• 제목/요약/키워드: electronic state

검색결과 3,085건 처리시간 0.029초

Structure and Physical Properties of Fe/Si Multiayered Films with Very Thin Sublayers

  • Baek, J.Y;Y.V.Kudryavtsev;J.Y.Rhee;Kim, K.W.;Y.P.Le
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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    • pp.173-173
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    • 2000
  • Multilayered films (MLF) consisting of transition metals and semiconductors have drawn a great deal of interest because of their unique properties and potential technological applications. Fe/Si MLF are a particular topic of research due to their interesting antiferromagnetic coupling behavior. although a number of experimental works have been done to understand the mechanism of the interlayer coupling in this system, the results are controversial and it is not yet well understood how the formation of an iron silicide in the spacer layers affects the coupling. The interpretation of the coupling data had been hampered by the lack of knowledge about the intermixed iron silicide layer which has been variously hypothesized to be a metallic compound in the B2 structure or a semiconductor in the more complex B20 structure. It is well known that both magneto-optical (MO0 and optical properties of a metal depend strongly on their electronic structure that is also correlated with the atomic and chemical ordering. In order to understand the structure and physical properties of the interfacial regions, Fe/Si multilayers with very thin sublayers were investigated by the MO and optical spectroscopies. The Fe/si MLF were prepared by rf-sputtering onto glass substrates at room temperature with a totall thickness of about 100nm. The thicknesses of Fe and Si sublayers were varied from 0.3 to 0.8 nm. In order to understand the fully intermixed state, the MLF were also annealed at various temperatures. The structure and magnetic properties of Fe/Si MLF were investigated by x-ray diffraction and vibrating sample magnertometer, respectively. The MO and optical properties were measured at toom temperature in the 1.0-4.7 eV energy range. The results were analyzed in connection with the MO and optical properties of bulk and thin-film silicides with various structures and stoichiometries.

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RBFNN을 가진 적응형 슬라이딩 모드를 이용한 쿼드로터 무인항공기의 제어 (Control of Quadrotor UAV Using Adaptive Sliding Mode with RBFNN)

  • 탁한호
    • 융합신호처리학회논문지
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    • 제23권4호
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    • pp.185-193
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    • 2022
  • 본 논문은 쿼드로터 무인기의 위치 및 자세 추적 제어 성능을 향상시키기 위해 RBFNN 방식을 이용한 적응형 슬라이딩 모드 제어를 제안한다. RBFNN은 UAV 동적 모델에서 비선형 함수의 근사화에 활용되며, RBFNN의 가중치는 슬라이딩 표면에 부딪혀 미끄러지는 상태를 보장하기 위해 Lyapunov 안정성 분석의 적응 법칙에 따라 온라인으로 조정된다. 네트워크 근사 오류를 보상하고 기존 채터링 문제를 제거하기 위해 슬라이딩 모드 제어 항은 적응 법칙에 의해 조정되어 시스템의 강력한 성능을 향상시킨다. 제안된 제어 방법의 시뮬레이션 결과는 비선형 쿼드로터 무인 항공기에 적용된 제안된 제어기의 효율성을 확인하였다. 그 결과, 제안된 제어 시스템이 만족스러운 제어 성능과 견고성을 달성함을 알 수 있었다.

교통정보 수집 및 감시 동시운영을 위한 CCTV 카메라 자율자세 보정 알고리즘 개발에 관한 연구 (A Study on the Development of CCTV Camera Autonomous Posture Calibration Algorithm for Simultaneous Operation of Traffic Information Collection and Monitoring)

