• Title/Summary/Keyword: Thermal compensation

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Thermal Kinetics of Color Changes of Purple Sweet Potato Anthocyanin Pigment (자색고구마 Anthocyanin 색소의 가열에 대한 속도론적 연구)

  • Lee, Lan-Sook;Rhim, Jong-Whan
    • Korean Journal of Food Science and Technology
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    • v.29 no.3
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    • pp.497-501
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    • 1997
  • Kinetic parameters on heat-induced color changes of anthocyanin pigment from purple sweet potato were determined in the temperature range of $121{\sim}141^{\circ}C$. Color change determined by a browning index $(A_{532}\;nm/A_{420}\;nm)$ followed second order reaction kinetics. Activation energy values of purple sweet potato pigment solutions of pH 2.0, 3.0, 4.0 and 5.0 were 69.57, 76.68, 81.07 and 92.98 kJ/mol, respectively, indicating that temperature dependency of the reaction increased with pH. Apparent kinetic compensation effect between preex-ponential factor and activation energy value was observed.

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A Study on the Design of a ROIC for Uncooled Bolometer Thermal Image Sensor Using Reference Resistor Compensation (기준저항 보상회로를 이용한 비냉각형 볼로미터 검출회로의 설계에 관한 연구)

  • Yu, Seung-Woo;Kwak, Sang-Hyeon;Jung, Eun-Sik;Hwang, Sang-Jun;Sung, Man-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.148-149
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    • 2008
  • As infrared light is radiated, the CMOS Readout IC (ROIC) for the microbolometer type infrared sensor detects voltage or current when the resistance value in the bolometer sensor varies. One of the serious problems in designing the ROIC is that resistances in the bolometer and reference resistor have process variation. This means that each pixel does not have the same resistance, causing serious fixed pattern noise problems in sensor operations. In this paper, Reference resistor compensation technique was proposed. This technique is to compensate the reference resistance considering the process variation, and it has the same reference resistance value as a bolometer cell resistance by using a comparator and a cross coupled latch.

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A Tuning Method for the Power System Stabilizer of a Large Thermal Power Plant and Its Application to Real Power System : PART II - Field Tests and Verification of PSS Performance (대형 화력발전기 전력계통 안정화장치(IEEEST-PSS)의 정수선정 기법과 실계통 적용: PART II - PSS 현장 성능시험 절차 및 성능검증)

  • Shin, Jeong-Hoon;Nam, Su-Chul;Baek, Seung-Mook;Song, Ji-Young;Lee, Jae-Gul;Kim, Tae-Kyun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.8
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    • pp.114-121
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    • 2011
  • This paper, as the second part of the paper, dealt with the field test and test results to validate PSS(Power System Stabilizer) parameters which are previously tuned in Part 1 paper. In Part 1 of the paper, the selection of parameters such as lead-lag time constants for phase compensation and system gain was optimized by using linear & eigenvalue analyses and they were verified through the time-domain transient stability analysis. In part 2, the performance of PSS was finally verified by the generator's on-line field test. Through the comparisons of simulation results and measured data before and after tuning of the PSS, the models of generator and its controllers including AVR, Governor and PSS used in the simulation are verified and confirmed.

Synthesis of Li-rich Cathode Material with Spherical Shape and High Crystallinity by Using Flame Spray Pyrolysis (화염분무열분해법을 이용한 구형의 고결정성 리튬 과잉 양극재 제조)

  • Sung Nam Lim
    • New & Renewable Energy
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    • v.20 no.3
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    • pp.20-27
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    • 2024
  • A Li-rich cathode material, Li1.167Mn0.548Ni0.18Co0.105O2, with a spherical shape and high crystallinity, is prepared using flame spray pyrolysis. The post-heat treatment condition influences the properties of the prepared material, such as its structure, morphology, and chemical composition, and optimum performance is achieved at 900℃. Various excess Li contents (0-12 wt.%) are introduced in the precursor solution to compensate for volatilized Li during synthesis, bringing it close to the target composition. Compensation for volatilized Li enhances the electrochemical performance, i.e., the Li-compensated sample shows a good discharge capacity of 247 mAh g-1 at a current density of 20 mA g-1 in a potential window of 4.6-2.5 V. In addition, the prepared Li-rich cathode material supplemented with 9 wt.% of the Li source shows increased discharge capacity of 175 and 148 mAh g-1 at 200 and 400 mA g-1, respectively, compared with those of a bare sample (164 and 127 mAh g-1, respectively).

Wind Energy Interface to Grid with Load Compensation by Diode Clamped Multilevel Inverters

  • Samuel, Paulson;Naik, M. Kishore;Gupta, Rajesh;Chandra, Dinesh
    • Journal of Power Electronics
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    • v.14 no.2
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    • pp.271-281
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    • 2014
  • Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

A Study on the Calculation of Optimal Compensation Capacity of Reactive Power for Grid Connection of Offshore Wind Farms (해상풍력단지 전력계통 연계를 위한 무효전력 최적 보상용량 계산에 관한 연구)

