• Journal of the Korean Geotechnical Society
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• v.38 no.5
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• pp.5-17
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• 2022

A pile is a type of medium for constructing superstructures in weak geotechnical conditions. A pretensioned spun high-strength concrete (PHC) pile is composed of high-strength concrete with a specified strength greater than 80 MPa. Therefore, it has advantages in resistance to axial and bending moments and quality control and management since it is manufactured in a factory. However, the skin friction of a pile, which accounts for a large portion of the pile bearing capacity, is only approximated using empirical equations or standard penetration test (SPT) N-values. Particularly, there are some poor research results on the pile-soil interface under the seismic loads in Korea. Additionally, some studies do not consider geoenvironmental elements, such as groundwater pH values. This study performs sets of cyclic simple shear tests using submerged concrete specimens for 1 month to consider pH values of groundwater and clay specimens composed of kaolinite to generate a pile-soil interface. 0.2 and 0.4 MPa of normal stress conditions are considered in the case of pH values. The disturbed state concept is employed to express the dynamic behavior of the interface, and the disturbed function parameters are newly suggested. Consequently, the largest disturbance increase under basic conditions is observed, and an early approach to the failure under low normal stress conditions is presented. The disturbance function parameters are also suggested to express this disposition quantitatively.

• Korean Journal of Plant Resources
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• v.35 no.4
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• pp.464-470
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• 2022

In this study, the morphological characteristics of flower and fruit in five varieties (Hancho 915ho, 930ho, 10ho, 1020ho, 1030ho) from Zanthoxylum schinifolium were investigated as new varieties with different fruiting seasons. Qualitative and quantitative characteristics were investigated, spectively. For quantitative characteristics can be measured numerically, such as size and number, the varieties were identified using ANOVA and Scheffe's multiple range test. In addition, the validity of whether the quantitative characteristics of five varieties can be explained by factor analysis was reviewed. Using UPGMA, the relationship between the five varieties was confirmed by dendrogram. As a result of ANOVA and Scheffe's multiple range test there was significant difference in inflorescence width and female flower length. It had a high contribution to distinguishing varieties, which was similar to the PCA results using factor analysis. As a result of dendrogram using cluster analysis, Hancho 915ho, 1020ho and 1030ho were similar, but there was a distinct difference in the characteristics of different flowering and fruiting periods, confirming that they were different varieties.

• Korea Trade Review
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• v.41 no.1
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• pp.67-90
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• 2016

This study examines whether there is any significant relation between executive compensation and future firm performance for the Korean export manufacturing small and medium-sized firms. We sorted the whole sample firms into the sub-groups of 10 deciles by firm size and the KSIC standard. We found the following empirical results. First, Korean export manufacturing small and medium-sized firms typically showed lower or even negative profitability in terms of return on equity and operating profit ratio to sales. Foreign equity ownership is very low with an average of 3.77%. Second, for the firms with higher ratio of excess executive compensation to asset had lower future firm performance. It implies that the typical owner-manager in Korean export manufacturing SMEs earns excess pay, but do not contribute much to firm performance. Third, as for future cumulative abnormal returns for future one- and three-year periods, firms with higher owner-executive pay had lower returns compared with firms with lower pay. So the stock market investors set a lower value on them. Fourth, there is a positive relation between excess executive pay and executive overconfidence, and it implies that owner-CEOs with higher pay may become overconfident, thereby lowering future firm performance somehow.

• Journal of Wetlands Research
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• v.26 no.1
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• pp.1-9
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• 2024

In this study, a HSPF model was developed to simulate runoff and water quality in the Haebancheon watershed, which has a high land area ratio and population density among the West Nakdong River watersheds. Various non-point source pollution control strategies were applied, and the reduction in pollutant loads and the exceedance rate of water quality standards were analyzed. The scenarios included basic road cleaning for reducing pollutant loads, runoff reduction measures considering extensive low-impact development techniques, and inflow reduction measures to mitigate non-point source pollution entering the river. In the first step, practical conditions such as the number of vehicles for road cleaning in Kimhae City were considered, while for the second and third steps, it was assumed that 50% of the applicable land use area was used to be applicable for the LID techniques. As a result of applying all three measures, it was analyzed that the BOD pollutant load could be reduced by 58.28%, T-N by 58.49%, and T-P by 51.56%. Furthermore, the 60th percentile of water quality measurements accumulated over 5 years was set as the target water quality, and a flow-duration curve was constructed. The exceedance rate of the flow-duration curve before and after applying non-point source pollution reduction measures was analyzed. As a result, for BOD, the exceedance rate decreased from 41.57% before applying the measures to 16.32% after, showing a 25.25% reduction in the exceedance rate. For T-N, the exceedance rate decreased significantly from 40.31% before the measures to 22.84% after, and for T-P, it decreased significantly from 62.43% to 27.22%.

