Nonlinear Aspects Research Articles

Narrative Nonlinearity and the Birth of the Wreader: A Hypertext Critical Reading of Selected Digital Literary Texts

ABSTRACT Drawing upon the critical views of hypertext theory, this paper seeks to investigate the genre of hypertext fiction, analyzing some of its aspects, especially the domination of narrative nonlinearity and the birth of the wreader. The paper argues that computer technologies have revolutionized the form and representation of literary texts as well as the relationship between writer and reader. The study first fathoms the aspects of narrative nonlinearity as represented in Michael Joyce’s novel Twelve Blue (1996), a representative of first-generation hypertext fiction, and the two short stories “From Head to Toe” by Arseniy Klishin and Laura Gray (2019) and “The Road” by Jason Malabed (2014), which belong to second-generation hypertext fiction. Instead of having narrative hierarchies, these hypertexts depend on hyperlinks, multiple reading pathways, and multimodal representation that contribute to optimizing narrative nonlinearity. The paper then analyzes the critical concept of wreader/wreading and applies it to the selected hypertexts, showing how electronic literary production is no longer an absolute creation of the author. The three selected hypertexts indicate that a work of hypertext fiction binds together reader and writer into a collaborative process in which the reader becomes a coauthor of the text.

Study on Critical Load for Multistage Hydraulic Cylinder

To prevent the appearance of buckling failure when the multistage hydraulic cylinder works, the finite element of compression rod simplified model instead of multistage hydraulic cylinder is established based on the importance of engineering safety operation. The linear and nonlinear buckling analysis for compression rod can be realized by the finite element analysis software called ABAQUS. Meanwhile, the value of critical load for compression rod can be calculated and compared from two aspects of linearity and nonlinearity. The results indicate that the value got from nonlinear buckling analysis is more conservative than linear buckling analysis and the value of critical load is proportional to the cross section area.

Transition mechanisms in cross-flow-dominated hypersonic flows with free-stream acoustic noise

Transition to turbulence in high-speed flows is determined by multiple parameters, many of which are not fully understood, leading to problems in developing physics-based prediction methods. In this contribution, we compare transition mechanisms in configurations with unswept and swept leading edges that are exposed to free-stream acoustic disturbances. Direct numerical simulations are run at a Mach number of six with the same free-stream noise, consisting of either fast or slow acoustic disturbances, with two different amplitudes to explore the linear and nonlinear aspects of receptivity and transition. For the unswept configuration, receptivity follows an established mechanism involving synchronisation of fast acoustic disturbances with boundary-layer modes. At high forcing amplitudes, transition proceeds via the formation of streaks and their eventual breakdown. In the swept case, the process of streak-induced transition is modified by the presence of a cross-flow instability in the leading-edge region. Linear stability analysis confirms the presence of a cross-flow mode as well as weaker first and second mode waves. Both fast and slow types of forcing independently stimulate an unusual transition mechanism involving significantly narrower streaks than those arising from the cross-flow instability behind the swept leading edge or those induced nonlinearly in the unswept case. In the observed transition process, the cross-flow mode leads to a thin layer of streamwise vorticity that breaks up under the influence of high spanwise wavenumber disturbances. These disturbances first appear in the leading-edge region.

Application of the nonlinear methods in pneumocardiogram signals.

In this work, the pneumocardiogram signals of nine rats were analysed by scale index, Boltzmann Gibbs entropy and maximum Lyapunov exponents. The scale index method, based on wavelet transform, was proposed for determining the degree of aperiodicity and chaos. It means that the scale index parameter is close to zero when the signal is periodic and has a value between zero and one when the signal is aperiodic. A new entropy calculation method by normalized inner scalogram was suggested very recently. In this work, we also used this method for the first time in an empirical data. We compared the both methods with maximum Lyapunov exponents and observed that using together the scale index and the entropy calculation method by normalized inner scalogram increases the reliability of the pneumocardiogram signal analysis. Thus, the analysis of the pneumocardiogram signals by those methods enables to compare periodical and/or nonlinear aspects for further understanding of dynamics of cardiorespiratory system.

