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151.
J. Gerstmayr H. J. Holl H. Irschik 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(2-3):135-145
Summary A numerical algorithm for studying the development of plastic and damaged zones in a vibrating structural element with a
large, guided rigid-body motion is presented. Beam-type elements vibrating in the small-strain regime are considered. A machine
element performing rotatory motions, similar to an element of a slider-crank mechanism, is treated as a benchmark problem.
Microstructural changes in the deforming material are described by the mesolevel variables of plastic strain and damage, which
are consistently included into a macroscopic analysis of the overall beam motion. The method is based on an eigenstrain formulation,
considering plastic strain and damage to contribute to an eigenstrain loading of a linear elastic background structure. Rigid-body
coordinates are incorporated into this beam-type structural formulation, and an implicit numerical scheme is presented for
iterative computation of the eigenstrains from the mesolevel constitutive behavior. Owing to the eigenstrain formulation,
any of the existing constitutive models with internal variables could in principle be implemented. Linear elastic/perfectly
plastic behavior is exemplarily treated in a numerical study, where plastic strain is connected to the Kachanov damage parameter
by a simple damage law. Inelastic effects like plastic shakedown and damage-induced low-cycle rupture are shown to occur in
the examplary problems.
Received 1 September 1999; accepted for publication 9 March 2000 相似文献
152.
M. R. Holl J. L. Garbini W. R. Murray V. Kumar 《Journal of Polymer Science.Polymer Physics》2001,39(8):868-880
A simple mechanism regulating polymer mobility is demonstrated to determine initial and final growth states of solid‐state microcellular foams. This mechanism, governed by the extent of plasticization of the polymer by the dissolved gases, is examined with a mass balance model and results from foam growth experiments. Polycarbonate was exposed to CO2, which acted as both a plasticizing gas and a physical blowing agent driving foam growth. The polycarbonate specimens were saturated to the equilibrium gas concentration at 25 °C for CO2 pressures of 1–6 MPa in 1‐MPa increments. Equilibrated specimens were heated in a glycerin bath until thermal equilibrium was reached, and a steady foam structure was attained. Glycerin bath temperatures of 30–150 °C in 10 °C increments were examined. Using knowledge of gas solubility, the equation of state for CO2, the effective glass‐transition temperature as a function of gas concentration, and a model for mass balance within a solid‐state foam, we demonstrate that foam growth terminates when sufficient gas is driven from the polycarbonate matrix into the foam cells. The foam cell walls freeze at the elevated bath temperature because of gas transport from the polycarbonate matrix and the associated rise in the polymer glass‐transition temperature to that of the heated bath. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 868–880, 2001 相似文献
153.
We consider the local-to-global principle for detecting linear dependence of points in groups of the Mordell-Weil type. As applications of our general setting we obtain corresponding statements for Mordell-Weil groups of non-CM elliptic curves and some higher-dimensional abelian varieties defined over number fields, and also for odd dimensional K-groups of number fields. 相似文献
154.
155.
Dr. Sven Weigelt Dr. Thomas Huber Frank Hofmann Dr. Micha Jost Markus Ritzefeld Prof. Dr. Burkhard Luy Dr. Christoph Freudenberger Prof. Dr. Zsuzsanna Majer Prof. Dr. Elemér Vass Dr. Jörg‐Christian Greie Dr. Lavinia Panella Dr. Bernard Kaptein Dr. Quirinus B. Broxterman Prof. Dr. Horst Kessler Prof. Dr. Karlheinz Altendorf Prof. Dr. Miklós Hollósi Prof. Dr. Norbert Sewald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(10):3264-3264
156.
