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Nonlinear Response (nonlinear + response)
Selected AbstractsAdvanced Analysis of Steel Frames Using Parallel Processing and VectorizationCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2001C. M. Foley Advanced methods of analysis have shown promise in providing economical building structures through accurate evaluation of inelastic structural response. One method of advanced analysis is the plastic zone (distributed plasticity) method. Plastic zone analysis often has been deemed impractical due to computational expense. The purpose of this article is to illustrate applications of plastic zone analysis on large steel frames using advanced computational methods. To this end, a plastic zone analysis algorithm capable of using parallel processing and vector computation is discussed. Applicable measures for evaluating program speedup and efficiency on a Cray Y-MP C90 multiprocessor supercomputer are described. Program performance (speedup and efficiency) for parallel and vector processing is evaluated. Nonlinear response including postcritical branches of three large-scale fully restrained and partially restrained steel frameworks is computed using the proposed method. The results of the study indicate that advanced analysis of practical steel frames can be accomplished using plastic zone analysis methods and alternate computational strategies. [source] Nonlinear response of N2O flux to incremental fertilizer addition in a continuous maize (Zea mays L.) cropping systemGLOBAL CHANGE BIOLOGY, Issue 10 2005Claire P. McSwiney Abstract The relationship between nitrous oxide (N2O) flux and N availability in agricultural ecosystems is usually assumed to be linear, with the same proportion of nitrogen lost as N2O regardless of input level. We conducted a 3-year, high-resolution N fertilizer response study in southwest Michigan USA to test the hypothesis that N2O fluxes increase mainly in response to N additions that exceed crop N needs. We added urea ammonium nitrate or granular urea at nine levels (0,292 kg N ha,1) to four replicate plots of continuous maize. We measured N2O fluxes and available soil N biweekly following fertilization and grain yields at the end of the growing season. From 2001 to 2003 N2O fluxes were moderately low (ca. 20 g N2O-N ha,1 day,1) at levels of N addition to 101 kg N ha,1, where grain yields were maximized, after which fluxes more than doubled (to >50 g N2O-N ha,1 day,1). This threshold N2O response to N fertilization suggests that agricultural N2O fluxes could be reduced with no or little yield penalty by reducing N fertilizer inputs to levels that just satisfy crop needs. [source] Nonlinear response of laterally loaded piles and pile groupsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2009Wei Dong Guo Abstract In spite of extensive studies on laterally loaded piles carried out over years, none of them offers an expedite approach as to gaining the nonlinear response and its associated depth of mobilization of limiting force along each pile in a group. To serve such a need, elastic,plastic solutions for free-head, laterally loaded piles were developed recently by the author. They allow the response to be readily computed from elastic state right up to failure, by assigning a series of slip depths, and a limiting force profile. In this paper, equivalent solutions for fixed-head (FixH) single piles were developed. They are subsequently extended to cater for response of pile groups by incorporating p -multipliers. The newly established solutions were substantiated by existing numerical solutions for piles and pile groups. They offer satisfactory prediction of the nonlinear response of all the 6 single piles and 24 pile groups investigated so far after properly considering the impact of semi-FixH restraints. They also offer the extent to ultimate state of pile groups via the evaluated slip depths. The study allows ad hoc guidelines to be established for determining input parameters for the solutions. The solutions are tailored for routine prediction of the nonlinear interaction of laterally loaded FixH piles and capped pile groups. Copyright © 2008 John Wiley & Sons, Ltd. [source] Spectrally-resolved nonlinear spectroscopy of in-plane anisotropy in uniaxially-strained GaN epilayersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2005Satoru Adachi Abstract Spectrally-resolved four-wave mixing technique has revealed the internal structures of excitons in uniaxially strained gallium nitride films. Nonlinear response of four-wave mixing on the oscillator strength highlights the polarized excitons, and therefore allows us to map out the uniaxial strain field and the resultant anisotropic exchange splitting. Such a measurement gives a kind of crystalline analysis achieved in X-ray diffraction spectroscopy as well as information of the exciton fine structures including their temporal dynamics. