Image-Guided Neurosurgery Systems with Microscope Integration of Intraoperative 3D-Ultrasound in Neuronavigation

Choi Sunghwan,Lee Min Ho,Lee Tae-Kyu 대한말초신경학회 2021 The Nerve Vol.7 No.1

Yaşargil has brought a paradigm shift to neurosurgery with the use of the microscope. Recent advances in radiosurgery and endoscopic surgery have challenged in microscopic surgery in the neurosurgical field. However, the more these challenges, the more experienced and technologies are being accumulated and developed. Through this, the accuracy of surgery is gradually improving. In addition, navigation systems have improved accuracy during surgery and indocyanine green (ICG) angiography has rendered the process easier. Furthermore, intraoperative computed tomography and magnetic resonance imaging have been used to provide safer and more accurate treatment for patients. Herein, our experience of surgery on a patient using the above-mentioned modalities with real-time ultrasound is reported.

Accuracy of Lagrange-sinc functions as a basis set for electronic structure calculations of atoms and molecules

Choi, Sunghwan,Hong, Kwangwoo,Kim, Jaewook,Kim, Woo Youn American Institute of Physics 2015 The Journal of chemical physics Vol.142 No.9

<P>We developed a self-consistent field program based on Kohn-Sham density functional theory using Lagrange-sinc functions as a basis set and examined its numerical accuracy for atoms and molecules through comparison with the results of Gaussian basis sets. The result of the Kohn-Sham inversion formula from the Lagrange-sinc basis set manifests that the pseudopotential method is essential for cost-effective calculations. The Lagrange-sinc basis set shows faster convergence of the kinetic and correlation energies of benzene as its size increases than the finite difference method does, though both share the same uniform grid. Using a scaling factor smaller than or equal to 0.226 bohr and pseudopotentials with nonlinear core correction, its accuracy for the atomization energies of the G2-1 set is comparable to all-electron complete basis set limits (mean absolute deviation 1 kcal/mol). The same basis set also shows small mean absolute deviations in the ionization energies, electron affinities, and static polarizabilities of atoms in the G2-1 set. In particular, the Lagrange-sinc basis set shows high accuracy with rapid convergence in describing density or orbital changes by an external electric field. Moreover, the Lagrange-sinc basis set can readily improve its accuracy toward a complete basis set limit by simply decreasing the scaling factor regardless of systems.</P>

Space-Time Hole Filling With Random Walks in View Extrapolation for 3D Video

Sunghwan Choi,Bumsub Ham,Kwanghoon Sohn IEEE 2013 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.22 No.6

<P>In this paper, a space-time hole filling approach is presented to deal with a disocclusion when a view is synthesized for the 3D video. The problem becomes even more complicated when the view is extrapolated from a single view, since the hole is large and has no stereo depth cues. Although many techniques have been developed to address this problem, most of them focus only on view interpolation. We propose a space-time joint filling method for color and depth videos in view extrapolation. For proper texture and depth to be sampled in the following hole filling process, the background of a scene is automatically segmented by the random walker segmentation in conjunction with the hole formation process. Then, the patch candidate selection process is formulated as a labeling problem, which can be solved with random walks. The patch candidates that best describe the hole region are dynamically selected in the space-time domain, and the hole is filled with the optimal patch for ensuring both spatial and temporal coherence. The experimental results show that the proposed method is superior to state-of-the-art methods and provides both spatially and temporally consistent results with significantly reduced flicker artifacts.</P>

Unsupervised Texture Flow Estimation Using Appearance-Space Clustering and Correspondence

Sunghwan Choi,Dongbo Min,Bumsub Ham,Kwanghoon Sohn IEEE 2015 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.24 No.11

<P>This paper presents a texture flow estimation method that uses an appearance-space clustering and a correspondence search in the space of deformed exemplars. To estimate the underlying texture flow, such as scale, orientation, and texture label, most existing approaches require a certain amount of user interactions. Strict assumptions on a geometric model further limit the flow estimation to such a near-regular texture as a gradient-like pattern. We address these problems by extracting distinct texture exemplars in an unsupervised way and using an efficient search strategy on a deformation parameter space. This enables estimating a coherent flow in a fully automatic manner, even when an input image contains multiple textures of different categories. A set of texture exemplars that describes the input texture image is first extracted via a medoid-based clustering in appearance space. The texture exemplars are then matched with the input image to infer deformation parameters. In particular, we define a distance function for measuring a similarity between the texture exemplar and a deformed target patch centered at each pixel from the input image, and then propose to use a randomized search strategy to estimate these parameters efficiently. The deformation flow field is further refined by adaptively smoothing the flow field under guidance of a matching confidence score. We show that a local visual similarity, directly measured from appearance space, explains local behaviors of the flow very well, and the flow field can be estimated very efficiently when the matching criterion meets the randomized search strategy. Experimental results on synthetic and natural images show that the proposed method outperforms existing methods.</P>