  • 김준규;정준호;한학용;신치현
    • 한국ITS학회 논문지
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    • 제22권1호
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    • pp.115-125
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    • 2023
  • 본 논문은 교통상태 감시 등 교통관제를 위해 설정한 CCTV 카메라의 화각 상태에서 교통량, 속도 등 교통정보 수집을 동시에 수행할 수 있는 CCTV 카메라 자세보정 알고리즘 개발에 관한 것이다. 개발한 자율자세보정 알고리즘은 차량인식 및 추적기법을 이용하여 도로를 식별하고, 운영자의 교통감시 및 교통정보 수집을 위한 화각을 결정한다. 제안 알고리즘의 성능검증은 현장에 설치한 CCTV를 이용하였으며, 교통감시 및 교통정보 수집을 위해 각각 설정한 화각에 대해 자율자세보정 알고리즘이 자동 산출한 화각의 결과와 비교하였다. 분석결과 운영자 감시를 위한 화각은 상호 96%의 일치성을 보였다. 교통정보의 경우는 교통량 및 속도의 정확도가 각각 96%, 95%로 산출됐으며 수동 설정한 화각과 비교할 때 약 2%의 오차가 발생하는 것으로 나타났다. 결과적으로 제안 알고리즘을 통해 관제용 CCTV를 이용하여 교통정보 수집 및 교통상황 감시를 동시에 수행할 수 있음을 확인하였다.

종설: 동적 부하가 배터리에 미치는 영향 (REVIEW: Dynamic force effects on batteries )

  • 지성현;정택수;백승훈;이병용
    • 한국음향학회지
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    • 제41권6호
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    • pp.669-679
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    • 2022
  • 리튬이온 배터리는 다양한 전자장치에 사용되어왔다. 리튬이온 배터리의 사용이 대중화됨에 따라, 온도, 진동, 쇼크 및 충전 환경과 같은 다양한 요인들이 배터리의 전기화학적 거동 변화에 미치는 영향을 밝히기 위한 연구가 활발히 진행되고 있다. 한편, 지구온난화가 심화되면서 자동차 회사들은 내연기관을 대체하는 파워시스템으로 리튬 이온 배터리를 사용하기 시작했다. 하지만, 배터리는 정적인 시스템을 기반으로 발전되어왔다. 이러한 관점에서, 구조 진동체의 변수와 배터리의 관계를 밝히기 위한 많은 노력이 이루어지고 있다. 본 종설 다이나믹 시스템과 배터리의 관계에 대한 그간의 연구를 요약하고 이를 바탕으로 앞으로의 연구에 대해 전망하고자 한다. 먼저, 전기차의 진동프로파일을 모델링하는 방법에 논하고, 이들이 배터리에 적용되었을 때의 전기화학적 거동에 대하여 다루었다. 이어서 물리적 충격 및 관통, 초음파 등이 배터리에 대해 미치는 영향을 기술하였다. 마지막 단락에서는 전기차와 배터리의 공존 관점에서, 다이내믹 구조물에 특화된 배터리의 디자인, 배터리에 초점을 맞춘 다이내믹 구조물의 관점에서 전기차 샤시 및 배터리에 대한 견해를 기술하였다.

인이 도핑된 NiCo2O4 전극 제조 공정의 간소화를 통한 전극 특성의 변화 (Variations in electrode characteristics through simplification of phosphorus-doped NiCo2O4 electrode manufacturing process)

  • 이석희;차현진;박정환;손영국;황동현
    • 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%.

한국의 원양어업 IUU어업지수 개선방안 연구 (A study on improving the IUU Fishing Index of Korea's distant water fisheries)

