Effect Of Small Changes Research Articles

Investigation of dual-band perfect absorption and their hybridization on multilayer tungsten disulfide (WS2) gratings

We investigate the dual-band perfect absorption and their hybridization on multilayer tungsten disulfide (WS2) gratings with metallic substrates by the finite-difference time-domain method and the coupled-mode theory. Numerical results suggest that, under the illumination of the transverse magnetic polarized plane wave, the special multilayer WS2 grating with high refractive index not only allows the circulating-current-drove magnetic resonance but also provides additional wavevectors to excite the plasmonic resonance on the substrate surface simultaneously. Consequently, the dual-band perfect absorption is obtained in the single-port system by two independent critical coupling. The effect of small changes in the grating period, width, and height on spectral positions of absorption peaks is presented. The inherent multiple dielectric resonances on the WS2 grating under the illumination of the transverse electric polarized plane wave are also demonstrated. Intriguingly, the simultaneous existence of angle-independent magnetic resonances and angle-dependent plasmonic resonances gives rise to the obvious hybridization between the two types of resonances under the oblique incidence. Numerical results are in excellent agreement with theoretical calculations. The structure under study undoubtedly opens perspectives for enhancing light–matter interactions in two-dimensional materials.

The effects of small changes in temperature on proteolysis during isothermal and non-isothermal aging of full-fat and reduced-fat Cheddar cheese

<abstract> <p>Effective approaches for modulating the evolution of cheese quality attributes are needed for mitigating challenges that are associated with fluctuating supply and demand as well as with disrupt supply chain. Proteolysis is the most important and most complex cascade of events that affects the evolution of cheese quality attributes. Information about the effects of small changes in temperature during isothermal and non-isothermal aging of Cheddar cheese at temperatures lower than 10 ℃ on proteolysis has been developed to a very limited extent. The objective of the research was to age FF and RF Cheddar cheeses for six months at different isothermal and non-isothermal time-at-temperature regimes at temperature ranging from 5 to 8 ℃ and to investigate the effects of these conditions on proteolysis. Changes in the level of cheese-N fractions that are soluble at pH 4.6, soluble in 12% TCA and soluble in 5% PTA were monitored. The proteolytic cascade during aging was significantly (p < 0.05) influenced by a combined impact of the time-at-temperature details of aging and cheese composition. The highest and lowest levels of the investigated fractions were found in cheeses that had been aged isothermally at 8 and 5 ℃, respectively. In most cases, proteolysis in the FF cheeses was to a higher extent than in the RF ones. Proteolysis during non-isothermal aging was significantly affected by the aging regime in a time-at-temperature-specific manner (p < 0.05). The results can offer new opportunities for modulating the rate of cheese aging. The demonstrated significant effect of a very small change in aging temperature on proteolysis during cheese aging also highlights the critical importance of establishing and maintaining isotropic temperature distribution in cheese aging rooms.</p> </abstract>

Characterization of open woodwind toneholes by the tube reversed method.

Woodwind tonehole's linear behavior is characterized by two complex quantities: the series and shunt acoustic impedances. A method to determine experimentally these two quantities is presented for the case of open toneholes. It is based on two input impedance measurements. The method can be applied to clarinet-like instruments, and can be used for undercut toneholes as well as toneholes with pads above their output, under the condition that a symmetry axis exists. The robustness of the method proposed is explored numerically through the simulation of the experiment when considering geometrical and measurement uncertainties. Experimental results confirm the relevance of the method proposed to estimate the shunt impedance. Even the effect of small changes in the hole's geometry, such as those induced by undercutting, are characterized experimentally. The main effect of undercutting is shown to be a decrease in the tonehole's acoustic mass, in agreement with theoretical considerations based on the shape of the tonehole. Investigation on the effects of pads will be studied in a further work. Experimental results also reveal that losses in toneholes are significantly higher than those predicted by the theory. Therefore, the method is suitable for the experimental determination of the shunt impedance, but it is not convenient for the characterization of the series impedance.

