• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.58-60
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• 2007

Magnetic Resonance Imaging(MRI) has become a very widely used medical procedur e. Clo.sed and open systems are typically used with static magnetic fields at or below 2 Tesla. BWhole body SAR(specific absorbsion rate) is the value of SAR averaged over the entire body of the patient over any period of 15 minutes. Head SAR is the value of SAR averaged over the head of the patient for any period of 10 minutes. SAR is a measure of the absorption of electromagnetic energy in the body' (typically in watts per kilogram (W/kg)). The normal operating mode comprises values of head SAR not higher than 3 W/kg. The second level controlled operating mode comprises values higher than 3 W/kg. Current FDA guidance limits the SAR in the whole body. including the head to a range of 1.5 to 4.0 W/kg, depending on the patient's clinical condition. SAR, limit restrictions are incorporated in all MRI systems. and domestic' s guidance limits the SAR in a part body. including the head to 3.2w/kg and less. The purpose of this study is to evaluate on change of head SAR in using MRI pulse sequence and to check if exceed 3.2(w/kg) level in domestic a part exposure through measured head SAR. 23 patient's the average head SAR of pulse sequence is that T2WI sagittal is 0.5375. T2WI axial(FSE) is 0.4817, T1WI axial(SE) is, 0.8179. FLAIR axial is 0.4580. GRE axial is 0.0077, Diffusion is 0.0824w/kg. The head SAR exposed per patient was proved 2.3845w/kg less than the international standard. Coefficient of correlation for the relations body weight and SAR or for the relations ETL(echo train length) and SAR is 1 value. Coefficient of correlation for the relations between TR(time to repeat) and SAR is -0.602 value. so SAR increased relative to weight body and ETL. But the relations between TR and SAR is negative definite.

• Journal of IKEEE
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• v.13 no.1
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• pp.65-70
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• 2009

We propose an ultrashort pulse optical code-division multiple-access (O-CDMA) scheme based on a pseudorandom binary M-sequence spectral phase encoding and decoding of coherent mode-locked laser pulses and perform a numerical simulation to analyze its feasibility. We demonstrate the ability to properly decode any of the multiple (eight) 10 Gbit/s users by the matched code selection of the spectral phase decoder. The peak power signal to noise ratio of properly and improperly decoded $8{\times}10 Gb/s$ signals could be greater than 15 for 127 M-sequence coding.

• Journal of the Korean Magnetic Resonance Society
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• v.2 no.1
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• pp.59-65
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• 1998

The correction of image artifacts due to misadjustment in tuning of RF coils (tip angle) and in the RF single sideband spectrometer was investigated using phase cycling of the $\pi$/2 and $\pi$ pulses in spin-echo sequences. A general procedure was developed for the systematic design of phase cycles that select desirable coherence transfer pathways. To analyze a phase cycling sequence, changes in the coherence level and phase factor for each RF pulse in the spin-echo cycle must be determined. Four different phase cycling schemes (FIXED, ALTERNATE, FORWARD, REVERSED) to suppress unwanted signal components such as mirror and ghost images were evaluated using two signal acquisitions. When the receiver phase factor is cycled counter-clockwise (REVERSED), these artifacts are completely removed.

• Journal of the Korean Magnetic Resonance Society
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• v.25 no.1
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• pp.1-7
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• 2021

Employing of 13C stable-isotopes in NMR metabolomics can give unique splitting patterns and coupling constants information originated from 13C-13C coupling interaction that provide an important structural information regarding the cellular metabolic process. But it has been known that an undesirable signal distortion in 2D heteronuclear correlation study, due to 13C-13C interaction, hampers an analysis of the coupling information. Recently, we proposed J-scaled distortion-free heteronuclear single-quantum coherence (HSQC) sequence which provides a distortion-free 13C-13C coupling information with a selective resolution enhancement of JCC splitting. In this paper, we dicuss theoretical aspect and practical feature of J-scaled HSQC pulse sequence. The conceptual explanation of orgin of the signal distortion by 13C-13C coupling interaction and design of J-scaled HSQC through exemplified results are provided in brief.

• Journal of the Korean Magnetic Resonance Society
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• v.10 no.1
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• pp.46-58
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• 2006

With a simple pulse sequence ($\pi/2$-{gradient, duration T}-acquisition) in solution NMR, detected signal has slowly grown up to percents of the equilibrium magnetization. The source of this unusual resurrection of dephased magnetization after a crushed gradient is cross-correlated effects of radiation damping and the distant dipolar field, which has been demonstrated by a numerical simulation and theoretical analysis.

