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- 저자 : 朴英錫(박영석) (검색결과 1,139 건)
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쿼드트리 계층구조를 이용한 내장형 프러그레시브 영상코딩 알고리즘
박영석 에스케이텔레콤 (주) 2004 Telecommunications Review Vol.14 No.5
In this paper, we propose a recursive set partitioning in quad-tree hierarchy trees(RSPIQTH) algorithm for embedded progressive image coding and evaluate its effectiveness experimentally. Also we describe a generalized progressive bit-plane transmission(PBT) algorithm for adapting the RSPIQTH algorithm. Various bit-plane coding algorithms including EZW(embedded zerotree wavelet coding) family are applicable to this PBT algorithm as it is. The proposed RSPIQTH algorithm takes the simple and regular form and the processing time complexity of O(n). From the viewpoint of processing time, the RSPIQTH algorithm takes about 11.3% improvement in average than the SPIHT algorithm for experimental images. Also from the viewpoint of coding rate, the algorithm takes about 10.8% improvement in average. 본 연구에서는 내장형 프러그레시브 영상코딩을 위해 쿼드트리 계층구조를 이용한 재귀적 SPIQTH(RSPIQTH) 알고리즘을 제안하고 그 유효성을 실험적으로 평가한다. 또한 이 알고리즘의 적용을 위해 일반화된 프러그레시브 비 트평면 전송알고리즘을 제시하였고, EZW(embedded zerotree wavelet coding)계열을 포함한 다양한 비트평면 코딩 알고리즘들 또한 제안한 비트평면 전송알고리즘에 그대로 적용할 수 있다. RSPIQTH 알고리즘은 매우 단순하고 정 형화된 형태를 지니면서 처리 시간복잡도 O(n)을 가진다. 실험영상들에 대해 SPIHT 알고리즘보다 평균 약 11.3%의 개선된 속도를 얻을 수 있었다. 압축율의 관점에서도 RSPIQTH 알고리즘은 평균 약 10.8%의 개선된 결과를 보였다.
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처음 뇌혈관 조영상 음성인 뇌지주막하 출혈 환자의 치료 방침
박영석,김용배,허승곤,이규창 대한신경외과학회 2003 Journal of Korean neurosurgical society Vol.34 No.5
Objective:The aim of this retrospective clinical study is to provide a proper management strategy for patients who present spontaneous subarachnoid emorrhage(SAH) with negative initial angiogram by investigating the clinical features, long-term outcomes and radiologic characteristics. Methods : One hundred and twenty-eight out of 2887 SAH patients who were admitted to neurosurgery department from 1986 to 2002 had negative initial angiogram. We classified the 128 patients into 3 groups(Group I : no evidence of SAH on CT but confirmed by lumbar puncture, Group II: perimesencephalic(PM) SAH pattern, Group III: non-perimesencephalic(NPM) SAH pattern), and reviewed the radiologic findings, the clinical features, the rebleeding rate, the long-term outcome, and the results of repeated angiogram. Factors related to the false negative initial angiogram were also reviewed. Results : The patients were 9(7.0%) in Group I, 85(66.4%) in Group II, and 34(26.6%) in Group III. There was no difference in long-term clinical outcome. Ninety-two out of 128 patients underwent a repeated angiogram in which 18 patients were found to have ruptured aneurysms that were not detected on the initial angiogram(false negative rate: overall 19.6%, 1.8% in Group II, 50.0% in Group III). Small size(<6mm) aneurysms, spasms, hematomas, and anterior communicating aneurysms were the factors affecting false negative initial angiogram. Conclusion : In SAH patients with negative initial angiogram, espeacially those who had a non-perimesencephalic SAH pattern on initial CT findings, a repeated angiogram should be considered for identifying the hidden ruptured aneurysm. Key words:Subarachnoid hemorrhage;CT findings;Cerebral angiogram;False negative.
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Thoracic Intradural Aspergillus Abscess - Case Report -
박영석,Sung-Bum Kim,조용은,정우희 대한신경외과학회 2003 Journal of Korean neurosurgical society Vol.34 No.1
We, herein present a case of intradural aspergillus abscess with flaccid paraplegia in a 41-year-old immuno-competent female. On her past medical history, the left pneumonectomy was performed for lung aspergilloma 7 months before admission. A magnetic resonance image disclosed a large intradural enhanced mass compressing spinal cord laterally from T9 to T10. She underwent extensive laminectomy(T8-T10) and removal of the granulation tissue. Postoperative aggressive medical treatment with antifungal agent(amphotericin-B) was done. Although her neurologic status is not fully recovered, no further progression of infection process is found up to the present. Key words:Spinal cord;Aspergillosis;Intradural abscess. .
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Al<sub>4</sub>C<sub>3</sub> 첨가 α-SiC의 열전변환특성
박영석,배철훈 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.10
SiC세라믹스의 열전변환물성에 미치는 A1$_4$C$_3$ 첨가효과에 대해 연구하였다. $\alpha$-SiC 분말에 A1$_4$C$_3$를 첨가하여 Ar분위기 2100∼220$0^{\circ}C$에서 3시간 소결하여 상대밀도 47∼59%인 다공질 SiC세라믹스를 제조하였다. X-선 회절분석 및 주사형 전자현미경으로 소결체의 상조성과 미세구조를 분석하였으며, A1$_4$C$_3$ 첨가에 의해 6H에서 4H로의 상전이 발생을 관찰할 수 있었다. 전기전도도와 Seebeck 계수를 Ar 분위기 550∼95$0^{\circ}C$에서 측정하였다. 무첨가 시료의 경우 출발원료중에 함유된 p형 불순물(Al, Fe)에 의해 Seebeck 계수가 정(+)의 값을 나타내었으며, 소결온도가 증가함에 따라 전기전도도가 증가하였다. A1$_4$C$_3$ 첨가 시료의 전기전도도는 상전이 및 캐리어농도 증가에 의해 무첨가 시료보다 높았으며, 또 Seebeck 계수도 크게 나타났다. 시료의 밀도, 첨가량 및 소결조건이 열전변환물성에 크게 기여하였다. The effect of A1$_4$C$_3$ additive on the thermoelectric properties of SiC ceramics were studied. Porous SiC ceramics with 47∼59% relative density were fabricated by sintering the pressed $\alpha$-SiC powder compacts with A1$_4$C$_3$at 2100∼220$0^{\circ}C$ for 3 h in Ar atmosphere. Crystalline phases of the sintered bodies were identified by powder X-Ray Diffraction (XRD) and their microstructures were observed with a Scanning Electron Microscope (SEM). In the case of A1$_4$C$_3$ addition, the phase transformation of 6H-SiC to 4H-SiC could be observed during sintering. The Seebeck coefficient and electrical conductivity were measured at 550∼95$0^{\circ}C$ in Ar atmosphere. In the case of undoped specimens, the Seebeck coefficients were positive (p-type semiconducting) possibly due to a dominant effect of the acceptor impurities (Al, Fe) contained in the starting powder and electrical conductivity increased as increasing sintering temperature. Electrical conductivity of A1$_4$C$_3$doped specimen is larger than that of undoped specimen under the same condition, which might be due to the reverse phase transformation and increasing of carrier density. And the Seebeck coefficient of A1$_4$C$_3$ doped specimen is also larger than that of undoped specimen. The density of specimen, the amount of addition and sintering atmosphere had significant effects on the thermoelectric property.
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