• 한국터널지하공간학회 논문집
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• 제9권1호
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• pp.1-18
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• 2007

본 연구는 쉴드터널 공사시 사용되는 사다리꼴 세그먼트라이닝의 배열방법에 관한 것이다. 사다리꼴 세그먼트라이닝은 공장에서 기제작된 Taper를 가진 콘크리트 세그먼트를 터널내에 반입과 동시에 조립하므로써 형성되는데, 이렇게 형성된 사다리꼴 세그먼트라이닝은 회전조립시 Taper량의 계산에 의하여 단 한가지 타입으로 다양한 터널노선에 맞는 배열을 가능하게 하므로 세그먼트에 의한 터널시공시 가장 효율적인 공법이라 할 수 있다. 본 연구는 사다리꼴 세그먼트라이닝의 설계제원 및 터널 노선의 선형(직선 혹은 곡선)의 조건을 분석하여 터널선형에 맞는 배열방법을 고안하고 실제 터널내에서 작업자가 활용할 수 있는 컴퓨터 프로그램을 제작하여 자동으로 배열순서를 결정하는 원리에 대하여 설명하고자 한다.또한,가변하는 실제 터널내에서 작업자가 세그먼트라이닝의 배치상태를 측정한 값이 컴퓨터 프로그램에서 계산된 결과와 상이할 때 작업자는 측정한 데이터를 컴퓨터 프로그램에 입력하여 프로그램의 계산상태를 실제 세그먼트 조립상태로 일치시킨 후, 다음 세그먼트라이닝의 배열자료로 사용하여 연속된 작업이 되도록 하는 방법을 제공하는 것이 본 연구의 기술적 요지이다.

• 한국주조공학회지
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• 제25권1호
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• pp.40-50
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• 2005

A series of heavy section ductile cast iron ingots with the cube length of 250mm were systematically investigated as functions of casting parameters of sand casting. Abnormal graphite formation was specially observed with the variation of Si content and Bi or Sb addition. Effects of chilling during casting and adaptation of riserless system were also examined, and proved to be effective for the prevention of both shrinkage and abnormal graphite such as chunky one. The formation of chunky graphite was effectively prevented by low Si content despite the promotion of pearlite matrix structure. The ferritic matrix was encouraged to form by high Si content and chunky graphite formation was effectively suppressed by the addition of Bi and Sb. Bi addition, however, was not good enough to control the microstructure owing to the sensitive cooling rate dependent inoculation behavior and relative low ability of nodulization. Sb addition, on the other hand, was proved to be effective for the microstructural control and enhancement of various mechanical properties such as strength, elongation, and impact energy. It may be suggested that optimized casting parameters should be applied to produce heavy section ductile cast iron with reliability.

• 미생물학회지
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• 제38권4호
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• pp.299-305
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• 2002

2001년 경북지역의 설사환자로부터 분리된, Salmonella Enteritidis SY9 균주로부터 ampicillin, chloramphenicol, sulfonamide, streptomycin, tetracycline에 내성을 가지는 40 kb plasmid를 분리하였다. pCAST2 라고 명명한 이 다제내성 plasmid로부터 sulfonamide, streptomycin, tetracycline 내성유전자를 가지는 약 7 kb의 Sacl 단편을 클로닝 하였다. 이 7 kb 단편 염기서열의 내성유전자의 구조는 sulII-strA-strB-tetR-tetA의 집락으로 기존에 보고되지 않은 새로운 유전자 배열을 나타내었다. 본 연구에서는 내성유전자 집락을 검출할수 있는 primer를 제작하여 PCR 분석을 통해서 이들 구조를 탐지할 수 있는 방법을 제시하였다. 또한 PCR 분석을 통한 구조 비교로, 이 집락이 2002년 8월에 경북지역에서 산발적으로 발생한 Salmonella 균주에서도 발견됨을 확인하였다.

• 대한족부족관절학회지
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• 제10권2호
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• pp.250-254
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• 2006

Purpose: The treatment of diabetic foot ulcers with total contact cast has been reported to be associated with numerous undesirable complications. This study shows that our technique of total contact casting that incorporates high concentration silver coated foam dressing. Materials and Methods: Forty-four diabetic foot ulcers were treated with total contact cast along with high concentration silver coated foam dressing. Complication and healing rates were evaluated. Results: Eighty five percent of the ulcers healed within 6 weeks with an overall complication rate of 7%. There were only two cases (5%) of infection and no recurrent ulceration and no another site new pressure ulcer in our study. Conclusion: Total contact casting incorporates high concentration silver coated foam dressing resulted in fewer complications rate and healing rate that is comparable to other studies.

• 한국유기농업학회지
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• 제13권4호
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• pp.423-433
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• 2005

본 실험에서는 우분과 톱밥의 혼합수준을 달리하여 지렁이 먹이로 이용하였을 때, 지렁이 생육과 증식에 미치는 영향과 지렁이 분립의 생산량 및 화학적 조성을 조사하여 우분의 효율적인 Vermicomposting의 기초자료로 이용하고자 실시하였다. 그 결과를 요약하면 다음과 같다. 먹이의 탄질율은 $20.43{\sim}45.20$으로 톱밥 혼합 수준이 증가함에 따라 탄질비도 높아졌으며 실험기간 동안 지렁이의 생존율은 $97.6{\sim}100%$로 나타났다. 산자수는 톱밥을 30과 40% 혼합한 구에서 각각 899.6과 927.8 마리로 우분 100%구의 769 마리보다는 유의하게 높게 나타났다(P<0.05). 산자중은 $8.00{\sim}14.35g$으로 톱밥 혼합 수준이 높을수록 유의하게 높아져 톱밥 40% 혼합구가 가장 높았다(P<0.05). 지렁이 분립생산은 톱밥 혼합 수준이 높을수록 낮게 나타났으며 소화량은 이와는 반대로 톱밥 혼합 수준이 높을수록 유의하게 높게 나타났다.