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Numerical simulation of reinforcement strengthening for high-arch dams to resist strong earthquakesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2008Yuchuan Long Abstract This paper focuses on analyzing the nonlinear seismic response of high-arch dams with cantilever reinforcement strengthening. A modified embedded-steel model is presented to evaluate the effects of the strengthening measure on alleviating the extension and opening of cracks under strong earthquakes. By stiffening reinforced steel, this model can easily consider the steel,concrete interaction for lightly reinforced concrete (RC) members without the need of dividing them into RC and plain concrete zones. The new tensile constitutive relations of reinforced steel are derived from the load,deformation relationship of RC members in direct tension. This model has been implemented in the finite element code and its applicability is verified by two numerical simulations for RC tests. Subsequently, numerical analyses for a 210-m high-arch dam (Dagangshan arch dam) are conducted with and without the presence of cantilever reinforcement. Numerical results show that reinforcement strengthening can reduce the nonlinear response of the arch dam, e.g. joint opening and crest displacement, and limit the extension and opening width of concrete cracks. Copyright © 2008 John Wiley & Sons, Ltd. [source] Influence of dynamic soil,structure interaction on the nonlinear response and seismic reliability of multistorey systemsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2007Armando Bárcena Abstract A set of reinforced concrete structures with gravitational loads and mechanical properties (strength and stiffness) representative of systems designed for earthquake resistance in accordance with current criteria and methods is selected to study the influence of dynamic soil,structure interaction on seismic response, ductility demands and reliability levels. The buildings are considered located at soft soil sites in the Valley of Mexico and subjected to ground motion time histories simulated in accordance with characteristic parameters of the maximum probable earthquake likely to occur during the system's expected life. For the near-resonance condition the effects of soil,structure interaction on the ductility demands depend mainly on radiation damping. According to the geometry of the structures studied this damping is strongly correlated with the aspect ratio, obtained by dividing the building height by its width. In this way, for structures with aspect ratio greater than 1.4 the storey and global ductility demands increase with respect to those obtained with the same structures but on rigid base, while for structures with aspect ratio less than 1.4 the ductility demands decrease with respect to those for the structures on rigid base. For the cases when the fundamental period of the structure has values very different from the dominant ground period, soil,structure interaction leads in all cases to a reduction of the ductility demands, independently of the aspect ratio. The reliability index , is obtained as a function of the base shear ratio and of the seismic intensity acting on the nonlinear systems subjected to the simulated motions. The resulting reliability functions are very similar for systems on rigid or on flexible foundation, provided that in the latter case the base rotation and the lateral displacement are removed from the total response of the system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Quantitative tests for stratigraphic cyclicityGEOLOGICAL JOURNAL, Issue 4 2008R. J. Bailey Abstract Periodic Milankovitch (M-) orbital forcing provides an explanation for subjectively recognized short-term repetition of lithofacies-,cycles'-in the stratigraphic record. Tests of this explanation often find no order in the lithofacies and/or no regularity in the recurrence of lithofacies. This does not disprove the influence of M-forcing, but a sedimentary response in terms of irregular M-forced ,cycles' is indistinguishable from one in which repetition of facies is not M-forced. Use of such cycles in time calibration is correspondingly suspect. Stricter, dimensional cyclicity invokes Sander's Rule, which suggests periodicity in sedimentation, for which M-forcing provides an obvious explanation. Time calibration on the basis of strict cyclicity thus appears more dependable. Objective tests for regular M-forced stratigraphic cyclicity commonly depend upon spectral analyses. Such tests are not unambiguous. Bilogarithmic thickness/frequency plots derived from objective layer thickness inventories (LTI) provide an alternative. Commonly, such plots show power-law relationships that preclude dimensional M-cyclicities. By contrast, a model data series that perfectly encodes the M-cyclic fluctuations in terrestrial insolation generates a strongly inflected, non-power-law LTI plot. Power-law plots result where the model data series is decimated by random hiatuses, with numbers and durations tuned to M-cycle frequencies. It seems improbable that natural data series record such tuning. The general absence of strict cyclicity in the M-frequency range is more likely to reflect the nonlinear response of sedimentary systems to cyclic M-forcing of insolation. Interestingly, when applied to the classically cyclic lacustrine Triassic sediments of the Newark Basin, USA, the LTI test suggests a decimated record, preserving some evidence of M-cyclicity. