• 제목/요약/키워드: Base region

검색결과 1,159건 처리시간 0.031초

Ag-Cu-Zn-Cd 계 용가재를 이용한 Bronze 소결체/강의 브레이징 접합부 특성 평가 (Characteristics of Brazed Joint of Sintered Bronze/steel Using Ag-Cu-Zn Type Filler Materials)

  • 이정훈;이창희
    • Journal of Welding and Joining
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    • 제17권3호
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    • pp.79-89
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    • 1999
  • The study was carried out to examine in more detail metallurgical and mechanical properties of brazed joints of diamond cutting wheel. In this work, shank(mild steel) and sintered bronze-base tips were brazed with three different filler materials(W-40, BAgl and BAg3S). The machine used in this work was a high frequency induction brazing equipment. The joint thickness, porosities and microstructure of brazed joints with brazing variables(brazing temperature, holding time) were evaluated with OLM, SEM, EDS and XRD. Bending(torque) test was also performed to evaluate strength of brazed joints. Further wetting test was performed in a vacuum furnace in order to evaluate the wettability of filler metals on base metals9shank and tips). The brazing temperature had a strong influence on the joint strength and the optimum brazing temperature range was about $700~850^{\circ}C$ for the bronze/steel combinations. The strength of the brazed joint was found to be influenced by the three factors : degree of reaction region, porosity content, joint thickness. The reaction region was formed in the bronze-base tip adjacent to the joint. The reaction region resulted in a bad influence on the strength due to the formation of Cu5.6Sn, CuZn4, $\beta(CuZn)$ and CdAg, etc. Porosities increased as brazing variables(brazing temperature, holding time) increased, and the brazed joints with porosities of less than about 3-5% had an optimum strength for the bronze-base tip.

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Identification of a Regulatory Region within the luxR Structural Gene in a Marine Symbiotic Bacterium, Vibrio fischeri

  • Choi, Sang-Ho
    • Journal of Microbiology and Biotechnology
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    • 제4권3호
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    • pp.176-182
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    • 1994
  • The light-organ symbiont of pine cone fish, Vibrio fischeri, senses its presence in the host and responds to environmental changes by differentially expressing its symbiosis-related luminescence genes. The V. fischeri luminescence genes are activated by LuxR protein in the presence of an autoinducer. In an effort to elucidate the mechanism of regulation of luxR, a plasmid containing luxR was mutagenized in vitro with hydroxylamine and a luxR mutant plasmid was isolated by its ability to activate luminescence genes cloned in E. coli in the absence of the autoinducer. The specific base change identified by DNA sequencing was only single base transition at +78 from the transcriptional start of luxR. Based on a Western immunoblot analysis, the nucleotide change directed the synthesis of much higher level of LuxR protein without any amino acid substitutions. The results suggest that the region including the +78th base is presumably internal operator required for autorepression of luxR, and the increased cellular level of LuxR results in activation of luminescence genes by autoinducer independent fashion.

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삼결정 실리콘 태양전지의 19%변환 효율 최적요건 고찰에 관한 연구 (The study of High-efficiency method usign Tri-crystalline Silicon solar cells)

  • 이욱재;박성현;고재경;김경해;이준신
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2002년도 하계학술대회 논문집
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    • pp.318-321
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    • 2002
  • This paper presents a proper condition to achieve high conversion efficiency using PC1D simulator on sri-crystalline Si solar cells. Various efficiency influencing parameters such as rear surface recombination velocity and minority carrier diffusion length in the base region, front surface recombination velocity, junction depth and doping concentration in the Emitter layer, BSF thickness and doping concentration were investigated. Optimized cell parameters were given as rear surface recombination of 1000 cm/s, minority carrier diffusion length in the base region 200 $\mu\textrm{m}$, front surface recombination velocity 100 cm/s, sheet resistivity of emitter layer 100 Ω/$\square$, BSF thickness 5 $\mu\textrm{m}$, doping concentration 5${\times}$10$\^$19/ cm$\^$-3/. Among the investigated variables, we learn that a diffusion length of base layer acts as a key factor to achieve conversion efficiency higher than 19 %.

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Mutational Analysis of the Region between vir Box and -35 Sequence in virE Promoter of pTiA6

  • Woong Seop Sim
    • Journal of Plant Biology
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    • 제38권3호
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    • pp.259-266
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    • 1995
  • To investigate how the dyad symmetry region (DSR) and the distance between vir box and -35 sequence of the virE promoter plays a role in virE gene expression, two mutants were constructed by base substitution and insertional mutagenesis. The base substitutional mutation, a AAlongrightarrowCG substitution at positions -39 and -40 on the DSR, showed the level of $\beta$-galactosidase activity approximately 91% of the wild type virE promoter activity. Therefore, the native structure of the DSR seems to be not essential for virE expression. The insertional mutation, constructed by inserting 8 bp ClaI linker between -49 and -50, displayed the $\beta$-galactosidase activity at 12% of the native virE promoter activity. However, this striking reduction appears to be not caused by destruction of the native DSR structure, but by shifting the vir box far from putative -35 sequence.

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속도 향상을 위한 병합트랜지스터를 이용한 ISL의 설계 (Design of ISL(Intergrated Schottky Logic) for improvement speed using merged transistor)

  • 장창덕;백도현;이정석;이용재
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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    • pp.21-25
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    • 1999
  • In order to remove minority carries of the base region at changing signal in conventional bipolar logic circuit, we made transistor which is composed of NPN transistor shortened buried layer under the Base region, PNP transistor which is merged in base, epi layer and substrate. Also the Ring-Oscillator for measuring transmission time-delay per gate was designed as well. In the result, we get amplitude of logic voltage of 200mV, the minimum of transmission delay-time of 211nS, and the minimum of transmission delay-time per gate of 7.26ns in AC characteristic output of Ring-Oscillator connected Gate.