  • Seong-Min Han;Joo-Hyuk Park;Chang-Hyun Hwang;Chae-Joo Moon
    • The Journal of the Korea institute of electronic communication sciences
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    • v.19 no.1
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    • pp.65-76
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    • 2024
  • With the recent activation of the offshore wind power industry, there has been a development of power plants with a scale exceeding 400MW, comparable to traditional thermal power plants. Renewable energy, characterized by intermittency depending on the energy source, is a prominent feature of modern renewable power generation facilities, which are structured based on controllable inverter technology. As the integration of renewable energy sources into the grid expands, the grid codes for power system connection are progressively becoming more defined, leading to active discussions and evaluations in this area. In this paper, we propose a method for selecting optimal reactive power compensation capacity when multiple offshore wind farms are integrated and connected through a shared interconnection facility to comply with grid codes. Based on the requirements of the grid code, we analyze the reactive power compensation and excessive stability of the 400MW wind power generation site under development in the southwest sea of Jeonbuk. This analysis involves constructing a generation site database using PSS/E (Power System Simulation for Engineering), incorporating turbine layouts and cable data. The study calculates reactive power due to charging current in internal and external network cables and determines the reactive power compensation capacity at the interconnection point. Additionally, static and dynamic stability assessments are conducted by integrating with the power system database.

A Study on Engine Performance at the Intake Air Compensation by Supercharging in the Low Speed Diesel-Atkinson Cycle (과급에 의한 흡입공기 보상 시 저속 디젤-아트킨슨사이클에서 엔진성능에 대한 연구)

  • Jang, Tae-Ik
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.8
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    • pp.1009-1015
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    • 2011
  • In this study, in the high expansion cycle was conduced by variable valve timing system composition to close intake valve late, and in the intake air reduction on the low compression was solved by supercharging pressure. In this wise, by constituting Diesel-Atkinson cycle, this study looked into a possibility of thermal efficiency improvement. As a result, there was improvement in thermal efficiency and output in a whole range of closing timing from ABDC $40^{\circ}$ to ABDC $80^{\circ}$. However, after ABDC $70^{\circ}$ of closing timing, the thermal efficiency increase was getting smaller. As the result of the study, the optimum intake valve closing timing was about ABDC $70^{\circ}$, high loading territory of engine was more effective than low loading territory, and engine operation in middle loading territory was stable. At this time, brake thermal efficiency was 12.5% higher than ordinary engine on average.

Design and Analysis of an Optical System for an Uncooled Thermal-imaging Camera Using a Hybrid Lens (Hybrid 렌즈를 이용한 비냉각 열상장비 광학계 설계 및 분석)

  • Ok, Chang-Min;Kong, Hyun-Bae;Park, Hyun-Woo
    • Korean Journal of Optics and Photonics
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    • v.28 no.5
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    • pp.241-249
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    • 2017
  • This paper presents the design and evaluation of the optical system for an uncooled thermal-imaging camera. The operating wavelength range of this system is from $7.7{\mu}m$ to $12.8{\mu}m$. Through optimization, we have obtained a LWIR (Long Wave Infrared) optical system with a focal length of 5.44 mm, which consists of four aspheric surfaces and two diffractive surfaces. The f-number of the optical system is F/1.2, and its field of view is $90^{\circ}{\times}67.5^{\circ}$. The hybrid lens was used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We calculated the polychromatic integrated diffraction efficiency, and the MTF drop generated by background noise. We have evaluated the thermal compensation of a LWIR fixed optical system, which is optically passively athermalized to maintain MTF performance in the focal depth. In conclusion, these design results are useful for an uncooled thermal-imaging camera.

Prediction of Relative Deformation between Cutting Tool and Workpiece by Cutting Force [$1^{st}$ paper] (절삭력에 의한 공구와 공작물의 상대적 변형량 예측 [1])

  • Hwang, Young-Kug;Lee, Choon-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.9
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    • pp.86-93
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    • 2010
  • Any relative deformation between the cutting tool and the workpiece at the machining point, results directly in form and dimensional errors. The source of relative deformations between the cutting tool and the workpiece at the contact point may be due to thermal, weight, and cutting forces. Thermal and weight deformations can be measured at various positions of the machine tool and stored in the compensation registers of the CNC unit and compensated the errors during machining. However, the cutting force induced errors are difficult to compensate because estimation of cutting forces are difficult. To minimize the error induced by cutting forces, it is important to improve the machining accuracy. This paper presents the pre-calculated method of form error induced by cutting forces. In order to estimate cutting forces, Isakov method is used and the method is verified by comparing with the experimental results. In order to this, a cylindrical-outer-diameter turning experiments are carried out according to cutting conditions.

Modeling of Heliostat Sun Tracking Error Using Multilayered Neural Network Trained by the Extended Kalman Filter (확장칼만필터에 의하여 학습된 다층뉴럴네트워크를 이용한 헬리오스타트 태양추적오차의 모델링)

  • Lee, Sang-Eun;Park, Young-Chil
    • Journal of Institute of Control, Robotics and Systems
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    • v.16 no.7
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    • pp.711-719
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    • 2010
  • Heliostat, as a concentrator reflecting the incident solar energy to the receiver located at the tower, is the most important system in the tower-type solar thermal power plant, since it determines the efficiency and performance of solar thermal plower plant. Thus, a good sun tracking ability as well as its good optical property are required. In this paper, we propose a method to compensate the heliostat sun tracking error. We first model the sun tracking error, which could be measured using BCS (Beam Characterization System), by multilayered neural network. Then the extended Kalman filter was employed to train the neural network. Finally the model is used to compensate the sun tracking errors. Simulated result shows that the method proposed in this paper improve the heliostat sun tracking performance dramatically. It also shows that the training of neural network by the extended Kalman filter provides faster convergence property, more accurate estimation and higher measurement noise rejection ability compared with the other training methods like gradient descent method.