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81.
Shengyuan Xu James Lam Zhiping Lin Krzysztof Galkowski Wojciech Paszke Bartek Sulikowski 《International journal of control》2013,86(11):1047-1058
This paper considers the problem of positive real control for two-dimensional (2-D) discrete systems described by the Roesser model and also discrete linear repetitive processes, which are another distinct sub-class of 2-D linear systems of both systems theoretic and applications interest. The purpose of this paper is to design a dynamic output feedback controller such that the resulting closed-loop system is asymptotically stable and the closed-loop system transfer function from the disturbance to the controlled output is extended strictly positive real. We first establish a version of positive realness for 2-D discrete systems described by the Roesser state space model, then a sufficient condition for the existence of the desired output feedback controllers is obtained in terms of four LMIs. When these LMIs are feasible, an explicit parameterization of the desired output feedback controllers is given. We then apply a similar approach to discrete linear repetitive processes represented in their equivalent 1-D state-space form. Finally, we provide numerical examples to demonstrate the applicability of the approach. 相似文献
82.
Amit Belwalkar Hongsheng Xiao Wojciech Z. Misiolek Jean Toulouse 《Journal of Materials Processing Technology》2010,210(14):2016-2022
The extrusion behavior of tellurite glass in the supercooled liquid region was investigated. Good extrusion formability was observed under low strain rates at various temperatures in the glass transformation region investigated. Tube and holey fiber (HF) preforms were fabricated from tellurite glass billets using a laboratory press. In particular, the results for three-spoke HF design and round tube preforms with composition 75TeO2·20ZnO·5Na2O (TZN) are presented. The extruded preforms with precise geometrical features, an excellent surface quality and no crystallization were achieved in the temperatures range from 344 to 360 °C and at ram speeds ranging from 0.002 to 0.01 mm/s. Discrete shear bands were observed in the preforms, increasing in number and/or becoming better defined with increasing load and ram speed. Fewer shear bands were present when increasing the extrusion temperature from 344 to 360 °C. Thus, subsequent extrudates were successfully fabricated free of shear bands, providing good optical homogeneity that yielded solid and holey fibers that could provide much improved optical performance. 相似文献
83.
Wojciech Blajer 《Computer Methods in Applied Mechanics and Engineering》2011,200(13-16):1568-1576
Multibody systems are frequently modeled as constrained systems, and the arising governing equations incorporate the closing constraint equations at the acceleration level. One consequence of accumulation of integration truncation errors is the phenomenon of violation of the lower-order constraint equations by the numerical solutions to the governing equations. The constraint drift usually tends to increase in time and may spoil reliability of the simulation results. In this paper a comparative study of three methods for constraint violation suppression is presented: the popular Baumgarte’s constraint violation stabilization method, a projective scheme for constraint violation elimination, and a novel scheme patterned after that proposed recently by Braun and Goldfarb [D.J. Braun, M. Goldfarb, Eliminating constraint drift in the numerical simulation of constrained dynamical systems, Comput. Meth. Appl. Mech. Engrg., 198 (2009) 3151–3160]. The methods are confronted with respect to simplicity in applications, numerical effectiveness and influence on accuracy of the constraint-consistent motion. 相似文献
84.
Neil D. Hurley William H. Van Geertruyden Wojciech Z. Misiolek 《Journal of Materials Processing Technology》2009,209(18-19):5990-5995
During hot deformation of Al–Mg–Si alloys, a non-uniform microstructure is developed due to differences in localized strain. Physical simulations were performed to examine the effects of processing parameters such as deformation temperature, total reduction, rolling schedule and alloying additions on the grain structure evolution. Overall, the kinetics of recrystallization followed the traditional trends predicted by JMAK kinetics. Electron backscatter diffraction (EBSD) was used to quantify the difference in recrystallization kinetics at the sample surface and mid-thickness. The results showed that the surface showed elevated kinetics when compared to the sample mid-thickness. 相似文献
85.
Anna Litwiniuk Wojciech Bik Magorzata Kalisz Agnieszka Baranowska-Bik 《International journal of molecular sciences》2021,22(11)
Alzheimer’s disease (AD) is the most common form of neurodegenerative dementia. Metabolic disorders including obesity and type 2 diabetes mellitus (T2DM) may stimulate amyloid β (Aβ) aggregate formation. AD, obesity, and T2DM share similar features such as chronic inflammation, increased oxidative stress, insulin resistance, and impaired energy metabolism. Adiposity is associated with the pro-inflammatory phenotype. Adiposity-related inflammatory factors lead to the formation of inflammasome complexes, which are responsible for the activation, maturation, and release of the pro-inflammatory cytokines including interleukin-1β (IL-1β) and interleukin-18 (IL-18). Activation of the inflammasome complex, particularly NLRP3, has a crucial role in obesity-induced inflammation, insulin resistance, and T2DM. The abnormal activation of the NLRP3 signaling pathway influences neuroinflammatory processes. NLRP3/IL-1β signaling could underlie the association between adiposity and cognitive impairment in humans. The review includes a broadened approach to the role of obesity-related diseases (obesity, low-grade chronic inflammation, type 2 diabetes, insulin resistance, and enhanced NLRP3 activity) in AD. Moreover, we also discuss the mechanisms by which the NLRP3 activation potentially links inflammation, peripheral and central insulin resistance, and metabolic changes with AD. 相似文献
86.
