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RISS 인기검색어
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- 저자 : 남원우 (검색결과 32 건)
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남원우,이상조 대한기계학회 1993 대한기계학회논문집 Vol.17 No.11
Most of the current 2-D object recognition systems are model-based. In such systems, the representation of each of a known set of objects are precompiled and stored in a database of models. Later, they are used to recognize the image of an object in each instance. In this thesis, the approach method for the 2-D object recognition is treating an object boundary as a string of structral units and utilizing string matching to analyze the scenes. To reduce string matching time, models are rebuilt by means of fuzzy c-means clustering algorithm. In this experiments, the image of objects were taken at initial position of a robot from the CCD camera, and the models are consturcted by the proposed algorithm. After that the image of an unknown object is taken by the camera at a random position, and then the unknown object is identified by a comparison between the unknown object and models. Finally, the amount of translation and rotation of object from the initial position is computed.
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Recyclable Porphyrin Catalyst with Core-shell Nanostructure
남원우,고수영,최보규,정병문 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.11
In the search for a simple preparation method of heterogeneous catalyst, the iron porphyrins were coordinated bonded to the surface of a polymeric core-shell nanosphere. The heterogeneous catalyst was characterized by FT-IR, scanning electron microscope, and UV-vis spectrophotometer. The iron porphyrin bound core-shell nanospheres was about 470 nm in diameter and their catalytic activity for cyclohexene oxidation was similar to a homogeneous iron porphyrin in a solvent composition range of 25-75% acetonitrile/water (v/v). In addition, they could be recovered by simple centrifugation and their catalytic activity was maintained more than the third cycle.
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Redox reactivity of LMCT and MLCT excited states of Earth-abundant metal complexes
남원우,이용민,Fukuzumi Shunichi 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.6
Precious metal complexes, which act as excellent photoredox catalysts, have now being replaced by earth-abundant metal complexes. This review focused on redox reactivity of ligand-to-metal charge transfer (LMCT) and metalto- ligand charge transfer (MLCT) excited states of earth-abundant metal complexes. Iron complexes with strongly σ-donating NHC-ligands (NHC = Nheterocyclic carbene) has emerged, featuring long lived LMCT excited states due to a significantly increased barrier for deactivation via metal centered states. A Fe(III)-NHC complex acts as an effective photoredox catalyst for various photocatalytic redox reactions. Although manganese(IV)-oxo complexes have no long-lived excited states (τ < < 1 ns). Once acids such as Sc(OTf)3 and HOTf are bound to the oxo moiety of Mn(IV)-oxo complexes, the photoexcitation of acid-bound Mn(IV)-oxo complexes resulted in formation of the excited states with microseconds lifetimes, which are capable of oxidation of substrates including benzene to phenol. Photoexcited states of Mn(III), Mn(II) and Mn(I) complexes act as photoreductants to reduce substrates including O2. On the other hand, photoexcited states of Co(IV) and Co(III) complexes act as photooxidants, whereas those of Co(II) and Co(I) complexes act as photoreductants. With regard to the excited state lifetime, [Cr(tpe)2]3+ (tpe = 1,1,1-tris (pyrid-2-yl)ethane) exhibited the longest luminescence lifetime (τ = 4500 μs), acting as an effective photoredox catalyst for photocatalytic redox reactions. The LMCT state of a Cr(0) complex acts as a super photoreductant. Thus, LMCT and MLCT excited states of earth-abundant metal complexes are utilized as strong photooxidants and photoreductants, respectively.
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