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91.
Virtualization has recently gained popularity largely due to its promise in increasing utilization,improving availability and enhancing security.Very often,the role of computer systems needs to change ... 相似文献
92.
Zongzhao Zhou Yew Soon Ong Prasanth B. Nair Andy J. Keane Kai Yew Lum 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2007,37(1):66-76
In this paper, we present a novel surrogate-assisted evolutionary optimization framework for solving computationally expensive problems. The proposed framework uses computationally cheap hierarchical surrogate models constructed through online learning to replace the exact computationally expensive objective functions during evolutionary search. At the first level, the framework employs a data-parallel Gaussian process based global surrogate model to filter the evolutionary algorithm (EA) population of promising individuals. Subsequently, these potential individuals undergo a memetic search in the form of Lamarckian learning at the second level. The Lamarckian evolution involves a trust-region enabled gradient-based search strategy that employs radial basis function local surrogate models to accelerate convergence. Numerical results are presented on a series of benchmark test functions and on an aerodynamic shape design problem. The results obtained suggest that the proposed optimization framework converges to good designs on a limited computational budget. Furthermore, it is shown that the new algorithm gives significant savings in computational cost when compared to the traditional evolutionary algorithm and other surrogate assisted optimization frameworks 相似文献
93.
The effects of different post-deposition annealing ambients (oxygen, argon, forming gas (95% N2 + 5% H2), and nitrogen) on radio frequency magnetron-sputtered yttrium oxide (Y2O3) films on n-type gallium nitride (GaN) substrate were studied in this work. X-ray photoelectron spectroscopy was utilized to extract the bandgap of Y2O3 and interfacial layer as well as establishing the energy band alignment of Y2O3/interfacial layer/GaN structure. Three different structures of energy band alignment were obtained, and the change of band alignment influenced leakage current density-electrical breakdown field characteristics of the samples subjected to different post-deposition annealing ambients. Of these investigated samples, ability of the sample annealed in O2 ambient to withstand the highest electric breakdown field (approximately 6.6 MV/cm) at 10−6 A/cm2 was related to the largest conduction band offset of interfacial layer/GaN (3.77 eV) and barrier height (3.72 eV). 相似文献
94.
Nonionic Mixed Surfactant Stabilized Water-in-Oil Microemulsions for Active Ingredient In Vitro Sustained Release 下载免费PDF全文
Olive oil is an excellent dispersing medium for water‐in‐oil microemulsions as it helps hydrate the skin and enhances the release of the active ingredients. In this study, mixed surfactants containing Span® 80 with varied Tween® series at 1:1 ratio were prepared with olive oil and water to produce water‐in‐oil microemulsions. The microemulsions were used to study the in vitro release of the active ingredients with different water solubilities. A microemulsion olive oil/water/mixed surfactant (56:4:40 by weight) was selected from the constructed phase diagram for further physical characterization. The analysis showed that the microemulsion composed of Span® 80 and Tween® 80 (ST80) was the most suitable surfactant combination. Equal amounts of ascorbic acid, caffeine and lidocaine were solubilized in ST80 microemulsions to study their release rate. Physical evaluation of ST80 microemulsions incorporating the active ingredients showed no apparent change compared to the ST80 microemulsion alone. The in vitro release study showed that the rate of active ingredients released from the microemulsion into the receptor chamber depends on their hydrophobicity, whereby lidocaine and caffeine were fivefold and twice as fast, respectively, with respect to ascorbic acid. ST80 microemulsions show constant rate of active ingredient release, demonstrating the sustained release properties of the system. 相似文献
95.
96.
This paper quantifies the impact of component sharing in a two-echelon assembled-to-stock system consisting of several common components and end-products. Whereas there is a benefit from risk pooling when component sharing is allowed, there is also a component-mismatch problem due to the demand uncertainty for end-products. We study these conflicting effects by comparing a particular component sharing policy, namely the equal-fractile allocation policy, with a make-to-stock system which does not allow the allocation of common components. The probabilistic analysis shows that when each type of component is shared by at least two end-products, the equal-fractile allocation policy will always help to reduce the safety stock required to be held at a sufficiently high service level. We also look at a special scenario of the equal-fractile allocation policy which takes into account inventory cost considerations. We show that this problem can be formulated as a newsvendor problem. 相似文献
97.
98.
Yew Hoong WongKuan Yew Cheong 《Journal of Alloys and Compounds》2011,509(35):8728-8737
Formation of ZrO2 by simultaneous thermal oxidation and nitridation in nitrous oxide of sputtered Zr on Si substrate is reported here for the first time. Sputtered Zr on Si substrate and followed by oxidation and nitridation in nitrous oxide ambient at 700 °C for various durations (5-20 min) have been systematically investigated. The structural and chemical properties of the samples were examined. Chemical depth profiles of the samples have been evaluated by X-ray photoelectron spectroscopy. Stoichiometric Zr-O (ZrO2) and its interfacial layer consisted of mixed sub-stoichiometric Zr-O, Zr-N, Zr-Si-O, Si-N, and/or Si-O-N phases were identified. A possible model related to the oxidation and nitridation mechanisms has been proposed and explained. Supportive results related to the model were obtained by energy filtered transmission electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier Transform infrared analysis. 相似文献
99.
This paper presents an integrated framework for small Unmanned Aerial Vehicle (UAV) flight control development. The approach provides a systematic procedure for flight control design process with a set of design tools that enables control engineers to rapidly synthesize, analyze and validate a candidate controller design. A model-based environment integrated with control synthesis, off-line and real-time simulation is developed for flight control synthesis, analysis and testings. The effectiveness of the proposed integrated framework is demonstrated by applying the framework approach to a small UAV testbed. Software-in-the-loop, processor-in-the-loop and flight testings are conducted with the synthesized controller implemented. Closed-loop performance and robustness results obtained are presented. 相似文献
100.
Thin (∼5.0 nm) Y2O3 films were deposited on n-type Si (1 0 0) substrate using RF magnetron sputtering. Detailed studies on the effects of post-deposition annealing (PDA) temperatures (400, 600, 800, and 1000 °C) in argon ambient on these films were performed by X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), field emission scanning electron microscopy, and atomic force microscopy. Interfacial layer (IL) of SiO2 in between Y2O3 and the Si substrate for sample annealed from 400 to 800 °C had been suggested from the results of FTIR. As for sample annealed at 1000 °C, presence of IL might consist of both Y2Si2O7 and/or SiO2 through the detection of Y2Si2O7 compound and Si–O chemical bonding from XRD and FTIR analysis, respectively. For as-deposited sample, no detectable chemical functional group at the IL was recorded. Electrical characteristics of the Y2O3 films were acquired by fabricating metal-oxide–semiconductor capacitor as test structure. An improvement in the breakdown voltage (VB) and leakage current density (J) was perceived as the PDA temperature increased. Of the PDA samples, the attainment of the lowest effective oxide charge, interface trap density, total interface trap density, and the highest barrier height at 1000 °C had contributed to the acquisition of the highest VB and lowest J. 相似文献