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폴리글리콜산 봉합재료의 역학적 성질 -유변학적 특성 및 분자량 결정-
김학용,김상용 한국섬유공학회 1996 한국섬유공학회지 Vol.33 No.2
The molecular weight of polyglycolic acid(PGA) suture materials was determined by Wu and Tuminello's method from dynamic melt rheological properties. The Plateau modulus, G and entanglement molecular weight(M) were 2.82 ×10 dyne/㎠ and 1.6 ×10 , respectively. The melt flow activation energy ranged from 31 to 44 kcal/mole for different molecular weights. After spinning at 245℃, the weight average molecular weight of PGA was decreased to one half of that before spinning. The tenacity increased with weight average molecular weight(M) until M reached 4.0 ×10 , but above this M it showed almost a constant value(0.8 GPa).
김학용,김병창,김승우 한국광학회 2001 한국광학회지 Vol.12 No.4
피조 간섭계의 측정 정밀도를 향상시키기 위해서 광 분할기를 제거한 형태의 피조 간섭계를 구현했다. 단일 모드 광섬유를 구면파 광원으로 사용했고 끝 단을 반사면으로 만들기 위해서 경면 가공했다. 반사면은 적당한 각도로 경사지게 가공되어 있는데 이것은 간섭무늬의 CCD관찰을 용이하게 한다. 경사 단면 광섬유 광원을 이용한 피조 간섭계는 기존의 피조 간섭계에서 구면파를 왜곡시키는 광 분할기를 제거함으로써 측정 정밀도를 향상시킬 수 있었다 또한 동일한 시편의 측정결과를 비교함으로써 기존의 피조 간섭계로부터 개선된 정밀도를 정량적으로 구할 수 있었다. 그리고 경사 단면 광섬유 광원의 구면파정도를 알아보기 위해서 PS/PDI(Phase Shifting/Point Diffraction Interferometer)를 구현함으로써 광원의 구면파 정도를 실험적으로 검증했다. A Fizeau interferometer without beam splitter was constructed. Single-mode optical fiber was used as a spherical wave source and the face of fiber end was polished and coated to be a reflecting surface. The reflecting surface was angled so that interference fringe could be detected by CCD camera. Beam splitter in front of a spherical wave source could distort the wave front and that was one of the component error sources. With the proposed configuration there was no need to place beam splitter in the system. Improvement of phase measuring accuracy was evaluated quantitatively by comparing the result of this setup with that of a conventional Fizeau interferometer. Wave front of the angled end-face optical fiber source was also measured to verify its sphericity by PS/PDI (Phase Shifting/Point Diffraction Interferometer). The principle of this technique was presented and the experimental results and its applications were discussed. ussed.
Non-independent system에서의 공정성 평가
김학용,김기선 에스케이텔레콤 (주) 2002 Telecommunications Review Vol.12 No.5
공정성은 공유 시스템의 성능 연구에 있어서 중요한 고려 사항의 하나이다. 현재까지는 Jain이 1984년에 정의한 공정성 및 공정성 지수를 사용해서 관측 시스템의 공정성을 정량적으로 평가하고 있다. 그러나 Jain의 정의는 단일 혹은 독립적인 시스템의 공정성만을 평가할 수 있어서, 서로 상관관계가 있는 시스템에서 공정성을 보장하려 할 때는 시스템 자원을 효율적으로 사용하지 못하는 문제점을 야기시킨다. 따라서 본 논문에서는 Jain의 공정성 정의를 변경시킴으로써 입력 큐잉 스위치를 비롯한 독립적이지 않은 시스템에서 적용할 수 있도록 하였다. 새로운 공정성 정의는 기존의 Jain의 공정성 지수가 가지고 있는 모든 특성을 유지하고 있으며, 시스템 자원을 효율적으로 사용할 수 있도록 하고 있다.
급성 뇌실내 출혈에서 FLAIR Magnetic Resonance 영상과 Computed Tomography와의 비교
김학용,이영배,최대섭,목진호,김한식,박형근 대한신경외과학회 2002 Journal of Korean neurosurgical society Vol.32 No.4
Objective:Our aim is to evaluate the usefulness of fluid-attenuated inversion recovery(FLAIR) magnetic resonance(MR) imaging for detection of acute intraventricular hemorrhage(IVH) compared with pre-contrast computed tomography(CT). Methods:Twenty-eight patients with acute IVH were evaluated with FLAIR MR imaging and precontrast CT. All MR and CT examination were performed within two days from symptom onset. One neurosurgeon and one radiologist evaluated the detectability and conspicuity of acute IVH on FLAIR MR imaging and pre-contrast CT. Results:Acute IVH was detected in all patients on FLAIR MR imaging and in 23(82%) of 28 patients on pre-contrast CT. The conspicuity of IVH on FLAIR MR imaging was as good as or better than that on pre-contrast CT in 28 patient. Conclusion:It is suggested that FLAIR MR imaging is superior to pre-contrast CT in the diagnosis of acute IVH. Key words:Acute intraventricular hemorrahage;FLAIR MR;Pre-contrast CT.
Phase Specific Activated Modules from a Protein Interaction Network of Yeast Cell Cycle
김학용,강희영,류재운,윤창노,한승기 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.1I
We have constructed the cell cycle-related protein interaction network of Saccharomyces cerevisiae from the MIPS (Munich Information center for Protein Sequence) database. The network shows a character of scale free and hierarchical networks. The protein interaction database obtained from a yeast two hybrid screen and a composite data set includes high random false positives. To filter the false positives, we employed cellular localization and then reconstructed the cell cycle network in which preserves the scale free and hierarchical organization and displays inherent modularity of protein clusters. Interestingly, several modules, denoted phase specific activated modules, active in response to the phase of cell cycle. From the derived modules, we predicted tentative functions for unannotated proteins and estimated some proteins that would be activated in a periodic manner coincident with the cell cycle.
김학용,김선호,이준희,권수한 한국섬유공학회 1999 한국섬유공학회지 Vol.36 No.2
Cyclic oligomers of poly(ethylene terephthalate)(PET) were separated by HPLC and they were analyzed. Pure cyclic trimer used as the standard for calibration was collected and structural analyses were conducted. A calibration curve for the quantification of the cyclic oligomers was obtained with very high confidence. Also an easy and reproducible sample preparation procedure of dissolution and reprecipitation using co-solvent and condition for high resolution HPLC separation were determined. Total amount of cyclic oligomer in melt polymerized PET with intrinsic viscosity(IV) 0.64 was 2.09$\pm$0.08 wt% at 95%-confidence level. The amount of cyclic trimer and tetramer were 1.08$\pm$0.06 wt% and 0.31$\pm$0.01 wt%, respectively. Also the amount of cyclic oligomer decreased with increasing ring size. Total amount of cyclic oligomer in solid state polymerized PET with IV 0.80 was 0.82$\pm$0.04 wt%. The amount of cyclic trimer and tetramer were 0.48$\pm$0.03 wt% and 0.11$\pm$0.01 wt%, respectively. The amount of cyclic oligomer in solid state polymerized PET was drastically decreased since some oligomers were polymerized and low molecular weight oligomers such as cyclic trimer and tetramer were eliminated during solid state polymerization.