• Title/Summary/Keyword: disadvantageous

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The Properties of Polymer Concrete Recycling Plastic Waste (폐플라스틱을 재활용한 폴리머 콘크리트 특성)

  • 조병완;문린곤;박승국;임상헌
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.441-444
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    • 2003
  • Polymer concrete has more useful than cement concrete in the strength and durability. So, it is widely utilizing as panel for wall, manhole for communication, foundation and underground connection box, etc. But polymer concrete is a defect that is disadvantageous in economical aspect because cost of resin is expensive. Polymer concrete (PC) using unsaturated polyester resins based on recycled polyethylene terephthalate(PET) plastic waste were used in our study for grasping its mechanical properties such as compressive strength, tensile strength, flexural strength and chemical resistance was tested by dealing with 20% HCl, 30% NaOH. As a result of it, compressive, tensile and flexural strength of PC indicated 752kgf/$\textrm{cm}^2$, 80kgf/$\textrm{cm}^2$ and 243kgf/$\textrm{cm}^2$ kind of satisfaction successively. Also, properties of chemical resistance are superior to those of cement concrete.

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Development and Measurement of Learners' Satisfaction Index Model for Cyber Education

  • Kim, Chang-Su;Jung, Hoe-Kyung
    • Journal of information and communication convergence engineering
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    • v.8 no.3
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    • pp.343-347
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    • 2010
  • Cyber education has been predicted that it would become the primary education system of 21st century as a way of education focusing on consumers, with the aspect that it seems to be able to satisfy the demand about re-education and lifelong education as the acceleration of fast knowledge accumulation throughout every field of society in the digital era. However, cyber education system has a lot of problems which are for that it lacks of human resources for effective interaction, and it can be disadvantageous to certain type of students with a class environment concentrated on reading and writing and with foundation on computer technology. Therefore, in this thesis, We intended to analyze factors influencing satisfaction of people studying in a situation that cyber education has been required to be a mainstream system of education in the midst of trend of changing paradigm of college education recently, and to suggest some possible solutions for cyber education at university.

The Traits of International Marriage in Rural Korea (한국농촌의 국제결혼의 특징)

  • Lim, Hyung-Baek
    • Journal of Agricultural Extension & Community Development
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    • v.14 no.2
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    • pp.471-491
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    • 2007
  • The purpose of this study were (1) to thumbnail sketch of present general condition of foreigners and international marriage in Korea, (2) to study special trend of international marriage in rural Korea, particularly immigration connected with poverty, and (3) to focus on prospect of the problem of mixed-bloods, especially half blood children in rural Korea. Many of foreigners were treated discriminatingly, for example racial discrimination and wage discrimination. And discrimination to mixed-blood children will be happen in future. They are in a disadvantageous position because of economic status and appearances. Half blood children have korean nationality because one of his parent is korean. When they grow up and reach their the age of puberty and the age of working, they will resist to discrimination in working and marriage. I had examined precedent studies, and class theory in general, and to suggest it is time to looking for way of reduce social cost and way of coexistence.

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A Study of Numerical Analysis for Uneven Stress of Tunnel (터널 편압 대책에 대한 수치해석적 연구)

  • 현기환;윤지선
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.501-508
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    • 2000
  • In recent years, as lines are selected In disadvantageous region, unavoidable developments is increased. Owing to such developments. environmental problems have been occurred frequently, In excavation of tunnels especially located in close to slope, uneven stress take place to tunnel due to a topographical factor. it is used assistant methods of construction which are excavation of slope, retaining wall, ground anchor, etc for uneven stress. these assistant methods raise problems of environmental. In this study, using slit, we could make better stress state by means of inducing stress concentration in boundary of tunnel. considering a variety of slit and rock mass condition, we use numerical analysis.

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Analysis of Inverter-Fed Induction Motor Using F.E.M and Harmonic Equivalent Circuit (슬롯피치 경계 조건을 이용한 인버터 구동 유도 전동기의 회전자 등가회로 정수 추출 및 특성해석)

  • Lee, Geon-Ho;Kim, Byeong-Tae;Gwon, Byeong-Il
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.51 no.7
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    • pp.331-338
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    • 2002
  • An inverter-fed induction is driven by a harmonic voltage source so that it is necessary to be analysed by time-stepping F.E.M. But it takes so long time that disadvantageous to design. This paper presents a simple analysis method for inverter-fed induction motor using FEM and harmonic equivalent circuit. First, the rotor bar resistance and the leakage reactance are determinated by FEA for 1 slot region in rotor to consider the skin effect and the saturation. Secondly, the characteristic of the motor is analyzed by the harmonic equivalent circuits consisting of the obtained parameters from the FEA. This method is carried out to analyze an induction motor driven by the sinusoidal voltage and the inverter. The results are verified by comparing with those of the time-step F.E.A and the experiment.

