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풍력 자원 평가를 위한 부유식 라이다의 모션 보정 프로그램 개발
유지환,김철웅,유정훈,이경훈,정믿음 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.10
The floating light detection and ranging (LiDAR), which measures wind resources at sea, is affected by its movement. Hence, it may overestimate the turbulence intensity. The aim of this study is to develop a program that calculates the corrected wind speed and turbulence intensity by compensating for the movement of the floating LiDAR using a motion reference unit (MRU) sensor. This program synchronizes the measurement time interval of LiDAR and MRU sensor and calculates the correction speed by synchronizing the coordinate system of both devices. For speed correction, it is essential to precisely select the neck position in the figure-of-eight shape that indicates the wind condition. A method for selecting it using machine learning is introduced. The configured program enables the user to select the desired height and time and evaluate the corresponding data. MATLAB® is used for programming and the machine learning process. 바다 위에서 풍황 자원을 측정하는 부유식 라이다(LiDAR)는 움직임으로 인해 측정에 영향을 받아 난류 강도를 과대평가하게된다. 본 연구에서는 MRU(motion reference unit) 센서로 부유식 라이다의움직 임을 측정, 보정하여 보정된 바람 속도와 난류 강도 값을 계산하는 프로그램을 개발하고자 하였다. 본 프로그램에서는 라이다와 MRU 센서의 측정 시간을 동기화하고 두 장비의 좌표계를 일치시켜 보정 속 도를계산한다. 속도보정에 있어서는 풍황을 나타내는 FOE(figure-of-eight) 형상에서의정확한 neck의 위 치선정이 요구되며, 이를 머신 러닝을 통해 선정하는 방법을 제시하였다. 제시된 보정 프로그램은 사용 자가 높이와 시간을 선택하여 해당하는 데이터를 확인할 수 있도록 구성되어 있으며, 프로그램 제작 및 머신러닝에는 상용 패키지인 MATLAB을 시용하였다.
Distributed Coding Scheme for Multi-view Video through Efficient Side Information Generation
유지환,유지상,고민수,권순철,서영호,김동욱 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
In this paper, a distributed image coding scheme for multi-view video through an efficientgeneration of side information is proposed. A distributed video coding technique corrects the errors inthe side information, which is generated with the original image, by using the channel codingtechnique at the decoder. Therefore, the more correct the generated side information is, the better theperformance of distributed video coding. The proposed technique is to apply the distributed videocoding schemes to the image coding for multi-view video. It generates side information by selectivelyand efficiently using both 3-dimensional warping based on the depth map with spatially adjacentframes and motion-compensated temporal interpolation with temporally adjacent frames. In thisscheme the difference between the adjacent frames, the sizes of the motion vectors for the adjacentblocks, and the edge information are used as the selection criteria. From the experiments, it wasobserved that the quality of the side information generated by the proposed technique was improved bythe average peak signal-to-noise ratio of 0.97dB than the one by motion-compensated temporalinterpolation or 3-dimensional warping. The result from analyzing the rate-distortion curves revealedthat the proposed scheme could reduce the bit-rate by 8.01% on average at the same peak signal-tonoiseratio value, compared to previous work.
Recent Update on Neurosurgical Management of Brain Metastasis
유지환,박현호,강석구,장종희 대한뇌종양학회 2022 Brain Tumor Research and Treatment Vol.10 No.3
Brain metastasis (BM), classified as a secondary brain tumor, is the most common malignant central nervous system tumor whose median overall survival is approximately 6 months. However, the survival rate of patients with BMs has increased with recent advancements in immunotherapy and targeted therapy. This means that clinicians should take a more active position in the treatment paradigm that passively treats BMs. Because patients with BM are treated in a variety of clinical settings, treatment planning requires a more sophisticated decision-making process than that for other primary malignan- cies. Therefore, an accurate prognostic prediction is essential, for which a graded prognostic as- sessment that reflects next-generation sequencing can be helpful. It is also essential to understand the indications for various treatment modalities, such as surgical resection, stereotactic radiosurgery, and whole-brain radiotherapy and consider their advantages and disadvantages when choosing a treat- ment plan. Surgical resection serves a limited auxiliary function in BM, but it can be an essential thera- peutic approach for increasing the survival rate of specific patients; therefore, this must be thoroughly recognized during the treatment process. The ultimate goal of surgical resection is maximal safe resec- tion; to this end, neuronavigation, intraoperative neuro-electrophysiologic assessment including evoked potential, and the use of fluorescent materials could be helpful. In this review, we summarize the con- siderations for neurosurgical treatment in a rapidly changing treatment environment.
