• 한국주조공학회지
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• 제17권4호
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• pp.402-410
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• 1997

Developing a salt core for squeeze casting process, two different salt cores(pure salt core and mixed salt core) were fabricated and investigated. Pure salt core was composed of 100% NaCl and mixed salt core was made by mixtures of NaCl with MgO(1%), $Na_2B_4O_7$(2%), and talc(1%) as a binder or a strengthening agent. Salt cores were compacted to various theoretical density, heat treated, and then squeeze-cast with molten Al alloy(AC8A). The compression strength of salt cores were measured and the squeeze-cast products were examined for shape retention, infiltration of molten metal into the cores, and microstructures. The shape of salt core compacted at above 75% of the theoretical density was maintained stably. The higher theoretical density of salt cores gave higher compression strength, and the compression strength of mixed salt core was higher than that of pure salt core. Namely at 90% theoretical density, the compression strength of mixed salt core was $6.3 kg/mm^2$, compared to $4.6 kgmm^2$ for pure salt core. At a squeeze casting pressure of $1000 kg/cm^2$, molten Al alloy was infiltrated into pure salt core of under 85% of the theoretical density. At squeeze casting pressure of $1000 kg/cm^2$, only mixed salt core above 90% of the theoretical density were valid, but the shape of the core was altered in the case of pure salt core at 90% of theoretical density. A key factor for developing a salt core for squeeze casting process was estimated as the ultimate compressive strength of salt core.

• 방사성폐기물학회지
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• 제16권3호
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• pp.359-367
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• 2018

Long-lived Small Modular Reactors are being promoted as an innovative way of catering to emerging markets and isolated regions. They can be operated continuously for decades without requiring additional fuel. A novel configuration of long-lived reactor core employs a mixed neutron spectrum, providing an improvement in nonproliferation metrics and in safety characteristics. Starting with a base sodium reactor design, moderating material is inserted in outer core assemblies to modify the fast spectrum. The assemblies are shuffled once during core lifetime to ensure that every fuel rod is exposed to the thermalized spectrum. The Mixed Spectrum Reactor is able to maintain a core lifetime over two decades while ensuring the plutonium it breeds is below the weapon-grade limit at the fuel discharge. The main drawbacks of the design are higher front-end fuel cycle costs and a 58% increase in core volume, although it is alleviated to some extent by a 48% higher power output.

• Nuclear Engineering and Technology
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• 제40권2호
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• pp.117-126
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• 2008

In this paper, a new reactor core design is proposed on the basis of a mixed core concept consisting of a thermal zone and a fast zone. The geometric structure of the fuel assembly of the thermal zone is similar to that of a conventional thermal supercritical water-cooled reactor(SCWR) core with two fuel pin rows between the moderator channels. In spite of the counter-current flow mode, the co-current flow mode is used to simplify the design of the reactor core and the fuel assembly. The water temperature at the exit of the thermal zone is much lower than the water temperature at the outlet of the pressure vessel. This lower temperature reduces the maximum cladding temperature of the thermal zone. Furthermore, due to the high velocity of the fast zone, a wider lattice can be used in the fuel assembly and the nonuniformity of the local heat transfer can be minimized. This mixed core, which combines the merits of some existing thermal SCWR cores and fast SCWR cores, is proposed for further detailed analysis.

• 펄프종이기술
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• 제30권2호
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• pp.74-84
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• 1998

This study was carried out to investigate the papermaking characteristics of paper mulberry(Broussonetia kazinoki) for new Korean traditional paper(Hanji). Hanji has been traditionally made only with the bast fiber of paper mulberry. Besides mulberry bast part, wood core was utilized separately or in mixed forms as raw materials for the new Hanji. Hanjis made from the solfomethylated pulp were shown higher brightness and sheet strengths than those from alkali and alkali-hydrogen peroxide pulps. The brightness of solfomethylated pulp was found to be high enough not to need additional bleaching. In the physical properties of the Hanjis mixed with bast part and wood core pulps, the handsheet strengths were decreased as the increase of the wood core pulp contents. But the sheet strengths of Hanjis containing 10∼30% of wood core pulps were higher than those of the Hanji containing bast part pulp only. The sheet formations were improved as the increase of wood core pulp contents, while the sheet strengths were decreased.

• 한국주거학회논문집
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• 제21권4호
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• pp.11-22
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• 2010

In the urban area where rapid suburbanization trend continues, the role of mixed use building is controversial. It is argued that the mixed use building is an effective tool to recover residential function of urban core(urban regeneration). It is also argued that the building is a cause of serious urban problems, such as congestion, public service shortages. The fundamental purpose of this study is to examine the role of mixed use building in terms of urban growth management in Seoul. For this purpose, data of mixed use building from 1981 to 2007 are collected and analysed. The results show that most of mixed use buildings are located in either sub-centers or population losing areas, rather than traditional urban core. Therefore, it is hard to accept that the two controversial arguments. The mixed use building noncore areas in most cases. However, it dose help to increase population inflow in non-core areas. it is difficult to accept the public service assertion which states that super-high rise mixed use building causes public service congestion, because the building is built in population losing or demand decreasing area. Based on these findings this study suggests some policy alternatives such as urban service boundary or concurrency program to management urban growth.

