• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2003년도 학술발표대회 발표논문초록집
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• pp.56-56
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• 2003

Beta-catenin is very important in early development including involvement in cell adhesion, cell signaling, and developmental fate specification. Cell-cell interaction is an important process during mammalian embryonic development. In preimplantation embryos, embryonic compaction is the process of increased cellular flattening and adhesion of junctional complexes and results in a polarized distribution. Beta-catenin is associated with embryonic compaction in mammals. Here, we examined the relationship between beta-catenin expression and compaction in porcine embryos derived from in vitro fertilization. First of all, we investigated beta-catenin expression in each embryonic developmental stage and also focused on expression pattern according to full, partial and non-compaction at morula stage. We used the immunocyto-chemical method in this research. To confirm compaction affects on the embryonic development, we compared between compaction and developmental rates to the blastocyst. The result showed that compaction and non-compaction rates were 14.6% and 63.8% at 4 days after IVF, respectively The developmental rates to the blastocyst and their total cell number were 50.9% vs 36.4% and 41.4$\pm$11.5 vs 26.8$\pm$12.7 in compaction and non-compaction groups. Although no difference was detected in the ratio of ICM to total cells between two groups, total cell number of the blastocysts in compaction group was superior to that of the blastocysts in non-compaction group (P<0.05). Expression of beta-catenin appeared in the boundary of membrane surface between blastomeres in 2- and 4-cell stage, and observed irregular pattern from 8-cell to blastocyst stage. We also investigated beta-catenin expression pattern according to the degree of compaction in the 3 groups; full, partial (>50%) and non-compaction. The expression signal in fully compacted embryos was stronger than those of partial and non-compacted embryos. Especially, beta-catenin expression appeared various patterns in morula stage suggesting the aberrant distribution of beta-catenin is affected by compaction patterns. Our results suggest that abnormal beta-catenin expression was affected by embryo quality and further development in porcine embryos in vitro.

• 농업과학연구
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• 제10권2호
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• pp.292-309
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• 1983

성토(盛土)의 현장(現場)다짐에서 토질(土質)의 종류(種類), 층(層)의 두께 및 전압회수(轉壓回數)를 변화(變化)시키면서 진동(振動)과 무진동(無振動)의 전압기계(轉壓機械)로 다진 효과(效果)를 비교(比較)하기 위(爲)하여 들밀도 시험(試驗) 및 현장(現場)C.B.R.시험(試驗)을 하여 다음과 같은 결론(結論)을 얻었다. 1. 전압회수(轉壓回數)가 적을 때는 진동(振動)다짐이 무진동(無振動) 다짐 보다 다짐 효과(效果)가 크게 나타났으며 전압회수(轉壓回數)가 커지면 진동(振動)과 무진동(無振動) 다짐의 다짐률의 차(差)가 작아지는 경향(傾向)을 나타냈다. 2. 현재(現在) 사용(使用)하고 있는 대형화(大型化)된 전압장비(轉壓裝備)로 3~5회(回) 전압(轉壓)하면 A-1다짐의 기준에 도달(到達)하므로 앞으로는 대형화(大型化)된 장비(裝備)에 대비(對備)하기 위(爲)하여 D-2다짐을 기준으로 함이 바람직 하다고 생각한다. 3. 건조밀도(乾操密度)가 증가(增加)함에 따라 C. B. R. 값이 증가(增加)되나 진동(振動)다짐의 경우가 무진동(無振動)다짐에 비(比)하여 C. B. R. 값의 증가율(增加率)이 크게 나타났다. 4. 전압회수(轉壓回數)가 증가(增加)함에 따라 C. B. R. 값의 증가(增加)현상은 완만(緩晩)하게 나타나고 C. B. R 값은 진동(振動)다짐에서 무진동(無振動)다짐보다 약 20%정도 더 큰 값을 나타냈다. 5. C-5 시료(試料)에서는 다짐두께가 증가(增加)할수록 다짐률이 감소(減少)하여 다짐두께가 20~30cm로 변(變)할 때 다짐률은 완만(緩慢)하게 감소(減少)되었으나 30~40cm로 변(變)할 때는 다짐률이 급격(急擊)히 떨어졌으므로 전압층(轉壓層)의 두께는 30cm 이하(以下)로 함이 바람직하다고 생각한다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.30-31
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• 2006

In a multi-action tooling system, which is usually used for the powder compaction process to fabricate the complex multilevel parts, crack formation is crucially detrimental and should be avoided. Among various process factors, tool shape is an important factor to prevent the crack formation during powder compaction process. In this work, the effects of different tool shapes were investigated through the experimental oberservation of pore distribution in real products and the finite element analysis of residual stresses. The results were interpreted based on non-uniform powder density in the compacted parts.

• Progress in Superconductivity
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• 제3권2호
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• pp.218-223
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• 2002

The void volume fraction of cables is one of the effective parameters to characterize the joints of superconducting magnet. Because electrical resistance and cooling stability in the CICC (Cable-in-Conduit Conductors) joint are governed by the void volume fraction, it should be controlled constantly in the termination of cable. The change of cross-section shape in the cable was fecund during the unidirectional compaction of terminal sleeve. The non-uniform thickness of the sleeve after compaction is expected because the loading is not taxi-symmetric, and the plastic flow is also not axi-symmetric. The CICC was compacted from 45% void volume fraction to 15% by using two-piece compaction jig, which could be pressed mini-directionally. Commercial code, ABAQUS, was used to analyze the plastic flow in the sleeve during the unidirectional compaction. The increment of radius of curvature of compaction jig could minimize the change of the deformed shape of cables. The calculated results were agreed with the experimental observations.

