• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.65-72
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• 1997

The horizontal corrosion fatigue tester has been developed for investigating environmental strength. Using this tester, we investigated about corrosion fatigue caracteristics for A106-Gr B steel weldments in 3.5% synthetic seawater and room temperature. Considered parameter is only frequency of 1, 3 and 5Hz.. and Corrosion fatigue crack length was measured by DC potential difference method. From the results, we could find that the horizontal corrosion fatigue tester could be well applied to estimation of fatigue strength. and, In case of 5Hz., corrosion fatigue crack growth pate of A106-Gr B steel weldment was transgranular, and of 1 and 3Hz. showed that transgranular and interfranular was mixed. Also, Material constants of corrosion fatigue crack growth estimated in each frequency were C=9.33$\times$$10^{-9}$ and m=2.93 in 1Hz., C=9.77$\times$$10^{-10}$ and m=3.47 in 3Hz., C=1.02$\times$$10^{-10}$ and m=4.05 in 5Hz

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.554-559
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• 2008

Most of vehicle manufacturers have applied exhaust gas recirculation (EGR) system to the development of diesel engines in order to obtain the high thermal efficiency without $NO_X$ and Particulate Matter (PM) emitted from the engine. EGR system, which reflow a cooled exhaust gas from vehicles burning diesel as fuel to a combustion chamber of engine, has been used to solve this problem. In order to confirm the safety of the EGR system, finite element analysis was carried out. The safety of EGR system against temperature variation in the shell and tubes was evaluated through the thermal and structural analysis, and the modal analysis using ANSYS was also performed. Finally, the performance of EGR system was verified through the experiment and numerical simulation using effectiveness-NTU method. Program for the estimation of the heat exchange efficiency of the EGR system with regard to the dimpled tube shape was developed.

• Ocean and Polar Research
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• v.31 no.1
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• pp.1-9
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• 2009

When evaluating acoustic methods for measuring physical parameters in the ocean, economical and technical considerations are paramount. As an indirect method of estimating ocean dynamics, acoustic tomography has advantages over more conventional approaches. It allows the reconstruction of temperature and flow fields from the acoustic impulse time-of-flight measured along the rays propagating from the source to the receiver. However, many problems require complicated and expensive systems. To use the acoustic tomography method to best effect, developing hardware systems with sources and receivers mounted permanently on the sea bottom is crucial. Akulichev et al. presented some experimental results from shallow zones of the World Ocean that served as a motive for developing a multifunction system with acoustic hardware and software. Here we present technical features and the sea test results of the system.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.511-516
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• 2001

Recently small punch creep testing (or miniature disc bend creep test) has received much attention through European collaborative research projects. This method was considered as a substitute for the conventional creep rupture testing by which the residual creep life is measured from the specimen taken out from serviced components of high temperature plants. It would be beneficial if the material creep properties such as power law creep constants as well as the creep rupture life can be measured from the small punch creep test. In this paper a method of assessing creep constants from the small punch creep testing is proposed. Finite element analyses were performed to investigate evolution of stress and strain rate at the weakest locations of the small punch creep specimen. Elastic-plastic-secondary creep analyses were carried out. The estimation equations for creep constants by the small punch creep testing are proposed based on the finite analysis results. Small punch creep tests were also performed with 9Cr steel and the accuracy of the proposed equation was verified by the experimental results.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.774-779
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• 1998

For the speed control of motors, the position or speed sensors are necessary to obtain the position information of the rotor. Specially, SRM(Switched Reluctance Motor) needs an accurate rotor position data because both the rotor and the stator have a salient pole structure. High functional sensors like resolver or encoder are expensive and have complex connecting lines to the controller so the pure signals are apt to be mixed with noised. In the sight of SRM drives, the high temperature, heavy dust, and the EMI surroundings reduce the reliability of speed and position sensors. Therefore, the speed and position sensorless control algorithms using observer have been accepted widely. In this paper An adaptive sliding observer is described to control the SRM without speed or position sensors. The adaptive sliding observer is set on the basis of variable structure control theory. The sliding surface is constructed by current error terms and this surface guarantees the errors converge to "zero". The stability of observer is affirmed by Lyapunov stability analysis and popov's hyper stability theory.ty theory.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.2
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• pp.83-88
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• 2006

