• Composites Research
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• 제19권2호
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• pp.13-19
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• 2006

본 논문에서는 미세 방전가공(Electrical Discharge Machining; EDM) 기계를 위한 샌드위치 구조를 설계하기 위해 복합재료의 적층 순서, 두께, 그리고 리브의 형상 등을 고려한 파라메트릭 연구를 수행하였다. 샌드위치 구조는 면재인 섬유강화 복합재료와 심재인 레진 콘크리트 및 고분자 포움으로 이루어졌다. 컬럼은 정적 굽힘강성과 비굽힘강성을 높이기 위해 십자 리브를 가진 형상으로 설계하였으며, 적층 순서와 두께를 조절하였다. 베드의 경우 양방향의 강성을 동시에 향상시키기 위해 적층 순서와 리브 형상을 조절하였다. 최적의 고강성을 얻기 위하여 리브의 두께와 면재의 두께 등 설계 파라메터의 최적치를 제안하였다. 각 설계 파라메터의 변화에 따른 구조의 정적, 동적 강성의 변화를 확인하기 위해 유한요소해석을 수행하였으며, 진동 실험을 통하여 각 요소의 고유진동수와 감쇠비를 측정하여 비교하였다. 이러한 결과로부터 고정밀 미세 방전가공 기계 구조를 위한 최적의 형상조건을 제안하였다.

• 한국표면공학회지
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• 제56권5호
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• pp.299-308
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• 2023

In this study, phosphorus (P)-doped nickel cobaltite (P-NiCo₂O₄) and nickel-cobalt layered double hydroxide (P-NiCo-LDH) were synthesized on nickel (Ni) foam as a conductive support using hydrothermal synthesis. The thermal properties, crystal structure, microscopic surface morphology, chemical distribution, electronic state of the constituent elements on the sample surface, and electrical properties of the synthesized P-NiCo₂O₄ and P-NiCo-LDH samples were analyzed using thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The P-NiCo₂O₄ electrode exhibited a specific capacitance of 1,129 Fg^-1 at a current density of 1 Ag^-1, while the P-NiCo-LDH electrode displayed a specific capacitance of 1,012 Fg^-1 at a current density of 1 Ag-1. When assessing capacity changes for 3,000 cycles, the P-NiCo₂O₄ electrode exhibited a capacity retention rate of 54%, whereas the P-NiCo-LDH electrode showed a capacity retention rate of 57%.

• 한국전자통신학회논문지
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• 제18권6호
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• pp.1151-1156
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• 2023

본 논문은 초기 리튬이온 배터리의 충·방전 데이터를 활용하여 리튬이온 배터리의 잔존 수명을 예측할 수 있는 딥러닝 모델을 제시한다. PNP(Positive and Negative Perceptron) 모델을 사용하여 DMP(Deep learning Model using PNP model)를 구축하였으며, DMP의 성능을 증명하기 위해 LSTM 모델을 사용하여 DML(Deep learning Model using LSTM model)을 구성하였다. DMP와 DML의 리튬이온 배터리의 잔존 수명 예측 성능을 비교하며, 오차 측정 방법은 RMSE(Root Mean Square Error)와 RMSPE(Root Mean Square Percentage Error)이다. 시험 데이터로 오차를 측정한 결과 DMP와 DML의 RMSE 차이는 144.62[Cycle]이며, RMSPE 차이는 3.37[%]로 DMP의 오차가 낮게 측정되었다. 이를 통해 우리는 DMP의 성능이 높은 것으로 증명하였으며, 이는 리튬이온 배터리 분야에서 PNP 모델이 LSTM 모델보다 성능이 뛰어남을 나타내었다.

