• Journal of Korean Neurosurgical Society
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• 제62권5호
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• pp.526-535
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• 2019

Objective : While the risk of aneurysmal rebleeding induced by catheter cerebral angiography is a serious concern and can delay angiography for a few hours after a subarachnoid hemorrhage (SAH), current angiographic technology and techniques have been much improved. Therefore, this study investigated the risk of aneurysmal rebleeding when using a recent angiographic technique immediately after SAH. Methods : Patients with acute SAH underwent immediate catheter angiography on admission. A four-vessel examination was conducted using a biplane digital subtraction angiography (DSA) system that applied a low injection rate and small volume of a diluted contrast, along with appropriate control of hypertension. Intra-angiographic aneurysmal rebleeding was diagnosed in cases of extravasation of the contrast medium during angiography or increased intracranial bleeding evident in flat-panel detector computed tomography scans. Results : In-hospital recurrent hemorrhages before definitive treatment to obliterate the ruptured aneurysm occurred in 11 of 266 patients (4.1%). Following a univariate analysis, a multivariate analysis using a logistic regression analysis revealed that modified Fisher grade 4 was a statistically significant risk factor for an in-hospital recurrent hemorrhage (p=0.032). Cerebral angiography after SAH was performed on 88 patients ${\leq}3$ hours, 74 patients between 3-6 hours, and 104 patients >6 hours. None of the time intervals showed any cases of intra-angiographic rebleeding. Moreover, even though the DSA ${\leq}3$ hours group included more patients with a poor clinical grade and modified Fisher grade 4, no case of aneurysmal rebleeding occurred during erebral angiography. Conclusion : Despite the high risk of aneurysmal rebleeding within a few hours after SAH, emergency cerebral angiography after SAH can be acceptable without increasing the risk of intra-angiographic rebleeding when using current angiographic techniques and equipment.

• 한국정보전자통신기술학회논문지
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• 제12권1호
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• pp.58-71
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• 2019

본 논문은 군 전술 무선 통신망에서의 가용 주파수 채널 확보를 위한 인지 라디오 엔진 플랫폼 구조 및 인지 라디오 무선기기를 위한 가용 주파수 채널 추론기법을 제안하였다. 현재의 군 전술 통신망은 동종 및 이종 군 무선기기 주파수의 효과적 운용을 위한 가용 주파수 확보 및 군 무선기기 간의 상호공존 방안에 대한 필요성이 빠르게 증가하고 있는 실정이다. 본 논문은 최적의 가용 주파수 채널확보 방안으로 동적 스펙트럼 접속(DSA, Dynamic Spectrum Access) 실현을 위한 인지 라디오 엔진 기술 기반의 가용채널 추론기법에 대해 소개하였다. 이를 위해 주사용자(PU, Primary User)의 채널 이용현황 모델링 및 채널 점유확률 계산을 통하여 인지 라디오 무선기기를 위한 사례 기반의 가용채널 추론기법을 제안하였으며, 성능분석 모의실험을 통하여 주사용자의 점유채널 정보 대비 인지 라디오 무전기의 가용채널 획득 정보 간의 충돌확률 변화율을 분석하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.335-342
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• 2002

A continuum-based design sensitivity analysis (DSA) method fur non-shape problems is developed for geometrically nonlinear elastic structures. The non-shape problem is characterized by the design variables that are not associated with the domain of system like sizing, material property, loading, and so on. Total Lagrangian formulation with the Green-Lagrange strain and the second Piola-Kirchhoff stress is employed to describe the geometrically nonlinear structures. The spatial domain is discretized using the 4-node isoparametric plane stress/strain elements. The resulting nonlinear system is solved using the Newton-Raphson iterative method. To take advantage of the derived analytical sensitivity In topology optimization, a fast and efficient design sensitivity analysis method, adjoint variable method, is employed and the material property of each element is selected as non-shape design variable. Combining the design sensitivity analysis method and a gradient-based design optimization algorithm, an automated design optimization method is developed. The comparison of the analytical sensitivity with the finite difference results shows excellent agreement. Also application to the topology design optimization problem suggests a very good insight for the layout design.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.609-612
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• 2000

본 논문에서는 음원에 관한 정보가 미지의 상황에서 마이크로폰 어레이를 사용하여 두 음원신호를 분리하는 ,시스템을 제안한다 이 시스템은 두 단계로 구성되어 있으며, 첫 번째 단계에서는 파워가 큰 제 1음원의 DOA(Direction Of Arrival)를 추정하고, AMUSE(Algorithm for Multiple Unknown Signals Extraction)법을 사용한 Blind Deconvolution에 의해 음원신호의 분리를 행한다 두 번째 단계에서는 파워가 낮은 제 2음원의 강조신호를 사용하여 DSA(Delay and Sum Array)법에 의해 제 2음원의 DOA를 추정하고,AMUSE법의 출력신호와 두 음원의 DOA를 이용하여 ANF(Adaptive Notch Filter)를 구성하고, 두 음원신호의 재 분리를 행한다. 그리고, 시뮬레이션을 통해 제안한 방법의 유효성을 검토한 결과 두 음원 신호가 분리 가능한 것이 확인되었다.

