• Smart Structures and Systems
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• 제23권6호
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• pp.565-577
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• 2019

One of the most effective countermeasures for mitigating cable vibration is to install mechanical dampers near the anchorage of the cable. Most of the dampers used in the field are so-called passive dampers where their parameters cannot be changed once designed. The parameters of passive dampers are usually determined based on the optimal damper force obtained from the universal design curve for linear dampers, which will provide a maximum additional damping for the cable. As the optimal damper force is chosen based on a predetermined principal vibration mode, passive dampers will be most effective if cable undergoes single-mode vibration where the vibration mode is the same as the principal mode used in the design. However, in the actual engineering practice, multi-mode vibrations are often observed for cables. Therefore, it is desirable to have dampers that can suppress different modes of cable vibrations simultaneously. In this paper, MR dampers are proposed for controlling multi-mode cable vibrations, because of its ability to change parameters and its adaptability of active control without inquiring large power resources. Although the highly nonlinear feature of the MR material leads to a relatively complex representation of its mathematical model, effective control strategies can still be derived for suppressing multi-mode cable vibrations based on nonlinear modelling, as proposed in this paper. Firstly, the nonlinear Bouc-wen model is employed to accurately portray the salient characteristics of the MR damper. Then, the desired optimal damper force is determined from the universal design curve of friction dampers. Finally, the input voltage (current) of MR damper corresponding to the desired optimal damper force is calculated from the nonlinear Bouc-wen model of the damper using a piecewise linear interpolation scheme. Numerical simulations are carried out to validate the effectiveness of the proposed control algorithm for mitigating multi-mode cable vibrations induced by different external excitations.

• 한국지반환경공학회 논문집
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• 제12권11호
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• pp.23-30
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• 2011

본 연구에서는 터널의 상부에 작용하는 토압을 평가하는데 있어서 기존의 Terzaghi 공식이 가지는 문제점을 해결하기 위해 흙의 팽창성(Dilatancy)을 고려하여 Terzaghi 공식을 수정하였다. Terzaghi 공식과 수정식에 대한 수학적 해석결과, 터널의 토압은 수정식이 Terzaghi 공식에 비해 작게 나타났으며 토피고가 커질수록 그 차이는 증가하였다. 터널모형실험 결과와 비교해 본 결과, Terzaghi 공식에 의해 계산된 상부토압은 굴착 전 토압의 약 70%이며, 수정식에 의하면 약 60% 정도로 나타났고, 터널모형실험에 의해 측정된 토압은 약 40% 정도 임을 볼 수 있었다. 또한 유한요소해석을 이용하여 Terzaghi 공식과 수정식에 의해 산정된 터널 상부토압과 전단변형률을 비교해본 결과 수학적 해석결과와 동일하게 수정식이 Terzaghi 공식보다 작게 나타났다.

• International Journal of Computer Science & Network Security
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• 제22권1호
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• pp.105-112
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• 2022

The development and spread of IT-technologies has raised interest in teaching programming pupils. The article deals with problems related to programming and ways to overcome them. The importance of programming skills is emphasized, as this process promotes the formation of algorithmic thinking of pupils. The authors determined the level of pupils' interest to programing learning depending on the age. The analysis has showed that the natural interest of younger pupils in programming is decreasing over the years and in the most productive period of its study is minimized. It is revealed that senior school pupils are characterized by low level of interest in the study of programming; lack of motivation; the presence of psychological blocks on their own abilities in the context of programming; law level of computer science understanding. To overcome these problems, we conducted the second stage of the experiment, which was based on a change in the approach to programing learning, which involved pupils of non-specialized classes of senior school (experimental group). During the study of programming, special attention was paid to the motivational and psychological component, as well as the use of game technologies and teamwork of pupils. The results of the pedagogical experiment on studying the effectiveness of teaching programming for pupils of nonspecialized classes are presented. Improvement of the results provided the use of social and cognitive motives; application of verbal and non-verbal, external and internal means; communicative attacks; stimulation and psychological setting; game techniques, independent work and reflection, teamwork. The positive effect of the implemented methods is shown by the results verified by the methods of mathematical statistics in the experimental and control groups of pupils.