• 한국분말재료학회지
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• 제28권1호
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• pp.1-6
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• 2021

Accurate and effective powder compaction analyses are performed for brittle materials such as graphite, utilized as a solid lubricant, by using the discrete element method (DEM). The reliability of the DEM analysis is confirmed by comparing the results of graphite powder compaction analyses using the DEM particle bonding contact model and particle non-bonding contact model with those from the powder compaction experiment under the same conditions. To improve the characteristics, the parameters influencing the compaction properties of the metal-graphite mixtures are explored. The compressibility increases as the size distribution of the graphite powder increases, where the shape of the graphite particles is uniform. The improved compaction characteristics of the metal-graphite (bonding model) mixtures are further verified by the stress transmission and compressive force distribution between the top and bottom punches. It is confirmed that the application of graphite (bonding model) powders resulted in improved stress transmission and compressive force distribution of 24% and 85%, respectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.385-390
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• 2000

In this study, the Non-Destructive Testing Equipment was introduced for the compaction control and the evaluation of pavements properties and the developing process was showed. Falling Weight Deflectometer(FWD) is a system for performing non-destructive testing of pavement and the other foundation structures. The system develops forces from the acceleration caused by the arrest of a falling weight and these forces are transmitted onto the surface of a structure causing it to deflect much as it would due to the weight of a passing wheel load. The structure will bend downward and exhibit a deflection basin. FWD uses a set of velocity sensors to determine the amplitude and shape of the deflection basin. The deflection response, when related to the applied loading, can provide information about the strength and condition of the various elements of the test structure. In this study, a computer program was developed that can be used to evaluate pavement and foundation structures from the data produced by FWD. The Falling Weight Deflectometer, non-destructive testing equipment, is increasing used at the whole world.

• 한국세라믹학회지
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• 제43권12호
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• pp.859-864
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• 2006

For the pressure compaction process of the ceramic powder, the green density is very different with both the ceramic body shape and the processing conditions. The density difference cause non-uniform shrinkages and deformations, and make cracks in the sintered ceramics. In this paper, Material properties of the alumina powder mixed with binder and the friction coefficient between the powder and the tool set were determined through the simple compaction experiments: Also the powder flow characteristics were simulated and the green density was analyzed during the powder compaction process with Finite Element Method (FEM). The results show that the density distributions of the green body were improved at the optimized processing condition and both the possibility of the farming crack generation and rho deformation of the sintered Alumina body were reduced.

• 한국지반공학회논문집
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• 제21권2호
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• pp.67-84
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• 2005

본 연구는 포화된 연약 점성토에 대한 보강효과를 분석하기 위하여 롤러 다짐장비를 사용하여 수행하였다. 시료는 12시간 수침으로 포화 상태를 만들었으며, 철재 롤러로 평면변형을 상태에서 5cm 층 두께로 4층의 다짐을 실시하였다. 보강효과를 분석하기 위하여 무보강 조건 및 부직포와 직포로 구성된 복합보강재를 사용한 보강조건으로 다짐 공시체를 제작하였다. 복합보강재의 배수효과와 인장 보강효과로 고함수비 점성토의 지지력을 증가시켜, 보강토에 대하여 큰 다짐하중을 가할 수 있게 되어 보다 큰 밀도를 효과적으로 얻을 수 있다. 또한 다짐 작업시 보강재에 의해 연직재하 하중에 대한 전단저항 반력의 감소에 의해 다짐효율을 증가시킨다. 공시체 저면에서의 최대 연직응력은 다짐두께가증가 할수록 감소하게 된다. 한편 보강재는 롤러의 연직하부의 지반강성을 증가시켜 응력집중현상이 발생한다. 이로인하여 공시체 저면에서 보다 높은 연직응력 수준을 유지하며 보다 효과적인 다짐 특성을 제공하게 된다. 시험결과로부터 연약점성토의 효과적인 다짐을 위해서는 보강재가 필수적으로 요구된다고 할 수 있다.

• 한국분말재료학회지
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• 제11권5호
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• pp.399-411
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• 2004

Crack generation during die compaction and distortion during sintering have been critical problems for the conventional pressing and sintering process. Until now, trial and error approach with engineers' industrial experiences has been only solution to protect the crack generation and distortion. However, with complexity in shape and process it is very difficult to design process conditions without CAE analysis. We developed the exclusive CAE software (PMsolver/Compaction) for die compaction process. The accuracy of PMsolver is verified by comparing the finite element simulation results with experimental results. The simplified procedures to find material properties are proposed and verified with iron based powder and tungsten carbide powder. Based on the accurate simulation result by PMsolver, the optimal process conditions are designed to get uniform density distribution in a powder compact after die compaction process by using a derivative based optimization scheme. In addition, the effect of non-uniform density distribution in a powder compact on distortion during sintering is shown in case of the fabrication of tungsten carbide insert.

• 지질공학
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• 제31권3호
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• pp.283-293
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• 2021

고해상 드론 기반의 지형 정보와 중력장 데이터를 이용하여 다짐지반의 모양과 균질성을 분석하였다. 지형과 수문 모형에서 계산된 지형요소 중 곡률은 다짐과정에서 발생한 지형의 변화를 효과적으로 보여 주었으며 이를 통해 불균질 다짐 영역을 확인할 수 있다. 지형 정보의 적정 해상도는 10 cm 정도였다. 성토지반의 공간적인 밀도변화를 분석하기 위해 중력장 해석을 수행하였으며 완전 부게이상의 변화로부터 불균질 다짐 영역과 지하 밀도구조 모델링을 통해 다짐도 차이에 의한 불균질 영역을 파악하였다. 연구결과로부터 지형요소와 중력장 해석법은 다짐된 지반의 균질성을 평가법이 될 수 있을 것으로 판단된다.