• Journal of Electrical Engineering and Technology
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• 제12권6호
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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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• 제25권2호
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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.

• 융합보안논문지
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• 제6권1호
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• pp.55-63
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• 2006

본 논문에서는 차세대 패킷 네트워크에서의 성능 품질을 개선시키기 위한 하나의 접근 방안으로 패킷 지연에 대한 절대적 차별화 기능을 제공하는 알고리듬을 제안한다. 제안된 알고리듬은 임의 시간 구간에 도착될 입력 트래픽을 예측하고 이를 기반으로 지연 제어 기능을 수행한 후 실제로 입력된 트래픽을 측정하여 예측 오차를 도출하고 이를 다음 시간 구간에서 보상하는 것을 특징으로 한다. 제안된 방식은 매 시간 구간마다 지속적으로 예측 오차를 보상함으로서 예측 편차가 높은 버스트 트래픽에 대하여 특히 우수한 성능을 제공한다. 모의 실험을 통해 제안된 방식은 절대적 성능 지표를 충족하고 기존 방식에 비해 버스트 트래픽에 대하여 우수한 적응성을 제공하는 것을 확인한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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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.

• 한국지진공학회논문집
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• 제27권4호
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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.

• 한국통신학회논문지
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• 제27권4B호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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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.

• 한국소음진동공학회논문집
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• 제17권8호
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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.

• 품질경영학회지
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• 제44권3호
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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.

• 한국잠사곤충학회지
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• 제25권1호
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• pp.44-50
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• 1983

現 生絲檢査規則 中 纖度偏差檢査項目에 관하여 檢討한 結果 약간의 矛盾點을 發見하였으므로 이를 지적하고 그 改善策을 設定하였다. 1. 現 纖度偏差檢査는 平均纖度가 50~69 denier에 標準偏差는 5.80以下, 4.61 以上일 때 A格으로 定하고 있으나 平均纖度 50 denier인 경우의 標準偏差 5.80과 平均纖度 69 denier인 경우의 標準差 5.80과는 同一分布라 할 수 없다. 2. C.V로 換算하여 볼 때 2A格의 C.V가 A格의 C.V보다 작아야 하는데 現 纖度檢査規定은 70denier 의 1A格의 C.V換算値는 9.00이며, 69denier의 A格의 C.V換算値는 8.41로서의 70denier 2A格이 69denier의 A格보다 變異의 分散이 크게 나타나는 矛盾點을 보였다. 3. 生絲의 纖度偏差檢査數値도 平均値가 다른 Sample끼리의 優劣을 나타내는 數値이며 이 數値로서 等級을 決定하기 때문에 標準偏差에 의하여 檢査할 것이 아니라 C. V에 의하여 檢査하여야 한다. 4. 33 denier 以上의 生絲에서 각 等級別로 볼 때 6A格에서 下位格으로 감에 따라 變異폭(變異係數)을 약간씩 크게 하였으나 곳에 따라 一貫性을 잃고 있으며 그리고 同一等級에서 纖度變化에 따른 變異係數數値의 變化도 같은 경향이므로 等級間 및 纖度間의 數値調整을 要한다. 5. 34 denier 以上에서는 標準偏差數 値를 代入하기 때문에 同一等級에서 平均纖度가 굵어짐에 따라 標準偏差數値를 크게 하였으나 C. V로 換算하여 보면 大同小異하므로 纖度變化에 따른 C. V數値를 달리 할 필요가 없다. 6. 以上의 1.2.3.4.5項의 矛盾點을 是正하기 위하여 是正하기 위하여 C.V에 의한 檢査方式을 導入하고 33denier 以上에서 각 纖度間과 각 等級間의 均衡을 바로 잡으며 또 34 denier 以上에서 각 等級間의 間隔을 바로 잡기 위하여 曲線回歸公式을 導入하여 調整할 必要가 있다. 7. 生絲檢査에서 纖度偏差檢査表를 다음과 같이 改正實施함이 보다 妥當하다.