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101.
John Mittenthal M. Raghavachari Arif Rana 《The Journal of the Operational Research Society》1996,47(11):1355-1365
In this paper, a number of non-regular bicriteria penalty functions of completion times on a single machine are studied. In each function, one criterion is a measure of central tendency (CT) of completion times, for example, mean or median, and the other is a measure of completion time dispersion (DSP). Five different DSP measures are considered in the paper. We discuss the characterizations of optimal sequences for some new functions and summarize previous results when appropriate for the pure bicriteria problem as well as for the convex combination of CT and DSP. Further, in the context of minimizing a dispersion measure, a comparison is made between the two dispersion measures of variance of completion times and total absolute deviations of completion times (TADC). 相似文献
102.
Dr. Elisabeth M. Fatila Dr. Eric B. Twum Arkajyoti Sengupta Dr. Maren Pink Dr. Jonathan A. Karty Prof. Krishnan Raghavachari Prof. Amar H. Flood 《Angewandte Chemie (International ed. in English)》2016,55(45):14057-14062
Contrary to the simple expectations from Coulomb's law, Weinhold proposed that anions can stabilize each other as metastable dimers, yet experimental evidence for these species and their mutual stabilization is missing. We show that two bisulfate anions can form such dimers, which stabilize each other with self‐complementary hydrogen bonds, by encapsulation inside a pair of cyanostar macrocycles. The resulting 2:2 complex of the bisulfate homodimer persists across all states of matter, including in solution. The bisulfate dimer's OH???O hydrogen bonding is seen in a 1H NMR peak at 13.75 ppm, which is consistent with borderline‐strong hydrogen bonds. 相似文献
103.
104.
Neelamegan Haridharan Raghavachari Dhamodharan 《Journal of polymer science. Part A, Polymer chemistry》2011,49(4):1021-1032
The polymerization of N‐vinylcarbazole (NVK) and carbazole methacrylate (CMA) was carried out using controlled radical polymerization methods such as atom transfer radical polymerization (ATRP), single electron transfer (SET)‐LRP, and single electron transfer initiation followed by reversible addition fragmentation chain transfer (SET‐RAFT). Well‐controlled polymerization with narrow molecular weight distribution (Mw/Mn) < 1.25 was achieved in the case of NVK by high‐temperature ATRP while ambient temperature SET‐RAFT polymerization was relatively slow and controlled. In the case of CMA, SET‐RAFT is found to be more suitable for the ambient temperature polymerization. The polymerization rate followed first order kinetics with respect to monomer conversion and the molecular weight of the polymer increased linearly with conversion. The controlled nature of the polymerization is further demonstrated by the synthesis of diblock copolymers from PNVK and PCMA macroinitiators using a new flavanone‐based methacrylate (FMA) as the second monomer. All the polymers exhibited fluorescence. The excimer bands in the homopolymers of PNVK and PCMA were very broad, which may be attributed to the carbazole–carbazole overlap interaction. The scanning electron microscopy analysis of the block copolymer reveals interesting morphological features. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
105.
Marcus K Weldon K.T Queeney Joseph Eng Jr Krishnan Raghavachari Yves J Chabal 《Surface science》2002,500(1-3):859-878
Due to the extreme dimensional scaling required by Moore's law, Si device technology is increasingly subject to the limitations imposed by the intrinsic physics and chemistry of surfaces and interfaces. In this review we outline ways in which fundamental surface science has contributed an understanding to the microelectronics community and discuss areas where surface science may impact future development. We focus on the example of silicon dioxide (SiO2) on silicon, since this interface lies at the heart of modern transistor technology and has therefore received a great deal of attention in recent years. We highlight a number of experimental and theoretical approaches that have elucidated the fundamental phenomena associated with the formation and evolution of this critical technological interface, revealing the remarkable interdependence of science and technology that now characterizes this rapidly evolving industry. 相似文献
106.
