• 제목/요약/키워드: Magnetic Barrier

검색결과 159건 처리시간 0.032초

Magnetic Resonance-Guided Focused Ultrasound in Neurosurgery: Taking Lessons from the Past to Inform the Future

  • Jung, Na Young;Chang, Jin Woo
    • Journal of Korean Medical Science
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    • 제33권44호
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    • pp.279.1-279.16
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    • 2018

  • Magnetic resonance-guided focused ultrasound (MRgFUS) is a new emerging neurosurgical procedure applied in a wide range of clinical fields. It can generate high-intensity energy at the focal zone in deep body areas without requiring incision of soft tissues. Although the effectiveness of the focused ultrasound technique had not been recognized because of the skull being a main barrier in the transmission of acoustic energy, the development of hemispheric distribution of ultrasound transducer phased arrays has solved this issue and enabled the performance of true transcranial procedures. Advanced imaging technologies such as magnetic resonance thermometry could enhance the safety of MRgFUS. The current clinical applications of MRgFUS in neurosurgery involve stereotactic ablative treatments for patients with essential tremor, Parkinson's disease, obsessive-compulsive disorder, major depressive disorder, or neuropathic pain. Other potential treatment candidates being examined in ongoing clinical trials include brain tumors, Alzheimer's disease, and epilepsy, based on MRgFUS abilities of thermal ablation and opening the blood-brain barrier. With the development of ultrasound technology to overcome the limitations, MRgFUS is gradually expanding the therapeutic field for intractable neurological disorders and serving as a trail for a promising future in noninvasive and safe neurosurgical care.

  • https://doi.org/10.3346/jkms.2018.33.e279 인용 KSCI

2단계 AlOx 절연층 공정에서 하부절연층의 산화시간에 따른 터널자기저항 특성연구 (Tunnel Magnetoresistance with Plasma Oxidation Time in Double Oxidized Barrier Process)

  • 이영민;송오성
    • 한국재료학회지
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    • 제12권3호
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    • pp.200-204
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    • 2002

  • We fabricated TMR devices which have double oxidized tunnel barrier using plasma oxidation method to form homogeneously oxidized AlO tunnel barrier. We sputtered 10 $\AA$-bottom Al layer and oxidized it by varying oxidation time for 5, 10, 20 sec. Subsequent sputtering of 13 $\AA$ - Al was performed and the matallic layer was oxidized for 120 sec. The electrical resistance changed from 700$\Omega$ to 2700$\Omega$ with increase of oxidation time, while variation of MR ratio was little spreading 27~31% which is larger than that of TMR device of ordinary single tunnel barrier. We calculated effective barrier height and width by measuring I-V curves, from which we found the barrier height was 1.3~1.5 eV, sufficient for tunnel barrier, and the barrier width(<16.2 $\AA$) was smaller than that of directly measured value by the tunneling electron microscopy. Our results may be caused by insufficient oxidation of Al precursor into $Al_2O_3$. However, double oxidized tunnel barriers were superior to conventional single tunnel barrier in uniformity and density. We found that the external magnetic field to switch spin direction of ferromagnetic layer of pinned layer breaking ferro-antiferro exchange coupling was increased as bottom layer oxidation time increased. Our results imply that we were able to improve MR ratio and tune switching field by employing double oxidized tunnel barrier process.

  • https://doi.org/10.3740/MRSK.2002.12.3.200 인용 PDF KSCI

Experimental Cats Model for Research of the Blood Ocular Barrier

  • Park Byung-Rae
    • 대한의생명과학회지
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    • 제11권4호
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    • pp.555-559
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    • 2005

  • Evaluate the triolein emulsion could disrupt the barriers and to suggest as an experimental model in blood-ocular barrier studies. Triolein emulsion was infused into the carotid artery in the experimental group ten cats. Normal saline was used in another the control group ten cats. Pre contrast and postcontrast T1-weighted MR images were obtained at 30 minutes and 3 hours after embolization. Signal intensities were evaluated in the anterior, posterior chamber and in the vitreus qualitatively and quantitatively. Postembolization 30 minutes MR images were not different from those of the control group. Postembolization 3 hour MR images demonstrated delayed contrast enhancement in the anterior chamber of the ipsilateral and contralateral eyeballs and in the posterior chamber of the ipsilateral eyeball. Delayed contrast enhancement of the posterior chamber of the ipsilateral eyeball was statistically significant (P<0.05). The present study demonstrated significant contrast enhancement in the posterior chamber with infusion of triolein emulsion and can be a model in blood-aqueous barrier studies.

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배리어 길이에 따른 매입형 영구자석 동기전동기의 Ld, Lq 특성 파라미터에 관한 연구 (Study on the Ld, Lq Characteristic Parameter of Interior Permanent Magnet Synchronous Motor in different barrier width)

  • 장익상;진창성;정대성;김승주;박재영;이주
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2008년도 제39회 하계학술대회
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    • pp.709-710
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    • 2008

  • In this paper, we calculated permanent magnetic linkage flux ${\psi}_{\alpha}$ and Ld, Lq parameters of IPMSM and compared two model which has different barrier width. IPMSM has two kinds of torque that reluctance torque and magnetic torque. In constant torque region, using the Maxwell stress tensor method, we calculated the torque and current phase angle ${\beta}$ which has appeared maximum torque. In weakening flux region, we calculated the current phase angle ${\beta}$ which flux ${\psi}_o$ lower than limited flux ${\psi}_{omax}$. From the current phase angle ${\beta}$, we calculated torque by torque equation and compared two model characteristic.

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