Dynamics of Charged Particles Moving around Kerr Black Hole with Inductive Charge and External Magnetic Field

We mainly focus on the effects of small changes of parameters on the dynamics of charged particles around Kerr black holes surrounded by an external magnetic field, which can be considered as a tidal environment. The radial motions of charged particles on the equatorial plane are studied via an effective potential. It is found that the particle energies at the local maxima values of the effective potentials increase with an increase in the black hole spin and the particle angular momenta, but decrease with an increase of one of the inductive charge parameter and magnetic field parameter. The radii of stable circular orbits on the equatorial plane also increase, whereas those of the innermost stable circular orbits decrease. On the other hand, the effects of small variations of the parameters on the orbital regular and chaotic dynamics of charged particles on the non-equatorial plane are traced by means of a time-transformed explicit symplectic integrator, Poincaré sections and fast Lyapunov indicators. It is shown that the dynamics sensitivity depends on small variations in the inductive charge parameter, magnetic field parameter, energy, and angular momentum. Chaos occurs easily as each of the inductive charge parameter, magnetic field parameter, and energy increases but is weakened as the angular momentum increases. When the dragging effects of the spacetime increase, the chaotic properties are not always weakened under some circumstances.

A simple numerical model for the variation of cubesat temperature along its orbit

A simple model for the variation of CubeSat temperature along its orbit is presented. First, an analytic solution for the satellite temperature variation with time when subjected to a bistable heat source: two segments with piece-wise constant power, such as orbits with an eclipsed segment when the Sun is not directly visible, is considered. The model assumes that at a given time a single temperature applies to the entire satellite body. Discussion is focused on CubeSat satellites in low-Earth orbits, the uncertainties in predicted temperatures due to uncertain input parameters, and it emphasizes the importance of the satellite thermal inertia in setting the amplitude of the temperature variation along the orbit. This simplified “spherical cow" model is suitable for studying the relative effects of surfaces with different emissivities, the effects of small changes in the solar flux between June and December, the impact of thermal inertia, and as a “sanity check" for the results obtained with numerical thermal models that utilize detailed geometrical and thermal descriptions of all satellite components. It was found that the mean satellite temperature depends on the extreme values of steady-state equilibrium temperatures for eclipsed and non-eclipsed parts of the orbit, and the duration of the eclipse relative to the orbital period; in contrast, the amplitude of temperature variation around the mean temperature is by and large controlled by the satellite thermal inertia. A numerical model with arbitrary time dependence of the heating power is also developed, including its dependence on the satellite temperature, and validated it using analytic solution for a bistable heat source. Analysis of a typical 2U CubeSat shows that low temperatures are more worrisome than high temperatures, and that low temperatures can be mitigated by active temperature control such as releasing heat when the satellite is in eclipse using electrical energy stored in batteries that are charged during non-eclipsed portion of the orbit.

Experimenting in Equilibrium

Classical approaches to experimental design assume that intervening on one unit does not affect other units. There are many important settings, however, where this noninterference assumption does not hold, as when running experiments on supply-side incentives on a ride-sharing platform or subsidies in an energy marketplace. In this paper, we introduce a new approach to experimental design in large-scale stochastic systems with considerable cross-unit interference, under an assumption that the interference is structured enough that it can be captured via mean-field modeling. Our approach enables us to accurately estimate the effect of small changes to system parameters by combining unobtrusive randomization with lightweight modeling, all while remaining in equilibrium. We can then use these estimates to optimize the system by gradient descent. Concretely, we focus on the problem of a platform that seeks to optimize supply-side payments [Formula: see text] in a centralized marketplace where different suppliers interact via their effects on the overall supply-demand equilibrium, and we show that our approach enables the platform to optimize [Formula: see text] in large systems using vanishingly small perturbations. This paper was accepted by Hamid Nazerzadeh, big data analytics.

