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71.
A new stochastic efficiency analysis approach, called stochastic efficiency with respect to a function (SERF), is applied to analyse optimal tree replanting on an area of recently harvested forest land. SERF partitions a set of risky alternative tree replanting strategies in terms of certainty equivalents (CEs) for a specified range of attitudes to risk. Both the entailed risk and the forest owner’s risk aversion are taken into account. The forest owner’s degree of risk aversion affects both the optimal tree replacement strategy and the reinvestment decision. The degree of risk aversion also needs to be taken into account when designing policy measures to affect forest investment. 相似文献
72.
本文讨论了由N个同型部件和一个服务设备组成的机器服务模型,在服务设备绝对可靠,或服务设备具有指数寿命,修理工对其修理的时间为PH分布,这两种情况下求得了系统的平稳概率分布,从而求得机器系统和服务设备的稳态可靠性指标,并证明了它们的首次失效时间均服从PH分布,服务设备和修理工的忙期亦服从PH分布. 相似文献
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Total energy calculations based on density functional theory (DFT) with generalized gradient approximation (GGA) and ultrasoft pseudopotential approximation and an analysis tool of atom‐resolved density of states (ADOS) have been used to investigate (1) the energetic profiles for the possible initial dissociative adsorption of XH4 (X?Si and Ge) onto the Si(100)? (2 × 2) surface to evaluate their reactivity and (2) the effect of surface electronic states of Si(100)? (2 × 2) on gaseous molecular precursors XH4 (X?Si and Ge) during initial dissociative adsorption to understand the factors governing their reactivity. Our calculated lower‐energy barrier for initial dissociative adsorption of GeH4 is due to the forming of stronger bond of Si? H between H within GeH4 and buckled‐down Si atom on the Si(100)? (2 × 2) surface accompanying the larger extent of unbuckling of the buckled Si?Si dimer on the Si(100)? (2 × 2) surface at the transition state. Our evaluated better reactivity for GeH4 than SiH4 (a factor of around 14.6) is slightly larger than observed higher reactivity for GeH4 than SiH4 (a factor of between 2 and 5 depending on the incident kinetic energy) employed supersonic molecular bean techniques. Finally, our calculated ADOS indicate that the surface electronic states of buckled Si?Si dimer on the Si(100)? (2 × 2) surface energetically favorably participate in the transition state during GeH4 initial dissociative adsorption to reduce the energy barrier, i.e., enhance its reactivity, in comparison with SiH4 initial dissociative adsorption onto the Si(100)? (2 × 2) surface under the same reaction conditions. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
76.
Identification and quantification of tamoxifen and four metabolites in serum by liquid chromatography-tandem mass spectrometry 总被引:1,自引:0,他引:1
Gjerde J Kisanga ER Hauglid M Holm PI Mellgren G Lien EA 《Journal of chromatography. A》2005,1082(1):6-14
We have developed a method for the determination of tamoxifen (tam) and its metabolites 4-hydroxytamoxifen (4OHtam), N-demethyltamoxifen (NDtam), N-dedimethyltamoxifen (NDDtam), tamoxifen-N-oxide (tamNox), and 4-hydroxy-N-demethyltamoxifen (4OHNDtam) in 50 microl human serum. Serum proteins were precipitated with acetonitrile. Deuterated-tamoxifen (D5 tam) was added as internal standard. Sample supernatant was injected into an on-line reversed-phase extraction column coupled with a C18 analytical column and analytes were detected by tandem mass spectrometry. The lower limits of quantification were 0.25 ng/mL for 4OHtam, NDtam and tam, 1.0 ng/mL for NDDtam and tamNox. Ranges of within- and between-day variation were 2.9-15.4% and 4.4-12.9%, respectively. 相似文献
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Minh Thang Le Hong Lien Nguyen Anh‐Tuan Vu Van Chuc Nguyen Jeffrey C. S. Wu 《中国化学会会志》2019,66(12):1713-1720
TiO2 loaded on several substrates such as carbon fiber, aluminum plate, silica plate, and glass plate was prepared using the chemical vapor deposition (CVD) method for the photocatalytic reduction of Cr(VI) in water with the presence of ethanol under Ultraviolet (UV) illumination. As‐prepared samples were characterized by X‐Ray Diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM). The catalyst with TiO2 loaded on carbon fiber possessed an extremely large surface area (1,463,91 m2/g), while the other catalysts possessed small surface areas (0.05–0.21 m2/g). The photocatalytic activity of TiO2 loaded on carbon fiber, which was determined by the conversion of Cr(VI) and the degradation of chemical oxygen demand (COD), was much higher than that of other catalysts. The reusability of TiO2 loaded on carbon fiber catalyst exhibited almost the same activity as the fresh catalyst. The results indicated that TiO2 loaded on carbon fiber is feasible for practical application. 相似文献
79.
Herein, an efficient Lewis acid catalyzed protocol for the homo-Nazarov cyclizations of alkenyl cyclopropyl ketones is reported. Alkenes bearing β-hydrogens (or silyl groups) provide 1.5:1 mixtures of methylene cyclohexenols and cyclohexenones. When no β-hydrogens (or silyl groups) are present, only cyclohexenones are observed. Products are rapidly formed in good to high yields (up to 93%) under mild conditions and could be readily derivatized. 相似文献
80.
Ting‐Hao Yang Chun‐Yen Liao Jen‐Lin Chang Chien‐Hung Lien Jyh‐Myng Zen 《Electroanalysis》2009,21(21):2390-2394
A simple electrochemical approach to evaluate oxygen reduction catalysts using an inexpensive screen‐printed ring disk carbon electrode system, consisting of a ring electrode deposited with MnO2 and a disk electrode modified with the catalysts for study, is developed in this study. The as‐prepared MnO2 is selective and sensitive for H2O2 oxidation in the presence of O2 and is crucial to the proposed approach. By coupling with a wall‐jet electrochemical cell, the product generated from the reduction reaction at the disk electrode can effectively be monitored at the MnO2‐deposited ring electrode. Model catalysts of nano‐Au and nano‐Pd representing 2e? reduction of O2 to H2O2 and 4e? reduction to H2O, respectively, were evaluated as electrode materials in oxygen reduction reaction to demonstrate the applicability of the proposed method. 相似文献