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nonlinear response of laterally loaded piles and pile groupsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2009Wei Dong Guo Abstract In spite of extensive studies on laterally loaded piles carried out over years, none of them offers an expedite approach as to gaining the nonlinear response and its associated depth of mobilization of limiting force along each pile in a group. To serve such a need, elastic,plastic solutions for free-head, laterally loaded piles were developed recently by the author. They allow the response to be readily computed from elastic state right up to failure, by assigning a series of slip depths, and a limiting force profile. In this paper, equivalent solutions for fixed-head (FixH) single piles were developed. They are subsequently extended to cater for response of pile groups by incorporating p -multipliers. The newly established solutions were substantiated by existing numerical solutions for piles and pile groups. They offer satisfactory prediction of the nonlinear response of all the 6 single piles and 24 pile groups investigated so far after properly considering the impact of semi-FixH restraints. They also offer the extent to ultimate state of pile groups via the evaluated slip depths. The study allows ad hoc guidelines to be established for determining input parameters for the solutions. The solutions are tailored for routine prediction of the nonlinear interaction of laterally loaded FixH piles and capped pile groups. Copyright © 2008 John Wiley & Sons, Ltd. [source] Facile synthesis, characterization, and potential applications of two kinds of polymeric pH indicators: Phenolphthalein formaldehyde and o -cresolphthalein formaldehydeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2005Zhihong Liu Abstract Two kinds of applicable polymeric pH indicators were synthesized by the reaction of phenolphthalein and o -cresolphthalein with formaldehyde under alkaline conditions by a one-pot method. The synthesized products were fully characterized with Fourier transform infrared, 1H NMR, ultraviolet,visible spectroscopy, and gel permeation chromatography. The results indicated that the reaction was a typical phenol formaldehyde reaction. The dosage of formaldehyde and the reaction time were well controlled to obtain soluble polymers, instead of crosslinked products. The polymeric-pH-indicator-immobilized poly(vinyl alcohol) (PVA) membranes were easily fabricated and had good long-term stability under highly basic conditions and a fast equilibrium response. Moreover, the phenolphthalein formaldehyde immobilized PVA membrane had a linear response from pH 10.0 to 14.0, and so it has promise as a optical transducer for high pH value determinations. The o -cresolphthalein formaldehyde immobilized PVA membrane had a nonlinear response from pH 9.0 to 13.0. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1019,1027, 2005 [source] Frequency shifting and pulse shaping with photonic-crystal fibers for coherent nonlinear spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2006Ya. M. Linik Abstract The frequency-shifted and pulse-shaped output of photonic-crystal fibers (PCFs) pumped by amplified femtosecond Cr:forsterite laser pulses is employed for frequency- and time-resolved four-wave mixing (FWM) spectroscopy. Cross-correlation frequency-resolved optically gated laser-induced grating (LIG) technique is applied for the characterization of the pulse-shaped blue-shifted PCF output. The light pulses produced in the PCF are combined with the second-harmonic output of the Cr:forsterite laser, to probe a doublet of Raman resonances in the nonlinear response of a test object by means of coherent anti-Stokes Raman scattering (CARS). Copyright © 2006 John Wiley & Sons, Ltd. [source] Ultra-large effective-area, higher-order mode fibers: a new strategy for high-power lasersLASER & PHOTONICS REVIEWS, Issue 6 2008S. Ramachandran Abstract This paper describes the physics and properties of a novel optical fiber that would be attractive for building high-power fiber lasers and amplifiers. Instead of propagating light in the fundamental, Gaussian-shaped mode, we describe a fiber in which the signal is forced to travel in a single, desired higher order mode (HOM). This provides for several advantages over the conventional approach, ranging from significantly higher ability to scale mode areas (and hence laser powers) to managing dispersion for ultra-short pulses , a capability that is practically nonexistent in conventional fibers. Particularly interesting is the fact that this approach challenges conventional wisdom, and demonstrates that for applications requiring meter-length fibers (as in high-power lasers), signal stability actually increases with mode order. Using this approach, we demonstrate mode areas exceeding 3200 ,m2, and propagate signals with negligible mode distortions over up to 50-meter lengths. We describe several pulse propagation experiments in which we test the nonlinear response of this fiber platform, ranging from managing dispersive effects in femtosecond pulse systems, to reducing Brillouin scattering impairments in systems operating with the nanosecond pulses. [source] Understanding the nonlinear-optical response of a liquid-core photonic-crystal fiberLASER PHYSICS LETTERS, Issue 1 2010A.A. Voronin Abstract We demonstrate single-mode guiding in a 4- , m-inner-diameter hollow photonic-crystal fiber filled with a highly nonlinear liquid. The nonlinear response of such a fiber is shown to drastically differ from a typical nonlinear response of a silica waveguide. Strong inertia of optical nonlinearity of the liquid filling the fiber core translates into a pulse-width-dependent red shift of the spectrally broadened fiber output. