• Journal of the Korean Geosynthetics Society
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• 제5권3호
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• pp.9-15
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• 2006

The Green Wall system is one of segmental concrete crib type earth retaining wall. Green wall is constructed as procedures that lay the front stretchers, rear stretchers and headers then making a rigid body through harden filled soil of interior cell. Recently, Green Wall method is applied in variable cutting ground construction because of advantage which minimize to cut base ground. In case of Green Wall method is constructed with soil nail method, expect that total system stability will increase more than flexible facing because of facing stiffness is big. However, in this case of design, facing stiffness is not considered so that is poor economy. Hence, in this study, stability increasing effect of total system analyze about that soil nail method is constructed with rigidity facing like a Green Wall method. In present study, laboratory model tests was performed for analysis on stability increasing effect of total system about changing stiffness of facing. LEM analysis conducted for evaluation on safety factor of total system sliding that facing condition changed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 1996년도 춘계학술대회논문집; 부산수산대학교, 10 May 1996
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• pp.11-21
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• 1996

선박은 화물 및 여객을 수송하는 해상교통 수단으로써 여객 및 승무원의 안락성, 탑재장비, 기기의 성능 보전 상, 화물 및 구조부재의 안전성 차원에서 진동제어가 주요 해결 기술의 하나이다. 또한 최근 선박의 대형화, 고속화로 인해 엔진과 프로펠러의 기진력은 커지는데 반해 구조 강도계산 기술의 발달로 인해 선체구조 경량화가 촉진되어 선체의 유연성이 커질 뿐 아니라 전통적인 선체 구조와 기관, 축계 강성사이의 균형이 깨어짐으로 선박의 진동제어는 더욱 중요시 되고 있다. 선박의 경우 건조 후에 진동제어를 위한 조치를 취하는 일은 매우 제한적이고 많은 비용이 들기 때문에 설계단게에서 선박진동제어를 위한 사전 노력이 충분히 이루어지는 것이 중요하다. 따라서 선박의 주 기진원인 프로펠러, 주기관 등의 기진력 자체를 적정화하는 노력과 함께 그로 인한 응답을 극소화하기 위해 설계 단계부터 인도까지 단게별로 많은 노력을 기울이고 있다. 단계별 진동제어의 한 예를 Fig.1에서 보여주고 있다[1]. 선체와 같이 복잡한 대형구조물의 진동특성 및 응답을 계산함에 있어서 컴퓨터의 발달과 유한요소법과 같은 해석기술의 발달로 실제 구조와 매우 유사한 3차원 모델링이 가능하게 되어 해석의 정도를 높일 수 있게 되었다. 그러나 프로펠러 기진력, 유체와의 연성효과, 감쇠특성 등을 정도 높게 산정하는 데는 아직도 많은 어려움이 있다. 이와같은 문제는 진동응답의 계산정도를 저하시키는 주요 요인이 되어 설게단계에서 충분히 진동 제어가 이루어졌다 하더라도 건조 후 실제운항 시 진동문제가 발생되는 경우가 있다. 건조 후 진동문제 발생시 구조변경을 통한 해결은 한계가 있기 때문에 각종 진동제어 장치의 연구개발이 최근에 활발히 이루어지고 있다[2]. 본 고에서는 설계단계에서부터 건조 후까지의 선박진동제어 과정[1,2,5,6]을 단계별로 고찰하여, 점점 까다로워져 가는 선박 진동규제[3,4]에 대처하고 승무원의 안락성에 대한 욕구, 구조물의 안전성, 장비의 성능보존이 만족되는 저진동 선박의 건조를 위해 향후 해결해야할 과제들을 도출하여 선박진동분야이 연구개발 방향을 제시하고자 한다.

• The Journal of the Korea Contents Association
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• 제15권9호
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• pp.509-526
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• 2015

The study investigated the N-Screen strategies of paid digital contents of foreign newspapers belonging to advanced companies: USA, United Kingdom, and Japan. This research employed the time to launch paid digital content business, whether or not to segment market, and 4p marketing mix strategies for analyzing the strategies. The results show that the strategies, starting around the year 2000, had experience chasm, and then revived since the year 2010, when the penetration rate of mobile devices proliferated. Most newspapers still supply contents under the assumption that they paly in a mass market. The items of paid digital contents are mainly composed of e-paper and digital contents. Regarding the price strategy, soft paywall and combination paywall are largely used. Distribution strategy is subject to whether or not to discriminate the path of digital contents. As for promotion strategy, bundling strategy with newspaper is mostly utilized. The difference between western countries and Japan was found in term of the free trial service.

