• Journal of Magnetics
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• 제20권3호
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• pp.295-301
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• 2015

We evaluated certain issues related to magnetic resonance imaging (MRI) coupled with the use of active 2.5 GHz radio frequency identification (RFID) tags for patient identification using low field (0.3 T) MRI and computed tomography (CT) scans. We also investigated the performance of the RFID reader located outside the MRI room by considering several factors. A total of ten active RFID tags were exposed to several MRI sequences and X-rays of CT scan. We found that only card type active RFID tags are suitable for patient identification purpose in MRI environment and both wristbands as well as card tags were suitable for the same in CT environment. Severe artifacts were found in the captured MRI and CT images when the area of the imaging was in proximity to the tags. No external factors affected the performance of active RFID reader stationed outside the MRI scan room.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.180-187
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• 2016

The independent operation of a color filter for incident polarization is demonstrated using a guided-mode resonance (GMR) filter employing a metal-insulator-metal (MIM) waveguide. To achieve independent operation, a rectangular MIM grating is proposed as a wave-guide resonator. The design considerations are discussed and include how to determine the grating period and slit width. Power flow distribution is observed with slit width variation. Blue-green, green-red, and blue-red filters for corresponding x- and y-polarizations are demonstrated as application examples with numerical simulation with rectangle-shaped MIM grating. As a practical application, feasibility as a chromatic polarizer is discussed.

• Structural Engineering and Mechanics
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• 제75권1호
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• pp.87-100
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• 2020

The present paper investigates the combination resonance behavior of imperfect spiral stiffened functionally graded (SSFG) cylindrical shells with internal and external functionally graded stiffeners under two-term large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation, which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness, to account for the vibration hardening/softening phenomena and damping considerations. With regard to classical plate theory of shells, von-Kármán equation and Hook law, the relations of stress-strain are derived for shell and stiffeners. The spiral stiffeners of the cylindrical shell are modeled according to the smeared stiffener technique. According to the Galerkin method, the discretized motion equation is obtained. The combination resonance is obtained by using the multiple scales method. Finally, the influences of the stiffeners angles, foundation type, the nonlinear elastic foundation coefficients, material distribution, and excitation amplitude on the system resonances are investigated comprehensively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.612-617
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• 2000

This paper describes the experience gained from the treatments for prevention of blade failure occurred in the low-pressure turbine. Some cracks due to high cycle fatigue were found at the blades in low-pressure turbines after long time operation. Such failure was mainly caused by the resonance of the blade with the vane passing frequency excitation. If a natural frequency of the blade exists near the excitation frequency, a resonant vibration can occur and leads to a large amount of stress which may cause fatigue failures in turbine blades. To avoid the resonance of the blade, some modifications have been performed and full-scaled mockup testing has been done to confirm the verification for modification. Test result shows that enlarging the span cover is very useful to change the natural frequency of the grouped blades effectively.

• Investigative Magnetic Resonance Imaging
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• 제22권4호
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• pp.272-276
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• 2018

Extra-articular tenosynovial giant cell tumor (TS-GCT) in retropharyngeal space is a rare case. We found only two case reports in the literature, in which one was located in retropharynx or prevertebral space of the cervical spine. We describe a rare case of TS-GCT in the retropharynx, which was initially misdiagnosed as oropharyngeal cancer. Furthermore, we want to assure that extraarticular diffuse type TS-GCT should be considered in the differential diagnosis of lesions showing low signal intensity in MRI scan.

• Bulletin of the Korean Chemical Society
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• 제11권3호
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• pp.235-238
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• 1990

Complexes of the type[Co(T)(L-pro)], where T is the quadridentate $N_2O_2$-type ligand, N,N'-dimethylethylenediamine-N,N'-diacetate or N,N'-dimethylethylenediamine-N,N'-di-$\alpha$-butyrate, have been prepared. The complexes were separated into the two stereoisomers, $\Delta$-s-cis-[Co(T)(L-pro)] and $\Lambda$-s-cis-[Co(T)(L-pro)]. They were characterized by their proton magnetic resonance, absorption and circular dichroism spectra, elemental analyses.