• 한국멀티미디어학회논문지
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• 제12권6호
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• pp.833-841
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• 2009

In this paper we propose a flexible video authentication scheme based on aggregate signature, which provides authenticity of a digital video by means of cryptographic signature to guarantee right of users. In contrast to previous works, the proposed scheme provides flexible usages on content distribution system, and it allows addition of new contents to the signed contents and deletion of some parts of the signed contents. A modification can be done by content owner or others. Although contents are modified by one or more users, our scheme can guarantee each user's right by aggregation of the each user's signatures. Moreover, proposed scheme has half size of Digital Signature Algorithm (DSA) with comparable security.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1994년도 추계학술대회
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• pp.26-27
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• 1994

The first step implementation of a hospital-wide Picture Archiving Communications System (PACS) at a newly built hospital Samsung Medical Center (SMC), is described. Current clinical operation encompasses the fiber optics delivery of direct-interfaced magnetic resonance imager (LRI), X-ray computed tomography (CT). digital subtraction angiography (DSA) and computed radiography (CR) digital images via high performance file server to the departments of radiology, neurosurgery, orthopedics surgery, neurology, emergency room and the surgical intensive care unit.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2003년도 제8차 학술대회 초록집
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• pp.23-23
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• 2003

To evaluate clinical visualization of intracranial aneurysms between 3D-TOF MRA with 3.0T MR and CTA with 16-slices MDCT. In a prospective series, 12 patients with 16 aneurysms were studies with 3D-TOF MRA and CTA. MRA were performed on a GE Signa 3.0 T system (Signa VH/i, GE) with 25/3/20 (TR/TE/FA). CTA were peformed on a 16 slice MDCT (Sensation 16, Somatom, Siemens) with IV shooting of 80 ml iodinated contrast mediumat antecubital vein at a rate of 3.5 ml/sec. Four among 12 patients underwent DSA for surgery. Size, shape, neck and parent vessel of aneurysms were evaluated for comparison of visualization and detectability of aneurysms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권12호
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• pp.2294-2314
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• 2011

The key issue in providing fast and reliable access on cloud services is the effective management of resources in a cloud system. However, the high variation in cloud service access rates affects the system performance considerably when there are no default routines to handle this type of occurrence. Adaptive techniques are used in resource management to support robust systems and maintain well-balanced loads within the servers. This paper presents an adaptive resource management for cloud systems which supports the integration of intelligent methods to promote quality of service (QoS) in provisioning of cloud services. A technique of dynamically assigning cloud services to a group of cloud servers is proposed for the adaptive resource management. Initially, cloud services are collected based on the excess cloud services load and then these are deployed to the assigned cloud servers. The assignment function uses the proposed proportional ordering which efficiently assigns cloud services based on its resource consumption. The difference in resource consumption rate in all nodes is analyzed periodically which decides the execution of service assignment. Performance evaluation showed that the proposed dynamic service assignment (DSA) performed best in throughput performance compared to other resource allocation algorithms.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2010년도 제42차 하계학술발표논문집 18권2호
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• pp.221-224
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• 2010

PACS(Picture Archiving Communication System)를 바탕으로 하는 DICOM(Digital Imaging and Communications in Medicine)은 주요 의료영상장비들 사이에 데이터와 영상을 효율적으로 교환하고 전송할 수 있도록 마련한 표준안으로 현재 대부분의 최신형 의료영상장비(CT, MR, DSA, CR(Computed Radiology), 초음파검사, 핵의학검사, 내시경검사, 조직병리검사, 등)들은 의료 영상 분야의 국제 표준인 DICOM 표준방식에 의해 영상을 제공하고 있다. 최근 이러한 의료영상장비들은 독립적으로 사용하기보다는 의료수술 모니터링 장비 등의 비 의학영상장비와 서로 연계하여 사용하는 경우가 많아졌다. 그러나 이러한 의료수술 모니터링 장비들은 DICOM 표준 데이터를 고려하지 못하므로 PACS를 통한 데이터 연계에 어려움이 있다. 따라서 본 논문에서는 표준 DICOM 포맷과 의료수술 모니터링 장비의 데이터 구조를 분석하여 non-DICOM 의료수술 모니터링 장비의 PACS 연동을 위한 방안을 제안하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.4823-4843
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• 2017

In this paper, an improved utility-based cross-layer dynamic subcarrier allocation (DSA) algorithm is proposed for single carrier frequency division multiple access (SC-FDMA) system, which adopts adaptive service rate control (ASRC) to eliminate the service rate waste and improve the spectral efficiency in heterogeneous network including non-real-time traffic and real-time traffic. In this algorithm, furthermore, a first in first out (FIFO) queuing model with finite space is established on the cross-layer scheduling framework. Simulation results indicate that by taking the service rate constraint as the necessary condition for optimality, the ASRC algorithm can effectively eliminate the service rate waste without compromising the scheduling performance. Moreover, the ASRC algorithm is able to further improve the quality of service (QoS) performance and transmission throughput by contributing an attractive performance trade-off between real-time and non-real-time applications.