Enhancing network activation in natural killer cells: predictions from in silico modeling.

Natural killer (NK) cells are part of the innate immune system and are capable of killing diseased cells. As a result, NK cells are being used for adoptive cell therapies for cancer patients. The activation of NK cell stimulatory receptors leads to a cascade of intracellular phosphorylation reactions, which activates key signaling species that facilitate the secretion of cytolytic molecules required for cell killing. Strategies that maximize the activation of such intracellular species can increase the likelihood of NK cell killing upon contact with a cancer cell and thereby improve efficacy of NK cell-based therapies. However, due to the complexity of intracellular signaling, it is difficult to deduce a priori which strategies can enhance species activation. Therefore, we constructed a mechanistic model of the CD16, 2B4 and NKG2D signaling pathways in NK cells to simulate strategies that enhance signaling. The model predictions were fit to published data and validated with a separate dataset. Model simulations demonstrate strong network activation when the CD16 pathway is stimulated. The magnitude of species activation is most sensitive to the receptor’s initial concentration and the rate at which the receptor is activated. Co-stimulation of CD16 and NKG2D in silico required fewer ligands to achieve half-maximal activation than other combinations, suggesting co-stimulating these pathways is most effective in activating the species. We applied the model to predict the effects of perturbing the signaling network and found two strategies that can potently enhance network activation. When the availability of ligands is low, it is more influential to engineer NK cell receptors that are resistant to proteolytic cleavage. In contrast, for high ligand concentrations, inhibiting phosphatase activity leads to sustained species activation. The work presented here establishes a framework for understanding the complex, nonlinear aspects of NK cell signaling and provides detailed strategies for enhancing NK cell activation.

Plunger lift optimization: A comparison of fuzzy and predictive controllers with manipulation of a secondary gas valve

One of the most common problems in the oil and gas industry is the excessive accumulation of liquids at the bottom of the well. This phenomenon usually results in reduced production rates due to high values of bottomhole flowing pressure. Plunger Lift represents a low-cost solution to this issue, using a controller to compensate parameter variations in the well and system disturbances. The use of a model predictive controller demands a precise mathematical description of the system behavior, which can be difficult to be obtained for processes with high nonlinear and hybrid aspects, such as Plunger Lift. The application of a fuzzy controller for this type of system, on the other hand, can be a more feasible task, since it dismisses the need of a mathematical model, being based solely on the experience of a human operator. This work presents the application of a fuzzy and a linear model predictive controllers to a Plunger Lift process. The controllers were designed to manipulate a secondary valve installed at the top of the annular in order to improve the range of control. The implemented control techniques aimed at production optimization and regulation of the average rise speed of the plunger. The fuzzy and predictive controllers were applied to a plunger lift well in two different configurations, with and without a secondary valve present in the surface, and compared with a fixed time controller. Disturbances in the production line and static pressures were present in the tests. Graphical and performance indexes analysis were conducted, being both implemented controllers successful in maintaining optimal production rates. The fuzzy and MPC controllers generated around 55% more gas and oil than the fixed time controller. In the configuration that utilized the secondary valve, the controllers achieved safe operational values for average plunger rise speed.

Systematically Exploring Associations among Multivariate Data

Detecting relationships among multivariate data is often of great importance in the analysis of high-dimensional data sets, and has received growing attention for decades from both academic and industrial fields. In this study, we propose a statistical tool named the neighbor correlation coefficient (nCor), which is based on a new idea that measures the local continuity of the reordered data points to quantify the strength of the global association between variables. With sufficient sample size, the new method is able to capture a wide range of functional relationship, whether it is linear or nonlinear, bivariate or multivariate, main effect or interaction. The score of nCor roughly approximates the coefficient of determination (R2) of the data which implies the proportion of variance in one variable that is predictable from one or more other variables. On this basis, three nCor based statistics are also proposed here to further characterize the intra and inter structures of the associations from the aspects of nonlinearity, interaction effect, and variable redundancy. The mechanisms of these measures are proved in theory and demonstrated with numerical analyses.

