• ETRI Journal
• /
• 제39권4호
• /
• pp.605-613
• /
• 2017

Simulated fault injection (SFI) is widely used to assess the effectiveness of fault tolerance mechanisms in safety-critical embedded systems (SCESs) because of its advantages such as controllability and observability. However, the long test time of SFI due to the large number of test cases and the complex simulation models of modern SCESs has been identified as a limiting factor. We present a method that can accelerate an SFI tool using a checkpoint forwarding (CF) technique. To evaluate the performance of CF-based SFI (CF-SFI), we have developed a CF mechanism using Verilog fault-injection tools and two systems under test (SUT): a single-core-based co-simulation model and a triple modular redundant co-simulation model. Both systems use the Verilog simulation model of the OpenRISC 1200 processor and can execute the embedded benchmarks from MiBench. We investigate the effectiveness of the CF mechanism and evaluate the two SUTs by measuring the test time as well as the failure rates. Compared to the SFI with no CF mechanism, the proposed CF-SFI approach reduces the test time of the two SUTs by 29%-45%.

• 대한기계학회논문집A
• /
• 제28권6호
• /
• pp.693-700
• /
• 2004

The probabilistic fracture mechanics(PFM) is a useful analytical tool to assess the integrity of reactor pressure vessel(RPV) at the event of pressurized thermal shock(PTS). In PFM, the probabilities of flaw initiation and propagation are estimated by comparing the applied stress intensity factor with the fracture toughness calculated by the simulation of various stochastic variables. It is known that the results of PFM analyses are dependent on the choice of the stochastic parameters and assumptions. Of the various variables and assumptions, we investigated the effects of the RT$_{NDT}$ shift equations, fracture toughness curves, and flaw distributions on the PFM results for the three PTS transients. The results showed that the combined effects of the RT$_{NDT}$ shift equations and fracture toughness curves are complicated and dependent on the characteristics of the transients, the chemistry of the materials, the fast neutron fluence, and so on.

• 대한기계학회논문집A
• /
• 제28권6호
• /
• pp.739-746
• /
• 2004

The plastic deformation behavior of an aluminum alloy containing a particle and porosities was investigated at room temperature during equal channel angular pressing (ECAP). Finite element analysis by using ABAQUS shows that ECAP is a useful tool for eliminating residual porosity in the specimen, and more effective under friction condition. The simulation, however, shows considerably low density distributions for matrix near a particle at which many defects may occur during severe deformation. Finite element results of effective strains and deformed shapes for matrix with a particle were compared with theoretical calculations under simple shear stress. Also, based on the distribution of the maximum principal stress in the specimen, Weibull fracture probability was obtained for particle sizes and particle-coating layer materials. The probability was useful to predict the trend of more susceptible failure of a brittle coating layer than a particle without an interphase in metal matrix composites.

• Tuberculosis and Respiratory Diseases
• /
• 제77권4호
• /
• pp.161-166
• /
• 2014

Since tuberculosis (TB) remains a major global health concern and the incidence of multi-drug resistant (MDR)-TB is increasing globally, new modalities for the detection of TB and drug resistant TB are needed to improve TB control. The Xpert MTB/RIF test can be a valuable new tool for early detection of TB and rifampicin resistance, with a high sensitivity and specificity. Late-generation fluoroquinolones, levofloxacin, and moxifloxacin, which are the principal drugs for the treatment of MDR-TB, show equally high efficacy and safety. Systemic steroids may reduce the overall TB mortality attributable to all forms of TB across all organ systems, although inhaled corticosteroids can increase the risk of TB development. Although fixed dose combinations were expected to reduce the risk of drug resistance and increase drug compliance, a recent meta-analysis found that they might actually increase the risk of relapse and treatment failure. Regarding treatment duration, patients with cavitation and culture positivity at 2 months of TB treatment may require more than 6 months of standard treatment. New anti-TB drugs, such as linezolid, bedaquiline, and delamanid, could improve the outcomes in drug-resistant TB. Nontuberculous mycobacterial lung disease has typical clinical and immunological phenotypes. Mycobacterial genotyping may predict disease progression, and whole genome sequencing may reveal the transmission of Mycobacterium abscessus. In refractory Mycobacterium avium complex lung disease, a moxifloxacin-containing regimen was expected to improve the treatment outcome.

• Journal of Mechanical Science and Technology
• /
• 제18권9호
• /
• pp.1537-1548
• /
• 2004

This paper presents a novel diagnostic technique for monitoring the system conditions and detecting failure modes and precursors based on wavelet-packet analysis of external noise/vibration measurements. The capability is based on extracting relevant features of noise/vibration data that best discriminate systems with different noise/vibration signatures by analyzing external measurements of noise/vibration in the time-frequency domain. By virtue of their localized nature both in time and frequency, the identified features help to reveal faults at the level of components in a mechanical system in addition to the existence of certain faults. A prima-facie case is made via application of the proposed approach to fault detection in scroll and rotary compressors, although the methods and algorithms are very general in nature. The proposed technique has successfully identified the existence of specific faults in the scroll and rotary compressors. In addition, its capability of tracking the severity of specific faults in the rotary compressors indicates that the technique has a potential to be used as a prognostic tool.

