• International Journal of Control, Automation, and Systems
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• 제5권1호
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• pp.43-50
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• 2007

Reheating furnace is an essential facility of a rod mill plant where a billet is heated to the required rolling temperature so that it can be milled to produce wire. Although it is very important to obtain information on billet temperatures, it is not feasible during furnace operation. Consequently, a billet temperature profile should be estimated. Moreover, this estimation should be done within an appropriate time interval for an on-line application. In this paper, a billet heat transfer model based on 2D FEM(Finite Element Method) with spatially distributed emission factors is proposed for an on-line billet temperature estimation and also a measurement is carried out for two extremely different furnace operation patterns. Finally, the difference between the model outputs and the measurements is minimized by using a new optimization algorithm named uDEAS(Univariate Dynamic Encoding Algorithm for Searches) with multi-step tuning strategy. The obtained emission factors are applied to a simulation for the data which are not used in the model tuning for validation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 B
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• pp.766-768
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• 1998

Optical Temperature Distribution measurement System (OTDS) is completely different from conventional electric point sensor in that it uses the optical fiber itself as the sensor. This new concept in temperature measuring system requires only one fiber to be laid. The use of optical fiber also gives the advantage of small diameter, light weight, explosion resistance, and electromagnetic noise resistance. The OTDS is a sensor which is capable of making a precise measurement over a wide range of areas using only a single optical fiber. Since current temperature sensors, such as the thermocouple, are only used to measure temperaturea of point, they are almost impractical for measuring a wider range because of the extremely high cost. In comparision with current sensors, the optical fiber distributed temperature sensor can make much quicker and more precise measurements at a comparatively low cost.

• 대한설비공학회지:설비저널
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• 제5권4호
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• pp.272-280
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• 1976

A natural ventilating type store was designed for the economic and effective storage of citrus fruits in Jejudo. The material used for the wall is scoria, widely distributed in Jejudo and known for high strength and insulation. Design condition was chosen for the period till March of a year and the dry bulb temperature was taken from TAC $5\%$ base. The temperature of the store can be maintained below the limiting temperature of $8^{\circ}C$ for the time length of $7\frac{1}{2}$ hours under the condition of the atmospheric temp, $15.3^{\circ}C$ and the solar insolation. The limiting temperature can he recovered to the initial temperature $(7^{\circ}C)$ by the natural ventilation for 8 hours in the night.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.78-91
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• 2002

In the thermal power plant, there are six manipulated variables: main steam flow, feedwater flow, fuel flow, air flow, spray flow, and gas recirculation flow. There are five controlled variables: generator output, main steam pressure, main steam temperature, exhaust gas density, and reheater steam temperature. Therefore, the thermal power plant control system is a multinput and output system. In the control system, the main steam temperature is typically regulated by the fuel flow rate and the spray flow rate, and the reheater steam temperature is regulated by the gas recirculation flow rate. However, strict control of the steam temperature must be maintained to avoid thermal stress. Maintaining the steam temperature can be difficult due to heating value variation to the fuel source, time delay changes in the main steam temperature versus changes in fuel flow rate, difficulty of control of the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, and the fluctuation of inner fluid water and steam flow rates during the load-following operation. Up to the present time, the Proportional-Integral-Derivative Controller has been used to operate this system. However, it is very difficult to achieve an optimal PID gain with no experience, since the gain of the PID controller has to be manually tuned by trial and error. This paper focuses on the characteristic comparison of the PID controller and the modified 2-DOF PID Controller (Two-Degrees-Freedom Proportional-Integral-Derivative) on the DCS (Distributed Control System). The method is to design an optimal controller that can be operated on the thermal generating plant in Seoul, Korea. The modified 2-DOF PID controller is designed to enable parameters to fit into the thermal plant during disturbances. To attain an optimal control method, transfer function and operating data from start-up, running, and stop procedures of the thermal plant have been acquired. Through this research, the stable range of a 2-DOF parameter for only this system could be found for the start-up procedure and this parameter could be used for the tuning problem. Also, this paper addressed whether an intelligent tuning method based on immune network algorithms can be used effectively in tuning these controllers.

