• 한국지형학회지
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• 제19권2호
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• pp.113-122
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• 2012

본 연구는 강원도 DMZ 지오파크의 지오사이트를 발굴하기 위하여, 인제군 내린천의 포트홀을 대상으로 지형 특성을 분석하였다. 내린천의 P1, P2 지역은 유수의 방향을 따라 고랑형 와지인 퍼로우형 포트홀이 주로 나타나고, P3 지역은 퍼로우형 포트홀이 밀집된 구역과 여러 유형의 포트홀이 산재된 구역이 구분되며, P4 지역은 여러 유형의 소규모 포트홀이 산재되어 있다. 총 44개 포트홀을 계측한 결과, 단면이 U자형인 포트홀, 유향과 일치하는 방향성을 가진 포트홀, 내부에 자갈이 퇴적되어 있는 포트홀 등이 길이, 폭, 깊이, 경사도에서 모두 큰 값을 보이는 것으로 나타났다. 내린천의 P1, P2 지역은 포트홀의 규모와 형태가 매우 특징적이며 경관이 아름답기 때문에 지오사이트로 개발하기 양호한 곳으로 판단된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.152-152
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• 2019

This study demonstrates a novel approach of remotely sensed estimates of stream flow at fifteen hydrological station in the Han River Basin, Korea. Multi-temporal data of the European Space Agency's Sentinel-1 SAR satellite from 19 January, 2015 to 25 August, 2018 is used to develop and validate the flow estimation model for each station. The flow estimation model is based on a power law relationship established between the remotely sensed surface area of water at a selected reach of the stream and the observed discharge. The satellite images were pre-processed for thermal noise, radiometric, speckle and terrain correction. The difference in SAR image brightness caused by the differences in SAR satellite look angle and atmospheric condition are corrected using the histogram matching technique. Selective area filtering is applied to identify the extent of the selected stream reach where the change in water surface area is highly sensitive to the change in stream discharge. Following this, an iterative procedure called the Optimum Threshold Classification Algorithm (OTC) is applied to the multi-temporal selective areas to extract a series of water surface areas. It is observed that the extracted water surface area and the stream discharge are related by the power law equation. A strong correlation coefficient ranging from 0.68 to 0.98 (mean=0.89) was observed for thirteen hydrological stations, while at two stations the relationship was highly affected by the hydraulic structures such as dam. It is further identified that the availability of remotely sensed data for a range of discharge conditions and the geometric properties of the selected stream reach such as the stream width and side slope influence the accuracy of the flow estimation model.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2016년도 학술발표회
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• pp.188-188
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• 2016

The Mekong which is one of the world's most significant rivers plays an extremely important role to South East Asia. Lying across six riparian countries including China, Myanmar, Thailand, Laos, Cambodia and Vietnam and being a greatly biological and ecological diversity of fishes, the river supports a huge population who living along Mekong Basin River. Therefore, much attention has been focused on the giant Mekong Basin River, particularly, the soil erosion and sedimentation problems which rise critical impacts on irrigation, agriculture, navigation, fisheries and aquatic ecosystem. In fact, there have been many methods to calculate these problems; however, in the case of Mekong, the available data have significant limitations because of large area (about 795 00 km2) and a failure by management agencies to analyze and publish of developing countries in Mekong Basin River. As a result, the Universal Soil Loss Equation (USLE) model in a GIS (Geographic Information System) framework was applied in this study. The USLE factors contain the rainfall erosivity, soil erodibility, slope length, steepness, crop management and conservation practices which are represented by raster layers in GIS environment. In the final step, these factors were multiplied together to estimate the soil erosion rate in the study area by using spatial analyst tool in the ArcGIS 10.2 software. The spatial distribution of soil loss result will be used to support river basin management to find the subtainable management practices by showing the position and amount of soil erosion and sediment load in the dangerous areas during the selected 56- year period from 1952 to 2007.