  • 김장근;권유정;이해원;김두남;이재봉
    • 수산해양기술연구
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    • 제59권4호
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    • pp.362-376
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    • 2023
  • The IUU Fishing Index is composed of 40 indicators. These indicators were grouped by state responsibilities (flag, coastal, port, and general including market) defined in the FAO IPOA-IUU (2001) and then by type into vulnerability, prevalence, and response. A total of 152 coastal nations was surveyed. Korea's total combined IUU Fishing Index was 2.49 in 2019 and 2.91 in 2021, indicating a drop in the ranking to the third worst out of 152 countries followed by China and Russia in 2021. The indicators that increased the IUU fishing risk in 2021 compared to 2019 included seven indicators of prevalence and two indicators of response while those reducing the risk included one prevalence and one response indicator. The IUU Fishing Index revealed that many fisheries observers and monitoring, control and surveillance (MCS) practitioners active in the waters of RFMOs jurisdiction where Korean distant water vessels operate have mentioned concerns about the compliance with RFMO conservation measures or fishing practices. It suggested that strengthening management intervention in the fishing sector is needed. The primary tool for management is the MCS system. Given the logistical difficulty of oversight from land, air and at-sea, there is a need to enhance MCS strategies through logbook data, at-sea observer and electronic monitoring program. It also suggested that MSC fisheries certification and fisheries improvement projects, which are widely used for improving fishing sector performance, could contribute to the eradication of IUU fishing and the promotion of sustainable distant water fisheries.

청각 연구에서 기능적 뇌 영상 기술 적용에 대한 고찰: 난청을 중심으로 (A review of the Implementation of Functional Brain Imaging Techniques in Auditory Research focusing on Hearing Loss)

  • 설혜윤;신재영
    • 대한의용생체공학회:의공학회지
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    • 제45권1호
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    • pp.26-36
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    • 2024
  • Functional brain imaging techniques have been used to diagnose psychiatric disorders such as dementia, depression, and autism. Recently, these techniques have also been actively used to study hearing loss. The present study reviewed the application of the functional brain imaging techniques in auditory research, especially those focusing on hearing loss, over the past decade. EEG, fMRI, fNIRS, MEG, and PET have been utilized in auditory research, and the number of research studies using these techniques has been increasing. In particular, fMRI and EEG were the most frequently used technique in auditory research. EEG studies mostly used event-related designs to analyze the direct relationship between stimulus and the related response, and in fMRI studies, resting-state functional connectivity and block designs were utilized to analyze alterations in brain functionality in hearing-related areas. In terms of age, while studies involving children mainly focused on congenital and pre- and post-lingual hearing loss to analyze developmental characteristics with and without hearing loss, those involving adults focused on age-related hearing loss to investigate changes in the characteristics of the brain based on the presence of hearing loss and the use of a hearing device. Overall, ranging from EEG to PET, various functional brain imaging techniques have been used in auditory research, but it is difficult to perform a comprehensive analysis due to the lack of consistency in experimental designs, analysis methods, and participant characteristics. Thus, it is necessary to develop standardized research protocols to obtain high-quality clinical and research evidence.

Unraveling the hypoxia modulating potential of VEGF family genes in pan-cancer

  • So-Hyun Bae;Taewon Hwang;Mi-Ryung Han
    • Genomics & Informatics
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    • 제21권4호
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    • pp.44.1-44.10
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    • 2023
  • Tumor hypoxia, oxygen deprivation state, occurs in most cancers and promotes angiogenesis, enhancing the potential for metastasis. The vascular endothelial growth factor (VEGF) family genes play crucial roles in tumorigenesis by promoting angiogenesis. To investigate the malignant processes triggered by hypoxia-induced angiogenesis across pan-cancers, we comprehensively analyzed the relationships between the expression of VEGF family genes and hypoxic microenvironment based on integrated bioinformatics methods. Our results suggest that the expression of VEGF family genes differs significantly among various cancers, highlighting their heterogeneity effect on human cancers. Across the 33 cancers, VEGFB and VEGFD showed the highest and lowest expression levels, respectively. The survival analysis showed that VEGFA and placental growth factor (PGF) were correlated with poor prognosis in many cancers, including kidney renal cell and liver hepatocellular carcinoma. VEGFC expression was positively correlated with glioma and stomach cancer. VEGFA and PGF showed distinct positive correlations with hypoxia scores in most cancers, indicating a potential correlation with tumor aggressiveness. The expression of miRNAs targeting VEGF family genes, including hsa-miR-130b-5p and hsa-miR-940, was positively correlated with hypoxia. In immune subtypes analysis, VEGFC was highly expressed in C3 (inflammatory) and C6 (transforming growth factor β dominant) across various cancers, indicating its potential role as a tumor promotor. VEGFC expression exhibited positive correlations with immune infiltration scores, suggesting low tumor purity. High expression of VEGFA and VEGFC showed favorable responses to various drugs, including BLU-667, which abrogates RET signaling, an oncogenic driver in liver and thyroid cancers. Our findings suggest potential roles of VEGF family genes in malignant processes related with hypoxia-induced angiogenesis.

