• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2099-2105
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• 2017

In a power system that has a high wind penetration, the output power fluctuation of a large-scale wind turbine generator (WTG) caused by the varying wind speed increases the maximum frequency deviation, which is an important metric to assess the quality of electricity, because of the reduced system inertia. This paper proposes a stable power-smoothing scheme of a doubly-fed induction generator (DFIG) that can suppress the maximum frequency deviation, particularly for a power system with a high wind penetration. To do this, the proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while guaranteeing the stable operation of a DFIG, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. The simulation results based on the IEEE 14-bus system demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WTG under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.

• Journal of Biosystems Engineering
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• v.25 no.2
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• pp.107-114
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• 2000

Low temperature storage method is to increase the value of agricultural products by reducing quality loss and regulate consignment time by controlling respiration rates of agricultural products. Respiration rate of agricultural products depends on several factors such as temperature, moisture, gas composition and a microbe inside the storage room. Temperature is the most important factor among these, which affects respiration rate and causes low or high temperature damage. Fuzzy logic was used to control the temperature of a storage room ,which uses information of uncertain facts and mathematical model for room temperature control . Room temperature was controlled better by using fuzzy logic control method rather than on-off control method. Refrigerant flow rates and temperature deviations were measured for on-off system using TEV(temperature expansion valve) and for fuzzy system using EEV(Electrical Expansion Valve) . Temperature of the Storage room was lowered faster by using fuzzy system than on -off system. Temperature deviation was -0.6~+0.9$^{\circ}C$ for on-off system and $\pm$0.2$^{\circ}C$ for fuzzy system developed. Temperature deviation and variation of temperature deviation were used as inout parameters for fuzzy system. The most suitable input and output value were found by experiment. Cooling rate of the storage room decreased while temperature deviation increased for the sampling time of 20 sec.

• Convergence Security Journal
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• v.6 no.1
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• pp.55-63
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• 2006

In this paper, an algorithm that provisions absolute differentiation of packet delays is proposed with an objective for enhancing quality of service (QoS) in future packet networks. It features an adaptive scheme that compensates the deviation for prediction on the traffic to be arrived continuously. It predicts the traffic to be arrived at the beginning of a time slot and measures the actual arrived traffic at the end of the time slot, and derives the deviation between the two quantity. The deviation is utilized to the delay control operation for the next time slot to offset it. As it compensates the prediction error continuously, it shows superior adaptability to the bursty traffic as well as the constant rate traffic. It is demonstrated through simulation that the algorithm meets the quantitative delay bounds and shows superiority to the traffic fluctuation in comparison with the conventional mechanism.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.961-966
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• 2000

It is difficult to change or remedy concrete structure after hardened. It is usual to evaluate the quality of hardened concrete using several test method. This study was performed to make fundamental data that could be used to evaluate the quality of hardened concrete. This study is to estimate mix proportion of hardened concrete. Each elements of concrete needed different estimation methods. First, the cement that handled by the most important compounds measured by XRF(X-ray fluorecence) machine with scanning Ca-K${\alpha}$. Second, the coarse aggregate that divided by maximum size measured by the area comparison method that starts from the assumption of uniform distribution. Third, the fine aggregate measured by the weight comparison method that needs several prerequsite constants which concerned cement hydration reaction. Fourth, the water content would be estimated by expert system that has data base of design data, the contents of above estimation results, the characteristics of concrete strength. As the result of the above research, some conclusions are as follows. The cement estimation method resulted by reliability of mean 96.7%, standard deviation 3.92. The area comparison method resulted by reliability of mean 95.3%, standard deviation 2.08. The weight comparison method resulted by reliability of mean 93.3%, standard deviation 3.35.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.4
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• pp.187-192
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• 2023

An elastic bearing must be strong against vertical loads and flexible against horizontal loads. However, due to the material characteristics of rubber, it may show variability due to the manufacturing process and environmental factors. If the value applied in the bridge design stage and the actual measured value have different values or if the performance during operation changes, the performance required in the design stage may not be achieved. In this paper, the seismic response of bridges was compared and analyzed by assuming a case where quality deviation occurs during construction compared to the design value for elastic bearings, which have not only always served as traditional bearings but also have had many applications in recent seismic reinforcement. The bearing's vertical stiffness and shear stiffness deviation were considered separately for the quality deviation. In order to investigate the seismic response, a time history analysis was performed using artificial seismic waves. The results confirmed that the change in the bearing's shear stiffness affects the natural period and response of the structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.338-344
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• 2002

