• Title/Summary/Keyword: defect engineering

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The Weldability of $6mm^t$ Primer-coated Steel for Shipbuilding Using $CO_2$ Laser (II) - Dynamic Behavior of Laser Welding Phenomenon and Composition of Porosity and Vaporized-particle - ($6mm^t$조선용 프라이머 코팅강판의 $CO_2$레이저 용접성 (II) - 레이저 용접현상의 동적거동과 기공 및 증발입자의 조성 -)

  • Kim, Jong-Do;Park, Hyun-Joon
    • Journal of Welding and Joining
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    • v.24 no.2
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    • pp.71-78
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    • 2006
  • It has been reported that good quality weld beads are not easily obtained during the $CO_2$ CW laser welding of primer coated plate. However, by introducing a small gap clearance in the lap position, the zinc vapor can escape through it and sound weld beads can be acquired. Therefore, this study examines for keyhole behavior by observing the laser-induced plasma and investigates the relation between keyhole behavior and formation of weld defect. Laser-induced plasma has accompanied with the vaporizing pressure of zinc ejecting from keyhole to surface of primer coated plate. This dynamic behavior of plasma was very unstable and this instability was closely related to the unstable motion of keyhole during laser welding. As a result of observing the composition of porosity, much of Zn element was found from inner surface of porosity. But Zn was not found from the dimple structure fractured at the weld metal. By analyzing of vaporizing element in laser welding, a component ratio of Zn was decreased by introducing a small gap clearance. Therefore we can prove that the major cause of porosity is the vaporization of primer in lap position. Mechanism of porosity-formation is that the primer vaporized from the lap position accelerates dynamic behavior of the key hole and the bubble separated from the key hole is trapped in the solidification boundary and romaines as porosity.

The Comparative Study for Software Reliability Model Based on Finite and Infinite Failure Property using Rayleigh Distribution (레일리분포를 이용한 유한고장과 무한고장 소프트웨어 신뢰성 모형에 대한 비교연구)

  • Kim, Kyung-Soo;Kim, Hee-Cheul
    • Journal of Digital Convergence
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    • v.12 no.12
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    • pp.277-284
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    • 2014
  • The NHPP software reliability models for failure analysis can have, in the literature, exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, finite failure NHPP models that assuming the expected value of the defect and infinite failures NHPP models that repairing software failure point in time reflects the situation, were presented for comparing property. Commonly used in the field of software reliability based on Rayleigh distribution software reliability model finite failures and infinite failures were presented for comparison problem. As a result, infinite fault model is effectively finite fault models, respectively. The parameters estimation using maximum likelihood estimation was conducted. In this research, can be able to help software developers for considering software failure property some extent.

Novel analysis model for implant osseointegration using ectopic bone formation via the recombinant human bone morphogenetic protein-2/macroporous biphasic calcium phosphate block system in rats: a proof-of-concept study

  • Park, Jung-Chul;Lee, Jong-Bin;Daculsi, Guy;Oh, Sang-Yeop;Cho, Kyoo-Sung;Im, Gun-Il;Kim, Byung-Soo;Kim, Chang-Sung
    • Journal of Periodontal and Implant Science
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    • v.42 no.4
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    • pp.136-143
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    • 2012
  • Purpose: The osseointegration around titanium mini-implants installed in macroporous biphasic calcium phosphate (MBCP) blocks was evaluated after incubation with recombinant human bone morphogenetic protein-2 (rhBMP-2) in an ectopic subcutaneous rat model. Methods: Mini-implants (${\varphi}1.8{\times}12$ mm) were installed in MBCP blocks (bMBCPs, $4{\times}5{\times}15$ mm) loaded with rhBMP-2 at 0.1 mg/mL, and then implanted for 8 weeks into subcutaneous pockets of male Sprague-Dawley rats (n=10). A histomorphometric analysis was performed, and the bone-to-implant contact (BIC) and bone density were evaluated. Results: Significant osteoinductive activity was induced in the rhBMP-2/bMBCP group. The percentage of BIC was $41.23{\pm}4.13%$ (mean${\pm}$standard deviation), while bone density was $33.47{\pm}5.73%$. In contrast, no bone formation was observed in the bMBCP only group. Conclusions: This model represents a more standardized tool for analyzing osseointegration and bone healing along the implant surface and in bMBCPs that excludes various healing factors derived from selected animals and defect models.