• Geomechanics and Engineering
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• 제29권2호
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• pp.145-154
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• 2022

Complex geological conditions have a great influence on the mining of coalbed methane (CBM), which affects the extraction efficiency of CBM. This investigation analyzed the complicated geological conditions in the Liujia CBM block of Fuxin. A geological model of heterogeneities CBM reservoirs was established to study the influence of strike direction of igneous rocks and fault structures on horizontal well layout. Subsequently, the dual-porosity and dual-permeability mathematical model was established, which considers the dynamic changes of porosity and permeability caused by gas adsorption, desorption, pressure change. The results show that the production curve is in good agreement with the actual by considering gas seepage in matrix pores in the model. Complicated geological structures affect the pressure expansion of horizontal wells, especially, the closer to the fault structure, the more significant the effect, the slower the pressure drop, and the smaller the desorption area. When the wellbore extends to the fault, the pressure expansion is blocked by the fault and the productivity is reduced. In the study area, the optimal distance to the fault is 70 m. When the horizontal wellbore is perpendicular to the direction of coal seam igneous rock, the productivity is higher than that of parallel igneous rock, and the horizontal well bore should be perpendicular to the cleat direction. However, the well length is limited due to the dense distribution of igneous rocks in the Liujia CBM block. Therefore, the horizontal well pumping in the study area should be arranged along the direction of igneous rock and parallel plane cleats. It is found that the larger the area surrounded by igneous rock, the more favorable the productivity. In summary, the reasonable layout of horizontal wells should make full use of the advantages of igneous rock, faults and other complex geological conditions to achieve the goal of high and stable production.

• Journal of Korea Trade
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• 제25권2호
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• pp.58-74
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• 2021

Purpose - This paper research on the embodied carbon emission in Sino-Korea trade. It calculates and analyzes the carbon emission coefficient and specific carbon emissions in Sino-Korea trade from 2005 to 2014. Design/methodology - This paper conducted an empirical analysis for embodied carbon emission in Sino-Korea trade during the years 2005-2014, using a multi-region input-output model. First, direct and complete CO2 emission coefficient of the two countries were calculated and compared. On this basis, combined with the world input-output table, the annual import and export volume and sector volume of embodied carbon emission are determined. Then through the comparative analysis of the empirical results, the reasons for the carbon imbalance in Sino-Korea trade are clarified, and the corresponding suggestions are put forward according to the environmental protection policies being implemented by the two countries. Findings - The results show that South Korea is in the state of net trade export and net embodied carbon import. The carbon emission coefficient of most sectors in South Korea is lower than that of China. However, the reduction of carbon emission coefficient in China is significantly faster than that in South Korea in this decade. The change of Korea's complete CO2 emission coefficient shows that policy factors have a great impact on environmental protection. The proportion of intra industry trade between China and South Korea is relatively large and concentrated in mechanical and electrical products, chemical products, etc. These sectors generally have large carbon emissions, which need to be noticed by both countries. Originality/value - To the best knowledge of the authors, this study is the first attempt to research the embodied carbon emission of ten consecutive years in Sino-Korea Trade. In addition, In this paper, some mathematical methods are used to overcome the error problem caused by different statistical caliber in different databases. Finally, the accurate measurement of carbon level in bilateral trade will provide some reference for trade development and environmental protection.

• International Journal of Computer Science & Network Security
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• 제22권11호
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• pp.11-18
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• 2022

Linking Ukraine's education system with the trends of global digitalization is mandatory to ensure the sustainable, long-term development of the country, as well as to increase the sustainability of the education system and the economy as a whole during the crisis period. Now the main problems of the education system in Ukraine are manifested in a complex context caused by Russian armed aggression. In the context of war, problems include differences in adaptation to online learning among educational institutions, limited access to education for vulnerable groups in the zone of active hostilities, the lack of digital educational resources suitable for online learning, and the lack of basic digital skills and competencies among students and teachers necessary to properly conduct online classes. Some of the problems of online learning were solved in the pandemic, but in the context of war Ukrainian society needs a new vision of education and continuous efforts of all social structures in the public and private environment. In the context of war, concerted action is needed to keep education on track and restore it in active zones, adapting to the needs of a dynamic society and an increasingly digitized economy. Among the urgent needs of the education system are a change in the teaching-learning paradigm, which is based on content presentation, memorization, and reproduction, and the adoption of a new, hybrid educational model that will encourage the development of necessary skills and abilities for students and learners in a digitized society and enable citizens close to war zones to learn.

• 자원ㆍ환경경제연구
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• 제32권3호
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• pp.149-166
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• 2023

온실가스 저감을 위해 도입된 배출권거래제가 2차 계획기간(2018~2020) 중 배출권 가격 급등에 따라 원활한 배출권 수급에 대한 수요는 증가한 반면 향후 배출권 부족을 예상한 공급자들의 거래참여 부진이 발생하였다. 이로 인해 2019년 당국은 시장 안정화 조치의 일환으로 배출권의 이월량이 거래량에 비례하도록 지침을 일시적으로 개정한 바 있다. 본고는 복수참여자 동태적 비선형 수리모형을 활용한 최적화 과정을 통해 이월정책에 대한 정부의 개입이 온실가스 저감 및 배출권 시장 가격 등에 미친 영향을 분석하였다. 시뮬레이션 분석 결과, 이월제한이라는 규제가 미리 예견되는 모형의 제약에도 불구하고 규제가 실시되는 기간 중에는 확실한 매물 출하 효과로 인해 가격인하가 발생하였음을 보여주고 있다.