• 조명전기설비학회논문지
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• 제18권2호
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• pp.115-124
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• 2004

본 논문은 링형 초음파모터의 진동모드에 의한 진동특성 개선을 제안하였다. 고정자의 압전세락믹과 탄성체에 대한 설계는 공진주파수, 진동모드 및 결합계수 등을 고려한 유한요소법(FEM)에 의해 계산되었다. 6차로부터 8차까지의 진동해석 결과를 통하여, 7차 모드는 결합효율, 최소전력소비 및 굴곡 진동에 있어서 매우 우수한 결과를 얻었다. 또한 7차 모드 이상에서는 입력전압에 대한 출력전류가 매우 크게 증가함을 알 수 있었다. 두께 0.5[mm]∼2[mm]까지의 진동계산 결과 0.5[mm]에서 진동변위가 매우 높은 값을 지님을 알 수 있었다. 이러한 해석결과로부터 본 연구에서는 약 43.86[KHz]의 공진주파수을 갖는 외경 50[mm], 내경 22[mm]의 초음파모터를 제조하였으며 다음의 시뮬레이션 결과 42.2[KHz]와 실험결과43.86(KHz)의 값을 얻었다. 따라서 본 논문의 타당성은 시뮬레이션 결과와 실험결과의 비교 검토를 통하여 거의 일치하는 결과를 입증하였다.

• Journal of Korean Neurosurgical Society
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• 제66권4호
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• pp.418-425
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• 2023

Objective : Deciphering the anatomy of posterior communicating artery (PCoA) aneurysms in relation to surrounding structures is essential to determine adjuvant surgical procedures. However, it is difficult to predict surgical structures through preoperative imaging studies. We aimed to present anatomical structures using preoperative high-resolution three-dimensional proton density-weighted turbo spin-echo magnetic resonance (PDMR) imaging with simple classification. Methods : From January 2020 to April 2022, 30 patients underwent PDMR before microsurgical clipping for unruptured PCoA aneurysms in a single tertiary institute. We retrospectively reviewed the radiographic images and operative data of these patients. The structural relationship described by PDMR and intraoperative findings were compared. Subsequently, we classified aneurysms into two groups and analyzed the rate of adjuvant surgical procedures and contact with the surrounding structures. Results : Correlations between preoperative PDMR predictions and actual intraoperative findings for PCoA aneurysm contact to the oculomotor nerve, temporal uncus, and anterior petroclinoid fold (APCF) reported a diagnostic accuracy of 0.90, 0.87, and 0.90, respectively. In 12 patients (40.0%), an aneurysm dome was located on the plane of the oculomotor triangle and was classified as the infratentorial type. Compared to the supratentorial type PCoA aneurysm, adjuvant procedures were required more frequently (66.7% vs. 22.2%, p=0.024) for infratentorial type PCoA aneurysm clipping. Conclusion : Preoperative PCoA aneurysm categorization using PDMR can be helpful for predicting surgical complexity and planning of microsurgical clipping.

• 한국항공우주학회지
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• 제32권10호
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• pp.112-117
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• 2004

본 연구는 공기역학적 운동에너지를 이용하여 점화장치를 구성하는데 따른 해석과 실험에 관한 연구로써 공기역학 점화기는 크게 노즐과 공명관으로 구성되어 있다. 압축가스가 노즐을 통과하여 공명관으로 유입되며, 이때 노즐과 공명관사이에 압력맥동이 발생한다. 이러한 압력맥동에 의한 운동에너지는 일정한 조건하에 공명관 내부에서 열에너지로 변화하게 된다. 본 연구에서는 음속노즐과 초음속 노즐을 두개의 각기 다른 공명관에서 실험과 수치해석을 실시하였으며, 노즐표면의 마찰손실과 공기역학 손실을 최소화하는 초음속 노즐의 최적형상을 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 합동춘계학술대회 논문집 전기물성,응용부문
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• pp.179-180
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• 2008

In this paper, the variable tendency piezoelectric constant and resonance characteristics piezoelectric ceramics due to the electric field is studied. The practical application of piezoelectric ceramics is not only applied in field of small signal. For example, in case of an ultrasonic motor, $120{\sim}130Vrms$ of driving voltage is needed and that of an piezoelectric pump, $200{\sim}220Vrms$ of voltage is required. Therefore, to examine the characteristics of piezoelectric ceramics in large signal contributes to reducing the susceptibility to the multifarious application and securing the ease of the production of control circuit. These contributions may be connected to the expansion of industrial application. We fabricated disk-type piezoelectric ceramic samples by using conventional method and measured the resonance characteristics of these samples under from low to high voltage driving conditions. According to increasing the value of the input voltage, we measured the resonance frequency of the piezoelectric ceramic, and inquired into the cause of these phenomena.