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제25권6호
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• pp.405-411
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• 2013

A sediment transport calculation considering cohesive force is proposed to deal with the transport phenomena of cohesive sediment. In the proposed calculation, each sand particle is assumed to be surrounded by a thin layer of mud. The critical Shields parameter and bed-load sediment transport rate are modified to include the cohesive force acting on the sand particle. The proposed calculation is incorporated into a two-way coupled fluid-structure-sediment interaction model, and applied to wave-induced topographic change of artificial shallows. Numerical results show that an increase in the content ratio of the mud, cohesive resistance force per unit surface area and water content cause increases in the critical Shields parameter and decreases in the bed-load sediment transport rate, reducing the topographic change of the shallow without changing its trend. This suggests that mixing mud in the pores of the sand particles can reduce the topographic change of shallows.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제20권1호
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• pp.23-29
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• 1984

Nowdays, the high strength aluminum alloys are broadly used for structural purpose, but the practical strengthening method by aging treatment are not much available. So that, in this study, in order to investigate the effect of aging treatment for strengthening on the fracture characteristics of the domestic high strength Al alloy (A2024BE), the variations of the aging temperature and time were taken after solution treatment. By microstructural examination, and by SEM fractographs of the fractures, the effects of aging temperature and time were investigated, considering on the fracture behaviour. The results obtained are as follows: 1) It was confirmed by microstructural investigation that the aging temperature of $190^{\circ}C$ and the aging time of 12hours were optimal to get more sound microstructure with distribution of uniform precipitation. 2) By step aging treatment, the proper aging time for obtaining the similar microstructure without any microstructural defects could be shortened in half the normal aging time. 3)By examining the SEM fractographs of the fracture surface, it was found that, regardless of the aging treatment time and temperature, all were intergranular ductile fractures, but the aging treatment at $190^{\circ}C$ for 12 hours resulted in dimple-type-transgranular and intergranular-ductile-frature.

• Elastomers and Composites
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• 제44권4호
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• pp.436-441
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• 2009

Semi flexible polyesters containing aromatic rings and pentamethylene groups in the main chain were synthesized by direct polycondensation reaction. The structures of these polymers were investigated by $^1H$-NMR and FT-IR and the phase transition behavior was characterized with DSC, TGA and crossed polarizing microscope. Inherent viscosities ($\eta_{inh}$) of polymers measured in phenol/p-chlorophenol/1,1,2,2-tetrachloroethane were between 0.46 and 1.30 dL/g. As increasing the linearlity of rigid moieties in polyster, melting transition temperatures ($T_m$) increased and solubilities in organic solvents decreased. P-H, P-mH and P-4H of the polymers formed turbid melts that showed stir-opalescence and nematic phase at the broad anisotropic region, However, P-R, P-C and P-2B did not exhibit any textures related to the liquid crystallinity.

• The Korean Journal of Air & Space Law and Policy
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• 제29권1호
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• pp.127-160
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• 2014

The UN COPUOS was established in 1959 as a permanent committee of the UN General Assembly with the aims to promote international cooperation in peaceful uses of outer space, to formulate space-related programmes within the UN, to encourage research and dissemination of information on space, and to study legal problems arising from the outer space activities. Its members have been enlarged from 24 members in 1959 to 76 in 2014. The Legal Subcommittee, which has been established under COPUOS in 1962 to deal with legal problems associated with space activities, through its first three decades of work has set up a framework of international space law: the five treaties and agreements - namely the Outer Space Treaty, Rescue Agreement, Liability Convention, Registration Convention, Moon Agreement - and the five declarations and legal principles. However, some sceptical views on this legal framework has been expressed, concerning the applicability of existing international space law to practical issues and new kinds of emerging space activities. UNISPACE III, which took place in 1999, served as a momentum to revitalize the discussions of the legal issues faced by the international community in outer space activities. The agenda of the Legal Subcommittee is currently structured into three categories: regular items, single issue/items, and items considered under a multi-year workplan. The regular items, which deal with basic legal issues, include definition and delimitation of outer space, status and application of the five UN treaties on outer space, and national legislation relevant to the peaceful exploration and use of outer space. The single issues/items, which are decided upon the preceding year, are discussed only for one year in the plenary unless renewed. They include items related to the use of nuclear power sources in outer space and to the space debris mitigation. The agenda items considered under a multi-year work plan are discussed in working group. Items under this category deal with non-legally binding UN instruments on outer space and international mechanism for cooperation. In recent years, the Subcommittee has made some progress on agenda items related to nuclear power sources, space debris, and international cooperation by means of establishing non-legally binding instruments, or soft law. The Republic of Korea became the member state of COPUOS in 2001, after rotating seats every two years with Cuba and Peru since 1994. Korea's joining of COPUOS seems to be late, in considering that some countries with hardly any space activity, such Chad, Sierra Leone, Kenya, Lebanon, Cameroon, joined COPUOS as early as 1960s and 1970s and contributed to the drafting of the aforementioned treaties, declarations, and legal principles. Given the difficulties to conclude a treaty and un urgency to regulate newly emerging space activities, Legal Subcommittee now focuses its effort on developing soft law such as resolutions and guideline to be adopted by UN General Assembly. In order to have its own practices reflected in the international practices, one of the constituent elements of international customary law, Korea should analyse its technical capability, policy, and law related to outer space activities and participate actively in the formation process of the soft law.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제32권3호
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• pp.320-332
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• 1999