Tuning of Molecular Electrostatic Potential Enables Efficient Charge Transport in Crystalline Azaacenes: A Computational Study.

The chemical versatility of organic semiconductors provides nearly unlimited opportunities for tuning their electronic properties. However, despite decades of research, the relationship between molecular structure, molecular packing and charge mobility in these materials remains poorly understood. This reduces the search for high-mobility organic semiconductors to the inefficient trial-and-error approach. For clarifying the abovementioned relationship, investigations of the effect of small changes in the chemical structure on organic semiconductor properties are particularly important. In this study, we computationally address the impact of the substitution of C-H atom pairs by nitrogen atoms (N-substitution) on the molecular properties, molecular packing and charge mobility of crystalline oligoacenes. We observe that besides decreasing frontier molecular orbital levels, N-substitution dramatically alters molecular electrostatic potential, yielding pronounced electron-rich and electron-deficient areas. These changes in the molecular electrostatic potential strengthen face-to-face and edge-to-edge interactions in the corresponding crystals and result in the crossover from the herringbone packing motif to π-stacking. When the electron-rich and electron-deficient areas are large, sharply defined and, probably, have a certain symmetry, calculated charge mobility increases up to 3–4 cm2V−1s−1. The results obtained highlight the potential of azaacenes for application in organic electronic devices and are expected to facilitate the rational design of organic semiconductors for the steady improvement of organic electronics.

Experimental Modal Analysis of an Aircraft Wing Prototype for SAE Aerodesign Competition

This work presents an experimental modal analysis of an aircraft wing prototype, designed by the Aerodesign team of the University of Brasilia, and performs a ground vibration testing of the prototype. The dynamic response data were acquired using the software LabVIEW, and the modal parameters were identified through the EasyMod toolbox. The modal parameters are characterised for the first seven vibration modes of the structure, with the firsts two being suspension modes of vibration. The effect of small changes in the experimental procedure on the identified modal parameters is discussed. It was observed that the use of an excitation signal as a logarithmic sine sweep and with a frequency range of excitation between 2 to 150 Hz resulted in less noise and more accurate measurement of the structure’s response. Results for different modal identification methods were verified using the Modal Assurance Criterion (MAC), and good correlation was achieved.

Sensitivity Analysis of Semi-Circular Bending Test using Plackett–Burman Matrix

The semi-circular bending (SCB) test is a recently developed test method, adopted by the American Society of Testing and Material (ASTM) as ASTM D8044, to evaluate the cracking resistance of asphalt mixtures. To measure the robustness of the SCB test, a ruggedness test is needed. In this study, the effect of small changes in the key parameters of the test method on the results of the test were numerically investigated. The test method has many variables and set up conditions. Examining all of these parameters would be cumbersome using traditional testing and statistical techniques, as they require a significantly high number of samples. The Plackett–Burman (PB) technique was used to conduct the ruggedness test while reducing the number of tests required. Seven parameters have been examined: notch location, notch depth (low, intermediate and high), air voids, loading rate, and span length. Even using the PB technique, 16 scenarios need to be tested, and each scenario requires three specimens, one for each of the three notch depths. Hence the process requires plenty of time and material. In this study, the SCB test was modeled using a discrete element method (DEM) approach to analyze the fracture behavior of the samples. DEM was used to develop a model that reduced the time and materials required for the SCB test. Results showed that the parameters with most positive effect were intermediate notch depth and notch location, while those with the most negative effect were loading rates and air voids.

Impact of Exchange Rate Volatility on the US Exports: A New Evidence From Multiple Threshold Nonlinear ARDL Model

This study extends previous literature by examining the effect of extremely large to extremely small changes in the exchange rate volatility on the US exports to developing countries such as Brazil, India, Mexico, and South Africa. We use novel approach called multiple threshold nonlinear ARDL (MTNARDL) and compare its results with ARDL and nonlinear ARDL models. The ARDL model supports insignificant results, whereas standard nonlinear ARDL model indicates asymmetric effect of exchange rate volatility on the US exports to Mexico only. Finally, the MTNARLD model indicates that in the short run, the effect of extremely large changes in exchange rate volatility does not significantly differ from the effect of small changes in exchange rate volatility on the US exports to all sample countries. Whereas in the long run, the effect of extremely large changes in exchange rate volatility is significantly different from the effect of small changes in exchange rate volatility on the US exports to all sample countries. The findings of this novel methodology suggest different policies in the long run and short run.