A double-side electrically-actuated arch microbeam for pressure sensing applications

In this study, we consider a pressure sensor whose main component is a clamped-clamped shallow arched microbeam. Two fixed electrodes are used to actuate the microbeam in the transverse direction. The lower electrode is powered by a combination of DC and AC voltages sources to excite the microbeam (drive mode). The upper electrode is polarized with a DC voltage and used to detect the change in the capacitance resulting from the transverse vibrations of the microbeam (sense mode). We formulate a fully-coupled multi-physics model of the electrically-actuated shallow arch microbeam combining the nonlinear Euler-Bernoulli beam theory with the nonlinear Reynolds equation governing the surrounding fluid domains (drive and sense zones). The model captures the inherent nonlinear physical aspects including the mid-plane stretching, the squeeze film damping, and fringing field effect. We validate the developed model by quantitatively comparing our nonlinear frequency-response against existing experimental results. We conduct static analysis to identify the occurrence of snap-through and pull-in instability for different initial midpoint rises. The coupled eigenvalue problem is also solved to compute the damped natural frequencies along with their corresponding beam and fluid mode shapes. The obtained natural frequencies are in good agreement with those reported in the literature. High sensitivity of the natural frequency to pressure variations is observed when decreasing the gap distance separating the microbeam from the fixed electrodes and reducing the initial midpoint rise of the curved microbeam.We also investigate the effect of breaking the symmetry of the microstructure on its dynamic response by introducing a slight perturbation in the mass distribution. The stability analysis reveals the occurrence of a new period doubling bifurcation point. Of interest, the location of this bifurcation point is observed to be sensitive to the pressure of the surrounding fluid medium. As such, we propose to exploit this nonlinear feature for design enhancement of the pressure sensor.

Lifecycle Assessment of Biomass Supply Chain with the Assistance of Agent-Based Modelling

Even though biomass is characterised as renewable energy, it produces anthropogenic greenhouse gas (GHG) emissions, especially from biomass logistics. Lifecycle assessment (LCA) is used as a tool to quantify the GHG emissions from logistics but in the past the majority of LCAs have been steady-state and linear, when in reality, non-linear and temporal aspects (such as weather conditions, seasonal biomass demand, storage capacity, etc.) also have an important role to play. Thus, the objective of this paper was to optimise the environmental sustainability of forest biomass logistics (in terms of GHG emissions) by introducing the dynamic aspects of the supply chain and using the geographical information system (GIS) and agent-based modelling (ABM). The use of the GIS and ABM adds local conditions to the assessment in order to make the study more relevant. In this study, GIS was used to investigate biomass availability, biomass supply points and the road network around a large-scale combined heat and power plant in Naantali, Finland. Furthermore, the temporal aspects of the supply chain (e.g., seasonal biomass demand and storage capacity) were added using ABM to make the assessment dynamic. Based on the outcomes of the GIS and ABM, a gate-to-gate LCA of the forest biomass supply chain was conducted in order to calculate GHG emissions. In addition to the domestic biomass, we added imported biomass from Riga, Latvia to the fuel mixture in order to investigate the effect of sea transportation on overall GHG emissions. Finally, as a sensitivity check, we studied the real-time measurement of biomass quality and its potential impact on overall logistical GHG emissions. According to the results, biomass logistics incurred GHG emissions ranging from 2.72 to 3.46 kg CO2-eq per MWh, depending on the type of biomass and its origin. On the other hand, having 7% imported biomass in the fuel mixture resulted in a 13% increase in GHG emissions. Finally, the real-time monitoring of biomass quality helped save 2% of the GHG emissions from the overall supply chain. The incorporation of the GIS and ABM helped in assessing the environmental impacts of the forest biomass supply chain in local conditions, and the combined approach looks promising for developing LCAs that are inclusive of the temporal aspects of the supply chain for any specific location.

