• 한국지반환경공학회 논문집
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• 제14권8호
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• pp.53-60
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• 2013

국내 도로 하부구조의 다짐관리 방법은 상대 다짐도를 구하기 위한 현장밀도 시험과 하중 지지력을 확인하는 평판재하시험을 이용하고 있다. 그러나 이 두 시험방법은 시공현장 관리자의 경험적 판단을 수치화한 것으로 역학적인 근거가 미약한 실정이다. 이러한 문제점을 해결하기 위해 최근 사용되고 있는 회복탄성계수법은 차량하중의 반복재하 조건에서 유발되는 포장재료의 응력-변형 상태를 합리적으로 반영할 수 있는 합리적인 포장구조 설계법으로 평가되고 있다. 그러나 회복탄성계수를 측정하는 방법이 어렵고 시간이 많이 소요되는 등 많은 문제점이 있으므로 이를 대체할 수 있는 간편한 시험법으로 최근 소형충격재하시험법이 제안되고 있다. 따라서 본 연구에서는 노상과 보조기층의 시공 및 유지관리 현장의 변형계수를 신속하고 간편하게 측정할 수 있는 동평판재하시험을 이용하여 도로 하부지층의 다짐관리 가능성을 판단하고 정적재하시험결과를 분석하여 관계식을 제안하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.57.1-57.1
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• 2011

The effects of relative humidity on the properties of the porous $ZrO_2$ ceramics were investigated in terms of the curing behavior of phenolic resin as a binder. The $ZrO_2$ powders containing 5wt% of phenolic resin were conditioned in a consistent chamber condition at a temperature of $50^{\circ}C$ and different humidity levels (25, 50, 75, and 95%) for 1 h. The exposure of humid atmosphere caused changes of density and microstructure in the green bodies. The higher level the powders were exposed to the humid atmosphere, the lower green density was obtained and the more irregular microstructure was observed due to aggregation by the curing of phenolic resin. After firing, the porosity of specimens has risen from 35.7% to 38.1% and Young's modulus has declined in response to the variation of green density. These results could be explained by the degree of resin cure which was associated with the area under the exothermic peak enclosed by a baseline of DSC thermogram curve. Also, the curing behavior of phenolic resin according to relative humidity has been confirmed by decrease of ether groups which have interacted with the phenolic-OH group and the hexamine as a curing agent. Consequently, it could be demonstrated that increase the relative humidity during fabrication of porous $ZrO_2$ diminished the compaction and properties of specimens after firing owing to curing of phenolic resin.

• 한국지반공학회논문집
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• 제27권6호
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• pp.81-95
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• 2011

본 연구에서는 표준사와 bottom ash를 No.40체, No.60체, No.100체, No.200체로 분류하여 상대밀도시험을 실시하였으며, 시험결과를 토대로 40%, 55%, 70%의 상대밀도로 공진주시험을 실시하였다. 또한, 각 체에 잔류한 bottom ash에 대해 55%의 상대밀도로 No.200체 통과시료를 함유하여 공진주시험을 실시하였다. 각 체 잔류시료에 대해 A다짐시험에 해당하는 다짐에너지로 다짐을 하면 No.200체 통과율이 약 30%까지 증가하게 되어 함유량을 10%, 20%, 30%로 조정하였다. 시험결과 bottom ash의 경우 파쇄강도와 단위중량이 표준사에 비해 작아 최대전단탄성계수, 감쇠비 등의 결과값이 표준사의 결과에 비해 작았다.

• 한국분말재료학회지
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• 제16권2호
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• pp.85-90
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• 2009

Magnesium and its alloys are attractive as light weight structural/functional materials for high performance application in automobile and electronics industries due to their superior physical properties. In order to obtain high quality products manufactured by the magnesium powders, it is important to control and understand the densification behavior of the powders. The effect of the sheath surrounding the magnesium powders on the plastic deformation and densification behavior during equal channel angular pressing was investigated in the study by experimental and the finite element methods. A modified version of Lee-Kim's plastic yield criterion, notably known as the critical relative density model, was applied to simulate the densification behavior of magnesium powders. In addition, a new approach that extracts the mechanical characteristics of both the powder and the matrix was developed. The model was implemented into the finite element method, with which powder compaction under equal channel angular pressing was simulated.

