• Title/Summary/Keyword: Steady State Performance

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Operating Frequency Design for Stable Initial Operation of Loosely Coupled Resonant DAB Converter (Loosely Coupled Resonant DAB 컨버터의 안정적인 초기 구동을 위한 동작 주파수 설계)

  • Baek, Seung-Hyuk;Kim, Sungmin;Lee, Jaehong;Lee, Seung-Hwan
    • The Transactions of the Korean Institute of Power Electronics
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    • v.26 no.6
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    • pp.437-445
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    • 2021
  • This paper proposes an operating frequency design method that limits the voltage applied to aload-side converter during the initial operation of a loosely coupled resonant dual-active bridge (LCR-DAB) converter and an initial operating strategy that applies it. The LCR-DAB converter uses two wireless power transfer coils instead of the high-frequency transformer of the general DAB converter. The wireless power coil has a physical distance of several tens of millimeter or more between the two coils; thus, the LCR-DAB converter is a bidirectional isolated power conversion system that can easily achieve high insulation performance. However, for the initial operation of the LCR-DAB, if the power-side converter is operated at the resonance frequency while the load-side converter is not operating, then a very high voltage due to resonance is applied to the load-side converter, thereby causing damage to the converter. Therefore, a method that can stably charge the DC link voltage of the secondary-side converter during the initial operation is needed. This paper proposes a method to initially charge the secondary-side DC link by operating the primary-side converter at a frequency with limited voltage gain rather than at a steady-state operating frequency. The validity of the proposed frequency design method and initial operating sequence is verified through simulation and experimentation of the 1 KW LCR-DAB converter.

A Control Algorithm Suitable for High-speed Response Battery Charging System for Elevator Car (승강기 Car용 고속응성 배터리 충전시스템에 적합한 제어알고리즘)

  • Lee, Jung-Hwan;Hwangbo, Chan;Park, Sung-Jun;Park, Seong-Mi;Ko, Jae-Ha
    • Journal of the Korean Society of Industry Convergence
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    • v.25 no.6_2
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    • pp.1071-1081
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    • 2022
  • As the demand for high-rise buildings increases, the demand for high-speed elevators is also increasing. In order to make a high-speed elevator, a method is needed to reduce the weight of the elevator's components, which is a constraint on the increase in speed. As a measure to reduce the weight, it is possible to remove the traveling cable for power and signal supply. Since the weight of the traveling cable varies depending on the position of the carriage, it is difficult to compensate the weight using the counter weight. The power supply is a structure in which a brush-rail type power input terminal is installed in the elevator hoistway to receive power in a contact-type manner while the carriage is moving. If a small-capacity ESS is installed in a passenger car, power can be supplied uninterruptedly inside the passenger car. A small-capacity ESS charging system to be applied to such an elevator system is required to perform several functions. First, the passenger Car must be able to charge as much as possible even during high-speed operation. A control algorithm with high responsiveness is required because charging starts and ends repeatedly by the partially installed input power stage. In addition, if the input-side line impedance is large due to the structure of the system and the response characteristic is increased, the stability of the system may be lowered. Accordingly, in this paper, we propose a control algorithm that has a stable steady-state output while having a fast response in a transient state. To verify the proposed control algorithm, simulation was conducted using PSIM, and the performance of the controller was verified by manufacturing a prototype buck conveter charger.

Functional Characterization of Drosophila melanogaster CYP6A8 Fatty Acid Hydroxylase

  • Sang-A Lee;Vitchan Kim;Byoungyun Choi;Hyein Lee;Young-Jin Chun;Kyoung Sang Cho;Donghak Kim
    • Biomolecules & Therapeutics
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    • v.31 no.1
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    • pp.82-88
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    • 2023
  • Genomic analysis indicated that the genome of Drosophila melanogaster contains more than 80 cytochrome P450 genes. To date, the enzymatic activity of these P450s has not been extensively studied. Here, the biochemical properties of CYP6A8 were characterized. CYP6A8 was cloned into the pCW vector, and its recombinant enzyme was expressed in Escherichia coli and purified using Ni2+-nitrilotriacetate affinity chromatography. Its expression level was approximately 130 nmol per liter of culture. Purified CYP6A8 exhibited a low-spin state in the absolute spectra of the ferric forms. Binding titration analysis indicated that lauric acid and capric acid produced type I spectral changes, with Kd values 28 ± 4 and 144 ± 20 µM, respectively. Ultra-performance liquid chromatography-mass spectrometry analysis showed that the oxidation reaction of lauric acid produced (ω-1)-hydroxylated lauric acid as a major product and ω-hydroxy-lauric acid as a minor product. Steady-state kinetic analysis of lauric acid hydroxylation yielded a kcat value of 0.038 ± 0.002 min-1 and a Km value of 10 ± 2 µM. In addition, capric acid hydroxylation of CYP6A8 yielded kinetic parameters with a kcat value of 0.135 ± 0.007 min-1 and a Km value of 21 ± 4 µM. Because of the importance of various lipids as carbon sources, the metabolic analysis of fatty acids using CYP6A8 in this study can provide an understanding of the biochemical roles of P450 enzymes in many insects, including Drosophila melanogaster.