크롬 취급 사업장의 작업환경 및 근로자 폭로 실태에 관한 연구 (A Study of Working Environments and Workers Exposed to Chromium)

  • 유병철;손병철;전진호;손혜숙;한용수;이채언;정운
    • Journal of Preventive Medicine and Public Health
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    • 제27권3호
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    • pp.517-530
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    • 1994
  • For the purpose of providing the basic data for health management of workers who are exposed to chromium and for improving the quality of working environment, the authors evaluated blood and urinary level of chromium, the occupational history. AST, ALT, Hb, Hct, nasal specular examinaton on 287 workers who have been dealed chromium compounds in 56 manufacturing Industries of five types, that is, 38 metal plating services(plating),4 manufacture of other fabricated metal products (fabricated metal product), 5 manufacturing of dyestuff(dyestuff), 6 dressing and dyeing of leather(leather), 3 others(manufacture of pottery and ceramic househod wares, motor vehicles, electronic valves and tubes and other electronic components) and also measured the level of chromium in air from February to October 1993. The results were as follows ; 1. The utilized type of chromium compounds was the hexavalent state in plating fabricated metal product dyestuff, leather and the trivalent state in .other, and atmosperic chromium concentration as geometric mean was $0.0138mg/m^3(0.001{\sim}0.068mg/m^3)$ in plating, $0.0115mg/m^3(0.006{\sim}0.015mg/m^3)$ in fabricated matal product, $0.068mg/m^3(0.002{\sim}0.019mg/m^3)$ in dyestuff, $0.0083mg/m^3(0.002{\sim}0.028mg/m^3)$ in leather $0.0039mg/m^3(0.003{\sim}0.005mg/m^3)$ in other by the type of industry and it exceeded TLV-TWA ($0.05mg/m^3$) in five (13.6%) of plating services. 2. The geometric mean of chromium in blood was $1.54{\mu}g/dl(0.10{\sim}3.62{\mu}g/dl)$ in Plantng, $0.94{\mu}g/dl(0.27{\sim}2.82{\mu}g/dl)$ in fabricated metal product, $0.51{\mu}g/dl(0.10{\sim}3.25{\mu}g/dl)$ in dyestuff, $0.87{\mu}g/dl(0.15{\sim}8.00{\mu}g/dl)$ in leather, $0.55{\mu}g/dl(0.20{\sim}2.28{\mu}g/dl)$ in other by the type of industry(p<0.001). 3. The geometric mean of chromium in urine was $14.47{\mu}g/l(6.90{\sim}28.00{\mu}g/l)$ in planting, $4.63{\mu}g/l(0.24{\sim}43.00{\mu}g/l)$ in fabricated metal product, $5.93{\mu}g/l(1.00{\sim}33.00{\mu}g/l)$ in dyestuff, $11.09{\mu}g/l(0.80{\sim}48.00{\mu}g/l)$ in leather, $12.41{\mu}g/l(10.10{\sim}41.00{\mu}g/l)$ in other by the type of industry(p<0.001). 4. As the result of nasal specular examination, twenty four cases (8.4%) of nasal septal perforation among 287 total subjects was observed, and there were 17 (9.7%) cases in plating, 4 csaes (14.3%) in dressing and dyeing of leather. In the comparison of chromium concentration in blood and urine between the perforated group and non-perforated group, the perforated group showed a significantly higher value as $1.883{\pm}3.055{\mu}g/dl\;and\;0.793{\pm}0.815{\mu}g/dl$(P<0.001), $21.31{\pm}34.610{\mu}g/L\;and\;9.304{\pm}11.079{\mu}g/L$ (P<0.001). 5. The mean concentration of chromium in blood, urine and the mean level of AST, ALT, Hb and Hct in exposure group were higher than those of control group(p<0.001).

