• Advances in concrete construction
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• v.4 no.2
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• pp.89-105
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• 2016

The post - fire investigation is conducted on a fire-affected reinforced concrete shear wall building to ascertain the level of its strength degradation due to the fire incident. Fire incident took place in a three-storey building made of reinforced concrete shear wall and roof with operating floors made of steel beams and chequered plates. The usage of the building is to handle explosives. Elevated temperature during the fire is estimated to be $350^{\circ}C$ based on visual inspection. Destructive (core extraction) and non-destructive (rebound hammer and ultrasonic pulse velocity) tests are conducted to evaluate the concrete strength. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) are used for analyzing micro structural changes of the concrete due to fire. Tests are conducted for concrete walls and roof slab on both burnt and unburnt locations. The analysis of test results reveals no significant degradation of the building after the fire which signifies that the structure can be used with full expectancy of performance for the remaining service life. This document can be used as a reference for future forensic investigations of similar fire affected concrete structures.

• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1144-1153
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• 2002

A hybrid performance prediction method is proposed in the present study. A channel diffuser is divided into four subregions: vaneless space, semi-vaneless space, channel, and channel exit region. One-dimensional compressible core flow and boundary layer calculation of each region with an incidence loss model and empirical correlation of residuary pressure recovery coefficient of a channel predict the performance of diffusers. Three channel diffusers are designed and tested for validating the developed prediction method. The pressure distributions from an impeller exit to the channel diffuser exit are measured and discussed for various operating conditions from choke to nearly surge conditions. The strong non-uniform pressure distribution which is caused by impeller-diffuser interaction is obtained over the vaneless and semi-vaneless spaces. The predicted performance shows good agreement with the measured performance of diffusers at a design condition as well as at off-design conditions.

• Journal of Korean Society for Quality Management
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• v.25 no.3
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• pp.96-107
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• 1997

The recent stream to reliability prediction is that it is totally inclusive in depth to consider even the operating and environmental condition at the level of finished goods as well as component itselves. In this study, firstly we present the reliability prediction methods by entire failure rate model which failure rate at the system level is added to the failure rate model at the component level. Secondly we build up the improved bases of reliability demonstration through a, pp.ication of Kaplan-Meier, Cumulative hazard, Johnson's methods as non-parametric and Maximum Likelihood Estimator under exponential & Weibull distribution as parametric. And also present the methods of curve fitting to piecewise failure rate under Weibull distribution, PRST (Probability Ratio Sequential Test), curve fitting to S-shaped reliability growth curve, computer programs of each methods. Lastly we show the practical for determination of optimal burn-in time as a method of reliability enhancement, and also verify the practical usefulness of the above study through the a, pp.ication of failure and test data during 1 year.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.9
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• pp.33-43
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• 2011

Since the fuzzy neural network(FNN) is universal approximators, the development of FNN control systems have also grown rapidly to deal with non-linearities and uncertainties. However, the major drawback of the existing FNNs is that their processor is limited to static problems due to their feedforward network structure. This paper proposes the recurrent FNN(RFNN) for high performance and robust control of SynRM. RFNN is applied to speed controller for SynRM drive and model reference adaptive fuzzy controller(MFC) that combine adaptive fuzzy learning controller(AFLC) and fuzzy logic control(FLC), is applied to current controller. Also, this paper proposes speed estimation algorithm using artificial neural network(ANN). The proposed method is analyzed and compared to conventional PI and FNN controller in various operating condition such as parameter variation, steady and transient states etc.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.120-125
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• 2006

Piezoelectric actuators have been investigated for flow control in the field of fluid dynamics. Numerical simulation for a single diaphragm piezoelectric actuator operating in quiescent air is performed to investigate the complex flow field around the slot exit. A periodic velocity transpiration condition is applied to simulate the effect of the moving diaphragm. The computational results for the flow field around the slot exit agree well with the experimental data. The results also show that low pressure regions due to the vortex pairing cause non-monotonic variations in the vertical velocity.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.2
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• pp.225-230
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• 2006

This study investigates drying condition when a small fan is added to a operating the free-breathing proton exchange membrane fuel cells (PEMFCs) with dry $H_2$ and Air. Polarization tests were conducted on PEMFCs at cell temperatures between 30 and $50^{\circ}C$ under dry operation. In the results, the cell performance strongly depended on the cell temperature and the cathode gas stoichiometric flow rates. The cell performance increases as cell temperature decreases from 50 to $30^{\circ}C$. In the domain where the stoichiometry of air is quite large, reduction of the concentration overpotential compensated the increased internal resistance due to drying. The maximum performance was obtained at the small air flow rate beyond which flooding occurs. This indicates that the fan should be operated in the stoichiometry domain with a well designed cell structure to avoid flooding.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.139-146
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• 2018

This work puts forward a theoretical analysis on position estimation performance of interior permanent magnet synchronous motor (IPMSM) according to the injection frequency in carrier-based sensorless operation. The effects of spatial harmonics on inductance and voltage distortion due to the nonideal characteristics of IPMSM and inverter are examined as factors influencing the position estimation performance. Furthermore, the position estimation performance is analyzed by calculating the current at the switching instant in several operating conditions. In summary, the half switching frequency injection is more robust to the nonideal characteristics of IPMSM, especially with light load condition. The validity of the analysis is verified by the simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.792-794
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• 2000

This paper describes the design and the analysis of electromagnetic system of Magnetic Switch using 2D parametric finite element method(EM-Pulse). Magnetic Switch is electrical equipment, which is widely used for switching on/off motors in industrial field. The transient state is simulated in order to calculate the response time of Magnetic Switch. The simulation is based upon a step-by-step integration of the electric circuit equations and the core movement. The contactor uses a permanent magnet for maintaining the closed state. The presented solution takes account of non-linear magnetic material property and spring force controlled by core position. The dynamic response of Magnetic Switch predicted by the simulation agrees closely with the required condition.

• KSBB Journal
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• v.27 no.1
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• pp.28-32
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• 2012

In this study, the treatment ability of the wastewater containing perchlorate by non-salt tolerant perchlorate reducing bacterial consortium (N-PRBC) was evaluated in a continuous stirred tank bioreactor (CSTR). To obtain the optimal operating condition the bioreactor was operated with the different wastewater empty bed retention time (EBRT). The treatment performance in the bioreactor could be maintained at 100 $mg-ClO_4{^-}L^{-1}$ up to a EBRT of 3 h, and the removal capacity in the CSTR was about 3.3 times higher than that in a batch operation. With a decrease from 9 h to 2 h in a EBRT, the volumetric perchlorate reduction rate was increased from 11.1 $mg-ClO_4{^-}L^{-1}h^{-1}$ to 50.0 $mg-ClO_4{^-}L^{-1}h^{-1}$, and the specific perchlorate reduction rates were increased from 3.01 $mg-ClO_4{^-}g-DCW^{-1}h^{-1}$. In conclusion, the treatment capacities in a CSTR were much better than those obtained in a batch operation.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.60-64
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• 2000

An experimental study was performed to investigate the optimal ejector and operating condition of vessel incinerator. Exhaust gas temperature and secondary air which makes vacuum pressure at ejector throat regions were considered as an important factor. According to the measurement of pressure temperature and nitrogen oxides between non combustion and combustion we found the stream and exhaust gas characteristics of incinerator. This results can give us the exhaust gas temperature control system air pollutant reduction method and the optimum ejector design.