이동컴퓨팅환경에서 데이타의 접근 빈도 및 시맨틱 관계를 고려한 방송 방법

최성환(Sunghwan Choi),정성원(Sungwon Jung),이송이(Song-Yi Yi) 한국정보과학회 2003 정보과학회논문지 : 데이타베이스 Vol.30 No.5

이동 컴퓨팅(mobile computing) 환경이 가지는 통신 대역의 협소함과 이동 기기의 에너지 제약 때문에 데이타 베이스 서버에서 다수의 이동 클라이언트로 데이타를 전달할 때는 브로드캐스트(broadcast)가 효과적이다. 기존의 여러 가지 브로드캐스트 방법은 클라이언트의 데이타 접근 빈도(access frequency)를 이용하여 전송 스케줄을 정하거나, 데이타들의 시맨틱 관계(semantic relationship)를 이용하여 전송 스케줄을 결정하였다. 데이타의 접근 빈도만을 반영하는 경우 클라이언트들이 접근하는 데이타들의 의미적 관계를 고려하지 않으므로 클라이언트가 밀접한 시맨틱 관계를 갖는 데이타를 차례로 접근해야 하는 경우 오랜 시간 동안 무선 채널을 듣고 있어야 한다. 시맨틱 관계만을 반영하여 전송 스케줄을 작성하면, 클라이언트가 시맨틱 관계는 없으나 접근 빈도가 높은 특정 데이타를 자주 접근할 필요가 있는 경우, 클라이언트의 데이타 접근 시간이 길어지게 된다. 이 논문에서는 데이타 접근 빈도와 시맨틱 관계를 함께 반영하여 이동 클라이언트의 데이타 접근 시간을 개선한 효율적인 하이브리드 데이타 브로드캐스트 방법을 제안한다. 우리가 제안하는 하이브리드 브로드캐스트 방법은 데이타 접근 빈도에 의해 브로드캐스트 스케줄을 생성한 후, 스케줄 상 데이타 전송 위치를 시맨틱 관계에 따라 조정한다. 시뮬레이션을 통해 기존의 방법들과 성능을 비교 분석하여 우리의 방법이 효율적임을 보인다. Data broadcast is an effective data transmission method from a data base server to numerous mobile clients due to the restrictions on mobile environment such as low wireless communication bandwidth and energy shortage of mobile devices. There are various broadcast methods based on clients' data access frequencies or semantic relationship of data. The broadcast schedule based only on the access frequencies does not consider semantic relations of data, so that when a client needs to access a series of semantically related data, the client has to listen to the wireless channel for a long time. On the other hand, the broadcast schedule based only on semantic relationship of data makes data access time longer when clients highly request specific data which are not semantically related but frequently accessed. In this paper, we present an efficient data broadcast method based on not only data access frequencies but also semantic relationship to improve mobile clients' query response time. The new hybrid broadcast method we propose creates a data broadcast schedule according to the data access frequencies and then the schedule is adjusted to reflect semantic relationship of data. We show our method is efficient by experimental performance analysis.

The Lifshitz-van der Waals acid-base theory assisted fabrication of MFI-containing mixed matrix membranes for gas separations

Park, Sunghwan,Jang, Eunhee,An, Heseong,Choi, Wansuk,Kim, Jeong-Hoon,Lee, Jung-Hyun,Choi, Jungkyu,Lee, Jong Suk Elsevier 2018 Microporous and mesoporous materials Vol.264 No.-