Analysis of rutile single crystals grown by skull melting method (Skull melting법에 의해 성장된 rutile 단결정 분석)

  • Seok, Jeong-Won;Choi, Jong-Koen
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.16 no.5
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    • pp.181-188
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    • 2006
  • Rutile single crystals grown by skull melting method were cut parallel and perpendicular to growth axis, and both sides of the cut wafers (${\phi}5.5mmx1.0mm$) were then polished to be mirror surfaces. The black wafers were changed into pale yellow color by annealing in air at 1200 and $1300^{\circ}C$ for $3{\sim}15\;and\;10{\sim}50$ hours, respectively. After annealing, structural and optical properties were examined by specific gravity (S.G), SEM-electron backscattered pattern (SEM-EBSP), X-ray diffraction (XRD), FT-IR transmittance spectra, laser Raman spectroscopy (LRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). These results are analyzed increase of weight in air, decrease of weight in water and specific gravity, shown secondary phase of needle shape, diffusion of oxygen ion and increase of $Ti^{3+}$. From the above results, we suggest that the skull melting method grown rutile single crystals contain defect centers such as $O_v,\;Ti^{3+},\;O_v-Ti^{3+}$ interstitials and $F^+-H^+$.

An Accuracy Improvement Method for the Analysis of Process Variation Effect on CNTFET-based Circuit Performance (CNTFET 기반 회로 성능의 공정 편차 영향 분석을 위한 정확도 향상 방법)

  • Cho, Geunho
    • Journal of IKEEE
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    • v.22 no.2
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    • pp.420-426
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    • 2018
  • In the near future, CNTFET(Carbon NanoTube Field Effect Transistor) is considered as one of the most promising candidate for the replacement of modern silicon-based transistors by utilizing the ballistic or near-ballistic transport capability of CNT(Carbon NanoTube). For the large-scale fabrication of high performance CNTFET, semiconducting CNTs have to be well-aligned with a fixed pitch and high densities in the each CNTFET. However, due to the immaturity of the CNTFET fabrication process, CNTs can be unevenly positioned in a CNTFET and existing HSPICE library file cannot support the circuit level evaluation of performance variation caused by the unevenly positioned CNTs. To evaluate the performance variation, linear programming methodology was suggested previously, but the errors can be made during the calculation of the current and the gate capacitance of a CNTFET. In this paper, the reasons causing errors will be discussed in detail and the new methodology to reduce the errors will be also suggested. Simulation results shows that the errors can be reduced from 7.096% to 3.15%.

Strength Estimation of Die Cast Beams Considering Equivalent Porous Defects (다이캐스팅 보의 등가 기공결함을 고려한 강도평가)

  • Park, Moon Shik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.5
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    • pp.337-343
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    • 2017
  • As a shop practice, a strength estimation method for die cast parts is suggested, in which various defects such as pores can be allowed. The equivalent porosity is evaluated by combining the stiffness data from a simple elastic test at the part level during the shop practice and the theoretical stiffness data, which are defect free. A porosity equation is derived from Eshelby's inclusion theory. Then, using the Mori-Tanaka method, the porosity value is used to draw a stress-strain curve for the porous material. In this paper, the Hollomon equation is used to capture the strain hardening effect. This stress-strain curve can be used to estimate the strength of a die cast part with porous defects. An elastoplastic theoretical solution is derived for the three-point bending of a die cast beam by using the plastic hinge method as a reference solution for a part with porous defects.

A Study on the Detection of Interfacial Defect to Boundary Surface in Semiconductor Package by Ultrasonic Signal Processing (초음파 신호처리에 의한 반도체 패키지의 접합경계면 결함 검출에 관한 연구)

  • Kim, Jae-Yeol;Hong, Won;Han, Jae-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.5
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    • pp.369-377
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    • 1999
  • Recently, it is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research. considering a thin film below the limit of ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness. Accordingly, for the detection of delamination between the junction condition of boundary microdefect of thin film sandwiched between three substances the results from digital image processing.

