• Korean Chemical Engineering Research
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• 제60권3호
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• pp.363-370
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• 2022

본 논문에서는 전기자동차용 배터리 충/방전 상태 추정의 정확도를 개선하기 위해 칼만 필터(Kalman Filter, KF) 알고리즘과 등가회로모델(Equivalent Circuit Model)을 활용한 State Of Charge (SOC) 추정 방법을 적용하였다. 특히 노화된 배터리 용량을 함께 추정 가능한 관측기(observer)를 설계하였다. 우선 노화가 없는 경우, 칼만 필터를 이용하여 SOC를 단일 추정하면, 관측기 없이 모델로 계산된 경우와 비교하여 평균 절대 오차율이 1.43%(관측기 미사용)에서 0.27%(관측기 사용)로 감소하였다. 차량 주행상태에서는 전류가 고정되지 않아 SOC와 배터리 용량을 모두 추정하는 것에 일반적인 KF 혹은 Extended KF 알고리즘을 이용할 수 없다. 배터리 노화에 의한 용량 변화는 단시간에 일어나지는 않다는 점에 착안하여, 충전 시 배터리 용량 추정을 주기적으로 실시하는 전략을 제시하였다. 충전 모드에서는 일정 구간마다 전류가 고정되기에, 해당 상황에서 배터리 노화 용량을 SOC와 함께 추정 전략을 제시하였다. 전류가 고정된 상태에서 SOC 추정의 평균 절대 오차율은 0.54% 였으며, 용량 추정의 평균 절대 오차율은 2.24%로 나타났다. 충전상태에서 전류가 고정됨으로 일반적인 EKF를 활용하여 배터리 용량과 SOC 동시 추정이 가능하도록 하였다. 이를 통하여 배터리 충전 시 주기적인 배터리 용량 보정을 수행할 수 있다. 그리고, 방전 시에는 해당 용량으로 고정한 채 SOC를 추정하는, 배터리 관리 시스템에서 활용 가능한 추정 알고리즘을 제안하였다.

• 정보학연구
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• 제3권4호
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• pp.107-128
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• 2000

세계각국은 컨벤션산업을 21세기 성장을 주도하는 전략산업으로 집중 육성하고 있다. 그러나 우리 나라의 컨벤션 산업은 대형 컨벤션센터의 부재, 국제회의 전문인력의 부족, 국제회의 관련 업의 수도권집중, 항공노선의 부족, 관련업계와의 공조체제 부족, 국제회의정보 부족 등 많은 현안 문제가 있을 뿐 아니라 국제회의 전용시설이 전혀 없는 게 현실이다. 따라서 국가의 이미지 제고, 국제 교역 활성화, 지역개발촉진, 고용기회확대, 세수증대라는 광범위한 파급효과를 가져오는 컨벤션 산업의 육성을 위하여 국내 컨벤션 산업의 실태를 분석하고 그 문제점을 파악하여 개선방안을 제시하는데 목적을 둔다.

• International Journal of Control, Automation, and Systems
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• 제4권4호
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• pp.414-427
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• 2006

This paper presents an adaptive feedback linearization control scheme for induction motors with simultaneous variation of rotor and stator resistances. Two typical modeling techniques, rotor flux model and stator flux model, have been developed and successfully applied to the controller design and adaptive observer design, respectively. By using stator fluxes as states, over-parametrization in adaptive control can be prevented and control strategy can be developed without the need of nonlinear transformation. It also decrease the relative degree for the flux modulus by one, thereby, yielding, a simple control algorithm. However, when this method is used for flux observer, it cannot guarantee the convergence of flux. Similarly, the rotor flux model may be appropriate for observers, but it is not so for adaptive controllers. In addition, if these two existing methods are merged into overall adaptive control system, it brings about structural complexies. In this paper, we did not use these two modeling methods, and opted for the airgap flux model which takes on only the positive aspects of the existing rotor flux model and stator flux model and prevents structural complexity from occuring. Through theoretical analysis by using Lyapunov's direct method, simulations, and actual experiments, it is shown that stator and rotor resistances converge to their actual values, flux is well estimated, and torque and flux are controlled independently with the measurements of rotor speed, stator currents, and stator voltages. These results were achieved under the persistent excitation condition, which is shown to hold in the simulation.

