• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1194-1205
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• 2005

The common-rail injection systems, as a new diesel injection system for passenger car, have more degrees of freedom in controlling both the injection timing and injection rate with the high pressure. In this study, a piezo-driven injector was applied to a high pressure common-rail type fuel injection system for the control capability of the high pressure injector's needle and firstly examined the piezo-electric characteristics of a piezo-driven injector. Also in order to analyze the effect of injector's needle response driven by different driving method on the injection, we investigated the diesel spray characteristics in a constant volume chamber pressurized by nitrogen gas for two injectors, a solenoid-driven injector and a piezo-driven injector, both equipped with the same injection nozzle with sac type and 5-injection hole. The experimental method for spray visualization was based on back-light photography technique by utilizing a high speed framing camera. The macroscopic spray propagation was geometrically measured and characterized in term of the spray tip penetration, spray cone angle and spray tip speed. For the evaluation of the needle response of the above two injectors, we indirectly estimated the needle's behavior with an accelerometer and injection rate measurement employing Bosch's method was conducted. The experimental results show that the spray tip penetrations of piezo­driven injector were longer, on the whole, than that of the solenoid-driven injector. Besides we found that the piezo-driven injector have a higher injection flow rate by a fast needle response and it was possible to control the injection rate slope in piezo-driven injector by altering the induced current.

• 한국컴퓨터정보학회논문지
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• 제12권2호
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• pp.83-91
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• 2007

본 논문에서는 삼차원 볼륨이미지로부터 정육면체형 셀의 분해를 통해 위상학적으로 정확한 삼중선형 등위면을 계산하고 가시화하는 알고리즘을 제시하였다. 등위면은 삼차원 볼륨이미지를 가시화하는데 자주 사용되며, 볼륨데이타의 각 정육면체형 셀안의 등위면을 삼각형의 집합으로 나타냄으로써 컴퓨터에서 가시화하기 쉽게 된다. 그러나, 대부분의 기존 등위면 계산 방식들은 이상적인 형태인 삼중선형 등위면의 위상을 보존하지 못하여 정확성이 떨어지는 단점을 가지고 있다. 본 논문은 삼차원 볼륨이미지를 구성하는 정육면체형 셀에서 일어날 수 있는 모든 등위면 형태에 대하여 정확한 삼중선형 등위면의 위상을 결정하고, 각 경우에 따라 적절한 정육면체 셀의 분해를 실시한 뒤, 분해된 셀들에 대하여 등위면을 나타내는 삼각형들을 추출하여, 위상학적으로 정확한 삼중선형 등위면을 만들어낸다. 마지막으로, 본 논문에서 제안된 알고리즘을 구현한 결과는 정확한 삼중선형을 가시화할 수 있음을 보여준다.

• 한국광물학회지
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• 제23권3호
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• pp.211-217
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• 2010

스카른 Zn-Pb-Cu 복합광석을 구성하는 주요 구성 광물의 정량분석을 목적으로, 마이크로 포커스 X-ray 단층촬영 장비를 이용한 스카른 복합광석의 3차원 비파괴검사를 수행하였다. X-ray 단층화상의 화상결함을 감소시키고자 제안된 화상보정법을 이용하여 화상들을 보정한 후에 3차원으로 재구성하였다. 주사전자현미경(SEM)에 의한 표면분석과 보정된 X-ray 단층화상을 비교하여 주요광물에 대한 CT 값의 범위를 결정하였다. 재구성화상 내 전체 광물의 체적비율을 분석한 결과, 황화광물 20.5%, 맥석광물 79.5%로 평가되었다. X-ray 3차원 단층화상 정량분석법은 광석 내 유용광물의 부존형상과 회수율 분석에 유용하게 적용될 것으로 기대된다.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.179-190
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• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.59-64
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• 2017

본 연구에서는 2유체노즐의 액체풀 (Liquid pool) 화재 소화 성능에 대하여 선행적인 검토를 수행하였다. 액체풀 화재의 경우, 에탄올 (Ethanol) 1200 ml를 이용하였으며, 물 공급 유량은 632 ml/min, 공기의 공급 유량은 40 l/min과 70 l/min으로 설정하였다. 본 실험조건에서 2유체노즐을 이용하여 화재 소화 실험을 수행하였고, 2유체노즐의 분사 특성 (액적 크기 및 유량 분포)을 측정하였다. 실험 결과, 공기의 유량이 많은 조건에서 빠른 시간 안에 성공적으로 화재를 소화할 수 있었고, 이러한 결과에 대하여 가시화 및 2유체노즐 분사 특성 데이터를 토대로 분석하였다. 또한, 기존 연구의 일부 결과와 비교를 통하여, 2유체노즐이 단일유체노즐에 비해 더욱 작은 물의 유량 조건에서도 화재 소화를 할 수 있을 가능성이 있음을 확인하였다.