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Nonstoichiometry of the Yttrium Oxide and the Holmium Oxide (산화이트륨 및 산화홀뮴의 비화학양론)

  • Chang, Soon-Ho;Yo, Chul-Hyun;Choi, Jae-Shi;Pyun, Mu-Sil
    • Journal of the Korean Chemical Society
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    • v.28 no.4
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    • pp.231-237
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    • 1984
  • The x-values in the nonstoichiometric chemical formulas $YO_{1.5+x}\;and\;HoO_{1.5+x}$, have been measured in the temperature range from 700$^{\circ}$C to 1000$^{\circ}$C under oxygen pressures from $2{\times}l0^{-1}\;to\;1{\times}10^{-6}$ atm by gravimetric method. The observed x-values increase with increasing temperature and oxygen pressure. The enthalpies of formation of excess oxygen in yttrium oxide and holmium oxide decrease with decreasing oxygen pressure and are all positive values representing an endothermic process. The 1/n values calculated from the slopes of the plots of log x vs. log $P_{O2}$ increase with temperature and are positive values which means the higher oxygen pressure dependence at higher temperature. We have examined the nonstoichiometric defect and conduction mechanism from x-values and thermodynamic data.

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The Wireless Controller using PCB mounted PIC MICOM Control Method for Tactical Training (PIC MICOM 전술훈련용 무선 센서 컨트롤러)

  • Kim, Sam-Taek
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.12 no.4
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    • pp.51-56
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    • 2012
  • Nowadays, For that reason, the tactical training system that were applied to recruit training center and police training, a real-life survivor game place is a drill using conventional training methods that there is no special training system at open terrain and field, there is no training accomplishment in conformity with battlefield situation portrayal. Therefore, this paper developed the tactical training evaluation system and real-time monitoring system that is compensated the defect and controlled sensing, interlock with PC as wireless a way of GUI using PCB mounted MICOM. This system evaluate drill that regulate sensor control module, tactical training system remotely according to what they should do, is installed to fit the occasion as to be reflected or transmission choosingly and is a 24V H/W drive module.

Study on Wear of Journal Bearings during Start-up and Coast-down Cycles of a Motoring Engine - II. Analysis Results (모터링 엔진의 시동 사이클 및 시동 정지 사이클에서 저어널베어링의 마모 연구 - II. 해석 결과)

  • Chun, Sang Myung
    • Tribology and Lubricants
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    • v.31 no.3
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    • pp.125-140
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    • 2015
  • In this paper, we present the results of the wear analysis of journal bearings on a stripped-down single-cylinder engine during start-up and coast-down by motoring. We calculate journal bearing wear by using a modified specific wear rate considering the fractional film defect coefficient and load-sharing ratio for the asperity portion of a mixed elastohydrodynamic lubrication (EHL) regime coupled with previously presented graphical data of experimental lifetime linear wear in radial journal bearings. Based on the calculated wear depth, we obtain a new oil film thickness for every crank angle. By examination of the oil film thickness, we determine whether the oil film thickness at the wear scar region is in a mixed lubrication regime by comparing dimensionless oil film thickness, h/σ, to 3.0 at every crank angle. We present the lift-off speed and the crank angles involved with the wear calculation for bearings #1 and #2. The dimensionless oil film thickness, h/σ, illustrates whether the lubrication region between the two surfaces is still within the bounds of the mixed lubrication regime after scarring of the surface by wear. In addition, we present in tables the asperity contact pressure, the real minimum film thickness at the wear scar region, the modified specific wear rate, and the wear angle, α, for bearings #1 & #2. To show the real shape of the oil film at wear scar region, we depict the actual oil film thickness in graphs. We also tabulated the ranges of bearing angles related with wear scar. We present the wear volume for bearings #1 and #2 after one turn-on and turn-off of the engine ignition switch for five kinds of equivalent surface roughness. We show that the accumulated wear volume after a single turn-on and turn-off of an ignition switch normally increases with increasing surface roughness, with a few exceptions.