• Investigative Magnetic Resonance Imaging
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• v.4 no.1
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• pp.1-6
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• 2000

Protocol이란 Dorland의 의학사전에 의하면 "어떤 술기의 절차에 대한 명백하고 상세한 계획서(an explicit detiled plan of a procedure)"로 정의된다. 그래서 liver MR imaging protocol은 간에 발생한 병적 문제를 해결하기 위해서, 자기공명 영상술을 실시하는 구체적이고 세부적인 지침서를 말하게 된다. 그러나 현실적으로 병원에 따라 imaging protocol은 조금씩 다르다. 왜냐하면 자기공명영상 장비가 다르고, 적절한 펄스파형(pulse sequence)에 대한 통일된 안이 없기 때문이다. 자기공명영상술은 지금도 계속해서 빠르게 발전하고 있기 때문에, 현재 통용되는 영상 술기에 대한 자세한 지침은 곧 소용이 없게 된다. 그래서 본 소고에서는 간의 자기공명영상화의 병변의 특성화에 대한 기본적인 면에 더욱 중점을 두고 기술하고자 한다.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.35-45
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• 2001

근골격계 관련 질환은 자기공명영상(MRI)에 있어서 중요한 적응증 중 하나이다. 조직간 대조도가 우수하고 원하는 방향으로 촬영이 가능한 자기공명영상은 근골격계 부위의 촬영에 적합하고 탁월한 역할을 나타낸다. 특히 최근까지 MRI는 표면코일, 경사자기(gradient)관련 기기 및 박동연쇄(pulse sequence)의 지속적이고 빠른 발달에 힘입어 영상의 질과 진단능력이 비약적으로 발전하였고 MR장비의 세대교체가 빠르게 진행되고 있다.

• Proceedings of the KSMRM Conference
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• 1999.04a
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• pp.43-54
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• 1999

Protocol이란 Dorland의 의학사전에 의하면 "어떤 술기의 절차에 대한 명백하고 상세한 계획서(an explicit detailed plan of a procedure)"로 정의된다. 그래서 liver MR imaging protocol은 간에 발생한 병적 문제를 해결하기 위해서, 자기공명영상술을 실시하는 구체적이고 세부적인 지침서를 말하게 된다. 그러나 현실적으로 병원에 따라 imaging protocol은 조금씩 다르다. 왜냐하면 MR장비가 다르고, 적절한 펄스파형(pulse sequence)에 대한 통일된 안이 없기 때문이다. 자기공명영상술은 지금도 계속해서 빠르게 발전하고 있기 때문에, 현재 통용되는 영상 술기에 대한 자세한 지침은 곧 소용이 없게 된다. 그래서 본 소고에서는 간의 MR 영상화와 병변의 특성화에 대한 기본 적인 면에 더욱 중점을 두고 기술하고자 한다. 기술하고자 한다.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.228-231
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• 1987

Microprocessor-based software DDA interpolator is developed and applied to two axis contouring control of X-Y table. Developed assembly program is composed of feedrate, linear and circular DDA interpolation routines. Reference-pulse type of open-loop stepping motor control system in which the micro-computer produces a sequence of reference pulses for each axis of motion is adopted. To test performance of the developed program, X-Y table drive system based on stepping motor and shaft encoder is designed. Contouring error of the system in linear and circular path is within .+-.0.2 mm.

• Proceedings of the Acoustical Society of Korea Conference
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• 1995.06a
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• pp.164-167
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• 1995

RPE 음성부호화기에서 합성 필터로 인한 구동벡터 양자화잡음의 증폭효과를 분석하고 regular pulse 시퀀스의 양자화로 인한 성능감쇄를 줄이기 위해 pyramid vector 양자화방식을 도입하였다. 제안된 방식의 성능평가는 구동시퀀스 양자화를 위해 adaptive PCM을 이용하는 GSM 표준 RPE 방식과의 객관적 및 주관적 성능비교를 통해 수행하였다.T JDSMDQLRY 결과 제안된 방식은 대략 1dB의 SNR 및 segmental SNR 값 증가를 가져왔고, 또한 비공식 청취시험결과 명료도의 증가를 느낄 수 있었다.