• 대한전자공학회논문지SD
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• 제41권6호
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• pp.33-41
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• 2004

본 논문에서는, 편광측정법에 의한 광섬유 전류 센서(P-FOCS)를 실험·제작하여, 실제 필드에 적용할 수 있는 P-FOCS의 상용화 가능성에 대하여 연구하였다. P-FOCS는 인가된 전류에 의해 발생한 자기장에 비례하는 Faraday 회전각을 측정함으로서 인가된 전류를 측정한다. P-FOCS의 센싱 광섬유로는 저복굴절 광섬유를 사용하여 밴딩에 의한 선복굴절의 영향을 최소화하였으며, 벌크(bulk)한 광학소자의 사용으로 인한 광 손실을 막기 위해 전 광섬유 소자를 사용하였다. 또한, 구성된 신호처리회로는 광섬유 소자들의 연결부에서의 손실로 인한 출력 신호의 강도 변화를 제거하기 위해 사용된다. Faraday 회전각은, 632.8nm 파장의 광원을 이용하여 권선수가 약 1500인 솔레노이드에 전류를 인가해 7500A의 전류원의 효과를 얻도록 하여, 솔레노이드 내부에 센싱 광섬유를 통과시켜 측정하였다. $1000A{\sim}7500A$ 범위에서, 선형성의 측정 오차는 약 1.5% 이내였다.

• Molecules and Cells
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• 제37권2호
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• pp.126-132
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• 2014

As a tumor suppressor homologue during mitosis, Chk2 is involved in replication checkpoints, DNA repair, and cell cycle arrest, although its functions during mouse oocyte meiosis and early embryo development remain uncertain. We investigated the functions of Chk2 during mouse oocyte maturation and early embryo development. Chk2 exhibited a dynamic localization pattern; Chk2 expression was restricted to germinal vesicles at the germinal vesicle (GV) stage, was associated with centromeres at pro-metaphase I (Pro-MI), and localized to spindle poles at metaphase I (MI). Disrupting Chk2 activity resulted in cell cycle progression defects. First, inhibitor-treated oocytes were arrested at the GV stage and failed to undergo germinal vesicle breakdown (GVBD); this could be rescued after Chk2 inhibition release. Second, Chk2 inhibition after oocyte GVBD caused MI arrest. Third, the first cleavage of early embryo development was disrupted by Chk2 inhibition. Additionally, in inhibitor-treated oocytes, checkpoint protein Bub3 expression was consistently localized at centromeres at the MI stage, which indicated that the spindle assembly checkpoint (SAC) was activated. Moreover, disrupting Chk2 activity in oocytes caused severe chromosome misalignments and spindle disruption. In inhibitor-treated oocytes, centrosome protein ${\gamma}$-tubulin and Polo-like kinase 1 (Plk1) were dissociated from spindle poles. These results indicated that Chk2 regulated cell cycle progression and spindle assembly during mouse oocyte maturation and early embryo development.

• 대한의용생체공학회:의공학회지
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• 제30권6호
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• pp.461-468
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• 2009

Magnetic resonance electrical impedance tomography (MREIT) enables us to perform high-resolution conductivity imaging of an electrically conducting object. Injecting low-frequency current through a pair of surface electrodes, we measure an induced magnetic flux density using an MRI scanner and this requires a sophisticated MR phase imaging method. Applying a conductivity image reconstruction algorithm to measured magnetic flux density data subject to multiple injection currents, we can produce multi-slice cross-sectional conductivity images. When there exists a local region of fat, the well-known chemical shift phenomenon produces misalignments of pixels in MR images. This may result in artifacts in magnetic flux density image and consequently in conductivity image. In this paper, we investigate chemical shift artifact correction in MREIT based on the well-known three-point Dixon technique. The major difference is in the fact that we must focus on the phase image in MREIT. Using three Dixon data sets, we explain how to calculate a magnetic flux density image without chemical shift artifact. We test the correction method through imaging experiments of a cheese phantom and postmortem canine head. Experimental results clearly show that the method effectively eliminates artifacts related with the chemical shift phenomenon in a reconstructed conductivity image.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1461-1469
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• 2011