This paper proposes a transient (predictive) connection admission control (CAC) scheme using the transient quality of service (QoS) measure for CDMA cellular systems with bursts On-Off sources. We need an approximate and bounded approach for real-time CAC applications. We derive the transient outage probability as the QoS measure using the Chernoff bound and the refuted large deviation approximation. Numerical results show that the predictive CAC is a promising approach for the multicell CDMA systems.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.909-917
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• 2007

Recently the trend of automobile industry is that IQS evaluation index against a sensitivity quality is increasing. To reduce rattle noise due to speaker sound at low frequencies, it is required the advanced investigation of a package tray panel and a door module panel. This paper optimized the design parameters of package tray panel according to the theoretical background about robust design and suggested the design guideline for resonance avoidance and the reduction of vibrational sensitivity considering the excitation frequency of woofer speaker. In addition, it is suggested the design guideline of a door module panel through the sensitivity analysis in case of the speaker excitation. Finally, the design factor analysis of the quality deviation of a mother-car will make it possible to guarantee the stable characteristics of vehicle vibration in the early stage of vehicle development. These improvements can lead to shortening the time needed to develop better vehicles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.673-682
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• 2007

Recently the trend of automobile industry is that IQS evaluation index against a sensitivity quality is increasing. To reduce rattle noise due to speaker sound at low frequencies, it is required the advanced technology analysis process of body structure. This paper optimized the design parameters of package tray panel according to the theoretical background about robust design and suggested the design guideline for resonance avoidance and the reduction of vibrational sensitivity considering the excitation frequency of woofer speaker. And this paper described the design process of a door module panel through the sensitivity analysis in case of the door speaker excitation. Finally, the analysis of the quality deviation using mother car is suggested to guarantee the stable characteristics of vehicle vibration in the early stage of vehicle development. These improvements can lead to shortening the time needed to develop better vehicles.

• Journal of Korean Society for Quality Management
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• v.44 no.3
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• pp.487-508
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• 2016

Purpose: Current testing method for drying rate used in military textiles has different results according to the public testing institute. So the purpose of this study was to suggest the alternative method which secure the reliability of the drying rate test. Methods: We measured the drying rate by various test methods for military clothes 14 species including quick drying function and compared the test results. Also, the collected data through the test was analyzed using one-way ANOVA. The p-value of results was compared by various testing institutions. Results: The results of this study are as follow; A deviation occurred among the testing institutions in original test method(KS K 0815). Whereas it is verified that there is no deviation among the institutions in 5% significance level by another test method(ISO 17617). Also it would increase work efficiency by reducing the testing time required to test by using ISO 17617. Conclusion: Based on the results, we can suggest the reliable test method of the drying rate.

• Journal of Sericultural and Entomological Science
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• v.25 no.1
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• pp.44-50
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• 1983

The study was carried out to suggest on opinion of the standardization of size deviation in the existing raw silk testing method. 1. The present grade A of size deviation stipulates 4.61 to 5.80 of standard deviation for 50 to 69 denier of mean value, however, the 5.80 standard deviation with the mean values of 50 and 69 denier belong to different distribution. 2. It is reasonable that the variation coefficients of grade 2A should be lower than that of grade A. However, the present testing method shows larger variation in grade 2A than in grade A. This is illustrated 9.00 for 69 denier in grade 2A and 8.41 for 70 denier in grade A. 3. The size deviation value compares the quality of raw silk with different mean value. Therefore, the standard deviation is recommended to be replaced by the C.V. value in determining the grade of silk. 4. The C.V. have a tendency to increase with lower grades below 6A for the size deviation below 33 denier with some inconsistencies. The figures should be adjusted so that the C.V. inconsistencies size deviation below 33 denier will be corrected. 5. The standard deviation increases with size under the same grade for the size deviations above 33 denier, however, the C.V. does not vary greatly with size deviation. 6. To rectify the above-mentioned inconsistencies the C.V. conversion and curvilinear regresion correction is recommended to improve the present silk testing method 7. The table of size deviation standard are as follows: Suggested standard of size deviation, unit: C.V. Value