• Economic and Environmental Geology
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• v.55 no.5
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• pp.541-550
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• 2022

A pre-existing landform is created by weathering and erosion along the bedrock fault and the weak zone. A neotectonic landform is formed by neotectonic movements such as earthquakes, volcanoes, and Quaternary faults. It is difficult to clearly distinguish the landform in the actual field because the influence of the tectonic activity in the Korean Peninsula is relatively small, and the magnitude of surface processes (e.g., erosion and weathering) is intense. Thus, to better understand the impact of tectonic activity and distinguish between pre-existing landforms and neotectonic landforms, it is necessary to understand the development process of pre-existing landforms depending on the bedrock characteristics. This study used a two-dimensional numerical landscape evolution model (LEM) to study the spatio-temporal development of landscape according to the different erodibility under the same factors of climate and the uplift rate. We used hill-slope indices (i.e., relief, mean elevation, and slope) and channels (i.e., longitudinal profile, normalized channel steepness index, and stream order) to distinguish the difference according to different bedrocks. As a result of the analysis, the terrain with high erosion potential shows low mean elevation, gentle slope, low stream order, and channel steepness index. However, the value of the landscape with low erosion potential differs from that with high erodibility. In addition, a knickpoint came out at the boundary of the bedrock. When researching the actual topography, the location around the border of difference in bedrock has only been considered a pre-existing factor. This study suggested that differences in bedrock and various topographic indices should be comprehensively considered to classify pre-existing and active tectonic topography.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.285-290
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• 2023

Poly-lactic acid (PLA) is the most promising polymer in additive manufacturing as an alternative to acrylonitrile butadiene styrene (ABS). Since it is produced from renewable resources such as corn starch and sugar beets, it is also biocompatible and biodegradable. However, PLA has a couple of issues that limit its use. First, it has a comparatively low glass transition temperature of around 60 ℃, such that it exhibits low thermal resistance. Second, PLA has low impact strength because it is brittle. Due to these problems, scientists have found methods to improve the crystallinity and ductility of PLA. Polyethylene glycol (PEG) is one of the most studied plasticizers for PLA to give it chain mobility. However, the blend of PLA and PEG becomes unstable, and phase separation occurs even at room temperature as PEG is self-crystallized. Thus, it is necessary to investigate the optimal mixing ratio of PLA-PEG at the molecular scale. In this study, molecular dynamics will be conducted with various ratios of L-type PLA (PLLA) or DL-type PLA-PEG (PDLA-PEG) systems by using BIOVIA Materials Studio.

• Composites Research
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• v.20 no.5
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• pp.13-19
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• 2007

Fiber-reinforced thermoplastic composites not only approach almost near to the strength of thermosetting composite but also has excellent productivity, recycling property, and impact resistance, which are pointed as weaknesses of thermosetting composites. The study for strength calculation of one direction fiber-reinforced thermoplastic composites and the study measuring precisely fiber orientation distribution were presented. Need the systematic study for the data base that can predict mechanical properties of composite material and fiber orientation distribution by the fiber content ratio was not constructed. Therefore, this study was investigated what affect the fiber content ratio and fiber orientation distribution have on the strength of composites. Fiber-reinforced thermoplastic composites by changing fiber orientation distribution and the fiber content ratio were made. Tensile strength ratio of $0^{\circ}$ direction of fiber-reinforced composites increased being proportional the fiber content and fiber orientation function as change from isotropy(J=0) to anisotropy(J=1). But, tensile strength ratio of $90^{\circ}$ direction by separation of fiber filament decreased when tensile load is imposed fur width direction of reinforcement fiber length direction.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.2
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• pp.33-42
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• 2023