• 열처리공학회지
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• 제16권5호
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• pp.253-259
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• 2003

In this study, to find out the reason of deterioration in surface roughness of steel and cast iron after Tufftride, it has been investigated on the relation between the surface roughness and various factors such as the evolution of compound layer, surface morphology, and surface hardness, and change of pore ratio in the compound layer during Tufftride at $580^{\circ}C$. It is found that the surface roughness was increased with the evolution of compound layer during Tufftride of steel and cast iron. The change of surface roughness after Tufftride was reduced with decreasing tho content of carbon and cementite ($Fe_3C$) in the materials. in the cast irons, the various shaped graphites that was exposed to the surface should induce the discontinuous growth of the compound layer, and this resulted in the incoherent interfaces between matrix and compound layer and the deterioration of surface roughness. In the steels, the existence of cementites in the matrix resulted in the incoherent interfaces between matrix and compound layer. It is considered that during Tufftride the surface roughness must be mainly influenced by the formation of the incoherent interface between compound layer and matrix that is affected by some factors such as the microstructure, the composition, and the hardness of the matrix.

• 대한기계학회논문집
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• 제10권6호
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• pp.807-813
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• 1986

본 연구에서는 국내에서 생산되고 있는 구상흑연주철을 이단으로 어니일링하 여 기타조직을 3가지(p$_{1}$:28.88% 페라이트, 63.5% 퍼얼라이트, p$_{2}$:49.7% 페 라이트, 42.2% 퍼얼라이트, p$_{3}$:71.26% 페라이트, 22.3% 퍼얼라이트)로 변화시켜 족삭에서 이차원절삭실험을 실시하여 기타조직에 따라 제절삭성(절삭력, 절삭비, 전단 각 및 침의 흐름속도)을 비교검토 하므로서 어니일링효과가 절삭성에 미치는 영향을 검토 연구하였다.

• 한국축산시설환경학회지
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• 제1권1호
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• pp.65-75
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• 1995

This experiment was carried out to the effects of population density and C/N ratios of feed on the growth, reproductive effciency and cast producation of the earthworm(Eisenia foetida). The population densities of 50, 100, 150, 200 and 250 individuals of the earthworm fed with different C/N ratios of 25, 35, 45 and 55 cow manures were studied in rearing box($6,400cm^3$), and at the fertility stage during a period of 60 days. The results were summarized as follows; The survial rate(SR), increasing rate(IR), reproductive efficiency(RE) and cast production of the earthworms showed highest values in C/N ratio of 25. These results may indicate that C/N ratio of 25 is a very favourable feed for the growth of the earthworms. The survial rate(SR) indicated significant positive correlation with reproductive efficiency(RE) in different C/N ratios of feeds. The survial rate(SR) showed highest values in population densities of $50{\sim}100$ worms/$6,400cm^3(64.0{\sim}128.0cm^3/worm$). On the contrary, increasing rate(IR) tended to decreased with the increased population densities. The survival rate(SR) indicated significant negative correlation with reproductive efficiency(RE) in different population densities of the earthworms. The cast production estimated were $31.6mg{\sim}67.4mg/day/worm$ grown in optimum population densities($50{\sim}100\;worms/6,400cm^3$). The earthworm casting are an excellent soil conditioning material or organic fertilizer sources with a high chemical composition and their physical properties.

• 소성∙가공
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• 제16권4호
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• pp.293-298
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• 2007

Recently, there is a need to produce a large forged part for the flight, shipping, some energies, and military industries, etc. Therefore, an open die forging technique of cast ingots is required to obtain higher quality of large size forged parts. Cogging process is one of the primary stages in many open die forging processes. In the cogging process prior to some open die forging processes, internal cavities have to be eliminated for defect-free. The present work is concerned with the elimination of the internal cavities in large ingots so as to obtain sound products. In this study, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The FEM analysis is performed to investigate the overlap defect of cast ingots during cogging stage. The measured flow stress data were used to simulate the cogging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}-3D$. The calculated results of cavity closure behavior are compared with the measured results before and after cogging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

• 한국물환경학회지
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• 제23권1호
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• pp.87-96
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• 2007

In this paper a methodology of identifying individual pipes according to the internal and external characteristics of pipe is developed, and the methodology is applied to a case study water distribution pipe break database. Using the newly defined individual pipes the hazard rates of the cast iron 6 inch pipes are modeled by implementing the proportional hazards modeling approach for consecutive pipe failures. The covariates to be considered in the modeling procedures are selected by considering the general availability of the data and the practical applicability of the modeling results. The individual cast iron 6 inch pipes are categorized into seven ordered survival time groups according to the total number of breaks recorded in a pipe to construct distinct proportional hazard model (PHM) for each survival time group (STG). The modeling results show that all of the PHMs have the hazard rate forms of the Weibull distribution. In addition, the estimated baseline survivor functions show that the survival probabilities of the STGs generally decrease as the number of break increases. It is found that STG I has an increasing hazard rate whereas the other STGs have decreasing hazard rates. Regarding the first failure the hazard ratio of spun-rigid and spun-flex cast iron pipes to pit cast iron pipes is estimated as 1.8 and 6.3, respectively. For the second or more failures the relative effects of pipe material/joint type on failure were not conclusive. The degree of land development affected pipe failure for STGs I, II, and V, and the average hazard ratio was estimated as 1.8. The effects of length on failure decreased as more breaks occur and the population in a GRID affected the hazard rate of the first pipe failure.