Sensitive Dependence Research Articles

Dispersion Management for Hyperbolic-Metamaterials Based Surface Plasmon Resonance Sensor Towards Extremely High Sensitivity

Extremely high sensitivity is the long-time pursing goal for surface plasmon resonance (SPR) sensors, which means the capability to detect analytes with lower concentrations or interactions for smaller biomolecules. It was suggested that a flat dispersion for the plasmon material enables to enhance the sensitivity dramatically. However, the regulation ability of inherent dispersion in natural materials is limited. With the appearance of hyperbolic metamaterials (HMMs), the management of the plasmon materials dispersion becomes possible. In this paper, the HMMs with metal/dielectric multilayer structure are proposed to construct the SPR sensors. Through numerical simulations and theoretical analysis, we find that the flat dispersion in the HMM structure could significantly benefit the sensitivity improvement for HMM-SPR sensors. As a result, the proposed HMM-SPR sensor obtains an ultrahigh sensitivity of 34.00 μm/RIU in the experiment, which is one order higher in magnitude than that of the conventional monolayer metallic SPR sensors. Thus, this research shows insight into understanding the dependence of the HMM-SPR sensitivity on dispersion management and provides a practical methodology to develop extremely high-sensitivity SPR sensors based on artificial plasmon materials.

Strain Rate-Dependent Compressive Properties of Bulk Cylindrical 3D-Printed Samples from 316L Stainless Steel.

The main aim of the study was to analyse the strain rate sensitivity of the compressive deformation response in bulk 3D-printed samples from 316L stainless steel according to the printing orientation. The laser powder bed fusion (LPBF) method of metal additive manufacturing was utilised for the production of the samples with three different printing orientations: 0, 45, and 90. The specimens were experimentally investigated during uni-axial quasi-static and dynamic loading. A split Hopkinson pressure bar (SHPB) apparatus was used for the dynamic experiments. The experiments were observed using a high-resolution (quasi-static loading) or a high-speed visible-light camera and a high-speed thermographic camera (dynamic loading) to allow for the quantitative and qualitative analysis of the deformation processes. Digital image correlation (DIC) software was used for the evaluation of displacement fields. To assess the deformation behaviour of the 3D-printed bulk samples and strain rate related properties, an analysis of the true stress–true strain diagrams from quasi-static and dynamic experiments as well as the thermograms captured during the dynamic loading was performed. The results revealed a strong strain rate effect on the mechanical response of the investigated material. Furthermore, a dependency of the strain-rate sensitivity on the printing orientation was identified.

Unveiling nonmonotonic chemical trends in the solubility of H in complex Fe-Cr-Mn carbides by means of ab initio based approaches

The microstructure of advanced high-strength steels often shows a sensitive dependence on alloying. For example, adding Cr to improve the corrosion resistance of medium-Mn steels also enhances the precipitation of carbides. The current study focuses on the behavior of H in such complex multicomponent carbides by employing different methodological strategies. We systematically analyze the impact of Cr, Mn, and Fe using density functional theory (DFT) for two prototype precipitate phases, ${\mathrm{M}}_{3}\mathrm{C}$ and ${\mathrm{M}}_{23}{\mathrm{C}}_{6}$, where M represents the metal sublattice. Our results show that the addition of these alloying elements yields strong nonmonotonic chemical trends for the H solubility. We identify magnetovolume effects as the origin for this behavior, which depend on the considered system, the sites occupied by H, and short- vs long-range interactions between H and the alloying elements. We further show that the H solubility is directly correlated with the occupation of its nearest-neighbor shells by Cr and Mn. Based on these insights, DFT data from H containing binary-metal carbides are used to design a ridge regression based model that predicts the solubility of H in the ternary-metal carbides (Fe-Cr-Mn-C).

