• Title/Summary/Keyword: Fundamental Parameters

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Experimental Study of Frost Heaving using Temperature Controlled Triaxial Cell (투명 온도제어형 삼축셀을 이용한 흙의 동상 실내실험)

  • Ryu, Byung-Hyun;Jin, Hyun-Woo;Lee, Jangguen
    • Journal of the Korean GEO-environmental Society
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    • v.17 no.6
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    • pp.23-31
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    • 2016
  • Nowadays abnormal coldness happens frequently in Korea and frost heaving causes unexpected ground deformation which results in severe problems for structures such as roadway, railroad and cutoff slope. 'Frost heave' as one of the primary phenomenon is considered to be an important factor together with 'adfreeze bond-strength' and 'creep deformation' for structural design process in permafrost area. Therefore, the fundamental study for frost heave has to be preceded for design of geo-structures in cold region. While various experimental apparatuses have been developed, there still exist a certain level of limitation to evaluate the frost-heave characteristics as design parameters. There are no standard testing method and criteria for analyzing frost heaving in Korea because temperature controlled testing apparatuses including a freezing chamber are expensive. In this paper, a new standard freezing and thawing testing apparatus is introduced, which simulates various freezing and thawing conditions in a soil specimen by using a temperature controlled triaxial cell. Frost heaving tests were performed to assess the new testing apparatus and experimental procedure to evaluate frost heaving for soils is proposed.

Advanced Lane Change Assist System for Automatic Vehicle Control in Merging Sections : An algorithm for Optimal Lane Change Start Point Positioning (고속도로 합류구간 첨단 차로변경 보조 시스템 개발 : 최적 차로변경 시작 지점 Positioning 알고리즘)

  • Kim, Jinsoo;Jeong, Jin-han;You, Sung-Hyun;Park, Janhg-Hyon;Young, Jhang-Kyung
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.14 no.3
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    • pp.9-23
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    • 2015
  • A lane change maneuver which has a high driver cognitive workload and skills sometimes leads to severe traffic accidents. In this study, the Advanced Lane Change Assist System (ALCAS) was developed to assist with the automatic lane changes in merging sections which is mainly based on an automatic control algorithm for detecting an available gap, determining the Optimal Lane Change Start Point (OLCSP) in various traffic conditions, and positioning the merging vehicle at the OLCSP safely by longitudinal automatic controlling. The analysis of lane change behavior and modeling of fundamental lane change feature were performed for determining the default parameters and the boundary conditions of the algorithm. The algorithm was composed of six steps with closed-loop. In order to confirm the algorithm performance, numerical scenario tests were performed in various surrounding vehicles conditions. Moreover, feasibility of the developed system was verified in microscopic traffic simulation(VISSIM 5.3 version). The results showed that merging vehicles using the system had a tendency to find the OLCSP readily and precisely, so improved merging performance was observed when the system was applied. The system is also effective even during increases in vehicle volume of the mainline.

A Study on the Ecological Restoration Strategies for the Disturbed Landscapes (경관훼손지의 생태적 복구방안에 관한 연구)