Transient analysis and selection of perturbation parameters for PV-MPPT implementation

ABSTRACT In this article, system dynamics of a complete photovoltaic system have been studied. A small signal transient analysis model has been established to examine the effects of small change in the duty cycle of the converter as well as the time steps between each perturbation on the system dynamics. All efforts have been made to do a detailed analysis using almost all the equations involved. Sample calculations (using the simulated system model) are also shown so as to approximately analyse the perturbation effects. It is shown that the value of the step size of the duty cycle should be taken large for points far away from the maximum power point (MPP) and small for points near the MPP. Also, the time between two consecutive perturbations should be at least equal to the settling time. This article is very useful for the researchers to choose a proper delay between two consecutive perturbations and selection of the optimum value of the step size.

Divergent Reactivity of CO2, CO, and Related Substrates at the Nickel Carbon Double Bond of (PCcarbeneP)Ni(II) Pincer Complexes

The addition of carbon monoxide (CO), carbon dioxide (CO2) and isoelectronic isocyanide and isocyanates to the nickel carbene bond in PCcarbeneP pincer complexes is reported. For CO and CNR, irreversible group transfer reactions are observed, while for CO2, a reversible 2 + 2 addition to the carbene moiety occurs. The course of the CO and CO2 reactions are strongly affected by the nature of the PCcarbeneP pincer ligand framework, and a new more rigid ligand based on a 10,10-dimethyl-9,10-dihydroanthracene core was designed in order to study these reactions, illustrating the profound effect of small changes in ligand structure on reaction outcomes.

“Click” generation of a conjugated polymer library for SWNT dispersion

ABSTRACTNoncovalent functionalization of single‐walled carbon nanotubes (SWNTs) with conjugated polymers enhances SWNT processability and allows for selective dispersion of various SWNT species. Selective dispersions can be obtained by tuning the nature of the polymer, which can involve using various polymer backbones or side‐chains. However, a clear understanding of selectivity determinants is elusive, as the degree of polymerization (DP) has a large effect on SWNT selectivity. Additionally, preparing libraries of conjugated polymers with varying functionality while keeping DP consistent is difficult. Here, we report the utilization of a strained cyclooctyne‐containing conjugated polymer that serves as a versatile scaffold, enabling systematic preparation of a small library of conjugated polymers with different side‐chain functionality, while maintaining a consistent DP. The resulting polymers were used as dispersants for SWNTs, forming supramolecular polymer‐SWNT complexes that were characterized by UV‐Vis‐NIR absorption and Raman spectroscopy. In the series of polymers, we were able to probe the effect of small changes within the side chains, such as the incorporation of a carbonyl group or an aromatic unit, on the quality of the polymer‐SWNT dispersion. The results of these studies provide new insight into the factors that dictate the ability of a polymer to form strong interactions with SWNTs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2053–2058

The Use of Size Exclusion Chromatography to Monitor Protein Self-Assembly

High resolution size exclusion chromatography (SEC) coupled with static light scattering (SLS) analyses were conducted to study the effect of the mobile phase ionic strength and protein concentration on the output of SEC experiments. The results highlight the effect of small changes in the mobile phase composition on the estimation of molar masses estimated from retention time-based calibration curve compared with those obtained from SLS analysis. By comparing the SLS data with the SEC chromatograms, we show that SEC can provide helpful information on the protein aggregation state as macromolecules approach known precipitation points in their phase diagrams. This suggests the potential use of SEC as an easily accessible lab-based scanning methodology to monitor protein self-assembly prior to nucleation and crystallization. Implications for the use of SEC to study protein phase diagrams are discussed.