• 한국공작기계학회논문집
• /
• 제14권2호
• /
• pp.96-103
• /
• 2005

The early detection of the bearing defects in rotating machinery is very important since the critical failure of bearing causes a machinery shutdown. However it is not easy to detect the vibration signal caused by the initial defects of bearing because of the high level of random noise. A signal processing technique, called the adaptive line enhancer(ALE) as one of adaptive filter, is used in this study. This technique is to eliminate random noise with little a prior knowledge of the noise and signal characteristics. Also we propose the optimal methods fir selecting the three main ALE parameters such as correlation length filter order and adaptation constant. Vibration signals f3r three abnormal bearings, including inner and outer raceways and ball defects, were acquired by Anderon(angular derivative of radius on) meter. The experimental results showed that ALE is very useful f3r detecting the bearing defective signals masked by random noise.

• 비파괴검사학회지
• /
• 제27권3호
• /
• pp.246-254
• /
• 2007

The scanning laser source (SLS) technique is a promising new laser ultrasonic tool for the detection of small surface-breaking defects. The SLS approach is based on monitoring the changes in laser-generated ultrasound as a laser source is scanned over a defect. Changes in amplitude and frequency content are observed for ultrasound generated by the laser over uniform and defective areas. The SLS technique uses a point or a short line-focused high-power laser beam which is swept across the test specimen surface and passes over surface-breaking or subsurface flaws. The ultrasonic signal that arrives at the Rayleigh wave speed is monitored as the SLS is scanned. It is found that the amplitude and frequency of the measured ultrasonic signal have specific variations when the laser source approaches, passes over and moves behind the defect. In this paper, the setup for SLS experiments with full B-scan capability is described and SLS signatures from small surface-breaking and subsurface flaws are discussed using a point or short line focused laser source.

• 소성∙가공
• /
• 제20권3호
• /
• pp.214-221
• /
• 2011

In recent years, automotive seat components have been manufactured by the fine blanking process, allowing an improvement of dimensional accuracy at sheared surface in series production. However, the rollover has increased and die failures have occurred more frequently when manufacturing gears by fine blanking. Consequently, important goals for manufacturing seat recliner parts with gears have been to decrease the rollover as well as to improve the tool life. In this study, the half blanking and shaving processes were introduced to improve aforementioned problems for the lower tooth, the main component of a seat recliner. For this purpose, the half blanking process was optimized using the finite element (FE) analysis and design of experiment (DOE). The optimized conditions resulting from this study were an offset of 0.2 mm, a clearance of 0.1 mm and a penetration depth of 4.5 mm. Fine blanking experiment conducted under the optimal condition resulted in a rollover depth decrease from 1.9 to 1.3 mm, and no die failure occurrence.

• The Korean Journal of Pain
• /
• 제12권2호
• /
• pp.268-271
• /
• 1999

Intrathecal phenol-glycerin block is a potent tool in stepwise approach to intractable perineal pain. At outpatient clinic, intrathecal phenol-glycerin block have been frequently used to control the cancer pain, as this procedure does not require special equipment. However, undesirable effects may occur with any given intrathecal injection. Although most side effects do not last long, they deserve well to prevent. Recently, we have been controlled the perineal and perianal cancer pain with intrathecal phenol-glycerin block without any specific complications. However, one patient we managed experienced that one patient, with this procedure for chronic non-malignant perineal pain control experience gait disturbance and one-week of voiding and defication difficulties. This research reports these practices, including the review of literature.

• Ocean and Polar Research
• /
• 제22권2호
• /
• pp.57-67
• /
• 2000

Time-selective self-triggering water sampler, AUTTLE developed by Jin et al. (1999) has been improved in order to prevent pre-deposition of suspended sediments (SS) before sampling. By using two solenoids, the improved sampler is able to be moored or deployed with inclination. Its position is changed to horizontal position by activating the first solenoid, and then the endcaps of the sampling bottle are closed by the second solenoid that is driven three times to minimize possible failure of sampling. An external control unit for setting sampling time has been also constructed. Additionally, the electric circuit housing of the sampler has been modified to be detached from the sampling bottle when operating manually. Its performance has been confirmed through flume tests and a field experiment. It will serve as a valuable tool in the various fields of oceanography and environmental engineering, especially where seawater sampling synchronized at several sites and/or the information in storm period is important.