• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.497-504
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• 2005

Stay cables, such as are used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Several methods have been proposed and implemented to mitigate this problem, though each has its limitations. Recently some studies have shown that active and semiactive control system using MR (Magnetorheological) damper can potentially achieve both higher performance levels than passive control system and adaptability with few of the detractions. However, a control system including a power supply, controller, and sensors is required to maximize the performance of the MR damper and this complicated control system is not effective to most of large civil structures. This paper proposes a smart passive damping system using MR dampers by introducing electromagnetic induction (EMI) system as an external power source to MR damper and verified the performance of smart passive damping system for mitigating the vibration of stay cables. The performances of smart passive damping system are compared with those of linear viscous damper and passive-mode MR damper.

• 한국미생물·생명공학회지
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• 제23권6호
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• pp.641-646
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• 1995

During the screening of inhibitors of melanin biosynthesis from microbial secondary metabolites, a fungal strain MR304 which was capable of producing high level of an inhibitor was selected. Based on taxonomic studies, this fungus could be classified as Trichoderma harzianum. The active compound (MR304-1) was purified from culture broth by Diaion HP-20 column chromatography, ethylacetate extraction, Sephadex LH-20 column chromatographv and HPLC. The inhibitor was identified as 3-(1,5-dihvdroxy-3-isocyanocyclopent-(E)-3-envl)prop-2-enoate by spectroscopic methods of UV, ESIMS, $^{1}$H-NMR, $^{13}$C-NMR, NOE, HMQC and HMBC. MR304-1 showed strong mushroom tyrosinase inhibitory activity with IC$_{50}$ value of 0.25 $\mu $g/ml. It inhibited melanin biosynthesis with 15 mm inhibition zone at 30 $\mu $g/paper disc in Streptomyces bikiniensis, a bacterium used as an indicator organism in this work. It also inhibited melanin biosynthesis in B16 melanoma cells with a niinimum inhibitory concentration of 0.05 $\mu $g/ml.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1170-1176
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• 2005

The structures and conformations of ortho-, meta-, and para-methyl red (MR) upon proton gain and loss were studied by density functional calculations, and compared to methyl yellow for the effects of a carboxyl substitution. Internal hydrogen bonding causes the geometry of neutral o-MR planar, otherwise twist. Monoprotonated species of MR are planar where the proton is attached to $\beta$-azo nitrogen. This loses its azo character a bit, and shows strong delocalization characterized as a quinonoid canonical structure. Di-protonated species of MR is proved to hold two protons at the amino and $\alpha$-azo nitrogen atoms, and planar. It regains somewhat of its azo character, but still shows fairly delocalized property in terms of carbocationic canonical structures. The carboxyl substitution on 4-dimethylamino-trans-azobenzene structure has some delocalization effects on the geometry or conformation of MR derivatives whether neutral, mono-, di- or de-protonated.

• Investigative Magnetic Resonance Imaging
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• 제23권2호
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• pp.81-99
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• 2019

Recently, deep learning methods have shown great potential in various tasks that involve handling large amounts of digital data. In the field of MR imaging research, deep learning methods are also rapidly being applied in a wide range of areas to complement or replace traditional model-based methods. Deep learning methods have shown remarkable improvements in several MR image processing areas such as image reconstruction, image quality improvement, parameter mapping, image contrast conversion, and image segmentation. With the current rapid development of deep learning technologies, the importance of the role of deep learning in MR imaging research appears to be growing. In this article, we introduce the basic concepts of deep learning and review recent studies on various MR image processing applications.

• 한국가스학회지
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• 제15권6호
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• pp.38-43
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• 2011

천연가스 액화공정은 극저온에서 운전되며 에너지 소비가 매우 크기 때문에 압축기의 에너지 소모를 최소화하는 것이 공정의 효율 측면에서 중요하다. 여러 가지 천연가스 액화공정 중 C3-MR(Propane Pre-cooled Mixed Refrigerant) 공정의 경우 순수냉매인 프로판과 혼합냉매를 사용하는 두 개의 냉각 사이클로 구성되어있다. 본 연구에서는 C3-MR 공정에서 최적의 프로판 압력 레벨을 찾기 위해 프로판 사이클을 별개로 구성하여 모사하였다. 또한, 압력 레벨에 따른 조건을 변화시켜가며 사례 연구를 수행하고 이를 통해 압축기에서 소모되는 에너지양을 비교하였다. 그 결과 압력 레벨이 높을수록 총 에너지 소모량이 감소하는 것을 확인 할 수 있었다. 압력 레벨이 3일때 보다 압력 레벨이 5일 때 에너지 소모는 약 23.7% 감소하는 값을 얻을 수 있었다.

• 대한방사성의약품학회지
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• 제1권2호
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• pp.130-136
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• 2015

We evaluate the influence of MR contrast agent on positron emission tomography (PET) image using phantom, animal and human studies. Phantom consisted of 15 solutions with the mixture of various concentrations of Gd-based MR contrast agent and fixed activity of [$^{18}F$]FDG. Animal study was performed using rabbit and two kinds of MR contrast agents. After injecting contrast agent, CT or MRI scanning was performed at 1, 2, 5, 10, and 20 minutes. PET image was obtained using clinical PET/CT scan, and attenuation correction was performed using the all CT images. The values of HU, PET activity and MRI intensity were obtained from ROIs in each phantom and organ regions. In clinical study, patients (n=20) with breast cancer underwent sequential acquisitions of early [$^{18}F$]FDG PET/CT, MRI and delayed PET/CT. In phantom study, as the concentration increased, the CT attenuation and PET activity also increased. However, there was no relationship between the PET activity and the concentration in the clinical dose range of contrast agent. In animal study, change of PET activity was not significant at all time point of CT scan both MR contrast agents. There was no significant change of HU between early and delayed CT, except for kidney. Early and delayed SUV in tumor and liver showed significant increase and decrease, respectively (P<0.05). Under the condition of most clinical study (< 0.2 mM), MR contrast agent did not influence on PET image quantitation.