• 한국수자원학회논문집
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• 제55권spc1호
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• pp.1223-1234
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• 2022

기후변화에 대처하기 위한 온실가스 저감 노력은 상하수도 분야에서도 활발하게 진행되어 왔으며, 특히, 상수도 생산 및 공급과정에서 많은 에너지를 소비하는 상수관망의 에너지를 절감하기 위한 많은 기술개발이 이루어져왔다. 상수관망의 에너지 절감은 지형의 기복으로 발생되는 구조적 손실의 저감과 누수 및 마찰손실로 인한 운영 상 손실의 효율화를 통해 성취될 수 있음에도 실제 상수관망의 에너지 수지를 분석하는 단계에서 이들 인자들 상호간의 복합적 작용으로 인해 해석적인 접근뿐 아니라 수치모형을 이용한 모의에서도 한계를 노출하여 왔다. 본 연구에서는 지형의 기복, 누수 및 마찰손실의 유무에 따라 변화하는 유량, 압력수두 및 에너지를 5가지의 상수관망 상태(가설적 상태, 이상적 상태, 누수가 포함된 이상적 상태, 누수가 배제된 실제 상태, 실제 상태)에 대하여 수리 물리적 방정식을 도출하고, 이를 단순한 형태의 상수관망에 적용함으로서 에너지의 정량적 분석 및 분류, 각종 에너지 수지 구성요소별 분석과 이를 이용한 상수도 시스템의 에너지 진단이 가능하도록 하였다.

• 한국수학교육학회지시리즈C:초등수학교육
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• 제26권2호
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• pp.83-97
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• 2023

명사화는 문법적 은유 중 하나로, 수식으로 변환해야 하는 대상의 수학화를 용이하게 한다는 장점과 함께 복잡하고 압축된 문장 구성으로 인해 문장 이해를 어렵게 할 가능성이 있다는 단점이 있다. 이러한 명사화가 실제 학생들의 문장제 해결 과정에 어떠한 영향을 미치는지 파악하기 위하여 초등학교 3학년을 대상으로 명사화 여부에 따른 사칙연산 문장제 8개를 제공하여 검사를 실시하였다. 분석 결과, 문장제의 명사화 여부는 문제 이해 및 수식화 가능 여부에 의미 있는 영향을 미치지 못하였다. 그러나, 검사에 참여한 학생에게 명사화에 대한 사전 경험이 없음에도 불구하고 문제 이해 단계에서 명사화 또는 탈명사화가 나타나는 것을 확인하였으며, 명사화의 유형 변화가 발생하는 경우 성공 비율이 높게 나타나는 등 수식화 단계를 용이하게 하였다. 이를 통하여 명사화가 문장제의 문제 이해 및 수식화 단계에서 교수학적 전략으로 활용될 수 있으며 문장제의 학습에서 더 깊이 있는 이해를 유도할 수 있을 것으로 기대할 수 있다. 

• 디자인융복합연구
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• 제14권5호
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• pp.31-45
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• 2015

근래 들어, 인터랙티브한 매체의 활성화로 인해, 사용자의 인풋과 인터랙션을 타이포그래피에 직접적으로 반영하는 인터랙티브 타이포그래피가 발전하고 있다. 기존의 고정(fixed) 되어 있던 매체에서의 타이포그래피 디자인과 달리, 유동적으로 변화하는 인터랙티브 타이포그래피는 인터랙티브 시스템(Interactive system)을 바탕으로, 다양한 디자인 결과물을 즉각적으로 양산해 낸다. 이 연구에서는 기초 연구를 통해 작품을 구현했다. 기초 연구 단계에서는 문헌 연구를 통해, 인터랙티브 타이포그래피에 대해 고찰해 보면서, 함수의 개념을 빌려 인터랙티브 시스템을 이해하고자 했다. 작품 구현 단계에서는 플래시 액션스크립 (Flash action script)을 이용해 인터랙티브 타이포그래피 작품 '인터랙티브 프로럴 타입(Interactive Floral Type)'을 디자인하고 구현했고, 사용자의 마우스와 키보드의 인풋에 따라 타입의 크기, 색상, 레이아웃, 모션이 변화함으로써, 타이포그래피의 기본 조형 요소인 '개별 글자'가 '꽃'의 모양으로 실시간 변화하는 실험적 타이포그래피 작품을 구현했다.