Dynamic strain ageing in an AlMg alloy at different strain rates and temperatures: Experiments and constitutive modelling

Uniaxial tension tests at strain rates from 10−4 to 10−1s−1 and temperatures from 298 to 418 K are performed to study the dynamic strain ageing (DSA) of an AA5182-O sheet. Digital image correlation (DIC) is used to obtain the stress-strain curves and characterize the heterogenous deformations. A constitutive model based on the mechanical threshold stress (MTS) framework is then proposed and used to calculate the stress–strain response at different strain rates and temperatures. The modified MTS model captures the dependence of the strain rate sensitivity (SRS) on strain, temperature and strain rate both inside and outside the Portevin–Le Chatelier (PLC) domain. Special attention is paid to re-interpret the occurrence of stress serrations. It is found that the competition between work hardening and DSA leads to different jerky flow scenarios. The modified MTS model is used to predict the PLC domain as a function of strain rate and temperature. To further test the validity of the model at various temperatures and alloys, it is also approximately calibrated to Ni-based superalloys, for which it captures earlier reported behaviour at elevated temperatures.

A Connection between Lyapunov Exponents and Sensitive Dependence on Parameters of Chaotic Systems

A Connection between Lyapunov Exponents and Sensitive Dependence on Parameters of Chaotic Systems

Development of single sensor fast response pressure probes

Multi-sensor fast response pressure probes are often used in turbomachinery investigations. However, the size of multi-sensor probes are often larger than is ideal. This paper describes the development of a single sensor pressure probe that has sufficient sensitivity for the measurements of unsteady 3D flow fields in turbomachines. Because there is only one sensor, the probe can be made much smaller than previous designs. Several types of probe were designed and tested using largescale models in a wind tunnel. Both the steady state and the dynamic response have been investigated. The relationship between the shape of the probe and its yaw and pitch sensitivity has been investigated through measurements of the pressure distribution on the large-scale models and through visualizations of the flow. Dambach and Hodson [3] proposed a new method of data reduction for a single sensor pressure probe. In that work, a single sensor pressure probe with the shape of a triangular prism was fabricated and tested with success in a radial flow turbine where the flow field was mainly 2D. The probe was shown to have only yaw sensitivity while pitch sensitivity is also important in the survey of three dimensional turbomachinery flows. In this paper, the model probes were used to assess the pitch sensitivity of single sensor pressure probes. All the probes have the sensing face at the end of a radially mounted stem so that they can be used for inter bladerow measurements. Through the steady state measurements, the dependency of pitch sensitivity on (1) the shape of the probe stem (e.g., Square, Circular, and Triangular) and (2) the angle of the slanted sensing face at the tip of the probe were investigated. Having assessed all the designs based on the steady state experiments, the dynamic behaviour of selected designs was investigated. The results indicate that a slanted face and appropriate probe tip design can be used to increase the pitch sensitivity of the single sensor probe to acceptable levels.

Mode Dependence of Refractive Index Sensitivity of Long-Period Gratings Induced by Periodically Embedded Multimode Fiber

Mode Dependence of Refractive Index Sensitivity of Long-Period Gratings Induced by Periodically Embedded Multimode Fiber

Structure and morphology effects on sensing properties Cd-=SUB=-x-=/SUB=-Pb-=SUB=-1-x-=/SUB=-S films

Polycrystalline films of CdxPb1-xS (0.021≤x≤0.090) supersaturated substitutional solid solutions with a cubic structure B1 (Fm3m space group) have been obtained with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01-0.10 mol/l on the sitall substrates. Their thickness changed from ~0.4 to ~1.0 microns. A correlation has been established between the structural-morphological and functional properties of CdxPb1-xS thin-film layers. The extreme character of the voltage sensitivity dependence on the cadmium salt concentration in the reaction bath is associated with the nonmonotonic introduction of cadmium into the PbS crystal lattice. It is shown that the maximum photocurrent is possessed by CdxPb1-xS thin-film layers formed from crystallites with pronounced faceting. We have found the surface sensitivity of the CdxPb1-xS films to the presence of ~0.02 mg/m3 NO2 in the air, which is significantly lower than the maximum allowable concentration. Keywords: chemical bath deposition, film morphology, structural properties, CdxPb1-xS solid solution, photosensitivity, sensing properties.

