• 한국환경복원기술학회지
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• 제26권1호
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• pp.1-16
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• 2023

The current study aims to analyze the vegetation characteristics of the rocky slopes in expressway applied by different types of greening work. A field survey on the current status of vegetation were conducted in 50 rock slopes along 13 expressways in two years, 2020 to 2021. Specifically, the type of implemented greening and slope stabilization work, the soil properties, the vegetation coverage, and the emerged species were investigated on a every single slope. As the result of the implemented work types, the soil-media hydroseeding and the gabion work appeared to be the most implemented greening and slope stabilization work, respectively. As a result of the vegetation survey, 126 classification groups (42 families, 93 genera and 126 species) were identified in total and it was observed 26 IAP species and 5 invasive species were growing. The longer the time after greening work, the more frequent appearance of IAP species were observed. Woody species such as Robinia pseudoacacia and Lespedeza bicolo, and perennial herbs such as Artemisia princeps, Erigeron annuus, and Festuca arundinacea were appeared with high frequencies at the rocky slopes in expressway. It was also observed Pinus densiflora, Quercus dentata, Rubus crataegifolius and Miscanthus sinensis which had invaded from the adjacent forests naturally, and the largest number of species were invaded between 5~10 years usually after greening work in this study.

• 한국해안해양공학회지
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• 제3권3호
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• pp.163-169
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• 1991

불규칙 사면에서의 파랑변형을 분석하기 위해 파랑-흐름 복합수조에서 67 종류의 규칙파에 대한 실험을 실시하였다. 사면은 합판과 Angle을 이용하여 제작하였으며 경사는 1/10, 1/20이다. 균일한 경사면에서는 쇄파수심 지수, 파의 쳐오름 등은 기존의 실험 결과와 큰 차이가 없었으나, 심해 파랑경사가 작은 경우 이들의 값은 더 작았다. 또, 파의 쳐오름은 Hunt식과 잘 일치하였으며, 쇄파가 발생하는 횟수와도 관계가 있다. 사주가 있는 경우, 쇄파수심 지수는 기존의 식과 큰 차이가 있다. 쇄파후의 파고는 Dally 등(1984)의 이론식에 비해 작게 관측되었다.

• The Korean Journal of Ecology
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• 제8권2호
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• pp.89-98
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• 1985

Correlations between horizontal distributions of bamboos (Bambusaceae) in the Korean peninsula and environmental factors were studied using taxanomic and geographical literatures, both old and current. The vertical distributions of bamboos on Mt. Chiri were also studied, and environmental factors limiting horizontal and vertical distributions were compared. There are 18 species of bamboos (belonging to 5 genera) distributed in the Korean peninsula. The distributional range of each genus were distinct, although overlapped. Northern limit of bamboos of any species was marked by the line connecting Paikryung Island (124。40'E, 38。00'N), Mt. Changsoo, Mt. Myungji, Mt. Myohyung and Myungchum (129。40'E, 41。10'N). The optimum range of bamboos was concluded to be restricted to several southern province, with annual precipitation over 1,200 mm. The limiting factors on the distribution were inferred to be low temperature and duration of it. Mean daily minimum temperature of January and the number of days with daily mean temperatures below zero during January showed close associations with the distributional range, and an environmental factors favouring the distributrion of bamboos appeared to be vicinity of warm sea current, deep and extended snow acculation and southern exposure. The vertical distribution of bamboos on Mt. Chiri was limited by low temperature, unfavorable topographic and edaphic conditions caused by steep slope. Difference in the vertical limits between SE and NW slopes are caused by the differences in temperature and precipitation between the slopes. Bamboos were more abundant in valleys than on the ridge, apparently because the deeper snow in the valleys protected the plants from low temperature, heavy winter winds and desiccation.

• 한국분말재료학회지
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• 제23권3호
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• pp.195-201
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• 2016

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제2B권4호
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• pp.174-182
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• 2002

This paper presents a comprehensive study on reducing commutation torque ripples generated in brushless DC motor drives with only a single do-link current sensor provided. In such drives, commutation torque ripple suppression techniques that are practically effective in low speed as well as high speed regions are scarcely found. The commutation compensation technique proposed here is based on a strategy that the current slopes of the incoming and the outgoing phases during the commutation interval can be equalized by a proper duty-ratio control. Being directly linked with deadbeat current control scheme, the proposed control method accomplishes suppression of the spikes and dips superimposed on the current and torque responses during the commutation intervals of the inverter. Effectiveness of the proposed control method is verified through simulations and experiments.