Three-Dimensional Explicit Finite Element Simulation of Piled-Raft Foundation

This paper aims to validate a proposed finite element model to be adopted in predicting displacement and soil stresses of a piled-raft foundation. The proposed model adopts the solid element to simulate the raft, piles, and soil mass. An explicit integration scheme has been used to simulate nonlinear static aspects of the piled-raft foundation and to avoid the computational difficulties associated with the implicit finite element analysis.
 The validation process is based on comparing the results of the proposed finite element model with those of a scaled-down experimental work achieved by other researchers. Centrifuge apparatus has been used in the experimental work to generate the required stresses to simulate the actual geostatic stress on the site. Comparing between numerical and experimental results indicate that the proposed finite element model is accurate and adequate and it can be used in future work to simulate more complicated practical problems of piled-raft foundations.
 After its validation, this model was used to investigate the effectiveness of using piled with a raft foundation that subjected to eccentric loading. In this parametric study, the value of eccentricity was taken equal to , , and . The numerical results indicated that there is a significant decrease in the bearing capacity for unpiled raft foundation compared to the piled raft foundation for the same eccentricity of the applied load.

Nonlinear evolution of perturbations in high Mach number wall-bounded flow: Pressure–dilatation effects

We characterize the nonlinear evolution of perturbations in a high Mach number Poiseuille flow and contrast the behavior against an equivalent incompressible flow. The focus is on the influence of pressure–dilatation on (i) internal energy evolution, (ii) kinetic–internal energy exchange, and (iii) kinetic energy spectrum evolution. We perform direct numerical simulations of plane Poiseuille flow at different Mach numbers subject to a variety of initial perturbations. In all high-speed cases considered, pressure dilatation leads to energy equipartition between wall-normal velocity fluctuations (dilatational kinetic energy) and pressure fluctuations (a measure of internal energy). However, the effect of pressure–dilatation on the kinetic energy spectral growth can be varied. In cases wherein pressure–dilatation is larger than the turbulent kinetic energy production, spectral growth is considerably slow relative to an equivalent low Mach number case. When pressure–dilatation is smaller than production, the spectral growth is only marginally affected. As a consequence, in a high-speed Poiseuille flow, the spectral growth rate varies with the wall-normal distance depending on the local pressure effects. These findings provide valuable insight into the nonlinear aspects of breakdown toward turbulence in high speed wall-bounded shear flows.

Deviating from the Beaten Track: New Twists in Brassinosteroid Receptor Function.

A key feature of plants is their plastic development tailored to the environmental conditions. To integrate environmental signals with genetic growth regulatory programs, plants rely on a number of hormonal pathways, which are intimately connected at multiple levels. Brassinosteroids (BRs), a class of plant sterol hormones, are perceived by cell surface receptors and trigger responses instrumental in tailoring developmental programs to environmental cues. Arguably, BR signalling is one of the best-characterized plant signalling pathways, and the molecular composition of the core signal transduction cascade seems clear. However, BR research continues to reveal new twists to re-shape our view on this key signalling circuit. Here, exciting novel findings pointing to the plasma membrane as a key site for BR signalling modulation and integration with other pathways are reviewed and new inputs into the BR signalling pathway and emerging “non-canonical” functions of the BR receptor complex are highlighted. Together, this new evidence underscores the complexity of plant signalling integration and serves as a reminder that highly-interconnected signalling pathways frequently comprise non-linear aspects which are difficult to convey in classical conceptual models.

Transportation of water-based trapped bolus of SWCNTs and MWCNTs with entropy optimization in a non-uniform channel

Here, we communicate the peristalsis of single- and multi-walled CNTs through nonlinear porous, non-uniform propagating channel boundaries. Non-uniform channel boundaries are of asymmetric characteristics. Flow equations are modeled by taking variable viscosity, linear and nonlinear porous medium (i.e., Darcy and Darcy–Forchheimer), nonlinear thermal radiation, mixed convection, heat generation and absorption aspects. Convective heat transfer aspects are at the convectively heated surface. The entropy generation rate is modeled via the second law of thermodynamics. Modeled equations are simplified with the help of long wavelength assumption. Dimensionless system of equations with respective boundary conditions is solved numerically via built-in shooting algorithm in Mathematica 8 software. Further, these numerical results are directly received in the form of curves. Such curves are made for velocity, temperature, pressure gradient, trapping, entropy rate and Bejan number. Heat transfer rate at lower and upper walls is achieved through bar charts.

