Equations For Components Research Articles

Dielectric relaxation in AC powder electroluminescent devices

Abstract The dielectric properties of AC powder electroluminescent devices were measured and analyzed using complex impedance spectroscopy to determine the relaxation processes occurring within the devices. The relaxation processes identified were ascribed to the electrode polarization caused by ion accumulation at the electrode/resin interfaces, the Maxwell-Wagner-Sillars effects at the (ZnS or BaTiO3) particle/resin interfaces, and the dipolar reorientation of polymer chains in the resin matrix. Each relaxation process was represented by its corresponding equivalent circuit component. Space charge polarization at the electrodes were represented by a Warburg element, a resistor, and a constant phase element. The resin matrix, ZnS/resin and BaTiO3/resin interfaces could each be modeled by a resistor and a capacitor in parallel. The simulated equivalent circuits for three different printed structures showed good fitting with their experimental impedance results.

An alternative numerical solution of 900/00/900 cross-ply laminated composite plate using displacement potential approach

ABSTRACTConventional loading with a composite plate has a very small moment of inertia due to its low height, and it was solved by shear deformation and other approaches. In the present study, a thin cross-ply 900/00/900 laminated composite plate is erected to increase its height, which increases its moment of inertia with load; increased moments of inertia of the plate increase its load-carrying capacity in a real structure. Finite difference solutions of a cross-ply 900/00/900 laminated plate made of T-300 carbon/epoxy are obtained using displacement potential approach. The plate behaves like a cantilever beam; one end of the plate is rigidly fixed and a uniformly distributed load is applied on its top span. The displacement potential approach is extended using the lamination theory of composite materials and plane stress concept. The different equivalent displacement, strain, and stress components at different sections of the plate with its deformed shape are discussed. Using the concept of the classical theory of laminations, different stress components along the lamina and inter-laminar regions are obtained. Besides to verify the reliability and soundness of the present numerical approach, the solutions of the present problem are compared with those of the finite element method.

Optimality and stability of intentional and unintentional actions: II. Motor equivalence and structure of variance.

We address the nature of unintentional changes in performance in two papers. This second paper tested hypotheses related to stability of task-specific performance variables estimated using the framework of the uncontrolled manifold (UCM) hypothesis. Our first hypothesis was that selective stability of performance variables would be observed even when the magnitudes of those variables drifted unintentionally because of the lack of visual feedback. Our second hypothesis was that stability of a variable would depend on the number of explicit task constraints. Subjects performed four-finger isometric pressing tasks that required the accurate production of a combination of total moment and total force with natural or modified finger involvement under full visual feedback, which was removed later for some or all of the salient variables. We used inter-trial analysis of variance and drifts in the space of finger forces within the UCM and within the orthogonal to the UCM space. The two variance components were used to estimate a synergy index stabilizing the force/moment combination, while the two drift components were used to estimate motor equivalent and non-motor equivalent force changes, respectively. Without visual feedback, both force and moment drifted toward lower absolute magnitudes. The non-motor equivalent component of motion in the finger force space was larger than the motor equivalent component for variables that stopped receiving visual feedback. In contrast, variables that continued to receive visual feedback showed larger motor equivalent component, compared to non-motor equivalent component, over the same time interval. These data falsified the first hypothesis; indeed, selective stabilization of a variable over the duration of a trial allows expecting comparably large motor equivalent components both with and without visual feedback. Adding a new constraint (presented as a target magnitude of middle finger force) resulted in a drop in the synergy index in support of the second hypothesis. We interpret the force drift as a natural relaxation process toward states with lower potential energy in the physical (physiological) system involved in the task. The results show that presenting sensory feedback on a performance variable makes synergies stabilizing that variable dependent on that particular sensory feedback.

A novel langasite crystal microbalance instrumentation for UV sensing application

