• 한국전자파학회논문지
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• 제28권8호
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• pp.636-645
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• 2017

실 개구(real-aperture)를 사용하는 스캐닝 레이다(scanning radar)는 지상을 감시하거나 재난 구조를 하는 등 폭 넓게 이용 가능하다. 그러나 스캐닝 레이다의 특성상 거리 방향의 분해능은 송신하는 신호의 대역폭에 의해 제한되며, 거리방향에 수직한 방향의 분해능은 빔 폭에 의해 결정된다. 본 논문에서는 초해상도(super-resolution) 레이다 영상 기법을 제안한다. 산란체가 스캔 영역에 드문드문 존재한다면 반사율의 분포를 sparse 신호로 간주할 수 있게 되고, '압축 감지(compressive sensing)' 문제로 수식화하는 것이 가능하다. 본 논문에서는 '재가중치 ${\ell}_1$-최소화'를 통해 2차원 레이다 이미지를 얻는다. 모의실험 결과에서는 제안하는 기법으로 얻은 이미지와 더불어 기존에 널리 쓰이는 Orthogonal Matching Pursuit(OMP), 합성 개구 레이다(Synthetic Aperture Radar : SAR)의 결과와 비교하였다.

• 한국정보통신학회논문지
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• 제20권10호
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• pp.1961-1966
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• 2016

최근 활발히 연구되고 있는 압축센싱 (compressive sensing) 이론에 따르면 나이퀴스트 주파수보다 적은 샘플율으로도 원 신호를 충실히 복원할 수 있음이 알려져 있다. 압축, 전송, 저장 등의 여러 분야에서 압축센싱 방법을 적용하려는 시도가 꾸준히 이어지고 있다. 특히 4K, 8K 등으로 요구되는 화소수가 제곱의 형태로 증가되는 영상처리 분야에서는 압축센싱에 기대하는 바가 크다. 본 논문에서는 압축센싱 기법을 적용한 영상의 획득 알고리듬을 제안한다. 영상의 일반적인 특성을 활용하여 높은 에너지 압축 성능을 가지는 DCT와 저상관도의 특성을 갖는 Noiselet 변환을 결합하여 영상 획득 과정을 구성한다. 원 영상은 2차 콘 프로그램 (SOCP)을 풀어 복원할 수 있다. 여러 영상에 대해 획득 및 복원 성능을 측정 및 비교하였으며 제안된 알고리듬이 우수한 복원 성능을 보임을 알 수 있다.

• Journal of Korean Neurosurgical Society
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• 제54권4호
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• pp.347-349
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• 2013

We report a very rare case of cervical compressive myelopathy by an anomalous bilateral vertebral artery (VA) entering the spinal canal at the C1 level and compressing the spinal cord. A 70-year-old woman had been suffering from progressive gait disturbance. Magnetic resonance imaging revealed that a bilateral VA at the V4 segment had abnormal courses and caused compression to the high cervical cord. VA repositioning was performed by anchoring a suture between the artery and around the arachnoid membrane and dentate ligament, and then, microvascular decompression using a Teflon sponge was done between the VA and the spinal cord. The weakness in the patient improved in the lower extremity after the operation. Anomalous VA could be one of the rare causes of cervical compressive myelopathy. Additionally, an anchoring suture and microvascular decompression around the VA could be a sufficient and safe method to indirectly decompress the spinal canal.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권11호
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• pp.5481-5495
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• 2018

Single pixel imaging technology has developed for years, however the video acquisition on the single pixel camera is not a well-studied problem in computer vision. This work proposes a new scheme for single pixel camera to acquire video data and a new regularization for robust signal recovery algorithm. The method establishes a single pixel video compressive sensing scheme to reconstruct the video clips in spatial domain by recovering the difference of the consecutive frames. Different from traditional data acquisition method works in transform domain, the proposed scheme reconstructs the video frames directly in spatial domain. At the same time, a new regularization called spatial cluster is introduced to improve the performance of signal reconstruction. The regularization derives from the observation that the nonzero coefficients often tend to be clustered in the difference of the consecutive video frames. We implement an experiment platform to illustrate the effectiveness of the proposed algorithm. Numerous experiments show the well performance of video acquisition and frame reconstruction on single pixel camera.

• Journal of Korean Neurosurgical Society
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• 제47권6호
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• pp.454-457
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• 2010

Pure ventral midline giant schwannoma is an extremely rare entity. Spinal intradural extramedullary schwannomas commonly occur posterolateral or anterolateral to the spinal cord. A case of a pure midline ventrally situated giant pan cervical extramedullary schwannoma in an 18-year-old male patient with compressive myelopathy and sphincter involvement is presented. Spinal MR imaging showed a midline ventrally situated extramedullary tumor with severe spinal cord compression extending from clivus to C7 vertebra. It was resected through a posterolateral approach. Histology was consistent with a schwannoma. Post operative MR imaging showed no evidence of the tumor. The radiological features, pathogenesis and surgical strategies in management of these difficult tumors are discussed and the relevant literature is briefly reviewed.