• Nuclear Medicine and Molecular Imaging
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• 제40권5호
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• pp.249-256
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• 2006

목적: 대장-직장암에서 간전이 여부를 진단하기 위한 영상 검사 방법으로 기존에는 CT 촬영을 시행하여 왔다. 최근에는 MR 및 FDG PET을 간전이 진단에 적극적으로 활용하고 있는 추세이다. 이에 이 연구에서는 대장-직장암 환자에서 간전이에 대한 FDG PET의 진단적 가치를 MR과 비교하여 보고자 하였다. 대상 및 방법 대장: 직장암으로 확진된 환자들 중에 간전이를 진단 또는 배제하기 위하여 CT 이외에도 MR 및 F-18-FDG PET (conventional PET 및 fusion PET)을 모두 시행한 환자는 26명이었다. 이 연구에서는 26명의 환자들에게서 영상화 된 35개의 병변을 분석의 대상으로 삼고, FDG PET과 MR의 민감도 및 특이도를 간분엽절제술 및 종양절제술을 통해 얻어진 병리소견 및 임상소견 또는 추적 영상 소견을 표준으로 하여 각각 구하였다. FDG PET과 MR은 평균 7일 간격으로 시행되었으며, 두 검사 사이에 치료적 요법을 시행 받은 환자는 한 명도 없었다. 결과: 병리 결과, 35개의 병변 중에서 18개(51.4%)의 병변은 간전이로 판명되었으며, 나머지 17개(48.6%)는 낭종, 지방, 혈관종, 농양, 호산구성농양 등의 양성 병변으로 판명되었다. 35개의 병변 중 MR과 FDG PET의 진단이 일치한 병변은 간전이 17개(94.4%)와 양성 병변 13개(76.5%)로 전체적으로는 85.7%의 일치도를 보였다. FDG PET의 민감도는 94.4% (17/18), 특이도는 94.1% (16/17)였으며 MR의 민감도는 100% (18/18), 특이도는 82.4% (14/17)이었다. MR에서 위양성을 보였던 3개의 병변은 낭종과 호산구성농양이었고, FDG PET에서 위음성을 보였던 1개의 병변은 직경 8 mm의 작은 병변이었다. 직경 10 mm 이하인 병변들만 분석했을 때, 총 20개의 병변에 대하여 FDG PET은 민감도 85.7%(6/7), 특이도 92.3%(12/13), MR은 민감도 100%(7/7), 특이도 76.9%(10/13)를 보였다. 그 외에도 간전이 병변의 평균 maxSUV는 $6.7{\pm}3.8$로 간전이와 양성병변을 최적으로 감별할 수 있는 maxSUV의 cutoff value는 3.1 이었다. (AUC=0.897, p<0.001, 민감도 83.3%, 특이도 94.1%) 결론: FDG PET은 간전이를 진단하는데 MR과 대등한 민감도와 특이도를 보였다. 통계적으로 유의한 차이를 보이지는 않았지만 간전이에 대한 FDG PET의 음성예측도는 MR보다 높았으며, 직경 10 mm 미만의 작은 병변에 대해서도 FDG PET은 우수한 성적을 보였다. 향후 대장암의 간전이 진단에 FDG PET이 유용하게 이용될 것이다.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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• pp.117-122
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• 2002

Contrast-enhanced MR angiography has become a widely used method useful for clinical diagnosis. Early studies identified a number of technical issues, and many of these have been addressed with various MRI physics innovations over the last several years. The quality of the results is high enough that CE MRA is replacing conventional x-ray angiography methods at many institutions. Ongoing research is expected to provide further improvements in performance, most notably in additional reductions in examination time, in time-resolved 3D imaging, and in improved imaging of the peripheral vasculature with extended fields of view.

• Smart Structures and Systems
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• 제1권3호
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• pp.235-256
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• 2005

The non-linear behaviour of electrorheological (ER) and magnetorheological (MR) dampers makes it difficult to design effective control strategies, and as a consequence a wide range of control systems have been proposed in the literature. These previous studies have not always compared the performance to equivalent passive systems, alternative control designs, or idealised active systems. As a result it is often impossible to compare the performance of different smart damper control strategies. This article provides some insight into the relative performance of two MR damper control strategies: on/off control and feedback linearisation. The performance of both strategies is benchmarked against ideal passive, semi-active and fully active damping. The study relies upon a previously developed model of an MR damper, which in this work is validated experimentally under closed-loop conditions with a broadband mechanical excitation. Two vibration isolation case studies are investigated: a single-degree-of-freedom mass-isolator, and a two-degree-of-freedom system that represents a vehicle suspension system. In both cases, a variety of broadband mechanical excitations are used and the results analysed in the frequency domain. It is shown that although on/off control is more straightforward to implement, its performance is worse than the feedback linearisation strategy, and can be extremely sensitive to the excitation conditions.

• 한국동물학회지
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• 제23권4호
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• pp.239-250
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• 1980

1974년부터 1979년까지 남한의 주요 하천에서 채집한 기름종개속 어류의 표본을 동정한 결과 Cobbits taenia striata Ikeda, 1936, C. taenia lutheri Rendahl, 1935의 2아종과 C. granoei Rendahl, 1935의 1종이 한국미기록이었으므로 그 형태적 특징을 기재하고 지리적 분포와 검색표에 대하여 보고한다. 이로써 우리나라의 기름종개속 어류는 모두 4종 3아종이 된다.