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961.
962.
Abstract. We propose the quasi‐maximum likelihood method to estimate the parameters of an RCA(1) process, i.e. a random coefficient autoregressive time series of order 1. The strong consistency and the asymptotic normality of the estimators are derived under optimal conditions. 相似文献
963.
Amy?Richards Chakra?WijesunderaEmail author Phil?Salisbury 《Journal of the American Oil Chemists' Society》2005,82(12):869-874
Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore
an important criterion by which oils are judged for usefulness in various food applications. In this study a method based
on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the
use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison
with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected
to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS.
Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile
lipid oxidation products hexanal and trans,trans-2,4-heptadienal. The PV calculated using this formula correlated (R
2=0.73) with those measured by conventional methods.
Presented in part at the 96th Annual Meeting of the AOCS, 1–4 May 2005, Salt Lake City, UT. 相似文献
964.
965.
Two conflicting structural models (platelet and fibril) have been proposed in the literature for pristine cis-poly(acetylene). The respective models have separate, distinct implications for the chemical, physical and electrical properties of the material, in particular, the cis-trans isomerization, doping and conduction mechanisms. Luttinger-type cis-poly(acetylene) was prepared and studied in the transmission electron microscope (TEM) by low-dose conventional imaging, in dark-field mode and by electron diffraction. Thin ‘films’ of the material were shown to consist of fibrillar nets, having fibrils of diameter 5–25 nm. Combined electron diffraction and dark-field observations in the TEM indicated the structural arrangement within the fibrils as that having polymer molecular chains aligned parallel to fibril axes. 相似文献
966.
A. Amara A. Ferdi A. Drici J.C. Bernde M. Morsli M. Guerioune 《Catalysis Today》2006,113(3-4):251-256
Co-evaporation technique from three sources was used to prepare Cu(In, Ga)Se2 polycrystalline thin films for photovoltaic conversion. Their conductivity was studied in the range 20–300 K. The grain boundary scattering mechanism is mainly responsible for the diffusion process in the latter materials. In the low temperature region, we interpret the data in terms of Mott law and the analysis is very consistent with the variable range hopping. However, thermoionic emission is predominant at high temperatures. When the conductivity deviates from the classical grain boundary conduction models, inhomogeneity is then considered and parameters such as the standard deviation and the mean potential barrier height are derived. Transmittance measurements yielded band gap values of 1.07 and 1.64 eV for CuInSe2 and CuGaSe2, respectively. 相似文献
967.
描述了PVC型材挤出真空定型模冷却排布的一种优化设计方法。这种方法使用下述的最小化标准可以同时确定冷却水道的直径和位置:型材平均温度、型材温度随时间积分的变化、不同型材表面的温度,基于Fletcher Reeves优化运算法则。 相似文献
968.
969.
Number of blends were prepared by intergrinding clinker, gypsum, fly ash, calcined clay, microsilica and limestone in laboratory ball mill in varying percentages, and their physical properties such as fineness, consistency, setting time and compressive strength have been determined. The durability tests on selected compositions were also conducted by exposing the mortar cubes separately in 5% Na2SO4 and 5% NaCl solutions till the age of 90 and 180 days. The performance was observed by compressive strength development criteria after various length of exposure. Results have been discussed and found that the durability of blended cement is higher than the ordinary Portland cement. 相似文献
970.
High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors. 相似文献