• 제목/요약/키워드: micro turning

검색결과 67건 처리시간 0.02초

윤활유의 수분혼입 및 베어링강의 표면 조도가 구름접촉 피로수명에 미치는 효과 (Effect of Water Contamination of the Lubricant and Surface Roughness of Bearing Steel on the Rolling Contact Fatigue Life)

  • 허태현;심충기;김홍석;신기훈;정성균
    • 한국안전학회지
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    • 제32권1호
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    • pp.15-20
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    • 2017
  • A large amount of research has been performed on the rolling contact fatigue(RCF) life of bearings, since it directly affects the safety and reliability of mechanical systems. It is well known that rolling contact fatigue life is influenced by several parameters including contact pressure, oil contamination by water or metal particles, and the surface conditions of bearings. However, the detailed damage mechanisms involved in rolling contact fatigue have not been clearly identified yet. In this paper the effects of water contamination of the lubricant and surface roughness of bearing steel on the rolling contact fatigue life were investigated. Two types of specimens with different surface roughness values were prepared through turning and lapping operations. They were tested under two different lubrication conditions, i.e. oil lubricant with 100% of oil and the water contaminated condition with 80% of oil and 20% of water using the rolling contact fatigue testing machine. The surface damage induced by the rolling contact fatigue was observed by using atomic force microscope(AFM). Experimental results show that the rolling contact fatigue life, $L_{10}$ was reduced by 24 to 33% depending on the lubrication condition. The reduction of fatigue life in the range of 53 to 57% was also observed at different surface roughness conditions.

Effect of missing values in detecting differentially expressed genes in a cDNA microarray experiment

  • Kim, Byung-Soo;Rha, Sun-Young
    • Bioinformatics and Biosystems
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    • 제1권1호
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    • pp.67-72
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    • 2006
  • The aim of this paper is to discuss the effect of missing values in detecting differentially expressed genes in a cDNA microarray experiment in the context of a one sample problem. We conducted a cDNA micro array experiment to detect differentially expressed genes for the metastasis of colorectal cancer based on twenty patients who underwent liver resection due to liver metastasis from colorectal cancer. Total RNAs from metastatic liver tumor and adjacent normal liver tissue from a single patient were labeled with cy5 and cy3, respectively, and competitively hybridized to a cDNA microarray with 7775 human genes. We used $M=log_2(R/G)$ for the signal evaluation, where Rand G denoted the fluorescent intensities of Cy5 and Cy3 dyes, respectively. The statistical problem comprises a one sample test of testing E(M)=0 for each gene and involves multiple tests. The twenty cDNA microarray data would comprise a matrix of dimension 7775 by 20, if there were no missing values. However, missing values occur for various reasons. For each gene, the no missing proportion (NMP) was defined to be the proportion of non-missing values out of twenty. In detecting differentially expressed (DE) genes, we used the genes whose NMP is greater than or equal to 0.4 and then sequentially increased NMP by 0.1 for investigating its effect on the detection of DE genes. For each fixed NMP, we imputed the missing values with K-nearest neighbor method (K=10) and applied the nonparametric t-test of Dudoit et al. (2002), SAM by Tusher et al. (2001) and empirical Bayes procedure by $L\ddot{o}nnstedt$ and Speed (2002) to find out the effect of missing values in the final outcome. These three procedures yielded substantially agreeable result in detecting DE genes. Of these three procedures we used SAM for exploring the acceptable NMP level. The result showed that the optimum no missing proportion (NMP) found in this data set turned out to be 80%. It is more desirable to find the optimum level of NMP for each data set by applying the method described in this note, when the plot of (NMP, Number of overlapping genes) shows a turning point.

