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11.
A new method for the determination of optical constants of absorbing inhomogeneous thin films is proposed. It requires measurements at normal incidence of the reflectance and transmittance of the film. In an inhomogeneous thin film, the optical constants vary along the thickness of the film. It has been reported in the literature that only the spatial integral value of the absorption index needs to be considered if its value is small. Therefore, in the proposed method, the mean value of the absorption index was used. The validity of this assumption was tested. On the other hand, the variation in the refractive index along the thickness of the film was taken into account. The method is discussed along with the nature of the solutions obtained and the effects of various parameters and assumptions. The method is applied successfully to inhomogeneous thin films of zirconium oxide. 相似文献
12.
Energy-saving transparent heat mirrors based on tungsten oxide–gold WO3/Au/WO3 multilayer structures
Transparent heat mirrors are multilayer structures that transmit visible light while reflecting infrared heat. Heat mirrors based on tungsten oxide and gold multilayers WO3/Au/WO3 were fabricated by thermal evaporation, and their performance was investigated as a function of the thickness of the gold layer. First, the properties of individual layers were investigated. Atomic force microscopy revealed that all layers possessed smooth surfaces that were suitable for optical applications. The transmittance of the gold layers was found to decrease as the thickness is increased, with an opposite trend followed by infrared reflectance. In the multilayers, the thickness of the WO3 was fixed at 34 nm, whereas the thickness of the gold layers was varied in the range 20–44 nm. X-ray photoelectron spectroscopy was used to investigate the elemental diffusion among the various layers, and it revealed the presence of inter-diffusion of elements throughout the layers. The performance of the heat mirrors was evaluated on the basis of their optical behavior. The optimum thickness of the gold layer was found to be 36 nm, with a peak spectral transmittance of 84%. 相似文献
13.
Air pollution assessment in urban areas and its impact on human health in the city of Quetta, Pakistan 总被引:1,自引:0,他引:1
Syed Zafar Ilyas Azmat Iqbal Khattak S. M. Nasir Tabnak Qurashi Rehana Durrani 《Clean Technologies and Environmental Policy》2010,12(3):291-299
Nowadays, air over major cities throughout the world has become overburdened with gases produced by automobiles. The death
rate due to automobile pollution is increasing rapidly in the metropolitan areas. With passage of time, people realized that
polluted air has serious effects on their health, climate and economics. Weather and climate have integrated impact on human
activities resulting in worldwide concentration of the particulates of environmental pollution, viz., chlorofluorocarbons,
carbon dioxide, methane, nitrogen oxide, lead and several other dust and gaseous particles. Like many other mega cities in
the world the ambient air quality of Quetta, Pakistan is also deteriorating nowadays. Automobile exhausts and certain industrial
pollutants produce O3 by photochemical reactions. The particulate matter, particularly less than 10 μm in size, can pass through the natural protective
mechanism of human respiratory system and plays an important role in genesis and augmentation of allergic disorders. Sources
of air pollution in the area and the unique problem arising out of the emission from the vehicles, industries, etc. have been
described. Ambient air quality was monitored along with micrometeorological data and the results are discussed. The status
of air pollution in the area has been evaluated and a questionnaire survey was conducted to estimate the allergic symptoms
and exposure to assess the respiratory disorders. The data are analyzed to evaluate the critical situation arising out of
the emission of air pollutants and the impact on human health due to respirable diseases (RDs) in middle class sub-population
(activity-wise) in the area assessed. A strategic air quality management plan has been proposed. For the mitigation of air
pollution problems in the city, different measures to be adopted to maintain the balance between sustainable development and
environmental management have been discussed. Air pollution has significant effects on exacerbation of asthma, allergy and
other respiratory diseases. 相似文献
14.