Wojciech Polkowski Natalia Sobczak Rafał Nowak Artur Kudyba Grzegorz Bruzda Adelajda Polkowska Marta Homa Patrycja Turalska Merete Tangstad Jafar Safarian Elmira Moosavi-Khoonsari Alejandro Datas 《Journal of Materials Engineering and Performance》2018,27(10):5040-5053
For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism. 相似文献
87.
Electropolishing and passivation of NiTi shape memory alloy 总被引:2,自引:0,他引:2
Electropolishing of NiTi alloy has been investigated. The influence of polishing bath composition and the operating conditions instead of the conditions of the process on the quality of the surface, evaluated by AFM and SEM methods, was established. Morphologically uniform surfaces were obtained only in the case of solutions containing hydrofluoric and sulfuric acids. Electropolished samples were sterilized and thermally passivated, then their corrosion resistance was measured in Tyrode's physiological solution. It was established that already after the electropolishing the corrosion resistance of NiTi alloy increases due to the spontaneously formed TiO2 layer. The increase of the thickness of the layer during sterilization and thermal passivation causes further increase in the corrosion resistance. 相似文献
88.
Kristopher Page Michael Wilson Nicola J. Mordan Wojciech Chrzanowski Jonathan Knowles Ivan P. Parkin 《Journal of Materials Science》2011,46(19):6355-6363
The adhesion of Staphylococcus aureus was studied using a selection of laboratory-prepared and commercially available coated glass substrates using a simple methodology.
Substrates were examined by scanning electron microscopy, atomic force microscopy and water droplet contact angles. It was
found that microbial adhesion was independent of surface roughness, when this was of a lower magnitude than microbial size.
It was also found that microbial adhesion was greater for hydrophilic surfaces than for hydrophobic ones, but that on a photoinduced
superhydrophilic surface, microbes were more spread out—a potential benefit for more effective photocatalytic disinfection.
It is suggested that hydrophobic and photoinduced superhydrophilic surface coatings both have potential as a means of reducing
microbial fouling of surfaces. 相似文献
89.
Anna Przybyła Mirosław Chorążewski Edward Zorębski Wojciech Marczak 《International Journal of Thermophysics》2011,32(4):852-866
Densities and speeds of ultrasound in binary mixtures of dibromomethane with heptane have been measured within the temperature
range from 288.15 K to 318.15 K. From the experimental data, the thermodynamic excess volume, molar isobaric expansion, molar
isentropic compression, and ultrasonic speed were calculated. The excess volume and excess isentropic compression have opposite
signs, whereas the excess isobaric expansion is an S-shaped function of the mole fraction. An explanation was suggested to
account for the excesses in terms of intermolecular interactions. It involved energetic and steric factors. Moreover, it was
shown that the positive excess sound speed results almost entirely from the negative excess compression. 相似文献
90.
The effect of γ‐rays sterilization at ambient (23°C) and at dry ice temperatures (?78°C) on two biodegradable semicrystalline polyesters, namely poly(L ‐lactide) (PLLA) and poly(ε‐caprolactone) (PCL), was studied. The radical processes generated by irradiation were investigated by electron paramagnetic resonance (EPR) spectroscopy, whereas postradiation changes were monitored for 5 months by scanning calorimetry, thermogravimetric analysis, and apparent viscosity measurements. It was confirmed that the radiation sterilization initiates degradation in both studied polymers, however, the effect is smaller in PCL than in PLLA, and that the range of changes might be limited by lowering temperature of the exposure to γ‐rays. Newly formed oxygen containing functional groups confirmed by EPR and thermogravimetric analysis methods are produced in the irradiated polyesters. In PCL, the process might give rise to thermally induced cross‐linking via oxygen containing intermolecular bridges. During storage, in both irradiated materials, morphology determined by differential scanning calorimetry is changing ‐ PCL ability toward crystallization decreases insignificantly, whereas in PLLA the tendency is opposite ‐ on irradiation a contribution of crystalline phase is growing considerably, from 18 and 19% to 41 and 31% for PLLA irradiated at 23°C and at ?78°C, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献