• Journal of the Korean Society of Radiology
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• v.18 no.2
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• pp.127-133
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• 2024

The elbow joint is made up of three different bones. X-rays or other radiological exams are commonly used to diagnose elbow injuries or disorders caused by physical activity and external forces. Previous research on the elbow joint reported a new examination method that meets the imaging evaluation criteria in the tilt position by Z-axis elevation of the forearm. Therefore, this study aims to design an optimized instrument and develop an aid applicable to other upper extremity exams. After completing the 2D drawing and 3D modeling design, the final design divided into four parts was fabricated with a 3D printer using ABS plastic and assembled. The developed examination aid consists of a four-stage Z-axis elevation tilt angle function (0°, 5°, 10°, and 15°) and can rotate and fixate 360° in 1-degree increments. It was designed to withstand a maximum equivalent stress of 56.107 Pa and a displacement of 1.6548e-5 mm through structural analysis to address loading issues caused by cumulative frequency of use and physical utilization. In addition to X-ray exams of the elbow joint, the developed aid can be used for shoulder function tests by rotating the humerus and also be applied to MRI and CT exams as it is made of non-metallic materials. It will contribute to the accuracy and efficiency of medical imaging diagnosis through clinical applications of various devices and medical imaging exams in the future.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.249-262
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• 2024

Retaining walls are widely used in the construction of underground structures. This study reviews the stability of the high-strength joint buried pile method at a site in Korea. [Consider giving details of the location.] The method is assessed by considering the amount of ground settlement, as calculated by finite element analysis and measured at the site. Comparison of the measured and numerical results confirmed the method's stability and field applicability. Settlement of 13.42~13.65 mm was calculated for seven cross-sections [The Abstract should be comprehensible without reference to the main text. The labels A-A' to G-G' should not be introduced here without explanation.] using numerical analysis, and the measured settlement reached a maximum of 2.00 mm. The observed differences and variations [Please state what differed/varied.] did not exceed the design expectations in any section. Instruments installed at the back of the excavation area were used to assess the conditions. An underground gradient meter recorded a cumulative horizontal displacement of between -0.40 and 0.60 mm, and an underground water meter recorded slight displacements of between -0.21 and 0.28 m compared with the initial measurements. A surface settlement meter observed very little movement, with a maximum of -2.00 mm compared with the initial measurement, thereby confirming the establishment of a stable state within the management criteria.

• Journal of Korean Elementary Science Education
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• v.43 no.3
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• pp.446-459
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• 2024

This study aims to examine the development and learning process of the argumentative abilities in elementary school students with regards to learning science. Toward this end, the SSI argumentation education program was implemented in conjunction with the science curriculum for sixth-grade students across 10 months. In this process, the scoring criteria in terms of formal and content aspects were developed and used to assess their argumentative text analysis and expression abilities. The results were as follows: First, the type of SSI influenced their ability to analyze argumentative texts. However, their formal and content aspects improved as learning progressed. Second, with regards to the formal aspect associated with the ability to express argumentative texts, reasons were initially most frequently cited. Over time, incorporating evidence to support these reasons and the use of rebuttal also increased. Third, in terms of content aspect, the level of use of all elements increased as learning progressed; however, level of acknowledgments and rebuttal elements exhibited a relatively slower progress. In summary, ability of the students to analyze and express argumentative texts improved as they increasingly gained experience in learning about argumentation. The study deduced that elementary school students can develop their argumentative abilities through appropriate learning support, such as teacher feedback, along with implementation of the SSI argumentation education program over an extended period. Based on these results, the study proposes the development of SSI materials and incorporation of SSI argumentative writing in the science curriculum.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.316-326
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• 2014

