• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.4
• /
• pp.408-413
• /
• 2014

In this paper, we propose a fault diagnosis method based on Park's Vector Approach using the Euler's theorem. If we interpreted it as Euler's theorem, it is possible to easily find the phase angle difference between the healthy condition and the fault condition. And, we analyzed the variation of the phase angle and performed the diagnostic method of the induction motor using feature vectors that were obtained by using a Fourier transform. The analysis of time and speed variation of the motor was performed and, as a result, we could find more soft variations than rough variations. In particular, the analysis of the distortion through each phase shows that two-turn and four-turn shorted motors are linearly separable. In this experiment, we know that the maximum breakdown threshold value for determining steady-state fault detection is 49.0788. Simulation and experimental results show the more detectable than conventional method.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.15 no.3
• /
• pp.179-184
• /
• 1982

The behavior of continuous flow culture of Lartobacillus bulgricus was investigated by application of Monod's kinetic model. The parameters obtained from Monod's chemostat theory successfully predicted the behavior of the chemostat. Then, it was found that Monod's kinetics were applicable to the growth rate dependence on glucose concentration. Under steady-state condition, the maximum growth rate, saturation constant, and wash out were found to be 0.62/hr, 7.69 g/1, 0.51/hr of continuous culture. And the optimum condition for the highest cell production was 0.41/hr in dilution rate, and at that point the cell production rate was 0.178g/1 hr.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.85-89
• /
• 2003

In a closed square cavity filled with a liquid, a cooled the upper horizontal wall and a heated the lower horizontal wall, the flow isn't generated under the ground-based condition when Rayleigh number is lower than 1700. In such case the flow phenomena near an air bubble under a cooled horizontal wall were investigated. The temperature and the flow fields were studied by using the Thermo-sensitive Liquid-Crystal and the image processing. The qualitative analysis for the temperature and the flow fields were carried out by applying the image processing technique to the original data. Injecting bubble at the center point of upper cooled wall, the symmetry shape of two vortexes near an air bubble was observed. The bubble size increased, the size of velocity and the magnitude of velocity increased. In spite of elapsed time, a pair of two vortexes was the unique and steady-state flow in a square cavity and wasn't induce to the other flow in the surround region.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.9
• /
• pp.871-876
• /
• 2011

In this paper, the equilibrium flight conditions of a Korean Traditional Bangpae Kite with low aspect ratio were analyzed by it's aerodynamic data of wind tunnel test. The data of aerodynamic forces and center of pressure of the Kite were used to calculate the relative length of bridles to satisfy the condition of settling the kite to the static equilibrium steady state between ${\theta}=30^{\circ}{\sim}60^{\circ}$. From this equilibrium flight performance analysis, we obtained ($0.88{\pm}0.02$)c of the rear bridle length corresponding to 0.88c of fixed front bridle length. These results were exact agreement with the relative bridle lengths by Korean classical method.

• Journal of Korean Society for Atmospheric Environment
• /
• v.12 no.4
• /
• pp.369-376
• /
• 1996

Major atmospheric stability classification methods were evaluated with meteorological data obtained by scoustic sounding profiler (SODAR/RASS) in Seoul. The Psequill classificatio method, the method most widely used because of its good agreement in respect of synoptic scope under the steady state, fails to describe the time lag, the response time on stability by heating or cooling caused by daily insolation or noctrunal surface radiation. Horizontal and vertical standard deviation of wind fluctuation $(\sigma_A and \sigma_E)$ method tend to classify night-time stable condition (E, F class) into unstable condition (A, B class). The classification matrix tables for Vogt's vertical temperature difference and wind speed using method ($\Delta$T $\cdot$ U) and bulk Richardson number (Rb) were amended for practical use over Seoul. The modified tables for $\Delta$T $\cdot$ U and Rb method were made by using comprehensive frequency distribution from Pasquill's method and other existing results, and the correlation coefficient(r) was equal to 0.829. It was confirmed that atmospheric stability could be changed with monitoring site characteristics, height and vertical difference between sensors of monitoring station, and classification method itself.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.10 no.1
• /
• pp.53-58
• /
• 2007

In an estuary, mixing and transport of contaminant sometimes occurs in the salt finger favorable condition (Hwang ang Rehmann, 2004). Linearized theory is applied to predict flow dynamics in salt finger favorable condition. The simulated results match well with previous laboratory experiments. When the density ratio is larger than 2, the heat and salt system shows $0.55{\sim}0.57$ as Turner (1967) found, and the salt and sugar system produces 0.87 of Griffiths (1980). As the ratio of molecular diffusivities of two scalars increases, the flux ratio increases. The flux and eddy diffusivity ratios decrease with increase of density ratio, and it takes longer time for flux ratio to be steady state at the higher density ratios.

