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윤예준,한준희,윤상현 한국과학영재교육학회 2024 과학영재교육 Vol.16 No.1
소파 이동(moving sofa) 문제는 직각의 모서리를 끼고 있는 폭이 1인 복도를 통과할 수 있는 최대 단면적 소파를 찾는 이산기하 분야의 문제로, 1966년 Moser에 의해 제시된 이후 아직 미해결 문제로 남아 있다. 현재까지 알려진 최대 단면적의 최대 하한은 1992년 Gerver에 의해 발견된 2.2195...이고 최소 상한은 2018년 Kallus & Romik에 의해 증명된 2.37이다. 최소 상한 2.37이 다소 느슨한 것으로 보이는 반면에 최대 하한 2.2195...을 향상할 여지가 작다는 실험적 근거가 제시되었는데, 본 연구에서는 이 점에 주목하여 상한을 Gerver의 최대 하한에 좀 더 근접하도록 낮추었다. 이를 위해 기하학적 분기 한정법(geometric branch-andbound)과 이차계획법(quadratic programming)에 기반한 최적화 알고리즘을 구성하고, 알고리즘의 효율적 탐색을 위해 다양한 기하학적 성질을 증명하였다. 약한 기하학적 가정하에서, 제안한 최적화 알고리즘을 이용하여 개선된 상한 2.3361을 Kallus & Romik에 비해 훨씬 짧은 계산시간으로 얻었다. The moving sofa problem is a problem in discrete geometry that involves finding a shape with the maximum area that can pass through a right-angled corner in a hallway with unit width, and has remained an open problem since it was posed by Moser in 1966. The largest lower bound on the maximum area known to date is 2.2195..., found by Gerver in 1992, and the smallest upper bound is 2.37, proved by Kallus and Romik in 2018. While the minimum upper bound of 2.37 appears to be somewhat loose, experimental evidence suggests that there is little room for improvement in the largest lower bound of 2.2195.... In this study, we aim to lower the upper bound to be closer to Gerver’s maximum lower bound. For this purpose, we construct an optimization algorithm based on geometric branch-and-bound and quadratic programming, and prove various geometric properties for efficient search of the algorithm. Under a reasonable geometric assumption, the proposed optimization algorithm obtains an improved upper bound of 2.3361 with much shorter computation time than Kallus and Romik.
자기펄스성형이 적용된 Ti-Mn-Cu 합금의 미세구조 및 기계적 특성
윤예준,박천웅,최원준,변종민 한국분말야금학회 2021 한국분말재료학회지 (KPMI) Vol.28 No.1
Ti-based alloys are widely used in biomaterials owing to their excellent biocompatibility. In this study, Ti- Mn-Cu alloys are prepared by high-energy ball milling, magnetic pulsed compaction, and pressureless sintering. The microstructure and microhardness of the Ti-Mn-Cu alloys with variation of the Cu addition and compaction pressure are analyzed. The correlation between the composition, compaction pressure, and density is investigated by measuring the green density and sintered density for samples with different compositions, subjected to various compaction pressures. For all compositions, it is confirmed that the green density increases proportionally as the compaction pressure increases, but the sintered density decreases owing to gas formation from the pyrolysis of TiH2 powders and reduction of oxides on the surface of the starting powders during the sintering process. In addition, an increase in the amount of Cu addition changes the volume fractions of the α-Ti and β-Ti phases, and the microstructure of the alloys with different compositions also changes. It is demonstrated that these changes in the phase volume fraction and microstructure are closely related to the mechanical properties of the Ti-Mn-Cu alloys.
범죄현장을 재연 촬영한 사진의 증거능력을 높이는 방안 : 재연 촬영 사진의 지침 설정 및 원본 사진과의 유사도 검사
윤예준 ( Yea June Yoon ) 한국사진학회 2015 AURA Vol.0 No.34
This research is for increasing the evidence ability of crime scene`s re-shoot photography. To implement the research, first, I suggested the basic elements of re-shoot photography through reference when re-shooting the crime scenes. Second, I suggested the reverse projection of re-shoot photography in order to draw objective results beyond the limitation of seeing with the naked eye when re-shooting. After that, to extract the similar rate of original and re-shoot photography I obtained the similat rate through SURF interest point experiment.