• 청정기술
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• 제30권3호
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• pp.267-275
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• 2024

Lithium-ion batteries (LIBs) have attracted significant attention as potential energy storage solutions due to their high energy density, minimal self-discharge, extended cycle life, and absence of memory effects. However, conventional LIBs use graphite as the anode material and as a result struggle to meet the increasing demand for higher energy density because of the low theoretical capacity of graphite. In order to enhance Li storage capacity and address the current limitations of LIBs, this study designed and analyzed SnO₂ nanoflakes/CNF, which is an advanced anode material with a unique hierarchical structure synthesized via a facile method involving incipient wetness followed by annealing. The in-situ formed SnO₂ nanoflakes improve the electrolyte accessibility and shorten the ion and electron transport pathways, thereby enhancing the reaction kinetics. Additionally, the CNF matrix enhances the electrical conductivity, accelerates electron transport, and mitigates volume changes. The integrated SnO₂ nanoflakes/CNF cell demonstrated outstanding cycling performance and excellent rate capability, achieving a notable reversible capacity of 636 mAh g^-1 after 100 cycles at 0.1 C. This study provides valuable insights into the design of high-efficiency anode materials for the advancement of high-performance LIBs.

• 전자공학회논문지
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• 제54권4호
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• pp.99-107
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• 2017

본 논문은 기존의 리튬 배터리(lithium battery) 등가모델의 정확도 개선을 위한 배터리 모델 계수 보정기법을 제안한다. 전기자동차 등 다양한 산업분야에 사용되는 리튬 배터리의 배터리 셀간 잔존용량(SOC, state of charge) 동일하게 유지하여 배터리 수명의 단축을 최소화하기 위해 BMS(battery management system)가 연구 개발 되었지만, 배터리 셀 전압 기반의 셀 밸런싱(cell balancing) 동작으로 내부저항 및 커패시터에 따른 SOC 변화를 따라가지 못한다. 배터리 내부저항 및 커패시터에 따른 배터리 SOC 추정을 위해 다양한 배터리 등가모델이 연구되었지만, 모든 배터리에 동일하게 적용하는 것은 한계가 있으며 특히 과도상태의 배터리 상태 추정이 어렵다. 기존의 배터리 전기적 등가모델 연구는 1종의 배터리를 대상으로 5~10% 오차율로 충 방전 동적특성을 모사하며 서로 다른 전기적 특성을 갖는 실제 배터리에 적용이 부적합하다. 따라서 본 논문에서는 모델 및 용량이 다른 실제 배터리 운용환경에 적합하며 오차율 5%이하의 동적특성 모사가 가능한 배터리 모델 계수 보정 알고리즘을 제안한다. 제안하는 배터리 모델 계수 보정법 검증을 위해 3.7 V 정격전압, 280 mAh, 1600 mAh 용량의 리튬 배터리를 사용하였으며, 리튬 배터리의 전기적 등가 모델로 2단 RC Tank 모델을 사용하였다. 또한 0.25C, 0.5C, 0.75C, 1C 4가지 C-rate를 사용하여 배터리 충 방전 실험 및 모델검증을 진행하였으며 제안하는 배터리 모델 계수 보정 알고리즘을 통해 구현한 두 종류의 배터리 모델의 배터리 충 방전 특성 및 과도상태 특성의 오차율은 최대 2.13%이다.

• E2M - 전기 전자와 첨단 소재
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• 제12권7호
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• pp.7-11
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• 1999