• 천문학회보
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• 제42권1호
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• pp.46.2-46.2
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• 2017

Atmospheric propagation effects at millimeter wavelengths can significantly alter the phases of radio signals and reduce the coherence time, putting tight constraints on high frequency Very Long Baseline Interferometry (VLBI) observations. In previous works it has been shown that non-dispersive (e.g. tropospheric) effects can be calibrated with the frequency phase transfer (FPT) technique. The coherence time can thus be significantly extended. Ionospheric effects, which can still be significant, remain however uncalibrated after FPT, as well as the instrumental effects. In this work, we implement a further phase transfer between two FPT residuals (i.e. so-called FPT2) to calibrate the ionospheric effects based on their frequency dependence. We show that after FPT2, the coherence time at 3 mm can be further extended beyond 8 hours, and the residual phase errors can be sufficiently canceled by applying the calibration of another source, which can have a large angular separation from the target (> $20{\circ}$). Calibrations for all-sky distributed sources with a few calibrators are also possible after FPT2. One of the strengths and uniqueness of this calibration strategy is the suitability for high frequency all-sky survey observations including very weak sources. We discuss the introduction of a pulse calibration system in the future to calibrate the remaining instrumental effects and allowing the possibility of imaging the source structure at high frequencies with FPT2, where all phases are fully calibrated without involving any sources other than the target itself.

• 한국융합학회논문지
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• 제9권9호
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• pp.199-207
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• 2018

본 연구는 4차 산업혁명으로 불리는 생산 패러다임 변화에 선도적으로 대응하기 위해 차세대 생산혁신 기술을 증거기반 키워드 네트워크를 통해 분석하는 것을 목적으로 한다. 분석을 위해 차세대 생산혁신 기술과 관련한 총 441건의 논문데이터를 추출하였고, 이 논문들의 저자 키워드 동시 등장 관계를 기반으로 차세대 생산혁신 기술 네트워크를 구축하였다. 구축된 기술 네트워크를 바탕으로 중심성 및 키워드 그룹 분석을 통해 주요 기술을 탐색하였다. 그 결과 'digital twin', 'modeling and simulation' 등 가상세계와 물리세계를 실시간으로 완벽하게 연결하여 인사이트를 발견하고, 이를 설계 및 공정에 반영하는 기술들이 주요 기술로 분석되었다. 이러한 결과는 관련 산업 내에서 4차 산업혁명으로 인한 변화를 대비하는 기업들에게 의미 있는 정보를 줄 수 있을 것으로 기대된다.

• International Journal of Control, Automation, and Systems
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• 제2권2호
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• pp.247-255
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• 2004

The majority of real-world problems encountered by engineers involve simultaneous optimization of competing objectives. In this case instead of single optima, there is a set of alternative trade-offs, generally known as Pareto-optimal solutions. The use of evolutionary algorithms Pareto GA, which was first introduced by Goldberg in 1989, has now become a sort of standard in solving Multiobjective Optimization Problems (MOPs). Though this approach was further developed leading to numerous applications, these applications are based on Pareto ranking and employ the use of the fitness sharing function to maintain diversity. Another scheme for solving MOPs has been presented by J. Nash to solve MOPs originated from Game Theory and Economics. Sefrioui introduced the Nash Genetic Algorithm in 1998. This approach combines genetic algorithms with Nash's idea. Another central achievement of Game Theory is the introduction of an Evolutionary Stable Strategy, introduced by Maynard Smith in 1982. In this paper, we will try to find ESS as a solution of MOPs using our game model based co-evolutionary algorithm. First, we will investigate the validity of our co-evolutionary approach to solve MOPs. That is, we will demonstrate how the evolutionary game can be embodied using co-evolutionary algorithms and also confirm whether it can reach the optimal equilibrium point of a MOP. Second, we will evaluate the effectiveness of our approach, comparing it with other methods through rigorous experiments on several MOPs.

• 한국발생생물학회지:발생과생식
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• 제22권2호
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• pp.133-142
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• 2018

Patients with type II diabetes mellitus are more susceptible to colorectal cancer (CRC) incidence than non-diabetics. The anti-diabetic drug metformin is most commonly prescribed for the treatment of this disease and has recently shown antitumor effect in preclinical studies. The aberrant mutational activation in the components of RAS/RAF/MEK/ERK and PI3K/AKT/mTOR signaling pathway is very frequently observed in CRC. We previously reported that metformin inhibits the phosphorylation of ERK and BEZ235, a dual inhibitor of PI3K and mTOR, has anti-tumor activity against HCT15 CRC cells harboring mutations of KRAS and PIK3CA. Therefore, we hypothesized that simultaneous inhibition of two pathways by combining metformin with BEZ235 could be more effective in the suppression of proliferation than single agent treatment in HCT15 CRC cells. Here, we investigated the combinatory effect of metformin and BEZ235 on the cell survival in HCT15 CRC cells. Our study shows that both of the two signaling pathways can be blocked by this combinational strategy: metformin suppressed both pathways by inhibiting the phosphorylation of ERK, 4E-BP1 and S6, and BEZ235 suppressed PI3K/AKT/mTOR pathway by reducing the phosphorylation of 4E-BP1 and S6. This combination treatment synergistically reduced cell viability. The combination index (CI) values ranged from 0.44 to 0.88, indicating synergism for the combination. These results offer a preclinical rationale for the potential therapeutic option for the treatment of CRC.