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Development and distribution of geo-hazards triggered by the 5.12 Wenchuan Earthquake in China

  • Runqiu, Huang;Weile, Li
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2009년도 춘계 학술발표회
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    • pp.1225-1234
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    • 2009
  • As the Wenchuan Earthquake was of high magnitude and shallow seismic focus, it caused great damage and serious geo-hazards. By the field investigation and remote-sensing interpretation after the earthquake and by using means of GIS, the distribution of geo-hazards triggered by the earthquake was analyzed and the conclusions are as follows: (1) the earthquake geo-hazards showed the feature of zonal distribution along the earthquake fault zone and linear distribution along the rivers; (2) the distribution of earthquake geo-hazards had a marked hanging wall effect, for the development density of geo-hazards in the hanging wall of earthquake fault was obviously higher than that in the foot wall and the width of strong development zone in the hanging wall was about 10 km; (3) the topographical slope was a main factor which controlled the development of earthquake geo-hazards and a vast majority of geo-hazards were distributed on the slopes of 20 to 50 degrees; (4) the earthquake geo-hazards had a corresponding relationship with the elevation and micro-landform, for most hazards happened in the river valleys and canyon sections below the elevation of 1500 to 2000 m, particularly in the upper segment of canyon sections (namely, the turning point from the dale to the canyon). Thin ridge, isolated or full-face space mountains were most sensitive to the seismic wave, and had a striking amplifying effect. In these areas, collapses and landslides were most likely to develop; (5) the study also showed that different lithologies determined the types of geo-hazards, and usually, landslides occurred in soft rocks, while collapses occurred in hard rocks.

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채광시스템과 인공조명설비의 통합기술 및 성능평가연구 (Predicted Performance of the Integrated Artificial Lighting System in Relation to Daylight Levels)

  • 김곤;김정태
    • 한국태양에너지학회 논문집
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    • 제22권3호
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    • pp.47-56
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    • 2002
  • The office is an excellent candidate for implementing daylighting techniques because of the relatively high electric lighting power densities and long daytime use pattern. The quantity of light available for a space can be translated in term of the amount of energy savings through a process of a building energy simulation. To get significant energy savings in general illumination, the electric lighting system must be incorporated with a daylight - activated dimmer control. A prototype configuration of an office interior has been established and the integration between the building envelope and lighting and HVAC systems is evaluated based on computer modeling of a lighting control facility. First of all, an energy-efficient luminaire system is designed for both a totally open-plan office interior and a partitioned office. A lighting design and analysis program, Lumen-Micro 2000 predicts the optimal layout of a conventional fluorescent lighting fixture to meet the designed lighting level and calculates unit power density, which translates the demanded amount of electric lighting energy. A dimming control system integrated with the contribution of daylighting has been applied to the operating of the artificial lighting. Annual cooling load due to lighting and the projecting saving amount of cooling load due to daylighting under overcast diffuse sky are evaluated by a computer software, ENER-Win. In brief, the results from building energy simulation with measured daylight illumination levels and the performance of lighting control system indicate that daylighting can save over 70 percent of the required energy for general illumination in the perimeter zones through the year. A 25 % of electric energy for cooling may be saved by dimming and turning off the luminaires in the perimeter zones.

통합 채광시스템의 건물 냉난방 에너지 성능평가 (Building Energy Savings due to Incorporated Daylight-Glazing Systems)

  • 김정태;안현태;김곤
    • 조명전기설비학회논문지
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    • 제19권6호
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    • pp.1-8
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    • 2005
  • 건물 내에 존재하는 자연광은 조명원으로 국한되지 않고 시각적, 심리적 자극을 통한 실내 환경의 질적 향상에 이르기까지 에너지절약 및 공간의 쾌적성에 큰 영향을 미친다. 유입되는 자연광량에 비례적으로 연동되는 건물에너지는 전기조명에너지를 절감시키고 난방 기간동안 일사열의 유입에 따른 난방에너지를 절감시킨다. 여름철에는 전기조명의 소등으로 인한 조명원의 발열량이 감소됨으로써 냉방부하의 감소에 이르기까지 포괄적인 영향을 미친다. 조명개발분야의 선진국에서는 에너지 절약형 광원의 대체와 아울러 자연채광과 통합된 최적 조명제어 기술의 운용만이 건물이 가지고 있는 에너지 절약의 잠재력을 현실화시킬 수 있다고 판단하고 있다. 따라서 본 연구는 일반적인 사무소 모델 공간의 에너지 절약형 인공조명을 대상으로 자연광 유입에 따른 연동적 조명제어 기법을 적용하는 경우를 대상으로, 인공조명의 소등량에 따른 조명에너지의 절감량과 이에 수반되는 냉방에너지의 점감량 및 일사열 취즉에 따른 겨울철 난방 부하 절감량을 분석함으로써 자연채광의 건물에너지에 대한 연간 기여도를 통합 분석하였다. 특히 자연채광의 성능은 실험을 통한 측정 데이터를 이용하고 에너지 해석 프로그램을 재구성하여 실질적인 절감량을 도출하도록 시도하였다.

