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RISS 인기검색어
- 검색키워드
- 저자 : Yufeng Tan (검색결과 4 건)
- 무료
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Thermal Control Analysis of a Primary Mirror for Large-Aperture Telescope
Yufeng Tan,Jihong Wang,Ge Ren,Zongliang Xie,Bi He 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.1
Extraneous thermal loads on the primary mirror of a large-aperture telescope directly influence the optical performance of the telescope through temperature gradients within the mirror and thermal boundary layer at the face sheet. In this paper, we propose a new thermal control system consisting of a flushing and sucking system for eliminating the excessive heat of a primary mirror. First, a 2.8 m-aperture lightweighted primary mirror is fabricated. Second, a thermo-optic analysis using finite element analysis is conducted in natural and forced convection. Finally, the optical performance denoted by Zernike polynomials with and without our proposed thermal control system is evaluated and examined. The comparative results reveal that the image quality of the primary mirror in forced convection is significantly enhanced with obvious reduction of optical surface distortion, thereby demonstrating the effectiveness of our proposed thermal control system.
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Thermal Oxidation of WSe<sub>2</sub> Nanosheets Adhered on SiO<sub>2</sub>/Si Substrates
Liu, Yingnan,Tan, Cheng,Chou, Harry,Nayak, Avinash,Wu, Di,Ghosh, Rudresh,Chang, Hsiao-Yu,Hao, Yufeng,Wang, Xiaohan,Kim, Joon-Seok,Piner, Richard,Ruoff, Rodney S.,Akinwande, Deji,Lai, Keji American Chemical Society 2015 NANO LETTERS Vol.15 No.8
<P>Because of the drastically different intralayer versus interlayer bonding strengths, the mechanical, thermal, and electrical properties of two-dimensional (2D) materials are highly anisotropic between the in-plane and out-of-plane directions. The structural anisotropy may also play a role in chemical reactions, such as oxidation, reduction, and etching. Here, the composition, structure, and electrical properties of mechanically exfoliated WSe<SUB>2</SUB> nanosheets on SiO<SUB>2</SUB>/Si substrates were studied as a function of the extent of thermal oxidation. A major component of the oxidation, as indicated from optical and Raman data, starts from the nanosheet edges and propagates laterally toward the center. Partial oxidation also occurs in certain areas at the surface of the flakes, which are shown to be highly conductive by microwave impedance microscopy. Using secondary ion mass spectroscopy, we also observed extensive oxidation at the WSe<SUB>2</SUB>–SiO<SUB>2</SUB> interface. The combination of multiple microcopy methods can thus provide vital information on the spatial evolution of chemical reactions on 2D materials and the nanoscale electrical properties of the reaction products.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-8/acs.nanolett.5b02069/production/images/medium/nl-2015-02069p_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b02069'>ACS Electronic Supporting Info</A></P>
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Monolayer Molybdenum Disulfide Transistors with Single-Atom-Thick Gates
Zhu, Yibo,Li, Yijun,Arefe, Ghidewon,Burke, Robert A.,Tan, Cheng,Hao, Yufeng,Liu, Xiaochi,Liu, Xue,Yoo, Won Jong,Dubey, Madan,Lin, Qiao,Hone, James C. American Chemical Society 2018 NANO LETTERS Vol.18 No.6
<P>Two-dimensional transition-metal dichalcogenides (TMDs) are unique candidates for the development of next-generation electronic devices. However, the large contact resistance between metal and the monolayer TMDs have significantly limited the devices’ performance. Also, the integration of ultrathin high-<I>k</I> dielectric layers with TMDs remains difficult due to the lack of dangling bonds on the surface of TMDs. We present monolayer molybdenum disulfide field-effect transistors with bottom local gates consisting of monolayer graphene. The atomic-level thickness and surface roughness of graphene facilitate the growth of high-quality ultrathin HfO<SUB>2</SUB> and suppress gate leakage. Strong displacement fields above 8 V/nm can be applied using a single graphene gate to electrostatically dope the MoS<SUB>2</SUB>, which reduces the contact resistances between Ni and monolayer MoS<SUB>2</SUB> to 2.3 kΩ·μm at low gate voltages. The devices exhibit excellent switching characteristics including a near-ideal subthreshold slope of 64 millivolts per decade, low threshold voltage (∼0.5 V), high channel conductance (>100 μS/μm), and low hysteresis. Scaled devices with 50 and 14 nm channels as well as ultrathin (5 nm) gate dielectrics show effective immunity to short-channel effects. The device fabricated on flexible polymeric substrate also exhibits high performance and has a fully transparent channel region that is desirable in optical-related studies and practical applications.</P> [FIG OMISSION]</BR>
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Improved Pupil-Size Diversity Technology for High-Resolution Imaging with Faint Objects
Xinxin Yang,Ge Ren,Haotong Ma,Qi Peng,Yufeng Tan,Jihong Wang 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.1
Phase aberration is one of the prime factors that degrade the quality of observed images. Pupil-size diversity technology (PSDT) is a newly developed post-processing method for aberration correction and image reconstruction. However, images reconstructed using PSDT suffer from massive grains when imaging astronomical faint objects, which extremely limits its further application. In this paper, we propose an improved PSDT with embedded denoising reprocessing to overcome this drawback. Diversity raw images, generated by modulating the size of the pupil, are firstly processed by blocking-matching and 3D filtering (BM3D), a state-of-art denoising algorithm. Then, the traditional PSDT can be employed to estimate the wavefront and reconstruct a high-resolution image. Both numerical simulations and experiment demonstrations show that our proposed strategy exhibits superior performance for aberrations correction and image restoration of faint objects in view of its efficiency and robustness. Being capable of realizing high-resolution imaging with faint objects, this proposed method may have important application prospects in the fields of astronomical object detection, remote sensing, \textit{etc.}
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