Integer and fractional order analysis of a 3D system and generalization of synchronization for a class of chaotic systems

In this article we studied a 3D autonomous system derived from Sprot B, C, Van der Schrier-Mass and Munmuangsaen Srisuchinwong chaotic systems for existence of zero Hopf bifurcation with the help of averaging theory of first order. Fractional order analysis of the derived system are discussed for stability of equilibrium points, chaotification condition, sensitivity dependence, Lyapunov exponents, Kaplan-Yorke dimension, chaotic time history and phase portraits. Novelty of the paper is investigation of integer and fractional order synchronization of derived system with famous Lorenz model by active control method under the same parametric values and initial conditions. By taking example of the model under consideration we generalized the synchronization for a class of integer and fractional order systems. We concluded that if a couple of integer order chaotic dynamical system is synchronized then its fractional order version will also be synchronized for same parametric values and initial conditions and vice versa. We also compared three different numerical techniques for synchronization. By calculating CPU timing for synchronization we determined that the integer order chaotic system was synchronized earlier than that of fractional order. The results so achieved show that it is sufficient to get synchronization of an integer order system if its fractional version also exists. This investigation contributes to minimize the cost of control for a class of dynamical systems when such control is made through synchronization. Numerical simulations are also provided to authenticate the analytical results.

Intrinsic Second-Order Anomalous Hall Effect and Its Application in Compensated Antiferromagnets.

Response properties that are purely intrinsic to physical systems are of paramount importance in physics research, as they probe fundamental properties of band structures and allow quantitative calculation and comparison with experiment. For anomalous Hall transport in magnets, an intrinsic effect can appear at the second order to the applied electric field. We show that this intrinsic second-order anomalous Hall effect is associated with an intrinsic band geometric property-the dipole moment of Berry-connection polarizability (BCP) in momentum space. The effect has scaling relation and symmetry constraints that are distinct from the previously studied extrinsic contributions. Particularly, in antiferromagnets with PT symmetry, the intrinsic effect dominates. Combined with first-principles calculations, we demonstrate the first quantitative evaluation of the effect in the antiferromagnet Mn_{2}Au. We show that the BCP dipole and the resulting intrinsic second-order conductivity are pronounced around band near degeneracies. Importantly, the intrinsic response exhibits sensitive dependence on the Néel vector orientation with a 2π periodicity, which offers a new route for electric detection of the magnetic order in PT-invariant antiferromagnets.

Angular dependence of polarisation contrast sensitivity in octopus

Cephalopod photoreceptors are polarisation-sensitive, giving them an ability to discriminate between lights of different angle and degree of polarisation. While colour vision is achieved by comparison of signals of photoreceptors tuned to different parts of light spectra, polarisation vision is achieved by comparison of signals of photoreceptors tuned to different orientations of e-vector. Therefore, from a theoretical point of view, polarisation vision is similar to colour vision. In particular, detection of polarised light against an unpolarised background is analogous to detection of chromatic light against grey. The dependence of polarisation contrast sensitivity on the angle of polarisation can be theoretically predicted using a receptor noise limited model in much the same way as it has been done for predicting the shape of the increment threshold spectral sensitivity in animals with colour vision. Here we report angular dependence of polarisation contrast sensitivity in octopus (O. tetricus, Gould 1852) and compare the theoretical predictions of polarisation contrast with the experimental results. Polarisation gratings were generated using LCD screens with removed polarisers and the orientation of polarisation was changed by rotating the screen. Reaction to the stimulus was recorded using a fixation reflex. We show that, in agreement with the theoretical predictions, the maximum contrast sensitivity is achieved at horizontal and vertical orientations of polarisation. Our results demonstrate that the dependence of polarisation contrast sensitivity on the angle of polarisation can be analysed in the same way as the dependence of colour thresholds on wavelength of monochromatic light added to a grey background.

Chaos in the Rulkov Neuron Model Based on Marotto’s Theorem

The existence of chaos in the Rulkov neuron model is proved based on Marotto’s theorem. Firstly, the stability conditions of the model are briefly renewed through analyzing the eigenvalues of the model, which are very important preconditions for the existence of a snap-back repeller. Secondly, the Rulkov neuron model is decomposed to a one-dimensional fast subsystem and a one-dimensional slow subsystem by the fast–slow dynamics technique, in which the fast subsystem has sensitive dependence on the initial conditions and its snap-back repeller and chaos can be verified by numerical methods, such as waveforms, Lyapunov exponents, and bifurcation diagrams. Thirdly, for the two-dimensional Rulkov neuron model, it is proved that there exists a snap-back repeller under two iterations by illustrating the existence of an intersection of three surfaces, which pave a new way to identify the existence of a snap-back repeller.