Throughout all industries, eco-friendliness is being promoted worldwide with focus on suppressing the environmental impact. With recent international environment policies and regulations supported by government, the electric vehicles demand is expected to increase rapidly. Battery system itself perform an essential role in EVs technology that is arranged in cells, modules, and packs, and each of them are connected mechanically and electrically. A multifaceted approach is necessary for battery pack bonding technologies. In this paper, pros and cons of applicable bonding technologies, such as resistance welding, laser and ultrasonic bonding used in constructing electric vehicle battery packs were compared. Each bonding technique has different advantages and limitations. Therefore, several criteria must be considered when determining which bonding technology is suitable for a battery cell. In particular, the shape and production scale of battery cells are seen as important factors in selecting a bonding method. While dealing with the types and components of battery cells, package bonding technologies and general issues, we will review suitable bonding technologies and suggest future directions.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.2
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• pp.108-116
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• 2023

Recently, the concentration of fine dust causative substances (NOx, VOC, etc.) in the atmosphere has increased, resulting in high concentrations of tropospheric ozone (O3) and increased damage to crops. This study aimed to analyze the impact of high concentrations of ozone gas on the initial growth of rice plants and investigate the relationship between ozone damage resistance and anthocyanin biosynthesis. To achieve this, rice plants were exposed to elevated levels of ozone g as using an ozone chamber, and subsequent measurements were taken to assess changes in growth, the percentage of damaged leaves, and the anthocyanin content. The results revealed that varieties with a higher proportion of damaged leaves exhibited a relative increase in anthocyanin biosynthesis following ozone exposure. Notably, detrimental effects on growth, such as decreased biomass, were mitigated. Additionally, Anthocyanin biosynthesis genes in rice were listed by selecting homologous genes from Arabidopsis and Maize. The expression of OsF3H2, OsFLS1 and OsLDOX3 was induced during ozone treatment. This result is expected to contribute to the study of the protection mechanism of plants from ozone damage.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.57-57
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• 2022

In many areas of the world, salt damage and drought have had a negative impact on human survival due to a decrease in agricultural productivity. For instance, about 50% of agricultural land will be affected by salt damage by 2050. Biostimulants such as plant extracts can not only increase the nutrient utilization efficiency of plants, but also promote plant growth and increase resistance to abiotic or biotic stress. Therefore, the objective of this study was to determine how selected plant extracts might reduce levels of stress caused by drought and salt and to better understand the physiological response mechanisms of rice plants. In this study, we used Soybean leaves, Soybean stems and Allium tuberosum, Allium cepa, Hizikia fusiforme, and Gracilaria verrucosa extracts were used. These extracts had been used in previous studies and were found to be effective. The materials were dried in a dry oven at 50℃ for 5 days and ground using a blender. Each 50 g of materials was put in 1 L of distilled water, stirred for 24 hours, filtered using 4 layers of mirocloth, and then concentrated using a concentrator. Rice (cv. Hopumbyeo) seeds were immersed and germinated, and then sown in seedbeds filled with commercial soil. In drought experiments, three rice seedlings at 1 week after seeding was transplanted into 100 ml cups filled with commercial soils and grown until the 4-leaf stage. For this experiment, the soil weight in a cup was equalized, and water was allowed to become 100% saturated and then drained for 24 hours. Thereafter, plant extracts at 3% concentrations were applied to the soils. For NaCl treatments, rice plants at 17 days after seeding were treated with either 100 mM NaCl or plant extracts at 1%+ 100 mM NaCl combinations in the growth chamber. Leaf injury, relative water content, photosynthetic efficiency, and chlorophyll contents were measured at 3, 5, and 6 days after treatments. Shoot fresh weight of rice under drought conditions increased 28-37% in response to treatments of Soybean leaf, Soybean stem, Allium tuberosum, Allium cepa, Hizikia fusiforme, and Gracilaria verrucosa extracts at 3% when compared with control plants. Shoot fresh weight of rice subjected to 100 mM NaCl treatments also increased by 6-24% in response to Soybean leaf, Soybean stem, Allium tuberosum, Allium cepa, Hizikia fusiforme, and Gracilaria verrucosa extracts at 3% when compared with control plants. Compared to the control, rice plants treated with these six extracts and subjected to drought conditions had significantly higher relative water content, Fv/Fm, total chlorophyll and total carotenoids than control plants. With the exception of relative water contents, rice plants treated with the six extracts and subjected to salt stress (100 mM NaCl treatments) had significantly higher Fv/Fm, total chlorophyll and total carotenoids than control plants. However, the type of extract used did not produce significant difference in these parameters. Thus, all the plant extracts used in this study could mitigate drought and NaCl stresses and could also contribute substantially to sustainable crop production.