In this paper, we present an overview of Gaussian-3 (G3) theory, a composite technique that employs a sequence of ab initio
molecular orbital calculations to derive a total energy of a given molecular species. This method provides accurate energies
of molecular systems for the calculation of enthalpies of formation, ionization potentials, electron affinities, proton affinities,
etc. Also covered in this review are several variants of G3 theory including one based on scale factors (G3S) and an extended
version (G3X) that uses improved geometries and larger Hartree-Fock basis sets. Finally, the G3/99 test set of accurate experimental
data that is used for critical assessment is described. Overall, G3 theory has a mean absolute deviation from experiment of
1.07 kcal mol−1 for the G3/99 test set and G3S theory has a similar accuracy of 1.08 kcal mol−1. G3X theory is significantly more accurate with the mean absolute deviation from experiment decreasing from 1.07 kcal mol−1 (G3) to 0.95 kcal mol−1 (G3X). The scaled version of G3X theory shows a similar improvement.
Received: 23 January 2002 / Accepted: 7 April 2002 / Published online: 4 July 2002 相似文献
107.
108.
Ronald J. Duchovic William L. Hase H. Bernhard Schlegel Michael J. Frisch Krishnan Raghavachari 《Chemical physics letters》1982,89(2):120-125
Ab initio calculations on CH4 → CH3 + H were performed at the MP4/6-31G** level including all single, double triple and quadruple excitations. Although triple excitations have little effect on the dissociation energy, they are very important in the 2–3 Å range. The potential curve appears to rise more sharply than a Morse curve in this region. Correlation effects are not important for the HCH angle optimization. 相似文献
109.
The dipolar character of 1,8-naphthalimide together with polarization of the C(4)-H and C(5)-H donors has been utilized in receptor 1 to effectively bind chloride alongside triazole and phenylene units. The Cl(-) binding strength of 1 shows that the naphthalimide provides greater anion stabilization than an unactivated phenylene, and DFT calculations show that its collinear donor array can be a "urea-like" analog for CH···anion interactions. 相似文献
110.
Hua Y Ramabhadran RO Uduehi EO Karty JA Raghavachari K Flood AH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(1):312-321
Triazolophanes are used as the venue to compete an aliphatic propylene CH hydrogen‐bond donor against an aromatic phenylene one. Longer aliphatic C? H ??? Cl? hydrogen bonds were calculated from the location of the chloride within the propylene‐based triazolophane. The gas‐phase energetics of chloride binding (ΔGbind, ΔHbind, ΔSbind) and the configurational entropy (ΔSconfig) were computed by taking all low‐energy conformations into account. Comparison between the phenylene‐ and propylene‐based triazolophanes shows the computed gas‐phase free energy of binding decreased from ΔGbind=?194 to ?182 kJ mol?1, respectively, with a modest enthalpy–entropy compensation. These differences were investigated experimentally. An 1H NMR spectroscopy study on the structure of the propylene triazolophane’s 1:1 chloride complex is consistent with a weaker propylene CH hydrogen bond. To quantify the affinity differences between the two triazolophanes in dichloromethane, it was critical to obtain an accurate binding model. Four equilibria were identified. In addition to 1:1 complexation and 2:1 sandwich formation, ion pairing of the tetrabutylammonium chloride salt (TBA+ ? Cl?) and cation pairing of TBA+ with the 1:1 triazolophane–chloride complex were observed and quantified. Each complex was independently verified by ESI‐MS or diffusion NMR spectroscopy. With ion pairing deconvoluted from the chloride–receptor binding, equilibrium constants were determined by using 1H NMR (500 μM ) and UV/Vis (50 μM ) spectroscopy titrations. The stabilities of the 1:1 complexes for the phenylene and propylene triazolophanes did not differ within experimental error, ΔG=(?38±2) and (?39±1) kJ mol?1, respectively, as verified by an NMR spectroscopy competition experiment. Thus, the aliphatic CH donor only revealed its weaker character when competing with aromatic CH donors within the propylene‐based triazolophane. 相似文献