In this paper, we present a novel low-power UV sensor instrumentation based on ZnO thin-film and langasite crystal microbalance (LCM) composite resonator. The design of this sensor utilizes the exceptional transient response characteristics of thickness shear mode langasite crystal and UV sensitivity of annealed ZnO thin film. Our comparative transient analysis of langasite and quartz crystals shows that langasite crystal has high stability and fast relaxation times, and requires a fraction of excitation power in comparison to that of quartz. Upon investigating the equivalent circuit components, we discovered that high value of motional capacitance of LCM resulted in these contrasting transient responses in LCM and QCM. This high motional capacitance can be further attributed to the high electromechanical coupling coefficient (K2) of piezoelectric langasite crystal. Motivated by these observed characteristics, we proposed a novel sensor instrumentation that is simple yet effective in simultaneous measurements of the frequency, dissipation factor, and the amplitude of oscillation of a LCM. Moreover, our measurements allow for direct monitoring of any change in piezoelectricity of ZnO thin film. Our new measurement approach uses a one-shot pulse instead of conventional sinusoidal waveform to drive the crystal, which allows for simple instrumentation and requires very low input power. The transient response of the crystal shows that the crystal oscillates at its fundamental frequency and the amplitude of oscillation decays exponentially. From the recorded decay curve, the frequency of the freely oscillating crystal, and other important crystal parameters were calculated. We have utilized this mechanism to demonstrate highly sensitive ZnO thin film and LCM based UV sensor. Highest sensitivity of 35.8ppm per μW/cm2 was observed for the LCM coated with 400nm ZnO film. Additionally, the influence of UV on the piezoelectric output of ZnO thin film was also characterized by monitoring the DC offset of the output oscillations. Our findings in this work opens scope for developing low-power acoustic sensors with significant implications towards self-powering sensors.

Reliability evaluation of voltage‐source converter‐based multi‐terminal direct current integrated offshore wind plants

A novel analytical approach to reliability evaluation of voltage-source converter-based multi-terminal direct current (VSC-MTDC) integrated offshore wind plants is presented in this study. To treat the multi-terminal grid precisely and efficiently, the approach combines the state evaluation method and network flow method. A DC line equivalent component is also proposed to consider the operation modes, failure clean measures as well as interactions between different DC lines of VSC-MTDC. Employing this approach, the authors can obtain both frequency and probability indexes of reliability. The usefulness and effectiveness of the proposed method are verified by case studies. The comparison between three popular schemes is also carried out.

Alternative Single-Solvent Electrolytes Based on Cyanoesters for Safer Lithium-Ion Batteries.

To identify alternative single-solvent-based electrolytes for application in lithium-ion batteries (LIBs), adequate computational methods were applied to screen specified physicochemical and electrochemical properties of new cyanoester-based compounds. Out of 2747 possible target compounds, two promising candidates and two structurally equivalent components were chosen. A constructive selection process including evaluation of basic physicochemical properties as well assessing the compatibility towards graphitic anodes was initiated to identify the most promising candidates. With addition of a film-forming additive in a low concentration, the most promising candidate showed an adequate long-term cycling stability with LiNi1/3 Mn1/3 Co1/3 O2 [NMC(111)] in a full-cell setup using graphite as anode material. The main advantages of the new electrolyte formulation are related to its good thermal behavior, especially with regard to safety in combination with satisfying electrochemical performance.

Mechanical discrete simulator of the electro-mechanical lift with n:1 roping

The design process of new products in lift engineering is a difficult task due to, mainly, the complexity and slenderness of the lift system, demanding a predictive tool for the lift mechanics. A mechanical ad-hoc discrete simulator, as an alternative to ‘general purpose’ mechanical simulators is proposed. Firstly, the synthesis and experimentation process that has led to establish a suitable model capable of simulating accurately the response of the electromechanical lift is discussed. Then, the equations of motion are derived. The model comprises a discrete system of 5 vertically displaceable masses (car, counterweight, car frame, passengers/loads and lift drive), an inertial mass of the assembly tension pulley-rotor shaft which can rotate about the machine axis and 6 mechanical connectors with 1:1 suspension layout. The model is extended to any n:1 roping lift by setting 6 equivalent mechanical components (suspension systems for car and counterweight, lift drive silent blocks, tension pulley-lift drive stator and passengers/load equivalent spring-damper) by inductive inference from 1:1 and generalized 2:1 roping system. The application to simulate real elevator systems is proposed by numeric time integration of the governing equations using the Kutta-Meden algorithm and implemented in a computer program for ad-hoc elevator simulation called ElevaCAD.

Bernoulli, Darwin, and Sagan: the probability of life on other planets

AbstractThe recent discovery that billions of planets in the Milky Way Galaxy may be in circumstellar habitable zones has renewed speculation over the possibility of extraterrestrial life. The Drake equation is a probabilistic framework for estimating the number of technological advanced civilizations in our Galaxy; however, many of the equation's component probabilities are either unknown or have large error intervals. In this paper, a different method of examining this question is explored, one that replaces the various Drake factors with the single estimate for the probability of life existing on Earth. This relationship can be described by the binomial distribution if the presence of life on a given number of planets is equated to successes in a Bernoulli trial. The question of exoplanet life may then be reformulated as follows – given the probability of one or more independent successes for a given number of trials, what is the probability of two or more successes? Some of the implications of this approach for finding life on exoplanets are discussed.