• Human Ecology Research
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• v.61 no.4
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• pp.673-686
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• 2023

The purpose of this study was to identify home economics (HE) teachers' concerns about and perceptions of HE education using the latest technologies in the era of the 4th Industrial Revolution and to reveal whether they differ according to teachers' general background variables. The questionnaire survey method to measure HE teachers' concerns and perceptions of HE education using the latest technologies in the era of the 4th Industrial Revolution was conducted online using the Google Questionnaire from which 150 responses were received. The main results were as follows. Firstly, HE teachers scored an average of 3.46 out of 5 for the latest technology. Among these interests in the latest technology, interest in "augmented reality and virtual reality technologies" scored the highest at an average of 3.80, while interest in "neural network machine learning" (2.78) was low. HE teacher's concerns about HE education using the latest technologies in the era of the 4th Industrial Revolution were high, with an average score of 4.40. Among these concerns for the latest technology, "concern about the results of HE education using the latest technology" scored the highest at 4.53. HE teachers' anxiety about the latest teaching technology in the era of the 4th Industrial Revolution was moderate, averaging 3.05. The highest form of anxiety was "anxiety about the impact on the job" (4.03) and the lowest was fear of "the disappearance of the teacher's job" (2.50). HE teachers' innovation resistance to the latest teaching technology was low at 2.18. Expectations of the latest technology in HE classes in the era of the 4th Industrial Revolution averaged 3.85, slightly higher than the middle of 3.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.706-713
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• 2021

Objective: To evaluate the impact of surgical simulation training using a three-dimensional (3D)-printed model of tetralogy of Fallot (TOF) on surgical skill development. Materials and Methods: A life-size congenital heart disease model was printed using a Stratasys Object500 Connex2 printer from preoperative electrocardiography-gated CT scans of a 6-month-old patient with TOF with complex pulmonary stenosis. Eleven cardiothoracic surgeons independently evaluated the suitability of four 3D-printed models using composite Tango 27, 40, 50, and 60 in terms of palpation, resistance, extensibility, gap, cut-through ability, and reusability of. Among these, Tango 27 was selected as the final model. Six attendees (two junior cardiothoracic surgery residents, two senior residents, and two clinical fellows) independently performed simulation surgeries three times each. Surgical proficiency was evaluated by an experienced cardiothoracic surgeon on a 1-10 scale for each of the 10 surgical procedures. The times required for each surgical procedure were also measured. Results: In the simulation surgeries, six surgeons required a median of 34.4 (range 32.5-43.5) and 21.4 (17.9-192.7) minutes to apply the ventricular septal defect (VSD) and right ventricular outflow tract (RVOT) patches, respectively, on their first simulation surgery. These times had significantly reduced to 17.3 (16.2-29.5) and 13.6 (10.3-30.0) minutes, respectively, in the third simulation surgery (p = 0.03 and p = 0.01, respectively). The decreases in the median patch appliance time among the six surgeons were 16.2 (range 13.6-17.7) and 8.0 (1.8-170.3) minutes for the VSD and RVOT patches, respectively. Summing the scores for the 10 procedures showed that the attendees scored an average of 28.58 ± 7.89 points on the first simulation surgery and improved their average score to 67.33 ± 15.10 on the third simulation surgery (p = 0.008). Conclusion: Inexperienced cardiothoracic surgeons improved their performance in terms of surgical proficiency and operation time during the experience of three simulation surgeries using a 3D-printed TOF model using Tango 27 composite.