The practical separation of cardanol from technical cashew nutshell liquid or its distillate has been effected by liquid chromatography
on Silica Gel H 60 (TLC type) with solute/absorbent in the range 1∶5–1∶6. Concentrates of the monoene, diene and triene constituents
of cardanol have been prepared by argentation liquid chromatography on Silica Gel H 60 with dry incorporation of 15% silver
nitrate. The present use of pressurized columns was made prior to the advent of flash chromatography.
This publication is Part 26 in the series of “Long Chain Phenols”. Reference 1 is Part 25. 相似文献
15.
Salabat Khan Abdul Rauf Baig Armughan Ali Bilal Haider Farman Ali Khan Mehr Yahya Durrani Muhammad Ishtiaq 《中国科学:信息科学(英文版)》2014,57(9):1-15
In this article,a novel unordered classification rule list discovery algorithm is presented based on Ant Colony Optimization(ACO). The proposed classifier is compared empirically with two other ACO-based classification techniques on 26 data sets,selected from miscellaneous domains,based on several performance measures. As opposed to its ancestors,our technique has the flexibility of generating a list of IF-THEN rules with unrestricted order. It makes the generated classification model more comprehensible and easily interpretable.The results indicate that the performance of the proposed method is statistically significantly better as compared with previous versions of AntMiner based on predictive accuracy and comprehensibility of the classification model. 相似文献
16.
Yamin Durrani 《电子设计技术》2010,17(6):64-64
正在采用开关式电源(SMPS)为射频功率放大器供电的蜂窝应用中,使用可变偏置WCDMA功率放大器和两阶GSM功率放大器可以最大化降低成本和复杂性,同时最大限 相似文献
17.
Xiangyun Zhou Sadeghi P. Lamahewa T.A. Durrani S. 《Signal Processing, IEEE Transactions on》2009,57(10):4014-4026
In this paper, we study the optimal training and data transmission strategies for block fading multiple-input multiple-output (MIMO) systems with feedback. We consider both the channel gain feedback (CGF) system and the channel covariance feedback (CCF) system. Using an accurate capacity lower bound as a figure of merit that takes channel estimation errors into account, we investigate the optimization problems on the temporal power allocation to training and data transmission as well as the training length. For CGF systems without feedback delay, we prove that the optimal solutions coincide with those for nonfeedback systems. Moreover, we show that these solutions stay nearly optimal even in the presence of feedback delay. This finding is important for practical MIMO training design. For CCF systems, the optimal training length can be less than the number of transmit antennas, which is verified through numerical analysis. Taking this fact into account, we propose a simple yet near optimal transmission strategy for CCF systems, and derive the optimal temporal power allocation over pilot and data transmission. 相似文献
18.
Optical properties of erbium oxide thin films deposited by electron beam evaporation 总被引:2,自引:0,他引:2
Erbium oxide thin films were deposited by electron beam evaporation on substrates heated to 300 °C. The effect of the introduction of oxygen on the structural, chemical and optical properties of the films was investigated. The films were characterized using X-ray diffraction, X-ray photoelectron spectroscopy and normal-incidence transmittance and reflectance. The films had microcrystallites embedded in an amorphous matrix, and their stoichiometry was dependent on the oxygen partial pressure. The transmittance spectra of the films revealed that they were optically inhomogeneous. A model based on an inhomogeneous layer was applied to extract the refractive index and extinction coefficient from the transmittance and reflectance spectra. 相似文献
19.
Weak amylopectin gels have been formed directly following dissolution of waxy maize granules. Rheological characterisation of these gels has been carried out as a function of stress and frequency. The gels are visually clear and homogeneous, and environmental scanning electron microscopy shows no trace of the original granules remaining. It is postulated that the origin of the gel network lies in pairwise aggregation of outer chains of the amylopectin molecules, presumably via double helix formation. However, these pairs of chain segments do not aggregate to develop crystallinity. 相似文献
20.
The letter presents a systolic architecture for computing the two-dimensional Wigner distribution. The system is based on exploiting a characterising array for the data and cordic cells to achieve structural modularity and parallelism. 相似文献