• 한국농공학회지
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• 제27권4호
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• pp.53-60
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• 1985

The plaster mixed to loam and sandy soil from 4 to 12 percent by dry soil weight, and the compaction, permeability, CBR, unconfined compressive strength and freezingthawing test were performed The results obtained are summarized as follows; 1.The coefficient of permeability reduced sharply at the plaster content of 4 percent, and in the CBR test, the swelling ratio reduced by the increment of plaster content. 2.The addition of plaster increased the unconfined compressive strength by the cementing effect, and it was found that the optimum plaster content, existed with the soil type, which showed the maximum strength 3.It was possible to enhance the unconfined compressive strength of the gypsum-lime-soil mixtures when the optimum content of plaster was mixed to the hydrated lime. 4.In case of sandy soil, the relative frost heave decreased with the mixture of plaster, however in loam soil, the relative frost heave began to increase at the plaster content of 12 percent than non-treated soil. Therefore the optimum plaster content existed for protecting frost heave by the different soil type. 5.The above summarized results make it possible to expect the effects such as improvement of soil properties, decrement of permeability, increment of unconfined compressive strength, and protection of frost heave, etc, therefore, it is considered that it is possible to it is plaster as sub-base materials of road.

• 대한기계학회논문집A
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• 제32권4호
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• pp.333-339
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• 2008

Densification behavior of copper powder was investigated to study the effect of an aluminum mold under warm pressing. The low flow stress of an aluminum mold is appropriate to apply hydrostatic stress to powder compacts during compaction under high temperature. The suggested powder metallurgy process is very useful under high temperature since copper powder compacts have higher relative density over axial stress of 100 MPa and show more homogeneity as compared with conventional warm pressing. Elastoplastic constitutive equation proposed by Shima and Oyane was implemented into a finite element program (ABAQUS) for densification behavior under warn pressing by using a metal mold. Finite element results agreed well with experimental data for densification and deformation of copper powder compacts in the mold.

• 생명과학회지
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• 제8권1호
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• pp.109-117
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• 1998

The synthesis and methylation in vivo of myleline basic protein(MBP) during the mouse brain devlopment was found to be the highest in youngest brain and declined progressively in mature brains. The relative rate of protein synthesis and methylation was a maximal ration in the youngest brain, This high ratio was wdll correlated with the higher protein methylase I (PM I) activity in younger brains. The jimpy mouse is the most severely affected dysmyelinating mutant and is characterized by failure to incorporate MBP into myelin. sheath. The MBP-specific PM I activity in 15-, 18-, and 21-days old hemizygous jimpy mice(jp/y)brains decreased by 20, 50 and 75%, respectively. Myelin fraction with different degrees of compaction were isolated from bovine brain, the most compact myelin fraction exhibited higher methylaccepting activity than the less compact dense fractions.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.827-830
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• 2008

In this study, large triaxia mpression tests of sand-gravel soils were carry out to clarify the influence of fines on shear strength characteries. Two soil specimens with/without fines that is used for construction material of dam were prepared. One was reproduced with wide range of grain size and the other was removed fines below 2mm from the one. The compaction tests proposed by our center were performed to obtain relative density of the specimens, and then each specimen was adjusted two dry density. The large triaxial compression tests were carry out under CD condition. Based on the results, the sand-gravel soils with low fines content has no effect on shear strength characteries.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.272-273
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• 2006

A new process of pulsed electric current sintering was developed. It combines compaction with activated sintering effectively and can manufacture bulky nano-crystalline materials very quickly. A nano-structured steel is obtained with high relative density and hardness by this process. The average grain size of iron matrix is 58nm and the carbide particulate size is less than 100 nm. The densification temperature of ball-milled powders is approximately $200^{\circ}C$ lower than that of blended powders. When the sintering temperature increases, the density of as-sintered specimen increases but the hardness of as-sintered specimen first increases and then decreases.

• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.24-30
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• 2020

The test results of the ITER toroidal field conductors demonstrated a decrease of the current sharing temperature (Tcs) with an increase in the number of electromagnetic cycles in general. This is associating with several factors. One of them is the superconducting Nb3Sn filaments cracking and another one is the redistribution of the relative deformation of the Nb3Sn strands under Lorentz forces. Despite these factors, some conductors have shown the absence or significantly less degradation of Tcs during electromagnetic cycling. This article considers another possible reason for a more stable conductors Tcs behavior, namely, the local compression of Nb3Sn wires in the cross section of a conductor. In this article presents the results of a quantitative analysis Nb3Sn superconducting filaments cracking of strands extracted from a conductor that has passed electromagnetic cycling and the model of a conductor compaction, as well as calculation results based on this model are presented also.