<P><B>Abstract</B></P> <P>A zeolite-containing mixed matrix membrane (MMM) is an attractive option to overcome the performance limits of polymeric membranes for large-scale gas separations. The poor interfacial adhesion between zeolites and polymers, however, should be addressed to realize the excellent separation performance of zeolites on large industrial scale. Herein, the interfacial void-free MMMs with incorporation of intact MFI type zeolite particles were successfully prepared by applying the Lifshitz-van der Waals acid-base theory for the selection of the appropriate polymer matrix. Our simple, but systematic approach was based on the adhesion force between MFI particles and a surrounding polymer matrix. The relatively high Lewis basicity of cellulose acetate (CA) leads to highest adhesion force with MFI particles among the tested polymer matrices, suppressing interfacial void formation. In addition, a careful analysis revealed that any residual surfactants on the surface of MFI particles are detrimental to fabricate interfacial void-free MMMs. Single gas (i.e. N<SUB>2</SUB> and NF<SUB>3</SUB>) transport in the CA/MFI MMMs were characterized by changing the concentration of MFI particles up to 30 wt%. N<SUB>2</SUB> permeability of CA/MFI MMMs was improved by as much as 304% compared to that of bare CA membranes with maintaining N<SUB>2</SUB>/NF<SUB>3</SUB> permselectivity. Furthermore, gas transports in CA/MFI MMMs by varying the size of MFI particles from 0.2 through 0.6 up to 1.5 <I>μ</I>m were analyzed by using the Lewis-Nielsen model. Our systematic theory-based guidance can be utilized to offer the appropriate polymer candidates for the zeolite-containing MMMs for high performance gas separations.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simple acid-base theory was systematically applied for ideal MFI-containing MMMs. </LI> <LI> The high carbonyl mole fractions of CA induced a good adhesion between CA and MFI. </LI> <LI> The effect of structure directing agents on the formation of MMMs was investigated. </LI> <LI> Gas transport behaviors in CA/MFI MMMs were analyzed by varying the size of MFI. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A Practical Solution to SLAM and Navigation in Home Environment

Jinwoo Choi,Kyoungmin Lee,Sunghwan Ahn,Minyong Choi,Wan Kyun Chung 제어로봇시스템학회 2006 제어로봇시스템학회 국제학술대회 논문집 Vol.2006 No.10

안구 운동량 검출을 이용한 스테레오 영상의 시각적 피로도 측정

최성환(Choi Sunghwan),김동현(Kim Donghyun),최재섭(Choi Jaeseob),손광훈(Sohn Kwanghoon) 한국방송·미디어공학회 2010 한국방송공학회 학술발표대회 논문집 Vol.2010 No.11

본 논문에서는 3차원 스테레오 영상에서의 시각적 피로도와 안구의 운동량과의 상관관계를 도출하고 시각적 피로도 측정시스템을 제안한다. 제안한 측정 방법은 3차원 스테레오 영상 시청자의 피로도가 누적되었을 때, 안구의 단속성 운동(saccade)이 감소할 것이라는 가정에 기반을 둔다. 액티브 셔터글라스 방식의 3D 안경을 착용한 시청자의 동공을 검출하고 추적하기 위해 적외선 광원 및 적외선 카메라를 이용한다. 획득한 영상에 대해 이진 임계화를 적용하고 타원 피팅을 수행하여 동공의 위치를 검출한다. 피팅된 타원의 이심률과 크기 및 위치를 제한하여 검출 오류를 줄인다. 검출된 동공의 위치를 바탕으로 안구의 단속성 운동량을 측정한다. 실험에는 변이 정도가 크지 않아 편안하게 시청 가능한 스테레오 영상과 과도한 변이를 가져 시청하는데 불편한 영상이 분리되어 사용되었다. 이들 영상에 대해 각각 실험자의 단속성 운동량을 측정하였다. 실험 결과에서 안구의 단속성 운동량이 변이가 큰 영상에서 그렇지 않은 영상에 비해 감소하는 경향이 나타났다.

