Browsing by Author "Yang, Cheng-Han"

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Color tuning associated with heteroleptic cyclometalated Ir(III) complexes: influence of the ancillary ligand
(2007)
Chang, Chau-Jiun
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Yang, Cheng-Han
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Chen, Kellen
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Chi, Yun
;
Shu, Ching-Fong
We report the preparation of a series of new heteroleptic Ir(III) metal complexes chelated by two cyclometalated 1-(2,4-difluorophenyl) pyrazole ligands (dfpz)H and a third ancillary bidentate ligand ( L. X). Such an intricate design lies in a core concept that the cyclometalated dfpz ligands always warrant a greater pi pi* gap in these series of iridium complexes. Accordingly, the lowest one-electron excitation would accommodate the pi* orbital of the ancillary L(boolean AND)X ligands, the functionalization of which is then exploited to fine-tune the phosphorescent emission wavelengths. Amongst the L. X ligands designed, three classes (series 1-3) can be categorized, and remarkable bathochromic shifts of phosphorescence were observed by (i) replacing the 2-benzoxazol-2-yl-substituent (1a) with the 2-benzothiazol-2-yl group (1b) in the phenolate complexes, (ii) converting the pyridyl group (2a) to the pyrazolyl group (2b) and even to the isoquinolyl group (2c) in the pyrazolate complexes and (iii) extending the pi-conjugation of the benzimidazolate ligand from 3a to 3b. Single-crystal X-ray diffraction study on complex [(dfpz)Ir(bzpz)] (2b) was conducted to confirm their general molecular architectures. Complex 2b was also used as a representative example for fabrication of multilayered, green-emitting phosphorescent OLEDs using the direct thermal evaporation technique.
Efficient bit allocation algorithm for MPEG-4 advanced audio coding
(2006)
Yang, Cheng-Han
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Hang, Hsueh-Ming
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
In this paper, a new bit allocation algorithm, called EBFOS (Enhanced BFOS), is proposed for the MTEG4 Advanced Audio Coding (AAC) scheme. The notion of "bit-use efficiency" is suggested and the basic idea behind our approach is "give bits to the band with the maximum NMR gain per bit" or "retrieve bits from the band with the maximum bits per NMR loss", which is similar to the basic concept of the generalized BFOS (Breiman, Friedman, Olshen, and Stone) algorithm. However, the inter-band dependency of coding process in AAC is also taken into consideration in our approach. Simulation results show that the performance of the EBFOS scheme is significantly better than that of the MPEG-4 AAC Verification Model and is close to that of the trellis-based scheme, which achieves the minimum of a predefined NMR cost function. Also proposed in this paper is a fast version of our algorithm to reduce its computational complexity.
Factors affecting public transportation usage rate: Geographically weighted regression
(2015-08-01)
Chiou, Yu-Chiun
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Jou, Rong-Chang
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Yang, Cheng-Han
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
As the number of private vehicles grows worldwide, so does air pollution and traffic congestion, which typically constrain economic development. To achieve transportation sustainability and continued economic development, the dependency on private vehicles must be decreased by increasing public transportation usage. However, without knowing the key factors that affect public transportation usage, developing strategies that effectively improve public transportation usage is impossible. Therefore, this study respectively applies global and local regression models to identify the key factors of usage rates for 348 regions (township or districts) in Taiwan. The global regression model, the Tobit regression model (TRM), is used to estimate one set of parameters that are associated with explanatory variables and explain regional differences in usage rates, while the local regression model, geographically weighted regression (GWR), estimates parameters differently depending on spatial correlations among neighbouring regions. By referencing related studies, 32 potential explanatory variables in four categories, social-economic, land use, public transportation, and private transportation, are chosen. Model performance is compared in terms of mean absolute percentage error (MAPE) and spatial autocorrelation coefficient (Moran\' I). Estimation results show that the GWR model has better prediction accuracy and better accommodation of spatial autocorrelation. Seven variables are significantly tested, and most have parameters that differ across regions in Taiwan. Based on these findings, strategies are proposed that improve public transportation usage. (C) 2015 Elsevier Ltd. All rights reserved.