Preference for the Diversity Policy Label Versus the Affirmative Action Policy Label

Study 1 assessed associations with the labels “diversity policy” (DP) and “affirmative action policy” (AAP) and perceptions of potential policy components. Student and community participants (N = 143) completed a survey assessing associations with one of the policy labels. Both policies evoked similar associations such as “race/minorities” and “equality/equal opportunity,” but the AAP was more often associated with “bias/inequality/discrimination,” “unfairness,” and “racism/prejudice.” When rating potential policy components, reverse discrimination was considered more likely under the AAP. In Study 2 we explored the evaluation of equivalent policy components associated with different policy labels. Student participants (N = 126) rated the policy labeled as the DP more favorably than the AAP. Both studies suggest more favorable attitudes toward the DP label.

Parameter Sensitivity Analysis for Fractional-Order Modeling of Lithium-Ion Batteries

This paper presents a novel-fractional-order lithium-ion battery model that is suitable for use in embedded applications. The proposed model uses fractional calculus with an improved Oustaloup approximation method to describe all the internal battery dynamic behaviors. The fractional-order model parameters, such as equivalent circuit component coefficients and fractional-order values, are identified by a genetic algorithm. A modeling parameters sensitivity study using the statistical Multi-Parameter Sensitivity Analysis (MPSA) method is then performed and discussed in detail. Through the analysis, the dynamic effects of parameters on the model output performance are obtained. It has been found out from the analysis that the fractional-order values and their corresponding internal dynamics have different degrees of impact on model outputs. Thus, they are considered as crucial parameters to accurately describe a battery’s dynamic voltage responses. To experimentally verify the accuracy of developed fractional-order model and evaluate its performance, the experimental tests are conducted with a hybrid pulse test and a dynamic stress test (DST) on two different types of lithium-ion batteries. The results demonstrate the accuracy and usefulness of the proposed fractional-order model on battery dynamic behavior prediction.

A facile and green preparation of nanosilica-supported antioxidant and its reinforcement and antioxidation effect on styrene-butadiene rubber

ABSTRACTA novel solid-phase method has been proposed to prepare a nanosilica-supported antioxidant by the reaction of nanosilica with 2-mercaptobenzimidazole (MB) and silane coupling agent γ-chloropropyltriethoxysilane. Fourier transform-infrared spectroscopy and other characterization methods confirmed that MB was chemically bonded onto the surface of nanosilica. Silica-s-MB was homogeneously dispersed in a styrene-butadiene rubber (SBR) matrix with strong filler-rubber interaction, leading to enhanced mechanical performance of SBR/silica-s-MB composites compared with SBR/m-silica composites. Based on the results of thermo-oxidation testing of SBR/silica-s-MB and SBR/m-silica/MB composites containing equivalent antioxidant component, silica-s-MB showed better antioxidative efficiency than the corresponding low-molecular-weight MB owing to its lower migration and volatility at high temperature.

Generalization of the moment of inertia method to estimate equivalent amplitudes for simplifying the analysis of arbitrary non-proportional multiaxial stress or strain histories

Several models have been proposed in the literature to account for fatigue damage under multiaxial load histories. Most of them require some measure of an equivalent stress or strain amplitude, in the sense of causing the same damage as the original history, which may be difficult to obtain for generic non-proportional multiaxial variable amplitude load histories. To identify individual load cycles, a multiaxial rainflow-like algorithm must be employed. For each rainflow-counted cycle, the equivalent stress or strain amplitude along its path is often computed using the so-called convex enclosure methods, which find minimum spheres, ellipsoids, or rectangular prisms that contain the load path in a deviatoric stress or strain space. However, such procedure involves information loss, in special if the path shape is very different from the shape of the enclosing convex surface, resulting in poor estimates of equivalent stress or strain amplitudes. To overcome this problem, the moment of inertia (MOI) method has been proposed in Meggiolaro and Castro (Int J Fatigue 42:217–226, 2012) to calculate equivalent amplitudes and mean components of two-dimensional stress or strain paths, generated, e.g., by tension–torsion or biaxial histories. In this work, the MOI method is extended to deal with generic 6D stress or strain paths, which include all normal and shear components. To accomplish that, the load history path is first represented in a 5D deviatoric stress or strain space and then assumed to be a homogeneous wire with unit mass, whose perimeter centroid is used to estimate the location of the path mean component. Then, the polar moment of inertia (PMOI) of such a hypothetical wire with respect to its mean component is calculated. The PMOI represents the distribution of the path about a single point, the perimeter centroid, giving a measure of how much the path stretches away from its mean component, which is used in the calculation of the equivalent amplitudes. Experimental results for 13 different multiaxial load histories prove the effectiveness of the proposed method to predict equivalent amplitudes and multiaxial fatigue lives.