• 지질공학
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• 제30권1호
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• pp.85-101
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• 2020

강도정수의 산정은 암반사면의 안정성 해석에 매우 중요하다. 강도정수를 결정하는 다양한 방법들이 여러 연구자들에 의하여 제안되었다. 암반사면의 안정성 해석을 위하여 강도정수 결정에 사용된 방법들의 빈도를 문헌조사를 통하여 조사하였다. 특히 파괴유형에 따른 강도정수 결정방법의 빈도수를 조사하였다. 사례연구를 통하여 암석과 불연속면의 점착력과 마찰각의 값을 조사하여 RMR값과 함께 제시하였다. 연구 결과에 의하면 점착력은 내부마찰각과 비교하여 상당히 큰 범위를 보였다. RMR은 점착력과는 상관관계를 보이지 않았으나 마찰각과는 뚜렷한 상관관계를 보였다. 파괴유형에 따라 강도정수 결정을 위하여 적절한 방법이 사용되어야 하며 문헌조사를 통하여 결과를 검증해야 한다. 향후 각 지역별로 역해석을 통하여 파괴가 발생한 사면에 대한 강도정수 자료가 축적된다면 강도정수 결정의 신뢰성이 향상될 것으로 기대한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.745-750
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• 2005

The demand of tunnels has been increased for the linear improvement of general national highway, and road construction and/or enlargement in Korea. Also, the collapses of tunnel portal slope have been increased in recent due to heavy rain caused by global warming. Therefore, it has been risen the requirement of system for the stability of tunnel portal slope in Korea as well as all over the world. The objective of this research is to develop an effective maintenance system for supervising the tunnel portal slope. This paper is a basic proposal to execute a survey on the current status and state of the tunnel portal slopes that were already installed along general national highways.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.972-976
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• 1997

Single phase ruthenium oxides with perovskite (ATi1-xRuxO3 (A=Ca, Sr)) and pyrochlore structure (Bi2Ru2O7, Pb2Ru2O6.5) have been prepared reproducibly by solid state reaction methods and their electrocatalytic activities for oxygen evolution have been examined by Tafel plots. Tafel slopes vary from a low value of 42 mV/decade up to 222 mV/decade at room temperature. The high exchange current densities and high Tafel slopes compared with those obtained from the RuO2 DSA electrode at the crystalline single phase metal oxide electrodes suggest that they are better electrocatalysts at low overpotentials. A favorable change in the Tafel slope for the oxygen evolution reaction occurs as the ruthenium content increases. Substitution of Ti for Ru in the perovskite solid solutions enhanced their chemical stability by losing marginal electrochemical activity.

• Current Optics and Photonics
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• 제6권1호
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• pp.1-9
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• 2022

This paper proposes a robust, simple zonal wavefront-estimation method in a grid sampling model. More slopes are added to the integral equation of the algorithm to improve the accuracy and convergence rate of this approach, especially for higher-order optical aberrations. The Taylor theorem is applied to clarify the mathematical description of the remaining error in the proposed method. Several numerical simulations are conducted to ensure the performance and improvement in comparison to the Southwell and previous algorithm. An experiment is also conducted according to deflectometry output and the results are verified using a reference measured with a stylus system.

• 전력전자학회논문지
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• 제21권4호
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• pp.343-350
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• 2016

Generally, the average phase current is sampled at the midpoint of a PWM signal for the vector control of an AC motor. The three-phase current can also be reconstructed from a DC-link shunt resistor by sampling the shunt voltage during the active vectors of the SVPWM. However, the reconstructed current is different from the average current because of the deviation of the sampling point from the midpoint of the PWM signal. This paper proposes an algorithm to estimate the average current from the reconstructed current in a single-shunt inverter. The proposed method is derived from the phase current slopes based on switching states and corresponding switching time. In addition, the proposed method is generalized for all the six sectors of the space vector hexagon. The validity of the proposed algorithm is verified with simulations and experiments.