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수명시간에 따른 NPT-IGBT의 N-drift 영역에서의 과잉소수 캐리어와 전하량 분석 (Analysis of excess minority carrier and charge wish lifetimes in N-dirft region of NPT-IGBT)

  • 류세환;이용국;안형근;한득영
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 하계학술대회 논문집
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    • pp.844-847
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    • 2001
  • In this work, transient characteristics of the Non-Punch Through(NPT) Insulated Gate Bipolar Transistor(IGBT) has been studied. we has analyzed with lifetimes excess minority carrier injected into N-dirft, base region of IGBT's BJT part and accumulated charge of on-state which affected swiching characteristic. In this paper, excess minority carrier and charge distribution in active base region is expressed analytically. This analysis proposed optical trade-off between lifetimes and accumulated charge for decreasing switching losses because charge result in switching loss when device was tuned off.

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초음속 유동에서 기저유동의 Detached Eddy Simulation (Detached Eddy Simulation of Base Flow in Supersonic Mainstream)

  • 신재렬;문성영;원수희;최정열
    • 한국항공우주학회지
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    • 제37권10호
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    • pp.955-966
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    • 2009
  • 초음속 유동장 내의 축대칭 기저유동에 DES 기법을 적용하였다. 이 기법은 RANS 모드에서는 Spalart-Allmaras (S-A) 난류 모델을 사용하고, Large-eddy simulation (LES) 모드에서는 부격자 모델을 기반으로 하고 있다. LES 보다 비교적 적은 비용을 갖는 DES 기법을 사용하여 기저 유동장과 기저 압력을 정교게 예측할 수 있었다. 기저유동의 정확한 예측을 위해 경계층 두께, 운동량 두께, 표면마찰과 같은 기저 가장자리 유동 물성치를 Dutton 등의 실험과 비교하였다. DES는 하류영역에서의 전단층 말림, 큰 에디 운동, 재순환영역 내의 작은 에디 운동 같은 비정상 난류 운동의 물리적 현상을 잘 모사 하였다. 또한, 경험상수 $C_{DES}$ 1.2를 사용한 현재 결과가 일반적인 경험상수 $C_{DES}$ 0.65에 비해 실험과 잘 일치함을 보여준다.

테일러드 블랭크 레이저 용접 강판의 피로균열 전파 거동 (Fatigue Crack Propagation Behavior of Steel Plate of Laser Welded Tailored Blank)

  • 한문식;이양섭
    • 한국공작기계학회논문집
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    • 제15권3호
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    • pp.120-126
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    • 2006
  • In this paper, we investigated the characteristics of fatigue fracture on TB(Tailored Blank) weldment by comparing the fatigue crack propagation characteristics of base metal with those of TB welded sheet used for vehicle body panels. We also investigated the influence of center crack on the fatigue characteristic of laser weld sheet of same thickness. We conducted an experiment on fatigue crack propagation on the base metal specimen of 1.2mm thickness of cold-rolled metal sheet(SPCSD) and 2.0mm thickness of hot-rolled metal sheet(SAPH440) and 1.2+2.0mm TB specimen. We also made an experiment on fatigue crack propagation on 2.0+2.0mm and 1.2+1.2mm thickness TB specimen which had center crack. The characteristics of fatigue crack growth on the base metal were different from those on 1.2+2.0mm thickness TB specimen. The fatigue crack growth rate of the TB welded specimens is slower in low stress intensity factor range$({\Delta}K)$ region and faster in high ${\Delta}K$ region than that of the base metal specimens.

후방 동체 항력에 대한 Jet의 영향 (Jet Effect on Afterbody Drag)

  • 허기훈;변우식
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2000년도 추계 학술대회논문집
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    • pp.170-175
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    • 2000
  • Parametric studies are performed of the factors influencing the afterbody drag. To display the effect of differing afterbody shapes, several ogive boattails with combinations of the base area and the angle of boattail end are computed using axisymmetric Navier-Stokes equations with central differencing and a DADI scheme. And Chien's $\kappa-\epsilon$ model is employed used for computations of turbulent flows around the base region. The effects of base area, boattail angle and jet on/off are illustrated on afterbody drag at transonic speed.

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고속제트 플럼에서의 기저압력 특성 (Characteristics of the Base Pressure in High-Speed Jet Plume)

  • ;김희동
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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    • pp.193-195
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    • 2011
  • An abrupt increase of duct cross-section is frequently encountered in pressure reducing devices, valves of internal combustion engines and in gas pipelines. Supersonic flow in a rectangular duct passing an abrupt increase of cross-section is studied numerically. The behavior of base pressure of the dead-air region at sudden enlargement of the duct is clarified. This investigation concerns the determination of the base pressure, which is independent of the size of the enlarged part. Several flow patterns are identified with different enlargements according to the ratio between the downstream ambient pressure and the upstream reservoir pressure. Base pressure and the resulting shock-structure are highly depending on the size of duct enlargement. For a given duct, base pressure tends to minimum for a particular pressure ratio. In addition, the locations of secondary separation and reattachment points of the jet plume are found with respect to different duct enlargements.

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