• 국제초고층학회논문집
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• 제7권3호
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• pp.197-214
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• 2018

Tall buildings which began from about 40 m tall office towers in the late $19^{th}$ century have evolved into mixed-use megatall towers over 800 m. It is expected that even mile-high towers will soon no longer be a dream. Structural systems have always been one of the most fundamental technologies for the dramatic developments of tall buildings. This paper presents structural systems employed for the world's tallest buildings of different periods since the emergence of supertall buildings in the early 1930s. Further, structural systems used for today's extremely tall buildings over 500 m, such as core-outrigger, braced mega-tube, mixed, and buttressed core systems, are reviewed and their performances are studied. Finally, this paper investigates the potential of superframed conjoined towers as a viable structural and architectural solution for mile-high and even taller towers in the future.

• 소성∙가공
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• 제26권4호
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• pp.240-245
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• 2017

Mixed-model production technology is a method of producing multiple products with one production process and production line in order to reduce wasted manpower and adjust to market trends. In other words, mixed-model production is a flexible production system that changes production volume by model according to market demand. This study has developed a progressive laminated stamping die technology to enable flexible production of a motor core consisting of attaching and detaching the Cam on the back of the punch so that two kinds of stator and two kinds of rotor could be produced in one progressive die.

• Nuclear Engineering and Technology
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• 제29권4호
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• pp.299-309
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• 1997

The neutronic feasibility of typical Korean three-loop 900MWe class PWR core loaded with mixed oxide fuels for both annual and 18-month cycle strategies has been investigated as a means for spent fuel management. For this study, a method of determining equivalent plutonium content was developed under the equivalence concept which gives the same cycle length as uranium fuel. Optimal plutonium zoning within the MOX assembly was also designed with the aim of minimizing the peak md power. Conceptual core designs hate hen developed for equilibrium cycle with the following variations: annual and 18-month cycle, 1/3 and full MOX loading schemes, and typical and high moderation lattice. The analysis of key core physics parameters shows that in all cases considered satisfactory core designs seem to be feasible, though addition of control rod system and change in Technical Specification for soluble boron concentration are required for full MOX loading in order to meet the current design requirements.

• 한국해양공학회지
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• 제18권1호
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• pp.16-21
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• 2004

In general, core materials of rubble mound breakwater are used at a restricted range of 0.015㎥～0.03㎥. However, it is not satisfied with the standard design in over fifty percent of the cases. In this study, model tests and numerical analysis are employed to examine the range of core material that has no problem with capacity maintenance and stability of rubble mound breakwater. Model tests measure the porosities that are mixed in various ratios, to classify core materials by three parameters. The slope stability of rubble mound breakwater is investigated, using numerical analysis, with a friction angle and a unit weight. The change of unit weight, which is followed by the mixed rate of size core material, has no large affect on slope stability, and there is no problem with ensuring slope stability of the rubble mound breakwater.

• 한국터널지하공간학회 논문집
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• 제21권3호
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• pp.323-345
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• 2019

토사지반과 핵석지반에서 EPB 쉴드 TBM을 통한 성공적인 터널 시공을 위해서 굴착면 전방의 지반 정보를 정확히 파악하는 것이 필요하다. 본 연구에서는 전기비저항 탐사와 유도분극(induced polarization) 탐사를 함께 활용하여 복합토사지반과 핵석지반에 대한 전방 예측 방안을 제시하고자 하였다. 토사지반의 구성은 EPB 쉴드 TBM에서 첨가재 선택에 필수요소이며, 핵석지반은 기계화 시공에서 난이도가 높은 지반이기 때문이다. 탐사는 TBM이 굴진을 멈추고 세그먼트 1링을 조립할 시에 커터헤드에 설치된 4개의 전극을 활용하여 수행된다고 보았다. 토사지반의 경우 화강풍화토, 모래, 점토로 구성된 복합지반에 대해 축소모사하여 실내실험을 수행하였다. 실험 결과 전기비저항은 복합지반 이론해와 상당히 일치하였으며 유도분극은 경우에 따라 전기비저항과 경향성이 일치하거나 완전히 상반되었다. 이러한 결과를 토대로 실제 현장에서 적용 가능한 토사지반 예측방안을 제시하였다. 핵석지반의 경우 균질지반에서 핵석지반으로 굴착해 나가는 상황을 축소모사하였으며 핵석의 불규칙성을 난수를 통해 모사하였다. 실험결과 전기비저항은 핵석지반에 접근할수록 증가하였고 유도분극은 불규칙하게 오르내림을 거듭하는 경향을 나타내었다.