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전자-정공 효과(Core-Hole Effect) 적용에 따른 SiO2 고압상들의 전자구조 및 O K-edge X-선 Raman 산란 스펙트럼 계산 결과 분석 (Core-hole Effect on Partial Electronic Density of State and O K-edge x-ray Raman Scattering Spectra of High-Pressure SiO2 Phases)

  • 김훈;이유수;이성근
    • 한국광물학회지
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    • 제30권2호
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    • pp.59-70
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    • 2017
  • $SiO_2$는 지각과 맨틀을 구성하는 풍부한 물질로 고압 상태의 $SiO_2$ 원자구조를 결정짓는 전자구조적 특성에 대한 상세한 이해는 지구 내부의 탄성과 열역학적 성질에 대한 통찰을 제공한다. $SiO_2$처럼 경원소(low-z)로 이루어진 지구 물질의 고압상 전자구조는 in situ 고압 XRS (x-ray Raman scattering) 실험을 통해 연구되어 왔다. 하지만 기존의 고압 실험 방법으로는 물질의 국소 원자구조와 XRS 스펙트럼 간 상관관계를 밝히는데 한계가 있다. 이를 극복하고 더 높은 압력에서 존재하는 $SiO_2$에 대한 XRS 정보를 얻기 위해 밀도 범함수 이론(density functional theory; DFT)에 기반을 둔 제1원리(ab initio) 계산법을 이용한 XRS 스펙트럼 계산 연구들이 진행되고 있다. 비탄성 X-선 산란에 의하여 원자핵 주변 1s 오비탈에 만들어지는 전자-정공(core-hole)은 경원소 물질의 국소 전자구조에 크게 영향을 미치기 때문에 O K-edge XRS 스펙트럼 형태를 계산할 때 중요하게 고려해야 한다. 본 연구에서는 온-퍼텐셜 선형보충파(full-potential linearized augmented plane wave; FP-LAPW) 방법론에 기반하는 WIEN2k 프로그램을 사용하여 ${\alpha}-quartz$, ${\alpha}-cristobalite$ 그리고 $CaCl_2$-구조를 갖는 $SiO_2$에 대한 O 원자 전자 오비탈의 부분 상태밀도(partial density of states; PDOS)와 O K-edge XRS 스펙트럼을 계산하였다. 또한, $CaCl_2$-구조를 갖는 $SiO_2$의 O 원자 PDOS의 전자-정공 효과의 적용 여부에 따른 차이를 비교하여, 원자핵 부근 전자구조 변화에 따른 PDOS의 피크 세기와 위치 변화가 크게 나타났다는 사실을 확인할 수 있었다. 또한 계산된 각 $SiO_2$ 구조의 O K-edge XRS 스펙트럼이 각 $SiO_2$ 구조에서 계산된 O 원자의 $p^*$ 오비탈의 PDOS 결과와 매우 유사한 형태를 갖고 있음을 확인하였다. 이는 O K-edge XRS 스펙트럼이 갖는 대부분의 특징적인 피크들이 O 원자의 점유 1s 오비탈에서 $2p^*$ 오비탈로의 전자전이에 기인하기 때문이다. 본 연구의 결과는 $SiO_2$에 대한 정확한 O K-edge XRS 스펙트럼을 계산하는데 있어 전자-정공 효과를 고려해야 한다는 사실을 보여준다. 또한, 실험적으로는 재현이 어려운 고압 환경에 존재하는 $CaCl_2$-구조를 갖는 $SiO_2$ (~63 GPa)에 대한 O K-edge XRS 스펙트럼 계산을 통해, 제1원리 계산이 고압상 물질의 물성 연구에 이용될 수 있다는 사실을 보여준다.