Browsing by Author "Liu, JH"

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Quantification on source/receptor relationship of primary pollutants and secondary aerosols from ground sources - Part II. Model description and case study
(2002-01-01)
Chen, CL
;
Tsuang, BJ
;
Pan, RC
;
Tu, CY
;
Liu, JH
A Circuit Trajectory transfer-coefficient model (CTx) is developed in this study based on the parameterization presented in a companion paper (Tsuang et al., Atmos. Environ., in this issue). CTx was tested by applying it to Metropolitan Taipei for the entire year 1998. The model was calibrated in January and verified throughout the year. The results indicate that the correlation coefficients (r) for daily concentrations of CO, NOx, SO2, PM2.5, and PM10 were 0.75, 0.69, 0.39, 0.55 and 0.55, respectively, with biases of the means ranging from 0% to 20% during the verification period. According to contour plots of contributed concentrations to the city, "teleconnections" between source emissions and their contributions to the city can be identified. In addition, the model captures most of the dust episodes except during the periods of Asian dust storms. The sensitivity analysis shows that the calculated PM10 concentration is most sensitive to its dry deposition velocity as well as its emission rate. A more thorough study on the deposition velocity of PM2.5 is suggested. (C) 2002 Elsevier Science Ltd. All rights reserved.
Quinoxalino-fused sultines and their application in Diels-Alder reactions
(1997-01-21)
Chung, WS
;
Liu, JH
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交大名義發表
;
應用化學系
;
National Chiao Tung University
The synthesis of 7,8-disubstituted quinoxalino[2,3-d]-[1,2 lambda(4)]oxathiine 2-oxides 7a-c, precursors for quinoxalino-o-quinodimethanes 3a-c, and their application in the Diels-Alder reactions are reported.
The photolysis and thermolysis of nitrogen-containing sultines in the preparation of heterocyclic-O-quinodimethanes.
(1998-08-23)
Chung, WS
;
Liu, JH
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應用化學系
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Department of Applied Chemistry
The syntheses of pyrazino-containing sultines and their application in Diels-Alder reactions with electron-poor olefins and [60]fullerene
(2000-06-02)
Liu, JH
;
Wu, AT
;
Huang, MH
;
Wu, CW
;
Chung, WS
The Diels-Alder reactions of heterocyclic o-quinodimethanes, generated in situ from 6,7-disubstituted quinoxalino[2,3-d]-[1,2 lambda(4)]oxathiine 2-oxides (6a-c), 2,3-disubstituted-8,9-dihydro-6H-8 lambda(4)-[1,2]oxathiino[4,5-g]quinoxalin-8-one (7a-c) (sultines), and pyrazinosultine (22), with electron-poor olefins and [60]fullerene are described. The heterocyclic-fused sultines 7a-c and 22 are readily prepared from the corresponding dibromides 9a-c and 24 with the commercially available Rongalite (sodium formaldehyde sulfoxylate). When heated in the presence of electron-poor dienophiles and [60]fullerene, all of the sultines underwent extrusion of SO2, and the resulting heterocyclic o-quinodimethanes (3a-d, 4a-c, and 25) were intercepted as the 1:1 adducts in good to excellent yields. The temperature-dependent H-1 NMR spectra of fullerene derivatives 31-38 show a dynamic process for the methylene protons. The activation free energies (Delta G(e)double dagger) determined for the boat-to-boat inversion of these pyrazino-containing C-60 compounds (31-34 and 38) are found to be in the range of 14.1-14.8 kcal/mol, but they are in the range of 15.2 to >17.1 kcal/mol for adducts 35-87. The activation free energies (Delta G(c)double dagger) are significantly affected by (1) the orientations and (2) the substituents of the quinoxaline rings and (3) the extended benzannulation in the arenes of C-60 adducts (see Table 2), which implies that both electronic interactions and steric effects between the aromatic addends and C-60 are important. Tautomerization of methylquinoxaline to its enamine is invoked as a rationalization for the lowering of Delta G(c)double dagger in some of the fulleroadducts.