본 논문은 3 차원 유한요소해석 기법을 이용하여 토오크 시험을 위한 표준시험시편의 각도 및 동심 오열이 시편의 응력과 변형률 변화에 미치는 영향을 분석하였다. 해석 결과의 정량적 비교를 위해 각, 동심 및 복합 축 오열에 대한 평균 굽힘 변형률을 적용하였으며, 시편 형상에 따른 축 오열 영향을 확인하기 위해 환봉형 시편과 튜브형 시편에 대해 각각 유한요소해석을 실시하였다. 해석결과로부터 얻어진 변형률과 응력의 변화로 축 오열의 종류와 방향을 예측하는 일반적인 기준을 제시하였으며, 초기 항복조건을 적용하여 축 오열이 토오크 시편의 초기 항복 모멘트에 미치는 영향을 분석하였다.

• 한국측량학회지
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• 제32권6호
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• pp.625-635
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• 2014

Multiple strips are required for large area mapping using ALS (Airborne Laser Scanner) system. LiDAR (Light Detection And Ranging) data collected from the ALS system has discrepancies between strips due to systematic errors of on-board laser scanner and GPS/INS, inaccurate processing of the system calibration as well as boresight misalignments. Such discrepancies deteriorate the overall geometric quality of the end products such as DEM (Digital Elevation Model), building models, and digital maps. Therefore, strip adjustment for minimizing discrepancies between overlapping strips is one of the most essential tasks to create seamless point cloud data. This study implemented area-based matching (ABM) to determine conjugate features for computing 3D transformation parameters. ABM is a well-known method and easily implemented for this purpose. It is obvious that the exact same LiDAR points do not exist in the overlapping strips. Therefore, the term "conjugate point" means that the location of occurring maximum similarity within the overlapping strips. Coordinates of the conjugate locations were determined with sub-pixel accuracy. The major drawbacks of the ABM are sensitive to scale change and rotation. However, there is almost no scale change and the rotation angles are quite small between adjacent strips to apply AMB. Experimental results from this study using both simulated and real datasets demonstrate validity of the proposed scheme.

• 한국항공우주학회지
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• 제30권6호
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• pp.101-106
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• 2002

BTT 조종방식을 갖는 유도탄내에서 2축 김발형 탐색기가 그 기준축에 장착된 레이트 자이로를 사용하여 안정화되어질 때, BTT조종방식에 의한 Rolling에 따른 시선의 변화가 실제 시선변화량과 더불어 탐색기에서 측정되어진다. 이러한 동체운동 상관효과는 BTT 유도탄의 호밍루프내에서 주로 의사표적기동과 레이트자이로 정렬오차가 관계되어 있다는 것을 알 수 있었다. 본 논문에서는 이러한 각각의 동체운동 상관을 포함하는 탐색기모델과 간단한 선형 BTT 호밍루프 모델을 구축하였다. 그리고 이 모델에서 호밍루프 안정성에 대한 상관효과를 분석하였으며, 안정성 회복을 위한 선형 보상기를 제시한다.

• 한국통신학회논문지
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• 제30권2A호
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• pp.34-42
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• 2005

본 논문에서는 비동기 사용자가 존재할 때 OFDMA 상향 시스템의 성능을 주파수 선택적 페이딩 채널 환경에 대해 분석한다. 이를 위해, 각 사용자의 시간오차를 기지국 기준시간에 대한 상대적인 시간오차로 표현하고 상대적인 시간오차에 의한 다중접속간섭을 유도한다. 다중접속간섭은 주파수 선택적 페이딩 채널의 WSSUS (Wide-sense stationary uncorrelated scattering) 채널 모델에 기반하여 유도된다. 성능 분석을 위하여 다중접속간섭을 포함한 평균 신호대 간섭잡음비를 유도하고 최종적으로 평균 심볼에러확률을 표현한다. 유도된 심볼에러확률은 컴퓨터 모의실험을 통하여 분석의 정확도를 확인한다.