• 대한조선학회논문집
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• 제42권5호
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• pp.479-486
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• 2005

The final goal of shift alignment design is that the bearing reaction forces or mean pressures are within design boundaries for various service conditions of a ship. However, it is found that calculated bearing load can be substantially variable according to the locations of the effective support points of after sterntube bearing which are determined by simple calculation or assumption suggested by classification societies. A new analysis method for shaft alignment calculation is introduced in order to resolve these problems. Key concept of the new method is featured by adopting both nonlinear elastic and multi-support elements to simulate a bearing support Hertz contact theory is basically applied for nonlinear elastic stiffness calculation instead of the projected area method suggested by most of classification societies. Three loading conditions according to the bearing offset and the hydrodynamic moment and twelve models according to the locations of the effective support points of sterntube bearings are prepared to carry out quantitative verifications for an actual shafting system of 8000 TEU class container vessel. It is found that there is relatively large difference between assumed and calculated effective support points.

• 지질공학
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• 제31권3호
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• pp.269-281
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• 2021

Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

• Journal of Ecology and Environment
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• 제42권4호
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• pp.308-316
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• 2018

Background: Genus Sasa, dwarf bamboos, are considered to be species that lower biodiversity in the temperate forests of East Asia. Although they have a long interval, they, the monocarpic species, have a unique characteristic of large-scale synchronized flowering. Therefore, once they have flowered and then declined, it may be an opportunity for suppressed surrounding species. A previous study reported that Sasa borealis showed specialized flowering nationwide with a peak in 2015. However, this was based on data from a social network service and field survey at Mt. Jeombong. Therefore, we investigated S. borealis in the forests of five national parks in order to determine whether this rare synchronized flowering occurred nationwide, as well as its spatial distribution. Results: We found a total of 436 patches under the closed canopy of Quercus mongolica-dominated deciduous forests in the surveyed transects from the five national parks. Of these patches, 75% occupied a whole slope area, resulting in an enormous area. The patch area tended to be larger in the southern parks. Half (219 patches) of the patches flowered massively. Among them, 76% bloomed in 2015, which was consistent with the results of the previous report. The flowering rate varied from park to park with that of Mt. Seorak being the highest. The culms of the flowering patches were significantly taller (F = 93.640, p < 0.000) and thicker (F = 61.172, p < 0.000). Following the event, the culms of the flowering patches declined, providing a good opportunity for the suppressed plant species. The concurrent massive flowering of the mature patches was believed to be triggered by some stress such as a spring drought. Conclusion: We confirmed that the rare synchronized flowering of S. borealis occurred with a peak in 2015 nationwide. In addition, we explored that S. borealis not only monopolized an enormous area, but also dominated the floors of the late-successional Q. mongolica-dominated deciduous forests. This presents a major problem for Korean forests. As it declined simultaneously after flowering, there are both possibilities of forest regeneration or resettlement of S. borealis by massively produced seeds.

• 농업과학연구
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• 제45권4호
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• pp.847-857
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• 2018

Recently, customers' demand and attention to dried agricultural products or foods have increased due to their convenience and nutritional values. Conventional drying methods such as solar drying and hot air drying have been most widely used for producing a large amount of dried agricultural products; however, those methods require quite a long time and high energy consumption. To compensate for these issues associated with conventional methods, dielectric heating such as microwave and radio frequency heating has been used as a supplemental method in the drying procedure. This study investigated the microwave drying characteristics of squash slices with different thicknesses under different microwave power intensities and determined the best drying model that could precisely describe the experimental drying curves of the squash slices. The squash was cut into slices with two different thicknesses (5 and 10 mm), and then, they were dried under different microwave power intensity ranges between 90 and 900 W with an increase interval of 90 W. Six drying models were tested to evaluate the fit to the experimental drying data, and the effective moisture diffusivity ($D_{eff}$) values of the squash slices under microwave drying were determined. The results clearly show that as the microwave power was increased, the drying time of both squash slices was significantly decreased, and the slope of the drying rate increased. The effective moisture diffusivity was also significantly related with the microwave power intensities and thicknesses of the slices. In addition, the Page model was most suitable to delineate the drying curves of both squash slices under different microwave power intensities.