Crude oil price changes and the United Kingdom real gross domestic product growth rate: An out-of-sample investigation

We evaluate the impact of changes in the price of crude oil on the United Kingdom (U.K.) real gross domestic product (GDP) growth rate by way of an out-of-sample forecasting analysis. We compare the performance of several nonlinear models and determine, which aspects of nonlinearities are most useful for obtaining forecast improvements. Likewise, our approach takes into account the possibility that relative predictive performance can vary over the out-of-sample period. Results based on quarterly data from 1974q1 through 2018q4 illustrate that our conclusions depend on the definition of forecast improvement and whether we rely on pairwise or multiple forecast comparison. For instance, it is very difficult to find evidence that point forecasts exploiting crude oil price variables are statistically significant more accurate than point forecasts produced under the benchmark. On the other hand, the null hypothesis of no population-level predictability is borderline rejected for certain nonlinear crude oil price variables. We also observe notable differences between using real-time and ex-post revised GDP data with regards to local out-of-sample performance. The predictive power associated with the more successful crude oil price measures appears to concentrate in the early 1990s and around the onset of the Great Recession.

Exploiting double jumping phenomenon for broadening bandwidth of an energy harvesting device

The steady state response of a particular harvesting system is investigated under the condition of external and internal resonance, with emphasis on the double jump phenomenon. Following the trend of recent researches on exploring nonlinearity aspects for broadening the frequency resonance bandwidth, the problem of effective energy harvesting from a broadband source is dealt with. The proposed harvester can be embedded within vibrational structures and can dually act as a vibration absorber. The governing non-linear partial differential equations are truncated into a set of perturbed equations via Galerkin method. The method of multiple scales is applied to derive the modulated amplitude versus frequency at the vicinity of flapwise and chordwise primary resonances, as well as around other internal resonance frequencies. The amplitude-frequency response plot reveals resonance peaks bending to the left and right, i.e., splitting into two different tongues in contrast to conventional jumps which lean only toward higher or lower frequency directions. Numerical results demonstrate that this internal resonance-based harvesting design can produce sufficient power for the consumption of typical MEMS devices.

Rijke Organ: Modeling and Control of Array of Rijke Tubes

Rijke tube is a popular physical experiment demonstrating a spontaneous generation of sound in an open vertical pipe with a heat source. This laboratory instance of thermoacoustic instability has been researched due to its significance in practical thermoacoustic systems. We revisit the experiment, focusing on the possible use of the Rijke tube as a musical instrument. The novelty presented in this paper consists in shifting the goal from sound suppression to active sound generation. This called for modifying the previously investigated methods for stabilization of thermoacoustic oscillations into their excitation and control of their amplitude. On our way towards this goal, we developed a time-domain mathematical model that considers the nonlinear and time-varying aspects of the Rijke tube. The model extends the existing modeling and analysis approaches, which are mainly based in frequency domain. We also present an extension of the basic laboratory setup in the form of an array of Rijke tubes equipped with a single speaker used to control multiple Rijke tubes with different natural frequencies simultaneously.

Nonlinear elastic aspects of multi-component iron oxide core-shell nanowires by means of atom probe tomography, analytical microscopy, and nonlinear mechanics.

