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71.
G. Fernández-Anaya J. C. Martínez-García V. Kučera 《International journal of control》2013,86(7):728-740
The preservation of both robust stability and weighted robust performance properties of controlled linear time-invariant single input single output (SISO) systems is studied, when performing substitutions (of the complex Laplace variable s ) by a particular class of rational strictly positive real functions ( SPR functions), the so-called strictly positive real functions of zero relative degree ( SPR0 functions). Concerning weighted robust performance and model-matching, we provide some results on preservation of controller optimality. 相似文献
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73.
M. Harničárová J. Valíček R. Grznárik H. Tozan P. Koštial M. Kušnerová 《Materialwissenschaft und Werkstofftechnik》2014,45(4):281-285
In recent years, laser cutting has been introduced and developed to such an extent that it is now thought to be one of the leading and indispensable manufacturing tools. At the present time, dross‐free and accurately‐cut parts are basically regarded as the major targets to aim for, because the costs and efforts associated with dross removal by postprocessing cut parts are considerable. Therefore, control of dross formation during laser cutting is an important factor in maintaining edge quality. The initial aim of this paper is to describe the importance of physico‐mechanical material properties that need to be taken into account in modeling of laser material processing in order to control melting of the material. 相似文献
74.
75.
Yung-Hsien Wu Chih-Ming Chang Chun-Yao Wang Chien-Kang Kao Alex Ku 《Microelectronic Engineering》2009,86(1):33-36
As the first step of DRAM manufacture, preanneal process plays an important role in determining the threshold voltage variation. It is found that the higher trans-1,2-dichloroethene flow in pad oxide growth and the higher nitrogen flow in high-temperature annealing step would respectively engender a lower boron segregation coefficient and higher nitridation of the oxide, both modify the boron distribution in the substrate and consequently the behavior of the threshold voltage. As the feature size of DRAM devices enter nanometer regime, besides gate oxidation, ion implantation and related thermal processes, the impact of preanneal process condition should be prudentially taken into consideration for rigorous control of the threshold voltage in the advanced DRAM production. 相似文献
76.
Porous membranes were prepared via phase inversion process from casting solutions composed of poly(vinylidene fluoride), hyperbranched polyglycerol (HPG), and N,N‐dimethylacetamide. To seek a stable presence of HPG in the resulting membranes, it was crosslinked in the casting solutions using 4,4′‐oxydiphthalic anhydride as the crosslinking agent. The membranes were characterized in terms of morphology, surface and bulk chemical compositions, water contact angle, porosity, water flux, and bovine serum albumin (BSA) adsorption experiments. The effects of HPG content and crosslinking degree on the membrane structure and properties were investigated. The increasing of crosslinking degree resulted in a significant improvement in HPG stability in the membrane matrix, and a remarkable enrichment of the crosslinked HPG at the separation surface was observed when the membrane was shaken in water at a relatively high temperature (60°C). This enrichment led to a decrease in the value of water contact angle and an improvement in fouling‐resistance. To optimize the membrane performance, a small amount of poly(vinylpyrrolidone) (PVP) was used as an additive, and it was found that the addition of PVP led to a considerable increase in water flux. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
77.
Danjela Kuščer Miha Skalar Janez Holc Marija Kosec 《Journal of the European Ceramic Society》2009,29(1):105-113
We have investigated the processing of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN–PT) thick films on platinised alumina substrates. Nanosized PMN–PT powder with 2 mol% of excess PbO was prepared by high-energy milling and deposited on the substrate using screen-printing technology. The films were then sintered at 950 °C in a PbO-rich atmosphere. The influence of the sintering time and the amount of PbO-containing packing powder was studied and related to the structural, microstructural, dielectric and piezoelectric properties of the film. In order to obtain a homogeneous and dense thick film without any secondary phase, the PMN–PT films had to be sintered in the presence of a PbO-based liquid phase that had to be completely removed from the thick film during the final stage of the sintering. Under optimal sintering conditions we obtained a room temperature relative dielectric permittivity of 3600, dielectric losses of 0.036, a Tm of 174 °C, a permittivity at the Tm of 21,000 and a d33 of 140 pC/N. 相似文献
78.
Perovskite structured La2Ti2O7 catalyst prepared by polymerized complex method was characterized and examined the photocatalytic activity by decomposing an azo dyestuff, Reactive Red 22, in aqueous solutions under UV irradiation. La2Ti2O7 powders prepared by polymerized complex method exhibit higher surface areas, better homogeneity and are more sensitive to solution than those prepared by solid-state method. The first derivatives of UV–vis DRS patterns confirmed the complete crystallization of La2Ti2O7 sintered at temperatures higher than 900 °C. The effects of sintering temperature of catalyst and solution pH of photocatalytic reaction were studied. The photocatalytic decomposition of Reactive Red 22 per unit surface area was found to be higher for experiments using La2Ti2O7 than using TiO2. However, the electron–hole recombination was found to be more obvious for La2Ti2O7 than for TiO2 because the network of metal cations constructed within La2Ti2O7 enhances the mobility of photogenerated electrons and holes. 相似文献
79.
A large number of data on mobility and mass have been newly obtained or reanalyzed for clusters of a diversity of materials, with the aim of determining the relation between electrical mobility (Z) and mass diameter d m = (6m/ π ρ ) 1/3 (m is the particle mass and ρ the bulk density of the material forming the cluster) for nanoparticles with d m ranging from 1 nm to 6.5 nm. The clusters were generated by electrospraying solutions of ionic liquids, tetra-alkyl ammonium salts, cyclodextrin, bradykinin, etc., in acetonitrile, ethanol, water, or formamide. Their electrical mobilities Z in air were measured directly by a differential mobility analyzer (DMA) of high resolution. Their masses m were determined either directly via mass spectrometry, or assigned indirectly by first distinguishing singly (z = 1) and doubly (z = 2) charged clusters, and then identifying monomers, dimers, … n-mers, etc., from their ordering in the mobility spectrum. Provided that d m > 1.3 nm, data of the form d m vs. [z(1+m g /m) 1/2 /Z)] 1/2 fall in a single curve for nanodrops of ionic liquids (ILs) for which ρ is known (m g is the mass of the molecules of suspending gas). Using an effective particle diameter d p = d m + d g and a gas molecule diameter d g = 0.300 nm, this curve is also in excellent agreement with the Stokes-Millikan law for spheres. Particles of solid materials fit similarly well the same Stokes-Millikan law when their (unknown) bulk density is assigned appropriately. 相似文献
80.
Ultrasound-modulated optical tomography based on the measurement of laser-speckle contrast was investigated. An ultrasonic beam was focused into a biological-tissue sample to modulate the laser light passing through the ultrasonic column inside the tissue. The contrast of the speckle pattern formed by the transmitted light was found to depend on the ultrasonic modulation and could be used for imaging. Variation in the speckle contrast reflected optical inhomogeneity in the tissue. With this technique, two-dimensional images of biological-tissue samples of as much as 25 mm thick were successfully obtained with a low-power laser. The technique was experimentally compared with speckle-contrast-based, purely optical imaging and with parallel-detection imaging techniques, and the advantages over each were demonstrated. 相似文献