AC loss is one of the main research area in AC power application using high temperature superconductor(HTS), such as HTS transformer, HTS current limiter and HTS cable, because it is closely related to efficiency, economic estimation and design of power device. A lot of research for various arrangements of HTS tapes have been performed to increase a capacity of transport current because single HTS tape can not satisfy the demanded current capacity in HTS power application. In this paper, we studied magnetization loss by different several arrangements of BSCCO tapes such as Edge-to-Edge type, Face-to-Face type and Matrix type through numerical analysis by 2D-FEM and measurement. As a result, we got the result that the magnetization loss of Face-to-Face type arrangements was lower than those of other arrangement types under the conditions of the same stacking number. We think that the result was due to shield effect by demagnetization of adjacent HTS tapes which are located face to face.

• Smart Media Journal
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• v.9 no.3
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• pp.80-89
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• 2020

Out - of - distribution (OOD) samples are frequently encountered when deploying a classification model in plenty of real-world machine learning-based applications. Those samples are normally sampling far away from the training distribution, but many classifiers still assign them high reliability to belong to one of the training categories. In this study, we address the problem of removing OOD examples by estimating marginal density estimation using variational autoencoder (VAE). We also investigate other proper methods, such as temperature scaling, Gaussian discrimination analysis, and label smoothing. We use Chonnam National University (CNU) weeds dataset as the in - distribution dataset and CIFAR-10, CalTeach as the OOD datasets. Quantitative results show that the proposed framework can reject the OOD test samples with a suitable threshold.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.43-51
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• 1983

The fatigue failure envelopes for the prediction of the fatigue life of asphalt pavements were obtained from the results of laboratory fatigue test for asphalt mixture. The envelopes did not depend on the experimental temperature and the number of loading, and varied with the types of asphalts. In the case of dense graded asphalt concrete, the envelopes formed a single curve regardless of the penetration of the asphalt. On the other hand, the method for the fatigue life prediction was presented based on the envelopes obtained and the triple layered elastic theory developed by Burmister.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.357-357
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• 2000

In this study, we consider a multi-input multi-output styrene polymerization reactor system for which the monomer conversion and the weight average molecular weight are controlled by manipulating the jacket inlet temperature and the feed flow rate. The reactor system is identified by using a linear subspace identification method and then the output feedback model predictive controller is constructed on the basis of the identified model. Here we use the Best Linear Unbiased Estimation (BLUE) filter as a stochastic estimator instead of the Kalman filter. The BLUE filter observes the state successfully without any a priori information of initial states. In contrast to the Kalman filter, the BLUE filter eliminates the offset by observing the state of the augmented system regardless of a priori information of the initial state for an integral white noise augmented system. A BLUE filter has a finite impulse response (FIR) structure which utilizes finite measurements and inputs on the most recent time interval [i-N, i] in order to avoid long processing times.

• Journal of Sensor Science and Technology
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• v.21 no.1
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• pp.75-81
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• 2012

Optimizing the tapping time of a blast furnace is important to a stable operation and life extension. To optimize the tapping time of the blast furnace, the location of Hearth Liquid Level should be recognized. There are several ways to measure the hearth liquid level in the blast furnace, such as Electromotive Force(EMF) measurement, pressure measurement by putting in nitrogen probe and manometry with strain gauge. In this paper, it will be discussed using strain gauge among the three methods. Conventional strain gauge must be revised periodically. Since, internal pressure, temperature of internal refractory material and wind pressure have effect on the strain gauge. However, static pressure value is required to compensate. To solve these problems, this paper suggests finding relationship between Hearth Liquid Level and strain gauge output, adding digital filter in strain gauge. Using the proposed method, it was possible to estimate the hearth liquid level and determine the appropriate tapping time. Usefulness of the proposed method through simulations and experimental results are confirmed.