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Humidity estimation using neural network and optical fiber sensorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2009Kirthi L. Sreenivasan Abstract An optical fiber (OF) sensor with enhanced dynamic range and high sensitivity is realized to detect varying range of relative humidity (RH). For precise and independent estimation/prediction of RH from its nonlinear response, feed forward artificial neural network (ANN) model is developed. Preprocessed stable sensor outputs and corresponding commercial sensor outputs were used to train ANN. Results show that ANN has been effective in successfully predicting RH from the response of OF sensor. Overall, neural network approach showed better performance in comparison to alternative calibration method. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 641,645, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24132 [source] Effects of plant phenology, nutrients and herbivory on growth and defensive chemistry of plantain, Plantago lanceolataOIKOS, Issue 2 2000C. M. Jarzomski To assess the combined effect of herbivory, nutrient availability and plant phenology on plant mass and defensive chemistry, we conducted a field experiment with plantain (Plantago lanceolata: Plantaginaceae) using three levels of herbivory, three levels of fertilizer and two harvest dates. Shoot mass of the no-herbivory plants showed a nonlinear response to increased fertilizer such that mass with high fertilizer was no greater than that with low fertilizer. In contrast, shoot mass of the low-herbivory plants (12% damage) was not influenced by fertilizer, but for high-herbivory plants (23% damage), there was a positive linear response to increased fertilizer. Increasing nutrient levels caused a decrease in iridoid glycoside concentration. Herbivory did not induce higher iridoid glycoside concentration in leaves of any age. But increasing herbivory resulted in a decrease in the concentration of catalpol in new leaves. Another experiment assessed how leaf age and plant age affected plant defensive chemistry. Total iridoid glycosides increased over 5 weeks, but catalpol only increased in new leaves. Overall, the order of importance in determining variation in iridoid glycoside concentration was plant phenology, nutrient availability and, to a much lesser extent, herbivory. [source] Thermo-optic nonlinear response of silver nanoparticle colloids under a low power laser irradiation at 532,nmPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2010Rouhollah Karimzadeh Abstract The thermo-optical properties of silver nanoparticles (AgNPs) in the water are investigated under irradiation of a continuous wave (CW) laser at 532,nm. Thermal conductivity of the AgNP colloids is estimated using the Maxwell model. The closed Z-scan measurements reveal thermal contribution for the nonlinear refractive index of the AgNPs. The Z-scan behavior is investigated based on nonlocal thermo-optic process. It is shown that the aberrant thermal lens model is in excellent agreement with the Z-scan experimental results of the sample. A fit allows extracting the values of nonlinear refractive index and thermo-optic coefficient to be ,1.0,×,10,8,cm2/W and ,0.99,×,10,4,W/mK, respectively. Our results suggest that thermal nonlinear effects play an important role in the development of photonic application involving metal nanoparticle colloids and in the investigation of nonlocal nonlinear processes. [source] Contrasting population changes in sympatric penguin species in association with climate warmingGLOBAL CHANGE BIOLOGY, Issue 3 2006JAUME FORCADA Abstract Climate warming and associated sea ice reductions in Antarctica have modified habitat conditions for some species. These include the congeneric Adélie, chinstrap and gentoo penguins, which now demonstrate remarkable population responses to regional warming. However, inconsistencies in the direction of population changes between species at different study sites complicate the understanding of causal processes. Here, we show that at the South Orkney Islands where the three species breed sympatrically, the less ice-adapted gentoo penguins increased significantly in numbers over the last 26 years, whereas chinstrap and Adélie penguins both declined. These trends occurred in parallel with regional long-term warming and significant reduction in sea ice extent. Periodical warm events, with teleconnections to the tropical Pacific, caused cycles in sea ice leading to reduced prey biomass, and simultaneous interannual population decreases in the three penguin species. With the loss of sea ice, Adélie penguins were less buffered against the environment, their numbers fluctuated greatly and their population response was strong and linear. Chinstrap penguins, considered to be better adapted to ice-free conditions, were affected by discrete events of locally increased ice cover, but showed less variable, nonlinear responses to sea ice loss. Gentoo penguins were temporarily affected by negative anomalies in regional sea ice, but persistent sea ice reductions were likely to increase their available niche, which is likely to be substantially segregated from that of their more abundant congeners. Thus, the regional consequences of global climate perturbations on the sea ice phenology affect the marine ecosystem, with repercussions for penguin food supply and competition for resources. Ultimately, variability in penguin populations with warming reflects the local balance between penguin adaptation to ice conditions and trophic-mediated changes cascading from global climate forcing. [source] Tree species range shifts at a continental scale: new predictive insights from a process-based modelJOURNAL OF ECOLOGY, Issue 4 2008Xavier Morin Summary 1Climate change has already caused distribution shifts in many species, and climate predictions strongly suggest that these will accelerate in the future. Obtaining reliable predictions of species range shifts under climate change is thus currently one of the most crucial challenges for both ecologists and stakeholders. 