• Journal of Korean Neurosurgical Society
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• 제66권3호
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• pp.324-331
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• 2023

Objective : We aimed to analyze the effectiveness of external neurolysis on the common peroneal nerve (CPN) in patients with posture-induced compressive peroneal neuropathy (PICPNe). Further, we aimed to examine the utility of magnetic resonance imaging (MRI) in assessing the severity of denervation status and predicting the postoperative prognosis. Methods : We included 13 patients (eight males and five females) with foot drop who underwent CPN decompression between 2018 and 2020. We designed a grading system for assessing the postoperative functional outcome. Additionally, we performed MRI to evaluate the denervation status of the affected musculature and its effect on postoperative recovery. Results : The median time to surgery was 3 months. The median preoperative ankle dorsiflexion and eversion grades were both 3, while the average functional grade was 1. Posterior crural intermuscular septum was the most common cause of nerve compression, followed by deep tendinous fascia and anterior crural intermuscular septum. There was a significant postoperative improvement in the median postoperative ankle dorsiflexion and eversion grades and average postoperative functional (4, 5, and 2.38, respectively). Preoperative ankle eversion was significantly correlated with denervation status. Additionally, the devernation status on MRI was positively correlated with the outcome favorability. However, denervation atrophy led to a less favorable outcome. Conclusion : Among patients with intractable PICPNe despite conservative management, surgical intervention could clinically improve motor function and functional ability. Additionally, MRI examination of the affected muscle could help diagnose CPNe and assess the postoperative prognosis.

• 한국산업정보학회논문지
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• 제20권3호
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• pp.81-86
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• 2015

본 논문에서는 인체의 CT/MRI에서 단층 촬영된 무릎관절을 영상처리 과정을 거쳐 3차원 관절 모델을 제작하였다. 실제 무릎관절의 형상을 추출할 때 설정 조건에 따라 3차원 형상정보가 달라질 수 있다. 이러한 미세한 3차원 형상정보의 차이에 따른 무릎관절의 구동특성을 분석하기 위해 2가지의 관절 모델을 3차원 프린터를 이용하여 제작하였다. 제작된 관절모델을 이용하여 관절구동 시 압축력 실험을 수행하였고 형상의 차이에 따라 결과값의 차이가 발생하였다. 따라서 생체모방형 바이오리액터를 개발할 경우에는 형상정보의 차이에 대한 연구가 선행되어야 할 것으로 사료된다.

• Journal of Biosystems Engineering
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• 제39권3호
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• pp.244-252
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• 2014

Purpose: The development of an efficient in vitro cell culture device to process various cells would represent a major milestone in biological science and engineering. However, the current conventional macro-scale in vitro cell culture platforms are limited in their capacity for detailed analysis and determination of cellular behavior in complex environments. This paper describes a microfluidic-based culture device that allows accurate control of parameters of physical cues such as pressure. Methods: A microfluidic device, as a model microbioreactor, was designed and fabricated to culture Saccharomyces cerevisiae and Chlamydomonas reinhardtii under various conditions of physical pressure stimulus. This device was compatible with live-cell imaging and allowed quantitative analysis of physical cue-induced behavior in yeast and microalgae. Results: A simple microfluidic-based in vitro cell culture device containing a cell culture channel and an air channel was developed to investigate physical pressure stress-induced behavior in yeasts and microalgae. The shapes of Saccharomyces cerevisiae and Chlamydomonas reinhardtii could be controlled under compressive stress. The lipid production by Chlamydomonas reinhardtii was significantly enhanced by compressive stress in the microfluidic device when compared to cells cultured without compressive stress. Conclusions: This microfluidic-based in vitro cell culture device can be used as a tool for quantitative analysis of cellular behavior under complex physical and chemical conditions.

• 구강회복응용과학지
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• 제33권2호
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• pp.80-87
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• 2017

목적: 이 연구는 새로운 레진계 근관실러인 Any-Seal의 여러 물성을 AH Plus Jet와 비교하여 평가하고자 했다. 연구 재료 및 방법: 흐름성, 방사선 불투과성, 압축 강도를 ISO 6876/2001기준에 의해 측정하였다. 흐름성은 실러 0.05 mL를 두 개의 유리판 사이에 놓고 100 g의 무게로 눌러 측정했다. 실러 혼합 10분 뒤 무게를 제거하고 눌려진 실러의 지름을 측정했다. 방사선 불투과성은 각 근관실러를 지름 10 mm, 높이 1 mm의 디스크형 시편으로 만들어 aluminum step wedge와 함께 방사선 촬영을 하여 분석했다. 압축 강도는 각 실러를 4 mm 지름과 6 mm 높이의 실린더 형태로 만든 다음 24시간 후와 1주일 후에 측정했다. 결과: 두 근관실러의 흐름성과 방사선 불투과성 값은 ISO 6876/2001조건에 맞았다. 흐름성은 AH Plus Jet와 Any-Seal 사이에 통계적으로 유의한 차이가 없었다(P > 0.05). AH Plus Jet가 방사선 불투과성 값을 나타냈다(P < 0.05). 24시간 후와 1주일 후 모두에서 AH Plus Jet가 더 높은 압축 강도를 보였다(P < 0.05). 결론: Any-Seal이 낮은 압축 강도를 보였으므로 다른 물리적, 생물적 특성에 대해 더 많은 연구가 임상적 활용 전에 필요할 것으로 생각한다.

• Nuclear Medicine and Molecular Imaging
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• 제41권3호
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• pp.258-259
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• 2007

Benign metastasizing leiomyoma(BML) is a rare condition affecting women with a history of having undergone hysterectomy or myomectomy for a benign uterine fibroid, that is found to have metastasized to extrauterine sites, usually many years after hysterectomy. 1,2) Patient with BML almost always asymptomatic, although if the lesions are large enough, they can cause compressive symptoms. Among several hypothesis of pathogenesis, most plausible theory is that these tumors represent a true metastatic lesion but are very low-grade sarcoma. 3) Because the tumor is responsive to estrogen, menopause and pregnancy have slowed the growth of these lesion 4) and it seems reasonable to perform hysterectomy in patients with a uterine mass and, at the same time, perform oophorectomy for hormonal control. BML is an unusual cause of diffuse pulmonary nodules which should be considered in females with unexplained nodules and a history of surgery for uterine leiomyoma.