윤예준 ( Yea June Yoon ) 한국사진학회 2014 AURA Vol.0 No.33
In this research, I will determine the minimum size that can recognize human and objects in the evidence photograph. In one of these studies, I focused on the face detection among the identification of human in the photograph. To determine the minimum size of faces in the photo, I used ``iphoto``. I randomly extracted 50 men and women faces from the Internet as the method of anlysis. Next, I set all the samples as 300 pixels and then resized them from 100% to 1%. That is to say, I checked the detection rate of these samples in ``iphoto``. As a result of the research, all the photos are able to be recognized to 21.4%, 64x64 pixel. This research can help appraise the photographs and criminal investigation.
이호준,윤예준,장진광,변종민,Lee, Hojun,Yun, Yejun,Jang, Jinkwang,Byun, Jongmin 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.2
Interest in eco-friendly materials with high efficiencies is increasing significantly as science and technology undergo a paradigm shift toward environment-friendly and sustainable development. MXenes, a class of two-dimensional inorganic compounds, are generally defined as transition metal carbides or nitrides composed of few-atoms-thick layers with functional groups. Recently MXenes, because of their desirable electrical, thermal, and mechanical properties that emerge from conductive layered structures with tunable surface terminations, have garnered significant attention as promising candidates for energy storage applications (e.g., supercapacitors and electrode materials for Li-ion batteries), water purification, and gas sensors. In this review, we introduce MXenes and describe their properties and research trends by classifying them into two main categories: transition metal carbides and nitrides, including Ti-based MXenes, Mo-based MXenes, and Nb-based MXenes.
회전형 원자층 증착기의 회전 속도에 따른 SnSe 분말 상 ZnO 박막 증착
정명준,윤예준,변종민,최병준,Jung, Myeong Jun,Yun, Ye Jun,Byun, Jongmin,Choi, Byung Joon 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.3
The SnSe single crystal shows an outstanding figure of merit (ZT) of 2.6 at 973 K; thus, it is considered to be a promising thermoelectric material. However, the mass production of SnSe single crystals is difficult, and their mechanical properties are poor. Alternatively, we can use polycrystalline SnSe powder, which has better mechanical properties. In this study, surface modification by atomic layer deposition (ALD) is chosen to increase the ZT value of SnSe polycrystalline powder. SnSe powder is ground by a ball mill. An ALD coating process using a rotary-type reactor is adopted. ZnO thin films are grown by 100 ALD cycles using diethylzinc and H<sub>2</sub>O as precursors at 100℃. ALD is performed at rotation speeds of 30, 40, 50, and 60 rpm to examine the effects of rotation speed on the thin film characteristics. The physical and chemical properties of ALD-coated SnSe powders are characterized by scanning and tunneling electron microscopy combined with energy-dispersive spectroscopy. The results reveal that a smooth oxygen-rich ZnO layer is grown on SnSe at a rotation speed of 30 rpm. This result can be applied for the uniform coating of a ZnO layer on various powder materials.
디지털 사진의 메타데이터가 삭제된 경로 탐색에 관한 연구
이용환 ( Yong Hwan Lee ),윤예준 ( Yea June Yoon ) 한국사진학회 2011 AURA Vol.0 No.25
After the image-editing techniques developed, anyone is now able to easily edit digital photographs. With the unaided eye it is hard to tell edited digital photos if they are edited or not. Digital photos are losing reliability owing to approachableness, the common characteristic of digital photos. For digital photos to achieve recognition as evidence in court, efforts are being made to find out forged photos. Accordingly, various techniques are being presented internally and externally to detect the fabrication of photos. However, the detection techniques which have been presented so far have limitation in a range of application. This is because they are only applicable when photos are in some particular condition. Once a photograph is fabricated, there remains information in the metadata. One can check whether it is forged or not by analyzing forged information theoretically. However, it is often undetectable as the metadata of photograph is deletable. If the metadata is deleted, one can use various techniques. In the case that the metadata of photograph is intentionally obliterated, one can raise the question of reliability on the photograph.