• 한국인터넷방송통신학회논문지
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• 제20권6호
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• pp.1-6
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• 2020

도로이동 오염원 대기환경 빅데이터는 상시 교통량 조사장비인 AVC, VDS, WIM, DTG를 활용한 차종, 속도, 하중 등 실시간 교통류 데이터와 GIS를 활용한 도로형상(오르막, 내리막, 회전구간) 데이터를 연계한 교통류 데이터로 구성되어 있다. 또한, 일반적인 데이터와 달리 단위시간 당 데이터가 많이 발생하고, 다양한 포맷을 가지고 있다. 특히, 이들 상세 교통류 정보로 수집되는 대용량의 실시간 데이터들은 약 총 740만 건/시간 이상이 수집되어 저장 및 가공되기 때문에 효율적으로 데이터를 처리할 수 있는 시스템이 필요하다. 따라서 본 연구에서는 도로이동 오염뭔 대기환경 빅데이터 시각화를 위한 오픈소스 기반의 데이터 병렬처리 성능 최적화 연구를 수행한다.

• 대한의용생체공학회:의공학회지
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• 제43권4호
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• pp.193-198
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• 2022

Contrast enhanced magnetic resonance imaging using gadolinium-based contrast agent (GBCA) is a very useful in vivo technique to visualize the inner ear pathology including endolymphatic hydrops. Although systemic intravenous (IV) administration can visualize the perilymph space, the visualization was possible by indirect passage of contrast agent through blood-perilymph barrier. All animal experimental procedures were performed under anesthesia with 5% isoflurane. Lipopolysaccharide (LPS) was instilled into the left tympanic cavity through the tympanic membrane using a sterile 27gauge needle to induce hydrops model. Tucker-Davis Technologies system was used to measure Auditory Brainstem Responses (ABRs). For intracerebroven-tricular (ICV) administration, 25 µmol of GADOVIST (Bayer, Berlin, Germany) was used and diluted GADOVIST injection was 10 µl. MR imaging was acquired with a 9.4 Tesla MRI scanner. Transmit-receive volume coil with 40 mm inner diameter and 75 mm out diameter was used. ICV administration well demonstrated the strong enhancement along the cerebrospinal fluid (CSF) microcirculation pathway including CSF fluid in the subarachnoid space and CSF space of the inner ear structures. On the other hand, IV administration showed no contrast enhancement along the CSF microcirculation pathway and showed weak enhancement in the inner ear structures. In case of rat hydrops model, ICV administration showed that the reduced contrast enhancement in the perilymph space of the hydrops induced inner ear compared to the contrast enhancement in the perilymph space of the normal inner ear. New systemic ICV administration method provide contrast enhancement of GBCA in the inner ear through CSF microcirculation pathway.

• 대한임베디드공학회논문지
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• 제18권6호
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• pp.267-275
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• 2023

This paper presents the development of specialized software for annotating volume-of-interest on ¹⁸F-FDG PET/CT images with the goal of facilitating the studies and diagnosis of head and neck cancer (HNC). To achieve an efficient annotation process, we employed the SE-Norm-Residual Layer-based U-Net model. This model exhibited outstanding proficiency to segment cancerous regions within ¹⁸F-FDG PET/CT scans of HNC cases. Manual annotation function was also integrated, allowing researchers and clinicians to validate and refine annotations based on dataset characteristics. Workspace has a display with fusion of both PET and CT images, providing enhance user convenience through simultaneous visualization. The performance of deeplearning model was validated using a Hecktor 2021 dataset, and subsequently developed semi-automatic annotation functionalities. We began by performing image preprocessing including resampling, normalization, and co-registration, followed by an evaluation of the deep learning model performance. This model was integrated into the software, serving as an initial automatic segmentation step. Users can manually refine pre-segmented regions to correct false positives and false negatives. Annotation images are subsequently saved along with their corresponding ¹⁸F-FDG PET/CT fusion images, enabling their application across various domains. In this study, we developed a semi-automatic annotation software designed for efficiently generating annotated lesion images, with applications in HNC research and diagnosis. The findings indicated that this software surpasses conventional tools, particularly in the context of HNC-specific annotation with ¹⁸F-FDG PET/CT data. Consequently, developed software offers a robust solution for producing annotated datasets, driving advances in the studies and diagnosis of HNC.

