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1.
Hayden J.D. Taft R.C. Kenkare P. Mazure C. Gunderson C. Nguyen B.-Y. Woo M. Lage C. Roman B.J. Radhakrishna S. Subrahmanyan R. Sitaram A.R. Pelley P. Lin J.-H. Kemp K. Kirsch H. 《Electron Devices, IEEE Transactions on》1994,41(12):2318-2325
An advanced, high-performance, quadruple well, quadruple polysilicon BiCMOS technology has been developed for fast 16 Mb SRAM's. A split word-line bitcell architecture, using four levels of polysilicon and two self-aligned contacts, achieves a cell area of 8.61 μm2 with conventional I-line lithography and 7.32 μm2 with I-line plus phase-shift or with deep UV lithography. The process features PELOX isolation to provide a 1.0 μm active pitch, MOSFET transistors designed for a 0.80 μm gate poly pitch, a double polysilicon bipolar transistor with aggressively scaled parasitics, and a thin-film polysilicon transistor to enhance bitcell stability. A quadruple-well structure improves soft error rate (SER) and allows simultaneous optimization of MOSFET and bipolar performance 相似文献
2.
J. D. Santos E. Longo M. E. Banja V. A. A. Espinoza C. A. Taft 《International journal of quantum chemistry》2005,102(3):302-312
We studied the interaction between H, Li, Na, and K with one and two C60 molecules using unrestricted Hartree–Fock (UHF) methods. We investigated the effects of distances between the doping atoms and the C60 clusters, total charges, interaction energies, stabilities, HOMO‐LUMO energy differences, charge distribution, and potential energy surfaces. The effect of each doping atom was analyzed and potential technological applications discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
3.
Gary Kemister Addy Pross Leo Radom Robert W. Taft 《Journal of computational chemistry》1981,2(4):470-477
Ab initio molecular orbital theory with the STO -3G basis set is used to examine both charge and energy interactions in a series of meta- and para-substituted phenylborate anions and toluenes. Comparison of the results is made with data for substituted anilinium cations. It is concluded that whereas NH is a powerful σ acceptor, with essentially no π interaction, BH is primarily a π donor, and, to a slight extent only, a π donor. CH3 is indicated to be both a weak σ and π donor. Energies of interaction of BH and NH with a series of substituents are an order of magnitude larger than corresponding values for CH3. Interaction energies for BH are of opposite sign to those for NH. The results may be understood qualitatively using perturbation molecular orbital (PMO ) theory. 相似文献
4.
15N NMR chemical shifts and n-->pi* electronic transition energy for metronidazole (1) has been calculated and compared with experimental data. A detailed computational study of 1 is presented, with special attention to the performance of various theoretical methods for reproducing spectroscopic parameters in solution. The most sophisticated approach involves density functional based on the Car-Parrinello molecular dynamics simulations of 1 in aqueous solution (BP86 level) and averaging chemical shifts and deltaE(n-->pi*) over snapshots from the trajectory. In the NMR and UV calculations for these snapshots (performed at the B3LYP level), a small number of discrete water molecules are retained, and the remaining bulk solution effects are included via a polarizable continuum model (PCM). A good agreement with experiment is also obtained using static geometry optimization and NMR computation of pristine 1 employing a PCM approach. Further theoretical predictions are also reported for 17O NMR and deltaE(n-->pi*) of three hydroxycinnamic acid derivatives, which suggest that it is essential to incorporate the dynamics and solvent effects for NMR and UV calculations in the condensed phase. 相似文献
5.
The indirect exchange interaction between localized magnetic moments via virtual excitations from the valence band in intrinsic semiconductors is calculated taking into account the temperature, energy gaps, finite valence bands and effective masses. The inclusion of finite temperature effects changes significantly the phase and magnitude of the oscillations. For small gap semiconductors the oscillatory character and the possibility of ferro-magnetic as well as anti-ferromagnetic coupling are obtained. The exchange interaction oscillates with temperature suggesting interesting applications of this model. 相似文献
6.
The solvatochromic comparison method is used to unravel solvent polarity and hydrogen bonding effects on a variety of NMR spectral shifts and coupling constants. Solvent effects are rationalized in terms of the solvatochromic parameters π*, δ, α and β. Properties analyzed include 19F shifts of 5-fluoroindole, 1H shifts of fluorodinitromethane, tert-butanol, phenol, 2-methylbut-1-en-3-yne, and thioacetamide, 1H and 13C shifts and J(13C1H) coupling constants of chloroform, 13C shifts of acetone, 15N shifts of pyridine, 15N and 29Si shifts of 1-methylsilatrane, and some J(119Sn,C,19F) coupling constants of polyalkyltin compounds. 相似文献
7.