• Journal of Korea Foundry Society
• /
• v.11 no.6
• /
• pp.455-462
• /
• 1991

The formation of brittle intermetallic compound such as $VAl_3$ tends tp lower the toughness of V-Al alloys. Also, due to the high melting point of vanadium, it is difficult to make that alloy by previous ingot metallurgy method. To depress the technique has been adopted. The effect of particle size and milling time on the phase has been thoroughly studied. For mechanical alloying, SPEX mixed/mill has been used. The milling time and the composition of V and Al are varied to find the optimum condition of forming amorphous phase. The X-Ray Diffrection pattern, microstructure detection, microhandess test, experiments are carried out to analyze MA product. When the final step is reached, no lamellar-structure is detected. The steady state condition is observed after 8 hours and 10 hours milling for 15wt.%Al and 30wt.%Al alloy, respectively. The microhardness continuously increases up to 10 hours after then it remains constant.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.5
• /
• pp.503-510
• /
• 2004

In this paper, the well-conditioned observer for a stochastic system is designed so that the observer is less sensitive to the ill-conditioning factors in transient and steady-state observer performance. These factors include not only deterministic uncertainties such as unknown initial estimation error, round-off error, modeling error and sensing bias, but also stochastic uncertainties such as disturbance and sensor noise. In deterministic perspectives, a small value in the L$_{2}$ norm condition number of the observer eigenvector matrix guarantees robust estimation performance to the deterministic uncertainties. In stochastic viewpoints, the estimation variance represents the robustness to the stochastic uncertainties and its upper bound can be minimized by reducing the observer gain and increasing the decay rate. Both deterministic and stochastic issues are considered as a weighted sum with a LMI (Linear Matrix Inequality) formulation. The gain in the well-conditioned observer is optimally chosen by the optimization technique. Simulation examples are given to evaluate the estimation performance of the proposed observer.

• IEIE Transactions on Smart Processing and Computing
• /
• v.2 no.3
• /
• pp.148-159
• /
• 2013

An analysis of the throughput and stability region of random access systems is currently of interest in research and industry. This study evaluated the performance of a multiuser random access channel with a retransmission gain. The channel was composed of a media access control (MAC) determined by the transmission probabilities and a multiuser communication channel characterized by the packet reception probabilities as functions of the number of packet transmissions and the collision status. The analysis began with an illustrative two-user channel, and was extended to a general multiuser channel. For the two-user channel, a sufficient condition was derived, under which the maximum throughput was achieved with a control-free MAC. For the channel with retransmission gain, the maximum steady throughput was obtained in a closed form. The condition under which the random access channel can acquire retransmission gain was also obtained. The stability region of the general random access channel was derived. These results include those of the well-known orthogonal channel, collision channel and slotted Aloha channel with packet reception as a special instance. The analytical and numerical results showed that exploiting the retransmission gain can increase the throughput significantly and expand the stability region of the random access channel. The analytical results predicted the performance in the simulations quite well.

• International Journal of Automotive Technology
• /
• v.7 no.1
• /
• pp.43-49
• /
• 2006

In this paper, an index for the evaluation of a vehicle intake booming noise and intake sound quality were developed through a correlation analysis and a multiple factor regression analysis of objective measurement and subjective evaluation data. At first, an intake orifice noise was measured at the wide-open throttle test condition. And then, an acoustic transfer function between intake orifice noise and interior noise at the steady state condition was estimated. Simultaneously, subjective evaluation was carried out with a 10-scale score by 8 intake noise and vibration expert evaluators. Next, the correlation analysis between the psychoacoustic parameters derived from the measured data and the subjective evaluation was performed. The most critical factor was determined and the corresponding index for intake booming noise and sound quality are obtained from the multiple factor regression method. And, the optimal design of intake system was studied using the booming noise and the sound quality evaluation index for expectation performance of intake system. Conclusively, the optimal designing parameters of intake system from noise level and sound quality whose point of view were extracted by adapting comparative weighting between the booming noise and sound quality evaluation index, which optimized the process. These work could be represented guideline to system engineers, designers and test engineers about optimization procedure of system performance by considering both of noise level and sound quality.