A Sutdy on the Water Quality Management using Fllow Paddy (유휴농지를 이용한 수질관리방안 연구)

  • Kim, Hyung-Joong;An, Yeul;Kim, Sun-Joo;Kim, Phil-Shik
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2005.10a
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    • pp.485-489
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    • 2005
  • Fallow paddy has been increased in disadvantageous farming condition area because of importation of foreign agricultural products, labor cost and the imbalance between farming cost and agricultural products price since 1990. The fallow paddy that has gradually increased needs to be prevented from the devastation by weed breeding for re-cultivation. In this study, two fallow paddies that manage with different water depth from the experimental field were selected for observation, and analysis of water quality, water balance and plant body change. The managed fallow paddy was more effective in water quality purification and plants growth control than non-managed fallow paddy. And the fallow paddy managed with a some degree water depth was the most effective field on weed control.

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Simulation and Measurement of Earth resistance Values in Common Earth Network (공동 접지망에서의 접지 저항값 시뮬레이션 및 측정)

  • Kim, Yong-Kyu;Kim, Jong-Gi;Yang, Doh-Chul;Park, Hyun-Joon
    • Proceedings of the KIEE Conference
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    • 2006.07b
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    • pp.1073-1074
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    • 2006
  • In this paper, we perform a simulation to verify the earth resistance values in Common Earth Network. The simulation is performed on the assumption that certain shorts are occurred in common earth network. Furthermore, from the result, we confirmed that very small earth resistance values in common earth network are given, by carrying out practical measurements in railway sections where common earth network is composed. From the effect, we could discover that the construction of common earth network is in a disadvantageous position on the financial aspect, while it is the most desirable way of construction for the purpose of Earth.

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Dynamic Characteristics Analysis of Landing Gear that Consider 6-Degree of Freedom of Helicopter (6자유도를 고려한 회전익 항공기 착륙장치의 동특성 해석)

  • Park, Wansoo;Hwang, Jaeup;Hyun, Youngho;Hwang, Jaehyuk;bae, Jaeseoung;Kim, Taewook
    • Journal of Aerospace System Engineering
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    • v.2 no.1
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    • pp.1-6
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    • 2008
  • In this paper, full body modeling and analysis of nose and main landing gear's characteristics of a helicopter are performed using the dynamics analysis program ADAMS. Also, when land limiting about helicopter body's degree-of-freedom, compared the characteristics. In the case of helicopter, because there are a lot of dangerous missions under flight condition that is disadvantageous than fixed wing airplane, need more detailed research for a helicopter.

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Numerical Analysis of Wave Transformation of Permeable Breakwater Permitting Wave Overtopping (월파를 허용하는 투과성 방파제의 파랑변형에 관한 수치해석)

  • 김도삼;이광호
    • Journal of Ocean Engineering and Technology
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    • v.16 no.2
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    • pp.1-5
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    • 2002
  • In the past, ports have been mainly developed in natural harbors but nowadays ports are built wherever they can be economically justified. Therefore, construction of breakwater in area that establishment of structure is disadvantageous is risen according to the change of conditions to the location for ports. In case of building gravity breakwater in such point, need that plane shapes of more reasonable section permitting wave overtopping is necessary. One of the earliest methods for solving unsteady incompressible flow including free surfaces is the MAC(Marker And Cell) method by Harlow and Welch (1965). Recently. VOF(Volume Of Fluid) method to improve several drawbacks of MAC method is suggested by Hirt and Nichols(1981) and utilized extensively in fields of hydrodynamics. Wave overtopping phenomenon is simulated including wave breaking for permeable breakwater by numerical analysis and investigated features of wave overtopping behind structure using VOF method.

Studies on Alumina Cement from Alunite (I) (Synthesis of monocalcium aluminate) (명반석을 이용한 알루미나 시멘트의 제조(I) (Monocalcium Aluminate의 합성))

  • 한기성
    • Journal of the Korean Ceramic Society
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    • v.15 no.4
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    • pp.199-204
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    • 1978
  • In the present investigation, refined alumina obtained from alunite locally available was used as a aluminous source to synthesize monocalcium aluminate $(CA)_3$ the major mineral constituent of alumina cement. The influence of $SiO_2$ and $Fe_2O_3$ contents on the formation of monocalcium aluminate was studied by X-ray diffraction analysis mainly. About 0.8-1.0 of $Al_2O_3/C_3O$ mol ratio and less than 4 percent of $SiO_2$ were desirable for the effective formation of CA. The small amount of alkali and sulphur contents contained in refined alumina from alunite as the impurities were affected to form $C_4A_3S$ and $C_3S_2$, disadvantageous compounds for the alumina cement, therefore the impurities should be restricted in minimum content as possible.

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