• 전자공학회논문지CI
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• 제48권2호
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• pp.16-27
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• 2011

배아란 동물이나 식물과 같은 다세포 생물의 초기 단계를 의미한다. 배아의 단계에서 다세포 생물의 기초적인 체제가 결정되기 때문에 배아는 개체발생의 기구를 연구하는 중요한 연구대상이 된다. 생물학자들은 배아 연구를 위해 대용량의 배아 이미지 데이터를 소유하고 있으며, 이러한 대용량 데이터 중 원하는 이미지를 효율적으로 검색하기 위해서는 데이터 구조화가 필요하다. 데이터베이스 구조화를 위해 주로 사용되는 방법으로 계층적 클러스터링이 있다. 그러나 기존의 계층적 클러스터링 방법은 데이터베이스를 트리 형태로 구조화 하는 과정에서 클러스터의 크기와 클러스터 내의 객체 수를 동시에 고려하지 못하기 때문에 결과 클러스터링 트리가 경사 트리일 가능성이 매우 높다. 경사 트리인 경우 사용자가 원하는 이미지를 검색하기 위해 트리를 순회할 때 많은 시간이 걸린다. 따라서 본 논문에서는 대용량의 배아 이미지 데이터를 경사 되지 않으며 균형 상태에 가까운 트리 형태로 구조화하기 위한 방안을 제시한다. 제안하는 방안은 데이터베이스 내에 저장된 배아 이미지를 그래프로 변환하고 반복적으로 그래프 분할 알고리즘을 적용하여 클러스터를 생성한다. 이 때 클러스터의 크기와 클러스터 내의 객체 수를 동시에 고려하여 특정 클러스터의 크기가 지나치게 커지거나 객체 수가 많아지는 것을 방지한다. 실험을 통해서 제안하는 방안의 우수성을 규명하고 시각화 툴을 제공하여 사용자가 원하는 배아 이미지를 쉽게 찾을 수 있도록 돕는다.

• Radiation Oncology Journal
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• 제37권4호
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• pp.259-264
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• 2019

Purpose: Accurate localization of the lumpectomy cavity during accelerated partial breast radiation (APBR) is essential for daily setup to ensure the prescribed dose encompasses the target and avoids unnecessary irradiation to surrounding normal tissues. Three-dimensional ultrasound (3D-US) allows direct visualization of the lumpectomy cavity without additional radiation exposure. The purpose of this study was to evaluate the feasibility of 3D-US in daily target localization for APBR. Materials and methods: Forty-seven patients with stage I breast cancer who underwent breast conserving surgery were treated with a 2-week course of APBR. Patients with visible lumpectomy cavities on high quality 3D-US images were included in this analysis. Prior to each treatment, X-ray and 3D-US images were acquired and compared to images from simulation to confirm accurate position and determine shifts. Volume change of the lumpectomy cavity was determined daily with 3D-US. Results: A total of 118 images of each modality from 12 eligible patients were analyzed. The average change in cavity volume was 7.8% (range, -24.1% to 14.4%) on 3D-US from simulation to the end-of-treatment. Based on 3D-US, significantly larger shifts were necessary compared to portal films in all three dimensions: anterior/posterior (p = 7E-11), left/right (p = 0.002), and superior/inferior (p = 0.004). Conclusion: Given that the lumpectomy cavity is not directly visible via X-ray images, accurate positioning may not be fully achieved by X-ray images. Therefore, when the lumpectomy cavity is visible on US, 3D-US can be considered as an alternative to X-ray imaging during daily positioning for selected patients treated with APBR, thus avoiding additional exposure to ionizing radiation.