Surface modification of halloysite nanotubes by vulcanization accelerator and properties of styrene-butadiene rubber nanocomposites with modified halloysite nanotubes

Vulcanization accelerant N-cyclohexyl-2-benzothiazole sulfenamide (CZ) was used as a surface modifier and chemically grafted on the surface of halloysite nanotubes (HNTs) to obtain CZ-functionalized HNTs (HNTs-s-CZ). It was found that HNTs-s-CZ could be homogeneously dispersed into styrene-butadiene rubber (SBR). The grafted CZ molecules, exactly located at the filler-rubber interface, reduced the activation energy of vulcanization of SBR/HNTs-s-CZ compounds. Besides, the density of chain segments introduced by the interfacial phase of SBR/HNTs-s-CZ nanocomposites was higher than the other nanocomposites with silane-modified HNTs (m-HNTs) or pristine HNTs, manifesting an indication of enhanced filler-rubber interfacial interaction in SBR/HNTs-s-CZ nanocomposites. Consequently, SBR/HNTs-s-CZ nanocomposites showed excellent mechanical properties. The tensile strength could be enhanced by as much as 38.6% and 102.5% compared to those of SBR/m-HNTs and SBR/HNTs nanocomposites, respectively, though containing equivalent accelerant component. The value of this work lies in the fact that apparent properties improvement of elastomer composites has been achieved by the incorporation of vulcanization accelerant-functionalized HNTs, which may be fruitful for the rational design of filler surface treatment and offer new scientific and technological opportunities for the preparation of high performance elastomer composites.

Adaptive wavelet network sliding mode control for a photovoltaic-pumping system

This paper presents an adaptive wavelet network sliding mode control (AWNSMC) scheme to track the maximum power point tracking in photovoltaic (PV) pumping systems. For the best use, the PV-generator must operate at its maximum power point. The proposed approach combines the advantages of the wavelet network (WN) and those of sliding mode control (SMC) to adjust the duty cycle control law in order to satisfy reaching conditions without producing chattering phenomenon. Indeed, due to its ability to approximate non-linear function and its fast convergence, a WN system is used to approximate the system uncertainties that are incorporated in the equivalent control component; as a result, it enables a lower switching gain to be used in the robust SMC term. The effectiveness of the designed AWNSMC is illustrated in simulations by a comparison with both standard SMC and neural network SMC techniques.

Characterizing Electrical Output of Bifacial Photovoltaic Modules by Altering Reflective Materials

Bifacial photovoltaic (PV) modules offer potentially enhanced power output over conventional modules due to their reported ability to harvest reflected radiation, increasing output up to an additional 30%. However, this enhancement has yet to be confirmed in the literature. This paper reports on a study comparing the power output of two nominally identical 700 W photovoltaic arrays utilizing equivalent system components and data logging equipment with varying configurations of reflecting geometries and materials. This study was undertaken at the Appalachian State University Solar Research Laboratory in Boone, NC, which houses two Class 1 pyranometers and pyrheliometer. PV power was reported under well-quantified irradiance conditions, including direct beam fraction. Six trials over six months (November-April) with varying reflective materials and geometries revealed that different reflecting materials did not significantly change power output. Mounting an array at 0˚ did adversely affect power output compared to the array at a 36° angle relative to horizontal using the same reflective material. Additional studies with varied materials, panel locations and geometries different from those tested may improve the power output.