• Korean Journal of Materials Research
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• v.34 no.4
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• pp.185-193
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• 2024

In this study, NASICON-type Li_1+XGa_XTi_2-X(PO₄)₃ (x = 0.1, 0.3 and 0.4) solid-state electrolytes for all-solid-state batteries were synthesized through the sol-gel method. In addition, the influence on the ion conductivity of solid-state electrolytes when partially substituted for Ti⁴⁺ (0.61Å) site to Ga³⁺ (0.62Å) of trivalent cations was investigated. The obtained precursor was heat treated at 450 ℃, and a single crystalline phase of Li_1+XGa_XTi_2-X(PO₄)₃ systems was obtained at a calcination temperature above 650 ℃. Additionally, the calcinated powders were pelletized and sintered at temperatures from 800 ℃ to 1,000 ℃ at 100 ℃ intervals. The synthesized powder and sintered bodies of Li_1+XGa_XTi_2-X(PO₄)₃ were characterized using TG-DTA, XRD, XPS and FE-SEM. The ionic conduction properties as solid-state electrolytes were investigated by AC impedance. As a result, Li_1+XGa_XTi_2-X(PO₄)₃ was successfully produced in all cases. However, a GaPO₄ impurity was formed due to the high sintering temperatures and high Ga content. The crystallinity of Li_1+XGa_XTi_2-X(PO₄)₃ increased with the sintering temperature as evidenced by FE-SEM observations, which demonstrated that the edges of the larger cube-shaped grains become sharper with increases in the sintering temperature. In samples with high sintering temperatures at 1,000 ℃ and high Ga content above 0.3, coarsening of grains occurred. This resulted in the formation of many grain boundaries, leading to low sinterability. These two factors, the impurity and grain boundary, have an enormous impact on the properties of Li_1+XGa_XTi_2-X(PO₄)₃. The Li_1.3Ga_0.3Ti_1.7(PO₄)₃ pellet sintered at 900 ℃ was denser than those sintered at other conditions, showing the highest total ion conductivity of 7.66 × 10^-5 S/cm at room temperature. The total activation energy of Li-ion transport for the Li_1.3Ga_0.3Ti_1.7(PO₄)₃ solid-state electrolyte was estimated to be as low as 0.36 eV. Although the Li_1+XGa_XTi_2-X(PO₄)₃ sintered at 1,000 ℃ had a relatively high apparent density, it had less total ionic conductivity due to an increase in the grain-boundary resistance with coarse grains.

• Korean Circulation Journal
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• v.53 no.7
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• pp.425-451
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• 2023

Most patients with heart failure (HF) have multiple comorbidities, which impact their quality of life, aggravate HF, and increase mortality. Cardiovascular comorbidities include systemic and pulmonary hypertension, ischemic and valvular heart diseases, and atrial fibrillation. Non-cardiovascular comorbidities include diabetes mellitus (DM), chronic kidney and pulmonary diseases, iron deficiency and anemia, and sleep apnea. In patients with HF with hypertension and left ventricular hypertrophy, renin-angiotensin system inhibitors combined with calcium channel blockers and/or diuretics is an effective treatment regimen. Measurement of pulmonary vascular resistance via right heart catheterization is recommended for patients with HF considered suitable for implantation of mechanical circulatory support devices or as heart transplantation candidates. Coronary angiography remains the gold standard for the diagnosis and reperfusion in patients with HF and angina pectoris refractory to antianginal medications. In patients with HF and atrial fibrillation, longterm anticoagulants are recommended according to the CHA₂DS₂-VASc scores. Valvular heart diseases should be treated medically and/or surgically. In patients with HF and DM, metformin is relatively safer; thiazolidinediones cause fluid retention and should be avoided in patients with HF and dyspnea. In renal insufficiency, both volume status and cardiac performance are important for therapy guidance. In patients with HF and pulmonary disease, beta-blockers are underused, which may be related to increased mortality. In patients with HF and anemia, iron supplementation can help improve symptoms. In obstructive sleep apnea, continuous positive airway pressure therapy helps avoid severe nocturnal hypoxia. Appropriate management of comorbidities is important for improving clinical outcomes in patients with HF.