Performance of Waste-air Treating System Composed of Two Alternatively-operating UV/photocatalytic Reactors and Evaluation of Its Characteristics (교대로 운전되는 두 개의 UV/광촉매반응기로 구성된 폐가스 처리시스템의 성능 및 특성 평가)

  • Lee, Eun Ju;Lim, Kwang-Hee
    • Korean Chemical Engineering Research
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    • v.59 no.4
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    • pp.574-583
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    • 2021
  • Waste air containing ethanol (100 ppmv) and hydrogen sulfide (10 ppmv) was continuously treated by waste air-treating system composed of two annular photocatalytic reactors (effective volume: 1.5 L) packed with porous SiO2 media carrying TiO2-anatase photocatalyst, one of which was alternately operated for 32 d/run while the other was regenerated by 100 ℃ hot air with 15 W UV(-A)-light on. As its elimination-behavior of ethanol, the removal efficiencies of ethanol at 1st, 2nd and 3rd operation of the photocatalytic reactor system(A), turned out to be ca. 60, 55 and 54%, respectively, at their steady state condition. Unlike the elimination-behavior of ethanol, its hydrogen sulfide-elimination behavior showed repeated decrease of hydrogen sulfide removal efficiency by its resultant arrival at a lower level of steady state condition. Nevertheless, the removal efficiencies of hydrogen sulfide at 1st, 2nd and 3rd operation of the photocatalytic reactor system, turned out to be ca. 80, 75 and 73%, respectively, at their final steady state condition, higher by ca. 20, 20 and 19% than those of ethanol, respectively. Therefore, assuming that adsorption on porous SiO2-photocatalyst carrier was regarded to belong to a reversible deactivation and that decreased % of removal efficiency due to the reversible deactivation of photocatalyst including the adsorption was independent of the number of its use upon regeneration, the increments of the decreased % of removal efficiency of ethanol and hydrogen sulfide, due to an irreversible deactivation of photocatalyst, for the 3rd use of regenerated photocatalyst, compared with the 2nd use of regenerated photocatalyst, were ca. 1 and 2%, respectively, which was insignificant or the less than those of ca. 5 and 5%, respectively, for the 2nd use of regenerated photocatalyst compared with the 1st use of virgin photocatalyst. This trend of the photocatalytic reactor system was observed to be similar to that of the other alternately-operating photocatalytic reactor system.

Simulation of an Absorption Power Cycle for Maximizing the Power Output of Low-Temperature Geothermal Power Generation (저온 지열발전의 출력 극대화를 위한 흡수식 동력 사이클의 시뮬레이션)

  • Baik, Young-Jin;Kim, Min-Sung;Chang, Ki-Chang;Lee, Young-Soo;Yoon, Hyung-Kee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.2
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    • pp.145-151
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    • 2010
  • In this study, an absorption power cycle, which can be used for a low-temperature heat source driven power cycle such as geothermal power generation, was investigated and optimized in terms of power by the simulation method. A steady-state simulation model was adopted to analyze and optimize its performance. Simulations were carried out for the given heat source and sink inlet temperatures, and the given flow rates were based on the typical power plant thermal-capacitance-rate ratio. The cycle performance was evaluated for two independent variables: the ammonia fraction at the separator inlet and the maximum cycle pressure. Results showed that the absorption power cycle can generate electricity up to about 14 kW per 1 kg/s of heat source when the heat source temperature, heat sink temperature, and thermal-capacitance-rate ratio are $100^{\circ}C$, $20^{\circ}C$, and 5, respectively.

A New Gradient Estimation of Euclidean Distance between Error Distributions (오차확률분포 사이 유클리드 거리의 새로운 기울기 추정법)

  • Kim, Namyong
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.8
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    • pp.126-135
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    • 2014
  • The Euclidean distance between error probability density functions (EDEP) has been used as a performance criterion for supervised adaptive signal processing in impulsive noise environments. One of the drawbacks of the EDEP algorithm is a heavy computational complexity due to the double summation operations at each iteration time. In this paper, a recursive method to reduce its computational burden in the estimation of the EDEP and its gradient is proposed. For the data block size N, the computational complexity for the estimation of the EDEP and its gradient can be reduced to O(N) by the proposed method, while the conventional estimation method has $O(N^2)$. In the performance test, the proposed EDEP and its gradient estimation yield the same estimation results in the steady state as the conventional block-processing method. The simulation results indicates that the proposed method can be effective in practical adaptive signal processing.