IGP Link Weight Assignment for Operational Tier-1 Backbones 总被引:1,自引:0,他引:1
Intradomain routing protocols, such as IS-IS or OSPF, associate a weight (or cost) with each link to compute traffic routes. Proposed methods for selecting link weights largely ignore two practical issues, that of service-level agreement (SLA) requirements and of failures. Optimizing the routing configuration, without bounding the SLA, could severely violate this requirement, which is one of the most important vehicles used by carriers to attract new customers. Since most failures are short-lived, it is much more practical not to have to change weight settings during these episodes. In this paper we propose a tabu-search heuristic for choosing link weights that takes into account both SLA requirements and link failures. Our algorithm selects link weights that still perform well, without having to be changed, even under failure events. To validate the heuristic, we develop a lower bound based on a formal integer linear program (ILP) model, and show that our heuristic solution is within 10% of the optimal ILP lower bound. We study the performance of the heuristic using two operational Tier-1 backbones. Our results illustrate two tradeoffs, between link utilization and the SLA provided, and between performances under failures versus performance without failures. We find that performance under transient failures can be dramatically improved at the expense of a small degradation during normal network operation (i.e., no failures), while simultaneously satisfying SLA requirements. We use our algorithm inside a prototype tool to conduct a case study and illustrate how systematic link weight selection can facilitate topology planning. 相似文献
8.
We have used the periodic quantum-mechanical method with density functional theory at the B3LYP level in order to study TiO2/Sn doped (1 1 0) surfaces and have investigated the structural, electronic and energy band properties of these oxides. Our calculated relaxation directions for TiO2 is the experimental one and is also in agreement with other theoretical results. We also observe for the doped systems relaxation of lattice positions of the atoms. Modification of Sn, O and Ti charges depend on the planes and positions of the substituted atoms. Doping can modify the Fermi levels, energy gaps as well as the localization and composition of both valence and conduction band main components. Doping can also modify the chemical, electronic and optical properties of these oxides surfaces increasing their suitability for use as gas sensors and optoelectronic devices. 相似文献
9.
M. B. C. Leo F. Neri de Souza C. A. Taft A. C. Pavo 《Journal of Molecular Structure》2003,640(1-3):163-165
Considering a DNA to carcinogen electron transfer mechanism for the carcinogenesis process whereas carcinogens react as a electrophilic and DNA as nucleophilic species we propose that the cancer protecting compounds will compete with the DNA for the donation of the electron for the carcinogens. In this work, theoretical calculations of several compounds with well-known protecting activity are performed. The results were treated by a multivariant analysis (principal component analysis) in order to relate the calculated electronic parameters with the protecting activities. 相似文献
10.
Jussara de Araújo Gonçalves André Luis Dantas Ramos Layla L. L. Rocha Anderson Kurunczi Domingos Robson S. Monteiro José Sotolongo Peres Nelson C. Furtado Carlton A. Taft Donato A. G. Aranda 《Journal of Physical Organic Chemistry》2011,24(1):54-64
Biodiesel can be obtained from fatty acid raw materials through esterification. The reactivity of lauric, palmitic, stearic, oleic, and linoleic fatty acids with methanol using powdered niobic acid as a heterogeneous catalyst was investigated in this work, both experimentally (in a batch reactor) and theoretically. A 23 experimental design was used, with methanol/fatty acid molar ratio, catalyst concentration, and temperature as main factors. An empirical model demonstrated that temperature is the most important variable. Fourteen heterogeneous and 56 homogeneous‐like kinetic models were tested. A homogeneous‐like model considering zero order for all species and inhibition by water was the most adequate for experiments without catalyst. A homogeneous‐like model considering a second‐order reaction in relation to the fatty acid and no water inhibition was the most adequate for niobic acid catalyzed reaction. Molecular modeling confirmed the experimental results showing that the reactivity is directly related to the increase of unsaturated bonds and the reduction of carbon chain length. The polarity of the fatty acid is determinant in the reactivity. At the molecular level, reaction occurs between the HOMO orbital of methanol and LUMO orbitals of fatty acids and reactivity is higher when the energy difference between these orbitals is lower. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献