비누화반응에 의한 폐 Poly(butylene terephthalate)의 해중합
유지환,나상권,홍완해,김정규 한국고무학회 2002 엘라스토머 및 콤포지트 Vol.37 No.2
온화한 조건(80∼110℃, 대기압)하에서 비누화반응에 의해 폐 PBT의 입자를 해중합하였다. PBT의 해중합은 KOH 보다 NaOH가 보다 효과적이었으며, 반응온도가 증가하고 입자의 크기가 작을수록 해중합은 증가하였다. 해중합속도는 표면반응이 율속단계로서 PBT 입자표면에 생성물이 형성되지 않은 미반응핵 모델에 의해 표현할수 있었다. 겉보기활성화에너지는 98.1KJ/mol 이었으며, 85.1, 105㎛인 PBT 입자를 6시간 동안 해중합하였을때 TPA의 회수율은 약 95%정도였다. Waste PBT powder was depolymerized by saponification under the mild temperature conditions(80 ~ 110℃) and atmospheric pressure. In depolymerization of PBT, sodium hydroxide was more effective than potassium hydroxide. The depolymerization increased with increasing reaction temperature and decreasing particle size. The reaction kinetics of depolymerization could be expressed by the shrinking unreacted core model without product layer, in which the surface reaction was a rate determining step. The activation energy was 98.1 KJ/mol. The recovery ratio of the TPA obtained from the depolymerized PBT particles of 85.1 and 105 ㎛for 6 hours was about 95%.
질산에 의한 폐 폴리부틸렌텔레프탈레이트의 화학적 리사이클에 관한 연구
유지환,나상권,김정규,홍완해 한국공업화학회 2001 한국공업화학회 연구논문 초록집 Vol.2001 No.-
환경을 염두에 둔 재료(environmentally conscious materials) 또는 생태계와 조화된 재료(ecological materials)로 일컬어지는 환경재료(ecomaterials)에 대한 개념이 확산되면서 가까운 장래에 모든 재료는 재활용을 전제로 설계되지 않으면 안되며, 기존에 사용되고 있는 물질에 대해서는 재활용 기술의 개발이 가장 시급한 과제가 되고 있다. 폐플라스틱을 고분자 소재로 재 사용하는 경우 물성의 열화가 불가피하고, 에너지원으로서 PE, PP, PS등의 경우 발열량이 10,000 kcal/kg 정도인데 비해 polyester 수지는 5,000 kcal/kg 정도로 낮은 편이며, 연소시 다이옥신과 같은 대기오염물질을 유발시키므로 사용이 제한적이다. 따라서 환경적인 측면이 외에 자원의 재생이라는 차원에서 폐기물 재활용의 연구가 이루어져야 하므로 폐 PBT를 화학적인 처리과정을 통하여 수지의 출발물질인 TPA를 회수하고자 하였으며, 실험결과 질산의 농도와 반응온도가 증가하면 PBT의 해중합은 증가하고, 또한 입자의 크기가 작을수록 해중합은 증가하였다. 용융온도 이하에서 질산으로 PBT를 가수분해하는 반응은 수정수축핵모델에 적용됨을 확인하였으며, 겉보기 활성화에너지는 98.04 kJ/mol 이었다. 회수한 TPA의 순도는 약 93% 이었다.