General Dynamic Equivalent Modeling of Microgrid Based on Physical Background

Microgrid is a new power system concept consisting of small-scale distributed energy resources; storage devices and loads. It is necessary to employ a simplified model of microgrid in the simulation of a distribution network integrating large-scale microgrids. Based on the detailed model of the components, an equivalent model of microgrid is proposed in this paper. The equivalent model comprises two parts: namely, equivalent machine component and equivalent static component. Equivalent machine component describes the dynamics of synchronous generator, asynchronous wind turbine and induction motor, equivalent static component describes the dynamics of photovoltaic, storage and static load. The trajectory sensitivities of the equivalent model parameters with respect to the output variables are analyzed. The key parameters that play important roles in the dynamics of the output variables of the equivalent model are identified and included in further parameter estimation. Particle Swarm Optimization (PSO) is improved for the parameter estimation of the equivalent model. Simulations are performed in different microgrid operation conditions to evaluate the effectiveness of the equivalent model of microgrid.

A semi-analytical numerical method for fast metamaterial absorber design

In this paper, a semi-analytical numerical approach utilizing a novel non-grounded model and interpolation technique is introduced to design the frequency selective surface (FSS) based metamaterial absorbers (MAs) with dramatically reduced time consumption. Different from commonly used trial-and-error technology, our method mainly utilize the numerically computed FSS layer impedance with slow-varying feature in the vicinity of operating frequency. The introduced non-grounded model establishes the quantitative relationship between geometry parameters and equivalent lumped circuit components in conventional transmission line (TL) model with reasonable accuracy. The interpolation technique, on the other hand, promises a relative sparse parameter sweep. The detailed design flow as well as analytical explanation with carefully deduced expressions is presented. With the purpose of validating the proposed method and analytical models, a MA with slotted patches is designed through both the semi-analytical numerical approach and the trial-and-error method, where an over 2300 times acceleration is observed. Additionally, results from the analytical computation and full wave simulation agree well with each other.

Reinforcement and reinforcing mechanism of styrene–butadiene rubber by antioxidant-modified silica

The focus of this study was on the reinforcement and reinforcing mechanism of the organically modified silica in styrene–butadiene rubber (SBR). It was shown that antioxidant 2-mercaptobenzimidazole (MB) modified silica (silica-s-MB) exhibited better dispersion in SBR than silane-modified silica (m-silica) and the interfacial interaction in SBR/silica-s-MB nanocomposites was stronger than that in SBR/m-silica nanocomposites, leading to a remarkable improvement of mechanical properties for SBR/silica-s-MB nanocomposites compared with those for SBR/m-silica nanocomposites containing equivalent antioxidant component. Based on the analysis of the large strain behavior of SBR nanocomposites, the reinforcing mechanisms of silica-s-MB and m-silica were comparativelyinvestigated. It was found that the physical entanglements between the crosslinked rubber chains in the immobilized polymer layer and the organic molecules grafted on the silica surface played an important role in the silica reinforcement of rubber, which may be useful for the rational design of filler surface modification.

Numerical method for optimizing design variables of carbon-fiber-reinforced epoxy composite coil springs

To successfully reduce a vehicle's weight by replacing steel with composite materials, it is essential to optimize the material parameters and design variables of the structure. In this study, we investigated numerical and experimental methods for determining the ply angles and wire diameters of carbon fiber/epoxy composite coil springs to attain a spring rate equal to that of an equivalent steel component. First, the shear modulus ratio for two materials was calculated as a function of the ply angles and compared with the experimental results. Then, by using the equation of the spring rate with respect to the shear modulus and design variables, normalized spring rates were obtained for specific ply angles and wire diameters. Finally, a finite element model for an optimal composite coil spring was constructed and analyzed to obtain the static spring rate, which was then compared with the experimental results.

A method to improve the mechanical performance of styrene-butadiene rubber via vulcanization accelerator modified silica

Abstract Accelerator ethylenethiourea (ETU) was chemically grafted onto the surface of silane modified silica (m-silica) to obtain ETU-modified silica (silica-s-ETU). Silica-s-ETU could be homogeneously dispersed into the matrix of styrene-butadiene rubber (SBR) with fairly strong filler-rubber interaction and the grafted ETU molecules were still able to accelerate the sulfur vulcanization. Owing to the improved modification effect, the prepared SBR/silica-s-ETU nanocomposites showed more excellent mechanical properties than SBR/m-silica and SBR/silica nanocomposites containing equivalent accelerator component. Based on the results of immobilized polymer layer, the strengthening mechanism of silica-s-ETU was analyzed and substantiated. The highlight of this work lies in the fact that apparent improvement has been achieved by the surface modification of silica with vulcanization accelerator, which may open up new opportunities for the preparation of high performance rubber composites.