  • Kim, Nam-Choon
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.1 no.1
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    • pp.28-44
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    • 1998
  • This study was conducted to suggest the ecological restoration strategies for the disturbed landscapes by theoretical study. Especially, it is aimed to suggest three objectives for restoration by using native plants ; (1) prevention or reduction of wind and water erosion, (2) provision of food and cover for variety of animal species, (3) improvement of the visual or aesthetic quality of disturbed sites. The main results were summarized as follows. 1. Cooperation between restoration ecologists and restoration practitioners is needed to delineate a scientific approach to restoration ; (1) Being aware of published literature that describes similar work and/or establish general principles. (2) Preparedness to carry out proper experiments to test ideas. (3) Preparedness to monitor fundamental parameters in a restoration scheme. (4) Providing information about the behavior of species. (5) Publish results. 2. There are three models of succession in theories of plant succession. The tolerance and facilitation models were recommended to ecological restoration. The inhibition model applies in most secondary succession, but the actual species which are introduced first may inhibit the germination and growth of slower-growing species, or they may prevent the growth of other species whose propagules arrive later. 3. The objectives of erosion control, wildlife habitat provision, and visual quality improvement are not mutually exclusive. However, many revegetation practices in the past have emphasized one of these aspects at the expense of the others. 4. A native plant community can be the model of ecological restoration. By stylization/abstraction of native plant community, trying to learn the most essential characteristics of community types - environmental factors ; dominant, prevalent, and "visual essence" species composition - in order to use such information in restoration. 5. After developing mass/spaces plan, match plant communities to the mass/space plan. In utilizing community grouping, there needs aesthetic ability to understand design elements. 6. Several hydrophytes such as Pennisetum saccharifluous, Themeda triandra, Cirsium pendulum show relatively good germination rates. In case of mesophytes and xerophytes, Arundinella hina, Artemisia princeps, Oenothera odorata and legumes seem to have quick-germinating abilities at barren sites. Pinus thunbergii, Rhus chinensis, Evodia daniellii, Alnus firma and Albizzia julibrissin can be considered as "late succession" woody plants because they show low germinating rates and slow growing habitat. 7. The seeds used for restoration should be collected within a certain radius of where it will be planted. Consideration in genetic issues in the collection and use of germplasm can increase the odds for successful restoration efforts. 8. The useful model in the "drift" pattern occurs so abundantly in naturally evolving landscapes. As one species diminishes in density, a second or third species are increased. Thus, dynamic interactions between species are created. Careful using of "drift phenomenon" in planting was recommended. 9. Virtually no stand of vegetation today is immune from the introduction and/or spreading of exotic species. Therefore, the perpetuation of a restored sites requires conscious monitoring and management. Thus, management would be the most important process in ecological restoration. 10. In order to keep the sites "natural", alternative management strategies would be applied in management ; Atenative management strategies are decelerating successional process, accelerating successional processes or modifying species composition. As management tools, mechanical, chemical, biological or environmental factor manipulation, e.g., fire could be used.

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The Fundamental Studies and Development of Modified Electrothermal Vaporization Hollow Cathode Glow Discharge Cell (개선된 전열증기화 속빈음극관 글로우 방전셀의 기초연구 및 개발)

  • Lee, Seong-Hun;Cho, Won-Bo;Jeong, Jong-Pil;Choi, Woo-Chang;Kim, Kyu-Whan;Woo, Jeong-Su;Lee, Chang-Su;Kang, Dong-Hyun;Lee, Sang-Chun
    • Analytical Science and Technology
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    • v.15 no.6
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    • pp.514-520
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    • 2002
  • The electrothermal vaporization (ETV) hollow cathode glow discharge atomic emission spectrometer for analysis of liquid sample has been developed and characterized. This system has improved the sample introduction method of electrothermal vaporization and the hollow cathode glow discharge. The sample introduction method was possible to provide high analyte transport efficiency to the plasma by helix coil made of tungsten material. In addition, small volume samples (<$30{\mu}{\ell}$) could be used. The system has glow discharge cell with special design for improvement of precision. The effect of discharge parameters such as discharge power, gas flow rate has been studied to find optimum condition. The emitted light was effectively carried into detector by fiber optic cable in UV region. The calibration curve of Pb, Cd were obtained with 3 samples.

Discrimination of geographical origin for soybeans using ED-XRF (ED-XRF (Energy Dispersive X-ray Fluorescence spectrometer)를 이용한 콩 원산지 판별)

  • Lee, Ji-Hye;Kang, Dong-Jin;Jang, Eun-Hee;Hur, Suel-Hye;Shin, Byeung-Kon;Han, Guk-Tak;Lee, Seong-Hun
    • Korean Journal of Food Science and Technology
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    • v.52 no.2
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    • pp.125-129
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    • 2020
  • In this study we developed a method for determining the geographic origin of soybeans by combining energy dispersive X-ray fluorescence spectrometry with statistical analysis. In 2018, 197 soybean samples (100 Korean domestic samples and 97 foreign samples) were collected for the construction of a geographic origin model. The mineral concentrations of 26 elements were measured and determined via the fundamental parameters approach. One-way analysis of variance, t-test, and canonical discriminant analysis were employed to reveal five elements (P, Ni, Br, Zn, and Mn) that could be used for the determination of geographic origins. The sensitivity, specificity, and efficiency for the above method were 91.0, 95.9, and 93.4%, respectively. Validation results from 60 samples collected in 2019 showed a predictive rate of 93.3% for Korean domestic soybeans and 100.0% for foreign soybeans. In conclusion, the combination of energy dispersive X-ray fluorescence spectrometry and chemometrics could be used to effectively determine the geographic origin of soybeans.