Dependence of field-effect biosensor sensitivity on photo-induced processes in Si and its conductivity type

The effect of photoelectron processes in n-Si and p-Si on the glucose sensitivity of a capacitive field-effect biosensor based on electrolyte/oxide/semiconductor structure was investigated. We obtained that illumination of n-Si/SiO2/PEI structure during the GOx adsorption increases the glucose sensitivity by three times compare to GOx adsorption in the dark. In contrast, p-Si illumination during the GOx adsorption led to a decrease in sensor sensitivity from 2.9 mV/mM to 2.2 mV/mM. The result is explained by a change in the density of immobilized GOx molecules due to a change in the electrostatic forces of attraction under illumination and stabilization of the photo-generated charge on the surface electronic states of the Si/SiO2 and SiO2/PEI interfaces after illumination.

On a Bertrand Duopoly Game With Heterogeneous Expectations and Emissions Costs

This study was based on the dynamics of a nonlinear Bertrand-type duopoly game with differentiated goods, linear demand and a cost function that included emissions costs. This duopoly game was modeled with a system of two difference equations. Existence and stability of equilibria of this system were studied. It was shown that the model gave more complex chaotic and unpredictable trajectories as a consequence of changes in the speed of adjustment parameter and horizontal product differentiation parameter. Numerical simulations showed that a higher value of the speed of adjustment and a higher or lower (negative) value of product differentiation (weaker or fiercer competition) can destabilize the economy. The chaotic features were justified numerically via computing Lyapunov numbers and sensitive dependence on initial conditions. Also, it was shown that in this case of a duopoly game, there were stable trajectories, and a higher (lower) degree of product differentiation did not tend to destabilize the economy.
 Keywords: Bertrand duopoly game, discrete dynamical system, heterogeneous expectations, stability, chaotic behavior

Effects of place of stimulation on the interaural time difference sensitivity in bilateral electrical intracochlear stimulations: Neurophysiological study in a rat model.

We examined the sensitivity of the neurons in the inferior colliculus (IC) in male and female rats to the interaural time differences (ITDs) conveyed in electrical pulse trains. Using bipolar pairs of electrodes that selectively activate the auditory nerve fibers at different intracochlear locations, we assessed whether the responses to electrical stimulation with ITDs in different frequency regions were processed differently. Most well-isolated single units responded to the electrical stimulation in only one of the apical or basal cochlear regions, and they were classified as either apical or basal units. Regardless of the cochlear stimulating location, more than 70% of both apical and basal units were sensitive to ITDs of electrical stimulation. However, the pulse rate dependence of neural ITD sensitivity differed significantly depending on the location of the stimulation. Moreover, ITD discrimination thresholds and the relative incidence of ITD tuning type markedly differed between units activated by apical and basal stimulations. With apical stimulation, IC neurons had a higher incidence of peak-type ITD function, which mostly exhibited the steepest position of the tuning curve within the rat's physiological ITD range of ±160μs and, accordingly, had better ITD discrimination thresholds than those with basal stimulation. These results support the idea that ITD processing in the IC might be determined by functionally segregated frequency-specific pathways from the cochlea to the auditory midbrain.

Understanding Hydrophobic Effects: Insights from Water Density Fluctuations

The aversion of hydrophobic solutes for water drives diverse interactions and assemblies across materials science, biology, and beyond. Here, we review the theoretical, computational, and experimental developments that underpin a contemporary understanding of hydrophobic effects. We discuss how an understanding of density fluctuations in bulk water can shed light on the fundamental differences in the hydration of molecular and macroscopic solutes; these differences, in turn, explain why hydrophobic interactions become stronger upon increasing temperature. We also illustrate the sensitive dependence of surface hydrophobicity on the chemical and topographical patterns the surface displays, which makes the use of approximate approaches for estimating hydrophobicity particularly challenging. Importantly, the hydrophobicity of complex surfaces, such as those of proteins, which display nanoscale heterogeneity, can nevertheless be characterized using interfacial water density fluctuations; such a characterization also informs protein regions that mediate their interactions. Finally, we build upon an understanding of hydrophobic hydration and the ability to characterize hydrophobicity to inform the context-dependent thermodynamic forces that drive hydrophobic interactions and the desolvation barriers that impede them.