• Journal of Microbiology and Biotechnology
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• 제22권12호
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• pp.1613-1620
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• 2012

Bacterial wilt caused by Ralstonia solanacearum is a devastating disease of many economically important crops. Since there is no promising control strategy for bacterial wilt, phage therapy could be adopted using virulent phages. We used phage PE204 as a model lytic bacteriophage to investigate its biocontrol potential for bacterial wilt on tomato plants. The phage PE204 has a short-tailed icosahedral structure and double-stranded DNA genome similar to that of the members of Podoviridae. PE204 is stable under a wide range of temperature and pH, and is also stable in the presence of the surfactant Silwet L-77. An artificial soil microcosm (ASM) to study phage stability in soil was adopted to investigate phage viability under a controlled system. Whereas phage showed less stability under elevated temperature in the ASM, the presence of host bacteria helped to maintain a stable phage population. Simultaneous treatment of phage PE204 at $10^8$ PFU/ml with R. solanacearum on tomato rhizosphere completely inhibited bacterial wilt occurrence, and amendment of Silwet L-77 at 0.1% to the phage suspension did not impair the disease control activity of PE204. The biocontrol activities of phage PE204 application onto tomato rhizosphere before or after R. solanacearum inoculation were also investigated. Whereas pretreatment with the phage was not effective in the control of bacterial wilt, post-treatment of PE204 delayed bacterial wilt development. Our results suggested that appropriate application of lytic phages to the plant root system with a surfactant such as Silwet L-77 could be used to control the bacterial wilt of crops.

• Journal of Electrochemical Science and Technology
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• 제10권3호
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• pp.302-312
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• 2019

The voltage produced from the salinity gradient in reverse electrodialysis (RED) increases proportionally with the number of cell pairs of alternating cation and anion exchange membranes. Large-scale RED systems consisting of hundreds of cell pairs exhibit high voltage of more than 10 V, which is sufficient to utilize water electrolysis as the electrode reaction even though there is no specific strategy for minimizing the overpotential of water electrolysis. Moreover, hydrogen gas can be simultaneously obtained as surplus energy from the electrochemical reduction of water at the cathode if the RED system is equipped with proper venting and collecting facilities. Therefore, RED-driven water electrolysis system can be a promising solution not only for sustainable electric power but also for eco-friendly hydrogen production with high purity without $CO_2$ emission. The RED system in this study includes a high membrane voltage from more than 50 cells, neutral-pH water as the electrolyte, and an artificial NaCl solution as the feed water, which are more universal, economical, and eco-friendly conditions than previous studies on RED with hydrogen production. We measure the amount of hydrogen produced at maximum power of the RED system using a batch-type electrode chamber with a gas bag and evaluate the interrelation between the electric power and hydrogen energy with varied cell pairs. A hydrogen production rate of $1.1{\times}10^{-4}mol\;cm^{-2}h^{-1}$ is obtained, which is larger than previously reported values for RED system with simultaneous hydrogen production.

• 대한본초학회지
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• 제36권1호
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• pp.67-76
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• 2021

Objective : Yukgunja-tang is one of the herbal prescriptions widely used for functional indigestion. In this study, we evaluated the pharmacological effect through the Yukgunja-tang formulation development. Methods : The RAW 264.7 cells were pretreated with Yukgunja-tang tablet (YGJT-T : 50, 100 and 200 ㎍/㎖) and then stimulated with lipopolysaccharide (LPS : 500 ng/㎖). Cell viability, inflammatory mediators such as nitric oxide (NO) and prostaglandin E2 (PGE2) and inflammatory cytokines (IL-1β, IL-6, and TNF-α) were measured. Also, ICR mice induced acute gastritis by oral administration of 150 mM HCl in 60% ethanol. The YGJT-T (30 mg/kg) was pretreated for 3 days, and 150 mM HCl in 60% ethanol was orally administered 1 hour after the last drug treatment. Mice were sacrificed 1 hour after oral administration of 150 mM HCl in 60% ethanol. The gastric mucosa was observed, and inflammatory cytokines in the gastric tissue were measured. Results : The marker components of YGJT-T were determined by simultaneous analysis using HPLC. In RAW 264.7 cells, pretreatment of YGJT-T was non-toxic and inhibited the production of inflammatory mediators such as NO and PGE2 and suppressed inflammatory cytokines. In addition, pretreatment of YGJT-T improved bleeding and edema due to gastric lesions caused by acute gastritis and suppressed inflammatory cytokines. Conclusion : In summary, our results confirmed that treatment with YGJT-T has anti-inflammatory and anti-gastritis effects in vitro and in vivo. Therefore, in this study, YGJT-T could support a potential strategy for the prevention and treatment of gastritis.