One-dimensional objects as nanowires have been proven to be building blocks in novel applications due to their unique functionalities. In the realm of magnetic materials, iron-oxides form an important class by providing potential solutions in catalysis, magnetic devices, drug delivery, or in the field of sensors. The accurate composition and spatial structure analysis are crucial to describe the mechanical aspects and optimize strategies for the design of multi-component NWs. Atom probe tomography offers a unique analytic characterization tool to map the (re-)distribution of the constituents leading to a deeper insight into NW growth, thermally-assisted kinetics, and related mechanisms. As NW-based devices critically rely on the mechanical properties of NWs, the appropriate mechanical modeling with the resulting material constants is also highly demanded and can open novel ways to potential applications. Here, we report a compositional and structural study of quasi-ceramic one-dimensional objects: α-Fe ⊕ α-FeOOH(goethite) ⊕ Pt and α-Fe ⊕ α-Fe3O4(magnetite) ⊕ Pt core–shell NWs. We provide a theoretical model for the elastic behavior with terms accounting for the geometrical and mechanical nonlinearity, prior and subsequent to thermal treatment. The as-deposited system with a homogeneous distribution of the constituents demonstrates strikingly different structural and elastic features than that of after annealing, as observed by applying atom probe tomography, energy-dispersive spectroscopy, analytic electron microscopy, and a micromanipulator nanoprobe system. During annealing at a temperature of 350 °C for 20 h, (i) compositional partitioning between phases (α-Fe, α-Fe3O4 and in a minority of α-Fe2O3) in diffusional solid–solid phase transformations takes place, (ii) a distinct newly-formed shell formation develops, (iii) the degree of crystallinity increases and (iv) nanosized precipitation of evolving phases is detected leading to a considerable change in the description of the elastic material properties. The as-deposited nanowires already exhibit a significantly large maximum strain (1–8%) and stress (3–13 GPa) in moderately large bending tests, which become even more enhanced after the annealing treatment resulting at a maximum of about 2.5–10.5% and 6–18 GPa, respectively. As a constitutive parameter, the strain-dependent stretch modulus undoubtedly represents changes in the material properties as the deformation progresses.

Optimal Sliding Mode Control Method for Active Suspension Control

A non-linear quarter car vehicle model is used in this study, for developing an active suspension control algorithm. The control method used is optimal sliding mode control, along with feedback linearization technique for compensating the nonlinear aspects of the plant. In addition to the work in recent literature that applies these control methods, estimation of the static suspension deflection; i.e. vehicle sprung mass is performed. Through simulation results, it is shown that correct information of vehicle sprung mass, compared to taking it as a constant parameter in control design, improves the performance of the controller. This in turn, reduces the sprung mass acceleration level, and enhances ride comfort.

Non-linear aspects of the tidal dynamics in the Sylt-Rømø Bight, south-eastern North Sea

Abstract. This study is dedicated to the tidal dynamics in the Sylt-Rømø Bight with a focus on the non-linear processes. The FESOM-C model was used as the numerical tool, which works with triangular, rectangular or mixed grids and is equipped with a wetting/drying option. As the model's success at resolving currents largely depends on the quality of the bathymetric data, we have created a new bathymetric map for an area based on recent studies of Lister Deep, Lister Ley, Højer Deep and Rømø Deep. This new bathymetric product made it feasible to work with high-resolution grids (up to 2 m in the wetting/drying zone). As a result, we were able to study the tidal energy transformation and the role of higher harmonics in the domain in detail. For the first time, the tidal ellipses, maximum tidally induced velocities, energy fluxes and residual circulation maps were constructed and analysed for the entire bight. Additionally, tidal asymmetry maps were introduced and constructed. The full analysis was performed on two grids with different structures and showed a convergence of the results as well as fulfilment of the energy balance. A great deal of attention has been paid to the selection of open-boundary conditions, model validation against tide gauges and recent in situ current data. The tidal residual circulation and asymmetric tidal cycles largely define the circulation pattern, transport and accumulation of sediment, and the distribution of bedforms in the bight; therefore, the results presented in the article are necessary and useful benchmarks for further studies in the area, including baroclinic and sediment dynamics investigations.

Developing and validating linear dynamic models for direct contact membrane distillation during start-up over wide operating conditions

This work concerns analyzing, modeling and validation of the dynamic behavior of a Direct Contact Membrane Distillation (DCMD) pilot-plant. The reaction curve method is used to analyze the dynamic characteristics of the outlet permeate and brine temperatures. The time constant for these two process outputs were extracted from the experimental data and analyzed. A low order and high-order linear models in the form of state-space and transfer functions were developed and used to approximate the dynamic of the permeate and brine temperatures, respectively. It is found that these linear dynamic models cannot fully describe the physical process behavior over wide operating conditions. The global deviation between the measured and simulated transient response of the brine temperature and permeate temperature over the entire operating conditions is found to be 15% and 24%, respectively. Hence, there is a potential to improve the dynamic model effectiveness by incorporating the nonlinearity aspects of the real process.