DEPENDENCE OF MAXIMAL SENSITIVITY OF THE MAGNETIC FIELD HALL SENSORS BASED ON GRAPHENE ON TEMPERATURE

A theory of graphene-based magnetic field Hall sensors sensitivity dependence on temperature is summarized. The existence of low-temperature range with sensitivity, almost independent on temperature, is predicted; at higher temperatures, when thermally-induced carrier concentration in graphene prevails, the sensitivity decreases with temperature. The experimental studies of the temperature dependence of magnetic sensitivity of Hall sensors on single layer graphene base were carried in temperature range from 300 °K to 430 °K. The values of sensitivity, obtained for room temperatures ~ 230 V·А‑1·Т‑1 exceed essentially the maximum sensitivity of the traditional Hall sensors on silicon base ~ 100 V·А‑1·Т‑1.

Efficient computation of minimal weak and strong control closure

Control dependency is a fundamental concept in many program analyses, transformation, parallelization, and compiler optimization techniques. An overwhelming number of definitions of control dependency relations are found in the literature that capture various kinds of program control flow structures. Weak and strong control closure (WCC and SCC) relations capture nontermination insensitive and sensitive control dependencies and subsume all previously defined control dependency relations. In this paper, we have shown that static dependency-based program slicing requires the repeated computation of WCC and SCC. The state-of-the-art WCC and SCC algorithm provided by Danicic et al. has the cubic and the quartic worst-case complexity in terms of the size of the control flow graph and is a major obstacle to be used in static program slicing. We have provided a simple yet efficient method to compute the minimal WCC and SCC which has the quadratic and cubic worst-case complexity and proved the correctness of our algorithms. We implemented ours and the state-of-the-art algorithms in the Clang/LLVM compiler framework and run experiments on a number of SPEC CPU 2017 benchmarks. Our WCC method performs a maximum of 23.8 times and on average 10.6 times faster than the state-of-the-art method to compute WCC. The performance curves of our WCC algorithm for practical applications are closer to the NlogN curve in the microsecond scale. Our SCC method performs a maximum of 226.86 times and on average 67.66 times faster than the state-of-the-art method to compute SCC. Evidently, we improve the practical performance of WCC and SCC computation by an order of magnitude.

Droplet trapping in bendotaxis caused by contact angle hysteresis

Passive droplet transport mechanisms, in which continuous external energy input is not required for motion, have received significant attention in recent years. Experimental studies of such mechanisms often ignore, or use careful treatments to minimize, contact angle hysteresis, which can impede droplet motion, or even arrest it completely. Here, we consider the effect of contact angle hysteresis on bendotaxis, a mechanism in which droplets spontaneously deform an elastic channel via capillary pressure and thereby move. Here, we seek to understand when contact angle hysteresis prevents bendotaxis. We supplement a previous mathematical model of the dynamics of bendotaxis with a simple model of contact angle hysteresis, and show that this model predicts droplet trapping when hysteresis is sufficiently strong. By identifying the equilibrium configurations adopted by these trapped droplets and assessing their linear stability, we uncover a sensitive dependence of bendotaxis on contact angle hysteresis and develop criteria to describe when droplets will be trapped.

Improved representation of atmospheric dynamics in CMIP6 models removes climate sensitivity dependence on Hadley cell climatological extent.

The persistent inter‐model spread in the response of global‐mean surface temperature to increased CO2 (known as the “Equilibrium Climate Sensitivity,” or “ECS”) is a crucial problem across model generations. This work examines the influence of the models' present‐day atmospheric circulation climatologies, and the accompanying climatological cloud radiative effects, in explaining that spread. We analyze the Coupled Model Intercomparison Project Phase 6 (CMIP6) models and find that they simulate a more poleward, and thus more realistic, edge of the Hadley cell (HC) in the Southern Hemisphere than the CMIP5 models, although the climatological shortwave cloud radiative effects are similar in the two generations of models. A few CMIP5 models with extreme equatorward biases in the HC edge exhibited high ECS due to strong Southern midlatitude shortwave cloud radiative warming in response to climate change, suggesting an ECS dependence on HC position. We find that such constraint no longer holds for the CMIP6 models, due to the absence of models with extreme HC climatologies. In spite of this, however, the CMIP6 models show an increased spread in ECS, with more models in the high ECS range. In addition, an improved representation of the climatological jet dynamics does not lead to a new emergent constraint in the CMIP6 models either.