• 수산해양기술연구
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• 제31권2호
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• pp.127-141
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• 1995

득량만의 키조개 어장의 해양 환경을 알아보기 위하여 1994년 7월 12일(대조기)과 19일(소조기)에 걸쳐 득량만의 수형 분포 특성을 조사하였다. 득량만은 관측 기간중에 대조기와 소조기에 따른 빛의 연직감쇠계수(k)가 0.6인 곳을 경계로 하여 3개 해역으로 구분될 수 있었다. 조석 주기에 따른 k가 0.6인 등치선의 변화는 대조기에는 약 10m인 등수심선, 소조기에는 약 5m인 등수심선과 유사하게 분포하였다. 따라서 득량만의 수심 약 5~10m인 해역은 조석 주기에 따라서 수형의 특성이 뚜렷하게 바뀌는 수역이라고 할 수 있다. 즉, 수심 약 5~10m인 만 중앙 해역은 T-S diagram에서 대조기때는 수심이 얕은 해역의 수형군에 가까이 분포하고, 소조기때에는 수심이 깊은 수형군에 가까이 분포하였다. 그리고 성층 정도를 나타내는 변수인 log 하(10)(H/U 상(3))의 값은 수심 5m와 10인 등수심선에서 약 2.1~2.2의 값을 나타내었다. 특히, 본 연구 기간인 1994년 7월 동안은 혹서와 갈수로 인하여 예년치보다도 기온은 약 2$^{\circ}C$이상 높았으며, 강수량은 예년치보다도 훨씬 낮은 음의 값을 나타내었다. 이러한 영향으로 인하여 득량만의 수괴의 밀도는 관측 기간동안 주로 수온에 의해서 결정되고 있었다. 앞으로는 기상 자료 및 득량만에서의 과거 누년자료를 분석하여, 이상(abnormal) 고수온년에 대한 만내의 물리적인 변동, 조류와 해저 지형에 기인한 내부파의 형성이나 연속 관측에 의한 급조등에 관한 연구도 필요하리라 생각된다.

• 대한지리학회지
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• 제39권1호
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• pp.13-26
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• 2004

본 연구는 상대적 날씨 스트레스 지수로 NET의 적용 가능성을 파악하고자 하였다. 기상청에서 예보하고 있는 기온, 습도, 바람 자료를 이용하여 NET 값의 시공간적 분포 특성을 분석하였다. 여름철 스트레스 지수인 일 최고 NET의 지역별 스트레스 기준값은 바람과 습도보다는 기온의 영향을 받으므로 일 최고 기온의 분포와 유사하다. 겨울철 스트레스 지수인 일 최저 NET의 스트레스 기준값은 산지 지역과 서울 이북 지역에서는 낮은 기온의 영향을. 해안 지역에서는 강한 바람의 영향으로 기준값이 여름철에 비하여 다양하게 나타난다. 스트레스가 강한 날의 발생 빈도는 여름철은 뚜렷한 연변화가 나타나지 않지만, 겨울철에는 1990년대 중반 이후 뚜렷한 증가 경향을 보인다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2006년도 총회 및 춘계학술발표회
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• pp.277-281
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• 2006

A study on stream-groundwater exchange was performed using head and temperature data of stream water, streambed, and groundwater. Groundwater level and temperature were obtained from multi-depth monitoring wells in small-scale watershed. In the summer time, time series of temperatrue data at streambed and groundwater were monitored for three months. In the winter time, we measured the temperature gradient between stream water and streambed. The observed data showed three typical types of temperature characteristics. First, the temperature of streambed was lower than that of stream water; second, the temperature of streambed and stream water was similar; and last, the temperature of streambed was higher than that of stream water. The interconnections between the stream and the streambed were not homogeneously distributed due to weakly developed sediments and heterogeneous bedrock exposed as bed of the stream. The temperature data may be used in formal solutions of the inverse problems to estimate groundwater flow and hydraulic conductivity.

• Journal of the Optical Society of Korea
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• 제7권2호
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• pp.106-112
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• 2003

In order to do continuous health monitoring of large structures, it is necessary that the distributed sensing of strain and temperature of the structures be measured. So, we present the temperature compensation of a signal from a fiber optic BOTDA (Brillouin Optical Time Domain Analysis) sensor. A fiber optic BOTDA sensor has good performance of strain measurement. However, the signal of a fiber optic BOTDA sensor is influenced by strain and temperature. Therefore, we applied an optical fiber on the beam as follows: one part of the fiber, which is sensitive to the strain and the temperature, is bonded on the surface of the beam and another part of the fiber, which is only sensitive to the temperature, is located nearby the strain sensing fiber. Therefore, the strains can be determined from the strain sensing fiber while compensating for the temperature from the temperature sensing fiber. These measured strains were compared with the strains from electrical strain gages. After temperature compensation, it was concluded that the strains from the fiber optic BOTDA sensor had good coincidence with those values of the conventional electrical strain gages.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2011년도 한국컴퓨터종합학술대회논문집 Vol.38 No.1(A)
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• pp.420-421
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• 2011

This paper derive an optimal distributed power control strategy under both the probability of dropping a packet due to buffer overflow constraints at the secondary users and the interference constraints to the primary users.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
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• pp.337-338
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• 2009