A computational continuum model of poroelastic beds.

Despite the ubiquity of fluid flows interacting with porous and elastic materials, we lack a validated non-empirical macroscale method for characterizing the flow over and through a poroelastic medium. We propose a computational tool to describe such configurations by deriving and validating a continuum model for the poroelastic bed and its interface with the above free fluid. We show that, using stress continuity condition and slip velocity condition at the interface, the effective model captures the effects of small changes in the microstructure anisotropy correctly and predicts the overall behaviour in a physically consistent and controllable manner. Moreover, we show that the performance of the effective model is accurate by validating with fully microscopic resolved simulations. The proposed computational tool can be used in investigations in a wide range of fields, including mechanical engineering, bio-engineering and geophysics.

Advancing the match-mismatch framework for large herbivores in the Arctic: Evaluating the evidence for a trophic mismatch in caribou.

Climate-induced shifts in plant phenology may adversely affect animals that cannot or do not shift the timing of their reproductive cycle. The realized effect of potential trophic “mismatches” between a consumer and its food varies with the degree to which species rely on dietary income and stored capital. Large Arctic herbivores rely heavily on maternal capital to reproduce and give birth near the onset of the growing season but are they vulnerable to trophic mismatch? We evaluated the long-term changes in the temperatures and characteristics of the growing seasons (1970–2013), and compared growing conditions and dynamics of forage quality for caribou at peak parturition, peak lactation, and peak forage biomass, and plant senescence between two distinct time periods over 36 years (1977 and 2011–13). Despite advanced thaw dates (7−12 days earlier), increased growing season lengths (15−21 days longer), and consistent parturition dates, we found no decline in forage quality and therefore no evidence within this dataset for a trophic mismatch at peak parturition or peak lactation from 1977 to 2011–13. In Arctic ungulates that use stored capital for reproduction, reproductive demands are largely met by body stores deposited in the previous summer and autumn, which reduces potential adverse effects of any mismatch between food availability and timing of parturition. Climate-induced effects on forages growing in the summer and autumn ranges, however, do correspond with the demands of female caribou and their offspring to gain mass for the next reproductive cycle and winter. Therefore, we suggest the window of time to examine the match-mismatch framework in Arctic ungulates is not at parturition but in late summer-autumn, where the multiplier effects of small changes in forage quality are amplified by forage abundance, peak forage intake, and resultant mass gains in mother-offspring pairs.

Partitioning beta‐diversity through different pond hydroperiod lengths reveals predominance of nestedness in assemblages of immature odonates

AbstractPatterns of freshwater invertebrate assemblage structure in the transition from permanent to non‐permanent lentic habitats are well described in the literature. However, the effects of small changes in the hydroperiod of non‐permanent ponds on invertebrate assemblage structure remain less studied, especially on β‐diversity. Thus, we tested the effects of different pond hydroperiod lengths on the assemblage structure of immature odonates, in terms of both α‐ and β‐diversity. Small high‐altitude ponds with different hydroperiod lengths (assigned to ‘short’, ‘medium’ and ‘long’ hydroperiods) were sampled in southern Brazil between 2013 and 2014. Based on the hypothesis that shorter hydroperiods filter constituents of lentic fauna, i.e. that long‐living species cannot inhabit shorter‐hydroperiod ponds, we expected to find higher α‐ and β‐diversity in longer hydroperiods, as well as predominance of the nestedness component in β‐diversity. Restricted occurrence of some genera and higher α‐diversity of immature odonate assemblages was detected in long‐hydroperiod ponds. Within‐hydroperiod β‐diversity values did not vary among hydroperiods, because the occasional occurrence of some genera with high dispersal ability of adults in short‐hydroperiod ponds yielded similar values of the β‐diversity among hydroperiods. Partitioning of β‐diversity among hydroperiods revealed a significant higher contribution of the nestedness component rather than turnover. This pattern is explained by the occurrence of some generalist genera across the whole gradient of hydroperiod, as a subset of fauna in longer‐hydroperiod ponds. Thus, our results suggest that reduction in hydroperiod length, if occurring in the future climate change, would favor habitat‐generalist taxa in lentic ecosystems.