Fully sealed field emission display in size of 4.5 inch has been fabricated using single-wall carbon nanotubes-organic vehicle com-posite. The fabricated display were fully scalable at low temperature below 415$^{\circ}C$ and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1V/${\mu}{\textrm}{m}$ and field emis-sion current of 1.5mA at 3V/${\mu}{\textrm}{m}$ (J=90${\mu}{\textrm}{m}$/$\textrm{cm}^2$)were observed. Brightness of 1800cd/$m^2$ at 3.7V/${\mu}{\textrm}{m}$ was observed on the entire area of 4.5-inch panel from the green phosphor-ITO glass. The fluctuation of the current was found to be about 7% over a 4.5-inch cath-ode area. This reliable result enables us to produce large area full-color flat panel dis-play in the near future. Carbon nanotubes (CNTs) have attracted much attention because of their unique elec-trical properties and their potential applica-tions [1, 2]. Large aspect ratio of CNTs together with high chemical stability. ther-mal conductivity, and high mechanical strength are advantageous for applications to the field emitter [3]. Several results have been reported on the field emissions from multi-walled nanotubes (MWNTs) and single-walled nanotubes (SWNTs) grown from arc discharge [4, 5]. De Heer et al. have reported the field emission from nan-otubes aligned by the suspension-filtering method. This approach is too difficult to be fully adopted in integration process. Recently, there have been efforts to make applications to field emission devices using nanotubes. Saito et al. demonstrated a car-bon nanotube-based lamp, which was oper-ated at high voltage (10KV) [8]. Aproto-type diode structure was tested by the size of 100mm $\times$ 10mm in vacuum chamber [9]. the difficulties arise from the arrangement of vertically aligned nanotubes after the growth. Recently vertically aligned carbon nanotubes have been synthesized using plasma-enhanced chemical vapor deposition(CVD) [6, 7]. Yet, control of a large area synthesis is still not easily accessible with such approaches. Here we report integra-tion processes of fully sealed 4.5-inch CNT-field emission displays (FEDs). Low turn-on voltage with high brightness, and stabili-ty clearly demonstrate the potential applica-bility of carbon nanotubes to full color dis-plays in near future. For flat panel display in a large area, car-bon nanotubes-based field emitters were fabricated by using nanotubes-organic vehi-cles. The purified SWNTs, which were syn-thesized by dc arc discharge, were dispersed in iso propyl alcohol, and then mixed with on organic binder. The paste of well-dis-persed carbon nanotubes was squeezed onto the metal-patterned sodalime glass throuhg the metal mesh of 20${\mu}{\textrm}{m}$ in size and subse-quently heat-treated in order to remove the organic binder. The insulating spacers in thickness of 200${\mu}{\textrm}{m}$ are inserted between the lower and upper glasses. The Y\ulcornerO\ulcornerS:Eu, ZnS:Cu, Al, and ZnS:Ag, Cl, phosphors are electrically deposited on the upper glass for red, green, and blue colors, respectively. The typical sizes of each phosphor are 2~3 micron. The assembled structure was sealed in an atmosphere of highly purified Ar gas by means of a glass frit. The display plate was evacuated down to the pressure level of 1$\times$10\ulcorner Torr. Three non-evaporable getters of Ti-Zr-V-Fe were activated during the final heat-exhausting procedure. Finally, the active area of 4.5-inch panel with fully sealed carbon nanotubes was pro-duced. Emission currents were character-ized by the DC-mode and pulse-modulating mode at the voltage up to 800 volts. The brightness of field emission was measured by the Luminance calorimeter (BM-7, Topcon).

• 전기학회논문지
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• 제60권6호
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• pp.1274-1279
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• 2011

The purpose of this paper is to present the manufacturing defect and damage pattern of a 3 phase 22.9/3.3kV oil immersed transformer, as well as to present an objective basis for the prevention of a similar accident and to secure data for the settlement of PL related disputes. It was found that in order to prevent the occurrence of accidents to transformers, insulating oil analysis, thermal image measurement, and corona discharge diagnosis, etc., were performed by establishing relevant regulation. The result of analysis performed on the external appearance of a transformer to which an accident occurred, the internal insulation resistance and protection system, etc., showed that most of the analysis items were judged to be acceptable. However, it was found that the insulation characteristics between the primary winding and the enclosure, those between the ground and the secondary winding, and those between the primary and secondary windings were inappropriate due to an insulating oil leak caused by damage to the pressure relief valve. From the analysis of the acidity values measured over the past 5 years, it is thought that an increase in carbon dioxide (CO2) caused an increase in the temperature inside the transformer and the increase in the ethylene gas increased the possibility of ignition. Even though 17 years have passed since the transformer was installed, it was found that the system's design, manufacture, maintenance and management have been performed well and the insulating paper was in good condition, and that there was no trace of public access or vandalism. However, in the case of transformers to which accidents have occurred, a melted area between the upper and the intermediate bobbins of the W-phase secondary winding as well as between its intermediate and lower bobbins. It can be seen that a V-pattern was formed at the carbonized area of the transformer and that the depth of the carbonization is deeper at the upper side than the lower side. In addition, it was found that physical bending and deformation occurred inside the secondary winding due to non-uniform pressure while performing transformer winding work. Therefore, since it is obvious that the accident occurred due to a manufacturing defect (winding work defect), it is thought that the manufacturer of the transformer is responsible for the accident and that it is lawful for the manufacture to investigate and prove the concrete cause of the accident according to the Product Liability Law (PLL).