Silvana Halac Ernesto García-Mendoza Anastazia T. Banaszak 《Photochemistry and photobiology》2009,85(3):807-815
This study demonstrates that UV radiation (UVR) reduces the photoprotective capacity of the diatom Phaeodactylum tricornutum by affecting xanthophyll cycle (XC) activity. The short‐term reduction of photosystem II (PSII) maximum efficiency of charge separation (Fv/Fm) in cells exposed to UVR could be explained mainly by a reduced photoprotective capacity under this condition. Phaeodactylum tricornutum cells acclimated to two different photosynthetically active radiation (PAR) intensities, high light (HL, 200 μmol quanta m?2 s?1) and low light (LL, 50 μmol quanta m?2 s?1), were exposed to saturating irradiance (1100 μmol quanta m?2 s?1) in the presence (PAR + UVR) and absence of UVR (PAR). HL cells exhibited a greater reduction in Fv/Fm in PAR + UVR when compared with the PAR treatment that was related to a reduction in the de‐epoxidation of XC pigments. In contrast, in LL cells, UVR did not considerably affect XC de‐epoxidation even though the reduction in Fv/Fm was greater than in HL cells. The negative effect of UVR on photoprotection was more pronounced in HL cells because they synthesized more XC pigments than LL cells. This was confirmed when XC activity was blocked with dithiothreitol and when PSII repair was inhibited with chloramphenicol (CAP). The differential reduction of Fv/Fm between PAR + UVR and PAR treatments disappeared when XC was blocked in HL cells. A higher reduction and an incomplete recovery of Fv/Fm were observed in cells incubated with CAP in the presence of UVR. Such responses confirm that UVR had a negative effect on photoprotective mechanisms causing an enhancement of damage by PAR, especially in HL‐acclimated cells in which heat dissipation is important for PSII regulation. 相似文献
157.
We simulate ABA triblock copolymer melts using a lattice Monte Carlo method, known as cooperative motion algorithm, probing various degrees of compositional asymmetry. Selected order-disorder transition lines are determined in terms of the segment incompatibility, quantified by product χN , and the triblock asymmetry parameters, α and β. We correlate the results of the simulation with the self-consistent field theory and an experimental study of polyisoprene-polystyrene-polyisoprene triblock melt by Hamersky and coworkers. In particular, we confirm the mean-field prediction that for highly asymmetric triblocks the short A -block is localized in the middle of the B -domain due to an entropic advantage. This results in the middle block relaxation and is consistent with the experimental data indicating that as the relatively short A -blocks are grown into AB diblock, from the B -block side, the order-disorder transition temperature is considerably depressed. 相似文献
158.
B. Hornberger M. D. De Jonge M. Feser P. Holl C. Holzner C. Jacobsen D. Legnini D. Paterson P. Rehak L. Strüder S. Vogt 《Journal of synchrotron radiation》2008,15(4):355-362
Scanning X‐ray microprobes are unique tools for the nanoscale investigation of specimens from the life, environmental, materials and other fields of sciences. Typically they utilize absorption and fluorescence as contrast mechanisms. Phase contrast is a complementary technique that can provide strong contrast with reduced radiation dose for weakly absorbing structures in the multi‐keV range. In this paper the development of a segmented charge‐integrating silicon detector which provides simultaneous absorption and differential phase contrast is reported. The detector can be used together with a fluorescence detector for the simultaneous acquisition of transmission and fluorescence data. It can be used over a wide range of photon energies, photon rates and exposure times at third‐generation synchrotron radiation sources, and is currently operating at two beamlines at the Advanced Photon Source. Images obtained at around 2 keV and 10 keV demonstrate the superiority of phase contrast over absorption for specimens composed of light elements. 相似文献
159.
C. Bauer A.K. Sharma U. Willer J. Burgmeier B. Braunschweig W. Schade S. Blaser L. Hvozdara A. Müller G. Holl 《Applied physics. B, Lasers and optics》2008,92(3):327-333
Optical methods are well-established for trace gas detection in many applications, such as industrial process control or environmental
sensing. Consequently, they gain much interest in the discussion of sensing methods for counterterrorism, e.g., the detection
of explosives. Explosives as well as their decomposition products possess strong absorption features in the mid-infrared (MIR)
spectral region between λ=5 and 11 μm. In this report we present two different laser spectroscopic approaches based on quantum
cascade lasers (QCLs) operating at wavelengths around λ=5 and 8 μm, respectively. Stand-off configuration for the remote detection
of nitro-based explosives (e.g., trinitrotoluene, TNT) and a fiber coupled sensor device for the detection of triacetone triperoxide
(TATP) are discussed.
PACS 42.62.Fi; 07.07.Df 相似文献
160.
Holló Berta Barta Petruševski Vladimir M. Kovács Gréta Bettina Franguelli Fernanda Paiva Farkas Attila Menyhárd Alfréd Lendvay György Sajó István E. Nagy-Bereczki Laura Pawar R. P. Szilágyi Imre Miklós Bódis Eszter Kótai László 《Journal of Thermal Analysis and Calorimetry》2019,138(2):1193-1205
Journal of Thermal Analysis and Calorimetry - A simple synthetic method was developed to prepare 4[Agpy2ClO4]·[Agpy4]ClO4 in a low-temperature decomposition process of [Agpy4]ClO4. A detailed... 相似文献