields. Soybeans were grown in both paddy soil and wasted coir slab with two planting densities (80×20 cm and 60×20 cm). The results showed that the coir substrates had better performance than the paddy soil in terms of soil physical and chemical properties and the growth and yield of upland crops are improved. The treatments using wasted coir substrate showed a 41.4% increase in yield and a 21.3% increase in protein content compared to PS treatment. Our findings demonstrate that recycling waste coir substrates to grow upland crops is a positive cultivation strategy to solve some drainage problems in paddy fields. This approach offers a sustainable solution for upland crop production while also addressing the issue of waste management in agriculture.

• Journal of Korean Society of Forest Science
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• v.102 no.4
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• pp.522-529
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• 2013

Climate change will affect the physiological traits and growth of forest trees. This study was conducted to investigate the effects of an experimental warming on growth and physiological characteristics of Pinus densiflora S. et Z. seedlings. One-year-old P. densiflora seedlings were planted in control and warmed plots in April 2010. The air temperature of warmed plots was increased by $3^{\circ}C$ using infrared lamps from November 2010. We measured shoot height, root collar diameter, above and below ground biomass, chlorophyll contents and leaf nitrogen concentration from March 2011 to March 2013. Seedling height and root collar diameter showed no significant difference between warmed and control plots except for root collar diameter measured in June 2012. Seedling leaf biomass was lower in the warmed ($23.94{\pm}2.10g$) than in the control ($26.08{\pm}1.72g$) plots in 2013. Shoot to root ratio (S/R ratio) was lower in the warmed ($1.09{\pm}0.07$) than in the control ($1.31{\pm}0.10$) plots in 2013. Leaf nitrogen concentrations and chlorophyll contents were not significantly different between warmed and control plots except for leaf nitrogen concentration in 2011. Leaf C/N ratio was increased in 2012 under the warming treatment. Low growth and S/R ratio in warmed plots might be related to the higher temperature and water stress. In the future, the below-ground carbon allocation of P. densiflora might be increased by global warming due to temperature and water stress.

• 한국해양학회지
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• v.30 no.6
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• pp.550-564
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• 1995

The temporal and spatial characteristics of wind fields over the neighbouring seas of the Korean peninsula are investigated using 10-years daily wind data during 1978${\sim}$1987 which have been spatially smoothed and low-pass filtered. Long term annual and monthly means are examined for synoptic patterns and spectral analyses are made for temporal variability and spatial coherence. Spatial patterns of the annual mean wind stress and curl have a strong resemblance with those of monthly means during the winter season. Two outstanding periodicities are observed at 1 and 2 cycles per year. The synoptic winds over the study area are highly coherent at both the annual and semi-annual periodicities. However, each basin has its own characteristic spatial pattern. For instance, the prevailing wind during the winter season is northerIy over the northern East Sea (ES), Yellow Sea (YS), and northern East China Sea (ECS), while it is northwesterly over the southern ES and northesterly over the northern ES and southern ECS. At the same time, the wind stress curl is positive over the northern ES and southern ECS, while it is negative over the southern ES, YS and northern ECS. On the other hand, the wind field during the summer season, with its strength being much reduced, is completely different from that during the winter season, and frequent passage of tropical storms provokes large temporal variability over ECS. One remarkable point is that the annual cycle, dominated by the Siberian High, tends to propagate from northeast to southwest, i.e., from northern 25 toward southern ES, YS and ECS, while the semi-annual cycle propagates in the opposite direction, from southwest to northeast. The semi-annual periodicity may reflect development of extratropical cyclones in spring and fall which frequently cross the Korean peninsula. In higher frequencies, there are no dominant periodicities, but local winds over YS and ES are highly correlated for frequencies larger than 0.1 cycles per day and phase difference increases linearly with frequency. This linear increase of phase corresponds to phase speed of 550 and 730 km/d at 0.1 and 0.3 cpd, respectively, The phase speed is apparently coincident with moving speed of extratropical cyclones across the Korean peninsula in the west-east direction.

• The Korean Journal of Petroleum Geology
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• v.13 no.1
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• pp.1-16
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• 2007

The southeastern Korean Peninsula has experienced crustal multi-deformations according to changes of global tectonic setting during the Cenozoic. Characteristic features of the crustal deformations in relation to major Cenozoic tectonic events are summarized as follows. (1) Collision of Indian and Eurasian continents and abrupt change of movement direction of the Pacific plate (50${\sim}$43 Ma): The collision of Indian and Eurasian continents caused the eastward extrusion of East Asia block as a trench-rollback, and then the movement direction of the Pacific plate was abruptly changed from NNW to WNW. As a result, the strong suction-force along the plate boundary produced a tensional stress field trending EW or WNW-ESE in southeastern Korea, which resultantly induced the passive intrusion of NS or NNE trending mafic dike swarm. (2) Opening of the East Sea (25${\sim}$16 Ma): The NS or NNW-SSE trending opening of the East Sea generated a dextral shear stress regime trending NNW-SSE along the eastern coast line of the Korean Peninsula. As a result, pull-apart basins were developed in right bending and overstepping parts along major dextral strike slip faults trending NNW-SSE in southeastern Korea. The basins can be divided into two types on the basis of geometry and kinematics: Parallelogram-shaped basin (rhombochasm) and wedged-shaped basin (sphenochasm), respectively. In those times, the basins and adjacent basement blocks experienced clockwise rotation and northwestward tilting contemporaneously, and the basins often experienced a kind of propagating rifting from NE toward SE. At about 17Ma, the Yonil Tectonic Line, which is the westernmost border fault of the Miocene crustal deformation in southeastern Korea, began to move as a major dextral strike slip fault. (3) Clockwise rotation of southeastern Japan Island (about 15 Ma): The collision of the Izu-Bonin Arc and southeastern Japan Island, as a result of northward movement of the Philippine sea-plate, induced the clockwise rotation of southeastern Japan Island. The event caused the NW-SE compression in the Korea Strait as a tectonic inversion, which resultantly tenninated the basin extension and caused local counterclockwise rotation of blocks in southeastern Korea. (4) E-W compression in the East Asia (after about 5 Ma): Decreasing subduction angle of the Pacific plate and eastward movement of the Amurian plate have constructed the-top-to-west thrusts and become a major cause for earthquakes in southeastern Korea until the present time.