Investigations were made on the community structure of macrobenthos in the subtidal soft bottom around semi-enclosed Youngsan River estuarine bay, southwest coast of Korea during the period from April 1995 to February 1996. Three macrobenthos samples were collected at 40 stations using a van Veen grab(0.1 m^2) during the study period. A total of 206 species of macrobenthos was identified. Their mean density and biomass (wet-weight, wwt) were $1,137 ind./m^2$ and $65.28 gwwt/m^2$, respectively. Of these, there were 74 species of polychaetes ($36\%$), 60 molluscs ($39\%$), 51 crustaceans ($25\%$) and 21 miscellaneous taxa. Molluscs were represented as a density- and biomass-dominant faunal group with a mean density of $601 ind./m^2$($53\%$ of the total benthic animals) and biomass of $25.37 gwwt/m^2$($39\%$ of total biomass): It was followed by polychaetes with $405 ind./m^2$($40\%$ of the total density). Total number of species and diversity were Bow in the inner estuarine bay containing high mud content and organic matter, whereas they were high in the outer stations containing low mud content and organic matter. Major dominant species were one biralve, Theora fragilis and three Polychaetes, Tharyx sp., Poeciloceatus johnonni and Lumbrineris lontifolia whose mean densities were $490ind./m^2$, $96ind./m^2$, $74ind./m^2$and $52 ind./m^2$, respectively. Cluster analysis indicated that the study area could be divided into four station groups: two innermost station groups, a central bay and an outer station group. The species diversity increased from the inner station group toward the outer groups. These results were discussed in terms of both the environmental factors and distribution of benthic community.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권5호
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• pp.399-409
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• 2018

The mechanically stabilized earth wall (MSEW) of the IPM bridge is an important structure that constitutes the bridge, and supports the horizontal earth pressure and approach slab. Therefore, it is necessary to carefully analyze the settlement of MSEW of the IPM bridge. This study examined the settlement according to the height and ground stiffness on the MSEW on the IPM Bridge. According to the design guideline, the IPM Bridge (2016) was designed to have a height of 4.0 ~ 10.0m and the elastic settlement was calculated. The base area and the grounding pressure of the MSE wall increased linearly with the height, and the elastic settlement also increased linearly. In addition, the stiffness of the foundations satisfying the allowable settlement of the approach slab is a N value of 35 or more. The settlement of finite element analysis was estimated to be smaller than the elastic settlement, and the stiffness of the foundation ground satisfied the allowable settlement of the approach slab above N value of 20. Because the elastic settlement of the MSEW of the IPM Bridge was overestimated, it will be necessary to examine it carefully by finite element analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• 제24권1호
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• pp.119-125
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• 2018

The particle based computational fluid dynamics (CFD) method, which follow Lagrangian approach for fluid dynamics, fluid particle behavior by tracking all particle calculation physical quantities of each particle. According to basic concept of particle based CFD method, it is difficult to satisfy continuum theory and measure influences from neighboring particle. Article number density and weight function were used to solve aforementioned issue. Difficulties continuum mean simulate non-continuum particles such as solid including granular and sand. In this regard, the particle based CFD method modified solid particle problems by replacing viscous and surface tension forces friction and drag forces. In this paper, particle interaction model for solid particle friction model implemented to simulate solid particle problems. The broken dam problem, which is common to verify particle based CFD method, used fluid or solid particles. The angle of repose was observed in the simulation results the solid particle not fluid particle.