2Here we simulate the distributions of 16 North American tree species at a continental scale for the 21st century according to two IPCC storylines, using a process-based species distribution model that for the first time allows identification of the possible causes of distribution change. 3Our projections show local extinctions in the south of species ranges (21% of the present distribution, on average), and colonizations of new habitats in the north, though these are limited by dispersal ability for most species. Areas undergoing local extinctions are slightly larger under climate scenario A2 (+3.2 C, +22% on average) than B2 (+1.0 C, +19% on average). This small difference is caused by nonlinear responses of processes (leaves and flowers phenological processes in particular) to temperature. We also show that local extinction may proceed at a slower rate than forecasted so far. 4Although predicted distribution shifts are very species-specific, we show that the loss of habitats southward will be mostly due to increased drought mortality and decreased reproductive success, while northward colonizations will be primarily promoted by increased probability of fruit ripening and flower frost survival. 5Synthesis. Our results show that different species will not face the same risks due to climate change, because their responses to climate differ as well as their dispersal rate. Focusing on processes, our study therefore tempers the alarming conclusions of widely used niche-based models about biodiversity loss, mainly because our predictions take into account the local adaptation and trait plasticity to climate of the species. [source] Effects of Fat on Temporal Cooling by Menthol in LozengesJOURNAL OF FOOD SCIENCE, Issue 8 2001A-M.A. Allison ABSTRACT: Ingredients such as fat may suppress or enhance menthol cooling in a finished product. In this study, trained descriptive sensory panelists tested oral and nasal cooling, oral burn, and other attributes in lozenges with various concentrations of fat (0 to 5%) and menthol (0 to 0.4%). Increasing fat content reduced oral and nasal cooling and burn. Linear increases in menthol resulted in linear responses to nasal cooling and oral burn and nonlinear responses to oral cooling. Residual oral and nasal cooling and burn illustrated that the effect of fat became less important after the lozenge was expectorated. [source] What does the stress-gradient hypothesis predict?OIKOS, Issue 10 2010Resolving the discrepancies In recent years the importance of facilitative interactions in ecological communities is increasingly recognized. This phenomenon has been observed repeatedly, particularly in vegetation communities, in a wide range of environmental conditions. The current hypothesis predicts that the role of facilitation becomes increasingly important in conjunction with increasing stress. Several empirical studies, however, failed to detect such patterns, particularly at the extreme ends of the stress gradients. Herein, we present a conceptual model that may resolve discrepancies between expected and observed and provides a more precise framework of the existing hypotheses. By relaxing two common assumptions commonly used by the stress-gradient hypothesis (SGH) we are able to demonstrate that under some circumstances the importance of facilitation may be less at the extreme ends of these gradients. Namely, we first re-emphasize the notion that physiological response is not linear with respect to environmental changes along stress gradients. Second, it is argued that the net outcome of facilitative and competitive interactions is reflected in the fitness of individuals as a product of these two processes, in contrast to the commonly applied assumption of additivity. Accordingly, a synthesis of the concepts of population biology (measures of fitness) and plant physiology (nonlinear responses) with the stress gradient hypothesis while retaining the original simplicity of the SGH model contributes to a better specification of the predictions of the stress-gradient hypothesis and the resolution of observed contradictions. [source] Nonlinear Optical Properties of Ferrocene- and Porphyrin,[60]Fullerene DyadsCHEMPHYSCHEM, Issue 7 2007Evangelia Xenogiannopoulou Dr. Abstract A series of novel [60]fullerene,ferrocene and [60]fullerene,porphyrin dyads, in which a fullerene and an electron donating moiety are attached through a flexible triethylene glycol linker are synthesized and their nonlinear optical (NLO) response studied. Specifically, the third-order susceptibility ,(3) of all fullerene derivatives are measured in toluene solutions by the optical Kerr effect (OKE) technique using 532 nm, 35 ps laser pulses and their second hyperpolarizability , are determined. All fullerene dyads studied exhibit enhancement of their NLO response compared to pristine fullerenes which has been attributed to the formation of a charge separated state. All experimentally measured hyperpolarizability , values are also calculated by the semiempirical methods AM1 and PM3. A good correlation is found between the theoretical and experimental values, suggesting that simple semiempirical methods can be employed for the designing and optimization of the fullerene-containing dyads displaying improved nonlinear responses. [source] | ||||||||||||||||||||||