• The Korean Journal of Pain
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• 제19권1호
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• pp.33-44
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• 2006

Background: Peripheral nerve injury leads to neuropathic pain, including mechanical hyperalgesia (MH). Nerve discharges produced by an injury to the primary afferents cause the release of glutamate from both central and peripheral terminals. While the role of centrally released glutamate in MH has been well studied, relatively little is known about its peripheral role. This study was carried out to determine if the peripherally conducting nerve impulses and peripheral glutamate receptors contribute to the generation of neuropathic pain. Methods: Rats that had previously received a left L5 dorsal rhizotomy were subjected to a spinal nerve lesion (SNL) or brief electrical stimulation (ES, 4 Hz pulses for 5 min) of the left L5 spinal nerve. The paw withdrawal threshold (PWT) to von Frey filaments was measured. The effects of an intraplantar (i.pl.) injection of a glutamate receptor (GluR) antagonist or agonist on the changes in the SNL- or ES-produced PWT was investigated. Results: SNL produced MH, as evidenced by decrease in the PWT, which lasted for more than 42 days. ES also produced MH lasting for 7 days. MK-801 (NMDAR antagonist), DL-AP3 (group-I mGluR antagonist), and APDC (group-II mGluR agonist) delayed the onset of MH when an i.pl. injection was given before SNL. The same application blocked the onset of ES-induced MH. NBQX (AMPA receptor antagonist) had no effect on either the SNL- or ES-induced onset of MH. When drugs were given after SNL or ES, MK-801 reversed the MH, whereas NBQX, DL-AP3, and APDC had no effect. Conclusions: Peripherally conducting impulses play an important role in the generation of neuropathic pain, which is mediated by the peripheral glutamate receptors.

• 지질공학
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• 제20권4호
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• pp.449-459
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• 2010

수치모델링은 지하굴착 지역의 지하수 유입량과 주변 지역의 지하수위 변회를 평가하기 위해서 수행하게 된다. 본 연구에서는 경기편마암복합체로 이루어진 경기도 용인시 기흥터널 지역의 터널 건설에 따른 지하수위 변동과 터널내 지하수 유출량을 평가하였다. 이를 위하여 수리지질학적 및 지질학적 자료와 전기비저항 탐사 자료를 이용하였으며, 특히 기흥터널의 남부에 위치하는 주향이동단층이 터널 내 지하수 유입량에 미치는 영향을 고려하였다. 부정류 수치 모델링 결과 그라우팅 효율이 40%일 때, 지하수 유출량은 약 $306\;m^3$/day로 평가되었으며, 이때 관측된 지하수위 변동폭(6.30 m)과 계 된 지하수위 변동폭(6.20 m)은 서로 비슷하였다.

• 한국조명전기설비학회지:조명전기설비
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• 제10권6호
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• pp.62-72
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• 1996

본 연구에서는 광화학반응법을 이용하여 오존 발생기로서의 역할과 광원으로서의 기능을 동시에 수행할 수 있는 U자형 Lamp(Olamp)를 사용한 오존 발생기를 설계 및 제작하여 Olamp의 방전 특성, 스팩트럼 특성, 조도특성, 오존생성특성 및 살균특성을 연구검토한 결과 다음과 같은 결론을 얻을 수 있었다.(1)Olamp의 스펙트럼특성을 조사한 결과 오존을 생성하는 단파장 자외선과 조명으로 활용가능한 가시광선이 방사됨을 확인할 수 있었다.(2)Olamp의 조도는 한국산업표준규격 조도 기준에 의하여 "어두운 분위기중의 시식별작업 및 간헐적인 시작업"에 사용가능한 조도 특성을 얻을 수 있었다. (3)원료가스의 유량이 작을수록 오존생성농도는 상승하고 오존 발생량은 감소하였으며, 유량이 동일할 때 모의 공기를 사용한 경우보다 산소를 사용한 경우가 오존생성농도 및 오존발생량이 상승하였다.(4)오존발생량 및 오존생성수율은 초기 오존생성농도가 높을수록 상승하였다.(5)액상에서의 용존오존농도 특성은 반응장치의 교반속도 및 오존생성속도가 높을수록 상승하였다.(6)대장균(Escherichia coli)에 대한 살균특성을 조사한 결과, 97[%]이상의 살균 특성을 얻을 수 있었다. 얻을 수 있었다.