• 한국음향학회지
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• 제6권2호
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• pp.30-37
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• 1987

한글 단모음의 음향특성을 기본진동수와 배진동수를 고러하여 포만트 분석하였으며, 성도내의 공명현상과 포만트진동수와의 상관관계를 고찰하였다. 성악을 전공하는 남성으로 하여금 한글 단모음 12개를 5개의 기본진동수에 맞추어 3초 동안 발음하게 하여 FFT스펙트럼 분석기를 통해 진동수 스펙트럼을 얻었다. 포만트 분석에 의해 제 1포만트는 인두강, 그리고 제 2포만트는 구강의 공명효과에 의함을 밝혔고, 원순화가 일어나므로서 제 2포만트 진동수가 낮아짐을 발견하였다. 제 1포만트와 제 2포만트 진동수로는 "어"의 $[\partial]와[\Lambda], "아"의[a]와 [\alpha]$, 그리고"에"와 "애"의 음향학적 차이를 뚜렷이 구분짓기는 어러웠다

• 대한기계학회논문집
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• 제16권11호
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• pp.2098-2110
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• 1992

본 연구에서는 중간평면의 비선형 신장을 고려한 원판의 강제진동을 해석하기 위해 Fig.1과 같은 경계조건 즉 꺽쇠로 고정된(clamped) 경우를 생각한다.이 경우 에 고유진동수 사이엔 .omega.$_{1}$＋2.omega.$_{2}$＝.omega.$_{3}$의 관계가 존재하는데 이 관계가 내부공진 조건이 됨이 입증된다. 원판에 작용하는 가진력으로는 조화가진을 가정하 고 가진진동수가 2.omega.$_{1}$＋.omega.$_{2}$에 가까운 경우 즉 조합공진(combination reso- nance)일 때를 고려한다.

• Investigative Magnetic Resonance Imaging
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• 제24권3호
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• pp.95-122
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• 2020

In this article, we evaluated the performance of radiofrequency (RF) coils in terms of the signal-to-noise ratio (S/N) and homogeneity of magnetic resonance images when used for ultrahigh-frequency (UHF) 7T magnetic resonance imaging (MRI). High-quality MRI can be obtained when these two basic requirements are met. However, because of the dielectric effect, 7T magnetic resonance imaging still produces essentially a non-uniform magnetic flux (|B₁|) density distribution. In general, heterogeneous and homogeneous RF coils may be designed using electromagnetic (EM) modeling. Heterogeneous coils, which are surface coils, are used in consideration of scalability in the |B₁| region with a high S/N as multichannel loop coils rather than selecting a single loop. Loop coils are considered state of the art for their simplicity yet effective |B₁|-field distribution and intensity. In addition, combining multiple loop coils allows phase arrays (PA). PA coils have gained great interest for use in receiving signals because of parallel imaging (PI) techniques, such as sensitivity encoding (SENSE) and generalized autocalibrating partial parallel acquisition (GRAPPA), which drastically reduce the acquisition time. With the introduction of a parallel transmit coil (pTx) system, a form of transceiver loop arrays has also been proposed. In this article, we discussed the applications and proposed designs of loop coils. RF homogeneous coils for volume imaging include Alderman-Grant resonators, birdcage coils, saddle coils, traveling wave coils, transmission line arrays, composite right-/left-handed arrays, and fusion coils. In this article, we also discussed the basic operation, design, and applications of these coils.

• Clinics in Shoulder and Elbow
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• 제4권2호
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• pp.186-190
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• 2001

Purpose: The aim of this study was to investigate the diagnostic accuracy of Neer, Hawkins provocative tests and supraspinatus manual muscle test for the assessment of impingement syndrome, partial tear and small complete tear of De rotator cuff. Materials and Methods: Seventy-one female and 115 male patients were included in the study. Patients were divided into four groups of no impingement, impingement without tear, partial tear and small complete tear of the rotator cuff, which were confirmed by sonogram, magnetic resonance imaging and surgery. Neer and Hawkins provocative tests and supraspinatus manual muscle test were performed respectively. SAS 6.12 version was used in statistical analysis. Results: We found that Neer test had 94% sensitivity, 54% specificity for impingement without tear and 89% sensitivity, 78% specificity for partial tear and 96% sensitivity, 23% specificity for small tear. Hawkins test revealed 95% sensitivity, 54% specificity for impingement without tear and 93% sensitivity, 78% specificity for partial tear and 100% sensitivity, 23% specificity for small tear. Supraspinatus manual muscle test revealed 27% sensitivity, 94% specificity for impingement without tear and 29% sensitivity, 82% specificity for partial tear and 48% sensitivity, 82% specificity for small tear. Conclusion: Neer and Hawkins tests have high sensitivity, low specificity for impingement syndrome, partial and small tear. Supraspinatus manual muscle test had low sensitivity and high specificity. However this test was not effective to differentiate the partial and small rotator cuff tear. We thought that more effective provocative test should be designed to detect the partial and small rotator cuff tear.