Advanced-CMA Blind Equalizer by Improvement of the RCA Cost Function (RCA 비용 함수를 개선한 Advanced CMA 등화기 알고리즘)

  • Yoon, Jae-Sun;Lim, Seung-Gag
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.12 no.2
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    • pp.127-133
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    • 2012
  • In this paper, the concerned CMA (Constant Modulus Algorithm) adaptive equalizer convergence rate and residual inter-symbol interference using cost function in order to improved to the ACMA (Advanced CMA). The CMA method compensates amplitude but does not compensate phase. On the other hand, The RCA (Reduced Constellation Algorithm) method compensates both the amplitude and the phase but it has the convergence rate problem. MCMA method is a way to solve the phase problem of CMA method compensates both the amplitude and the phase after respectively calculating the real and imaginary components. But it is more than poor CMA method in the complexity of hardware and the compensation performance. The cost function can advantages by improving the CMA and a MCMA (Modified CMA) equalizer so that the amplitude and phase retrieval the equalization steady-state to reduce the error by using ISI and faster convergence rate and performance is good SER (Symbol Error Ratio) was confirmed by computer simulations.

Effect of annealing temperature on Al2O3 layer for the passivation of crystalline silicon solar cell

  • Nam, Yoon Chung;Lee, Kyung Dong;Kim, JaeEun;Bae, Soohyun;Kim, Soo Min;Park, Hyomin;Kang, Yoonmook;Lee, Hae-Seok;Kim, Donghwan
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.335.2-335.2
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    • 2016
  • The fixed negative charge of the Al2O3 passivation layer gives excellent passivation performance for both n-type and p-type silicon wafers. For the best passivation quality, annealing is known to be a prerequisite step and a lot of studies concerning annealing effect on the passivation characteristics have been performed. Meanwhile, for manufacturing a crystalline silicon solar cell, firing process is applied to the Al2O3 passivation layer. Therefore, study on not only annealing effect but also on firing effect is necessary. In this work, Al2O3 passivation performance (minority carrier lifetime) for p-type silicon wafer was evaluated with Quasi-Steady-State Photoconductance(QSSPC) measurement after annealing at different temperatures. For the samples which showed different aspects, C-V measurement was performed for the cause - whether it is due to the chemical effect or field-effect. The change in Al2O3 passivation property after firing processes was investigated and the mechanism for the change could be estimated.

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Study on Cooling System Characteristics of 400W Active Speaker (400W급 액티브 스피커의 냉각시스템 특성에 관한 연구)

  • Seo, Jae-Hyeong;Bang, You-Ma;Lee, Moo-Yeon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.12
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    • pp.8140-8146
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    • 2015
  • The objective of this study is to experimentally investigate the cooling performance characteristics with the consideration of the temperature variations of the enclosure of the 400W ferrofluid active speaker having both woofer and amplifier heat sinks. In order to do this, the heat sinks for both woofer and amplifier was designed ant applied to 400W ferrofluid active speaker. As a result, the cooling performance of the developed 400W ferrofluid active speaker was improved and the temperature of the enclosure after 120 min at steady state increased by $2.8^{\circ}C$ with the increase of the outdoor temperatures from $25^{\circ}C$ to $29^{\circ}C$. In addition, the overall sound pressure level of the developed 400W ferrofluid active speaker showed 111.8 dB and improved 1.9 dB higher than 109.9 dB of the existed speaker.

Experimental Study on Millimeter Scale Two Phase Catalytic Reactor (밀리미터 스케일의 이상 분해 반응기에 대한 실험적 연구)

  • Cho, Chung-Hun;Lee, Dae-Hoon;Kwon, Se-JIn
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.3
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    • pp.265-270
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    • 2004
  • Experiment study on a down scaled two-phase catalytic reactor is presented. As a preliminary step for the development of catalytic reactor, nano-particulate catalyst was prepared. Perovskite La$\_$0.8/Sr$\_$0.2/CoO$_3$is chosen and synthesized as a catalyst considering superior catalytic performance in reduction and oxidation process where oxygen is involved among the reagent. Reactor that has a scale of 2${\times}$10${\times}$25mm was made by machining of A1 block as a layered structure considering further extension to micro-machining. Hydrogen peroxide of 70wt% was adopted as reactant and was provided to the reactor loaded with 1.5 g of catalyst. Reactant flow rate was varied by precision pump with a range of 0.15cc/min to 17.2cc/min. Temperature distribution within reactor was recorded by 3 thermocouples and total amount of liquid product was measured. Temperature distribution and factors that affect temperature were observed and relation between temperature distribution and production rate was also analyzed. Relative time scale plays a significant role in the performance of the reactor. To obtain steady state operation, appropriate ratio of flow rate, catalyst mass and reactor geometry is required and furthermore to get more efficient production rate temperature distribution should be evenly distributed. The database obtained by the experiment will be used as a design parameter for micro reactor.