Path-following Control for Autonomous Navigation of Marine Vessels Considering Disturbances (외력을 고려한 선박의 자율운항을 위한 경로추종 제어)

  • Lee, Sang-Do
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.5
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    • pp.557-565
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    • 2021
  • Path-following control is considered as one of the most fundamental skills to realize autonomous navigation of marine vessels in the ocean. This study addresses with the path-following control for a ship in which there are environmental disturbances in the directions of the surge, sway, and yaw motions. The guiding principle and back-stepping method was utilized to solve the ship's tracking problem on the reference path generated by a virtual ship. For path-following control, error dynamics is one of the most important skills, and it extends to the research fields of automatic collision avoidance and automatic berthing control. The algorithms for the guiding principles and error variables have been verified by numerical simulation. As a result, most error variables converged to zero values with the controller except for the yaw angle error. One of the most interesting results is that the tracking errors of path-following control between two ships are smaller than the existing safe passing distances considering interaction forces from near passing ships. Moreover, a trade-off between tracking performance and the ship's safety should be considered for determining the proper control parameters to prevent the destructive failure of actuators such as propellers, fins, and rudders during the path-following of marine vessels.

Ab-initio Calculations of Mg Silicate and (hydr)oxide Core-level Absorption Spectra (Mg 규산염 및 (수)산화물에 대한 제일원리 내각준위 흡수 스펙트럼 계산 연구)

  • Son, Sangbo;Kwon, Kideok D.
    • Korean Journal of Mineralogy and Petrology
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    • v.34 no.2
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    • pp.121-131
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    • 2021
  • Magnesium (Mg) present in carbonate minerals as impurities has been used as a geochemical proxy to infer the environmental conditions where the minerals precipitated. The reliability of Mg geochemical proxies requires fundamental understanding of Mg incorporation into minerals based on accurate speciation of Mg 2+ in the crystal structure, which is determined mainly by application of X-ray absorption spectroscopy (XAS). However, high uncertainties are involved in interpreting the XAS spectra of minerals containing trace amount of Mg 2+. Because density function theory (DFT) can predict an XAS spectrum for a crystal structure, DFT calculations can reduce the uncertainties in the interpretation of the XAS spectrum. In this study, we calculated ab initio Mg K-edge absorption spectra of Mg silicates and (hydr)oxides based on DFT and analyzed the correlation between the calculated spectra and Mg structural parameters. Our ab initio Mg K-edge absorption spectra well reproduced the key features of the experimental spectra. The absorption-edge positions of the calculated spectra showed the weak positive correlation with the average Mg-O bond distance or Mg effective coordination number. The current study shows that DFT-based core-level spectroscopy method is a powerful tool in providing standard Mg K-edge spectra of diverse Mg minerals and determining the Mg chemical species within carbonate minerals.

Development of a Coupled Eulerian-Lagrangian Finite Element Model for Dissimilar Friction Stir Welding (Coupled Eulerian-Lagrangian기법을 이용한 이종 마찰교반용접 해석모델 개발)

  • Lim, Jae-Yong;Lee, Jinho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.2
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    • pp.7-13
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    • 2019
  • This study aims to develop a FE Model to simulate dissimilar friction stir welding and to address its potential for fundamental analysis and practical applications. The FE model is based on Coupled Eulerian-Lagrangian approach. Multiphysics systems are calculated using explicit time integration algorithm, and heat generations by friction and inelastic heat conversion as well as heat transfer through the bottom surface are included. Using the developed model, friction stir welding between an Al6061T6 plate and an AZ61 plate were simulated. Three simulations are carried out varying the welding parameters. The model is capable of predicting the temperature and plastic strain fields and the distribution of void. The simulation results showed that temperature was generally greater in Mg plates and that, as a rotation speed increase, not the maximum temperature of Mg plate increased, but did the temperature of Al plate. In addition, the model could predict flash defects, however, the prediction of void near the welding tool was not satisfactory. Since the model includes the complex physics closely occurring during FSW, the model possibly analyze a lot of phenomena hard to discovered by experiments. However, practical applications may be limited due to huge simulation time.