• Journal of Korean Neurosurgical Society
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• 제63권2호
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• pp.248-260
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• 2020

Objective : To investigate the efficiency of diffusion tensor imaging (DTI) fiber-tracking based neuronavigation and assess its usefulness in the preoperative surgical planning, prognostic prediction, intraoperative course and outcome improvement. Methods : Seventeen patients with cerebral masses adjacent to corticospinal tract (CST) were given standard magnetic resonance imaging and DTI examination. By incorporation of DTI data, the relation between tumor and adjacent white matter tracts was reconstructed and assessed in the neuronavigation system. Distance from tumor border to CST was measured. Results : The sub-portion of CST in closest proximity to tumor was found displaced in all patients. The chief disruptive changes were classified as follows : complete interruption, partial interruption, or simple displacement. Partial interruption was evident in seven patients (41.2%) whose lesions were close to cortex. In the other 10 patients (58.8%), delineated CSTs were intact but distorted. No complete CST interruption was identified. Overall, the mean distance from resection border to CST was 6.12 mm (range, 0-21), as opposed to 8.18 mm (range, 2-21) with simple displacement and 2.33 mm (range, 0-5) with partial interruption. The clinical outcomes were analyzed in groups stratified by intervening distances (close, <5 mm; moderated, 5-10 mm; far, >10 mm). For the primary brain tumor patients, the proportion of completely resected tumors increased progressively from close to far grouping (42.9%, 50%, and 100%, respectively). Five patients out of seven (71.4%) experienced new neurologic deficits postoperatively in the close group. At meantime, motor deterioration was found in six cases in the close group. All patients in the far and moderate groups received excellent (modified Rankin Scale [mRS] score, 0-1) or good (mRS score, 2-3) rankings, but only 57.1% of patients in the close group earned good outcome scores. Conclusion : DTI fiber tracking based neuronavigation has merit in assessing the relation between lesions and adjacent white matter tracts, allowing prediction of patient outcomes based on lesion-CST distance. It has also proven beneficial in formulating surgical strategies.

• 한국자기공명학회논문지
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• 제4권1호
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• pp.1-11
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• 2000

Supported vanadium oxides are being used extensively as catalysts for a variety of reactions, including partial oxidations and ammoxidations. A series of vanadium oxide supported on TiO2-ZrO2 was obtained by impregnating ammonium metavanadate slowly into a mixed precipitateof Ti(OH)4-Zr(OH)4, followed by calcining in air at high temperatures. The prepared catalysts were characterized by 51V solid-state NMR. In the calcined catalysts 51V NMR studies indicated the peaks corresponding to distorted tetrahedral vanadia species at low V2O5 contents and octahedral vanadia species at high vanadia loadings. These results illustrate the suitability of 51V NMR as a unique quantitative spectroscopic tool in the structural analysis of vanadium(V) oxide catalytic materials.

• Journal of Korean Neurosurgical Society
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• 제38권5호
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• pp.355-358
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• 2005

Objective : The purpose of this study is to analyze the patterns of intervertebral disc enhancement seen in infectious spondylitis, differentiate between two groups[tuberculous vs pyogenic spondylitis]. Methods : Between January 1994 and December 2002, 83patients underwent operative procedure with confirmed to histopathologic evaluation. Magnetic resonance[MR] images were obtained in all patients and were analyzed retrospectively. 57patients had tuberculosis and 26patients were infected by pyogens. The patterns of gadolinium enhancement of disc were classified into 4 types[post's classification] : Type I, non-enhancing; Type II, enhancement of the peripheral rim; Type III, Type II with central area and partial endplate; Type IV, general enhancement. Results : The enhancement patterns observed were as follows : Common pattern of tuberculous spondylitis was Type II, and pyogenic spondylitis was Type III. [p < 0.01] This difference may result from pathophysiologic varieties of organisms. Conclusion : Careful preoperative MR analysis of the patterns of disc enhancement occuring in infectious spondylitis can be useful for differentiating between the tuberculous and pyogenic spondylitis.

• 대한관절경학회지
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• 제11권1호
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• pp.50-53
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• 2007

슬관절에서 원판형 연골은 주로 외측에 발생하는 것이 보통이며, 내측 원판형 연골의 경우 보고가 매우 드물다. 저자들은 슬관절 동통을 주소로 내원한 22세 여자에서 자기 공명 영상 및 관절경을 이용하여 내측 원판형 연골 및 수평 파열을 진단하고 관절경하 부분 절제술로 치료하였기에 보고하고자 한다.

• 한국자기공명학회논문지
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• 제5권2호
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• pp.118-129
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• 2001

Binding interactions of cationic porphyrins, T4MPyP and TMAP with DNA oligomer d(CGCGAATTCGCG), were studied with NMR spectroscopy, W and CD spectroscopic method. Two porphyrins showed significant differences in NMR, UV and CD data upon binding to DNA. T4MPyP was considered to position more closely to DNA bases through partial intercalation as well as ionic intercalation between the positive charges of porphyrin and phosphate group of DNA at 5’-GC-3’steps. Contrast to this, TMAP was thought to bind to phosphate of DNA more or less outside of the groove.

• 대한기계학회논문집A
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• 제21권2호
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• pp.337-345
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• 1997

An analysis is presented for the response of a beam constrained by a nonlinear spring to a harmonic excitation. The system is governed by a linear partial differential equation with a nonlinear boundary condition. The method of multiple scales is used to reduce the nonlinear boundary value problem to a system of autonomous ordinary differential equations of the amplitudes and phases. The case of the third-order subharmonic resonance is considered in this study. The autonomous system is used to determine the steady-state responses and their stability.