• 보건행정학회지
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• 제22권4호
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• pp.597-627
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• 2012

As misalignments among images, identity, and legitimacy of health professionals and institutions have been on the rise, CEOs of health care organizations have been required to enhance organizational accountability. Despite the accumulation of literature on the conceptual discussions of accountability, only a few studies empirically investigated key barriers to accountability and its facilitators. To identify perception on accountability with key barriers and facilitators of organizational accountability, a semi-structured interview with 11 CEOs of Korean hospitals was conducted. A short survey was taken to get quantitative data on CEO's perception on organizational accountability. To CEOs, accountability was very complex and unfamiliar concept, but understood as physician's code of ethics by nature and basic principle of hospital management. CEOs thought accountability could be improved through ethical leadership, financial stability and learning climate of hospitals. Distrust of the government, which failed to provide economic incentives for hospitals to increase accountability activities, was emphasized as a serious barrier to hospital accountability. There was consensus among hospital CEOs as to the importance of accountability in management. However, there were concerns that, without policy instruments to motivate hospitals toward increasing community benefits as well as collective efforts among health professionals to rebuild moral climate for being accountable, greater accountability would not be achieved in hospitals.

• 국제물리치료학회지
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• 제11권4호
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• pp.2253-2260
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• 2020

Background: Patients with low back pain (LBP) experience misalignments in the center of pressure (COP) and muscle imbalances due to frequent onesided posture adjustments to avoid pain. Objectives: To identify the effects of Squat Exercises with Vertical Whole-Body Vibration on the Center of Pressure and Trunk Muscle Activity. Design: Randomized controlled trial. Methods: Thirty LBP patients with an imbalance in the COP were sampled and randomly assigned to an experimental group of 15 patients who under went an intervention involving squat exercises with vertical WBV and a control group of 15 patients who were treated via a walking intervention. As pretests before the interventions, the subjects' COP was identified by measuring their stability index (ST), and erector spinae, rectus abdominis, transverse abdominis, gluteus medius muscle activity was analyzed by determining the % reference voluntary contraction (%RVC) value using surface electromyography while sit to stand. After four weeks, a post test was conducted to remeasure the same variables using the same methods. Results: Statistically significant differences were found in the ST (P<.01) and trunk muscle (P<.05, P<.001) in the experimental group before and after the intervention. In terms of the differences between the left- and right-side (RL) muscle activity, only the transverse abdominis (TrA) and gluteus medius (GM) exhibited statistically significant increase (P<.05). A comparison of the groups showed statistically significant differences in the TrA with respect to muscle activity (P<.05) and in the RLTrA and RLGM in terms ofthe difference between left- and right-side muscle activity (P<.01). Conclusion: Squat exercises with vertical WBV produced effective changes in the COP of patients with LBP by reducing muscle imbalances through the delivery of a uniform force. In particular, strengthening the TrA and reducing an imbalance in the GM were determined to be important factors in improving the COP.

• 천문학회보
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• 제46권1호
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• pp.38.4-39
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• 2021

The Local Volume Mapper (LVM), for the Sloan Digital Sky Survey V, consists of four 16 cm telescopes with three fiber spectrographs in the Las Campanas Observatory in Chile. With the fixed telescopes on optical tables, the Alt-Alt mounted siderostats point and guide targets during spectrograph exposures. We are developing the integrated LVM instrument control software. Considering international travel restrictions caused by the COVID-19 pandemic in 2021, we decided to make a simplified version of siderostat to test the LVM telescope control system in Korea. The prototype siderostat consists of two aluminum flat mirrors, optomechanical housing structures made by aluminum profiles, and the Planewave L-350 mount. We designed the optical mirrors and the optomechanical structure of the siderostat. From structural analysis at various pointing cases, we estimated the tilt misalignments of mirrors within 4 arcsec, which would affect the telescope pointing errors.