235 rRNA Monomethyltransferase인 tlrD의 클로닝, 이의 대장균에서 대량생산과 활성 검색 (Cloning of tlrD, 23S rRNA Monomethyltransferase Gene, Overexpression in Eschepichia coli and Its Activity)

  • 진형종
    • 미생물학회지
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    • 제43권3호
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    • pp.166-172
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    • 2007
  • ERM 단백질은 23S rRNA의 A2058에 methylation시킴으로써 macrolide-lincosamide- streptogramin B $(MLS_B)$계 항생제의 부착을 저해하여 항생제의 활성을 억제하는 내성 인자 단백질로 monomethylase와 dimethylase로 나누어진다. Dimethylase와 비교되는 monomethylase의 특성을 밝히기 위해 dimethylase (ErmSF)와 monomethylase (TlrD)를 동시에 보유한 Streptomyces fradiae에서 tlrD를 클론하고 대장균에서 최초로 대략생산을 시도하여 $37^{\circ}C$에서 세포내 전체 단백질의 55%를 차지할 정도로 대량생산된 불용성 단백질을 얻어내었다. 그러나 ErmSF와는 달리 낮은 온도에서 대량생산된 단백질이 용해성 단백질로 전환되지 않고 불용성 단백질로 남아있었다. Thioredoxin과 샤페론인 GroESL은 모두 ErmSF의 경우와 마찬가지로 용해성 단백질로의 전환에 도움을 주지 않았다. 이러한 차이점은 천재까지 전혀 밝혀지지 않은 단백질내의 구조적 특성에 의한 monomethylase와 dimethylase의 차이점을 밝힐 수 있다는 가능성을 말해주는 것으로 추정된다. 그러나 ErmSF의 경우와 동일하게 SDS-PAGE에서 검색되지 않은 미량의 발현된 용해성 단백질이 TlrD를 함유한 세포에 항생제에 대한 내성을 나타내게 하였고 이렇게 발현된 내성은 monomethylase에 의한 내성에서 기대되는 내성과 일치하였다.

지정차로제의 합리적 운영방안에 대한 연구 (Study on the improvements for Managerial Efficiency of the Designated Lane Law)

  • 이승준;이철기;이용주;김용만
    • 한국ITS학회 논문지
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    • 제15권2호
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    • pp.85-94
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    • 2016
  • 지정차로제란 차량특성에 따라 차로별 통행 가능한 차종을 지정한 제도로서, 도로이용 효율성 증대 및 교통안전을 위해 시행된 제도이다. 1999년 폐지되었지만, 2000년 대형차의 1차로 주행, 난폭운전 및 교통사고 증가의 이유로 재규정 되었다. 2010년 일부 개선되었지만, 지나친 세분화에 따른 인식률 저조와 차량회전이 빈번한 일반도로에서의 준수 어려움, 이륜차 및 화물차의 주행차로 확대 요청 등 개선 필요성이 증대된 상황이다. 이에 본 연구에서는 설문조사, 시뮬레이션 및 안전도 평가 등을 통하여 차종별 특성을 고려한 지정차로제 개선방안을 제시하였다. 차종 명시로 저속차량의 상위차로 이용과 단속의 어려움, 교통량 및 차로이용 불균형, 국제 표준과의 미 부합 등의 문제점에 대하여 설문조사를 통해 5개 대안을 제시하였다. 각 대안별 운영효과와 실현성을 검토하기 위해 미시적 시뮬레이션을 이용한 통행속도, 효율성 등을 분석하였고, 시야범위 측면 안전도 평가를 시행하여 차량 간 제원차이에 의한 시야확보 용이성을 검토하였다. 이러한 분석결과를 토대로 고속 소형 차량은 좌측, 저속 대형 차량은 우측차로로 통행하는 포괄적인 차로지정을 본 논문에서 제시하였다.