Comparison of Mesoscale Eddy Detection from Satellite Altimeter Data and Ocean Color Data in the East Sea (인공위성 고도계 자료와 해색 위성 자료 기반의 동해 중규모 소용돌이 탐지 비교)

  • PARK, JI-EUN;PARK, KYUNG-AE
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.24 no.2
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    • pp.282-297
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    • 2019
  • Detection of mesoscale oceanic eddies using satellite data can utilize various ocean parameters such as sea surface temperature (SST), chlorophyll-a pigment concentration in phytoplankton, and sea level altimetry measurements. Observation methods vary for each satellite dataset, as it is obtained using different temporal and spatial resolution, and optimized data processing. Different detection results can be derived for the same oceanic eddies; therefore, fundamental research on eddy detection using satellite data is required. In this study, we used ocean color satellite data, sea level altimetry data, and infrared SST data to detect mesoscale eddies in the East Sea and compared results from different detection methods. The sea surface current field derived from the consecutive ocean color chlorophyll-a concentration images using the maximum cross correlation coefficient and the geostrophic current field obtained from the sea level altimetry data were used to detect the mesoscale eddies in the East Sea. In order to compare the eddy detection from satellite data, the results were divided into three cases as follows: 1) the eddy was detected in both the ocean color and altimeter images simultaneously; 2) the eddy was detected from ocean color and SST images, but no eddy was detected in the altimeter data; 3) the eddy was not detected in ocean color image, while the altimeter data detected the eddy. Through these three cases, we described the difficulties with satellite altimetry data and the limitations of ocean color and infrared SST data for eddy detection. It was also emphasized that study on eddy detection and related research required an in-depth understanding of the mesoscale oceanic phenomenon and the principles of satellite observation.

Developmental and reproductive toxicity assessment in rats with KGC-HJ3, Korean Red Ginseng with Angelica gigas and Deer antlers

  • Lee, Jinsoo;Jeong, Ji-Seong;Cho, Kyung-Jin;Moon, Kyeong-Nang;Kim, Sang Yun;Han, Byungcheol;Kim, Yong-Soon;Jeong, Eun Ju;Chung, Moon-Koo;Yu, Wook-Joon
    • Journal of Ginseng Research
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    • v.43 no.2
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    • pp.242-251
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    • 2019
  • Background: Korean Red Ginseng has been widely used in traditional oriental medicine for a prolonged period, and its pharmacological effects have been extensively investigated. In addition, Angelica gigas and deer antlers were also used as a tonic medicine with Korean Red Ginseng as the oriental herbal therapy. Methods: This study was conducted to evaluate the potential toxicological effect of KGC-HJ3, Korean Red Ginseng with angelica gigas and deer antlers, on reproductive and developmental functions including fertility, early embryonic development, maternal function, and embryo-fetal development. KGC-HJ3 was administered by oral gavage to Sprague-Dawley rats (22 animals per sex per group) at dose levels of 0 mg/kg (control), 500 mg/kg, 1000 mg/kg, and 2000 mg/kg to evaluate the potential toxicological effect on fertility and early embryonic development. In addition, KGC-HJ3 was also administered by oral gavage to mating-proven Sprague-Dawley rats (22 females per group) during the major organogenesis period at dose levels of 0 mg/kg (control), 500 mg/kg, 1000 mg/kg, and 2000 mg/kg to evaluate the potential toxicological effect on maternal function and embryo-fetal development. Results and conclusion: No test item-related changes in parameters for fertility, early embryonic development, maternal function, and embryo-fetal development were observed during the study period. On the basis of these results, it was concluded that KGC-HJ3 did not have toxicological potential on developmental and reproductive functions. Therefore, no observed adverse effect levels of KGC-HJ3 for fertility, early embryonic development, maternal function, and embryo-fetal development is considered to be at least 2000 mg/kg/day.