Determination of the late marginal heading date (LMHD), which would allow estimation of the late marginal seeding date and the late marginal transplanting date, would help identification of potential double cropping areas and, as a result, establishment of cropping systems. The objective of this study was to determine the LMHD at 51 sites in Korea. For these sites, weather data were obtained from 1971 to 2000 and from 1981 to 2010, which represent past and current normal climate conditions, respectively. To examine crop productivity on the LMHD, climatic yield potential (CYP) was determined to represent the potential yield under a given climate condition. The LMHD was calculated using accumulated temperature for 40 days with threshold values of $760^{\circ}C$, $800^{\circ}C$, $840^{\circ}C$ and $880^{\circ}C$. The value of CYP on a given LMHD was determined using mean temperature and sunshine duration for 40 days from the LMHD. The value of CYP on the LMHD was divided by the maximum value of CYP (CYPmax) in a season to represent the relative yield on the LMHD compared with the potential yield in the season. Our results indicated that the LMHD was delayed at most sites under current normal conditions compared with past conditions. Spatial variation of the LMHD differed by the threshold temperature. Overall, the minimum value of CYP/CYPmax was 81.8% under all of given conditions. In most cases, the value of CYP/CYPmax was >90%, which suggested that yield could be comparable to the potential yield even though heading would have occurred on the LMHD. When the LMHD could be scheduled later without considerable reduction in yield, the late marginal transplanting date could also be delayed accordingly, which would facilitate doublecropping in many areas in Korea. Yield could be affected by sudden change of temperature during a grain filling period. Yet, CYP was calculated using mean temperature and sunshine duration for 40 days after heading. Thus, the value of CYP/CYPmax may not represent actual yield potential due to change of the LMHD, which suggested that further study would be merited to take into account the effect of weather events during grain filling periods on yield using crop growth model and field experiments.

• Journal of Korean Society of Forest Science
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• v.81 no.1
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• pp.1-10
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• 1992

This study was conducted to explain the characters of the structure of biomass production in the thrifty-mature Quercus mongolica stands and investigate the relationships between the leaf weight or leaf area and the sapwood area in the bole. Also we intended to identify the allocation ratio of stem, branches, and leaves or heartwood, sapwood and bark in trees and the characters of productive structure of stem and leaf biomass by the tree height. The results obtained were as follows : 1. The allocation ratio of biomass based on dry weight was 70-84% in stem, 11-25% in branches, and 3-6% in leaves. 2. In the bole, the ratios of composition of heartwood, sapwood, and bark were showed 37-43%, 38-46%, and 16-19%, respectively. 3. The volume of sapmood was exceeded more than that of heartwood in dominant and intermediate trees, while it was reversely appeared in suppressed trees. 4. The weight and area of leases significantly correlated with the sectional area of sapwood in bole (r>0.9. 1% significant level). 5. The ratio of leaf area($m^2$) to sapwood areal($cm^2$), k varied 0.35 to 2.05. 6. The basal diameter and the cross sectional area of a branch significantly correlated with the leaf weight r>0.9. 1% significant level. 7. The leaf weight in a tree is showed a normal distribution curve and the accumulative volume of bole is showed a tapering type.

• Economic and Environmental Geology
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• v.43 no.4
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• pp.305-314
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• 2010

The stabilization process using limestone ($CaCO_3$) and steel making slag as the immobilization amendments was investigated for As contaminated farmland soils around Chonam abandoned mine, Korea. Batch and continuous column experiments were performed to quantify As-immobilization efficiency in soil and the analyses using XRD and SEM/EDS for secondary minerals precipitated in soil were also conducted to understand the mechanism of Asimmobilization by the amendments. For the batch experiment, with 3% of limestone and steel making slag, leaching concentration of As from the contaminated soil decreased by 62% and 52% respectively, compared to that without the amendment. When the mixed amendment (2% of limestone and 1% of steel making slag) was used, As concentration in the effluent solution decreased by 72%, showing that the mixed of limestone and steel making slag has a great capability to immobilize As in the soil. For the continuous column experiments without the amendment, As concentration from the effluent of the column ranged from 50 to $80\;{\mu}g/L$. However, with 2% limestone and 1% steel making slag, more than 80% diminution of As leaching concentration occurred within 1 year and maintained mostly below $10\;{\mu}g/L$. Results from XRD and SEM/EDS analysis for the secondary minerals created from the reaction of the amendments with $As^{+3}$ (arsenite) investigated that portlandite ($Ca(OH)_2$), calcium-arsenite (Ca-As-O) and calcite ($CaCO_3$) were main secondary minerals and the distinct As peaks in the EDS spectra of the secondary minerals can be observed. These findings suggest that the co-precipitation might be the major mechanisms to immobilize As in the soil medium with limestone and steel making slag.