• 천문학회보
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• 제44권1호
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• pp.38.4-38.4
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• 2019

Ultra-diffuse galaxies (UDGs) are intriguing in the sense that they are much larger than dwarf galaxies but have much lower surface brightness than normal galaxies. To date, UDGs have been found only in the local universe. Taking advantage of deep and high-resolution HST images, we search for UDGs in massive galaxy clusters in the distant universe. In this work, we present our search results of UDGs in three massive clusters of the Hubble Frontier Fields: Abell 2744 (z=0.308), Abell S1063 (z=0.348), and Abell 370 (z=0.375). These clusters are the most distant and massive among the host systems of known UDGs. The color-magnitude diagrams of these clusters show that UDGs are mainly located in the faint end of the red sequence. This means that most UDGs in these clusters consist of old stars. Interestingly, we found a few blue UDGs, which implies that they had recent star formation. The radial number densities of UDGs clearly decrease in the central region of the clusters in contrast to those of bright galaxies which keep rising. This implies that a large fraction of UDGs in the central region were tidally disrupted. These features are consistent with those of UDGs in nearby galaxy clusters. We estimate the total number of UDGs (N(UDG)) in each cluster. The abundance of UDGs shows a tight relation with the virial masses (M_200) of thier host systems: M_200 \propto N(UDG)^(1.01+/-0.05). This slope is found to be very close to one, indicating that efficiency of UDGs does not significantly depend on the host environments. Furthermore, estimation of dynamical masses of UDGs indicates that most UDGs have dwarf-like masses (M_200 < 10^11 M_Sun), but a few UDGs have $L{\ast}$-like masses (M_200 > 10^11 M_Sun). In summary, UDGs in distant massive clusters are found to be similar to those in the local universe.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.949-956
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• 2020

It's important to measure fuel consumption of vehicles. It's possible to monitor green house gas from vehicles for various traffic conditions with the measured data. It's effective to eco-drive for drivers with fuel consumption data also. There's a display of fuel consumption in the modern vehicles, but it's not useful to get the data from the display. An estimating method for fuel consumption of a vehicle is suggested in the study. It's a simple but an effective method using GPS data. The GPS data(speed, acceleration, road slope) and vehicle data(weight, frontal area, model year, certified fuel economy) is necessary to estimate the fuel consumption for the method. It calculates driving resistance force to estimate engine power. Then it estimates the necessary fuel consumption to maintain the engine power with fuel-power conversion factor. The conversion factor is corrected with certified fuel economy, model year and rated power. The precision of the methods is checked with road test data. The test driving data was measured with GPS and OBD. The error of the estimated fuel consumption for the measured one is about 1.8%. But the error is large for the 1000 and 100 data number from the total data number of about 10,000. The error is from the larger change range of the GPS data than the one of the measured fuel consumption data. But the proposed estimating method is useful to percept the fuel consumption change for better fuel economy with simple gadget like smart phone or other GPS instruments.

• Journal of Ecology and Environment
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• 제44권4호
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• pp.229-240
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• 2020

Background: Genus Quercus is a successful group that has occupied the largest area of forest around the world including South Korea. The acorns are an important food source for both wild animals and humans. Although the reproductive characteristics of this genus are highly variable, it had been rarely studied in South Korea. Therefore, in Seoraksan and Odaesan National Parks (i) we measured the acorn production of Quercus mongolica, an overwhelmingly dominant species in South Korea, for 3 years (2017-2019), (ii) evaluated the spatial-temporal variation of acorn production, and (iii) analyzed the effects of oak- and site-related variables on the acorn production. Results: The annual acorn production of Q. mongolica increased 36 times from 1.2 g m-2 in 2017 to 43.2 g m-2 in 2018, and decreased to 16.7 g m-2 in 2019, resulting in an annual coefficient of variation of 104%. The coefficient of spatial variation was high and reached a maximum of 142%, and the tree size was the greatest influencing factor. That is, with an increase in tree size, acorn production increased significantly (2018 F = 16.3, p < 0.001; 2019 F = 8.2, p < 0.01). Elevation and slope also significantly affected the production in 2019. However, since elevation and tree size showed a positive correlation (r = 0.517, p < 0.001), the increase in acorn production with increasing elevation was possibly due to the effect of tree size. The acorn production of Odaesan for 3 years was 2.2 times greater than that of Seoraksan. This was presumed that there are more distribution of thick oak trees and more favorable site conditions such as deep soil A-layer depth, high organic matter, and slower slopes. Conclusion: As reported for other species of the genus Quercus, the acorn production of Q. mongolica showed large spatial and annual variations. The temporal variability was presumed to be a weather-influenced masting, while the spatial variability was mainly caused by oak tree size.