Optical path length and trajectory stability in rotationally asymmetric multipass cells.

We describe the behavior of optical trajectories in multipass rotationally asymmetric cavities (RACs) using a phase-space motivated approach. Emphasis is placed on generating long optical paths. A trajectory with an optical path length of 18 m is generated within a 68 cm3 volume. This path length to volume ratio (26.6 cm-2) is large compared to current state of the art multipass cells such as the cylindrical multipass cell (6.6 cm-2) and astigmatic Herriott cell (9 cm-2). Additionally, the effect of small changes to the input conditions on the path length is studied and compared to the astigmatic Herriott cell. This work simplifies the process of designing RACs with long optical path lengths and could lead to broader implementation of these multipass cells.

Acute effects of small changes in crank length on gross efficiency and pedalling technique during submaximal cycling

ABSTRACTThe main purpose of this study was to assess the acute effects of small changes in crank length (assumable by competitive cyclists) on metabolic cost and pedalling technique during submaximal cycling. Twelve amateur road cyclists performed three sets of submaximal pedalling (150, 200 and 250 W) at a constant cadence (91.3 ± 0.8 rpm) in a randomised order with three commonly used crank lengths, preferred (172.5–175 mm), +5 mm and −5 mm. Energy cost of pedalling, kinetic and kinematic variables were simultaneously registered. Changes in crank length had no significant effect on heart rate (144 ± 13, 145 ± 12 and 145 ± 13 bpm, respectively) and gross efficiency (GE) (20.4 ± 2.1, 20.1 ± 2.2 and 20.3 ± 2.4%, respectively). A longer crank induced a significant (P < 0.05) reduction of positive impulse proportion (PIP) (0.9–1.9%) due to a greater maximum (1.0–2.3 N · m) and minimum torque (1.0–2.2 N · m). At the same time, the maximum flexion and range of motion of the hip and knee joints were significantly increased (1.8–3.4° and P < 0.05), whereas the ankle joint was not affected. In conclusion, the biomechanical changes due to a longer crank did not alter the metabolic cost of pedalling, although they could have long-term adverse effects. Therefore, in case of doubt between two lengths, the shorter one might be recommended.

Potassium ions in extender differentially influence the post-thaw sperm motility of salmonid fish

Potassium ions are known to have an inhibitory effect on the sperm motility of salmonids. For this reason, the addition of K+ to the extender is frequently applied. However, the effect of the addition of K+ to the extender has not yet been tested. The aim of this study was to test the influence of potassium ion supplementation of the extender on the sperm motility parameters from five Salmonidae species (rainbow trout (Oncorhynchus mykiss), sex-reversed female rainbow trout, whitefish (Coregonus lavaretus), brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis)). Semen samples were diluted in extender containing 0.18 M glucose in 9% methanol (GM) supplemented with 0, 20 or 40 mM potassium chloride. After thawing sperm were stored for 30, 60, 120 and 240 min at 4 °C. Our results demonstrated that the presence of potassium ions in the extender had a negative effect on percentage of motile sperm in four of the salmonid species. In contrast, potassium ions appeared to have a positive effect on percentage of post-thaw motile sperm in whitefish semen. However, this effect could be mimicked by changing the osmolality of the extender (which was achieved by increasing the glucose concentration to 0.22 M). The addition of potassium ions turned out to have no positive effect on post-thaw storage time. Our results suggest that osmolality, rather than potassium ions, seems to be essential for cryopreservation success of salmonids sperm. Further studies should focus on the effects of small changes in osmolality on the post-thaw quality of semen.