섬사람들의 탈경계적 공간인식과 지적전통

최성환(Choi, Sunghwan) 국립목포대학교 도서문화연구원 2013 島嶼文化 Vol.0 No.41

그동안 한국사회가 지녀온 편견에서 보면, ‘섬’은 ‘고립의 공간’으로 인식되어 왔다. 그러나 정작 섬에 살고 있는 사람들에게는 자신들의 공간을 ‘소통의 공간’으로 인식하는 유교이념이 존재했다. 본 연구자는 이를 섬에 대한 탈경계적 공간인식이라는 측면에서 주목하였고, 본고에서는 유교이념과 신안군 사례를 중심으로 섬사람들의 知的傳統이 지닌 특징에 대해 고찰하였다. 연구 성과는 다음과 같다. 첫째, 섬사람들의 생활상과 유교문화의 관련성이다. 현재 남아있는 ‘문화유적’, ‘고문서’, ‘民家의 구조’ 등에서 섬이라는 환경에 수용되고. 변화 발전 된 섬 고유의 유교문화가 존재했음을 확인하였다. 둘째, 유배인․은둔학자․토착 지식인들의 기록에 섬에 대한 탈경계적인 공간인식의 다양한 사례가 남아있음을 분석하였다. 하나의 지적전통으로 형성되어 왔으며, 학문적으로 발현되는 발전 양상을 보이기도 한다. 셋째, 하의도 ‘김연’의 사례를 통해 독특한 공간인식과 지적전통이 지속적으로 계승되었음을 살폈다. 김연의 삶은 섬의 인문환경과 지적전통에서 많은 시사점을 주었다. 본 연구를 통해 섬은 문화적으로 단절된 공간이 아니라 소통의 공간이라는 사실을 확인하였다. 섬 환경에 맞게 변화 발전된 유교이념은 육지에 비해 受容性이 강하다는 특징을 지녔다. 이는 섬사람들의 지적전통에 많은 영향을 주었고, 독특한 인문환경으로 전해오고 있다. According to the prejudice that Korean society has had so far, an ‘island’ has been regarded as ‘space of isolation’. However, in fact, those living in an island have Confucian ideas that they recognize their space as ‘space for communication’. This researcher focuses on islands from the aspects of trans-border spatial cognition, and this article considers the characteristics of islanders’ intellectual tradition centering around Confucian ideas and the case of Shinan-gun. And the paper has gained the findings as follows: First, it is about the relationship between islanders’ lives and Confucian culture. It has been found that such things as remaining ‘cultural relics’, ‘ancient documents’, and ‘the structure of private houses’ accept the environment of an island, and there exists an island’s original Confucian culture that has been transformed and developed. Second, the study has analyzed from the records written by the exiles, hermits, or native intellectuals that there have been various cases of trans-border spatial cognition on an island. It has been formed as a kind of intellectual tradition, and sometimes it shows the aspects of development that emerges academically. Third, the study has examined with the case of Haui-do ‘Kim Yeon’ that the unique spatial cognition and intellectual tradition have succeeded continually. Kim Yeon’s life has a lot of implications regarding an island’s environment for humanities and intellectual tradition. This study has verified the fact that an island is not culturally isolated space but space of communication. Confucian ideas that have been changed and developed according to the environment that an island has are characterized by having stronger acceptability than the land’s. This has affected islanders’ intellectual tradition significantly and has been transmitted as unique environment for humanities.

비금도 천일염전 개발과정과 사회적 확산

최성환(Choi, Sunghwan) 목포대학교 도서문화연구소 2012 島嶼文化 Vol.0 No.40

본고는 신안군 비금도 천일염전의 개발과정과 사회적 확산을 검토한 것이다. 염전개발과 관련된 각종 기록물과 최초 개발에 주도적인 역할을 한 손봉훈과 박삼만의 후손, 당시 염부였던 손정우 등의 구술 내용을 종합적으로 비교분석하였다. 연구결과는 다음과 같다. 광복이후 1946년 비금도에서 민간차원 최초로 천일염전 개발에 성공하였다. 이는 손봉훈의 개척정신과 지도력, 박삼만의 현장 활동, 뜻을 함께하는 비금도 주민들의 노력이 융합되어 나타난 결과물이다. 이후 비금도는 각종 개발조합의 활동과 제염기술원양성소를 통해 천일염전의 사회적 확산에 기여했다. 천일염전의 개발은 오늘날 섬사람들이 섬을 지키며 살아갈 수 있는 사회경제적 기반 형성에 크게 기여하였다. 현재 신안군에는 천일염전 개발과 관련된 각종 기록물들이 잘 보존되어 있다. 이는 우리나라 천일염 산업의 발달과정을 보여주는 매우 중요한 사료이다. 이러한 기록물을 통해 비금도 자체가 광복이후 한국 천일염전의 새로운 始發地였고, 호남권 천일염전 개발기술의 보급처였음이 확인되었다. Bigeumdo, Shinan-gun is the island located in the southeast edge in Korea, and it is located in the region that is 54.5km distant from Mokpo. This article examines the developmental process of the bay salt pond that was formed first in Bigeumdo after the Liberation and its social expansion. Centering around all sorts of records regarding salt pond development, this paper analyzed what the descendants of Son Bong-Hun and Park Sam-Man who played initiative roles in its initial development said and also the salt makers then including Son Jeong-Woo said comparatively as well as synthetically. Thereupon, this study gained the following study results: In Bigeumdo, they succeeded in developing the first bay salt pond in 1946. It was the result of combination among Son Bong-Hun’s pioneering spirit and leadership, Park Sam-Man’s activities at the spot, and Bigeumdo residents’ efforts pursuing the same goal. After that, Bigeumdo has contributed to the social expansion of bay salt ponds through the activities of development associations and salt manufacturing engineer training centers. The development of bay salt ponds has contributed greatly to the establishment of socioeconomic foundation with which the islanders can preserve the island and live there today. Presently, Shinan-gun has well kept all the records regarding the development of bay salt ponds. Those are the crucial materials that show Korea’s developmental process of bay salt industry. With those records, we can see that Bigeumdo itself was the new starting point for bay salt ponds in Korea after the Liberation and also the supplier of technology to develop bay salt ponds in Honam area.