Fast bit allocation method for audio coding
(2005-10-13)
Yang, Cheng-Han
;
Hang, Hsueh-Ming
A fast bit allocation algorithm for audio coding is disclosed. A virtual Huffman codebook model is referred in a trellis-based optimization approach to obtain a set of optimized scale factors, and then the set of optimized scale factors is referred in a trellis-based optimization approach to obtain a set of optimized Huffman codebooks. Therefore, the present invention can significantly reduce the amount of computation for the bit allocation. Further, according to the experimental data, the present invention can keep almost the same compression efficiency as the prior art JTB optimization. Hence, the present invention is more suitable for practical applications.
Novel host material for highly efficient blue phosphorescent OLEDs
(2007)
Shih, Ping-I
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Chien, Chen-Han
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Chuang, Chu-Ying
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Shu, Ching-Fong
;
Yang, Cheng-Han
We report the synthesis and characterization of a novel silane - fluorene hybrid, triphenyl-(4-(9-phenyl- 9H-fluoren-9-yl) phenyl) silane (TPSi-F), used as the host material for blue phosphorescent devices. TPSi-F is constructed by linking p-substituted tetraphenylsilane to the fluorene framework through a non-conjugated, sp(3)-hybridized carbon atom (C- 9) to enhance thermal and morphological stabilities, while maintaining the much needed higher singlet and triplet energy gap. Highly efficient sky-blue phosphorescent OLEDs were obtained when employing TPSi-F as the host and iridium(III) bis[(4,6-difluorophenyl) pyridinato-N,C-2'] (FIrpic) as the guest. The maximum external quantum efficiency (max. E. Q. E.) of this device reached as high as 15% (30.6 cd A(-1)). Furthermore, upon switching the guest from FIrpic to a new blue phosphor FIrfpy, better blue-emitting OLEDs were produced with a max. E. Q. E. of 9.4% (15.1 cd A(-1)). These TPSi-F based blue phosphorescent devices show a 2-fold enhancement in device efficiency compared with reference devices based on the conventional host material 1,3-bis(9-carbazolyl) benzene (mCP).
Vaccinia viral A26 protein is a fusion suppressor of mature virus and triggers membrane fusion through conformational change at low pH
(2019-06-01)
Chang, Hung-Wei
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Yang, Cheng-Han
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Luo, Yu-Chun
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Su, Bo-Gang
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Cheng, Huei-Yin
Vaccinia mature virus requires A26 envelope protein to mediate acid-dependent endocytosis into HeLa cells in which we hypothesized that A26 protein functions as an acid-sensitive membrane fusion suppressor. Here, we provide evidence showing that N-terminal domain (aa1-75) of A26 protein is an acid-sensitive region that regulates membrane fusion. Crystal structure of A26 protein revealed that His48 and His53 are in close contact with Lys47, Arg57, His314 and Arg312, suggesting that at low pH these His-cation pairs could initiate conformational changes through protonation of His48 and His53 and subsequent electrostatic repulsion. All the A26 mutant mature viruses that interrupted His-cation pair interactions of His48 and His 53 indeed have lost virion infectivity. Isolation of revertant viruses revealed that second site mutations caused frame shifts and premature termination of A26 protein such that reverent viruses regained cell entry through plasma membrane fusion. Together, we conclude that viral A26 protein functions as an acid-sensitive fusion suppressor during vaccinia mature virus endocytosis. Author summary Vaccinia virus is a complex large DNA virus with a large number of viral membrane proteins to facilitate cell entry. Although it is well established that vaccinia mature virus uses endocytosis to enter cells, it remains unclear how it triggers membrane fusion in the acidic environment of endosomes. Recently, we hypothesized that A26 protein in vaccinia mature virus functions as an acid-sensitive membrane fusion suppressor, which suggests a novel viral regulation not present in other enveloped viruses. We postulated that conformational changes of A26 protein at low pH result in de-repression of viral fusion complex activity to trigger viral and endosomal membrane fusion. Here, we provide structural, biochemical and biological evidence demonstrating that vaccinia A26 protein does indeed function as an acid-sensitive fusion suppressor protein to regulate vaccinia mature virus membrane fusion during endocytosis. Our data reveal an important and unique checkpoint for vaccinia mature virus endocytosis that has not been described for other viruses. Furthermore, by isolating adaptive vaccinia mutants that escaped endocytic blockage, we discovered that mutations within the A26L gene serve as an effective strategy for switching the viral infection route from endocytosis to plasma membrane fusion, expanding viral host range.